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Fix taint-handling in rDNS name construction
[exim.git] / src / src / tls-openssl.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2019 */
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 # define OPENSSL_AUTO_SHA256
50 #else
51 # define EXIM_HAVE_EPHEM_RSA_KEX
52 # define EXIM_HAVE_RAND_PSEUDO
53 #endif
54 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
55 # define EXIM_HAVE_SHA256
56 #endif
57
58 /* X509_check_host provides sane certificate hostname checking, but was added
59 to OpenSSL late, after other projects forked off the code-base. So in
60 addition to guarding against the base version number, beware that LibreSSL
61 does not (at this time) support this function.
62
63 If LibreSSL gains a different API, perhaps via libtls, then we'll probably
64 opt to disentangle and ask a LibreSSL user to provide glue for a third
65 crypto provider for libtls instead of continuing to tie the OpenSSL glue
66 into even twistier knots. If LibreSSL gains the same API, we can just
67 change this guard and punt the issue for a while longer. */
68
69 #ifndef LIBRESSL_VERSION_NUMBER
70 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
71 # define EXIM_HAVE_OPENSSL_CHECKHOST
72 # define EXIM_HAVE_OPENSSL_DH_BITS
73 # define EXIM_HAVE_OPENSSL_TLS_METHOD
74 # define EXIM_HAVE_OPENSSL_KEYLOG
75 # define EXIM_HAVE_OPENSSL_CIPHER_GET_ID
76 # define EXIM_HAVE_SESSION_TICKET
77 # define EXIM_HAVE_OPESSL_TRACE
78 # define EXIM_HAVE_OPESSL_GET0_SERIAL
79 # ifndef DISABLE_OCSP
80 # define EXIM_HAVE_OCSP
81 # endif
82 # else
83 # define EXIM_NEED_OPENSSL_INIT
84 # endif
85 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
86 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
87 # define EXIM_HAVE_OPENSSL_CHECKHOST
88 # endif
89 #endif
90
91 #if !defined(LIBRESSL_VERSION_NUMBER) \
92 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
93 # if !defined(OPENSSL_NO_ECDH)
94 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
95 # define EXIM_HAVE_ECDH
96 # endif
97 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
98 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
99 # endif
100 # endif
101 #endif
102
103 #ifndef LIBRESSL_VERSION_NUMBER
104 # if OPENSSL_VERSION_NUMBER >= 0x010101000L
105 # define OPENSSL_HAVE_KEYLOG_CB
106 # define OPENSSL_HAVE_NUM_TICKETS
107 # define EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
108 # else
109 # define OPENSSL_BAD_SRVR_OURCERT
110 # endif
111 #endif
112
113 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
114 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
115 # define DISABLE_OCSP
116 #endif
117
118 #ifdef EXPERIMENTAL_TLS_RESUME
119 # if OPENSSL_VERSION_NUMBER < 0x0101010L
120 # error OpenSSL version too old for session-resumption
121 # endif
122 #endif
123
124 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
125 # include <openssl/x509v3.h>
126 #endif
127
128 #ifndef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
129 # ifndef EXIM_HAVE_OPENSSL_CIPHER_GET_ID
130 # define SSL_CIPHER_get_id(c) (c->id)
131 # endif
132 # ifndef MACRO_PREDEF
133 # include "tls-cipher-stdname.c"
134 # endif
135 #endif
136
137 /*************************************************
138 * OpenSSL option parse *
139 *************************************************/
140
141 typedef struct exim_openssl_option {
142 uschar *name;
143 long value;
144 } exim_openssl_option;
145 /* We could use a macro to expand, but we need the ifdef and not all the
146 options document which version they were introduced in. Policylet: include
147 all options unless explicitly for DTLS, let the administrator choose which
148 to apply.
149
150 This list is current as of:
151 ==> 1.0.1b <==
152 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
153 Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev
154 */
155 static exim_openssl_option exim_openssl_options[] = {
156 /* KEEP SORTED ALPHABETICALLY! */
157 #ifdef SSL_OP_ALL
158 { US"all", (long) SSL_OP_ALL },
159 #endif
160 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
161 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
162 #endif
163 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
164 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
165 #endif
166 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
167 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
168 #endif
169 #ifdef SSL_OP_EPHEMERAL_RSA
170 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
171 #endif
172 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
173 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
174 #endif
175 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
176 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
177 #endif
178 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
179 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
180 #endif
181 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
182 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
183 #endif
184 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
185 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
186 #endif
187 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
188 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
189 #endif
190 #ifdef SSL_OP_NO_COMPRESSION
191 { US"no_compression", SSL_OP_NO_COMPRESSION },
192 #endif
193 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
194 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
195 #endif
196 #ifdef SSL_OP_NO_SSLv2
197 { US"no_sslv2", SSL_OP_NO_SSLv2 },
198 #endif
199 #ifdef SSL_OP_NO_SSLv3
200 { US"no_sslv3", SSL_OP_NO_SSLv3 },
201 #endif
202 #ifdef SSL_OP_NO_TICKET
203 { US"no_ticket", SSL_OP_NO_TICKET },
204 #endif
205 #ifdef SSL_OP_NO_TLSv1
206 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
207 #endif
208 #ifdef SSL_OP_NO_TLSv1_1
209 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
210 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
211 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
212 #else
213 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
214 #endif
215 #endif
216 #ifdef SSL_OP_NO_TLSv1_2
217 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
218 #endif
219 #ifdef SSL_OP_NO_TLSv1_3
220 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
221 #endif
222 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
223 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
224 #endif
225 #ifdef SSL_OP_SINGLE_DH_USE
226 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
227 #endif
228 #ifdef SSL_OP_SINGLE_ECDH_USE
229 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
230 #endif
231 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
232 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
233 #endif
234 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
235 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
236 #endif
237 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
238 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
239 #endif
240 #ifdef SSL_OP_TLS_D5_BUG
241 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
242 #endif
243 #ifdef SSL_OP_TLS_ROLLBACK_BUG
244 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
245 #endif
246 };
247
248 #ifndef MACRO_PREDEF
249 static int exim_openssl_options_size = nelem(exim_openssl_options);
250 #endif
251
252 #ifdef MACRO_PREDEF
253 void
254 options_tls(void)
255 {
256 uschar buf[64];
257
258 for (struct exim_openssl_option * o = exim_openssl_options;
259 o < exim_openssl_options + nelem(exim_openssl_options); o++)
260 {
261 /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
262 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
263
264 spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
265 builtin_macro_create(buf);
266 }
267
268 # ifdef EXPERIMENTAL_TLS_RESUME
269 builtin_macro_create_var(US"_RESUME_DECODE", RESUME_DECODE_STRING );
270 # endif
271 # ifdef SSL_OP_NO_TLSv1_3
272 builtin_macro_create(US"_HAVE_TLS1_3");
273 # endif
274 # ifdef OPENSSL_BAD_SRVR_OURCERT
275 builtin_macro_create(US"_TLS_BAD_MULTICERT_IN_OURCERT");
276 # endif
277 # ifdef EXIM_HAVE_OCSP
278 builtin_macro_create(US"_HAVE_TLS_OCSP");
279 builtin_macro_create(US"_HAVE_TLS_OCSP_LIST");
280 # endif
281 }
282 #else
283
284 /******************************************************************************/
285
286 /* Structure for collecting random data for seeding. */
287
288 typedef struct randstuff {
289 struct timeval tv;
290 pid_t p;
291 } randstuff;
292
293 /* Local static variables */
294
295 static BOOL client_verify_callback_called = FALSE;
296 static BOOL server_verify_callback_called = FALSE;
297 static const uschar *sid_ctx = US"exim";
298
299 /* We have three different contexts to care about.
300
301 Simple case: client, `client_ctx`
302 As a client, we can be doing a callout or cut-through delivery while receiving
303 a message. So we have a client context, which should have options initialised
304 from the SMTP Transport. We may also concurrently want to make TLS connections
305 to utility daemons, so client-contexts are allocated and passed around in call
306 args rather than using a gobal.
307
308 Server:
309 There are two cases: with and without ServerNameIndication from the client.
310 Given TLS SNI, we can be using different keys, certs and various other
311 configuration settings, because they're re-expanded with $tls_sni set. This
312 allows vhosting with TLS. This SNI is sent in the handshake.
313 A client might not send SNI, so we need a fallback, and an initial setup too.
314 So as a server, we start out using `server_ctx`.
315 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
316 `server_sni` from `server_ctx` and then initialise settings by re-expanding
317 configuration.
318 */
319
320 typedef struct {
321 SSL_CTX * ctx;
322 SSL * ssl;
323 gstring * corked;
324 } exim_openssl_client_tls_ctx;
325
326 static SSL_CTX *server_ctx = NULL;
327 static SSL *server_ssl = NULL;
328
329 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
330 static SSL_CTX *server_sni = NULL;
331 #endif
332
333 static char ssl_errstring[256];
334
335 static int ssl_session_timeout = 7200; /* Two hours */
336 static BOOL client_verify_optional = FALSE;
337 static BOOL server_verify_optional = FALSE;
338
339 static BOOL reexpand_tls_files_for_sni = FALSE;
340
341
342 typedef struct ocsp_resp {
343 struct ocsp_resp * next;
344 OCSP_RESPONSE * resp;
345 } ocsp_resplist;
346
347 typedef struct tls_ext_ctx_cb {
348 tls_support * tlsp;
349 uschar *certificate;
350 uschar *privatekey;
351 BOOL is_server;
352 #ifndef DISABLE_OCSP
353 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
354 union {
355 struct {
356 uschar *file;
357 const uschar *file_expanded;
358 ocsp_resplist *olist;
359 } server;
360 struct {
361 X509_STORE *verify_store; /* non-null if status requested */
362 BOOL verify_required;
363 } client;
364 } u_ocsp;
365 #endif
366 uschar *dhparam;
367 /* these are cached from first expand */
368 uschar *server_cipher_list;
369 /* only passed down to tls_error: */
370 host_item *host;
371 const uschar * verify_cert_hostnames;
372 #ifndef DISABLE_EVENT
373 uschar * event_action;
374 #endif
375 } tls_ext_ctx_cb;
376
377 /* should figure out a cleanup of API to handle state preserved per
378 implementation, for various reasons, which can be void * in the APIs.
379 For now, we hack around it. */
380 tls_ext_ctx_cb *client_static_cbinfo = NULL; /*XXX should not use static; multiple concurrent clients! */
381 tls_ext_ctx_cb *server_static_cbinfo = NULL;
382
383 static int
384 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
385 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
386
387 /* Callbacks */
388 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
389 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
390 #endif
391 #ifndef DISABLE_OCSP
392 static int tls_server_stapling_cb(SSL *s, void *arg);
393 #endif
394
395
396
397 /* Daemon-called, before every connection, key create/rotate */
398 #ifdef EXPERIMENTAL_TLS_RESUME
399 static void tk_init(void);
400 static int tls_exdata_idx = -1;
401 #endif
402
403 void
404 tls_daemon_init(void)
405 {
406 #ifdef EXPERIMENTAL_TLS_RESUME
407 tk_init();
408 #endif
409 return;
410 }
411
412
413 /*************************************************
414 * Handle TLS error *
415 *************************************************/
416
417 /* Called from lots of places when errors occur before actually starting to do
418 the TLS handshake, that is, while the session is still in clear. Always returns
419 DEFER for a server and FAIL for a client so that most calls can use "return
420 tls_error(...)" to do this processing and then give an appropriate return. A
421 single function is used for both server and client, because it is called from
422 some shared functions.
423
424 Argument:
425 prefix text to include in the logged error
426 host NULL if setting up a server;
427 the connected host if setting up a client
428 msg error message or NULL if we should ask OpenSSL
429 errstr pointer to output error message
430
431 Returns: OK/DEFER/FAIL
432 */
433
434 static int
435 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
436 {
437 if (!msg)
438 {
439 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
440 msg = US ssl_errstring;
441 }
442
443 msg = string_sprintf("(%s): %s", prefix, msg);
444 DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg);
445 if (errstr) *errstr = msg;
446 return host ? FAIL : DEFER;
447 }
448
449
450
451 /*************************************************
452 * Callback to generate RSA key *
453 *************************************************/
454
455 /*
456 Arguments:
457 s SSL connection (not used)
458 export not used
459 keylength keylength
460
461 Returns: pointer to generated key
462 */
463
464 static RSA *
465 rsa_callback(SSL *s, int export, int keylength)
466 {
467 RSA *rsa_key;
468 #ifdef EXIM_HAVE_RSA_GENKEY_EX
469 BIGNUM *bn = BN_new();
470 #endif
471
472 export = export; /* Shut picky compilers up */
473 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
474
475 #ifdef EXIM_HAVE_RSA_GENKEY_EX
476 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
477 || !(rsa_key = RSA_new())
478 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
479 )
480 #else
481 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
482 #endif
483
484 {
485 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
486 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
487 ssl_errstring);
488 return NULL;
489 }
490 return rsa_key;
491 }
492
493
494
495 /* Extreme debug
496 #ifndef DISABLE_OCSP
497 void
498 x509_store_dump_cert_s_names(X509_STORE * store)
499 {
500 STACK_OF(X509_OBJECT) * roots= store->objs;
501 static uschar name[256];
502
503 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
504 {
505 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
506 if(tmp_obj->type == X509_LU_X509)
507 {
508 X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
509 if (X509_NAME_oneline(sn, CS name, sizeof(name)))
510 {
511 name[sizeof(name)-1] = '\0';
512 debug_printf(" %s\n", name);
513 }
514 }
515 }
516 }
517 #endif
518 */
519
520
521 #ifndef DISABLE_EVENT
522 static int
523 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
524 BOOL *calledp, const BOOL *optionalp, const uschar * what)
525 {
526 uschar * ev;
527 uschar * yield;
528 X509 * old_cert;
529
530 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
531 if (ev)
532 {
533 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
534 old_cert = tlsp->peercert;
535 tlsp->peercert = X509_dup(cert);
536 /* NB we do not bother setting peerdn */
537 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
538 {
539 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
540 "depth=%d cert=%s: %s",
541 tlsp == &tls_out ? deliver_host_address : sender_host_address,
542 what, depth, dn, yield);
543 *calledp = TRUE;
544 if (!*optionalp)
545 {
546 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
547 return 1; /* reject (leaving peercert set) */
548 }
549 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
550 "(host in tls_try_verify_hosts)\n");
551 tlsp->verify_override = TRUE;
552 }
553 X509_free(tlsp->peercert);
554 tlsp->peercert = old_cert;
555 }
556 return 0;
557 }
558 #endif
559
560 /*************************************************
561 * Callback for verification *
562 *************************************************/
563
564 /* The SSL library does certificate verification if set up to do so. This
565 callback has the current yes/no state is in "state". If verification succeeded,
566 we set the certificate-verified flag. If verification failed, what happens
567 depends on whether the client is required to present a verifiable certificate
568 or not.
