xnu-2782.1.97.tar.gz

[apple/xnu.git] / bsd / security / audit / audit.c

/*-
 * Copyright (c) 1999-2009 Apple Inc.
 * Copyright (c) 2006-2007 Robert N. M. Watson
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */
/*
 * NOTICE: This file was modified by McAfee Research in 2004 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

#include <sys/param.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/namei.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/queue.h>
#include <sys/systm.h>
#include <sys/time.h>
#include <sys/ucred.h>
#include <sys/uio.h>
#include <sys/unistd.h>
#include <sys/file_internal.h>
#include <sys/vnode_internal.h>
#include <sys/user.h>
#include <sys/syscall.h>
#include <sys/malloc.h>
#include <sys/un.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/vfs_context.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socketvar.h>

#include <bsm/audit.h>
#include <bsm/audit_internal.h>
#include <bsm/audit_kevents.h>

#include <security/audit/audit.h>
#include <security/audit/audit_bsd.h>
#include <security/audit/audit_private.h>

#include <mach/host_priv.h>
#include <mach/host_special_ports.h>
#include <mach/audit_triggers_server.h>

#include <kern/host.h>
#include <kern/kalloc.h>
#include <kern/zalloc.h>
#include <kern/wait_queue.h>
#include <kern/sched_prim.h>

#include <net/route.h>

#include <netinet/in.h>
#include <netinet/in_pcb.h>

#if CONFIG_AUDIT
MALLOC_DEFINE(M_AUDITDATA, "audit_data", "Audit data storage");
MALLOC_DEFINE(M_AUDITPATH, "audit_path", "Audit path storage");
MALLOC_DEFINE(M_AUDITTEXT, "audit_text", "Audit text storage");

/*
 * Audit control settings that are set/read by system calls and are hence
 * non-static.
 *
 * Define the audit control flags.
 */
int                     audit_enabled;
int                     audit_suspended;

int                     audit_syscalls;
au_class_t              audit_kevent_mask;

/*
 * Flags controlling behavior in low storage situations.  Should we panic if
 * a write fails?  Should we fail stop if we're out of disk space?
 */
int                     audit_panic_on_write_fail;
int                     audit_fail_stop;
int                     audit_argv;
int                     audit_arge;

/*
 * Are we currently "failing stop" due to out of disk space?
 */
int                     audit_in_failure;

/*
 * Global audit statistics.
 */
struct audit_fstat      audit_fstat;

/*
 * Preselection mask for non-attributable events.
 */
struct au_mask          audit_nae_mask;

/*
 * Mutex to protect global variables shared between various threads and
 * processes.
 */
struct mtx              audit_mtx;

/*
 * Queue of audit records ready for delivery to disk.  We insert new records
 * at the tail, and remove records from the head.  Also, a count of the
 * number of records used for checking queue depth.  In addition, a counter
 * of records that we have allocated but are not yet in the queue, which is
 * needed to estimate the total size of the combined set of records
 * outstanding in the system.
 */
struct kaudit_queue     audit_q;
int                     audit_q_len;
int                     audit_pre_q_len;

/*
 * Audit queue control settings (minimum free, low/high water marks, etc.)
 */
struct au_qctrl         audit_qctrl;

/*
 * Condition variable to signal to the worker that it has work to do: either
 * new records are in the queue, or a log replacement is taking place.
 */
struct cv               audit_worker_cv;

/*
 * Condition variable to signal when the worker is done draining the audit
 * queue.
 */
struct cv               audit_drain_cv;

/*
 * Condition variable to flag when crossing the low watermark, meaning that
 * threads blocked due to hitting the high watermark can wake up and continue
 * to commit records.
 */
struct cv               audit_watermark_cv;

/*
 * Condition variable for  auditing threads wait on when in fail-stop mode.
 * Threads wait on this CV forever (and ever), never seeing the light of day
 * again.
 */
static struct cv        audit_fail_cv;

static zone_t           audit_record_zone;

