1 /*
2 * DTLS cookie callbacks implementation
3 *
4 * Copyright The Mbed TLS Contributors
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 /*
20 * These session callbacks use a simple chained list
21 * to store and retrieve the session information.
22 */
23
24 #include "common.h"
25
26 #if defined(MBEDTLS_SSL_COOKIE_C)
27
28 #include "mbedtls/platform.h"
29
30 #include "mbedtls/ssl_cookie.h"
31 #include "ssl_misc.h"
32 #include "mbedtls/error.h"
33 #include "mbedtls/platform_util.h"
34 #include "mbedtls/constant_time.h"
35
36 #include "mbedtls/legacy_or_psa.h"
37
38 #include <string.h>
39
40 /*
41 * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-384 is
42 * available. Try SHA-256 first, 384 wastes resources
43 */
44 #if defined(MBEDTLS_HAS_ALG_SHA_224_VIA_LOWLEVEL_OR_PSA)
45 #define COOKIE_MD MBEDTLS_MD_SHA224
46 #define COOKIE_MD_OUTLEN 32
47 #define COOKIE_HMAC_LEN 28
48 #elif defined(MBEDTLS_HAS_ALG_SHA_384_VIA_LOWLEVEL_OR_PSA)
49 #define COOKIE_MD MBEDTLS_MD_SHA384
50 #define COOKIE_MD_OUTLEN 48
51 #define COOKIE_HMAC_LEN 28
52 #elif defined(MBEDTLS_HAS_ALG_SHA_1_VIA_LOWLEVEL_OR_PSA)
53 #define COOKIE_MD MBEDTLS_MD_SHA1
54 #define COOKIE_MD_OUTLEN 20
55 #define COOKIE_HMAC_LEN 20
56 #else
57 #error "DTLS hello verify needs SHA-1 or SHA-2"
58 #endif
59
60 /*
61 * Cookies are formed of a 4-bytes timestamp (or serial number) and
62 * an HMAC of timestamp and client ID.
63 */
64 #define COOKIE_LEN ( 4 + COOKIE_HMAC_LEN )
65
mbedtls_ssl_cookie_init(mbedtls_ssl_cookie_ctx * ctx)66 void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx )
67 {
68 #if defined(MBEDTLS_USE_PSA_CRYPTO)
69 ctx->psa_hmac_key = MBEDTLS_SVC_KEY_ID_INIT;
70 #else
71 mbedtls_md_init( &ctx->hmac_ctx );
72 #endif /* MBEDTLS_USE_PSA_CRYPTO */
73 #if !defined(MBEDTLS_HAVE_TIME)
74 ctx->serial = 0;
75 #endif
76 ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;
77
78 #if !defined(MBEDTLS_USE_PSA_CRYPTO)
79 #if defined(MBEDTLS_THREADING_C)
80 mbedtls_mutex_init( &ctx->mutex );
81 #endif
82 #endif /* !MBEDTLS_USE_PSA_CRYPTO */
83 }
84
mbedtls_ssl_cookie_set_timeout(mbedtls_ssl_cookie_ctx * ctx,unsigned long delay)85 void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay )
86 {
87 ctx->timeout = delay;
88 }
89
mbedtls_ssl_cookie_free(mbedtls_ssl_cookie_ctx * ctx)90 void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx )
91 {
92 #if defined(MBEDTLS_USE_PSA_CRYPTO)
93 psa_destroy_key( ctx->psa_hmac_key );
94 #else
95 mbedtls_md_free( &ctx->hmac_ctx );
96
97 #if defined(MBEDTLS_THREADING_C)
98 mbedtls_mutex_free( &ctx->mutex );
99 #endif
100 #endif /* MBEDTLS_USE_PSA_CRYPTO */
101
102 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) );
103 }
104
mbedtls_ssl_cookie_setup(mbedtls_ssl_cookie_ctx * ctx,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)105 int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx,
106 int (*f_rng)(void *, unsigned char *, size_t),
107 void *p_rng )
108 {
109 #if defined(MBEDTLS_USE_PSA_CRYPTO)
110 psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
111 psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
112 psa_algorithm_t alg;
113
114 (void)f_rng;
115 (void)p_rng;
116
117 alg = mbedtls_hash_info_psa_from_md( COOKIE_MD );
118 if( alg == 0 )
119 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
120
121 ctx->psa_hmac_alg = PSA_ALG_TRUNCATED_MAC( PSA_ALG_HMAC( alg ),
122 COOKIE_HMAC_LEN );
123
124 psa_set_key_usage_flags( &attributes, PSA_KEY_USAGE_VERIFY_MESSAGE |
125 PSA_KEY_USAGE_SIGN_MESSAGE );
126 psa_set_key_algorithm( &attributes, ctx->psa_hmac_alg );
127 psa_set_key_type( &attributes, PSA_KEY_TYPE_HMAC );
128 psa_set_key_bits( &attributes, PSA_BYTES_TO_BITS( COOKIE_MD_OUTLEN ) );
129
130 if( ( status = psa_generate_key( &attributes,
131 &ctx->psa_hmac_key ) ) != PSA_SUCCESS )
