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Commit | Line | Data |
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0f113f3e | 1 | /* |
846e33c7 | 2 | * Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved. |
36d16f8e | 3 | * |
846e33c7 RS |
4 | * Licensed under the OpenSSL license (the "License"). You may not use |
5 | * this file except in compliance with the License. You can obtain a copy | |
6 | * in the file LICENSE in the source distribution or at | |
7 | * https://www.openssl.org/source/license.html | |
36d16f8e BL |
8 | */ |
9 | ||
10 | #include <stdio.h> | |
9289f21b | 11 | #define USE_SOCKETS |
36d16f8e | 12 | #include <openssl/objects.h> |
8ba708e5 | 13 | #include <openssl/rand.h> |
36d16f8e BL |
14 | #include "ssl_locl.h" |
15 | ||
a006fef7 | 16 | #if defined(OPENSSL_SYS_VMS) |
0f113f3e | 17 | # include <sys/timeb.h> |
fb456902 MC |
18 | #elif defined(OPENSSL_SYS_VXWORKS) |
19 | # include <sys/times.h> | |
20 | #elif !defined(OPENSSL_SYS_WIN32) | |
21 | # include <sys/time.h> | |
eb38b26d DSH |
22 | #endif |
23 | ||
24 | static void get_current_time(struct timeval *t); | |
173e72e6 | 25 | static int dtls1_handshake_write(SSL *s); |
7ee8627f | 26 | static size_t dtls1_link_min_mtu(void); |
36d16f8e | 27 | |
8ba708e5 | 28 | /* XDTLS: figure out the right values */ |
7ee8627f | 29 | static const size_t g_probable_mtu[] = { 1500, 512, 256 }; |
8ba708e5 | 30 | |
0f113f3e MC |
31 | const SSL3_ENC_METHOD DTLSv1_enc_data = { |
32 | tls1_enc, | |
33 | tls1_mac, | |
34 | tls1_setup_key_block, | |
35 | tls1_generate_master_secret, | |
36 | tls1_change_cipher_state, | |
37 | tls1_final_finish_mac, | |
0f113f3e MC |
38 | TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE, |
39 | TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE, | |
40 | tls1_alert_code, | |
41 | tls1_export_keying_material, | |
42 | SSL_ENC_FLAG_DTLS | SSL_ENC_FLAG_EXPLICIT_IV, | |
a29fa98c | 43 | dtls1_set_handshake_header, |
2c7b4dbc | 44 | dtls1_close_construct_packet, |
0f113f3e MC |
45 | dtls1_handshake_write |
46 | }; | |
47 | ||
48 | const SSL3_ENC_METHOD DTLSv1_2_enc_data = { | |
49 | tls1_enc, | |
50 | tls1_mac, | |
51 | tls1_setup_key_block, | |
52 | tls1_generate_master_secret, | |
53 | tls1_change_cipher_state, | |
54 | tls1_final_finish_mac, | |
0f113f3e MC |
55 | TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE, |
56 | TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE, | |
57 | tls1_alert_code, | |
58 | tls1_export_keying_material, | |
59 | SSL_ENC_FLAG_DTLS | SSL_ENC_FLAG_EXPLICIT_IV | SSL_ENC_FLAG_SIGALGS | |
60 | | SSL_ENC_FLAG_SHA256_PRF | SSL_ENC_FLAG_TLS1_2_CIPHERS, | |
a29fa98c | 61 | dtls1_set_handshake_header, |
2c7b4dbc | 62 | dtls1_close_construct_packet, |
0f113f3e MC |
63 | dtls1_handshake_write |
64 | }; | |
c3b344e3 | 65 | |
f3b656b2 | 66 | long dtls1_default_timeout(void) |
0f113f3e MC |
67 | { |
68 | /* | |
69 | * 2 hours, the 24 hours mentioned in the DTLSv1 spec is way too long for | |
70 | * http, the cache would over fill | |
71 | */ | |
72 | return (60 * 60 * 2); | |
73 | } | |
36d16f8e | 74 | |
36d16f8e | 75 | int dtls1_new(SSL *s) |
0f113f3e MC |
76 | { |
77 | DTLS1_STATE *d1; | |
78 | ||
61986d32 | 79 | if (!DTLS_RECORD_LAYER_new(&s->rlayer)) { |
5fb6f80c MC |
80 | return 0; |
81 | } | |
0485d540 | 82 | |
0f113f3e MC |
83 | if (!ssl3_new(s)) |
84 | return (0); | |
b51bce94 | 85 | if ((d1 = OPENSSL_zalloc(sizeof(*d1))) == NULL) { |
0f113f3e MC |
86 | ssl3_free(s); |
87 | return (0); | |
88 | } | |
0f113f3e | 89 | |
0f113f3e MC |
90 | d1->buffered_messages = pqueue_new(); |
91 | d1->sent_messages = pqueue_new(); | |
0f113f3e MC |
92 | |
93 | if (s->server) { | |
94 | d1->cookie_len = sizeof(s->d1->cookie); | |
95 | } | |
96 | ||
97 | d1->link_mtu = 0; | |
98 | d1->mtu = 0; | |
99 | ||
a71edf3b | 100 | if (d1->buffered_messages == NULL || d1->sent_messages == NULL) { |
25aaa98a RS |
101 | pqueue_free(d1->buffered_messages); |
102 | pqueue_free(d1->sent_messages); | |
0f113f3e MC |
103 | OPENSSL_free(d1); |
104 | ssl3_free(s); | |
105 | return (0); | |
106 | } | |
107 | ||
108 | s->d1 = d1; | |
109 | s->method->ssl_clear(s); | |
110 | return (1); | |
111 | } | |
36d16f8e | 112 | |
7832d6ab | 113 | static void dtls1_clear_queues(SSL *s) |
f5c7f5df MC |
114 | { |
115 | dtls1_clear_received_buffer(s); | |
116 | dtls1_clear_sent_buffer(s); | |
117 | } | |
118 | ||
119 | void dtls1_clear_received_buffer(SSL *s) | |
0f113f3e | 120 | { |
36d16f8e BL |
121 | pitem *item = NULL; |
122 | hm_fragment *frag = NULL; | |
