Disable SSLv2 by default.
[exim.git] / src / src / tls-openssl.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2009 */
6 /* See the file NOTICE for conditions of use and distribution. */
7
8 /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL
9 library. It is #included into the tls.c file when that library is used. The
10 code herein is based on a patch that was originally contributed by Steve
11 Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara.
12
13 No cryptographic code is included in Exim. All this module does is to call
14 functions from the OpenSSL library. */
15
16
17 /* Heading stuff */
18
19 #include <openssl/lhash.h>
20 #include <openssl/ssl.h>
21 #include <openssl/err.h>
22 #include <openssl/rand.h>
23
24 /* Structure for collecting random data for seeding. */
25
26 typedef struct randstuff {
27 struct timeval tv;
28 pid_t p;
29 } randstuff;
30
31 /* Local static variables */
32
33 static BOOL verify_callback_called = FALSE;
34 static const uschar *sid_ctx = US"exim";
35
36 static SSL_CTX *ctx = NULL;
37 static SSL_CTX *ctx_sni = NULL;
38 static SSL *ssl = NULL;
39
40 static char ssl_errstring[256];
41
42 static int ssl_session_timeout = 200;
43 static BOOL verify_optional = FALSE;
44
45 static BOOL reexpand_tls_files_for_sni = FALSE;
46
47
48 typedef struct tls_ext_ctx_cb {
49 uschar *certificate;
50 uschar *privatekey;
51 uschar *dhparam;
52 /* these are cached from first expand */
53 uschar *server_cipher_list;
54 /* only passed down to tls_error: */
55 host_item *host;
56 } tls_ext_ctx_cb;
57
58 /* should figure out a cleanup of API to handle state preserved per
59 implementation, for various reasons, which can be void * in the APIs.
60 For now, we hack around it. */
61 tls_ext_ctx_cb *static_cbinfo = NULL;
62
63 static int
64 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional);
65
66
67 /*************************************************
68 * Handle TLS error *
69 *************************************************/
70
71 /* Called from lots of places when errors occur before actually starting to do
72 the TLS handshake, that is, while the session is still in clear. Always returns
73 DEFER for a server and FAIL for a client so that most calls can use "return
74 tls_error(...)" to do this processing and then give an appropriate return. A
75 single function is used for both server and client, because it is called from
76 some shared functions.
77
78 Argument:
79 prefix text to include in the logged error
80 host NULL if setting up a server;
81 the connected host if setting up a client
82 msg error message or NULL if we should ask OpenSSL
83
84 Returns: OK/DEFER/FAIL
85 */
86
87 static int
88 tls_error(uschar *prefix, host_item *host, uschar *msg)
89 {
90 if (msg == NULL)
91 {
92 ERR_error_string(ERR_get_error(), ssl_errstring);
93 msg = (uschar *)ssl_errstring;
94 }
95
96 if (host == NULL)
97 {
98 uschar *conn_info = smtp_get_connection_info();
99 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
100 conn_info += 5;
101 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
102 conn_info, prefix, msg);
103 return DEFER;
104 }
105 else
106 {
107 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
108 host->name, host->address, prefix, msg);
109 return FAIL;
110 }
111 }
112
113
114
115 /*************************************************
116 * Callback to generate RSA key *
117 *************************************************/
118
119 /*
120 Arguments:
121 s SSL connection
122 export not used
123 keylength keylength
124
125 Returns: pointer to generated key
126 */
127
128 static RSA *
129 rsa_callback(SSL *s, int export, int keylength)
130 {
131 RSA *rsa_key;
132 export = export; /* Shut picky compilers up */
133 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
134 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
135 if (rsa_key == NULL)
136 {
137 ERR_error_string(ERR_get_error(), ssl_errstring);
138 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
139 ssl_errstring);
140 return NULL;
141 }
142 return rsa_key;
143 }
144
145
146
147
148 /*************************************************
149 * Callback for verification *
150 *************************************************/
151
152 /* The SSL library does certificate verification if set up to do so. This
153 callback has the current yes/no state is in "state". If verification succeeded,
154 we set up the tls_peerdn string. If verification failed, what happens depends
155 on whether the client is required to present a verifiable certificate or not.
156
157 If verification is optional, we change the state to yes, but still log the
158 verification error. For some reason (it really would help to have proper
159 documentation of OpenSSL), this callback function then gets called again, this
160 time with state = 1. In fact, that's useful, because we can set up the peerdn
161 value, but we must take care not to set the private verified flag on the second
162 time through.
163
164 Note: this function is not called if the client fails to present a certificate
165 when asked. We get here only if a certificate has been received. Handling of
166 optional verification for this case is done when requesting SSL to verify, by
167 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
168
169 Arguments:
170 state current yes/no state as 1/0
171 x509ctx certificate information.
