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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 <limits.h>
113 #include <string.h>
114 
115 #include <openssl/buf.h>
116 #include <openssl/err.h>
117 #include <openssl/evp.h>
118 #include <openssl/mem.h>
119 #include <openssl/rand.h>
120 
121 #include "../crypto/internal.h"
122 #include "internal.h"
123 
124 
125 static int do_ssl3_write(SSL *ssl, int type, const uint8_t *buf, unsigned len);
126 
127 /* ssl3_get_record reads a new input record. On success, it places it in
128  * |ssl->s3->rrec| and returns one. Otherwise it returns <= 0 on error or if
129  * more data is needed. */
ssl3_get_record(SSL * ssl)130 static int ssl3_get_record(SSL *ssl) {
131 again:
132   switch (ssl->s3->recv_shutdown) {
133     case ssl_shutdown_none:
134       break;
135     case ssl_shutdown_fatal_alert:
136       OPENSSL_PUT_ERROR(SSL, SSL_R_PROTOCOL_IS_SHUTDOWN);
137       return -1;
138     case ssl_shutdown_close_notify:
139       return 0;
140   }
141 
142   CBS body;
143   uint8_t type, alert = SSL_AD_DECODE_ERROR;
144   size_t consumed;
145   enum ssl_open_record_t open_ret =
146       tls_open_record(ssl, &type, &body, &consumed, &alert,
147                       ssl_read_buffer(ssl), ssl_read_buffer_len(ssl));
148   if (open_ret != ssl_open_record_partial) {
149     ssl_read_buffer_consume(ssl, consumed);
150   }
151   switch (open_ret) {
152     case ssl_open_record_partial: {
153       int read_ret = ssl_read_buffer_extend_to(ssl, consumed);
154       if (read_ret <= 0) {
155         return read_ret;
156       }
157       goto again;
158     }
159 
160     case ssl_open_record_success: {
161       if (CBS_len(&body) > 0xffff) {
162         OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW);
163         return -1;
164       }
165 
166       SSL3_RECORD *rr = &ssl->s3->rrec;
167       rr->type = type;
168       rr->length = (uint16_t)CBS_len(&body);
169       rr->data = (uint8_t *)CBS_data(&body);
170       return 1;
171     }
172 
173     case ssl_open_record_discard:
174       goto again;
175 
176     case ssl_open_record_close_notify:
177       return 0;
178 
179     case ssl_open_record_fatal_alert:
180       return -1;
181 
182     case ssl_open_record_error:
183       ssl3_send_alert(ssl, SSL3_AL_FATAL, alert);
184       return -1;
185   }
186 
187   assert(0);
188   OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
189   return -1;
190 }
191 
ssl3_write_app_data(SSL * ssl,int * out_needs_handshake,const uint8_t * buf,int len)192 int ssl3_write_app_data(SSL *ssl, int *out_needs_handshake, const uint8_t *buf,
193                         int len) {
194   assert(ssl_can_write(ssl));
195   assert(ssl->s3->aead_write_ctx != NULL);
196 
197   *out_needs_handshake = 0;
198 
199   unsigned tot, n, nw;
200 
201   assert(ssl->s3->wnum <= INT_MAX);
202   tot = ssl->s3->wnum;
203   ssl->s3->wnum = 0;
204 
205   /* Ensure that if we end up with a smaller value of data to write out than
206    * the the original len from a write which didn't complete for non-blocking
207    * I/O and also somehow ended up avoiding the check for this in
208    * ssl3_write_pending/SSL_R_BAD_WRITE_RETRY as it must never be possible to
209    * end up with (len-tot) as a large number that will then promptly send
210    * beyond the end of the users buffer ... so we trap and report the error in
211    * a way the user will notice. */
212   if (len < 0 || (size_t)len < tot) {
213     OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_LENGTH);
214     return -1;
215   }
216 
217   const int is_early_data_write =
218       !ssl->server && SSL_in_early_data(ssl) && ssl->s3->hs->can_early_write;
219 
220   n = len - tot;
221   for (;;) {
222     /* max contains the maximum number of bytes that we can put into a
223      * record. */
224     unsigned max = ssl->max_send_fragment;
225     if (is_early_data_write && max > ssl->session->ticket_max_early_data -
226                                          ssl->s3->hs->early_data_written) {
227       max = ssl->session->ticket_max_early_data - ssl->s3->hs->early_data_written;
228       if (max == 0) {
229         ssl->s3->wnum = tot;