0f113f3e | 123 | |
0f113f3e | 124 | while ((item = pqueue_pop(s->d1->buffered_messages)) != NULL) { |
36d16f8e | 125 | frag = (hm_fragment *)item->data; |
8a35dbb6 | 126 | dtls1_hm_fragment_free(frag); |
36d16f8e | 127 | pitem_free(item); |
0f113f3e | 128 | } |
f5c7f5df MC |
129 | } |
130 | ||
131 | void dtls1_clear_sent_buffer(SSL *s) | |
132 | { | |
133 | pitem *item = NULL; | |
134 | hm_fragment *frag = NULL; | |
36d16f8e | 135 | |
0f113f3e | 136 | while ((item = pqueue_pop(s->d1->sent_messages)) != NULL) { |
36d16f8e | 137 | frag = (hm_fragment *)item->data; |
8a35dbb6 | 138 | dtls1_hm_fragment_free(frag); |
36d16f8e | 139 | pitem_free(item); |
0f113f3e | 140 | } |
0f113f3e | 141 | } |
7832d6ab | 142 | |
f5c7f5df | 143 | |
7832d6ab | 144 | void dtls1_free(SSL *s) |
0f113f3e | 145 | { |
40f37188 MC |
146 | DTLS_RECORD_LAYER_free(&s->rlayer); |
147 | ||
0f113f3e | 148 | ssl3_free(s); |
7832d6ab | 149 | |
0f113f3e | 150 | dtls1_clear_queues(s); |
7832d6ab | 151 | |
7832d6ab | 152 | pqueue_free(s->d1->buffered_messages); |
0f113f3e | 153 | pqueue_free(s->d1->sent_messages); |
e5fa864f | 154 | |
0f113f3e MC |
155 | OPENSSL_free(s->d1); |
156 | s->d1 = NULL; | |
157 | } | |
36d16f8e BL |
158 | |
159 | void dtls1_clear(SSL *s) | |
0f113f3e | 160 | { |
cf2cede4 RS |
161 | pqueue *buffered_messages; |
162 | pqueue *sent_messages; | |
7ee8627f MC |
163 | size_t mtu; |
164 | size_t link_mtu; | |
0f113f3e | 165 | |
40f37188 MC |
166 | DTLS_RECORD_LAYER_clear(&s->rlayer); |
167 | ||
0f113f3e | 168 | if (s->d1) { |
0f113f3e MC |
169 | buffered_messages = s->d1->buffered_messages; |
170 | sent_messages = s->d1->sent_messages; | |
0f113f3e MC |
171 | mtu = s->d1->mtu; |
172 | link_mtu = s->d1->link_mtu; | |
173 | ||
174 | dtls1_clear_queues(s); | |
175 | ||
16f8d4eb | 176 | memset(s->d1, 0, sizeof(*s->d1)); |
0f113f3e MC |
177 | |
178 | if (s->server) { | |
179 | s->d1->cookie_len = sizeof(s->d1->cookie); | |
180 | } | |
181 | ||
182 | if (SSL_get_options(s) & SSL_OP_NO_QUERY_MTU) { | |
183 | s->d1->mtu = mtu; | |
184 | s->d1->link_mtu = link_mtu; | |
185 | } | |
186 | ||
0f113f3e MC |
187 | s->d1->buffered_messages = buffered_messages; |
188 | s->d1->sent_messages = sent_messages; | |
0f113f3e MC |
189 | } |
190 | ||
191 | ssl3_clear(s); | |
032924c4 DW |
192 | |
193 | if (s->method->version == DTLS_ANY_VERSION) | |
4fa52141 | 194 | s->version = DTLS_MAX_VERSION; |
032924c4 DW |
195 | #ifndef OPENSSL_NO_DTLS1_METHOD |
196 | else if (s->options & SSL_OP_CISCO_ANYCONNECT) | |
197 | s->client_version = s->version = DTLS1_BAD_VER; | |
198 | #endif | |
0f113f3e MC |
199 | else |
200 | s->version = s->method->version; | |
201 | } | |
5d58f1bb | 202 | |
b972fbaa | 203 | long dtls1_ctrl(SSL *s, int cmd, long larg, void *parg) |
0f113f3e MC |
204 | { |
205 | int ret = 0; | |
206 | ||
207 | switch (cmd) { | |
208 | case DTLS_CTRL_GET_TIMEOUT: | |
209 | if (dtls1_get_timeout(s, (struct timeval *)parg) != NULL) { | |
210 | ret = 1; | |
211 | } | |
212 | break; | |
213 | case DTLS_CTRL_HANDLE_TIMEOUT: | |
214 | ret = dtls1_handle_timeout(s); | |
215 | break; | |
0f113f3e MC |
216 | case DTLS_CTRL_SET_LINK_MTU: |
217 | if (larg < (long)dtls1_link_min_mtu()) | |
218 | return 0; | |
219 | s->d1->link_mtu = larg; | |
220 | return 1; | |
221 | case DTLS_CTRL_GET_LINK_MIN_MTU: | |
222 | return (long)dtls1_link_min_mtu(); | |
223 | case SSL_CTRL_SET_MTU: | |
224 | /* | |
225 | * We may not have a BIO set yet so can't call dtls1_min_mtu() | |
226 | * We'll have to make do with dtls1_link_min_mtu() and max overhead | |
227 | */ | |
228 | if (larg < (long)dtls1_link_min_mtu() - DTLS1_MAX_MTU_OVERHEAD) | |
229 | return 0; | |
230 | s->d1->mtu = larg; | |
231 | return larg; | |
232 | default: | |
233 | ret = ssl3_ctrl(s, cmd, larg, parg); | |
234 | break; | |
235 | } | |
236 | return (ret); | |
237 | } | |
b972fbaa | 238 | |
eb38b26d | 239 | void dtls1_start_timer(SSL *s) |
0f113f3e | 240 | { |
7e159e01 | 241 | #ifndef OPENSSL_NO_SCTP |
0f113f3e MC |
242 | /* Disable timer for SCTP */ |
243 | if (BIO_dgram_is_sctp(SSL_get_wbio(s))) { | |
16f8d4eb | 244 | memset(&s->d1->next_timeout, 0, sizeof(s->d1->next_timeout)); |
0f113f3e MC |
245 | return; |
246 | } | |
7e159e01 DSH |
247 | #endif |
248 | ||
0f113f3e MC |
249 | /* If timer is not set, initialize duration with 1 second */ |
250 | if (s->d1->next_timeout.tv_sec == 0 && s->d1->next_timeout.tv_usec == 0) { | |
251 | s->d1->timeout_duration = 1; | |
252 | } | |
253 | ||
254 | /* Set timeout to current time */ | |
