Testsuite: more robust fix for SHELL vs /bin/sh, take two.
[exim.git] / src / src / tls-openssl.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2012 */
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 #ifdef EXPERIMENTAL_OCSP
24 #include <openssl/ocsp.h>
25 #endif
26
27 #ifdef EXPERIMENTAL_OCSP
28 #define EXIM_OCSP_SKEW_SECONDS (300L)
29 #define EXIM_OCSP_MAX_AGE (-1L)
30 #endif
31
32 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
33 #define EXIM_HAVE_OPENSSL_TLSEXT
34 #endif
35
36 /* Structure for collecting random data for seeding. */
37
38 typedef struct randstuff {
39 struct timeval tv;
40 pid_t p;
41 } randstuff;
42
43 /* Local static variables */
44
45 static BOOL verify_callback_called = FALSE;
46 static const uschar *sid_ctx = US"exim";
47
48 static SSL_CTX *ctx = NULL;
49 static SSL_CTX *ctx_sni = NULL;
50 static SSL *ssl = NULL;
51
52 static char ssl_errstring[256];
53
54 static int ssl_session_timeout = 200;
55 static BOOL verify_optional = FALSE;
56
57 static BOOL reexpand_tls_files_for_sni = FALSE;
58
59
60 typedef struct tls_ext_ctx_cb {
61 uschar *certificate;
62 uschar *privatekey;
63 #ifdef EXPERIMENTAL_OCSP
64 uschar *ocsp_file;
65 uschar *ocsp_file_expanded;
66 OCSP_RESPONSE *ocsp_response;
67 #endif
68 uschar *dhparam;
69 /* these are cached from first expand */
70 uschar *server_cipher_list;
71 /* only passed down to tls_error: */
72 host_item *host;
73 } tls_ext_ctx_cb;
74
75 /* should figure out a cleanup of API to handle state preserved per
76 implementation, for various reasons, which can be void * in the APIs.
77 For now, we hack around it. */
78 tls_ext_ctx_cb *static_cbinfo = NULL;
79
80 static int
81 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional);
82
83 /* Callbacks */
84 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
85 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
86 #endif
87 #ifdef EXPERIMENTAL_OCSP
88 static int tls_stapling_cb(SSL *s, void *arg);
89 #endif
90
91
92 /*************************************************
93 * Handle TLS error *
94 *************************************************/
95
96 /* Called from lots of places when errors occur before actually starting to do
97 the TLS handshake, that is, while the session is still in clear. Always returns
98 DEFER for a server and FAIL for a client so that most calls can use "return
99 tls_error(...)" to do this processing and then give an appropriate return. A
100 single function is used for both server and client, because it is called from
101 some shared functions.
102
103 Argument:
104 prefix text to include in the logged error
105 host NULL if setting up a server;
106 the connected host if setting up a client
107 msg error message or NULL if we should ask OpenSSL
108
109 Returns: OK/DEFER/FAIL
110 */
111
112 static int
113 tls_error(uschar *prefix, host_item *host, uschar *msg)
114 {
115 if (msg == NULL)
116 {
117 ERR_error_string(ERR_get_error(), ssl_errstring);
118 msg = (uschar *)ssl_errstring;
119 }
120
121 if (host == NULL)
122 {
123 uschar *conn_info = smtp_get_connection_info();
124 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
125 conn_info += 5;
126 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
127 conn_info, prefix, msg);
128 return DEFER;
129 }
130 else
131 {
132 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
133 host->name, host->address, prefix, msg);
134 return FAIL;
135 }
136 }
137
138
139
140 /*************************************************
141 * Callback to generate RSA key *
142 *************************************************/
143
144 /*
145 Arguments:
146 s SSL connection
147 export not used
148 keylength keylength
149
150 Returns: pointer to generated key
151 */
152
153 static RSA *
154 rsa_callback(SSL *s, int export, int keylength)
155 {
156 RSA *rsa_key;
157 export = export; /* Shut picky compilers up */
158 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
159 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
160 if (rsa_key == NULL)
161 {
162 ERR_error_string(ERR_get_error(), ssl_errstring);
163 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
164 ssl_errstring);
165 return NULL;
166 }
167 return rsa_key;
168 }
169
170
171
172
173 /*************************************************
174 * Callback for verification *
175 *************************************************/
176
177 /* The SSL library does certificate verification if set up to do so. This
178 callback has the current yes/no state is in "state". If verification succeeded,
179 we set up the tls_peerdn string. If verification failed, what happens depends
180 on whether the client is required to present a verifiable certificate or not.
181
182 If verification is optional, we change the state to yes, but still log the
183 verification error. For some reason (it really would help to have proper
184 documentation of OpenSSL), this callback function then gets called again, this
185 time with state = 1. In fact, that's useful, because we can set up the peerdn
186 value, but we must take care not to set the private verified flag on the second
187 time through.
188
189 Note: this function is not called if the client fails to present a certificate
190 when asked. We get here only if a certificate has been received. Handling of
191 optional verification for this case is done when requesting SSL to verify, by
192 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
193
194 Arguments:
195 state current yes/no state as 1/0
196 x509ctx certificate information.
197
198 Returns: 1 if verified, 0 if not
199 */
200
201 static int
202 verify_callback(int state, X509_STORE_CTX *x509ctx)
203 {
204 static uschar txt[256];
205
206 X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert),
207 CS txt, sizeof(txt));
208
209 if (state == 0)
210 {
211 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
212 x509ctx->error_depth,
213 X509_verify_cert_error_string(x509ctx->error),
214 txt);
215 tls_certificate_verified = FALSE;
216 verify_callback_called = TRUE;
217 if (!verify_optional) return 0; /* reject */
218 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
219 "tls_try_verify_hosts)\n");
220 return 1; /* accept */
221 }
222
223 if (x509ctx->error_depth != 0)
224 {
225 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n",
226 x509ctx->error_depth, txt);
227 }
228 else
229 {
230 DEBUG(D_tls) debug_printf("SSL%s peer: %s\n",
231 verify_callback_called? "" : " authenticated", txt);
232 tls_peerdn = txt;
233 }
234
235 if (!verify_callback_called) tls_certificate_verified = TRUE;
236 verify_callback_called = TRUE;
237
238 return 1; /* accept */
239 }
240
241
242
243 /*************************************************
244 * Information callback *
245 *************************************************/
246
247 /* The SSL library functions call this from time to time to indicate what they
248 are doing. We copy the string to the debugging output when TLS debugging has
249 been requested.
