FreeBSD/Linux Kernel Cross Reference
sys/dev/random/fenestrasX/fx_rng.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2019 Conrad Meyer <cem@FreeBSD.org>
      *
      * 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.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND 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 THE AUTHOR OR 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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/fail.h>
    #include <sys/limits.h>
    #include <sys/lock.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/mutex.h>
    #include <sys/random.h>
    #include <sys/sdt.h>
    #include <sys/sysctl.h>
    #include <sys/systm.h>
    
    #include <machine/cpu.h>
    #include <machine/stdarg.h>
    
    #define CHACHA_EMBED
    #define KEYSTREAM_ONLY
    #define CHACHA_NONCE0_CTR128
    #include <crypto/chacha20/chacha.h>
    #include <crypto/rijndael/rijndael-api-fst.h>
    #include <crypto/sha2/sha256.h>
    
    #include <dev/random/hash.h>
    #include <dev/random/randomdev.h>
    #include <dev/random/random_harvestq.h>
    #include <dev/random/uint128.h>
    
    #include <dev/random/fenestrasX/fx_hash.h>
    #include <dev/random/fenestrasX/fx_priv.h>
    #include <dev/random/fenestrasX/fx_rng.h>
    
    _Static_assert(FX_CHACHA20_KEYSIZE == RANDOM_KEYSIZE, "");
    
    #include <crypto/chacha20/chacha.c>
    
    static void
    fxrng_rng_keystream_internal(struct chacha_ctx *prf, void *buf, size_t nbytes)
    {
            size_t chunklen;
    
            while (nbytes > 0) {
                    chunklen = MIN(nbytes,
                        rounddown((size_t)UINT32_MAX, CHACHA_BLOCKLEN));
    
                    chacha_encrypt_bytes(prf, NULL, buf, chunklen);
                    buf = (uint8_t *)buf + chunklen;
                    nbytes -= chunklen;
            }
    }
    
    /*
     * This subroutine pulls the counter out of Chacha, which for whatever reason
     * always encodes and decodes counters in a little endian format, and adds
     * 'addend' to it, saving the result in Chacha.
     */
    static void
    fxrng_chacha_nonce_add64(struct chacha_ctx *ctx, uint64_t addend)
    {
            uint128_t ctr;  /* Native-endian. */
    #if BYTE_ORDER == BIG_ENDIAN
            uint128_t lectr;
    
            chacha_ctrsave(ctx, (void *)&lectr);
            ctr = le128dec(&lectr);
    #else
            chacha_ctrsave(ctx, (void *)&ctr);
    #endif
    
            uint128_add64(&ctr, addend);
   
           /* chacha_ivsetup() does not modify the key, and we rely on that. */
   #if BYTE_ORDER == BIG_ENDIAN
           le128enc(&lectr, ctr);
           chacha_ivsetup(ctx, NULL, (const void *)&lectr);
           explicit_bzero(&lectr, sizeof(lectr));
   #else
           chacha_ivsetup(ctx, NULL, (const void *)&ctr);
   #endif
           explicit_bzero(&ctr, sizeof(ctr));
   }
   
   /*
    * Generate from the unbuffered source PRNG.
    *
    * Handles fast key erasure (rekeys the PRF with a generated key under lock).
    *
    * RNG lock is required on entry.  If return_unlocked is true, RNG lock will
    * be dropped on return.
    */
   void
   fxrng_rng_genrandom_internal(struct fxrng_basic_rng *rng, void *buf,
       size_t nbytes, bool return_unlocked)
   {
           struct chacha_ctx ctx_copy, *p_ctx;
           uint8_t newkey[FX_CHACHA20_KEYSIZE];
           size_t blockcount;
   
           FXRNG_RNG_ASSERT(rng);
   
           /* Save off the initial output of the generator for rekeying. */
           fxrng_rng_keystream_internal(&rng->rng_prf, newkey, sizeof(newkey));
   
           if (return_unlocked) {
                   memcpy(&ctx_copy, &rng->rng_prf, sizeof(ctx_copy));
                   p_ctx = &ctx_copy;
   
