[apple/xnu.git] / bsd / nfs / nfs_gss.c

/*
 * Copyright (c) 2007-2020 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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 *
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 */

#include <nfs/nfs_conf.h>
#if CONFIG_NFS

/*************
 * These functions implement RPCSEC_GSS security for the NFS client and server.
 * The code is specific to the use of Kerberos v5 and the use of DES MAC MD5
 * protection as described in Internet RFC 2203 and 2623.
 *
 * In contrast to the original AUTH_SYS authentication, RPCSEC_GSS is stateful.
 * It requires the client and server negotiate a secure connection as part of a
 * security context. The context state is maintained in client and server structures.
 * On the client side, each user of an NFS mount is assigned their own context,
 * identified by UID, on their first use of the mount, and it persists until the
 * unmount or until the context is renewed.  Each user context has a corresponding
 * server context which the server maintains until the client destroys it, or
 * until the context expires.
 *
 * The client and server contexts are set up dynamically.  When a user attempts
 * to send an NFS request, if there is no context for the user, then one is
 * set up via an exchange of NFS null procedure calls as described in RFC 2203.
 * During this exchange, the client and server pass a security token that is
 * forwarded via Mach upcall to the gssd, which invokes the GSS-API to authenticate
 * the user to the server (and vice-versa). The client and server also receive
 * a unique session key that can be used to digitally sign the credentials and
 * verifier or optionally to provide data integrity and/or privacy.
 *
 * Once the context is complete, the client and server enter a normal data
 * exchange phase - beginning with the NFS request that prompted the context
 * creation. During this phase, the client's RPC header contains an RPCSEC_GSS
 * credential and verifier, and the server returns a verifier as well.
 * For simple authentication, the verifier contains a signed checksum of the
 * RPC header, including the credential.  The server's verifier has a signed
 * checksum of the current sequence number.
 *
 * Each client call contains a sequence number that nominally increases by one
 * on each request.  The sequence number is intended to prevent replay attacks.
 * Since the protocol can be used over UDP, there is some allowance for
 * out-of-sequence requests, so the server checks whether the sequence numbers
 * are within a sequence "window". If a sequence number is outside the lower
 * bound of the window, the server silently drops the request. This has some
 * implications for retransmission. If a request needs to be retransmitted, the
 * client must bump the sequence number even if the request XID is unchanged.
 *
 * When the NFS mount is unmounted, the client sends a "destroy" credential
 * to delete the server's context for each user of the mount. Since it's
 * possible for the client to crash or disconnect without sending the destroy
 * message, the server has a thread that reaps contexts that have been idle
 * too long.
 */

#include <stdint.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/kauth.h>
#include <sys/kernel.h>
#include <sys/mount_internal.h>
#include <sys/vnode.h>
#include <sys/ubc.h>
#include <sys/malloc.h>
#include <sys/kpi_mbuf.h>
#include <sys/ucred.h>

#include <kern/host.h>
#include <kern/task.h>
#include <libkern/libkern.h>

#include <mach/task.h>
#include <mach/host_special_ports.h>
#include <mach/host_priv.h>
#include <mach/thread_act.h>
#include <mach/mig_errors.h>
#include <mach/vm_map.h>
#include <vm/vm_map.h>
#include <vm/vm_kern.h>
#include <gssd/gssd_mach.h>

#include <nfs/rpcv2.h>
#include <nfs/nfsproto.h>
#include <nfs/nfs.h>
#include <nfs/nfsnode.h>
#include <nfs/nfs_gss.h>
#include <nfs/nfsmount.h>
#include <nfs/xdr_subs.h>
#include <nfs/nfsm_subs.h>
#include <nfs/nfs_gss.h>
#include <mach_assert.h>
#include <kern/assert.h>

#define ASSERT(EX) assert(EX)

#define NFS_GSS_MACH_MAX_RETRIES 3

#define NFS_GSS_DBG(...) NFS_DBG(NFS_FAC_GSS, 7, ## __VA_ARGS__)
#define NFS_GSS_ISDBG  (NFS_DEBUG_FACILITY &  NFS_FAC_GSS)


#if CONFIG_NFS_SERVER
u_long nfs_gss_svc_ctx_hash;
struct nfs_gss_svc_ctx_hashhead *nfs_gss_svc_ctx_hashtbl;
static LCK_GRP_DECLARE(nfs_gss_svc_grp, "rpcsec_gss_svc");
static LCK_MTX_DECLARE(nfs_gss_svc_ctx_mutex, &nfs_gss_svc_grp);
uint32_t nfsrv_gss_context_ttl = GSS_CTX_EXPIRE;
#define GSS_SVC_CTX_TTL ((uint64_t)max(2*GSS_CTX_PEND, nfsrv_gss_context_ttl) * NSEC_PER_SEC)
#endif /* CONFIG_NFS_SERVER */

#if CONFIG_NFS_CLIENT
LCK_GRP_DECLARE(nfs_gss_clnt_grp, "rpcsec_gss_clnt");
#endif /* CONFIG_NFS_CLIENT */

#define KRB5_MAX_MIC_SIZE 128
uint8_t krb5_mech_oid[11] = { 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x12, 0x01, 0x02, 0x02 };
static uint8_t xdrpad[] = { 0x00, 0x00, 0x00, 0x00};

#if CONFIG_NFS_CLIENT
static int      nfs_gss_clnt_ctx_find(struct nfsreq *);
static int      nfs_gss_clnt_ctx_init(struct nfsreq *, struct nfs_gss_clnt_ctx *);
static int      nfs_gss_clnt_ctx_init_retry(struct nfsreq *, struct nfs_gss_clnt_ctx *);
static int      nfs_gss_clnt_ctx_callserver(struct nfsreq *, struct nfs_gss_clnt_ctx *);
static uint8_t  *nfs_gss_clnt_svcname(struct nfsmount *, gssd_nametype *, size_t *);
static int      nfs_gss_clnt_gssd_upcall(struct nfsreq *, struct nfs_gss_clnt_ctx *, uint32_t);
void            nfs_gss_clnt_ctx_neg_cache_reap(struct nfsmount *);
static void     nfs_gss_clnt_ctx_clean(struct nfs_gss_clnt_ctx *);
static int      nfs_gss_clnt_ctx_copy(struct nfs_gss_clnt_ctx *, struct nfs_gss_clnt_ctx **);
static void     nfs_gss_clnt_ctx_destroy(struct nfs_gss_clnt_ctx *);
static void     nfs_gss_clnt_log_error(struct nfsreq *, struct nfs_gss_clnt_ctx *, uint32_t, uint32_t);
#endif /* CONFIG_NFS_CLIENT */

#if CONFIG_NFS_SERVER
static struct nfs_gss_svc_ctx *nfs_gss_svc_ctx_find(uint32_t);
static void     nfs_gss_svc_ctx_insert(struct nfs_gss_svc_ctx *);
static void     nfs_gss_svc_ctx_timer(void *, void *);
static int      nfs_gss_svc_gssd_upcall(struct nfs_gss_svc_ctx *);
static int      nfs_gss_svc_seqnum_valid(struct nfs_gss_svc_ctx *, uint32_t);

/* This is only used by server code */
static void     nfs_gss_nfsm_chain(struct nfsm_chain *, mbuf_t);
#endif /* CONFIG_NFS_SERVER */

static void     host_release_special_port(mach_port_t);
static mach_port_t host_copy_special_port(mach_port_t);
static void     nfs_gss_mach_alloc_buffer(u_char *, size_t, vm_map_copy_t *);
static int      nfs_gss_mach_vmcopyout(vm_map_copy_t, uint32_t, u_char *);

static int      nfs_gss_mchain_length(mbuf_t);
static int      nfs_gss_append_chain(struct nfsm_chain *, mbuf_t);

#if CONFIG_NFS_SERVER
thread_call_t nfs_gss_svc_ctx_timer_call;
int nfs_gss_timer_on = 0;
uint32_t nfs_gss_ctx_count = 0;
const uint32_t nfs_gss_ctx_max = GSS_SVC_MAXCONTEXTS;
#endif /* CONFIG_NFS_SERVER */

/*
 * Initialization when NFS starts
 */
void
nfs_gss_init(void)
{
#if CONFIG_NFS_SERVER
        nfs_gss_svc_ctx_hashtbl = hashinit(SVC_CTX_HASHSZ, M_TEMP, &nfs_gss_svc_ctx_hash);

        nfs_gss_svc_ctx_timer_call = thread_call_allocate(nfs_gss_svc_ctx_timer, NULL);
#endif /* CONFIG_NFS_SERVER */
}

/*
 * Common RPCSEC_GSS support routines
 */

static errno_t
rpc_gss_prepend_32(mbuf_t *mb, uint32_t value)
{
        int error;
        uint32_t *data;

#if 0
        data = mbuf_data(*mb);
        /*
         * If a wap token comes back and is not aligned
         * get a new buffer (which should be aligned) to put the
         * length in.
         */
        if ((uintptr_t)data & 0x3) {
                mbuf_t nmb;

                error = mbuf_get(MBUF_WAITOK, MBUF_TYPE_DATA, &nmb);
                if (error) {
                        return error;
                }
                mbuf_setnext(nmb, *mb);
                *mb = nmb;
        }
#endif
        error = mbuf_prepend(mb, sizeof(uint32_t), MBUF_WAITOK);
        if (error) {
                return error;
        }

        data = mbuf_data(*mb);
        *data = txdr_unsigned(value);

        return 0;
}

/*
 * Prepend the sequence number to the xdr encode argumen or result
 * Sequence number is prepended in its own mbuf.
 *
 * On successful return mbp_head will point to the old mbuf chain
 * prepended  with a new mbuf that has the sequence number.
 */

static errno_t
rpc_gss_data_create(mbuf_t *mbp_head, uint32_t seqnum)
{
        int error;
        mbuf_t mb;
        struct nfsm_chain nmc;
        struct nfsm_chain *nmcp = &nmc;
        uint8_t *data;

        error = mbuf_get(MBUF_WAITOK, MBUF_TYPE_DATA, &mb);
        if (error) {
                return error;
        }
        data = mbuf_data(mb);
#if 0
        /* Reserve space for prepending */
        len = mbuf_maxlen(mb);
        len = (len & ~0x3) - NFSX_UNSIGNED;
        printf("%s: data = %p, len = %d\n", __func__, data, (int)len);
        error = mbuf_setdata(mb, data + len, 0);
        if (error || mbuf_trailingspace(mb)) {
                printf("%s: data = %p trailingspace = %d error = %d\n", __func__, mbuf_data(mb), (int)mbuf_trailingspace(mb), error);
        }
#endif
        /* Reserve 16 words for prepending */
        error = mbuf_setdata(mb, data + 16 * sizeof(uint32_t), 0);
        nfsm_chain_init(nmcp, mb);
        nfsm_chain_add_32(error, nmcp, seqnum);
        nfsm_chain_build_done(error, nmcp);
        if (error) {
                return EINVAL;
        }
        mbuf_setnext(nmcp->nmc_mcur, *mbp_head);
        *mbp_head = nmcp->nmc_mhead;

        return 0;
}

/*
 * Create an rpc_gss_integ_data_t given an argument or result in mb_head.
 * On successful return mb_head will point to the rpc_gss_integ_data_t of length len.
 *      Note mb_head will now point to a 4 byte sequence number. len does not include
 *      any extra xdr padding.
 * Returns 0 on success, else an errno_t
 */

static errno_t
rpc_gss_integ_data_create(gss_ctx_id_t ctx, mbuf_t *mb_head, uint32_t seqnum, uint32_t *len)
{
        uint32_t error;
        uint32_t major;
        uint32_t length;
        gss_buffer_desc mic;
        struct nfsm_chain nmc;

        /* Length of the argument or result */
        length = nfs_gss_mchain_length(*mb_head);
        if (len) {
                *len = length;
        }
        error = rpc_gss_data_create(mb_head, seqnum);
        if (error) {
                return error;
        }

        /*
         * length is the length of the rpc_gss_data
         */
        length += NFSX_UNSIGNED;  /* Add the sequence number to the length */
        major = gss_krb5_get_mic_mbuf(&error, ctx, 0, *mb_head, 0, length, &mic);
        if (major != GSS_S_COMPLETE) {
                printf("gss_krb5_get_mic_mbuf failed %d\n", error);
                return error;
        }

        error = rpc_gss_prepend_32(mb_head, length);
        if (error) {
                return error;
        }

        nfsm_chain_dissect_init(error, &nmc, *mb_head);
        /* Append GSS mic token by advancing rpc_gss_data_t length + NFSX_UNSIGNED (size of the length field) */
        nfsm_chain_adv(error, &nmc, length + NFSX_UNSIGNED);
        nfsm_chain_finish_mbuf(error, &nmc); // Force the mic into its own sub chain.
        nfsm_chain_add_32(error, &nmc, mic.length);
        nfsm_chain_add_opaque(error, &nmc, mic.value, mic.length);
        nfsm_chain_build_done(error, &nmc);
        gss_release_buffer(NULL, &mic);

//      printmbuf("rpc_gss_integ_data_create done", *mb_head, 0, 0);
        assert(nmc.nmc_mhead == *mb_head);

        return error;
}

/*
 * Create an rpc_gss_priv_data_t out of the supplied raw arguments or results in mb_head.
 * On successful return mb_head will point to a wrap token of lenght len.
 *      Note len does not include any xdr padding
 * Returns 0 on success, else an errno_t
 */
static errno_t
rpc_gss_priv_data_create(gss_ctx_id_t ctx, mbuf_t *mb_head, uint32_t seqnum, uint32_t *len)
{
        uint32_t error;
        uint32_t major;
        struct nfsm_chain nmc;
        uint32_t pad;
        uint32_t length;

        error = rpc_gss_data_create(mb_head, seqnum);
        if (error) {
                return error;
        }

        length = nfs_gss_mchain_length(*mb_head);
        major = gss_krb5_wrap_mbuf(&error, ctx, 1, 0, mb_head, 0, length, NULL);
        if (major != GSS_S_COMPLETE) {
                return error;
        }

        length = nfs_gss_mchain_length(*mb_head);
        if (len) {
                *len = length;
        }
        pad = nfsm_pad(length);

        /* Prepend the opaque length of rep rpc_gss_priv_data */
        error = rpc_gss_prepend_32(mb_head, length);

        if (error) {
                return error;
        }
        if (pad) {
                nfsm_chain_dissect_init(error, &nmc, *mb_head);
                /* Advance the opauque size of length and length data */
                nfsm_chain_adv(error, &nmc, NFSX_UNSIGNED + length);
                nfsm_chain_finish_mbuf(error, &nmc);
                nfsm_chain_add_opaque_nopad(error, &nmc, xdrpad, pad);
                nfsm_chain_build_done(error, &nmc);
        }

        return error;
}

#if CONFIG_NFS_CLIENT

/*
 * Restore the argument or result from an rpc_gss_integ_data mbuf chain
 * We have a four byte seqence number, len arguments, and an opaque
 * encoded mic, possibly followed by some pad bytes. The mic and possible
 * pad bytes are on their own sub mbuf chains.
 *
 * On successful return mb_head is the chain of the xdr args or results sans
 * the sequence number and mic and return 0. Otherwise return an errno.
 *
 */
static errno_t
rpc_gss_integ_data_restore(gss_ctx_id_t ctx __unused, mbuf_t *mb_head, size_t len)
{
        mbuf_t mb = *mb_head;
        mbuf_t tail = NULL, next;

        /* Chop of the opaque length and seq number */
        mbuf_adj(mb, 2 * NFSX_UNSIGNED);

        /* should only be one, ... but */
        for (; mb; mb = next) {
                next = mbuf_next(mb);
                if (mbuf_len(mb) == 0) {
                        mbuf_free(mb);
                } else {
                        break;
                }
        }
        *mb_head = mb;

        for (; mb && len; mb = mbuf_next(mb)) {
                tail = mb;
                if (mbuf_len(mb) <= len) {
                        len -= mbuf_len(mb);
                } else {
                        return EBADRPC;
                }
        }
        /* drop the mic */
        if (tail) {
                mbuf_setnext(tail, NULL);
                mbuf_freem(mb);
        }

        return 0;
}

/*
 * Restore the argument or result rfom an rpc_gss_priv_data mbuf chain
 * mb_head points to the wrap token of length len.
 *
 * On successful return mb_head is our original xdr arg or result an
 * the return value is 0. Otherise return an errno
 */
static errno_t
rpc_gss_priv_data_restore(gss_ctx_id_t ctx, mbuf_t *mb_head, size_t len)
{
        uint32_t major, error;
        mbuf_t mb = *mb_head, next;
        size_t plen, length;
        gss_qop_t qop = GSS_C_QOP_REVERSE;

        /* Chop of the opaque length */
        mbuf_adj(mb, NFSX_UNSIGNED);
        /* If we have padding, drop it */
        plen = nfsm_pad(len);
        if (plen) {
                mbuf_t tail = NULL;

                for (length = 0; length < len && mb; mb = mbuf_next(mb)) {
                        tail = mb;
                        length += mbuf_len(mb);
                }
                if ((length != len) || (mb == NULL) || (tail == NULL)) {
                        return EBADRPC;
                }

                mbuf_freem(mb);
                mbuf_setnext(tail, NULL);
        }

        major = gss_krb5_unwrap_mbuf(&error, ctx, mb_head, 0, len, NULL, &qop);
        if (major != GSS_S_COMPLETE) {
                printf("gss_krb5_unwrap_mbuf failed. major = %d minor = %d\n", (int)major, error);
                return error;
        }
        mb = *mb_head;

        /* Drop the seqence number */
        mbuf_adj(mb, NFSX_UNSIGNED);
        assert(mbuf_len(mb) == 0);

        /* Chop of any empty mbufs */
        for (mb = *mb_head; mb; mb = next) {
                next = mbuf_next(mb);
                if (mbuf_len(mb) == 0) {
                        mbuf_free(mb);
                } else {
                        break;
                }
        }
        *mb_head = mb;

        return 0;
}

/*
 * Find the context for a particular user.
 *
 * If the context doesn't already exist
 * then create a new context for this user.
 *
 * Note that the code allows superuser (uid == 0)
 * to adopt the context of another user.
 *
 * We'll match on the audit session ids, since those
 * processes will have acccess to the same credential cache.
 */

#define kauth_cred_getasid(cred) ((cred)->cr_audit.as_aia_p->ai_asid)
#define kauth_cred_getauid(cred) ((cred)->cr_audit.as_aia_p->ai_auid)

#define SAFE_CAST_INTTYPE( type, intval ) \
        ( (type)(intval)/(sizeof(type) < sizeof(intval) ? 0 : 1) )

uid_t
nfs_cred_getasid2uid(kauth_cred_t cred)
{
        uid_t result = SAFE_CAST_INTTYPE(uid_t, kauth_cred_getasid(cred));
        return result;
}