255 | get_current_time(&(s->d1->next_timeout)); | |
256 | ||
257 | /* Add duration to current time */ | |
258 | s->d1->next_timeout.tv_sec += s->d1->timeout_duration; | |
259 | BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT, 0, | |
260 | &(s->d1->next_timeout)); | |
261 | } | |
262 | ||
263 | struct timeval *dtls1_get_timeout(SSL *s, struct timeval *timeleft) | |
264 | { | |
265 | struct timeval timenow; | |
266 | ||
267 | /* If no timeout is set, just return NULL */ | |
268 | if (s->d1->next_timeout.tv_sec == 0 && s->d1->next_timeout.tv_usec == 0) { | |
269 | return NULL; | |
270 | } | |
271 | ||
272 | /* Get current time */ | |
273 | get_current_time(&timenow); | |
274 | ||
275 | /* If timer already expired, set remaining time to 0 */ | |
276 | if (s->d1->next_timeout.tv_sec < timenow.tv_sec || | |
277 | (s->d1->next_timeout.tv_sec == timenow.tv_sec && | |
278 | s->d1->next_timeout.tv_usec <= timenow.tv_usec)) { | |
16f8d4eb | 279 | memset(timeleft, 0, sizeof(*timeleft)); |
0f113f3e MC |
280 | return timeleft; |
281 | } | |
282 | ||
283 | /* Calculate time left until timer expires */ | |
284 | memcpy(timeleft, &(s->d1->next_timeout), sizeof(struct timeval)); | |
285 | timeleft->tv_sec -= timenow.tv_sec; | |
286 | timeleft->tv_usec -= timenow.tv_usec; | |
287 | if (timeleft->tv_usec < 0) { | |
288 | timeleft->tv_sec--; | |
289 | timeleft->tv_usec += 1000000; | |
290 | } | |
291 | ||
292 | /* | |
293 | * If remaining time is less than 15 ms, set it to 0 to prevent issues | |
f430ba31 | 294 | * because of small divergences with socket timeouts. |
0f113f3e MC |
295 | */ |
296 | if (timeleft->tv_sec == 0 && timeleft->tv_usec < 15000) { | |
16f8d4eb | 297 | memset(timeleft, 0, sizeof(*timeleft)); |
0f113f3e MC |
298 | } |
299 | ||
300 | return timeleft; | |
301 | } | |
eb38b26d DSH |
302 | |
303 | int dtls1_is_timer_expired(SSL *s) | |
0f113f3e MC |
304 | { |
305 | struct timeval timeleft; | |
eb38b26d | 306 | |
0f113f3e MC |
307 | /* Get time left until timeout, return false if no timer running */ |
308 | if (dtls1_get_timeout(s, &timeleft) == NULL) { | |
309 | return 0; | |
310 | } | |
eb38b26d | 311 | |
0f113f3e MC |
312 | /* Return false if timer is not expired yet */ |
313 | if (timeleft.tv_sec > 0 || timeleft.tv_usec > 0) { | |
314 | return 0; | |
315 | } | |
eb38b26d | 316 | |
0f113f3e MC |
317 | /* Timer expired, so return true */ |
318 | return 1; | |
319 | } | |
eb38b26d DSH |
320 | |
321 | void dtls1_double_timeout(SSL *s) | |
0f113f3e MC |
322 | { |
323 | s->d1->timeout_duration *= 2; | |
324 | if (s->d1->timeout_duration > 60) | |
325 | s->d1->timeout_duration = 60; | |
326 | dtls1_start_timer(s); | |
327 | } | |
eb38b26d DSH |
328 | |
329 | void dtls1_stop_timer(SSL *s) | |
0f113f3e MC |
330 | { |
331 | /* Reset everything */ | |
16f8d4eb RS |
332 | memset(&s->d1->timeout, 0, sizeof(s->d1->timeout)); |
333 | memset(&s->d1->next_timeout, 0, sizeof(s->d1->next_timeout)); | |
0f113f3e MC |
334 | s->d1->timeout_duration = 1; |
335 | BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT, 0, | |
336 | &(s->d1->next_timeout)); | |
337 | /* Clear retransmission buffer */ | |
f5c7f5df | 338 | dtls1_clear_sent_buffer(s); |
0f113f3e | 339 | } |
eb38b26d | 340 | |
ea6e3860 | 341 | int dtls1_check_timeout_num(SSL *s) |
0f113f3e | 342 | { |
7ee8627f | 343 | size_t mtu; |
0f113f3e MC |
344 | |
345 | s->d1->timeout.num_alerts++; | |
346 | ||
347 | /* Reduce MTU after 2 unsuccessful retransmissions */ | |
348 | if (s->d1->timeout.num_alerts > 2 | |
349 | && !(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) { | |
350 | mtu = | |
a230b26e | 351 | BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_GET_FALLBACK_MTU, 0, NULL); |
0f113f3e MC |
352 | if (mtu < s->d1->mtu) |
353 | s->d1->mtu = mtu; | |
354 | } | |
355 | ||
356 | if (s->d1->timeout.num_alerts > DTLS1_TMO_ALERT_COUNT) { | |
357 | /* fail the connection, enough alerts have been sent */ | |
358 | SSLerr(SSL_F_DTLS1_CHECK_TIMEOUT_NUM, SSL_R_READ_TIMEOUT_EXPIRED); | |
359 | return -1; | |
360 | } | |
361 | ||
362 | return 0; | |
363 | } | |
ea6e3860 DSH |
364 | |
365 | int dtls1_handle_timeout(SSL *s) | |
0f113f3e MC |
366 | { |
367 | /* if no timer is expired, don't do anything */ | |
368 | if (!dtls1_is_timer_expired(s)) { | |
369 | return 0; | |
370 | } | |
ea6e3860 | 371 | |
0f113f3e | 372 | dtls1_double_timeout(s); |
ea6e3860 | 373 | |
0f113f3e MC |
374 | if (dtls1_check_timeout_num(s) < 0) |
375 | return -1; | |
62b6948a | 376 | |
0f113f3e MC |
377 | s->d1->timeout.read_timeouts++; |
