1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2017 */
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>
31 #ifdef EXPERIMENTAL_DANE
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
58 * X509_check_host provides sane certificate hostname checking, but was added
59 * to OpenSSL late, after other projects forked off the code-base. So in
60 * addition to guarding against the base version number, beware that LibreSSL
61 * does not (at this time) support this function.
63 * If LibreSSL gains a different API, perhaps via libtls, then we'll probably
64 * opt to disentangle and ask a LibreSSL user to provide glue for a third
65 * crypto provider for libtls instead of continuing to tie the OpenSSL glue
66 * into even twistier knots. If LibreSSL gains the same API, we can just
67 * change this guard and punt the issue for a while longer.
69 #ifndef LIBRESSL_VERSION_NUMBER
70 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
71 # define EXIM_HAVE_OPENSSL_CHECKHOST
72 # define EXIM_HAVE_OPENSSL_DH_BITS
74 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
75 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
76 # define EXIM_HAVE_OPENSSL_CHECKHOST
80 #if !defined(LIBRESSL_VERSION_NUMBER) \
81 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
82 # if !defined(OPENSSL_NO_ECDH)
83 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
84 # define EXIM_HAVE_ECDH
86 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
87 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
92 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
93 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
97 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
98 # include <openssl/x509v3.h>
101 /* Structure for collecting random data for seeding. */
103 typedef struct randstuff {
108 /* Local static variables */
110 static BOOL client_verify_callback_called = FALSE;
111 static BOOL server_verify_callback_called = FALSE;
112 static const uschar *sid_ctx = US"exim";
114 /* We have three different contexts to care about.
116 Simple case: client, `client_ctx`
117 As a client, we can be doing a callout or cut-through delivery while receiving
118 a message. So we have a client context, which should have options initialised
119 from the SMTP Transport.
122 There are two cases: with and without ServerNameIndication from the client.
123 Given TLS SNI, we can be using different keys, certs and various other
124 configuration settings, because they're re-expanded with $tls_sni set. This
125 allows vhosting with TLS. This SNI is sent in the handshake.
126 A client might not send SNI, so we need a fallback, and an initial setup too.
127 So as a server, we start out using `server_ctx`.
128 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
129 `server_sni` from `server_ctx` and then initialise settings by re-expanding
133 static SSL_CTX *client_ctx = NULL;
134 static SSL_CTX *server_ctx = NULL;
135 static SSL *client_ssl = NULL;
136 static SSL *server_ssl = NULL;
138 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
139 static SSL_CTX *server_sni = NULL;
142 static char ssl_errstring[256];
144 static int ssl_session_timeout = 200;
145 static BOOL client_verify_optional = FALSE;
146 static BOOL server_verify_optional = FALSE;
148 static BOOL reexpand_tls_files_for_sni = FALSE;
151 typedef struct tls_ext_ctx_cb {
156 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
160 uschar *file_expanded;
161 OCSP_RESPONSE *response;
164 X509_STORE *verify_store; /* non-null if status requested */
165 BOOL verify_required;
170 /* these are cached from first expand */
171 uschar *server_cipher_list;
172 /* only passed down to tls_error: */
174 const uschar * verify_cert_hostnames;
175 #ifndef DISABLE_EVENT
176 uschar * event_action;
180 /* should figure out a cleanup of API to handle state preserved per
181 implementation, for various reasons, which can be void * in the APIs.
182 For now, we hack around it. */
183 tls_ext_ctx_cb *client_static_cbinfo = NULL;
184 tls_ext_ctx_cb *server_static_cbinfo = NULL;
187 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
188 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
191 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
192 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
195 static int tls_server_stapling_cb(SSL *s, void *arg);
199 /*************************************************
201 *************************************************/
203 /* Called from lots of places when errors occur before actually starting to do
204 the TLS handshake, that is, while the session is still in clear. Always returns
205 DEFER for a server and FAIL for a client so that most calls can use "return
206 tls_error(...)" to do this processing and then give an appropriate return. A
207 single function is used for both server and client, because it is called from
208 some shared functions.