172
173 Returns: 1 if verified, 0 if not
174 */
175
176 static int
177 verify_callback(int state, X509_STORE_CTX *x509ctx)
178 {
179 static uschar txt[256];
180
181 X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert),
182 CS txt, sizeof(txt));
183
184 if (state == 0)
185 {
186 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
187 x509ctx->error_depth,
188 X509_verify_cert_error_string(x509ctx->error),
189 txt);
190 tls_certificate_verified = FALSE;
191 verify_callback_called = TRUE;
192 if (!verify_optional) return 0; /* reject */
193 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
194 "tls_try_verify_hosts)\n");
195 return 1; /* accept */
196 }
197
198 if (x509ctx->error_depth != 0)
199 {
200 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n",
201 x509ctx->error_depth, txt);
202 }
203 else
204 {
205 DEBUG(D_tls) debug_printf("SSL%s peer: %s\n",
206 verify_callback_called? "" : " authenticated", txt);
207 tls_peerdn = txt;
208 }
209
210 if (!verify_callback_called) tls_certificate_verified = TRUE;
211 verify_callback_called = TRUE;
212
213 return 1; /* accept */
214 }
215
216
217
218 /*************************************************
219 * Information callback *
220 *************************************************/
221
222 /* The SSL library functions call this from time to time to indicate what they
223 are doing. We copy the string to the debugging output when TLS debugging has
224 been requested.
225
226 Arguments:
227 s the SSL connection
228 where
229 ret
230
231 Returns: nothing
232 */
233
234 static void
235 info_callback(SSL *s, int where, int ret)
236 {
237 where = where;
238 ret = ret;
239 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
240 }
241
242
243
244 /*************************************************
245 * Initialize for DH *
246 *************************************************/
247
248 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
249
250 Arguments:
251 dhparam DH parameter file
252 host connected host, if client; NULL if server
253
254 Returns: TRUE if OK (nothing to set up, or setup worked)
255 */
256
257 static BOOL
258 init_dh(uschar *dhparam, host_item *host)
259 {
260 BOOL yield = TRUE;
261 BIO *bio;
262 DH *dh;
263 uschar *dhexpanded;
264
265 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
266 return FALSE;
267
268 if (dhexpanded == NULL) return TRUE;
269
270 if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL)
271 {
272 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
273 host, (uschar *)strerror(errno));
274 yield = FALSE;
275 }
276 else
277 {
278 if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL)
279 {
280 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
281 host, NULL);
282 yield = FALSE;
283 }
284 else
285 {
286 SSL_CTX_set_tmp_dh(ctx, dh);
287 DEBUG(D_tls)
288 debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n",
289 dhexpanded, 8*DH_size(dh));
290 DH_free(dh);
291 }
292 BIO_free(bio);
293 }
294
295 return yield;
296 }
297
298
299
300
301 /*************************************************
302 * Expand key and cert file specs *
303 *************************************************/
304
305 /* Called once during tls_init and possibly againt during TLS setup, for a
306 new context, if Server Name Indication was used and tls_sni was seen in
307 the certificate string.
308
309 Arguments:
310 sctx the SSL_CTX* to update
311 cbinfo various parts of session state
312
313 Returns: OK/DEFER/FAIL
314 */
315
316 static int
317 tls_expand_session_files(SSL_CTX *sctx, const tls_ext_ctx_cb *cbinfo)
318 {
319 uschar *expanded;
320
321 if (cbinfo->certificate == NULL)
322 return OK;
323
324 if (Ustrstr(cbinfo->certificate, US"tls_sni"))
325 reexpand_tls_files_for_sni = TRUE;
326
327 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
328 return DEFER;
329
330 if (expanded != NULL)
331 {
332 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
333 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
334 return tls_error(string_sprintf(
335 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
336 cbinfo->host, NULL);
337 }
338
339 if (cbinfo->privatekey != NULL &&
340 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
341 return DEFER;
342
343 /* If expansion was forced to fail, key_expanded will be NULL. If the result
344 of the expansion is an empty string, ignore it also, and assume the private
345 key is in the same file as the certificate. */
346
347 if (expanded != NULL && *expanded != 0)
348 {
349 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
350 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
351 return tls_error(string_sprintf(
352 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
353 }
354
355 return OK;
356 }
357
358
359
360
361 /*************************************************
362 * Callback to handle SNI *
363 *************************************************/
364
365 /* Called when acting as server during the TLS session setup if a Server Name
366 Indication extension was sent by the client.
367
368 API documentation is OpenSSL s_server.c implementation.
369
370 Arguments:
371 s SSL* of the current session
372 ad unknown (part of OpenSSL API) (unused)
373 arg Callback of "our" registered data
374
375 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
376 */
377
378 static int
379 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
380 /* pre-declared for SSL_CTX_set_tlsext_servername_callback call within func */
381
382 static int
383 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
384 {
385 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
386 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
387 int rc;
388 int old_pool = store_pool;
389
390 if (!servername)
391 return SSL_TLSEXT_ERR_OK;
392
393 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
394 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
395
396 /* Make the extension value available for expansion */
397 store_pool = POOL_PERM;
398 tls_sni = string_copy(US servername);
399 store_pool = old_pool;
400
401 if (!reexpand_tls_files_for_sni)
402 return SSL_TLSEXT_ERR_OK;
403
404 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
405 not confident that memcpy wouldn't break some internal reference counting.
