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1 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
2  * All rights reserved.
3  *
4  * This package is an SSL implementation written
5  * by Eric Young (eay@cryptsoft.com).
6  * The implementation was written so as to conform with Netscapes SSL.
7  *
8  * This library is free for commercial and non-commercial use as long as
9  * the following conditions are aheared to.  The following conditions
10  * apply to all code found in this distribution, be it the RC4, RSA,
11  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
12  * included with this distribution is covered by the same copyright terms
13  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
14  *
15  * Copyright remains Eric Young's, and as such any Copyright notices in
16  * the code are not to be removed.
17  * If this package is used in a product, Eric Young should be given attribution
18  * as the author of the parts of the library used.
19  * This can be in the form of a textual message at program startup or
20  * in documentation (online or textual) provided with the package.
21  *
22  * Redistribution and use in source and binary forms, with or without
23  * modification, are permitted provided that the following conditions
24  * are met:
25  * 1. Redistributions of source code must retain the copyright
26  *    notice, this list of conditions and the following disclaimer.
27  * 2. Redistributions in binary form must reproduce the above copyright
28  *    notice, this list of conditions and the following disclaimer in the
29  *    documentation and/or other materials provided with the distribution.
30  * 3. All advertising materials mentioning features or use of this software
31  *    must display the following acknowledgement:
32  *    "This product includes cryptographic software written by
33  *     Eric Young (eay@cryptsoft.com)"
34  *    The word 'cryptographic' can be left out if the rouines from the library
35  *    being used are not cryptographic related :-).
36  * 4. If you include any Windows specific code (or a derivative thereof) from
37  *    the apps directory (application code) you must include an acknowledgement:
38  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
39  *
40  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50  * SUCH DAMAGE.
51  *
52  * The licence and distribution terms for any publically available version or
53  * derivative of this code cannot be changed.  i.e. this code cannot simply be
54  * copied and put under another distribution licence
55  * [including the GNU Public Licence.]
56  */
57 /* ====================================================================
58  * Copyright (c) 1998-2002 The OpenSSL Project.  All rights reserved.
59  *
60  * Redistribution and use in source and binary forms, with or without
61  * modification, are permitted provided that the following conditions
62  * are met:
63  *
64  * 1. Redistributions of source code must retain the above copyright
65  *    notice, this list of conditions and the following disclaimer.
66  *
67  * 2. Redistributions in binary form must reproduce the above copyright
68  *    notice, this list of conditions and the following disclaimer in
69  *    the documentation and/or other materials provided with the
70  *    distribution.
71  *
72  * 3. All advertising materials mentioning features or use of this
73  *    software must display the following acknowledgment:
74  *    "This product includes software developed by the OpenSSL Project
75  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
76  *
77  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
78  *    endorse or promote products derived from this software without
79  *    prior written permission. For written permission, please contact
80  *    openssl-core@openssl.org.
81  *
82  * 5. Products derived from this software may not be called "OpenSSL"
83  *    nor may "OpenSSL" appear in their names without prior written
84  *    permission of the OpenSSL Project.
85  *
86  * 6. Redistributions of any form whatsoever must retain the following
87  *    acknowledgment:
88  *    "This product includes software developed by the OpenSSL Project
89  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
90  *
91  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
92  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
93  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
94  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
95  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
96  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
97  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
98  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
99  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
100  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
101  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
102  * OF THE POSSIBILITY OF SUCH DAMAGE.
103  * ====================================================================
104  *
105  * This product includes cryptographic software written by Eric Young
106  * (eay@cryptsoft.com).  This product includes software written by Tim
107  * Hudson (tjh@cryptsoft.com). */
108 
109 #include <openssl/ssl.h>
110 
111 #include <assert.h>
112 #include <string.h>
113 
114 #include <openssl/bytestring.h>
115 #include <openssl/err.h>
116 #include <openssl/mem.h>
117 
118 #include "internal.h"
119 #include "../crypto/internal.h"
120 
121 
122 BSSL_NAMESPACE_BEGIN
123 
124 // kMaxEmptyRecords is the number of consecutive, empty records that will be
125 // processed. Without this limit an attacker could send empty records at a
126 // faster rate than we can process and cause record processing to loop
127 // forever.