/*
 * Debugging
 */
static void
nfs_gss_clnt_ctx_dump(struct nfsmount *nmp)
{
        struct nfs_gss_clnt_ctx *cp;

        lck_mtx_lock(&nmp->nm_lock);
        NFS_GSS_DBG("Enter\n");
        TAILQ_FOREACH(cp, &nmp->nm_gsscl, gss_clnt_entries) {
                lck_mtx_lock(&cp->gss_clnt_mtx);
                printf("context %d/%d: refcnt = %d, flags = %x\n",
                    kauth_cred_getasid(cp->gss_clnt_cred),
                    kauth_cred_getauid(cp->gss_clnt_cred),
                    cp->gss_clnt_refcnt, cp->gss_clnt_flags);
                lck_mtx_unlock(&cp->gss_clnt_mtx);
        }
        NFS_GSS_DBG("Exit\n");
        lck_mtx_unlock(&nmp->nm_lock);
}

static char *
nfs_gss_clnt_ctx_name(struct nfsmount *nmp, struct nfs_gss_clnt_ctx *cp, char *buf, int len)
{
        char *np;
        size_t nlen;
        const char *server = "";

        if (nmp && nmp->nm_mountp) {
                server = vfs_statfs(nmp->nm_mountp)->f_mntfromname;
        }

        if (cp == NULL) {
                snprintf(buf, len, "[%s] NULL context", server);
                return buf;
        }

        if (cp->gss_clnt_principal && !cp->gss_clnt_display) {
                np = (char *)cp->gss_clnt_principal;
                nlen = cp->gss_clnt_prinlen;
        } else {
                np = cp->gss_clnt_display;
                nlen = np ? strlen(cp->gss_clnt_display) : 0;
        }
        if (nlen) {
                snprintf(buf, len, "[%s] %.*s %d/%d %s", server, nlen > INT_MAX ? INT_MAX : (int)nlen, np,
                    kauth_cred_getasid(cp->gss_clnt_cred),
                    kauth_cred_getuid(cp->gss_clnt_cred),
                    cp->gss_clnt_principal ? "" : "[from default cred] ");
        } else {
                snprintf(buf, len, "[%s] using default %d/%d ", server,
                    kauth_cred_getasid(cp->gss_clnt_cred),
                    kauth_cred_getuid(cp->gss_clnt_cred));
        }
        return buf;
}

#define NFS_CTXBUFSZ 80
#define NFS_GSS_CTX(req, cp) nfs_gss_clnt_ctx_name((req)->r_nmp, cp ? cp : (req)->r_gss_ctx, CTXBUF, sizeof(CTXBUF))

#define NFS_GSS_CLNT_CTX_DUMP(nmp)              \
        do {                  \
                if (NFS_GSS_ISDBG && (NFS_DEBUG_FLAGS & 0x2))   \
                        nfs_gss_clnt_ctx_dump((nmp));   \
        } while (0)

static int
nfs_gss_clnt_ctx_cred_match(kauth_cred_t cred1, kauth_cred_t cred2)
{
        if (kauth_cred_getasid(cred1) == kauth_cred_getasid(cred2)) {
                return 1;
        }
        return 0;
}

/*
 * Busy the mount for each principal set on the mount
 * so that the automounter will not unmount the file
 * system underneath us. With out this, if an unmount
 * occurs the principal that is set for an audit session
 * will be lost and we may end up with a different identity.
 *
 * Note setting principals on the mount is a bad idea. This
 * really should be handle by KIM (Kerberos Identity Management)
 * so that defaults can be set by service identities.
 */

static int
nfs_gss_clnt_mnt_ref(struct nfsmount *nmp)
{
        int error;
        vnode_t rvp;

        if (nmp == NULL ||
            !(vfs_flags(nmp->nm_mountp) & MNT_AUTOMOUNTED)) {
                return EINVAL;
        }

        error = VFS_ROOT(nmp->nm_mountp, &rvp, NULL);
        if (!error) {
                error = vnode_ref(rvp);
                vnode_put(rvp);
        }

        return error;
}

/*
 * Unbusy the mount. See above comment,
 */

static int
nfs_gss_clnt_mnt_rele(struct nfsmount *nmp)
{
        int error;
        vnode_t rvp;

        if (nmp == NULL ||
            !(vfs_flags(nmp->nm_mountp) & MNT_AUTOMOUNTED)) {
                return EINVAL;
        }

        error = VFS_ROOT(nmp->nm_mountp, &rvp, NULL);
        if (!error) {
                vnode_rele(rvp);
                vnode_put(rvp);
        }

        return error;
}

int nfs_root_steals_ctx = 0;

static int
nfs_gss_clnt_ctx_find_principal(struct nfsreq *req, uint8_t *principal, size_t plen, uint32_t nt)
{
        struct nfsmount *nmp = req->r_nmp;
        struct nfs_gss_clnt_ctx *cp, *tcp;
        struct nfsreq *treq;
        int error = 0;
        struct timeval now;
        char CTXBUF[NFS_CTXBUFSZ];

        treq = zalloc_flags(nfs_req_zone, Z_WAITOK | Z_ZERO);
        treq->r_nmp = nmp;

        microuptime(&now);
        lck_mtx_lock(&nmp->nm_lock);
        TAILQ_FOREACH_SAFE(cp, &nmp->nm_gsscl, gss_clnt_entries, tcp) {
                lck_mtx_lock(&cp->gss_clnt_mtx);
                if (cp->gss_clnt_flags & GSS_CTX_DESTROY) {
                        NFS_GSS_DBG("Found destroyed context %s refcnt = %d continuing\n",
                            NFS_GSS_CTX(req, cp),
                            cp->gss_clnt_refcnt);
                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                        continue;
                }
                if (nfs_gss_clnt_ctx_cred_match(cp->gss_clnt_cred, req->r_cred)) {
                        if (nmp->nm_gsscl.tqh_first != cp) {
                                TAILQ_REMOVE(&nmp->nm_gsscl, cp, gss_clnt_entries);
                                TAILQ_INSERT_HEAD(&nmp->nm_gsscl, cp, gss_clnt_entries);
                        }
                        if (principal) {
                                /*
                                 * If we have a principal, but it does not match the current cred
                                 * mark it for removal
                                 */
                                if (cp->gss_clnt_prinlen != plen || cp->gss_clnt_prinnt != nt ||
                                    bcmp(cp->gss_clnt_principal, principal, plen) != 0) {
                                        cp->gss_clnt_flags |= (GSS_CTX_INVAL | GSS_CTX_DESTROY);
                                        cp->gss_clnt_refcnt++;
                                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                                        NFS_GSS_DBG("Marking %s for deletion because %s does not match\n",
                                            NFS_GSS_CTX(req, cp), principal);
                                        NFS_GSS_DBG("len = (%zu,%zu), nt = (%d,%d)\n", cp->gss_clnt_prinlen, plen,
                                            cp->gss_clnt_prinnt, nt);
                                        treq->r_gss_ctx  = cp;
                                        cp = NULL;
                                        break;
                                }
                        }
                        if (cp->gss_clnt_flags & GSS_CTX_INVAL) {
                                /*
                                 * If we're still being used and we're not expired
                                 * just return and don't bother gssd again. Note if
                                 * gss_clnt_nctime is zero it is about to be set to now.
                                 */
                                if (cp->gss_clnt_nctime + GSS_NEG_CACHE_TO >= now.tv_sec || cp->gss_clnt_nctime == 0) {
                                        NFS_GSS_DBG("Context %s (refcnt = %d) not expired returning EAUTH nctime = %ld now = %ld\n",
                                            NFS_GSS_CTX(req, cp), cp->gss_clnt_refcnt, cp->gss_clnt_nctime, now.tv_sec);
                                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                                        lck_mtx_unlock(&nmp->nm_lock);
                                        NFS_ZFREE(nfs_req_zone, treq);
                                        return NFSERR_EAUTH;
                                }
                                if (cp->gss_clnt_refcnt) {
                                        struct nfs_gss_clnt_ctx *ncp;
                                        /*
                                         * If this context has references, we can't use it so we mark if for
                                         * destruction and create a new context based on this one in the
                                         * same manner as renewing one.
                                         */
                                        cp->gss_clnt_flags |= GSS_CTX_DESTROY;
                                        NFS_GSS_DBG("Context %s has expired but we still have %d references\n",
                                            NFS_GSS_CTX(req, cp), cp->gss_clnt_refcnt);
                                        error = nfs_gss_clnt_ctx_copy(cp, &ncp);
                                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                                        if (error) {
                                                lck_mtx_unlock(&nmp->nm_lock);
                                                NFS_ZFREE(nfs_req_zone, treq);
                                                return error;
                                        }
                                        cp = ncp;
                                        break;
                                } else {
                                        if (cp->gss_clnt_nctime) {
                                                nmp->nm_ncentries--;
                                        }
                                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                                        TAILQ_REMOVE(&nmp->nm_gsscl, cp, gss_clnt_entries);
                                        break;
                                }
                        }
                        /* Found a valid context to return */
                        cp->gss_clnt_refcnt++;
                        req->r_gss_ctx = cp;
                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                        lck_mtx_unlock(&nmp->nm_lock);
                        NFS_ZFREE(nfs_req_zone, treq);
                        return 0;
                }
                lck_mtx_unlock(&cp->gss_clnt_mtx);
        }

        if (!cp && nfs_root_steals_ctx && principal == NULL && kauth_cred_getuid(req->r_cred) == 0) {
                /*
                 * If superuser is trying to get access, then co-opt
                 * the first valid context in the list.
                 * XXX Ultimately, we need to allow superuser to
                 * go ahead and attempt to set up its own context
                 * in case one is set up for it.
                 */
                TAILQ_FOREACH(cp, &nmp->nm_gsscl, gss_clnt_entries) {
                        if (!(cp->gss_clnt_flags & (GSS_CTX_INVAL | GSS_CTX_DESTROY))) {
                                nfs_gss_clnt_ctx_ref(req, cp);
                                lck_mtx_unlock(&nmp->nm_lock);
                                NFS_GSS_DBG("Root stole context %s\n", NFS_GSS_CTX(req, NULL));
                                NFS_ZFREE(nfs_req_zone, treq);
                                return 0;
                        }
                }
        }

        NFS_GSS_DBG("Context %s%sfound in Neg Cache @  %ld\n",
            NFS_GSS_CTX(req, cp),
            cp == NULL ? " not " : "",
            cp == NULL ? 0L : cp->gss_clnt_nctime);

        /*
         * Not found - create a new context
         */

        if (cp == NULL) {
                MALLOC(cp, struct nfs_gss_clnt_ctx *, sizeof(*cp), M_TEMP, M_WAITOK | M_ZERO);
                if (cp == NULL) {
                        lck_mtx_unlock(&nmp->nm_lock);
                        NFS_ZFREE(nfs_req_zone, treq);
                        return ENOMEM;
                }
                cp->gss_clnt_cred = req->r_cred;
                kauth_cred_ref(cp->gss_clnt_cred);
                lck_mtx_init(&cp->gss_clnt_mtx, &nfs_gss_clnt_grp, LCK_ATTR_NULL);
                cp->gss_clnt_ptime = now.tv_sec - GSS_PRINT_DELAY;
                if (principal) {
                        MALLOC(cp->gss_clnt_principal, uint8_t *, plen + 1, M_TEMP, M_WAITOK | M_ZERO);
                        memcpy(cp->gss_clnt_principal, principal, plen);
                        cp->gss_clnt_prinlen = plen;
                        cp->gss_clnt_prinnt = nt;
                        cp->gss_clnt_flags |= GSS_CTX_STICKY;
                        if (!nfs_gss_clnt_mnt_ref(nmp)) {
                                cp->gss_clnt_flags |= GSS_CTX_USECOUNT;
                        }
                }
        } else {
                uint32_t oldflags = cp->gss_clnt_flags;
                nfs_gss_clnt_ctx_clean(cp);
                if (principal) {
                        /*
                         * If we have a principal and we found a matching audit
                         * session, then to get here, the principal had to match.
                         * In walking the context list if it has a principal
                         * or the principal is not set then we mark the context
                         * for destruction and set cp to NULL and we fall to the
                         * if clause above. If the context still has references
                         * again we copy the context which will preserve the principal
                         * and we end up here with the correct principal set.
                         * If we don't have references the the principal must have
                         * match and we will fall through here.
                         */
                        cp->gss_clnt_flags |= GSS_CTX_STICKY;

                        /*
                         * We are preserving old flags if it set, and we take a ref if not set.
                         * Also, because of the short circuit we will not take extra refs here.
                         */
                        if ((oldflags & GSS_CTX_USECOUNT) || !nfs_gss_clnt_mnt_ref(nmp)) {
                                cp->gss_clnt_flags |= GSS_CTX_USECOUNT;
                        }
                }
        }

        cp->gss_clnt_thread = current_thread();
        nfs_gss_clnt_ctx_ref(req, cp);
        TAILQ_INSERT_HEAD(&nmp->nm_gsscl, cp, gss_clnt_entries);
        lck_mtx_unlock(&nmp->nm_lock);

        error = nfs_gss_clnt_ctx_init_retry(req, cp); // Initialize new context
        if (error) {
                NFS_GSS_DBG("nfs_gss_clnt_ctx_init_retry returned %d for %s\n", error, NFS_GSS_CTX(req, cp));
                nfs_gss_clnt_ctx_unref(req);
        }

        /* Remove any old matching contex that had a different principal */
        nfs_gss_clnt_ctx_unref(treq);
        NFS_ZFREE(nfs_req_zone, treq);
        return error;
}

static int
nfs_gss_clnt_ctx_find(struct nfsreq *req)
{
        return nfs_gss_clnt_ctx_find_principal(req, NULL, 0, 0);
}

/*
 * Inserts an RPCSEC_GSS credential into an RPC header.
 * After the credential is inserted, the code continues
 * to build the verifier which contains a signed checksum
 * of the RPC header.
 */

int
nfs_gss_clnt_cred_put(struct nfsreq *req, struct nfsm_chain *nmc, mbuf_t args)
{
        struct nfs_gss_clnt_ctx *cp;
        uint32_t seqnum = 0;
        uint32_t major;
        uint32_t error = 0;
        int slpflag, recordmark = 0, offset;
        struct gss_seq *gsp;
        gss_buffer_desc mic;

        slpflag = (PZERO - 1);
        if (req->r_nmp) {
                slpflag |= (NMFLAG(req->r_nmp, INTR) && req->r_thread && !(req->r_flags & R_NOINTR)) ? PCATCH : 0;
                recordmark = (req->r_nmp->nm_sotype == SOCK_STREAM);
        }

retry:
        if (req->r_gss_ctx == NULL) {
                /*
                 * Find the context for this user.
                 * If no context is found, one will
                 * be created.
                 */
                error = nfs_gss_clnt_ctx_find(req);
                if (error) {
                        return error;
                }
        }
        cp = req->r_gss_ctx;

        /*
         * If the context thread isn't null, then the context isn't
         * yet complete and is for the exclusive use of the thread
         * doing the context setup. Wait until the context thread
         * is null.
         */
        lck_mtx_lock(&cp->gss_clnt_mtx);
        if (cp->gss_clnt_thread && cp->gss_clnt_thread != current_thread()) {
                cp->gss_clnt_flags |= GSS_NEEDCTX;
                msleep(cp, &cp->gss_clnt_mtx, slpflag | PDROP, "ctxwait", NULL);
                slpflag &= ~PCATCH;
                if ((error = nfs_sigintr(req->r_nmp, req, req->r_thread, 0))) {
                        return error;
                }
                nfs_gss_clnt_ctx_unref(req);
                goto retry;
        }
        lck_mtx_unlock(&cp->gss_clnt_mtx);

        if (cp->gss_clnt_flags & GSS_CTX_COMPLETE) {
                /*
                 * Get a sequence number for this request.
                 * Check whether the oldest request in the window is complete.
                 * If it's still pending, then wait until it's done before
                 * we allocate a new sequence number and allow this request
                 * to proceed.
                 */
                lck_mtx_lock(&cp->gss_clnt_mtx);
                while (win_getbit(cp->gss_clnt_seqbits,
                    ((cp->gss_clnt_seqnum - cp->gss_clnt_seqwin) + 1) % cp->gss_clnt_seqwin)) {
                        cp->gss_clnt_flags |= GSS_NEEDSEQ;
                        msleep(cp, &cp->gss_clnt_mtx, slpflag | PDROP, "seqwin", NULL);
                        slpflag &= ~PCATCH;
                        if ((error = nfs_sigintr(req->r_nmp, req, req->r_thread, 0))) {
                                return error;
                        }
                        lck_mtx_lock(&cp->gss_clnt_mtx);
                        if (cp->gss_clnt_flags & GSS_CTX_INVAL) {
                                /* Renewed while while we were waiting */
                                lck_mtx_unlock(&cp->gss_clnt_mtx);
                                nfs_gss_clnt_ctx_unref(req);
                                goto retry;
                        }
                }
                seqnum = ++cp->gss_clnt_seqnum;
                win_setbit(cp->gss_clnt_seqbits, seqnum % cp->gss_clnt_seqwin);
                lck_mtx_unlock(&cp->gss_clnt_mtx);

                MALLOC(gsp, struct gss_seq *, sizeof(*gsp), M_TEMP, M_WAITOK | M_ZERO);
                if (gsp == NULL) {
                        return ENOMEM;
                }
                gsp->gss_seqnum = seqnum;
                SLIST_INSERT_HEAD(&req->r_gss_seqlist, gsp, gss_seqnext);
        }

        /* Insert the credential */
        nfsm_chain_add_32(error, nmc, RPCSEC_GSS);
        nfsm_chain_add_32(error, nmc, 5 * NFSX_UNSIGNED + cp->gss_clnt_handle_len);
        nfsm_chain_add_32(error, nmc, RPCSEC_GSS_VERS_1);
        nfsm_chain_add_32(error, nmc, cp->gss_clnt_proc);
        nfsm_chain_add_32(error, nmc, seqnum);
        nfsm_chain_add_32(error, nmc, cp->gss_clnt_service);
        nfsm_chain_add_32(error, nmc, cp->gss_clnt_handle_len);
        if (cp->gss_clnt_handle_len > 0) {
                if (cp->gss_clnt_handle == NULL) {
                        return EBADRPC;
                }
                nfsm_chain_add_opaque(error, nmc, cp->gss_clnt_handle, cp->gss_clnt_handle_len);
        }
        if (error) {
                return error;
        }
        /*
         * Now add the verifier
         */
        if (cp->gss_clnt_proc == RPCSEC_GSS_INIT ||
            cp->gss_clnt_proc == RPCSEC_GSS_CONTINUE_INIT) {
                /*
                 * If the context is still being created
                 * then use a null verifier.
                 */
                nfsm_chain_add_32(error, nmc, RPCAUTH_NULL);    // flavor
                nfsm_chain_add_32(error, nmc, 0);               // length
                nfsm_chain_build_done(error, nmc);
                if (!error) {
                        nfs_gss_append_chain(nmc, args);
                }
                return error;
        }

        offset = recordmark ? NFSX_UNSIGNED : 0; // record mark
        nfsm_chain_build_done(error, nmc);

        major = gss_krb5_get_mic_mbuf((uint32_t *)&error, cp->gss_clnt_ctx_id, 0, nmc->nmc_mhead, offset, 0, &mic);
        if (major != GSS_S_COMPLETE) {
                printf("gss_krb5_get_mic_buf failed %d\n", error);
                return error;
        }

        nfsm_chain_add_32(error, nmc, RPCSEC_GSS);      // flavor
        nfsm_chain_add_32(error, nmc, mic.length);              // length
        nfsm_chain_add_opaque(error, nmc, mic.value, mic.length);
        (void)gss_release_buffer(NULL, &mic);
        nfsm_chain_build_done(error, nmc);
        if (error) {
                return error;
        }

