c8349e7c54459c27fb1513af6f4a0db66d0f5229
[exim.git] / src / src / tls-openssl.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
6 /* See the file NOTICE for conditions of use and distribution. */
7
8 /* Portions Copyright (c) The OpenSSL Project 1999 */
9
10 /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL
11 library. It is #included into the tls.c file when that library is used. The
12 code herein is based on a patch that was originally contributed by Steve
13 Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara.
14
15 No cryptographic code is included in Exim. All this module does is to call
16 functions from the OpenSSL library. */
17
18
19 /* Heading stuff */
20
21 #include <openssl/lhash.h>
22 #include <openssl/ssl.h>
23 #include <openssl/err.h>
24 #include <openssl/rand.h>
25 #ifndef OPENSSL_NO_ECDH
26 # include <openssl/ec.h>
27 #endif
28 #ifndef DISABLE_OCSP
29 # include <openssl/ocsp.h>
30 #endif
31 #ifdef SUPPORT_DANE
32 # include "danessl.h"
33 #endif
34
35
36 #ifndef DISABLE_OCSP
37 # define EXIM_OCSP_SKEW_SECONDS (300L)
38 # define EXIM_OCSP_MAX_AGE (-1L)
39 #endif
40
41 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
42 # define EXIM_HAVE_OPENSSL_TLSEXT
43 #endif
44 #if OPENSSL_VERSION_NUMBER >= 0x00908000L
45 # define EXIM_HAVE_RSA_GENKEY_EX
46 #endif
47 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
48 # define EXIM_HAVE_OCSP_RESP_COUNT
49 #else
50 # define EXIM_HAVE_EPHEM_RSA_KEX
51 # define EXIM_HAVE_RAND_PSEUDO
52 #endif
53 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
54 # define EXIM_HAVE_SHA256
55 #endif
56
57 /* X509_check_host provides sane certificate hostname checking, but was added
58 to OpenSSL late, after other projects forked off the code-base. So in
59 addition to guarding against the base version number, beware that LibreSSL
60 does not (at this time) support this function.
61
62 If LibreSSL gains a different API, perhaps via libtls, then we'll probably
63 opt to disentangle and ask a LibreSSL user to provide glue for a third
64 crypto provider for libtls instead of continuing to tie the OpenSSL glue
65 into even twistier knots. If LibreSSL gains the same API, we can just
66 change this guard and punt the issue for a while longer. */
67
68 #ifndef LIBRESSL_VERSION_NUMBER
69 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
70 # define EXIM_HAVE_OPENSSL_CHECKHOST
71 # define EXIM_HAVE_OPENSSL_DH_BITS
72 # define EXIM_HAVE_OPENSSL_TLS_METHOD
73 # define EXIM_HAVE_OPENSSL_KEYLOG
74 # else
75 # define EXIM_NEED_OPENSSL_INIT
76 # endif
77 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
78 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
79 # define EXIM_HAVE_OPENSSL_CHECKHOST
80 # endif
81 #endif
82
83 #if !defined(LIBRESSL_VERSION_NUMBER) \
84 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
85 # if !defined(OPENSSL_NO_ECDH)
86 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
87 # define EXIM_HAVE_ECDH
88 # endif
89 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
90 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
91 # endif
92 # endif
93 #endif
94
95 #ifndef LIBRESSL_VERSION_NUMBER
96 # if OPENSSL_VERSION_NUMBER >= 0x010101000L
97 # define OPENSSL_HAVE_KEYLOG_CB
98 # define OPENSSL_HAVE_NUM_TICKETS
99 # endif
100 #endif
101
102 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
103 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
104 # define DISABLE_OCSP
105 #endif
106
107 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
108 # include <openssl/x509v3.h>
109 #endif
110
111 /*************************************************
112 * OpenSSL option parse *
113 *************************************************/
114
115 typedef struct exim_openssl_option {
116 uschar *name;
117 long value;
118 } exim_openssl_option;
119 /* We could use a macro to expand, but we need the ifdef and not all the
120 options document which version they were introduced in. Policylet: include
121 all options unless explicitly for DTLS, let the administrator choose which
122 to apply.
123
124 This list is current as of:
125 ==> 1.0.1b <==
126 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
127 Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev
128 */
129 static exim_openssl_option exim_openssl_options[] = {
130 /* KEEP SORTED ALPHABETICALLY! */
131 #ifdef SSL_OP_ALL
132 { US"all", SSL_OP_ALL },
133 #endif
134 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
135 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
136 #endif
137 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
138 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
139 #endif
140 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
141 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
142 #endif
143 #ifdef SSL_OP_EPHEMERAL_RSA
144 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
145 #endif
146 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
147 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
148 #endif
149 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
150 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
151 #endif
152 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
153 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
154 #endif
155 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
156 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
157 #endif
158 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
159 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
160 #endif
161 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
162 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
163 #endif
164 #ifdef SSL_OP_NO_COMPRESSION
165 { US"no_compression", SSL_OP_NO_COMPRESSION },
166 #endif
167 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
168 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
169 #endif
170 #ifdef SSL_OP_NO_SSLv2
171 { US"no_sslv2", SSL_OP_NO_SSLv2 },
172 #endif
173 #ifdef SSL_OP_NO_SSLv3
174 { US"no_sslv3", SSL_OP_NO_SSLv3 },
175 #endif
176 #ifdef SSL_OP_NO_TICKET
177 { US"no_ticket", SSL_OP_NO_TICKET },
178 #endif
179 #ifdef SSL_OP_NO_TLSv1
180 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
181 #endif
182 #ifdef SSL_OP_NO_TLSv1_1
183 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
184 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
185 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
186 #else
187 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
188 #endif
189 #endif
190 #ifdef SSL_OP_NO_TLSv1_2
191 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
192 #endif
193 #ifdef SSL_OP_NO_TLSv1_3
194 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
195 #endif
196 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
197 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
198 #endif
199 #ifdef SSL_OP_SINGLE_DH_USE
200 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
201 #endif
202 #ifdef SSL_OP_SINGLE_ECDH_USE
203 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
204 #endif
205 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
206 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
207 #endif
208 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
209 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
210 #endif
211 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
212 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
213 #endif
214 #ifdef SSL_OP_TLS_D5_BUG
215 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
216 #endif
217 #ifdef SSL_OP_TLS_ROLLBACK_BUG
218 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
219 #endif
220 };
221
222 #ifndef MACRO_PREDEF
223 static int exim_openssl_options_size = nelem(exim_openssl_options);
224 #endif
225
226 #ifdef MACRO_PREDEF
227 void
228 options_tls(void)
229 {
230 uschar buf[64];
231
232 for (struct exim_openssl_option * o = exim_openssl_options;
233 o < exim_openssl_options + nelem(exim_openssl_options); o++)
234 {
235 /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
236 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
237
238 spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
239 builtin_macro_create(buf);
240 }
241 }
242 #else
243
244 /******************************************************************************/
245
246 /* Structure for collecting random data for seeding. */
247
248 typedef struct randstuff {
249 struct timeval tv;
250 pid_t p;
251 } randstuff;
252
253 /* Local static variables */
254
255 static BOOL client_verify_callback_called = FALSE;
256 static BOOL server_verify_callback_called = FALSE;
257 static const uschar *sid_ctx = US"exim";
258
259 /* We have three different contexts to care about.
260
261 Simple case: client, `client_ctx`
262 As a client, we can be doing a callout or cut-through delivery while receiving
263 a message. So we have a client context, which should have options initialised
264 from the SMTP Transport. We may also concurrently want to make TLS connections
265 to utility daemons, so client-contexts are allocated and passed around in call
266 args rather than using a gobal.
267
268 Server:
269 There are two cases: with and without ServerNameIndication from the client.
270 Given TLS SNI, we can be using different keys, certs and various other
271 configuration settings, because they're re-expanded with $tls_sni set. This
272 allows vhosting with TLS. This SNI is sent in the handshake.
273 A client might not send SNI, so we need a fallback, and an initial setup too.
274 So as a server, we start out using `server_ctx`.
275 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
276 `server_sni` from `server_ctx` and then initialise settings by re-expanding
277 configuration.
278 */
279
280 typedef struct {
281 SSL_CTX * ctx;
282 SSL * ssl;
283 } exim_openssl_client_tls_ctx;
284
285 static SSL_CTX *server_ctx = NULL;
286 static SSL *server_ssl = NULL;
287
288 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
289 static SSL_CTX *server_sni = NULL;
290 #endif
291
292 static char ssl_errstring[256];
293
294 static int ssl_session_timeout = 200;
295 static BOOL client_verify_optional = FALSE;
296 static BOOL server_verify_optional = FALSE;
297
298 static BOOL reexpand_tls_files_for_sni = FALSE;
299
300
301 typedef struct tls_ext_ctx_cb {
302 uschar *certificate;
303 uschar *privatekey;
304 BOOL is_server;
305 #ifndef DISABLE_OCSP
306 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
307 union {
308 struct {
309 uschar *file;
310 uschar *file_expanded;
311 OCSP_RESPONSE *response;
312 } server;
313 struct {
314 X509_STORE *verify_store; /* non-null if status requested */
315 BOOL verify_required;
316 } client;
317 } u_ocsp;
318 #endif
319 uschar *dhparam;
320 /* these are cached from first expand */
321 uschar *server_cipher_list;
322 /* only passed down to tls_error: */
323 host_item *host;
324 const uschar * verify_cert_hostnames;
325 #ifndef DISABLE_EVENT
326 uschar * event_action;
327 #endif
328 } tls_ext_ctx_cb;
329
330 /* should figure out a cleanup of API to handle state preserved per
331 implementation, for various reasons, which can be void * in the APIs.
332 For now, we hack around it. */
333 tls_ext_ctx_cb *client_static_cbinfo = NULL;
334 tls_ext_ctx_cb *server_static_cbinfo = NULL;
335
336 static int
337 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
338 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
339
340 /* Callbacks */
341 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
342 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
343 #endif
344 #ifndef DISABLE_OCSP
345 static int tls_server_stapling_cb(SSL *s, void *arg);
346 #endif
347
348
349 /*************************************************
350 * Handle TLS error *
351 *************************************************/
352
353 /* Called from lots of places when errors occur before actually starting to do
354 the TLS handshake, that is, while the session is still in clear. Always returns
355 DEFER for a server and FAIL for a client so that most calls can use "return
356 tls_error(...)" to do this processing and then give an appropriate return. A
357 single function is used for both server and client, because it is called from
358 some shared functions.
