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1 /* ====================================================================
2  * Copyright (c) 2010 The OpenSSL Project.  All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  *
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in
13  *    the documentation and/or other materials provided with the
14  *    distribution.
15  *
16  * 3. All advertising materials mentioning features or use of this
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/)"
20  *
21  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
22  *    endorse or promote products derived from this software without
23  *    prior written permission. For written permission, please contact
24  *    licensing@OpenSSL.org.
25  *
26  * 5. Products derived from this software may not be called "OpenSSL"
27  *    nor may "OpenSSL" appear in their names without prior written
28  *    permission of the OpenSSL Project.
29  *
30  * 6. Redistributions of any form whatsoever must retain the following
31  *    acknowledgment:
32  *    "This product includes software developed by the OpenSSL Project
33  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
34  *
35  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
36  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
37  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
38  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
39  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
40  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
41  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
42  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
43  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
44  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
45  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
46  * OF THE POSSIBILITY OF SUCH DAMAGE.
47  * ==================================================================== */
48 
49 #include <openssl/cmac.h>
50 
51 #include <assert.h>
52 #include <string.h>
53 
54 #include <openssl/aes.h>
55 #include <openssl/cipher.h>
56 #include <openssl/mem.h>
57 
58 #include "../internal.h"
59 
60 
61 struct cmac_ctx_st {
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|. */
70   unsigned block_used;
71 };
72 
CMAC_CTX_init(CMAC_CTX * ctx)73 static void CMAC_CTX_init(CMAC_CTX *ctx) {
74   EVP_CIPHER_CTX_init(&ctx->cipher_ctx);
75 }
76 
CMAC_CTX_cleanup(CMAC_CTX * 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));
82 }
83 
AES_CMAC(uint8_t out[16],const uint8_t * key,size_t key_len,const uint8_t * in,size_t in_len)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;
87   switch (key_len) {
88     case 16:
89       cipher = EVP_aes_128_cbc();
90       break;
91     case 32:
92       cipher = EVP_aes_256_cbc();
93       break;
94     default:
95       return 0;
96   }
97 
98   size_t scratch_out_len;
99   CMAC_CTX ctx;
100   CMAC_CTX_init(&ctx);
101 
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);
105 
106   CMAC_CTX_cleanup(&ctx);
107   return ok;
108 }
109 
CMAC_CTX_new(void)110 CMAC_CTX *CMAC_CTX_new(void) {
111   CMAC_CTX *ctx = OPENSSL_malloc(sizeof(*ctx));
112   if (ctx != NULL) {
113     CMAC_CTX_init(ctx);
114   }
115   return ctx;
116 }
117 
CMAC_CTX_free(CMAC_CTX * ctx)118 void CMAC_CTX_free(CMAC_CTX *ctx) {
119   if (ctx == NULL) {
120     return;
121   }
122 
123   CMAC_CTX_cleanup(ctx);
124   OPENSSL_free(ctx);
125 }
126 
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
129  * input.
130  *
131  * See https://tools.ietf.org/html/rfc4493#section-2.3 */
binary_field_mul_x(uint8_t out[16],const uint8_t in[16])132 static void binary_field_mul_x(uint8_t out[16], const uint8_t in[16]) {
133   unsigned i;
134 
135   /* Shift |in| to left, including carry. */
136   for (i = 0; i < 15; i++) {
137     out[i] = (in[i] << 1) | (in[i+1] >> 7);
138   }
139 
140   /* If MSB set fixup with R. */
141   const uint8_t carry = in[0] >> 7;
142   out[i] = (in[i] << 1) ^ ((0 - carry) & 0x87);
143 }
144 
145 static const uint8_t kZeroIV[AES_BLOCK_SIZE] = {0};
146 
CMAC_Init(CMAC_CTX * ctx,const void * key,size_t key_len,const EVP_CIPHER * cipher,ENGINE * engine)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];
150 
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)) {
157     return 0;
158   }
159 
160   binary_field_mul_x(ctx->k1, scratch);
161   binary_field_mul_x(ctx->k2, ctx->k1);
162   ctx->block_used = 0;
163 
164   return 1;
165 }
166 
CMAC_Reset(CMAC_CTX * ctx)167 int CMAC_Reset(CMAC_CTX *ctx) {
168   ctx->block_used = 0;
169   return EVP_EncryptInit_ex(&ctx->cipher_ctx, NULL, NULL, NULL, kZeroIV);
170 }
171 
CMAC_Update(CMAC_CTX * ctx,const uint8_t * in,size_t in_len)172 int CMAC_Update(CMAC_CTX *ctx, const uint8_t *in, size_t in_len) {
173   uint8_t scratch[AES_BLOCK_SIZE];
174 
175   if (ctx->block_used > 0) {
176     size_t todo = AES_BLOCK_SIZE - ctx->block_used;
177     if (in_len < todo) {
178       todo = in_len;
179     }
180 
181     OPENSSL_memcpy(ctx->block + ctx->block_used, in, todo);
182     in += todo;
183     in_len -= todo;
184     ctx->block_used += todo;
185 
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. */
191     if (in_len == 0) {
192       return 1;
193     }
194 
195     assert(ctx->block_used == AES_BLOCK_SIZE);
196 
197     if (!EVP_Cipher(&ctx->cipher_ctx, scratch, ctx->block, AES_BLOCK_SIZE)) {
198       return 0;
199     }
200   }
201 
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)) {
205       return 0;
206     }
207     in += AES_BLOCK_SIZE;
208     in_len -= AES_BLOCK_SIZE;
209   }
210 
211   OPENSSL_memcpy(ctx->block, in, in_len);
212   ctx->block_used = in_len;
213 
214   return 1;
215 }
216 
CMAC_Final(CMAC_CTX * ctx,uint8_t * out,size_t * out_len)217 int CMAC_Final(CMAC_CTX *ctx, uint8_t *out, size_t *out_len) {
218   *out_len = AES_BLOCK_SIZE;
219   if (out == NULL) {
220     return 1;
221   }
222 
223   const uint8_t *mask = ctx->k1;
224 
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));
231 
232     mask = ctx->k2;
233   }
234 
235   unsigned i;
236   for (i = 0; i < AES_BLOCK_SIZE; i++) {
237     out[i] = ctx->block[i] ^ mask[i];
238   }
239 
240   return EVP_Cipher(&ctx->cipher_ctx, out, out, AES_BLOCK_SIZE);
241 }
242