1 /*
2 * DTLS cookie callbacks 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 * These session callbacks use a simple chained list
23 * to store and retrieve the session information.
24 */
25
26 #if !defined(MBEDTLS_CONFIG_FILE)
27 #include "mbedtls/config.h"
28 #else
29 #include MBEDTLS_CONFIG_FILE
30 #endif
31
32 #if defined(MBEDTLS_SSL_COOKIE_C)
33
34 #if defined(MBEDTLS_PLATFORM_C)
35 #include "mbedtls/platform.h"
36 #else
37 #define mbedtls_calloc calloc
38 #define mbedtls_free free
39 #endif
40
41 #include "mbedtls/ssl_cookie.h"
42 #include "mbedtls/ssl_internal.h"
43 #include "mbedtls/platform_util.h"
44
45 #include <string.h>
46
47 /*
48 * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is
49 * available. Try SHA-256 first, 512 wastes resources since we need to stay
50 * with max 32 bytes of cookie for DTLS 1.0
51 */
52 #if defined(MBEDTLS_SHA256_C)
53 #define COOKIE_MD MBEDTLS_MD_SHA224
54 #define COOKIE_MD_OUTLEN 32
55 #define COOKIE_HMAC_LEN 28
56 #elif defined(MBEDTLS_SHA512_C)
57 #define COOKIE_MD MBEDTLS_MD_SHA384
58 #define COOKIE_MD_OUTLEN 48
59 #define COOKIE_HMAC_LEN 28
60 #elif defined(MBEDTLS_SHA1_C)
61 #define COOKIE_MD MBEDTLS_MD_SHA1
62 #define COOKIE_MD_OUTLEN 20
63 #define COOKIE_HMAC_LEN 20
64 #else
65 #error "DTLS hello verify needs SHA-1 or SHA-2"
66 #endif
67
68 /*
69 * Cookies are formed of a 4-bytes timestamp (or serial number) and
70 * an HMAC of timestemp and client ID.
71 */
72 #define COOKIE_LEN ( 4 + COOKIE_HMAC_LEN )
73
mbedtls_ssl_cookie_init(mbedtls_ssl_cookie_ctx * ctx)74 void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx )
75 {
76 mbedtls_md_init( &ctx->hmac_ctx );
77 #if !defined(MBEDTLS_HAVE_TIME)
78 ctx->serial = 0;
79 #endif
80 ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;
81
82 #if defined(MBEDTLS_THREADING_C)
83 mbedtls_mutex_init( &ctx->mutex );
84 #endif
85 }
86
mbedtls_ssl_cookie_set_timeout(mbedtls_ssl_cookie_ctx * ctx,unsigned long delay)87 void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay )
88 {
89 ctx->timeout = delay;
90 }
91
mbedtls_ssl_cookie_free(mbedtls_ssl_cookie_ctx * ctx)92 void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx )
93 {
94 mbedtls_md_free( &ctx->hmac_ctx );
95
96 #if defined(MBEDTLS_THREADING_C)
97 mbedtls_mutex_free( &ctx->mutex );
98 #endif
99
100 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) );
101 }
102
mbedtls_ssl_cookie_setup(mbedtls_ssl_cookie_ctx * ctx,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)103 int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx,
104 int (*f_rng)(void *, unsigned char *, size_t),
105 void *p_rng )
106 {
107 int ret;
108 unsigned char key[COOKIE_MD_OUTLEN];
109
110 if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 )
111 return( ret );
112
113 ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 );
114 if( ret != 0 )
115 return( ret );
116
117 ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) );
118 if( ret != 0 )
119 return( ret );
120
121 mbedtls_platform_zeroize( key, sizeof( key ) );
122
123 return( 0 );
124 }
125
126 /*
127 * Generate the HMAC part of a cookie
128 */
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)129 static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,
130 const unsigned char time[4],
131 unsigned char **p, unsigned char *end,
132 const unsigned char *cli_id, size_t cli_id_len )
133 {
134 unsigned char hmac_out[COOKIE_MD_OUTLEN];
135
136 if( (size_t)( end - *p ) < COOKIE_HMAC_LEN )
137 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
138
139 if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 ||
140 mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
141 mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 ||
142 mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 )
143 {
144 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
145 }
146
147 memcpy( *p, hmac_out, COOKIE_HMAC_LEN );
148 *p += COOKIE_HMAC_LEN;
149
150 return( 0 );
151 }
152
153 /*
154 * Generate cookie for DTLS ClientHello verification
155 */
mbedtls_ssl_cookie_write(void * p_ctx,unsigned char ** p,unsigned char * end,const unsigned char * cli_id,size_t cli_id_len)156 int mbedtls_ssl_cookie_write( void *p_ctx,
157 unsigned char **p, unsigned char *end,
158 const unsigned char *cli_id, size_t cli_id_len )
159 {
160 int ret;
161 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
162 unsigned long t;
163
164 if( ctx == NULL || cli_id == NULL )
165 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
166
167 if( (size_t)( end - *p ) < COOKIE_LEN )
168 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
169
170 #if defined(MBEDTLS_HAVE_TIME)
171 t = (unsigned long) mbedtls_time( NULL );
172 #else
173 t = ctx->serial++;
174 #endif
175
176 (*p)[0] = (unsigned char)( t >> 24 );
177 (*p)[1] = (unsigned char)( t >> 16 );
178 (*p)[2] = (unsigned char)( t >> 8 );
179 (*p)[3] = (unsigned char)( t );
180 *p += 4;
181
182 #if defined(MBEDTLS_THREADING_C)
183 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
184 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );
185 #endif
186
187 ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4,
188 p, end, cli_id, cli_id_len );
189
190 #if defined(MBEDTLS_THREADING_C)
191 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
192 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +
193 MBEDTLS_ERR_THREADING_MUTEX_ERROR );
194 #endif
195
196 return( ret );
197 }
198
199 /*
200 * Check a cookie
201 */
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)202 int mbedtls_ssl_cookie_check( void *p_ctx,
203 const unsigned char *cookie, size_t cookie_len,
204 const unsigned char *cli_id, size_t cli_id_len )
205 {
206 unsigned char ref_hmac[COOKIE_HMAC_LEN];
207 int ret = 0;
208 unsigned char *p = ref_hmac;
209 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
210 unsigned long cur_time, cookie_time;
211
212 if( ctx == NULL || cli_id == NULL )
213 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
214
215 if( cookie_len != COOKIE_LEN )
216 return( -1 );
217
218 #if defined(MBEDTLS_THREADING_C)
219 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
220 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );
221 #endif
222
223 if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie,
224 &p, p + sizeof( ref_hmac ),
225 cli_id, cli_id_len ) != 0 )
226 ret = -1;
227
228 #if defined(MBEDTLS_THREADING_C)
229 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
230 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +
231 MBEDTLS_ERR_THREADING_MUTEX_ERROR );
232 #endif
233
234 if( ret != 0 )
235 return( ret );
236
237 if( mbedtls_ssl_safer_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 )
238 return( -1 );
239
240 #if defined(MBEDTLS_HAVE_TIME)
241 cur_time = (unsigned long) mbedtls_time( NULL );
242 #else
243 cur_time = ctx->serial;
244 #endif
245
246 cookie_time = ( (unsigned long) cookie[0] << 24 ) |
247 ( (unsigned long) cookie[1] << 16 ) |
248 ( (unsigned long) cookie[2] << 8 ) |
249 ( (unsigned long) cookie[3] );
250
251 if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout )
252 return( -1 );
253
254 return( 0 );
255 }
256 #endif /* MBEDTLS_SSL_COOKIE_C */
257