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 #if defined(MBEDTLS_PLATFORM_C)
29 #include "mbedtls/platform.h"
30 #else
31 #define mbedtls_calloc calloc
32 #define mbedtls_free free
33 #endif
34
35 #include "mbedtls/ssl_cookie.h"
36 #include "mbedtls/ssl_internal.h"
37 #include "mbedtls/error.h"
38 #include "mbedtls/platform_util.h"
39
40 #include <string.h>
41
42 /*
43 * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is
44 * available. Try SHA-256 first, 512 wastes resources since we need to stay
45 * with max 32 bytes of cookie for DTLS 1.0
46 */
47 #if defined(MBEDTLS_SHA256_C)
48 #define COOKIE_MD MBEDTLS_MD_SHA224
49 #define COOKIE_MD_OUTLEN 32
50 #define COOKIE_HMAC_LEN 28
51 #elif defined(MBEDTLS_SHA512_C)
52 #define COOKIE_MD MBEDTLS_MD_SHA384
53 #define COOKIE_MD_OUTLEN 48
54 #define COOKIE_HMAC_LEN 28
55 #elif defined(MBEDTLS_SHA1_C)
56 #define COOKIE_MD MBEDTLS_MD_SHA1
57 #define COOKIE_MD_OUTLEN 20
58 #define COOKIE_HMAC_LEN 20
59 #else
60 #error "DTLS hello verify needs SHA-1 or SHA-2"
61 #endif
62
63 /*
64 * Cookies are formed of a 4-bytes timestamp (or serial number) and
65 * an HMAC of timestemp and client ID.
66 */
67 #define COOKIE_LEN ( 4 + COOKIE_HMAC_LEN )
68
mbedtls_ssl_cookie_init(mbedtls_ssl_cookie_ctx * ctx)69 void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx )
70 {
71 mbedtls_md_init( &ctx->hmac_ctx );
72 #if !defined(MBEDTLS_HAVE_TIME)
73 ctx->serial = 0;
74 #endif
75 ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;
76
77 #if defined(MBEDTLS_THREADING_C)
78 mbedtls_mutex_init( &ctx->mutex );
79 #endif
80 }
81
mbedtls_ssl_cookie_set_timeout(mbedtls_ssl_cookie_ctx * ctx,unsigned long delay)82 void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay )
83 {
84 ctx->timeout = delay;
85 }
86
mbedtls_ssl_cookie_free(mbedtls_ssl_cookie_ctx * ctx)87 void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx )
88 {
89 mbedtls_md_free( &ctx->hmac_ctx );
90
91 #if defined(MBEDTLS_THREADING_C)
92 mbedtls_mutex_free( &ctx->mutex );
93 #endif
94
95 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) );
96 }
97
mbedtls_ssl_cookie_setup(mbedtls_ssl_cookie_ctx * ctx,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)98 int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx,
99 int (*f_rng)(void *, unsigned char *, size_t),
100 void *p_rng )
101 {
102 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
103 unsigned char key[COOKIE_MD_OUTLEN];
104
105 if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 )
106 return( ret );
107
108 ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 );
109 if( ret != 0 )
110 return( ret );
111
112 ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) );
113 if( ret != 0 )
114 return( ret );
115
116 mbedtls_platform_zeroize( key, sizeof( key ) );
117
118 return( 0 );
119 }
120
121 /*
122 * Generate the HMAC part of a cookie
123 */
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)124 static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,
125 const unsigned char time[4],
126 unsigned char **p, unsigned char *end,
127 const unsigned char *cli_id, size_t cli_id_len )
128 {
129 unsigned char hmac_out[COOKIE_MD_OUTLEN];
130
131 MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_HMAC_LEN );
132
133 if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 ||
134 mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
135 mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 ||
136 mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 )
137 {
138 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
139 }
140
141 memcpy( *p, hmac_out, COOKIE_HMAC_LEN );
142 *p += COOKIE_HMAC_LEN;
143
144 return( 0 );
145 }
146
147 /*
148 * Generate cookie for DTLS ClientHello verification
149 */
mbedtls_ssl_cookie_write(void * p_ctx,unsigned char ** p,unsigned char * end,const unsigned char * cli_id,size_t cli_id_len)150 int mbedtls_ssl_cookie_write( void *p_ctx,
151 unsigned char **p, unsigned char *end,
152 const unsigned char *cli_id, size_t cli_id_len )
153 {
154 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
155 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
156 unsigned long t;
157
158 if( ctx == NULL || cli_id == NULL )
159 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
160
161 MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_LEN );
162
163 #if defined(MBEDTLS_HAVE_TIME)
164 t = (unsigned long) mbedtls_time( NULL );
165 #else
166 t = ctx->serial++;
167 #endif
168
169 (*p)[0] = (unsigned char)( t >> 24 );
170 (*p)[1] = (unsigned char)( t >> 16 );
171 (*p)[2] = (unsigned char)( t >> 8 );
172 (*p)[3] = (unsigned char)( t );
173 *p += 4;
174
175 #if defined(MBEDTLS_THREADING_C)
176 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
177 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );
178 #endif
179
180 ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4,
181 p, end, cli_id, cli_id_len );
182
183 #if defined(MBEDTLS_THREADING_C)
184 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
185 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +
186 MBEDTLS_ERR_THREADING_MUTEX_ERROR );
187 #endif
188
189 return( ret );
190 }
191
192 /*
193 * Check a cookie
194 */
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)195 int mbedtls_ssl_cookie_check( void *p_ctx,
196 const unsigned char *cookie, size_t cookie_len,
197 const unsigned char *cli_id, size_t cli_id_len )
198 {
199 unsigned char ref_hmac[COOKIE_HMAC_LEN];
200 int ret = 0;
201 unsigned char *p = ref_hmac;
202 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
203 unsigned long cur_time, cookie_time;
204
205 if( ctx == NULL || cli_id == NULL )
206 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
207
208 if( cookie_len != COOKIE_LEN )
209 return( -1 );
210
211 #if defined(MBEDTLS_THREADING_C)
212 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
213 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );
214 #endif
215
216 if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie,
217 &p, p + sizeof( ref_hmac ),
218 cli_id, cli_id_len ) != 0 )
219 ret = -1;
220
221 #if defined(MBEDTLS_THREADING_C)
222 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
223 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +
224 MBEDTLS_ERR_THREADING_MUTEX_ERROR );
225 #endif
226
227 if( ret != 0 )
228 return( ret );
229
230 if( mbedtls_ssl_safer_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 )
231 return( -1 );
232
233 #if defined(MBEDTLS_HAVE_TIME)
234 cur_time = (unsigned long) mbedtls_time( NULL );
235 #else
236 cur_time = ctx->serial;
237 #endif
238
239 cookie_time = ( (unsigned long) cookie[0] << 24 ) |
240 ( (unsigned long) cookie[1] << 16 ) |
241 ( (unsigned long) cookie[2] << 8 ) |
242 ( (unsigned long) cookie[3] );
243
244 if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout )
245 return( -1 );
246
247 return( 0 );
248 }
249 #endif /* MBEDTLS_SSL_COOKIE_C */
250