        /*
         * Now we may have to compute integrity or encrypt the call args
         * per RFC 2203 Section 5.3.2
         */
        switch (cp->gss_clnt_service) {
        case RPCSEC_GSS_SVC_NONE:
                if (args) {
                        nfs_gss_append_chain(nmc, args);
                }
                break;
        case RPCSEC_GSS_SVC_INTEGRITY:
                /*
                 * r_gss_arglen is the length of args mbuf going into the routine.
                 * Its used to find the mic if we need to restore the args.
                 */
                /* Note the mbufs that were used in r_mrest are being encapsulated in the rpc_gss_integ_data_t */
                assert(req->r_mrest == args);
                nfsm_chain_finish_mbuf(error, nmc);
                if (error) {
                        return error;
                }
                error = rpc_gss_integ_data_create(cp->gss_clnt_ctx_id, &args, seqnum, &req->r_gss_arglen);
                if (error) {
                        break;
                }
                req->r_mrest = args;
                req->r_gss_argoff = nfsm_chain_offset(nmc);
                nfs_gss_append_chain(nmc, args);
                break;
        case RPCSEC_GSS_SVC_PRIVACY:
                /*
                 * r_gss_arglen is the length of the wrap token sans any padding length.
                 * Its used to find any XDR padding of the wrap token.
                 */
                /* Note the mbufs that were used in r_mrest are being encapsulated in the rpc_gss_priv_data_t */
                assert(req->r_mrest == args);
                nfsm_chain_finish_mbuf(error, nmc);
                if (error) {
                        return error;
                }
                error = rpc_gss_priv_data_create(cp->gss_clnt_ctx_id, &args, seqnum, &req->r_gss_arglen);
                if (error) {
                        break;
                }
                req->r_mrest = args;
                req->r_gss_argoff = nfsm_chain_offset(nmc);
                nfs_gss_append_chain(nmc, args);
                break;
        default:
                return EINVAL;
        }

        return error;
}

/*
 * When receiving a reply, the client checks the verifier
 * returned by the server. Check that the verifier is the
 * correct type, then extract the sequence number checksum
 * from the token in the credential and compare it with a
 * computed checksum of the sequence number in the request
 * that was sent.
 */
int
nfs_gss_clnt_verf_get(
        struct nfsreq *req,
        struct nfsm_chain *nmc,
        uint32_t verftype,
        uint32_t verflen,
        uint32_t *accepted_statusp)
{
        gss_buffer_desc cksum;
        uint32_t seqnum = 0;
        uint32_t major;
        struct nfs_gss_clnt_ctx *cp = req->r_gss_ctx;
        struct nfsm_chain nmc_tmp;
        struct gss_seq *gsp;
        uint32_t reslen;
        int error = 0;
        mbuf_t results_mbuf, prev_mbuf, pad_mbuf;
        size_t ressize, offset;

        reslen = 0;
        *accepted_statusp = 0;

        if (cp == NULL) {
                return NFSERR_EAUTH;
        }
        /*
         * If it's not an RPCSEC_GSS verifier, then it has to
         * be a null verifier that resulted from either
         * a CONTINUE_NEEDED reply during context setup or
         * from the reply to an AUTH_UNIX call from a dummy
         * context that resulted from a fallback to sec=sys.
         */
        if (verftype != RPCSEC_GSS) {
                if (verftype != RPCAUTH_NULL) {
                        return NFSERR_EAUTH;
                }
                if (cp->gss_clnt_flags & GSS_CTX_COMPLETE) {
                        return NFSERR_EAUTH;
                }
                if (verflen > 0) {
                        nfsm_chain_adv(error, nmc, nfsm_rndup(verflen));
                }
                nfsm_chain_get_32(error, nmc, *accepted_statusp);
                return error;
        }

        /*
         * If we received an RPCSEC_GSS verifier but the
         * context isn't yet complete, then it must be
         * the context complete message from the server.
         * The verifier will contain an encrypted checksum
         * of the window but we don't have the session key
         * yet so we can't decrypt it. Stash the verifier
         * and check it later in nfs_gss_clnt_ctx_init() when
         * the context is complete.
         */
        if (!(cp->gss_clnt_flags & GSS_CTX_COMPLETE)) {
                if (verflen > KRB5_MAX_MIC_SIZE) {
                        return EBADRPC;
                }
                MALLOC(cp->gss_clnt_verf, u_char *, verflen, M_TEMP, M_WAITOK | M_ZERO);
                if (cp->gss_clnt_verf == NULL) {
                        return ENOMEM;
                }
                cp->gss_clnt_verflen = verflen;
                nfsm_chain_get_opaque(error, nmc, verflen, cp->gss_clnt_verf);
                nfsm_chain_get_32(error, nmc, *accepted_statusp);
                return error;
        }

        if (verflen > KRB5_MAX_MIC_SIZE) {
                return EBADRPC;
        }
        cksum.length = verflen;
        MALLOC(cksum.value, void *, verflen, M_TEMP, M_WAITOK);

        /*
         * Get the gss mic
         */
        nfsm_chain_get_opaque(error, nmc, verflen, cksum.value);
        if (error) {
                FREE(cksum.value, M_TEMP);
                goto nfsmout;
        }

        /*
         * Search the request sequence numbers for this reply, starting
         * with the most recent, looking for a checksum that matches
         * the one in the verifier returned by the server.
         */
        SLIST_FOREACH(gsp, &req->r_gss_seqlist, gss_seqnext) {
                gss_buffer_desc seqnum_buf;
                uint32_t network_seqnum = htonl(gsp->gss_seqnum);

                seqnum_buf.length = sizeof(network_seqnum);
                seqnum_buf.value = &network_seqnum;
                major = gss_krb5_verify_mic(NULL, cp->gss_clnt_ctx_id, &seqnum_buf, &cksum, NULL);
                if (major == GSS_S_COMPLETE) {
                        break;
                }
        }
        FREE(cksum.value, M_TEMP);
        if (gsp == NULL) {
                return NFSERR_EAUTH;
        }

        /*
         * Get the RPC accepted status
         */
        nfsm_chain_get_32(error, nmc, *accepted_statusp);
        if (*accepted_statusp != RPC_SUCCESS) {
                return 0;
        }

        /*
         * Now we may have to check integrity or decrypt the results
         * per RFC 2203 Section 5.3.2
         */
        switch (cp->gss_clnt_service) {
        case RPCSEC_GSS_SVC_NONE:
                /* nothing to do */
                break;
        case RPCSEC_GSS_SVC_INTEGRITY:
                /*
                 * Here's what we expect in the integrity results from RFC 2203:
                 *
                 * - length of seq num + results (4 bytes)
                 * - sequence number (4 bytes)
                 * - results (variable bytes)
                 * - length of checksum token
                 * - checksum of seqnum + results
                 */

                nfsm_chain_get_32(error, nmc, reslen);          // length of results
                if (reslen > NFS_MAXPACKET) {
                        error = EBADRPC;
                        goto nfsmout;
                }

                /* Advance and fetch the mic */
                nmc_tmp = *nmc;
                nfsm_chain_adv(error, &nmc_tmp, reslen);        // skip over the results
                nfsm_chain_get_32(error, &nmc_tmp, cksum.length);
                if (cksum.length > KRB5_MAX_MIC_SIZE) {
                        error = EBADRPC;
                        goto nfsmout;
                }
                MALLOC(cksum.value, void *, cksum.length, M_TEMP, M_WAITOK);
                nfsm_chain_get_opaque(error, &nmc_tmp, cksum.length, cksum.value);
                //XXX chop offf the cksum?

                /* Call verify mic */
                offset = nfsm_chain_offset(nmc);
                major = gss_krb5_verify_mic_mbuf((uint32_t *)&error, cp->gss_clnt_ctx_id, nmc->nmc_mhead, offset, reslen, &cksum, NULL);
                FREE(cksum.value, M_TEMP);
                if (major != GSS_S_COMPLETE) {
                        printf("client results: gss_krb5_verify_mic_mbuf failed %d\n", error);
                        error = EBADRPC;
                        goto nfsmout;
                }

                /*
                 * Get the sequence number prepended to the results
                 * and compare it against the header.
                 */
                nfsm_chain_get_32(error, nmc, seqnum);
                if (gsp->gss_seqnum != seqnum) {
                        error = EBADRPC;
                        goto nfsmout;
                }
#if 0
                SLIST_FOREACH(gsp, &req->r_gss_seqlist, gss_seqnext) {
                        if (seqnum == gsp->gss_seqnum) {
                                break;
                        }
                }
                if (gsp == NULL) {
                        error = EBADRPC;
                        goto nfsmout;
                }
#endif
                break;
        case RPCSEC_GSS_SVC_PRIVACY:
                /*
                 * Here's what we expect in the privacy results:
                 *
                 * opaque encodeing of the wrap token
                 * - length of wrap token
                 * - wrap token
                 */
                prev_mbuf = nmc->nmc_mcur;
                nfsm_chain_get_32(error, nmc, reslen);          // length of results
                if (reslen == 0 || reslen > NFS_MAXPACKET) {
                        error = EBADRPC;
                        goto nfsmout;
                }

                /* Get the wrap token (current mbuf in the chain starting at the current offset) */
                offset = nmc->nmc_ptr - (caddr_t)mbuf_data(nmc->nmc_mcur);

                /* split out the wrap token */
                ressize = reslen;
                error = gss_normalize_mbuf(nmc->nmc_mcur, offset, &ressize, &results_mbuf, &pad_mbuf, 0);
                if (error) {
                        goto nfsmout;
                }

                if (pad_mbuf) {
                        assert(nfsm_pad(reslen) == mbuf_len(pad_mbuf));
                        mbuf_free(pad_mbuf);
                }

                major = gss_krb5_unwrap_mbuf((uint32_t *)&error, cp->gss_clnt_ctx_id, &results_mbuf, 0, ressize, NULL, NULL);
                if (major) {
                        printf("%s unwraped failed %d\n", __func__, error);
                        goto nfsmout;
                }

                /* Now replace the wrapped arguments with the unwrapped ones */
                mbuf_setnext(prev_mbuf, results_mbuf);
                nmc->nmc_mcur = results_mbuf;
                nmc->nmc_ptr = mbuf_data(results_mbuf);
                nmc->nmc_left = mbuf_len(results_mbuf);

                /*
                 * Get the sequence number prepended to the results
                 * and compare it against the header
                 */
                nfsm_chain_get_32(error, nmc, seqnum);
                if (gsp->gss_seqnum != seqnum) {
                        printf("%s bad seqnum\n", __func__);
                        error = EBADRPC;
                        goto nfsmout;
                }
#if 0
                SLIST_FOREACH(gsp, &req->r_gss_seqlist, gss_seqnext) {
                        if (seqnum == gsp->gss_seqnum) {
                                break;
                        }
                }
                if (gsp == NULL) {
                        error = EBADRPC;
                        goto nfsmout;
                }
#endif
                break;
        }
nfsmout:
        return error;
}

/*
 * An RPCSEC_GSS request with no integrity or privacy consists
 * of just the header mbufs followed by the arg mbufs.
 *
 * However, integrity or privacy the original mbufs have mbufs
 * prepended and appended to, which means we have to do some work to
 * restore the arg mbuf chain to its previous state in case we need to
 * retransmit.
 *
 * The location and length of the args is marked by two fields
 * in the request structure: r_gss_argoff and r_gss_arglen,
 * which are stashed when the NFS request is built.
 */
int
nfs_gss_clnt_args_restore(struct nfsreq *req)
{
        struct nfs_gss_clnt_ctx *cp = req->r_gss_ctx;
        struct nfsm_chain mchain, *nmc = &mchain;
        int error = 0, merr;

        if (cp == NULL) {
                return NFSERR_EAUTH;
        }

        if ((cp->gss_clnt_flags & GSS_CTX_COMPLETE) == 0) {
                return ENEEDAUTH;
        }

        /* Nothing to restore for SVC_NONE */
        if (cp->gss_clnt_service == RPCSEC_GSS_SVC_NONE) {
                return 0;
        }

        nfsm_chain_dissect_init(error, nmc, req->r_mhead);      // start at RPC header
        nfsm_chain_adv(error, nmc, req->r_gss_argoff);          // advance to args
        if (error) {
                return error;
        }

        if (cp->gss_clnt_service == RPCSEC_GSS_SVC_INTEGRITY) {
                error = rpc_gss_integ_data_restore(cp->gss_clnt_ctx_id, &req->r_mrest, req->r_gss_arglen);
        } else {
                error = rpc_gss_priv_data_restore(cp->gss_clnt_ctx_id, &req->r_mrest, req->r_gss_arglen);
        }

        merr = mbuf_setnext(nmc->nmc_mcur, req->r_mrest);  /* Should always succeed */
        assert(merr == 0);

        return error ? error : merr;
}

/*
 * This function sets up  a new context on the client.
 * Context setup alternates upcalls to the gssd with NFS nullproc calls
 * to the server.  Each of these calls exchanges an opaque token, obtained
 * via the gssd's calls into the GSS-API on either the client or the server.
 * This cycle of calls ends when the client's upcall to the gssd and the
 * server's response both return GSS_S_COMPLETE.  At this point, the client
 * should have its session key and a handle that it can use to refer to its
 * new context on the server.
 */
static int
nfs_gss_clnt_ctx_init(struct nfsreq *req, struct nfs_gss_clnt_ctx *cp)
{
        struct nfsmount *nmp = req->r_nmp;
        gss_buffer_desc cksum, window;
        uint32_t network_seqnum;
        int client_complete = 0;
        int server_complete = 0;
        int error = 0;
        int retrycnt = 0;
        uint32_t major;

        /* Initialize a new client context */

        if (cp->gss_clnt_svcname == NULL) {
                cp->gss_clnt_svcname = nfs_gss_clnt_svcname(nmp, &cp->gss_clnt_svcnt, &cp->gss_clnt_svcnamlen);
                if (cp->gss_clnt_svcname == NULL) {
                        error = NFSERR_EAUTH;
                        goto nfsmout;
                }
        }

        cp->gss_clnt_proc = RPCSEC_GSS_INIT;

        cp->gss_clnt_service =
            req->r_auth == RPCAUTH_KRB5  ? RPCSEC_GSS_SVC_NONE :
            req->r_auth == RPCAUTH_KRB5I ? RPCSEC_GSS_SVC_INTEGRITY :
            req->r_auth == RPCAUTH_KRB5P ? RPCSEC_GSS_SVC_PRIVACY : 0;

        /*
         * Now loop around alternating gss_init_sec_context and
         * gss_accept_sec_context upcalls to the gssd on the client
         * and server side until the context is complete - or fails.
         */
        for (;;) {
retry:
                /* Upcall to the gss_init_sec_context in the gssd */
                error = nfs_gss_clnt_gssd_upcall(req, cp, retrycnt);
                if (error) {
                        goto nfsmout;
                }

                if (cp->gss_clnt_major == GSS_S_COMPLETE) {
                        client_complete = 1;
                        NFS_GSS_DBG("Client complete\n");
                        if (server_complete) {
                                break;
                        }
                } else if (cp->gss_clnt_major != GSS_S_CONTINUE_NEEDED) {
                        /*
                         * We may have gotten here because the accept sec context
                         * from the server failed and sent back a GSS token that
                         * encapsulates a kerberos error token per RFC 1964/4121
                         * with a status of GSS_S_CONTINUE_NEEDED. That caused us
                         * to loop to the above up call and received the now
                         * decoded errors.
                         */
                        retrycnt++;
                        cp->gss_clnt_gssd_flags |= GSSD_RESTART;
                        NFS_GSS_DBG("Retrying major = %x minor = %d\n", cp->gss_clnt_major, (int)cp->gss_clnt_minor);
                        goto retry;
                }

                /*
                 * Pass the token to the server.
                 */
                error = nfs_gss_clnt_ctx_callserver(req, cp);
                if (error) {
                        if (error == ENEEDAUTH &&
                            (cp->gss_clnt_proc == RPCSEC_GSS_INIT ||
                            cp->gss_clnt_proc == RPCSEC_GSS_CONTINUE_INIT)) {
                                /*
                                 * We got here because the server had a problem
                                 * trying to establish a context and sent that there
                                 * was a context problem at the rpc sec layer. Perhaps
                                 * gss_accept_sec_context succeeded  in user space,
                                 * but the kernel could not handle the etype
                                 * to generate the mic for the verifier of the rpc_sec
                                 * window size.
                                 */
                                retrycnt++;
                                cp->gss_clnt_gssd_flags |= GSSD_RESTART;
                                NFS_GSS_DBG("Retrying major = %x minor = %d\n", cp->gss_clnt_major, (int)cp->gss_clnt_minor);
                                goto retry;
                        }
                        goto nfsmout;
                }
                if (cp->gss_clnt_major == GSS_S_COMPLETE) {
                        NFS_GSS_DBG("Server complete\n");
                        server_complete = 1;
                        if (client_complete) {
                                break;
                        }
                } else if (cp->gss_clnt_major == GSS_S_CONTINUE_NEEDED) {
                        cp->gss_clnt_proc = RPCSEC_GSS_CONTINUE_INIT;
                } else {
                        /* Server didn't like us. Try something else */
                        retrycnt++;
                        cp->gss_clnt_gssd_flags |= GSSD_RESTART;
                        NFS_GSS_DBG("Retrying major = %x minor = %d\n", cp->gss_clnt_major, (int)cp->gss_clnt_minor);
                }
        }

        /*
         * The context is apparently established successfully
         */
        lck_mtx_lock(&cp->gss_clnt_mtx);
        cp->gss_clnt_flags |= GSS_CTX_COMPLETE;
        lck_mtx_unlock(&cp->gss_clnt_mtx);
        cp->gss_clnt_proc = RPCSEC_GSS_DATA;

        network_seqnum = htonl(cp->gss_clnt_seqwin);
        window.length = sizeof(cp->gss_clnt_seqwin);
        window.value = &network_seqnum;
        cksum.value = cp->gss_clnt_verf;
        cksum.length = cp->gss_clnt_verflen;
        major = gss_krb5_verify_mic((uint32_t *)&error, cp->gss_clnt_ctx_id, &window, &cksum, NULL);
        cp->gss_clnt_verflen = 0;
        FREE(cp->gss_clnt_verf, M_TEMP);
        cp->gss_clnt_verf = NULL;
        if (major != GSS_S_COMPLETE) {
                printf("%s: could not verify window\n", __func__);
                error = NFSERR_EAUTH;
                goto nfsmout;
        }

        /*
         * Set an initial sequence number somewhat randomized.
         * Start small so we don't overflow GSS_MAXSEQ too quickly.
         * Add the size of the sequence window so seqbits arithmetic
         * doesn't go negative.
         */
        cp->gss_clnt_seqnum = (random() & 0xffff) + cp->gss_clnt_seqwin;

        /*
         * Allocate a bitmap to keep track of which requests
         * are pending within the sequence number window.
         */
        MALLOC(cp->gss_clnt_seqbits, uint32_t *,
            nfsm_rndup((cp->gss_clnt_seqwin + 7) / 8), M_TEMP, M_WAITOK | M_ZERO);
        if (cp->gss_clnt_seqbits == NULL) {
                error = NFSERR_EAUTH;
        }

nfsmout:
        /*
         * If the error is ENEEDAUTH we're not done, so no need
         * to wake up other threads again. This thread will retry in
         * the find or renew routines.
         */
        if (error == ENEEDAUTH) {
                NFS_GSS_DBG("Returning ENEEDAUTH\n");
                return error;
        }

        /*
         * If there's an error, just mark it as invalid.
         * It will be removed when the reference count
         * drops to zero.
         */
        lck_mtx_lock(&cp->gss_clnt_mtx);
        if (error) {
                cp->gss_clnt_flags |= GSS_CTX_INVAL;
        }

