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c988f1f4 | 1 | /* $Cambridge: exim/src/src/tls-openssl.c,v 1.3 2005/01/04 10:00:42 ph10 Exp $ */ |
059ec3d9 PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
c988f1f4 | 7 | /* Copyright (c) University of Cambridge 1995 - 2005 */ |
059ec3d9 PH |
8 | /* See the file NOTICE for conditions of use and distribution. */ |
9 | ||
10 | /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL | |
11 | library. It is #included into the tls.c file when that library is used. The | |
12 | code herein is based on a patch that was originally contributed by Steve | |
13 | Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara. | |
14 | ||
15 | No cryptographic code is included in Exim. All this module does is to call | |
16 | functions from the OpenSSL library. */ | |
17 | ||
18 | ||
19 | /* Heading stuff */ | |
20 | ||
21 | #include <openssl/lhash.h> | |
22 | #include <openssl/ssl.h> | |
23 | #include <openssl/err.h> | |
24 | #include <openssl/rand.h> | |
25 | ||
26 | /* Structure for collecting random data for seeding. */ | |
27 | ||
28 | typedef struct randstuff { | |
29 | time_t t; | |
30 | pid_t p; | |
31 | } randstuff; | |
32 | ||
33 | /* Local static variables */ | |
34 | ||
35 | static BOOL verify_callback_called = FALSE; | |
36 | static const uschar *sid_ctx = US"exim"; | |
37 | ||
38 | static SSL_CTX *ctx = NULL; | |
39 | static SSL *ssl = NULL; | |
40 | ||
41 | static char ssl_errstring[256]; | |
42 | ||
43 | static int ssl_session_timeout = 200; | |
44 | static BOOL verify_optional = FALSE; | |
45 | ||
46 | ||
47 | ||
48 | ||
49 | ||
50 | /************************************************* | |
51 | * Handle TLS error * | |
52 | *************************************************/ | |
53 | ||
54 | /* Called from lots of places when errors occur before actually starting to do | |
55 | the TLS handshake, that is, while the session is still in clear. Always returns | |
56 | DEFER for a server and FAIL for a client so that most calls can use "return | |
57 | tls_error(...)" to do this processing and then give an appropriate return. A | |
58 | single function is used for both server and client, because it is called from | |
59 | some shared functions. | |
60 | ||
61 | Argument: | |
62 | prefix text to include in the logged error | |
63 | host NULL if setting up a server; | |
64 | the connected host if setting up a client | |
65 | ||
66 | Returns: OK/DEFER/FAIL | |
67 | */ | |
68 | ||
69 | static int | |
70 | tls_error(uschar *prefix, host_item *host) | |
71 | { | |
72 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
73 | if (host == NULL) | |
74 | { | |
75 | log_write(0, LOG_MAIN, "TLS error on connection from %s (%s): %s", | |
76 | (sender_fullhost != NULL)? sender_fullhost : US"local process", | |
77 | prefix, ssl_errstring); | |
78 | return DEFER; | |
79 | } | |
80 | else | |
81 | { | |
82 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s", | |
83 | host->name, host->address, prefix, ssl_errstring); | |
84 | return FAIL; | |
85 | } | |
86 | } | |
87 | ||
88 | ||
89 | ||
90 | /************************************************* | |
91 | * Callback to generate RSA key * | |
92 | *************************************************/ | |
93 | ||
94 | /* | |
95 | Arguments: | |
96 | s SSL connection | |
97 | export not used | |
98 | keylength keylength | |
99 | ||
100 | Returns: pointer to generated key | |
101 | */ | |
102 | ||
103 | static RSA * | |
104 | rsa_callback(SSL *s, int export, int keylength) | |
105 | { | |
106 | RSA *rsa_key; | |
107 | export = export; /* Shut picky compilers up */ | |
108 | DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength); | |
109 | rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL); | |
110 | if (rsa_key == NULL) | |
111 | { | |
112 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
113 | log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s", | |
114 | ssl_errstring); | |
115 | return NULL; | |
116 | } | |
117 | return rsa_key; | |
118 | } | |
119 | ||
120 | ||
121 | ||
122 | ||
123 | /************************************************* | |
124 | * Callback for verification * | |
125 | *************************************************/ | |
126 | ||