250
251 Arguments:
252 s the SSL connection
253 where
254 ret
255
256 Returns: nothing
257 */
258
259 static void
260 info_callback(SSL *s, int where, int ret)
261 {
262 where = where;
263 ret = ret;
264 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
265 }
266
267
268
269 /*************************************************
270 * Initialize for DH *
271 *************************************************/
272
273 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
274
275 Arguments:
276 dhparam DH parameter file
277 host connected host, if client; NULL if server
278
279 Returns: TRUE if OK (nothing to set up, or setup worked)
280 */
281
282 static BOOL
283 init_dh(uschar *dhparam, host_item *host)
284 {
285 BOOL yield = TRUE;
286 BIO *bio;
287 DH *dh;
288 uschar *dhexpanded;
289
290 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
291 return FALSE;
292
293 if (dhexpanded == NULL) return TRUE;
294
295 if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL)
296 {
297 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
298 host, (uschar *)strerror(errno));
299 yield = FALSE;
300 }
301 else
302 {
303 if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL)
304 {
305 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
306 host, NULL);
307 yield = FALSE;
308 }
309 else
310 {
311 if ((8*DH_size(dh)) > tls_dh_max_bits)
312 {
313 DEBUG(D_tls)
314 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
315 8*DH_size(dh), tls_dh_max_bits);
316 }
317 else
318 {
319 SSL_CTX_set_tmp_dh(ctx, dh);
320 DEBUG(D_tls)
321 debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n",
322 dhexpanded, 8*DH_size(dh));
323 }
324 DH_free(dh);
325 }
326 BIO_free(bio);
327 }
328
329 return yield;
330 }
331
332
333
334
335 #ifdef EXPERIMENTAL_OCSP
336 /*************************************************
337 * Load OCSP information into state *
338 *************************************************/
339
340 /* Called to load the OCSP response from the given file into memory, once
341 caller has determined this is needed. Checks validity. Debugs a message
342 if invalid.
343
344 ASSUMES: single response, for single cert.
345
346 Arguments:
347 sctx the SSL_CTX* to update
348 cbinfo various parts of session state
349 expanded the filename putatively holding an OCSP response
350
351 */
352
353 static void
354 ocsp_load_response(SSL_CTX *sctx,
355 tls_ext_ctx_cb *cbinfo,
356 const uschar *expanded)
357 {
358 BIO *bio;
359 OCSP_RESPONSE *resp;
360 OCSP_BASICRESP *basic_response;
361 OCSP_SINGLERESP *single_response;
362 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
363 X509_STORE *store;
364 unsigned long verify_flags;
365 int status, reason, i;
366
367 cbinfo->ocsp_file_expanded = string_copy(expanded);
368 if (cbinfo->ocsp_response)
369 {
370 OCSP_RESPONSE_free(cbinfo->ocsp_response);
371 cbinfo->ocsp_response = NULL;
372 }
373
374 bio = BIO_new_file(CS cbinfo->ocsp_file_expanded, "rb");
375 if (!bio)
376 {
377 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
378 cbinfo->ocsp_file_expanded);
379 return;
380 }
381
382 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
383 BIO_free(bio);
384 if (!resp)
385 {
386 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
387 return;
388 }
389
390 status = OCSP_response_status(resp);
391 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
392 {
393 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
394 OCSP_response_status_str(status), status);
395 return;
396 }
397
398 basic_response = OCSP_response_get1_basic(resp);
399 if (!basic_response)
400 {
401 DEBUG(D_tls)
402 debug_printf("OCSP response parse error: unable to extract basic response.\n");
403 return;
404 }
405
406 store = SSL_CTX_get_cert_store(sctx);
407 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
408
409 /* May need to expose ability to adjust those flags?
410 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
411 OCSP_TRUSTOTHER OCSP_NOINTERN */
412
413 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
414 if (i <= 0)
415 {
416 DEBUG(D_tls) {
417 ERR_error_string(ERR_get_error(), ssl_errstring);
418 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
419 }
420 return;
421 }
422
423 /* Here's the simplifying assumption: there's only one response, for the
424 one certificate we use, and nothing for anything else in a chain. If this
425 proves false, we need to extract a cert id from our issued cert
426 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
427 right cert in the stack and then calls OCSP_single_get0_status()).
428
429 I'm hoping to avoid reworking a bunch more of how we handle state here. */
430 single_response = OCSP_resp_get0(basic_response, 0);
431 if (!single_response)
432 {
433 DEBUG(D_tls)
434 debug_printf("Unable to get first response from OCSP basic response.\n");
435 return;
436 }
437
438 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
439 /* how does this status differ from the one above? */
440 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
441 {
442 DEBUG(D_tls) debug_printf("OCSP response not valid (take 2): %s (%d)\n",
443 OCSP_response_status_str(status), status);
444 return;
445 }
446
447 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
448 {
449 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
450 return;
451 }
452
453 cbinfo->ocsp_response = resp;
454 }
455 #endif
456
457
458
459
460 /*************************************************
461 * Expand key and cert file specs *
462 *************************************************/
463
464 /* Called once during tls_init and possibly againt during TLS setup, for a
465 new context, if Server Name Indication was used and tls_sni was seen in
466 the certificate string.