230         ssl->s3->hs->can_early_write = 0;
231         *out_needs_handshake = 1;
232         return -1;
233       }
234     }
235 
236     if (n > max) {
237       nw = max;
238     } else {
239       nw = n;
240     }
241 
242     int ret = do_ssl3_write(ssl, SSL3_RT_APPLICATION_DATA, &buf[tot], nw);
243     if (ret <= 0) {
244       ssl->s3->wnum = tot;
245       return ret;
246     }
247 
248     if (is_early_data_write) {
249       ssl->s3->hs->early_data_written += ret;
250     }
251 
252     if (ret == (int)n || (ssl->mode & SSL_MODE_ENABLE_PARTIAL_WRITE)) {
253       return tot + ret;
254     }
255 
256     n -= ret;
257     tot += ret;
258   }
259 }
260 
ssl3_write_pending(SSL * ssl,int type,const uint8_t * buf,unsigned int len)261 static int ssl3_write_pending(SSL *ssl, int type, const uint8_t *buf,
262                               unsigned int len) {
263   if (ssl->s3->wpend_tot > (int)len ||
264       (!(ssl->mode & SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER) &&
265        ssl->s3->wpend_buf != buf) ||
266       ssl->s3->wpend_type != type) {
267     OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_WRITE_RETRY);
268     return -1;
269   }
270 
271   int ret = ssl_write_buffer_flush(ssl);
272   if (ret <= 0) {
273     return ret;
274   }
275   ssl->s3->wpend_pending = 0;
276   return ssl->s3->wpend_ret;
277 }
278 
279 /* do_ssl3_write writes an SSL record of the given type. */
do_ssl3_write(SSL * ssl,int type,const uint8_t * buf,unsigned len)280 static int do_ssl3_write(SSL *ssl, int type, const uint8_t *buf, unsigned len) {
281   /* If there is still data from the previous record, flush it. */
282   if (ssl->s3->wpend_pending) {
283     return ssl3_write_pending(ssl, type, buf, len);
284   }
285 
286   if (len > SSL3_RT_MAX_PLAIN_LENGTH) {
287     OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
288     return -1;
289   }
290 
291   if (len == 0) {
292     return 0;
293   }
294 
295   size_t flight_len = 0;
296   if (ssl->s3->pending_flight != NULL) {
297     flight_len =
298         ssl->s3->pending_flight->length - ssl->s3->pending_flight_offset;
299   }
300 
301   size_t max_out = len + SSL_max_seal_overhead(ssl);
302   if (max_out < len || max_out + flight_len < max_out) {
303     OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW);
304     return -1;
305   }
306   max_out += flight_len;
307 
308   uint8_t *out;
309   size_t ciphertext_len;
310   if (!ssl_write_buffer_init(ssl, &out, max_out)) {
311     return -1;
312   }
313 
314   /* Add any unflushed handshake data as a prefix. This may be a KeyUpdate
315    * acknowledgment or 0-RTT key change messages. |pending_flight| must be clear
316    * when data is added to |write_buffer| or it will be written in the wrong
317    * order. */
318   if (ssl->s3->pending_flight != NULL) {
319     OPENSSL_memcpy(
320         out, ssl->s3->pending_flight->data + ssl->s3->pending_flight_offset,
321         flight_len);
322     BUF_MEM_free(ssl->s3->pending_flight);
323     ssl->s3->pending_flight = NULL;
324     ssl->s3->pending_flight_offset = 0;
325   }
326 
327   if (!tls_seal_record(ssl, out + flight_len, &ciphertext_len,
328                        max_out - flight_len, type, buf, len)) {
329     return -1;
330   }
331   ssl_write_buffer_set_len(ssl, flight_len + ciphertext_len);
332 
333   /* Now that we've made progress on the connection, uncork KeyUpdate
334    * acknowledgments. */
335   ssl->s3->key_update_pending = 0;
336 
337   /* memorize arguments so that ssl3_write_pending can detect bad write retries
338    * later */
339   ssl->s3->wpend_tot = len;
340   ssl->s3->wpend_buf = buf;
341   ssl->s3->wpend_type = type;
342   ssl->s3->wpend_ret = len;
343   ssl->s3->wpend_pending = 1;
344 
345   /* we now just need to write the buffer */
346   return ssl3_write_pending(ssl, type, buf, len);
347 }
348 
consume_record(SSL * ssl,uint8_t * out,int len,int peek)349 static int consume_record(SSL *ssl, uint8_t *out, int len, int peek) {
350   SSL3_RECORD *rr = &ssl->s3->rrec;
351 
352   if (len <= 0) {
353     return len;
354   }
355 
356   if (len > (int)rr->length) {
357     len = (int)rr->length;