211 prefix text to include in the logged error
212 host NULL if setting up a server;
213 the connected host if setting up a client
214 msg error message or NULL if we should ask OpenSSL
215 errstr pointer to output error message
217 Returns: OK/DEFER/FAIL
221 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
225 ERR_error_string(ERR_get_error(), ssl_errstring);
226 msg = US ssl_errstring;
229 if (errstr) *errstr = string_sprintf("(%s): %s", prefix, msg);
230 return host ? FAIL : DEFER;
235 /*************************************************
236 * Callback to generate RSA key *
237 *************************************************/
241 s SSL connection (not used)
245 Returns: pointer to generated key
249 rsa_callback(SSL *s, int export, int keylength)
252 #ifdef EXIM_HAVE_RSA_GENKEY_EX
253 BIGNUM *bn = BN_new();
256 export = export; /* Shut picky compilers up */
257 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
259 #ifdef EXIM_HAVE_RSA_GENKEY_EX
260 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
261 || !(rsa_key = RSA_new())
262 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
265 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
269 ERR_error_string(ERR_get_error(), ssl_errstring);
270 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
282 x509_store_dump_cert_s_names(X509_STORE * store)
284 STACK_OF(X509_OBJECT) * roots= store->objs;
286 static uschar name[256];
288 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
290 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
291 if(tmp_obj->type == X509_LU_X509)
293 X509 * current_cert= tmp_obj->data.x509;
294 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
295 name[sizeof(name)-1] = '\0';
296 debug_printf(" %s\n", name);
304 #ifndef DISABLE_EVENT
306 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
307 BOOL *calledp, const BOOL *optionalp, const uschar * what)
313 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
316 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
317 old_cert = tlsp->peercert;
318 tlsp->peercert = X509_dup(cert);
319 /* NB we do not bother setting peerdn */
320 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
322 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
323 "depth=%d cert=%s: %s",
324 tlsp == &tls_out ? deliver_host_address : sender_host_address,
325 what, depth, dn, yield);
329 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
330 return 1; /* reject (leaving peercert set) */
332 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
333 "(host in tls_try_verify_hosts)\n");
335 X509_free(tlsp->peercert);
336 tlsp->peercert = old_cert;
342 /*************************************************
343 * Callback for verification *
344 *************************************************/
346 /* The SSL library does certificate verification if set up to do so. This
347 callback has the current yes/no state is in "state". If verification succeeded,
348 we set the certificate-verified flag. If verification failed, what happens
349 depends on whether the client is required to present a verifiable certificate
352 If verification is optional, we change the state to yes, but still log the
353 verification error. For some reason (it really would help to have proper
354 documentation of OpenSSL), this callback function then gets called again, this
355 time with state = 1. We must take care not to set the private verified flag on
356 the second time through.
358 Note: this function is not called if the client fails to present a certificate
359 when asked. We get here only if a certificate has been received. Handling of
360 optional verification for this case is done when requesting SSL to verify, by
361 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
363 May be called multiple times for different issues with a certificate, even
364 for a given "depth" in the certificate chain.
367 preverify_ok current yes/no state as 1/0
368 x509ctx certificate information.
369 tlsp per-direction (client vs. server) support data
370 calledp has-been-called flag
371 optionalp verification-is-optional flag
373 Returns: 0 if verification should fail, otherwise 1
377 verify_callback(int preverify_ok, X509_STORE_CTX *x509ctx,
378 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
380 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
381 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
384 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
385 dn[sizeof(dn)-1] = '\0';
387 if (preverify_ok == 0)
389 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
390 *verify_mode, sender_host_address)
392 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
393 tlsp == &tls_out ? deliver_host_address : sender_host_address,
395 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
400 tlsp->peercert = X509_dup(cert); /* record failing cert */
401 return 0; /* reject */
403 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
404 "tls_try_verify_hosts)\n");
409 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
411 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
412 { /* client, wanting stapling */
413 /* Add the server cert's signing chain as the one
414 for the verification of the OCSP stapled information. */
416 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
419 sk_X509_push(client_static_cbinfo->verify_stack, cert);
422 #ifndef DISABLE_EVENT
423 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
424 return 0; /* reject, with peercert set */
429 const uschar * verify_cert_hostnames;
431 if ( tlsp == &tls_out
432 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
433 /* client, wanting hostname check */
436 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
437 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
438 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
440 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
441 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
444 const uschar * list = verify_cert_hostnames;
447 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
448 if ((rc = X509_check_host(cert, CCS name, 0,
449 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
450 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
455 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
456 tlsp == &tls_out ? deliver_host_address : sender_host_address);
463 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
466 uschar * extra = verify_mode
467 ? string_sprintf(" (during %c-verify for [%s])",
468 *verify_mode, sender_host_address)
470 log_write(0, LOG_MAIN,
471 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
472 tlsp == &tls_out ? deliver_host_address : sender_host_address,
473 extra, dn, verify_cert_hostnames);
478 tlsp->peercert = X509_dup(cert); /* record failing cert */
479 return 0; /* reject */
481 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
482 "tls_try_verify_hosts)\n");
486 #ifndef DISABLE_EVENT
487 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
488 return 0; /* reject, with peercert set */
491 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
492 *calledp ? "" : " authenticated", dn);
493 if (!*calledp) tlsp->certificate_verified = TRUE;
497 return 1; /* accept, at least for this level */
501 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
503 return verify_callback(preverify_ok, x509ctx, &tls_out,
504 &client_verify_callback_called, &client_verify_optional);
508 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
510 return verify_callback(preverify_ok, x509ctx, &tls_in,
511 &server_verify_callback_called, &server_verify_optional);
515 #ifdef EXPERIMENTAL_DANE
517 /* This gets called *by* the dane library verify callback, which interposes
521 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
523 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
525 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
526 #ifndef DISABLE_EVENT
527 BOOL dummy_called, optional = FALSE;
530 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