569
570 If verification is optional, we change the state to yes, but still log the
571 verification error. For some reason (it really would help to have proper
572 documentation of OpenSSL), this callback function then gets called again, this
573 time with state = 1. We must take care not to set the private verified flag on
574 the second time through.
575
576 Note: this function is not called if the client fails to present a certificate
577 when asked. We get here only if a certificate has been received. Handling of
578 optional verification for this case is done when requesting SSL to verify, by
579 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
580
581 May be called multiple times for different issues with a certificate, even
582 for a given "depth" in the certificate chain.
583
584 Arguments:
585 preverify_ok current yes/no state as 1/0
586 x509ctx certificate information.
587 tlsp per-direction (client vs. server) support data
588 calledp has-been-called flag
589 optionalp verification-is-optional flag
590
591 Returns: 0 if verification should fail, otherwise 1
592 */
593
594 static int
595 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
596 tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
597 {
598 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
599 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
600 uschar dn[256];
601
602 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
603 {
604 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
605 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
606 tlsp == &tls_out ? deliver_host_address : sender_host_address);
607 return 0;
608 }
609 dn[sizeof(dn)-1] = '\0';
610
611 tlsp->verify_override = FALSE;
612 if (preverify_ok == 0)
613 {
614 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
615 *verify_mode, sender_host_address)
616 : US"";
617 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
618 tlsp == &tls_out ? deliver_host_address : sender_host_address,
619 extra, depth,
620 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
621 *calledp = TRUE;
622 if (!*optionalp)
623 {
624 if (!tlsp->peercert)
625 tlsp->peercert = X509_dup(cert); /* record failing cert */
626 return 0; /* reject */
627 }
628 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
629 "tls_try_verify_hosts)\n");
630 tlsp->verify_override = TRUE;
631 }
632
633 else if (depth != 0)
634 {
635 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
636 #ifndef DISABLE_OCSP
637 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
638 { /* client, wanting stapling */
639 /* Add the server cert's signing chain as the one
640 for the verification of the OCSP stapled information. */
641
642 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
643 cert))
644 ERR_clear_error();
645 sk_X509_push(client_static_cbinfo->verify_stack, cert);
646 }
647 #endif
648 #ifndef DISABLE_EVENT
649 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
650 return 0; /* reject, with peercert set */
651 #endif
652 }
653 else
654 {
655 const uschar * verify_cert_hostnames;
656
657 if ( tlsp == &tls_out
658 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
659 /* client, wanting hostname check */
660 {
661
662 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
663 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
664 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
665 # endif
666 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
667 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
668 # endif
669 int sep = 0;
670 const uschar * list = verify_cert_hostnames;
671 uschar * name;
672 int rc;
673 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
674 if ((rc = X509_check_host(cert, CCS name, 0,
675 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
676 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
677 NULL)))
678 {
679 if (rc < 0)
680 {
681 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
682 tlsp == &tls_out ? deliver_host_address : sender_host_address);
683 name = NULL;
684 }
685 break;
686 }
687 if (!name)
688 #else
689 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
690 #endif
691 {
692 uschar * extra = verify_mode
693 ? string_sprintf(" (during %c-verify for [%s])",
694 *verify_mode, sender_host_address)
695 : US"";
696 log_write(0, LOG_MAIN,
697 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
698 tlsp == &tls_out ? deliver_host_address : sender_host_address,
699 extra, dn, verify_cert_hostnames);
700 *calledp = TRUE;
701 if (!*optionalp)
702 {
703 if (!tlsp->peercert)
704 tlsp->peercert = X509_dup(cert); /* record failing cert */
705 return 0; /* reject */
706 }
707 DEBUG(D_tls) debug_printf("SSL verify name failure overridden (host in "
708 "tls_try_verify_hosts)\n");
709 tlsp->verify_override = TRUE;
710 }
711 }
712
713 #ifndef DISABLE_EVENT
714 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
715 return 0; /* reject, with peercert set */
716 #endif
717
718 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
719 *calledp ? "" : " authenticated", dn);
720 *calledp = TRUE;
721 }
722
723 return 1; /* accept, at least for this level */
724 }
725
726 static int
727 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
728 {
729 return verify_callback(preverify_ok, x509ctx, &tls_out,
730 &client_verify_callback_called, &client_verify_optional);
731 }
732
733 static int
734 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
735 {
736 return verify_callback(preverify_ok, x509ctx, &tls_in,
737 &server_verify_callback_called, &server_verify_optional);
738 }
739
740
741 #ifdef SUPPORT_DANE
742
743 /* This gets called *by* the dane library verify callback, which interposes
744 itself.
745 */
746 static int
747 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
748 {
749 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
750 uschar dn[256];
751 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
752 #ifndef DISABLE_EVENT
753 BOOL dummy_called, optional = FALSE;
754 #endif
755
756 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
757 {
758 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
759 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
760 deliver_host_address);
761 return 0;
762 }
763 dn[sizeof(dn)-1] = '\0';
764
765 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
766 preverify_ok ? "ok":"BAD", depth, dn);
767
768 #ifndef DISABLE_EVENT
769 if (verify_event(&tls_out, cert, depth, dn,
770 &dummy_called, &optional, US"DANE"))
771 return 0; /* reject, with peercert set */
772 #endif
773
774 if (preverify_ok == 1)
775 {
776 tls_out.dane_verified = TRUE;
777 #ifndef DISABLE_OCSP
778 if (client_static_cbinfo->u_ocsp.client.verify_store)
779 { /* client, wanting stapling */
780 /* Add the server cert's signing chain as the one
781 for the verification of the OCSP stapled information. */
782
783 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
784 cert))
785 ERR_clear_error();
786 sk_X509_push(client_static_cbinfo->verify_stack, cert);
787 }
788 #endif
789 }
790 else
791 {
792 int err = X509_STORE_CTX_get_error(x509ctx);
793 DEBUG(D_tls)
794 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
795 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
796 preverify_ok = 1;
797 }
798 return preverify_ok;
799 }
800
801 #endif /*SUPPORT_DANE*/
802
803
804 /*************************************************
805 * Information callback *
806 *************************************************/
807
808 /* The SSL library functions call this from time to time to indicate what they
809 are doing. We copy the string to the debugging output when TLS debugging has
810 been requested.
811
812 Arguments:
813 s the SSL connection
814 where
815 ret
816
817 Returns: nothing
818 */
819
820 static void
821 info_callback(SSL *s, int where, int ret)
822 {
823 DEBUG(D_tls)
824 {
825 const uschar * str;
826
827 if (where & SSL_ST_CONNECT)
828 str = US"SSL_connect";
829 else if (where & SSL_ST_ACCEPT)
830 str = US"SSL_accept";
831 else
832 str = US"SSL info (undefined)";
833
834 if (where & SSL_CB_LOOP)
835 debug_printf("%s: %s\n", str, SSL_state_string_long(s));
836 else if (where & SSL_CB_ALERT)
837 debug_printf("SSL3 alert %s:%s:%s\n",
838 str = where & SSL_CB_READ ? US"read" : US"write",
839 SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
840 else if (where & SSL_CB_EXIT)
841 if (ret == 0)
842 debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
843 else if (ret < 0)
844 debug_printf("%s: error in %s\n", str, SSL_state_string_long(s));
845 else if (where & SSL_CB_HANDSHAKE_START)
846 debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s));
847 else if (where & SSL_CB_HANDSHAKE_DONE)
848 debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s));
849 }
850 }
851
852 #ifdef OPENSSL_HAVE_KEYLOG_CB
853 static void
854 keylog_callback(const SSL *ssl, const char *line)
855 {
856 char * filename;
857 FILE * fp;
858 DEBUG(D_tls) debug_printf("%.200s\n", line);
859 if (!(filename = getenv("SSLKEYLOGFILE"))) return;
860 if (!(fp = fopen(filename, "a"))) return;
861 fprintf(fp, "%s\n", line);
862 fclose(fp);
863 }
864 #endif
865
866
867 #ifdef EXPERIMENTAL_TLS_RESUME
868 /* Manage the keysets used for encrypting the session tickets, on the server. */
869
870 typedef struct { /* Session ticket encryption key */
871 uschar name[16];
872
873 const EVP_CIPHER * aes_cipher;
874 uschar aes_key[32]; /* size needed depends on cipher. aes_128 implies 128/8 = 16? */
875 const EVP_MD * hmac_hash;
876 uschar hmac_key[16];
877 time_t renew;
878 time_t expire;
879 } exim_stek;
880
881 static exim_stek exim_tk; /* current key */
882 static exim_stek exim_tk_old; /* previous key */
883
884 static void
885 tk_init(void)
886 {
887 time_t t = time(NULL);
888
889 if (exim_tk.name[0])
890 {
891 if (exim_tk.renew >= t) return;
892 exim_tk_old = exim_tk;
893 }
894
895 if (f.running_in_test_harness) ssl_session_timeout = 6;
896
897 DEBUG(D_tls) debug_printf("OpenSSL: %s STEK\n", exim_tk.name[0] ? "rotating" : "creating");
898 if (RAND_bytes(exim_tk.aes_key, sizeof(exim_tk.aes_key)) <= 0) return;
899 if (RAND_bytes(exim_tk.hmac_key, sizeof(exim_tk.hmac_key)) <= 0) return;
900 if (RAND_bytes(exim_tk.name+1, sizeof(exim_tk.name)-1) <= 0) return;
901
902 exim_tk.name[0] = 'E';
903 exim_tk.aes_cipher = EVP_aes_256_cbc();
904 exim_tk.hmac_hash = EVP_sha256();
905 exim_tk.expire = t + ssl_session_timeout;
906 exim_tk.renew = t + ssl_session_timeout/2;
907 }
908
909 static exim_stek *
910 tk_current(void)
911 {
912 if (!exim_tk.name[0]) return NULL;
913 return &exim_tk;
914 }
915
916 static exim_stek *
917 tk_find(const uschar * name)
918 {
919 return memcmp(name, exim_tk.name, sizeof(exim_tk.name)) == 0 ? &exim_tk
920 : memcmp(name, exim_tk_old.name, sizeof(exim_tk_old.name)) == 0 ? &exim_tk_old
921 : NULL;
922 }
923
924 /* Callback for session tickets, on server */
925 static int
926 ticket_key_callback(SSL * ssl, uschar key_name[16],
927 uschar * iv, EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int enc)
928 {
929 tls_support * tlsp = server_static_cbinfo->tlsp;
930 exim_stek * key;
931
932 if (enc)
933 {
934 DEBUG(D_tls) debug_printf("ticket_key_callback: create new session\n");
935 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
936
937 if (RAND_bytes(iv, EVP_MAX_IV_LENGTH) <= 0)
938 return -1; /* insufficient random */
939
940 if (!(key = tk_current())) /* current key doesn't exist or isn't valid */
941 return 0; /* key couldn't be created */
942 memcpy(key_name, key->name, 16);
943 DEBUG(D_tls) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - time(NULL));
944
945 /*XXX will want these dependent on the ssl session strength */
946 HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
947 key->hmac_hash, NULL);
948 EVP_EncryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv);
949
950 DEBUG(D_tls) debug_printf("ticket created\n");
951 return 1;
952 }
953 else
954 {
955 time_t now = time(NULL);
956
957 DEBUG(D_tls) debug_printf("ticket_key_callback: retrieve session\n");
958 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
959
960 if (!(key = tk_find(key_name)) || key->expire < now)
961 {
962 DEBUG(D_tls)
963 {
964 debug_printf("ticket not usable (%s)\n", key ? "expired" : "not found");
965 if (key) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - now);
966 }
967 return 0;
968 }
969
970 HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
971 key->hmac_hash, NULL);
972 EVP_DecryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv);
973
974 DEBUG(D_tls) debug_printf("ticket usable, STEK expire " TIME_T_FMT "\n", key->expire - now);
975
976 /* The ticket lifetime and renewal are the same as the STEK lifetime and
977 renewal, which is overenthusiastic. A factor of, say, 3x longer STEK would
978 be better. To do that we'd have to encode ticket lifetime in the name as
979 we don't yet see the restored session. Could check posthandshake for TLS1.3
980 and trigger a new ticket then, but cannot do that for TLS1.2 */
981 return key->renew < now ? 2 : 1;
982 }
983 }
984 #endif
985
986
987
988 /*************************************************
989 * Initialize for DH *
990 *************************************************/
991
992 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
993
994 Arguments:
995 sctx The current SSL CTX (inbound or outbound)
996 dhparam DH parameter file or fixed parameter identity string
997 host connected host, if client; NULL if server
998 errstr error string pointer
999
1000 Returns: TRUE if OK (nothing to set up, or setup worked)
1001 */
1002
1003 static BOOL
1004 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
1005 {
1006 BIO *bio;
1007 DH *dh;
1008 uschar *dhexpanded;
1009 const char *pem;
1010 int dh_bitsize;
1011
1012 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
1013 return FALSE;
1014
1015 if (!dhexpanded || !*dhexpanded)
1016 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
1017 else if (dhexpanded[0] == '/')
1018 {
1019 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
1020 {
1021 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
1022 host, US strerror(errno), errstr);
1023 return FALSE;
1024 }
1025 }
1026 else
1027 {
1028 if (Ustrcmp(dhexpanded, "none") == 0)
1029 {
1030 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
1031 return TRUE;
1032 }
1033
1034 if (!(pem = std_dh_prime_named(dhexpanded)))
1035 {
1036 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
1037 host, US strerror(errno), errstr);
1038 return FALSE;
1039 }
1040 bio = BIO_new_mem_buf(CS pem, -1);
1041 }
1042
1043 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
1044 {
1045 BIO_free(bio);
1046 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
1047 host, NULL, errstr);
1048 return FALSE;
1049 }
1050
1051 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
1052 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
1053 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
1054 * If someone wants to dance at the edge, then they can raise the limit or use
1055 * current libraries. */
1056 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
1057 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
1058 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
1059 dh_bitsize = DH_bits(dh);
1060 #else
1061 dh_bitsize = 8 * DH_size(dh);
1062 #endif
1063
1064 /* Even if it is larger, we silently return success rather than cause things
1065 * to fail out, so that a too-large DH will not knock out all TLS; it's a
1066 * debatable choice. */
1067 if (dh_bitsize > tls_dh_max_bits)
1068 {
1069 DEBUG(D_tls)
1070 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
1071 dh_bitsize, tls_dh_max_bits);
1072 }
1073 else
1074 {
1075 SSL_CTX_set_tmp_dh(sctx, dh);
1076 DEBUG(D_tls)
1077 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
1078 dhexpanded ? dhexpanded : US"default", dh_bitsize);
1079 }
1080
1081 DH_free(dh);
1082 BIO_free(bio);
1083
1084 return TRUE;
1085 }
1086
1087
1088
1089
1090 /*************************************************
1091 * Initialize for ECDH *
1092 *************************************************/
1093
1094 /* Load parameters for ECDH encryption.