378 | if (s->d1->timeout.read_timeouts > DTLS1_TMO_READ_COUNT) { | |
379 | s->d1->timeout.read_timeouts = 1; | |
380 | } | |
4817504d | 381 | |
0f113f3e MC |
382 | dtls1_start_timer(s); |
383 | return dtls1_retransmit_buffered_messages(s); | |
384 | } | |
b972fbaa | 385 | |
eb38b26d DSH |
386 | static void get_current_time(struct timeval *t) |
387 | { | |
a006fef7 | 388 | #if defined(_WIN32) |
0f113f3e MC |
389 | SYSTEMTIME st; |
390 | union { | |
391 | unsigned __int64 ul; | |
392 | FILETIME ft; | |
393 | } now; | |
394 | ||
395 | GetSystemTime(&st); | |
396 | SystemTimeToFileTime(&st, &now.ft); | |
a230b26e | 397 | /* re-bias to 1/1/1970 */ |
0f113f3e MC |
398 | # ifdef __MINGW32__ |
399 | now.ul -= 116444736000000000ULL; | |
400 | # else | |
a230b26e EK |
401 | /* *INDENT-OFF* */ |
402 | now.ul -= 116444736000000000UI64; | |
403 | /* *INDENT-ON* */ | |
0f113f3e MC |
404 | # endif |
405 | t->tv_sec = (long)(now.ul / 10000000); | |
406 | t->tv_usec = ((int)(now.ul % 10000000)) / 10; | |
eb38b26d | 407 | #elif defined(OPENSSL_SYS_VMS) |
0f113f3e MC |
408 | struct timeb tb; |
409 | ftime(&tb); | |
410 | t->tv_sec = (long)tb.time; | |
411 | t->tv_usec = (long)tb.millitm * 1000; | |
eb38b26d | 412 | #else |
0f113f3e | 413 | gettimeofday(t, NULL); |
eb38b26d DSH |
414 | #endif |
415 | } | |
1fc3ac80 | 416 | |
e3d0dae7 MC |
417 | #define LISTEN_SUCCESS 2 |
418 | #define LISTEN_SEND_VERIFY_REQUEST 1 | |
419 | ||
f9e55034 | 420 | #ifndef OPENSSL_NO_SOCK |
3edeb622 | 421 | int DTLSv1_listen(SSL *s, BIO_ADDR *client) |
0f113f3e | 422 | { |
e3d0dae7 MC |
423 | int next, n, ret = 0, clearpkt = 0; |
424 | unsigned char cookie[DTLS1_COOKIE_LENGTH]; | |
425 | unsigned char seq[SEQ_NUM_SIZE]; | |
b6981744 | 426 | const unsigned char *data; |
c536b6be | 427 | unsigned char *buf; |
8b0e934a | 428 | size_t fragoff, fraglen, msglen; |
e3d0dae7 MC |
429 | unsigned int rectype, versmajor, msgseq, msgtype, clientvers, cookielen; |
430 | BIO *rbio, *wbio; | |
431 | BUF_MEM *bufm; | |
d858c876 | 432 | BIO_ADDR *tmpclient = NULL; |
e3d0dae7 | 433 | PACKET pkt, msgpkt, msgpayload, session, cookiepkt; |
0f113f3e | 434 | |
5bdcd362 MC |
435 | if (s->handshake_func == NULL) { |
436 | /* Not properly initialized yet */ | |
437 | SSL_set_accept_state(s); | |
438 | } | |
439 | ||
e83ee04b | 440 | /* Ensure there is no state left over from a previous invocation */ |
61986d32 | 441 | if (!SSL_clear(s)) |
c7f5b5d7 | 442 | return -1; |
e83ee04b | 443 | |
e3d0dae7 MC |
444 | ERR_clear_error(); |
445 | ||
446 | rbio = SSL_get_rbio(s); | |
447 | wbio = SSL_get_wbio(s); | |
448 | ||
e8aa8b6c | 449 | if (!rbio || !wbio) { |
3edeb622 | 450 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_BIO_NOT_SET); |
e3d0dae7 MC |
451 | return -1; |
452 | } | |
453 | ||
454 | /* | |
455 | * We only peek at incoming ClientHello's until we're sure we are going to | |
456 | * to respond with a HelloVerifyRequest. If its a ClientHello with a valid | |
aea145e3 | 457 | * cookie then we leave it in the BIO for accept to handle. |
e3d0dae7 MC |
458 | */ |
459 | BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL); | |
460 | ||
461 | /* | |
462 | * Note: This check deliberately excludes DTLS1_BAD_VER because that version | |
463 | * requires the MAC to be calculated *including* the first ClientHello | |
464 | * (without the cookie). Since DTLSv1_listen is stateless that cannot be | |
465 | * supported. DTLS1_BAD_VER must use cookies in a stateful manner (e.g. via | |
466 | * SSL_accept) | |
467 | */ | |
468 | if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00)) { | |
3edeb622 | 469 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNSUPPORTED_SSL_VERSION); |
e3d0dae7 MC |
470 | return -1; |
471 | } | |
472 | ||
473 | if (s->init_buf == NULL) { | |
474 | if ((bufm = BUF_MEM_new()) == NULL) { | |
3edeb622 | 475 | SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE); |
e3d0dae7 MC |
476 | return -1; |
477 | } | |
478 | ||
479 | if (!BUF_MEM_grow(bufm, SSL3_RT_MAX_PLAIN_LENGTH)) { | |
480 | BUF_MEM_free(bufm); | |
3edeb622 | 481 | SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE); |
e3d0dae7 MC |
482 | return -1; |
483 | } | |
484 | s->init_buf = bufm; | |
485 | } | |
486 | buf = (unsigned char *)s->init_buf->data; | |
487 | ||
488 | do { | |
489 | /* Get a packet */ | |
490 | ||
491 | clear_sys_error(); | |
492 | /* | |
493 | * Technically a ClientHello could be SSL3_RT_MAX_PLAIN_LENGTH | |
494 | * + DTLS1_RT_HEADER_LENGTH bytes long. Normally init_buf does not store | |