127 | /* The SSL library does certificate verification if set up to do so. This | |
128 | callback has the current yes/no state is in "state". If verification succeeded, | |
129 | we set up the tls_peerdn string. If verification failed, what happens depends | |
130 | on whether the client is required to present a verifiable certificate or not. | |
131 | ||
132 | If verification is optional, we change the state to yes, but still log the | |
133 | verification error. For some reason (it really would help to have proper | |
134 | documentation of OpenSSL), this callback function then gets called again, this | |
135 | time with state = 1. In fact, that's useful, because we can set up the peerdn | |
136 | value, but we must take care not to set the private verified flag on the second | |
137 | time through. | |
138 | ||
139 | Note: this function is not called if the client fails to present a certificate | |
140 | when asked. We get here only if a certificate has been received. Handling of | |
141 | optional verification for this case is done when requesting SSL to verify, by | |
142 | setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case. | |
143 | ||
144 | Arguments: | |
145 | state current yes/no state as 1/0 | |
146 | x509ctx certificate information. | |
147 | ||
148 | Returns: 1 if verified, 0 if not | |
149 | */ | |
150 | ||
151 | static int | |
152 | verify_callback(int state, X509_STORE_CTX *x509ctx) | |
153 | { | |
154 | static uschar txt[256]; | |
155 | ||
156 | X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert), | |
157 | CS txt, sizeof(txt)); | |
158 | ||
159 | if (state == 0) | |
160 | { | |
161 | log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s", | |
162 | x509ctx->error_depth, | |
163 | X509_verify_cert_error_string(x509ctx->error), | |
164 | txt); | |
165 | tls_certificate_verified = FALSE; | |
166 | verify_callback_called = TRUE; | |
167 | if (!verify_optional) return 0; /* reject */ | |
168 | DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in " | |
169 | "tls_try_verify_hosts)\n"); | |
170 | return 1; /* accept */ | |
171 | } | |
172 | ||
173 | if (x509ctx->error_depth != 0) | |
174 | { | |
175 | DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n", | |
176 | x509ctx->error_depth, txt); | |
177 | } | |
178 | else | |
179 | { | |
180 | DEBUG(D_tls) debug_printf("SSL%s peer: %s\n", | |
181 | verify_callback_called? "" : " authenticated", txt); | |
182 | tls_peerdn = txt; | |
183 | } | |
184 | ||
185 | ||
186 | debug_printf("+++verify_callback_called=%d\n", verify_callback_called); | |
187 | ||
188 | if (!verify_callback_called) tls_certificate_verified = TRUE; | |
189 | verify_callback_called = TRUE; | |
190 | ||
191 | return 1; /* accept */ | |
192 | } | |
193 | ||
194 | ||
195 | ||
196 | /************************************************* | |
197 | * Information callback * | |
198 | *************************************************/ | |
199 | ||
200 | /* The SSL library functions call this from time to time to indicate what they | |
201 | are doing. We copy the string to the debugging output when the level is high | |
202 | enough. | |
203 | ||
204 | Arguments: | |
205 | s the SSL connection | |
206 | where | |
207 | ret | |
208 | ||
209 | Returns: nothing | |
210 | */ | |
211 | ||
212 | static void | |
213 | info_callback(SSL *s, int where, int ret) | |
214 | { | |
215 | where = where; | |
216 | ret = ret; | |
217 | DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s)); | |
218 | } | |
219 | ||
220 | ||
221 | ||
222 | /************************************************* | |
223 | * Initialize for DH * | |
224 | *************************************************/ | |
225 | ||
226 | /* If dhparam is set, expand it, and load up the parameters for DH encryption. | |
227 | ||
228 | Arguments: | |
229 | dhparam DH parameter file | |
230 | ||
231 | Returns: TRUE if OK (nothing to set up, or setup worked) | |
232 | */ | |
233 | ||
234 | static BOOL | |
235 | init_dh(uschar *dhparam) | |
236 | { | |
237 | BOOL yield = TRUE; | |
238 | BIO *bio; | |
239 | DH *dh; | |
240 | uschar *dhexpanded; | |
241 | ||
242 | if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded)) | |
243 | return FALSE; | |
244 | ||