467
468 Arguments:
469 sctx the SSL_CTX* to update
470 cbinfo various parts of session state
471
472 Returns: OK/DEFER/FAIL
473 */
474
475 static int
476 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
477 {
478 uschar *expanded;
479
480 if (cbinfo->certificate == NULL)
481 return OK;
482
483 if (Ustrstr(cbinfo->certificate, US"tls_sni"))
484 reexpand_tls_files_for_sni = TRUE;
485
486 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
487 return DEFER;
488
489 if (expanded != NULL)
490 {
491 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
492 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
493 return tls_error(string_sprintf(
494 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
495 cbinfo->host, NULL);
496 }
497
498 if (cbinfo->privatekey != NULL &&
499 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
500 return DEFER;
501
502 /* If expansion was forced to fail, key_expanded will be NULL. If the result
503 of the expansion is an empty string, ignore it also, and assume the private
504 key is in the same file as the certificate. */
505
506 if (expanded != NULL && *expanded != 0)
507 {
508 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
509 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
510 return tls_error(string_sprintf(
511 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
512 }
513
514 #ifdef EXPERIMENTAL_OCSP
515 if (cbinfo->ocsp_file != NULL)
516 {
517 if (!expand_check(cbinfo->ocsp_file, US"tls_ocsp_file", &expanded))
518 return DEFER;
519
520 if (expanded != NULL && *expanded != 0)
521 {
522 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
523 if (cbinfo->ocsp_file_expanded &&
524 (Ustrcmp(expanded, cbinfo->ocsp_file_expanded) == 0))
525 {
526 DEBUG(D_tls)
527 debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
528 } else {
529 ocsp_load_response(sctx, cbinfo, expanded);
530 }
531 }
532 }
533 #endif
534
535 return OK;
536 }
537
538
539
540
541 /*************************************************
542 * Callback to handle SNI *
543 *************************************************/
544
545 /* Called when acting as server during the TLS session setup if a Server Name
546 Indication extension was sent by the client.
547
548 API documentation is OpenSSL s_server.c implementation.
549
550 Arguments:
551 s SSL* of the current session
552 ad unknown (part of OpenSSL API) (unused)
553 arg Callback of "our" registered data
554
555 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
556 */
557
558 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
559 static int
560 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
561 {
562 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
563 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
564 int rc;
565 int old_pool = store_pool;
566
567 if (!servername)
568 return SSL_TLSEXT_ERR_OK;
569
570 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
571 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
572
573 /* Make the extension value available for expansion */
574 store_pool = POOL_PERM;
575 tls_sni = string_copy(US servername);
576 store_pool = old_pool;
577
578 if (!reexpand_tls_files_for_sni)
579 return SSL_TLSEXT_ERR_OK;
580
581 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
582 not confident that memcpy wouldn't break some internal reference counting.
583 Especially since there's a references struct member, which would be off. */
584
585 ctx_sni = SSL_CTX_new(SSLv23_server_method());
586 if (!ctx_sni)
587 {
588 ERR_error_string(ERR_get_error(), ssl_errstring);
589 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
590 return SSL_TLSEXT_ERR_NOACK;
591 }
592
593 /* Not sure how many of these are actually needed, since SSL object
594 already exists. Might even need this selfsame callback, for reneg? */
595
596 SSL_CTX_set_info_callback(ctx_sni, SSL_CTX_get_info_callback(ctx));
597 SSL_CTX_set_mode(ctx_sni, SSL_CTX_get_mode(ctx));
598 SSL_CTX_set_options(ctx_sni, SSL_CTX_get_options(ctx));
599 SSL_CTX_set_timeout(ctx_sni, SSL_CTX_get_timeout(ctx));
600 SSL_CTX_set_tlsext_servername_callback(ctx_sni, tls_servername_cb);
601 SSL_CTX_set_tlsext_servername_arg(ctx_sni, cbinfo);
602 if (cbinfo->server_cipher_list)
603 SSL_CTX_set_cipher_list(ctx_sni, CS cbinfo->server_cipher_list);
604 #ifdef EXPERIMENTAL_OCSP
605 if (cbinfo->ocsp_file)
606 {
607 SSL_CTX_set_tlsext_status_cb(ctx_sni, tls_stapling_cb);
608 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
609 }
610 #endif
611
612 rc = setup_certs(ctx_sni, tls_verify_certificates, tls_crl, NULL, FALSE);
613 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
614
615 /* do this after setup_certs, because this can require the certs for verifying
616 OCSP information. */
617 rc = tls_expand_session_files(ctx_sni, cbinfo);
618 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
619
620 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
621 SSL_set_SSL_CTX(s, ctx_sni);
622
623 return SSL_TLSEXT_ERR_OK;
624 }
625 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
626
627
628
629
630 #ifdef EXPERIMENTAL_OCSP
631 /*************************************************
632 * Callback to handle OCSP Stapling *
633 *************************************************/
634
635 /* Called when acting as server during the TLS session setup if the client
636 requests OCSP information with a Certificate Status Request.
637
638 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
639 project.
640
641 */
642
643 static int
644 tls_stapling_cb(SSL *s, void *arg)
645 {
646 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
647 uschar *response_der;
648 int response_der_len;
649
650 DEBUG(D_tls) debug_printf("Received TLS status request (OCSP stapling); %s response.\n",
651 cbinfo->ocsp_response ? "have" : "lack");
652 if (!cbinfo->ocsp_response)
653 return SSL_TLSEXT_ERR_NOACK;
654
655 response_der = NULL;
656 response_der_len = i2d_OCSP_RESPONSE(cbinfo->ocsp_response, &response_der);
657 if (response_der_len <= 0)
658 return SSL_TLSEXT_ERR_NOACK;
659
660 SSL_set_tlsext_status_ocsp_resp(ssl, response_der, response_der_len);
661 return SSL_TLSEXT_ERR_OK;
662 }
663
664 #endif /* EXPERIMENTAL_OCSP */
665
666
667
668
669 /*************************************************
670 * Initialize for TLS *
671 *************************************************/
672
673 /* Called from both server and client code, to do preliminary initialization of
674 the library.
675
676 Arguments:
677 host connected host, if client; NULL if server
678 dhparam DH parameter file
679 certificate certificate file
680 privatekey private key
681 addr address if client; NULL if server (for some randomness)
682
683 Returns: OK/DEFER/FAIL
684 */
685
686 static int
687 tls_init(host_item *host, uschar *dhparam, uschar *certificate,
688 uschar *privatekey,
689 #ifdef EXPERIMENTAL_OCSP
690 uschar *ocsp_file,
691 #endif
692 address_item *addr)
693 {
694 long init_options;
695 int rc;
696 BOOL okay;
697 tls_ext_ctx_cb *cbinfo;
698
699 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
700 cbinfo->certificate = certificate;
701 cbinfo->privatekey = privatekey;
702 #ifdef EXPERIMENTAL_OCSP
703 cbinfo->ocsp_file = ocsp_file;
704 #endif
705 cbinfo->dhparam = dhparam;
706 cbinfo->host = host;
707
708 SSL_load_error_strings(); /* basic set up */
709 OpenSSL_add_ssl_algorithms();
710
711 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
712 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
713 list of available digests. */
714 EVP_add_digest(EVP_sha256());
715 #endif
716
717 /* Create a context */
718
719 ctx = SSL_CTX_new((host == NULL)?