495 | * the record header as well, but we do here. We've set up init_buf to | |
496 | * be the standard size for simplicity. In practice we shouldn't ever | |
497 | * receive a ClientHello as long as this. If we do it will get dropped | |
498 | * in the record length check below. | |
499 | */ | |
500 | n = BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH); | |
501 | ||
502 | if (n <= 0) { | |
e8aa8b6c | 503 | if (BIO_should_retry(rbio)) { |
e3d0dae7 MC |
504 | /* Non-blocking IO */ |
505 | goto end; | |
506 | } | |
507 | return -1; | |
508 | } | |
509 | ||
510 | /* If we hit any problems we need to clear this packet from the BIO */ | |
511 | clearpkt = 1; | |
512 | ||
513 | if (!PACKET_buf_init(&pkt, buf, n)) { | |
3edeb622 | 514 | SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_INTERNAL_ERROR); |
e3d0dae7 MC |
515 | return -1; |
516 | } | |
517 | ||
518 | /* | |
519 | * Parse the received record. If there are any problems with it we just | |
520 | * dump it - with no alert. RFC6347 says this "Unlike TLS, DTLS is | |
521 | * resilient in the face of invalid records (e.g., invalid formatting, | |
522 | * length, MAC, etc.). In general, invalid records SHOULD be silently | |
523 | * discarded, thus preserving the association; however, an error MAY be | |
524 | * logged for diagnostic purposes." | |
525 | */ | |
526 | ||
527 | /* this packet contained a partial record, dump it */ | |
528 | if (n < DTLS1_RT_HEADER_LENGTH) { | |
3edeb622 | 529 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_RECORD_TOO_SMALL); |
e3d0dae7 MC |
530 | goto end; |
531 | } | |
532 | ||
533 | if (s->msg_callback) | |
534 | s->msg_callback(0, 0, SSL3_RT_HEADER, buf, | |
535 | DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg); | |
536 | ||
537 | /* Get the record header */ | |
538 | if (!PACKET_get_1(&pkt, &rectype) | |
539 | || !PACKET_get_1(&pkt, &versmajor)) { | |
3edeb622 | 540 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH); |
e3d0dae7 MC |
541 | goto end; |
542 | } | |
543 | ||
a230b26e | 544 | if (rectype != SSL3_RT_HANDSHAKE) { |
3edeb622 | 545 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE); |
e3d0dae7 MC |
546 | goto end; |
547 | } | |
548 | ||
549 | /* | |
550 | * Check record version number. We only check that the major version is | |
551 | * the same. | |
552 | */ | |
553 | if (versmajor != DTLS1_VERSION_MAJOR) { | |
3edeb622 | 554 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_BAD_PROTOCOL_VERSION_NUMBER); |
e3d0dae7 MC |
555 | goto end; |
556 | } | |
557 | ||
558 | if (!PACKET_forward(&pkt, 1) | |
559 | /* Save the sequence number: 64 bits, with top 2 bytes = epoch */ | |
560 | || !PACKET_copy_bytes(&pkt, seq, SEQ_NUM_SIZE) | |
4b1043ef | 561 | || !PACKET_get_length_prefixed_2(&pkt, &msgpkt)) { |
3edeb622 | 562 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH); |
e3d0dae7 MC |
563 | goto end; |
564 | } | |
4b1043ef MC |
565 | /* |
566 | * We allow data remaining at the end of the packet because there could | |
567 | * be a second record (but we ignore it) | |
568 | */ | |
e3d0dae7 MC |
569 | |
570 | /* This is an initial ClientHello so the epoch has to be 0 */ | |
571 | if (seq[0] != 0 || seq[1] != 0) { | |
3edeb622 | 572 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE); |
e3d0dae7 MC |
573 | goto end; |
574 | } | |
575 | ||
576 | /* Get a pointer to the raw message for the later callback */ | |
577 | data = PACKET_data(&msgpkt); | |
578 | ||
579 | /* Finished processing the record header, now process the message */ | |
580 | if (!PACKET_get_1(&msgpkt, &msgtype) | |
153703df | 581 | || !PACKET_get_net_3_len(&msgpkt, &msglen) |
e3d0dae7 | 582 | || !PACKET_get_net_2(&msgpkt, &msgseq) |
153703df MC |
583 | || !PACKET_get_net_3_len(&msgpkt, &fragoff) |
584 | || !PACKET_get_net_3_len(&msgpkt, &fraglen) | |
4b1043ef | 585 | || !PACKET_get_sub_packet(&msgpkt, &msgpayload, fraglen) |
e3d0dae7 | 586 | || PACKET_remaining(&msgpkt) != 0) { |
3edeb622 | 587 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH); |
e3d0dae7 MC |
588 | goto end; |
589 | } | |
590 | ||
591 | if (msgtype != SSL3_MT_CLIENT_HELLO) { | |
3edeb622 | 592 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE); |
e3d0dae7 MC |
593 | goto end; |
594 | } | |
595 | ||
596 | /* Message sequence number can only be 0 or 1 */ | |
e8aa8b6c | 597 | if (msgseq > 2) { |
3edeb622 | 598 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_INVALID_SEQUENCE_NUMBER); |
e3d0dae7 MC |
599 | goto end; |
600 | } | |
601 | ||
4b1043ef MC |
602 | /* |