128 static const uint8_t kMaxEmptyRecords = 32;
129 
130 // kMaxEarlyDataSkipped is the maximum number of rejected early data bytes that
131 // will be skipped. Without this limit an attacker could send records at a
132 // faster rate than we can process and cause trial decryption to loop forever.
133 // This value should be slightly above kMaxEarlyDataAccepted, which is measured
134 // in plaintext.
135 static const size_t kMaxEarlyDataSkipped = 16384;
136 
137 // kMaxWarningAlerts is the number of consecutive warning alerts that will be
138 // processed.
139 static const uint8_t kMaxWarningAlerts = 4;
140 
141 // ssl_needs_record_splitting returns one if |ssl|'s current outgoing cipher
142 // state needs record-splitting and zero otherwise.
ssl_needs_record_splitting(const SSL * ssl)143 static bool ssl_needs_record_splitting(const SSL *ssl) {
144 #if !defined(BORINGSSL_UNSAFE_FUZZER_MODE)
145   return !ssl->s3->aead_write_ctx->is_null_cipher() &&
146          ssl->s3->aead_write_ctx->ProtocolVersion() < TLS1_1_VERSION &&
147          (ssl->mode & SSL_MODE_CBC_RECORD_SPLITTING) != 0 &&
148          SSL_CIPHER_is_block_cipher(ssl->s3->aead_write_ctx->cipher());
149 #else
150   return false;
151 #endif
152 }
153 
ssl_record_sequence_update(uint8_t * seq,size_t seq_len)154 bool ssl_record_sequence_update(uint8_t *seq, size_t seq_len) {
155   for (size_t i = seq_len - 1; i < seq_len; i--) {
156     ++seq[i];
157     if (seq[i] != 0) {
158       return true;
159     }
160   }
161   OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW);
162   return false;
163 }
164 
ssl_record_prefix_len(const SSL * ssl)165 size_t ssl_record_prefix_len(const SSL *ssl) {
166   size_t header_len;
167   if (SSL_is_dtls(ssl)) {
168     header_len = DTLS1_RT_HEADER_LENGTH;
169   } else {
170     header_len = SSL3_RT_HEADER_LENGTH;
171   }
172 
173   return header_len + ssl->s3->aead_read_ctx->ExplicitNonceLen();
174 }
175 
ssl_seal_align_prefix_len(const SSL * ssl)176 size_t ssl_seal_align_prefix_len(const SSL *ssl) {
177   if (SSL_is_dtls(ssl)) {
178     return DTLS1_RT_HEADER_LENGTH + ssl->s3->aead_write_ctx->ExplicitNonceLen();
179   }
180 
181   size_t ret =
182       SSL3_RT_HEADER_LENGTH + ssl->s3->aead_write_ctx->ExplicitNonceLen();
183   if (ssl_needs_record_splitting(ssl)) {
184     ret += SSL3_RT_HEADER_LENGTH;
185     ret += ssl_cipher_get_record_split_len(ssl->s3->aead_write_ctx->cipher());
186   }
187   return ret;
188 }
189 
skip_early_data(SSL * ssl,uint8_t * out_alert,size_t consumed)190 static ssl_open_record_t skip_early_data(SSL *ssl, uint8_t *out_alert,
191                                          size_t consumed) {
192   ssl->s3->early_data_skipped += consumed;
193   if (ssl->s3->early_data_skipped < consumed) {
194     ssl->s3->early_data_skipped = kMaxEarlyDataSkipped + 1;
195   }
196 
197   if (ssl->s3->early_data_skipped > kMaxEarlyDataSkipped) {
198     OPENSSL_PUT_ERROR(SSL, SSL_R_TOO_MUCH_SKIPPED_EARLY_DATA);
199     *out_alert = SSL_AD_UNEXPECTED_MESSAGE;
200     return ssl_open_record_error;
201   }
202 
203   return ssl_open_record_discard;
204 }
205 
tls_open_record(SSL * ssl,uint8_t * out_type,Span<uint8_t> * out,size_t * out_consumed,uint8_t * out_alert,Span<uint8_t> in)206 ssl_open_record_t tls_open_record(SSL *ssl, uint8_t *out_type,
207                                   Span<uint8_t> *out, size_t *out_consumed,
208                                   uint8_t *out_alert, Span<uint8_t> in) {
209   *out_consumed = 0;
210   if (ssl->s3->read_shutdown == ssl_shutdown_close_notify) {
211     return ssl_open_record_close_notify;
212   }
213 
214   // If there is an unprocessed handshake message or we are already buffering
215   // too much, stop before decrypting another handshake record.