359
360 Argument:
361 prefix text to include in the logged error
362 host NULL if setting up a server;
363 the connected host if setting up a client
364 msg error message or NULL if we should ask OpenSSL
365 errstr pointer to output error message
366
367 Returns: OK/DEFER/FAIL
368 */
369
370 static int
371 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
372 {
373 if (!msg)
374 {
375 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
376 msg = US ssl_errstring;
377 }
378
379 msg = string_sprintf("(%s): %s", prefix, msg);
380 DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg);
381 if (errstr) *errstr = msg;
382 return host ? FAIL : DEFER;
383 }
384
385
386
387 /*************************************************
388 * Callback to generate RSA key *
389 *************************************************/
390
391 /*
392 Arguments:
393 s SSL connection (not used)
394 export not used
395 keylength keylength
396
397 Returns: pointer to generated key
398 */
399
400 static RSA *
401 rsa_callback(SSL *s, int export, int keylength)
402 {
403 RSA *rsa_key;
404 #ifdef EXIM_HAVE_RSA_GENKEY_EX
405 BIGNUM *bn = BN_new();
406 #endif
407
408 export = export; /* Shut picky compilers up */
409 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
410
411 #ifdef EXIM_HAVE_RSA_GENKEY_EX
412 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
413 || !(rsa_key = RSA_new())
414 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
415 )
416 #else
417 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
418 #endif
419
420 {
421 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
422 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
423 ssl_errstring);
424 return NULL;
425 }
426 return rsa_key;
427 }
428
429
430
431 /* Extreme debug
432 #ifndef DISABLE_OCSP
433 void
434 x509_store_dump_cert_s_names(X509_STORE * store)
435 {
436 STACK_OF(X509_OBJECT) * roots= store->objs;
437 static uschar name[256];
438
439 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
440 {
441 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
442 if(tmp_obj->type == X509_LU_X509)
443 {
444 X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
445 if (X509_NAME_oneline(sn, CS name, sizeof(name)))
446 {
447 name[sizeof(name)-1] = '\0';
448 debug_printf(" %s\n", name);
449 }
450 }
451 }
452 }
453 #endif
454 */
455
456
457 #ifndef DISABLE_EVENT
458 static int
459 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
460 BOOL *calledp, const BOOL *optionalp, const uschar * what)
461 {
462 uschar * ev;
463 uschar * yield;
464 X509 * old_cert;
465
466 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
467 if (ev)
468 {
469 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
470 old_cert = tlsp->peercert;
471 tlsp->peercert = X509_dup(cert);
472 /* NB we do not bother setting peerdn */
473 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
474 {
475 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
476 "depth=%d cert=%s: %s",
477 tlsp == &tls_out ? deliver_host_address : sender_host_address,
478 what, depth, dn, yield);
479 *calledp = TRUE;
480 if (!*optionalp)
481 {
482 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
483 return 1; /* reject (leaving peercert set) */
484 }
485 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
486 "(host in tls_try_verify_hosts)\n");
487 }
488 X509_free(tlsp->peercert);
489 tlsp->peercert = old_cert;
490 }
491 return 0;
492 }
493 #endif
494
495 /*************************************************
496 * Callback for verification *
497 *************************************************/
498
499 /* The SSL library does certificate verification if set up to do so. This
500 callback has the current yes/no state is in "state". If verification succeeded,
501 we set the certificate-verified flag. If verification failed, what happens
502 depends on whether the client is required to present a verifiable certificate
503 or not.
504
505 If verification is optional, we change the state to yes, but still log the
506 verification error. For some reason (it really would help to have proper
507 documentation of OpenSSL), this callback function then gets called again, this
508 time with state = 1. We must take care not to set the private verified flag on
509 the second time through.
510
511 Note: this function is not called if the client fails to present a certificate
512 when asked. We get here only if a certificate has been received. Handling of
513 optional verification for this case is done when requesting SSL to verify, by
514 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
515
516 May be called multiple times for different issues with a certificate, even
517 for a given "depth" in the certificate chain.
518
519 Arguments:
520 preverify_ok current yes/no state as 1/0
521 x509ctx certificate information.
522 tlsp per-direction (client vs. server) support data
523 calledp has-been-called flag
524 optionalp verification-is-optional flag
525
526 Returns: 0 if verification should fail, otherwise 1
527 */
528
529 static int
530 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
531 tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
532 {
533 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
534 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
535 uschar dn[256];
536
537 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
538 {
539 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
540 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
541 tlsp == &tls_out ? deliver_host_address : sender_host_address);
542 return 0;
543 }
544 dn[sizeof(dn)-1] = '\0';
545
546 if (preverify_ok == 0)
547 {
548 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
549 *verify_mode, sender_host_address)
550 : US"";
551 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
552 tlsp == &tls_out ? deliver_host_address : sender_host_address,
553 extra, depth,
554 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
555 *calledp = TRUE;
556 if (!*optionalp)
557 {
558 if (!tlsp->peercert)
559 tlsp->peercert = X509_dup(cert); /* record failing cert */
560 return 0; /* reject */
561 }
562 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
563 "tls_try_verify_hosts)\n");
564 }
565
566 else if (depth != 0)
567 {
568 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
569 #ifndef DISABLE_OCSP
570 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
571 { /* client, wanting stapling */
572 /* Add the server cert's signing chain as the one
573 for the verification of the OCSP stapled information. */
574
575 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
576 cert))
577 ERR_clear_error();
578 sk_X509_push(client_static_cbinfo->verify_stack, cert);
579 }
580 #endif
581 #ifndef DISABLE_EVENT
582 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
583 return 0; /* reject, with peercert set */
584 #endif
585 }
586 else
587 {
588 const uschar * verify_cert_hostnames;
589
590 if ( tlsp == &tls_out
591 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
592 /* client, wanting hostname check */
593 {
594
595 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
596 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
597 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
598 # endif
599 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
600 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
601 # endif
602 int sep = 0;
603 const uschar * list = verify_cert_hostnames;
604 uschar * name;
605 int rc;
606 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
607 if ((rc = X509_check_host(cert, CCS name, 0,
608 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
609 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
610 NULL)))
611 {
612 if (rc < 0)
613 {
614 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
615 tlsp == &tls_out ? deliver_host_address : sender_host_address);
616 name = NULL;
617 }
618 break;
619 }
620 if (!name)
621 #else
622 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
623 #endif
624 {
625 uschar * extra = verify_mode
626 ? string_sprintf(" (during %c-verify for [%s])",
627 *verify_mode, sender_host_address)
628 : US"";
629 log_write(0, LOG_MAIN,
630 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
631 tlsp == &tls_out ? deliver_host_address : sender_host_address,
632 extra, dn, verify_cert_hostnames);
633 *calledp = TRUE;
634 if (!*optionalp)
635 {
636 if (!tlsp->peercert)
637 tlsp->peercert = X509_dup(cert); /* record failing cert */
638 return 0; /* reject */
639 }
640 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
641 "tls_try_verify_hosts)\n");
642 }
643 }
644
645 #ifndef DISABLE_EVENT
646 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
647 return 0; /* reject, with peercert set */
648 #endif
649
650 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
651 *calledp ? "" : " authenticated", dn);
652 if (!*calledp) tlsp->certificate_verified = TRUE;
653 *calledp = TRUE;
654 }
655
656 return 1; /* accept, at least for this level */
657 }
658
659 static int
660 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
661 {
662 return verify_callback(preverify_ok, x509ctx, &tls_out,
663 &client_verify_callback_called, &client_verify_optional);
664 }
665
666 static int
667 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
668 {
669 return verify_callback(preverify_ok, x509ctx, &tls_in,
670 &server_verify_callback_called, &server_verify_optional);
671 }
672
673
674 #ifdef SUPPORT_DANE
675
676 /* This gets called *by* the dane library verify callback, which interposes
677 itself.
678 */
679 static int
680 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
681 {
682 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
683 uschar dn[256];
684 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
685 #ifndef DISABLE_EVENT
686 BOOL dummy_called, optional = FALSE;
687 #endif
688
689 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
690 {
691 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
692 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
693 deliver_host_address);
694 return 0;
695 }
696 dn[sizeof(dn)-1] = '\0';
697
698 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
699 preverify_ok ? "ok":"BAD", depth, dn);
700
701 #ifndef DISABLE_EVENT
702 if (verify_event(&tls_out, cert, depth, dn,
703 &dummy_called, &optional, US"DANE"))
704 return 0; /* reject, with peercert set */
705 #endif
706
707 if (preverify_ok == 1)
708 {
709 tls_out.dane_verified = tls_out.certificate_verified = TRUE;
710 #ifndef DISABLE_OCSP
711 if (client_static_cbinfo->u_ocsp.client.verify_store)
712 { /* client, wanting stapling */
713 /* Add the server cert's signing chain as the one
714 for the verification of the OCSP stapled information. */
715
716 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
717 cert))
718 ERR_clear_error();
719 sk_X509_push(client_static_cbinfo->verify_stack, cert);
720 }
721 #endif
722 }
723 else
724 {
725 int err = X509_STORE_CTX_get_error(x509ctx);
726 DEBUG(D_tls)
727 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
728 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
729 preverify_ok = 1;
730 }
731 return preverify_ok;
732 }
733
734 #endif /*SUPPORT_DANE*/
735
736
737 /*************************************************
738 * Information callback *
739 *************************************************/
740
741 /* The SSL library functions call this from time to time to indicate what they
742 are doing. We copy the string to the debugging output when TLS debugging has
743 been requested.
744
745 Arguments:
746 s the SSL connection
747 where
748 ret
749
750 Returns: nothing
751 */
752
753 static void
754 info_callback(SSL *s, int where, int ret)
755 {
756 DEBUG(D_tls)
757 {
758 const uschar * str;
759
760 if (where & SSL_ST_CONNECT)
761 str = US"SSL_connect";
762 else if (where & SSL_ST_ACCEPT)
763 str = US"SSL_accept";
764 else
765 str = US"SSL info (undefined)";
766
767 if (where & SSL_CB_LOOP)
768 debug_printf("%s: %s\n", str, SSL_state_string_long(s));
769 else if (where & SSL_CB_ALERT)
770 debug_printf("SSL3 alert %s:%s:%s\n",
771 str = where & SSL_CB_READ ? US"read" : US"write",
772 SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
773 else if (where & SSL_CB_EXIT)
774 if (ret == 0)
775 debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
776 else if (ret < 0)
777 debug_printf("%s: error in %s\n", str, SSL_state_string_long(s));
778 else if (where & SSL_CB_HANDSHAKE_START)
779 debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s));
780 else if (where & SSL_CB_HANDSHAKE_DONE)
781 debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s));
782 }
783 }
784
785 #ifdef OPENSSL_HAVE_KEYLOG_CB
786 static void
787 keylog_callback(const SSL *ssl, const char *line)
788 {
789 DEBUG(D_tls) debug_printf("%.200s\n", line);
790 }
791 #endif
792
793
794
795 /*************************************************
796 * Initialize for DH *
797 *************************************************/
798
799 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
800
801 Arguments:
802 sctx The current SSL CTX (inbound or outbound)
803 dhparam DH parameter file or fixed parameter identity string
804 host connected host, if client; NULL if server
805 errstr error string pointer
806
807 Returns: TRUE if OK (nothing to set up, or setup worked)
808 */
809
810 static BOOL
811 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
812 {
813 BIO *bio;
814 DH *dh;
815 uschar *dhexpanded;
816 const char *pem;
817 int dh_bitsize;
818
819 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
820 return FALSE;
821
822 if (!dhexpanded || !*dhexpanded)
823 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
824 else if (dhexpanded[0] == '/')
825 {
826 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
827 {
828 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
829 host, US strerror(errno), errstr);
830 return FALSE;
831 }
832 }
833 else
834 {
835 if (Ustrcmp(dhexpanded, "none") == 0)
836 {
837 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
838 return TRUE;
839 }
840
841 if (!(pem = std_dh_prime_named(dhexpanded)))
842 {
843 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
844 host, US strerror(errno), errstr);
845 return FALSE;
846 }
847 bio = BIO_new_mem_buf(CS pem, -1);
848 }
849
850 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
851 {
852 BIO_free(bio);
853 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
854 host, NULL, errstr);
855 return FALSE;
856 }
857
858 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
859 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
860 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
861 * If someone wants to dance at the edge, then they can raise the limit or use
862 * current libraries. */
863 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
864 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
865 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
866 dh_bitsize = DH_bits(dh);
867 #else
868 dh_bitsize = 8 * DH_size(dh);
869 #endif
870
871 /* Even if it is larger, we silently return success rather than cause things
872 * to fail out, so that a too-large DH will not knock out all TLS; it's a
873 * debatable choice. */
874 if (dh_bitsize > tls_dh_max_bits)
875 {
876 DEBUG(D_tls)
877 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
878 dh_bitsize, tls_dh_max_bits);
879 }
880 else
881 {
882 SSL_CTX_set_tmp_dh(sctx, dh);
883 DEBUG(D_tls)
884 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
885 dhexpanded ? dhexpanded : US"default", dh_bitsize);
886 }
887
888 DH_free(dh);
889 BIO_free(bio);
890
891 return TRUE;
892 }
893
894
895
896
897 /*************************************************
898 * Initialize for ECDH *
899 *************************************************/
900
901 /* Load parameters for ECDH encryption.
