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#include "../crypto/internal.h"
122
123
124BSSL_NAMESPACE_BEGIN
125
126// to_u64_be treats |in| as a 8-byte big-endian integer and returns the value as
127// a |uint64_t|.
128static uint64_t to_u64_be(const uint8_t in[8]) {
129 uint64_t ret = 0;
130 unsigned i;
131 for (i = 0; i < 8; i++) {
132 ret <<= 8;
133 ret |= in[i];
134 }
135 return ret;
136}
137
138// dtls1_bitmap_should_discard returns one if |seq_num| has been seen in
139// |bitmap| or is stale. Otherwise it returns zero.
140static bool dtls1_bitmap_should_discard(DTLS1_BITMAP *bitmap,
141 const uint8_t seq_num[8]) {
142 const unsigned kWindowSize = sizeof(bitmap->map) * 8;
143
144 uint64_t seq_num_u = to_u64_be(seq_num);
145 if (seq_num_u > bitmap->max_seq_num) {
146 return false;
147 }
148 uint64_t idx = bitmap->max_seq_num - seq_num_u;
149 return idx >= kWindowSize || (bitmap->map & (((uint64_t)1) << idx));
150}
151
152// dtls1_bitmap_record updates |bitmap| to record receipt of sequence number
153// |seq_num|. It slides the window forward if needed. It is an error to call
154// this function on a stale sequence number.
155static void dtls1_bitmap_record(DTLS1_BITMAP *bitmap,
156 const uint8_t seq_num[8]) {
157 const unsigned kWindowSize = sizeof(bitmap->map) * 8;
158
159 uint64_t seq_num_u = to_u64_be(seq_num);
160 // Shift the window if necessary.
161 if (seq_num_u > bitmap->max_seq_num) {
162 uint64_t shift = seq_num_u - bitmap->max_seq_num;
163 if (shift >= kWindowSize) {
164 bitmap->map = 0;
165 } else {
166 bitmap->map <<= shift;
167 }
168 bitmap->max_seq_num = seq_num_u;
169 }
170
171 uint64_t idx = bitmap->max_seq_num - seq_num_u;
172 if (idx < kWindowSize) {
173 bitmap->map |= ((uint64_t)1) << idx;
174 }
175}
176
177enum ssl_open_record_t dtls_open_record(SSL *ssl, uint8_t *out_type,
178 Span<uint8_t> *out,
179 size_t *out_consumed,
180 uint8_t *out_alert, Span<uint8_t> in) {
181 *out_consumed = 0;
182 if (ssl->s3->read_shutdown == ssl_shutdown_close_notify) {
183 return ssl_open_record_close_notify;
184 }
185
186 if (in.empty()) {
187 return ssl_open_record_partial;
188 }
189
190 CBS cbs = CBS(in);
191
192 // Decode the record.
193 uint8_t type;
194 uint16_t version;
195 uint8_t sequence[8];
196 CBS body;
197 if (!CBS_get_u8(&cbs, &type) ||
198 !CBS_get_u16(&cbs, &version) ||
199 !CBS_copy_bytes(&cbs, sequence, 8) ||
200 !CBS_get_u16_length_prefixed(&cbs, &body) ||
201 CBS_len(&body) > SSL3_RT_MAX_ENCRYPTED_LENGTH) {
202 // The record header was incomplete or malformed. Drop the entire packet.
203 *out_consumed = in.size();
204 return ssl_open_record_discard;
205 }
206
207 bool version_ok;
208 if (ssl->s3->aead_read_ctx->is_null_cipher()) {
209 // Only check the first byte. Enforcing beyond that can prevent decoding
210 // version negotiation failure alerts.
211 version_ok = (version >> 8) == DTLS1_VERSION_MAJOR;
212 } else {
213 version_ok = version == ssl->s3->aead_read_ctx->RecordVersion();
214 }
215
216 if (!version_ok) {
217 // The record header was incomplete or malformed. Drop the entire packet.
218 *out_consumed = in.size();
219 return ssl_open_record_discard;
220 }
221
222 Span<const uint8_t> header = in.subspan(0, DTLS1_RT_HEADER_LENGTH);
223 ssl_do_msg_callback(ssl, 0 /* read */, SSL3_RT_HEADER, header);
224
225 uint16_t epoch = (((uint16_t)sequence[0]) << 8) | sequence[1];
226 if (epoch != ssl->d1->r_epoch ||
227 dtls1_bitmap_should_discard(&ssl->d1->bitmap, sequence)) {
228 // Drop this record. It's from the wrong epoch or is a replay. Note that if
229 // |epoch| is the next epoch, the record could be buffered for later. For
230 // simplicity, drop it and expect retransmit to handle it later; DTLS must
231 // handle packet loss anyway.
232 *out_consumed = in.size() - CBS_len(&cbs);
233 return ssl_open_record_discard;
234 }
235
236 // discard the body in-place.
237 if (!ssl->s3->aead_read_ctx->Open(
238 out, type, version, sequence, header,
239 MakeSpan(const_cast<uint8_t *>(CBS_data(&body)), CBS_len(&body)))) {
240 // Bad packets are silently dropped in DTLS. See section 4.2.1 of RFC 6347.
