1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
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
50 # define EXIM_HAVE_EPHEM_RSA_KEX
51 # define EXIM_HAVE_RAND_PSEUDO
53 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
54 # define EXIM_HAVE_SHA256
57 /* X509_check_host provides sane certificate hostname checking, but was added
58 to OpenSSL late, after other projects forked off the code-base. So in
59 addition to guarding against the base version number, beware that LibreSSL
60 does not (at this time) support this function.
62 If LibreSSL gains a different API, perhaps via libtls, then we'll probably
63 opt to disentangle and ask a LibreSSL user to provide glue for a third
64 crypto provider for libtls instead of continuing to tie the OpenSSL glue
65 into even twistier knots. If LibreSSL gains the same API, we can just
66 change this guard and punt the issue for a while longer. */
68 #ifndef LIBRESSL_VERSION_NUMBER
69 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
70 # define EXIM_HAVE_OPENSSL_CHECKHOST
71 # define EXIM_HAVE_OPENSSL_DH_BITS
72 # define EXIM_HAVE_OPENSSL_TLS_METHOD
73 # define EXIM_HAVE_OPENSSL_KEYLOG
74 # define EXIM_HAVE_OPENSSL_CIPHER_GET_ID
76 # define EXIM_NEED_OPENSSL_INIT
78 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
79 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
80 # define EXIM_HAVE_OPENSSL_CHECKHOST
84 #if !defined(LIBRESSL_VERSION_NUMBER) \
85 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
86 # if !defined(OPENSSL_NO_ECDH)
87 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
88 # define EXIM_HAVE_ECDH
90 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
91 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
96 #ifndef LIBRESSL_VERSION_NUMBER
97 # if OPENSSL_VERSION_NUMBER >= 0x010101000L
98 # define OPENSSL_HAVE_KEYLOG_CB
99 # define OPENSSL_HAVE_NUM_TICKETS
100 # define EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
104 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
105 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
106 # define DISABLE_OCSP
109 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
110 # include <openssl/x509v3.h>
113 #ifndef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
114 # ifndef EXIM_HAVE_OPENSSL_CIPHER_GET_ID
115 # define SSL_CIPHER_get_id(c) (c->id)
117 # include "tls-cipher-stdname.c"
120 /*************************************************
121 * OpenSSL option parse *
122 *************************************************/
124 typedef struct exim_openssl_option {
127 } exim_openssl_option;
128 /* We could use a macro to expand, but we need the ifdef and not all the
129 options document which version they were introduced in. Policylet: include
130 all options unless explicitly for DTLS, let the administrator choose which
133 This list is current as of:
135 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
136 Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev
138 static exim_openssl_option exim_openssl_options[] = {
139 /* KEEP SORTED ALPHABETICALLY! */
141 { US"all", SSL_OP_ALL },
143 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
144 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
146 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
147 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
149 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
150 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
152 #ifdef SSL_OP_EPHEMERAL_RSA
153 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
155 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
156 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
158 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
159 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
161 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
162 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
164 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
165 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
167 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
168 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
170 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
171 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
173 #ifdef SSL_OP_NO_COMPRESSION
174 { US"no_compression", SSL_OP_NO_COMPRESSION },
176 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
177 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
179 #ifdef SSL_OP_NO_SSLv2
180 { US"no_sslv2", SSL_OP_NO_SSLv2 },
182 #ifdef SSL_OP_NO_SSLv3
183 { US"no_sslv3", SSL_OP_NO_SSLv3 },
185 #ifdef SSL_OP_NO_TICKET
186 { US"no_ticket", SSL_OP_NO_TICKET },
188 #ifdef SSL_OP_NO_TLSv1
189 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
191 #ifdef SSL_OP_NO_TLSv1_1
192 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
193 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
194 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
196 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
199 #ifdef SSL_OP_NO_TLSv1_2
200 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
202 #ifdef SSL_OP_NO_TLSv1_3
203 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
205 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
206 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
208 #ifdef SSL_OP_SINGLE_DH_USE
209 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
211 #ifdef SSL_OP_SINGLE_ECDH_USE
212 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
214 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
215 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
217 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
218 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
220 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
221 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
223 #ifdef SSL_OP_TLS_D5_BUG
224 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
226 #ifdef SSL_OP_TLS_ROLLBACK_BUG
227 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
232 static int exim_openssl_options_size = nelem(exim_openssl_options);
241 for (struct exim_openssl_option * o = exim_openssl_options;
242 o < exim_openssl_options + nelem(exim_openssl_options); o++)
244 /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
245 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
247 spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
248 builtin_macro_create(buf);
253 /******************************************************************************/
255 /* Structure for collecting random data for seeding. */
257 typedef struct randstuff {
262 /* Local static variables */
264 static BOOL client_verify_callback_called = FALSE;
265 static BOOL server_verify_callback_called = FALSE;
266 static const uschar *sid_ctx = US"exim";
268 /* We have three different contexts to care about.
270 Simple case: client, `client_ctx`
271 As a client, we can be doing a callout or cut-through delivery while receiving
272 a message. So we have a client context, which should have options initialised
273 from the SMTP Transport. We may also concurrently want to make TLS connections
274 to utility daemons, so client-contexts are allocated and passed around in call
275 args rather than using a gobal.
278 There are two cases: with and without ServerNameIndication from the client.
279 Given TLS SNI, we can be using different keys, certs and various other
280 configuration settings, because they're re-expanded with $tls_sni set. This
281 allows vhosting with TLS. This SNI is sent in the handshake.
282 A client might not send SNI, so we need a fallback, and an initial setup too.
283 So as a server, we start out using `server_ctx`.
284 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
285 `server_sni` from `server_ctx` and then initialise settings by re-expanding
293 } exim_openssl_client_tls_ctx;
295 static SSL_CTX *server_ctx = NULL;
296 static SSL *server_ssl = NULL;
298 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
299 static SSL_CTX *server_sni = NULL;
302 static char ssl_errstring[256];
304 static int ssl_session_timeout = 200;
305 static BOOL client_verify_optional = FALSE;
306 static BOOL server_verify_optional = FALSE;
308 static BOOL reexpand_tls_files_for_sni = FALSE;
311 typedef struct tls_ext_ctx_cb {
316 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
320 uschar *file_expanded;
321 OCSP_RESPONSE *response;
324 X509_STORE *verify_store; /* non-null if status requested */
325 BOOL verify_required;
330 /* these are cached from first expand */
331 uschar *server_cipher_list;
332 /* only passed down to tls_error: */
334 const uschar * verify_cert_hostnames;
335 #ifndef DISABLE_EVENT
336 uschar * event_action;
340 /* should figure out a cleanup of API to handle state preserved per
341 implementation, for various reasons, which can be void * in the APIs.
342 For now, we hack around it. */
343 tls_ext_ctx_cb *client_static_cbinfo = NULL;
344 tls_ext_ctx_cb *server_static_cbinfo = NULL;
347 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
348 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
351 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
352 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
355 static int tls_server_stapling_cb(SSL *s, void *arg);
359 /*************************************************
361 *************************************************/
363 /* Called from lots of places when errors occur before actually starting to do
364 the TLS handshake, that is, while the session is still in clear. Always returns
365 DEFER for a server and FAIL for a client so that most calls can use "return
366 tls_error(...)" to do this processing and then give an appropriate return. A
367 single function is used for both server and client, because it is called from
368 some shared functions.