531 dn[sizeof(dn)-1] = '\0';
533 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
534 preverify_ok ? "ok":"BAD", depth, dn);
536 #ifndef DISABLE_EVENT
537 if (verify_event(&tls_out, cert, depth, dn,
538 &dummy_called, &optional, US"DANE"))
539 return 0; /* reject, with peercert set */
542 if (preverify_ok == 1)
543 tls_out.dane_verified =
544 tls_out.certificate_verified = TRUE;
547 int err = X509_STORE_CTX_get_error(x509ctx);
549 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
550 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
556 #endif /*EXPERIMENTAL_DANE*/
559 /*************************************************
560 * Information callback *
561 *************************************************/
563 /* The SSL library functions call this from time to time to indicate what they
564 are doing. We copy the string to the debugging output when TLS debugging has
576 info_callback(SSL *s, int where, int ret)
580 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
585 /*************************************************
586 * Initialize for DH *
587 *************************************************/
589 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
592 sctx The current SSL CTX (inbound or outbound)
593 dhparam DH parameter file or fixed parameter identity string
594 host connected host, if client; NULL if server
595 errstr error string pointer
597 Returns: TRUE if OK (nothing to set up, or setup worked)
601 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
609 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
612 if (!dhexpanded || !*dhexpanded)
613 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
614 else if (dhexpanded[0] == '/')
616 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
618 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
619 host, US strerror(errno), errstr);
625 if (Ustrcmp(dhexpanded, "none") == 0)
627 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
631 if (!(pem = std_dh_prime_named(dhexpanded)))
633 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
634 host, US strerror(errno), errstr);
637 bio = BIO_new_mem_buf(CS pem, -1);
640 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
643 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
648 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
649 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
650 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
651 * If someone wants to dance at the edge, then they can raise the limit or use
652 * current libraries. */
653 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
654 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
655 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
656 dh_bitsize = DH_bits(dh);
658 dh_bitsize = 8 * DH_size(dh);
661 /* Even if it is larger, we silently return success rather than cause things
662 * to fail out, so that a too-large DH will not knock out all TLS; it's a
663 * debatable choice. */
664 if (dh_bitsize > tls_dh_max_bits)
667 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
668 dh_bitsize, tls_dh_max_bits);
672 SSL_CTX_set_tmp_dh(sctx, dh);
674 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
675 dhexpanded ? dhexpanded : US"default", dh_bitsize);
687 /*************************************************
688 * Initialize for ECDH *
689 *************************************************/
691 /* Load parameters for ECDH encryption.
693 For now, we stick to NIST P-256 because: it's simple and easy to configure;
694 it avoids any patent issues that might bite redistributors; despite events in
695 the news and concerns over curve choices, we're not cryptographers, we're not
696 pretending to be, and this is "good enough" to be better than no support,
697 protecting against most adversaries. Given another year or two, there might
698 be sufficient clarity about a "right" way forward to let us make an informed
699 decision, instead of a knee-jerk reaction.
701 Longer-term, we should look at supporting both various named curves and
702 external files generated with "openssl ecparam", much as we do for init_dh().
703 We should also support "none" as a value, to explicitly avoid initialisation.
708 sctx The current SSL CTX (inbound or outbound)
709 host connected host, if client; NULL if server
710 errstr error string pointer
712 Returns: TRUE if OK (nothing to set up, or setup worked)
716 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
718 #ifdef OPENSSL_NO_ECDH
727 if (host) /* No ECDH setup for clients, only for servers */
730 # ifndef EXIM_HAVE_ECDH
732 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
736 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
738 if (!exp_curve || !*exp_curve)
741 /* "auto" needs to be handled carefully.
742 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
743 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
744 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
745 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
746 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
748 if (Ustrcmp(exp_curve, "auto") == 0)
750 #if OPENSSL_VERSION_NUMBER < 0x10002000L
751 DEBUG(D_tls) debug_printf(
752 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
753 exp_curve = US"prime256v1";
755 # if defined SSL_CTRL_SET_ECDH_AUTO
756 DEBUG(D_tls) debug_printf(
757 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
758 SSL_CTX_set_ecdh_auto(sctx, 1);
761 DEBUG(D_tls) debug_printf(
762 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
768 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
769 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
770 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
771 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
775 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
780 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
782 tls_error(US"Unable to create ec curve", host, NULL, errstr);
786 /* The "tmp" in the name here refers to setting a temporary key
787 not to the stability of the interface. */
789 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
790 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
792 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
797 # endif /*EXIM_HAVE_ECDH*/
798 #endif /*OPENSSL_NO_ECDH*/
805 /*************************************************
806 * Load OCSP information into state *
807 *************************************************/
808 /* Called to load the server OCSP response from the given file into memory, once
809 caller has determined this is needed. Checks validity. Debugs a message
812 ASSUMES: single response, for single cert.
815 sctx the SSL_CTX* to update
816 cbinfo various parts of session state
817 expanded the filename putatively holding an OCSP response
822 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
825 OCSP_RESPONSE * resp;
826 OCSP_BASICRESP * basic_response;
827 OCSP_SINGLERESP * single_response;
828 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
830 unsigned long verify_flags;
831 int status, reason, i;
833 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
834 if (cbinfo->u_ocsp.server.response)
836 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
837 cbinfo->u_ocsp.server.response = NULL;
840 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
842 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
843 cbinfo->u_ocsp.server.file_expanded);
847 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
851 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
855 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
857 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
858 OCSP_response_status_str(status), status);
862 if (!(basic_response = OCSP_response_get1_basic(resp)))
865 debug_printf("OCSP response parse error: unable to extract basic response.\n");
869 sk = cbinfo->verify_stack;
870 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
872 /* May need to expose ability to adjust those flags?
