mirror of
https://github.com/trezor/trezor-firmware.git
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89 lines
3.2 KiB
C
89 lines
3.2 KiB
C
/**
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* Copyright (c) 2023 Andrew R. Kozlik
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
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* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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/*
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* For a specification of TLS-PRF see
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* https://datatracker.ietf.org/doc/html/rfc5246#section-5
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*/
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#include <string.h>
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#include "hmac.h"
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#include "memzero.h"
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#include "sha2.h"
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void tls_prf_sha256(const uint8_t *secret, size_t secret_len,
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const uint8_t *label, size_t label_len, const uint8_t *seed,
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size_t seed_len, uint8_t *output, size_t out_len) {
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uint32_t idig[SHA256_DIGEST_LENGTH / sizeof(uint32_t)] = {0};
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uint32_t odig[SHA256_DIGEST_LENGTH / sizeof(uint32_t)] = {0};
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uint8_t a[SHA256_DIGEST_LENGTH] = {0};
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uint8_t result[SHA256_DIGEST_LENGTH] = {0};
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SHA256_CTX ctx = {0};
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// Prepare inner and outer digest.
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hmac_sha256_prepare(secret, secret_len, odig, idig);
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// a = HMAC(secret, label + seed)
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sha256_Init_ex(&ctx, idig, 8 * SHA256_BLOCK_LENGTH);
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sha256_Update(&ctx, label, label_len);
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sha256_Update(&ctx, seed, seed_len);
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sha256_Final(&ctx, a);
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sha256_Init_ex(&ctx, odig, 8 * SHA256_BLOCK_LENGTH);
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sha256_Update(&ctx, a, SHA256_DIGEST_LENGTH);
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sha256_Final(&ctx, a);
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while (1) {
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// result = HMAC(secret, a + label + seed)
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sha256_Init_ex(&ctx, idig, 8 * SHA256_BLOCK_LENGTH);
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sha256_Update(&ctx, a, SHA256_DIGEST_LENGTH);
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sha256_Update(&ctx, label, label_len);
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sha256_Update(&ctx, seed, seed_len);
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sha256_Final(&ctx, result);
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sha256_Init_ex(&ctx, odig, 8 * SHA256_BLOCK_LENGTH);
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sha256_Update(&ctx, result, SHA256_DIGEST_LENGTH);
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sha256_Final(&ctx, result);
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if (out_len <= SHA256_DIGEST_LENGTH) {
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break;
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}
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memcpy(output, result, SHA256_DIGEST_LENGTH);
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output += SHA256_DIGEST_LENGTH;
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out_len -= SHA256_DIGEST_LENGTH;
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// a = HMAC(secret, a)
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sha256_Init_ex(&ctx, idig, 8 * SHA256_BLOCK_LENGTH);
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sha256_Update(&ctx, a, SHA256_DIGEST_LENGTH);
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sha256_Final(&ctx, a);
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sha256_Init_ex(&ctx, odig, 8 * SHA256_BLOCK_LENGTH);
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sha256_Update(&ctx, a, SHA256_DIGEST_LENGTH);
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sha256_Final(&ctx, a);
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}
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memcpy(output, result, out_len);
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memzero(idig, sizeof(idig));
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memzero(odig, sizeof(odig));
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memzero(a, sizeof(a));
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memzero(result, sizeof(result));
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}
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