371 prefix text to include in the logged error
372 host NULL if setting up a server;
373 the connected host if setting up a client
374 msg error message or NULL if we should ask OpenSSL
375 errstr pointer to output error message
377 Returns: OK/DEFER/FAIL
381 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
385 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
386 msg = US ssl_errstring;
389 msg = string_sprintf("(%s): %s", prefix, msg);
390 DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg);
391 if (errstr) *errstr = msg;
392 return host ? FAIL : DEFER;
397 /*************************************************
398 * Callback to generate RSA key *
399 *************************************************/
403 s SSL connection (not used)
407 Returns: pointer to generated key
411 rsa_callback(SSL *s, int export, int keylength)
414 #ifdef EXIM_HAVE_RSA_GENKEY_EX
415 BIGNUM *bn = BN_new();
418 export = export; /* Shut picky compilers up */
419 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
421 #ifdef EXIM_HAVE_RSA_GENKEY_EX
422 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
423 || !(rsa_key = RSA_new())
424 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
427 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
431 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
432 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
444 x509_store_dump_cert_s_names(X509_STORE * store)
446 STACK_OF(X509_OBJECT) * roots= store->objs;
447 static uschar name[256];
449 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
451 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
452 if(tmp_obj->type == X509_LU_X509)
454 X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
455 if (X509_NAME_oneline(sn, CS name, sizeof(name)))
457 name[sizeof(name)-1] = '\0';
458 debug_printf(" %s\n", name);
467 #ifndef DISABLE_EVENT
469 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
470 BOOL *calledp, const BOOL *optionalp, const uschar * what)
476 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
479 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
480 old_cert = tlsp->peercert;
481 tlsp->peercert = X509_dup(cert);
482 /* NB we do not bother setting peerdn */
483 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
485 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
486 "depth=%d cert=%s: %s",
487 tlsp == &tls_out ? deliver_host_address : sender_host_address,
488 what, depth, dn, yield);
492 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
493 return 1; /* reject (leaving peercert set) */
495 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
496 "(host in tls_try_verify_hosts)\n");
498 X509_free(tlsp->peercert);
499 tlsp->peercert = old_cert;
505 /*************************************************
506 * Callback for verification *
507 *************************************************/
509 /* The SSL library does certificate verification if set up to do so. This
510 callback has the current yes/no state is in "state". If verification succeeded,
511 we set the certificate-verified flag. If verification failed, what happens
512 depends on whether the client is required to present a verifiable certificate
515 If verification is optional, we change the state to yes, but still log the
516 verification error. For some reason (it really would help to have proper
517 documentation of OpenSSL), this callback function then gets called again, this
518 time with state = 1. We must take care not to set the private verified flag on
519 the second time through.
521 Note: this function is not called if the client fails to present a certificate
522 when asked. We get here only if a certificate has been received. Handling of
523 optional verification for this case is done when requesting SSL to verify, by
524 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
526 May be called multiple times for different issues with a certificate, even
527 for a given "depth" in the certificate chain.
530 preverify_ok current yes/no state as 1/0
531 x509ctx certificate information.
532 tlsp per-direction (client vs. server) support data
533 calledp has-been-called flag
534 optionalp verification-is-optional flag
536 Returns: 0 if verification should fail, otherwise 1
540 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
541 tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
543 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
544 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
547 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
549 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
550 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
551 tlsp == &tls_out ? deliver_host_address : sender_host_address);
554 dn[sizeof(dn)-1] = '\0';
556 if (preverify_ok == 0)
558 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
559 *verify_mode, sender_host_address)
561 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
562 tlsp == &tls_out ? deliver_host_address : sender_host_address,
564 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
569 tlsp->peercert = X509_dup(cert); /* record failing cert */
570 return 0; /* reject */
572 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
573 "tls_try_verify_hosts)\n");
578 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
580 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
581 { /* client, wanting stapling */
582 /* Add the server cert's signing chain as the one
583 for the verification of the OCSP stapled information. */
585 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
588 sk_X509_push(client_static_cbinfo->verify_stack, cert);
591 #ifndef DISABLE_EVENT
592 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
593 return 0; /* reject, with peercert set */
598 const uschar * verify_cert_hostnames;
600 if ( tlsp == &tls_out
601 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
602 /* client, wanting hostname check */
605 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
606 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
607 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
609 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
610 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
613 const uschar * list = verify_cert_hostnames;
616 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
617 if ((rc = X509_check_host(cert, CCS name, 0,
618 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
619 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
624 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
625 tlsp == &tls_out ? deliver_host_address : sender_host_address);
632 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
635 uschar * extra = verify_mode
636 ? string_sprintf(" (during %c-verify for [%s])",
637 *verify_mode, sender_host_address)
639 log_write(0, LOG_MAIN,
640 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
641 tlsp == &tls_out ? deliver_host_address : sender_host_address,
642 extra, dn, verify_cert_hostnames);
647 tlsp->peercert = X509_dup(cert); /* record failing cert */
648 return 0; /* reject */
650 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
651 "tls_try_verify_hosts)\n");
655 #ifndef DISABLE_EVENT
656 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
657 return 0; /* reject, with peercert set */
660 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
661 *calledp ? "" : " authenticated", dn);
662 if (!*calledp) tlsp->certificate_verified = TRUE;
666 return 1; /* accept, at least for this level */
670 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
672 return verify_callback(preverify_ok, x509ctx, &tls_out,
673 &client_verify_callback_called, &client_verify_optional);
677 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
679 return verify_callback(preverify_ok, x509ctx, &tls_in,
680 &server_verify_callback_called, &server_verify_optional);
686 /* This gets called *by* the dane library verify callback, which interposes
690 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
692 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
694 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
695 #ifndef DISABLE_EVENT
696 BOOL dummy_called, optional = FALSE;
699 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
701 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
702 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
703 deliver_host_address);
706 dn[sizeof(dn)-1] = '\0';
708 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
709 preverify_ok ? "ok":"BAD", depth, dn);
711 #ifndef DISABLE_EVENT
712 if (verify_event(&tls_out, cert, depth, dn,
713 &dummy_called, &optional, US"DANE"))
714 return 0; /* reject, with peercert set */
717 if (preverify_ok == 1)
719 tls_out.dane_verified = tls_out.certificate_verified = TRUE;
721 if (client_static_cbinfo->u_ocsp.client.verify_store)
722 { /* client, wanting stapling */
723 /* Add the server cert's signing chain as the one
724 for the verification of the OCSP stapled information. */
726 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
729 sk_X509_push(client_static_cbinfo->verify_stack, cert);
735 int err = X509_STORE_CTX_get_error(x509ctx);
737 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
738 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
744 #endif /*SUPPORT_DANE*/
747 /*************************************************
748 * Information callback *
749 *************************************************/
751 /* The SSL library functions call this from time to time to indicate what they
752 are doing. We copy the string to the debugging output when TLS debugging has
764 info_callback(SSL *s, int where, int ret)
770 if (where & SSL_ST_CONNECT)
771 str = US"SSL_connect";
772 else if (where & SSL_ST_ACCEPT)
773 str = US"SSL_accept";
775 str = US"SSL info (undefined)";
777 if (where & SSL_CB_LOOP)
778 debug_printf("%s: %s\n", str, SSL_state_string_long(s));
779 else if (where & SSL_CB_ALERT)
780 debug_printf("SSL3 alert %s:%s:%s\n",
781 str = where & SSL_CB_READ ? US"read" : US"write",
782 SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
783 else if (where & SSL_CB_EXIT)
785 debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
787 debug_printf("%s: error in %s\n", str, SSL_state_string_long(s));
788 else if (where & SSL_CB_HANDSHAKE_START)
789 debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s));
790 else if (where & SSL_CB_HANDSHAKE_DONE)
791 debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s));
795 #ifdef OPENSSL_HAVE_KEYLOG_CB
797 keylog_callback(const SSL *ssl, const char *line)
799 DEBUG(D_tls) debug_printf("%.200s\n", line);
805 /*************************************************
806 * Initialize for DH *
807 *************************************************/
809 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
812 sctx The current SSL CTX (inbound or outbound)
813 dhparam DH parameter file or fixed parameter identity string
814 host connected host, if client; NULL if server
815 errstr error string pointer
817 Returns: TRUE if OK (nothing to set up, or setup worked)
821 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
829 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
832 if (!dhexpanded || !*dhexpanded)
833 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
834 else if (dhexpanded[0] == '/')
836 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
838 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
839 host, US strerror(errno), errstr);
845 if (Ustrcmp(dhexpanded, "none") == 0)
847 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
851 if (!(pem = std_dh_prime_named(dhexpanded)))
853 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
854 host, US strerror(errno), errstr);
857 bio = BIO_new_mem_buf(CS pem, -1);
860 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
863 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
868 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
869 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
870 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
871 * If someone wants to dance at the edge, then they can raise the limit or use
872 * current libraries. */
873 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
874 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
875 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
876 dh_bitsize = DH_bits(dh);
878 dh_bitsize = 8 * DH_size(dh);
881 /* Even if it is larger, we silently return success rather than cause things
882 * to fail out, so that a too-large DH will not knock out all TLS; it's a
883 * debatable choice. */
884 if (dh_bitsize > tls_dh_max_bits)
887 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
888 dh_bitsize, tls_dh_max_bits);
892 SSL_CTX_set_tmp_dh(sctx, dh);
894 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
895 dhexpanded ? dhexpanded : US"default", dh_bitsize);
907 /*************************************************
908 * Initialize for ECDH *
909 *************************************************/
911 /* Load parameters for ECDH encryption.