216   if (!tls_can_accept_handshake_data(ssl, out_alert)) {
217     return ssl_open_record_error;
218   }
219 
220   CBS cbs = CBS(in);
221 
222   // Decode the record header.
223   uint8_t type;
224   uint16_t version, ciphertext_len;
225   if (!CBS_get_u8(&cbs, &type) ||
226       !CBS_get_u16(&cbs, &version) ||
227       !CBS_get_u16(&cbs, &ciphertext_len)) {
228     *out_consumed = SSL3_RT_HEADER_LENGTH;
229     return ssl_open_record_partial;
230   }
231 
232   bool version_ok;
233   if (ssl->s3->aead_read_ctx->is_null_cipher()) {
234     // Only check the first byte. Enforcing beyond that can prevent decoding
235     // version negotiation failure alerts.
236     version_ok = (version >> 8) == SSL3_VERSION_MAJOR;
237   } else {
238     version_ok = version == ssl->s3->aead_read_ctx->RecordVersion();
239   }
240 
241   if (!version_ok) {
242     OPENSSL_PUT_ERROR(SSL, SSL_R_WRONG_VERSION_NUMBER);
243     *out_alert = SSL_AD_PROTOCOL_VERSION;
244     return ssl_open_record_error;
245   }
246 
247   // Check the ciphertext length.
248   if (ciphertext_len > SSL3_RT_MAX_ENCRYPTED_LENGTH) {
249     OPENSSL_PUT_ERROR(SSL, SSL_R_ENCRYPTED_LENGTH_TOO_LONG);
250     *out_alert = SSL_AD_RECORD_OVERFLOW;
251     return ssl_open_record_error;
252   }
253 
254   // Extract the body.
255   CBS body;
256   if (!CBS_get_bytes(&cbs, &body, ciphertext_len)) {
257     *out_consumed = SSL3_RT_HEADER_LENGTH + (size_t)ciphertext_len;
258     return ssl_open_record_partial;
259   }
260 
261   Span<const uint8_t> header = in.subspan(0, SSL3_RT_HEADER_LENGTH);
262   ssl_do_msg_callback(ssl, 0 /* read */, SSL3_RT_HEADER, header);
263 
264   *out_consumed = in.size() - CBS_len(&cbs);
265 
266   if (ssl->s3->have_version &&
267       ssl_protocol_version(ssl) >= TLS1_3_VERSION &&
268       SSL_in_init(ssl) &&
269       type == SSL3_RT_CHANGE_CIPHER_SPEC &&
270       ciphertext_len == 1 &&
271       CBS_data(&body)[0] == 1) {
272     ssl->s3->empty_record_count++;
273     if (ssl->s3->empty_record_count > kMaxEmptyRecords) {
274       OPENSSL_PUT_ERROR(SSL, SSL_R_TOO_MANY_EMPTY_FRAGMENTS);
275       *out_alert = SSL_AD_UNEXPECTED_MESSAGE;
276       return ssl_open_record_error;
277     }
278     return ssl_open_record_discard;
279   }
280 
281   // Skip early data received when expecting a second ClientHello if we rejected
282   // 0RTT.
283   if (ssl->s3->skip_early_data &&
284       ssl->s3->aead_read_ctx->is_null_cipher() &&
285       type == SSL3_RT_APPLICATION_DATA) {
286     return skip_early_data(ssl, out_alert, *out_consumed);
287   }
288 
289   // Decrypt the body in-place.