720 SSLv23_server_method() : SSLv23_client_method());
721
722 if (ctx == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
723
724 /* It turns out that we need to seed the random number generator this early in
725 order to get the full complement of ciphers to work. It took me roughly a day
726 of work to discover this by experiment.
727
728 On systems that have /dev/urandom, SSL may automatically seed itself from
729 there. Otherwise, we have to make something up as best we can. Double check
730 afterwards. */
731
732 if (!RAND_status())
733 {
734 randstuff r;
735 gettimeofday(&r.tv, NULL);
736 r.p = getpid();
737
738 RAND_seed((uschar *)(&r), sizeof(r));
739 RAND_seed((uschar *)big_buffer, big_buffer_size);
740 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
741
742 if (!RAND_status())
743 return tls_error(US"RAND_status", host,
744 US"unable to seed random number generator");
745 }
746
747 /* Set up the information callback, which outputs if debugging is at a suitable
748 level. */
749
750 SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
751
752 /* Automatically re-try reads/writes after renegotiation. */
753 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
754
755 /* Apply administrator-supplied work-arounds.
756 Historically we applied just one requested option,
757 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
758 moved to an administrator-controlled list of options to specify and
759 grandfathered in the first one as the default value for "openssl_options".
760
761 No OpenSSL version number checks: the options we accept depend upon the
762 availability of the option value macros from OpenSSL. */
763
764 okay = tls_openssl_options_parse(openssl_options, &init_options);
765 if (!okay)
766 return tls_error(US"openssl_options parsing failed", host, NULL);
767
768 if (init_options)
769 {
770 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
771 if (!(SSL_CTX_set_options(ctx, init_options)))
772 return tls_error(string_sprintf(
773 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
774 }
775 else
776 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
777
778 /* Initialize with DH parameters if supplied */
779
780 if (!init_dh(dhparam, host)) return DEFER;
781
782 /* Set up certificate and key (and perhaps OCSP info) */
783
784 rc = tls_expand_session_files(ctx, cbinfo);
785 if (rc != OK) return rc;
786
787 /* If we need to handle SNI, do so */
788 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
789 if (host == NULL)
790 {
791 #ifdef EXPERIMENTAL_OCSP
792 /* We check ocsp_file, not ocsp_response, because we care about if
793 the option exists, not what the current expansion might be, as SNI might
794 change the certificate and OCSP file in use between now and the time the
795 callback is invoked. */
796 if (cbinfo->ocsp_file)
797 {
798 SSL_CTX_set_tlsext_status_cb(ctx, tls_stapling_cb);
799 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
800 }
801 #endif
802 /* We always do this, so that $tls_sni is available even if not used in
803 tls_certificate */
804 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
805 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
806 }
807 #endif
808
809 /* Set up the RSA callback */
810
811 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
812
813 /* Finally, set the timeout, and we are done */
814
815 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
816 DEBUG(D_tls) debug_printf("Initialized TLS\n");
817
818 static_cbinfo = cbinfo;
819
820 return OK;
821 }
822
823
824
825
826 /*************************************************
827 * Get name of cipher in use *
828 *************************************************/
829
830 /* The answer is left in a static buffer, and tls_cipher is set to point
831 to it.
832
833 Argument: pointer to an SSL structure for the connection
834 Returns: nothing
835 */
836
837 static void
838 construct_cipher_name(SSL *ssl)
839 {
840 static uschar cipherbuf[256];
841 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
842 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
843 the accessor functions use const in the prototype. */
844 const SSL_CIPHER *c;
845 uschar *ver;
846
847 switch (ssl->session->ssl_version)
848 {
849 case SSL2_VERSION:
850 ver = US"SSLv2";
851 break;
852
853 case SSL3_VERSION:
854 ver = US"SSLv3";
855 break;
856
857 case TLS1_VERSION:
858 ver = US"TLSv1";
859 break;
860
861 #ifdef TLS1_1_VERSION
862 case TLS1_1_VERSION:
863 ver = US"TLSv1.1";
864 break;
865 #endif
866
867 #ifdef TLS1_2_VERSION
868 case TLS1_2_VERSION:
869 ver = US"TLSv1.2";
870 break;
871 #endif
872
873 default:
874 ver = US"UNKNOWN";
875 }
876
877 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
878 SSL_CIPHER_get_bits(c, &tls_bits);
879
880 string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver,
881 SSL_CIPHER_get_name(c), tls_bits);
882 tls_cipher = cipherbuf;
883
884 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
885 }
886
887
888
889
890
891 /*************************************************
892 * Set up for verifying certificates *
893 *************************************************/
894
895 /* Called by both client and server startup
896
897 Arguments:
898 sctx SSL_CTX* to initialise
899 certs certs file or NULL
900 crl CRL file or NULL
901 host NULL in a server; the remote host in a client
902 optional TRUE if called from a server for a host in tls_try_verify_hosts;
903 otherwise passed as FALSE
904
905 Returns: OK/DEFER/FAIL
906 */
907
908 static int
909 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional)
910 {
911 uschar *expcerts, *expcrl;
912
913 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
914 return DEFER;
915
916 if (expcerts != NULL)
917 {
918 struct stat statbuf;
919 if (!SSL_CTX_set_default_verify_paths(sctx))
920 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
921
922 if (Ustat(expcerts, &statbuf) < 0)
923 {
924 log_write(0, LOG_MAIN|LOG_PANIC,
925 "failed to stat %s for certificates", expcerts);
926 return DEFER;
927 }
928 else
929 {
930 uschar *file, *dir;
931 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
932 { file = NULL; dir = expcerts; }
933 else
934 { file = expcerts; dir = NULL; }
935
936 /* If a certificate file is empty, the next function fails with an
937 unhelpful error message. If we skip it, we get the correct behaviour (no
938 certificates are recognized, but the error message is still misleading (it
939 says no certificate was supplied.) But this is better. */
940
941 if ((file == NULL || statbuf.st_size > 0) &&
942 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
943 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
944
945 if (file != NULL)
946 {
947 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
948 }
949 }
950
951 /* Handle a certificate revocation list. */
952
953 #if OPENSSL_VERSION_NUMBER > 0x00907000L
954
955 /* This bit of code is now the version supplied by Lars Mainka. (I have
956 * merely reformatted it into the Exim code style.)
