99 lines
3.4 KiB
C
99 lines
3.4 KiB
C
/*
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* hmac.c - HMAC
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*
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* Copyright (C) 2017 Sergei Glushchenko
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* Author: Sergei Glushchenko <gl.sergei@gmail.com>
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*
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* This file is a part of U2F firmware for STM32
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*
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* This program is free software: you can redistribute it and/or modify it
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* 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, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* 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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* As additional permission under GNU GPL version 3 section 7, you may
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* distribute non-source form of the Program without the copy of the
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* GNU GPL normally required by section 4, provided you inform the
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* recipients of GNU GPL by a written offer.
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*
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*/
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#include <stdint.h>
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#include "sha256.h"
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#include "hmac_sha256.h"
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static void _hmac_sha256_init(const hmac_context* ctx) {
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hmac_sha256_context* context = (hmac_sha256_context*)ctx;
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sha256_start(&context->sha_ctx);
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}
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static void
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_hmac_sha256_update(const hmac_context* ctx, const uint8_t* message, unsigned message_size) {
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hmac_sha256_context* context = (hmac_sha256_context*)ctx;
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sha256_update(&context->sha_ctx, message, message_size);
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}
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static void _hmac_sha256_finish(const hmac_context* ctx, uint8_t* hash_result) {
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hmac_sha256_context* context = (hmac_sha256_context*)ctx;
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sha256_finish(&context->sha_ctx, hash_result);
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}
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/* Compute an HMAC using K as a key (as in RFC 6979). Note that K is always
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the same size as the hash result size. */
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static void hmac_init(const hmac_context* ctx, const uint8_t* K) {
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uint8_t* pad = ctx->tmp + 2 * ctx->result_size;
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unsigned i;
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for(i = 0; i < ctx->result_size; ++i) pad[i] = K[i] ^ 0x36;
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for(; i < ctx->block_size; ++i) pad[i] = 0x36;
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ctx->init_hash(ctx);
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ctx->update_hash(ctx, pad, ctx->block_size);
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}
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static void hmac_update(const hmac_context* ctx, const uint8_t* message, unsigned message_size) {
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ctx->update_hash(ctx, message, message_size);
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}
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static void hmac_finish(const hmac_context* ctx, const uint8_t* K, uint8_t* result) {
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uint8_t* pad = ctx->tmp + 2 * ctx->result_size;
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unsigned i;
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for(i = 0; i < ctx->result_size; ++i) pad[i] = K[i] ^ 0x5c;
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for(; i < ctx->block_size; ++i) pad[i] = 0x5c;
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ctx->finish_hash(ctx, result);
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ctx->init_hash(ctx);
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ctx->update_hash(ctx, pad, ctx->block_size);
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ctx->update_hash(ctx, result, ctx->result_size);
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ctx->finish_hash(ctx, result);
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}
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void hmac_sha256_init(hmac_sha256_context* ctx, const uint8_t* K) {
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ctx->hmac_ctx.init_hash = _hmac_sha256_init;
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ctx->hmac_ctx.update_hash = _hmac_sha256_update;
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ctx->hmac_ctx.finish_hash = _hmac_sha256_finish;
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ctx->hmac_ctx.block_size = 64;
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ctx->hmac_ctx.result_size = 32;
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ctx->hmac_ctx.tmp = ctx->tmp;
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hmac_init(&ctx->hmac_ctx, K);
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}
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void hmac_sha256_update(
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const hmac_sha256_context* ctx,
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const uint8_t* message,
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unsigned message_size) {
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hmac_update(&ctx->hmac_ctx, message, message_size);
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}
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void hmac_sha256_finish(const hmac_sha256_context* ctx, const uint8_t* K, uint8_t* hash_result) {
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hmac_finish(&ctx->hmac_ctx, K, hash_result);
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}
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