        /*
         * Wake any threads waiting to use the context
         */
        cp->gss_clnt_thread = NULL;
        if (cp->gss_clnt_flags & GSS_NEEDCTX) {
                cp->gss_clnt_flags &= ~GSS_NEEDCTX;
                wakeup(cp);
        }
        lck_mtx_unlock(&cp->gss_clnt_mtx);

        NFS_GSS_DBG("Returning error = %d\n", error);
        return error;
}

/*
 * This function calls nfs_gss_clnt_ctx_init() to set up a new context.
 * But if there's a failure in trying to establish the context it keeps
 * retrying at progressively longer intervals in case the failure is
 * due to some transient condition.  For instance, the server might be
 * failing the context setup because directory services is not coming
 * up in a timely fashion.
 */
static int
nfs_gss_clnt_ctx_init_retry(struct nfsreq *req, struct nfs_gss_clnt_ctx *cp)
{
        struct nfsmount *nmp = req->r_nmp;
        struct timeval now;
        time_t waituntil;
        int error, slpflag;
        int retries = 0;
        int timeo = NFS_TRYLATERDEL;

        if (nfs_mount_gone(nmp)) {
                error = ENXIO;
                goto bad;
        }

        /* For an "intr" mount allow a signal to interrupt the retries */
        slpflag = (NMFLAG(nmp, INTR) && !(req->r_flags & R_NOINTR)) ? PCATCH : 0;

        while ((error = nfs_gss_clnt_ctx_init(req, cp)) == ENEEDAUTH) {
                microuptime(&now);
                waituntil = now.tv_sec + timeo;
                while (now.tv_sec < waituntil) {
                        tsleep(NULL, PSOCK | slpflag, "nfs_gss_clnt_ctx_init_retry", hz);
                        slpflag = 0;
                        error = nfs_sigintr(req->r_nmp, req, current_thread(), 0);
                        if (error) {
                                goto bad;
                        }
                        microuptime(&now);
                }

                retries++;
                /* If it's a soft mount just give up after a while */
                if ((NMFLAG(nmp, SOFT) || (req->r_flags & R_SOFT)) && (retries > nmp->nm_retry)) {
                        error = ETIMEDOUT;
                        goto bad;
                }
                timeo *= 2;
                if (timeo > 60) {
                        timeo = 60;
                }
        }

        if (error == 0) {
                return 0;       // success
        }
bad:
        /*
         * Give up on this context
         */
        lck_mtx_lock(&cp->gss_clnt_mtx);
        cp->gss_clnt_flags |= GSS_CTX_INVAL;

        /*
         * Wake any threads waiting to use the context
         */
        cp->gss_clnt_thread = NULL;
        if (cp->gss_clnt_flags & GSS_NEEDCTX) {
                cp->gss_clnt_flags &= ~GSS_NEEDCTX;
                wakeup(cp);
        }
        lck_mtx_unlock(&cp->gss_clnt_mtx);

        return error;
}

/*
 * Call the NFS server using a null procedure for context setup.
 * Even though it's a null procedure and nominally has no arguments
 * RFC 2203 requires that the GSS-API token be passed as an argument
 * and received as a reply.
 */
static int
nfs_gss_clnt_ctx_callserver(struct nfsreq *req, struct nfs_gss_clnt_ctx *cp)
{
        struct nfsm_chain nmreq, nmrep;
        int error = 0, status;
        uint32_t major = cp->gss_clnt_major, minor = cp->gss_clnt_minor;
        int sz;

        if (nfs_mount_gone(req->r_nmp)) {
                return ENXIO;
        }
        nfsm_chain_null(&nmreq);
        nfsm_chain_null(&nmrep);
        sz = NFSX_UNSIGNED + nfsm_rndup(cp->gss_clnt_tokenlen);
        nfsm_chain_build_alloc_init(error, &nmreq, sz);
        nfsm_chain_add_32(error, &nmreq, cp->gss_clnt_tokenlen);
        if (cp->gss_clnt_tokenlen > 0) {
                nfsm_chain_add_opaque(error, &nmreq, cp->gss_clnt_token, cp->gss_clnt_tokenlen);
        }
        nfsm_chain_build_done(error, &nmreq);
        if (error) {
                goto nfsmout;
        }

        /* Call the server */
        error = nfs_request_gss(req->r_nmp->nm_mountp, &nmreq, req->r_thread, req->r_cred,
            (req->r_flags & R_OPTMASK), cp, &nmrep, &status);
        if (cp->gss_clnt_token != NULL) {
                FREE(cp->gss_clnt_token, M_TEMP);
                cp->gss_clnt_token = NULL;
        }
        if (!error) {
                error = status;
        }
        if (error) {
                goto nfsmout;
        }

        /* Get the server's reply */

        nfsm_chain_get_32(error, &nmrep, cp->gss_clnt_handle_len);
        if (cp->gss_clnt_handle != NULL) {
                FREE(cp->gss_clnt_handle, M_TEMP);
                cp->gss_clnt_handle = NULL;
        }
        if (cp->gss_clnt_handle_len > 0 && cp->gss_clnt_handle_len < GSS_MAX_CTX_HANDLE_LEN) {
                MALLOC(cp->gss_clnt_handle, u_char *, cp->gss_clnt_handle_len, M_TEMP, M_WAITOK);
                if (cp->gss_clnt_handle == NULL) {
                        error = ENOMEM;
                        goto nfsmout;
                }
                nfsm_chain_get_opaque(error, &nmrep, cp->gss_clnt_handle_len, cp->gss_clnt_handle);
        } else {
                error = EBADRPC;
        }
        nfsm_chain_get_32(error, &nmrep, cp->gss_clnt_major);
        nfsm_chain_get_32(error, &nmrep, cp->gss_clnt_minor);
        nfsm_chain_get_32(error, &nmrep, cp->gss_clnt_seqwin);
        nfsm_chain_get_32(error, &nmrep, cp->gss_clnt_tokenlen);
        if (error) {
                goto nfsmout;
        }
        if (cp->gss_clnt_tokenlen > 0 && cp->gss_clnt_tokenlen < GSS_MAX_TOKEN_LEN) {
                MALLOC(cp->gss_clnt_token, u_char *, cp->gss_clnt_tokenlen, M_TEMP, M_WAITOK);
                if (cp->gss_clnt_token == NULL) {
                        error = ENOMEM;
                        goto nfsmout;
                }
                nfsm_chain_get_opaque(error, &nmrep, cp->gss_clnt_tokenlen, cp->gss_clnt_token);
        } else {
                error = EBADRPC;
        }

        /*
         * Make sure any unusual errors are expanded and logged by gssd
         */
        if (cp->gss_clnt_major != GSS_S_COMPLETE &&
            cp->gss_clnt_major != GSS_S_CONTINUE_NEEDED) {
                printf("nfs_gss_clnt_ctx_callserver: gss_clnt_major = %d\n", cp->gss_clnt_major);
                nfs_gss_clnt_log_error(req, cp, major, minor);
        }

nfsmout:
        nfsm_chain_cleanup(&nmreq);
        nfsm_chain_cleanup(&nmrep);

        return error;
}

/*
 * We construct the service principal as a gss hostbased service principal of
 * the form nfs@<server>, unless the servers principal was passed down in the
 * mount arguments. If the arguments don't specify the service principal, the
 * server name is extracted the location passed in the mount argument if
 * available.  Otherwise assume a format of <server>:<path> in the
 * mntfromname. We don't currently support url's or other bizarre formats like
 * path@server. Mount_url will convert the nfs url into <server>:<path> when
 * calling mount, so this works out well in practice.
 *
 */

static uint8_t *
nfs_gss_clnt_svcname(struct nfsmount *nmp, gssd_nametype *nt, size_t *len)
{
        char *svcname, *d, *server;
        int lindx, sindx;

        if (nfs_mount_gone(nmp)) {
                return NULL;
        }

        if (nmp->nm_sprinc) {
                *len = strlen(nmp->nm_sprinc) + 1;
                MALLOC(svcname, char *, *len, M_TEMP, M_WAITOK);
                *nt = GSSD_HOSTBASED;
                if (svcname == NULL) {
                        return NULL;
                }
                strlcpy(svcname, nmp->nm_sprinc, *len);

                return (uint8_t *)svcname;
        }

        *nt = GSSD_HOSTBASED;
        if (nmp->nm_locations.nl_numlocs && !(NFS_GSS_ISDBG && (NFS_DEBUG_FLAGS & 0x1))) {
                lindx = nmp->nm_locations.nl_current.nli_loc;
                sindx = nmp->nm_locations.nl_current.nli_serv;
                server = nmp->nm_locations.nl_locations[lindx]->nl_servers[sindx]->ns_name;
                *len = (uint32_t)strlen(server);
        } else {
                /* Older binaries using older mount args end up here */
                server = vfs_statfs(nmp->nm_mountp)->f_mntfromname;
                NFS_GSS_DBG("nfs getting gss svcname from %s\n", server);
                d = strchr(server, ':');
                *len = (uint32_t)(d ? (d - server) : strlen(server));
        }

        *len +=  5; /* "nfs@" plus null */
        MALLOC(svcname, char *, *len, M_TEMP, M_WAITOK);
        strlcpy(svcname, "nfs", *len);
        strlcat(svcname, "@", *len);
        strlcat(svcname, server, *len);
        NFS_GSS_DBG("nfs svcname = %s\n", svcname);

        return (uint8_t *)svcname;
}

/*
 * Get a mach port to talk to gssd.
 * gssd lives in the root bootstrap, so we call gssd's lookup routine
 * to get a send right to talk to a new gssd instance that launchd has launched
 * based on the cred's uid and audit session id.
 */

static mach_port_t
nfs_gss_clnt_get_upcall_port(kauth_cred_t credp)
{
        mach_port_t gssd_host_port, uc_port = IPC_PORT_NULL;
        kern_return_t kr;
        au_asid_t asid;
        uid_t uid;

        kr = host_get_gssd_port(host_priv_self(), &gssd_host_port);
        if (kr != KERN_SUCCESS) {
                printf("nfs_gss_get_upcall_port: can't get gssd port, status %x (%d)\n", kr, kr);
                return IPC_PORT_NULL;
        }
        if (!IPC_PORT_VALID(gssd_host_port)) {
                printf("nfs_gss_get_upcall_port: gssd port not valid\n");
                return IPC_PORT_NULL;
        }

        asid = kauth_cred_getasid(credp);
        uid = kauth_cred_getauid(credp);
        if (uid == AU_DEFAUDITID) {
                uid = kauth_cred_getuid(credp);
        }
        kr = mach_gss_lookup(gssd_host_port, uid, asid, &uc_port);
        if (kr != KERN_SUCCESS) {
                printf("nfs_gss_clnt_get_upcall_port: mach_gssd_lookup failed: status %x (%d)\n", kr, kr);
        }
        host_release_special_port(gssd_host_port);

        return uc_port;
}


static void
nfs_gss_clnt_log_error(struct nfsreq *req, struct nfs_gss_clnt_ctx *cp, uint32_t major, uint32_t minor)
{
#define GETMAJERROR(x) (((x) >> GSS_C_ROUTINE_ERROR_OFFSET) & GSS_C_ROUTINE_ERROR_MASK)
        struct nfsmount *nmp = req->r_nmp;
        char who[] = "client";
        uint32_t gss_error = GETMAJERROR(cp->gss_clnt_major);
        const char *procn = "unkown";
        proc_t proc;
        pid_t pid = -1;
        struct timeval now;

        if (req->r_thread) {
                proc = (proc_t)get_bsdthreadtask_info(req->r_thread);
                if (proc != NULL && (proc->p_fd == NULL || (proc->p_lflag & P_LVFORK))) {
                        proc = NULL;
                }
                if (proc) {
                        if (*proc->p_comm) {
                                procn = proc->p_comm;
                        }
                        pid = proc->p_pid;
                }
        } else {
                procn = "kernproc";
                pid = 0;
        }

        microuptime(&now);
        if ((cp->gss_clnt_major != major || cp->gss_clnt_minor != minor ||
            cp->gss_clnt_ptime + GSS_PRINT_DELAY < now.tv_sec) &&
            (nmp->nm_state & NFSSTA_MOUNTED)) {
                /*
                 * Will let gssd do some logging in hopes that it can translate
                 * the minor code.
                 */
                if (cp->gss_clnt_minor && cp->gss_clnt_minor != minor) {
                        (void) mach_gss_log_error(
                                cp->gss_clnt_mport,
                                vfs_statfs(nmp->nm_mountp)->f_mntfromname,
                                kauth_cred_getuid(cp->gss_clnt_cred),
                                who,
                                cp->gss_clnt_major,
                                cp->gss_clnt_minor);
                }
                gss_error = gss_error ? gss_error : cp->gss_clnt_major;

                /*
                 *%%% It would be really nice to get the terminal from the proc or auditinfo_addr struct and print that here.
                 */
                printf("NFS: gssd auth failure by %s on audit session %d uid %d proc %s/%d for mount %s. Error: major = %d minor = %d\n",
                    cp->gss_clnt_display ? cp->gss_clnt_display : who, kauth_cred_getasid(req->r_cred), kauth_cred_getuid(req->r_cred),
                    procn, pid, vfs_statfs(nmp->nm_mountp)->f_mntfromname, gss_error, (int32_t)cp->gss_clnt_minor);
                cp->gss_clnt_ptime = now.tv_sec;
                switch (gss_error) {
                case 7: printf("NFS: gssd does not have credentials for session %d/%d, (kinit)?\n",
                            kauth_cred_getasid(req->r_cred), kauth_cred_getauid(req->r_cred));
                        break;
                case 11: printf("NFS: gssd has expired credentals for session %d/%d, (kinit)?\n",
                            kauth_cred_getasid(req->r_cred), kauth_cred_getauid(req->r_cred));
                        break;
                }
        } else {
                NFS_GSS_DBG("NFS: gssd auth failure by %s on audit session %d uid %d proc %s/%d for mount %s. Error: major = %d minor = %d\n",
                    cp->gss_clnt_display ? cp->gss_clnt_display : who, kauth_cred_getasid(req->r_cred), kauth_cred_getuid(req->r_cred),
                    procn, pid, vfs_statfs(nmp->nm_mountp)->f_mntfromname, gss_error, (int32_t)cp->gss_clnt_minor);
        }
}

/*
 * Make an upcall to the gssd using Mach RPC
 * The upcall is made using a host special port.
 * This allows launchd to fire up the gssd in the
 * user's session.  This is important, since gssd
 * must have access to the user's credential cache.
 */
static int
nfs_gss_clnt_gssd_upcall(struct nfsreq *req, struct nfs_gss_clnt_ctx *cp, uint32_t retrycnt)
{
        kern_return_t kr;
        gssd_byte_buffer octx = NULL;
        uint32_t lucidlen = 0;
        void *lucid_ctx_buffer;
        int retry_cnt = 0;
        vm_map_copy_t itoken = NULL;
        gssd_byte_buffer otoken = NULL;
        mach_msg_type_number_t otokenlen;
        int error = 0;
        uint8_t *principal = NULL;
        size_t plen = 0;
        int32_t nt = GSSD_STRING_NAME;
        vm_map_copy_t pname = NULL;
        vm_map_copy_t svcname = NULL;
        char display_name[MAX_DISPLAY_STR] = "";
        uint32_t ret_flags;
        struct nfsmount *nmp = req->r_nmp;
        uint32_t major = cp->gss_clnt_major, minor = cp->gss_clnt_minor;
        uint32_t selected = (uint32_t)-1;
        struct nfs_etype etype;

        if (nmp == NULL || vfs_isforce(nmp->nm_mountp) || (nmp->nm_state & (NFSSTA_FORCE | NFSSTA_DEAD))) {
                return ENXIO;
        }

        if (cp->gss_clnt_gssd_flags & GSSD_RESTART) {
                if (cp->gss_clnt_token) {
                        FREE(cp->gss_clnt_token, M_TEMP);
                }
                cp->gss_clnt_token = NULL;
                cp->gss_clnt_tokenlen = 0;
                cp->gss_clnt_proc = RPCSEC_GSS_INIT;
                /* Server's handle isn't valid. Don't reuse */
                cp->gss_clnt_handle_len = 0;
                if (cp->gss_clnt_handle != NULL) {
                        FREE(cp->gss_clnt_handle, M_TEMP);
                        cp->gss_clnt_handle = NULL;
                }
        }

        NFS_GSS_DBG("Retrycnt = %d nm_etype.count = %d\n", retrycnt, nmp->nm_etype.count);
        if (retrycnt >= nmp->nm_etype.count) {
                return EACCES;
        }

        /* Copy the mount etypes to an order set of etypes to try */
        etype = nmp->nm_etype;

        /*
         * If we've already selected an etype, lets put that first in our
         * array of etypes to try, since overwhelmingly, that is likely
         * to be the etype we want.
         */
        if (etype.selected < etype.count) {
                etype.etypes[0] = nmp->nm_etype.etypes[etype.selected];
                for (uint32_t i = 0; i < etype.selected; i++) {
                        etype.etypes[i + 1] = nmp->nm_etype.etypes[i];
                }
                for (uint32_t i = etype.selected + 1; i < etype.count; i++) {
                        etype.etypes[i] = nmp->nm_etype.etypes[i];
                }
        }

        /* Remove the ones we've already have tried */
        for (uint32_t i = retrycnt; i < etype.count; i++) {
                etype.etypes[i - retrycnt] = etype.etypes[i];
        }
        etype.count = etype.count - retrycnt;

        NFS_GSS_DBG("etype count = %d preferred etype = %d\n", etype.count, etype.etypes[0]);

        /*
         * NFS currently only supports default principals or
         * principals based on the uid of the caller, unless
         * the principal to use for the mounting cred was specified
         * in the mount argmuments. If the realm to use was specified
         * then will send that up as the principal since the realm is
         * preceed by an "@" gssd that will try and select the default
         * principal for that realm.
         */

        if (cp->gss_clnt_principal && cp->gss_clnt_prinlen) {
                principal = cp->gss_clnt_principal;
                plen = cp->gss_clnt_prinlen;
                nt = cp->gss_clnt_prinnt;
        } else if (nmp->nm_principal && IS_VALID_CRED(nmp->nm_mcred) && req->r_cred == nmp->nm_mcred) {
                plen = (uint32_t)strlen(nmp->nm_principal);
                principal = (uint8_t *)nmp->nm_principal;
                cp->gss_clnt_prinnt = nt = GSSD_USER;
        } else if (nmp->nm_realm) {
                plen = (uint32_t)strlen(nmp->nm_realm);
                principal = (uint8_t *)nmp->nm_realm;
                nt = GSSD_USER;
        }

        if (!IPC_PORT_VALID(cp->gss_clnt_mport)) {
                cp->gss_clnt_mport = nfs_gss_clnt_get_upcall_port(req->r_cred);
                if (cp->gss_clnt_mport == IPC_PORT_NULL) {
                        goto out;
                }
        }

        if (plen) {
                nfs_gss_mach_alloc_buffer(principal, plen, &pname);
        }
        if (cp->gss_clnt_svcnamlen) {
                nfs_gss_mach_alloc_buffer(cp->gss_clnt_svcname, cp->gss_clnt_svcnamlen, &svcname);
        }
        if (cp->gss_clnt_tokenlen) {
                nfs_gss_mach_alloc_buffer(cp->gss_clnt_token, cp->gss_clnt_tokenlen, &itoken);
        }