1095
1096 For now, we stick to NIST P-256 because: it's simple and easy to configure;
1097 it avoids any patent issues that might bite redistributors; despite events in
1098 the news and concerns over curve choices, we're not cryptographers, we're not
1099 pretending to be, and this is "good enough" to be better than no support,
1100 protecting against most adversaries. Given another year or two, there might
1101 be sufficient clarity about a "right" way forward to let us make an informed
1102 decision, instead of a knee-jerk reaction.
1103
1104 Longer-term, we should look at supporting both various named curves and
1105 external files generated with "openssl ecparam", much as we do for init_dh().
1106 We should also support "none" as a value, to explicitly avoid initialisation.
1107
1108 Patches welcome.
1109
1110 Arguments:
1111 sctx The current SSL CTX (inbound or outbound)
1112 host connected host, if client; NULL if server
1113 errstr error string pointer
1114
1115 Returns: TRUE if OK (nothing to set up, or setup worked)
1116 */
1117
1118 static BOOL
1119 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
1120 {
1121 #ifdef OPENSSL_NO_ECDH
1122 return TRUE;
1123 #else
1124
1125 EC_KEY * ecdh;
1126 uschar * exp_curve;
1127 int nid;
1128 BOOL rv;
1129
1130 if (host) /* No ECDH setup for clients, only for servers */
1131 return TRUE;
1132
1133 # ifndef EXIM_HAVE_ECDH
1134 DEBUG(D_tls)
1135 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
1136 return TRUE;
1137 # else
1138
1139 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
1140 return FALSE;
1141 if (!exp_curve || !*exp_curve)
1142 return TRUE;
1143
1144 /* "auto" needs to be handled carefully.
1145 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
1146 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
1147 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
1148 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
1149 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
1150 */
1151 if (Ustrcmp(exp_curve, "auto") == 0)
1152 {
1153 #if OPENSSL_VERSION_NUMBER < 0x10002000L
1154 DEBUG(D_tls) debug_printf(
1155 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
1156 exp_curve = US"prime256v1";
1157 #else
1158 # if defined SSL_CTRL_SET_ECDH_AUTO
1159 DEBUG(D_tls) debug_printf(
1160 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
1161 SSL_CTX_set_ecdh_auto(sctx, 1);
1162 return TRUE;
1163 # else
1164 DEBUG(D_tls) debug_printf(
1165 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
1166 return TRUE;
1167 # endif
1168 #endif
1169 }
1170
1171 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
1172 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
1173 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
1174 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
1175 # endif
1176 )
1177 {
1178 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
1179 host, NULL, errstr);
1180 return FALSE;
1181 }
1182
1183 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
1184 {
1185 tls_error(US"Unable to create ec curve", host, NULL, errstr);
1186 return FALSE;
1187 }
1188
1189 /* The "tmp" in the name here refers to setting a temporary key
1190 not to the stability of the interface. */
1191
1192 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
1193 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
1194 else
1195 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1196
1197 EC_KEY_free(ecdh);
1198 return !rv;
1199
1200 # endif /*EXIM_HAVE_ECDH*/
1201 #endif /*OPENSSL_NO_ECDH*/
1202 }
1203
1204
1205
1206
1207 #ifndef DISABLE_OCSP
1208 /*************************************************
1209 * Load OCSP information into state *
1210 *************************************************/
1211 /* Called to load the server OCSP response from the given file into memory, once
1212 caller has determined this is needed. Checks validity. Debugs a message
1213 if invalid.
1214
1215 ASSUMES: single response, for single cert.
1216
1217 Arguments:
1218 sctx the SSL_CTX* to update
1219 cbinfo various parts of session state
1220 filename the filename putatively holding an OCSP response
1221 is_pem file is PEM format; otherwise is DER
1222
1223 */
1224
1225 static void
1226 ocsp_load_response(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo,
1227 const uschar * filename, BOOL is_pem)
1228 {
1229 BIO * bio;
1230 OCSP_RESPONSE * resp;
1231 OCSP_BASICRESP * basic_response;
1232 OCSP_SINGLERESP * single_response;
1233 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1234 STACK_OF(X509) * sk;
1235 unsigned long verify_flags;
1236 int status, reason, i;
1237
1238 DEBUG(D_tls)
1239 debug_printf("tls_ocsp_file (%s) '%s'\n", is_pem ? "PEM" : "DER", filename);
1240
1241 if (!(bio = BIO_new_file(CS filename, "rb")))
1242 {
1243 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1244 filename);
1245 return;
1246 }
1247
1248 if (is_pem)
1249 {
1250 uschar * data, * freep;
1251 char * dummy;
1252 long len;
1253 if (!PEM_read_bio(bio, &dummy, &dummy, &data, &len))
1254 {
1255 DEBUG(D_tls) debug_printf("Failed to read PEM file \"%s\"\n",
1256 filename);
1257 return;
1258 }
1259 debug_printf("read pem file\n");
1260 freep = data;
1261 resp = d2i_OCSP_RESPONSE(NULL, CUSS &data, len);
1262 OPENSSL_free(freep);
1263 }
1264 else
1265 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1266 BIO_free(bio);
1267
1268 if (!resp)
1269 {
1270 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1271 return;
1272 }
1273
1274 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1275 {
1276 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1277 OCSP_response_status_str(status), status);
1278 goto bad;
1279 }
1280
1281 #ifdef notdef
1282 {
1283 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1284 OCSP_RESPONSE_print(bp, resp, 0); /* extreme debug: stapling content */
1285 BIO_free(bp);
1286 }
1287 #endif
1288
1289 if (!(basic_response = OCSP_response_get1_basic(resp)))
1290 {
1291 DEBUG(D_tls)
1292 debug_printf("OCSP response parse error: unable to extract basic response.\n");
1293 goto bad;
1294 }
1295
1296 sk = cbinfo->verify_stack;
1297 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
1298
1299 /* May need to expose ability to adjust those flags?
1300 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
1301 OCSP_TRUSTOTHER OCSP_NOINTERN */
1302
1303 /* This does a full verify on the OCSP proof before we load it for serving
1304 up; possibly overkill - just date-checks might be nice enough.
1305
1306 OCSP_basic_verify takes a "store" arg, but does not
1307 use it for the chain verification, which is all we do
1308 when OCSP_NOVERIFY is set. The content from the wire
1309 "basic_response" and a cert-stack "sk" are all that is used.
1310
1311 We have a stack, loaded in setup_certs() if tls_verify_certificates
1312 was a file (not a directory, or "system"). It is unfortunate we
1313 cannot used the connection context store, as that would neatly
1314 handle the "system" case too, but there seems to be no library
1315 function for getting a stack from a store.
1316 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
1317 We do not free the stack since it could be needed a second time for
1318 SNI handling.
1319
1320 Separately we might try to replace using OCSP_basic_verify() - which seems to not
1321 be a public interface into the OpenSSL library (there's no manual entry) -
1322 But what with? We also use OCSP_basic_verify in the client stapling callback.
1323 And there we NEED it; we must verify that status... unless the
1324 library does it for us anyway? */
1325
1326 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
1327 {
1328 DEBUG(D_tls)
1329 {
1330 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1331 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
1332 }
1333 goto bad;
1334 }
1335
1336 /* Here's the simplifying assumption: there's only one response, for the
1337 one certificate we use, and nothing for anything else in a chain. If this
1338 proves false, we need to extract a cert id from our issued cert
1339 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
1340 right cert in the stack and then calls OCSP_single_get0_status()).
1341
1342 I'm hoping to avoid reworking a bunch more of how we handle state here.
1343
1344 XXX that will change when we add support for (TLS1.3) whole-chain stapling
1345 */
1346
1347 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1348 {
1349 DEBUG(D_tls)
1350 debug_printf("Unable to get first response from OCSP basic response.\n");
1351 goto bad;
1352 }
1353
1354 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1355 if (status != V_OCSP_CERTSTATUS_GOOD)
1356 {
1357 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
1358 OCSP_cert_status_str(status), status,
1359 OCSP_crl_reason_str(reason), reason);
1360 goto bad;
1361 }
1362
1363 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1364 {
1365 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1366 goto bad;
1367 }
1368
1369 supply_response:
1370 /* Add the resp to the list used by tls_server_stapling_cb() */
1371 {
1372 ocsp_resplist ** op = &cbinfo->u_ocsp.server.olist, * oentry;
1373 while (oentry = *op)
1374 op = &oentry->next;
1375 *op = oentry = store_get(sizeof(ocsp_resplist), FALSE);
1376 oentry->next = NULL;
1377 oentry->resp = resp;
1378 }
1379 return;
1380
1381 bad:
1382 if (f.running_in_test_harness)
1383 {
1384 extern char ** environ;
1385 if (environ) for (uschar ** p = USS environ; *p; p++)
1386 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1387 {
1388 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1389 goto supply_response;
1390 }
1391 }
1392 return;
1393 }
1394
1395
1396 static void
1397 ocsp_free_response_list(tls_ext_ctx_cb * cbinfo)
1398 {
1399 for (ocsp_resplist * olist = cbinfo->u_ocsp.server.olist; olist;
1400 olist = olist->next)
1401 OCSP_RESPONSE_free(olist->resp);
1402 cbinfo->u_ocsp.server.olist = NULL;
1403 }
1404 #endif /*!DISABLE_OCSP*/
1405
1406
1407
1408
1409 /* Create and install a selfsigned certificate, for use in server mode */
1410
1411 static int
1412 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1413 {
1414 X509 * x509 = NULL;
1415 EVP_PKEY * pkey;
1416 RSA * rsa;
1417 X509_NAME * name;
1418 uschar * where;
1419
1420 where = US"allocating pkey";
1421 if (!(pkey = EVP_PKEY_new()))
1422 goto err;
1423
1424 where = US"allocating cert";
1425 if (!(x509 = X509_new()))
1426 goto err;
1427
1428 where = US"generating pkey";
1429 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1430 goto err;
1431
1432 where = US"assigning pkey";
1433 if (!EVP_PKEY_assign_RSA(pkey, rsa))
1434 goto err;
1435
1436 X509_set_version(x509, 2); /* N+1 - version 3 */
1437 ASN1_INTEGER_set(X509_get_serialNumber(x509), 1);
1438 X509_gmtime_adj(X509_get_notBefore(x509), 0);
1439 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
1440 X509_set_pubkey(x509, pkey);
1441
1442 name = X509_get_subject_name(x509);
1443 X509_NAME_add_entry_by_txt(name, "C",
1444 MBSTRING_ASC, CUS "UK", -1, -1, 0);
1445 X509_NAME_add_entry_by_txt(name, "O",
1446 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1447 X509_NAME_add_entry_by_txt(name, "CN",
1448 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1449 X509_set_issuer_name(x509, name);
1450
1451 where = US"signing cert";
1452 if (!X509_sign(x509, pkey, EVP_md5()))
1453 goto err;
1454
1455 where = US"installing selfsign cert";
1456 if (!SSL_CTX_use_certificate(sctx, x509))
1457 goto err;
1458
1459 where = US"installing selfsign key";
1460 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1461 goto err;
1462
1463 return OK;
1464
1465 err:
1466 (void) tls_error(where, NULL, NULL, errstr);
1467 if (x509) X509_free(x509);
1468 if (pkey) EVP_PKEY_free(pkey);
1469 return DEFER;
1470 }
1471
1472
1473
1474
1475 static int
1476 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1477 uschar ** errstr)
1478 {
1479 DEBUG(D_tls) debug_printf("tls_certificate file '%s'\n", file);
1480 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1481 return tls_error(string_sprintf(
1482 "SSL_CTX_use_certificate_chain_file file=%s", file),
1483 cbinfo->host, NULL, errstr);
1484 return 0;
1485 }
1486
1487 static int
1488 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1489 uschar ** errstr)
1490 {
1491 DEBUG(D_tls) debug_printf("tls_privatekey file '%s'\n", file);
1492 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1493 return tls_error(string_sprintf(
1494 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1495 return 0;
1496 }
1497
1498
1499 /*************************************************
1500 * Expand key and cert file specs *
1501 *************************************************/
1502
1503 /* Called once during tls_init and possibly again during TLS setup, for a
1504 new context, if Server Name Indication was used and tls_sni was seen in
1505 the certificate string.
1506
1507 Arguments:
1508 sctx the SSL_CTX* to update
1509 cbinfo various parts of session state
1510 errstr error string pointer
1511
1512 Returns: OK/DEFER/FAIL
1513 */
1514
1515 static int
1516 tls_expand_session_files(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo,
1517 uschar ** errstr)
1518 {
1519 uschar * expanded;
1520
1521 if (!cbinfo->certificate)
1522 {
1523 if (!cbinfo->is_server) /* client */
1524 return OK;
1525 /* server */
1526 if (tls_install_selfsign(sctx, errstr) != OK)
1527 return DEFER;
1528 }
1529 else
1530 {
1531 int err;
1532
1533 if ( !reexpand_tls_files_for_sni
1534 && ( Ustrstr(cbinfo->certificate, US"tls_sni")
1535 || Ustrstr(cbinfo->certificate, US"tls_in_sni")
1536 || Ustrstr(cbinfo->certificate, US"tls_out_sni")
1537 ) )
1538 reexpand_tls_files_for_sni = TRUE;
1539
1540 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1541 return DEFER;
1542
1543 if (expanded)
1544 if (cbinfo->is_server)
1545 {
1546 const uschar * file_list = expanded;
1547 int sep = 0;
1548 uschar * file;
1549 #ifndef DISABLE_OCSP
1550 const uschar * olist = cbinfo->u_ocsp.server.file;
1551 int osep = 0;
1552 uschar * ofile;
1553 BOOL fmt_pem = FALSE;
1554
1555 if (olist)
1556 if (!expand_check(olist, US"tls_ocsp_file", USS &olist, errstr))
1557 return DEFER;
1558 if (olist && !*olist)
1559 olist = NULL;
1560
1561 if ( cbinfo->u_ocsp.server.file_expanded && olist
1562 && (Ustrcmp(olist, cbinfo->u_ocsp.server.file_expanded) == 0))
1563 {
1564 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1565 olist = NULL;
1566 }
1567 else
1568 {
1569 ocsp_free_response_list(cbinfo);
1570 cbinfo->u_ocsp.server.file_expanded = olist;
1571 }
1572 #endif
1573
1574 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1575 {
1576 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1577 return err;
1578
1579 #ifndef DISABLE_OCSP
1580 if (olist)
1581 if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1582 {
1583 if (Ustrncmp(ofile, US"PEM ", 4) == 0)
1584 {
1585 fmt_pem = TRUE;
1586 ofile += 4;
1587 }
1588 else if (Ustrncmp(ofile, US"DER ", 4) == 0)
1589 {
1590 fmt_pem = FALSE;
1591 ofile += 4;
1592 }
1593 ocsp_load_response(sctx, cbinfo, ofile, fmt_pem);
1594 }
1595 else
1596 DEBUG(D_tls) debug_printf("ran out of ocsp file list\n");
1597 #endif
1598 }
1599 }
1600 else /* would there ever be a need for multiple client certs? */
1601 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1602 return err;
1603
1604 if ( cbinfo->privatekey
1605 && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1606 return DEFER;
1607
1608 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1609 of the expansion is an empty string, ignore it also, and assume the private
1610 key is in the same file as the certificate. */
1611
1612 if (expanded && *expanded)
1613 if (cbinfo->is_server)
1614 {
1615 const uschar * file_list = expanded;
1616 int sep = 0;
1617 uschar * file;
1618
1619 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1620 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1621 return err;
1622 }
1623 else /* would there ever be a need for multiple client certs? */
1624 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1625 return err;
1626 }
1627
1628 return OK;
1629 }
1630
1631
1632
1633
1634 /*************************************************
1635 * Callback to handle SNI *
1636 *************************************************/
1637
1638 /* Called when acting as server during the TLS session setup if a Server Name
1639 Indication extension was sent by the client.
1640
1641 API documentation is OpenSSL s_server.c implementation.
1642
1643 Arguments:
1644 s SSL* of the current session
1645 ad unknown (part of OpenSSL API) (unused)
1646 arg Callback of "our" registered data
1647
1648 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1649
1650 XXX might need to change to using ClientHello callback,
1651 per https://www.openssl.org/docs/manmaster/man3/SSL_client_hello_cb_fn.html
1652 */
1653
1654 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1655 static int
1656 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1657 {
1658 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1659 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1660 int rc;
1661 int old_pool = store_pool;
1662 uschar * dummy_errstr;
1663
1664 if (!servername)
1665 return SSL_TLSEXT_ERR_OK;
1666
1667 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1668 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1669
1670 /* Make the extension value available for expansion */
1671 store_pool = POOL_PERM;
1672 tls_in.sni = string_copy_taint(US servername, TRUE);
1673 store_pool = old_pool;
1674
1675 if (!reexpand_tls_files_for_sni)
1676 return SSL_TLSEXT_ERR_OK;
1677
1678 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1679 not confident that memcpy wouldn't break some internal reference counting.