245 | if (dhexpanded == NULL) return TRUE; | |
246 | ||
247 | if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL) | |
248 | { | |
249 | log_write(0, LOG_MAIN, "DH: could not read %s: %s", dhexpanded, | |
250 | strerror(errno)); | |
251 | yield = FALSE; | |
252 | } | |
253 | else | |
254 | { | |
255 | if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL) | |
256 | { | |
257 | log_write(0, LOG_MAIN, "DH: could not load params from %s", | |
258 | dhexpanded); | |
259 | yield = FALSE; | |
260 | } | |
261 | else | |
262 | { | |
263 | SSL_CTX_set_tmp_dh(ctx, dh); | |
264 | DEBUG(D_tls) | |
265 | debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n", | |
266 | dhexpanded, 8*DH_size(dh)); | |
267 | DH_free(dh); | |
268 | } | |
269 | BIO_free(bio); | |
270 | } | |
271 | ||
272 | return yield; | |
273 | } | |
274 | ||
275 | ||
276 | ||
277 | ||
278 | /************************************************* | |
279 | * Initialize for TLS * | |
280 | *************************************************/ | |
281 | ||
282 | /* Called from both server and client code, to do preliminary initialization of | |
283 | the library. | |
284 | ||
285 | Arguments: | |
286 | host connected host, if client; NULL if server | |
287 | dhparam DH parameter file | |
288 | certificate certificate file | |
289 | privatekey private key | |
290 | addr address if client; NULL if server (for some randomness) | |
291 | ||
292 | Returns: OK/DEFER/FAIL | |
293 | */ | |
294 | ||
295 | static int | |
296 | tls_init(host_item *host, uschar *dhparam, uschar *certificate, uschar *privatekey, | |
297 | address_item *addr) | |
298 | { | |
299 | SSL_load_error_strings(); /* basic set up */ | |
300 | OpenSSL_add_ssl_algorithms(); | |
301 | ||
302 | /* Create a context */ | |
303 | ||
304 | ctx = SSL_CTX_new((host == NULL)? | |
305 | SSLv23_server_method() : SSLv23_client_method()); | |
306 | ||
307 | if (ctx == NULL) return tls_error(US"SSL_CTX_new", host); | |
308 | ||
309 | /* It turns out that we need to seed the random number generator this early in | |
310 | order to get the full complement of ciphers to work. It took me roughly a day | |
311 | of work to discover this by experiment. | |
312 | ||
313 | On systems that have /dev/urandom, SSL may automatically seed itself from | |
314 | there. Otherwise, we have to make something up as best we can. Double check | |
315 | afterwards. */ | |
316 | ||
317 | if (!RAND_status()) | |
318 | { | |
319 | randstuff r; | |
320 | r.t = time(NULL); | |
321 | r.p = getpid(); | |
322 | ||
323 | RAND_seed((uschar *)(&r), sizeof(r)); | |
324 | RAND_seed((uschar *)big_buffer, big_buffer_size); | |
325 | if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr)); | |
326 | ||
327 | if (!RAND_status()) | |
328 | { | |
329 | if (host == NULL) | |
330 | { | |
331 | log_write(0, LOG_MAIN, "TLS error on connection from %s: " | |
332 | "unable to seed random number generator", | |
333 | (sender_fullhost != NULL)? sender_fullhost : US"local process"); | |
334 | return DEFER; | |
335 | } | |
336 | else | |
337 | { | |
338 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s]: " | |
339 | "unable to seed random number generator", | |
340 | host->name, host->address); | |
341 | return FAIL; | |
342 | } | |
343 | } | |
344 | } | |
345 | ||
346 | /* Set up the information callback, which outputs if debugging is at a suitable | |
347 | level. */ | |
348 | ||
349 | if (!(SSL_CTX_set_info_callback(ctx, (void (*)())info_callback))) | |
350 | return tls_error(US"SSL_CTX_set_info_callback", host); | |
351 | ||
352 | /* The following patch was supplied by Robert Roselius */ | |
353 | ||
354 | #if OPENSSL_VERSION_NUMBER > 0x00906040L | |
355 | /* Enable client-bug workaround. | |
356 | Versions of OpenSSL as of 0.9.6d include a "CBC countermeasure" feature, | |
357 | which causes problems with some clients (such as the Certicom SSL Plus | |
358 | library used by Eudora). This option, SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, | |
359 | disables the coutermeasure allowing Eudora to connect. | |
360 | Some poppers and MTAs use SSL_OP_ALL, which enables all such bug | |
361 | workarounds. */ | |
362 | /* XXX (Silently?) ignore failure here? XXX*/ | |
363 | ||
