1 /*
2 * aes_icm_ossl.c
3 *
4 * AES Integer Counter Mode
5 *
6 * John A. Foley
7 * Cisco Systems, Inc.
8 *
9 * 2/24/2012: This module was modified to use CiscoSSL for AES counter
10 * mode. Eddy Lem contributed the code to allow this.
11 *
12 * 12/20/2012: Added support for AES-192 and AES-256.
13 */
14
15 /*
16 *
17 * Copyright (c) 2013-2017, Cisco Systems, Inc.
18 * All rights reserved.
19 *
20 * Redistribution and use in source and binary forms, with or without
21 * modification, are permitted provided that the following conditions
22 * are met:
23 *
24 * Redistributions of source code must retain the above copyright
25 * notice, this list of conditions and the following disclaimer.
26 *
27 * Redistributions in binary form must reproduce the above
28 * copyright notice, this list of conditions and the following
29 * disclaimer in the documentation and/or other materials provided
30 * with the distribution.
31 *
32 * Neither the name of the Cisco Systems, Inc. nor the names of its
33 * contributors may be used to endorse or promote products derived
34 * from this software without specific prior written permission.
35 *
36 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
37 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
38 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
39 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
40 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
41 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
42 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
43 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
45 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
46 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
47 * OF THE POSSIBILITY OF SUCH DAMAGE.
48 *
49 */
50
51 #ifdef HAVE_CONFIG_H
52 #include <config.h>
53 #endif
54
55 #include <openssl/evp.h>
56 #include "aes_icm_ext.h"
57 #include "crypto_types.h"
58 #include "err.h" /* for srtp_debug */
59 #include "alloc.h"
60 #include "cipher_types.h"
61 #include "cipher_test_cases.h"
62
63 srtp_debug_module_t srtp_mod_aes_icm = {
64 0, /* debugging is off by default */
65 "aes icm ossl" /* printable module name */
66 };
67
68 /*
69 * integer counter mode works as follows:
70 *
71 * 16 bits
72 * <----->
73 * +------+------+------+------+------+------+------+------+
74 * | nonce | packet index | ctr |---+
75 * +------+------+------+------+------+------+------+------+ |
76 * |
77 * +------+------+------+------+------+------+------+------+ v
78 * | salt |000000|->(+)
79 * +------+------+------+------+------+------+------+------+ |
80 * |
81 * +---------+
82 * | encrypt |
83 * +---------+
84 * |
85 * +------+------+------+------+------+------+------+------+ |
86 * | keystream block |<--+
87 * +------+------+------+------+------+------+------+------+
88 *
89 * All fields are big-endian
90 *
91 * ctr is the block counter, which increments from zero for
92 * each packet (16 bits wide)
93 *
94 * packet index is distinct for each packet (48 bits wide)
95 *
96 * nonce can be distinct across many uses of the same key, or
97 * can be a fixed value per key, or can be per-packet randomness
98 * (64 bits)
99 *
100 */
101
102 /*
103 * This function allocates a new instance of this crypto engine.
104 * The key_len parameter should be one of 30, 38, or 46 for
105 * AES-128, AES-192, and AES-256 respectively. Note, this key_len
106 * value is inflated, as it also accounts for the 112 bit salt
107 * value. The tlen argument is for the AEAD tag length, which
108 * isn't used in counter mode.
109 */
srtp_aes_icm_openssl_alloc(srtp_cipher_t ** c,int key_len,int tlen)110 static srtp_err_status_t srtp_aes_icm_openssl_alloc(srtp_cipher_t **c,
111 int key_len,
112 int tlen)
113 {
114 srtp_aes_icm_ctx_t *icm;
115
116 debug_print(srtp_mod_aes_icm, "allocating cipher with key length %d",
117 key_len);
118
119 /*
120 * Verify the key_len is valid for one of: AES-128/192/256
121 */