957
958 * "From here I changed the code to add support for multiple crl's
959 * in pem format in one file or to support hashed directory entries in
960 * pem format instead of a file. This method now uses the library function
961 * X509_STORE_load_locations to add the CRL location to the SSL context.
962 * OpenSSL will then handle the verify against CA certs and CRLs by
963 * itself in the verify callback." */
964
965 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
966 if (expcrl != NULL && *expcrl != 0)
967 {
968 struct stat statbufcrl;
969 if (Ustat(expcrl, &statbufcrl) < 0)
970 {
971 log_write(0, LOG_MAIN|LOG_PANIC,
972 "failed to stat %s for certificates revocation lists", expcrl);
973 return DEFER;
974 }
975 else
976 {
977 /* is it a file or directory? */
978 uschar *file, *dir;
979 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
980 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
981 {
982 file = NULL;
983 dir = expcrl;
984 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
985 }
986 else
987 {
988 file = expcrl;
989 dir = NULL;
990 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
991 }
992 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
993 return tls_error(US"X509_STORE_load_locations", host, NULL);
994
995 /* setting the flags to check against the complete crl chain */
996
997 X509_STORE_set_flags(cvstore,
998 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
999 }
1000 }
1001
1002 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1003
1004 /* If verification is optional, don't fail if no certificate */
1005
1006 SSL_CTX_set_verify(sctx,
1007 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1008 verify_callback);
1009 }
1010
1011 return OK;
1012 }
1013
1014
1015
1016 /*************************************************
1017 * Start a TLS session in a server *
1018 *************************************************/
1019
1020 /* This is called when Exim is running as a server, after having received
1021 the STARTTLS command. It must respond to that command, and then negotiate
1022 a TLS session.
1023
1024 Arguments:
1025 require_ciphers allowed ciphers
1026
1027 Returns: OK on success
1028 DEFER for errors before the start of the negotiation
1029 FAIL for errors during the negotation; the server can't
1030 continue running.
1031 */
1032
1033 int
1034 tls_server_start(const uschar *require_ciphers)
1035 {
1036 int rc;
1037 uschar *expciphers;
1038 tls_ext_ctx_cb *cbinfo;
1039
1040 /* Check for previous activation */
1041
1042 if (tls_active >= 0)
1043 {
1044 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1045 smtp_printf("554 Already in TLS\r\n");
1046 return FAIL;
1047 }
1048
1049 /* Initialize the SSL library. If it fails, it will already have logged
1050 the error. */
1051
1052 rc = tls_init(NULL, tls_dhparam, tls_certificate, tls_privatekey,
1053 #ifdef EXPERIMENTAL_OCSP
1054 tls_ocsp_file,
1055 #endif
1056 NULL);
1057 if (rc != OK) return rc;
1058 cbinfo = static_cbinfo;
1059
1060 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1061 return FAIL;
1062
1063 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1064 were historically separated by underscores. So that I can use either form in my
1065 tests, and also for general convenience, we turn underscores into hyphens here.
1066 */
1067
1068 if (expciphers != NULL)
1069 {
1070 uschar *s = expciphers;
1071 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1072 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1073 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1074 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1075 cbinfo->server_cipher_list = expciphers;
1076 }
1077
1078 /* If this is a host for which certificate verification is mandatory or
1079 optional, set up appropriately. */
1080
1081 tls_certificate_verified = FALSE;
1082 verify_callback_called = FALSE;
1083
1084 if (verify_check_host(&tls_verify_hosts) == OK)
1085 {
1086 rc = setup_certs(ctx, tls_verify_certificates, tls_crl, NULL, FALSE);
1087 if (rc != OK) return rc;
1088 verify_optional = FALSE;
1089 }
1090 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1091 {
1092 rc = setup_certs(ctx, tls_verify_certificates, tls_crl, NULL, TRUE);
1093 if (rc != OK) return rc;
1094 verify_optional = TRUE;
1095 }
1096
1097 /* Prepare for new connection */
1098
1099 if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1100
1101 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1102 *
1103 * With the SSL_clear(), we get strange interoperability bugs with
1104 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1105 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1106 *
1107 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1108 * session shutdown. In this case, we have a brand new object and there's no
1109 * obvious reason to immediately clear it. I'm guessing that this was
1110 * originally added because of incomplete initialisation which the clear fixed,
1111 * in some historic release.
1112 */
1113
1114 /* Set context and tell client to go ahead, except in the case of TLS startup
1115 on connection, where outputting anything now upsets the clients and tends to
1116 make them disconnect. We need to have an explicit fflush() here, to force out
1117 the response. Other smtp_printf() calls do not need it, because in non-TLS
1118 mode, the fflush() happens when smtp_getc() is called. */
1119
1120 SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx));
1121 if (!tls_on_connect)
1122 {
1123 smtp_printf("220 TLS go ahead\r\n");
1124 fflush(smtp_out);
1125 }
1126
1127 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1128 that the OpenSSL library doesn't. */
1129
1130 SSL_set_wfd(ssl, fileno(smtp_out));
1131 SSL_set_rfd(ssl, fileno(smtp_in));
1132 SSL_set_accept_state(ssl);
1133
1134 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1135
1136 sigalrm_seen = FALSE;
1137 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1138 rc = SSL_accept(ssl);
1139 alarm(0);
1140
1141 if (rc <= 0)
1142 {
1143 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1144 if (ERR_get_error() == 0)
1145 log_write(0, LOG_MAIN,
1146 "TLS client disconnected cleanly (rejected our certificate?)");
1147 return FAIL;
1148 }
1149
1150 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1151
1152 /* TLS has been set up. Adjust the input functions to read via TLS,
1153 and initialize things. */
1154
1155 construct_cipher_name(ssl);
1156
1157 DEBUG(D_tls)
1158 {
1159 uschar buf[2048];
1160 if (SSL_get_shared_ciphers(ssl, CS buf, sizeof(buf)) != NULL)
1161 debug_printf("Shared ciphers: %s\n", buf);
1162 }
1163
1164
1165 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1166 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1167 ssl_xfer_eof = ssl_xfer_error = 0;
1168
1169 receive_getc = tls_getc;
1170 receive_ungetc = tls_ungetc;
1171 receive_feof = tls_feof;
1172 receive_ferror = tls_ferror;
1173 receive_smtp_buffered = tls_smtp_buffered;
1174
1175 tls_active = fileno(smtp_out);
1176 return OK;
1177 }
1178
1179
1180
1181
1182
1183 /*************************************************
1184 * Start a TLS session in a client *
1185 *************************************************/
1186
1187 /* Called from the smtp transport after STARTTLS has been accepted.
