[apple/xnu.git] / osfmk / prng / random.c

/*
 * Copyright (c) 2013 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.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

#include <mach/machine.h>
#include <mach/processor.h>
#include <kern/processor.h>
#include <kern/cpu_data.h>
#include <kern/cpu_number.h>
#include <kern/kalloc.h>
#include <kern/machine.h>
#include <kern/misc_protos.h>
#include <kern/startup.h>
#include <kern/sched.h>
#include <kern/thread.h>
#include <kern/thread_call.h>
#include <machine/cpu_data.h>
#include <machine/simple_lock.h>
#include <vm/pmap.h>
#include <vm/vm_page.h>
#include <sys/kdebug.h>
#include <sys/random.h>

#include <prng/random.h>
#include <corecrypto/ccdrbg.h>
#include <corecrypto/ccsha1.h>

#include <pexpert/pexpert.h>
#include <console/serial_protos.h>
#include <IOKit/IOPlatformExpert.h>

static lck_grp_t *gPRNGGrp;
static lck_attr_t *gPRNGAttr;
static lck_grp_attr_t *gPRNGGrpAttr;
static lck_mtx_t *gPRNGMutex = NULL;

typedef struct prngContext {
        struct ccdrbg_info      *infop;
        struct ccdrbg_state     *statep;
        uint64_t                bytes_generated;
        uint64_t                bytes_reseeded;
} *prngContextp;

ccdrbg_factory_t prng_ccdrbg_factory = NULL;

entropy_data_t  EntropyData = { .index_ptr = EntropyData.buffer };

boolean_t               erandom_seed_set = FALSE;
char                    erandom_seed[EARLY_RANDOM_SEED_SIZE];
typedef struct ccdrbg_state ccdrbg_state_t;
uint8_t                 master_erandom_state[EARLY_RANDOM_STATE_STATIC_SIZE];
ccdrbg_state_t          *erandom_state[MAX_CPUS];
struct ccdrbg_info      erandom_info;
decl_simple_lock_data(,entropy_lock);

struct ccdrbg_nisthmac_custom erandom_custom = {
        .di = &ccsha1_eay_di,
        .strictFIPS = 0,
};

static void read_erandom(void *buffer, u_int numBytes); /* Forward */

void 
entropy_buffer_read(char                *buffer,
                    unsigned int        *count)
{
        boolean_t       current_state;
        unsigned int    i, j;

        if (!erandom_seed_set) {
                panic("early_random was never invoked");
        }

        if ((*count) > (ENTROPY_BUFFER_SIZE * sizeof(unsigned int)))
                *count = ENTROPY_BUFFER_SIZE * sizeof(unsigned int);

        current_state = ml_set_interrupts_enabled(FALSE);
#if defined (__x86_64__)
        simple_lock(&entropy_lock);
#endif

        memcpy((char *) buffer, (char *) EntropyData.buffer, *count);

        for (i = 0, j = (ENTROPY_BUFFER_SIZE - 1); i < ENTROPY_BUFFER_SIZE; j = i, i++)
                EntropyData.buffer[i] = EntropyData.buffer[i] ^ EntropyData.buffer[j];

#if defined (__x86_64__)
        simple_unlock(&entropy_lock);
#endif
        (void) ml_set_interrupts_enabled(current_state);

#if DEVELOPMENT || DEBUG
        uint32_t        *word = (uint32_t *) (void *) buffer;
        /* Good for both 32-bit and 64-bit kernels. */
        for (i = 0; i < ENTROPY_BUFFER_SIZE; i += 4)
                /* 
                 * We use "EARLY" here so that we can grab early entropy on
                 * ARM, where tracing is not started until after PRNG is
                 * initialized.
                */
                KERNEL_DEBUG_EARLY(ENTROPY_READ(i/4),
                        word[i+0], word[i+1], word[i+2], word[i+3]);
#endif
}