358   }
359 
360   OPENSSL_memcpy(out, rr->data, len);
361   if (!peek) {
362     rr->length -= len;
363     rr->data += len;
364     if (rr->length == 0) {
365       /* The record has been consumed, so we may now clear the buffer. */
366       ssl_read_buffer_discard(ssl);
367     }
368   }
369   return len;
370 }
371 
ssl3_read_app_data(SSL * ssl,int * out_got_handshake,uint8_t * buf,int len,int peek)372 int ssl3_read_app_data(SSL *ssl, int *out_got_handshake, uint8_t *buf, int len,
373                        int peek) {
374   assert(ssl_can_read(ssl));
375   assert(ssl->s3->aead_read_ctx != NULL);
376   *out_got_handshake = 0;
377 
378   ssl->method->release_current_message(ssl, 0 /* don't free buffer */);
379 
380   SSL3_RECORD *rr = &ssl->s3->rrec;
381 
382   for (;;) {
383     /* A previous iteration may have read a partial handshake message. Do not
384      * allow more app data in that case. */
385     int has_hs_data = ssl->init_buf != NULL && ssl->init_buf->length > 0;
386 
387     /* Get new packet if necessary. */
388     if (rr->length == 0 && !has_hs_data) {
389       int ret = ssl3_get_record(ssl);
390       if (ret <= 0) {
391         return ret;
392       }
393     }
394 
395     if (has_hs_data || rr->type == SSL3_RT_HANDSHAKE) {
396       /* If reading 0-RTT data, reject handshake data. 0-RTT data is terminated
397        * by an alert. */
398       if (SSL_in_init(ssl)) {
399         OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);
400         ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
401         return -1;
402       }
403 
404       /* Post-handshake data prior to TLS 1.3 is always renegotiation, which we
405        * never accept as a server. Otherwise |ssl3_get_message| will send
406        * |SSL_R_EXCESSIVE_MESSAGE_SIZE|. */
407       if (ssl->server && ssl3_protocol_version(ssl) < TLS1_3_VERSION) {
408         ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_NO_RENEGOTIATION);
409         OPENSSL_PUT_ERROR(SSL, SSL_R_NO_RENEGOTIATION);
410         return -1;
411       }
412 
413       /* Parse post-handshake handshake messages. */
414       int ret = ssl3_get_message(ssl);
415       if (ret <= 0) {
416         return ret;
417       }
418       *out_got_handshake = 1;
419       return -1;
420     }
421 
422     const int is_early_data_read = ssl->server &&
423                                    ssl->s3->hs != NULL &&
424                                    ssl->s3->hs->can_early_read &&
425                                    ssl3_protocol_version(ssl) >= TLS1_3_VERSION;
426 
427     /* Handle the end_of_early_data alert. */
428     if (rr->type == SSL3_RT_ALERT &&
429         rr->length == 2 &&
430         rr->data[0] == SSL3_AL_WARNING &&
431         rr->data[1] == TLS1_AD_END_OF_EARLY_DATA &&
432         is_early_data_read) {
433       /* Consume the record. */
434       rr->length = 0;
435       ssl_read_buffer_discard(ssl);
436       /* Stop accepting early data. */
437       ssl->s3->hs->can_early_read = 0;
438       *out_got_handshake = 1;
439       return -1;
440     }
441 
442     if (rr->type != SSL3_RT_APPLICATION_DATA) {
443       OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);
444       ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
445       return -1;
446     }
447 
448     if (is_early_data_read) {
449       if (rr->length > kMaxEarlyDataAccepted - ssl->s3->hs->early_data_read) {
450         OPENSSL_PUT_ERROR(SSL, SSL_R_TOO_MUCH_READ_EARLY_DATA);
451         ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL3_AD_UNEXPECTED_MESSAGE);
452         return -1;
453       }
454 
455       ssl->s3->hs->early_data_read += rr->length;
456     }
457 
458     if (rr->length != 0) {
459       return consume_record(ssl, buf, len, peek);
460     }
461 
462     /* Discard empty records and loop again. */
463   }
464 }
465 
ssl3_read_change_cipher_spec(SSL * ssl)466 int ssl3_read_change_cipher_spec(SSL *ssl) {
467   SSL3_RECORD *rr = &ssl->s3->rrec;
468 
469   if (rr->length == 0) {
470     int ret = ssl3_get_record(ssl);
471     if (ret <= 0) {
472       return ret;
473     }
474   }
475 
476   if (rr->type != SSL3_RT_CHANGE_CIPHER_SPEC) {
