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trezor-firmware/crypto/hmac_drbg.c
2019-10-09 17:05:33 +02:00

131 lines
4.6 KiB
C

/**
* Copyright (c) 2019 Andrew R. Kozlik
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include "hmac_drbg.h"
#include <string.h>
#include "memzero.h"
#include "sha2.h"
static void update_k(HMAC_DRBG_CTX *ctx, uint8_t domain, const uint8_t *data1,
size_t len1, const uint8_t *data2, size_t len2) {
// Computes K = HMAC(K, V || domain || data1 || data 2).
// First hash operation of HMAC.
uint32_t h[SHA256_BLOCK_LENGTH / sizeof(uint32_t)] = {0};
if (len1 + len2 == 0) {
ctx->v[8] = 0x00800000;
ctx->v[15] = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH + 1) * 8;
sha256_Transform(ctx->idig, ctx->v, h);
ctx->v[8] = 0x80000000;
ctx->v[15] = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH) * 8;
} else {
SHA256_CTX sha_ctx = {0};
memcpy(sha_ctx.state, ctx->idig, SHA256_DIGEST_LENGTH);
for (size_t i = 0; i < SHA256_DIGEST_LENGTH / sizeof(uint32_t); i++) {
#if BYTE_ORDER == LITTLE_ENDIAN
REVERSE32(ctx->v[i], sha_ctx.buffer[i]);
#else
sha_ctx.buffer[i] = ctx->v[i];
#endif
}
((uint8_t *)sha_ctx.buffer)[SHA256_DIGEST_LENGTH] = domain;
sha_ctx.bitcount = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH + 1) * 8;
sha256_Update(&sha_ctx, data1, len1);
sha256_Update(&sha_ctx, data2, len2);
sha256_Final(&sha_ctx, (uint8_t *)h);
#if BYTE_ORDER == LITTLE_ENDIAN
for (size_t i = 0; i < SHA256_DIGEST_LENGTH / sizeof(uint32_t); i++)
REVERSE32(h[i], h[i]);
#endif
}
// Second hash operation of HMAC.
h[8] = 0x80000000;
h[15] = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH) * 8;
sha256_Transform(ctx->odig, h, h);
// Precompute the inner digest and outer digest of K.
h[8] = 0;
h[15] = 0;
for (size_t i = 0; i < SHA256_BLOCK_LENGTH / sizeof(uint32_t); i++) {
h[i] ^= 0x36363636;
}
sha256_Transform(sha256_initial_hash_value, h, ctx->idig);
for (size_t i = 0; i < SHA256_BLOCK_LENGTH / sizeof(uint32_t); i++) {
h[i] = h[i] ^ 0x36363636 ^ 0x5c5c5c5c;
}
sha256_Transform(sha256_initial_hash_value, h, ctx->odig);
memzero(h, sizeof(h));
}
static void update_v(HMAC_DRBG_CTX *ctx) {
sha256_Transform(ctx->idig, ctx->v, ctx->v);
sha256_Transform(ctx->odig, ctx->v, ctx->v);
}
void hmac_drbg_init(HMAC_DRBG_CTX *ctx, const uint8_t *entropy,
size_t entropy_len, const uint8_t *nonce,
size_t nonce_len) {
uint32_t h[SHA256_BLOCK_LENGTH / sizeof(uint32_t)] = {0};
// Precompute the inner digest and outer digest of K = 0x00 ... 0x00.
memset(h, 0x36, sizeof(h));
sha256_Transform(sha256_initial_hash_value, h, ctx->idig);
memset(h, 0x5c, sizeof(h));
sha256_Transform(sha256_initial_hash_value, h, ctx->odig);
// Let V = 0x01 ... 0x01.
memset(ctx->v, 1, SHA256_DIGEST_LENGTH);
for (size_t i = 9; i < 15; i++) ctx->v[i] = 0;
ctx->v[8] = 0x80000000;
ctx->v[15] = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH) * 8;
hmac_drbg_reseed(ctx, entropy, entropy_len, nonce, nonce_len);
memzero(h, sizeof(h));
}
void hmac_drbg_reseed(HMAC_DRBG_CTX *ctx, const uint8_t *entropy, size_t len,
const uint8_t *addin, size_t addin_len) {
update_k(ctx, 0, entropy, len, addin, addin_len);
update_v(ctx);
if (len == 0) return;
update_k(ctx, 1, entropy, len, addin, addin_len);
update_v(ctx);
}
void hmac_drbg_generate(HMAC_DRBG_CTX *ctx, uint8_t *buf, size_t len) {
size_t i = 0;
while (i < len) {
update_v(ctx);
for (size_t j = 0; j < 8 && i < len; j++) {
uint32_t r = ctx->v[j];
for (int k = 24; k >= 0 && i < len; k -= 8) {
buf[i++] = (r >> k) & 0xFF;
}
}
}
update_k(ctx, 0, NULL, 0, NULL, 0);
update_v(ctx);
}