406 Especially since there's a references struct member, which would be off. */
407
408 ctx_sni = SSL_CTX_new(SSLv23_server_method());
409 if (!ctx_sni)
410 {
411 ERR_error_string(ERR_get_error(), ssl_errstring);
412 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
413 return SSL_TLSEXT_ERR_NOACK;
414 }
415
416 /* Not sure how many of these are actually needed, since SSL object
417 already exists. Might even need this selfsame callback, for reneg? */
418
419 SSL_CTX_set_info_callback(ctx_sni, SSL_CTX_get_info_callback(ctx));
420 SSL_CTX_set_mode(ctx_sni, SSL_CTX_get_mode(ctx));
421 SSL_CTX_set_options(ctx_sni, SSL_CTX_get_options(ctx));
422 SSL_CTX_set_timeout(ctx_sni, SSL_CTX_get_timeout(ctx));
423 SSL_CTX_set_tlsext_servername_callback(ctx_sni, tls_servername_cb);
424 SSL_CTX_set_tlsext_servername_arg(ctx_sni, cbinfo);
425 if (cbinfo->server_cipher_list)
426 SSL_CTX_set_cipher_list(ctx_sni, CS cbinfo->server_cipher_list);
427
428 rc = tls_expand_session_files(ctx_sni, cbinfo);
429 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
430
431 rc = setup_certs(ctx_sni, tls_verify_certificates, tls_crl, NULL, FALSE);
432 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
433
434 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
435 SSL_set_SSL_CTX(s, ctx_sni);
436
437 return SSL_TLSEXT_ERR_OK;
438 }
439
440
441
442
443 /*************************************************
444 * Initialize for TLS *
445 *************************************************/
446
447 /* Called from both server and client code, to do preliminary initialization of
448 the library.
449
450 Arguments:
451 host connected host, if client; NULL if server
452 dhparam DH parameter file
453 certificate certificate file
454 privatekey private key
455 addr address if client; NULL if server (for some randomness)
456
457 Returns: OK/DEFER/FAIL
458 */
459
460 static int
461 tls_init(host_item *host, uschar *dhparam, uschar *certificate,
462 uschar *privatekey, address_item *addr)
463 {
464 long init_options;
465 int rc;
466 BOOL okay;
467 tls_ext_ctx_cb *cbinfo;
468
469 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
470 cbinfo->certificate = certificate;
471 cbinfo->privatekey = privatekey;
472 cbinfo->dhparam = dhparam;
473 cbinfo->host = host;
474
475 SSL_load_error_strings(); /* basic set up */
476 OpenSSL_add_ssl_algorithms();
477
478 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
479 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
480 list of available digests. */
481 EVP_add_digest(EVP_sha256());
482 #endif
483
484 /* Create a context.
485 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
486 negotiation in the different methods; as far as I can tell, the only
487 *_{server,client}_method which allows negotiation is SSLv23, which exists even
488 when OpenSSL is built without SSLv2 support.
489 By disabling with openssl_options, we can let admins re-enable with the
490 existing knob. */
491
492 ctx = SSL_CTX_new((host == NULL)?
493 SSLv23_server_method() : SSLv23_client_method());
494
495 if (ctx == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
496
497 /* It turns out that we need to seed the random number generator this early in
498 order to get the full complement of ciphers to work. It took me roughly a day
499 of work to discover this by experiment.
500
501 On systems that have /dev/urandom, SSL may automatically seed itself from
502 there. Otherwise, we have to make something up as best we can. Double check
503 afterwards. */
504
505 if (!RAND_status())
506 {
507 randstuff r;
508 gettimeofday(&r.tv, NULL);
509 r.p = getpid();
510
511 RAND_seed((uschar *)(&r), sizeof(r));
512 RAND_seed((uschar *)big_buffer, big_buffer_size);
513 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
514
515 if (!RAND_status())
516 return tls_error(US"RAND_status", host,
517 US"unable to seed random number generator");
518 }
519
520 /* Set up the information callback, which outputs if debugging is at a suitable
521 level. */
522
523 SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
524
525 /* Automatically re-try reads/writes after renegotiation. */
526 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
527
528 /* Apply administrator-supplied work-arounds.
529 Historically we applied just one requested option,
530 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
531 moved to an administrator-controlled list of options to specify and
532 grandfathered in the first one as the default value for "openssl_options".
533
534 No OpenSSL version number checks: the options we accept depend upon the
535 availability of the option value macros from OpenSSL. */
536
537 okay = tls_openssl_options_parse(openssl_options, &init_options);
538 if (!okay)
539 return tls_error(US"openssl_options parsing failed", host, NULL);
540
541 if (init_options)
542 {
543 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
544 if (!(SSL_CTX_set_options(ctx, init_options)))
545 return tls_error(string_sprintf(
546 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
547 }
548 else
549 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
550
551 /* Initialize with DH parameters if supplied */
552
553 if (!init_dh(dhparam, host)) return DEFER;
554
555 /* Set up certificate and key */
556
557 rc = tls_expand_session_files(ctx, cbinfo);
558 if (rc != OK) return rc;
559
560 /* If we need to handle SNI, do so */
561 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
562 if (host == NULL)
563 {
564 /* We always do this, so that $tls_sni is available even if not used in
565 tls_certificate */
566 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
567 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
568 }
569 #endif
570
571 /* Set up the RSA callback */
572
573 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
574
575 /* Finally, set the timeout, and we are done */
576
577 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
578 DEBUG(D_tls) debug_printf("Initialized TLS\n");
579
580 static_cbinfo = cbinfo;
581
582 return OK;
583 }
584
585
586
587
588 /*************************************************
589 * Get name of cipher in use *
590 *************************************************/
591
592 /* The answer is left in a static buffer, and tls_cipher is set to point
593 to it.