1680 Especially since there's a references struct member, which would be off. */
1681
1682 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1683 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1684 #else
1685 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1686 #endif
1687 {
1688 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1689 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1690 goto bad;
1691 }
1692
1693 /* Not sure how many of these are actually needed, since SSL object
1694 already exists. Might even need this selfsame callback, for reneg? */
1695
1696 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1697 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1698 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1699 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1700 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1701 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1702
1703 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1704 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1705 )
1706 goto bad;
1707
1708 if ( cbinfo->server_cipher_list
1709 && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1710 goto bad;
1711
1712 #ifndef DISABLE_OCSP
1713 if (cbinfo->u_ocsp.server.file)
1714 {
1715 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1716 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1717 }
1718 #endif
1719
1720 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1721 verify_callback_server, &dummy_errstr)) != OK)
1722 goto bad;
1723
1724 /* do this after setup_certs, because this can require the certs for verifying
1725 OCSP information. */
1726 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1727 goto bad;
1728
1729 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1730 SSL_set_SSL_CTX(s, server_sni);
1731 return SSL_TLSEXT_ERR_OK;
1732
1733 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1734 }
1735 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1736
1737
1738
1739
1740 #ifndef DISABLE_OCSP
1741
1742 /*************************************************
1743 * Callback to handle OCSP Stapling *
1744 *************************************************/
1745
1746 /* Called when acting as server during the TLS session setup if the client
1747 requests OCSP information with a Certificate Status Request.
1748
1749 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1750 project.
1751
1752 */
1753
1754 static int
1755 tls_server_stapling_cb(SSL *s, void *arg)
1756 {
1757 const tls_ext_ctx_cb * cbinfo = (tls_ext_ctx_cb *) arg;
1758 ocsp_resplist * olist = cbinfo->u_ocsp.server.olist;
1759 uschar * response_der; /*XXX blob */
1760 int response_der_len;
1761
1762 DEBUG(D_tls)
1763 debug_printf("Received TLS status request (OCSP stapling); %s response list\n",
1764 olist ? "have" : "lack");
1765
1766 tls_in.ocsp = OCSP_NOT_RESP;
1767 if (!olist)
1768 return SSL_TLSEXT_ERR_NOACK;
1769
1770 #ifdef EXIM_HAVE_OPESSL_GET0_SERIAL
1771 {
1772 const X509 * cert_sent = SSL_get_certificate(s);
1773 const ASN1_INTEGER * cert_serial = X509_get0_serialNumber(cert_sent);
1774 const BIGNUM * cert_bn = ASN1_INTEGER_to_BN(cert_serial, NULL);
1775 const X509_NAME * cert_issuer = X509_get_issuer_name(cert_sent);
1776 uschar * chash;
1777 uint chash_len;
1778
1779 for (; olist; olist = olist->next)
1780 {
1781 OCSP_BASICRESP * bs = OCSP_response_get1_basic(olist->resp);
1782 const OCSP_SINGLERESP * single = OCSP_resp_get0(bs, 0);
1783 const OCSP_CERTID * cid = OCSP_SINGLERESP_get0_id(single);
1784 ASN1_INTEGER * res_cert_serial;
1785 const BIGNUM * resp_bn;
1786 ASN1_OCTET_STRING * res_cert_iNameHash;
1787
1788
1789 (void) OCSP_id_get0_info(&res_cert_iNameHash, NULL, NULL, &res_cert_serial,
1790 (OCSP_CERTID *) cid);
1791 resp_bn = ASN1_INTEGER_to_BN(res_cert_serial, NULL);
1792
1793 DEBUG(D_tls)
1794 {
1795 debug_printf("cert serial: %s\n", BN_bn2hex(cert_bn));
1796 debug_printf("resp serial: %s\n", BN_bn2hex(resp_bn));
1797 }
1798
1799 if (BN_cmp(cert_bn, resp_bn) == 0)
1800 {
1801 DEBUG(D_tls) debug_printf("matched serial for ocsp\n");
1802
1803 /*XXX TODO: check the rest of the list for duplicate matches.
1804 If any, need to also check the Issuer Name hash.
1805 Without this, we will provide the wrong status in the case of
1806 duplicate id. */
1807
1808 break;
1809 }
1810 DEBUG(D_tls) debug_printf("not match serial for ocsp\n");
1811 }
1812 if (!olist)
1813 {
1814 DEBUG(D_tls) debug_printf("failed to find match for ocsp\n");
1815 return SSL_TLSEXT_ERR_NOACK;
1816 }
1817 }
1818 #else
1819 if (olist->next)
1820 {
1821 DEBUG(D_tls) debug_printf("OpenSSL version too early to support multi-leaf OCSP\n");
1822 return SSL_TLSEXT_ERR_NOACK;
1823 }
1824 #endif
1825
1826 /*XXX could we do the i2d earlier, rather than during the callback? */
1827 response_der = NULL;
1828 response_der_len = i2d_OCSP_RESPONSE(olist->resp, &response_der);
1829 if (response_der_len <= 0)
1830 return SSL_TLSEXT_ERR_NOACK;
1831
1832 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1833 tls_in.ocsp = OCSP_VFIED;
1834 return SSL_TLSEXT_ERR_OK;
1835 }
1836
1837
1838 static void
1839 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1840 {
1841 BIO_printf(bp, "\t%s: ", str);
1842 ASN1_GENERALIZEDTIME_print(bp, time);
1843 BIO_puts(bp, "\n");
1844 }
1845
1846 static int
1847 tls_client_stapling_cb(SSL *s, void *arg)
1848 {
1849 tls_ext_ctx_cb * cbinfo = arg;
1850 const unsigned char * p;
1851 int len;
1852 OCSP_RESPONSE * rsp;
1853 OCSP_BASICRESP * bs;
1854 int i;
1855
1856 DEBUG(D_tls) debug_printf("Received TLS status callback (OCSP stapling):\n");
1857 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1858 if(!p)
1859 {
1860 /* Expect this when we requested ocsp but got none */
1861 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1862 log_write(0, LOG_MAIN, "Required TLS certificate status not received");
1863 else
1864 DEBUG(D_tls) debug_printf(" null\n");
1865 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1866 }
1867
1868 if (!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1869 {
1870 tls_out.ocsp = OCSP_FAILED; /*XXX should use tlsp-> to permit concurrent outbound */
1871 if (LOGGING(tls_cipher))
1872 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1873 else
1874 DEBUG(D_tls) debug_printf(" parse error\n");
1875 return 0;
1876 }
1877
1878 if (!(bs = OCSP_response_get1_basic(rsp)))
1879 {
1880 tls_out.ocsp = OCSP_FAILED;
1881 if (LOGGING(tls_cipher))
1882 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1883 else
1884 DEBUG(D_tls) debug_printf(" error parsing response\n");
1885 OCSP_RESPONSE_free(rsp);
1886 return 0;
1887 }
1888
1889 /* We'd check the nonce here if we'd put one in the request. */
1890 /* However that would defeat cacheability on the server so we don't. */
1891
1892 /* This section of code reworked from OpenSSL apps source;
1893 The OpenSSL Project retains copyright:
1894 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1895 */
1896 {
1897 BIO * bp = NULL;
1898 #ifndef EXIM_HAVE_OCSP_RESP_COUNT
1899 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1900 #endif
1901
1902 DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1903
1904 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1905
1906 /* Use the chain that verified the server cert to verify the stapled info */
1907 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1908
1909 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1910 cbinfo->u_ocsp.client.verify_store, OCSP_NOEXPLICIT)) <= 0)
1911 if (ERR_peek_error())
1912 {
1913 tls_out.ocsp = OCSP_FAILED;
1914 if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN,
1915 "Received TLS cert status response, itself unverifiable: %s",
1916 ERR_reason_error_string(ERR_peek_error()));
1917 BIO_printf(bp, "OCSP response verify failure\n");
1918 ERR_print_errors(bp);
1919 OCSP_RESPONSE_print(bp, rsp, 0);
1920 goto failed;
1921 }
1922 else
1923 DEBUG(D_tls) debug_printf("no explicit trust for OCSP signing"
1924 " in the root CA certificate; ignoring\n");
1925
1926 DEBUG(D_tls) debug_printf("OCSP response well-formed and signed OK\n");
1927
1928 /*XXX So we have a good stapled OCSP status. How do we know
1929 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1930 OCSP_resp_find_status() which matches on a cert id, which presumably
1931 we should use. Making an id needs OCSP_cert_id_new(), which takes
1932 issuerName, issuerKey, serialNumber. Are they all in the cert?
1933
1934 For now, carry on blindly accepting the resp. */
1935
1936 for (int idx =
1937 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1938 OCSP_resp_count(bs) - 1;
1939 #else
1940 sk_OCSP_SINGLERESP_num(sresp) - 1;
1941 #endif
1942 idx >= 0; idx--)
1943 {
1944 OCSP_SINGLERESP * single = OCSP_resp_get0(bs, idx);
1945 int status, reason;
1946 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1947
1948 /*XXX so I can see putting a loop in here to handle a rsp with >1 singleresp
1949 - but what happens with a GnuTLS-style input?
1950
1951 we could do with a debug label for each singleresp
1952 - it has a certID with a serialNumber, but I see no API to get that
1953 */
1954 status = OCSP_single_get0_status(single, &reason, &rev,
1955 &thisupd, &nextupd);
1956
1957 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1958 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1959 if (!OCSP_check_validity(thisupd, nextupd,
1960 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1961 {
1962 tls_out.ocsp = OCSP_FAILED;
1963 DEBUG(D_tls) ERR_print_errors(bp);
1964 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1965 goto failed;
1966 }
1967
1968 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1969 OCSP_cert_status_str(status));
1970 switch(status)
1971 {
1972 case V_OCSP_CERTSTATUS_GOOD:
1973 continue; /* the idx loop */
1974 case V_OCSP_CERTSTATUS_REVOKED:
1975 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1976 reason != -1 ? "; reason: " : "",
1977 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1978 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1979 break;
1980 default:
1981 log_write(0, LOG_MAIN,
1982 "Server certificate status unknown, in OCSP stapling");
1983 break;
1984 }
1985
1986 goto failed;
1987 }
1988
1989 i = 1;
1990 tls_out.ocsp = OCSP_VFIED;
1991 goto good;
1992
1993 failed:
1994 tls_out.ocsp = OCSP_FAILED;
1995 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1996 good:
1997 BIO_free(bp);
1998 }
1999
2000 OCSP_RESPONSE_free(rsp);
2001 return i;
2002 }
2003 #endif /*!DISABLE_OCSP*/
2004
2005
2006 /*************************************************
2007 * Initialize for TLS *
2008 *************************************************/
2009
2010 static void
2011 tls_openssl_init(void)
2012 {
2013 #ifdef EXIM_NEED_OPENSSL_INIT
2014 SSL_load_error_strings(); /* basic set up */
2015 OpenSSL_add_ssl_algorithms();
2016 #endif
2017
2018 #if defined(EXIM_HAVE_SHA256) && !defined(OPENSSL_AUTO_SHA256)
2019 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2020 list of available digests. */
2021 EVP_add_digest(EVP_sha256());
2022 #endif
2023 }
2024
2025
2026
2027 /* Called from both server and client code, to do preliminary initialization
2028 of the library. We allocate and return a context structure.
2029
2030 Arguments:
2031 ctxp returned SSL context
2032 host connected host, if client; NULL if server
2033 dhparam DH parameter file
2034 certificate certificate file
2035 privatekey private key
2036 ocsp_file file of stapling info (server); flag for require ocsp (client)
2037 addr address if client; NULL if server (for some randomness)
2038 cbp place to put allocated callback context
2039 errstr error string pointer
2040
2041 Returns: OK/DEFER/FAIL
2042 */
2043
2044 static int
2045 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
2046 uschar *privatekey,
2047 #ifndef DISABLE_OCSP
2048 uschar *ocsp_file,
2049 #endif
2050 address_item *addr, tls_ext_ctx_cb ** cbp,
2051 tls_support * tlsp,
2052 uschar ** errstr)
2053 {
2054 SSL_CTX * ctx;
2055 long init_options;
2056 int rc;
2057 tls_ext_ctx_cb * cbinfo;
2058
2059 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
2060 cbinfo->tlsp = tlsp;
2061 cbinfo->certificate = certificate;
2062 cbinfo->privatekey = privatekey;
2063 cbinfo->is_server = host==NULL;
2064 #ifndef DISABLE_OCSP
2065 cbinfo->verify_stack = NULL;
2066 if (!host)
2067 {
2068 cbinfo->u_ocsp.server.file = ocsp_file;
2069 cbinfo->u_ocsp.server.file_expanded = NULL;
2070 cbinfo->u_ocsp.server.olist = NULL;
2071 }
2072 else
2073 cbinfo->u_ocsp.client.verify_store = NULL;
2074 #endif
2075 cbinfo->dhparam = dhparam;
2076 cbinfo->server_cipher_list = NULL;
2077 cbinfo->host = host;
2078 #ifndef DISABLE_EVENT
2079 cbinfo->event_action = NULL;
2080 #endif
2081
2082 tls_openssl_init();
2083
2084 /* Create a context.
