/* * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD * * SPDX-License-Identifier: Apache-2.0 */ /* * Copyright (C) 2017 by Intel Corporation, All Rights Reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * - Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * * - 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. * * - Neither the name of Intel Corporation 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 THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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. */ /* hmac_prng.c - TinyCrypt implementation of HMAC-PRNG */ #include #include #include #include /* * min bytes in the seed string. * MIN_SLEN*8 must be at least the expected security level. */ static const unsigned int MIN_SLEN = 32; /* * max bytes in the seed string; * SP800-90A specifies a maximum of 2^35 bits (i.e., 2^32 bytes). */ static const unsigned int MAX_SLEN = UINT32_MAX; /* * max bytes in the personalization string; * SP800-90A specifies a maximum of 2^35 bits (i.e., 2^32 bytes). */ static const unsigned int MAX_PLEN = UINT32_MAX; /* * max bytes in the additional_info string; * SP800-90A specifies a maximum of 2^35 bits (i.e., 2^32 bytes). */ static const unsigned int MAX_ALEN = UINT32_MAX; /* * max number of generates between re-seeds; * TinyCrypt accepts up to (2^32 - 1) which is the maximal value of * a 32-bit unsigned int variable, while SP800-90A specifies a maximum of 2^48. */ static const unsigned int MAX_GENS = UINT32_MAX; /* * maximum bytes per generate call; * SP800-90A specifies a maximum up to 2^19. */ static const unsigned int MAX_OUT = (1 << 19); /* * Assumes: prng != NULL, e != NULL, len >= 0. */ static void update(TCHmacPrng_t prng, const uint8_t *e, unsigned int len) { const uint8_t separator0 = 0x00; const uint8_t separator1 = 0x01; /* use current state, e and separator 0 to compute a new prng key: */ (void)tc_hmac_init(&prng->h); (void)tc_hmac_update(&prng->h, prng->v, sizeof(prng->v)); (void)tc_hmac_update(&prng->h, &separator0, sizeof(separator0)); (void)tc_hmac_update(&prng->h, e, len); (void)tc_hmac_final(prng->key, sizeof(prng->key), &prng->h); /* configure the new prng key into the prng's instance of hmac */ (void)tc_hmac_set_key(&prng->h, prng->key, sizeof(prng->key)); /* use the new key to compute a new state variable v */ (void)tc_hmac_init(&prng->h); (void)tc_hmac_update(&prng->h, prng->v, sizeof(prng->v)); (void)tc_hmac_final(prng->v, sizeof(prng->v), &prng->h); /* use current state, e and separator 1 to compute a new prng key: */ (void)tc_hmac_init(&prng->h); (void)tc_hmac_update(&prng->h, prng->v, sizeof(prng->v)); (void)tc_hmac_update(&prng->h, &separator1, sizeof(separator1)); (void)tc_hmac_update(&prng->h, e, len); (void)tc_hmac_final(prng->key, sizeof(prng->key), &prng->h); /* configure the new prng key into the prng's instance of hmac */ (void)tc_hmac_set_key(&prng->h, prng->key, sizeof(prng->key)); /* use the new key to compute a new state variable v */ (void)tc_hmac_init(&prng->h); (void)tc_hmac_update(&prng->h, prng->v, sizeof(prng->v)); (void)tc_hmac_final(prng->v, sizeof(prng->v), &prng->h); } int tc_hmac_prng_init(TCHmacPrng_t prng, const uint8_t *personalization, unsigned int plen) { /* input sanity check: */ if (prng == (TCHmacPrng_t) 0 || personalization == (uint8_t *) 0 || plen > MAX_PLEN) { return TC_CRYPTO_FAIL; } /* put the generator into a known state: */ _set(prng->key, 0x00, sizeof(prng->key)); _set(prng->v, 0x01, sizeof(prng->v)); tc_hmac_set_key(&prng->h, prng->key, sizeof(prng->key)); /* update assumes SOME key has been configured into HMAC */ update(prng, personalization, plen); /* force a reseed before allowing tc_hmac_prng_generate to succeed: */ prng->countdown = 0; return TC_CRYPTO_SUCCESS; } int tc_hmac_prng_reseed(TCHmacPrng_t prng, const uint8_t *seed, unsigned int seedlen, const uint8_t *additional_input, unsigned int additionallen) { /* input sanity check: */ if (prng == (TCHmacPrng_t) 0 || seed == (const uint8_t *) 0 || seedlen < MIN_SLEN || seedlen > MAX_SLEN) { return TC_CRYPTO_FAIL; } if (additional_input != (const uint8_t *) 0) { /* * Abort if additional_input is provided but has inappropriate * length */ if (additionallen == 0 || additionallen > MAX_ALEN) { return TC_CRYPTO_FAIL; } else { /* call update for the seed and additional_input */ update(prng, seed, seedlen); update(prng, additional_input, additionallen); } } else { /* call update only for the seed */ update(prng, seed, seedlen); } /* ... and enable hmac_prng_generate */ prng->countdown = MAX_GENS; return TC_CRYPTO_SUCCESS; } int tc_hmac_prng_generate(uint8_t *out, unsigned int outlen, TCHmacPrng_t prng) { unsigned int bufferlen; /* input sanity check: */ if (out == (uint8_t *) 0 || prng == (TCHmacPrng_t) 0 || outlen == 0 || outlen > MAX_OUT) { return TC_CRYPTO_FAIL; } else if (prng->countdown == 0) { return TC_HMAC_PRNG_RESEED_REQ; } prng->countdown--; while (outlen != 0) { /* operate HMAC in OFB mode to create "random" outputs */ (void)tc_hmac_init(&prng->h); (void)tc_hmac_update(&prng->h, prng->v, sizeof(prng->v)); (void)tc_hmac_final(prng->v, sizeof(prng->v), &prng->h); bufferlen = (TC_SHA256_DIGEST_SIZE > outlen) ? outlen : TC_SHA256_DIGEST_SIZE; (void)_copy(out, bufferlen, prng->v, bufferlen); out += bufferlen; outlen = (outlen > TC_SHA256_DIGEST_SIZE) ? (outlen - TC_SHA256_DIGEST_SIZE) : 0; } /* block future PRNG compromises from revealing past state */ update(prng, prng->v, TC_SHA256_DIGEST_SIZE); return TC_CRYPTO_SUCCESS; }