1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2019 */
6 /* See the file NOTICE for conditions of use and distribution. */
8 /* Portions Copyright (c) The OpenSSL Project 1999 */
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.
15 No cryptographic code is included in Exim. All this module does is to call
16 functions from the OpenSSL library. */
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>
29 # include <openssl/ocsp.h>
37 # define EXIM_OCSP_SKEW_SECONDS (300L)
38 # define EXIM_OCSP_MAX_AGE (-1L)
41 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
42 # define EXIM_HAVE_OPENSSL_TLSEXT
44 #if OPENSSL_VERSION_NUMBER >= 0x00908000L
45 # define EXIM_HAVE_RSA_GENKEY_EX
47 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
48 # define EXIM_HAVE_OCSP_RESP_COUNT
49 # define OPENSSL_AUTO_SHA256
51 # define EXIM_HAVE_EPHEM_RSA_KEX
52 # define EXIM_HAVE_RAND_PSEUDO
54 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
55 # define EXIM_HAVE_SHA256
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.
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. */
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
80 # define EXIM_HAVE_OCSP
83 # define EXIM_NEED_OPENSSL_INIT
85 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
86 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
87 # define EXIM_HAVE_OPENSSL_CHECKHOST
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
97 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
98 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
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
109 # define OPENSSL_BAD_SRVR_OURCERT
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
118 #ifdef EXPERIMENTAL_TLS_RESUME
119 # if OPENSSL_VERSION_NUMBER < 0x0101010L
120 # error OpenSSL version too old for session-resumption
124 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
125 # include <openssl/x509v3.h>
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)
132 # ifndef MACRO_PREDEF
133 # include "tls-cipher-stdname.c"
137 /*************************************************
138 * OpenSSL option parse *
139 *************************************************/
141 typedef struct exim_openssl_option {
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
150 This list is current as of:
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
155 static exim_openssl_option exim_openssl_options[] = {
156 /* KEEP SORTED ALPHABETICALLY! */
158 { US"all", (long) SSL_OP_ALL },
160 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
161 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
163 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
164 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
166 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
167 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
169 #ifdef SSL_OP_EPHEMERAL_RSA
170 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
172 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
173 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
175 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
176 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
178 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
179 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
181 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
182 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
184 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
185 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
187 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
188 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
190 #ifdef SSL_OP_NO_COMPRESSION
191 { US"no_compression", SSL_OP_NO_COMPRESSION },
193 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
194 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
196 #ifdef SSL_OP_NO_SSLv2
197 { US"no_sslv2", SSL_OP_NO_SSLv2 },
199 #ifdef SSL_OP_NO_SSLv3
200 { US"no_sslv3", SSL_OP_NO_SSLv3 },
202 #ifdef SSL_OP_NO_TICKET
203 { US"no_ticket", SSL_OP_NO_TICKET },
205 #ifdef SSL_OP_NO_TLSv1
206 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
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
213 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
216 #ifdef SSL_OP_NO_TLSv1_2
217 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
219 #ifdef SSL_OP_NO_TLSv1_3
220 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
222 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
223 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
225 #ifdef SSL_OP_SINGLE_DH_USE
226 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
228 #ifdef SSL_OP_SINGLE_ECDH_USE
229 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
231 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
232 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
234 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
235 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
237 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
238 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
240 #ifdef SSL_OP_TLS_D5_BUG
241 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
243 #ifdef SSL_OP_TLS_ROLLBACK_BUG
244 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
249 static int exim_openssl_options_size = nelem(exim_openssl_options);
258 for (struct exim_openssl_option * o = exim_openssl_options;
259 o < exim_openssl_options + nelem(exim_openssl_options); o++)
261 /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
262 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
264 spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
265 builtin_macro_create(buf);
268 # ifdef EXPERIMENTAL_TLS_RESUME
269 builtin_macro_create_var(US"_RESUME_DECODE", RESUME_DECODE_STRING );
271 # ifdef SSL_OP_NO_TLSv1_3
272 builtin_macro_create(US"_HAVE_TLS1_3");
274 # ifdef OPENSSL_BAD_SRVR_OURCERT
275 builtin_macro_create(US"_TLS_BAD_MULTICERT_IN_OURCERT");
277 # ifdef EXIM_HAVE_OCSP
278 builtin_macro_create(US"_HAVE_TLS_OCSP");
279 builtin_macro_create(US"_HAVE_TLS_OCSP_LIST");
284 /******************************************************************************/
286 /* Structure for collecting random data for seeding. */
288 typedef struct randstuff {
293 /* Local static variables */
295 static BOOL client_verify_callback_called = FALSE;
296 static BOOL server_verify_callback_called = FALSE;
297 static const uschar *sid_ctx = US"exim";
299 /* We have three different contexts to care about.
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.
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
324 } exim_openssl_client_tls_ctx;
326 static SSL_CTX *server_ctx = NULL;
327 static SSL *server_ssl = NULL;
329 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
330 static SSL_CTX *server_sni = NULL;
333 static char ssl_errstring[256];
335 static int ssl_session_timeout = 7200; /* Two hours */
336 static BOOL client_verify_optional = FALSE;
337 static BOOL server_verify_optional = FALSE;
339 static BOOL reexpand_tls_files_for_sni = FALSE;
342 typedef struct ocsp_resp {
343 struct ocsp_resp * next;
344 OCSP_RESPONSE * resp;
347 typedef struct tls_ext_ctx_cb {
353 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
357 const uschar *file_expanded;
358 ocsp_resplist *olist;
361 X509_STORE *verify_store; /* non-null if status requested */
362 BOOL verify_required;
367 /* these are cached from first expand */
368 uschar *server_cipher_list;
369 /* only passed down to tls_error: */
371 const uschar * verify_cert_hostnames;
372 #ifndef DISABLE_EVENT
373 uschar * event_action;
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;
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 );
388 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
389 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
392 static int tls_server_stapling_cb(SSL *s, void *arg);
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;
404 tls_daemon_init(void)
406 #ifdef EXPERIMENTAL_TLS_RESUME
413 /*************************************************
415 *************************************************/
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.