        /* Always want to export the lucid context */
        cp->gss_clnt_gssd_flags |= GSSD_LUCID_CONTEXT;

retry:
        kr = mach_gss_init_sec_context_v3(
                cp->gss_clnt_mport,
                GSSD_KRB5_MECH,
                (gssd_byte_buffer) itoken, (mach_msg_type_number_t) cp->gss_clnt_tokenlen,
                kauth_cred_getuid(cp->gss_clnt_cred),
                nt,
                (gssd_byte_buffer)pname, (mach_msg_type_number_t) plen,
                cp->gss_clnt_svcnt,
                (gssd_byte_buffer)svcname, (mach_msg_type_number_t) cp->gss_clnt_svcnamlen,
                GSSD_MUTUAL_FLAG,
                (gssd_etype_list)etype.etypes, (mach_msg_type_number_t)etype.count,
                &cp->gss_clnt_gssd_flags,
                &cp->gss_clnt_context,
                &cp->gss_clnt_cred_handle,
                &ret_flags,
                &octx, (mach_msg_type_number_t *) &lucidlen,
                &otoken, &otokenlen,
                cp->gss_clnt_display ? NULL : display_name,
                &cp->gss_clnt_major,
                &cp->gss_clnt_minor);

        /* Clear the RESTART flag */
        cp->gss_clnt_gssd_flags &= ~GSSD_RESTART;
        if (cp->gss_clnt_major != GSS_S_CONTINUE_NEEDED) {
                /* We're done with the gssd handles */
                cp->gss_clnt_context = 0;
                cp->gss_clnt_cred_handle = 0;
        }

        if (kr != KERN_SUCCESS) {
                printf("nfs_gss_clnt_gssd_upcall: mach_gss_init_sec_context failed: %x (%d)\n", kr, kr);
                if (kr == MIG_SERVER_DIED && cp->gss_clnt_cred_handle == 0 &&
                    retry_cnt++ < NFS_GSS_MACH_MAX_RETRIES &&
                    !vfs_isforce(nmp->nm_mountp) && (nmp->nm_state & (NFSSTA_FORCE | NFSSTA_DEAD)) == 0) {
                        if (plen) {
                                nfs_gss_mach_alloc_buffer(principal, plen, &pname);
                        }
                        if (cp->gss_clnt_svcnamlen) {
                                nfs_gss_mach_alloc_buffer(cp->gss_clnt_svcname, cp->gss_clnt_svcnamlen, &svcname);
                        }
                        if (cp->gss_clnt_tokenlen > 0) {
                                nfs_gss_mach_alloc_buffer(cp->gss_clnt_token, cp->gss_clnt_tokenlen, &itoken);
                        }
                        goto retry;
                }

                host_release_special_port(cp->gss_clnt_mport);
                cp->gss_clnt_mport = IPC_PORT_NULL;
                goto out;
        }

        if (cp->gss_clnt_display == NULL && *display_name != '\0') {
                size_t dlen = strnlen(display_name, MAX_DISPLAY_STR) + 1;  /* Add extra byte to include '\0' */

                if (dlen < MAX_DISPLAY_STR) {
                        MALLOC(cp->gss_clnt_display, char *, dlen, M_TEMP, M_WAITOK);
                        if (cp->gss_clnt_display == NULL) {
                                goto skip;
                        }
                        bcopy(display_name, cp->gss_clnt_display, dlen);
                } else {
                        goto skip;
                }
        }
skip:
        /*
         * Make sure any unusual errors are expanded and logged by gssd
         *
         * XXXX, we need to rethink this and just have gssd return a string for the major and minor codes.
         */
        if (cp->gss_clnt_major != GSS_S_COMPLETE &&
            cp->gss_clnt_major != GSS_S_CONTINUE_NEEDED) {
                NFS_GSS_DBG("Up call returned error\n");
                nfs_gss_clnt_log_error(req, cp, major, minor);
                /* Server's handle isn't valid. Don't reuse */
                cp->gss_clnt_handle_len = 0;
                if (cp->gss_clnt_handle != NULL) {
                        FREE(cp->gss_clnt_handle, M_TEMP);
                        cp->gss_clnt_handle = NULL;
                }
        }

        if (lucidlen > 0) {
                if (lucidlen > MAX_LUCIDLEN) {
                        printf("nfs_gss_clnt_gssd_upcall: bad context length (%d)\n", lucidlen);
                        vm_map_copy_discard((vm_map_copy_t) octx);
                        vm_map_copy_discard((vm_map_copy_t) otoken);
                        goto out;
                }
                MALLOC(lucid_ctx_buffer, void *, lucidlen, M_TEMP, M_WAITOK | M_ZERO);
                error = nfs_gss_mach_vmcopyout((vm_map_copy_t) octx, lucidlen, lucid_ctx_buffer);
                if (error) {
                        vm_map_copy_discard((vm_map_copy_t) otoken);
                        goto out;
                }

                if (cp->gss_clnt_ctx_id) {
                        gss_krb5_destroy_context(cp->gss_clnt_ctx_id);
                }
                cp->gss_clnt_ctx_id = gss_krb5_make_context(lucid_ctx_buffer, lucidlen);
                if (cp->gss_clnt_ctx_id == NULL) {
                        printf("Failed to make context from lucid_ctx_buffer\n");
                        goto out;
                }
                for (uint32_t i = 0; i < nmp->nm_etype.count; i++) {
                        if (nmp->nm_etype.etypes[i] == cp->gss_clnt_ctx_id->gss_cryptor.etype) {
                                selected = i;
                                break;
                        }
                }
        }

        /* Free context token used as input */
        if (cp->gss_clnt_token) {
                FREE(cp->gss_clnt_token, M_TEMP);
        }
        cp->gss_clnt_token = NULL;
        cp->gss_clnt_tokenlen = 0;

        if (otokenlen > 0) {
                /* Set context token to gss output token */
                MALLOC(cp->gss_clnt_token, u_char *, otokenlen, M_TEMP, M_WAITOK);
                if (cp->gss_clnt_token == NULL) {
                        printf("nfs_gss_clnt_gssd_upcall: could not allocate %d bytes\n", otokenlen);
                        vm_map_copy_discard((vm_map_copy_t) otoken);
                        return ENOMEM;
                }
                error = nfs_gss_mach_vmcopyout((vm_map_copy_t) otoken, otokenlen, cp->gss_clnt_token);
                if (error) {
                        printf("Could not copyout gss token\n");
                        FREE(cp->gss_clnt_token, M_TEMP);
                        cp->gss_clnt_token = NULL;
                        return NFSERR_EAUTH;
                }
                cp->gss_clnt_tokenlen = otokenlen;
        }

        if (selected != (uint32_t)-1) {
                nmp->nm_etype.selected = selected;
                NFS_GSS_DBG("etype selected = %d\n", nmp->nm_etype.etypes[selected]);
        }
        NFS_GSS_DBG("Up call succeeded major = %d\n", cp->gss_clnt_major);
        return 0;

out:
        if (cp->gss_clnt_token) {
                FREE(cp->gss_clnt_token, M_TEMP);
        }
        cp->gss_clnt_token = NULL;
        cp->gss_clnt_tokenlen = 0;
        /* Server's handle isn't valid. Don't reuse */
        cp->gss_clnt_handle_len = 0;
        if (cp->gss_clnt_handle != NULL) {
                FREE(cp->gss_clnt_handle, M_TEMP);
                cp->gss_clnt_handle = NULL;
        }

        NFS_GSS_DBG("Up call returned NFSERR_EAUTH");
        return NFSERR_EAUTH;
}

/*
 * Invoked at the completion of an RPC call that uses an RPCSEC_GSS
 * credential. The sequence number window that the server returns
 * at context setup indicates the maximum number of client calls that
 * can be outstanding on a context. The client maintains a bitmap that
 * represents the server's window.  Each pending request has a bit set
 * in the window bitmap.  When a reply comes in or times out, we reset
 * the bit in the bitmap and if there are any other threads waiting for
 * a context slot we notify the waiting thread(s).
 *
 * Note that if a request is retransmitted, it will have a single XID
 * but it may be associated with multiple sequence numbers.  So we
 * may have to reset multiple sequence number bits in the window bitmap.
 */
void
nfs_gss_clnt_rpcdone(struct nfsreq *req)
{
        struct nfs_gss_clnt_ctx *cp = req->r_gss_ctx;
        struct gss_seq *gsp, *ngsp;
        int i = 0;

        if (cp == NULL || !(cp->gss_clnt_flags & GSS_CTX_COMPLETE)) {
                return; // no context - don't bother
        }
        /*
         * Reset the bit for this request in the
         * sequence number window to indicate it's done.
         * We do this even if the request timed out.
         */
        lck_mtx_lock(&cp->gss_clnt_mtx);
        gsp = SLIST_FIRST(&req->r_gss_seqlist);
        if (gsp && gsp->gss_seqnum > (cp->gss_clnt_seqnum - cp->gss_clnt_seqwin)) {
                win_resetbit(cp->gss_clnt_seqbits,
                    gsp->gss_seqnum % cp->gss_clnt_seqwin);
        }

        /*
         * Limit the seqnum list to GSS_CLNT_SEQLISTMAX entries
         */
        SLIST_FOREACH_SAFE(gsp, &req->r_gss_seqlist, gss_seqnext, ngsp) {
                if (++i > GSS_CLNT_SEQLISTMAX) {
                        SLIST_REMOVE(&req->r_gss_seqlist, gsp, gss_seq, gss_seqnext);
                        FREE(gsp, M_TEMP);
                }
        }

        /*
         * If there's a thread waiting for
         * the window to advance, wake it up.
         */
        if (cp->gss_clnt_flags & GSS_NEEDSEQ) {
                cp->gss_clnt_flags &= ~GSS_NEEDSEQ;
                wakeup(cp);
        }
        lck_mtx_unlock(&cp->gss_clnt_mtx);
}

/*
 * Create a reference to a context from a request
 * and bump the reference count
 */
void
nfs_gss_clnt_ctx_ref(struct nfsreq *req, struct nfs_gss_clnt_ctx *cp)
{
        req->r_gss_ctx = cp;

        lck_mtx_lock(&cp->gss_clnt_mtx);
        cp->gss_clnt_refcnt++;
        lck_mtx_unlock(&cp->gss_clnt_mtx);
}

/*
 * Remove a context reference from a request
 * If the reference count drops to zero, and the
 * context is invalid, destroy the context
 */
void
nfs_gss_clnt_ctx_unref(struct nfsreq *req)
{
        struct nfsmount *nmp = req->r_nmp;
        struct nfs_gss_clnt_ctx *cp = req->r_gss_ctx;
        int on_neg_cache = 0;
        int neg_cache = 0;
        int destroy = 0;
        struct timeval now;
        char CTXBUF[NFS_CTXBUFSZ];

        if (cp == NULL) {
                return;
        }

        req->r_gss_ctx = NULL;

        lck_mtx_lock(&cp->gss_clnt_mtx);
        if (--cp->gss_clnt_refcnt < 0) {
                panic("Over release of gss context!\n");
        }

        if (cp->gss_clnt_refcnt == 0) {
                if ((cp->gss_clnt_flags & GSS_CTX_INVAL) &&
                    cp->gss_clnt_ctx_id) {
                        gss_krb5_destroy_context(cp->gss_clnt_ctx_id);
                        cp->gss_clnt_ctx_id = NULL;
                }
                if (cp->gss_clnt_flags & GSS_CTX_DESTROY) {
                        destroy = 1;
                        if ((cp->gss_clnt_flags & GSS_CTX_USECOUNT) && !nfs_gss_clnt_mnt_rele(nmp)) {
                                cp->gss_clnt_flags &= ~GSS_CTX_USECOUNT;
                        }
                        if (cp->gss_clnt_nctime) {
                                on_neg_cache = 1;
                        }
                }
        }
        if (!destroy && cp->gss_clnt_nctime == 0 &&
            (cp->gss_clnt_flags & GSS_CTX_INVAL)) {
                microuptime(&now);
                cp->gss_clnt_nctime = now.tv_sec;
                neg_cache = 1;
        }
        lck_mtx_unlock(&cp->gss_clnt_mtx);
        if (destroy) {
                NFS_GSS_DBG("Destroying context %s\n", NFS_GSS_CTX(req, cp));
                if (nmp) {
                        lck_mtx_lock(&nmp->nm_lock);
                        if (cp->gss_clnt_entries.tqe_next != NFSNOLIST) {
                                TAILQ_REMOVE(&nmp->nm_gsscl, cp, gss_clnt_entries);
                        }
                        if (on_neg_cache) {
                                nmp->nm_ncentries--;
                        }
                        lck_mtx_unlock(&nmp->nm_lock);
                }
                nfs_gss_clnt_ctx_destroy(cp);
        } else if (neg_cache) {
                NFS_GSS_DBG("Entering context %s into negative cache\n", NFS_GSS_CTX(req, cp));
                if (nmp) {
                        lck_mtx_lock(&nmp->nm_lock);
                        nmp->nm_ncentries++;
                        nfs_gss_clnt_ctx_neg_cache_reap(nmp);
                        lck_mtx_unlock(&nmp->nm_lock);
                }
        }
        NFS_GSS_CLNT_CTX_DUMP(nmp);
}

/*
 * Try and reap any old negative cache entries.
 * cache queue.
 */
void
nfs_gss_clnt_ctx_neg_cache_reap(struct nfsmount *nmp)
{
        struct nfs_gss_clnt_ctx *cp, *tcp;
        struct timeval now;
        int reaped = 0;

        /* Try and reap old, unreferenced, expired contexts */
        microuptime(&now);

        NFS_GSS_DBG("Reaping contexts ncentries = %d\n", nmp->nm_ncentries);

        TAILQ_FOREACH_SAFE(cp, &nmp->nm_gsscl, gss_clnt_entries, tcp) {
                int destroy = 0;

                /* Don't reap STICKY contexts */
                if ((cp->gss_clnt_flags & GSS_CTX_STICKY) ||
                    !(cp->gss_clnt_flags & GSS_CTX_INVAL)) {
                        continue;
                }
                /* Keep up to GSS_MAX_NEG_CACHE_ENTRIES */
                if (nmp->nm_ncentries <= GSS_MAX_NEG_CACHE_ENTRIES) {
                        break;
                }
                /* Contexts too young */
                if (cp->gss_clnt_nctime + GSS_NEG_CACHE_TO >= now.tv_sec) {
                        continue;
                }
                /* Not referenced, remove it. */
                lck_mtx_lock(&cp->gss_clnt_mtx);
                if (cp->gss_clnt_refcnt == 0) {
                        cp->gss_clnt_flags |= GSS_CTX_DESTROY;
                        destroy = 1;
                }
                lck_mtx_unlock(&cp->gss_clnt_mtx);
                if (destroy) {
                        TAILQ_REMOVE(&nmp->nm_gsscl, cp, gss_clnt_entries);
                        nmp->nm_ncentries++;
                        reaped++;
                        nfs_gss_clnt_ctx_destroy(cp);
                }
        }
        NFS_GSS_DBG("Reaped %d contexts ncentries = %d\n", reaped, nmp->nm_ncentries);
}

/*
 * Clean a context to be cached
 */
static void
nfs_gss_clnt_ctx_clean(struct nfs_gss_clnt_ctx *cp)
{
        /* Preserve gss_clnt_mtx */
        assert(cp->gss_clnt_thread == NULL);  /* Will be set to this thread */
        /* gss_clnt_entries  we should not be on any list at this point */
        cp->gss_clnt_flags = 0;
        /* gss_clnt_refcnt should be zero */
        assert(cp->gss_clnt_refcnt == 0);
        /*
         * We are who we are preserve:
         * gss_clnt_cred
         * gss_clnt_principal
         * gss_clnt_prinlen
         * gss_clnt_prinnt
         * gss_clnt_desplay
         */
        /* gss_clnt_proc will be set in nfs_gss_clnt_ctx_init */
        cp->gss_clnt_seqnum = 0;
        /* Preserve gss_clnt_service, we're not changing flavors */
        if (cp->gss_clnt_handle) {
                FREE(cp->gss_clnt_handle, M_TEMP);
                cp->gss_clnt_handle = NULL;
        }
        cp->gss_clnt_handle_len = 0;
        cp->gss_clnt_nctime = 0;
        cp->gss_clnt_seqwin = 0;
        if (cp->gss_clnt_seqbits) {
                FREE(cp->gss_clnt_seqbits, M_TEMP);
                cp->gss_clnt_seqbits = NULL;
        }
        /* Preserve gss_clnt_mport. Still talking to the same gssd */
        if (cp->gss_clnt_verf) {
                FREE(cp->gss_clnt_verf, M_TEMP);
                cp->gss_clnt_verf = NULL;
        }
        /* Service name might change on failover, so reset it */
        if (cp->gss_clnt_svcname) {
                FREE(cp->gss_clnt_svcname, M_TEMP);
                cp->gss_clnt_svcname = NULL;
                cp->gss_clnt_svcnt = 0;
        }
        cp->gss_clnt_svcnamlen = 0;
        cp->gss_clnt_cred_handle = 0;
        cp->gss_clnt_context = 0;
        if (cp->gss_clnt_token) {
                FREE(cp->gss_clnt_token, M_TEMP);
                cp->gss_clnt_token = NULL;
        }
        cp->gss_clnt_tokenlen = 0;
        /* XXX gss_clnt_ctx_id ??? */
        /*
         * Preserve:
         * gss_clnt_gssd_flags
         * gss_clnt_major
         * gss_clnt_minor
         * gss_clnt_ptime
         */
}

/*
 * Copy a source context to a new context. This is used to create a new context
 * with the identity of the old context for renewal. The old context is invalid
 * at this point but may have reference still to it, so it is not safe to use that
 * context.
 */
static int
nfs_gss_clnt_ctx_copy(struct nfs_gss_clnt_ctx *scp, struct nfs_gss_clnt_ctx **dcpp)
{
        struct nfs_gss_clnt_ctx *dcp;

        *dcpp = (struct nfs_gss_clnt_ctx *)NULL;
        MALLOC(dcp, struct nfs_gss_clnt_ctx *, sizeof(struct nfs_gss_clnt_ctx), M_TEMP, M_WAITOK);
        if (dcp == NULL) {
                return ENOMEM;
        }
        bzero(dcp, sizeof(struct nfs_gss_clnt_ctx));
        lck_mtx_init(&dcp->gss_clnt_mtx, &nfs_gss_clnt_grp, LCK_ATTR_NULL);
        dcp->gss_clnt_cred = scp->gss_clnt_cred;
        kauth_cred_ref(dcp->gss_clnt_cred);
        dcp->gss_clnt_prinlen = scp->gss_clnt_prinlen;
        dcp->gss_clnt_prinnt = scp->gss_clnt_prinnt;
        if (scp->gss_clnt_principal) {
                MALLOC(dcp->gss_clnt_principal, uint8_t *, dcp->gss_clnt_prinlen, M_TEMP, M_WAITOK | M_ZERO);
                if (dcp->gss_clnt_principal == NULL) {
                        FREE(dcp, M_TEMP);
                        return ENOMEM;
                }
                bcopy(scp->gss_clnt_principal, dcp->gss_clnt_principal, dcp->gss_clnt_prinlen);
        }
        /* Note we don't preserve the display name, that will be set by a successful up call */
        dcp->gss_clnt_service = scp->gss_clnt_service;
        dcp->gss_clnt_mport = host_copy_special_port(scp->gss_clnt_mport);
        dcp->gss_clnt_ctx_id = NULL;   /* Will be set from successful upcall */
        dcp->gss_clnt_gssd_flags = scp->gss_clnt_gssd_flags;
        dcp->gss_clnt_major = scp->gss_clnt_major;
        dcp->gss_clnt_minor = scp->gss_clnt_minor;
        dcp->gss_clnt_ptime = scp->gss_clnt_ptime;