290   if (!ssl->s3->aead_read_ctx->Open(
291           out, type, version, ssl->s3->read_sequence, header,
292           MakeSpan(const_cast<uint8_t *>(CBS_data(&body)), CBS_len(&body)))) {
293     if (ssl->s3->skip_early_data && !ssl->s3->aead_read_ctx->is_null_cipher()) {
294       ERR_clear_error();
295       return skip_early_data(ssl, out_alert, *out_consumed);
296     }
297 
298     OPENSSL_PUT_ERROR(SSL, SSL_R_DECRYPTION_FAILED_OR_BAD_RECORD_MAC);
299     *out_alert = SSL_AD_BAD_RECORD_MAC;
300     return ssl_open_record_error;
301   }
302 
303   ssl->s3->skip_early_data = false;
304 
305   if (!ssl_record_sequence_update(ssl->s3->read_sequence, 8)) {
306     *out_alert = SSL_AD_INTERNAL_ERROR;
307     return ssl_open_record_error;
308   }
309 
310   // TLS 1.3 hides the record type inside the encrypted data.
311   bool has_padding =
312       !ssl->s3->aead_read_ctx->is_null_cipher() &&
313       ssl->s3->aead_read_ctx->ProtocolVersion() >= TLS1_3_VERSION;
314 
315   // If there is padding, the plaintext limit includes the padding, but includes
316   // extra room for the inner content type.
317   size_t plaintext_limit =
318       has_padding ? SSL3_RT_MAX_PLAIN_LENGTH + 1 : SSL3_RT_MAX_PLAIN_LENGTH;
319   if (out->size() > plaintext_limit) {
320     OPENSSL_PUT_ERROR(SSL, SSL_R_DATA_LENGTH_TOO_LONG);
321     *out_alert = SSL_AD_RECORD_OVERFLOW;
322     return ssl_open_record_error;
323   }
324 
325   if (has_padding) {
326     // The outer record type is always application_data.
327     if (type != SSL3_RT_APPLICATION_DATA) {
328       OPENSSL_PUT_ERROR(SSL, SSL_R_INVALID_OUTER_RECORD_TYPE);
329       *out_alert = SSL_AD_DECODE_ERROR;
330       return ssl_open_record_error;
331     }
332 
333     do {
334       if (out->empty()) {
335         OPENSSL_PUT_ERROR(SSL, SSL_R_DECRYPTION_FAILED_OR_BAD_RECORD_MAC);
336         *out_alert = SSL_AD_DECRYPT_ERROR;
337         return ssl_open_record_error;
338       }
339       type = out->back();
340       *out = out->subspan(0, out->size() - 1);
341     } while (type == 0);
342   }
343 
344   // Limit the number of consecutive empty records.
345   if (out->empty()) {
346     ssl->s3->empty_record_count++;
347     if (ssl->s3->empty_record_count > kMaxEmptyRecords) {
348       OPENSSL_PUT_ERROR(SSL, SSL_R_TOO_MANY_EMPTY_FRAGMENTS);
349       *out_alert = SSL_AD_UNEXPECTED_MESSAGE;
350       return ssl_open_record_error;
351     }
352     // Apart from the limit, empty records are returned up to the caller. This
353     // allows the caller to reject records of the wrong type.
354   } else {
355     ssl->s3->empty_record_count = 0;
356   }
357 
358   if (type == SSL3_RT_ALERT) {
359     return ssl_process_alert(ssl, out_alert, *out);
360   }
361 
362   // Handshake messages may not interleave with any other record type.
363   if (type != SSL3_RT_HANDSHAKE &&
364       tls_has_unprocessed_handshake_data(ssl)) {
365     OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);
366     *out_alert = SSL_AD_UNEXPECTED_MESSAGE;
367     return ssl_open_record_error;
368   }
369 
370   ssl->s3->warning_alert_count = 0;
371 
372   *out_type = type;
373   return ssl_open_record_success;
374 }
375 
do_seal_record(SSL * ssl,uint8_t * out_prefix,uint8_t * out,uint8_t * out_suffix,uint8_t type,const uint8_t * in,const size_t in_len)376 static bool do_seal_record(SSL *ssl, uint8_t *out_prefix, uint8_t *out,
377                            uint8_t *out_suffix, uint8_t type, const uint8_t *in,
378                            const size_t in_len) {
379   SSLAEADContext *aead = ssl->s3->aead_write_ctx.get();
380   uint8_t *extra_in = NULL;
381   size_t extra_in_len = 0;
382   if (!aead->is_null_cipher() &&
383       aead->ProtocolVersion() >= TLS1_3_VERSION) {
384     // TLS 1.3 hides the actual record type inside the encrypted data.