594
595 Argument: pointer to an SSL structure for the connection
596 Returns: nothing
597 */
598
599 static void
600 construct_cipher_name(SSL *ssl)
601 {
602 static uschar cipherbuf[256];
603 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
604 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
605 the accessor functions use const in the prototype. */
606 const SSL_CIPHER *c;
607 uschar *ver;
608
609 switch (ssl->session->ssl_version)
610 {
611 case SSL2_VERSION:
612 ver = US"SSLv2";
613 break;
614
615 case SSL3_VERSION:
616 ver = US"SSLv3";
617 break;
618
619 case TLS1_VERSION:
620 ver = US"TLSv1";
621 break;
622
623 #ifdef TLS1_1_VERSION
624 case TLS1_1_VERSION:
625 ver = US"TLSv1.1";
626 break;
627 #endif
628
629 #ifdef TLS1_2_VERSION
630 case TLS1_2_VERSION:
631 ver = US"TLSv1.2";
632 break;
633 #endif
634
635 default:
636 ver = US"UNKNOWN";
637 }
638
639 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
640 SSL_CIPHER_get_bits(c, &tls_bits);
641
642 string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver,
643 SSL_CIPHER_get_name(c), tls_bits);
644 tls_cipher = cipherbuf;
645
646 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
647 }
648
649
650
651
652
653 /*************************************************
654 * Set up for verifying certificates *
655 *************************************************/
656
657 /* Called by both client and server startup
658
659 Arguments:
660 sctx SSL_CTX* to initialise
661 certs certs file or NULL
662 crl CRL file or NULL
663 host NULL in a server; the remote host in a client
664 optional TRUE if called from a server for a host in tls_try_verify_hosts;
665 otherwise passed as FALSE
666
667 Returns: OK/DEFER/FAIL
668 */
669
670 static int
671 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional)
672 {
673 uschar *expcerts, *expcrl;
674
675 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
676 return DEFER;
677
678 if (expcerts != NULL)
679 {
680 struct stat statbuf;
681 if (!SSL_CTX_set_default_verify_paths(sctx))
682 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
683
684 if (Ustat(expcerts, &statbuf) < 0)
685 {
686 log_write(0, LOG_MAIN|LOG_PANIC,
687 "failed to stat %s for certificates", expcerts);
688 return DEFER;
689 }
690 else
691 {
692 uschar *file, *dir;
693 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
694 { file = NULL; dir = expcerts; }
695 else
696 { file = expcerts; dir = NULL; }
697
698 /* If a certificate file is empty, the next function fails with an
699 unhelpful error message. If we skip it, we get the correct behaviour (no
700 certificates are recognized, but the error message is still misleading (it
701 says no certificate was supplied.) But this is better. */
702
703 if ((file == NULL || statbuf.st_size > 0) &&
704 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
705 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
706
707 if (file != NULL)
708 {
709 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
710 }
711 }
712
713 /* Handle a certificate revocation list. */
714
715 #if OPENSSL_VERSION_NUMBER > 0x00907000L
716
717 /* This bit of code is now the version supplied by Lars Mainka. (I have
718 * merely reformatted it into the Exim code style.)
719
720 * "From here I changed the code to add support for multiple crl's
721 * in pem format in one file or to support hashed directory entries in
722 * pem format instead of a file. This method now uses the library function
723 * X509_STORE_load_locations to add the CRL location to the SSL context.
724 * OpenSSL will then handle the verify against CA certs and CRLs by
725 * itself in the verify callback." */
726
727 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
728 if (expcrl != NULL && *expcrl != 0)
729 {
730 struct stat statbufcrl;
731 if (Ustat(expcrl, &statbufcrl) < 0)
732 {
733 log_write(0, LOG_MAIN|LOG_PANIC,
734 "failed to stat %s for certificates revocation lists", expcrl);
735 return DEFER;
736 }
737 else
738 {
739 /* is it a file or directory? */
740 uschar *file, *dir;
741 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
742 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
743 {
744 file = NULL;
745 dir = expcrl;
746 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
747 }
748 else
749 {
750 file = expcrl;
751 dir = NULL;
752 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
753 }
754 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
755 return tls_error(US"X509_STORE_load_locations", host, NULL);
756
757 /* setting the flags to check against the complete crl chain */
758
759 X509_STORE_set_flags(cvstore,
760 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
761 }
762 }
763
764 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
765
766 /* If verification is optional, don't fail if no certificate */
767
768 SSL_CTX_set_verify(sctx,
769 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
770 verify_callback);
771 }
772
773 return OK;
774 }
775
776
777
778 /*************************************************
779 * Start a TLS session in a server *
780 *************************************************/
781
782 /* This is called when Exim is running as a server, after having received
783 the STARTTLS command. It must respond to that command, and then negotiate
784 a TLS session.
785
786 Arguments:
787 require_ciphers allowed ciphers
788 ------------------------------------------------------
789 require_mac list of allowed MACs ) Not used
790 require_kx list of allowed key_exchange methods ) for
791 require_proto list of allowed protocols ) OpenSSL
792 ------------------------------------------------------
793
794 Returns: OK on success
795 DEFER for errors before the start of the negotiation
796 FAIL for errors during the negotation; the server can't
797 continue running.