/*
 * Return a uniformly distributed 64-bit random number.
 *
 * This interface should have minimal dependencies on kernel
 * services, and thus be available very early in the life
 * of the kernel.
 * This provides cryptographically secure randomness.
 * Each processor has its own generator instance.
 * It is seeded (lazily) with entropy provided by the Booter.
*
 * For <rdar://problem/17292592> the algorithm switched from LCG to
 * NIST HMAC DBRG as follows:
 *  - When first called (on OSX this is very early while page tables are being
 *    built) early_random() calls ccdrbg_factory_hmac() to set-up a ccdbrg info
 *    structure.
 *  - The boot processor's ccdrbg state structure is a statically allocated area
 *    which is then initialized by calling the ccdbrg_init method.
 *    The initial entropy is 16 bytes of boot entropy.
 *    The nonce is the first 8 bytes of entropy xor'ed with a timestamp
 *    from ml_get_timebase().
 *    The personalization data provided is null. 
 *  - The first 64-bit random value is returned on the boot processor from
 *    an invocation of the ccdbrg_generate method.
 *  - Non-boot processor's DRBG state structures are allocated dynamically
 *    from prng_init(). Each is initialized with the same 16 bytes of entropy
 *    but with a different timestamped nonce and cpu number as personalization.
 *  - Subsequent calls to early_random() pass to read_erandom() to generate
 *    an 8-byte random value.  read_erandom() ensures that pre-emption is
 *    disabled and selects the DBRG state from the current processor.
 *    The ccdbrg_generate method is called for the required random output.
 *    If this method returns CCDRBG_STATUS_NEED_RESEED, the erandom_seed buffer
 *    is re-filled with kernel-harvested entropy and the ccdbrg_reseed method is
 *    called with this new entropy. The kernel panics if a reseed fails.
 */
uint64_t
early_random(void)
{
        uint32_t        cnt = 0;
        uint64_t        result;
        uint64_t        nonce;
        int             rc;
        ccdrbg_state_t  *state;

        if (!erandom_seed_set) {
                simple_lock_init(&entropy_lock,0);
                erandom_seed_set = TRUE;
                cnt = PE_get_random_seed((unsigned char *) EntropyData.buffer,
                                         sizeof(EntropyData.buffer));

                if (cnt < sizeof(EntropyData.buffer)) {
                        /*
                         * Insufficient entropy is fatal.  We must fill the
                         * entire entropy buffer during initializaton.
                         */
                        panic("EntropyData needed %lu bytes, but got %u.\n",
                                sizeof(EntropyData.buffer), cnt);
                }               

                /*
                 * Use some of the supplied entropy as a basis for early_random;
                 * reuse is ugly, but simplifies things. Ideally, we would guard
                 * early random values well enough that it isn't safe to attack
                 * them, but this cannot be guaranteed; thus, initial entropy
                 * can be considered 8 bytes weaker for a given boot if any
                 * early random values are conclusively determined.
                 *
                 * early_random_seed could be larger than EntopyData.buffer...
                 * but it won't be.
                 */
                bcopy(EntropyData.buffer, &erandom_seed, sizeof(erandom_seed));

                /* Init DRBG for NIST HMAC */
                ccdrbg_factory_nisthmac(&erandom_info, &erandom_custom);
                assert(erandom_info.size <= sizeof(master_erandom_state));
                state = (ccdrbg_state_t *) master_erandom_state;
                erandom_state[0] = state;

                /*
                 * Init our DBRG from the boot entropy and a nonce composed of
                 * a timestamp swizzled with the first 8 bytes of this entropy.
                 */
                assert(sizeof(erandom_seed) > sizeof(nonce));
                bcopy(erandom_seed, &nonce, sizeof(nonce));
                nonce ^= ml_get_timebase();
                rc = ccdrbg_init(&erandom_info, state,
                                 sizeof(erandom_seed), erandom_seed,
                                 sizeof(nonce), &nonce,
                                 0, NULL);
                assert(rc == CCDRBG_STATUS_OK);