913 For now, we stick to NIST P-256 because: it's simple and easy to configure;
914 it avoids any patent issues that might bite redistributors; despite events in
915 the news and concerns over curve choices, we're not cryptographers, we're not
916 pretending to be, and this is "good enough" to be better than no support,
917 protecting against most adversaries. Given another year or two, there might
918 be sufficient clarity about a "right" way forward to let us make an informed
919 decision, instead of a knee-jerk reaction.
921 Longer-term, we should look at supporting both various named curves and
922 external files generated with "openssl ecparam", much as we do for init_dh().
923 We should also support "none" as a value, to explicitly avoid initialisation.
928 sctx The current SSL CTX (inbound or outbound)
929 host connected host, if client; NULL if server
930 errstr error string pointer
932 Returns: TRUE if OK (nothing to set up, or setup worked)
936 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
938 #ifdef OPENSSL_NO_ECDH
947 if (host) /* No ECDH setup for clients, only for servers */
950 # ifndef EXIM_HAVE_ECDH
952 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
956 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
958 if (!exp_curve || !*exp_curve)
961 /* "auto" needs to be handled carefully.
962 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
963 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
964 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
965 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
966 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
968 if (Ustrcmp(exp_curve, "auto") == 0)
970 #if OPENSSL_VERSION_NUMBER < 0x10002000L
971 DEBUG(D_tls) debug_printf(
972 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
973 exp_curve = US"prime256v1";
975 # if defined SSL_CTRL_SET_ECDH_AUTO
976 DEBUG(D_tls) debug_printf(
977 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
978 SSL_CTX_set_ecdh_auto(sctx, 1);
981 DEBUG(D_tls) debug_printf(
982 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
988 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
989 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
990 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
991 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
995 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
1000 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
1002 tls_error(US"Unable to create ec curve", host, NULL, errstr);
1006 /* The "tmp" in the name here refers to setting a temporary key
1007 not to the stability of the interface. */
1009 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
1010 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
1012 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1017 # endif /*EXIM_HAVE_ECDH*/
1018 #endif /*OPENSSL_NO_ECDH*/
1024 #ifndef DISABLE_OCSP
1025 /*************************************************
1026 * Load OCSP information into state *
1027 *************************************************/
1028 /* Called to load the server OCSP response from the given file into memory, once
1029 caller has determined this is needed. Checks validity. Debugs a message
1032 ASSUMES: single response, for single cert.
1035 sctx the SSL_CTX* to update
1036 cbinfo various parts of session state
1037 expanded the filename putatively holding an OCSP response
1042 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
1045 OCSP_RESPONSE * resp;
1046 OCSP_BASICRESP * basic_response;
1047 OCSP_SINGLERESP * single_response;
1048 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1049 STACK_OF(X509) * sk;
1050 unsigned long verify_flags;
1051 int status, reason, i;
1053 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
1054 if (cbinfo->u_ocsp.server.response)
1056 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
1057 cbinfo->u_ocsp.server.response = NULL;
1060 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
1062 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1063 cbinfo->u_ocsp.server.file_expanded);
1067 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1071 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1075 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1077 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1078 OCSP_response_status_str(status), status);
1082 if (!(basic_response = OCSP_response_get1_basic(resp)))
1085 debug_printf("OCSP response parse error: unable to extract basic response.\n");
1089 sk = cbinfo->verify_stack;
1090 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
1092 /* May need to expose ability to adjust those flags?
1093 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
1094 OCSP_TRUSTOTHER OCSP_NOINTERN */
1096 /* This does a full verify on the OCSP proof before we load it for serving
1097 up; possibly overkill - just date-checks might be nice enough.
1099 OCSP_basic_verify takes a "store" arg, but does not
1100 use it for the chain verification, which is all we do
1101 when OCSP_NOVERIFY is set. The content from the wire
1102 "basic_response" and a cert-stack "sk" are all that is used.
1104 We have a stack, loaded in setup_certs() if tls_verify_certificates
1105 was a file (not a directory, or "system"). It is unfortunate we
1106 cannot used the connection context store, as that would neatly
1107 handle the "system" case too, but there seems to be no library
1108 function for getting a stack from a store.
1109 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
1110 We do not free the stack since it could be needed a second time for
1113 Separately we might try to replace using OCSP_basic_verify() - which seems to not
1114 be a public interface into the OpenSSL library (there's no manual entry) -
1115 But what with? We also use OCSP_basic_verify in the client stapling callback.
1116 And there we NEED it; we must verify that status... unless the
1117 library does it for us anyway? */
1119 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
1123 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1124 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
1129 /* Here's the simplifying assumption: there's only one response, for the
1130 one certificate we use, and nothing for anything else in a chain. If this
1131 proves false, we need to extract a cert id from our issued cert
1132 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
1133 right cert in the stack and then calls OCSP_single_get0_status()).
1135 I'm hoping to avoid reworking a bunch more of how we handle state here. */
1137 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1140 debug_printf("Unable to get first response from OCSP basic response.\n");
1144 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1145 if (status != V_OCSP_CERTSTATUS_GOOD)
1147 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
1148 OCSP_cert_status_str(status), status,
1149 OCSP_crl_reason_str(reason), reason);
1153 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1155 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1160 cbinfo->u_ocsp.server.response = resp; /*XXX stack?*/
1164 if (f.running_in_test_harness)
1166 extern char ** environ;
1167 if (environ) for (uschar ** p = USS environ; *p; p++)
1168 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1170 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1171 goto supply_response;
1176 #endif /*!DISABLE_OCSP*/
1181 /* Create and install a selfsigned certificate, for use in server mode */
1184 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1192 where = US"allocating pkey";
1193 if (!(pkey = EVP_PKEY_new()))
1196 where = US"allocating cert";
1197 if (!(x509 = X509_new()))
1200 where = US"generating pkey";
1201 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1204 where = US"assigning pkey";
1205 if (!EVP_PKEY_assign_RSA(pkey, rsa))
1208 X509_set_version(x509, 2); /* N+1 - version 3 */
1209 ASN1_INTEGER_set(X509_get_serialNumber(x509), 1);
1210 X509_gmtime_adj(X509_get_notBefore(x509), 0);
1211 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
1212 X509_set_pubkey(x509, pkey);
1214 name = X509_get_subject_name(x509);
1215 X509_NAME_add_entry_by_txt(name, "C",
1216 MBSTRING_ASC, CUS "UK", -1, -1, 0);
1217 X509_NAME_add_entry_by_txt(name, "O",
1218 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1219 X509_NAME_add_entry_by_txt(name, "CN",
1220 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1221 X509_set_issuer_name(x509, name);
1223 where = US"signing cert";
1224 if (!X509_sign(x509, pkey, EVP_md5()))
1227 where = US"installing selfsign cert";
1228 if (!SSL_CTX_use_certificate(sctx, x509))
1231 where = US"installing selfsign key";
1232 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1238 (void) tls_error(where, NULL, NULL, errstr);
1239 if (x509) X509_free(x509);
1240 if (pkey) EVP_PKEY_free(pkey);
1248 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1251 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1252 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1253 return tls_error(string_sprintf(
1254 "SSL_CTX_use_certificate_chain_file file=%s", file),
1255 cbinfo->host, NULL, errstr);
1260 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1263 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1264 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1265 return tls_error(string_sprintf(
1266 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1271 /*************************************************
1272 * Expand key and cert file specs *
1273 *************************************************/
1275 /* Called once during tls_init and possibly again during TLS setup, for a
1276 new context, if Server Name Indication was used and tls_sni was seen in
1277 the certificate string.
1280 sctx the SSL_CTX* to update
1281 cbinfo various parts of session state
1282 errstr error string pointer
1284 Returns: OK/DEFER/FAIL
1288 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1293 if (!cbinfo->certificate)
1295 if (!cbinfo->is_server) /* client */
1298 if (tls_install_selfsign(sctx, errstr) != OK)
1305 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1306 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1307 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1309 reexpand_tls_files_for_sni = TRUE;
1311 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1315 if (cbinfo->is_server)
1317 const uschar * file_list = expanded;
1321 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1322 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1325 else /* would there ever be a need for multiple client certs? */
1326 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1329 if ( cbinfo->privatekey
1330 && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1333 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1334 of the expansion is an empty string, ignore it also, and assume the private
1335 key is in the same file as the certificate. */
1337 if (expanded && *expanded)
1338 if (cbinfo->is_server)
1340 const uschar * file_list = expanded;
1344 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1345 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1348 else /* would there ever be a need for multiple client certs? */
1349 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1353 #ifndef DISABLE_OCSP
1354 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1357 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1360 if (expanded && *expanded)
1362 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1363 if ( cbinfo->u_ocsp.server.file_expanded
1364 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1366 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1369 ocsp_load_response(sctx, cbinfo, expanded);
1380 /*************************************************
1381 * Callback to handle SNI *
1382 *************************************************/
1384 /* Called when acting as server during the TLS session setup if a Server Name
1385 Indication extension was sent by the client.
1387 API documentation is OpenSSL s_server.c implementation.
1390 s SSL* of the current session
1391 ad unknown (part of OpenSSL API) (unused)
1392 arg Callback of "our" registered data
1394 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1397 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1399 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1401 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1402 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1404 int old_pool = store_pool;
1405 uschar * dummy_errstr;
1408 return SSL_TLSEXT_ERR_OK;
1410 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1411 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1413 /* Make the extension value available for expansion */
1414 store_pool = POOL_PERM;
1415 tls_in.sni = string_copy(US servername);
1416 store_pool = old_pool;
1418 if (!reexpand_tls_files_for_sni)
1419 return SSL_TLSEXT_ERR_OK;
1421 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1422 not confident that memcpy wouldn't break some internal reference counting.