873 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
874 OCSP_TRUSTOTHER OCSP_NOINTERN */
876 /* This does a full verify on the OCSP proof before we load it for serving
877 up; possibly overkill - just date-checks might be nice enough.
879 OCSP_basic_verify takes a "store" arg, but does not
880 use it for the chain verification, which is all we do
881 when OCSP_NOVERIFY is set. The content from the wire
882 "basic_response" and a cert-stack "sk" are all that is used.
884 We have a stack, loaded in setup_certs() if tls_verify_certificates
885 was a file (not a directory, or "system"). It is unfortunate we
886 cannot used the connection context store, as that would neatly
887 handle the "system" case too, but there seems to be no library
888 function for getting a stack from a store.
889 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
890 We do not free the stack since it could be needed a second time for
893 Separately we might try to replace using OCSP_basic_verify() - which seems to not
894 be a public interface into the OpenSSL library (there's no manual entry) -
895 But what with? We also use OCSP_basic_verify in the client stapling callback.
896 And there we NEED it; we must verify that status... unless the
897 library does it for us anyway? */
899 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
903 ERR_error_string(ERR_get_error(), ssl_errstring);
904 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
909 /* Here's the simplifying assumption: there's only one response, for the
910 one certificate we use, and nothing for anything else in a chain. If this
911 proves false, we need to extract a cert id from our issued cert
912 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
913 right cert in the stack and then calls OCSP_single_get0_status()).
915 I'm hoping to avoid reworking a bunch more of how we handle state here. */
917 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
920 debug_printf("Unable to get first response from OCSP basic response.\n");
924 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
925 if (status != V_OCSP_CERTSTATUS_GOOD)
927 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
928 OCSP_cert_status_str(status), status,
929 OCSP_crl_reason_str(reason), reason);
933 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
935 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
940 cbinfo->u_ocsp.server.response = resp; /*XXX stack?*/
944 if (running_in_test_harness)
946 extern char ** environ;
948 if (environ) for (p = USS environ; *p; p++)
949 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
951 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
952 goto supply_response;
957 #endif /*!DISABLE_OCSP*/
962 /* Create and install a selfsigned certificate, for use in server mode */
965 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
973 where = US"allocating pkey";
974 if (!(pkey = EVP_PKEY_new()))
977 where = US"allocating cert";
978 if (!(x509 = X509_new()))
981 where = US"generating pkey";
982 if (!(rsa = rsa_callback(NULL, 0, 1024)))
985 where = US"assigning pkey";
986 if (!EVP_PKEY_assign_RSA(pkey, rsa))
989 X509_set_version(x509, 2); /* N+1 - version 3 */
990 ASN1_INTEGER_set(X509_get_serialNumber(x509), 0);
991 X509_gmtime_adj(X509_get_notBefore(x509), 0);
992 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
993 X509_set_pubkey(x509, pkey);
995 name = X509_get_subject_name(x509);
996 X509_NAME_add_entry_by_txt(name, "C",
997 MBSTRING_ASC, CUS "UK", -1, -1, 0);
998 X509_NAME_add_entry_by_txt(name, "O",
999 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1000 X509_NAME_add_entry_by_txt(name, "CN",
1001 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1002 X509_set_issuer_name(x509, name);
1004 where = US"signing cert";
1005 if (!X509_sign(x509, pkey, EVP_md5()))
1008 where = US"installing selfsign cert";
1009 if (!SSL_CTX_use_certificate(sctx, x509))
1012 where = US"installing selfsign key";
1013 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1019 (void) tls_error(where, NULL, NULL, errstr);
1020 if (x509) X509_free(x509);
1021 if (pkey) EVP_PKEY_free(pkey);
1029 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1032 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1033 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1034 return tls_error(string_sprintf(
1035 "SSL_CTX_use_certificate_chain_file file=%s", file),
1036 cbinfo->host, NULL, errstr);
1041 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1044 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1045 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1046 return tls_error(string_sprintf(
1047 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1052 /*************************************************
1053 * Expand key and cert file specs *
1054 *************************************************/
1056 /* Called once during tls_init and possibly again during TLS setup, for a
1057 new context, if Server Name Indication was used and tls_sni was seen in
1058 the certificate string.