902
903 For now, we stick to NIST P-256 because: it's simple and easy to configure;
904 it avoids any patent issues that might bite redistributors; despite events in
905 the news and concerns over curve choices, we're not cryptographers, we're not
906 pretending to be, and this is "good enough" to be better than no support,
907 protecting against most adversaries. Given another year or two, there might
908 be sufficient clarity about a "right" way forward to let us make an informed
909 decision, instead of a knee-jerk reaction.
910
911 Longer-term, we should look at supporting both various named curves and
912 external files generated with "openssl ecparam", much as we do for init_dh().
913 We should also support "none" as a value, to explicitly avoid initialisation.
914
915 Patches welcome.
916
917 Arguments:
918 sctx The current SSL CTX (inbound or outbound)
919 host connected host, if client; NULL if server
920 errstr error string pointer
921
922 Returns: TRUE if OK (nothing to set up, or setup worked)
923 */
924
925 static BOOL
926 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
927 {
928 #ifdef OPENSSL_NO_ECDH
929 return TRUE;
930 #else
931
932 EC_KEY * ecdh;
933 uschar * exp_curve;
934 int nid;
935 BOOL rv;
936
937 if (host) /* No ECDH setup for clients, only for servers */
938 return TRUE;
939
940 # ifndef EXIM_HAVE_ECDH
941 DEBUG(D_tls)
942 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
943 return TRUE;
944 # else
945
946 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
947 return FALSE;
948 if (!exp_curve || !*exp_curve)
949 return TRUE;
950
951 /* "auto" needs to be handled carefully.
952 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
953 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
954 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
955 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
956 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
957 */
958 if (Ustrcmp(exp_curve, "auto") == 0)
959 {
960 #if OPENSSL_VERSION_NUMBER < 0x10002000L
961 DEBUG(D_tls) debug_printf(
962 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
963 exp_curve = US"prime256v1";
964 #else
965 # if defined SSL_CTRL_SET_ECDH_AUTO
966 DEBUG(D_tls) debug_printf(
967 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
968 SSL_CTX_set_ecdh_auto(sctx, 1);
969 return TRUE;
970 # else
971 DEBUG(D_tls) debug_printf(
972 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
973 return TRUE;
974 # endif
975 #endif
976 }
977
978 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
979 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
980 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
981 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
982 # endif
983 )
984 {
985 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
986 host, NULL, errstr);
987 return FALSE;
988 }
989
990 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
991 {
992 tls_error(US"Unable to create ec curve", host, NULL, errstr);
993 return FALSE;
994 }
995
996 /* The "tmp" in the name here refers to setting a temporary key
997 not to the stability of the interface. */
998
999 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
1000 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
1001 else
1002 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1003
1004 EC_KEY_free(ecdh);
1005 return !rv;
1006
1007 # endif /*EXIM_HAVE_ECDH*/
1008 #endif /*OPENSSL_NO_ECDH*/
1009 }
1010
1011
1012
1013
1014 #ifndef DISABLE_OCSP
1015 /*************************************************
1016 * Load OCSP information into state *
1017 *************************************************/
1018 /* Called to load the server OCSP response from the given file into memory, once
1019 caller has determined this is needed. Checks validity. Debugs a message
1020 if invalid.
1021
1022 ASSUMES: single response, for single cert.
1023
1024 Arguments:
1025 sctx the SSL_CTX* to update
1026 cbinfo various parts of session state
1027 expanded the filename putatively holding an OCSP response
1028
1029 */
1030
1031 static void
1032 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
1033 {
1034 BIO * bio;
1035 OCSP_RESPONSE * resp;
1036 OCSP_BASICRESP * basic_response;
1037 OCSP_SINGLERESP * single_response;
1038 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1039 STACK_OF(X509) * sk;
1040 unsigned long verify_flags;
1041 int status, reason, i;
1042
1043 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
1044 if (cbinfo->u_ocsp.server.response)
1045 {
1046 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
1047 cbinfo->u_ocsp.server.response = NULL;
1048 }
1049
1050 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
1051 {
1052 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1053 cbinfo->u_ocsp.server.file_expanded);
1054 return;
1055 }
1056
1057 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1058 BIO_free(bio);
1059 if (!resp)
1060 {
1061 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1062 return;
1063 }
1064
1065 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1066 {
1067 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1068 OCSP_response_status_str(status), status);
1069 goto bad;
1070 }
1071
1072 if (!(basic_response = OCSP_response_get1_basic(resp)))
1073 {
1074 DEBUG(D_tls)
1075 debug_printf("OCSP response parse error: unable to extract basic response.\n");
1076 goto bad;
1077 }
1078
1079 sk = cbinfo->verify_stack;
1080 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
1081
1082 /* May need to expose ability to adjust those flags?
1083 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
1084 OCSP_TRUSTOTHER OCSP_NOINTERN */
1085
1086 /* This does a full verify on the OCSP proof before we load it for serving
1087 up; possibly overkill - just date-checks might be nice enough.
1088
1089 OCSP_basic_verify takes a "store" arg, but does not
1090 use it for the chain verification, which is all we do
1091 when OCSP_NOVERIFY is set. The content from the wire
1092 "basic_response" and a cert-stack "sk" are all that is used.
1093
1094 We have a stack, loaded in setup_certs() if tls_verify_certificates
1095 was a file (not a directory, or "system"). It is unfortunate we
1096 cannot used the connection context store, as that would neatly
1097 handle the "system" case too, but there seems to be no library
1098 function for getting a stack from a store.
1099 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
1100 We do not free the stack since it could be needed a second time for
1101 SNI handling.
1102
1103 Separately we might try to replace using OCSP_basic_verify() - which seems to not
1104 be a public interface into the OpenSSL library (there's no manual entry) -
1105 But what with? We also use OCSP_basic_verify in the client stapling callback.
1106 And there we NEED it; we must verify that status... unless the
1107 library does it for us anyway? */
1108
1109 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
1110 {
1111 DEBUG(D_tls)
1112 {
1113 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1114 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
1115 }
1116 goto bad;
1117 }
1118
1119 /* Here's the simplifying assumption: there's only one response, for the
1120 one certificate we use, and nothing for anything else in a chain. If this
1121 proves false, we need to extract a cert id from our issued cert
1122 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
1123 right cert in the stack and then calls OCSP_single_get0_status()).
1124
1125 I'm hoping to avoid reworking a bunch more of how we handle state here. */
1126
1127 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1128 {
1129 DEBUG(D_tls)
1130 debug_printf("Unable to get first response from OCSP basic response.\n");
1131 goto bad;
1132 }
1133
1134 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1135 if (status != V_OCSP_CERTSTATUS_GOOD)
1136 {
1137 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
1138 OCSP_cert_status_str(status), status,
1139 OCSP_crl_reason_str(reason), reason);
1140 goto bad;
1141 }
1142
1143 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1144 {
1145 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1146 goto bad;
1147 }
1148
1149 supply_response:
1150 cbinfo->u_ocsp.server.response = resp; /*XXX stack?*/
1151 return;
1152
1153 bad:
1154 if (f.running_in_test_harness)
1155 {
1156 extern char ** environ;
1157 if (environ) for (uschar ** p = USS environ; *p; p++)
1158 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1159 {
1160 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1161 goto supply_response;
1162 }
1163 }
1164 return;
1165 }
1166 #endif /*!DISABLE_OCSP*/
1167
1168
1169
1170
1171 /* Create and install a selfsigned certificate, for use in server mode */
1172
1173 static int
1174 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1175 {
1176 X509 * x509 = NULL;
1177 EVP_PKEY * pkey;
1178 RSA * rsa;
1179 X509_NAME * name;
1180 uschar * where;
1181
1182 where = US"allocating pkey";
1183 if (!(pkey = EVP_PKEY_new()))
1184 goto err;
1185
1186 where = US"allocating cert";
1187 if (!(x509 = X509_new()))
1188 goto err;
1189
1190 where = US"generating pkey";
1191 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1192 goto err;
1193
1194 where = US"assigning pkey";
1195 if (!EVP_PKEY_assign_RSA(pkey, rsa))
1196 goto err;
1197
1198 X509_set_version(x509, 2); /* N+1 - version 3 */
1199 ASN1_INTEGER_set(X509_get_serialNumber(x509), 1);
1200 X509_gmtime_adj(X509_get_notBefore(x509), 0);
1201 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
1202 X509_set_pubkey(x509, pkey);
1203
1204 name = X509_get_subject_name(x509);
1205 X509_NAME_add_entry_by_txt(name, "C",
1206 MBSTRING_ASC, CUS "UK", -1, -1, 0);
1207 X509_NAME_add_entry_by_txt(name, "O",
1208 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1209 X509_NAME_add_entry_by_txt(name, "CN",
1210 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1211 X509_set_issuer_name(x509, name);
1212
1213 where = US"signing cert";
1214 if (!X509_sign(x509, pkey, EVP_md5()))
1215 goto err;
1216
1217 where = US"installing selfsign cert";
1218 if (!SSL_CTX_use_certificate(sctx, x509))
1219 goto err;
1220
1221 where = US"installing selfsign key";
1222 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1223 goto err;
1224
1225 return OK;
1226
1227 err:
1228 (void) tls_error(where, NULL, NULL, errstr);
1229 if (x509) X509_free(x509);
1230 if (pkey) EVP_PKEY_free(pkey);
1231 return DEFER;
1232 }
1233
1234
1235
1236
1237 static int
1238 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1239 uschar ** errstr)
1240 {
1241 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1242 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1243 return tls_error(string_sprintf(
1244 "SSL_CTX_use_certificate_chain_file file=%s", file),
1245 cbinfo->host, NULL, errstr);
1246 return 0;
1247 }
1248
1249 static int
1250 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1251 uschar ** errstr)
1252 {
1253 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1254 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1255 return tls_error(string_sprintf(
1256 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1257 return 0;
1258 }
1259
1260
1261 /*************************************************
1262 * Expand key and cert file specs *
1263 *************************************************/
1264
1265 /* Called once during tls_init and possibly again during TLS setup, for a
1266 new context, if Server Name Indication was used and tls_sni was seen in
1267 the certificate string.