/*
 * Kernel audit information.  This will store the current audit address
 * or host information that the kernel will use when it's generating
 * audit records.  This data is modified by the A_GET{SET}KAUDIT auditon(2)
 * command.
 */
static struct auditinfo_addr    audit_kinfo;
static struct rwlock            audit_kinfo_lock;

#define KINFO_LOCK_INIT()       rw_init(&audit_kinfo_lock,              \
                                        "audit_kinfo_lock")
#define KINFO_RLOCK()           rw_rlock(&audit_kinfo_lock)
#define KINFO_WLOCK()           rw_wlock(&audit_kinfo_lock)
#define KINFO_RUNLOCK()         rw_runlock(&audit_kinfo_lock)
#define KINFO_WUNLOCK()         rw_wunlock(&audit_kinfo_lock)

void
audit_set_kinfo(struct auditinfo_addr *ak)
{

        KASSERT(ak->ai_termid.at_type == AU_IPv4 ||
            ak->ai_termid.at_type == AU_IPv6,
            ("audit_set_kinfo: invalid address type"));

        KINFO_WLOCK();
        bcopy(ak, &audit_kinfo, sizeof(audit_kinfo));
        KINFO_WUNLOCK();
}

void
audit_get_kinfo(struct auditinfo_addr *ak)
{

        KASSERT(audit_kinfo.ai_termid.at_type == AU_IPv4 ||
            audit_kinfo.ai_termid.at_type == AU_IPv6,
            ("audit_set_kinfo: invalid address type"));

        KINFO_RLOCK();
        bcopy(&audit_kinfo, ak, sizeof(*ak));
        KINFO_RUNLOCK();
}

/*
 * Construct an audit record for the passed thread.
 */
static void
audit_record_ctor(proc_t p, struct kaudit_record *ar)
{
        kauth_cred_t cred;

        bzero(ar, sizeof(*ar));
        ar->k_ar.ar_magic = AUDIT_RECORD_MAGIC;
        nanotime(&ar->k_ar.ar_starttime);

        if (PROC_NULL != p) {
                cred = kauth_cred_proc_ref(p);

                /*
                 * Export the subject credential.
                 */
                cru2x(cred, &ar->k_ar.ar_subj_cred);
                ar->k_ar.ar_subj_ruid = kauth_cred_getruid(cred);
                ar->k_ar.ar_subj_rgid = kauth_cred_getrgid(cred);
                ar->k_ar.ar_subj_egid = kauth_cred_getgid(cred);
                ar->k_ar.ar_subj_pid = p->p_pid;
                ar->k_ar.ar_subj_auid = cred->cr_audit.as_aia_p->ai_auid;
                ar->k_ar.ar_subj_asid = cred->cr_audit.as_aia_p->ai_asid;
                bcopy(&cred->cr_audit.as_mask, &ar->k_ar.ar_subj_amask,
                    sizeof(struct au_mask));
                bcopy(&cred->cr_audit.as_aia_p->ai_termid,
                    &ar->k_ar.ar_subj_term_addr, sizeof(struct au_tid_addr));
                kauth_cred_unref(&cred);
        }
}