798 */
799
800 int
801 tls_server_start(uschar *require_ciphers, uschar *require_mac,
802 uschar *require_kx, uschar *require_proto)
803 {
804 int rc;
805 uschar *expciphers;
806 tls_ext_ctx_cb *cbinfo;
807
808 /* Check for previous activation */
809
810 if (tls_active >= 0)
811 {
812 tls_error(US"STARTTLS received after TLS started", NULL, US"");
813 smtp_printf("554 Already in TLS\r\n");
814 return FAIL;
815 }
816
817 /* Initialize the SSL library. If it fails, it will already have logged
818 the error. */
819
820 rc = tls_init(NULL, tls_dhparam, tls_certificate, tls_privatekey, NULL);
821 if (rc != OK) return rc;
822 cbinfo = static_cbinfo;
823
824 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
825 return FAIL;
826
827 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
828 are separated by underscores. So that I can use either form in my tests, and
829 also for general convenience, we turn underscores into hyphens here. */
830
831 if (expciphers != NULL)
832 {
833 uschar *s = expciphers;
834 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
835 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
836 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
837 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
838 cbinfo->server_cipher_list = expciphers;
839 }
840
841 /* If this is a host for which certificate verification is mandatory or
842 optional, set up appropriately. */
843
844 tls_certificate_verified = FALSE;
845 verify_callback_called = FALSE;
846
847 if (verify_check_host(&tls_verify_hosts) == OK)
848 {
849 rc = setup_certs(ctx, tls_verify_certificates, tls_crl, NULL, FALSE);
850 if (rc != OK) return rc;
851 verify_optional = FALSE;
852 }
853 else if (verify_check_host(&tls_try_verify_hosts) == OK)
854 {
855 rc = setup_certs(ctx, tls_verify_certificates, tls_crl, NULL, TRUE);
856 if (rc != OK) return rc;
857 verify_optional = TRUE;
858 }
859
860 /* Prepare for new connection */
861
862 if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
863
864 /* Warning: we used to SSL_clear(ssl) here, it was removed.
865 *
866 * With the SSL_clear(), we get strange interoperability bugs with
867 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
868 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
869 *
870 * The SSL_clear() call is to let an existing SSL* be reused, typically after
871 * session shutdown. In this case, we have a brand new object and there's no
872 * obvious reason to immediately clear it. I'm guessing that this was
873 * originally added because of incomplete initialisation which the clear fixed,
874 * in some historic release.
875 */
876
877 /* Set context and tell client to go ahead, except in the case of TLS startup
878 on connection, where outputting anything now upsets the clients and tends to
879 make them disconnect. We need to have an explicit fflush() here, to force out
880 the response. Other smtp_printf() calls do not need it, because in non-TLS
881 mode, the fflush() happens when smtp_getc() is called. */
882
883 SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx));
884 if (!tls_on_connect)
885 {
886 smtp_printf("220 TLS go ahead\r\n");
887 fflush(smtp_out);
888 }
889
890 /* Now negotiate the TLS session. We put our own timer on it, since it seems
891 that the OpenSSL library doesn't. */
892
893 SSL_set_wfd(ssl, fileno(smtp_out));
894 SSL_set_rfd(ssl, fileno(smtp_in));
895 SSL_set_accept_state(ssl);
896
897 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
898
899 sigalrm_seen = FALSE;
900 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
901 rc = SSL_accept(ssl);
902 alarm(0);
903
904 if (rc <= 0)
905 {
906 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
907 if (ERR_get_error() == 0)
908 log_write(0, LOG_MAIN,
909 "TLS client disconnected cleanly (rejected our certificate?)");
910 return FAIL;
911 }
912
913 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
914
915 /* TLS has been set up. Adjust the input functions to read via TLS,
916 and initialize things. */
917
918 construct_cipher_name(ssl);
919
920 DEBUG(D_tls)
921 {
922 uschar buf[2048];
923 if (SSL_get_shared_ciphers(ssl, CS buf, sizeof(buf)) != NULL)
924 debug_printf("Shared ciphers: %s\n", buf);
925 }
926
927
928 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
929 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
930 ssl_xfer_eof = ssl_xfer_error = 0;
931
932 receive_getc = tls_getc;
933 receive_ungetc = tls_ungetc;
934 receive_feof = tls_feof;
935 receive_ferror = tls_ferror;
936 receive_smtp_buffered = tls_smtp_buffered;
937
938 tls_active = fileno(smtp_out);
939 return OK;
940 }
941
942
943
944
945
946 /*************************************************
947 * Start a TLS session in a client *
948 *************************************************/
949
950 /* Called from the smtp transport after STARTTLS has been accepted.