1188
1189 Argument:
1190 fd the fd of the connection
1191 host connected host (for messages)
1192 addr the first address
1193 dhparam DH parameter file
1194 certificate certificate file
1195 privatekey private key file
1196 sni TLS SNI to send to remote host
1197 verify_certs file for certificate verify
1198 crl file containing CRL
1199 require_ciphers list of allowed ciphers
1200 timeout startup timeout
1201
1202 Returns: OK on success
1203 FAIL otherwise - note that tls_error() will not give DEFER
1204 because this is not a server
1205 */
1206
1207 int
1208 tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam,
1209 uschar *certificate, uschar *privatekey, uschar *sni,
1210 uschar *verify_certs, uschar *crl,
1211 uschar *require_ciphers, int timeout)
1212 {
1213 static uschar txt[256];
1214 uschar *expciphers;
1215 X509* server_cert;
1216 int rc;
1217
1218 rc = tls_init(host, dhparam, certificate, privatekey,
1219 #ifdef EXPERIMENTAL_OCSP
1220 NULL,
1221 #endif
1222 addr);
1223 if (rc != OK) return rc;
1224
1225 tls_certificate_verified = FALSE;
1226 verify_callback_called = FALSE;
1227
1228 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1229 return FAIL;
1230
1231 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1232 are separated by underscores. So that I can use either form in my tests, and
1233 also for general convenience, we turn underscores into hyphens here. */
1234
1235 if (expciphers != NULL)
1236 {
1237 uschar *s = expciphers;
1238 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1239 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1240 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1241 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1242 }
1243
1244 rc = setup_certs(ctx, verify_certs, crl, host, FALSE);
1245 if (rc != OK) return rc;
1246
1247 if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", host, NULL);
1248 SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx));
1249 SSL_set_fd(ssl, fd);
1250 SSL_set_connect_state(ssl);
1251
1252 if (sni)
1253 {
1254 if (!expand_check(sni, US"tls_sni", &tls_sni))
1255 return FAIL;
1256 if (!Ustrlen(tls_sni))
1257 tls_sni = NULL;
1258 else
1259 {
1260 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_sni);
1261 SSL_set_tlsext_host_name(ssl, tls_sni);
1262 }
1263 }
1264
1265 /* There doesn't seem to be a built-in timeout on connection. */
1266
1267 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1268 sigalrm_seen = FALSE;
1269 alarm(timeout);
1270 rc = SSL_connect(ssl);
1271 alarm(0);
1272
1273 if (rc <= 0)
1274 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1275
1276 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1277
1278 /* Beware anonymous ciphers which lead to server_cert being NULL */
1279 server_cert = SSL_get_peer_certificate (ssl);
1280 if (server_cert)
1281 {
1282 tls_peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1283 CS txt, sizeof(txt));
1284 tls_peerdn = txt;
1285 }
1286 else
1287 tls_peerdn = NULL;
1288
1289 construct_cipher_name(ssl); /* Sets tls_cipher */
1290
1291 tls_active = fd;
1292 return OK;
1293 }
1294
1295
1296
1297
1298
1299 /*************************************************
1300 * TLS version of getc *
1301 *************************************************/
1302
1303 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1304 it refills the buffer via the SSL reading function.
1305
1306 Arguments: none
1307 Returns: the next character or EOF
1308 */
1309
1310 int
1311 tls_getc(void)
1312 {
1313 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1314 {
1315 int error;
1316 int inbytes;
1317
1318 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1319 ssl_xfer_buffer, ssl_xfer_buffer_size);
1320
1321 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1322 inbytes = SSL_read(ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1323 error = SSL_get_error(ssl, inbytes);
1324 alarm(0);
1325
1326 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1327 closed down, not that the socket itself has been closed down. Revert to
1328 non-SSL handling. */
1329
1330 if (error == SSL_ERROR_ZERO_RETURN)
1331 {
1332 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1333
1334 receive_getc = smtp_getc;
1335 receive_ungetc = smtp_ungetc;
1336 receive_feof = smtp_feof;
1337 receive_ferror = smtp_ferror;
1338 receive_smtp_buffered = smtp_buffered;
1339
1340 SSL_free(ssl);
1341 ssl = NULL;
1342 tls_active = -1;
1343 tls_bits = 0;
1344 tls_cipher = NULL;
1345 tls_peerdn = NULL;
1346 tls_sni = NULL;
1347
1348 return smtp_getc();
1349 }
1350
1351 /* Handle genuine errors */
1352
1353 else if (error == SSL_ERROR_SSL)
1354 {
1355 ERR_error_string(ERR_get_error(), ssl_errstring);
1356 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1357 ssl_xfer_error = 1;
1358 return EOF;
1359 }
1360
1361 else if (error != SSL_ERROR_NONE)
1362 {
1363 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1364 ssl_xfer_error = 1;
1365 return EOF;
1366 }
1367
1368 #ifndef DISABLE_DKIM
1369 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1370 #endif
1371 ssl_xfer_buffer_hwm = inbytes;
1372 ssl_xfer_buffer_lwm = 0;
1373 }
1374
1375 /* Something in the buffer; return next uschar */
1376
1377 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1378 }
1379
1380
1381
1382 /*************************************************
1383 * Read bytes from TLS channel *
1384 *************************************************/
1385
1386 /*
1387 Arguments:
1388 buff buffer of data
1389 len size of buffer
1390
1391 Returns: the number of bytes read
1392 -1 after a failed read
1393 */
1394
1395 int
1396 tls_read(uschar *buff, size_t len)
1397 {
1398 int inbytes;
1399 int error;
1400
1401 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1402 buff, (unsigned int)len);
1403
1404 inbytes = SSL_read(ssl, CS buff, len);
1405 error = SSL_get_error(ssl, inbytes);
1406
1407 if (error == SSL_ERROR_ZERO_RETURN)
1408 {
1409 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1410 return -1;
1411 }
1412 else if (error != SSL_ERROR_NONE)
1413 {
1414 return -1;
1415 }
1416
1417 return inbytes;
1418 }
1419
1420
1421
1422
1423
1424 /*************************************************
1425 * Write bytes down TLS channel *
1426 *************************************************/
1427
1428 /*
1429 Arguments:
1430 buff buffer of data
1431 len number of bytes
1432
1433 Returns: the number of bytes after a successful write,
1434 -1 after a failed write
1435 */
1436
1437 int
1438 tls_write(const uschar *buff, size_t len)
1439 {
1440 int outbytes;
1441 int error;
1442 int left = len;
1443
1444 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1445 while (left > 0)
1446 {
1447 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1448 outbytes = SSL_write(ssl, CS buff, left);
1449 error = SSL_get_error(ssl, outbytes);
1450 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1451 switch (error)
1452 {
1453 case SSL_ERROR_SSL:
1454 ERR_error_string(ERR_get_error(), ssl_errstring);
1455 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1456 return -1;
1457
1458 case SSL_ERROR_NONE:
1459 left -= outbytes;
1460 buff += outbytes;
1461 break;
1462
1463 case SSL_ERROR_ZERO_RETURN:
1464 log_write(0, LOG_MAIN, "SSL channel closed on write");
1465 return -1;
1466
1467 default:
1468 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1469 return -1;
1470 }
1471 }
1472 return len;
1473 }
1474
1475
1476
1477 /*************************************************
1478 * Close down a TLS session *
1479 *************************************************/
1480
1481 /* This is also called from within a delivery subprocess forked from the
1482 daemon, to shut down the TLS library, without actually doing a shutdown (which
1483 would tamper with the SSL session in the parent process).