static void
audit_record_dtor(struct kaudit_record *ar)
{

        if (ar->k_ar.ar_arg_upath1 != NULL)
                free(ar->k_ar.ar_arg_upath1, M_AUDITPATH);
        if (ar->k_ar.ar_arg_upath2 != NULL)
                free(ar->k_ar.ar_arg_upath2, M_AUDITPATH);
        if (ar->k_ar.ar_arg_kpath1 != NULL)
                free(ar->k_ar.ar_arg_kpath1, M_AUDITPATH);
        if (ar->k_ar.ar_arg_kpath2 != NULL)
                free(ar->k_ar.ar_arg_kpath2, M_AUDITPATH);
        if (ar->k_ar.ar_arg_text != NULL)
                free(ar->k_ar.ar_arg_text, M_AUDITTEXT);
        if (ar->k_ar.ar_arg_opaque != NULL)
                free(ar->k_ar.ar_arg_opaque, M_AUDITDATA);
        if (ar->k_ar.ar_arg_data != NULL)
                free(ar->k_ar.ar_arg_data, M_AUDITDATA);
        if (ar->k_udata != NULL)
                free(ar->k_udata, M_AUDITDATA);
        if (ar->k_ar.ar_arg_argv != NULL)
                free(ar->k_ar.ar_arg_argv, M_AUDITTEXT);
        if (ar->k_ar.ar_arg_envv != NULL)
                free(ar->k_ar.ar_arg_envv, M_AUDITTEXT);
}

/*
 * Initialize the Audit subsystem: configuration state, work queue,
 * synchronization primitives, worker thread, and trigger device node.  Also
 * call into the BSM assembly code to initialize it.
 */
void
audit_init(void)
{

        audit_enabled = 0;
        audit_syscalls = 0;
        audit_kevent_mask = 0;
        audit_suspended = 0;
        audit_panic_on_write_fail = 0;
        audit_fail_stop = 0;
        audit_in_failure = 0;
        audit_argv = 0;
        audit_arge = 0;

        audit_fstat.af_filesz = 0;      /* '0' means unset, unbounded. */
        audit_fstat.af_currsz = 0;
        audit_nae_mask.am_success = 0;
        audit_nae_mask.am_failure = 0;

        TAILQ_INIT(&audit_q);
        audit_q_len = 0;
        audit_pre_q_len = 0;
        audit_qctrl.aq_hiwater = AQ_HIWATER;
        audit_qctrl.aq_lowater = AQ_LOWATER;
        audit_qctrl.aq_bufsz = AQ_BUFSZ;
        audit_qctrl.aq_minfree = AU_FS_MINFREE;

        audit_kinfo.ai_termid.at_type = AU_IPv4;
        audit_kinfo.ai_termid.at_addr[0] = INADDR_ANY;

        _audit_lck_grp_init();
        mtx_init(&audit_mtx, "audit_mtx", NULL, MTX_DEF);
        KINFO_LOCK_INIT();
        cv_init(&audit_worker_cv, "audit_worker_cv");
        cv_init(&audit_drain_cv, "audit_drain_cv");
        cv_init(&audit_watermark_cv, "audit_watermark_cv");
        cv_init(&audit_fail_cv, "audit_fail_cv");

        audit_record_zone = zinit(sizeof(struct kaudit_record),
            AQ_HIWATER*sizeof(struct kaudit_record), 8192, "audit_zone");
#if CONFIG_MACF
        audit_mac_init();
#endif
        /* Init audit session subsystem. */
        audit_session_init();

        /* Initialize the BSM audit subsystem. */
        kau_init();

        /* audit_trigger_init(); */

        /* Start audit worker thread. */
        (void) audit_pipe_init();

        /* Start audit worker thread. */
        audit_worker_init();
}

/*
 * Drain the audit queue and close the log at shutdown.  Note that this can
 * be called both from the system shutdown path and also from audit
 * configuration syscalls, so 'arg' and 'howto' are ignored.
 */
void
audit_shutdown(void)
{

        audit_rotate_vnode(NULL, NULL);
}

/*
 * Return the current thread's audit record, if any.
 */
struct kaudit_record *
currecord(void)
{

        return (curthread()->uu_ar);
}

/*
 * XXXAUDIT: There are a number of races present in the code below due to
 * release and re-grab of the mutex.  The code should be revised to become
 * slightly less racy.
 *
 * XXXAUDIT: Shouldn't there be logic here to sleep waiting on available
 * pre_q space, suspending the system call until there is room?
 */
struct kaudit_record *
audit_new(int event, proc_t p, __unused struct uthread *uthread)
{
        struct kaudit_record *ar;
        int no_record;
        int audit_override;