2085 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
2086 negotiation in the different methods; as far as I can tell, the only
2087 *_{server,client}_method which allows negotiation is SSLv23, which exists even
2088 when OpenSSL is built without SSLv2 support.
2089 By disabling with openssl_options, we can let admins re-enable with the
2090 existing knob. */
2091
2092 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
2093 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
2094 #else
2095 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
2096 #endif
2097 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
2098
2099 /* It turns out that we need to seed the random number generator this early in
2100 order to get the full complement of ciphers to work. It took me roughly a day
2101 of work to discover this by experiment.
2102
2103 On systems that have /dev/urandom, SSL may automatically seed itself from
2104 there. Otherwise, we have to make something up as best we can. Double check
2105 afterwards. */
2106
2107 if (!RAND_status())
2108 {
2109 randstuff r;
2110 gettimeofday(&r.tv, NULL);
2111 r.p = getpid();
2112
2113 RAND_seed(US (&r), sizeof(r));
2114 RAND_seed(US big_buffer, big_buffer_size);
2115 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
2116
2117 if (!RAND_status())
2118 return tls_error(US"RAND_status", host,
2119 US"unable to seed random number generator", errstr);
2120 }
2121
2122 /* Set up the information callback, which outputs if debugging is at a suitable
2123 level. */
2124
2125 DEBUG(D_tls)
2126 {
2127 SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
2128 #if defined(EXIM_HAVE_OPESSL_TRACE) && !defined(OPENSSL_NO_SSL_TRACE)
2129 /* this needs a debug build of OpenSSL */
2130 SSL_CTX_set_msg_callback(ctx, (void (*)())SSL_trace);
2131 #endif
2132 #ifdef OPENSSL_HAVE_KEYLOG_CB
2133 SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
2134 #endif
2135 }
2136
2137 /* Automatically re-try reads/writes after renegotiation. */
2138 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
2139
2140 /* Apply administrator-supplied work-arounds.
2141 Historically we applied just one requested option,
2142 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
2143 moved to an administrator-controlled list of options to specify and
2144 grandfathered in the first one as the default value for "openssl_options".
2145
2146 No OpenSSL version number checks: the options we accept depend upon the
2147 availability of the option value macros from OpenSSL. */
2148
2149 if (!tls_openssl_options_parse(openssl_options, &init_options))
2150 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
2151
2152 #ifdef EXPERIMENTAL_TLS_RESUME
2153 tlsp->resumption = RESUME_SUPPORTED;
2154 #endif
2155 if (init_options)
2156 {
2157 #ifdef EXPERIMENTAL_TLS_RESUME
2158 /* Should the server offer session resumption? */
2159 if (!host && verify_check_host(&tls_resumption_hosts) == OK)
2160 {
2161 DEBUG(D_tls) debug_printf("tls_resumption_hosts overrides openssl_options\n");
2162 init_options &= ~SSL_OP_NO_TICKET;
2163 tlsp->resumption |= RESUME_SERVER_TICKET; /* server will give ticket on request */
2164 tlsp->host_resumable = TRUE;
2165 }
2166 #endif
2167
2168 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
2169 if (!(SSL_CTX_set_options(ctx, init_options)))
2170 return tls_error(string_sprintf(
2171 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
2172 }
2173 else
2174 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
2175
2176 /* We'd like to disable session cache unconditionally, but foolish Outlook
2177 Express clients then give up the first TLS connection and make a second one
2178 (which works). Only when there is an IMAP service on the same machine.
2179 Presumably OE is trying to use the cache for A on B. Leave it enabled for
2180 now, until we work out a decent way of presenting control to the config. It
2181 will never be used because we use a new context every time. */
2182 #ifdef notdef
2183 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
2184 #endif
2185
2186 /* Initialize with DH parameters if supplied */
2187 /* Initialize ECDH temp key parameter selection */
2188
2189 if ( !init_dh(ctx, dhparam, host, errstr)
2190 || !init_ecdh(ctx, host, errstr)
2191 )
2192 return DEFER;
2193
2194 /* Set up certificate and key (and perhaps OCSP info) */
2195
2196 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
2197 return rc;
2198
2199 /* If we need to handle SNI or OCSP, do so */
2200
2201 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2202 # ifndef DISABLE_OCSP
2203 if (!(cbinfo->verify_stack = sk_X509_new_null()))
2204 {
2205 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
2206 return FAIL;
2207 }
2208 # endif
2209
2210 if (!host) /* server */
2211 {
2212 # ifndef DISABLE_OCSP
2213 /* We check u_ocsp.server.file, not server.olist, because we care about if
2214 the option exists, not what the current expansion might be, as SNI might
2215 change the certificate and OCSP file in use between now and the time the
2216 callback is invoked. */
2217 if (cbinfo->u_ocsp.server.file)
2218 {
2219 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
2220 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2221 }
2222 # endif
2223 /* We always do this, so that $tls_sni is available even if not used in
2224 tls_certificate */
2225 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
2226 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
2227 }
2228 # ifndef DISABLE_OCSP
2229 else /* client */
2230 if(ocsp_file) /* wanting stapling */
2231 {
2232 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
2233 {
2234 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
2235 return FAIL;
2236 }
2237 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
2238 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2239 }
2240 # endif
2241 #endif
2242
2243 cbinfo->verify_cert_hostnames = NULL;
2244
2245 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
2246 /* Set up the RSA callback */
2247 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
2248 #endif
2249
2250 /* Finally, set the session cache timeout, and we are done.
2251 The period appears to be also used for (server-generated) session tickets */
2252
2253 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
2254 DEBUG(D_tls) debug_printf("Initialized TLS\n");
2255
2256 *cbp = cbinfo;
2257 *ctxp = ctx;
2258
2259 return OK;
2260 }
2261
2262
2263
2264
2265 /*************************************************
2266 * Get name of cipher in use *
2267 *************************************************/
2268
2269 /*
2270 Argument: pointer to an SSL structure for the connection
2271 pointer to number of bits for cipher
2272 Returns: pointer to allocated string in perm-pool
2273 */
2274
2275 static uschar *
2276 construct_cipher_name(SSL * ssl, int * bits)
2277 {
2278 int pool = store_pool;
2279 /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't
2280 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
2281 the accessor functions use const in the prototype. */
2282
2283 const uschar * ver = CUS SSL_get_version(ssl);
2284 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
2285 uschar * s;
2286
2287 SSL_CIPHER_get_bits(c, bits);
2288
2289 store_pool = POOL_PERM;
2290 s = string_sprintf("%s:%s:%u", ver, SSL_CIPHER_get_name(c), *bits);
2291 store_pool = pool;
2292 DEBUG(D_tls) debug_printf("Cipher: %s\n", s);
2293 return s;
2294 }
2295
2296
2297 /* Get IETF-standard name for ciphersuite.
2298 Argument: pointer to an SSL structure for the connection
2299 Returns: pointer to string
2300 */
2301
2302 static const uschar *
2303 cipher_stdname_ssl(SSL * ssl)
2304 {
2305 #ifdef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
2306 return CUS SSL_CIPHER_standard_name(SSL_get_current_cipher(ssl));
2307 #else
2308 ushort id = 0xffff & SSL_CIPHER_get_id(SSL_get_current_cipher(ssl));
2309 return cipher_stdname(id >> 8, id & 0xff);
2310 #endif
2311 }
2312
2313
2314 static void
2315 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
2316 {
2317 /*XXX we might consider a list-of-certs variable for the cert chain.
2318 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
2319 in list-handling functions, also consider the difference between the entire
2320 chain and the elements sent by the peer. */
2321
2322 tlsp->peerdn = NULL;
2323
2324 /* Will have already noted peercert on a verify fail; possibly not the leaf */
2325 if (!tlsp->peercert)
2326 tlsp->peercert = SSL_get_peer_certificate(ssl);
2327 /* Beware anonymous ciphers which lead to server_cert being NULL */
2328 if (tlsp->peercert)
2329 if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz))
2330 { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); }
2331 else
2332 {
2333 int oldpool = store_pool;
2334
2335 peerdn[siz-1] = '\0'; /* paranoia */
2336 store_pool = POOL_PERM;
2337 tlsp->peerdn = string_copy(peerdn);
2338 store_pool = oldpool;
2339
2340 /* We used to set CV in the cert-verify callbacks (either plain or dane)
2341 but they don't get called on session-resumption. So use the official
2342 interface, which uses the resumed value. Unfortunately this claims verified
2343 when it actually failed but we're in try-verify mode, due to us wanting the
2344 knowlege that it failed so needing to have the callback and forcing a
2345 permissive return. If we don't force it, the TLS startup is failed.
2346 The extra bit of information is set in verify_override in the cb, stashed
2347 for resumption next to the TLS session, and used here. */
2348
2349 if (!tlsp->verify_override)
2350 tlsp->certificate_verified =
2351 #ifdef SUPPORT_DANE
2352 tlsp->dane_verified ||
2353 #endif
2354 SSL_get_verify_result(ssl) == X509_V_OK;
2355 }
2356 }
2357
2358
2359
2360
2361
2362 /*************************************************
2363 * Set up for verifying certificates *
2364 *************************************************/
2365
2366 #ifndef DISABLE_OCSP
2367 /* Load certs from file, return TRUE on success */
2368
2369 static BOOL
2370 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
2371 {
2372 BIO * bp;
2373 X509 * x;
2374
2375 while (sk_X509_num(verify_stack) > 0)
2376 X509_free(sk_X509_pop(verify_stack));
2377
2378 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
2379 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
2380 sk_X509_push(verify_stack, x);
2381 BIO_free(bp);
2382 return TRUE;
2383 }
2384 #endif
2385
2386
2387
2388 /* Called by both client and server startup; on the server possibly
2389 repeated after a Server Name Indication.
2390
2391 Arguments:
2392 sctx SSL_CTX* to initialise
2393 certs certs file or NULL
2394 crl CRL file or NULL
2395 host NULL in a server; the remote host in a client
2396 optional TRUE if called from a server for a host in tls_try_verify_hosts;
2397 otherwise passed as FALSE
2398 cert_vfy_cb Callback function for certificate verification
2399 errstr error string pointer
2400
2401 Returns: OK/DEFER/FAIL
2402 */
2403
2404 static int
2405 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
2406 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
2407 {
2408 uschar *expcerts, *expcrl;
2409
2410 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2411 return DEFER;
2412 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2413
2414 if (expcerts && *expcerts)
2415 {
2416 /* Tell the library to use its compiled-in location for the system default
2417 CA bundle. Then add the ones specified in the config, if any. */
2418
2419 if (!SSL_CTX_set_default_verify_paths(sctx))
2420 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2421
2422 if (Ustrcmp(expcerts, "system") != 0)
2423 {
2424 struct stat statbuf;
2425
2426 if (Ustat(expcerts, &statbuf) < 0)
2427 {
2428 log_write(0, LOG_MAIN|LOG_PANIC,
2429 "failed to stat %s for certificates", expcerts);
2430 return DEFER;
2431 }
2432 else
2433 {
2434 uschar *file, *dir;
2435 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2436 { file = NULL; dir = expcerts; }
2437 else
2438 {
2439 file = expcerts; dir = NULL;
2440 #ifndef DISABLE_OCSP
2441 /* In the server if we will be offering an OCSP proof, load chain from
2442 file for verifying the OCSP proof at load time. */
2443
2444 /*XXX Glitch! The file here is tls_verify_certs: the chain for verifying the client cert.
2445 This is inconsistent with the need to verify the OCSP proof of the server cert.
2446 */
2447
2448 if ( !host
2449 && statbuf.st_size > 0
2450 && server_static_cbinfo->u_ocsp.server.file
2451 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2452 )
2453 {
2454 log_write(0, LOG_MAIN|LOG_PANIC,
2455 "failed to load cert chain from %s", file);
2456 return DEFER;
2457 }
2458 #endif
2459 }
2460
2461 /* If a certificate file is empty, the next function fails with an
2462 unhelpful error message. If we skip it, we get the correct behaviour (no
2463 certificates are recognized, but the error message is still misleading (it
2464 says no certificate was supplied). But this is better. */
2465
2466 if ( (!file || statbuf.st_size > 0)
2467 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
2468 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
2469
2470 /* Load the list of CAs for which we will accept certs, for sending
2471 to the client. This is only for the one-file tls_verify_certificates
2472 variant.
2473 If a list isn't loaded into the server, but some verify locations are set,
2474 the server end appears to make a wildcard request for client certs.
2475 Meanwhile, the client library as default behaviour *ignores* the list
2476 we send over the wire - see man SSL_CTX_set_client_cert_cb.
2477 Because of this, and that the dir variant is likely only used for
2478 the public-CA bundle (not for a private CA), not worth fixing. */
2479
2480 if (file)
2481 {
2482 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
2483
2484 SSL_CTX_set_client_CA_list(sctx, names);
2485 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
2486 sk_X509_NAME_num(names));
2487 }
2488 }
2489 }
2490
2491 /* Handle a certificate revocation list. */
2492
2493 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2494
2495 /* This bit of code is now the version supplied by Lars Mainka. (I have
2496 merely reformatted it into the Exim code style.)
2497
2498 "From here I changed the code to add support for multiple crl's
2499 in pem format in one file or to support hashed directory entries in
2500 pem format instead of a file. This method now uses the library function
2501 X509_STORE_load_locations to add the CRL location to the SSL context.
2502 OpenSSL will then handle the verify against CA certs and CRLs by
2503 itself in the verify callback." */
2504
2505 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2506 if (expcrl && *expcrl)
2507 {
2508 struct stat statbufcrl;
2509 if (Ustat(expcrl, &statbufcrl) < 0)
2510 {
2511 log_write(0, LOG_MAIN|LOG_PANIC,
2512 "failed to stat %s for certificates revocation lists", expcrl);
2513 return DEFER;
2514 }
2515 else
2516 {
2517 /* is it a file or directory? */
2518 uschar *file, *dir;
2519 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2520 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2521 {
2522 file = NULL;
2523 dir = expcrl;
2524 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2525 }
2526 else
2527 {
2528 file = expcrl;
2529 dir = NULL;
2530 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2531 }
2532 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2533 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2534
2535 /* setting the flags to check against the complete crl chain */
2536
2537 X509_STORE_set_flags(cvstore,
2538 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2539 }
2540 }
2541
2542 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2543
2544 /* If verification is optional, don't fail if no certificate */
2545
2546 SSL_CTX_set_verify(sctx,
2547 SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2548 cert_vfy_cb);
2549 }
2550
2551 return OK;
2552 }
2553
2554
2555
2556 /*************************************************
2557 * Start a TLS session in a server *
2558 *************************************************/
2559
2560 /* This is called when Exim is running as a server, after having received
2561 the STARTTLS command. It must respond to that command, and then negotiate
2562 a TLS session.