241 // Clear the error queue of any errors decryption may have added. Drop the
242 // entire packet as it must not have come from the peer.
243 //
244 // TODO(davidben): This doesn't distinguish malloc failures from encryption
245 // failures.
246 ERR_clear_error();
247 *out_consumed = in.size() - CBS_len(&cbs);
248 return ssl_open_record_discard;
249 }
250 *out_consumed = in.size() - CBS_len(&cbs);
251
252 // Check the plaintext length.
253 if (out->size() > SSL3_RT_MAX_PLAIN_LENGTH) {
254 OPENSSL_PUT_ERROR(SSL, SSL_R_DATA_LENGTH_TOO_LONG);
255 *out_alert = SSL_AD_RECORD_OVERFLOW;
256 return ssl_open_record_error;
257 }
258
259 dtls1_bitmap_record(&ssl->d1->bitmap, sequence);
260
261 // TODO(davidben): Limit the number of empty records as in TLS? This is only
262 // useful if we also limit discarded packets.
263
264 if (type == SSL3_RT_ALERT) {
265 return ssl_process_alert(ssl, out_alert, *out);
266 }
267
268 ssl->s3->warning_alert_count = 0;
269
270 *out_type = type;
271 return ssl_open_record_success;
272}
273
274static const SSLAEADContext *get_write_aead(const SSL *ssl,
275 enum dtls1_use_epoch_t use_epoch) {
276 if (use_epoch == dtls1_use_previous_epoch) {
277 assert(ssl->d1->w_epoch >= 1);
278 return ssl->d1->last_aead_write_ctx.get();
279 }
280
281 return ssl->s3->aead_write_ctx.get();
282}
283
284size_t dtls_max_seal_overhead(const SSL *ssl,
285 enum dtls1_use_epoch_t use_epoch) {
286 return DTLS1_RT_HEADER_LENGTH + get_write_aead(ssl, use_epoch)->MaxOverhead();
287}
288
289size_t dtls_seal_prefix_len(const SSL *ssl, enum dtls1_use_epoch_t use_epoch) {
290 return DTLS1_RT_HEADER_LENGTH +
291 get_write_aead(ssl, use_epoch)->ExplicitNonceLen();
292}
293
294bool dtls_seal_record(SSL *ssl, uint8_t *out, size_t *out_len, size_t max_out,
295 uint8_t type, const uint8_t *in, size_t in_len,
296 enum dtls1_use_epoch_t use_epoch) {
297 const size_t prefix = dtls_seal_prefix_len(ssl, use_epoch);
298 if (buffers_alias(in, in_len, out, max_out) &&
299 (max_out < prefix || out + prefix != in)) {
300 OPENSSL_PUT_ERROR(SSL, SSL_R_OUTPUT_ALIASES_INPUT);
301 return false;
302 }
303
304 // Determine the parameters for the current epoch.
305 uint16_t epoch = ssl->d1->w_epoch;
306 SSLAEADContext *aead = ssl->s3->aead_write_ctx.get();
307 uint8_t *seq = ssl->s3->write_sequence;
308 if (use_epoch == dtls1_use_previous_epoch) {
309 assert(ssl->d1->w_epoch >= 1);
310 epoch = ssl->d1->w_epoch - 1;
311 aead = ssl->d1->last_aead_write_ctx.get();
312 seq = ssl->d1->last_write_sequence;
313 }
314
315 if (max_out < DTLS1_RT_HEADER_LENGTH) {
316 OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
317 return false;
318 }
319
320 out[0] = type;
321
322 uint16_t record_version = ssl->s3->aead_write_ctx->RecordVersion();
323 out[1] = record_version >> 8;
324 out[2] = record_version & 0xff;
325
326 out[3] = epoch >> 8;
327 out[4] = epoch & 0xff;
328 OPENSSL_memcpy(&out[5], &seq[2], 6);
329
330 size_t ciphertext_len;
331 if (!aead->CiphertextLen(&ciphertext_len, in_len, 0)) {
332 OPENSSL_PUT_ERROR(SSL, SSL_R_RECORD_TOO_LARGE);
333 return false;
334 }
335 out[11] = ciphertext_len >> 8;
336 out[12] = ciphertext_len & 0xff;
337 Span<const uint8_t> header = MakeConstSpan(out, DTLS1_RT_HEADER_LENGTH);
338
339 size_t len_copy;
340 if (!aead->Seal(out + DTLS1_RT_HEADER_LENGTH, &len_copy,
341 max_out - DTLS1_RT_HEADER_LENGTH, type, record_version,
342 &out[3] /* seq */, header, in, in_len) ||
343 !ssl_record_sequence_update(&seq[2], 6)) {
344 return false;
345 }
346 assert(ciphertext_len == len_copy);
347
348 *out_len = DTLS1_RT_HEADER_LENGTH + ciphertext_len;
349 ssl_do_msg_callback(ssl, 1 /* write */, SSL3_RT_HEADER, header);
350 return true;
351}
352
353BSSL_NAMESPACE_END
354