364 | if (!(SSL_CTX_set_options(ctx, SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS))) | |
365 | return tls_error(US"SSL_CTX_set_option", host); | |
366 | #endif | |
367 | ||
368 | /* Initialize with DH parameters if supplied */ | |
369 | ||
370 | if (!init_dh(dhparam)) return DEFER; | |
371 | ||
372 | /* Set up certificate and key */ | |
373 | ||
374 | if (certificate != NULL) | |
375 | { | |
376 | uschar *expanded; | |
377 | if (!expand_check(certificate, US"tls_certificate", &expanded)) | |
378 | return DEFER; | |
379 | ||
380 | if (expanded != NULL) | |
381 | { | |
382 | DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded); | |
383 | if (!SSL_CTX_use_certificate_chain_file(ctx, CS expanded)) | |
d6453af2 PH |
384 | return tls_error(string_sprintf( |
385 | "SSL_CTX_use_certificate_chain_file file=%s", expanded), host); | |
059ec3d9 PH |
386 | } |
387 | ||
388 | if (privatekey != NULL && | |
389 | !expand_check(privatekey, US"tls_privatekey", &expanded)) | |
390 | return DEFER; | |
391 | ||
392 | if (expanded != NULL) | |
393 | { | |
394 | DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded); | |
395 | if (!SSL_CTX_use_PrivateKey_file(ctx, CS expanded, SSL_FILETYPE_PEM)) | |
d6453af2 PH |
396 | return tls_error(string_sprintf( |
397 | "SSL_CTX_use_PrivateKey_file file=%s", expanded), host); | |
059ec3d9 PH |
398 | } |
399 | } | |
400 | ||
401 | /* Set up the RSA callback */ | |
402 | ||
403 | SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback); | |
404 | ||
405 | /* Finally, set the timeout, and we are done */ | |
406 | ||
407 | SSL_CTX_set_timeout(ctx, ssl_session_timeout); | |
408 | DEBUG(D_tls) debug_printf("Initialized TLS\n"); | |
409 | return OK; | |
410 | } | |
411 | ||
412 | ||
413 | ||
414 | ||
415 | /************************************************* | |
416 | * Get name of cipher in use * | |
417 | *************************************************/ | |
418 | ||
419 | /* The answer is left in a static buffer, and tls_cipher is set to point | |
420 | to it. | |
421 | ||
422 | Argument: pointer to an SSL structure for the connection | |
423 | Returns: nothing | |
424 | */ | |
425 | ||
426 | static void | |
427 | construct_cipher_name(SSL *ssl) | |
428 | { | |
429 | static uschar cipherbuf[256]; | |
430 | SSL_CIPHER *c; | |
431 | uschar *ver; | |
432 | int bits; | |
433 | ||
434 | switch (ssl->session->ssl_version) | |
435 | { | |
436 | case SSL2_VERSION: | |
437 | ver = US"SSLv2"; | |
438 | break; | |
439 | ||
440 | case SSL3_VERSION: | |
441 | ver = US"SSLv3"; | |
442 | break; | |
443 | ||
444 | case TLS1_VERSION: | |
445 | ver = US"TLSv1"; | |
446 | break; | |
447 | ||
448 | default: | |
449 | ver = US"UNKNOWN"; | |
450 | } | |
451 | ||
452 | c = SSL_get_current_cipher(ssl); | |
453 | SSL_CIPHER_get_bits(c, &bits); | |
454 | ||
455 | string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver, | |
456 | SSL_CIPHER_get_name(c), bits); | |
457 | tls_cipher = cipherbuf; | |
458 | ||
459 | DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf); | |
460 | } | |
461 | ||
462 | ||
463 | ||
464 | ||
465 | ||
466 | /************************************************* | |
467 | * Set up for verifying certificates * | |
468 | *************************************************/ | |
469 | ||
470 | /* Called by both client and server startup | |
471 | ||
472 | Arguments: | |
473 | certs certs file or NULL | |
474 | crl CRL file or NULL | |
475 | host NULL in a server; the remote host in a client | |
476 | optional TRUE if called from a server for a host in tls_try_verify_hosts; | |
477 | otherwise passed as FALSE | |
478 | ||
479 | Returns: OK/DEFER/FAIL | |
480 | */ | |
481 | ||
482 | static int | |
483 | setup_certs(uschar *certs, uschar *crl, host_item *host, BOOL optional) | |
484 | { | |
485 | uschar *expcerts, *expcrl; | |
486 | ||
487 | if (!expand_check(certs, US"tls_verify_certificates", &expcerts)) | |
488 | return DEFER; | |
489 | ||
490 | if (expcerts != NULL) | |
491 | { | |
492 | struct stat statbuf; | |
493 | if (!SSL_CTX_set_default_verify_paths(ctx)) | |
494 | return tls_error(US"SSL_CTX_set_default_verify_paths", host); | |
495 | ||
496 | if (Ustat(expcerts, &statbuf) < 0) | |
497 | { | |
498 | log_write(0, LOG_MAIN|LOG_PANIC, | |