2563
2564 Arguments:
2565 require_ciphers allowed ciphers
2566 errstr pointer to error message
2567
2568 Returns: OK on success
2569 DEFER for errors before the start of the negotiation
2570 FAIL for errors during the negotiation; the server can't
2571 continue running.
2572 */
2573
2574 int
2575 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2576 {
2577 int rc;
2578 uschar * expciphers;
2579 tls_ext_ctx_cb * cbinfo;
2580 static uschar peerdn[256];
2581
2582 /* Check for previous activation */
2583
2584 if (tls_in.active.sock >= 0)
2585 {
2586 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2587 smtp_printf("554 Already in TLS\r\n", FALSE);
2588 return FAIL;
2589 }
2590
2591 /* Initialize the SSL library. If it fails, it will already have logged
2592 the error. */
2593
2594 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2595 #ifndef DISABLE_OCSP
2596 tls_ocsp_file,
2597 #endif
2598 NULL, &server_static_cbinfo, &tls_in, errstr);
2599 if (rc != OK) return rc;
2600 cbinfo = server_static_cbinfo;
2601
2602 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
2603 return FAIL;
2604
2605 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2606 were historically separated by underscores. So that I can use either form in my
2607 tests, and also for general convenience, we turn underscores into hyphens here.
2608
2609 XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites()
2610 for TLS 1.3 . Since we do not call it at present we get the default list:
2611 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
2612 */
2613
2614 if (expciphers)
2615 {
2616 for (uschar * s = expciphers; *s; s++ ) if (*s == '_') *s = '-';
2617 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2618 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
2619 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
2620 cbinfo->server_cipher_list = expciphers;
2621 }
2622
2623 /* If this is a host for which certificate verification is mandatory or
2624 optional, set up appropriately. */
2625
2626 tls_in.certificate_verified = FALSE;
2627 #ifdef SUPPORT_DANE
2628 tls_in.dane_verified = FALSE;
2629 #endif
2630 server_verify_callback_called = FALSE;
2631
2632 if (verify_check_host(&tls_verify_hosts) == OK)
2633 {
2634 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2635 FALSE, verify_callback_server, errstr);
2636 if (rc != OK) return rc;
2637 server_verify_optional = FALSE;
2638 }
2639 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2640 {
2641 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2642 TRUE, verify_callback_server, errstr);
2643 if (rc != OK) return rc;
2644 server_verify_optional = TRUE;
2645 }
2646
2647 #ifdef EXPERIMENTAL_TLS_RESUME
2648 SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_key_callback);
2649 /* despite working, appears to always return failure, so ignoring */
2650 #endif
2651 #ifdef OPENSSL_HAVE_NUM_TICKETS
2652 # ifdef EXPERIMENTAL_TLS_RESUME
2653 SSL_CTX_set_num_tickets(server_ctx, tls_in.host_resumable ? 1 : 0);
2654 # else
2655 SSL_CTX_set_num_tickets(server_ctx, 0); /* send no TLS1.3 stateful-tickets */
2656 # endif
2657 #endif
2658
2659
2660 /* Prepare for new connection */
2661
2662 if (!(server_ssl = SSL_new(server_ctx)))
2663 return tls_error(US"SSL_new", NULL, NULL, errstr);
2664
2665 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2666 *
2667 * With the SSL_clear(), we get strange interoperability bugs with
2668 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2669 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2670 *
2671 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2672 * session shutdown. In this case, we have a brand new object and there's no
2673 * obvious reason to immediately clear it. I'm guessing that this was
2674 * originally added because of incomplete initialisation which the clear fixed,
2675 * in some historic release.
2676 */
2677
2678 /* Set context and tell client to go ahead, except in the case of TLS startup
2679 on connection, where outputting anything now upsets the clients and tends to
2680 make them disconnect. We need to have an explicit fflush() here, to force out
2681 the response. Other smtp_printf() calls do not need it, because in non-TLS
2682 mode, the fflush() happens when smtp_getc() is called. */
2683
2684 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2685 if (!tls_in.on_connect)
2686 {
2687 smtp_printf("220 TLS go ahead\r\n", FALSE);
2688 fflush(smtp_out);
2689 }
2690
2691 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2692 that the OpenSSL library doesn't. */
2693
2694 SSL_set_wfd(server_ssl, fileno(smtp_out));
2695 SSL_set_rfd(server_ssl, fileno(smtp_in));
2696 SSL_set_accept_state(server_ssl);
2697
2698 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2699
2700 sigalrm_seen = FALSE;
2701 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2702 rc = SSL_accept(server_ssl);
2703 ALARM_CLR(0);
2704
2705 if (rc <= 0)
2706 {
2707 int error = SSL_get_error(server_ssl, rc);
2708 switch(error)
2709 {
2710 case SSL_ERROR_NONE:
2711 break;
2712
2713 case SSL_ERROR_ZERO_RETURN:
2714 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2715 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2716
2717 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
2718 SSL_shutdown(server_ssl);
2719
2720 tls_close(NULL, TLS_NO_SHUTDOWN);
2721 return FAIL;
2722
2723 /* Handle genuine errors */
2724 case SSL_ERROR_SSL:
2725 {
2726 uschar * s = US"SSL_accept";
2727 unsigned long e = ERR_peek_error();
2728 if (ERR_GET_REASON(e) == SSL_R_WRONG_VERSION_NUMBER)
2729 s = string_sprintf("%s (%s)", s, SSL_get_version(server_ssl));
2730 (void) tls_error(s, NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2731 return FAIL;
2732 }
2733
2734 default:
2735 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2736 if (error == SSL_ERROR_SYSCALL)
2737 {
2738 if (!errno)
2739 {
2740 *errstr = US"SSL_accept: TCP connection closed by peer";
2741 return FAIL;
2742 }
2743 DEBUG(D_tls) debug_printf(" - syscall %s\n", strerror(errno));
2744 }
2745 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2746 return FAIL;
2747 }
2748 }
2749
2750 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2751 ERR_clear_error(); /* Even success can leave errors in the stack. Seen with
2752 anon-authentication ciphersuite negotiated. */
2753
2754 #ifdef EXPERIMENTAL_TLS_RESUME
2755 if (SSL_session_reused(server_ssl))
2756 {
2757 tls_in.resumption |= RESUME_USED;
2758 DEBUG(D_tls) debug_printf("Session reused\n");
2759 }
2760 #endif
2761
2762 /* TLS has been set up. Adjust the input functions to read via TLS,
2763 and initialize things. */
2764
2765 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2766
2767 tls_in.cipher = construct_cipher_name(server_ssl, &tls_in.bits);
2768 tls_in.cipher_stdname = cipher_stdname_ssl(server_ssl);
2769
2770 DEBUG(D_tls)
2771 {
2772 uschar buf[2048];
2773 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)))
2774 debug_printf("Shared ciphers: %s\n", buf);
2775
2776 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2777 {
2778 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
2779 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2780 BIO_free(bp);
2781 }
2782 #endif
2783
2784 #ifdef EXIM_HAVE_SESSION_TICKET
2785 {
2786 SSL_SESSION * ss = SSL_get_session(server_ssl);
2787 if (SSL_SESSION_has_ticket(ss)) /* 1.1.0 */
2788 debug_printf("The session has a ticket, life %lu seconds\n",
2789 SSL_SESSION_get_ticket_lifetime_hint(ss));
2790 }
2791 #endif
2792 }
2793
2794 /* Record the certificate we presented */
2795 {
2796 X509 * crt = SSL_get_certificate(server_ssl);
2797 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2798 }
2799
2800 /* Only used by the server-side tls (tls_in), including tls_getc.
2801 Client-side (tls_out) reads (seem to?) go via
2802 smtp_read_response()/ip_recv().
2803 Hence no need to duplicate for _in and _out.
2804 */
2805 if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2806 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2807 ssl_xfer_eof = ssl_xfer_error = FALSE;
2808
2809 receive_getc = tls_getc;
2810 receive_getbuf = tls_getbuf;
2811 receive_get_cache = tls_get_cache;
2812 receive_ungetc = tls_ungetc;
2813 receive_feof = tls_feof;
2814 receive_ferror = tls_ferror;
2815 receive_smtp_buffered = tls_smtp_buffered;
2816
2817 tls_in.active.sock = fileno(smtp_out);
2818 tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */
2819 return OK;
2820 }
2821
2822
2823
2824
2825 static int
2826 tls_client_basic_ctx_init(SSL_CTX * ctx,
2827 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2828 uschar ** errstr)
2829 {
2830 int rc;
2831 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2832 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2833 the specified host patterns if one of them is defined */
2834
2835 if ( ( !ob->tls_verify_hosts
2836 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2837 )
2838 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2839 )
2840 client_verify_optional = FALSE;
2841 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2842 client_verify_optional = TRUE;
2843 else
2844 return OK;
2845
2846 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2847 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2848 errstr)) != OK)
2849 return rc;
2850
2851 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2852 {
2853 cbinfo->verify_cert_hostnames =
2854 #ifdef SUPPORT_I18N
2855 string_domain_utf8_to_alabel(host->name, NULL);
2856 #else
2857 host->name;
2858 #endif
2859 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2860 cbinfo->verify_cert_hostnames);
2861 }
2862 return OK;
2863 }
2864
2865
2866 #ifdef SUPPORT_DANE
2867 static int
2868 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2869 {
2870 dns_scan dnss;
2871 const char * hostnames[2] = { CS host->name, NULL };
2872 int found = 0;
2873
2874 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2875 return tls_error(US"hostnames load", host, NULL, errstr);
2876
2877 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2878 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2879 ) if (rr->type == T_TLSA && rr->size > 3)
2880 {
2881 const uschar * p = rr->data;
2882 uint8_t usage, selector, mtype;
2883 const char * mdname;
2884
2885 usage = *p++;
2886
2887 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2888 if (usage != 2 && usage != 3) continue;
2889
2890 selector = *p++;
2891 mtype = *p++;
2892
2893 switch (mtype)
2894 {
2895 default: continue; /* Only match-types 0, 1, 2 are supported */
2896 case 0: mdname = NULL; break;
2897 case 1: mdname = "sha256"; break;
2898 case 2: mdname = "sha512"; break;
2899 }
2900
2901 found++;
2902 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2903 {
2904 default:
2905 return tls_error(US"tlsa load", host, NULL, errstr);
2906 case 0: /* action not taken */
2907 case 1: break;
2908 }
2909
2910 tls_out.tlsa_usage |= 1<<usage;
2911 }
2912
2913 if (found)
2914 return OK;
2915
2916 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2917 return DEFER;
2918 }
2919 #endif /*SUPPORT_DANE*/
2920
2921
2922
2923 #ifdef EXPERIMENTAL_TLS_RESUME
2924 /* On the client, get any stashed session for the given IP from hints db
2925 and apply it to the ssl-connection for attempted resumption. */
2926
2927 static void
2928 tls_retrieve_session(tls_support * tlsp, SSL * ssl, const uschar * key)
2929 {
2930 tlsp->resumption |= RESUME_SUPPORTED;
2931 if (tlsp->host_resumable)
2932 {
2933 dbdata_tls_session * dt;
2934 int len;
2935 open_db dbblock, * dbm_file;
2936
2937 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
2938 DEBUG(D_tls) debug_printf("checking for resumable session for %s\n", key);
2939 if ((dbm_file = dbfn_open(US"tls", O_RDONLY, &dbblock, FALSE, FALSE)))
2940 {
2941 /* key for the db is the IP */
2942 if ((dt = dbfn_read_with_length(dbm_file, key, &len)))
2943 {
2944 SSL_SESSION * ss = NULL;
2945 const uschar * sess_asn1 = dt->session;
2946
2947 len -= sizeof(dbdata_tls_session);
2948 if (!(d2i_SSL_SESSION(&ss, &sess_asn1, (long)len)))
2949 {
2950 DEBUG(D_tls)
2951 {
2952 ERR_error_string_n(ERR_get_error(),
2953 ssl_errstring, sizeof(ssl_errstring));
2954 debug_printf("decoding session: %s\n", ssl_errstring);
2955 }
2956 }
2957 #ifdef EXIM_HAVE_SESSION_TICKET
2958 else if ( SSL_SESSION_get_ticket_lifetime_hint(ss) + dt->time_stamp
2959 < time(NULL))
2960 {
2961 DEBUG(D_tls) debug_printf("session expired\n");
2962 dbfn_delete(dbm_file, key);
2963 }
2964 #endif
2965 else if (!SSL_set_session(ssl, ss))
2966 {
2967 DEBUG(D_tls)
2968 {
2969 ERR_error_string_n(ERR_get_error(),
2970 ssl_errstring, sizeof(ssl_errstring));
2971 debug_printf("applying session to ssl: %s\n", ssl_errstring);
2972 }
2973 }
2974 else
2975 {
2976 DEBUG(D_tls) debug_printf("good session\n");
2977 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
2978 tlsp->verify_override = dt->verify_override;
2979 tlsp->ocsp = dt->ocsp;
2980 }
2981 }
2982 else
2983 DEBUG(D_tls) debug_printf("no session record\n");
2984 dbfn_close(dbm_file);
2985 }
2986 }
2987 }
2988
2989
2990 /* On the client, save the session for later resumption */
2991
2992 static int
2993 tls_save_session_cb(SSL * ssl, SSL_SESSION * ss)
2994 {
2995 tls_ext_ctx_cb * cbinfo = SSL_get_ex_data(ssl, tls_exdata_idx);
2996 tls_support * tlsp;
2997
2998 DEBUG(D_tls) debug_printf("tls_save_session_cb\n");
2999
3000 if (!cbinfo || !(tlsp = cbinfo->tlsp)->host_resumable) return 0;
3001
3002 # ifdef OPENSSL_HAVE_NUM_TICKETS
3003 if (SSL_SESSION_is_resumable(ss)) /* 1.1.1 */
3004 # endif
3005 {
3006 int len = i2d_SSL_SESSION(ss, NULL);
3007 int dlen = sizeof(dbdata_tls_session) + len;
3008 dbdata_tls_session * dt = store_get(dlen, TRUE);
3009 uschar * s = dt->session;
3010 open_db dbblock, * dbm_file;
3011
3012 DEBUG(D_tls) debug_printf("session is resumable\n");
3013 tlsp->resumption |= RESUME_SERVER_TICKET; /* server gave us a ticket */
3014
3015 dt->verify_override = tlsp->verify_override;
3016 dt->ocsp = tlsp->ocsp;
3017 (void) i2d_SSL_SESSION(ss, &s); /* s gets bumped to end */
3018
3019 if ((dbm_file = dbfn_open(US"tls", O_RDWR, &dbblock, FALSE, FALSE)))
3020 {
3021 const uschar * key = cbinfo->host->address;
3022 dbfn_delete(dbm_file, key);
3023 dbfn_write(dbm_file, key, dt, dlen);
3024 dbfn_close(dbm_file);
3025 DEBUG(D_tls) debug_printf("wrote session (len %u) to db\n",
3026 (unsigned)dlen);
3027 }
3028 }
3029 return 1;
3030 }
3031
3032
3033 static void
3034 tls_client_ctx_resume_prehandshake(
3035 exim_openssl_client_tls_ctx * exim_client_ctx, tls_support * tlsp,
3036 smtp_transport_options_block * ob, host_item * host)
3037 {
3038 /* Should the client request a session resumption ticket? */
3039 if (verify_check_given_host(CUSS &ob->tls_resumption_hosts, host) == OK)
3040 {
3041 tlsp->host_resumable = TRUE;
3042
3043 SSL_CTX_set_session_cache_mode(exim_client_ctx->ctx,
3044 SSL_SESS_CACHE_CLIENT
3045 | SSL_SESS_CACHE_NO_INTERNAL | SSL_SESS_CACHE_NO_AUTO_CLEAR);
3046 SSL_CTX_sess_set_new_cb(exim_client_ctx->ctx, tls_save_session_cb);
3047 }
3048 }
3049
3050 static BOOL
3051 tls_client_ssl_resume_prehandshake(SSL * ssl, tls_support * tlsp,
3052 host_item * host, uschar ** errstr)
3053 {
3054 if (tlsp->host_resumable)
3055 {
3056 DEBUG(D_tls)
3057 debug_printf("tls_resumption_hosts overrides openssl_options, enabling tickets\n");
3058 SSL_clear_options(ssl, SSL_OP_NO_TICKET);
3059
3060 tls_exdata_idx = SSL_get_ex_new_index(0, 0, 0, 0, 0);
3061 if (!SSL_set_ex_data(ssl, tls_exdata_idx, client_static_cbinfo))
3062 {
3063 tls_error(US"set ex_data", host, NULL, errstr);
3064 return FALSE;
3065 }
3066 debug_printf("tls_exdata_idx %d cbinfo %p\n", tls_exdata_idx, client_static_cbinfo);
3067 }
3068
3069 tlsp->resumption = RESUME_SUPPORTED;
3070 /* Pick up a previous session, saved on an old ticket */
3071 tls_retrieve_session(tlsp, ssl, host->address);
3072 return TRUE;
3073 }
3074
3075 static void
3076 tls_client_resume_posthandshake(exim_openssl_client_tls_ctx * exim_client_ctx,
3077 tls_support * tlsp)
3078 {
3079 if (SSL_session_reused(exim_client_ctx->ssl))
3080 {
3081 DEBUG(D_tls) debug_printf("The session was reused\n");
3082 tlsp->resumption |= RESUME_USED;
3083 }
3084 }
3085 #endif /* EXPERIMENTAL_TLS_RESUME */
3086
3087
3088 /*************************************************
3089 * Start a TLS session in a client *
3090 *************************************************/
3091
3092 /* Called from the smtp transport after STARTTLS has been accepted.