1423 Especially since there's a references struct member, which would be off. */
1425 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1426 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1428 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1431 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1432 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1436 /* Not sure how many of these are actually needed, since SSL object
1437 already exists. Might even need this selfsame callback, for reneg? */
1439 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1440 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1441 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1442 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1443 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1444 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1446 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1447 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1451 if ( cbinfo->server_cipher_list
1452 && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1455 #ifndef DISABLE_OCSP
1456 if (cbinfo->u_ocsp.server.file)
1458 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1459 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1463 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1464 verify_callback_server, &dummy_errstr)) != OK)
1467 /* do this after setup_certs, because this can require the certs for verifying
1468 OCSP information. */
1469 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1472 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1473 SSL_set_SSL_CTX(s, server_sni);
1474 return SSL_TLSEXT_ERR_OK;
1476 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1478 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1483 #ifndef DISABLE_OCSP
1485 /*************************************************
1486 * Callback to handle OCSP Stapling *
1487 *************************************************/
1489 /* Called when acting as server during the TLS session setup if the client
1490 requests OCSP information with a Certificate Status Request.
1492 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1498 tls_server_stapling_cb(SSL *s, void *arg)
1500 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1501 uschar *response_der; /*XXX blob */
1502 int response_der_len;
1504 /*XXX stack: use SSL_get_certificate() to see which cert; from that work
1505 out which ocsp blob to send. Unfortunately, SSL_get_certificate is known
1506 buggy in current OpenSSL; it returns the last cert loaded always rather than
1507 the one actually presented. So we can't support a stack of OCSP proofs at
1511 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1512 cbinfo->u_ocsp.server.response ? "have" : "lack");
1514 tls_in.ocsp = OCSP_NOT_RESP;
1515 if (!cbinfo->u_ocsp.server.response)
1516 return SSL_TLSEXT_ERR_NOACK;
1518 response_der = NULL;
1519 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response, /*XXX stack*/
1521 if (response_der_len <= 0)
1522 return SSL_TLSEXT_ERR_NOACK;
1524 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1525 tls_in.ocsp = OCSP_VFIED;
1526 return SSL_TLSEXT_ERR_OK;
1531 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1533 BIO_printf(bp, "\t%s: ", str);
1534 ASN1_GENERALIZEDTIME_print(bp, time);
1539 tls_client_stapling_cb(SSL *s, void *arg)
1541 tls_ext_ctx_cb * cbinfo = arg;
1542 const unsigned char * p;
1544 OCSP_RESPONSE * rsp;
1545 OCSP_BASICRESP * bs;
1548 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1549 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1552 /* Expect this when we requested ocsp but got none */
1553 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1554 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1556 DEBUG(D_tls) debug_printf(" null\n");
1557 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1560 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1562 tls_out.ocsp = OCSP_FAILED;
1563 if (LOGGING(tls_cipher))
1564 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1566 DEBUG(D_tls) debug_printf(" parse error\n");
1570 if(!(bs = OCSP_response_get1_basic(rsp)))
1572 tls_out.ocsp = OCSP_FAILED;
1573 if (LOGGING(tls_cipher))
1574 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1576 DEBUG(D_tls) debug_printf(" error parsing response\n");
1577 OCSP_RESPONSE_free(rsp);
1581 /* We'd check the nonce here if we'd put one in the request. */
1582 /* However that would defeat cacheability on the server so we don't. */
1584 /* This section of code reworked from OpenSSL apps source;
1585 The OpenSSL Project retains copyright:
1586 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1591 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1593 DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1595 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1597 /* Use the chain that verified the server cert to verify the stapled info */
1598 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1600 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1601 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1603 tls_out.ocsp = OCSP_FAILED;
1604 if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN,
1605 "Received TLS cert status response, itself unverifiable: %s",
1606 ERR_reason_error_string(ERR_peek_error()));
1607 BIO_printf(bp, "OCSP response verify failure\n");
1608 ERR_print_errors(bp);
1609 OCSP_RESPONSE_print(bp, rsp, 0);
1613 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1615 /*XXX So we have a good stapled OCSP status. How do we know
1616 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1617 OCSP_resp_find_status() which matches on a cert id, which presumably
1618 we should use. Making an id needs OCSP_cert_id_new(), which takes
1619 issuerName, issuerKey, serialNumber. Are they all in the cert?
1621 For now, carry on blindly accepting the resp. */
1624 OCSP_SINGLERESP * single;
1626 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1627 if (OCSP_resp_count(bs) != 1)
1629 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1630 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1633 tls_out.ocsp = OCSP_FAILED;
1634 log_write(0, LOG_MAIN, "OCSP stapling "
1635 "with multiple responses not handled");
1638 single = OCSP_resp_get0(bs, 0);
1639 status = OCSP_single_get0_status(single, &reason, &rev,
1640 &thisupd, &nextupd);
1643 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1644 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1645 if (!OCSP_check_validity(thisupd, nextupd,
1646 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1648 tls_out.ocsp = OCSP_FAILED;
1649 DEBUG(D_tls) ERR_print_errors(bp);
1650 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1654 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1655 OCSP_cert_status_str(status));
1658 case V_OCSP_CERTSTATUS_GOOD:
1659 tls_out.ocsp = OCSP_VFIED;
1662 case V_OCSP_CERTSTATUS_REVOKED:
1663 tls_out.ocsp = OCSP_FAILED;
1664 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1665 reason != -1 ? "; reason: " : "",
1666 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1667 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1670 tls_out.ocsp = OCSP_FAILED;
1671 log_write(0, LOG_MAIN,
1672 "Server certificate status unknown, in OCSP stapling");
1677 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1682 OCSP_RESPONSE_free(rsp);
1685 #endif /*!DISABLE_OCSP*/
1688 /*************************************************
1689 * Initialize for TLS *
1690 *************************************************/
1692 /* Called from both server and client code, to do preliminary initialization
1693 of the library. We allocate and return a context structure.
1696 ctxp returned SSL context
1697 host connected host, if client; NULL if server
1698 dhparam DH parameter file
1699 certificate certificate file
1700 privatekey private key
1701 ocsp_file file of stapling info (server); flag for require ocsp (client)
1702 addr address if client; NULL if server (for some randomness)
1703 cbp place to put allocated callback context
1704 errstr error string pointer
1706 Returns: OK/DEFER/FAIL
1710 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1712 #ifndef DISABLE_OCSP
1713 uschar *ocsp_file, /*XXX stack, in server*/
1715 address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1720 tls_ext_ctx_cb * cbinfo;
1722 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1723 cbinfo->certificate = certificate;
1724 cbinfo->privatekey = privatekey;
1725 cbinfo->is_server = host==NULL;
1726 #ifndef DISABLE_OCSP
1727 cbinfo->verify_stack = NULL;
1730 cbinfo->u_ocsp.server.file = ocsp_file;
1731 cbinfo->u_ocsp.server.file_expanded = NULL;
1732 cbinfo->u_ocsp.server.response = NULL;
1735 cbinfo->u_ocsp.client.verify_store = NULL;
1737 cbinfo->dhparam = dhparam;
1738 cbinfo->server_cipher_list = NULL;
1739 cbinfo->host = host;
1740 #ifndef DISABLE_EVENT
1741 cbinfo->event_action = NULL;
1744 #ifdef EXIM_NEED_OPENSSL_INIT
1745 SSL_load_error_strings(); /* basic set up */
1746 OpenSSL_add_ssl_algorithms();
1749 #ifdef EXIM_HAVE_SHA256
1750 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1751 list of available digests. */
1752 EVP_add_digest(EVP_sha256());
1755 /* Create a context.