603 | * We don't support fragment reassembly for ClientHellos whilst | |
604 | * listening because that would require server side state (which is | |
605 | * against the whole point of the ClientHello/HelloVerifyRequest | |
606 | * mechanism). Instead we only look at the first ClientHello fragment | |
607 | * and require that the cookie must be contained within it. | |
608 | */ | |
609 | if (fragoff != 0 || fraglen > msglen) { | |
610 | /* Non initial ClientHello fragment (or bad fragment) */ | |
3edeb622 | 611 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_FRAGMENTED_CLIENT_HELLO); |
e3d0dae7 MC |
612 | goto end; |
613 | } | |
614 | ||
615 | if (s->msg_callback) | |
616 | s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, data, | |
4b1043ef | 617 | fraglen + DTLS1_HM_HEADER_LENGTH, s, |
e3d0dae7 MC |
618 | s->msg_callback_arg); |
619 | ||
620 | if (!PACKET_get_net_2(&msgpayload, &clientvers)) { | |
3edeb622 | 621 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH); |
e3d0dae7 MC |
622 | goto end; |
623 | } | |
624 | ||
625 | /* | |
626 | * Verify client version is supported | |
627 | */ | |
4fa52141 VD |
628 | if (DTLS_VERSION_LT(clientvers, (unsigned int)s->method->version) && |
629 | s->method->version != DTLS_ANY_VERSION) { | |
3edeb622 | 630 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_WRONG_VERSION_NUMBER); |
e3d0dae7 MC |
631 | goto end; |
632 | } | |
633 | ||
634 | if (!PACKET_forward(&msgpayload, SSL3_RANDOM_SIZE) | |
635 | || !PACKET_get_length_prefixed_1(&msgpayload, &session) | |
636 | || !PACKET_get_length_prefixed_1(&msgpayload, &cookiepkt)) { | |
4b1043ef MC |
637 | /* |
638 | * Could be malformed or the cookie does not fit within the initial | |
639 | * ClientHello fragment. Either way we can't handle it. | |
640 | */ | |
3edeb622 | 641 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH); |
e3d0dae7 MC |
642 | goto end; |
643 | } | |
644 | ||
645 | /* | |
646 | * Check if we have a cookie or not. If not we need to send a | |
647 | * HelloVerifyRequest. | |
648 | */ | |
649 | if (PACKET_remaining(&cookiepkt) == 0) { | |
650 | next = LISTEN_SEND_VERIFY_REQUEST; | |
651 | } else { | |
652 | /* | |
653 | * We have a cookie, so lets check it. | |
654 | */ | |
655 | if (s->ctx->app_verify_cookie_cb == NULL) { | |
3edeb622 | 656 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_NO_VERIFY_COOKIE_CALLBACK); |
e3d0dae7 MC |
657 | /* This is fatal */ |
658 | return -1; | |
659 | } | |
31011544 | 660 | if (s->ctx->app_verify_cookie_cb(s, PACKET_data(&cookiepkt), |
8b0e934a | 661 | (unsigned int)PACKET_remaining(&cookiepkt)) == 0) { |
e3d0dae7 MC |
662 | /* |
663 | * We treat invalid cookies in the same was as no cookie as | |
664 | * per RFC6347 | |
665 | */ | |
666 | next = LISTEN_SEND_VERIFY_REQUEST; | |
667 | } else { | |
668 | /* Cookie verification succeeded */ | |
669 | next = LISTEN_SUCCESS; | |
670 | } | |
671 | } | |
672 | ||
673 | if (next == LISTEN_SEND_VERIFY_REQUEST) { | |
c536b6be MC |
674 | WPACKET wpkt; |
675 | unsigned int version; | |
676 | size_t wreclen; | |
677 | ||
e3d0dae7 MC |
678 | /* |
679 | * There was no cookie in the ClientHello so we need to send a | |
680 | * HelloVerifyRequest. If this fails we do not worry about trying | |
681 | * to resend, we just drop it. | |
682 | */ | |
683 | ||
684 | /* | |
685 | * Dump the read packet, we don't need it any more. Ignore return | |
686 | * value | |
687 | */ | |
688 | BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL); | |
689 | BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH); | |
690 | BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL); | |
691 | ||
692 | /* Generate the cookie */ | |
693 | if (s->ctx->app_gen_cookie_cb == NULL || | |
373dc6e1 MC |
694 | s->ctx->app_gen_cookie_cb(s, cookie, &cookielen) == 0 || |
695 | cookielen > 255) { | |
3edeb622 | 696 | SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_COOKIE_GEN_CALLBACK_FAILURE); |
e3d0dae7 MC |
697 | /* This is fatal */ |
698 | return -1; | |
699 | } | |
700 | ||
e3d0dae7 MC |
701 | /* |
702 | * Special case: for hello verify request, client version 1.0 and we | |
703 | * haven't decided which version to use yet send back using version | |
704 | * 1.0 header: otherwise some clients will ignore it. | |
705 | */ | |
c536b6be MC |
706 | version = (s->method->version == DTLS_ANY_VERSION) ? DTLS1_VERSION |
707 | : s->version; | |
708 | ||
709 | /* Construct the record and message headers */ | |
710 | if (!WPACKET_init(&wpkt, s->init_buf) | |
711 | || !WPACKET_put_bytes_u8(&wpkt, SSL3_RT_HANDSHAKE) | |