951
952 Argument:
953 fd the fd of the connection
954 host connected host (for messages)
955 addr the first address
956 dhparam DH parameter file
957 certificate certificate file
958 privatekey private key file
959 sni TLS SNI to send to remote host
960 verify_certs file for certificate verify
961 crl file containing CRL
962 require_ciphers list of allowed ciphers
963 ------------------------------------------------------
964 require_mac list of allowed MACs ) Not used
965 require_kx list of allowed key_exchange methods ) for
966 require_proto list of allowed protocols ) OpenSSL
967 ------------------------------------------------------
968 timeout startup timeout
969
970 Returns: OK on success
971 FAIL otherwise - note that tls_error() will not give DEFER
972 because this is not a server
973 */
974
975 int
976 tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam,
977 uschar *certificate, uschar *privatekey, uschar *sni,
978 uschar *verify_certs, uschar *crl,
979 uschar *require_ciphers, uschar *require_mac, uschar *require_kx,
980 uschar *require_proto, int timeout)
981 {
982 static uschar txt[256];
983 uschar *expciphers;
984 X509* server_cert;
985 int rc;
986
987 rc = tls_init(host, dhparam, certificate, privatekey, addr);
988 if (rc != OK) return rc;
989
990 tls_certificate_verified = FALSE;
991 verify_callback_called = FALSE;
992
993 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
994 return FAIL;
995
996 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
997 are separated by underscores. So that I can use either form in my tests, and
998 also for general convenience, we turn underscores into hyphens here. */
999
1000 if (expciphers != NULL)
1001 {
1002 uschar *s = expciphers;
1003 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1004 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1005 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1006 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1007 }
1008
1009 rc = setup_certs(ctx, verify_certs, crl, host, FALSE);
1010 if (rc != OK) return rc;
1011
1012 if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", host, NULL);
1013 SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx));
1014 SSL_set_fd(ssl, fd);
1015 SSL_set_connect_state(ssl);
1016
1017 if (sni)
1018 {
1019 if (!expand_check(sni, US"tls_sni", &tls_sni))
1020 return FAIL;
1021 if (!Ustrlen(tls_sni))
1022 tls_sni = NULL;
1023 else
1024 {
1025 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_sni);
1026 SSL_set_tlsext_host_name(ssl, tls_sni);
1027 }
1028 }
1029
1030 /* There doesn't seem to be a built-in timeout on connection. */
1031
1032 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1033 sigalrm_seen = FALSE;
1034 alarm(timeout);
1035 rc = SSL_connect(ssl);
1036 alarm(0);
1037
1038 if (rc <= 0)
1039 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1040
1041 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1042
1043 /* Beware anonymous ciphers which lead to server_cert being NULL */
1044 server_cert = SSL_get_peer_certificate (ssl);
1045 if (server_cert)
1046 {
1047 tls_peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1048 CS txt, sizeof(txt));
1049 tls_peerdn = txt;
1050 }
1051 else
1052 tls_peerdn = NULL;
1053
1054 construct_cipher_name(ssl); /* Sets tls_cipher */
1055
1056 tls_active = fd;
1057 return OK;
1058 }
1059
1060
1061
1062
1063
1064 /*************************************************
1065 * TLS version of getc *
1066 *************************************************/
1067
1068 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1069 it refills the buffer via the SSL reading function.
1070
1071 Arguments: none
1072 Returns: the next character or EOF
1073 */
1074
1075 int
1076 tls_getc(void)
1077 {
1078 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1079 {
1080 int error;
1081 int inbytes;
1082
1083 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1084 ssl_xfer_buffer, ssl_xfer_buffer_size);
1085
1086 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1087 inbytes = SSL_read(ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1088 error = SSL_get_error(ssl, inbytes);
1089 alarm(0);
1090
1091 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1092 closed down, not that the socket itself has been closed down. Revert to
1093 non-SSL handling. */
1094
1095 if (error == SSL_ERROR_ZERO_RETURN)
1096 {
1097 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1098
1099 receive_getc = smtp_getc;
1100 receive_ungetc = smtp_ungetc;
1101 receive_feof = smtp_feof;
1102 receive_ferror = smtp_ferror;
1103 receive_smtp_buffered = smtp_buffered;
1104
1105 SSL_free(ssl);
1106 ssl = NULL;
1107 tls_active = -1;
1108 tls_bits = 0;
1109 tls_cipher = NULL;
1110 tls_peerdn = NULL;
1111 tls_sni = NULL;
1112
1113 return smtp_getc();
1114 }
1115
1116 /* Handle genuine errors */
1117
1118 else if (error == SSL_ERROR_SSL)
1119 {
1120 ERR_error_string(ERR_get_error(), ssl_errstring);
1121 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1122 ssl_xfer_error = 1;
1123 return EOF;
1124 }
1125
1126 else if (error != SSL_ERROR_NONE)
1127 {
1128 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1129 ssl_xfer_error = 1;
1130 return EOF;
1131 }
1132
1133 #ifndef DISABLE_DKIM
1134 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1135 #endif
1136 ssl_xfer_buffer_hwm = inbytes;
1137 ssl_xfer_buffer_lwm = 0;
1138 }
1139
1140 /* Something in the buffer; return next uschar */
1141
1142 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1143 }
1144
1145
1146
1147 /*************************************************
1148 * Read bytes from TLS channel *
1149 *************************************************/
1150
1151 /*
1152 Arguments:
1153 buff buffer of data
1154 len size of buffer
1155
1156 Returns: the number of bytes read
1157 -1 after a failed read
1158 */
1159
1160 int
1161 tls_read(uschar *buff, size_t len)
1162 {
1163 int inbytes;
1164 int error;
1165
1166 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1167 buff, (unsigned int)len);
1168
1169 inbytes = SSL_read(ssl, CS buff, len);
1170 error = SSL_get_error(ssl, inbytes);
1171
1172 if (error == SSL_ERROR_ZERO_RETURN)
1173 {
1174 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1175 return -1;
1176 }
1177 else if (error != SSL_ERROR_NONE)
1178 {
1179 return -1;
1180 }
1181
1182 return inbytes;
1183 }
1184
1185
1186
1187
1188
1189 /*************************************************
1190 * Write bytes down TLS channel *
1191 *************************************************/
1192
1193 /*
1194 Arguments:
1195 buff buffer of data
1196 len number of bytes
1197
1198 Returns: the number of bytes after a successful write,
1199 -1 after a failed write
1200 */
1201
1202 int
1203 tls_write(const uschar *buff, size_t len)
1204 {
1205 int outbytes;
1206 int error;
1207 int left = len;
1208
1209 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1210 while (left > 0)
1211 {
1212 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1213 outbytes = SSL_write(ssl, CS buff, left);
1214 error = SSL_get_error(ssl, outbytes);
1215 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1216 switch (error)
1217 {
1218 case SSL_ERROR_SSL:
1219 ERR_error_string(ERR_get_error(), ssl_errstring);
1220 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1221 return -1;
1222
1223 case SSL_ERROR_NONE:
1224 left -= outbytes;
1225 buff += outbytes;
1226 break;
1227
1228 case SSL_ERROR_ZERO_RETURN:
1229 log_write(0, LOG_MAIN, "SSL channel closed on write");
1230 return -1;
1231
1232 default:
1233 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1234 return -1;
1235 }
1236 }
1237 return len;
1238 }
1239
1240
1241
1242 /*************************************************
1243 * Close down a TLS session *
1244 *************************************************/
1245
1246 /* This is also called from within a delivery subprocess forked from the
1247 daemon, to shut down the TLS library, without actually doing a shutdown (which
1248 would tamper with the SSL session in the parent process).