1756 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1757 negotiation in the different methods; as far as I can tell, the only
1758 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1759 when OpenSSL is built without SSLv2 support.
1760 By disabling with openssl_options, we can let admins re-enable with the
1763 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1764 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
1766 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1768 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1770 /* It turns out that we need to seed the random number generator this early in
1771 order to get the full complement of ciphers to work. It took me roughly a day
1772 of work to discover this by experiment.
1774 On systems that have /dev/urandom, SSL may automatically seed itself from
1775 there. Otherwise, we have to make something up as best we can. Double check
1781 gettimeofday(&r.tv, NULL);
1784 RAND_seed(US (&r), sizeof(r));
1785 RAND_seed(US big_buffer, big_buffer_size);
1786 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1789 return tls_error(US"RAND_status", host,
1790 US"unable to seed random number generator", errstr);
1793 /* Set up the information callback, which outputs if debugging is at a suitable
1796 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1797 #ifdef OPENSSL_HAVE_KEYLOG_CB
1798 DEBUG(D_tls) SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
1801 /* Automatically re-try reads/writes after renegotiation. */
1802 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1804 /* Apply administrator-supplied work-arounds.
1805 Historically we applied just one requested option,
1806 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1807 moved to an administrator-controlled list of options to specify and
1808 grandfathered in the first one as the default value for "openssl_options".
1810 No OpenSSL version number checks: the options we accept depend upon the
1811 availability of the option value macros from OpenSSL. */
1813 if (!tls_openssl_options_parse(openssl_options, &init_options))
1814 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1818 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1819 if (!(SSL_CTX_set_options(ctx, init_options)))
1820 return tls_error(string_sprintf(
1821 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1824 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1826 #ifdef OPENSSL_HAVE_NUM_TICKETS
1827 SSL_CTX_set_num_tickets(ctx, 0); /* send no TLS1.3 stateful-tickets */
1830 /* We'd like to disable session cache unconditionally, but foolish Outlook
1831 Express clients then give up the first TLS connection and make a second one
1832 (which works). Only when there is an IMAP service on the same machine.
1833 Presumably OE is trying to use the cache for A on B. Leave it enabled for
1834 now, until we work out a decent way of presenting control to the config. It
1835 will never be used because we use a new context every time. */
1837 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1840 /* Initialize with DH parameters if supplied */
1841 /* Initialize ECDH temp key parameter selection */
1843 if ( !init_dh(ctx, dhparam, host, errstr)
1844 || !init_ecdh(ctx, host, errstr)
1848 /* Set up certificate and key (and perhaps OCSP info) */
1850 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1853 /* If we need to handle SNI or OCSP, do so */
1855 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1856 # ifndef DISABLE_OCSP
1857 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1859 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1864 if (!host) /* server */
1866 # ifndef DISABLE_OCSP
1867 /* We check u_ocsp.server.file, not server.response, because we care about if
1868 the option exists, not what the current expansion might be, as SNI might
1869 change the certificate and OCSP file in use between now and the time the
1870 callback is invoked. */
1871 if (cbinfo->u_ocsp.server.file)
1873 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1874 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1877 /* We always do this, so that $tls_sni is available even if not used in
1879 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1880 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1882 # ifndef DISABLE_OCSP
1884 if(ocsp_file) /* wanting stapling */
1886 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1888 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1891 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1892 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1897 cbinfo->verify_cert_hostnames = NULL;
1899 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1900 /* Set up the RSA callback */
1901 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1904 /* Finally, set the timeout, and we are done */
1906 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1907 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1918 /*************************************************
1919 * Get name of cipher in use *
1920 *************************************************/
1923 Argument: pointer to an SSL structure for the connection
1924 pointer to number of bits for cipher
1925 Returns: pointer to allocated string in perm-pool
1929 construct_cipher_name(SSL * ssl, int * bits)
1931 int pool = store_pool;
1932 /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't
1933 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1934 the accessor functions use const in the prototype. */
1936 const uschar * ver = CUS SSL_get_version(ssl);
1937 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1940 SSL_CIPHER_get_bits(c, bits);
1942 store_pool = POOL_PERM;
1943 s = string_sprintf("%s:%s:%u", ver, SSL_CIPHER_get_name(c), *bits);
1945 DEBUG(D_tls) debug_printf("Cipher: %s\n", s);
1950 /* Get IETF-standard name for ciphersuite.
1951 Argument: pointer to an SSL structure for the connection
1952 Returns: pointer to string
1955 static const uschar *
1956 cipher_stdname_ssl(SSL * ssl)
1958 #ifdef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
1959 return CUS SSL_CIPHER_standard_name(SSL_get_current_cipher(ssl));
1961 ushort id = 0xffff & SSL_CIPHER_get_id(SSL_get_current_cipher(ssl));
1962 return cipher_stdname(id >> 8, id & 0xff);
1968 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
1970 /*XXX we might consider a list-of-certs variable for the cert chain.
1971 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1972 in list-handling functions, also consider the difference between the entire
1973 chain and the elements sent by the peer. */
1975 tlsp->peerdn = NULL;
1977 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1978 if (!tlsp->peercert)
1979 tlsp->peercert = SSL_get_peer_certificate(ssl);
1980 /* Beware anonymous ciphers which lead to server_cert being NULL */
1982 if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz))
1983 { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); }
1986 peerdn[siz-1] = '\0';
1987 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1995 /*************************************************
1996 * Set up for verifying certificates *
1997 *************************************************/
1999 #ifndef DISABLE_OCSP
2000 /* Load certs from file, return TRUE on success */
2003 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
2008 while (sk_X509_num(verify_stack) > 0)
2009 X509_free(sk_X509_pop(verify_stack));
2011 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
2012 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
2013 sk_X509_push(verify_stack, x);
2021 /* Called by both client and server startup; on the server possibly
2022 repeated after a Server Name Indication.
2025 sctx SSL_CTX* to initialise
2026 certs certs file or NULL
2027 crl CRL file or NULL
2028 host NULL in a server; the remote host in a client
2029 optional TRUE if called from a server for a host in tls_try_verify_hosts;
2030 otherwise passed as FALSE
2031 cert_vfy_cb Callback function for certificate verification
2032 errstr error string pointer
2034 Returns: OK/DEFER/FAIL
2038 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
2039 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
2041 uschar *expcerts, *expcrl;
2043 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2045 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2047 if (expcerts && *expcerts)
2049 /* Tell the library to use its compiled-in location for the system default
2050 CA bundle. Then add the ones specified in the config, if any. */
2052 if (!SSL_CTX_set_default_verify_paths(sctx))
2053 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2055 if (Ustrcmp(expcerts, "system") != 0)
2057 struct stat statbuf;
2059 if (Ustat(expcerts, &statbuf) < 0)
2061 log_write(0, LOG_MAIN|LOG_PANIC,
2062 "failed to stat %s for certificates", expcerts);
2068 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2069 { file = NULL; dir = expcerts; }
2072 file = expcerts; dir = NULL;
2073 #ifndef DISABLE_OCSP
2074 /* In the server if we will be offering an OCSP proof, load chain from
2075 file for verifying the OCSP proof at load time. */
2078 && statbuf.st_size > 0
2079 && server_static_cbinfo->u_ocsp.server.file
2080 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2083 log_write(0, LOG_MAIN|LOG_PANIC,
2084 "failed to load cert chain from %s", file);
2090 /* If a certificate file is empty, the next function fails with an
2091 unhelpful error message. If we skip it, we get the correct behaviour (no
2092 certificates are recognized, but the error message is still misleading (it
2093 says no certificate was supplied). But this is better. */
2095 if ( (!file || statbuf.st_size > 0)
2096 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
2097 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
2099 /* Load the list of CAs for which we will accept certs, for sending
2100 to the client. This is only for the one-file tls_verify_certificates
2102 If a list isn't loaded into the server, but some verify locations are set,
2103 the server end appears to make a wildcard request for client certs.
2104 Meanwhile, the client library as default behaviour *ignores* the list
2105 we send over the wire - see man SSL_CTX_set_client_cert_cb.
2106 Because of this, and that the dir variant is likely only used for
2107 the public-CA bundle (not for a private CA), not worth fixing. */
2111 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
2113 SSL_CTX_set_client_CA_list(sctx, names);
2114 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
2115 sk_X509_NAME_num(names));
2120 /* Handle a certificate revocation list. */
2122 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2124 /* This bit of code is now the version supplied by Lars Mainka. (I have
2125 merely reformatted it into the Exim code style.)