1268
1269 Arguments:
1270 sctx the SSL_CTX* to update
1271 cbinfo various parts of session state
1272 errstr error string pointer
1273
1274 Returns: OK/DEFER/FAIL
1275 */
1276
1277 static int
1278 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1279 uschar ** errstr)
1280 {
1281 uschar *expanded;
1282
1283 if (!cbinfo->certificate)
1284 {
1285 if (!cbinfo->is_server) /* client */
1286 return OK;
1287 /* server */
1288 if (tls_install_selfsign(sctx, errstr) != OK)
1289 return DEFER;
1290 }
1291 else
1292 {
1293 int err;
1294
1295 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1296 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1297 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1298 )
1299 reexpand_tls_files_for_sni = TRUE;
1300
1301 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1302 return DEFER;
1303
1304 if (expanded)
1305 if (cbinfo->is_server)
1306 {
1307 const uschar * file_list = expanded;
1308 int sep = 0;
1309 uschar * file;
1310
1311 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1312 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1313 return err;
1314 }
1315 else /* would there ever be a need for multiple client certs? */
1316 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1317 return err;
1318
1319 if ( cbinfo->privatekey
1320 && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1321 return DEFER;
1322
1323 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1324 of the expansion is an empty string, ignore it also, and assume the private
1325 key is in the same file as the certificate. */
1326
1327 if (expanded && *expanded)
1328 if (cbinfo->is_server)
1329 {
1330 const uschar * file_list = expanded;
1331 int sep = 0;
1332 uschar * file;
1333
1334 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1335 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1336 return err;
1337 }
1338 else /* would there ever be a need for multiple client certs? */
1339 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1340 return err;
1341 }
1342
1343 #ifndef DISABLE_OCSP
1344 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1345 {
1346 /*XXX stack*/
1347 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1348 return DEFER;
1349
1350 if (expanded && *expanded)
1351 {
1352 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1353 if ( cbinfo->u_ocsp.server.file_expanded
1354 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1355 {
1356 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1357 }
1358 else
1359 ocsp_load_response(sctx, cbinfo, expanded);
1360 }
1361 }
1362 #endif
1363
1364 return OK;
1365 }
1366
1367
1368
1369
1370 /*************************************************
1371 * Callback to handle SNI *
1372 *************************************************/
1373
1374 /* Called when acting as server during the TLS session setup if a Server Name
1375 Indication extension was sent by the client.
1376
1377 API documentation is OpenSSL s_server.c implementation.
1378
1379 Arguments:
1380 s SSL* of the current session
1381 ad unknown (part of OpenSSL API) (unused)
1382 arg Callback of "our" registered data
1383
1384 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1385 */
1386
1387 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1388 static int
1389 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1390 {
1391 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1392 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1393 int rc;
1394 int old_pool = store_pool;
1395 uschar * dummy_errstr;
1396
1397 if (!servername)
1398 return SSL_TLSEXT_ERR_OK;
1399
1400 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1401 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1402
1403 /* Make the extension value available for expansion */
1404 store_pool = POOL_PERM;
1405 tls_in.sni = string_copy(US servername);
1406 store_pool = old_pool;
1407
1408 if (!reexpand_tls_files_for_sni)
1409 return SSL_TLSEXT_ERR_OK;
1410
1411 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1412 not confident that memcpy wouldn't break some internal reference counting.
1413 Especially since there's a references struct member, which would be off. */
1414
1415 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1416 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1417 #else
1418 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1419 #endif
1420 {
1421 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1422 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1423 goto bad;
1424 }
1425
1426 /* Not sure how many of these are actually needed, since SSL object
1427 already exists. Might even need this selfsame callback, for reneg? */
1428
1429 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1430 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1431 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1432 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1433 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1434 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1435
1436 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1437 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1438 )
1439 goto bad;
1440
1441 if ( cbinfo->server_cipher_list
1442 && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1443 goto bad;
1444
1445 #ifndef DISABLE_OCSP
1446 if (cbinfo->u_ocsp.server.file)
1447 {
1448 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1449 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1450 }
1451 #endif
1452
1453 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1454 verify_callback_server, &dummy_errstr)) != OK)
1455 goto bad;
1456
1457 /* do this after setup_certs, because this can require the certs for verifying
1458 OCSP information. */
1459 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1460 goto bad;
1461
1462 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1463 SSL_set_SSL_CTX(s, server_sni);
1464 return SSL_TLSEXT_ERR_OK;
1465
1466 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1467 }
1468 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1469
1470
1471
1472
1473 #ifndef DISABLE_OCSP
1474
1475 /*************************************************
1476 * Callback to handle OCSP Stapling *
1477 *************************************************/
1478
1479 /* Called when acting as server during the TLS session setup if the client
1480 requests OCSP information with a Certificate Status Request.
1481
1482 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1483 project.
1484
1485 */
1486
1487 static int
1488 tls_server_stapling_cb(SSL *s, void *arg)
1489 {
1490 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1491 uschar *response_der; /*XXX blob */
1492 int response_der_len;
1493
1494 /*XXX stack: use SSL_get_certificate() to see which cert; from that work
1495 out which ocsp blob to send. Unfortunately, SSL_get_certificate is known
1496 buggy in current OpenSSL; it returns the last cert loaded always rather than
1497 the one actually presented. So we can't support a stack of OCSP proofs at
1498 this time. */
1499
1500 DEBUG(D_tls)
1501 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1502 cbinfo->u_ocsp.server.response ? "have" : "lack");
1503
1504 tls_in.ocsp = OCSP_NOT_RESP;
1505 if (!cbinfo->u_ocsp.server.response)
1506 return SSL_TLSEXT_ERR_NOACK;
1507
1508 response_der = NULL;
1509 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response, /*XXX stack*/
1510 &response_der);
1511 if (response_der_len <= 0)
1512 return SSL_TLSEXT_ERR_NOACK;
1513
1514 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1515 tls_in.ocsp = OCSP_VFIED;
1516 return SSL_TLSEXT_ERR_OK;
1517 }
1518
1519
1520 static void
1521 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1522 {
1523 BIO_printf(bp, "\t%s: ", str);
1524 ASN1_GENERALIZEDTIME_print(bp, time);
1525 BIO_puts(bp, "\n");
1526 }
1527
1528 static int
1529 tls_client_stapling_cb(SSL *s, void *arg)
1530 {
1531 tls_ext_ctx_cb * cbinfo = arg;
1532 const unsigned char * p;
1533 int len;
1534 OCSP_RESPONSE * rsp;
1535 OCSP_BASICRESP * bs;
1536 int i;
1537
1538 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1539 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1540 if(!p)
1541 {
1542 /* Expect this when we requested ocsp but got none */
1543 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1544 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1545 else
1546 DEBUG(D_tls) debug_printf(" null\n");
1547 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1548 }
1549
1550 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1551 {
1552 tls_out.ocsp = OCSP_FAILED;
1553 if (LOGGING(tls_cipher))
1554 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1555 else
1556 DEBUG(D_tls) debug_printf(" parse error\n");
1557 return 0;
1558 }
1559
1560 if(!(bs = OCSP_response_get1_basic(rsp)))
1561 {
1562 tls_out.ocsp = OCSP_FAILED;
1563 if (LOGGING(tls_cipher))
1564 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1565 else
1566 DEBUG(D_tls) debug_printf(" error parsing response\n");
1567 OCSP_RESPONSE_free(rsp);
1568 return 0;
1569 }
1570
1571 /* We'd check the nonce here if we'd put one in the request. */
1572 /* However that would defeat cacheability on the server so we don't. */
1573
1574 /* This section of code reworked from OpenSSL apps source;
1575 The OpenSSL Project retains copyright:
1576 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1577 */
1578 {
1579 BIO * bp = NULL;
1580 int status, reason;
1581 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1582
1583 DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1584
1585 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1586
1587 /* Use the chain that verified the server cert to verify the stapled info */
1588 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1589
1590 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1591 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1592 {
1593 tls_out.ocsp = OCSP_FAILED;
1594 if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN,
1595 "Received TLS cert status response, itself unverifiable: %s",
1596 ERR_reason_error_string(ERR_peek_error()));
1597 BIO_printf(bp, "OCSP response verify failure\n");
1598 ERR_print_errors(bp);
1599 OCSP_RESPONSE_print(bp, rsp, 0);
1600 goto failed;
1601 }
1602
1603 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1604
1605 /*XXX So we have a good stapled OCSP status. How do we know
1606 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1607 OCSP_resp_find_status() which matches on a cert id, which presumably
1608 we should use. Making an id needs OCSP_cert_id_new(), which takes
1609 issuerName, issuerKey, serialNumber. Are they all in the cert?
1610
1611 For now, carry on blindly accepting the resp. */
1612
1613 {
1614 OCSP_SINGLERESP * single;
1615
1616 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1617 if (OCSP_resp_count(bs) != 1)
1618 #else
1619 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1620 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1621 #endif
1622 {
1623 tls_out.ocsp = OCSP_FAILED;
1624 log_write(0, LOG_MAIN, "OCSP stapling "
1625 "with multiple responses not handled");
1626 goto failed;
1627 }
1628 single = OCSP_resp_get0(bs, 0);
1629 status = OCSP_single_get0_status(single, &reason, &rev,
1630 &thisupd, &nextupd);
1631 }
1632
1633 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1634 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1635 if (!OCSP_check_validity(thisupd, nextupd,
1636 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1637 {
1638 tls_out.ocsp = OCSP_FAILED;
1639 DEBUG(D_tls) ERR_print_errors(bp);
1640 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1641 }
1642 else
1643 {
1644 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1645 OCSP_cert_status_str(status));
1646 switch(status)
1647 {
1648 case V_OCSP_CERTSTATUS_GOOD:
1649 tls_out.ocsp = OCSP_VFIED;
1650 i = 1;
1651 goto good;
1652 case V_OCSP_CERTSTATUS_REVOKED:
1653 tls_out.ocsp = OCSP_FAILED;
1654 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1655 reason != -1 ? "; reason: " : "",
1656 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1657 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1658 break;
1659 default:
1660 tls_out.ocsp = OCSP_FAILED;
1661 log_write(0, LOG_MAIN,
1662 "Server certificate status unknown, in OCSP stapling");
1663 break;
1664 }
1665 }
1666 failed:
1667 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1668 good:
1669 BIO_free(bp);
1670 }
1671
1672 OCSP_RESPONSE_free(rsp);
1673 return i;
1674 }
1675 #endif /*!DISABLE_OCSP*/
1676
1677
1678 /*************************************************
1679 * Initialize for TLS *
1680 *************************************************/
1681
1682 /* Called from both server and client code, to do preliminary initialization
1683 of the library. We allocate and return a context structure.
1684
1685 Arguments:
1686 ctxp returned SSL context
1687 host connected host, if client; NULL if server
1688 dhparam DH parameter file
1689 certificate certificate file
1690 privatekey private key
1691 ocsp_file file of stapling info (server); flag for require ocsp (client)
1692 addr address if client; NULL if server (for some randomness)
1693 cbp place to put allocated callback context
1694 errstr error string pointer
1695
1696 Returns: OK/DEFER/FAIL
1697 */
1698
1699 static int
1700 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1701 uschar *privatekey,
1702 #ifndef DISABLE_OCSP
1703 uschar *ocsp_file, /*XXX stack, in server*/
1704 #endif
1705 address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1706 {
1707 SSL_CTX * ctx;
1708 long init_options;
1709 int rc;
1710 tls_ext_ctx_cb * cbinfo;
1711
1712 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1713 cbinfo->certificate = certificate;
1714 cbinfo->privatekey = privatekey;
1715 cbinfo->is_server = host==NULL;
1716 #ifndef DISABLE_OCSP
1717 cbinfo->verify_stack = NULL;
1718 if (!host)
1719 {
1720 cbinfo->u_ocsp.server.file = ocsp_file;
1721 cbinfo->u_ocsp.server.file_expanded = NULL;
1722 cbinfo->u_ocsp.server.response = NULL;
1723 }
1724 else
1725 cbinfo->u_ocsp.client.verify_store = NULL;
1726 #endif
1727 cbinfo->dhparam = dhparam;
1728 cbinfo->server_cipher_list = NULL;
1729 cbinfo->host = host;
1730 #ifndef DISABLE_EVENT
1731 cbinfo->event_action = NULL;
1732 #endif
1733
1734 #ifdef EXIM_NEED_OPENSSL_INIT
1735 SSL_load_error_strings(); /* basic set up */
1736 OpenSSL_add_ssl_algorithms();
1737 #endif
1738
1739 #ifdef EXIM_HAVE_SHA256
1740 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1741 list of available digests. */
1742 EVP_add_digest(EVP_sha256());
1743 #endif
1744
1745 /* Create a context.