385     extra_in = &type;
386     extra_in_len = 1;
387   }
388 
389   size_t suffix_len, ciphertext_len;
390   if (!aead->SuffixLen(&suffix_len, in_len, extra_in_len) ||
391       !aead->CiphertextLen(&ciphertext_len, in_len, extra_in_len)) {
392     OPENSSL_PUT_ERROR(SSL, SSL_R_RECORD_TOO_LARGE);
393     return false;
394   }
395 
396   assert(in == out || !buffers_alias(in, in_len, out, in_len));
397   assert(!buffers_alias(in, in_len, out_prefix, ssl_record_prefix_len(ssl)));
398   assert(!buffers_alias(in, in_len, out_suffix, suffix_len));
399 
400   if (extra_in_len) {
401     out_prefix[0] = SSL3_RT_APPLICATION_DATA;
402   } else {
403     out_prefix[0] = type;
404   }
405 
406   uint16_t record_version = aead->RecordVersion();
407 
408   out_prefix[1] = record_version >> 8;
409   out_prefix[2] = record_version & 0xff;
410   out_prefix[3] = ciphertext_len >> 8;
411   out_prefix[4] = ciphertext_len & 0xff;
412   Span<const uint8_t> header = MakeSpan(out_prefix, SSL3_RT_HEADER_LENGTH);
413 
414   if (!aead->SealScatter(out_prefix + SSL3_RT_HEADER_LENGTH, out, out_suffix,
415                          out_prefix[0], record_version, ssl->s3->write_sequence,
416                          header, in, in_len, extra_in, extra_in_len) ||
417       !ssl_record_sequence_update(ssl->s3->write_sequence, 8)) {
418     return false;
419   }
420 
421   ssl_do_msg_callback(ssl, 1 /* write */, SSL3_RT_HEADER, header);
422   return true;
423 }
424 
tls_seal_scatter_prefix_len(const SSL * ssl,uint8_t type,size_t in_len)425 static size_t tls_seal_scatter_prefix_len(const SSL *ssl, uint8_t type,
426                                           size_t in_len) {
427   size_t ret = SSL3_RT_HEADER_LENGTH;
428   if (type == SSL3_RT_APPLICATION_DATA && in_len > 1 &&
429       ssl_needs_record_splitting(ssl)) {
430     // In the case of record splitting, the 1-byte record (of the 1/n-1 split)
431     // will be placed in the prefix, as will four of the five bytes of the
432     // record header for the main record. The final byte will replace the first
433     // byte of the plaintext that was used in the small record.
434     ret += ssl_cipher_get_record_split_len(ssl->s3->aead_write_ctx->cipher());
435     ret += SSL3_RT_HEADER_LENGTH - 1;
436   } else {
437     ret += ssl->s3->aead_write_ctx->ExplicitNonceLen();
438   }
439   return ret;
440 }
441 
tls_seal_scatter_suffix_len(const SSL * ssl,size_t * out_suffix_len,uint8_t type,size_t in_len)442 static bool tls_seal_scatter_suffix_len(const SSL *ssl, size_t *out_suffix_len,
443                                         uint8_t type, size_t in_len) {
444   size_t extra_in_len = 0;
445   if (!ssl->s3->aead_write_ctx->is_null_cipher() &&
446       ssl->s3->aead_write_ctx->ProtocolVersion() >= TLS1_3_VERSION) {
447     // TLS 1.3 adds an extra byte for encrypted record type.
448     extra_in_len = 1;
449   }
450   if (type == SSL3_RT_APPLICATION_DATA &&  // clang-format off
451       in_len > 1 &&
452       ssl_needs_record_splitting(ssl)) {
453     // With record splitting enabled, the first byte gets sealed into a separate
454     // record which is written into the prefix.