712 | || !WPACKET_put_bytes_u16(&wpkt, version) | |
713 | /* | |
714 | * Record sequence number is always the same as in the | |
715 | * received ClientHello | |
716 | */ | |
717 | || !WPACKET_memcpy(&wpkt, seq, SEQ_NUM_SIZE) | |
718 | /* End of record, start sub packet for message */ | |
719 | || !WPACKET_start_sub_packet_u16(&wpkt) | |
720 | /* Message type */ | |
721 | || !WPACKET_put_bytes_u8(&wpkt, | |
722 | DTLS1_MT_HELLO_VERIFY_REQUEST) | |
723 | /* | |
724 | * Message length - doesn't follow normal TLS convention: | |
725 | * the length isn't the last thing in the message header. | |
726 | * We'll need to fill this in later when we know the | |
727 | * length. Set it to zero for now | |
728 | */ | |
729 | || !WPACKET_put_bytes_u24(&wpkt, 0) | |
730 | /* | |
731 | * Message sequence number is always 0 for a | |
732 | * HelloVerifyRequest | |
733 | */ | |
734 | || !WPACKET_put_bytes_u16(&wpkt, 0) | |
735 | /* | |
736 | * We never fragment a HelloVerifyRequest, so fragment | |
737 | * offset is 0 | |
738 | */ | |
739 | || !WPACKET_put_bytes_u24(&wpkt, 0) | |
740 | /* | |
741 | * Fragment length is the same as message length, but | |
742 | * this *is* the last thing in the message header so we | |
743 | * can just start a sub-packet. No need to come back | |
744 | * later for this one. | |
745 | */ | |
746 | || !WPACKET_start_sub_packet_u24(&wpkt) | |
747 | /* Create the actual HelloVerifyRequest body */ | |
748 | || !dtls_raw_hello_verify_request(&wpkt, cookie, cookielen) | |
749 | /* Close message body */ | |
750 | || !WPACKET_close(&wpkt) | |
751 | /* Close record body */ | |
752 | || !WPACKET_close(&wpkt) | |
753 | || !WPACKET_get_total_written(&wpkt, &wreclen) | |
754 | || !WPACKET_finish(&wpkt)) { | |
755 | SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_INTERNAL_ERROR); | |
756 | WPACKET_cleanup(&wpkt); | |
757 | /* This is fatal */ | |
758 | return -1; | |
e3d0dae7 MC |
759 | } |
760 | ||
761 | /* | |
c536b6be MC |
762 | * Fix up the message len in the message header. Its the same as the |
763 | * fragment len which has been filled in by WPACKET, so just copy | |
764 | * that. Destination for the message len is after the record header | |
765 | * plus one byte for the message content type. The source is the | |
766 | * last 3 bytes of the message header | |
e3d0dae7 | 767 | */ |
c536b6be MC |
768 | memcpy(&buf[DTLS1_RT_HEADER_LENGTH + 1], |
769 | &buf[DTLS1_RT_HEADER_LENGTH + DTLS1_HM_HEADER_LENGTH - 3], | |
770 | 3); | |
e3d0dae7 MC |
771 | |
772 | if (s->msg_callback) | |
773 | s->msg_callback(1, 0, SSL3_RT_HEADER, buf, | |
774 | DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg); | |
775 | ||
ce0865d8 MC |
776 | if ((tmpclient = BIO_ADDR_new()) == NULL) { |
777 | SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE); | |
778 | goto end; | |
779 | } | |
780 | ||
e3d0dae7 | 781 | /* |
8483a003 | 782 | * This is unnecessary if rbio and wbio are one and the same - but |
ce0865d8 MC |
783 | * maybe they're not. We ignore errors here - some BIOs do not |
784 | * support this. | |
e3d0dae7 | 785 | */ |
e8aa8b6c | 786 | if (BIO_dgram_get_peer(rbio, tmpclient) > 0) { |
ce0865d8 | 787 | (void)BIO_dgram_set_peer(wbio, tmpclient); |
e3d0dae7 | 788 | } |
d858c876 RL |
789 | BIO_ADDR_free(tmpclient); |
790 | tmpclient = NULL; | |
e3d0dae7 | 791 | |
8b0e934a | 792 | /* TODO(size_t): convert this call */ |
c536b6be | 793 | if (BIO_write(wbio, buf, wreclen) < (int)wreclen) { |
e8aa8b6c | 794 | if (BIO_should_retry(wbio)) { |
e3d0dae7 MC |
795 | /* |
796 | * Non-blocking IO...but we're stateless, so we're just | |
797 | * going to drop this packet. | |
798 | */ | |
799 | goto end; | |
800 | } | |
801 | return -1; | |
802 | } | |
803 | ||
804 | if (BIO_flush(wbio) <= 0) { | |
e8aa8b6c | 805 | if (BIO_should_retry(wbio)) { |
e3d0dae7 MC |
806 | /* |
807 | * Non-blocking IO...but we're stateless, so we're just | |
808 | * going to drop this packet. | |
809 | */ | |
810 | goto end; | |
811 | } | |
812 | return -1; | |
813 | } | |
814 | } | |
815 | } while (next != LISTEN_SUCCESS); | |
816 | ||
817 | /* | |
818 | * Set expected sequence numbers to continue the handshake. | |
819 | */ | |
820 | s->d1->handshake_read_seq = 1; | |
821 | s->d1->handshake_write_seq = 1; | |
822 | s->d1->next_handshake_write_seq = 1; | |
823 | DTLS_RECORD_LAYER_set_write_sequence(&s->rlayer, seq); | |
824 | ||
825 | /* | |
826 | * We are doing cookie exchange, so make sure we set that option in the | |
827 | * SSL object | |
828 | */ | |