        /*
         * Override the audit_suspended and audit_enabled if it always
         * audits session events.
         *
         * XXXss - This really needs to be a generalized call to a filter
         * interface so if other things that use the audit subsystem in the
         * future can simply plugged in.
         */
        audit_override = (AUE_SESSION_START == event ||
            AUE_SESSION_UPDATE == event || AUE_SESSION_END == event ||
            AUE_SESSION_CLOSE == event);
        
        mtx_lock(&audit_mtx);
        no_record = (audit_suspended || !audit_enabled);
        mtx_unlock(&audit_mtx);
        if (!audit_override && no_record)
                return (NULL);

        /*
         * Initialize the audit record header.
         * XXX: We may want to fail-stop if allocation fails.
         *
         * Note: the number of outstanding uncommitted audit records is
         * limited to the number of concurrent threads servicing system calls
         * in the kernel.
         */
        ar = zalloc(audit_record_zone);
        if (ar == NULL)
                return NULL;
        audit_record_ctor(p, ar);
        ar->k_ar.ar_event = event;

#if CONFIG_MACF
        if (PROC_NULL != p) {
                if (audit_mac_new(p, ar) != 0) {
                        zfree(audit_record_zone, ar);
                        return (NULL);
                }
        } else
                ar->k_ar.ar_mac_records = NULL;
#endif

        mtx_lock(&audit_mtx);
        audit_pre_q_len++;
        mtx_unlock(&audit_mtx);

        return (ar);
}

void
audit_free(struct kaudit_record *ar)
{

        audit_record_dtor(ar);
#if CONFIG_MACF
        if (NULL != ar->k_ar.ar_mac_records)
                audit_mac_free(ar);
#endif
        zfree(audit_record_zone, ar);
}

void
audit_commit(struct kaudit_record *ar, int error, int retval)
{
        au_event_t event;
        au_class_t class;
        au_id_t auid;
        int sorf;
        struct au_mask *aumask;
        int audit_override;

        if (ar == NULL)
                return;

        /*
         * Decide whether to commit the audit record by checking the error
         * value from the system call and using the appropriate audit mask.
         */
        if (ar->k_ar.ar_subj_auid == AU_DEFAUDITID)
                aumask = &audit_nae_mask;
        else
                aumask = &ar->k_ar.ar_subj_amask;

        if (error)
                sorf = AU_PRS_FAILURE;
        else
                sorf = AU_PRS_SUCCESS;

        switch(ar->k_ar.ar_event) {
        case AUE_OPEN_RWTC:
                /*
                 * The open syscall always writes a AUE_OPEN_RWTC event;
                 * change it to the proper type of event based on the flags
                 * and the error value.
                 */
                ar->k_ar.ar_event = audit_flags_and_error_to_openevent(
                    ar->k_ar.ar_arg_fflags, error);
                break;

        case AUE_OPEN_EXTENDED_RWTC:
                /*
                 * The open_extended syscall always writes a
                 * AUE_OPEN_EXTENDEDRWTC event; change it to the proper type of
                 * event based on the flags and the error value.
                 */
                ar->k_ar.ar_event = audit_flags_and_error_to_openextendedevent(
                    ar->k_ar.ar_arg_fflags, error);
                break;

        case AUE_OPENAT_RWTC:
                /*
                 * The openat syscall always writes a
                 * AUE_OPENAT_RWTC event; change it to the proper type of
                 * event based on the flags and the error value.
                 */
                ar->k_ar.ar_event = audit_flags_and_error_to_openatevent(
                    ar->k_ar.ar_arg_fflags, error);
                break;

        case AUE_OPENBYID_RWT:
                /*
                 * The openbyid syscall always writes a
                 * AUE_OPENBYID_RWT event; change it to the proper type of
                 * event based on the flags and the error value.
                 */
                ar->k_ar.ar_event = audit_flags_and_error_to_openbyidevent(
                    ar->k_ar.ar_arg_fflags, error);
                break;