1484
1485 Arguments: TRUE if SSL_shutdown is to be called
1486 Returns: nothing
1487 */
1488
1489 void
1490 tls_close(BOOL shutdown)
1491 {
1492 if (tls_active < 0) return; /* TLS was not active */
1493
1494 if (shutdown)
1495 {
1496 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1497 SSL_shutdown(ssl);
1498 }
1499
1500 SSL_free(ssl);
1501 ssl = NULL;
1502
1503 tls_active = -1;
1504 }
1505
1506
1507
1508
1509 /*************************************************
1510 * Let tls_require_ciphers be checked at startup *
1511 *************************************************/
1512
1513 /* The tls_require_ciphers option, if set, must be something which the
1514 library can parse.
1515
1516 Returns: NULL on success, or error message
1517 */
1518
1519 uschar *
1520 tls_validate_require_cipher(void)
1521 {
1522 SSL_CTX *ctx;
1523 uschar *s, *expciphers, *err;
1524
1525 /* this duplicates from tls_init(), we need a better "init just global
1526 state, for no specific purpose" singleton function of our own */
1527
1528 SSL_load_error_strings();
1529 OpenSSL_add_ssl_algorithms();
1530 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1531 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1532 list of available digests. */
1533 EVP_add_digest(EVP_sha256());
1534 #endif
1535
1536 if (!(tls_require_ciphers && *tls_require_ciphers))
1537 return NULL;
1538
1539 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1540 return US"failed to expand tls_require_ciphers";
1541
1542 if (!(expciphers && *expciphers))
1543 return NULL;
1544
1545 /* normalisation ripped from above */
1546 s = expciphers;
1547 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1548
1549 err = NULL;
1550
1551 ctx = SSL_CTX_new(SSLv23_server_method());
1552 if (!ctx)
1553 {
1554 ERR_error_string(ERR_get_error(), ssl_errstring);
1555 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1556 }
1557
1558 DEBUG(D_tls)
1559 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1560
1561 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1562 {
1563 ERR_error_string(ERR_get_error(), ssl_errstring);
1564 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
1565 }
1566
1567 SSL_CTX_free(ctx);
1568
1569 return err;
1570 }
1571
1572
1573
1574
1575 /*************************************************
1576 * Report the library versions. *
1577 *************************************************/
1578
1579 /* There have historically been some issues with binary compatibility in
1580 OpenSSL libraries; if Exim (like many other applications) is built against
1581 one version of OpenSSL but the run-time linker picks up another version,
1582 it can result in serious failures, including crashing with a SIGSEGV. So
1583 report the version found by the compiler and the run-time version.
1584
1585 Arguments: a FILE* to print the results to
1586 Returns: nothing
1587 */
1588
1589 void
1590 tls_version_report(FILE *f)
1591 {
1592 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
1593 " Runtime: %s\n",
1594 OPENSSL_VERSION_TEXT,
1595 SSLeay_version(SSLEAY_VERSION));
1596 }
1597
1598
1599
1600
1601 /*************************************************
1602 * Random number generation *
1603 *************************************************/
1604
1605 /* Pseudo-random number generation. The result is not expected to be
1606 cryptographically strong but not so weak that someone will shoot themselves
1607 in the foot using it as a nonce in input in some email header scheme or
1608 whatever weirdness they'll twist this into. The result should handle fork()
1609 and avoid repeating sequences. OpenSSL handles that for us.