122 if (key_len != SRTP_AES_ICM_128_KEY_LEN_WSALT &&
123 key_len != SRTP_AES_ICM_192_KEY_LEN_WSALT &&
124 key_len != SRTP_AES_ICM_256_KEY_LEN_WSALT) {
125 return srtp_err_status_bad_param;
126 }
127
128 /* allocate memory a cipher of type aes_icm */
129 *c = (srtp_cipher_t *)srtp_crypto_alloc(sizeof(srtp_cipher_t));
130 if (*c == NULL) {
131 return srtp_err_status_alloc_fail;
132 }
133
134 icm = (srtp_aes_icm_ctx_t *)srtp_crypto_alloc(sizeof(srtp_aes_icm_ctx_t));
135 if (icm == NULL) {
136 srtp_crypto_free(*c);
137 *c = NULL;
138 return srtp_err_status_alloc_fail;
139 }
140
141 icm->ctx = EVP_CIPHER_CTX_new();
142 if (icm->ctx == NULL) {
143 srtp_crypto_free(icm);
144 srtp_crypto_free(*c);
145 *c = NULL;
146 return srtp_err_status_alloc_fail;
147 }
148
149 /* set pointers */
150 (*c)->state = icm;
151
152 /* setup cipher parameters */
153 switch (key_len) {
154 case SRTP_AES_ICM_128_KEY_LEN_WSALT:
155 (*c)->algorithm = SRTP_AES_ICM_128;
156 (*c)->type = &srtp_aes_icm_128;
157 icm->key_size = SRTP_AES_128_KEY_LEN;
158 break;
159 case SRTP_AES_ICM_192_KEY_LEN_WSALT:
160 (*c)->algorithm = SRTP_AES_ICM_192;
161 (*c)->type = &srtp_aes_icm_192;
162 icm->key_size = SRTP_AES_192_KEY_LEN;
163 break;
164 case SRTP_AES_ICM_256_KEY_LEN_WSALT:
165 (*c)->algorithm = SRTP_AES_ICM_256;
166 (*c)->type = &srtp_aes_icm_256;
167 icm->key_size = SRTP_AES_256_KEY_LEN;
168 break;
169 }
170
171 /* set key size */
172 (*c)->key_len = key_len;
173
174 return srtp_err_status_ok;
175 }
176
177 /*
178 * This function deallocates an instance of this engine
179 */
srtp_aes_icm_openssl_dealloc(srtp_cipher_t * c)180 static srtp_err_status_t srtp_aes_icm_openssl_dealloc(srtp_cipher_t *c)
181 {
182 srtp_aes_icm_ctx_t *ctx;
183
184 if (c == NULL) {
185 return srtp_err_status_bad_param;
186 }
187
188 /*
189 * Free the EVP context
190 */
191 ctx = (srtp_aes_icm_ctx_t *)c->state;
192 if (ctx != NULL) {
193 EVP_CIPHER_CTX_free(ctx->ctx);
194 /* zeroize the key material */
195 octet_string_set_to_zero(ctx, sizeof(srtp_aes_icm_ctx_t));
196 srtp_crypto_free(ctx);
197 }
198
199 /* free memory */
200 srtp_crypto_free(c);
201
202 return srtp_err_status_ok;
203 }
204
205 /*
206 * aes_icm_openssl_context_init(...) initializes the aes_icm_context
207 * using the value in key[].
208 *
209 * the key is the secret key
210 *
211 * the salt is unpredictable (but not necessarily secret) data which
212 * randomizes the starting point in the keystream
213 */
srtp_aes_icm_openssl_context_init(void * cv,const uint8_t * key)214 static srtp_err_status_t srtp_aes_icm_openssl_context_init(void *cv,
215 const uint8_t *key)
216 {
217 srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv;
218 const EVP_CIPHER *evp;
219
220 /*
221 * set counter and initial values to 'offset' value, being careful not to
222 * go past the end of the key buffer
223 */
224 v128_set_to_zero(&c->counter);
225 v128_set_to_zero(&c->offset);
226 memcpy(&c->counter, key + c->key_size, SRTP_SALT_LEN);
227 memcpy(&c->offset, key + c->key_size, SRTP_SALT_LEN);
228
229 /* force last two octets of the offset to zero (for srtp compatibility) */
230 c->offset.v8[SRTP_SALT_LEN] = c->offset.v8[SRTP_SALT_LEN + 1] = 0;
231 c->counter.v8[SRTP_SALT_LEN] = c->counter.v8[SRTP_SALT_LEN + 1] = 0;
232
233 debug_print(srtp_mod_aes_icm, "key: %s",
234 srtp_octet_string_hex_string(key, c->key_size));
235 debug_print(srtp_mod_aes_icm, "offset: %s", v128_hex_string(&c->offset));
236
237 switch (c->key_size) {
238 case SRTP_AES_256_KEY_LEN:
239 evp = EVP_aes_256_ctr();
240 break;
241 case SRTP_AES_192_KEY_LEN:
242 evp = EVP_aes_192_ctr();
243 break;
244 case SRTP_AES_128_KEY_LEN:
245 evp = EVP_aes_128_ctr();
246 break;
247 default:
248 return srtp_err_status_bad_param;
249 break;
250 }
251
252 EVP_CIPHER_CTX_cleanup(c->ctx);
253 if (!EVP_EncryptInit_ex(c->ctx, evp, NULL, key, NULL)) {
254 return srtp_err_status_fail;
255 } else {
256 return srtp_err_status_ok;
257 }
258
