1 /*
2 * NIST SP800-38C compliant CCM implementation
3 *
4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 *
19 * This file is part of mbed TLS (https://tls.mbed.org)
20 */
21
22 /*
23 * Definition of CCM:
24 * http://csrc.nist.gov/publications/nistpubs/800-38C/SP800-38C_updated-July20_2007.pdf
25 * RFC 3610 "Counter with CBC-MAC (CCM)"
26 *
27 * Related:
28 * RFC 5116 "An Interface and Algorithms for Authenticated Encryption"
29 */
30
31 #if !defined(MBEDTLS_CONFIG_FILE)
32 #include "mbedtls/config.h"
33 #else
34 #include MBEDTLS_CONFIG_FILE
35 #endif
36
37 #if defined(MBEDTLS_CCM_C)
38
39 #include "mbedtls/ccm.h"
40
41 #include <string.h>
42
43 #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
44 #if defined(MBEDTLS_PLATFORM_C)
45 #include "mbedtls/platform.h"
46 #else
47 #include <stdio.h>
48 #define mbedtls_printf printf
49 #endif /* MBEDTLS_PLATFORM_C */
50 #endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */
51
52 /* Implementation that should never be optimized out by the compiler */
mbedtls_zeroize(void * v,size_t n)53 static void mbedtls_zeroize( void *v, size_t n ) {
54 volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
55 }
56
57 #define CCM_ENCRYPT 0
58 #define CCM_DECRYPT 1
59
60 /*
61 * Initialize context
62 */
mbedtls_ccm_init(mbedtls_ccm_context * ctx)63 void mbedtls_ccm_init( mbedtls_ccm_context *ctx )
64 {
65 memset( ctx, 0, sizeof( mbedtls_ccm_context ) );
66 }
67
mbedtls_ccm_setkey(mbedtls_ccm_context * ctx,mbedtls_cipher_id_t cipher,const unsigned char * key,unsigned int keybits)68 int mbedtls_ccm_setkey( mbedtls_ccm_context *ctx,
69 mbedtls_cipher_id_t cipher,
70 const unsigned char *key,
71 unsigned int keybits )
72 {
73 int ret;
74 const mbedtls_cipher_info_t *cipher_info;
75
76 cipher_info = mbedtls_cipher_info_from_values( cipher, keybits, MBEDTLS_MODE_ECB );
77 if( cipher_info == NULL )
78 return( MBEDTLS_ERR_CCM_BAD_INPUT );
79
80 if( cipher_info->block_size != 16 )
81 return( MBEDTLS_ERR_CCM_BAD_INPUT );
82
83 mbedtls_cipher_free( &ctx->cipher_ctx );
84
85 if( ( ret = mbedtls_cipher_setup( &ctx->cipher_ctx, cipher_info ) ) != 0 )
86 return( ret );
87
88 if( ( ret = mbedtls_cipher_setkey( &ctx->cipher_ctx, key, keybits,
89 MBEDTLS_ENCRYPT ) ) != 0 )
90 {
91 return( ret );
92 }
93
94 return( 0 );
95 }
96
97 /*
98 * Free context
99 */
mbedtls_ccm_free(mbedtls_ccm_context * ctx)100 void mbedtls_ccm_free( mbedtls_ccm_context *ctx )
101 {
102 mbedtls_cipher_free( &ctx->cipher_ctx );
103 mbedtls_zeroize( ctx, sizeof( mbedtls_ccm_context ) );
104 }
105
106 /*
107 * Macros for common operations.
108 * Results in smaller compiled code than static inline functions.
109 */
110
111 /*
112 * Update the CBC-MAC state in y using a block in b
113 * (Always using b as the source helps the compiler optimise a bit better.)
114 */
115 #define UPDATE_CBC_MAC \
116 for( i = 0; i < 16; i++ ) \
117 y[i] ^= b[i]; \
118 \
119 if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, y, 16, y, &olen ) ) != 0 ) \
120 return( ret );
121
122 /*
123 * Encrypt or decrypt a partial block with CTR
124 * Warning: using b for temporary storage! src and dst must not be b!