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
431 Returns: OK/DEFER/FAIL
435 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
439 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
440 msg = US ssl_errstring;
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;
451 /*************************************************
452 * Callback to generate RSA key *
453 *************************************************/
457 s SSL connection (not used)
461 Returns: pointer to generated key
465 rsa_callback(SSL *s, int export, int keylength)
468 #ifdef EXIM_HAVE_RSA_GENKEY_EX
469 BIGNUM *bn = BN_new();
472 export = export; /* Shut picky compilers up */
473 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
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)
481 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
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",
498 x509_store_dump_cert_s_names(X509_STORE * store)
500 STACK_OF(X509_OBJECT) * roots= store->objs;
501 static uschar name[256];
503 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
505 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
506 if(tmp_obj->type == X509_LU_X509)
508 X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
509 if (X509_NAME_oneline(sn, CS name, sizeof(name)))
511 name[sizeof(name)-1] = '\0';
512 debug_printf(" %s\n", name);
521 #ifndef DISABLE_EVENT
523 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
524 BOOL *calledp, const BOOL *optionalp, const uschar * what)
530 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
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))))
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);
546 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
547 return 1; /* reject (leaving peercert set) */
549 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
550 "(host in tls_try_verify_hosts)\n");
551 tlsp->verify_override = TRUE;
553 X509_free(tlsp->peercert);
554 tlsp->peercert = old_cert;
560 /*************************************************
561 * Callback for verification *
562 *************************************************/
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
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.
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.
581 May be called multiple times for different issues with a certificate, even
582 for a given "depth" in the certificate chain.
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
591 Returns: 0 if verification should fail, otherwise 1
595 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
596 tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
598 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
599 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
602 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
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);
609 dn[sizeof(dn)-1] = '\0';
611 tlsp->verify_override = FALSE;
612 if (preverify_ok == 0)
614 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
615 *verify_mode, sender_host_address)
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,
620 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
625 tlsp->peercert = X509_dup(cert); /* record failing cert */
626 return 0; /* reject */
628 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
629 "tls_try_verify_hosts)\n");
630 tlsp->verify_override = TRUE;
635 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
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. */
642 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
645 sk_X509_push(client_static_cbinfo->verify_stack, cert);
648 #ifndef DISABLE_EVENT
649 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
650 return 0; /* reject, with peercert set */
655 const uschar * verify_cert_hostnames;
657 if ( tlsp == &tls_out
658 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
659 /* client, wanting hostname check */
662 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
663 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
664 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
666 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
667 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
670 const uschar * list = verify_cert_hostnames;
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,
681 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
682 tlsp == &tls_out ? deliver_host_address : sender_host_address);
689 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
692 uschar * extra = verify_mode
693 ? string_sprintf(" (during %c-verify for [%s])",
694 *verify_mode, sender_host_address)
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);
704 tlsp->peercert = X509_dup(cert); /* record failing cert */
705 return 0; /* reject */
707 DEBUG(D_tls) debug_printf("SSL verify name failure overridden (host in "
708 "tls_try_verify_hosts)\n");
709 tlsp->verify_override = TRUE;
713 #ifndef DISABLE_EVENT
714 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
715 return 0; /* reject, with peercert set */
718 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
719 *calledp ? "" : " authenticated", dn);
723 return 1; /* accept, at least for this level */
727 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
729 return verify_callback(preverify_ok, x509ctx, &tls_out,
730 &client_verify_callback_called, &client_verify_optional);
734 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
736 return verify_callback(preverify_ok, x509ctx, &tls_in,
737 &server_verify_callback_called, &server_verify_optional);
743 /* This gets called *by* the dane library verify callback, which interposes
747 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
749 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
751 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
752 #ifndef DISABLE_EVENT
753 BOOL dummy_called, optional = FALSE;
756 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
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);
763 dn[sizeof(dn)-1] = '\0';
765 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
766 preverify_ok ? "ok":"BAD", depth, dn);
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 */
774 if (preverify_ok == 1)
776 tls_out.dane_verified = TRUE;
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. */
783 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
786 sk_X509_push(client_static_cbinfo->verify_stack, cert);
792 int err = X509_STORE_CTX_get_error(x509ctx);
794 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
795 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
801 #endif /*SUPPORT_DANE*/
804 /*************************************************
805 * Information callback *
806 *************************************************/
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
821 info_callback(SSL *s, int where, int ret)
827 if (where & SSL_ST_CONNECT)
828 str = US"SSL_connect";
829 else if (where & SSL_ST_ACCEPT)
830 str = US"SSL_accept";
832 str = US"SSL info (undefined)";
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)
842 debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
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));
852 #ifdef OPENSSL_HAVE_KEYLOG_CB
854 keylog_callback(const SSL *ssl, const char *line)
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);
867 #ifdef EXPERIMENTAL_TLS_RESUME
868 /* Manage the keysets used for encrypting the session tickets, on the server. */
870 typedef struct { /* Session ticket encryption key */
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;
881 static exim_stek exim_tk; /* current key */
882 static exim_stek exim_tk_old; /* previous key */
887 time_t t = time(NULL);
891 if (exim_tk.renew >= t) return;
892 exim_tk_old = exim_tk;
895 if (f.running_in_test_harness) ssl_session_timeout = 6;
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;
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;
912 if (!exim_tk.name[0]) return NULL;
917 tk_find(const uschar * name)
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
924 /* Callback for session tickets, on server */
926 ticket_key_callback(SSL * ssl, uschar key_name[16],
927 uschar * iv, EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int enc)
929 tls_support * tlsp = server_static_cbinfo->tlsp;
934 DEBUG(D_tls) debug_printf("ticket_key_callback: create new session\n");
935 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
937 if (RAND_bytes(iv, EVP_MAX_IV_LENGTH) <= 0)
938 return -1; /* insufficient random */
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));
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);
950 DEBUG(D_tls) debug_printf("ticket created\n");
955 time_t now = time(NULL);
957 DEBUG(D_tls) debug_printf("ticket_key_callback: retrieve session\n");
958 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
960 if (!(key = tk_find(key_name)) || key->expire < now)
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);
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);
974 DEBUG(D_tls) debug_printf("ticket usable, STEK expire " TIME_T_FMT "\n", key->expire - now);
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;
988 /*************************************************
989 * Initialize for DH *
990 *************************************************/
992 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
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
1000 Returns: TRUE if OK (nothing to set up, or setup worked)
1004 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
1012 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
1015 if (!dhexpanded || !*dhexpanded)
1016 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
1017 else if (dhexpanded[0] == '/')
1019 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
1021 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
1022 host, US strerror(errno), errstr);
1028 if (Ustrcmp(dhexpanded, "none") == 0)
1030 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
1034 if (!(pem = std_dh_prime_named(dhexpanded)))
1036 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
1037 host, US strerror(errno), errstr);
1040 bio = BIO_new_mem_buf(CS pem, -1);
1043 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
1046 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
1047 host, NULL, errstr);
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);
1061 dh_bitsize = 8 * DH_size(dh);
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)
1070 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
1071 dh_bitsize, tls_dh_max_bits);
1075 SSL_CTX_set_tmp_dh(sctx, dh);
1077 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
1078 dhexpanded ? dhexpanded : US"default", dh_bitsize);
1090 /*************************************************
1091 * Initialize for ECDH *
1092 *************************************************/
1094 /* Load parameters for ECDH encryption.