1746 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1747 negotiation in the different methods; as far as I can tell, the only
1748 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1749 when OpenSSL is built without SSLv2 support.
1750 By disabling with openssl_options, we can let admins re-enable with the
1751 existing knob. */
1752
1753 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1754 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
1755 #else
1756 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1757 #endif
1758 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1759
1760 /* It turns out that we need to seed the random number generator this early in
1761 order to get the full complement of ciphers to work. It took me roughly a day
1762 of work to discover this by experiment.
1763
1764 On systems that have /dev/urandom, SSL may automatically seed itself from
1765 there. Otherwise, we have to make something up as best we can. Double check
1766 afterwards. */
1767
1768 if (!RAND_status())
1769 {
1770 randstuff r;
1771 gettimeofday(&r.tv, NULL);
1772 r.p = getpid();
1773
1774 RAND_seed(US (&r), sizeof(r));
1775 RAND_seed(US big_buffer, big_buffer_size);
1776 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1777
1778 if (!RAND_status())
1779 return tls_error(US"RAND_status", host,
1780 US"unable to seed random number generator", errstr);
1781 }
1782
1783 /* Set up the information callback, which outputs if debugging is at a suitable
1784 level. */
1785
1786 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1787 #ifdef OPENSSL_HAVE_KEYLOG_CB
1788 DEBUG(D_tls) SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
1789 #endif
1790
1791 /* Automatically re-try reads/writes after renegotiation. */
1792 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1793
1794 /* Apply administrator-supplied work-arounds.
1795 Historically we applied just one requested option,
1796 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1797 moved to an administrator-controlled list of options to specify and
1798 grandfathered in the first one as the default value for "openssl_options".
1799
1800 No OpenSSL version number checks: the options we accept depend upon the
1801 availability of the option value macros from OpenSSL. */
1802
1803 if (!tls_openssl_options_parse(openssl_options, &init_options))
1804 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1805
1806 if (init_options)
1807 {
1808 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1809 if (!(SSL_CTX_set_options(ctx, init_options)))
1810 return tls_error(string_sprintf(
1811 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1812 }
1813 else
1814 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1815
1816 #ifdef OPENSSL_HAVE_NUM_TICKETS
1817 SSL_CTX_set_num_tickets(ctx, 0); /* send no TLS1.3 stateful-tickets */
1818 #endif
1819
1820 /* We'd like to disable session cache unconditionally, but foolish Outlook
1821 Express clients then give up the first TLS connection and make a second one
1822 (which works). Only when there is an IMAP service on the same machine.
1823 Presumably OE is trying to use the cache for A on B. Leave it enabled for
1824 now, until we work out a decent way of presenting control to the config. It
1825 will never be used because we use a new context every time. */
1826 #ifdef notdef
1827 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1828 #endif
1829
1830 /* Initialize with DH parameters if supplied */
1831 /* Initialize ECDH temp key parameter selection */
1832
1833 if ( !init_dh(ctx, dhparam, host, errstr)
1834 || !init_ecdh(ctx, host, errstr)
1835 )
1836 return DEFER;
1837
1838 /* Set up certificate and key (and perhaps OCSP info) */
1839
1840 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1841 return rc;
1842
1843 /* If we need to handle SNI or OCSP, do so */
1844
1845 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1846 # ifndef DISABLE_OCSP
1847 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1848 {
1849 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1850 return FAIL;
1851 }
1852 # endif
1853
1854 if (!host) /* server */
1855 {
1856 # ifndef DISABLE_OCSP
1857 /* We check u_ocsp.server.file, not server.response, because we care about if
1858 the option exists, not what the current expansion might be, as SNI might
1859 change the certificate and OCSP file in use between now and the time the
1860 callback is invoked. */
1861 if (cbinfo->u_ocsp.server.file)
1862 {
1863 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1864 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1865 }
1866 # endif
1867 /* We always do this, so that $tls_sni is available even if not used in
1868 tls_certificate */
1869 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1870 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1871 }
1872 # ifndef DISABLE_OCSP
1873 else /* client */
1874 if(ocsp_file) /* wanting stapling */
1875 {
1876 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1877 {
1878 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1879 return FAIL;
1880 }
1881 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1882 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1883 }
1884 # endif
1885 #endif
1886
1887 cbinfo->verify_cert_hostnames = NULL;
1888
1889 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1890 /* Set up the RSA callback */
1891 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1892 #endif
1893
1894 /* Finally, set the timeout, and we are done */
1895
1896 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1897 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1898
1899 *cbp = cbinfo;
1900 *ctxp = ctx;
1901
1902 return OK;
1903 }
1904
1905
1906
1907
1908 /*************************************************
1909 * Get name of cipher in use *
1910 *************************************************/
1911
1912 /*
1913 Argument: pointer to an SSL structure for the connection
1914 buffer to use for answer
1915 size of buffer
1916 pointer to number of bits for cipher
1917 Returns: nothing
1918 */
1919
1920 static void
1921 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1922 {
1923 /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't
1924 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1925 the accessor functions use const in the prototype. */
1926
1927 const uschar * ver = CUS SSL_get_version(ssl);
1928 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1929
1930 SSL_CIPHER_get_bits(c, bits);
1931
1932 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1933 SSL_CIPHER_get_name(c), *bits);
1934
1935 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1936 }
1937
1938
1939 static void
1940 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
1941 {
1942 /*XXX we might consider a list-of-certs variable for the cert chain.
1943 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1944 in list-handling functions, also consider the difference between the entire
1945 chain and the elements sent by the peer. */
1946
1947 tlsp->peerdn = NULL;
1948
1949 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1950 if (!tlsp->peercert)
1951 tlsp->peercert = SSL_get_peer_certificate(ssl);
1952 /* Beware anonymous ciphers which lead to server_cert being NULL */
1953 if (tlsp->peercert)
1954 if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz))
1955 { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); }
1956 else
1957 {
1958 peerdn[siz-1] = '\0';
1959 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1960 }
1961 }
1962
1963
1964
1965
1966
1967 /*************************************************
1968 * Set up for verifying certificates *
1969 *************************************************/
1970
1971 #ifndef DISABLE_OCSP
1972 /* Load certs from file, return TRUE on success */
1973
1974 static BOOL
1975 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
1976 {
1977 BIO * bp;
1978 X509 * x;
1979
1980 while (sk_X509_num(verify_stack) > 0)
1981 X509_free(sk_X509_pop(verify_stack));
1982
1983 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
1984 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
1985 sk_X509_push(verify_stack, x);
1986 BIO_free(bp);
1987 return TRUE;
1988 }
1989 #endif
1990
1991
1992
1993 /* Called by both client and server startup; on the server possibly
1994 repeated after a Server Name Indication.
1995
1996 Arguments:
1997 sctx SSL_CTX* to initialise
1998 certs certs file or NULL
1999 crl CRL file or NULL
2000 host NULL in a server; the remote host in a client
2001 optional TRUE if called from a server for a host in tls_try_verify_hosts;
2002 otherwise passed as FALSE
2003 cert_vfy_cb Callback function for certificate verification
2004 errstr error string pointer
2005
2006 Returns: OK/DEFER/FAIL
2007 */
2008
2009 static int
2010 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
2011 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
2012 {
2013 uschar *expcerts, *expcrl;
2014
2015 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2016 return DEFER;
2017 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2018
2019 if (expcerts && *expcerts)
2020 {
2021 /* Tell the library to use its compiled-in location for the system default
2022 CA bundle. Then add the ones specified in the config, if any. */
2023
2024 if (!SSL_CTX_set_default_verify_paths(sctx))
2025 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2026
2027 if (Ustrcmp(expcerts, "system") != 0)
2028 {
2029 struct stat statbuf;
2030
2031 if (Ustat(expcerts, &statbuf) < 0)
2032 {
2033 log_write(0, LOG_MAIN|LOG_PANIC,
2034 "failed to stat %s for certificates", expcerts);
2035 return DEFER;
2036 }
2037 else
2038 {
2039 uschar *file, *dir;
2040 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2041 { file = NULL; dir = expcerts; }
2042 else
2043 {
2044 file = expcerts; dir = NULL;
2045 #ifndef DISABLE_OCSP
2046 /* In the server if we will be offering an OCSP proof, load chain from
2047 file for verifying the OCSP proof at load time. */
2048
2049 if ( !host
2050 && statbuf.st_size > 0
2051 && server_static_cbinfo->u_ocsp.server.file
2052 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2053 )
2054 {
2055 log_write(0, LOG_MAIN|LOG_PANIC,
2056 "failed to load cert chain from %s", file);
2057 return DEFER;
2058 }
2059 #endif
2060 }
2061
2062 /* If a certificate file is empty, the next function fails with an
2063 unhelpful error message. If we skip it, we get the correct behaviour (no
2064 certificates are recognized, but the error message is still misleading (it
2065 says no certificate was supplied). But this is better. */
2066
2067 if ( (!file || statbuf.st_size > 0)
2068 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
2069 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
2070
2071 /* Load the list of CAs for which we will accept certs, for sending
2072 to the client. This is only for the one-file tls_verify_certificates
2073 variant.
2074 If a list isn't loaded into the server, but some verify locations are set,
2075 the server end appears to make a wildcard request for client certs.
2076 Meanwhile, the client library as default behaviour *ignores* the list
2077 we send over the wire - see man SSL_CTX_set_client_cert_cb.
2078 Because of this, and that the dir variant is likely only used for
2079 the public-CA bundle (not for a private CA), not worth fixing. */
2080
2081 if (file)
2082 {
2083 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
2084
2085 SSL_CTX_set_client_CA_list(sctx, names);
2086 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
2087 sk_X509_NAME_num(names));
2088 }
2089 }
2090 }
2091
2092 /* Handle a certificate revocation list. */
2093
2094 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2095
2096 /* This bit of code is now the version supplied by Lars Mainka. (I have
2097 merely reformatted it into the Exim code style.)
2098
2099 "From here I changed the code to add support for multiple crl's
2100 in pem format in one file or to support hashed directory entries in
2101 pem format instead of a file. This method now uses the library function
2102 X509_STORE_load_locations to add the CRL location to the SSL context.
2103 OpenSSL will then handle the verify against CA certs and CRLs by
2104 itself in the verify callback." */
2105
2106 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2107 if (expcrl && *expcrl)
2108 {
2109 struct stat statbufcrl;
2110 if (Ustat(expcrl, &statbufcrl) < 0)
2111 {
2112 log_write(0, LOG_MAIN|LOG_PANIC,
2113 "failed to stat %s for certificates revocation lists", expcrl);
2114 return DEFER;
2115 }
2116 else
2117 {
2118 /* is it a file or directory? */
2119 uschar *file, *dir;
2120 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2121 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2122 {
2123 file = NULL;
2124 dir = expcrl;
2125 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2126 }
2127 else
2128 {
2129 file = expcrl;
2130 dir = NULL;
2131 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2132 }
2133 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2134 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2135
2136 /* setting the flags to check against the complete crl chain */
2137
2138 X509_STORE_set_flags(cvstore,
2139 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2140 }
2141 }
2142
2143 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2144
2145 /* If verification is optional, don't fail if no certificate */
2146
2147 SSL_CTX_set_verify(sctx,
2148 SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2149 cert_vfy_cb);
2150 }
2151
2152 return OK;
2153 }
2154
2155
2156
2157 /*************************************************
2158 * Start a TLS session in a server *
2159 *************************************************/
2160
2161 /* This is called when Exim is running as a server, after having received
2162 the STARTTLS command. It must respond to that command, and then negotiate
2163 a TLS session.