2127 "From here I changed the code to add support for multiple crl's
2128 in pem format in one file or to support hashed directory entries in
2129 pem format instead of a file. This method now uses the library function
2130 X509_STORE_load_locations to add the CRL location to the SSL context.
2131 OpenSSL will then handle the verify against CA certs and CRLs by
2132 itself in the verify callback." */
2134 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2135 if (expcrl && *expcrl)
2137 struct stat statbufcrl;
2138 if (Ustat(expcrl, &statbufcrl) < 0)
2140 log_write(0, LOG_MAIN|LOG_PANIC,
2141 "failed to stat %s for certificates revocation lists", expcrl);
2146 /* is it a file or directory? */
2148 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2149 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2153 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2159 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2161 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2162 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2164 /* setting the flags to check against the complete crl chain */
2166 X509_STORE_set_flags(cvstore,
2167 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2171 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2173 /* If verification is optional, don't fail if no certificate */
2175 SSL_CTX_set_verify(sctx,
2176 SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2185 /*************************************************
2186 * Start a TLS session in a server *
2187 *************************************************/
2189 /* This is called when Exim is running as a server, after having received
2190 the STARTTLS command. It must respond to that command, and then negotiate
2194 require_ciphers allowed ciphers
2195 errstr pointer to error message
2197 Returns: OK on success
2198 DEFER for errors before the start of the negotiation
2199 FAIL for errors during the negotiation; the server can't
2204 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2207 uschar * expciphers;
2208 tls_ext_ctx_cb * cbinfo;
2209 static uschar peerdn[256];
2211 /* Check for previous activation */
2213 if (tls_in.active.sock >= 0)
2215 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2216 smtp_printf("554 Already in TLS\r\n", FALSE);
2220 /* Initialize the SSL library. If it fails, it will already have logged
2223 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2224 #ifndef DISABLE_OCSP
2225 tls_ocsp_file, /*XXX stack*/
2227 NULL, &server_static_cbinfo, errstr);
2228 if (rc != OK) return rc;
2229 cbinfo = server_static_cbinfo;
2231 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
2234 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2235 were historically separated by underscores. So that I can use either form in my
2236 tests, and also for general convenience, we turn underscores into hyphens here.
2238 XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites()
2239 for TLS 1.3 . Since we do not call it at present we get the default list:
2240 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
2245 uschar * s = expciphers;
2246 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2247 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2248 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
2249 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
2250 cbinfo->server_cipher_list = expciphers;
2253 /* If this is a host for which certificate verification is mandatory or
2254 optional, set up appropriately. */
2256 tls_in.certificate_verified = FALSE;
2258 tls_in.dane_verified = FALSE;
2260 server_verify_callback_called = FALSE;
2262 if (verify_check_host(&tls_verify_hosts) == OK)
2264 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2265 FALSE, verify_callback_server, errstr);
2266 if (rc != OK) return rc;
2267 server_verify_optional = FALSE;
2269 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2271 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2272 TRUE, verify_callback_server, errstr);
2273 if (rc != OK) return rc;
2274 server_verify_optional = TRUE;
2277 /* Prepare for new connection */
2279 if (!(server_ssl = SSL_new(server_ctx)))
2280 return tls_error(US"SSL_new", NULL, NULL, errstr);
2282 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2284 * With the SSL_clear(), we get strange interoperability bugs with
2285 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2286 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2288 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2289 * session shutdown. In this case, we have a brand new object and there's no
2290 * obvious reason to immediately clear it. I'm guessing that this was
2291 * originally added because of incomplete initialisation which the clear fixed,
2292 * in some historic release.
2295 /* Set context and tell client to go ahead, except in the case of TLS startup
2296 on connection, where outputting anything now upsets the clients and tends to
2297 make them disconnect. We need to have an explicit fflush() here, to force out
2298 the response. Other smtp_printf() calls do not need it, because in non-TLS
2299 mode, the fflush() happens when smtp_getc() is called. */
2301 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2302 if (!tls_in.on_connect)
2304 smtp_printf("220 TLS go ahead\r\n", FALSE);
2308 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2309 that the OpenSSL library doesn't. */
2311 SSL_set_wfd(server_ssl, fileno(smtp_out));
2312 SSL_set_rfd(server_ssl, fileno(smtp_in));
2313 SSL_set_accept_state(server_ssl);
2315 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2317 sigalrm_seen = FALSE;
2318 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2319 rc = SSL_accept(server_ssl);
2324 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2328 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2329 ERR_clear_error(); /* Even success can leave errors in the stack. Seen with
2330 anon-authentication ciphersuite negociated. */
2332 /* TLS has been set up. Adjust the input functions to read via TLS,
2333 and initialize things. */
2335 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2337 tls_in.cipher = construct_cipher_name(server_ssl, &tls_in.bits);
2338 tls_in.cipher_stdname = cipher_stdname_ssl(server_ssl);
2343 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)))
2344 debug_printf("Shared ciphers: %s\n", buf);
2346 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2348 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
2349 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2355 /* Record the certificate we presented */
2357 X509 * crt = SSL_get_certificate(server_ssl);
2358 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2361 /* Only used by the server-side tls (tls_in), including tls_getc.
2362 Client-side (tls_out) reads (seem to?) go via
2363 smtp_read_response()/ip_recv().
2364 Hence no need to duplicate for _in and _out.
2366 if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2367 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2368 ssl_xfer_eof = ssl_xfer_error = FALSE;
2370 receive_getc = tls_getc;
2371 receive_getbuf = tls_getbuf;
2372 receive_get_cache = tls_get_cache;
2373 receive_ungetc = tls_ungetc;
2374 receive_feof = tls_feof;
2375 receive_ferror = tls_ferror;
2376 receive_smtp_buffered = tls_smtp_buffered;
2378 tls_in.active.sock = fileno(smtp_out);
2379 tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */
2387 tls_client_basic_ctx_init(SSL_CTX * ctx,
2388 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2392 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2393 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2394 the specified host patterns if one of them is defined */
2396 if ( ( !ob->tls_verify_hosts
2397 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2399 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2401 client_verify_optional = FALSE;
2402 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2403 client_verify_optional = TRUE;
2407 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2408 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2412 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2414 cbinfo->verify_cert_hostnames =
2416 string_domain_utf8_to_alabel(host->name, NULL);
2420 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2421 cbinfo->verify_cert_hostnames);
2429 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2432 const char * hostnames[2] = { CS host->name, NULL };
2435 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2436 return tls_error(US"hostnames load", host, NULL, errstr);
2438 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2439 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2440 ) if (rr->type == T_TLSA && rr->size > 3)
2442 const uschar * p = rr->data;
2443 uint8_t usage, selector, mtype;
2444 const char * mdname;
2448 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2449 if (usage != 2 && usage != 3) continue;
2456 default: continue; /* Only match-types 0, 1, 2 are supported */
2457 case 0: mdname = NULL; break;
2458 case 1: mdname = "sha256"; break;
2459 case 2: mdname = "sha512"; break;
2463 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2466 return tls_error(US"tlsa load", host, NULL, errstr);
2467 case 0: /* action not taken */
2471 tls_out.tlsa_usage |= 1<<usage;
2477 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2480 #endif /*SUPPORT_DANE*/
2484 /*************************************************
2485 * Start a TLS session in a client *
2486 *************************************************/
2488 /* Called from the smtp transport after STARTTLS has been accepted.