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.
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.
1111 sctx The current SSL CTX (inbound or outbound)
1112 host connected host, if client; NULL if server
1113 errstr error string pointer
1115 Returns: TRUE if OK (nothing to set up, or setup worked)
1119 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
1121 #ifdef OPENSSL_NO_ECDH
1130 if (host) /* No ECDH setup for clients, only for servers */
1133 # ifndef EXIM_HAVE_ECDH
1135 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
1139 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
1141 if (!exp_curve || !*exp_curve)
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
1151 if (Ustrcmp(exp_curve, "auto") == 0)
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";
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);
1164 DEBUG(D_tls) debug_printf(
1165 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
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
1178 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
1179 host, NULL, errstr);
1183 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
1185 tls_error(US"Unable to create ec curve", host, NULL, errstr);
1189 /* The "tmp" in the name here refers to setting a temporary key
1190 not to the stability of the interface. */
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);
1195 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1200 # endif /*EXIM_HAVE_ECDH*/
1201 #endif /*OPENSSL_NO_ECDH*/
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
1215 ASSUMES: single response, for single cert.
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
1226 ocsp_load_response(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo,
1227 const uschar * filename, BOOL is_pem)
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;
1239 debug_printf("tls_ocsp_file (%s) '%s'\n", is_pem ? "PEM" : "DER", filename);
1241 if (!(bio = BIO_new_file(CS filename, "rb")))
1243 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1250 uschar * data, * freep;
1253 if (!PEM_read_bio(bio, &dummy, &dummy, &data, &len))
1255 DEBUG(D_tls) debug_printf("Failed to read PEM file \"%s\"\n",
1259 debug_printf("read pem file\n");
1261 resp = d2i_OCSP_RESPONSE(NULL, CUSS &data, len);
1262 OPENSSL_free(freep);
1265 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1270 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1274 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1276 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1277 OCSP_response_status_str(status), status);
1283 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1284 OCSP_RESPONSE_print(bp, resp, 0); /* extreme debug: stapling content */
1289 if (!(basic_response = OCSP_response_get1_basic(resp)))
1292 debug_printf("OCSP response parse error: unable to extract basic response.\n");
1296 sk = cbinfo->verify_stack;
1297 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
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 */
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.
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.
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
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? */
1326 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
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);
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()).
1342 I'm hoping to avoid reworking a bunch more of how we handle state here.
1344 XXX that will change when we add support for (TLS1.3) whole-chain stapling
1347 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1350 debug_printf("Unable to get first response from OCSP basic response.\n");
1354 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1355 if (status != V_OCSP_CERTSTATUS_GOOD)
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);
1363 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1365 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1370 /* Add the resp to the list used by tls_server_stapling_cb() */
1372 ocsp_resplist ** op = &cbinfo->u_ocsp.server.olist, * oentry;
1373 while (oentry = *op)
1375 *op = oentry = store_get(sizeof(ocsp_resplist), FALSE);
1376 oentry->next = NULL;
1377 oentry->resp = resp;
1382 if (f.running_in_test_harness)
1384 extern char ** environ;
1385 if (environ) for (uschar ** p = USS environ; *p; p++)
1386 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1388 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1389 goto supply_response;
1397 ocsp_free_response_list(tls_ext_ctx_cb * cbinfo)
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;
1404 #endif /*!DISABLE_OCSP*/
1409 /* Create and install a selfsigned certificate, for use in server mode */
1412 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1420 where = US"allocating pkey";
1421 if (!(pkey = EVP_PKEY_new()))
1424 where = US"allocating cert";
1425 if (!(x509 = X509_new()))
1428 where = US"generating pkey";
1429 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1432 where = US"assigning pkey";
1433 if (!EVP_PKEY_assign_RSA(pkey, rsa))
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);
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);
1451 where = US"signing cert";
1452 if (!X509_sign(x509, pkey, EVP_md5()))
1455 where = US"installing selfsign cert";
1456 if (!SSL_CTX_use_certificate(sctx, x509))
1459 where = US"installing selfsign key";
1460 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1466 (void) tls_error(where, NULL, NULL, errstr);
1467 if (x509) X509_free(x509);
1468 if (pkey) EVP_PKEY_free(pkey);
1476 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
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);
1488 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
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);
1499 /*************************************************
1500 * Expand key and cert file specs *
1501 *************************************************/
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.
1508 sctx the SSL_CTX* to update
1509 cbinfo various parts of session state
1510 errstr error string pointer
1512 Returns: OK/DEFER/FAIL
1516 tls_expand_session_files(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo,
1521 if (!cbinfo->certificate)
1523 if (!cbinfo->is_server) /* client */
1526 if (tls_install_selfsign(sctx, errstr) != OK)
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")
1538 reexpand_tls_files_for_sni = TRUE;
1540 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1544 if (cbinfo->is_server)
1546 const uschar * file_list = expanded;
1549 #ifndef DISABLE_OCSP
1550 const uschar * olist = cbinfo->u_ocsp.server.file;
1553 BOOL fmt_pem = FALSE;
1556 if (!expand_check(olist, US"tls_ocsp_file", USS &olist, errstr))
1558 if (olist && !*olist)
1561 if ( cbinfo->u_ocsp.server.file_expanded && olist
1562 && (Ustrcmp(olist, cbinfo->u_ocsp.server.file_expanded) == 0))
1564 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1569 ocsp_free_response_list(cbinfo);
1570 cbinfo->u_ocsp.server.file_expanded = olist;
1574 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1576 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1579 #ifndef DISABLE_OCSP
1581 if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1583 if (Ustrncmp(ofile, US"PEM ", 4) == 0)
1588 else if (Ustrncmp(ofile, US"DER ", 4) == 0)
1593 ocsp_load_response(sctx, cbinfo, ofile, fmt_pem);
1596 DEBUG(D_tls) debug_printf("ran out of ocsp file list\n");
1600 else /* would there ever be a need for multiple client certs? */
1601 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1604 if ( cbinfo->privatekey
1605 && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
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. */
1612 if (expanded && *expanded)
1613 if (cbinfo->is_server)
1615 const uschar * file_list = expanded;
1619 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1620 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1623 else /* would there ever be a need for multiple client certs? */
1624 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1634 /*************************************************
1635 * Callback to handle SNI *
1636 *************************************************/
1638 /* Called when acting as server during the TLS session setup if a Server Name