2164
2165 Arguments:
2166 require_ciphers allowed ciphers
2167 errstr pointer to error message
2168
2169 Returns: OK on success
2170 DEFER for errors before the start of the negotiation
2171 FAIL for errors during the negotiation; the server can't
2172 continue running.
2173 */
2174
2175 int
2176 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2177 {
2178 int rc;
2179 uschar * expciphers;
2180 tls_ext_ctx_cb * cbinfo;
2181 static uschar peerdn[256];
2182 static uschar cipherbuf[256];
2183
2184 /* Check for previous activation */
2185
2186 if (tls_in.active.sock >= 0)
2187 {
2188 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2189 smtp_printf("554 Already in TLS\r\n", FALSE);
2190 return FAIL;
2191 }
2192
2193 /* Initialize the SSL library. If it fails, it will already have logged
2194 the error. */
2195
2196 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2197 #ifndef DISABLE_OCSP
2198 tls_ocsp_file, /*XXX stack*/
2199 #endif
2200 NULL, &server_static_cbinfo, errstr);
2201 if (rc != OK) return rc;
2202 cbinfo = server_static_cbinfo;
2203
2204 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
2205 return FAIL;
2206
2207 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2208 were historically separated by underscores. So that I can use either form in my
2209 tests, and also for general convenience, we turn underscores into hyphens here.
2210
2211 XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites()
2212 for TLS 1.3 . Since we do not call it at present we get the default list:
2213 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
2214 */
2215
2216 if (expciphers)
2217 {
2218 uschar * s = expciphers;
2219 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2220 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2221 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
2222 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
2223 cbinfo->server_cipher_list = expciphers;
2224 }
2225
2226 /* If this is a host for which certificate verification is mandatory or
2227 optional, set up appropriately. */
2228
2229 tls_in.certificate_verified = FALSE;
2230 #ifdef SUPPORT_DANE
2231 tls_in.dane_verified = FALSE;
2232 #endif
2233 server_verify_callback_called = FALSE;
2234
2235 if (verify_check_host(&tls_verify_hosts) == OK)
2236 {
2237 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2238 FALSE, verify_callback_server, errstr);
2239 if (rc != OK) return rc;
2240 server_verify_optional = FALSE;
2241 }
2242 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2243 {
2244 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2245 TRUE, verify_callback_server, errstr);
2246 if (rc != OK) return rc;
2247 server_verify_optional = TRUE;
2248 }
2249
2250 /* Prepare for new connection */
2251
2252 if (!(server_ssl = SSL_new(server_ctx)))
2253 return tls_error(US"SSL_new", NULL, NULL, errstr);
2254
2255 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2256 *
2257 * With the SSL_clear(), we get strange interoperability bugs with
2258 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2259 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2260 *
2261 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2262 * session shutdown. In this case, we have a brand new object and there's no
2263 * obvious reason to immediately clear it. I'm guessing that this was
2264 * originally added because of incomplete initialisation which the clear fixed,
2265 * in some historic release.
2266 */
2267
2268 /* Set context and tell client to go ahead, except in the case of TLS startup
2269 on connection, where outputting anything now upsets the clients and tends to
2270 make them disconnect. We need to have an explicit fflush() here, to force out
2271 the response. Other smtp_printf() calls do not need it, because in non-TLS
2272 mode, the fflush() happens when smtp_getc() is called. */
2273
2274 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2275 if (!tls_in.on_connect)
2276 {
2277 smtp_printf("220 TLS go ahead\r\n", FALSE);
2278 fflush(smtp_out);
2279 }
2280
2281 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2282 that the OpenSSL library doesn't. */
2283
2284 SSL_set_wfd(server_ssl, fileno(smtp_out));
2285 SSL_set_rfd(server_ssl, fileno(smtp_in));
2286 SSL_set_accept_state(server_ssl);
2287
2288 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2289
2290 sigalrm_seen = FALSE;
2291 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2292 rc = SSL_accept(server_ssl);
2293 ALARM_CLR(0);
2294
2295 if (rc <= 0)
2296 {
2297 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2298 return FAIL;
2299 }
2300
2301 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2302
2303 /* TLS has been set up. Adjust the input functions to read via TLS,
2304 and initialize things. */
2305
2306 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2307
2308 DEBUG(D_tls)
2309 {
2310 uschar buf[2048];
2311 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
2312 debug_printf("Shared ciphers: %s\n", buf);
2313
2314 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2315 {
2316 BIO * bp = BIO_new(BIO_s_mem());
2317 uschar * s;
2318 int len;
2319 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2320 len = (int) BIO_get_mem_data(bp, CSS &s);
2321 debug_printf("%.*s", len, s);
2322 BIO_free(bp);
2323 }
2324 #endif
2325 }
2326
2327 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
2328 tls_in.cipher = cipherbuf;
2329
2330 /* Record the certificate we presented */
2331 {
2332 X509 * crt = SSL_get_certificate(server_ssl);
2333 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2334 }
2335
2336 /* Only used by the server-side tls (tls_in), including tls_getc.
2337 Client-side (tls_out) reads (seem to?) go via
2338 smtp_read_response()/ip_recv().
2339 Hence no need to duplicate for _in and _out.
2340 */
2341 if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2342 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2343 ssl_xfer_eof = ssl_xfer_error = FALSE;
2344
2345 receive_getc = tls_getc;
2346 receive_getbuf = tls_getbuf;
2347 receive_get_cache = tls_get_cache;
2348 receive_ungetc = tls_ungetc;
2349 receive_feof = tls_feof;
2350 receive_ferror = tls_ferror;
2351 receive_smtp_buffered = tls_smtp_buffered;
2352
2353 tls_in.active.sock = fileno(smtp_out);
2354 tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */
2355 return OK;
2356 }
2357
2358
2359
2360
2361 static int
2362 tls_client_basic_ctx_init(SSL_CTX * ctx,
2363 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2364 uschar ** errstr)
2365 {
2366 int rc;
2367 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2368 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2369 the specified host patterns if one of them is defined */
2370
2371 if ( ( !ob->tls_verify_hosts
2372 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2373 )
2374 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2375 )
2376 client_verify_optional = FALSE;
2377 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2378 client_verify_optional = TRUE;
2379 else
2380 return OK;
2381
2382 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2383 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2384 errstr)) != OK)
2385 return rc;
2386
2387 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2388 {
2389 cbinfo->verify_cert_hostnames =
2390 #ifdef SUPPORT_I18N
2391 string_domain_utf8_to_alabel(host->name, NULL);
2392 #else
2393 host->name;
2394 #endif
2395 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2396 cbinfo->verify_cert_hostnames);
2397 }
2398 return OK;
2399 }
2400
2401
2402 #ifdef SUPPORT_DANE
2403 static int
2404 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2405 {
2406 dns_scan dnss;
2407 const char * hostnames[2] = { CS host->name, NULL };
2408 int found = 0;
2409
2410 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2411 return tls_error(US"hostnames load", host, NULL, errstr);
2412
2413 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2414 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2415 ) if (rr->type == T_TLSA && rr->size > 3)
2416 {
2417 const uschar * p = rr->data;
2418 uint8_t usage, selector, mtype;
2419 const char * mdname;
2420
2421 usage = *p++;
2422
2423 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2424 if (usage != 2 && usage != 3) continue;
2425
2426 selector = *p++;
2427 mtype = *p++;
2428
2429 switch (mtype)
2430 {
2431 default: continue; /* Only match-types 0, 1, 2 are supported */
2432 case 0: mdname = NULL; break;
2433 case 1: mdname = "sha256"; break;
2434 case 2: mdname = "sha512"; break;
2435 }
2436
2437 found++;
2438 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2439 {
2440 default:
2441 return tls_error(US"tlsa load", host, NULL, errstr);
2442 case 0: /* action not taken */
2443 case 1: break;
2444 }
2445
2446 tls_out.tlsa_usage |= 1<<usage;
2447 }
2448
2449 if (found)
2450 return OK;
2451
2452 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2453 return DEFER;
2454 }
2455 #endif /*SUPPORT_DANE*/
2456
2457
2458
2459 /*************************************************
2460 * Start a TLS session in a client *
2461 *************************************************/
2462
2463 /* Called from the smtp transport after STARTTLS has been accepted.