        *dcpp = dcp;

        return 0;
}

/*
 * Remove a context
 */
static void
nfs_gss_clnt_ctx_destroy(struct nfs_gss_clnt_ctx *cp)
{
        NFS_GSS_DBG("Destroying context %d/%d\n",
            kauth_cred_getasid(cp->gss_clnt_cred),
            kauth_cred_getauid(cp->gss_clnt_cred));

        host_release_special_port(cp->gss_clnt_mport);
        cp->gss_clnt_mport = IPC_PORT_NULL;

        lck_mtx_destroy(&cp->gss_clnt_mtx, &nfs_gss_clnt_grp);

        if (IS_VALID_CRED(cp->gss_clnt_cred)) {
                kauth_cred_unref(&cp->gss_clnt_cred);
        }
        cp->gss_clnt_entries.tqe_next = NFSNOLIST;
        cp->gss_clnt_entries.tqe_prev = NFSNOLIST;
        if (cp->gss_clnt_principal) {
                FREE(cp->gss_clnt_principal, M_TEMP);
                cp->gss_clnt_principal = NULL;
        }
        if (cp->gss_clnt_display) {
                FREE(cp->gss_clnt_display, M_TEMP);
                cp->gss_clnt_display = NULL;
        }
        if (cp->gss_clnt_ctx_id) {
                gss_krb5_destroy_context(cp->gss_clnt_ctx_id);
                cp->gss_clnt_ctx_id = NULL;
        }

        nfs_gss_clnt_ctx_clean(cp);

        FREE(cp, M_TEMP);
}

/*
 * The context for a user is invalid.
 * Mark the context as invalid, then
 * create a new context.
 */
int
nfs_gss_clnt_ctx_renew(struct nfsreq *req)
{
        struct nfs_gss_clnt_ctx *cp = req->r_gss_ctx;
        struct nfs_gss_clnt_ctx *ncp;
        struct nfsmount *nmp;
        int error = 0;
        char CTXBUF[NFS_CTXBUFSZ];

        if (cp == NULL) {
                return 0;
        }

        if (req->r_nmp == NULL) {
                return ENXIO;
        }
        nmp = req->r_nmp;

        lck_mtx_lock(&cp->gss_clnt_mtx);
        if (cp->gss_clnt_flags & GSS_CTX_INVAL) {
                lck_mtx_unlock(&cp->gss_clnt_mtx);
                nfs_gss_clnt_ctx_unref(req);
                return 0;     // already being renewed
        }

        cp->gss_clnt_flags |= (GSS_CTX_INVAL | GSS_CTX_DESTROY);

        if (cp->gss_clnt_flags & (GSS_NEEDCTX | GSS_NEEDSEQ)) {
                cp->gss_clnt_flags &= ~GSS_NEEDSEQ;
                wakeup(cp);
        }
        lck_mtx_unlock(&cp->gss_clnt_mtx);

        if (cp->gss_clnt_proc == RPCSEC_GSS_DESTROY) {
                return EACCES;  /* Destroying a context is best effort. Don't renew. */
        }
        /*
         * If we're setting up a context let nfs_gss_clnt_ctx_init know this is not working
         * and to try some other etype.
         */
        if (cp->gss_clnt_proc != RPCSEC_GSS_DATA) {
                return ENEEDAUTH;
        }
        error =  nfs_gss_clnt_ctx_copy(cp, &ncp);
        NFS_GSS_DBG("Renewing context %s\n", NFS_GSS_CTX(req, ncp));
        nfs_gss_clnt_ctx_unref(req);
        if (error) {
                return error;
        }

        lck_mtx_lock(&nmp->nm_lock);
        /*
         * Note we don't bother taking the new context mutex as we're
         * not findable at the moment.
         */
        ncp->gss_clnt_thread = current_thread();
        nfs_gss_clnt_ctx_ref(req, ncp);
        TAILQ_INSERT_HEAD(&nmp->nm_gsscl, ncp, gss_clnt_entries);
        lck_mtx_unlock(&nmp->nm_lock);

        error = nfs_gss_clnt_ctx_init_retry(req, ncp); // Initialize new context
        if (error) {
                nfs_gss_clnt_ctx_unref(req);
        }

        return error;
}


/*
 * Destroy all the contexts associated with a mount.
 * The contexts are also destroyed by the server.
 */
void
nfs_gss_clnt_ctx_unmount(struct nfsmount *nmp)
{
        struct nfs_gss_clnt_ctx *cp;
        struct nfsm_chain nmreq, nmrep;
        int error, status;
        struct nfsreq *req;

        if (!nmp) {
                return;
        }

        req = zalloc(nfs_req_zone);
        req->r_nmp = nmp;
        lck_mtx_lock(&nmp->nm_lock);
        while ((cp = TAILQ_FIRST(&nmp->nm_gsscl))) {
                TAILQ_REMOVE(&nmp->nm_gsscl, cp, gss_clnt_entries);
                cp->gss_clnt_entries.tqe_next = NFSNOLIST;
                lck_mtx_lock(&cp->gss_clnt_mtx);
                if (cp->gss_clnt_flags & GSS_CTX_DESTROY) {
                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                        continue;
                }
                cp->gss_clnt_refcnt++;
                lck_mtx_unlock(&cp->gss_clnt_mtx);
                req->r_gss_ctx = cp;

                lck_mtx_unlock(&nmp->nm_lock);
                /*
                 * Tell the server to destroy its context.
                 * But don't bother if it's a forced unmount.
                 */
                if (!nfs_mount_gone(nmp) &&
                    (cp->gss_clnt_flags & (GSS_CTX_INVAL | GSS_CTX_DESTROY | GSS_CTX_COMPLETE)) == GSS_CTX_COMPLETE) {
                        cp->gss_clnt_proc = RPCSEC_GSS_DESTROY;

                        error = 0;
                        nfsm_chain_null(&nmreq);
                        nfsm_chain_null(&nmrep);
                        nfsm_chain_build_alloc_init(error, &nmreq, 0);
                        nfsm_chain_build_done(error, &nmreq);
                        if (!error) {
                                nfs_request_gss(nmp->nm_mountp, &nmreq,
                                    current_thread(), cp->gss_clnt_cred, 0, cp, &nmrep, &status);
                        }
                        nfsm_chain_cleanup(&nmreq);
                        nfsm_chain_cleanup(&nmrep);
                }

                /*
                 * Mark the context invalid then drop
                 * the reference to remove it if its
                 * refcount is zero.
                 */
                lck_mtx_lock(&cp->gss_clnt_mtx);
                cp->gss_clnt_flags |= (GSS_CTX_INVAL | GSS_CTX_DESTROY);
                lck_mtx_unlock(&cp->gss_clnt_mtx);
                nfs_gss_clnt_ctx_unref(req);
                lck_mtx_lock(&nmp->nm_lock);
        }
        lck_mtx_unlock(&nmp->nm_lock);
        assert(TAILQ_EMPTY(&nmp->nm_gsscl));
        NFS_ZFREE(nfs_req_zone, req);
}


/*
 * Removes a mounts context for a credential
 */
int
nfs_gss_clnt_ctx_remove(struct nfsmount *nmp, kauth_cred_t cred)
{
        struct nfs_gss_clnt_ctx *cp, *tcp;
        struct nfsreq *req;

        req = zalloc(nfs_req_zone);
        req->r_nmp = nmp;

        NFS_GSS_DBG("Enter\n");
        NFS_GSS_CLNT_CTX_DUMP(nmp);
        lck_mtx_lock(&nmp->nm_lock);
        TAILQ_FOREACH_SAFE(cp, &nmp->nm_gsscl, gss_clnt_entries, tcp) {
                lck_mtx_lock(&cp->gss_clnt_mtx);
                if (nfs_gss_clnt_ctx_cred_match(cp->gss_clnt_cred, cred)) {
                        if (cp->gss_clnt_flags & GSS_CTX_DESTROY) {
                                NFS_GSS_DBG("Found destroyed context %d/%d. refcnt = %d continuing\n",
                                    kauth_cred_getasid(cp->gss_clnt_cred),
                                    kauth_cred_getauid(cp->gss_clnt_cred),
                                    cp->gss_clnt_refcnt);
                                lck_mtx_unlock(&cp->gss_clnt_mtx);
                                continue;
                        }
                        cp->gss_clnt_refcnt++;
                        cp->gss_clnt_flags |= (GSS_CTX_INVAL | GSS_CTX_DESTROY);
                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                        req->r_gss_ctx = cp;
                        lck_mtx_unlock(&nmp->nm_lock);
                        /*
                         * Drop the reference to remove it if its
                         * refcount is zero.
                         */
                        NFS_GSS_DBG("Removed context %d/%d refcnt = %d\n",
                            kauth_cred_getasid(cp->gss_clnt_cred),
                            kauth_cred_getuid(cp->gss_clnt_cred),
                            cp->gss_clnt_refcnt);
                        nfs_gss_clnt_ctx_unref(req);
                        NFS_ZFREE(nfs_req_zone, req);
                        return 0;
                }
                lck_mtx_unlock(&cp->gss_clnt_mtx);
        }

        lck_mtx_unlock(&nmp->nm_lock);

        NFS_ZFREE(nfs_req_zone, req);
        NFS_GSS_DBG("Returning ENOENT\n");
        return ENOENT;
}

/*
 * Sets a mounts principal for a session associated with cred.
 */
int
nfs_gss_clnt_ctx_set_principal(struct nfsmount *nmp, vfs_context_t ctx,
    uint8_t *principal, size_t princlen, uint32_t nametype)
{
        struct nfsreq *req;
        int error;

        NFS_GSS_DBG("Enter:\n");

        req = zalloc_flags(nfs_req_zone, Z_WAITOK | Z_ZERO);
        req->r_nmp = nmp;
        req->r_auth = nmp->nm_auth;
        req->r_thread = vfs_context_thread(ctx);
        req->r_cred = vfs_context_ucred(ctx);

        error = nfs_gss_clnt_ctx_find_principal(req, principal, princlen, nametype);
        NFS_GSS_DBG("nfs_gss_clnt_ctx_find_principal returned %d\n", error);
        /*
         * We don't care about auth errors. Those would indicate that the context is in the
         * neagative cache and if and when the user has credentials for the principal
         * we should be good to go in that we will select those credentials for this principal.
         */
        if (error == EACCES || error == EAUTH || error == ENEEDAUTH) {
                error = 0;
        }

        /* We're done with this request */
        nfs_gss_clnt_ctx_unref(req);
        NFS_ZFREE(nfs_req_zone, req);
        return error;
}

/*
 * Gets a mounts principal from a session associated with cred
 */
int
nfs_gss_clnt_ctx_get_principal(struct nfsmount *nmp, vfs_context_t ctx,
    struct user_nfs_gss_principal *p)
{
        struct nfsreq *req;
        int error = 0;
        struct nfs_gss_clnt_ctx *cp;
        kauth_cred_t cred = vfs_context_ucred(ctx);
        const char *princ = NULL;
        char CTXBUF[NFS_CTXBUFSZ];

        /* Make sure the the members of the struct user_nfs_gss_principal are initialized */
        p->nametype = GSSD_STRING_NAME;
        p->principal = USER_ADDR_NULL;
        p->princlen = 0;
        p->flags = 0;

        req = zalloc_flags(nfs_req_zone, Z_WAITOK);
        req->r_nmp = nmp;
        lck_mtx_lock(&nmp->nm_lock);
        TAILQ_FOREACH(cp, &nmp->nm_gsscl, gss_clnt_entries) {
                lck_mtx_lock(&cp->gss_clnt_mtx);
                if (cp->gss_clnt_flags & GSS_CTX_DESTROY) {
                        NFS_GSS_DBG("Found destroyed context %s refcnt = %d continuing\n",
                            NFS_GSS_CTX(req, cp),
                            cp->gss_clnt_refcnt);
                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                        continue;
                }
                if (nfs_gss_clnt_ctx_cred_match(cp->gss_clnt_cred, cred)) {
                        cp->gss_clnt_refcnt++;
                        lck_mtx_unlock(&cp->gss_clnt_mtx);
                        goto out;
                }
                lck_mtx_unlock(&cp->gss_clnt_mtx);
        }

out:
        if (cp == NULL) {
                lck_mtx_unlock(&nmp->nm_lock);
                p->flags |= NFS_IOC_NO_CRED_FLAG;  /* No credentials, valid or invalid on this mount */
                NFS_GSS_DBG("No context found for session %d by uid %d\n",
                    kauth_cred_getasid(cred), kauth_cred_getuid(cred));
                NFS_ZFREE(nfs_req_zone, req);
                return 0;
        }

        /* Indicate if the cred is INVALID */
        if (cp->gss_clnt_flags & GSS_CTX_INVAL) {
                p->flags |= NFS_IOC_INVALID_CRED_FLAG;
        }

        /* We have set a principal on the mount */
        if (cp->gss_clnt_principal) {
                princ = (char *)cp->gss_clnt_principal;
                p->princlen = cp->gss_clnt_prinlen;
                p->nametype = cp->gss_clnt_prinnt;
        } else if (cp->gss_clnt_display) {
                /* We have a successful use the the default credential */
                princ = cp->gss_clnt_display;
                p->princlen = strlen(cp->gss_clnt_display);
        }

        /*
         * If neither of the above is true we have an invalid default credential
         * So from above p->principal is USER_ADDR_NULL and princ is NULL
         */

        if (princ) {
                char *pp;

                MALLOC(pp, char *, p->princlen, M_TEMP, M_WAITOK);
                bcopy(princ, pp, p->princlen);
                p->principal = CAST_USER_ADDR_T(pp);
        }

        lck_mtx_unlock(&nmp->nm_lock);

        req->r_gss_ctx = cp;
        NFS_GSS_DBG("Found context %s\n", NFS_GSS_CTX(req, NULL));
        nfs_gss_clnt_ctx_unref(req);
        NFS_ZFREE(nfs_req_zone, req);
        return error;
}
#endif /* CONFIG_NFS_CLIENT */

/*************
 *
 * Server functions
 */

#if CONFIG_NFS_SERVER

/*
 * Find a server context based on a handle value received
 * in an RPCSEC_GSS credential.
 */
static struct nfs_gss_svc_ctx *
nfs_gss_svc_ctx_find(uint32_t handle)
{
        struct nfs_gss_svc_ctx_hashhead *head;
        struct nfs_gss_svc_ctx *cp;
        uint64_t timenow;

        if (handle == 0) {
                return NULL;
        }

        head = &nfs_gss_svc_ctx_hashtbl[SVC_CTX_HASH(handle)];
        /*
         * Don't return a context that is going to expire in GSS_CTX_PEND seconds
         */
        clock_interval_to_deadline(GSS_CTX_PEND, NSEC_PER_SEC, &timenow);

        lck_mtx_lock(&nfs_gss_svc_ctx_mutex);

        LIST_FOREACH(cp, head, gss_svc_entries) {
                if (cp->gss_svc_handle == handle) {
                        if (timenow > cp->gss_svc_incarnation + GSS_SVC_CTX_TTL) {
                                /*
                                 * Context has or is about to expire. Don't use.
                                 * We'll return null and the client will have to create
                                 * a new context.
                                 */
                                cp->gss_svc_handle = 0;
                                /*
                                 * Make sure though that we stay around for GSS_CTX_PEND seconds
                                 * for other threads that might be using the context.
                                 */
                                cp->gss_svc_incarnation = timenow;

                                cp = NULL;
                                break;
                        }
                        lck_mtx_lock(&cp->gss_svc_mtx);
                        cp->gss_svc_refcnt++;
                        lck_mtx_unlock(&cp->gss_svc_mtx);
                        break;
                }
        }

        lck_mtx_unlock(&nfs_gss_svc_ctx_mutex);

        return cp;
}

/*
 * Insert a new server context into the hash table
 * and start the context reap thread if necessary.
 */
static void
nfs_gss_svc_ctx_insert(struct nfs_gss_svc_ctx *cp)
{
        struct nfs_gss_svc_ctx_hashhead *head;
        struct nfs_gss_svc_ctx *p;

        lck_mtx_lock(&nfs_gss_svc_ctx_mutex);

        /*
         * Give the client a random handle so that if we reboot
         * it's unlikely the client will get a bad context match.
         * Make sure it's not zero or already assigned.
         */
retry:
        cp->gss_svc_handle = random();
        if (cp->gss_svc_handle == 0) {
                goto retry;
        }
        head = &nfs_gss_svc_ctx_hashtbl[SVC_CTX_HASH(cp->gss_svc_handle)];
        LIST_FOREACH(p, head, gss_svc_entries)
        if (p->gss_svc_handle == cp->gss_svc_handle) {
                goto retry;
        }

        clock_interval_to_deadline(GSS_CTX_PEND, NSEC_PER_SEC,
            &cp->gss_svc_incarnation);
        LIST_INSERT_HEAD(head, cp, gss_svc_entries);
        nfs_gss_ctx_count++;

        if (!nfs_gss_timer_on) {
                nfs_gss_timer_on = 1;

                nfs_interval_timer_start(nfs_gss_svc_ctx_timer_call,
                    min(GSS_TIMER_PERIOD, max(GSS_CTX_TTL_MIN, nfsrv_gss_context_ttl)) * MSECS_PER_SEC);
        }

        lck_mtx_unlock(&nfs_gss_svc_ctx_mutex);
}

/*
 * This function is called via the kernel's callout
 * mechanism.  It runs only when there are
 * cached RPCSEC_GSS contexts.
 */
void
nfs_gss_svc_ctx_timer(__unused void *param1, __unused void *param2)
{
        struct nfs_gss_svc_ctx *cp, *next;
        uint64_t timenow;
        int contexts = 0;
        int i;

        lck_mtx_lock(&nfs_gss_svc_ctx_mutex);
        clock_get_uptime(&timenow);

        NFS_GSS_DBG("is running\n");

        /*
         * Scan all the hash chains
         */
        for (i = 0; i < SVC_CTX_HASHSZ; i++) {
                /*
                 * For each hash chain, look for entries
                 * that haven't been used in a while.
                 */
                LIST_FOREACH_SAFE(cp, &nfs_gss_svc_ctx_hashtbl[i], gss_svc_entries, next) {
                        contexts++;
                        if (timenow > cp->gss_svc_incarnation +
                            (cp->gss_svc_handle ? GSS_SVC_CTX_TTL : 0)
                            && cp->gss_svc_refcnt == 0) {
                                /*
                                 * A stale context - remove it
                                 */
                                LIST_REMOVE(cp, gss_svc_entries);
                                NFS_GSS_DBG("Removing contex for %d\n", cp->gss_svc_uid);
                                if (cp->gss_svc_seqbits) {
                                        FREE(cp->gss_svc_seqbits, M_TEMP);
                                }
                                lck_mtx_destroy(&cp->gss_svc_mtx, &nfs_gss_svc_grp);
                                FREE(cp, M_TEMP);
                                contexts--;
                        }
                }
        }

        nfs_gss_ctx_count = contexts;