125 * This avoids allocating one more 16 bytes buffer while allowing src == dst.
126 */
127 #define CTR_CRYPT( dst, src, len ) \
128 if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctr, 16, b, &olen ) ) != 0 ) \
129 return( ret ); \
130 \
131 for( i = 0; i < len; i++ ) \
132 dst[i] = src[i] ^ b[i];
133
134 /*
135 * Authenticated encryption or decryption
136 */
ccm_auth_crypt(mbedtls_ccm_context * ctx,int mode,size_t length,const unsigned char * iv,size_t iv_len,const unsigned char * add,size_t add_len,const unsigned char * input,unsigned char * output,unsigned char * tag,size_t tag_len)137 static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length,
138 const unsigned char *iv, size_t iv_len,
139 const unsigned char *add, size_t add_len,
140 const unsigned char *input, unsigned char *output,
141 unsigned char *tag, size_t tag_len )
142 {
143 int ret;
144 unsigned char i;
145 unsigned char q;
146 size_t len_left, olen;
147 unsigned char b[16];
148 unsigned char y[16];
149 unsigned char ctr[16];
150 const unsigned char *src;
151 unsigned char *dst;
152
153 /*
154 * Check length requirements: SP800-38C A.1
155 * Additional requirement: a < 2^16 - 2^8 to simplify the code.
156 * 'length' checked later (when writing it to the first block)
157 */
158 if( tag_len < 4 || tag_len > 16 || tag_len % 2 != 0 )
159 return( MBEDTLS_ERR_CCM_BAD_INPUT );
160
161 /* Also implies q is within bounds */
162 if( iv_len < 7 || iv_len > 13 )
163 return( MBEDTLS_ERR_CCM_BAD_INPUT );
164
165 if( add_len > 0xFF00 )
166 return( MBEDTLS_ERR_CCM_BAD_INPUT );
167
168 q = 16 - 1 - (unsigned char) iv_len;
169
170 /*
171 * First block B_0:
172 * 0 .. 0 flags
173 * 1 .. iv_len nonce (aka iv)
174 * iv_len+1 .. 15 length
175 *
176 * With flags as (bits):
177 * 7 0
178 * 6 add present?
179 * 5 .. 3 (t - 2) / 2
180 * 2 .. 0 q - 1
181 */
182 b[0] = 0;
183 b[0] |= ( add_len > 0 ) << 6;
184 b[0] |= ( ( tag_len - 2 ) / 2 ) << 3;
185 b[0] |= q - 1;
186
187 memcpy( b + 1, iv, iv_len );
188
189 for( i = 0, len_left = length; i < q; i++, len_left >>= 8 )
190 b[15-i] = (unsigned char)( len_left & 0xFF );
191
192 if( len_left > 0 )
193 return( MBEDTLS_ERR_CCM_BAD_INPUT );
194
195
196 /* Start CBC-MAC with first block */
197 memset( y, 0, 16 );
198 UPDATE_CBC_MAC;
199
200 /*
201 * If there is additional data, update CBC-MAC with
202 * add_len, add, 0 (padding to a block boundary)
203 */
204 if( add_len > 0 )
205 {
206 size_t use_len;
207 len_left = add_len;
208 src = add;
209
210 memset( b, 0, 16 );
211 b[0] = (unsigned char)( ( add_len >> 8 ) & 0xFF );
212 b[1] = (unsigned char)( ( add_len ) & 0xFF );
213
214 use_len = len_left < 16 - 2 ? len_left : 16 - 2;
215 memcpy( b + 2, src, use_len );
216 len_left -= use_len;
217 src += use_len;
218
219 UPDATE_CBC_MAC;
220
221 while( len_left > 0 )
222 {
223 use_len = len_left > 16 ? 16 : len_left;
224
225 memset( b, 0, 16 );
226 memcpy( b, src, use_len );
227 UPDATE_CBC_MAC;
228
229 len_left -= use_len;
230 src += use_len;
231 }
232 }
233
234 /*
235 * Prepare counter block for encryption:
236 * 0 .. 0 flags
237 * 1 .. iv_len nonce (aka iv)
238 * iv_len+1 .. 15 counter (initially 1)
239 *
240 * With flags as (bits):
241 * 7 .. 3 0
242 * 2 .. 0 q - 1
243 */
244 ctr[0] = q - 1;
245 memcpy( ctr + 1, iv, iv_len );
246 memset( ctr + 1 + iv_len, 0, q );
247 ctr[15] = 1;
248
249 /*
250 * Authenticate and {en,de}crypt the message.