2464
2465 Argument:
2466 fd the fd of the connection
2467 host connected host (for messages and option-tests)
2468 addr the first address (for some randomness; can be NULL)
2469 tb transport (always smtp)
2470 tlsa_dnsa tlsa lookup, if DANE, else null
2471 tlsp record details of channel configuration here; must be non-NULL
2472 errstr error string pointer
2473
2474 Returns: Pointer to TLS session context, or NULL on error
2475 */
2476
2477 void *
2478 tls_client_start(int fd, host_item *host, address_item *addr,
2479 transport_instance * tb,
2480 #ifdef SUPPORT_DANE
2481 dns_answer * tlsa_dnsa,
2482 #endif
2483 tls_support * tlsp, uschar ** errstr)
2484 {
2485 smtp_transport_options_block * ob = tb
2486 ? (smtp_transport_options_block *)tb->options_block
2487 : &smtp_transport_option_defaults;
2488 exim_openssl_client_tls_ctx * exim_client_ctx;
2489 static uschar peerdn[256];
2490 uschar * expciphers;
2491 int rc;
2492 static uschar cipherbuf[256];
2493
2494 #ifndef DISABLE_OCSP
2495 BOOL request_ocsp = FALSE;
2496 BOOL require_ocsp = FALSE;
2497 #endif
2498
2499 rc = store_pool;
2500 store_pool = POOL_PERM;
2501 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx));
2502 store_pool = rc;
2503
2504 #ifdef SUPPORT_DANE
2505 tlsp->tlsa_usage = 0;
2506 #endif
2507
2508 #ifndef DISABLE_OCSP
2509 {
2510 # ifdef SUPPORT_DANE
2511 if ( tlsa_dnsa
2512 && ob->hosts_request_ocsp[0] == '*'
2513 && ob->hosts_request_ocsp[1] == '\0'
2514 )
2515 {
2516 /* Unchanged from default. Use a safer one under DANE */
2517 request_ocsp = TRUE;
2518 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2519 " {= {4}{$tls_out_tlsa_usage}} } "
2520 " {*}{}}";
2521 }
2522 # endif
2523
2524 if ((require_ocsp =
2525 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
2526 request_ocsp = TRUE;
2527 else
2528 # ifdef SUPPORT_DANE
2529 if (!request_ocsp)
2530 # endif
2531 request_ocsp =
2532 verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2533 }
2534 #endif
2535
2536 rc = tls_init(&exim_client_ctx->ctx, host, NULL,
2537 ob->tls_certificate, ob->tls_privatekey,
2538 #ifndef DISABLE_OCSP
2539 (void *)(long)request_ocsp,
2540 #endif
2541 addr, &client_static_cbinfo, errstr);
2542 if (rc != OK) return NULL;
2543
2544 tlsp->certificate_verified = FALSE;
2545 client_verify_callback_called = FALSE;
2546
2547 expciphers = NULL;
2548 #ifdef SUPPORT_DANE
2549 if (tlsa_dnsa)
2550 {
2551 /* We fall back to tls_require_ciphers if unset, empty or forced failure, but
2552 other failures should be treated as problems. */
2553 if (ob->dane_require_tls_ciphers &&
2554 !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2555 &expciphers, errstr))
2556 return NULL;
2557 if (expciphers && *expciphers == '\0')
2558 expciphers = NULL;
2559 }
2560 #endif
2561 if (!expciphers &&
2562 !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2563 &expciphers, errstr))
2564 return NULL;
2565
2566 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2567 are separated by underscores. So that I can use either form in my tests, and
2568 also for general convenience, we turn underscores into hyphens here. */
2569
2570 if (expciphers)
2571 {
2572 uschar *s = expciphers;
2573 while (*s) { if (*s == '_') *s = '-'; s++; }
2574 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2575 if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers))
2576 {
2577 tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2578 return NULL;
2579 }
2580 }
2581
2582 #ifdef SUPPORT_DANE
2583 if (tlsa_dnsa)
2584 {
2585 SSL_CTX_set_verify(exim_client_ctx->ctx,
2586 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2587 verify_callback_client_dane);
2588
2589 if (!DANESSL_library_init())
2590 {
2591 tls_error(US"library init", host, NULL, errstr);
2592 return NULL;
2593 }
2594 if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
2595 {
2596 tls_error(US"context init", host, NULL, errstr);
2597 return NULL;
2598 }
2599 }
2600 else
2601
2602 #endif
2603
2604 if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
2605 client_static_cbinfo, errstr) != OK)
2606 return NULL;
2607
2608 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
2609 {
2610 tls_error(US"SSL_new", host, NULL, errstr);
2611 return NULL;
2612 }
2613 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
2614 SSL_set_fd(exim_client_ctx->ssl, fd);
2615 SSL_set_connect_state(exim_client_ctx->ssl);
2616
2617 if (ob->tls_sni)
2618 {
2619 if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
2620 return NULL;
2621 if (!tlsp->sni)
2622 {
2623 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2624 }
2625 else if (!Ustrlen(tlsp->sni))
2626 tlsp->sni = NULL;
2627 else
2628 {
2629 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2630 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni);
2631 SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni);
2632 #else
2633 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2634 tlsp->sni);
2635 #endif
2636 }
2637 }
2638
2639 #ifdef SUPPORT_DANE
2640 if (tlsa_dnsa)
2641 if (dane_tlsa_load(exim_client_ctx->ssl, host, tlsa_dnsa, errstr) != OK)
2642 return NULL;
2643 #endif
2644
2645 #ifndef DISABLE_OCSP
2646 /* Request certificate status at connection-time. If the server
2647 does OCSP stapling we will get the callback (set in tls_init()) */
2648 # ifdef SUPPORT_DANE
2649 if (request_ocsp)
2650 {
2651 const uschar * s;
2652 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2653 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2654 )
2655 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2656 this means we avoid the OCSP request, we wasted the setup
2657 cost in tls_init(). */
2658 require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2659 request_ocsp = require_ocsp
2660 || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2661 }
2662 }
2663 # endif
2664
2665 if (request_ocsp)
2666 {
2667 SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp);
2668 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2669 tlsp->ocsp = OCSP_NOT_RESP;
2670 }
2671 #endif
2672
2673 #ifndef DISABLE_EVENT
2674 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
2675 #endif
2676
2677 /* There doesn't seem to be a built-in timeout on connection. */
2678
2679 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2680 sigalrm_seen = FALSE;
2681 ALARM(ob->command_timeout);
2682 rc = SSL_connect(exim_client_ctx->ssl);
2683 ALARM_CLR(0);
2684
2685 #ifdef SUPPORT_DANE
2686 if (tlsa_dnsa)
2687 DANESSL_cleanup(exim_client_ctx->ssl);
2688 #endif
2689
2690 if (rc <= 0)
2691 {
2692 tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
2693 return NULL;
2694 }
2695
2696 DEBUG(D_tls)
2697 {
2698 debug_printf("SSL_connect succeeded\n");
2699 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2700 {
2701 BIO * bp = BIO_new(BIO_s_mem());
2702 uschar * s;
2703 int len;
2704 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2705 len = (int) BIO_get_mem_data(bp, CSS &s);
2706 debug_printf("%.*s", len, s);
2707 BIO_free(bp);
2708 }
2709 #endif
2710 }
2711
2712 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
2713
2714 construct_cipher_name(exim_client_ctx->ssl, cipherbuf, sizeof(cipherbuf), &tlsp->bits);
2715 tlsp->cipher = cipherbuf;
2716
2717 /* Record the certificate we presented */
2718 {
2719 X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
2720 tlsp->ourcert = crt ? X509_dup(crt) : NULL;
2721 }
2722
2723 tlsp->active.sock = fd;
2724 tlsp->active.tls_ctx = exim_client_ctx;
2725 return exim_client_ctx;
2726 }
2727
2728
2729
2730
2731
2732 static BOOL
2733 tls_refill(unsigned lim)
2734 {
2735 int error;
2736 int inbytes;
2737
2738 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2739 ssl_xfer_buffer, ssl_xfer_buffer_size);
2740
2741 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2742 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2743 MIN(ssl_xfer_buffer_size, lim));
2744 error = SSL_get_error(server_ssl, inbytes);
2745 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2746
2747 if (had_command_timeout) /* set by signal handler */
2748 smtp_command_timeout_exit(); /* does not return */
2749 if (had_command_sigterm)
2750 smtp_command_sigterm_exit();
2751 if (had_data_timeout)
2752 smtp_data_timeout_exit();
2753 if (had_data_sigint)
2754 smtp_data_sigint_exit();
2755
2756 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2757 closed down, not that the socket itself has been closed down. Revert to
2758 non-SSL handling. */
2759
2760 switch(error)
2761 {
2762 case SSL_ERROR_NONE:
2763 break;
2764
2765 case SSL_ERROR_ZERO_RETURN:
2766 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2767
2768 receive_getc = smtp_getc;
2769 receive_getbuf = smtp_getbuf;
2770 receive_get_cache = smtp_get_cache;
2771 receive_ungetc = smtp_ungetc;
2772 receive_feof = smtp_feof;
2773 receive_ferror = smtp_ferror;
2774 receive_smtp_buffered = smtp_buffered;
2775
2776 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
2777 SSL_shutdown(server_ssl);
2778
2779 #ifndef DISABLE_OCSP
2780 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
2781 server_static_cbinfo->verify_stack = NULL;
2782 #endif
2783 SSL_free(server_ssl);
2784 SSL_CTX_free(server_ctx);
2785 server_ctx = NULL;
2786 server_ssl = NULL;
2787 tls_in.active.sock = -1;
2788 tls_in.active.tls_ctx = NULL;
2789 tls_in.bits = 0;
2790 tls_in.cipher = NULL;
2791 tls_in.peerdn = NULL;
2792 tls_in.sni = NULL;
2793
2794 return FALSE;
2795
2796 /* Handle genuine errors */
2797 case SSL_ERROR_SSL:
2798 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
2799 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2800 ssl_xfer_error = TRUE;
2801 return FALSE;
2802
2803 default:
2804 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2805 DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL)
2806 debug_printf(" - syscall %s\n", strerror(errno));
2807 ssl_xfer_error = TRUE;
2808 return FALSE;
2809 }
2810
2811 #ifndef DISABLE_DKIM
2812 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2813 #endif
2814 ssl_xfer_buffer_hwm = inbytes;
2815 ssl_xfer_buffer_lwm = 0;
2816 return TRUE;
2817 }
2818
2819
2820 /*************************************************
2821 * TLS version of getc *
2822 *************************************************/
2823
2824 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2825 it refills the buffer via the SSL reading function.
2826
2827 Arguments: lim Maximum amount to read/buffer
2828 Returns: the next character or EOF
2829
2830 Only used by the server-side TLS.
2831 */
2832
2833 int
2834 tls_getc(unsigned lim)
2835 {
2836 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2837 if (!tls_refill(lim))
2838 return ssl_xfer_error ? EOF : smtp_getc(lim);
2839
2840 /* Something in the buffer; return next uschar */
2841
2842 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2843 }
2844
2845 uschar *
2846 tls_getbuf(unsigned * len)
2847 {
2848 unsigned size;
2849 uschar * buf;
2850
2851 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2852 if (!tls_refill(*len))
2853 {
2854 if (!ssl_xfer_error) return smtp_getbuf(len);
2855 *len = 0;
2856 return NULL;
2857 }
2858
2859 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2860 size = *len;
2861 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2862 ssl_xfer_buffer_lwm += size;
2863 *len = size;
2864 return buf;
2865 }
2866
2867
2868 void
2869 tls_get_cache()
2870 {
2871 #ifndef DISABLE_DKIM
2872 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2873 if (n > 0)
2874 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2875 #endif
2876 }
2877
2878
2879 BOOL
2880 tls_could_read(void)
2881 {
2882 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2883 }
2884
2885
2886 /*************************************************
2887 * Read bytes from TLS channel *
2888 *************************************************/
2889
2890 /*
2891 Arguments:
2892 ct_ctx client context pointer, or NULL for the one global server context
2893 buff buffer of data
2894 len size of buffer
2895
2896 Returns: the number of bytes read
2897 -1 after a failed read, including EOF
2898
2899 Only used by the client-side TLS.
2900 */
2901
2902 int
2903 tls_read(void * ct_ctx, uschar *buff, size_t len)
2904 {
2905 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2906 int inbytes;
2907 int error;
2908
2909 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2910 buff, (unsigned int)len);
2911
2912 inbytes = SSL_read(ssl, CS buff, len);
2913 error = SSL_get_error(ssl, inbytes);
2914
2915 if (error == SSL_ERROR_ZERO_RETURN)
2916 {
2917 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2918 return -1;
2919 }
2920 else if (error != SSL_ERROR_NONE)
2921 return -1;
2922
2923 return inbytes;
2924 }
2925
2926
2927
2928
2929
2930 /*************************************************
2931 * Write bytes down TLS channel *
2932 *************************************************/
2933
2934 /*
2935 Arguments:
2936 ct_ctx client context pointer, or NULL for the one global server context
2937 buff buffer of data
2938 len number of bytes
2939 more further data expected soon
2940
2941 Returns: the number of bytes after a successful write,
2942 -1 after a failed write
2943
2944 Used by both server-side and client-side TLS.
2945 */
2946
2947 int
2948 tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more)
2949 {
2950 size_t olen = len;
2951 int outbytes, error;
2952 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2953 static gstring * corked = NULL;
2954
2955 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
2956 buff, (unsigned long)len, more ? ", more" : "");
2957
2958 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2959 "more" is notified. This hack is only ok if small amounts are involved AND only
2960 one stream does it, in one context (i.e. no store reset). Currently it is used
2961 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. */
2962 /* + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's
2963 a store reset there, so use POOL_PERM. */
2964 /* + if CHUNKING, cmds EHLO,MAIL,RCPT(s),BDAT */
2965
2966 if ((more || corked))
2967 {
2968 #ifdef EXPERIMENTAL_PIPE_CONNECT
2969 int save_pool = store_pool;
2970 store_pool = POOL_PERM;
2971 #endif
2972
2973 corked = string_catn(corked, buff, len);
2974
2975 #ifdef EXPERIMENTAL_PIPE_CONNECT
2976 store_pool = save_pool;
2977 #endif
2978
2979 if (more)
2980 return len;
2981 buff = CUS corked->s;
2982 len = corked->ptr;
2983 corked = NULL;
2984 }
2985
2986 for (int left = len; left > 0;)
2987 {
2988 DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left);
2989 outbytes = SSL_write(ssl, CS buff, left);
2990 error = SSL_get_error(ssl, outbytes);
2991 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2992 switch (error)
2993 {
2994 case SSL_ERROR_SSL:
2995 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
2996 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2997 return -1;
2998
2999 case SSL_ERROR_NONE:
3000 left -= outbytes;
3001 buff += outbytes;
3002 break;
3003
3004 case SSL_ERROR_ZERO_RETURN:
3005 log_write(0, LOG_MAIN, "SSL channel closed on write");
3006 return -1;
3007
3008 case SSL_ERROR_SYSCALL:
3009 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
3010 sender_fullhost ? sender_fullhost : US"<unknown>",
3011 strerror(errno));
3012 return -1;
3013
3014 default:
3015 log_write(0, LOG_MAIN, "SSL_write error %d", error);
3016 return -1;
3017 }
3018 }
3019 return olen;
3020 }
3021
3022
3023
3024 /*************************************************
3025 * Close down a TLS session *
3026 *************************************************/
3027
3028 /* This is also called from within a delivery subprocess forked from the
3029 daemon, to shut down the TLS library, without actually doing a shutdown (which
3030 would tamper with the SSL session in the parent process).