499 | "failed to stat %s for certificates", expcerts); | |
500 | return DEFER; | |
501 | } | |
502 | else | |
503 | { | |
504 | uschar *file, *dir; | |
505 | if ((statbuf.st_mode & S_IFMT) == S_IFDIR) | |
506 | { file = NULL; dir = expcerts; } | |
507 | else | |
508 | { file = expcerts; dir = NULL; } | |
509 | ||
510 | /* If a certificate file is empty, the next function fails with an | |
511 | unhelpful error message. If we skip it, we get the correct behaviour (no | |
512 | certificates are recognized, but the error message is still misleading (it | |
513 | says no certificate was supplied.) But this is better. */ | |
514 | ||
515 | if ((file == NULL || statbuf.st_size > 0) && | |
516 | !SSL_CTX_load_verify_locations(ctx, CS file, CS dir)) | |
517 | return tls_error(US"SSL_CTX_load_verify_locations", host); | |
518 | ||
519 | if (file != NULL) | |
520 | { | |
521 | SSL_CTX_set_client_CA_list(ctx, SSL_load_client_CA_file(CS file)); | |
522 | } | |
523 | } | |
524 | ||
525 | /* Handle a certificate revocation list. */ | |
526 | ||
527 | #if OPENSSL_VERSION_NUMBER > 0x00907000L | |
528 | ||
529 | if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER; | |
530 | if (expcrl != NULL && *expcrl != 0) | |
531 | { | |
532 | BIO *crl_bio; | |
533 | X509_CRL *crl_x509; | |
534 | X509_STORE *cvstore; | |
535 | ||
536 | cvstore = SSL_CTX_get_cert_store(ctx); /* cert validation store */ | |
537 | ||
538 | crl_bio = BIO_new(BIO_s_file_internal()); | |
539 | if (crl_bio != NULL) | |
540 | { | |
541 | if (BIO_read_filename(crl_bio, expcrl)) | |
542 | { | |
543 | crl_x509 = PEM_read_bio_X509_CRL(crl_bio, NULL, NULL, NULL); | |
544 | BIO_free(crl_bio); | |
545 | X509_STORE_add_crl(cvstore, crl_x509); | |
546 | X509_CRL_free(crl_x509); | |
547 | X509_STORE_set_flags(cvstore, | |
548 | X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL); | |
549 | } | |
550 | else | |
551 | { | |
552 | BIO_free(crl_bio); | |
553 | return tls_error(US"BIO_read_filename", host); | |
554 | } | |
555 | } | |
556 | else return tls_error(US"BIO_new", host); | |
557 | } | |
558 | ||
559 | #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */ | |
560 | ||
561 | /* If verification is optional, don't fail if no certificate */ | |
562 | ||
563 | SSL_CTX_set_verify(ctx, | |
564 | SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT), | |
565 | verify_callback); | |
566 | } | |
567 | ||
568 | return OK; | |
569 | } | |
570 | ||
571 | ||
572 | ||
573 | /************************************************* | |
574 | * Start a TLS session in a server * | |
575 | *************************************************/ | |
576 | ||
577 | /* This is called when Exim is running as a server, after having received | |
578 | the STARTTLS command. It must respond to that command, and then negotiate | |
579 | a TLS session. | |
580 | ||
581 | Arguments: | |
582 | require_ciphers allowed ciphers | |
583 | ||
584 | Returns: OK on success | |
585 | DEFER for errors before the start of the negotiation | |
586 | FAIL for errors during the negotation; the server can't | |
587 | continue running. | |
588 | */ | |
589 | ||
590 | int | |
591 | tls_server_start(uschar *require_ciphers) | |
592 | { | |
593 | int rc; | |
594 | uschar *expciphers; | |
595 | ||
596 | /* Check for previous activation */ | |
597 | ||
598 | if (tls_active >= 0) | |
599 | { | |
600 | log_write(0, LOG_MAIN, "STARTTLS received in already encrypted " | |
601 | "connection from %s", | |
602 | (sender_fullhost != NULL)? sender_fullhost : US"local process"); | |
603 | smtp_printf("554 Already in TLS\r\n"); | |
604 | return FAIL; | |
605 | } | |
606 | ||
607 | /* Initialize the SSL library. If it fails, it will already have logged | |
608 | the error. */ | |
609 | ||
610 | rc = tls_init(NULL, tls_dhparam, tls_certificate, tls_privatekey, NULL); | |
611 | if (rc != OK) return rc; | |
612 | ||
613 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) | |
614 | return FAIL; | |
615 | ||
616 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they | |
617 | are separated by underscores. So that I can use either form in my tests, and | |
618 | also for general convenience, we turn underscores into hyphens here. */ | |
619 | ||
620 | if (expciphers != NULL) | |