477     ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
478     OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);
479     return -1;
480   }
481 
482   if (rr->length != 1 || rr->data[0] != SSL3_MT_CCS) {
483     OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_CHANGE_CIPHER_SPEC);
484     ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
485     return -1;
486   }
487 
488   ssl_do_msg_callback(ssl, 0 /* read */, SSL3_RT_CHANGE_CIPHER_SPEC, rr->data,
489                       rr->length);
490 
491   rr->length = 0;
492   ssl_read_buffer_discard(ssl);
493   return 1;
494 }
495 
ssl3_read_close_notify(SSL * ssl)496 void ssl3_read_close_notify(SSL *ssl) {
497   /* Read records until an error or close_notify. */
498   while (ssl3_get_record(ssl) > 0) {
499     ;
500   }
501 }
502 
ssl3_read_handshake_bytes(SSL * ssl,uint8_t * buf,int len)503 int ssl3_read_handshake_bytes(SSL *ssl, uint8_t *buf, int len) {
504   SSL3_RECORD *rr = &ssl->s3->rrec;
505 
506   for (;;) {
507     /* Get new packet if necessary. */
508     if (rr->length == 0) {
509       int ret = ssl3_get_record(ssl);
510       if (ret <= 0) {
511         return ret;
512       }
513     }
514 
515     /* WatchGuard's TLS 1.3 interference bug is very distinctive: they drop the
516      * ServerHello and send the remaining encrypted application data records
517      * as-is. This manifests as an application data record when we expect
518      * handshake. Report a dedicated error code for this case. */
519     if (!ssl->server && rr->type == SSL3_RT_APPLICATION_DATA &&
520         ssl->s3->aead_read_ctx == NULL) {
521       OPENSSL_PUT_ERROR(SSL, SSL_R_APPLICATION_DATA_INSTEAD_OF_HANDSHAKE);
522       ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
523       return -1;
524     }
525 
526     /* Accept server_plaintext_handshake records when the content type TLS 1.3
527      * variant is enabled. */
528     if (rr->type != SSL3_RT_HANDSHAKE &&
529         !(!ssl->server &&
530           ssl->tls13_variant == tls13_record_type_experiment &&
531           ssl->s3->aead_read_ctx == NULL &&
532           rr->type == SSL3_RT_PLAINTEXT_HANDSHAKE)) {
533       OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);
534       ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
535       return -1;
536     }
537 
538     if (rr->length != 0) {
539       return consume_record(ssl, buf, len, 0 /* consume data */);
540     }
541 
542     /* Discard empty records and loop again. */
543   }
544 }
545 
ssl3_send_alert(SSL * ssl,int level,int desc)546 int ssl3_send_alert(SSL *ssl, int level, int desc) {
547   /* It is illegal to send an alert when we've already sent a closing one. */
548   if (ssl->s3->send_shutdown != ssl_shutdown_none) {
549     OPENSSL_PUT_ERROR(SSL, SSL_R_PROTOCOL_IS_SHUTDOWN);
550     return -1;
551   }
552 
553   if (level == SSL3_AL_WARNING && desc == SSL_AD_CLOSE_NOTIFY) {
554     ssl->s3->send_shutdown = ssl_shutdown_close_notify;
555   } else {
556     assert(level == SSL3_AL_FATAL);
557     ssl->s3->send_shutdown = ssl_shutdown_fatal_alert;
558   }
559 
560   ssl->s3->alert_dispatch = 1;
561   ssl->s3->send_alert[0] = level;
562   ssl->s3->send_alert[1] = desc;
563   if (!ssl_write_buffer_is_pending(ssl)) {
564     /* Nothing is being written out, so the alert may be dispatched
565      * immediately. */
566     return ssl->method->dispatch_alert(ssl);
567   }
568 
569   /* The alert will be dispatched later. */
570   return -1;
571 }
572 
ssl3_dispatch_alert(SSL * ssl)573 int ssl3_dispatch_alert(SSL *ssl) {
574   int ret = do_ssl3_write(ssl, SSL3_RT_ALERT, &ssl->s3->send_alert[0], 2);
575   if (ret <= 0) {
576     return ret;
577   }
578   ssl->s3->alert_dispatch = 0;
579 
580   /* If the alert is fatal, flush the BIO now. */
581   if (ssl->s3->send_alert[0] == SSL3_AL_FATAL) {
582     BIO_flush(ssl->wbio);
583   }
584 
585   ssl_do_msg_callback(ssl, 1 /* write */, SSL3_RT_ALERT, ssl->s3->send_alert,
586                       2);
587 
588   int alert = (ssl->s3->send_alert[0] << 8) | ssl->s3->send_alert[1];
589   ssl_do_info_callback(ssl, SSL_CB_WRITE_ALERT, alert);
590 
591   return 1;
592 }
593