132 {
133 return psa_ssl_status_to_mbedtls( status );
134 }
135 #else
136 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
137 unsigned char key[COOKIE_MD_OUTLEN];
138
139 if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 )
140 return( ret );
141
142 ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 );
143 if( ret != 0 )
144 return( ret );
145
146 ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) );
147 if( ret != 0 )
148 return( ret );
149
150 mbedtls_platform_zeroize( key, sizeof( key ) );
151 #endif /* MBEDTLS_USE_PSA_CRYPTO */
152
153 return( 0 );
154 }
155
156 #if !defined(MBEDTLS_USE_PSA_CRYPTO)
157 /*
158 * Generate the HMAC part of a cookie
159 */
160 MBEDTLS_CHECK_RETURN_CRITICAL
ssl_cookie_hmac(mbedtls_md_context_t * hmac_ctx,const unsigned char time[4],unsigned char ** p,unsigned char * end,const unsigned char * cli_id,size_t cli_id_len)161 static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,
162 const unsigned char time[4],
163 unsigned char **p, unsigned char *end,
164 const unsigned char *cli_id, size_t cli_id_len )
165 {
166 unsigned char hmac_out[COOKIE_MD_OUTLEN];
167
168 MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_HMAC_LEN );
169
170 if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 ||
171 mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
172 mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 ||
173 mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 )
174 {
175 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
176 }
177
178 memcpy( *p, hmac_out, COOKIE_HMAC_LEN );
179 *p += COOKIE_HMAC_LEN;
180
181 return( 0 );
182 }
183 #endif /* !MBEDTLS_USE_PSA_CRYPTO */
184
185 /*
186 * Generate cookie for DTLS ClientHello verification
187 */
mbedtls_ssl_cookie_write(void * p_ctx,unsigned char ** p,unsigned char * end,const unsigned char * cli_id,size_t cli_id_len)188 int mbedtls_ssl_cookie_write( void *p_ctx,
189 unsigned char **p, unsigned char *end,
190 const unsigned char *cli_id, size_t cli_id_len )
191 {
192 #if defined(MBEDTLS_USE_PSA_CRYPTO)
193 psa_mac_operation_t operation = PSA_MAC_OPERATION_INIT;
194 psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
195 size_t sign_mac_length = 0;
196 #endif
197 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
198 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
199 unsigned long t;
200
201 if( ctx == NULL || cli_id == NULL )
202 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
203
204 MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_LEN );
205
206 #if defined(MBEDTLS_HAVE_TIME)
207 t = (unsigned long) mbedtls_time( NULL );
208 #else
209 t = ctx->serial++;
210 #endif
211
212 MBEDTLS_PUT_UINT32_BE(t, *p, 0);
213 *p += 4;
214
215 #if defined(MBEDTLS_USE_PSA_CRYPTO)
216 status = psa_mac_sign_setup( &operation, ctx->psa_hmac_key,
217 ctx->psa_hmac_alg );
218 if( status != PSA_SUCCESS )
219 {
220 ret = psa_ssl_status_to_mbedtls( status );
221 goto exit;
222 }
223
224 status = psa_mac_update( &operation, *p - 4, 4 );
225 if( status != PSA_SUCCESS )
226 {
227 ret = psa_ssl_status_to_mbedtls( status );
228 goto exit;
229 }
230
231 status = psa_mac_update( &operation, cli_id, cli_id_len );
232 if( status != PSA_SUCCESS )
233 {
234 ret = psa_ssl_status_to_mbedtls( status );
235 goto exit;
236 }
237
238 status = psa_mac_sign_finish( &operation, *p, COOKIE_MD_OUTLEN,
239 &sign_mac_length );
240 if( status != PSA_SUCCESS )
241 {
242 ret = psa_ssl_status_to_mbedtls( status );
243 goto exit;
244 }
245
246 *p += COOKIE_HMAC_LEN;
247
248 ret = 0;
249 #else
250 #if defined(MBEDTLS_THREADING_C)
251 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
252 return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR, ret ) );
253 #endif
254