621 | { | |
622 | uschar *s = expciphers; | |
623 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } | |
624 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); | |
625 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) | |
626 | return tls_error(US"SSL_CTX_set_cipher_list", NULL); | |
627 | } | |
628 | ||
629 | /* If this is a host for which certificate verification is mandatory or | |
630 | optional, set up appropriately. */ | |
631 | ||
632 | tls_certificate_verified = FALSE; | |
633 | verify_callback_called = FALSE; | |
634 | ||
635 | if (verify_check_host(&tls_verify_hosts) == OK) | |
636 | { | |
637 | rc = setup_certs(tls_verify_certificates, tls_crl, NULL, FALSE); | |
638 | if (rc != OK) return rc; | |
639 | verify_optional = FALSE; | |
640 | } | |
641 | else if (verify_check_host(&tls_try_verify_hosts) == OK) | |
642 | { | |
643 | rc = setup_certs(tls_verify_certificates, tls_crl, NULL, TRUE); | |
644 | if (rc != OK) return rc; | |
645 | verify_optional = TRUE; | |
646 | } | |
647 | ||
648 | /* Prepare for new connection */ | |
649 | ||
650 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", NULL); | |
651 | SSL_clear(ssl); | |
652 | ||
653 | /* Set context and tell client to go ahead, except in the case of TLS startup | |
654 | on connection, where outputting anything now upsets the clients and tends to | |
655 | make them disconnect. We need to have an explicit fflush() here, to force out | |
656 | the response. Other smtp_printf() calls do not need it, because in non-TLS | |
657 | mode, the fflush() happens when smtp_getc() is called. */ | |
658 | ||
659 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); | |
660 | if (!tls_on_connect) | |
661 | { | |
662 | smtp_printf("220 TLS go ahead\r\n"); | |
663 | fflush(smtp_out); | |
664 | } | |
665 | ||
666 | /* Now negotiate the TLS session. We put our own timer on it, since it seems | |
667 | that the OpenSSL library doesn't. */ | |
668 | ||
669 | SSL_set_fd(ssl, fileno(smtp_out)); | |
670 | SSL_set_accept_state(ssl); | |
671 | ||
672 | DEBUG(D_tls) debug_printf("Calling SSL_accept\n"); | |
673 | ||
674 | sigalrm_seen = FALSE; | |
675 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
676 | rc = SSL_accept(ssl); | |
677 | alarm(0); | |
678 | ||
679 | if (rc <= 0) | |
680 | { | |
681 | if (sigalrm_seen) Ustrcpy(ssl_errstring, "timed out"); | |
682 | else ERR_error_string(ERR_get_error(), ssl_errstring); | |
683 | log_write(0, LOG_MAIN, "TLS error on connection from %s (SSL_accept): %s", | |
684 | (sender_fullhost != NULL)? sender_fullhost : US"local process", | |
685 | ssl_errstring); | |
686 | return FAIL; | |
687 | } | |
688 | ||
689 | DEBUG(D_tls) debug_printf("SSL_accept was successful\n"); | |
690 | ||
691 | /* TLS has been set up. Adjust the input functions to read via TLS, | |
692 | and initialize things. */ | |
693 | ||
694 | construct_cipher_name(ssl); | |
695 | ||
696 | DEBUG(D_tls) | |
697 | { | |
698 | uschar buf[2048]; | |
699 | if (SSL_get_shared_ciphers(ssl, CS buf, sizeof(buf)) != NULL) | |
700 | debug_printf("Shared ciphers: %s\n", buf); | |
701 | } | |
702 | ||
703 | ||
704 | ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); | |
705 | ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; | |
706 | ssl_xfer_eof = ssl_xfer_error = 0; | |
707 | ||
708 | receive_getc = tls_getc; | |
709 | receive_ungetc = tls_ungetc; | |
710 | receive_feof = tls_feof; | |
711 | receive_ferror = tls_ferror; | |
712 | ||
713 | tls_active = fileno(smtp_out); | |
714 | return OK; | |
715 | } | |
716 | ||
717 | ||
718 | ||
719 | ||
720 | ||
721 | /************************************************* | |
722 | * Start a TLS session in a client * | |
723 | *************************************************/ | |
724 | ||
725 | /* Called from the smtp transport after STARTTLS has been accepted. | |
726 | ||
727 | Argument: | |
728 | fd the fd of the connection | |
729 | host connected host (for messages) | |
730 | dhparam DH parameter file | |
731 | certificate certificate file | |
732 | privatekey private key file | |
733 | verify_certs file for certificate verify | |
734 | crl file containing CRL | |
735 | require_ciphers list of allowed ciphers | |
736 | ||
737 | Returns: OK on success | |
