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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 
124 namespace bssl {
125 
126 // to_u64_be treats |in| as a 8-byte big-endian integer and returns the value as
127 // a |uint64_t|.
to_u64_be(const uint8_t in[8])128 static 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.
dtls1_bitmap_should_discard(DTLS1_BITMAP * bitmap,const uint8_t seq_num[8])140 static int 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 0;
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.
dtls1_bitmap_record(DTLS1_BITMAP * bitmap,const uint8_t seq_num[8])155 static 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 
dtls_open_record(SSL * ssl,uint8_t * out_type,Span<uint8_t> * out,size_t * out_consumed,uint8_t * out_alert,Span<uint8_t> in)177 enum 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   ssl_do_msg_callback(ssl, 0 /* read */, SSL3_RT_HEADER,
223                       in.subspan(0, DTLS1_RT_HEADER_LENGTH));
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,
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 
get_write_aead(const SSL * ssl,enum dtls1_use_epoch_t use_epoch)274 static 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 
dtls_max_seal_overhead(const SSL * ssl,enum dtls1_use_epoch_t use_epoch)284 size_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 
dtls_seal_prefix_len(const SSL * ssl,enum dtls1_use_epoch_t use_epoch)289 size_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 
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)294 int 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 0;
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 0;
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->Seal(out + DTLS1_RT_HEADER_LENGTH, &ciphertext_len,
332                   max_out - DTLS1_RT_HEADER_LENGTH, type, record_version,
333                   &out[3] /* seq */, in, in_len) ||
334       !ssl_record_sequence_update(&seq[2], 6)) {
335     return 0;
336   }
337 
338   if (ciphertext_len >= 1 << 16) {
339     OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW);
340     return 0;
341   }
342   out[11] = ciphertext_len >> 8;
343   out[12] = ciphertext_len & 0xff;
344 
345   *out_len = DTLS1_RT_HEADER_LENGTH + ciphertext_len;
346 
347   ssl_do_msg_callback(ssl, 1 /* write */, SSL3_RT_HEADER,
348                       MakeSpan(out, DTLS1_RT_HEADER_LENGTH));
349 
350   return 1;
351 }
352 
353 }  // namespace bssl
354