        case AUE_SYSCTL:
                ar->k_ar.ar_event = audit_ctlname_to_sysctlevent(
                    ar->k_ar.ar_arg_ctlname, ar->k_ar.ar_valid_arg);
                break;

        case AUE_AUDITON:
                /* Convert the auditon() command to an event. */
                ar->k_ar.ar_event = auditon_command_event(ar->k_ar.ar_arg_cmd);
                break;

        case AUE_FCNTL:
                /* Convert some fcntl() commands to their own events. */
                ar->k_ar.ar_event = audit_fcntl_command_event(
                    ar->k_ar.ar_arg_cmd, ar->k_ar.ar_arg_fflags, error);
                break;
        }

        auid = ar->k_ar.ar_subj_auid;
        event = ar->k_ar.ar_event;
        class = au_event_class(event);

        /*
         * See if we need to override the audit_suspend and audit_enabled
         * flags.
         *
         * XXXss - This check needs to be generalized so new filters can
         * easily be added.
         */
        audit_override = (AUE_SESSION_START == event ||
            AUE_SESSION_UPDATE == event || AUE_SESSION_END == event ||
            AUE_SESSION_CLOSE == event);

        ar->k_ar_commit |= AR_COMMIT_KERNEL;
        if (au_preselect(event, class, aumask, sorf) != 0)
                ar->k_ar_commit |= AR_PRESELECT_TRAIL;
        if (audit_pipe_preselect(auid, event, class, sorf,
            ar->k_ar_commit & AR_PRESELECT_TRAIL) != 0)
                ar->k_ar_commit |= AR_PRESELECT_PIPE;
        if ((ar->k_ar_commit & (AR_PRESELECT_TRAIL | AR_PRESELECT_PIPE |
            AR_PRESELECT_USER_TRAIL | AR_PRESELECT_USER_PIPE |
            AR_PRESELECT_FILTER)) == 0) {
                mtx_lock(&audit_mtx);
                audit_pre_q_len--;
                mtx_unlock(&audit_mtx);
                audit_free(ar);
                return;
        }

        ar->k_ar.ar_errno = error;
        ar->k_ar.ar_retval = retval;
        nanotime(&ar->k_ar.ar_endtime);

        /*
         * Note: it could be that some records initiated while audit was
         * enabled should still be committed?
         */
        mtx_lock(&audit_mtx);
        if (!audit_override && (audit_suspended || !audit_enabled)) {
                audit_pre_q_len--;
                mtx_unlock(&audit_mtx);
                audit_free(ar);
                return;
        }

        /*
         * Constrain the number of committed audit records based on the
         * configurable parameter.
         */
        while (audit_q_len >= audit_qctrl.aq_hiwater)
                cv_wait(&audit_watermark_cv, &audit_mtx);

        TAILQ_INSERT_TAIL(&audit_q, ar, k_q);
        audit_q_len++;
        audit_pre_q_len--;
        cv_signal(&audit_worker_cv);
        mtx_unlock(&audit_mtx);
}

/*
 * audit_syscall_enter() is called on entry to each system call.  It is
 * responsible for deciding whether or not to audit the call (preselection),
 * and if so, allocating a per-thread audit record.  audit_new() will fill in
 * basic thread/credential properties.
 */
void
audit_syscall_enter(unsigned int code, proc_t proc, struct uthread *uthread)
{
        struct au_mask *aumask;
        au_class_t class;
        au_event_t event;
        au_id_t auid;
        kauth_cred_t cred;

        /*
         * In FreeBSD, each ABI has its own system call table, and hence
         * mapping of system call codes to audit events.  Convert the code to
         * an audit event identifier using the process system call table
         * reference.  In Darwin, there's only one, so we use the global
         * symbol for the system call table.  No audit record is generated
         * for bad system calls, as no operation has been performed.
         *
         * In Mac OS X, the audit events are stored in a table seperate from
         * the syscall table(s).  This table is generated by makesyscalls.sh
         * from syscalls.master and stored in audit_kevents.c.
         */
        if (code > NUM_SYSENT)
                return;
        event = sys_au_event[code];
        if (event == AUE_NULL)
                return;