455     in_len -= 1;
456   }
457   return ssl->s3->aead_write_ctx->SuffixLen(out_suffix_len, in_len, extra_in_len);
458 }
459 
460 // tls_seal_scatter_record seals a new record of type |type| and body |in| and
461 // splits it between |out_prefix|, |out|, and |out_suffix|. Exactly
462 // |tls_seal_scatter_prefix_len| bytes are written to |out_prefix|, |in_len|
463 // bytes to |out|, and |tls_seal_scatter_suffix_len| bytes to |out_suffix|. It
464 // returns one on success and zero on error. If enabled,
465 // |tls_seal_scatter_record| implements TLS 1.0 CBC 1/n-1 record splitting and
466 // may write two records concatenated.
tls_seal_scatter_record(SSL * ssl,uint8_t * out_prefix,uint8_t * out,uint8_t * out_suffix,uint8_t type,const uint8_t * in,size_t in_len)467 static bool tls_seal_scatter_record(SSL *ssl, uint8_t *out_prefix, uint8_t *out,
468                                    uint8_t *out_suffix, uint8_t type,
469                                    const uint8_t *in, size_t in_len) {
470   if (type == SSL3_RT_APPLICATION_DATA && in_len > 1 &&
471       ssl_needs_record_splitting(ssl)) {
472     assert(ssl->s3->aead_write_ctx->ExplicitNonceLen() == 0);
473     const size_t prefix_len = SSL3_RT_HEADER_LENGTH;
474 
475     // Write the 1-byte fragment into |out_prefix|.
476     uint8_t *split_body = out_prefix + prefix_len;
477     uint8_t *split_suffix = split_body + 1;
478 
479     if (!do_seal_record(ssl, out_prefix, split_body, split_suffix, type, in,
480                         1)) {
481       return false;
482     }
483 
484     size_t split_record_suffix_len;
485     if (!ssl->s3->aead_write_ctx->SuffixLen(&split_record_suffix_len, 1, 0)) {
486       assert(false);
487       return false;
488     }
489     const size_t split_record_len = prefix_len + 1 + split_record_suffix_len;
490     assert(SSL3_RT_HEADER_LENGTH + ssl_cipher_get_record_split_len(
491                                        ssl->s3->aead_write_ctx->cipher()) ==
492            split_record_len);
493 
494     // Write the n-1-byte fragment. The header gets split between |out_prefix|
495     // (header[:-1]) and |out| (header[-1:]).
496     uint8_t tmp_prefix[SSL3_RT_HEADER_LENGTH];
497     if (!do_seal_record(ssl, tmp_prefix, out + 1, out_suffix, type, in + 1,
498                         in_len - 1)) {
499       return false;
500     }
501     assert(tls_seal_scatter_prefix_len(ssl, type, in_len) ==
502            split_record_len + SSL3_RT_HEADER_LENGTH - 1);
503     OPENSSL_memcpy(out_prefix + split_record_len, tmp_prefix,
504                    SSL3_RT_HEADER_LENGTH - 1);
505     OPENSSL_memcpy(out, tmp_prefix + SSL3_RT_HEADER_LENGTH - 1, 1);
506     return true;
507   }
508 
509   return do_seal_record(ssl, out_prefix, out, out_suffix, type, in, in_len);
510 }
511 
tls_seal_record(SSL * ssl,uint8_t * out,size_t * out_len,size_t max_out_len,uint8_t type,const uint8_t * in,size_t in_len)512 bool tls_seal_record(SSL *ssl, uint8_t *out, size_t *out_len,
513                      size_t max_out_len, uint8_t type, const uint8_t *in,
514                      size_t in_len) {
515   if (buffers_alias(in, in_len, out, max_out_len)) {
516     OPENSSL_PUT_ERROR(SSL, SSL_R_OUTPUT_ALIASES_INPUT);
517     return false;
518   }
519 
520   const size_t prefix_len = tls_seal_scatter_prefix_len(ssl, type, in_len);
521   size_t suffix_len;
522   if (!tls_seal_scatter_suffix_len(ssl, &suffix_len, type, in_len)) {
523     return false;
524   }
525   if (in_len + prefix_len < in_len ||
526       prefix_len + in_len + suffix_len < prefix_len + in_len) {
527     OPENSSL_PUT_ERROR(SSL, SSL_R_RECORD_TOO_LARGE);
528     return false;
529   }
530   if (max_out_len < in_len + prefix_len + suffix_len) {
531     OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
532     return false;
533   }
534 
535   uint8_t *prefix = out;
536   uint8_t *body = out + prefix_len;
537   uint8_t *suffix = body + in_len;
538   if (!tls_seal_scatter_record(ssl, prefix, body, suffix, type, in, in_len)) {
539     return false;
540   }
541 
542   *out_len = prefix_len + in_len + suffix_len;
543   return true;
544 }
545 
ssl_process_alert(SSL * ssl,uint8_t * out_alert,Span<const uint8_t> in)546 enum ssl_open_record_t ssl_process_alert(SSL *ssl, uint8_t *out_alert,
547                                          Span<const uint8_t> in) {
548   // Alerts records may not contain fragmented or multiple alerts.