1061 sctx the SSL_CTX* to update
1062 cbinfo various parts of session state
1063 errstr error string pointer
1065 Returns: OK/DEFER/FAIL
1069 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1074 if (!cbinfo->certificate)
1076 if (!cbinfo->is_server) /* client */
1079 if (tls_install_selfsign(sctx, errstr) != OK)
1086 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1087 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1088 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1090 reexpand_tls_files_for_sni = TRUE;
1092 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1096 if (cbinfo->is_server)
1098 const uschar * file_list = expanded;
1102 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1103 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1106 else /* would there ever be a need for multiple client certs? */
1107 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1110 if (cbinfo->privatekey != NULL &&
1111 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1114 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1115 of the expansion is an empty string, ignore it also, and assume the private
1116 key is in the same file as the certificate. */
1118 if (expanded && *expanded)
1119 if (cbinfo->is_server)
1121 const uschar * file_list = expanded;
1125 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1126 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1129 else /* would there ever be a need for multiple client certs? */
1130 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1134 #ifndef DISABLE_OCSP
1135 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1138 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1141 if (expanded && *expanded)
1143 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1144 if ( cbinfo->u_ocsp.server.file_expanded
1145 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1147 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1150 ocsp_load_response(sctx, cbinfo, expanded);
1161 /*************************************************
1162 * Callback to handle SNI *
1163 *************************************************/
1165 /* Called when acting as server during the TLS session setup if a Server Name
1166 Indication extension was sent by the client.
1168 API documentation is OpenSSL s_server.c implementation.
1171 s SSL* of the current session
1172 ad unknown (part of OpenSSL API) (unused)
1173 arg Callback of "our" registered data
1175 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1178 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1180 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1182 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1183 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1185 int old_pool = store_pool;
1186 uschar * dummy_errstr;
1189 return SSL_TLSEXT_ERR_OK;
1191 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1192 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1194 /* Make the extension value available for expansion */
1195 store_pool = POOL_PERM;
1196 tls_in.sni = string_copy(US servername);
1197 store_pool = old_pool;
1199 if (!reexpand_tls_files_for_sni)
1200 return SSL_TLSEXT_ERR_OK;
1202 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1203 not confident that memcpy wouldn't break some internal reference counting.
1204 Especially since there's a references struct member, which would be off. */
1206 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1208 ERR_error_string(ERR_get_error(), ssl_errstring);
1209 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1210 return SSL_TLSEXT_ERR_NOACK;
1213 /* Not sure how many of these are actually needed, since SSL object
1214 already exists. Might even need this selfsame callback, for reneg? */
1216 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1217 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1218 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1219 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1220 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1221 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1223 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1224 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1226 return SSL_TLSEXT_ERR_NOACK;
1228 if (cbinfo->server_cipher_list)
1229 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
1230 #ifndef DISABLE_OCSP
1231 if (cbinfo->u_ocsp.server.file)
1233 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1234 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1238 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1239 verify_callback_server, &dummy_errstr)) != OK)
1240 return SSL_TLSEXT_ERR_NOACK;
1242 /* do this after setup_certs, because this can require the certs for verifying
1243 OCSP information. */
1244 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1245 return SSL_TLSEXT_ERR_NOACK;
1247 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1248 SSL_set_SSL_CTX(s, server_sni);
1250 return SSL_TLSEXT_ERR_OK;
1252 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1257 #ifndef DISABLE_OCSP
1259 /*************************************************
1260 * Callback to handle OCSP Stapling *
1261 *************************************************/
1263 /* Called when acting as server during the TLS session setup if the client
1264 requests OCSP information with a Certificate Status Request.
1266 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1272 tls_server_stapling_cb(SSL *s, void *arg)
1274 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1275 uschar *response_der; /*XXX blob */
1276 int response_der_len;
1278 /*XXX stack: use SSL_get_certificate() to see which cert; from that work
1279 out which ocsp blob to send. Unfortunately, SSL_get_certificate is known
1280 buggy in current OpenSSL; it returns the last cert loaded always rather than
1281 the one actually presented. So we can't support a stack of OCSP proofs at
1285 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1286 cbinfo->u_ocsp.server.response ? "have" : "lack");
1288 tls_in.ocsp = OCSP_NOT_RESP;
1289 if (!cbinfo->u_ocsp.server.response)
1290 return SSL_TLSEXT_ERR_NOACK;
1292 response_der = NULL;
1293 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response, /*XXX stack*/
1295 if (response_der_len <= 0)
1296 return SSL_TLSEXT_ERR_NOACK;
1298 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1299 tls_in.ocsp = OCSP_VFIED;
1300 return SSL_TLSEXT_ERR_OK;
1305 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1307 BIO_printf(bp, "\t%s: ", str);
1308 ASN1_GENERALIZEDTIME_print(bp, time);
1313 tls_client_stapling_cb(SSL *s, void *arg)
1315 tls_ext_ctx_cb * cbinfo = arg;
1316 const unsigned char * p;
1318 OCSP_RESPONSE * rsp;
1319 OCSP_BASICRESP * bs;
1322 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1323 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1326 /* Expect this when we requested ocsp but got none */
1327 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1328 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1330 DEBUG(D_tls) debug_printf(" null\n");
1331 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1334 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1336 tls_out.ocsp = OCSP_FAILED;
1337 if (LOGGING(tls_cipher))
1338 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1340 DEBUG(D_tls) debug_printf(" parse error\n");
1344 if(!(bs = OCSP_response_get1_basic(rsp)))
1346 tls_out.ocsp = OCSP_FAILED;
1347 if (LOGGING(tls_cipher))
1348 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1350 DEBUG(D_tls) debug_printf(" error parsing response\n");
1351 OCSP_RESPONSE_free(rsp);
1355 /* We'd check the nonce here if we'd put one in the request. */
1356 /* However that would defeat cacheability on the server so we don't. */
1358 /* This section of code reworked from OpenSSL apps source;
1359 The OpenSSL Project retains copyright:
1360 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1365 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1367 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
1369 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1371 /* Use the chain that verified the server cert to verify the stapled info */
1372 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1374 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1375 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1377 tls_out.ocsp = OCSP_FAILED;
1378 if (LOGGING(tls_cipher))
1379 log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
1380 BIO_printf(bp, "OCSP response verify failure\n");
1381 ERR_print_errors(bp);
1385 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1387 /*XXX So we have a good stapled OCSP status. How do we know
1388 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1389 OCSP_resp_find_status() which matches on a cert id, which presumably
1390 we should use. Making an id needs OCSP_cert_id_new(), which takes
1391 issuerName, issuerKey, serialNumber. Are they all in the cert?