        KASSERT(uthread->uu_ar == NULL,
            ("audit_syscall_enter: uthread->uu_ar != NULL"));

        /*
         * Check which audit mask to use; either the kernel non-attributable
         * event mask or the process audit mask.
         */
        cred = kauth_cred_proc_ref(proc);
        auid = cred->cr_audit.as_aia_p->ai_auid;
        if (auid == AU_DEFAUDITID) 
                aumask = &audit_nae_mask;
        else
                aumask = &cred->cr_audit.as_mask;

        /*
         * Allocate an audit record, if preselection allows it, and store in
         * the thread for later use.
         */
        class = au_event_class(event);
#if CONFIG_MACF
        /*
         * Note: audit_mac_syscall_enter() may call audit_new() and allocate
         * memory for the audit record (uu_ar).
         */
        if (audit_mac_syscall_enter(code, proc, uthread, cred, event) == 0)
                goto out;
#endif
        if (au_preselect(event, class, aumask, AU_PRS_BOTH)) {
                /*
                 * If we're out of space and need to suspend unprivileged
                 * processes, do that here rather than trying to allocate
                 * another audit record.
                 *
                 * Note: we might wish to be able to continue here in the
                 * future, if the system recovers.  That should be possible
                 * by means of checking the condition in a loop around
                 * cv_wait().  It might be desirable to reevaluate whether an
                 * audit record is still required for this event by
                 * re-calling au_preselect().
                 */
                if (audit_in_failure &&
                    suser(cred, &proc->p_acflag) != 0) {
                        cv_wait(&audit_fail_cv, &audit_mtx);
                        panic("audit_failing_stop: thread continued");
                }
                if (uthread->uu_ar == NULL)
                        uthread->uu_ar = audit_new(event, proc, uthread);
        } else if (audit_pipe_preselect(auid, event, class, AU_PRS_BOTH, 0)) {
                if (uthread->uu_ar == NULL)
                        uthread->uu_ar = audit_new(event, proc, uthread);
        } 

out:
        kauth_cred_unref(&cred);
}

/*
 * audit_syscall_exit() is called from the return of every system call, or in
 * the event of exit1(), during the execution of exit1().  It is responsible
 * for committing the audit record, if any, along with return condition.
 *
 * Note: The audit_syscall_exit() parameter list was modified to support
 * mac_audit_check_postselect(), which requires the syscall number.
 */
#if CONFIG_MACF
void
audit_syscall_exit(unsigned int code, int error, __unused proc_t proc,
    struct uthread *uthread)
#else
void
audit_syscall_exit(int error, __unsed proc_t proc, struct uthread *uthread)
#endif
{
        int retval;

        /*
         * Commit the audit record as desired; once we pass the record into
         * audit_commit(), the memory is owned by the audit subsystem.  The
         * return value from the system call is stored on the user thread.
         * If there was an error, the return value is set to -1, imitating
         * the behavior of the cerror routine.
         */
        if (error)
                retval = -1;
        else
                retval = uthread->uu_rval[0];

#if CONFIG_MACF
        if (audit_mac_syscall_exit(code, uthread, error, retval) != 0)
                goto out;
#endif
        audit_commit(uthread->uu_ar, error, retval);

out:
        uthread->uu_ar = NULL;
}

/*
 * Calls to set up and tear down audit structures used during Mach system
 * calls.
 */
void
audit_mach_syscall_enter(unsigned short event)
{
        struct uthread *uthread;
        proc_t proc;
        struct au_mask *aumask;
        kauth_cred_t cred;
        au_class_t class;
        au_id_t auid;

        if (event == AUE_NULL)
                return;

        uthread = curthread();
        if (uthread == NULL)
                return;

        proc = current_proc();
        if (proc == NULL)
                return;