549   if (in.size() != 2) {
550     *out_alert = SSL_AD_DECODE_ERROR;
551     OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_ALERT);
552     return ssl_open_record_error;
553   }
554 
555   ssl_do_msg_callback(ssl, 0 /* read */, SSL3_RT_ALERT, in);
556 
557   const uint8_t alert_level = in[0];
558   const uint8_t alert_descr = in[1];
559 
560   uint16_t alert = (alert_level << 8) | alert_descr;
561   ssl_do_info_callback(ssl, SSL_CB_READ_ALERT, alert);
562 
563   if (alert_level == SSL3_AL_WARNING) {
564     if (alert_descr == SSL_AD_CLOSE_NOTIFY) {
565       ssl->s3->read_shutdown = ssl_shutdown_close_notify;
566       return ssl_open_record_close_notify;
567     }
568 
569     // Warning alerts do not exist in TLS 1.3.
570     if (ssl->s3->have_version &&
571         ssl_protocol_version(ssl) >= TLS1_3_VERSION) {
572       *out_alert = SSL_AD_DECODE_ERROR;
573       OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_ALERT);
574       return ssl_open_record_error;
575     }
576 
577     ssl->s3->warning_alert_count++;
578     if (ssl->s3->warning_alert_count > kMaxWarningAlerts) {
579       *out_alert = SSL_AD_UNEXPECTED_MESSAGE;
580       OPENSSL_PUT_ERROR(SSL, SSL_R_TOO_MANY_WARNING_ALERTS);
581       return ssl_open_record_error;
582     }
583     return ssl_open_record_discard;
584   }
585 
586   if (alert_level == SSL3_AL_FATAL) {
587     OPENSSL_PUT_ERROR(SSL, SSL_AD_REASON_OFFSET + alert_descr);
588     ERR_add_error_dataf("SSL alert number %d", alert_descr);
589     *out_alert = 0;  // No alert to send back to the peer.
590     return ssl_open_record_error;
591   }
592 
593   *out_alert = SSL_AD_ILLEGAL_PARAMETER;
594   OPENSSL_PUT_ERROR(SSL, SSL_R_UNKNOWN_ALERT_TYPE);
595   return ssl_open_record_error;
596 }
597 
OpenRecord(SSL * ssl,Span<uint8_t> * out,size_t * out_record_len,uint8_t * out_alert,const Span<uint8_t> in)598 OpenRecordResult OpenRecord(SSL *ssl, Span<uint8_t> *out,
599                             size_t *out_record_len, uint8_t *out_alert,
600                             const Span<uint8_t> in) {
601   // This API is a work in progress and currently only works for TLS 1.2 servers
602   // and below.