738 | FAIL otherwise - note that tls_error() will not give DEFER | |
739 | because this is not a server | |
740 | */ | |
741 | ||
742 | int | |
743 | tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam, | |
744 | uschar *certificate, uschar *privatekey, uschar *verify_certs, uschar *crl, | |
745 | uschar *require_ciphers, int timeout) | |
746 | { | |
747 | static uschar txt[256]; | |
748 | uschar *expciphers; | |
749 | X509* server_cert; | |
750 | int rc; | |
751 | ||
752 | rc = tls_init(host, dhparam, certificate, privatekey, addr); | |
753 | if (rc != OK) return rc; | |
754 | ||
755 | tls_certificate_verified = FALSE; | |
756 | verify_callback_called = FALSE; | |
757 | ||
758 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) | |
759 | return FAIL; | |
760 | ||
761 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they | |
762 | are separated by underscores. So that I can use either form in my tests, and | |
763 | also for general convenience, we turn underscores into hyphens here. */ | |
764 | ||
765 | if (expciphers != NULL) | |
766 | { | |
767 | uschar *s = expciphers; | |
768 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } | |
769 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); | |
770 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) | |
771 | return tls_error(US"SSL_CTX_set_cipher_list", host); | |
772 | } | |
773 | ||
774 | rc = setup_certs(verify_certs, crl, host, FALSE); | |
775 | if (rc != OK) return rc; | |
776 | ||
777 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", host); | |
778 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); | |
779 | SSL_set_fd(ssl, fd); | |
780 | SSL_set_connect_state(ssl); | |
781 | ||
782 | /* There doesn't seem to be a built-in timeout on connection. */ | |
783 | ||
784 | DEBUG(D_tls) debug_printf("Calling SSL_connect\n"); | |
785 | sigalrm_seen = FALSE; | |
786 | alarm(timeout); | |
787 | rc = SSL_connect(ssl); | |
788 | alarm(0); | |
789 | ||
790 | if (rc <= 0) | |
791 | { | |
792 | if (sigalrm_seen) | |
793 | { | |
794 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s]: " | |
795 | "SSL_connect timed out", host->name, host->address); | |
796 | return FAIL; | |
797 | } | |
798 | else return tls_error(US"SSL_connect", host); | |
799 | } | |
800 | ||
801 | DEBUG(D_tls) debug_printf("SSL_connect succeeded\n"); | |
802 | ||
803 | server_cert = SSL_get_peer_certificate (ssl); | |
804 | tls_peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert), | |
805 | CS txt, sizeof(txt)); | |
806 | tls_peerdn = txt; | |
807 | ||
808 | construct_cipher_name(ssl); /* Sets tls_cipher */ | |
809 | ||
810 | tls_active = fd; | |
811 | return OK; | |
812 | } | |
813 | ||
814 | ||
815 | ||
816 | ||
817 | ||
818 | /************************************************* | |
819 | * TLS version of getc * | |
820 | *************************************************/ | |
821 | ||
822 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, | |
823 | it refills the buffer via the SSL reading function. | |
824 | ||
825 | Arguments: none | |
826 | Returns: the next character or EOF | |
827 | */ | |
828 | ||
829 | int | |
830 | tls_getc(void) | |
831 | { | |
832 | if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) | |
833 | { | |
834 | int error; | |
835 | int inbytes; | |
836 | ||
837 | DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl, | |
838 | (long)ssl_xfer_buffer, ssl_xfer_buffer_size); | |
839 | ||
840 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
841 | inbytes = SSL_read(ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size); | |
842 | error = SSL_get_error(ssl, inbytes); | |
843 | alarm(0); | |
844 | ||
845 | /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been | |
846 | closed down, not that the socket itself has been closed down. Revert to | |
847 | non-SSL handling. */ | |
848 | ||
849 | if (error == SSL_ERROR_ZERO_RETURN) | |
850 | { | |
851 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); | |
852 | ||
853 | receive_getc = smtp_getc; | |
854 | receive_ungetc = smtp_ungetc; | |
855 | receive_feof = smtp_feof; | |
856 | receive_ferror = smtp_ferror; | |
857 | ||
858 | SSL_free(ssl); | |
859 | ssl = NULL; | |
860 | tls_active = -1; | |
861 | tls_cipher = NULL; | |
