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
44 #include <string.h>
45
46 /* Implementation that should never be optimized out by the compiler */
mbedtls_zeroize(void * v,size_t n)47 static void mbedtls_zeroize( void *v, size_t n ) {
48 volatile unsigned char *p = v; while( n-- ) *p++ = 0;
49 }
50
51 /*
52 * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is
53 * available. Try SHA-256 first, 512 wastes resources since we need to stay
54 * with max 32 bytes of cookie for DTLS 1.0
55 */
56 #if defined(MBEDTLS_SHA256_C)
57 #define COOKIE_MD MBEDTLS_MD_SHA224
58 #define COOKIE_MD_OUTLEN 32
59 #define COOKIE_HMAC_LEN 28
60 #elif defined(MBEDTLS_SHA512_C)
61 #define COOKIE_MD MBEDTLS_MD_SHA384
62 #define COOKIE_MD_OUTLEN 48
63 #define COOKIE_HMAC_LEN 28
64 #elif defined(MBEDTLS_SHA1_C)
65 #define COOKIE_MD MBEDTLS_MD_SHA1
66 #define COOKIE_MD_OUTLEN 20
67 #define COOKIE_HMAC_LEN 20
68 #else
69 #error "DTLS hello verify needs SHA-1 or SHA-2"
70 #endif
71
72 /*
73 * Cookies are formed of a 4-bytes timestamp (or serial number) and
74 * an HMAC of timestemp and client ID.
75 */
76 #define COOKIE_LEN ( 4 + COOKIE_HMAC_LEN )
77
mbedtls_ssl_cookie_init(mbedtls_ssl_cookie_ctx * ctx)78 void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx )
79 {
80 mbedtls_md_init( &ctx->hmac_ctx );
81 #if !defined(MBEDTLS_HAVE_TIME)
82 ctx->serial = 0;
83 #endif
84 ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;
85
86 #if defined(MBEDTLS_THREADING_C)
87 mbedtls_mutex_init( &ctx->mutex );
88 #endif
89 }
90
mbedtls_ssl_cookie_set_timeout(mbedtls_ssl_cookie_ctx * ctx,unsigned long delay)91 void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay )
92 {
93 ctx->timeout = delay;
94 }
95
mbedtls_ssl_cookie_free(mbedtls_ssl_cookie_ctx * ctx)96 void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx )
97 {
98 mbedtls_md_free( &ctx->hmac_ctx );
99
100 #if defined(MBEDTLS_THREADING_C)
101 mbedtls_mutex_init( &ctx->mutex );
102 #endif
103
104 mbedtls_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) );
105 }
106
mbedtls_ssl_cookie_setup(mbedtls_ssl_cookie_ctx * ctx,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)107 int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx,
108 int (*f_rng)(void *, unsigned char *, size_t),
109 void *p_rng )
110 {
111 int ret;
112 unsigned char key[COOKIE_MD_OUTLEN];
113
114 if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 )
115 return( ret );
116
117 ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 );
118 if( ret != 0 )
119 return( ret );
120
121 ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) );
122 if( ret != 0 )
123 return( ret );
124
125 mbedtls_zeroize( key, sizeof( key ) );
126
127 return( 0 );
128 }
129
130 /*
131 * Generate the HMAC part of a cookie
132 */
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)133 static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,
134 const unsigned char time[4],
135 unsigned char **p, unsigned char *end,
136 const unsigned char *cli_id, size_t cli_id_len )
137 {
138 unsigned char hmac_out[COOKIE_MD_OUTLEN];
139
140 if( (size_t)( end - *p ) < COOKIE_HMAC_LEN )
141 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
142
143 if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 ||
144 mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
145 mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 ||
146 mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 )
147 {
148 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
149 }
150
151 memcpy( *p, hmac_out, COOKIE_HMAC_LEN );
152 *p += COOKIE_HMAC_LEN;
153
154 return( 0 );
155 }
156
157 /*
158 * Generate cookie for DTLS ClientHello verification
159 */
mbedtls_ssl_cookie_write(void * p_ctx,unsigned char ** p,unsigned char * end,const unsigned char * cli_id,size_t cli_id_len)160 int mbedtls_ssl_cookie_write( void *p_ctx,
161 unsigned char **p, unsigned char *end,
162 const unsigned char *cli_id, size_t cli_id_len )
163 {
164 int ret;
165 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
166 unsigned long t;
167
168 if( ctx == NULL || cli_id == NULL )
169 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
170
171 if( (size_t)( end - *p ) < COOKIE_LEN )
172 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
173
174 #if defined(MBEDTLS_HAVE_TIME)
175 t = (unsigned long) mbedtls_time( NULL );
176 #else
177 t = ctx->serial++;
178 #endif
179
180 (*p)[0] = (unsigned char)( t >> 24 );
181 (*p)[1] = (unsigned char)( t >> 16 );
182 (*p)[2] = (unsigned char)( t >> 8 );
183 (*p)[3] = (unsigned char)( t );
184 *p += 4;
185
186 #if defined(MBEDTLS_THREADING_C)
187 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
188 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );
189 #endif
190
191 ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4,
192 p, end, cli_id, cli_id_len );
193
194 #if defined(MBEDTLS_THREADING_C)
195 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
196 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +
197 MBEDTLS_ERR_THREADING_MUTEX_ERROR );
198 #endif
199
200 return( ret );
201 }
202
203 /*
204 * Check a cookie
205 */
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)206 int mbedtls_ssl_cookie_check( void *p_ctx,
207 const unsigned char *cookie, size_t cookie_len,
208 const unsigned char *cli_id, size_t cli_id_len )
209 {
210 unsigned char ref_hmac[COOKIE_HMAC_LEN];
211 int ret = 0;
212 unsigned char *p = ref_hmac;
213 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
214 unsigned long cur_time, cookie_time;
215
216 if( ctx == NULL || cli_id == NULL )
217 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
218
219 if( cookie_len != COOKIE_LEN )
220 return( -1 );
221
222 #if defined(MBEDTLS_THREADING_C)
223 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
224 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );
225 #endif
226
227 if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie,
228 &p, p + sizeof( ref_hmac ),
229 cli_id, cli_id_len ) != 0 )
230 ret = -1;
231
232 #if defined(MBEDTLS_THREADING_C)
233 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
234 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +
235 MBEDTLS_ERR_THREADING_MUTEX_ERROR );
236 #endif
237
238 if( ret != 0 )
239 return( ret );
240
241 if( mbedtls_ssl_safer_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 )
242 return( -1 );
243
244 #if defined(MBEDTLS_HAVE_TIME)
245 cur_time = (unsigned long) mbedtls_time( NULL );
246 #else
247 cur_time = ctx->serial;
248 #endif
249
250 cookie_time = ( (unsigned long) cookie[0] << 24 ) |
251 ( (unsigned long) cookie[1] << 16 ) |
252 ( (unsigned long) cookie[2] << 8 ) |
253 ( (unsigned long) cookie[3] );
254
255 if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout )
256 return( -1 );
257
258 return( 0 );
259 }
260 #endif /* MBEDTLS_SSL_COOKIE_C */
261