1249
1250 Arguments: TRUE if SSL_shutdown is to be called
1251 Returns: nothing
1252 */
1253
1254 void
1255 tls_close(BOOL shutdown)
1256 {
1257 if (tls_active < 0) return; /* TLS was not active */
1258
1259 if (shutdown)
1260 {
1261 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1262 SSL_shutdown(ssl);
1263 }
1264
1265 SSL_free(ssl);
1266 ssl = NULL;
1267
1268 tls_active = -1;
1269 }
1270
1271
1272
1273
1274 /*************************************************
1275 * Report the library versions. *
1276 *************************************************/
1277
1278 /* There have historically been some issues with binary compatibility in
1279 OpenSSL libraries; if Exim (like many other applications) is built against
1280 one version of OpenSSL but the run-time linker picks up another version,
1281 it can result in serious failures, including crashing with a SIGSEGV. So
1282 report the version found by the compiler and the run-time version.
1283
1284 Arguments: a FILE* to print the results to
1285 Returns: nothing
1286 */
1287
1288 void
1289 tls_version_report(FILE *f)
1290 {
1291 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
1292 " Runtime: %s\n",
1293 OPENSSL_VERSION_TEXT,
1294 SSLeay_version(SSLEAY_VERSION));
1295 }
1296
1297
1298
1299
1300 /*************************************************
1301 * Pseudo-random number generation *
1302 *************************************************/
1303
1304 /* Pseudo-random number generation. The result is not expected to be
1305 cryptographically strong but not so weak that someone will shoot themselves
1306 in the foot using it as a nonce in input in some email header scheme or
1307 whatever weirdness they'll twist this into. The result should handle fork()
1308 and avoid repeating sequences. OpenSSL handles that for us.
1309
1310 Arguments:
1311 max range maximum
1312 Returns a random number in range [0, max-1]
1313 */
1314
1315 int
1316 pseudo_random_number(int max)
1317 {
1318 unsigned int r;
1319 int i, needed_len;
1320 uschar *p;
1321 uschar smallbuf[sizeof(r)];
1322
1323 if (max <= 1)
1324 return 0;
1325
1326 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
1327 if (!RAND_status())
1328 {
1329 randstuff r;
1330 gettimeofday(&r.tv, NULL);
1331 r.p = getpid();
1332
1333 RAND_seed((uschar *)(&r), sizeof(r));
1334 }
1335 /* We're after pseudo-random, not random; if we still don't have enough data
1336 in the internal PRNG then our options are limited. We could sleep and hope
1337 for entropy to come along (prayer technique) but if the system is so depleted
1338 in the first place then something is likely to just keep taking it. Instead,
1339 we'll just take whatever little bit of pseudo-random we can still manage to
1340 get. */
1341
1342 needed_len = sizeof(r);
1343 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1344 asked for a number less than 10. */
1345 for (r = max, i = 0; r; ++i)
1346 r >>= 1;
1347 i = (i + 7) / 8;
1348 if (i < needed_len)
1349 needed_len = i;
1350
1351 /* We do not care if crypto-strong */
1352 (void) RAND_pseudo_bytes(smallbuf, needed_len);
1353 r = 0;
1354 for (p = smallbuf; needed_len; --needed_len, ++p)
1355 {
1356 r *= 256;
1357 r += *p;
1358 }
1359
1360 /* We don't particularly care about weighted results; if someone wants
1361 smooth distribution and cares enough then they should submit a patch then. */
1362 return r % max;
1363 }
1364
1365
1366
1367
1368 /*************************************************
1369 * OpenSSL option parse *
1370 *************************************************/
1371
1372 /* Parse one option for tls_openssl_options_parse below
1373
1374 Arguments:
1375 name one option name
1376 value place to store a value for it
1377 Returns success or failure in parsing
1378 */
1379
1380 struct exim_openssl_option {
1381 uschar *name;
1382 long value;
1383 };
1384 /* We could use a macro to expand, but we need the ifdef and not all the
1385 options document which version they were introduced in. Policylet: include
1386 all options unless explicitly for DTLS, let the administrator choose which
1387 to apply.
