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131 lines
4.6 KiB
131 lines
4.6 KiB
/**
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* Copyright (c) 2019 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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#include "hmac_drbg.h"
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#include <string.h>
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#include "memzero.h"
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#include "sha2.h"
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static void update_k(HMAC_DRBG_CTX *ctx, uint8_t domain, const uint8_t *data1,
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size_t len1, const uint8_t *data2, size_t len2) {
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// Computes K = HMAC(K, V || domain || data1 || data 2).
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// First hash operation of HMAC.
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uint32_t h[SHA256_BLOCK_LENGTH / sizeof(uint32_t)] = {0};
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if (len1 + len2 == 0) {
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ctx->v[8] = 0x00800000;
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ctx->v[15] = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH + 1) * 8;
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sha256_Transform(ctx->idig, ctx->v, h);
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ctx->v[8] = 0x80000000;
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ctx->v[15] = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH) * 8;
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} else {
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SHA256_CTX sha_ctx = {0};
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memcpy(sha_ctx.state, ctx->idig, SHA256_DIGEST_LENGTH);
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for (size_t i = 0; i < SHA256_DIGEST_LENGTH / sizeof(uint32_t); i++) {
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#if BYTE_ORDER == LITTLE_ENDIAN
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REVERSE32(ctx->v[i], sha_ctx.buffer[i]);
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#else
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sha_ctx.buffer[i] = ctx->v[i];
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#endif
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}
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((uint8_t *)sha_ctx.buffer)[SHA256_DIGEST_LENGTH] = domain;
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sha_ctx.bitcount = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH + 1) * 8;
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sha256_Update(&sha_ctx, data1, len1);
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sha256_Update(&sha_ctx, data2, len2);
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sha256_Final(&sha_ctx, (uint8_t *)h);
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#if BYTE_ORDER == LITTLE_ENDIAN
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for (size_t i = 0; i < SHA256_DIGEST_LENGTH / sizeof(uint32_t); i++)
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REVERSE32(h[i], h[i]);
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#endif
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}
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// Second hash operation of HMAC.
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h[8] = 0x80000000;
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h[15] = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH) * 8;
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sha256_Transform(ctx->odig, h, h);
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// Precompute the inner digest and outer digest of K.
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h[8] = 0;
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h[15] = 0;
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for (size_t i = 0; i < SHA256_BLOCK_LENGTH / sizeof(uint32_t); i++) {
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h[i] ^= 0x36363636;
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}
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sha256_Transform(sha256_initial_hash_value, h, ctx->idig);
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for (size_t i = 0; i < SHA256_BLOCK_LENGTH / sizeof(uint32_t); i++) {
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h[i] = h[i] ^ 0x36363636 ^ 0x5c5c5c5c;
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}
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sha256_Transform(sha256_initial_hash_value, h, ctx->odig);
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memzero(h, sizeof(h));
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}
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static void update_v(HMAC_DRBG_CTX *ctx) {
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sha256_Transform(ctx->idig, ctx->v, ctx->v);
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sha256_Transform(ctx->odig, ctx->v, ctx->v);
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}
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void hmac_drbg_init(HMAC_DRBG_CTX *ctx, const uint8_t *entropy,
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size_t entropy_len, const uint8_t *nonce,
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size_t nonce_len) {
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uint32_t h[SHA256_BLOCK_LENGTH / sizeof(uint32_t)] = {0};
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// Precompute the inner digest and outer digest of K = 0x00 ... 0x00.
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memset(h, 0x36, sizeof(h));
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sha256_Transform(sha256_initial_hash_value, h, ctx->idig);
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memset(h, 0x5c, sizeof(h));
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sha256_Transform(sha256_initial_hash_value, h, ctx->odig);
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// Let V = 0x01 ... 0x01.
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memset(ctx->v, 1, SHA256_DIGEST_LENGTH);
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for (size_t i = 9; i < 15; i++) ctx->v[i] = 0;
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ctx->v[8] = 0x80000000;
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ctx->v[15] = (SHA256_BLOCK_LENGTH + SHA256_DIGEST_LENGTH) * 8;
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hmac_drbg_reseed(ctx, entropy, entropy_len, nonce, nonce_len);
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memzero(h, sizeof(h));
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}
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void hmac_drbg_reseed(HMAC_DRBG_CTX *ctx, const uint8_t *entropy, size_t len,
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const uint8_t *addin, size_t addin_len) {
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update_k(ctx, 0, entropy, len, addin, addin_len);
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update_v(ctx);
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if (len == 0) return;
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update_k(ctx, 1, entropy, len, addin, addin_len);
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update_v(ctx);
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}
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void hmac_drbg_generate(HMAC_DRBG_CTX *ctx, uint8_t *buf, size_t len) {
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size_t i = 0;
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while (i < len) {
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update_v(ctx);
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for (size_t j = 0; j < 8 && i < len; j++) {
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uint32_t r = ctx->v[j];
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for (int k = 24; k >= 0 && i < len; k -= 8) {
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buf[i++] = (r >> k) & 0xFF;
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}
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}
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}
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update_k(ctx, 0, NULL, 0, NULL, 0);
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update_v(ctx);
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}
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