3031
3032 Arguments:
3033 ct_ctx client TLS context pointer, or NULL for the one global server context
3034 shutdown 1 if TLS close-alert is to be sent,
3035 2 if also response to be waited for
3036
3037 Returns: nothing
3038
3039 Used by both server-side and client-side TLS.
3040 */
3041
3042 void
3043 tls_close(void * ct_ctx, int shutdown)
3044 {
3045 exim_openssl_client_tls_ctx * o_ctx = ct_ctx;
3046 SSL_CTX **ctxp = o_ctx ? &o_ctx->ctx : &server_ctx;
3047 SSL **sslp = o_ctx ? &o_ctx->ssl : &server_ssl;
3048 int *fdp = o_ctx ? &tls_out.active.sock : &tls_in.active.sock;
3049
3050 if (*fdp < 0) return; /* TLS was not active */
3051
3052 if (shutdown)
3053 {
3054 int rc;
3055 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
3056 shutdown > 1 ? " (with response-wait)" : "");
3057
3058 if ( (rc = SSL_shutdown(*sslp)) == 0 /* send "close notify" alert */
3059 && shutdown > 1)
3060 {
3061 ALARM(2);
3062 rc = SSL_shutdown(*sslp); /* wait for response */
3063 ALARM_CLR(0);
3064 }
3065
3066 if (rc < 0) DEBUG(D_tls)
3067 {
3068 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3069 debug_printf("SSL_shutdown: %s\n", ssl_errstring);
3070 }
3071 }
3072
3073 #ifndef DISABLE_OCSP
3074 if (!o_ctx) /* server side */
3075 {
3076 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
3077 server_static_cbinfo->verify_stack = NULL;
3078 }
3079 #endif
3080
3081 SSL_CTX_free(*ctxp);
3082 SSL_free(*sslp);
3083 *ctxp = NULL;
3084 *sslp = NULL;
3085 *fdp = -1;
3086 }
3087
3088
3089
3090
3091 /*************************************************
3092 * Let tls_require_ciphers be checked at startup *
3093 *************************************************/
3094
3095 /* The tls_require_ciphers option, if set, must be something which the
3096 library can parse.
3097
3098 Returns: NULL on success, or error message
3099 */
3100
3101 uschar *
3102 tls_validate_require_cipher(void)
3103 {
3104 SSL_CTX *ctx;
3105 uschar *s, *expciphers, *err;
3106
3107 /* this duplicates from tls_init(), we need a better "init just global
3108 state, for no specific purpose" singleton function of our own */
3109
3110 #ifdef EXIM_NEED_OPENSSL_INIT
3111 SSL_load_error_strings();
3112 OpenSSL_add_ssl_algorithms();
3113 #endif
3114 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
3115 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
3116 list of available digests. */
3117 EVP_add_digest(EVP_sha256());
3118 #endif
3119
3120 if (!(tls_require_ciphers && *tls_require_ciphers))
3121 return NULL;
3122
3123 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3124 &err))
3125 return US"failed to expand tls_require_ciphers";
3126
3127 if (!(expciphers && *expciphers))
3128 return NULL;
3129
3130 /* normalisation ripped from above */
3131 s = expciphers;
3132 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
3133
3134 err = NULL;
3135
3136 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
3137 if (!(ctx = SSL_CTX_new(TLS_server_method())))
3138 #else
3139 if (!(ctx = SSL_CTX_new(SSLv23_server_method())))
3140 #endif
3141 {
3142 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3143 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
3144 }
3145
3146 DEBUG(D_tls)
3147 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3148
3149 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
3150 {
3151 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3152 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
3153 expciphers, ssl_errstring);
3154 }
3155
3156 SSL_CTX_free(ctx);
3157
3158 return err;
3159 }
3160
3161
3162
3163
3164 /*************************************************
3165 * Report the library versions. *
3166 *************************************************/
3167
3168 /* There have historically been some issues with binary compatibility in
3169 OpenSSL libraries; if Exim (like many other applications) is built against
3170 one version of OpenSSL but the run-time linker picks up another version,
3171 it can result in serious failures, including crashing with a SIGSEGV. So
3172 report the version found by the compiler and the run-time version.
3173
3174 Note: some OS vendors backport security fixes without changing the version
3175 number/string, and the version date remains unchanged. The _build_ date
3176 will change, so we can more usefully assist with version diagnosis by also
3177 reporting the build date.
3178
3179 Arguments: a FILE* to print the results to
3180 Returns: nothing
3181 */
3182
3183 void
3184 tls_version_report(FILE *f)
3185 {
3186 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
3187 " Runtime: %s\n"
3188 " : %s\n",
3189 OPENSSL_VERSION_TEXT,
3190 SSLeay_version(SSLEAY_VERSION),
3191 SSLeay_version(SSLEAY_BUILT_ON));
3192 /* third line is 38 characters for the %s and the line is 73 chars long;
3193 the OpenSSL output includes a "built on: " prefix already. */
3194 }
3195
3196
3197
3198
3199 /*************************************************
3200 * Random number generation *
3201 *************************************************/
3202
3203 /* Pseudo-random number generation. The result is not expected to be
3204 cryptographically strong but not so weak that someone will shoot themselves
3205 in the foot using it as a nonce in input in some email header scheme or
3206 whatever weirdness they'll twist this into. The result should handle fork()
3207 and avoid repeating sequences. OpenSSL handles that for us.
3208
3209 Arguments:
3210 max range maximum
3211 Returns a random number in range [0, max-1]
3212 */
3213
3214 int
3215 vaguely_random_number(int max)
3216 {
3217 unsigned int r;
3218 int i, needed_len;
3219 static pid_t pidlast = 0;
3220 pid_t pidnow;
3221 uschar smallbuf[sizeof(r)];
3222
3223 if (max <= 1)
3224 return 0;
3225
3226 pidnow = getpid();
3227 if (pidnow != pidlast)
3228 {
3229 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
3230 is unique for each thread", this doesn't apparently apply across processes,
3231 so our own warning from vaguely_random_number_fallback() applies here too.
3232 Fix per PostgreSQL. */
3233 if (pidlast != 0)
3234 RAND_cleanup();
3235 pidlast = pidnow;
3236 }
3237
3238 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
3239 if (!RAND_status())
3240 {
3241 randstuff r;
3242 gettimeofday(&r.tv, NULL);
3243 r.p = getpid();
3244
3245 RAND_seed(US (&r), sizeof(r));
3246 }
3247 /* We're after pseudo-random, not random; if we still don't have enough data
3248 in the internal PRNG then our options are limited. We could sleep and hope
3249 for entropy to come along (prayer technique) but if the system is so depleted
3250 in the first place then something is likely to just keep taking it. Instead,
3251 we'll just take whatever little bit of pseudo-random we can still manage to
3252 get. */
3253
3254 needed_len = sizeof(r);
3255 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
3256 asked for a number less than 10. */
3257 for (r = max, i = 0; r; ++i)
3258 r >>= 1;
3259 i = (i + 7) / 8;
3260 if (i < needed_len)
3261 needed_len = i;
3262
3263 #ifdef EXIM_HAVE_RAND_PSEUDO
3264 /* We do not care if crypto-strong */
3265 i = RAND_pseudo_bytes(smallbuf, needed_len);
3266 #else
3267 i = RAND_bytes(smallbuf, needed_len);
3268 #endif
3269
3270 if (i < 0)
3271 {
3272 DEBUG(D_all)
3273 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
3274 return vaguely_random_number_fallback(max);
3275 }
3276
3277 r = 0;
3278 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
3279 r = 256 * r + *p;
3280
3281 /* We don't particularly care about weighted results; if someone wants
3282 smooth distribution and cares enough then they should submit a patch then. */
3283 return r % max;
3284 }
3285
3286
3287
3288
3289 /*************************************************
3290 * OpenSSL option parse *
3291 *************************************************/
3292
3293 /* Parse one option for tls_openssl_options_parse below
3294
3295 Arguments:
3296 name one option name
3297 value place to store a value for it
3298 Returns success or failure in parsing
3299 */
3300
3301
3302
3303 static BOOL
3304 tls_openssl_one_option_parse(uschar *name, long *value)
3305 {
3306 int first = 0;
3307 int last = exim_openssl_options_size;
3308 while (last > first)
3309 {
3310 int middle = (first + last)/2;
3311 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3312 if (c == 0)
3313 {
3314 *value = exim_openssl_options[middle].value;
3315 return TRUE;
3316 }
3317 else if (c > 0)
3318 first = middle + 1;
3319 else
3320 last = middle;
3321 }
3322 return FALSE;
3323 }
3324
3325
3326
3327
3328 /*************************************************
3329 * OpenSSL option parsing logic *
3330 *************************************************/
3331
3332 /* OpenSSL has a number of compatibility options which an administrator might
3333 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3334 we look like log_selector.
3335
3336 Arguments:
3337 option_spec the administrator-supplied string of options
3338 results ptr to long storage for the options bitmap
3339 Returns success or failure
3340 */
3341
3342 BOOL
3343 tls_openssl_options_parse(uschar *option_spec, long *results)
3344 {
3345 long result, item;
3346 uschar *end;
3347 uschar keep_c;
3348 BOOL adding, item_parsed;
3349
3350 result = SSL_OP_NO_TICKET;
3351 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3352 * from default because it increases BEAST susceptibility. */
3353 #ifdef SSL_OP_NO_SSLv2
3354 result |= SSL_OP_NO_SSLv2;
3355 #endif
3356 #ifdef SSL_OP_SINGLE_DH_USE
3357 result |= SSL_OP_SINGLE_DH_USE;
3358 #endif
3359
3360 if (!option_spec)
3361 {
3362 *results = result;
3363 return TRUE;
3364 }
3365
3366 for (uschar * s = option_spec; *s != '\0'; /**/)
3367 {
3368 while (isspace(*s)) ++s;
3369 if (*s == '\0')
3370 break;
3371 if (*s != '+' && *s != '-')
3372 {
3373 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3374 "+ or - expected but found \"%s\"\n", s);
3375 return FALSE;
3376 }
3377 adding = *s++ == '+';
3378 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3379 keep_c = *end;
3380 *end = '\0';
3381 item_parsed = tls_openssl_one_option_parse(s, &item);
3382 *end = keep_c;
3383 if (!item_parsed)
3384 {
3385 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3386 return FALSE;
3387 }
3388 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
3389 adding ? "adding" : "removing", result, item, s);
3390 if (adding)
3391 result |= item;
3392 else
3393 result &= ~item;
3394 s = end;
3395 }
3396
3397 *results = result;
3398 return TRUE;
3399 }
3400
3401 #endif /*!MACRO_PREDEF*/
3402 /* vi: aw ai sw=2
3403 */
3404 /* End of tls-openssl.c */