1639 Indication extension was sent by the client.
1641 API documentation is OpenSSL s_server.c implementation.
1644 s SSL* of the current session
1645 ad unknown (part of OpenSSL API) (unused)
1646 arg Callback of "our" registered data
1648 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
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
1654 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1656 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1658 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1659 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1661 int old_pool = store_pool;
1662 uschar * dummy_errstr;
1665 return SSL_TLSEXT_ERR_OK;
1667 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1668 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
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;
1675 if (!reexpand_tls_files_for_sni)
1676 return SSL_TLSEXT_ERR_OK;
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. */
1682 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1683 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1685 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
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);
1693 /* Not sure how many of these are actually needed, since SSL object
1694 already exists. Might even need this selfsame callback, for reneg? */
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);
1703 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1704 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1708 if ( cbinfo->server_cipher_list
1709 && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1712 #ifndef DISABLE_OCSP
1713 if (cbinfo->u_ocsp.server.file)
1715 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1716 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1720 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1721 verify_callback_server, &dummy_errstr)) != OK)
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)
1729 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1730 SSL_set_SSL_CTX(s, server_sni);
1731 return SSL_TLSEXT_ERR_OK;
1733 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1735 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1740 #ifndef DISABLE_OCSP
1742 /*************************************************
1743 * Callback to handle OCSP Stapling *
1744 *************************************************/
1746 /* Called when acting as server during the TLS session setup if the client
1747 requests OCSP information with a Certificate Status Request.
1749 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1755 tls_server_stapling_cb(SSL *s, void *arg)
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;
1763 debug_printf("Received TLS status request (OCSP stapling); %s response list\n",
1764 olist ? "have" : "lack");
1766 tls_in.ocsp = OCSP_NOT_RESP;
1768 return SSL_TLSEXT_ERR_NOACK;
1770 #ifdef EXIM_HAVE_OPESSL_GET0_SERIAL
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);
1779 for (; olist; olist = olist->next)
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;
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);
1795 debug_printf("cert serial: %s\n", BN_bn2hex(cert_bn));
1796 debug_printf("resp serial: %s\n", BN_bn2hex(resp_bn));
1799 if (BN_cmp(cert_bn, resp_bn) == 0)
1801 DEBUG(D_tls) debug_printf("matched serial for ocsp\n");
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
1810 DEBUG(D_tls) debug_printf("not match serial for ocsp\n");
1814 DEBUG(D_tls) debug_printf("failed to find match for ocsp\n");
1815 return SSL_TLSEXT_ERR_NOACK;
1821 DEBUG(D_tls) debug_printf("OpenSSL version too early to support multi-leaf OCSP\n");
1822 return SSL_TLSEXT_ERR_NOACK;
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;
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;
1839 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1841 BIO_printf(bp, "\t%s: ", str);
1842 ASN1_GENERALIZEDTIME_print(bp, time);
1847 tls_client_stapling_cb(SSL *s, void *arg)
1849 tls_ext_ctx_cb * cbinfo = arg;
1850 const unsigned char * p;
1852 OCSP_RESPONSE * rsp;
1853 OCSP_BASICRESP * bs;
1856 DEBUG(D_tls) debug_printf("Received TLS status callback (OCSP stapling):\n");
1857 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
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");
1864 DEBUG(D_tls) debug_printf(" null\n");
1865 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1868 if (!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
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");
1874 DEBUG(D_tls) debug_printf(" parse error\n");
1878 if (!(bs = OCSP_response_get1_basic(rsp)))
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");
1884 DEBUG(D_tls) debug_printf(" error parsing response\n");
1885 OCSP_RESPONSE_free(rsp);
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. */
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.
1898 #ifndef EXIM_HAVE_OCSP_RESP_COUNT
1899 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1902 DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1904 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
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); */
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())
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);
1923 DEBUG(D_tls) debug_printf("no explicit trust for OCSP signing"
1924 " in the root CA certificate; ignoring\n");
1926 DEBUG(D_tls) debug_printf("OCSP response well-formed and signed OK\n");
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?
1934 For now, carry on blindly accepting the resp. */
1937 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1938 OCSP_resp_count(bs) - 1;
1940 sk_OCSP_SINGLERESP_num(sresp) - 1;
1944 OCSP_SINGLERESP * single = OCSP_resp_get0(bs, idx);
1946 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
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?
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
1954 status = OCSP_single_get0_status(single, &reason, &rev,
1955 &thisupd, &nextupd);
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))
1962 tls_out.ocsp = OCSP_FAILED;
1963 DEBUG(D_tls) ERR_print_errors(bp);
1964 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1968 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1969 OCSP_cert_status_str(status));
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);
1981 log_write(0, LOG_MAIN,
1982 "Server certificate status unknown, in OCSP stapling");
1990 tls_out.ocsp = OCSP_VFIED;
1994 tls_out.ocsp = OCSP_FAILED;
1995 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
2000 OCSP_RESPONSE_free(rsp);
2003 #endif /*!DISABLE_OCSP*/
2006 /*************************************************
2007 * Initialize for TLS *
2008 *************************************************/
2011 tls_openssl_init(void)
2013 #ifdef EXIM_NEED_OPENSSL_INIT
2014 SSL_load_error_strings(); /* basic set up */
2015 OpenSSL_add_ssl_algorithms();
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());
2027 /* Called from both server and client code, to do preliminary initialization
2028 of the library. We allocate and return a context structure.
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
2041 Returns: OK/DEFER/FAIL
2045 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
2047 #ifndef DISABLE_OCSP
2050 address_item *addr, tls_ext_ctx_cb ** cbp,
2057 tls_ext_ctx_cb * cbinfo;
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;
2068 cbinfo->u_ocsp.server.file = ocsp_file;
2069 cbinfo->u_ocsp.server.file_expanded = NULL;
2070 cbinfo->u_ocsp.server.olist = NULL;
2073 cbinfo->u_ocsp.client.verify_store = NULL;
2075 cbinfo->dhparam = dhparam;
2076 cbinfo->server_cipher_list = NULL;
2077 cbinfo->host = host;
2078 #ifndef DISABLE_EVENT
2079 cbinfo->event_action = NULL;
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
2092 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
2093 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
2095 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
2097 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
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.
