1 /* ====================================================================
2 * Copyright (c) 2010 The OpenSSL Project. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
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13 * the documentation and/or other materials provided with the
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17 * software must display the following acknowledgment:
18 * "This product includes software developed by the OpenSSL Project
19 * for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
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30 * 6. Redistributions of any form whatsoever must retain the following
32 * "This product includes software developed by the OpenSSL Project
33 * for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
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36 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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47 * ==================================================================== */
49 #include <openssl/cmac.h>
54 #include <openssl/aes.h>
55 #include <openssl/cipher.h>
56 #include <openssl/mem.h>
58 #include "../internal.h"
62 EVP_CIPHER_CTX cipher_ctx;
63 // k1 and k2 are the CMAC subkeys. See
64 // https://tools.ietf.org/html/rfc4493#section-2.3
65 uint8_t k1[AES_BLOCK_SIZE];
66 uint8_t k2[AES_BLOCK_SIZE];
67 // Last (possibly partial) scratch
68 uint8_t block[AES_BLOCK_SIZE];
69 // block_used contains the number of valid bytes in |block|.
73 static void CMAC_CTX_init(CMAC_CTX *ctx) {
74 EVP_CIPHER_CTX_init(&ctx->cipher_ctx);
77 static void CMAC_CTX_cleanup(CMAC_CTX *ctx) {
78 EVP_CIPHER_CTX_cleanup(&ctx->cipher_ctx);
79 OPENSSL_cleanse(ctx->k1, sizeof(ctx->k1));
80 OPENSSL_cleanse(ctx->k2, sizeof(ctx->k2));
81 OPENSSL_cleanse(ctx->block, sizeof(ctx->block));
84 int AES_CMAC(uint8_t out[16], const uint8_t *key, size_t key_len,
85 const uint8_t *in, size_t in_len) {
86 const EVP_CIPHER *cipher;
89 cipher = EVP_aes_128_cbc();
92 cipher = EVP_aes_256_cbc();
98 size_t scratch_out_len;
102 const int ok = CMAC_Init(&ctx, key, key_len, cipher, NULL /* engine */) &&
103 CMAC_Update(&ctx, in, in_len) &&
104 CMAC_Final(&ctx, out, &scratch_out_len);
106 CMAC_CTX_cleanup(&ctx);
110 CMAC_CTX *CMAC_CTX_new(void) {
111 CMAC_CTX *ctx = OPENSSL_malloc(sizeof(*ctx));
118 void CMAC_CTX_free(CMAC_CTX *ctx) {
123 CMAC_CTX_cleanup(ctx);
127 // binary_field_mul_x treats the 128 bits at |in| as an element of GF(2¹²⁸)
128 // with a hard-coded reduction polynomial and sets |out| as x times the
131 // See https://tools.ietf.org/html/rfc4493#section-2.3
132 static void binary_field_mul_x(uint8_t out[16], const uint8_t in[16]) {
135 // Shift |in| to left, including carry.
136 for (i = 0; i < 15; i++) {
137 out[i] = (in[i] << 1) | (in[i+1] >> 7);
140 // If MSB set fixup with R.
141 const uint8_t carry = in[0] >> 7;
142 out[i] = (in[i] << 1) ^ ((0 - carry) & 0x87);
145 static const uint8_t kZeroIV[AES_BLOCK_SIZE] = {0};
147 int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t key_len,
148 const EVP_CIPHER *cipher, ENGINE *engine) {
149 uint8_t scratch[AES_BLOCK_SIZE];
151 if (EVP_CIPHER_block_size(cipher) != AES_BLOCK_SIZE ||
152 EVP_CIPHER_key_length(cipher) != key_len ||
153 !EVP_EncryptInit_ex(&ctx->cipher_ctx, cipher, NULL, key, kZeroIV) ||
154 !EVP_Cipher(&ctx->cipher_ctx, scratch, kZeroIV, AES_BLOCK_SIZE) ||
155 // Reset context again ready for first data.
156 !EVP_EncryptInit_ex(&ctx->cipher_ctx, NULL, NULL, NULL, kZeroIV)) {
160 binary_field_mul_x(ctx->k1, scratch);
161 binary_field_mul_x(ctx->k2, ctx->k1);
167 int CMAC_Reset(CMAC_CTX *ctx) {
169 return EVP_EncryptInit_ex(&ctx->cipher_ctx, NULL, NULL, NULL, kZeroIV);
172 int CMAC_Update(CMAC_CTX *ctx, const uint8_t *in, size_t in_len) {
173 uint8_t scratch[AES_BLOCK_SIZE];
175 if (ctx->block_used > 0) {
176 size_t todo = AES_BLOCK_SIZE - ctx->block_used;
181 OPENSSL_memcpy(ctx->block + ctx->block_used, in, todo);
184 ctx->block_used += todo;
186 // If |in_len| is zero then either |ctx->block_used| is less than
187 // |AES_BLOCK_SIZE|, in which case we can stop here, or |ctx->block_used|
188 // is exactly |AES_BLOCK_SIZE| but there's no more data to process. In the
189 // latter case we don't want to process this block now because it might be
190 // the last block and that block is treated specially.
195 assert(ctx->block_used == AES_BLOCK_SIZE);
197 if (!EVP_Cipher(&ctx->cipher_ctx, scratch, ctx->block, AES_BLOCK_SIZE)) {
202 // Encrypt all but one of the remaining blocks.
203 while (in_len > AES_BLOCK_SIZE) {
204 if (!EVP_Cipher(&ctx->cipher_ctx, scratch, in, AES_BLOCK_SIZE)) {
207 in += AES_BLOCK_SIZE;
208 in_len -= AES_BLOCK_SIZE;
211 OPENSSL_memcpy(ctx->block, in, in_len);
212 ctx->block_used = in_len;
217 int CMAC_Final(CMAC_CTX *ctx, uint8_t *out, size_t *out_len) {
218 *out_len = AES_BLOCK_SIZE;
223 const uint8_t *mask = ctx->k1;
225 if (ctx->block_used != AES_BLOCK_SIZE) {
226 // If the last block is incomplete, terminate it with a single 'one' bit
227 // followed by zeros.
228 ctx->block[ctx->block_used] = 0x80;
229 OPENSSL_memset(ctx->block + ctx->block_used + 1, 0,
230 AES_BLOCK_SIZE - (ctx->block_used + 1));
236 for (i = 0; i < AES_BLOCK_SIZE; i++) {
237 out[i] = ctx->block[i] ^ mask[i];
240 return EVP_Cipher(&ctx->cipher_ctx, out, out, AES_BLOCK_SIZE);