1 /* DTLS implementation written by Nagendra Modadugu
2 * (nagendra@cs.stanford.edu) for the OpenSSL project 2005. */
3 /* ====================================================================
4 * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 *
18 * 3. All advertising materials mentioning features or use of this
19 * software must display the following acknowledgment:
20 * "This product includes software developed by the OpenSSL Project
21 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
22 *
23 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
24 * endorse or promote products derived from this software without
25 * prior written permission. For written permission, please contact
26 * openssl-core@openssl.org.
27 *
28 * 5. Products derived from this software may not be called "OpenSSL"
29 * nor may "OpenSSL" appear in their names without prior written
30 * permission of the OpenSSL Project.
31 *
32 * 6. Redistributions of any form whatsoever must retain the following
33 * acknowledgment:
34 * "This product includes software developed by the OpenSSL Project
35 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
36 *
37 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
38 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
39 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
40 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
43 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
44 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
45 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
46 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
47 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
48 * OF THE POSSIBILITY OF SUCH DAMAGE.
49 * ====================================================================
50 *
51 * This product includes cryptographic software written by Eric Young
52 * (eay@cryptsoft.com). This product includes software written by Tim
53 * Hudson (tjh@cryptsoft.com).
54 *
55 */
56 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
57 * All rights reserved.
58 *
59 * This package is an SSL implementation written
60 * by Eric Young (eay@cryptsoft.com).
61 * The implementation was written so as to conform with Netscapes SSL.
62 *
63 * This library is free for commercial and non-commercial use as long as
64 * the following conditions are aheared to. The following conditions
65 * apply to all code found in this distribution, be it the RC4, RSA,
66 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
67 * included with this distribution is covered by the same copyright terms
68 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
69 *
70 * Copyright remains Eric Young's, and as such any Copyright notices in
71 * the code are not to be removed.
72 * If this package is used in a product, Eric Young should be given attribution
73 * as the author of the parts of the library used.
74 * This can be in the form of a textual message at program startup or
75 * in documentation (online or textual) provided with the package.
76 *
77 * Redistribution and use in source and binary forms, with or without
78 * modification, are permitted provided that the following conditions
79 * are met:
80 * 1. Redistributions of source code must retain the copyright
81 * notice, this list of conditions and the following disclaimer.
82 * 2. Redistributions in binary form must reproduce the above copyright
83 * notice, this list of conditions and the following disclaimer in the
84 * documentation and/or other materials provided with the distribution.
85 * 3. All advertising materials mentioning features or use of this software
86 * must display the following acknowledgement:
87 * "This product includes cryptographic software written by
88 * Eric Young (eay@cryptsoft.com)"
89 * The word 'cryptographic' can be left out if the rouines from the library
90 * being used are not cryptographic related :-).
91 * 4. If you include any Windows specific code (or a derivative thereof) from
92 * the apps directory (application code) you must include an acknowledgement:
93 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
94 *
95 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
96 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
97 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
98 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
99 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
100 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
101 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
102 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
103 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
104 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
105 * SUCH DAMAGE.