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
2110 gettimeofday(&r.tv, NULL);
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));
2118 return tls_error(US"RAND_status", host,
2119 US"unable to seed random number generator", errstr);
2122 /* Set up the information callback, which outputs if debugging is at a suitable
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);
2132 #ifdef OPENSSL_HAVE_KEYLOG_CB
2133 SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
2137 /* Automatically re-try reads/writes after renegotiation. */
2138 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
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".
2146 No OpenSSL version number checks: the options we accept depend upon the
2147 availability of the option value macros from OpenSSL. */
2149 if (!tls_openssl_options_parse(openssl_options, &init_options))
2150 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
2152 #ifdef EXPERIMENTAL_TLS_RESUME
2153 tlsp->resumption = RESUME_SUPPORTED;
2157 #ifdef EXPERIMENTAL_TLS_RESUME
2158 /* Should the server offer session resumption? */
2159 if (!host && verify_check_host(&tls_resumption_hosts) == OK)
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;
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);
2174 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
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. */
2183 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
2186 /* Initialize with DH parameters if supplied */
2187 /* Initialize ECDH temp key parameter selection */
2189 if ( !init_dh(ctx, dhparam, host, errstr)
2190 || !init_ecdh(ctx, host, errstr)
2194 /* Set up certificate and key (and perhaps OCSP info) */
2196 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
2199 /* If we need to handle SNI or OCSP, do so */
2201 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2202 # ifndef DISABLE_OCSP
2203 if (!(cbinfo->verify_stack = sk_X509_new_null()))
2205 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
2210 if (!host) /* server */
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)
2219 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
2220 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2223 /* We always do this, so that $tls_sni is available even if not used in
2225 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
2226 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
2228 # ifndef DISABLE_OCSP
2230 if(ocsp_file) /* wanting stapling */
2232 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
2234 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
2237 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
2238 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2243 cbinfo->verify_cert_hostnames = NULL;
2245 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
2246 /* Set up the RSA callback */
2247 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
2250 /* Finally, set the session cache timeout, and we are done.
2251 The period appears to be also used for (server-generated) session tickets */
2253 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
2254 DEBUG(D_tls) debug_printf("Initialized TLS\n");
2265 /*************************************************
2266 * Get name of cipher in use *
2267 *************************************************/
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
2276 construct_cipher_name(SSL * ssl, int * bits)
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. */
2283 const uschar * ver = CUS SSL_get_version(ssl);
2284 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
2287 SSL_CIPHER_get_bits(c, bits);
2289 store_pool = POOL_PERM;
2290 s = string_sprintf("%s:%s:%u", ver, SSL_CIPHER_get_name(c), *bits);
2292 DEBUG(D_tls) debug_printf("Cipher: %s\n", s);
2297 /* Get IETF-standard name for ciphersuite.
2298 Argument: pointer to an SSL structure for the connection
2299 Returns: pointer to string
2302 static const uschar *
2303 cipher_stdname_ssl(SSL * ssl)
2305 #ifdef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
2306 return CUS SSL_CIPHER_standard_name(SSL_get_current_cipher(ssl));
2308 ushort id = 0xffff & SSL_CIPHER_get_id(SSL_get_current_cipher(ssl));
2309 return cipher_stdname(id >> 8, id & 0xff);
2315 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
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. */
2322 tlsp->peerdn = NULL;
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 */
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"); }
2333 int oldpool = store_pool;
2335 peerdn[siz-1] = '\0'; /* paranoia */
2336 store_pool = POOL_PERM;
2337 tlsp->peerdn = string_copy(peerdn);
2338 store_pool = oldpool;
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. */
2349 if (!tlsp->verify_override)
2350 tlsp->certificate_verified =
2352 tlsp->dane_verified ||
2354 SSL_get_verify_result(ssl) == X509_V_OK;
2362 /*************************************************
2363 * Set up for verifying certificates *
2364 *************************************************/
2366 #ifndef DISABLE_OCSP
2367 /* Load certs from file, return TRUE on success */
2370 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
2375 while (sk_X509_num(verify_stack) > 0)
2376 X509_free(sk_X509_pop(verify_stack));
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);
2388 /* Called by both client and server startup; on the server possibly
2389 repeated after a Server Name Indication.
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
2401 Returns: OK/DEFER/FAIL
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)
2408 uschar *expcerts, *expcrl;
2410 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2412 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2414 if (expcerts && *expcerts)
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. */
2419 if (!SSL_CTX_set_default_verify_paths(sctx))
2420 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2422 if (Ustrcmp(expcerts, "system") != 0)
2424 struct stat statbuf;
2426 if (Ustat(expcerts, &statbuf) < 0)
2428 log_write(0, LOG_MAIN|LOG_PANIC,
2429 "failed to stat %s for certificates", expcerts);
2435 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2436 { file = NULL; dir = expcerts; }
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. */
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.
2449 && statbuf.st_size > 0
2450 && server_static_cbinfo->u_ocsp.server.file
2451 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2454 log_write(0, LOG_MAIN|LOG_PANIC,
2455 "failed to load cert chain from %s", file);
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. */
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);
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
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. */
2482 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
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));
2491 /* Handle a certificate revocation list. */
2493 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2495 /* This bit of code is now the version supplied by Lars Mainka. (I have
2496 merely reformatted it into the Exim code style.)
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." */
2505 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2506 if (expcrl && *expcrl)
2508 struct stat statbufcrl;
2509 if (Ustat(expcrl, &statbufcrl) < 0)
2511 log_write(0, LOG_MAIN|LOG_PANIC,
2512 "failed to stat %s for certificates revocation lists", expcrl);
2517 /* is it a file or directory? */
2519 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2520 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2524 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2530 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2532 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2533 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2535 /* setting the flags to check against the complete crl chain */
2537 X509_STORE_set_flags(cvstore,
2538 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2542 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2544 /* If verification is optional, don't fail if no certificate */
2546 SSL_CTX_set_verify(sctx,
2547 SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2556 /*************************************************
2557 * Start a TLS session in a server *
2558 *************************************************/
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
2565 require_ciphers allowed ciphers
2566 errstr pointer to error message
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
2575 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2578 uschar * expciphers;
2579 tls_ext_ctx_cb * cbinfo;
2580 static uschar peerdn[256];
2582 /* Check for previous activation */
2584 if (tls_in.active.sock >= 0)
2586 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2587 smtp_printf("554 Already in TLS\r\n", FALSE);
2591 /* Initialize the SSL library. If it fails, it will already have logged
2594 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2595 #ifndef DISABLE_OCSP
2598 NULL, &server_static_cbinfo, &tls_in, errstr);
2599 if (rc != OK) return rc;
2600 cbinfo = server_static_cbinfo;
2602 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
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.