                /* Generate output */
                rc = ccdrbg_generate(&erandom_info, state,
                                     sizeof(result), &result,
                                     0, NULL);
                assert(rc == CCDRBG_STATUS_OK);
        
                return result;
        };

        read_erandom(&result, sizeof(result));

        return result;
}

void
read_erandom(void *buffer, u_int numBytes)
{
        int             cpu;
        int             rc;
        uint32_t        cnt;
        ccdrbg_state_t  *state;

        mp_disable_preemption();
        cpu = cpu_number();
        state = erandom_state[cpu];
        assert(state);
        while (TRUE) {
                /* Generate output */
                rc = ccdrbg_generate(&erandom_info, state,
                                     numBytes, buffer,
                                     0, NULL);
                if (rc == CCDRBG_STATUS_OK)
                        break;
                if (rc == CCDRBG_STATUS_NEED_RESEED) {
                        /* It's time to reseed. Get more entropy */
                        cnt = sizeof(erandom_seed);
                        entropy_buffer_read(erandom_seed, &cnt);
                        assert(cnt == sizeof(erandom_seed));
                        rc = ccdrbg_reseed(&erandom_info, state,
                                           sizeof(erandom_seed), erandom_seed,
                                           0, NULL);
                        if (rc == CCDRBG_STATUS_OK)
                                continue;
                        panic("read_erandom reseed error %d\n", rc);
                }
                panic("read_erandom ccdrbg error %d\n", rc);
        }
        mp_enable_preemption();
}

void
read_frandom(void *buffer, u_int numBytes)
{
        char            *cp = (char *) buffer;
        int             nbytes;

        /*
         * Split up into requests for blocks smaller than
         * than the DBRG request limit. iThis limit is private but
         * for NISTHMAC it's known to be greater then 4096.
         */
        while (numBytes) {
                nbytes = MIN(numBytes, PAGE_SIZE);
                read_erandom(cp, nbytes);
                cp += nbytes;
                numBytes -= nbytes;
        }
}

/*
 * Register a DRBG factory routine to e used in constructing the kernel PRNG.
 * XXX to be called from the corecrypto kext.
 */
void
prng_factory_register(ccdrbg_factory_t factory)
{
        prng_ccdrbg_factory = factory;
        thread_wakeup((event_t) &prng_ccdrbg_factory);
}

void
prng_cpu_init(int cpu)
{       
        uint64_t        nonce;
        int             rc;
        ccdrbg_state_t  *state;
        prngContextp    pp;

        /*
         * Allocate state and initialize DBRG state for early_random()
         * for this processor, if necessary.
         */
        if (erandom_state[cpu] == NULL) {
                
                state = kalloc(erandom_info.size);
                if (state == NULL) {
                        panic("prng_init kalloc failed\n");
                }
                erandom_state[cpu] = state;

                /*
                 * Init our DBRG from boot entropy, nonce as timestamp xor'ed
                 * with the first 8 bytes of entropy, and use the cpu number
                 * as the personalization parameter.
                 */
                bcopy(erandom_seed, &nonce, sizeof(nonce));
                nonce ^= ml_get_timebase();
                rc = ccdrbg_init(&erandom_info, state,
                                 sizeof(erandom_seed), erandom_seed,
                                 sizeof(nonce), &nonce,
                                 sizeof(cpu), &cpu);
                assert(rc == CCDRBG_STATUS_OK);
        }

        /* Non-boot cpus use the master cpu's global context */
        if (cpu != master_cpu) {
                cpu_datap(cpu)->cpu_prng = master_prng_context();
                return;
        }

        assert(gPRNGMutex == NULL);             /* Once only, please */

        /* make a mutex to control access */
        gPRNGGrpAttr = lck_grp_attr_alloc_init();
        gPRNGGrp     = lck_grp_alloc_init("random", gPRNGGrpAttr);
        gPRNGAttr    = lck_attr_alloc_init();
        gPRNGMutex   = lck_mtx_alloc_init(gPRNGGrp, gPRNGAttr);

        pp = kalloc(sizeof(*pp));
        if (pp == NULL)
                panic("Unable to allocate prng context");
        pp->bytes_generated = 0;
        pp->bytes_reseeded = 0;
        pp->infop = NULL;