259 return srtp_err_status_ok;
260 }
261
262 /*
263 * aes_icm_set_iv(c, iv) sets the counter value to the exor of iv with
264 * the offset
265 */
srtp_aes_icm_openssl_set_iv(void * cv,uint8_t * iv,srtp_cipher_direction_t dir)266 static srtp_err_status_t srtp_aes_icm_openssl_set_iv(
267 void *cv,
268 uint8_t *iv,
269 srtp_cipher_direction_t dir)
270 {
271 srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv;
272 v128_t nonce;
273
274 /* set nonce (for alignment) */
275 v128_copy_octet_string(&nonce, iv);
276
277 debug_print(srtp_mod_aes_icm, "setting iv: %s", v128_hex_string(&nonce));
278
279 v128_xor(&c->counter, &c->offset, &nonce);
280
281 debug_print(srtp_mod_aes_icm, "set_counter: %s",
282 v128_hex_string(&c->counter));
283
284 if (!EVP_EncryptInit_ex(c->ctx, NULL, NULL, NULL, c->counter.v8)) {
285 return srtp_err_status_fail;
286 } else {
287 return srtp_err_status_ok;
288 }
289 }
290
291 /*
292 * This function encrypts a buffer using AES CTR mode
293 *
294 * Parameters:
295 * c Crypto context
296 * buf data to encrypt
297 * enc_len length of encrypt buffer
298 */
srtp_aes_icm_openssl_encrypt(void * cv,unsigned char * buf,unsigned int * enc_len)299 static srtp_err_status_t srtp_aes_icm_openssl_encrypt(void *cv,
300 unsigned char *buf,
301 unsigned int *enc_len)
302 {
303 srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv;
304 int len = 0;
305
306 debug_print(srtp_mod_aes_icm, "rs0: %s", v128_hex_string(&c->counter));
307
308 if (!EVP_EncryptUpdate(c->ctx, buf, &len, buf, *enc_len)) {
309 return srtp_err_status_cipher_fail;
310 }
311 *enc_len = len;
312
313 if (!EVP_EncryptFinal_ex(c->ctx, buf + len, &len)) {
314 return srtp_err_status_cipher_fail;
315 }
316 *enc_len += len;
317
318 return srtp_err_status_ok;
319 }
320
321 /*
322 * Name of this crypto engine
323 */
324 static const char srtp_aes_icm_128_openssl_description[] =
325 "AES-128 counter mode using openssl";
326 static const char srtp_aes_icm_192_openssl_description[] =
327 "AES-192 counter mode using openssl";
328 static const char srtp_aes_icm_256_openssl_description[] =
329 "AES-256 counter mode using openssl";
330
331 /*
332 * This is the function table for this crypto engine.
333 * note: the encrypt function is identical to the decrypt function
334 */
335 const srtp_cipher_type_t srtp_aes_icm_128 = {
336 srtp_aes_icm_openssl_alloc, /* */
337 srtp_aes_icm_openssl_dealloc, /* */
338 srtp_aes_icm_openssl_context_init, /* */
339 0, /* set_aad */
340 srtp_aes_icm_openssl_encrypt, /* */
341 srtp_aes_icm_openssl_encrypt, /* */
342 srtp_aes_icm_openssl_set_iv, /* */
343 0, /* get_tag */
344 srtp_aes_icm_128_openssl_description, /* */
345 &srtp_aes_icm_128_test_case_0, /* */
346 SRTP_AES_ICM_128 /* */
347 };
348
349 /*
350 * This is the function table for this crypto engine.
351 * note: the encrypt function is identical to the decrypt function
352 */
353 const srtp_cipher_type_t srtp_aes_icm_192 = {
354 srtp_aes_icm_openssl_alloc, /* */
355 srtp_aes_icm_openssl_dealloc, /* */
356 srtp_aes_icm_openssl_context_init, /* */
357 0, /* set_aad */
358 srtp_aes_icm_openssl_encrypt, /* */
359 srtp_aes_icm_openssl_encrypt, /* */
360 srtp_aes_icm_openssl_set_iv, /* */
361 0, /* get_tag */
362 srtp_aes_icm_192_openssl_description, /* */
363 &srtp_aes_icm_192_test_case_0, /* */
364 SRTP_AES_ICM_192 /* */
365 };
366
367 /*
368 * This is the function table for this crypto engine.
369 * note: the encrypt function is identical to the decrypt function
370 */
371 const srtp_cipher_type_t srtp_aes_icm_256 = {
372 srtp_aes_icm_openssl_alloc, /* */
373 srtp_aes_icm_openssl_dealloc, /* */
374 srtp_aes_icm_openssl_context_init, /* */
375 0, /* set_aad */
376 srtp_aes_icm_openssl_encrypt, /* */
377 srtp_aes_icm_openssl_encrypt, /* */
378 srtp_aes_icm_openssl_set_iv, /* */
379 0, /* get_tag */
380 srtp_aes_icm_256_openssl_description, /* */
381 &srtp_aes_icm_256_test_case_0, /* */
382 SRTP_AES_ICM_256 /* */
383 };
384