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 "ssl_misc.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
45 */
46 #if defined(MBEDTLS_SHA224_C)
47 #define COOKIE_MD MBEDTLS_MD_SHA224
48 #define COOKIE_MD_OUTLEN 32
49 #define COOKIE_HMAC_LEN 28
50 #elif defined(MBEDTLS_SHA384_C)
51 #define COOKIE_MD MBEDTLS_MD_SHA384
52 #define COOKIE_MD_OUTLEN 48
53 #define COOKIE_HMAC_LEN 28
54 #elif defined(MBEDTLS_SHA1_C)
55 #define COOKIE_MD MBEDTLS_MD_SHA1
56 #define COOKIE_MD_OUTLEN 20
57 #define COOKIE_HMAC_LEN 20
58 #else
59 #error "DTLS hello verify needs SHA-1 or SHA-2"
60 #endif
61
62 /*
63 * Cookies are formed of a 4-bytes timestamp (or serial number) and
64 * an HMAC of timestemp and client ID.
65 */
66 #define COOKIE_LEN ( 4 + COOKIE_HMAC_LEN )
67
mbedtls_ssl_cookie_init(mbedtls_ssl_cookie_ctx * ctx)68 void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx )
69 {
70 mbedtls_md_init( &ctx->hmac_ctx );
71 #if !defined(MBEDTLS_HAVE_TIME)
72 ctx->serial = 0;
73 #endif
74 ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;
75
76 #if defined(MBEDTLS_THREADING_C)
77 mbedtls_mutex_init( &ctx->mutex );
78 #endif
79 }
80
mbedtls_ssl_cookie_set_timeout(mbedtls_ssl_cookie_ctx * ctx,unsigned long delay)81 void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay )
82 {
83 ctx->timeout = delay;
84 }
85
mbedtls_ssl_cookie_free(mbedtls_ssl_cookie_ctx * ctx)86 void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx )
87 {
88 mbedtls_md_free( &ctx->hmac_ctx );
89
90 #if defined(MBEDTLS_THREADING_C)
91 mbedtls_mutex_free( &ctx->mutex );
92 #endif
93
94 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) );
95 }
96
mbedtls_ssl_cookie_setup(mbedtls_ssl_cookie_ctx * ctx,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)97 int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx,
98 int (*f_rng)(void *, unsigned char *, size_t),
99 void *p_rng )
100 {
101 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
102 unsigned char key[COOKIE_MD_OUTLEN];
103
104 if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 )
105 return( ret );
106
107 ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 );
108 if( ret != 0 )
109 return( ret );
110
111 ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) );
112 if( ret != 0 )
113 return( ret );
114
115 mbedtls_platform_zeroize( key, sizeof( key ) );
116
117 return( 0 );
118 }
119
120 /*
121 * Generate the HMAC part of a cookie
122 */
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)123 static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,
124 const unsigned char time[4],
125 unsigned char **p, unsigned char *end,
126 const unsigned char *cli_id, size_t cli_id_len )
127 {
128 unsigned char hmac_out[COOKIE_MD_OUTLEN];
129
130 MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_HMAC_LEN );
131
132 if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 ||
133 mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
134 mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 ||
135 mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 )
136 {
137 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
138 }
139
140 memcpy( *p, hmac_out, COOKIE_HMAC_LEN );
141 *p += COOKIE_HMAC_LEN;
142
143 return( 0 );
144 }
145
146 /*
147 * Generate cookie for DTLS ClientHello verification
148 */
mbedtls_ssl_cookie_write(void * p_ctx,unsigned char ** p,unsigned char * end,const unsigned char * cli_id,size_t cli_id_len)149 int mbedtls_ssl_cookie_write( void *p_ctx,
150 unsigned char **p, unsigned char *end,
151 const unsigned char *cli_id, size_t cli_id_len )
152 {
153 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
154 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
155 unsigned long t;
156
157 if( ctx == NULL || cli_id == NULL )
158 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
159
160 MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_LEN );
161
162 #if defined(MBEDTLS_HAVE_TIME)
163 t = (unsigned long) mbedtls_time( NULL );
164 #else
165 t = ctx->serial++;
166 #endif
167
168 MBEDTLS_PUT_UINT32_BE(t, *p, 0);
169 *p += 4;
170
171 #if defined(MBEDTLS_THREADING_C)
172 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
173 return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR, ret ) );
174 #endif
175
176 ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4,
177 p, end, cli_id, cli_id_len );
178
179 #if defined(MBEDTLS_THREADING_C)
180 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
181 return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR,
182 MBEDTLS_ERR_THREADING_MUTEX_ERROR ) );
183 #endif
184
185 return( ret );
186 }
187
188 /*
189 * Check a cookie
190 */
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)191 int mbedtls_ssl_cookie_check( void *p_ctx,
192 const unsigned char *cookie, size_t cookie_len,
193 const unsigned char *cli_id, size_t cli_id_len )
194 {
195 unsigned char ref_hmac[COOKIE_HMAC_LEN];
196 int ret = 0;
197 unsigned char *p = ref_hmac;
198 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
199 unsigned long cur_time, cookie_time;
200
201 if( ctx == NULL || cli_id == NULL )
202 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
203
204 if( cookie_len != COOKIE_LEN )
205 return( -1 );
206
207 #if defined(MBEDTLS_THREADING_C)
208 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
209 return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR, ret ) );
210 #endif
211
212 if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie,
213 &p, p + sizeof( ref_hmac ),
214 cli_id, cli_id_len ) != 0 )
215 ret = -1;
216
217 #if defined(MBEDTLS_THREADING_C)
218 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
219 return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR,
220 MBEDTLS_ERR_THREADING_MUTEX_ERROR ) );
221 #endif
222
223 if( ret != 0 )
224 return( ret );
225
226 if( mbedtls_ssl_safer_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 )
227 return( -1 );
228
229 #if defined(MBEDTLS_HAVE_TIME)
230 cur_time = (unsigned long) mbedtls_time( NULL );
231 #else
232 cur_time = ctx->serial;
233 #endif
234
235 cookie_time = ( (unsigned long) cookie[0] << 24 ) |
236 ( (unsigned long) cookie[1] << 16 ) |
237 ( (unsigned long) cookie[2] << 8 ) |
238 ( (unsigned long) cookie[3] );
239
240 if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout )
241 return( -1 );
242
243 return( 0 );
244 }
245 #endif /* MBEDTLS_SSL_COOKIE_C */
246