106 *
107 * The licence and distribution terms for any publically available version or
108 * derivative of this code cannot be changed. i.e. this code cannot simply be
109 * copied and put under another distribution licence
110 * [including the GNU Public Licence.] */
111
112 #include <openssl/ssl.h>
113
114 #include <assert.h>
115 #include <string.h>
116
117 #include <openssl/bytestring.h>
118 #include <openssl/err.h>
119
120 #include "internal.h"
121
122
123 /* to_u64_be treats |in| as a 8-byte big-endian integer and returns the value as
124 * a |uint64_t|. */
to_u64_be(const uint8_t in[8])125 static uint64_t to_u64_be(const uint8_t in[8]) {
126 uint64_t ret = 0;
127 unsigned i;
128 for (i = 0; i < 8; i++) {
129 ret <<= 8;
130 ret |= in[i];
131 }
132 return ret;
133 }
134
135 /* dtls1_bitmap_should_discard returns one if |seq_num| has been seen in |bitmap|
136 * or is stale. Otherwise it returns zero. */
dtls1_bitmap_should_discard(DTLS1_BITMAP * bitmap,const uint8_t seq_num[8])137 static int dtls1_bitmap_should_discard(DTLS1_BITMAP *bitmap,
138 const uint8_t seq_num[8]) {
139 const unsigned kWindowSize = sizeof(bitmap->map) * 8;
140
141 uint64_t seq_num_u = to_u64_be(seq_num);
142 if (seq_num_u > bitmap->max_seq_num) {
143 return 0;
144 }
145 uint64_t idx = bitmap->max_seq_num - seq_num_u;
146 return idx >= kWindowSize || (bitmap->map & (((uint64_t)1) << idx));
147 }
148
149 /* dtls1_bitmap_record updates |bitmap| to record receipt of sequence number
150 * |seq_num|. It slides the window forward if needed. It is an error to call
151 * this function on a stale sequence number. */
dtls1_bitmap_record(DTLS1_BITMAP * bitmap,const uint8_t seq_num[8])152 static void dtls1_bitmap_record(DTLS1_BITMAP *bitmap,
153 const uint8_t seq_num[8]) {
154 const unsigned kWindowSize = sizeof(bitmap->map) * 8;
155
156 uint64_t seq_num_u = to_u64_be(seq_num);
157 /* Shift the window if necessary. */
158 if (seq_num_u > bitmap->max_seq_num) {
159 uint64_t shift = seq_num_u - bitmap->max_seq_num;
160 if (shift >= kWindowSize) {
161 bitmap->map = 0;
162 } else {
163 bitmap->map <<= shift;
164 }
165 bitmap->max_seq_num = seq_num_u;
166 }
167
168 uint64_t idx = bitmap->max_seq_num - seq_num_u;
169 if (idx < kWindowSize) {
170 bitmap->map |= ((uint64_t)1) << idx;
171 }
172 }
173
dtls_open_record(SSL * ssl,uint8_t * out_type,uint8_t * out,size_t * out_len,size_t * out_consumed,uint8_t * out_alert,size_t max_out,const uint8_t * in,size_t in_len)174 enum ssl_open_record_t dtls_open_record(
175 SSL *ssl, uint8_t *out_type, uint8_t *out, size_t *out_len,
176 size_t *out_consumed, uint8_t *out_alert, size_t max_out, const uint8_t *in,
177 size_t in_len) {
178 CBS cbs;
179 CBS_init(&cbs, in, in_len);
180
181 /* Decode the record. */
182 uint8_t type;
183 uint16_t version;
184 uint8_t sequence[8];
185 CBS body;
186 if (!CBS_get_u8(&cbs, &type) ||
187 !CBS_get_u16(&cbs, &version) ||
188 !CBS_copy_bytes(&cbs, sequence, 8) ||
189 !CBS_get_u16_length_prefixed(&cbs, &body) ||
190 (ssl->s3->have_version && version != ssl->version) ||
191 (version >> 8) != DTLS1_VERSION_MAJOR ||
192 CBS_len(&body) > SSL3_RT_MAX_ENCRYPTED_LENGTH) {
193 /* The record header was incomplete or malformed. Drop the entire packet. */
194 *out_consumed = in_len;
195 return ssl_open_record_discard;
196 }
197
198 if (ssl->msg_callback != NULL) {
199 ssl->msg_callback(0 /* read */, 0, SSL3_RT_HEADER, in,
200 DTLS1_RT_HEADER_LENGTH, ssl, ssl->msg_callback_arg);
201 }
202
203 uint16_t epoch = (((uint16_t)sequence[0]) << 8) | sequence[1];
204 if (epoch != ssl->d1->r_epoch ||
205 dtls1_bitmap_should_discard(&ssl->d1->bitmap, sequence)) {
206 /* Drop this record. It's from the wrong epoch or is a replay. Note that if
207 * |epoch| is the next epoch, the record could be buffered for later. For
208 * simplicity, drop it and expect retransmit to handle it later; DTLS must
209 * handle packet loss anyway. */
210 *out_consumed = in_len - CBS_len(&cbs);
211 return ssl_open_record_discard;
212 }
213
214 /* Decrypt the body. */
215 size_t plaintext_len;
216 if (!SSL_AEAD_CTX_open(ssl->aead_read_ctx, out, &plaintext_len, max_out,
217 type, version, sequence, CBS_data(&body),
218 CBS_len(&body))) {
219 /* Bad packets are silently dropped in DTLS. See section 4.2.1 of RFC 6347.