2491 cctx connection context
2492 conn_args connection details
2493 cookie datum for randomness; can be NULL
2494 tlsp record details of TLS channel configuration here; must be non-NULL
2495 errstr error string pointer
2497 Returns: TRUE for success with TLS session context set in connection context,
2502 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
2503 void * cookie, tls_support * tlsp, uschar ** errstr)
2505 host_item * host = conn_args->host; /* for msgs and option-tests */
2506 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
2507 smtp_transport_options_block * ob = tb
2508 ? (smtp_transport_options_block *)tb->options_block
2509 : &smtp_transport_option_defaults;
2510 exim_openssl_client_tls_ctx * exim_client_ctx;
2511 uschar * expciphers;
2513 static uschar peerdn[256];
2515 #ifndef DISABLE_OCSP
2516 BOOL request_ocsp = FALSE;
2517 BOOL require_ocsp = FALSE;
2521 store_pool = POOL_PERM;
2522 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx));
2523 exim_client_ctx->corked = NULL;
2527 tlsp->tlsa_usage = 0;
2530 #ifndef DISABLE_OCSP
2532 # ifdef SUPPORT_DANE
2533 if ( conn_args->dane
2534 && ob->hosts_request_ocsp[0] == '*'
2535 && ob->hosts_request_ocsp[1] == '\0'
2538 /* Unchanged from default. Use a safer one under DANE */
2539 request_ocsp = TRUE;
2540 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2541 " {= {4}{$tls_out_tlsa_usage}} } "
2547 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
2548 request_ocsp = TRUE;
2550 # ifdef SUPPORT_DANE
2554 verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2558 rc = tls_init(&exim_client_ctx->ctx, host, NULL,
2559 ob->tls_certificate, ob->tls_privatekey,
2560 #ifndef DISABLE_OCSP
2561 (void *)(long)request_ocsp,
2563 cookie, &client_static_cbinfo, errstr);
2564 if (rc != OK) return FALSE;
2566 tlsp->certificate_verified = FALSE;
2567 client_verify_callback_called = FALSE;
2571 if (conn_args->dane)
2573 /* We fall back to tls_require_ciphers if unset, empty or forced failure, but
2574 other failures should be treated as problems. */
2575 if (ob->dane_require_tls_ciphers &&
2576 !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2577 &expciphers, errstr))
2579 if (expciphers && *expciphers == '\0')
2584 !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2585 &expciphers, errstr))
2588 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2589 are separated by underscores. So that I can use either form in my tests, and
2590 also for general convenience, we turn underscores into hyphens here. */
2594 uschar *s = expciphers;
2595 while (*s) { if (*s == '_') *s = '-'; s++; }
2596 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2597 if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers))
2599 tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2605 if (conn_args->dane)
2607 SSL_CTX_set_verify(exim_client_ctx->ctx,
2608 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2609 verify_callback_client_dane);
2611 if (!DANESSL_library_init())
2613 tls_error(US"library init", host, NULL, errstr);
2616 if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
2618 tls_error(US"context init", host, NULL, errstr);
2626 if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
2627 client_static_cbinfo, errstr) != OK)
2630 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
2632 tls_error(US"SSL_new", host, NULL, errstr);
2635 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
2636 SSL_set_fd(exim_client_ctx->ssl, cctx->sock);
2637 SSL_set_connect_state(exim_client_ctx->ssl);
2641 if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
2645 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2647 else if (!Ustrlen(tlsp->sni))
2651 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2652 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni);
2653 SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni);
2655 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2662 if (conn_args->dane)
2663 if (dane_tlsa_load(exim_client_ctx->ssl, host, &conn_args->tlsa_dnsa, errstr) != OK)
2667 #ifndef DISABLE_OCSP
2668 /* Request certificate status at connection-time. If the server
2669 does OCSP stapling we will get the callback (set in tls_init()) */
2670 # ifdef SUPPORT_DANE
2674 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2675 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2677 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2678 this means we avoid the OCSP request, we wasted the setup
2679 cost in tls_init(). */
2680 require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2681 request_ocsp = require_ocsp
2682 || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2689 SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp);
2690 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2691 tlsp->ocsp = OCSP_NOT_RESP;
2695 #ifndef DISABLE_EVENT
2696 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
2699 /* There doesn't seem to be a built-in timeout on connection. */
2701 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2702 sigalrm_seen = FALSE;
2703 ALARM(ob->command_timeout);
2704 rc = SSL_connect(exim_client_ctx->ssl);
2708 if (conn_args->dane)
2709 DANESSL_cleanup(exim_client_ctx->ssl);
2714 tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
2720 debug_printf("SSL_connect succeeded\n");
2721 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2723 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
2724 SSL_SESSION_print_keylog(bp, SSL_get_session(exim_client_ctx->ssl));
2730 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
2732 tlsp->cipher = construct_cipher_name(exim_client_ctx->ssl, &tlsp->bits);
2733 tlsp->cipher_stdname = cipher_stdname_ssl(exim_client_ctx->ssl);
2735 /* Record the certificate we presented */
2737 X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
2738 tlsp->ourcert = crt ? X509_dup(crt) : NULL;
2741 tlsp->active.sock = cctx->sock;
2742 tlsp->active.tls_ctx = exim_client_ctx;
2743 cctx->tls_ctx = exim_client_ctx;
2752 tls_refill(unsigned lim)
2757 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2758 ssl_xfer_buffer, ssl_xfer_buffer_size);
2760 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2761 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2762 MIN(ssl_xfer_buffer_size, lim));
2763 error = SSL_get_error(server_ssl, inbytes);
2764 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2766 if (had_command_timeout) /* set by signal handler */
2767 smtp_command_timeout_exit(); /* does not return */
2768 if (had_command_sigterm)
2769 smtp_command_sigterm_exit();
2770 if (had_data_timeout)
2771 smtp_data_timeout_exit();
2772 if (had_data_sigint)
2773 smtp_data_sigint_exit();
2775 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2776 closed down, not that the socket itself has been closed down. Revert to
2777 non-SSL handling. */
2781 case SSL_ERROR_NONE:
2784 case SSL_ERROR_ZERO_RETURN:
2785 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2787 receive_getc = smtp_getc;
2788 receive_getbuf = smtp_getbuf;
2789 receive_get_cache = smtp_get_cache;
2790 receive_ungetc = smtp_ungetc;
2791 receive_feof = smtp_feof;
2792 receive_ferror = smtp_ferror;
2793 receive_smtp_buffered = smtp_buffered;
2795 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
2796 SSL_shutdown(server_ssl);
2798 #ifndef DISABLE_OCSP
2799 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
2800 server_static_cbinfo->verify_stack = NULL;
2802 SSL_free(server_ssl);
2803 SSL_CTX_free(server_ctx);
2806 tls_in.active.sock = -1;
2807 tls_in.active.tls_ctx = NULL;
2809 tls_in.cipher = NULL;
2810 tls_in.peerdn = NULL;
2815 /* Handle genuine errors */
2817 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
2818 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2819 ssl_xfer_error = TRUE;
2823 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2824 DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL)
2825 debug_printf(" - syscall %s\n", strerror(errno));
2826 ssl_xfer_error = TRUE;
2830 #ifndef DISABLE_DKIM
2831 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2833 ssl_xfer_buffer_hwm = inbytes;
2834 ssl_xfer_buffer_lwm = 0;
2839 /*************************************************
2840 * TLS version of getc *
2841 *************************************************/
2843 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2844 it refills the buffer via the SSL reading function.
2846 Arguments: lim Maximum amount to read/buffer
2847 Returns: the next character or EOF
2849 Only used by the server-side TLS.
2853 tls_getc(unsigned lim)
2855 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2856 if (!tls_refill(lim))
2857 return ssl_xfer_error ? EOF : smtp_getc(lim);
2859 /* Something in the buffer; return next uschar */
2861 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2865 tls_getbuf(unsigned * len)
2870 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2871 if (!tls_refill(*len))
2873 if (!ssl_xfer_error) return smtp_getbuf(len);
2878 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2880 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2881 ssl_xfer_buffer_lwm += size;
2890 #ifndef DISABLE_DKIM
2891 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2893 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2899 tls_could_read(void)
2901 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2905 /*************************************************
2906 * Read bytes from TLS channel *
2907 *************************************************/
2911 ct_ctx client context pointer, or NULL for the one global server context
2915 Returns: the number of bytes read
2916 -1 after a failed read, including EOF
2918 Only used by the client-side TLS.
2922 tls_read(void * ct_ctx, uschar *buff, size_t len)
2924 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2928 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2929 buff, (unsigned int)len);
2931 inbytes = SSL_read(ssl, CS buff, len);
2932 error = SSL_get_error(ssl, inbytes);
2934 if (error == SSL_ERROR_ZERO_RETURN)
2936 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2939 else if (error != SSL_ERROR_NONE)
2949 /*************************************************
2950 * Write bytes down TLS channel *
2951 *************************************************/
2955 ct_ctx client context pointer, or NULL for the one global server context
2958 more further data expected soon
2960 Returns: the number of bytes after a successful write,
2961 -1 after a failed write
2963 Used by both server-side and client-side TLS.
2967 tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more)
2970 int outbytes, error;
2972 ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2973 static gstring * server_corked = NULL;
2974 gstring ** corkedp = ct_ctx
2975 ? &((exim_openssl_client_tls_ctx *)ct_ctx)->corked : &server_corked;
2976 gstring * corked = *corkedp;
2978 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
2979 buff, (unsigned long)len, more ? ", more" : "");
2981 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2982 "more" is notified. This hack is only ok if small amounts are involved AND only
2983 one stream does it, in one context (i.e. no store reset). Currently it is used
2984 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only.