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
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;
2623 /* If this is a host for which certificate verification is mandatory or
2624 optional, set up appropriately. */
2626 tls_in.certificate_verified = FALSE;
2628 tls_in.dane_verified = FALSE;
2630 server_verify_callback_called = FALSE;
2632 if (verify_check_host(&tls_verify_hosts) == OK)
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;
2639 else if (verify_check_host(&tls_try_verify_hosts) == OK)
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;
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 */
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);
2655 SSL_CTX_set_num_tickets(server_ctx, 0); /* send no TLS1.3 stateful-tickets */
2660 /* Prepare for new connection */
2662 if (!(server_ssl = SSL_new(server_ctx)))
2663 return tls_error(US"SSL_new", NULL, NULL, errstr);
2665 /* Warning: we used to SSL_clear(ssl) here, it was removed.
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.
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.
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. */
2684 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2685 if (!tls_in.on_connect)
2687 smtp_printf("220 TLS go ahead\r\n", FALSE);
2691 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2692 that the OpenSSL library doesn't. */
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);
2698 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2700 sigalrm_seen = FALSE;
2701 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2702 rc = SSL_accept(server_ssl);
2707 int error = SSL_get_error(server_ssl, rc);
2710 case SSL_ERROR_NONE:
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);
2717 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
2718 SSL_shutdown(server_ssl);
2720 tls_close(NULL, TLS_NO_SHUTDOWN);
2723 /* Handle genuine errors */
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);
2735 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2736 if (error == SSL_ERROR_SYSCALL)
2740 *errstr = US"SSL_accept: TCP connection closed by peer";
2743 DEBUG(D_tls) debug_printf(" - syscall %s\n", strerror(errno));
2745 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
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. */
2754 #ifdef EXPERIMENTAL_TLS_RESUME
2755 if (SSL_session_reused(server_ssl))
2757 tls_in.resumption |= RESUME_USED;
2758 DEBUG(D_tls) debug_printf("Session reused\n");
2762 /* TLS has been set up. Adjust the input functions to read via TLS,
2763 and initialize things. */
2765 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2767 tls_in.cipher = construct_cipher_name(server_ssl, &tls_in.bits);
2768 tls_in.cipher_stdname = cipher_stdname_ssl(server_ssl);
2773 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)))
2774 debug_printf("Shared ciphers: %s\n", buf);
2776 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2778 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
2779 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2784 #ifdef EXIM_HAVE_SESSION_TICKET
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));
2794 /* Record the certificate we presented */
2796 X509 * crt = SSL_get_certificate(server_ssl);
2797 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
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.
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;
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;
2817 tls_in.active.sock = fileno(smtp_out);
2818 tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */
2826 tls_client_basic_ctx_init(SSL_CTX * ctx,
2827 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
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 */
2835 if ( ( !ob->tls_verify_hosts
2836 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2838 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
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;
2846 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2847 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2851 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2853 cbinfo->verify_cert_hostnames =
2855 string_domain_utf8_to_alabel(host->name, NULL);
2859 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2860 cbinfo->verify_cert_hostnames);
2868 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2871 const char * hostnames[2] = { CS host->name, NULL };
2874 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2875 return tls_error(US"hostnames load", host, NULL, errstr);
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)
2881 const uschar * p = rr->data;
2882 uint8_t usage, selector, mtype;
2883 const char * mdname;
2887 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2888 if (usage != 2 && usage != 3) continue;
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;
2902 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2905 return tls_error(US"tlsa load", host, NULL, errstr);
2906 case 0: /* action not taken */
2910 tls_out.tlsa_usage |= 1<<usage;
2916 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2919 #endif /*SUPPORT_DANE*/
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. */
2928 tls_retrieve_session(tls_support * tlsp, SSL * ssl, const uschar * key)
2930 tlsp->resumption |= RESUME_SUPPORTED;
2931 if (tlsp->host_resumable)
2933 dbdata_tls_session * dt;
2935 open_db dbblock, * dbm_file;
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)))
2941 /* key for the db is the IP */
2942 if ((dt = dbfn_read_with_length(dbm_file, key, &len)))
2944 SSL_SESSION * ss = NULL;
2945 const uschar * sess_asn1 = dt->session;
2947 len -= sizeof(dbdata_tls_session);
2948 if (!(d2i_SSL_SESSION(&ss, &sess_asn1, (long)len)))
2952 ERR_error_string_n(ERR_get_error(),
2953 ssl_errstring, sizeof(ssl_errstring));
2954 debug_printf("decoding session: %s\n", ssl_errstring);
2957 #ifdef EXIM_HAVE_SESSION_TICKET
2958 else if ( SSL_SESSION_get_ticket_lifetime_hint(ss) + dt->time_stamp
2961 DEBUG(D_tls) debug_printf("session expired\n");
2962 dbfn_delete(dbm_file, key);
2965 else if (!SSL_set_session(ssl, ss))
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);
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;
2983 DEBUG(D_tls) debug_printf("no session record\n");
2984 dbfn_close(dbm_file);
2990 /* On the client, save the session for later resumption */
2993 tls_save_session_cb(SSL * ssl, SSL_SESSION * ss)
2995 tls_ext_ctx_cb * cbinfo = SSL_get_ex_data(ssl, tls_exdata_idx);
2998 DEBUG(D_tls) debug_printf("tls_save_session_cb\n");
3000 if (!cbinfo || !(tlsp = cbinfo->tlsp)->host_resumable) return 0;
3002 # ifdef OPENSSL_HAVE_NUM_TICKETS
3003 if (SSL_SESSION_is_resumable(ss)) /* 1.1.1 */
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;
3012 DEBUG(D_tls) debug_printf("session is resumable\n");
3013 tlsp->resumption |= RESUME_SERVER_TICKET; /* server gave us a ticket */
3015 dt->verify_override = tlsp->verify_override;
3016 dt->ocsp = tlsp->ocsp;
3017 (void) i2d_SSL_SESSION(ss, &s); /* s gets bumped to end */
3019 if ((dbm_file = dbfn_open(US"tls", O_RDWR, &dbblock, FALSE, FALSE)))
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",
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)
3038 /* Should the client request a session resumption ticket? */
3039 if (verify_check_given_host(CUSS &ob->tls_resumption_hosts, host) == OK)
3041 tlsp->host_resumable = TRUE;
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);
3051 tls_client_ssl_resume_prehandshake(SSL * ssl, tls_support * tlsp,
3052 host_item * host, uschar ** errstr)
3054 if (tlsp->host_resumable)
3057 debug_printf("tls_resumption_hosts overrides openssl_options, enabling tickets\n");
3058 SSL_clear_options(ssl, SSL_OP_NO_TICKET);
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))
3063 tls_error(US"set ex_data", host, NULL, errstr);
3066 debug_printf("tls_exdata_idx %d cbinfo %p\n", tls_exdata_idx, client_static_cbinfo);
3069 tlsp->resumption = RESUME_SUPPORTED;
3070 /* Pick up a previous session, saved on an old ticket */
3071 tls_retrieve_session(tlsp, ssl, host->address);
3076 tls_client_resume_posthandshake(exim_openssl_client_tls_ctx * exim_client_ctx,
3079 if (SSL_session_reused(exim_client_ctx->ssl))
3081 DEBUG(D_tls) debug_printf("The session was reused\n");
3082 tlsp->resumption |= RESUME_USED;
3085 #endif /* EXPERIMENTAL_TLS_RESUME */
3088 /*************************************************
3089 * Start a TLS session in a client *
3090 *************************************************/
3092 /* Called from the smtp transport after STARTTLS has been accepted.