3093
3094 Arguments:
3095 cctx connection context
3096 conn_args connection details
3097 cookie datum for randomness; can be NULL
3098 tlsp record details of TLS channel configuration here; must be non-NULL
3099 errstr error string pointer
3100
3101 Returns: TRUE for success with TLS session context set in connection context,
3102 FALSE on error
3103 */
3104
3105 BOOL
3106 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
3107 void * cookie, tls_support * tlsp, uschar ** errstr)
3108 {
3109 host_item * host = conn_args->host; /* for msgs and option-tests */
3110 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
3111 smtp_transport_options_block * ob = tb
3112 ? (smtp_transport_options_block *)tb->options_block
3113 : &smtp_transport_option_defaults;
3114 exim_openssl_client_tls_ctx * exim_client_ctx;
3115 uschar * expciphers;
3116 int rc;
3117 static uschar peerdn[256];
3118
3119 #ifndef DISABLE_OCSP
3120 BOOL request_ocsp = FALSE;
3121 BOOL require_ocsp = FALSE;
3122 #endif
3123
3124 rc = store_pool;
3125 store_pool = POOL_PERM;
3126 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx), FALSE);
3127 exim_client_ctx->corked = NULL;
3128 store_pool = rc;
3129
3130 #ifdef SUPPORT_DANE
3131 tlsp->tlsa_usage = 0;
3132 #endif
3133
3134 #ifndef DISABLE_OCSP
3135 {
3136 # ifdef SUPPORT_DANE
3137 if ( conn_args->dane
3138 && ob->hosts_request_ocsp[0] == '*'
3139 && ob->hosts_request_ocsp[1] == '\0'
3140 )
3141 {
3142 /* Unchanged from default. Use a safer one under DANE */
3143 request_ocsp = TRUE;
3144 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
3145 " {= {4}{$tls_out_tlsa_usage}} } "
3146 " {*}{}}";
3147 }
3148 # endif
3149
3150 if ((require_ocsp =
3151 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
3152 request_ocsp = TRUE;
3153 else
3154 # ifdef SUPPORT_DANE
3155 if (!request_ocsp)
3156 # endif
3157 request_ocsp =
3158 verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
3159 }
3160 #endif
3161
3162 rc = tls_init(&exim_client_ctx->ctx, host, NULL,
3163 ob->tls_certificate, ob->tls_privatekey,
3164 #ifndef DISABLE_OCSP
3165 (void *)(long)request_ocsp,
3166 #endif
3167 cookie, &client_static_cbinfo, tlsp, errstr);
3168 if (rc != OK) return FALSE;
3169
3170 tlsp->certificate_verified = FALSE;
3171 client_verify_callback_called = FALSE;
3172
3173 expciphers = NULL;
3174 #ifdef SUPPORT_DANE
3175 if (conn_args->dane)
3176 {
3177 /* We fall back to tls_require_ciphers if unset, empty or forced failure, but
3178 other failures should be treated as problems. */
3179 if (ob->dane_require_tls_ciphers &&
3180 !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
3181 &expciphers, errstr))
3182 return FALSE;
3183 if (expciphers && *expciphers == '\0')
3184 expciphers = NULL;
3185 }
3186 #endif
3187 if (!expciphers &&
3188 !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
3189 &expciphers, errstr))
3190 return FALSE;
3191
3192 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
3193 are separated by underscores. So that I can use either form in my tests, and
3194 also for general convenience, we turn underscores into hyphens here. */
3195
3196 if (expciphers)
3197 {
3198 uschar *s = expciphers;
3199 while (*s) { if (*s == '_') *s = '-'; s++; }
3200 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
3201 if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers))
3202 {
3203 tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
3204 return FALSE;
3205 }
3206 }
3207
3208 #ifdef SUPPORT_DANE
3209 if (conn_args->dane)
3210 {
3211 SSL_CTX_set_verify(exim_client_ctx->ctx,
3212 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
3213 verify_callback_client_dane);
3214
3215 if (!DANESSL_library_init())
3216 {
3217 tls_error(US"library init", host, NULL, errstr);
3218 return FALSE;
3219 }
3220 if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
3221 {
3222 tls_error(US"context init", host, NULL, errstr);
3223 return FALSE;
3224 }
3225 }
3226 else
3227
3228 #endif
3229
3230 if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
3231 client_static_cbinfo, errstr) != OK)
3232 return FALSE;
3233
3234 #ifdef EXPERIMENTAL_TLS_RESUME
3235 tls_client_ctx_resume_prehandshake(exim_client_ctx, tlsp, ob, host);
3236 #endif
3237
3238
3239 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
3240 {
3241 tls_error(US"SSL_new", host, NULL, errstr);
3242 return FALSE;
3243 }
3244 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
3245
3246 SSL_set_fd(exim_client_ctx->ssl, cctx->sock);
3247 SSL_set_connect_state(exim_client_ctx->ssl);
3248
3249 if (ob->tls_sni)
3250 {
3251 if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
3252 return FALSE;
3253 if (!tlsp->sni)
3254 {
3255 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
3256 }
3257 else if (!Ustrlen(tlsp->sni))
3258 tlsp->sni = NULL;
3259 else
3260 {
3261 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
3262 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni);
3263 SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni);
3264 #else
3265 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
3266 tlsp->sni);
3267 #endif
3268 }
3269 }
3270
3271 #ifdef SUPPORT_DANE
3272 if (conn_args->dane)
3273 if (dane_tlsa_load(exim_client_ctx->ssl, host, &conn_args->tlsa_dnsa, errstr) != OK)
3274 return FALSE;
3275 #endif
3276
3277 #ifndef DISABLE_OCSP
3278 /* Request certificate status at connection-time. If the server
3279 does OCSP stapling we will get the callback (set in tls_init()) */
3280 # ifdef SUPPORT_DANE
3281 if (request_ocsp)
3282 {
3283 const uschar * s;
3284 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
3285 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
3286 )
3287 { /* Re-eval now $tls_out_tlsa_usage is populated. If
3288 this means we avoid the OCSP request, we wasted the setup
3289 cost in tls_init(). */
3290 require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
3291 request_ocsp = require_ocsp
3292 || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
3293 }
3294 }
3295 # endif
3296
3297 if (request_ocsp)
3298 {
3299 SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp);
3300 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
3301 tlsp->ocsp = OCSP_NOT_RESP;
3302 }
3303 #endif
3304
3305 #ifdef EXPERIMENTAL_TLS_RESUME
3306 if (!tls_client_ssl_resume_prehandshake(exim_client_ctx->ssl, tlsp, host,
3307 errstr))
3308 return FALSE;
3309 #endif
3310
3311 #ifndef DISABLE_EVENT
3312 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
3313 #endif
3314
3315 /* There doesn't seem to be a built-in timeout on connection. */
3316
3317 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
3318 sigalrm_seen = FALSE;
3319 ALARM(ob->command_timeout);
3320 rc = SSL_connect(exim_client_ctx->ssl);
3321 ALARM_CLR(0);
3322
3323 #ifdef SUPPORT_DANE
3324 if (conn_args->dane)
3325 DANESSL_cleanup(exim_client_ctx->ssl);
3326 #endif
3327
3328 if (rc <= 0)
3329 {
3330 tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
3331 return FALSE;
3332 }
3333
3334 DEBUG(D_tls)
3335 {
3336 debug_printf("SSL_connect succeeded\n");
3337 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
3338 {
3339 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
3340 SSL_SESSION_print_keylog(bp, SSL_get_session(exim_client_ctx->ssl));
3341 BIO_free(bp);
3342 }
3343 #endif
3344 }
3345
3346 #ifdef EXPERIMENTAL_TLS_RESUME
3347 tls_client_resume_posthandshake(exim_client_ctx, tlsp);
3348 #endif
3349
3350 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
3351
3352 tlsp->cipher = construct_cipher_name(exim_client_ctx->ssl, &tlsp->bits);
3353 tlsp->cipher_stdname = cipher_stdname_ssl(exim_client_ctx->ssl);
3354
3355 /* Record the certificate we presented */
3356 {
3357 X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
3358 tlsp->ourcert = crt ? X509_dup(crt) : NULL;
3359 }
3360
3361 tlsp->active.sock = cctx->sock;
3362 tlsp->active.tls_ctx = exim_client_ctx;
3363 cctx->tls_ctx = exim_client_ctx;
3364 return TRUE;
3365 }
3366
3367
3368
3369
3370
3371 static BOOL
3372 tls_refill(unsigned lim)
3373 {
3374 int error;
3375 int inbytes;
3376
3377 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
3378 ssl_xfer_buffer, ssl_xfer_buffer_size);
3379
3380 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
3381 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
3382 MIN(ssl_xfer_buffer_size, lim));
3383 error = SSL_get_error(server_ssl, inbytes);
3384 if (smtp_receive_timeout > 0) ALARM_CLR(0);
3385
3386 if (had_command_timeout) /* set by signal handler */
3387 smtp_command_timeout_exit(); /* does not return */
3388 if (had_command_sigterm)
3389 smtp_command_sigterm_exit();
3390 if (had_data_timeout)
3391 smtp_data_timeout_exit();
3392 if (had_data_sigint)
3393 smtp_data_sigint_exit();
3394
3395 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
3396 closed down, not that the socket itself has been closed down. Revert to
3397 non-SSL handling. */
3398
3399 switch(error)
3400 {
3401 case SSL_ERROR_NONE:
3402 break;
3403
3404 case SSL_ERROR_ZERO_RETURN:
3405 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
3406
3407 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
3408 SSL_shutdown(server_ssl);
3409
3410 tls_close(NULL, TLS_NO_SHUTDOWN);
3411 return FALSE;
3412
3413 /* Handle genuine errors */
3414 case SSL_ERROR_SSL:
3415 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3416 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
3417 ssl_xfer_error = TRUE;
3418 return FALSE;
3419
3420 default:
3421 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
3422 DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL)
3423 debug_printf(" - syscall %s\n", strerror(errno));
3424 ssl_xfer_error = TRUE;
3425 return FALSE;
3426 }
3427
3428 #ifndef DISABLE_DKIM
3429 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
3430 #endif
3431 ssl_xfer_buffer_hwm = inbytes;
3432 ssl_xfer_buffer_lwm = 0;
3433 return TRUE;
3434 }
3435
3436
3437 /*************************************************
3438 * TLS version of getc *
3439 *************************************************/
3440
3441 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
3442 it refills the buffer via the SSL reading function.
3443
3444 Arguments: lim Maximum amount to read/buffer
3445 Returns: the next character or EOF
3446
3447 Only used by the server-side TLS.
3448 */
3449
3450 int
3451 tls_getc(unsigned lim)
3452 {
3453 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3454 if (!tls_refill(lim))
3455 return ssl_xfer_error ? EOF : smtp_getc(lim);
3456
3457 /* Something in the buffer; return next uschar */
3458
3459 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
3460 }
3461
3462 uschar *
3463 tls_getbuf(unsigned * len)
3464 {
3465 unsigned size;
3466 uschar * buf;
3467
3468 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3469 if (!tls_refill(*len))
3470 {
3471 if (!ssl_xfer_error) return smtp_getbuf(len);
3472 *len = 0;
3473 return NULL;
3474 }
3475
3476 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
3477 size = *len;
3478 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
3479 ssl_xfer_buffer_lwm += size;
3480 *len = size;
3481 return buf;
3482 }
3483
3484
3485 void
3486 tls_get_cache()
3487 {
3488 #ifndef DISABLE_DKIM
3489 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
3490 if (n > 0)
3491 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
3492 #endif
3493 }
3494
3495
3496 BOOL
3497 tls_could_read(void)
3498 {
3499 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
3500 }
3501
3502
3503 /*************************************************
3504 * Read bytes from TLS channel *
3505 *************************************************/
3506
3507 /*
3508 Arguments:
3509 ct_ctx client context pointer, or NULL for the one global server context
3510 buff buffer of data
3511 len size of buffer
3512
3513 Returns: the number of bytes read
3514 -1 after a failed read, including EOF
3515
3516 Only used by the client-side TLS.
3517 */
3518
3519 int
3520 tls_read(void * ct_ctx, uschar *buff, size_t len)
3521 {
3522 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
3523 int inbytes;
3524 int error;
3525
3526 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
3527 buff, (unsigned int)len);
3528
3529 inbytes = SSL_read(ssl, CS buff, len);
3530 error = SSL_get_error(ssl, inbytes);
3531
3532 if (error == SSL_ERROR_ZERO_RETURN)
3533 {
3534 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
3535 return -1;
3536 }
3537 else if (error != SSL_ERROR_NONE)
3538 return -1;
3539
3540 return inbytes;
3541 }
3542
3543
3544
3545
3546
3547 /*************************************************
3548 * Write bytes down TLS channel *
3549 *************************************************/
3550
3551 /*
3552 Arguments:
3553 ct_ctx client context pointer, or NULL for the one global server context
3554 buff buffer of data
3555 len number of bytes
3556 more further data expected soon
3557
3558 Returns: the number of bytes after a successful write,
3559 -1 after a failed write
3560
3561 Used by both server-side and client-side TLS.
3562 */
3563
3564 int
3565 tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more)
3566 {
3567 size_t olen = len;
3568 int outbytes, error;
3569 SSL * ssl = ct_ctx
3570 ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
3571 static gstring * server_corked = NULL;
3572 gstring ** corkedp = ct_ctx
3573 ? &((exim_openssl_client_tls_ctx *)ct_ctx)->corked : &server_corked;
3574 gstring * corked = *corkedp;
3575
3576 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
3577 buff, (unsigned long)len, more ? ", more" : "");
3578
3579 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
3580 "more" is notified. This hack is only ok if small amounts are involved AND only
3581 one stream does it, in one context (i.e. no store reset). Currently it is used
3582 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only.