                   /*
                    * Forward the Chacha counter state over the blocks we promise
                    * to generate for the caller without the lock.
                    */
                   blockcount = howmany(nbytes, CHACHA_BLOCKLEN);
                   fxrng_chacha_nonce_add64(&rng->rng_prf, blockcount);
   
                   /* Re-key before dropping the lock. */
                   chacha_keysetup(&rng->rng_prf, newkey, sizeof(newkey) * 8);
                   explicit_bzero(newkey, sizeof(newkey));
   
                   FXRNG_RNG_UNLOCK(rng);
           } else {
                   p_ctx = &rng->rng_prf;
           }
   
           fxrng_rng_keystream_internal(p_ctx, buf, nbytes);
   
           if (return_unlocked) {
                   explicit_bzero(&ctx_copy, sizeof(ctx_copy));
                   FXRNG_RNG_ASSERT_NOT(rng);
           } else {
                   /* Re-key before exit. */
                   chacha_keysetup(&rng->rng_prf, newkey, sizeof(newkey) * 8);
                   explicit_bzero(newkey, sizeof(newkey));
                   FXRNG_RNG_ASSERT(rng);
           }
   }
   
   /*
    * Helper to reseed the root RNG, incorporating the existing RNG state.
    *
    * The root RNG is locked on entry and locked on return.
    */
   static void
   fxrng_rng_reseed_internal(struct fxrng_basic_rng *rng, bool seeded,
       const void *src, size_t sz, ...)
   {
           union {
                   uint8_t root_state[FX_CHACHA20_KEYSIZE];
                   uint8_t hash_out[FXRNG_HASH_SZ];
           } u;
           struct fxrng_hash mix;
           va_list ap;
   
           _Static_assert(FX_CHACHA20_KEYSIZE <= FXRNG_HASH_SZ, "");
   
           FXRNG_RNG_ASSERT(rng);
   
           fxrng_hash_init(&mix);
           if (seeded) {
                   fxrng_rng_keystream_internal(&rng->rng_prf, u.root_state,
                       sizeof(u.root_state));
                   fxrng_hash_update(&mix, u.root_state, sizeof(u.root_state));
           }
           fxrng_hash_update(&mix, src, sz);
   
           va_start(ap, sz);
           while (true) {
                   src = va_arg(ap, const void *);
                   if (src == NULL)
                           break;
                   sz = va_arg(ap, size_t);
                   fxrng_hash_update(&mix, src, sz);
           }
           va_end(ap);
   
           fxrng_hash_finish(&mix, u.hash_out, sizeof(u.hash_out));
   
           /*
            * Take the first keysize (32) bytes of our digest (64 bytes).  It is
            * also possible to just have Blake2 emit fewer bytes, but our wrapper
            * API doesn't provide that functionality and there isn't anything
            * obviously wrong with emitting more hash bytes.
            *
            * keysetup does not reset the embedded counter, and we rely on that
            * property.
            */
           chacha_keysetup(&rng->rng_prf, u.hash_out, FX_CHACHA20_KEYSIZE * 8);
   
           /* 'mix' zeroed by fxrng_hash_finish(). */
           explicit_bzero(u.hash_out, sizeof(u.hash_out));
   
           FXRNG_RNG_ASSERT(rng);
   }
   
   /*
    * Directly reseed the root RNG from a first-time entropy source,
    * incorporating the existing RNG state, called by fxrng_brng_src_reseed.
    *
    * The root RNG is locked on entry and locked on return.
    */
   void
   fxrng_rng_src_reseed(struct fxrng_basic_rng *rng,
       const struct harvest_event *event)
   {
           fxrng_rng_reseed_internal(rng, true, &event->he_somecounter,
               sizeof(event->he_somecounter), (const void *)event->he_entropy,
               (size_t)event->he_size, NULL);
   }
   
   /*
    * Reseed the root RNG from pooled entropy, incorporating the existing RNG
    * state, called by fxrng_brng_reseed.
    *
    * The root RNG is locked on entry and locked on return.
    */
   void
   fxrng_rng_reseed(struct fxrng_basic_rng *rng, bool seeded, const void *entr,
       size_t sz)
   {
           fxrng_rng_reseed_internal(rng, seeded, entr, sz, NULL);
   }

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