603   if (SSL_in_init(ssl) ||
604       SSL_is_dtls(ssl) ||
605       ssl_protocol_version(ssl) > TLS1_2_VERSION) {
606     assert(false);
607     *out_alert = SSL_AD_INTERNAL_ERROR;
608     return OpenRecordResult::kError;
609   }
610 
611   Span<uint8_t> plaintext;
612   uint8_t type = 0;
613   const ssl_open_record_t result = tls_open_record(
614       ssl, &type, &plaintext, out_record_len, out_alert, in);
615 
616   switch (result) {
617     case ssl_open_record_success:
618       if (type != SSL3_RT_APPLICATION_DATA && type != SSL3_RT_ALERT) {
619         *out_alert = SSL_AD_UNEXPECTED_MESSAGE;
620         return OpenRecordResult::kError;
621       }
622       *out = plaintext;
623       return OpenRecordResult::kOK;
624     case ssl_open_record_discard:
625       return OpenRecordResult::kDiscard;
626     case ssl_open_record_partial:
627       return OpenRecordResult::kIncompleteRecord;
628     case ssl_open_record_close_notify:
629       return OpenRecordResult::kAlertCloseNotify;
630     case ssl_open_record_error:
631       return OpenRecordResult::kError;
632   }
633   assert(false);
634   return OpenRecordResult::kError;
635 }
636 
SealRecordPrefixLen(const SSL * ssl,const size_t record_len)637 size_t SealRecordPrefixLen(const SSL *ssl, const size_t record_len) {
638   return tls_seal_scatter_prefix_len(ssl, SSL3_RT_APPLICATION_DATA, record_len);
639 }
640 
SealRecordSuffixLen(const SSL * ssl,const size_t plaintext_len)641 size_t SealRecordSuffixLen(const SSL *ssl, const size_t plaintext_len) {
642   assert(plaintext_len <= SSL3_RT_MAX_PLAIN_LENGTH);
643   size_t suffix_len;
644   if (!tls_seal_scatter_suffix_len(ssl, &suffix_len, SSL3_RT_APPLICATION_DATA,
645                                    plaintext_len)) {
646     assert(false);
647     OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
648     return 0;
649   }
650   assert(suffix_len <= SSL3_RT_MAX_ENCRYPTED_OVERHEAD);
651   return suffix_len;
652 }
653 
SealRecord(SSL * ssl,const Span<uint8_t> out_prefix,const Span<uint8_t> out,Span<uint8_t> out_suffix,const Span<const uint8_t> in)654 bool SealRecord(SSL *ssl, const Span<uint8_t> out_prefix,
655                 const Span<uint8_t> out, Span<uint8_t> out_suffix,
656                 const Span<const uint8_t> in) {
657   // This API is a work in progress and currently only works for TLS 1.2 servers
658   // and below.
659   if (SSL_in_init(ssl) ||
660       SSL_is_dtls(ssl) ||
661       ssl_protocol_version(ssl) > TLS1_2_VERSION) {
662     assert(false);
663     OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
664     return false;
665   }
666 
667   if (out_prefix.size() != SealRecordPrefixLen(ssl, in.size()) ||
668       out.size() != in.size() ||
669       out_suffix.size() != SealRecordSuffixLen(ssl, in.size())) {
670     OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
671     return false;
672   }
673   return tls_seal_scatter_record(ssl, out_prefix.data(), out.data(),
674                                  out_suffix.data(), SSL3_RT_APPLICATION_DATA,
675                                  in.data(), in.size());
676 }
677 
678 BSSL_NAMESPACE_END
679 
680 using namespace bssl;
681 
SSL_max_seal_overhead(const SSL * ssl)682 size_t SSL_max_seal_overhead(const SSL *ssl) {
683   if (SSL_is_dtls(ssl)) {
684     return dtls_max_seal_overhead(ssl, dtls1_use_current_epoch);
685   }
686 
687   size_t ret = SSL3_RT_HEADER_LENGTH;
688   ret += ssl->s3->aead_write_ctx->MaxOverhead();
689   // TLS 1.3 needs an extra byte for the encrypted record type.
690   if (!ssl->s3->aead_write_ctx->is_null_cipher() &&
691       ssl->s3->aead_write_ctx->ProtocolVersion() >= TLS1_3_VERSION) {
692     ret += 1;
693   }
694   if (ssl_needs_record_splitting(ssl)) {
695     ret *= 2;
696   }
697   return ret;
698 }
699