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