1388
1389 This list is current as of:
1390 ==> 1.0.1b <== */
1391 static struct exim_openssl_option exim_openssl_options[] = {
1392 /* KEEP SORTED ALPHABETICALLY! */
1393 #ifdef SSL_OP_ALL
1394 { US"all", SSL_OP_ALL },
1395 #endif
1396 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
1397 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
1398 #endif
1399 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
1400 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
1401 #endif
1402 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
1403 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
1404 #endif
1405 #ifdef SSL_OP_EPHEMERAL_RSA
1406 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
1407 #endif
1408 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
1409 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
1410 #endif
1411 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
1412 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
1413 #endif
1414 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
1415 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
1416 #endif
1417 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
1418 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
1419 #endif
1420 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
1421 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
1422 #endif
1423 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
1424 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
1425 #endif
1426 #ifdef SSL_OP_NO_COMPRESSION
1427 { US"no_compression", SSL_OP_NO_COMPRESSION },
1428 #endif
1429 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
1430 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
1431 #endif
1432 #ifdef SSL_OP_NO_SSLv2
1433 { US"no_sslv2", SSL_OP_NO_SSLv2 },
1434 #endif
1435 #ifdef SSL_OP_NO_SSLv3
1436 { US"no_sslv3", SSL_OP_NO_SSLv3 },
1437 #endif
1438 #ifdef SSL_OP_NO_TICKET
1439 { US"no_ticket", SSL_OP_NO_TICKET },
1440 #endif
1441 #ifdef SSL_OP_NO_TLSv1
1442 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
1443 #endif
1444 #ifdef SSL_OP_NO_TLSv1_1
1445 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
1446 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
1447 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
1448 #else
1449 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
1450 #endif
1451 #endif
1452 #ifdef SSL_OP_NO_TLSv1_2
1453 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
1454 #endif
1455 #ifdef SSL_OP_SINGLE_DH_USE
1456 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
1457 #endif
1458 #ifdef SSL_OP_SINGLE_ECDH_USE
1459 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
1460 #endif
1461 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
1462 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
1463 #endif
1464 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
1465 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
1466 #endif
1467 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
1468 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
1469 #endif
1470 #ifdef SSL_OP_TLS_D5_BUG
1471 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
1472 #endif
1473 #ifdef SSL_OP_TLS_ROLLBACK_BUG
1474 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
1475 #endif
1476 };
1477 static int exim_openssl_options_size =
1478 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
1479
1480
1481 static BOOL
1482 tls_openssl_one_option_parse(uschar *name, long *value)
1483 {
1484 int first = 0;
1485 int last = exim_openssl_options_size;
1486 while (last > first)
1487 {
1488 int middle = (first + last)/2;
1489 int c = Ustrcmp(name, exim_openssl_options[middle].name);
1490 if (c == 0)
1491 {
1492 *value = exim_openssl_options[middle].value;
1493 return TRUE;
1494 }
1495 else if (c > 0)
1496 first = middle + 1;
1497 else
1498 last = middle;
1499 }
1500 return FALSE;
1501 }
1502
1503
1504
1505
1506 /*************************************************
1507 * OpenSSL option parsing logic *
1508 *************************************************/
1509
1510 /* OpenSSL has a number of compatibility options which an administrator might
1511 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
1512 we look like log_selector.
1513
1514 Arguments:
1515 option_spec the administrator-supplied string of options
1516 results ptr to long storage for the options bitmap
1517 Returns success or failure
1518 */
1519
1520 BOOL
1521 tls_openssl_options_parse(uschar *option_spec, long *results)
1522 {
1523 long result, item;
1524 uschar *s, *end;
1525 uschar keep_c;
1526 BOOL adding, item_parsed;
1527
1528 result = 0L;
1529 /* Prior to 4.78 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
1530 * from default because it increases BEAST susceptibility. */
1531 #ifdef SSL_OP_NO_SSLv2
1532 result |= SSL_OP_NO_SSLv2;
1533 #endif
1534
1535 if (option_spec == NULL)
1536 {
1537 *results = result;
1538 return TRUE;
1539 }
1540
1541 for (s=option_spec; *s != '\0'; /**/)
1542 {
1543 while (isspace(*s)) ++s;
1544 if (*s == '\0')
1545 break;
1546 if (*s != '+' && *s != '-')
1547 {
1548 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
1549 "+ or - expected but found \"%s\"\n", s);
1550 return FALSE;
1551 }
1552 adding = *s++ == '+';
1553 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
1554 keep_c = *end;
1555 *end = '\0';
1556 item_parsed = tls_openssl_one_option_parse(s, &item);
1557 if (!item_parsed)
1558 {
1559 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
1560 return FALSE;
1561 }
1562 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
1563 adding ? "adding" : "removing", result, item, s);
1564 if (adding)
1565 result |= item;
1566 else
1567 result &= ~item;
1568 *end = keep_c;
1569 s = end;
1570 }
1571
1572 *results = result;
1573 return TRUE;
1574 }
1575
1576 /* End of tls-openssl.c */