        /* XXX Temporary registration */
        prng_factory_register(ccdrbg_factory_yarrow);

        master_prng_context() = pp;
}

static ccdrbg_info_t *
prng_infop(prngContextp pp)
{
        lck_mtx_assert(gPRNGMutex, LCK_MTX_ASSERT_OWNED);

        /* Usual case: the info is all set */
        if (pp->infop)
                return pp->infop;

        /*
         * Possibly wait for the CCDRBG factory routune to be registered
         * by corecypto. But panic after waiting for more than 10 seconds.
         */
        while (prng_ccdrbg_factory == NULL ) {
                wait_result_t   wait_result;
                assert_wait_timeout((event_t) &prng_ccdrbg_factory, TRUE,
                                    10, NSEC_PER_USEC);
                lck_mtx_unlock(gPRNGMutex);
                wait_result = thread_block(THREAD_CONTINUE_NULL);
                if (wait_result == THREAD_TIMED_OUT)
                        panic("prng_ccdrbg_factory registration timeout");
                lck_mtx_lock(gPRNGMutex);
        }
        /* Check we didn't lose the set-up race */
        if (pp->infop)
                return pp->infop;

        pp->infop = (ccdrbg_info_t *) kalloc(sizeof(ccdrbg_info_t));
        if (pp->infop == NULL)
                panic("Unable to allocate prng info");

        prng_ccdrbg_factory(pp->infop, NULL);

        pp->statep = kalloc(pp->infop->size);
        if (pp->statep == NULL)
                panic("Unable to allocate prng state");

        char rdBuffer[ENTROPY_BUFFER_BYTE_SIZE];
        unsigned int bytesToInput = sizeof(rdBuffer);

        entropy_buffer_read(rdBuffer, &bytesToInput);

        (void) ccdrbg_init(pp->infop, pp->statep,
                           bytesToInput, rdBuffer,
                           0, NULL,
                           0, NULL);
        return pp->infop;
}

static void
Reseed(prngContextp pp)
{
        char            rdBuffer[ENTROPY_BUFFER_BYTE_SIZE];
        unsigned int    bytesToInput = sizeof(rdBuffer);

        entropy_buffer_read(rdBuffer, &bytesToInput);

        PRNG_CCDRBG((void) ccdrbg_reseed(pp->infop, pp->statep,
                                         bytesToInput, rdBuffer,
                                         0, NULL)); 

        pp->bytes_reseeded = pp->bytes_generated;
}


/* export good random numbers to the rest of the kernel */
void
read_random(void* buffer, u_int numbytes)
{
        prngContextp    pp;
        ccdrbg_info_t   *infop;
        int             ccdrbg_err;

        lck_mtx_lock(gPRNGMutex);

        pp = current_prng_context();
        infop = prng_infop(pp);

        /*
         * Call DRBG, reseeding and retrying if requested.
         */
        while (TRUE) {
                PRNG_CCDRBG(
                        ccdrbg_err = ccdrbg_generate(infop, pp->statep,
                                                     numbytes, buffer,
                                                     0, NULL));
                if (ccdrbg_err == CCDRBG_STATUS_OK)
                        break;
                if (ccdrbg_err == CCDRBG_STATUS_NEED_RESEED) {
                        Reseed(pp);
                        continue;
                }
                panic("read_random ccdrbg error %d\n", ccdrbg_err);
        }

        pp->bytes_generated += numbytes;
        lck_mtx_unlock(gPRNGMutex);
}

int
write_random(void* buffer, u_int numbytes)
{
#if 0
        int             retval = 0;
        prngContextp    pp;

        lck_mtx_lock(gPRNGMutex);

        pp = current_prng_context();

        if (ccdrbg_reseed(prng_infop(pp), pp->statep,
                          bytesToInput, rdBuffer, 0, NULL) != 0)
                retval = EIO;

        lck_mtx_unlock(gPRNGMutex);
        return retval;
#else
#pragma  unused(buffer, numbytes)
    return 0;
#endif
}