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127 lines
4.4 KiB
127 lines
4.4 KiB
/*
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* This file is part of the Trezor project, https://trezor.io/
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*
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* Copyright (c) SatoshiLabs
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "chacha_drbg.h"
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#include <assert.h>
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#include <stdint.h>
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#include <string.h>
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#include "chacha20poly1305/ecrypt-portable.h"
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#include "memzero.h"
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#include "sha2.h"
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#define CHACHA_DRBG_KEY_LENGTH 32
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#define CHACHA_DRBG_COUNTER_LENGTH 8
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#define CHACHA_DRBG_IV_LENGTH 8
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#define CHACHA_DRBG_SEED_LENGTH \
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(CHACHA_DRBG_KEY_LENGTH + CHACHA_DRBG_COUNTER_LENGTH + CHACHA_DRBG_IV_LENGTH)
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#define MAX(a, b) (a) > (b) ? (a) : (b)
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static void derivation_function(const uint8_t *input1, size_t input1_length,
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const uint8_t *input2, size_t input2_length,
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uint8_t *output, size_t output_length) {
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// Implementation of Hash_df from NIST SP 800-90A
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uint32_t block_count = (output_length - 1) / SHA256_DIGEST_LENGTH + 1;
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size_t partial_block_length = output_length % SHA256_DIGEST_LENGTH;
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assert(block_count <= 255);
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uint32_t output_length_bits = output_length * 8;
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#if BYTE_ORDER == LITTLE_ENDIAN
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REVERSE32(output_length_bits, output_length_bits);
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#endif
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SHA256_CTX ctx = {0};
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for (uint8_t counter = 1; counter <= block_count; counter++) {
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sha256_Init(&ctx);
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sha256_Update(&ctx, &counter, sizeof(counter));
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sha256_Update(&ctx, (uint8_t *)&output_length_bits,
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sizeof(output_length_bits));
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sha256_Update(&ctx, input1, input1_length);
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sha256_Update(&ctx, input2, input2_length);
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if (counter != block_count || partial_block_length == 0) {
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sha256_Final(&ctx, output);
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output += SHA256_DIGEST_LENGTH;
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} else { // last block is partial
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uint8_t digest[SHA256_DIGEST_LENGTH] = {0};
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sha256_Final(&ctx, digest);
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memcpy(output, digest, partial_block_length);
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memzero(digest, sizeof(digest));
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}
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}
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memzero(&ctx, sizeof(ctx));
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}
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void chacha_drbg_init(CHACHA_DRBG_CTX *ctx, const uint8_t *entropy,
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size_t entropy_length, const uint8_t *nonce,
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size_t nonce_length) {
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uint8_t buffer[MAX(CHACHA_DRBG_KEY_LENGTH, CHACHA_DRBG_IV_LENGTH)] = {0};
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ECRYPT_keysetup(&ctx->chacha_ctx, buffer, CHACHA_DRBG_KEY_LENGTH * 8,
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CHACHA_DRBG_IV_LENGTH * 8);
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ECRYPT_ivsetup(&ctx->chacha_ctx, buffer);
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chacha_drbg_reseed(ctx, entropy, entropy_length, nonce, nonce_length);
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}
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static void chacha_drbg_update(CHACHA_DRBG_CTX *ctx,
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const uint8_t data[CHACHA_DRBG_SEED_LENGTH]) {
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uint8_t seed[CHACHA_DRBG_SEED_LENGTH] = {0};
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if (data)
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ECRYPT_encrypt_bytes(&ctx->chacha_ctx, data, seed, CHACHA_DRBG_SEED_LENGTH);
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else
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ECRYPT_keystream_bytes(&ctx->chacha_ctx, seed, CHACHA_DRBG_SEED_LENGTH);
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ECRYPT_keysetup(&ctx->chacha_ctx, seed, CHACHA_DRBG_KEY_LENGTH * 8,
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CHACHA_DRBG_IV_LENGTH * 8);
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ECRYPT_ivsetup(&ctx->chacha_ctx,
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seed + CHACHA_DRBG_KEY_LENGTH + CHACHA_DRBG_COUNTER_LENGTH);
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ECRYPT_ctrsetup(&ctx->chacha_ctx, seed + CHACHA_DRBG_KEY_LENGTH);
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memzero(seed, sizeof(seed));
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}
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void chacha_drbg_generate(CHACHA_DRBG_CTX *ctx, uint8_t *output,
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size_t output_length) {
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assert(output_length < 65536);
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assert(ctx->reseed_counter + 1 != 0);
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ECRYPT_keystream_bytes(&ctx->chacha_ctx, output, output_length);
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chacha_drbg_update(ctx, NULL);
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ctx->reseed_counter++;
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}
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void chacha_drbg_reseed(CHACHA_DRBG_CTX *ctx, const uint8_t *entropy,
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size_t entropy_length, const uint8_t *additional_input,
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size_t additional_input_length) {
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uint8_t seed[CHACHA_DRBG_SEED_LENGTH] = {0};
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derivation_function(entropy, entropy_length, additional_input,
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additional_input_length, seed, sizeof(seed));
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chacha_drbg_update(ctx, seed);
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memzero(seed, sizeof(seed));
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ctx->reseed_counter = 1;
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}
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