251 *
252 * The only difference between encryption and decryption is
253 * the respective order of authentication and {en,de}cryption.
254 */
255 len_left = length;
256 src = input;
257 dst = output;
258
259 while( len_left > 0 )
260 {
261 size_t use_len = len_left > 16 ? 16 : len_left;
262
263 if( mode == CCM_ENCRYPT )
264 {
265 memset( b, 0, 16 );
266 memcpy( b, src, use_len );
267 UPDATE_CBC_MAC;
268 }
269
270 CTR_CRYPT( dst, src, use_len );
271
272 if( mode == CCM_DECRYPT )
273 {
274 memset( b, 0, 16 );
275 memcpy( b, dst, use_len );
276 UPDATE_CBC_MAC;
277 }
278
279 dst += use_len;
280 src += use_len;
281 len_left -= use_len;
282
283 /*
284 * Increment counter.
285 * No need to check for overflow thanks to the length check above.
286 */
287 for( i = 0; i < q; i++ )
288 if( ++ctr[15-i] != 0 )
289 break;
290 }
291
292 /*
293 * Authentication: reset counter and crypt/mask internal tag
294 */
295 for( i = 0; i < q; i++ )
296 ctr[15-i] = 0;
297
298 CTR_CRYPT( y, y, 16 );
299 memcpy( tag, y, tag_len );
300
301 return( 0 );
302 }
303
304 /*
305 * Authenticated encryption
306 */
mbedtls_ccm_encrypt_and_tag(mbedtls_ccm_context * ctx,size_t length,const unsigned char * iv,size_t iv_len,const unsigned char * add,size_t add_len,const unsigned char * input,unsigned char * output,unsigned char * tag,size_t tag_len)307 int mbedtls_ccm_encrypt_and_tag( mbedtls_ccm_context *ctx, size_t length,
308 const unsigned char *iv, size_t iv_len,
309 const unsigned char *add, size_t add_len,
310 const unsigned char *input, unsigned char *output,
311 unsigned char *tag, size_t tag_len )
312 {
313 return( ccm_auth_crypt( ctx, CCM_ENCRYPT, length, iv, iv_len,
314 add, add_len, input, output, tag, tag_len ) );
315 }
316
317 /*
318 * Authenticated decryption
319 */
mbedtls_ccm_auth_decrypt(mbedtls_ccm_context * ctx,size_t length,const unsigned char * iv,size_t iv_len,const unsigned char * add,size_t add_len,const unsigned char * input,unsigned char * output,const unsigned char * tag,size_t tag_len)320 int mbedtls_ccm_auth_decrypt( mbedtls_ccm_context *ctx, size_t length,
321 const unsigned char *iv, size_t iv_len,
322 const unsigned char *add, size_t add_len,
323 const unsigned char *input, unsigned char *output,
324 const unsigned char *tag, size_t tag_len )
325 {
326 int ret;
327 unsigned char check_tag[16];
328 unsigned char i;
329 int diff;
330
331 if( ( ret = ccm_auth_crypt( ctx, CCM_DECRYPT, length,
332 iv, iv_len, add, add_len,
333 input, output, check_tag, tag_len ) ) != 0 )
334 {
335 return( ret );
336 }
337
338 /* Check tag in "constant-time" */
339 for( diff = 0, i = 0; i < tag_len; i++ )
340 diff |= tag[i] ^ check_tag[i];
341
342 if( diff != 0 )
343 {
344 mbedtls_zeroize( output, length );
345 return( MBEDTLS_ERR_CCM_AUTH_FAILED );
346 }
347
348 return( 0 );
349 }
350
351
352 #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
353 /*
354 * Examples 1 to 3 from SP800-38C Appendix C
355 */
356
357 #define NB_TESTS 3
358
