Differential D22837 Diff 78088 head/sys/dev/random/fenestrasX/fx_rng.c

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head/sys/dev/random/fenestrasX/fx_rng.c

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				/*-
				* 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);
				}