/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright (c) 2019 Conrad Meyer * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #define CHACHA_EMBED #define KEYSTREAM_ONLY #define CHACHA_NONCE0_CTR128 #include #include #include #include #include #include #include #include #include #include _Static_assert(FX_CHACHA20_KEYSIZE == RANDOM_KEYSIZE, ""); #include 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); }