1393 For now, carry on blindly accepting the resp. */
1396 OCSP_SINGLERESP * single;
1398 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1399 if (OCSP_resp_count(bs) != 1)
1401 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1402 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1405 tls_out.ocsp = OCSP_FAILED;
1406 log_write(0, LOG_MAIN, "OCSP stapling "
1407 "with multiple responses not handled");
1410 single = OCSP_resp_get0(bs, 0);
1411 status = OCSP_single_get0_status(single, &reason, &rev,
1412 &thisupd, &nextupd);
1415 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1416 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1417 if (!OCSP_check_validity(thisupd, nextupd,
1418 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1420 tls_out.ocsp = OCSP_FAILED;
1421 DEBUG(D_tls) ERR_print_errors(bp);
1422 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1426 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1427 OCSP_cert_status_str(status));
1430 case V_OCSP_CERTSTATUS_GOOD:
1431 tls_out.ocsp = OCSP_VFIED;
1434 case V_OCSP_CERTSTATUS_REVOKED:
1435 tls_out.ocsp = OCSP_FAILED;
1436 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1437 reason != -1 ? "; reason: " : "",
1438 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1439 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1442 tls_out.ocsp = OCSP_FAILED;
1443 log_write(0, LOG_MAIN,
1444 "Server certificate status unknown, in OCSP stapling");
1449 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1454 OCSP_RESPONSE_free(rsp);
1457 #endif /*!DISABLE_OCSP*/
1460 /*************************************************
1461 * Initialize for TLS *
1462 *************************************************/
1464 /* Called from both server and client code, to do preliminary initialization
1465 of the library. We allocate and return a context structure.
1468 ctxp returned SSL context
1469 host connected host, if client; NULL if server
1470 dhparam DH parameter file
1471 certificate certificate file
1472 privatekey private key
1473 ocsp_file file of stapling info (server); flag for require ocsp (client)
1474 addr address if client; NULL if server (for some randomness)
1475 cbp place to put allocated callback context
1476 errstr error string pointer
1478 Returns: OK/DEFER/FAIL
1482 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1484 #ifndef DISABLE_OCSP
1485 uschar *ocsp_file, /*XXX stack, in server*/
1487 address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1492 tls_ext_ctx_cb * cbinfo;
1494 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1495 cbinfo->certificate = certificate;
1496 cbinfo->privatekey = privatekey;
1497 cbinfo->is_server = host==NULL;
1498 #ifndef DISABLE_OCSP
1499 cbinfo->verify_stack = NULL;
1502 cbinfo->u_ocsp.server.file = ocsp_file;
1503 cbinfo->u_ocsp.server.file_expanded = NULL;
1504 cbinfo->u_ocsp.server.response = NULL;
1507 cbinfo->u_ocsp.client.verify_store = NULL;
1509 cbinfo->dhparam = dhparam;
1510 cbinfo->server_cipher_list = NULL;
1511 cbinfo->host = host;
1512 #ifndef DISABLE_EVENT
1513 cbinfo->event_action = NULL;
1516 SSL_load_error_strings(); /* basic set up */
1517 OpenSSL_add_ssl_algorithms();
1519 #ifdef EXIM_HAVE_SHA256
1520 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1521 list of available digests. */
1522 EVP_add_digest(EVP_sha256());
1525 /* Create a context.
1526 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1527 negotiation in the different methods; as far as I can tell, the only
1528 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1529 when OpenSSL is built without SSLv2 support.
1530 By disabling with openssl_options, we can let admins re-enable with the
1533 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1534 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1536 /* It turns out that we need to seed the random number generator this early in
1537 order to get the full complement of ciphers to work. It took me roughly a day
1538 of work to discover this by experiment.