0f113f3e | 829 | SSL_set_options(s, SSL_OP_COOKIE_EXCHANGE); |
1fc3ac80 | 830 | |
31fd10e6 MC |
831 | /* |
832 | * Tell the state machine that we've done the initial hello verify | |
833 | * exchange | |
834 | */ | |
835 | ossl_statem_set_hello_verify_done(s); | |
e3d0dae7 | 836 | |
a230b26e EK |
837 | /* |
838 | * Some BIOs may not support this. If we fail we clear the client address | |
839 | */ | |
ce0865d8 MC |
840 | if (BIO_dgram_get_peer(rbio, client) <= 0) |
841 | BIO_ADDR_clear(client); | |
1fc3ac80 | 842 | |
e3d0dae7 MC |
843 | ret = 1; |
844 | clearpkt = 0; | |
a230b26e | 845 | end: |
d858c876 | 846 | BIO_ADDR_free(tmpclient); |
e3d0dae7 MC |
847 | BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL); |
848 | if (clearpkt) { | |
849 | /* Dump this packet. Ignore return value */ | |
850 | BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH); | |
851 | } | |
852 | return ret; | |
0f113f3e | 853 | } |
f9e55034 | 854 | #endif |
173e72e6 | 855 | |
173e72e6 | 856 | static int dtls1_handshake_write(SSL *s) |
0f113f3e MC |
857 | { |
858 | return dtls1_do_write(s, SSL3_RT_HANDSHAKE); | |
859 | } | |
8ba708e5 | 860 | |
8ba708e5 MC |
861 | int dtls1_shutdown(SSL *s) |
862 | { | |
863 | int ret; | |
864 | #ifndef OPENSSL_NO_SCTP | |
865 | BIO *wbio; | |
866 | ||
867 | wbio = SSL_get_wbio(s); | |
868 | if (wbio != NULL && BIO_dgram_is_sctp(wbio) && | |
869 | !(s->shutdown & SSL_SENT_SHUTDOWN)) { | |
870 | ret = BIO_dgram_sctp_wait_for_dry(wbio); | |
871 | if (ret < 0) | |
872 | return -1; | |
873 | ||
874 | if (ret == 0) | |
875 | BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 1, | |
876 | NULL); | |
877 | } | |
878 | #endif | |
879 | ret = ssl3_shutdown(s); | |
880 | #ifndef OPENSSL_NO_SCTP | |
881 | BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 0, NULL); | |
882 | #endif | |
883 | return ret; | |
884 | } | |
885 | ||
886 | int dtls1_query_mtu(SSL *s) | |
887 | { | |
888 | if (s->d1->link_mtu) { | |
889 | s->d1->mtu = | |
890 | s->d1->link_mtu - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s)); | |
891 | s->d1->link_mtu = 0; | |
892 | } | |
893 | ||
894 | /* AHA! Figure out the MTU, and stick to the right size */ | |
895 | if (s->d1->mtu < dtls1_min_mtu(s)) { | |
896 | if (!(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) { | |
897 | s->d1->mtu = | |
898 | BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL); | |
899 | ||
900 | /* | |
901 | * I've seen the kernel return bogus numbers when it doesn't know | |
902 | * (initial write), so just make sure we have a reasonable number | |
903 | */ | |
904 | if (s->d1->mtu < dtls1_min_mtu(s)) { | |
905 | /* Set to min mtu */ | |
906 | s->d1->mtu = dtls1_min_mtu(s); | |
907 | BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU, | |
8b0e934a | 908 | (long)s->d1->mtu, NULL); |
8ba708e5 MC |
909 | } |
910 | } else | |
911 | return 0; | |
912 | } | |
913 | return 1; | |
914 | } | |
915 | ||
7ee8627f | 916 | static size_t dtls1_link_min_mtu(void) |
8ba708e5 MC |
917 | { |
918 | return (g_probable_mtu[(sizeof(g_probable_mtu) / | |
919 | sizeof(g_probable_mtu[0])) - 1]); | |
920 | } | |
921 | ||
7ee8627f | 922 | size_t dtls1_min_mtu(SSL *s) |
8ba708e5 MC |
923 | { |
924 | return dtls1_link_min_mtu() - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s)); | |
925 | } | |
045bd047 DW |
926 | |
927 | size_t DTLS_get_data_mtu(const SSL *s) | |
928 | { | |
929 | size_t mac_overhead, int_overhead, blocksize, ext_overhead; | |
930 | const SSL_CIPHER *ciph = SSL_get_current_cipher(s); | |
931 | size_t mtu = s->d1->mtu; | |
932 | ||
933 | if (ciph == NULL) | |
934 | return 0; | |
935 | ||
936 | if (!ssl_cipher_get_overhead(ciph, &mac_overhead, &int_overhead, | |
937 | &blocksize, &ext_overhead)) | |
938 | return 0; | |
939 | ||
940 | if (SSL_USE_ETM(s)) | |
941 | ext_overhead += mac_overhead; | |
942 | else | |
943 | int_overhead += mac_overhead; | |
944 | ||
945 | /* Subtract external overhead (e.g. IV/nonce, separate MAC) */ | |
946 | if (ext_overhead + DTLS1_RT_HEADER_LENGTH >= mtu) | |
947 | return 0; | |
948 | mtu -= ext_overhead + DTLS1_RT_HEADER_LENGTH; | |
949 | ||
950 | /* Round encrypted payload down to cipher block size (for CBC etc.) | |
951 | * No check for overflow since 'mtu % blocksize' cannot exceed mtu. */ | |
952 | if (blocksize) | |
953 | mtu -= (mtu % blocksize); | |
954 | ||
955 | /* Subtract internal overhead (e.g. CBC padding len byte) */ | |
956 | if (int_overhead >= mtu) | |
957 | return 0; | |
958 | mtu -= int_overhead; | |
959 | ||
960 | return mtu; | |
961 | } |