2985 We support callouts done by the server process by using a separate client
2986 context for the stashed information. */
2987 /* + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's
2988 a store reset there, so use POOL_PERM. */
2989 /* + if CHUNKING, cmds EHLO,MAIL,RCPT(s),BDAT */
2991 if ((more || corked))
2993 #ifdef EXPERIMENTAL_PIPE_CONNECT
2994 int save_pool = store_pool;
2995 store_pool = POOL_PERM;
2998 corked = string_catn(corked, buff, len);
3000 #ifdef EXPERIMENTAL_PIPE_CONNECT
3001 store_pool = save_pool;
3009 buff = CUS corked->s;
3014 for (int left = len; left > 0;)
3016 DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left);
3017 outbytes = SSL_write(ssl, CS buff, left);
3018 error = SSL_get_error(ssl, outbytes);
3019 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
3023 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3024 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
3027 case SSL_ERROR_NONE:
3032 case SSL_ERROR_ZERO_RETURN:
3033 log_write(0, LOG_MAIN, "SSL channel closed on write");
3036 case SSL_ERROR_SYSCALL:
3037 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
3038 sender_fullhost ? sender_fullhost : US"<unknown>",
3043 log_write(0, LOG_MAIN, "SSL_write error %d", error);
3052 /*************************************************
3053 * Close down a TLS session *
3054 *************************************************/
3056 /* This is also called from within a delivery subprocess forked from the
3057 daemon, to shut down the TLS library, without actually doing a shutdown (which
3058 would tamper with the SSL session in the parent process).
3061 ct_ctx client TLS context pointer, or NULL for the one global server context
3062 shutdown 1 if TLS close-alert is to be sent,
3063 2 if also response to be waited for
3067 Used by both server-side and client-side TLS.
3071 tls_close(void * ct_ctx, int shutdown)
3073 exim_openssl_client_tls_ctx * o_ctx = ct_ctx;
3074 SSL_CTX **ctxp = o_ctx ? &o_ctx->ctx : &server_ctx;
3075 SSL **sslp = o_ctx ? &o_ctx->ssl : &server_ssl;
3076 int *fdp = o_ctx ? &tls_out.active.sock : &tls_in.active.sock;
3078 if (*fdp < 0) return; /* TLS was not active */
3083 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
3084 shutdown > 1 ? " (with response-wait)" : "");
3086 if ( (rc = SSL_shutdown(*sslp)) == 0 /* send "close notify" alert */
3090 rc = SSL_shutdown(*sslp); /* wait for response */
3094 if (rc < 0) DEBUG(D_tls)
3096 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3097 debug_printf("SSL_shutdown: %s\n", ssl_errstring);
3101 #ifndef DISABLE_OCSP
3102 if (!o_ctx) /* server side */
3104 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
3105 server_static_cbinfo->verify_stack = NULL;
3109 SSL_CTX_free(*ctxp);
3119 /*************************************************
3120 * Let tls_require_ciphers be checked at startup *
3121 *************************************************/
3123 /* The tls_require_ciphers option, if set, must be something which the
3126 Returns: NULL on success, or error message
3130 tls_validate_require_cipher(void)
3133 uschar *s, *expciphers, *err;
3135 /* this duplicates from tls_init(), we need a better "init just global
3136 state, for no specific purpose" singleton function of our own */
3138 #ifdef EXIM_NEED_OPENSSL_INIT
3139 SSL_load_error_strings();
3140 OpenSSL_add_ssl_algorithms();
3142 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
3143 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
3144 list of available digests. */
3145 EVP_add_digest(EVP_sha256());
3148 if (!(tls_require_ciphers && *tls_require_ciphers))
3151 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3153 return US"failed to expand tls_require_ciphers";
3155 if (!(expciphers && *expciphers))
3158 /* normalisation ripped from above */
3160 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
3164 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
3165 if (!(ctx = SSL_CTX_new(TLS_server_method())))
3167 if (!(ctx = SSL_CTX_new(SSLv23_server_method())))
3170 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3171 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
3175 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3177 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
3179 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3180 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
3181 expciphers, ssl_errstring);
3192 /*************************************************
3193 * Report the library versions. *
3194 *************************************************/
3196 /* There have historically been some issues with binary compatibility in
3197 OpenSSL libraries; if Exim (like many other applications) is built against
3198 one version of OpenSSL but the run-time linker picks up another version,
3199 it can result in serious failures, including crashing with a SIGSEGV. So
3200 report the version found by the compiler and the run-time version.
3202 Note: some OS vendors backport security fixes without changing the version
3203 number/string, and the version date remains unchanged. The _build_ date
3204 will change, so we can more usefully assist with version diagnosis by also
3205 reporting the build date.
3207 Arguments: a FILE* to print the results to
3212 tls_version_report(FILE *f)
3214 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
3217 OPENSSL_VERSION_TEXT,
3218 SSLeay_version(SSLEAY_VERSION),
3219 SSLeay_version(SSLEAY_BUILT_ON));
3220 /* third line is 38 characters for the %s and the line is 73 chars long;
3221 the OpenSSL output includes a "built on: " prefix already. */
3227 /*************************************************
3228 * Random number generation *
3229 *************************************************/
3231 /* Pseudo-random number generation. The result is not expected to be
3232 cryptographically strong but not so weak that someone will shoot themselves
3233 in the foot using it as a nonce in input in some email header scheme or
3234 whatever weirdness they'll twist this into. The result should handle fork()
3235 and avoid repeating sequences. OpenSSL handles that for us.
3239 Returns a random number in range [0, max-1]
3243 vaguely_random_number(int max)
3247 static pid_t pidlast = 0;
3249 uschar smallbuf[sizeof(r)];
3255 if (pidnow != pidlast)
3257 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
3258 is unique for each thread", this doesn't apparently apply across processes,
3259 so our own warning from vaguely_random_number_fallback() applies here too.
3260 Fix per PostgreSQL. */
3266 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
3270 gettimeofday(&r.tv, NULL);
3273 RAND_seed(US (&r), sizeof(r));
3275 /* We're after pseudo-random, not random; if we still don't have enough data
3276 in the internal PRNG then our options are limited. We could sleep and hope
3277 for entropy to come along (prayer technique) but if the system is so depleted
3278 in the first place then something is likely to just keep taking it. Instead,
3279 we'll just take whatever little bit of pseudo-random we can still manage to
3282 needed_len = sizeof(r);
3283 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
3284 asked for a number less than 10. */
3285 for (r = max, i = 0; r; ++i)
3291 #ifdef EXIM_HAVE_RAND_PSEUDO
3292 /* We do not care if crypto-strong */
3293 i = RAND_pseudo_bytes(smallbuf, needed_len);
3295 i = RAND_bytes(smallbuf, needed_len);
3301 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
3302 return vaguely_random_number_fallback(max);
3306 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
3309 /* We don't particularly care about weighted results; if someone wants
3310 smooth distribution and cares enough then they should submit a patch then. */
3317 /*************************************************
3318 * OpenSSL option parse *
3319 *************************************************/
3321 /* Parse one option for tls_openssl_options_parse below
3324 name one option name
3325 value place to store a value for it
3326 Returns success or failure in parsing
3332 tls_openssl_one_option_parse(uschar *name, long *value)
3335 int last = exim_openssl_options_size;
3336 while (last > first)
3338 int middle = (first + last)/2;
3339 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3342 *value = exim_openssl_options[middle].value;
3356 /*************************************************
3357 * OpenSSL option parsing logic *
3358 *************************************************/
3360 /* OpenSSL has a number of compatibility options which an administrator might
3361 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3362 we look like log_selector.
3365 option_spec the administrator-supplied string of options
3366 results ptr to long storage for the options bitmap
3367 Returns success or failure
3371 tls_openssl_options_parse(uschar *option_spec, long *results)
3376 BOOL adding, item_parsed;
3378 result = SSL_OP_NO_TICKET;
3379 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3380 * from default because it increases BEAST susceptibility. */
3381 #ifdef SSL_OP_NO_SSLv2
3382 result |= SSL_OP_NO_SSLv2;
3384 #ifdef SSL_OP_SINGLE_DH_USE
3385 result |= SSL_OP_SINGLE_DH_USE;
3394 for (uschar * s = option_spec; *s != '\0'; /**/)
3396 while (isspace(*s)) ++s;
3399 if (*s != '+' && *s != '-')
3401 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3402 "+ or - expected but found \"%s\"\n", s);
3405 adding = *s++ == '+';
3406 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3409 item_parsed = tls_openssl_one_option_parse(s, &item);
3413 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3416 DEBUG(D_tls) debug_printf("openssl option, %s %8lx: %lx (%s)\n",
3417 adding ? "adding to " : "removing from", result, item, s);
3429 #endif /*!MACRO_PREDEF*/
3432 /* End of tls-openssl.c */