1540 On systems that have /dev/urandom, SSL may automatically seed itself from
1541 there. Otherwise, we have to make something up as best we can. Double check
1547 gettimeofday(&r.tv, NULL);
1550 RAND_seed(US (&r), sizeof(r));
1551 RAND_seed(US big_buffer, big_buffer_size);
1552 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1555 return tls_error(US"RAND_status", host,
1556 US"unable to seed random number generator", errstr);
1559 /* Set up the information callback, which outputs if debugging is at a suitable
1562 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1564 /* Automatically re-try reads/writes after renegotiation. */
1565 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1567 /* Apply administrator-supplied work-arounds.
1568 Historically we applied just one requested option,
1569 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1570 moved to an administrator-controlled list of options to specify and
1571 grandfathered in the first one as the default value for "openssl_options".
1573 No OpenSSL version number checks: the options we accept depend upon the
1574 availability of the option value macros from OpenSSL. */
1576 if (!tls_openssl_options_parse(openssl_options, &init_options))
1577 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1581 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1582 if (!(SSL_CTX_set_options(ctx, init_options)))
1583 return tls_error(string_sprintf(
1584 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1587 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1589 /* Disable session cache unconditionally */
1591 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1593 /* Initialize with DH parameters if supplied */
1594 /* Initialize ECDH temp key parameter selection */
1596 if ( !init_dh(ctx, dhparam, host, errstr)
1597 || !init_ecdh(ctx, host, errstr)
1601 /* Set up certificate and key (and perhaps OCSP info) */
1603 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1606 /* If we need to handle SNI or OCSP, do so */
1608 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1609 # ifndef DISABLE_OCSP
1610 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1612 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1617 if (host == NULL) /* server */
1619 # ifndef DISABLE_OCSP
1620 /* We check u_ocsp.server.file, not server.response, because we care about if
1621 the option exists, not what the current expansion might be, as SNI might
1622 change the certificate and OCSP file in use between now and the time the
1623 callback is invoked. */
1624 if (cbinfo->u_ocsp.server.file)
1626 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1627 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1630 /* We always do this, so that $tls_sni is available even if not used in
1632 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1633 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1635 # ifndef DISABLE_OCSP
1637 if(ocsp_file) /* wanting stapling */
1639 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1641 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1644 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1645 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1650 cbinfo->verify_cert_hostnames = NULL;
1652 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1653 /* Set up the RSA callback */
1654 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1657 /* Finally, set the timeout, and we are done */
1659 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1660 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1671 /*************************************************
1672 * Get name of cipher in use *
1673 *************************************************/
1676 Argument: pointer to an SSL structure for the connection
1677 buffer to use for answer
1679 pointer to number of bits for cipher
1684 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1686 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1687 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1688 the accessor functions use const in the prototype. */
1689 const SSL_CIPHER *c;
1692 ver = (const uschar *)SSL_get_version(ssl);
1694 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1695 SSL_CIPHER_get_bits(c, bits);
1697 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1698 SSL_CIPHER_get_name(c), *bits);
1700 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1705 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned bsize)
1707 /*XXX we might consider a list-of-certs variable for the cert chain.
1708 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1709 in list-handling functions, also consider the difference between the entire
1710 chain and the elements sent by the peer. */
1712 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1713 if (!tlsp->peercert)
1714 tlsp->peercert = SSL_get_peer_certificate(ssl);
1715 /* Beware anonymous ciphers which lead to server_cert being NULL */
1718 X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, bsize);
1719 peerdn[bsize-1] = '\0';
1720 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1723 tlsp->peerdn = NULL;
1730 /*************************************************
1731 * Set up for verifying certificates *
1732 *************************************************/
1734 /* Load certs from file, return TRUE on success */
1737 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
1742 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
1743 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
1744 sk_X509_push(verify_stack, x);
1751 /* Called by both client and server startup
1754 sctx SSL_CTX* to initialise
1755 certs certs file or NULL
1756 crl CRL file or NULL
1757 host NULL in a server; the remote host in a client
1758 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1759 otherwise passed as FALSE
1760 cert_vfy_cb Callback function for certificate verification
1761 errstr error string pointer
1763 Returns: OK/DEFER/FAIL
1767 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1768 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
1770 uschar *expcerts, *expcrl;
1772 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
1774 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
1776 if (expcerts && *expcerts)
1778 /* Tell the library to use its compiled-in location for the system default
1779 CA bundle. Then add the ones specified in the config, if any. */
1781 if (!SSL_CTX_set_default_verify_paths(sctx))
1782 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
1784 if (Ustrcmp(expcerts, "system") != 0)
1786 struct stat statbuf;
1788 if (Ustat(expcerts, &statbuf) < 0)
1790 log_write(0, LOG_MAIN|LOG_PANIC,
1791 "failed to stat %s for certificates", expcerts);
1797 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1798 { file = NULL; dir = expcerts; }
1801 file = expcerts; dir = NULL;
1802 #ifndef DISABLE_OCSP
1803 /* In the server if we will be offering an OCSP proof, load chain from
1804 file for verifying the OCSP proof at load time. */
1807 && statbuf.st_size > 0
1808 && server_static_cbinfo->u_ocsp.server.file
1809 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
1812 log_write(0, LOG_MAIN|LOG_PANIC,
1813 "failed to load cert hain from %s", file);
1819 /* If a certificate file is empty, the next function fails with an
1820 unhelpful error message. If we skip it, we get the correct behaviour (no
1821 certificates are recognized, but the error message is still misleading (it
1822 says no certificate was supplied). But this is better. */
1824 if ( (!file || statbuf.st_size > 0)
1825 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1826 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
1828 /* Load the list of CAs for which we will accept certs, for sending
1829 to the client. This is only for the one-file tls_verify_certificates
1831 If a list isn't loaded into the server, but
1832 some verify locations are set, the server end appears to make
1833 a wildcard request for client certs.