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
3101 Returns: TRUE for success with TLS session context set in connection context,
3106 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
3107 void * cookie, tls_support * tlsp, uschar ** errstr)
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;
3117 static uschar peerdn[256];
3119 #ifndef DISABLE_OCSP
3120 BOOL request_ocsp = FALSE;
3121 BOOL require_ocsp = FALSE;
3125 store_pool = POOL_PERM;
3126 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx), FALSE);
3127 exim_client_ctx->corked = NULL;
3131 tlsp->tlsa_usage = 0;
3134 #ifndef DISABLE_OCSP
3136 # ifdef SUPPORT_DANE
3137 if ( conn_args->dane
3138 && ob->hosts_request_ocsp[0] == '*'
3139 && ob->hosts_request_ocsp[1] == '\0'
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}} } "
3151 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
3152 request_ocsp = TRUE;
3154 # ifdef SUPPORT_DANE
3158 verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
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,
3167 cookie, &client_static_cbinfo, tlsp, errstr);
3168 if (rc != OK) return FALSE;
3170 tlsp->certificate_verified = FALSE;
3171 client_verify_callback_called = FALSE;
3175 if (conn_args->dane)
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))
3183 if (expciphers && *expciphers == '\0')
3188 !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
3189 &expciphers, errstr))
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. */
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))
3203 tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
3209 if (conn_args->dane)
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);
3215 if (!DANESSL_library_init())
3217 tls_error(US"library init", host, NULL, errstr);
3220 if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
3222 tls_error(US"context init", host, NULL, errstr);
3230 if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
3231 client_static_cbinfo, errstr) != OK)
3234 #ifdef EXPERIMENTAL_TLS_RESUME
3235 tls_client_ctx_resume_prehandshake(exim_client_ctx, tlsp, ob, host);
3239 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
3241 tls_error(US"SSL_new", host, NULL, errstr);
3244 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
3246 SSL_set_fd(exim_client_ctx->ssl, cctx->sock);
3247 SSL_set_connect_state(exim_client_ctx->ssl);
3251 if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
3255 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
3257 else if (!Ustrlen(tlsp->sni))
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);
3265 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
3272 if (conn_args->dane)
3273 if (dane_tlsa_load(exim_client_ctx->ssl, host, &conn_args->tlsa_dnsa, errstr) != OK)
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
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"))
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;
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;
3305 #ifdef EXPERIMENTAL_TLS_RESUME
3306 if (!tls_client_ssl_resume_prehandshake(exim_client_ctx->ssl, tlsp, host,
3311 #ifndef DISABLE_EVENT
3312 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
3315 /* There doesn't seem to be a built-in timeout on connection. */
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);
3324 if (conn_args->dane)
3325 DANESSL_cleanup(exim_client_ctx->ssl);
3330 tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
3336 debug_printf("SSL_connect succeeded\n");
3337 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
3339 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
3340 SSL_SESSION_print_keylog(bp, SSL_get_session(exim_client_ctx->ssl));
3346 #ifdef EXPERIMENTAL_TLS_RESUME
3347 tls_client_resume_posthandshake(exim_client_ctx, tlsp);
3350 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
3352 tlsp->cipher = construct_cipher_name(exim_client_ctx->ssl, &tlsp->bits);
3353 tlsp->cipher_stdname = cipher_stdname_ssl(exim_client_ctx->ssl);
3355 /* Record the certificate we presented */
3357 X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
3358 tlsp->ourcert = crt ? X509_dup(crt) : NULL;
3361 tlsp->active.sock = cctx->sock;
3362 tlsp->active.tls_ctx = exim_client_ctx;
3363 cctx->tls_ctx = exim_client_ctx;
3372 tls_refill(unsigned lim)
3377 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
3378 ssl_xfer_buffer, ssl_xfer_buffer_size);
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);
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();
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. */
3401 case SSL_ERROR_NONE:
3404 case SSL_ERROR_ZERO_RETURN:
3405 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
3407 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
3408 SSL_shutdown(server_ssl);
3410 tls_close(NULL, TLS_NO_SHUTDOWN);
3413 /* Handle genuine errors */
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;
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;
3428 #ifndef DISABLE_DKIM
3429 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
3431 ssl_xfer_buffer_hwm = inbytes;
3432 ssl_xfer_buffer_lwm = 0;
3437 /*************************************************
3438 * TLS version of getc *
3439 *************************************************/
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.
