1 /* DTLS implementation written by Nagendra Modadugu 2 * (nagendra (at) 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 (at) 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 (at) cryptsoft.com). This product includes software written by Tim 53 * Hudson (tjh (at) cryptsoft.com). 54 * 55 */ 56 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com) 57 * All rights reserved. 58 * 59 * This package is an SSL implementation written 60 * by Eric Young (eay (at) 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 (at) 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 (at) 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 (at) 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|. 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. 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. 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 } 176 177 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 } 273 274 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 } 283 284 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 } 288 289 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 } 293 294 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