359 /*
360 * The data is the same for all tests, only the used length changes
361 */
362 static const unsigned char key[] = {
363 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
364 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f
365 };
366
367 static const unsigned char iv[] = {
368 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
369 0x18, 0x19, 0x1a, 0x1b
370 };
371
372 static const unsigned char ad[] = {
373 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
374 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
375 0x10, 0x11, 0x12, 0x13
376 };
377
378 static const unsigned char msg[] = {
379 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
380 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
381 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
382 };
383
384 static const size_t iv_len [NB_TESTS] = { 7, 8, 12 };
385 static const size_t add_len[NB_TESTS] = { 8, 16, 20 };
386 static const size_t msg_len[NB_TESTS] = { 4, 16, 24 };
387 static const size_t tag_len[NB_TESTS] = { 4, 6, 8 };
388
389 static const unsigned char res[NB_TESTS][32] = {
390 { 0x71, 0x62, 0x01, 0x5b, 0x4d, 0xac, 0x25, 0x5d },
391 { 0xd2, 0xa1, 0xf0, 0xe0, 0x51, 0xea, 0x5f, 0x62,
392 0x08, 0x1a, 0x77, 0x92, 0x07, 0x3d, 0x59, 0x3d,
393 0x1f, 0xc6, 0x4f, 0xbf, 0xac, 0xcd },
394 { 0xe3, 0xb2, 0x01, 0xa9, 0xf5, 0xb7, 0x1a, 0x7a,
395 0x9b, 0x1c, 0xea, 0xec, 0xcd, 0x97, 0xe7, 0x0b,
396 0x61, 0x76, 0xaa, 0xd9, 0xa4, 0x42, 0x8a, 0xa5,
397 0x48, 0x43, 0x92, 0xfb, 0xc1, 0xb0, 0x99, 0x51 }
398 };
399
mbedtls_ccm_self_test(int verbose)400 int mbedtls_ccm_self_test( int verbose )
401 {
402 mbedtls_ccm_context ctx;
403 unsigned char out[32];
404 size_t i;
405 int ret;
406
407 mbedtls_ccm_init( &ctx );
408
409 if( mbedtls_ccm_setkey( &ctx, MBEDTLS_CIPHER_ID_AES, key, 8 * sizeof key ) != 0 )
410 {
411 if( verbose != 0 )
412 mbedtls_printf( " CCM: setup failed" );
413
414 return( 1 );
415 }
416
417 for( i = 0; i < NB_TESTS; i++ )
418 {
419 if( verbose != 0 )
420 mbedtls_printf( " CCM-AES #%u: ", (unsigned int) i + 1 );
421
422 ret = mbedtls_ccm_encrypt_and_tag( &ctx, msg_len[i],
423 iv, iv_len[i], ad, add_len[i],
424 msg, out,
425 out + msg_len[i], tag_len[i] );
426
427 if( ret != 0 ||
428 memcmp( out, res[i], msg_len[i] + tag_len[i] ) != 0 )
429 {
430 if( verbose != 0 )
431 mbedtls_printf( "failed\n" );
432
433 return( 1 );
434 }
435
436 ret = mbedtls_ccm_auth_decrypt( &ctx, msg_len[i],
437 iv, iv_len[i], ad, add_len[i],
438 res[i], out,
439 res[i] + msg_len[i], tag_len[i] );
440
441 if( ret != 0 ||
442 memcmp( out, msg, msg_len[i] ) != 0 )
443 {
444 if( verbose != 0 )
445 mbedtls_printf( "failed\n" );
446
447 return( 1 );
448 }
449
450 if( verbose != 0 )
451 mbedtls_printf( "passed\n" );
452 }
453
454 mbedtls_ccm_free( &ctx );
455
456 if( verbose != 0 )
457 mbedtls_printf( "\n" );
458
459 return( 0 );
460 }
461
462 #endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */
463
464 #endif /* MBEDTLS_CCM_C */
465