220 * Clear the error queue of any errors decryption may have added. Drop the
221 * entire packet as it must not have come from the peer.
222 *
223 * TODO(davidben): This doesn't distinguish malloc failures from encryption
224 * failures. */
225 ERR_clear_error();
226 *out_consumed = in_len - CBS_len(&cbs);
227 return ssl_open_record_discard;
228 }
229
230 /* Check the plaintext length. */
231 if (plaintext_len > SSL3_RT_MAX_PLAIN_LENGTH) {
232 OPENSSL_PUT_ERROR(SSL, SSL_R_DATA_LENGTH_TOO_LONG);
233 *out_alert = SSL_AD_RECORD_OVERFLOW;
234 return ssl_open_record_error;
235 }
236
237 dtls1_bitmap_record(&ssl->d1->bitmap, sequence);
238
239 /* TODO(davidben): Limit the number of empty records as in TLS? This is only
240 * useful if we also limit discarded packets. */
241
242 *out_type = type;
243 *out_len = plaintext_len;
244 *out_consumed = in_len - CBS_len(&cbs);
245 return ssl_open_record_success;
246 }
247
dtls_seal_record(SSL * ssl,uint8_t * out,size_t * out_len,size_t max_out,uint8_t type,const uint8_t * in,size_t in_len,enum dtls1_use_epoch_t use_epoch)248 int dtls_seal_record(SSL *ssl, uint8_t *out, size_t *out_len, size_t max_out,
249 uint8_t type, const uint8_t *in, size_t in_len,
250 enum dtls1_use_epoch_t use_epoch) {
251 /* Determine the parameters for the current epoch. */
252 uint16_t epoch = ssl->d1->w_epoch;
253 SSL_AEAD_CTX *aead = ssl->aead_write_ctx;
254 uint8_t *seq = ssl->s3->write_sequence;
255 if (use_epoch == dtls1_use_previous_epoch) {
256 /* DTLS renegotiation is unsupported, so only epochs 0 (NULL cipher) and 1
257 * (negotiated cipher) exist. */
258 assert(ssl->d1->w_epoch == 1);
259 epoch = ssl->d1->w_epoch - 1;
260 aead = NULL;
261 seq = ssl->d1->last_write_sequence;
262 }
263
264 if (max_out < DTLS1_RT_HEADER_LENGTH) {
265 OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
266 return 0;
267 }
268 /* Check the record header does not alias any part of the input.
269 * |SSL_AEAD_CTX_seal| will internally enforce other aliasing requirements. */
270 if (in < out + DTLS1_RT_HEADER_LENGTH && out < in + in_len) {
271 OPENSSL_PUT_ERROR(SSL, SSL_R_OUTPUT_ALIASES_INPUT);
272 return 0;
273 }
274
275 out[0] = type;
276
277 uint16_t wire_version = ssl->s3->have_version ? ssl->version : DTLS1_VERSION;
278 out[1] = wire_version >> 8;
279 out[2] = wire_version & 0xff;
280
281 out[3] = epoch >> 8;
282 out[4] = epoch & 0xff;
283 memcpy(&out[5], &seq[2], 6);
284
285 size_t ciphertext_len;
286 if (!SSL_AEAD_CTX_seal(aead, out + DTLS1_RT_HEADER_LENGTH, &ciphertext_len,
287 max_out - DTLS1_RT_HEADER_LENGTH, type, wire_version,
288 &out[3] /* seq */, in, in_len) ||
289 !ssl3_record_sequence_update(&seq[2], 6)) {
290 return 0;
291 }
292
293 if (ciphertext_len >= 1 << 16) {
294 OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW);
295 return 0;
296 }
297 out[11] = ciphertext_len >> 8;
298 out[12] = ciphertext_len & 0xff;
299
300 *out_len = DTLS1_RT_HEADER_LENGTH + ciphertext_len;
301
302 if (ssl->msg_callback) {
303 ssl->msg_callback(1 /* write */, 0, SSL3_RT_HEADER, out,
304 DTLS1_RT_HEADER_LENGTH, ssl, ssl->msg_callback_arg);
305 }
306
307 return 1;
308 }
309