        KASSERT(uthread->uu_ar == NULL,
            ("audit_mach_syscall_enter: uthread->uu_ar != NULL"));

        cred = kauth_cred_proc_ref(proc);
        auid = cred->cr_audit.as_aia_p->ai_auid;

        /*
         * Check which audit mask to use; either the kernel non-attributable
         * event mask or the process audit mask.
         */
        if (auid == AU_DEFAUDITID) 
                aumask = &audit_nae_mask;
        else
                aumask = &cred->cr_audit.as_mask;

        /*
         * Allocate an audit record, if desired, and store in the BSD thread
         * for later use.
         */
        class = au_event_class(event);
        if (au_preselect(event, class, aumask, AU_PRS_BOTH))
                uthread->uu_ar = audit_new(event, proc, uthread);
        else if (audit_pipe_preselect(auid, event, class, AU_PRS_BOTH, 0))
                uthread->uu_ar = audit_new(event, proc, uthread);
        else
                uthread->uu_ar = NULL;

        kauth_cred_unref(&cred);
}

void
audit_mach_syscall_exit(int retval, struct uthread *uthread)
{
        /*
         * The error code from Mach system calls is the same as the
         * return value
         */
        /* XXX Is the above statement always true? */
        audit_commit(uthread->uu_ar, retval, retval);
        uthread->uu_ar = NULL;
}

/*
 * kau_will_audit can be used by a security policy to determine
 * if an audit record will be stored, reducing wasted memory allocation
 * and string handling.
 */
int
kau_will_audit(void)
{

        return (audit_enabled && currecord() != NULL);
}

void
audit_proc_coredump(proc_t proc, char *path, int errcode)
{
        struct kaudit_record *ar;
        struct au_mask *aumask;
        au_class_t class;
        int ret, sorf;
        char **pathp;
        au_id_t auid;
        kauth_cred_t my_cred;
        struct uthread *uthread;

        ret = 0;

        /*
         * Make sure we are using the correct preselection mask.
         */
        my_cred = kauth_cred_proc_ref(proc);
        auid = my_cred->cr_audit.as_aia_p->ai_auid;
        if (auid == AU_DEFAUDITID) 
                aumask = &audit_nae_mask;
        else
                aumask = &my_cred->cr_audit.as_mask;
        kauth_cred_unref(&my_cred);
        /*
         * It's possible for coredump(9) generation to fail.  Make sure that
         * we handle this case correctly for preselection.
         */
        if (errcode != 0)
                sorf = AU_PRS_FAILURE;
        else
                sorf = AU_PRS_SUCCESS;
        class = au_event_class(AUE_CORE);
        if (au_preselect(AUE_CORE, class, aumask, sorf) == 0 &&
            audit_pipe_preselect(auid, AUE_CORE, class, sorf, 0) == 0)
                return;
        /*
         * If we are interested in seeing this audit record, allocate it.
         * Where possible coredump records should contain a pathname and arg32
         * (signal) tokens.
         */
        uthread = curthread();
        ar = audit_new(AUE_CORE, proc, uthread);
        if (path != NULL) {
                pathp = &ar->k_ar.ar_arg_upath1;
                *pathp = malloc(MAXPATHLEN, M_AUDITPATH, M_WAITOK);
                if (audit_canon_path(vfs_context_cwd(vfs_context_current()), path,
                    *pathp))
                        free(*pathp, M_AUDITPATH);
                else
                        ARG_SET_VALID(ar, ARG_UPATH1);
        }
        ar->k_ar.ar_arg_signum = proc->p_sigacts->ps_sig;
        ARG_SET_VALID(ar, ARG_SIGNUM);
        if (errcode != 0)
                ret = 1;
        audit_commit(ar, errcode, ret);
}
#endif /* CONFIG_AUDIT */