3583 We support callouts done by the server process by using a separate client
3584 context for the stashed information. */
3585 /* + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's
3586 a store reset there, so use POOL_PERM. */
3587 /* + if CHUNKING, cmds EHLO,MAIL,RCPT(s),BDAT */
3588
3589 if ((more || corked))
3590 {
3591 #ifdef SUPPORT_PIPE_CONNECT
3592 int save_pool = store_pool;
3593 store_pool = POOL_PERM;
3594 #endif
3595
3596 corked = string_catn(corked, buff, len);
3597
3598 #ifdef SUPPORT_PIPE_CONNECT
3599 store_pool = save_pool;
3600 #endif
3601
3602 if (more)
3603 {
3604 *corkedp = corked;
3605 return len;
3606 }
3607 buff = CUS corked->s;
3608 len = corked->ptr;
3609 *corkedp = NULL;
3610 }
3611
3612 for (int left = len; left > 0;)
3613 {
3614 DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left);
3615 outbytes = SSL_write(ssl, CS buff, left);
3616 error = SSL_get_error(ssl, outbytes);
3617 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
3618 switch (error)
3619 {
3620 case SSL_ERROR_SSL:
3621 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3622 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
3623 return -1;
3624
3625 case SSL_ERROR_NONE:
3626 left -= outbytes;
3627 buff += outbytes;
3628 break;
3629
3630 case SSL_ERROR_ZERO_RETURN:
3631 log_write(0, LOG_MAIN, "SSL channel closed on write");
3632 return -1;
3633
3634 case SSL_ERROR_SYSCALL:
3635 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
3636 sender_fullhost ? sender_fullhost : US"<unknown>",
3637 strerror(errno));
3638 return -1;
3639
3640 default:
3641 log_write(0, LOG_MAIN, "SSL_write error %d", error);
3642 return -1;
3643 }
3644 }
3645 return olen;
3646 }
3647
3648
3649
3650 /*************************************************
3651 * Close down a TLS session *
3652 *************************************************/
3653
3654 /* This is also called from within a delivery subprocess forked from the
3655 daemon, to shut down the TLS library, without actually doing a shutdown (which
3656 would tamper with the SSL session in the parent process).
3657
3658 Arguments:
3659 ct_ctx client TLS context pointer, or NULL for the one global server context
3660 shutdown 1 if TLS close-alert is to be sent,
3661 2 if also response to be waited for
3662
3663 Returns: nothing
3664
3665 Used by both server-side and client-side TLS.
3666 */
3667
3668 void
3669 tls_close(void * ct_ctx, int shutdown)
3670 {
3671 exim_openssl_client_tls_ctx * o_ctx = ct_ctx;
3672 SSL_CTX **ctxp = o_ctx ? &o_ctx->ctx : &server_ctx;
3673 SSL **sslp = o_ctx ? &o_ctx->ssl : &server_ssl;
3674 int *fdp = o_ctx ? &tls_out.active.sock : &tls_in.active.sock;
3675
3676 if (*fdp < 0) return; /* TLS was not active */
3677
3678 if (shutdown)
3679 {
3680 int rc;
3681 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
3682 shutdown > 1 ? " (with response-wait)" : "");
3683
3684 if ( (rc = SSL_shutdown(*sslp)) == 0 /* send "close notify" alert */
3685 && shutdown > 1)
3686 {
3687 ALARM(2);
3688 rc = SSL_shutdown(*sslp); /* wait for response */
3689 ALARM_CLR(0);
3690 }
3691
3692 if (rc < 0) DEBUG(D_tls)
3693 {
3694 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3695 debug_printf("SSL_shutdown: %s\n", ssl_errstring);
3696 }
3697 }
3698
3699 if (!o_ctx) /* server side */
3700 {
3701 #ifndef DISABLE_OCSP
3702 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
3703 server_static_cbinfo->verify_stack = NULL;
3704 #endif
3705
3706 receive_getc = smtp_getc;
3707 receive_getbuf = smtp_getbuf;
3708 receive_get_cache = smtp_get_cache;
3709 receive_ungetc = smtp_ungetc;
3710 receive_feof = smtp_feof;
3711 receive_ferror = smtp_ferror;
3712 receive_smtp_buffered = smtp_buffered;
3713 tls_in.active.tls_ctx = NULL;
3714 tls_in.sni = NULL;
3715 /* Leave bits, peercert, cipher, peerdn, certificate_verified set, for logging */
3716 }
3717
3718 SSL_CTX_free(*ctxp);
3719 SSL_free(*sslp);
3720 *ctxp = NULL;
3721 *sslp = NULL;
3722 *fdp = -1;
3723 }
3724
3725
3726
3727
3728 /*************************************************
3729 * Let tls_require_ciphers be checked at startup *
3730 *************************************************/
3731
3732 /* The tls_require_ciphers option, if set, must be something which the
3733 library can parse.
3734
3735 Returns: NULL on success, or error message
3736 */
3737
3738 uschar *
3739 tls_validate_require_cipher(void)
3740 {
3741 SSL_CTX *ctx;
3742 uschar *s, *expciphers, *err;
3743
3744 tls_openssl_init();
3745
3746 if (!(tls_require_ciphers && *tls_require_ciphers))
3747 return NULL;
3748
3749 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3750 &err))
3751 return US"failed to expand tls_require_ciphers";
3752
3753 if (!(expciphers && *expciphers))
3754 return NULL;
3755
3756 /* normalisation ripped from above */
3757 s = expciphers;
3758 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
3759
3760 err = NULL;
3761
3762 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
3763 if (!(ctx = SSL_CTX_new(TLS_server_method())))
3764 #else
3765 if (!(ctx = SSL_CTX_new(SSLv23_server_method())))
3766 #endif
3767 {
3768 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3769 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
3770 }
3771
3772 DEBUG(D_tls)
3773 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3774
3775 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
3776 {
3777 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3778 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
3779 expciphers, ssl_errstring);
3780 }
3781
3782 SSL_CTX_free(ctx);
3783
3784 return err;
3785 }
3786
3787
3788
3789
3790 /*************************************************
3791 * Report the library versions. *
3792 *************************************************/
3793
3794 /* There have historically been some issues with binary compatibility in
3795 OpenSSL libraries; if Exim (like many other applications) is built against
3796 one version of OpenSSL but the run-time linker picks up another version,
3797 it can result in serious failures, including crashing with a SIGSEGV. So
3798 report the version found by the compiler and the run-time version.
3799
3800 Note: some OS vendors backport security fixes without changing the version
3801 number/string, and the version date remains unchanged. The _build_ date
3802 will change, so we can more usefully assist with version diagnosis by also
3803 reporting the build date.
3804
3805 Arguments: a FILE* to print the results to
3806 Returns: nothing
3807 */
3808
3809 void
3810 tls_version_report(FILE *f)
3811 {
3812 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
3813 " Runtime: %s\n"
3814 " : %s\n",
3815 OPENSSL_VERSION_TEXT,
3816 SSLeay_version(SSLEAY_VERSION),
3817 SSLeay_version(SSLEAY_BUILT_ON));
3818 /* third line is 38 characters for the %s and the line is 73 chars long;
3819 the OpenSSL output includes a "built on: " prefix already. */
3820 }
3821
3822
3823
3824
3825 /*************************************************
3826 * Random number generation *
3827 *************************************************/
3828
3829 /* Pseudo-random number generation. The result is not expected to be
3830 cryptographically strong but not so weak that someone will shoot themselves
3831 in the foot using it as a nonce in input in some email header scheme or
3832 whatever weirdness they'll twist this into. The result should handle fork()
3833 and avoid repeating sequences. OpenSSL handles that for us.
3834
3835 Arguments:
3836 max range maximum
3837 Returns a random number in range [0, max-1]
3838 */
3839
3840 int
3841 vaguely_random_number(int max)
3842 {
3843 unsigned int r;
3844 int i, needed_len;
3845 static pid_t pidlast = 0;
3846 pid_t pidnow;
3847 uschar smallbuf[sizeof(r)];
3848
3849 if (max <= 1)
3850 return 0;
3851
3852 pidnow = getpid();
3853 if (pidnow != pidlast)
3854 {
3855 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
3856 is unique for each thread", this doesn't apparently apply across processes,
3857 so our own warning from vaguely_random_number_fallback() applies here too.
3858 Fix per PostgreSQL. */
3859 if (pidlast != 0)
3860 RAND_cleanup();
3861 pidlast = pidnow;
3862 }
3863
3864 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
3865 if (!RAND_status())
3866 {
3867 randstuff r;
3868 gettimeofday(&r.tv, NULL);
3869 r.p = getpid();
3870
3871 RAND_seed(US (&r), sizeof(r));
3872 }
3873 /* We're after pseudo-random, not random; if we still don't have enough data
3874 in the internal PRNG then our options are limited. We could sleep and hope
3875 for entropy to come along (prayer technique) but if the system is so depleted
3876 in the first place then something is likely to just keep taking it. Instead,
3877 we'll just take whatever little bit of pseudo-random we can still manage to
3878 get. */
3879
3880 needed_len = sizeof(r);
3881 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
3882 asked for a number less than 10. */
3883 for (r = max, i = 0; r; ++i)
3884 r >>= 1;
3885 i = (i + 7) / 8;
3886 if (i < needed_len)
3887 needed_len = i;
3888
3889 #ifdef EXIM_HAVE_RAND_PSEUDO
3890 /* We do not care if crypto-strong */
3891 i = RAND_pseudo_bytes(smallbuf, needed_len);
3892 #else
3893 i = RAND_bytes(smallbuf, needed_len);
3894 #endif
3895
3896 if (i < 0)
3897 {
3898 DEBUG(D_all)
3899 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
3900 return vaguely_random_number_fallback(max);
3901 }
3902
3903 r = 0;
3904 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
3905 r = 256 * r + *p;
3906
3907 /* We don't particularly care about weighted results; if someone wants
3908 smooth distribution and cares enough then they should submit a patch then. */
3909 return r % max;
3910 }
3911
3912
3913
3914
3915 /*************************************************
3916 * OpenSSL option parse *
3917 *************************************************/
3918
3919 /* Parse one option for tls_openssl_options_parse below
3920
3921 Arguments:
3922 name one option name
3923 value place to store a value for it
3924 Returns success or failure in parsing
3925 */
3926
3927
3928
3929 static BOOL
3930 tls_openssl_one_option_parse(uschar *name, long *value)
3931 {
3932 int first = 0;
3933 int last = exim_openssl_options_size;
3934 while (last > first)
3935 {
3936 int middle = (first + last)/2;
3937 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3938 if (c == 0)
3939 {
3940 *value = exim_openssl_options[middle].value;
3941 return TRUE;
3942 }
3943 else if (c > 0)
3944 first = middle + 1;
3945 else
3946 last = middle;
3947 }
3948 return FALSE;
3949 }
3950
3951
3952
3953
3954 /*************************************************
3955 * OpenSSL option parsing logic *
3956 *************************************************/
3957
3958 /* OpenSSL has a number of compatibility options which an administrator might
3959 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3960 we look like log_selector.
3961
3962 Arguments:
3963 option_spec the administrator-supplied string of options
3964 results ptr to long storage for the options bitmap
3965 Returns success or failure
3966 */
3967
3968 BOOL
3969 tls_openssl_options_parse(uschar *option_spec, long *results)
3970 {
3971 long result, item;
3972 uschar * exp, * end;
3973 uschar keep_c;
3974 BOOL adding, item_parsed;
3975
3976 /* Server: send no (<= TLS1.2) session tickets */
3977 result = SSL_OP_NO_TICKET;
3978
3979 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3980 from default because it increases BEAST susceptibility. */
3981 #ifdef SSL_OP_NO_SSLv2
3982 result |= SSL_OP_NO_SSLv2;
3983 #endif
3984 #ifdef SSL_OP_NO_SSLv3
3985 result |= SSL_OP_NO_SSLv3;
3986 #endif
3987 #ifdef SSL_OP_SINGLE_DH_USE
3988 result |= SSL_OP_SINGLE_DH_USE;
3989 #endif
3990
3991 if (!option_spec)
3992 {
3993 *results = result;
3994 return TRUE;
3995 }
3996
3997 if (!expand_check(option_spec, US"openssl_options", &exp, &end))
3998 return FALSE;
3999
4000 for (uschar * s = exp; *s; /**/)
4001 {
4002 while (isspace(*s)) ++s;
4003 if (*s == '\0')
4004 break;
4005 if (*s != '+' && *s != '-')
4006 {
4007 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
4008 "+ or - expected but found \"%s\"\n", s);
4009 return FALSE;
4010 }
4011 adding = *s++ == '+';
4012 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
4013 keep_c = *end;
4014 *end = '\0';
4015 item_parsed = tls_openssl_one_option_parse(s, &item);
4016 *end = keep_c;
4017 if (!item_parsed)
4018 {
4019 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
4020 return FALSE;
4021 }
4022 DEBUG(D_tls) debug_printf("openssl option, %s %8lx: %lx (%s)\n",
4023 adding ? "adding to " : "removing from", result, item, s);
4024 if (adding)
4025 result |= item;
4026 else
4027 result &= ~item;
4028 s = end;
4029 }
4030
4031 *results = result;
4032 return TRUE;
4033 }
4034
4035 #endif /*!MACRO_PREDEF*/
4036 /* vi: aw ai sw=2
4037 */
4038 /* End of tls-openssl.c */
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