        /*
         * If there are still some cached contexts left,
         * set up another callout to check on them later.
         */
        nfs_gss_timer_on = nfs_gss_ctx_count > 0;
        if (nfs_gss_timer_on) {
                nfs_interval_timer_start(nfs_gss_svc_ctx_timer_call,
                    min(GSS_TIMER_PERIOD, max(GSS_CTX_TTL_MIN, nfsrv_gss_context_ttl)) * MSECS_PER_SEC);
        }

        lck_mtx_unlock(&nfs_gss_svc_ctx_mutex);
}

/*
 * Here the server receives an RPCSEC_GSS credential in an
 * RPC call header.  First there's some checking to make sure
 * the credential is appropriate - whether the context is still
 * being set up, or is complete.  Then we use the handle to find
 * the server's context and validate the verifier, which contains
 * a signed checksum of the RPC header. If the verifier checks
 * out, we extract the user's UID and groups from the context
 * and use it to set up a UNIX credential for the user's request.
 */
int
nfs_gss_svc_cred_get(struct nfsrv_descript *nd, struct nfsm_chain *nmc)
{
        uint32_t vers, proc, seqnum, service;
        uint32_t handle, handle_len;
        uint32_t major;
        struct nfs_gss_svc_ctx *cp = NULL;
        uint32_t flavor = 0;
        int error = 0;
        uint32_t arglen;
        size_t argsize, start, header_len;
        gss_buffer_desc cksum;
        struct nfsm_chain nmc_tmp;
        mbuf_t reply_mbuf, prev_mbuf, pad_mbuf;

        vers = proc = seqnum = service = handle_len = 0;
        arglen = 0;

        nfsm_chain_get_32(error, nmc, vers);
        if (vers != RPCSEC_GSS_VERS_1) {
                error = NFSERR_AUTHERR | AUTH_REJECTCRED;
                goto nfsmout;
        }

        nfsm_chain_get_32(error, nmc, proc);
        nfsm_chain_get_32(error, nmc, seqnum);
        nfsm_chain_get_32(error, nmc, service);
        nfsm_chain_get_32(error, nmc, handle_len);
        if (error) {
                goto nfsmout;
        }

        /*
         * Make sure context setup/destroy is being done with a nullproc
         */
        if (proc != RPCSEC_GSS_DATA && nd->nd_procnum != NFSPROC_NULL) {
                error = NFSERR_AUTHERR | RPCSEC_GSS_CREDPROBLEM;
                goto nfsmout;
        }

        /*
         * If the sequence number is greater than the max
         * allowable, reject and have the client init a
         * new context.
         */
        if (seqnum > GSS_MAXSEQ) {
                error = NFSERR_AUTHERR | RPCSEC_GSS_CTXPROBLEM;
                goto nfsmout;
        }

        nd->nd_sec =
            service == RPCSEC_GSS_SVC_NONE ?      RPCAUTH_KRB5 :
            service == RPCSEC_GSS_SVC_INTEGRITY ? RPCAUTH_KRB5I :
            service == RPCSEC_GSS_SVC_PRIVACY ?   RPCAUTH_KRB5P : 0;

        if (proc == RPCSEC_GSS_INIT) {
                /*
                 * Limit the total number of contexts
                 */
                if (nfs_gss_ctx_count > nfs_gss_ctx_max) {
                        error = NFSERR_AUTHERR | RPCSEC_GSS_CTXPROBLEM;
                        goto nfsmout;
                }

                /*
                 * Set up a new context
                 */
                MALLOC(cp, struct nfs_gss_svc_ctx *, sizeof(*cp), M_TEMP, M_WAITOK | M_ZERO);
                if (cp == NULL) {
                        error = ENOMEM;
                        goto nfsmout;
                }
                lck_mtx_init(&cp->gss_svc_mtx, &nfs_gss_svc_grp, LCK_ATTR_NULL);
                cp->gss_svc_refcnt = 1;
        } else {
                /*
                 * Use the handle to find the context
                 */
                if (handle_len != sizeof(handle)) {
                        error = NFSERR_AUTHERR | RPCSEC_GSS_CREDPROBLEM;
                        goto nfsmout;
                }
                nfsm_chain_get_32(error, nmc, handle);
                if (error) {
                        goto nfsmout;
                }
                cp = nfs_gss_svc_ctx_find(handle);
                if (cp == NULL) {
                        error = NFSERR_AUTHERR | RPCSEC_GSS_CTXPROBLEM;
                        goto nfsmout;
                }
        }

        cp->gss_svc_proc = proc;

        if (proc == RPCSEC_GSS_DATA || proc == RPCSEC_GSS_DESTROY) {
                struct posix_cred temp_pcred;

                if (cp->gss_svc_seqwin == 0) {
                        /*
                         * Context isn't complete
                         */
                        error = NFSERR_AUTHERR | RPCSEC_GSS_CTXPROBLEM;
                        goto nfsmout;
                }

                if (!nfs_gss_svc_seqnum_valid(cp, seqnum)) {
                        /*
                         * Sequence number is bad
                         */
                        error = EINVAL; // drop the request
                        goto nfsmout;
                }

                /*
                 * Validate the verifier.
                 * The verifier contains an encrypted checksum
                 * of the call header from the XID up to and
                 * including the credential.  We compute the
                 * checksum and compare it with what came in
                 * the verifier.
                 */
                header_len = nfsm_chain_offset(nmc);
                nfsm_chain_get_32(error, nmc, flavor);
                nfsm_chain_get_32(error, nmc, cksum.length);
                if (error) {
                        goto nfsmout;
                }
                if (flavor != RPCSEC_GSS || cksum.length > KRB5_MAX_MIC_SIZE) {
                        error = NFSERR_AUTHERR | AUTH_BADVERF;
                } else {
                        MALLOC(cksum.value, void *, cksum.length, M_TEMP, M_WAITOK);
                        nfsm_chain_get_opaque(error, nmc, cksum.length, cksum.value);
                }
                if (error) {
                        goto nfsmout;
                }

                /* Now verify the client's call header checksum */
                major = gss_krb5_verify_mic_mbuf((uint32_t *)&error, cp->gss_svc_ctx_id, nmc->nmc_mhead, 0, header_len, &cksum, NULL);
                (void)gss_release_buffer(NULL, &cksum);
                if (major != GSS_S_COMPLETE) {
                        printf("Server header: gss_krb5_verify_mic_mbuf failed %d\n", error);
                        error = NFSERR_AUTHERR | RPCSEC_GSS_CTXPROBLEM;
                        goto nfsmout;
                }

                nd->nd_gss_seqnum = seqnum;

                /*
                 * Set up the user's cred
                 */
                bzero(&temp_pcred, sizeof(temp_pcred));
                temp_pcred.cr_uid = cp->gss_svc_uid;
                bcopy(cp->gss_svc_gids, temp_pcred.cr_groups,
                    sizeof(gid_t) * cp->gss_svc_ngroups);
                temp_pcred.cr_ngroups = (short)cp->gss_svc_ngroups;

                nd->nd_cr = posix_cred_create(&temp_pcred);
                if (nd->nd_cr == NULL) {
                        error = ENOMEM;
                        goto nfsmout;
                }
                clock_get_uptime(&cp->gss_svc_incarnation);

                /*
                 * If the call arguments are integrity or privacy protected
                 * then we need to check them here.
                 */
                switch (service) {
                case RPCSEC_GSS_SVC_NONE:
                        /* nothing to do */
                        break;
                case RPCSEC_GSS_SVC_INTEGRITY:
                        /*
                         * Here's what we expect in the integrity call args:
                         *
                         * - length of seq num + call args (4 bytes)
                         * - sequence number (4 bytes)
                         * - call args (variable bytes)
                         * - length of checksum token
                         * - checksum of seqnum + call args
                         */
                        nfsm_chain_get_32(error, nmc, arglen);          // length of args
                        if (arglen > NFS_MAXPACKET) {
                                error = EBADRPC;
                                goto nfsmout;
                        }

                        nmc_tmp = *nmc;
                        nfsm_chain_adv(error, &nmc_tmp, arglen);
                        nfsm_chain_get_32(error, &nmc_tmp, cksum.length);
                        cksum.value = NULL;
                        if (cksum.length > 0 && cksum.length < GSS_MAX_MIC_LEN) {
                                MALLOC(cksum.value, void *, cksum.length, M_TEMP, M_WAITOK);
                        }

                        if (cksum.value == NULL) {
                                error = EBADRPC;
                                goto nfsmout;
                        }
                        nfsm_chain_get_opaque(error, &nmc_tmp, cksum.length, cksum.value);

                        /* Verify the checksum over the call args */
                        start = nfsm_chain_offset(nmc);

                        major = gss_krb5_verify_mic_mbuf((uint32_t *)&error, cp->gss_svc_ctx_id,
                            nmc->nmc_mhead, start, arglen, &cksum, NULL);
                        FREE(cksum.value, M_TEMP);
                        if (major != GSS_S_COMPLETE) {
                                printf("Server args: gss_krb5_verify_mic_mbuf failed %d\n", error);
                                error = EBADRPC;
                                goto nfsmout;
                        }

                        /*
                         * Get the sequence number prepended to the args
                         * and compare it against the one sent in the
                         * call credential.
                         */
                        nfsm_chain_get_32(error, nmc, seqnum);
                        if (seqnum != nd->nd_gss_seqnum) {
                                error = EBADRPC;                        // returns as GARBAGEARGS
                                goto nfsmout;
                        }
                        break;
                case RPCSEC_GSS_SVC_PRIVACY:
                        /*
                         * Here's what we expect in the privacy call args:
                         *
                         * - length of wrap token
                         * - wrap token (37-40 bytes)
                         */
                        prev_mbuf = nmc->nmc_mcur;
                        nfsm_chain_get_32(error, nmc, arglen);          // length of args
                        if (arglen > NFS_MAXPACKET) {
                                error = EBADRPC;
                                goto nfsmout;
                        }

                        /* Get the wrap token (current mbuf in the chain starting at the current offset) */
                        start = nmc->nmc_ptr - (caddr_t)mbuf_data(nmc->nmc_mcur);

                        /* split out the wrap token */
                        argsize = arglen;
                        error = gss_normalize_mbuf(nmc->nmc_mcur, start, &argsize, &reply_mbuf, &pad_mbuf, 0);
                        if (error) {
                                goto nfsmout;
                        }

                        assert(argsize == arglen);
                        if (pad_mbuf) {
                                assert(nfsm_pad(arglen) == mbuf_len(pad_mbuf));
                                mbuf_free(pad_mbuf);
                        } else {
                                assert(nfsm_pad(arglen) == 0);
                        }

                        major = gss_krb5_unwrap_mbuf((uint32_t *)&error, cp->gss_svc_ctx_id, &reply_mbuf, 0, arglen, NULL, NULL);
                        if (major != GSS_S_COMPLETE) {
                                printf("%s: gss_krb5_unwrap_mbuf failes %d\n", __func__, error);
                                goto nfsmout;
                        }

                        /* Now replace the wrapped arguments with the unwrapped ones */
                        mbuf_setnext(prev_mbuf, reply_mbuf);
                        nmc->nmc_mcur = reply_mbuf;
                        nmc->nmc_ptr = mbuf_data(reply_mbuf);
                        nmc->nmc_left = mbuf_len(reply_mbuf);

                        /*
                         * - sequence number (4 bytes)
                         * - call args
                         */

                        // nfsm_chain_reverse(nmc, nfsm_pad(toklen));

                        /*
                         * Get the sequence number prepended to the args
                         * and compare it against the one sent in the
                         * call credential.
                         */
                        nfsm_chain_get_32(error, nmc, seqnum);
                        if (seqnum != nd->nd_gss_seqnum) {
                                printf("%s: Sequence number mismatch seqnum = %d nd->nd_gss_seqnum = %d\n",
                                    __func__, seqnum, nd->nd_gss_seqnum);
                                printmbuf("reply_mbuf", nmc->nmc_mhead, 0, 0);
                                printf("reply_mbuf %p nmc_head %p\n", reply_mbuf, nmc->nmc_mhead);
                                error = EBADRPC;                        // returns as GARBAGEARGS
                                goto nfsmout;
                        }
                        break;
                }
        } else {
                uint32_t verflen;
                /*
                 * If the proc is RPCSEC_GSS_INIT or RPCSEC_GSS_CONTINUE_INIT
                 * then we expect a null verifier.
                 */
                nfsm_chain_get_32(error, nmc, flavor);
                nfsm_chain_get_32(error, nmc, verflen);
                if (error || flavor != RPCAUTH_NULL || verflen > 0) {
                        error = NFSERR_AUTHERR | RPCSEC_GSS_CREDPROBLEM;
                }
                if (error) {
                        if (proc == RPCSEC_GSS_INIT) {
                                lck_mtx_destroy(&cp->gss_svc_mtx, &nfs_gss_svc_grp);
                                FREE(cp, M_TEMP);
                                cp = NULL;
                        }
                        goto nfsmout;
                }
        }

        nd->nd_gss_context = cp;
        return 0;
nfsmout:
        if (cp) {
                nfs_gss_svc_ctx_deref(cp);
        }
        return error;
}

/*
 * Insert the server's verifier into the RPC reply header.
 * It contains a signed checksum of the sequence number that
 * was received in the RPC call.
 * Then go on to add integrity or privacy if necessary.
 */
int
nfs_gss_svc_verf_put(struct nfsrv_descript *nd, struct nfsm_chain *nmc)
{
        struct nfs_gss_svc_ctx *cp;
        int error = 0;
        gss_buffer_desc cksum, seqbuf;
        uint32_t network_seqnum;
        cp = nd->nd_gss_context;
        uint32_t major;

        if (cp->gss_svc_major != GSS_S_COMPLETE) {
                /*
                 * If the context isn't yet complete
                 * then return a null verifier.
                 */
                nfsm_chain_add_32(error, nmc, RPCAUTH_NULL);
                nfsm_chain_add_32(error, nmc, 0);
                return error;
        }

        /*
         * Compute checksum of the request seq number
         * If it's the final reply of context setup
         * then return the checksum of the context
         * window size.
         */
        seqbuf.length = NFSX_UNSIGNED;
        if (cp->gss_svc_proc == RPCSEC_GSS_INIT ||
            cp->gss_svc_proc == RPCSEC_GSS_CONTINUE_INIT) {
                network_seqnum = htonl(cp->gss_svc_seqwin);
        } else {
                network_seqnum = htonl(nd->nd_gss_seqnum);
        }
        seqbuf.value = &network_seqnum;

        major = gss_krb5_get_mic((uint32_t *)&error, cp->gss_svc_ctx_id, 0, &seqbuf, &cksum);
        if (major != GSS_S_COMPLETE) {
                return error;
        }

        /*
         * Now wrap it in a token and add
         * the verifier to the reply.
         */
        nfsm_chain_add_32(error, nmc, RPCSEC_GSS);
        nfsm_chain_add_32(error, nmc, cksum.length);
        nfsm_chain_add_opaque(error, nmc, cksum.value, cksum.length);
        gss_release_buffer(NULL, &cksum);

        return error;
}

/*
 * The results aren't available yet, but if they need to be
 * checksummed for integrity protection or encrypted, then
 * we can record the start offset here, insert a place-holder
 * for the results length, as well as the sequence number.
 * The rest of the work is done later by nfs_gss_svc_protect_reply()
 * when the results are available.
 */
int
nfs_gss_svc_prepare_reply(struct nfsrv_descript *nd, struct nfsm_chain *nmc)
{
        struct nfs_gss_svc_ctx *cp = nd->nd_gss_context;
        int error = 0;

        if (cp->gss_svc_proc == RPCSEC_GSS_INIT ||
            cp->gss_svc_proc == RPCSEC_GSS_CONTINUE_INIT) {
                return 0;
        }

        switch (nd->nd_sec) {
        case RPCAUTH_KRB5:
                /* Nothing to do */
                break;
        case RPCAUTH_KRB5I:
        case RPCAUTH_KRB5P:
                nd->nd_gss_mb = nmc->nmc_mcur;                  // record current mbuf
                nfsm_chain_finish_mbuf(error, nmc);             // split the chain here
                break;
        }

        return error;
}

/*
 * The results are checksummed or encrypted for return to the client
 */
int
nfs_gss_svc_protect_reply(struct nfsrv_descript *nd, mbuf_t mrep __unused)
{
        struct nfs_gss_svc_ctx *cp = nd->nd_gss_context;
        struct nfsm_chain nmrep_res, *nmc_res = &nmrep_res;
        mbuf_t mb, results;
        uint32_t reslen;
        int error = 0;

        /* XXX
         * Using a reference to the mbuf where we previously split the reply
         * mbuf chain, we split the mbuf chain argument into two mbuf chains,
         * one that allows us to prepend a length field or token, (nmc_pre)
         * and the second which holds just the results that we're going to
         * checksum and/or encrypt.  When we're done, we join the chains back
         * together.
         */

        mb = nd->nd_gss_mb;                             // the mbuf where we split
        results = mbuf_next(mb);                        // first mbuf in the results
        error = mbuf_setnext(mb, NULL);                 // disconnect the chains
        if (error) {
                return error;
        }
        nfs_gss_nfsm_chain(nmc_res, mb);                // set up the prepend chain
        nfsm_chain_build_done(error, nmc_res);
        if (error) {
                return error;
        }

        if (nd->nd_sec == RPCAUTH_KRB5I) {
                error = rpc_gss_integ_data_create(cp->gss_svc_ctx_id, &results, nd->nd_gss_seqnum, &reslen);
        } else {
                /* RPCAUTH_KRB5P */
                error = rpc_gss_priv_data_create(cp->gss_svc_ctx_id, &results, nd->nd_gss_seqnum, &reslen);
        }
        nfs_gss_append_chain(nmc_res, results); // Append the results mbufs
        nfsm_chain_build_done(error, nmc_res);

        return error;
}

/*
 * This function handles the context setup calls from the client.
 * Essentially, it implements the NFS null procedure calls when
 * an RPCSEC_GSS credential is used.
 * This is the context maintenance function.  It creates and
 * destroys server contexts at the whim of the client.
 * During context creation, it receives GSS-API tokens from the
 * client, passes them up to gssd, and returns a received token
 * back to the client in the null procedure reply.
 */
int
nfs_gss_svc_ctx_init(struct nfsrv_descript *nd, struct nfsrv_sock *slp, mbuf_t *mrepp)
{
        struct nfs_gss_svc_ctx *cp = NULL;
        int error = 0;
        int autherr = 0;
        struct nfsm_chain *nmreq, nmrep;
        int sz;

        nmreq = &nd->nd_nmreq;
        nfsm_chain_null(&nmrep);
        *mrepp = NULL;
        cp = nd->nd_gss_context;
        nd->nd_repstat = 0;

        switch (cp->gss_svc_proc) {
        case RPCSEC_GSS_INIT:
                nfs_gss_svc_ctx_insert(cp);
                OS_FALLTHROUGH;

        case RPCSEC_GSS_CONTINUE_INIT:
                /* Get the token from the request */
                nfsm_chain_get_32(error, nmreq, cp->gss_svc_tokenlen);
                cp->gss_svc_token = NULL;
                if (cp->gss_svc_tokenlen > 0 && cp->gss_svc_tokenlen < GSS_MAX_TOKEN_LEN) {
                        MALLOC(cp->gss_svc_token, u_char *, cp->gss_svc_tokenlen, M_TEMP, M_WAITOK);
                }
                if (cp->gss_svc_token == NULL) {
                        autherr = RPCSEC_GSS_CREDPROBLEM;
                        break;
                }
                nfsm_chain_get_opaque(error, nmreq, cp->gss_svc_tokenlen, cp->gss_svc_token);