862 | tls_peerdn = NULL; | |
863 | ||
864 | return smtp_getc(); | |
865 | } | |
866 | ||
867 | /* Handle genuine errors */ | |
868 | ||
869 | else if (error != SSL_ERROR_NONE) | |
870 | { | |
871 | DEBUG(D_tls) debug_printf("Got SSL error %d\n", error); | |
872 | ssl_xfer_error = 1; | |
873 | return EOF; | |
874 | } | |
875 | ||
876 | ssl_xfer_buffer_hwm = inbytes; | |
877 | ssl_xfer_buffer_lwm = 0; | |
878 | } | |
879 | ||
880 | /* Something in the buffer; return next uschar */ | |
881 | ||
882 | return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; | |
883 | } | |
884 | ||
885 | ||
886 | ||
887 | /************************************************* | |
888 | * Read bytes from TLS channel * | |
889 | *************************************************/ | |
890 | ||
891 | /* | |
892 | Arguments: | |
893 | buff buffer of data | |
894 | len size of buffer | |
895 | ||
896 | Returns: the number of bytes read | |
897 | -1 after a failed read | |
898 | */ | |
899 | ||
900 | int | |
901 | tls_read(uschar *buff, size_t len) | |
902 | { | |
903 | int inbytes; | |
904 | int error; | |
905 | ||
906 | DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl, | |
907 | (long)buff, (unsigned int)len); | |
908 | ||
909 | inbytes = SSL_read(ssl, CS buff, len); | |
910 | error = SSL_get_error(ssl, inbytes); | |
911 | ||
912 | if (error == SSL_ERROR_ZERO_RETURN) | |
913 | { | |
914 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); | |
915 | return -1; | |
916 | } | |
917 | else if (error != SSL_ERROR_NONE) | |
918 | { | |
919 | return -1; | |
920 | } | |
921 | ||
922 | return inbytes; | |
923 | } | |
924 | ||
925 | ||
926 | ||
927 | ||
928 | ||
929 | /************************************************* | |
930 | * Write bytes down TLS channel * | |
931 | *************************************************/ | |
932 | ||
933 | /* | |
934 | Arguments: | |
935 | buff buffer of data | |
936 | len number of bytes | |
937 | ||
938 | Returns: the number of bytes after a successful write, | |
939 | -1 after a failed write | |
940 | */ | |
941 | ||
942 | int | |
943 | tls_write(const uschar *buff, size_t len) | |
944 | { | |
945 | int outbytes; | |
946 | int error; | |
947 | int left = len; | |
948 | ||
949 | DEBUG(D_tls) debug_printf("tls_do_write(%lx, %d)\n", (long)buff, left); | |
950 | while (left > 0) | |
951 | { | |
952 | DEBUG(D_tls) debug_printf("SSL_write(SSL, %lx, %d)\n", (long)buff, left); | |
953 | outbytes = SSL_write(ssl, CS buff, left); | |
954 | error = SSL_get_error(ssl, outbytes); | |
955 | DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error); | |
956 | switch (error) | |
957 | { | |
958 | case SSL_ERROR_SSL: | |
959 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
960 | log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring); | |
961 | return -1; | |
962 | ||
963 | case SSL_ERROR_NONE: | |
964 | left -= outbytes; | |
965 | buff += outbytes; | |
966 | break; | |
967 | ||
968 | case SSL_ERROR_ZERO_RETURN: | |
969 | log_write(0, LOG_MAIN, "SSL channel closed on write"); | |
970 | return -1; | |
971 | ||
972 | default: | |
973 | log_write(0, LOG_MAIN, "SSL_write error %d", error); | |
974 | return -1; | |
975 | } | |
976 | } | |
977 | return len; | |
978 | } | |
979 | ||
980 | ||
981 | ||
982 | /************************************************* | |
983 | * Close down a TLS session * | |
984 | *************************************************/ | |
985 | ||
986 | /* This is also called from within a delivery subprocess forked from the | |
987 | daemon, to shut down the TLS library, without actually doing a shutdown (which | |
988 | would tamper with the SSL session in the parent process). | |
989 | ||
990 | Arguments: TRUE if SSL_shutdown is to be called | |
991 | Returns: nothing | |
992 | */ | |
993 | ||
994 | void | |
995 | tls_close(BOOL shutdown) | |
996 | { | |
997 | if (tls_active < 0) return; /* TLS was not active */ | |
998 | ||
999 | if (shutdown) | |
1000 | { | |
1001 | DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n"); | |
1002 | SSL_shutdown(ssl); | |
1003 | } | |
1004 | ||
1005 | SSL_free(ssl); | |
1006 | ssl = NULL; | |
1007 | ||
1008 | tls_active = -1; | |
1009 | } | |
1010 | ||
1011 | /* End of tls-openssl.c */ |