3444 Arguments: lim Maximum amount to read/buffer
3445 Returns: the next character or EOF
3447 Only used by the server-side TLS.
3451 tls_getc(unsigned lim)
3453 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3454 if (!tls_refill(lim))
3455 return ssl_xfer_error ? EOF : smtp_getc(lim);
3457 /* Something in the buffer; return next uschar */
3459 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
3463 tls_getbuf(unsigned * len)
3468 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3469 if (!tls_refill(*len))
3471 if (!ssl_xfer_error) return smtp_getbuf(len);
3476 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
3478 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
3479 ssl_xfer_buffer_lwm += size;
3488 #ifndef DISABLE_DKIM
3489 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
3491 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
3497 tls_could_read(void)
3499 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
3503 /*************************************************
3504 * Read bytes from TLS channel *
3505 *************************************************/
3509 ct_ctx client context pointer, or NULL for the one global server context
3513 Returns: the number of bytes read
3514 -1 after a failed read, including EOF
3516 Only used by the client-side TLS.
3520 tls_read(void * ct_ctx, uschar *buff, size_t len)
3522 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
3526 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
3527 buff, (unsigned int)len);
3529 inbytes = SSL_read(ssl, CS buff, len);
3530 error = SSL_get_error(ssl, inbytes);
3532 if (error == SSL_ERROR_ZERO_RETURN)
3534 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
3537 else if (error != SSL_ERROR_NONE)
3547 /*************************************************
3548 * Write bytes down TLS channel *
3549 *************************************************/
3553 ct_ctx client context pointer, or NULL for the one global server context
3556 more further data expected soon
3558 Returns: the number of bytes after a successful write,
3559 -1 after a failed write
3561 Used by both server-side and client-side TLS.
3565 tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more)
3568 int outbytes, error;
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;
3576 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
3577 buff, (unsigned long)len, more ? ", more" : "");
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 */
3589 if ((more || corked))
3591 #ifdef SUPPORT_PIPE_CONNECT
3592 int save_pool = store_pool;
3593 store_pool = POOL_PERM;
3596 corked = string_catn(corked, buff, len);
3598 #ifdef SUPPORT_PIPE_CONNECT
3599 store_pool = save_pool;
3607 buff = CUS corked->s;
3612 for (int left = len; left > 0;)
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);
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);
3625 case SSL_ERROR_NONE:
3630 case SSL_ERROR_ZERO_RETURN:
3631 log_write(0, LOG_MAIN, "SSL channel closed on write");
3634 case SSL_ERROR_SYSCALL:
3635 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
3636 sender_fullhost ? sender_fullhost : US"<unknown>",
3641 log_write(0, LOG_MAIN, "SSL_write error %d", error);
3650 /*************************************************
3651 * Close down a TLS session *
3652 *************************************************/
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).
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
3665 Used by both server-side and client-side TLS.
3669 tls_close(void * ct_ctx, int shutdown)
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;
3676 if (*fdp < 0) return; /* TLS was not active */
3681 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
3682 shutdown > 1 ? " (with response-wait)" : "");
3684 if ( (rc = SSL_shutdown(*sslp)) == 0 /* send "close notify" alert */
3688 rc = SSL_shutdown(*sslp); /* wait for response */
3692 if (rc < 0) DEBUG(D_tls)
3694 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3695 debug_printf("SSL_shutdown: %s\n", ssl_errstring);
3699 if (!o_ctx) /* server side */
3701 #ifndef DISABLE_OCSP
3702 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
3703 server_static_cbinfo->verify_stack = NULL;
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;
3715 /* Leave bits, peercert, cipher, peerdn, certificate_verified set, for logging */
3718 SSL_CTX_free(*ctxp);
3728 /*************************************************
3729 * Let tls_require_ciphers be checked at startup *
3730 *************************************************/
3732 /* The tls_require_ciphers option, if set, must be something which the
3735 Returns: NULL on success, or error message
3739 tls_validate_require_cipher(void)
3742 uschar *s, *expciphers, *err;
3746 if (!(tls_require_ciphers && *tls_require_ciphers))
3749 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3751 return US"failed to expand tls_require_ciphers";
3753 if (!(expciphers && *expciphers))
3756 /* normalisation ripped from above */
3758 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
3762 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
3763 if (!(ctx = SSL_CTX_new(TLS_server_method())))
3765 if (!(ctx = SSL_CTX_new(SSLv23_server_method())))
3768 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3769 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
3773 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3775 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
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);
3790 /*************************************************
3791 * Report the library versions. *
3792 *************************************************/
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.
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.
3805 Arguments: a FILE* to print the results to
3810 tls_version_report(FILE *f)
3812 fprintf(f, "Library version: OpenSSL: Compile: %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. */
3825 /*************************************************
3826 * Random number generation *
3827 *************************************************/
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.
3837 Returns a random number in range [0, max-1]
3841 vaguely_random_number(int max)
3845 static pid_t pidlast = 0;
3847 uschar smallbuf[sizeof(r)];
3853 if (pidnow != pidlast)
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. */
3864 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
3868 gettimeofday(&r.tv, NULL);
3871 RAND_seed(US (&r), sizeof(r));
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
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)
3889 #ifdef EXIM_HAVE_RAND_PSEUDO
3890 /* We do not care if crypto-strong */
3891 i = RAND_pseudo_bytes(smallbuf, needed_len);
3893 i = RAND_bytes(smallbuf, needed_len);
3899 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
3900 return vaguely_random_number_fallback(max);
3904 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
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. */
3915 /*************************************************
3916 * OpenSSL option parse *
3917 *************************************************/
3919 /* Parse one option for tls_openssl_options_parse below
3922 name one option name
3923 value place to store a value for it
3924 Returns success or failure in parsing
3930 tls_openssl_one_option_parse(uschar *name, long *value)
3933 int last = exim_openssl_options_size;
3934 while (last > first)
3936 int middle = (first + last)/2;
3937 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3940 *value = exim_openssl_options[middle].value;
3954 /*************************************************
3955 * OpenSSL option parsing logic *
3956 *************************************************/
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.
3963 option_spec the administrator-supplied string of options
3964 results ptr to long storage for the options bitmap
3965 Returns success or failure
3969 tls_openssl_options_parse(uschar *option_spec, long *results)
3972 uschar * exp, * end;
3974 BOOL adding, item_parsed;
3976 /* Server: send no (<= TLS1.2) session tickets */
3977 result = SSL_OP_NO_TICKET;
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;
3984 #ifdef SSL_OP_NO_SSLv3
3985 result |= SSL_OP_NO_SSLv3;
3987 #ifdef SSL_OP_SINGLE_DH_USE
3988 result |= SSL_OP_SINGLE_DH_USE;
3997 if (!expand_check(option_spec, US"openssl_options", &exp, &end))
4000 for (uschar * s = exp; *s; /**/)
4002 while (isspace(*s)) ++s;
4005 if (*s != '+' && *s != '-')
4007 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
4008 "+ or - expected but found \"%s\"\n", s);
4011 adding = *s++ == '+';
4012 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
4015 item_parsed = tls_openssl_one_option_parse(s, &item);
4019 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
4022 DEBUG(D_tls) debug_printf("openssl option, %s %8lx: %lx (%s)\n",
4023 adding ? "adding to " : "removing from", result, item, s);
4035 #endif /*!MACRO_PREDEF*/
4038 /* End of tls-openssl.c */