255 ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4,
256 p, end, cli_id, cli_id_len );
257
258 #if defined(MBEDTLS_THREADING_C)
259 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
260 return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR,
261 MBEDTLS_ERR_THREADING_MUTEX_ERROR ) );
262 #endif
263 #endif /* MBEDTLS_USE_PSA_CRYPTO */
264
265 #if defined(MBEDTLS_USE_PSA_CRYPTO)
266 exit:
267 status = psa_mac_abort( &operation );
268 if( status != PSA_SUCCESS )
269 ret = psa_ssl_status_to_mbedtls( status );
270 #endif /* MBEDTLS_USE_PSA_CRYPTO */
271 return( ret );
272 }
273
274 /*
275 * Check a cookie
276 */
mbedtls_ssl_cookie_check(void * p_ctx,const unsigned char * cookie,size_t cookie_len,const unsigned char * cli_id,size_t cli_id_len)277 int mbedtls_ssl_cookie_check( void *p_ctx,
278 const unsigned char *cookie, size_t cookie_len,
279 const unsigned char *cli_id, size_t cli_id_len )
280 {
281 #if defined(MBEDTLS_USE_PSA_CRYPTO)
282 psa_mac_operation_t operation = PSA_MAC_OPERATION_INIT;
283 psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
284 #else
285 unsigned char ref_hmac[COOKIE_HMAC_LEN];
286 unsigned char *p = ref_hmac;
287 #endif
288 int ret = 0;
289 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
290 unsigned long cur_time, cookie_time;
291
292 if( ctx == NULL || cli_id == NULL )
293 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
294
295 if( cookie_len != COOKIE_LEN )
296 return( -1 );
297
298 #if defined(MBEDTLS_USE_PSA_CRYPTO)
299 status = psa_mac_verify_setup( &operation, ctx->psa_hmac_key,
300 ctx->psa_hmac_alg );
301 if( status != PSA_SUCCESS )
302 {
303 ret = psa_ssl_status_to_mbedtls( status );
304 goto exit;
305 }
306
307 status = psa_mac_update( &operation, cookie, 4 );
308 if( status != PSA_SUCCESS )
309 {
310 ret = psa_ssl_status_to_mbedtls( status );
311 goto exit;
312 }
313
314 status = psa_mac_update( &operation, cli_id,
315 cli_id_len );
316 if( status != PSA_SUCCESS )
317 {
318 ret = psa_ssl_status_to_mbedtls( status );
319 goto exit;
320 }
321
322 status = psa_mac_verify_finish( &operation, cookie + 4,
323 COOKIE_HMAC_LEN );
324 if( status != PSA_SUCCESS )
325 {
326 ret = psa_ssl_status_to_mbedtls( status );
327 goto exit;
328 }
329
330 ret = 0;
331 #else
332 #if defined(MBEDTLS_THREADING_C)
333 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
334 return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR, ret ) );
335 #endif
336
337 if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie,
338 &p, p + sizeof( ref_hmac ),
339 cli_id, cli_id_len ) != 0 )
340 ret = -1;
341
342 #if defined(MBEDTLS_THREADING_C)
343 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
344 {
345 ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR,
346 MBEDTLS_ERR_THREADING_MUTEX_ERROR );
347 }
348 #endif
349
350 if( ret != 0 )
351 goto exit;
352
353 if( mbedtls_ct_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 )
354 {
355 ret = -1;
356 goto exit;
357 }
358 #endif /* MBEDTLS_USE_PSA_CRYPTO */
359
360 #if defined(MBEDTLS_HAVE_TIME)
361 cur_time = (unsigned long) mbedtls_time( NULL );
362 #else
363 cur_time = ctx->serial;
364 #endif
365
366 cookie_time = ( (unsigned long) cookie[0] << 24 ) |
367 ( (unsigned long) cookie[1] << 16 ) |
368 ( (unsigned long) cookie[2] << 8 ) |
369 ( (unsigned long) cookie[3] );
370
371 if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout )
372 {
373 ret = -1;
374 goto exit;
375 }
376
377 exit:
378 #if defined(MBEDTLS_USE_PSA_CRYPTO)
379 status = psa_mac_abort( &operation );
380 if( status != PSA_SUCCESS )
381 ret = psa_ssl_status_to_mbedtls( status );
382 #else
383 mbedtls_platform_zeroize( ref_hmac, sizeof( ref_hmac ) );
384 #endif /* MBEDTLS_USE_PSA_CRYPTO */
385 return( ret );
386 }
387 #endif /* MBEDTLS_SSL_COOKIE_C */
388