                /* Use the token in a gss_accept_sec_context upcall */
                error = nfs_gss_svc_gssd_upcall(cp);
                if (error) {
                        autherr = RPCSEC_GSS_CREDPROBLEM;
                        if (error == NFSERR_EAUTH) {
                                error = 0;
                        }
                        break;
                }

                /*
                 * If the context isn't complete, pass the new token
                 * back to the client for another round.
                 */
                if (cp->gss_svc_major != GSS_S_COMPLETE) {
                        break;
                }

                /*
                 * Now the server context is complete.
                 * Finish setup.
                 */
                clock_get_uptime(&cp->gss_svc_incarnation);

                cp->gss_svc_seqwin = GSS_SVC_SEQWINDOW;
                MALLOC(cp->gss_svc_seqbits, uint32_t *,
                    nfsm_rndup((cp->gss_svc_seqwin + 7) / 8), M_TEMP, M_WAITOK | M_ZERO);
                if (cp->gss_svc_seqbits == NULL) {
                        autherr = RPCSEC_GSS_CREDPROBLEM;
                        break;
                }
                break;

        case RPCSEC_GSS_DATA:
                /* Just a nullproc ping - do nothing */
                break;

        case RPCSEC_GSS_DESTROY:
                /*
                 * Don't destroy the context immediately because
                 * other active requests might still be using it.
                 * Instead, schedule it for destruction after
                 * GSS_CTX_PEND time has elapsed.
                 */
                cp = nfs_gss_svc_ctx_find(cp->gss_svc_handle);
                if (cp != NULL) {
                        cp->gss_svc_handle = 0; // so it can't be found
                        lck_mtx_lock(&cp->gss_svc_mtx);
                        clock_interval_to_deadline(GSS_CTX_PEND, NSEC_PER_SEC,
                            &cp->gss_svc_incarnation);
                        lck_mtx_unlock(&cp->gss_svc_mtx);
                }
                break;
        default:
                autherr = RPCSEC_GSS_CREDPROBLEM;
                break;
        }

        /* Now build the reply  */

        if (nd->nd_repstat == 0) {
                nd->nd_repstat = autherr ? (NFSERR_AUTHERR | autherr) : NFSERR_RETVOID;
        }
        sz = 7 * NFSX_UNSIGNED + nfsm_rndup(cp->gss_svc_tokenlen); // size of results
        error = nfsrv_rephead(nd, slp, &nmrep, sz);
        *mrepp = nmrep.nmc_mhead;
        if (error || autherr) {
                goto nfsmout;
        }

        if (cp->gss_svc_proc == RPCSEC_GSS_INIT ||
            cp->gss_svc_proc == RPCSEC_GSS_CONTINUE_INIT) {
                nfsm_chain_add_32(error, &nmrep, sizeof(cp->gss_svc_handle));
                nfsm_chain_add_32(error, &nmrep, cp->gss_svc_handle);

                nfsm_chain_add_32(error, &nmrep, cp->gss_svc_major);
                nfsm_chain_add_32(error, &nmrep, cp->gss_svc_minor);
                nfsm_chain_add_32(error, &nmrep, cp->gss_svc_seqwin);

                nfsm_chain_add_32(error, &nmrep, cp->gss_svc_tokenlen);
                if (cp->gss_svc_token != NULL) {
                        nfsm_chain_add_opaque(error, &nmrep, cp->gss_svc_token, cp->gss_svc_tokenlen);
                        FREE(cp->gss_svc_token, M_TEMP);
                        cp->gss_svc_token = NULL;
                }
        }

nfsmout:
        if (autherr != 0) {
                nd->nd_gss_context = NULL;
                LIST_REMOVE(cp, gss_svc_entries);
                if (cp->gss_svc_seqbits != NULL) {
                        FREE(cp->gss_svc_seqbits, M_TEMP);
                }
                if (cp->gss_svc_token != NULL) {
                        FREE(cp->gss_svc_token, M_TEMP);
                }
                lck_mtx_destroy(&cp->gss_svc_mtx, &nfs_gss_svc_grp);
                FREE(cp, M_TEMP);
        }

        nfsm_chain_build_done(error, &nmrep);
        if (error) {
                nfsm_chain_cleanup(&nmrep);
                *mrepp = NULL;
        }
        return error;
}

/*
 * This is almost a mirror-image of the client side upcall.
 * It passes and receives a token, but invokes gss_accept_sec_context.
 * If it's the final call of the context setup, then gssd also returns
 * the session key and the user's UID.
 */
static int
nfs_gss_svc_gssd_upcall(struct nfs_gss_svc_ctx *cp)
{
        kern_return_t kr;
        mach_port_t mp;
        int retry_cnt = 0;
        gssd_byte_buffer octx = NULL;
        uint32_t lucidlen = 0;
        void *lucid_ctx_buffer;
        uint32_t ret_flags;
        vm_map_copy_t itoken = NULL;
        gssd_byte_buffer otoken = NULL;
        mach_msg_type_number_t otokenlen;
        int error = 0;
        char svcname[] = "nfs";

        kr = host_get_gssd_port(host_priv_self(), &mp);
        if (kr != KERN_SUCCESS) {
                printf("nfs_gss_svc_gssd_upcall: can't get gssd port, status %x (%d)\n", kr, kr);
                goto out;
        }
        if (!IPC_PORT_VALID(mp)) {
                printf("nfs_gss_svc_gssd_upcall: gssd port not valid\n");
                goto out;
        }

        if (cp->gss_svc_tokenlen > 0) {
                nfs_gss_mach_alloc_buffer(cp->gss_svc_token, cp->gss_svc_tokenlen, &itoken);
        }

retry:
        printf("Calling mach_gss_accept_sec_context\n");
        kr = mach_gss_accept_sec_context(
                mp,
                (gssd_byte_buffer) itoken, (mach_msg_type_number_t) cp->gss_svc_tokenlen,
                svcname,
                0,
                &cp->gss_svc_context,
                &cp->gss_svc_cred_handle,
                &ret_flags,
                &cp->gss_svc_uid,
                cp->gss_svc_gids,
                &cp->gss_svc_ngroups,
                &octx, (mach_msg_type_number_t *) &lucidlen,
                &otoken, &otokenlen,
                &cp->gss_svc_major,
                &cp->gss_svc_minor);

        printf("mach_gss_accept_sec_context returned %d\n", kr);
        if (kr != KERN_SUCCESS) {
                printf("nfs_gss_svc_gssd_upcall failed: %x (%d)\n", kr, kr);
                if (kr == MIG_SERVER_DIED && cp->gss_svc_context == 0 &&
                    retry_cnt++ < NFS_GSS_MACH_MAX_RETRIES) {
                        if (cp->gss_svc_tokenlen > 0) {
                                nfs_gss_mach_alloc_buffer(cp->gss_svc_token, cp->gss_svc_tokenlen, &itoken);
                        }
                        goto retry;
                }
                host_release_special_port(mp);
                goto out;
        }

        host_release_special_port(mp);

        if (lucidlen > 0) {
                if (lucidlen > MAX_LUCIDLEN) {
                        printf("nfs_gss_svc_gssd_upcall: bad context length (%d)\n", lucidlen);
                        vm_map_copy_discard((vm_map_copy_t) octx);
                        vm_map_copy_discard((vm_map_copy_t) otoken);
                        goto out;
                }
                MALLOC(lucid_ctx_buffer, void *, lucidlen, M_TEMP, M_WAITOK | M_ZERO);
                error = nfs_gss_mach_vmcopyout((vm_map_copy_t) octx, lucidlen, lucid_ctx_buffer);
                if (error) {
                        vm_map_copy_discard((vm_map_copy_t) otoken);
                        FREE(lucid_ctx_buffer, M_TEMP);
                        goto out;
                }
                if (cp->gss_svc_ctx_id) {
                        gss_krb5_destroy_context(cp->gss_svc_ctx_id);
                }
                cp->gss_svc_ctx_id = gss_krb5_make_context(lucid_ctx_buffer, lucidlen);
                if (cp->gss_svc_ctx_id == NULL) {
                        printf("Failed to make context from lucid_ctx_buffer\n");
                        goto out;
                }
        }

        /* Free context token used as input */
        if (cp->gss_svc_token) {
                FREE(cp->gss_svc_token, M_TEMP);
        }
        cp->gss_svc_token = NULL;
        cp->gss_svc_tokenlen = 0;

        if (otokenlen > 0) {
                /* Set context token to gss output token */
                MALLOC(cp->gss_svc_token, u_char *, otokenlen, M_TEMP, M_WAITOK);
                if (cp->gss_svc_token == NULL) {
                        printf("nfs_gss_svc_gssd_upcall: could not allocate %d bytes\n", otokenlen);
                        vm_map_copy_discard((vm_map_copy_t) otoken);
                        return ENOMEM;
                }
                error = nfs_gss_mach_vmcopyout((vm_map_copy_t) otoken, otokenlen, cp->gss_svc_token);
                if (error) {
                        FREE(cp->gss_svc_token, M_TEMP);
                        cp->gss_svc_token = NULL;
                        return NFSERR_EAUTH;
                }
                cp->gss_svc_tokenlen = otokenlen;
        }

        return 0;

out:
        FREE(cp->gss_svc_token, M_TEMP);
        cp->gss_svc_tokenlen = 0;
        cp->gss_svc_token = NULL;

        return NFSERR_EAUTH;
}

/*
 * Validate the sequence number in the credential as described
 * in RFC 2203 Section 5.3.3.1
 *
 * Here the window of valid sequence numbers is represented by
 * a bitmap.  As each sequence number is received, its bit is
 * set in the bitmap.  An invalid sequence number lies below
 * the lower bound of the window, or is within the window but
 * has its bit already set.
 */
static int
nfs_gss_svc_seqnum_valid(struct nfs_gss_svc_ctx *cp, uint32_t seq)
{
        uint32_t *bits = cp->gss_svc_seqbits;
        uint32_t win = cp->gss_svc_seqwin;
        uint32_t i;

        lck_mtx_lock(&cp->gss_svc_mtx);

        /*
         * If greater than the window upper bound,
         * move the window up, and set the bit.
         */
        if (seq > cp->gss_svc_seqmax) {
                if (seq - cp->gss_svc_seqmax > win) {
                        bzero(bits, nfsm_rndup((win + 7) / 8));
                } else {
                        for (i = cp->gss_svc_seqmax + 1; i < seq; i++) {
                                win_resetbit(bits, i % win);
                        }
                }
                win_setbit(bits, seq % win);
                cp->gss_svc_seqmax = seq;
                lck_mtx_unlock(&cp->gss_svc_mtx);
                return 1;
        }

        /*
         * Invalid if below the lower bound of the window
         */
        if (seq <= cp->gss_svc_seqmax - win) {
                lck_mtx_unlock(&cp->gss_svc_mtx);
                return 0;
        }

        /*
         * In the window, invalid if the bit is already set
         */
        if (win_getbit(bits, seq % win)) {
                lck_mtx_unlock(&cp->gss_svc_mtx);
                return 0;
        }
        win_setbit(bits, seq % win);
        lck_mtx_unlock(&cp->gss_svc_mtx);
        return 1;
}

/*
 * Drop a reference to a context
 *
 * Note that it's OK for the context to exist
 * with a refcount of zero.  The refcount isn't
 * checked until we're about to reap an expired one.
 */
void
nfs_gss_svc_ctx_deref(struct nfs_gss_svc_ctx *cp)
{
        lck_mtx_lock(&cp->gss_svc_mtx);
        if (cp->gss_svc_refcnt > 0) {
                cp->gss_svc_refcnt--;
        } else {
                printf("nfs_gss_ctx_deref: zero refcount\n");
        }
        lck_mtx_unlock(&cp->gss_svc_mtx);
}

/*
 * Called at NFS server shutdown - destroy all contexts
 */
void
nfs_gss_svc_cleanup(void)
{
        struct nfs_gss_svc_ctx_hashhead *head;
        struct nfs_gss_svc_ctx *cp, *ncp;
        int i;

        lck_mtx_lock(&nfs_gss_svc_ctx_mutex);

        /*
         * Run through all the buckets
         */
        for (i = 0; i < SVC_CTX_HASHSZ; i++) {
                /*
                 * Remove and free all entries in the bucket
                 */
                head = &nfs_gss_svc_ctx_hashtbl[i];
                LIST_FOREACH_SAFE(cp, head, gss_svc_entries, ncp) {
                        LIST_REMOVE(cp, gss_svc_entries);
                        if (cp->gss_svc_seqbits) {
                                FREE(cp->gss_svc_seqbits, M_TEMP);
                        }
                        lck_mtx_destroy(&cp->gss_svc_mtx, &nfs_gss_svc_grp);
                        FREE(cp, M_TEMP);
                }
        }

        lck_mtx_unlock(&nfs_gss_svc_ctx_mutex);
}

#endif /* CONFIG_NFS_SERVER */


/*************
 * The following functions are used by both client and server.
 */

/*
 * Release a host special port that was obtained by host_get_special_port
 * or one of its macros (host_get_gssd_port in this case).
 * This really should be in a public kpi.
 */

/* This should be in a public header if this routine is not */
extern void ipc_port_release_send(ipc_port_t);
extern ipc_port_t ipc_port_copy_send(ipc_port_t);

static void
host_release_special_port(mach_port_t mp)
{
        if (IPC_PORT_VALID(mp)) {
                ipc_port_release_send(mp);
        }
}

static mach_port_t
host_copy_special_port(mach_port_t mp)
{
        return ipc_port_copy_send(mp);
}

/*
 * The token that is sent and received in the gssd upcall
 * has unbounded variable length.  Mach RPC does not pass
 * the token in-line.  Instead it uses page mapping to handle
 * these parameters.  This function allocates a VM buffer
 * to hold the token for an upcall and copies the token
 * (received from the client) into it.  The VM buffer is
 * marked with a src_destroy flag so that the upcall will
 * automatically de-allocate the buffer when the upcall is
 * complete.
 */
static void
nfs_gss_mach_alloc_buffer(u_char *buf, size_t buflen, vm_map_copy_t *addr)
{
        kern_return_t kr;
        vm_offset_t kmem_buf;
        vm_size_t tbuflen;

        *addr = NULL;
        if (buf == NULL || buflen == 0) {
                return;
        }

        tbuflen = vm_map_round_page(buflen,
            vm_map_page_mask(ipc_kernel_map));

        if (tbuflen < buflen) {
                printf("nfs_gss_mach_alloc_buffer: vm_map_round_page failed\n");
                return;
        }

        kr = vm_allocate_kernel(ipc_kernel_map, &kmem_buf, tbuflen, VM_FLAGS_ANYWHERE, VM_KERN_MEMORY_FILE);
        if (kr != 0) {
                printf("nfs_gss_mach_alloc_buffer: vm_allocate failed\n");
                return;
        }

        kr = vm_map_wire_kernel(ipc_kernel_map,
            vm_map_trunc_page(kmem_buf,
            vm_map_page_mask(ipc_kernel_map)),
            vm_map_round_page(kmem_buf + tbuflen,
            vm_map_page_mask(ipc_kernel_map)),
            VM_PROT_READ | VM_PROT_WRITE, VM_KERN_MEMORY_FILE, FALSE);
        if (kr != 0) {
                printf("nfs_gss_mach_alloc_buffer: vm_map_wire failed\n");
                return;
        }

        bcopy(buf, (void *) kmem_buf, buflen);
        // Shouldn't need to bzero below since vm_allocate returns zeroed pages
        // bzero(kmem_buf + buflen, tbuflen - buflen);

        kr = vm_map_unwire(ipc_kernel_map,
            vm_map_trunc_page(kmem_buf,
            vm_map_page_mask(ipc_kernel_map)),
            vm_map_round_page(kmem_buf + tbuflen,
            vm_map_page_mask(ipc_kernel_map)),
            FALSE);
        if (kr != 0) {
                printf("nfs_gss_mach_alloc_buffer: vm_map_unwire failed\n");
                return;
        }

        kr = vm_map_copyin(ipc_kernel_map, (vm_map_address_t) kmem_buf,
            (vm_map_size_t) buflen, TRUE, addr);
        if (kr != 0) {
                printf("nfs_gss_mach_alloc_buffer: vm_map_copyin failed\n");
                return;
        }
}

/*
 * Here we handle a token received from the gssd via an upcall.
 * The received token resides in an allocate VM buffer.
 * We copy the token out of this buffer to a chunk of malloc'ed
 * memory of the right size, then de-allocate the VM buffer.
 */
static int
nfs_gss_mach_vmcopyout(vm_map_copy_t in, uint32_t len, u_char *out)
{
        vm_map_offset_t map_data;
        vm_offset_t data;
        int error;

        error = vm_map_copyout(ipc_kernel_map, &map_data, in);
        if (error) {
                return error;
        }

        data = CAST_DOWN(vm_offset_t, map_data);
        bcopy((void *) data, out, len);
        vm_deallocate(ipc_kernel_map, data, len);

        return 0;
}

/*
 * Return the number of bytes in an mbuf chain.
 */
static int
nfs_gss_mchain_length(mbuf_t mhead)
{
        mbuf_t mb;
        int len = 0;

        for (mb = mhead; mb; mb = mbuf_next(mb)) {
                len += mbuf_len(mb);
        }

        return len;
}

/*
 * Append an args or results mbuf chain to the header chain
 */
static int
nfs_gss_append_chain(struct nfsm_chain *nmc, mbuf_t mc)
{
        int error = 0;
        mbuf_t mb, tail;

        /* Connect the mbuf chains */
        error = mbuf_setnext(nmc->nmc_mcur, mc);
        if (error) {
                return error;
        }

        /* Find the last mbuf in the chain */
        tail = NULL;
        for (mb = mc; mb; mb = mbuf_next(mb)) {
                tail = mb;
        }

        nmc->nmc_mcur = tail;
        nmc->nmc_ptr = (caddr_t) mbuf_data(tail) + mbuf_len(tail);
        nmc->nmc_left = mbuf_trailingspace(tail);

        return 0;
}

#if CONFIG_NFS_SERVER /* Only used by CONFIG_NFS_SERVER */
/*
 * Convert an mbuf chain to an NFS mbuf chain
 */
static void
nfs_gss_nfsm_chain(struct nfsm_chain *nmc, mbuf_t mc)
{
        mbuf_t mb, tail;

        /* Find the last mbuf in the chain */
        tail = NULL;
        for (mb = mc; mb; mb = mbuf_next(mb)) {
                tail = mb;
        }

        nmc->nmc_mhead = mc;
        nmc->nmc_mcur = tail;
        nmc->nmc_ptr = (caddr_t) mbuf_data(tail) + mbuf_len(tail);
        nmc->nmc_left = mbuf_trailingspace(tail);
        nmc->nmc_flags = 0;
}
#endif /* CONFIG_NFS_SERVER */


#if 0
#define DISPLAYLEN 16
#define MAXDISPLAYLEN 256

static void
hexdump(const char *msg, void *data, size_t len)
{
        size_t i, j;
        u_char *d = data;
        char *p, disbuf[3 * DISPLAYLEN + 1];

        printf("NFS DEBUG %s len=%d:\n", msg, (uint32_t)len);
        if (len > MAXDISPLAYLEN) {
                len = MAXDISPLAYLEN;
        }

        for (i = 0; i < len; i += DISPLAYLEN) {
                for (p = disbuf, j = 0; (j + i) < len && j < DISPLAYLEN; j++, p += 3) {
                        snprintf(p, 4, "%02x ", d[i + j]);
                }
                printf("\t%s\n", disbuf);
        }
}
#endif

#endif /* CONFIG_NFS */