1610
1611 Arguments:
1612 max range maximum
1613 Returns a random number in range [0, max-1]
1614 */
1615
1616 int
1617 vaguely_random_number(int max)
1618 {
1619 unsigned int r;
1620 int i, needed_len;
1621 uschar *p;
1622 uschar smallbuf[sizeof(r)];
1623
1624 if (max <= 1)
1625 return 0;
1626
1627 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
1628 if (!RAND_status())
1629 {
1630 randstuff r;
1631 gettimeofday(&r.tv, NULL);
1632 r.p = getpid();
1633
1634 RAND_seed((uschar *)(&r), sizeof(r));
1635 }
1636 /* We're after pseudo-random, not random; if we still don't have enough data
1637 in the internal PRNG then our options are limited. We could sleep and hope
1638 for entropy to come along (prayer technique) but if the system is so depleted
1639 in the first place then something is likely to just keep taking it. Instead,
1640 we'll just take whatever little bit of pseudo-random we can still manage to
1641 get. */
1642
1643 needed_len = sizeof(r);
1644 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1645 asked for a number less than 10. */
1646 for (r = max, i = 0; r; ++i)
1647 r >>= 1;
1648 i = (i + 7) / 8;
1649 if (i < needed_len)
1650 needed_len = i;
1651
1652 /* We do not care if crypto-strong */
1653 i = RAND_pseudo_bytes(smallbuf, needed_len);
1654 if (i < 0)
1655 {
1656 DEBUG(D_all)
1657 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
1658 return vaguely_random_number_fallback(max);
1659 }
1660
1661 r = 0;
1662 for (p = smallbuf; needed_len; --needed_len, ++p)
1663 {
1664 r *= 256;
1665 r += *p;
1666 }
1667
1668 /* We don't particularly care about weighted results; if someone wants
1669 smooth distribution and cares enough then they should submit a patch then. */
1670 return r % max;
1671 }
1672
1673
1674
1675
1676 /*************************************************
1677 * OpenSSL option parse *
1678 *************************************************/
1679
1680 /* Parse one option for tls_openssl_options_parse below
1681
1682 Arguments:
1683 name one option name
1684 value place to store a value for it
1685 Returns success or failure in parsing
1686 */
1687
1688 struct exim_openssl_option {
1689 uschar *name;
1690 long value;
1691 };
1692 /* We could use a macro to expand, but we need the ifdef and not all the
1693 options document which version they were introduced in. Policylet: include
1694 all options unless explicitly for DTLS, let the administrator choose which
1695 to apply.
1696
1697 This list is current as of:
1698 ==> 1.0.1b <== */
1699 static struct exim_openssl_option exim_openssl_options[] = {
1700 /* KEEP SORTED ALPHABETICALLY! */
1701 #ifdef SSL_OP_ALL
1702 { US"all", SSL_OP_ALL },
1703 #endif
1704 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
1705 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
1706 #endif
1707 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
1708 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
1709 #endif
1710 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
1711 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
1712 #endif
1713 #ifdef SSL_OP_EPHEMERAL_RSA
1714 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
1715 #endif
1716 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
1717 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
1718 #endif
1719 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
1720 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
1721 #endif
1722 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
1723 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
1724 #endif
1725 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
1726 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
1727 #endif
1728 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
1729 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
1730 #endif
1731 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
1732 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
1733 #endif
1734 #ifdef SSL_OP_NO_COMPRESSION
1735 { US"no_compression", SSL_OP_NO_COMPRESSION },
1736 #endif
1737 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
1738 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
1739 #endif
1740 #ifdef SSL_OP_NO_SSLv2
1741 { US"no_sslv2", SSL_OP_NO_SSLv2 },
1742 #endif
1743 #ifdef SSL_OP_NO_SSLv3
1744 { US"no_sslv3", SSL_OP_NO_SSLv3 },
1745 #endif
1746 #ifdef SSL_OP_NO_TICKET
1747 { US"no_ticket", SSL_OP_NO_TICKET },
1748 #endif
1749 #ifdef SSL_OP_NO_TLSv1
1750 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
1751 #endif
1752 #ifdef SSL_OP_NO_TLSv1_1
1753 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
1754 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
1755 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
1756 #else
1757 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
1758 #endif
1759 #endif
1760 #ifdef SSL_OP_NO_TLSv1_2
1761 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
1762 #endif
1763 #ifdef SSL_OP_SINGLE_DH_USE
1764 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
1765 #endif
1766 #ifdef SSL_OP_SINGLE_ECDH_USE
1767 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
1768 #endif
1769 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
1770 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
1771 #endif
1772 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
1773 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
1774 #endif
1775 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
1776 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
1777 #endif
1778 #ifdef SSL_OP_TLS_D5_BUG
1779 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
1780 #endif
1781 #ifdef SSL_OP_TLS_ROLLBACK_BUG
1782 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
1783 #endif
1784 };
1785 static int exim_openssl_options_size =
1786 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
1787
1788
1789 static BOOL
1790 tls_openssl_one_option_parse(uschar *name, long *value)
1791 {
1792 int first = 0;
1793 int last = exim_openssl_options_size;
1794 while (last > first)
1795 {
1796 int middle = (first + last)/2;
1797 int c = Ustrcmp(name, exim_openssl_options[middle].name);
1798 if (c == 0)
1799 {
1800 *value = exim_openssl_options[middle].value;
1801 return TRUE;
1802 }
1803 else if (c > 0)
1804 first = middle + 1;
1805 else
1806 last = middle;
1807 }
1808 return FALSE;
1809 }
1810
1811
1812
1813
1814 /*************************************************
1815 * OpenSSL option parsing logic *
1816 *************************************************/
1817
1818 /* OpenSSL has a number of compatibility options which an administrator might
1819 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
1820 we look like log_selector.
1821
1822 Arguments:
1823 option_spec the administrator-supplied string of options
1824 results ptr to long storage for the options bitmap
1825 Returns success or failure
1826 */
1827
1828 BOOL
1829 tls_openssl_options_parse(uschar *option_spec, long *results)
1830 {
1831 long result, item;
1832 uschar *s, *end;
1833 uschar keep_c;
1834 BOOL adding, item_parsed;
1835
1836 result = 0L;
1837 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
1838 * from default because it increases BEAST susceptibility. */
1839
1840 if (option_spec == NULL)
1841 {
1842 *results = result;
1843 return TRUE;
1844 }
1845
1846 for (s=option_spec; *s != '\0'; /**/)
1847 {
1848 while (isspace(*s)) ++s;
1849 if (*s == '\0')
1850 break;
1851 if (*s != '+' && *s != '-')
1852 {
1853 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
1854 "+ or - expected but found \"%s\"\n", s);
1855 return FALSE;
1856 }
1857 adding = *s++ == '+';
1858 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
1859 keep_c = *end;
1860 *end = '\0';
1861 item_parsed = tls_openssl_one_option_parse(s, &item);
1862 if (!item_parsed)
1863 {
1864 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
1865 return FALSE;
1866 }
1867 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
1868 adding ? "adding" : "removing", result, item, s);
1869 if (adding)
1870 result |= item;
1871 else
1872 result &= ~item;
1873 *end = keep_c;
1874 s = end;
1875 }
1876
1877 *results = result;
1878 return TRUE;
1879 }
1880
1881 /* End of tls-openssl.c */