1834 Meanwhile, the client library as default behaviour *ignores* the list
1835 we send over the wire - see man SSL_CTX_set_client_cert_cb.
1836 Because of this, and that the dir variant is likely only used for
1837 the public-CA bundle (not for a private CA), not worth fixing.
1841 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
1843 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
1844 sk_X509_NAME_num(names));
1845 SSL_CTX_set_client_CA_list(sctx, names);
1850 /* Handle a certificate revocation list. */
1852 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1854 /* This bit of code is now the version supplied by Lars Mainka. (I have
1855 merely reformatted it into the Exim code style.)
1857 "From here I changed the code to add support for multiple crl's
1858 in pem format in one file or to support hashed directory entries in
1859 pem format instead of a file. This method now uses the library function
1860 X509_STORE_load_locations to add the CRL location to the SSL context.
1861 OpenSSL will then handle the verify against CA certs and CRLs by
1862 itself in the verify callback." */
1864 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
1865 if (expcrl && *expcrl)
1867 struct stat statbufcrl;
1868 if (Ustat(expcrl, &statbufcrl) < 0)
1870 log_write(0, LOG_MAIN|LOG_PANIC,
1871 "failed to stat %s for certificates revocation lists", expcrl);
1876 /* is it a file or directory? */
1878 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1879 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1883 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1889 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1891 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1892 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
1894 /* setting the flags to check against the complete crl chain */
1896 X509_STORE_set_flags(cvstore,
1897 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1901 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1903 /* If verification is optional, don't fail if no certificate */
1905 SSL_CTX_set_verify(sctx,
1906 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1915 /*************************************************
1916 * Start a TLS session in a server *
1917 *************************************************/
1919 /* This is called when Exim is running as a server, after having received
1920 the STARTTLS command. It must respond to that command, and then negotiate
1924 require_ciphers allowed ciphers
1925 errstr pointer to error message
1927 Returns: OK on success
1928 DEFER for errors before the start of the negotiation
1929 FAIL for errors during the negotiation; the server can't
1934 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
1937 uschar * expciphers;
1938 tls_ext_ctx_cb * cbinfo;
1939 static uschar peerdn[256];
1940 static uschar cipherbuf[256];
1942 /* Check for previous activation */
1944 if (tls_in.active >= 0)
1946 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
1947 smtp_printf("554 Already in TLS\r\n", FALSE);
1951 /* Initialize the SSL library. If it fails, it will already have logged
1954 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1955 #ifndef DISABLE_OCSP
1956 tls_ocsp_file, /*XXX stack*/
1958 NULL, &server_static_cbinfo, errstr);
1959 if (rc != OK) return rc;
1960 cbinfo = server_static_cbinfo;
1962 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
1965 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1966 were historically separated by underscores. So that I can use either form in my
1967 tests, and also for general convenience, we turn underscores into hyphens here.
1972 uschar * s = expciphers;
1973 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1974 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1975 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1976 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
1977 cbinfo->server_cipher_list = expciphers;
1980 /* If this is a host for which certificate verification is mandatory or
1981 optional, set up appropriately. */
1983 tls_in.certificate_verified = FALSE;
1984 #ifdef EXPERIMENTAL_DANE
1985 tls_in.dane_verified = FALSE;
1987 server_verify_callback_called = FALSE;
1989 if (verify_check_host(&tls_verify_hosts) == OK)
1991 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1992 FALSE, verify_callback_server, errstr);
1993 if (rc != OK) return rc;
1994 server_verify_optional = FALSE;
1996 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1998 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1999 TRUE, verify_callback_server, errstr);
2000 if (rc != OK) return rc;
2001 server_verify_optional = TRUE;
2004 /* Prepare for new connection */
2006 if (!(server_ssl = SSL_new(server_ctx)))
2007 return tls_error(US"SSL_new", NULL, NULL, errstr);
2009 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2011 * With the SSL_clear(), we get strange interoperability bugs with
2012 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2013 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2015 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2016 * session shutdown. In this case, we have a brand new object and there's no
2017 * obvious reason to immediately clear it. I'm guessing that this was
2018 * originally added because of incomplete initialisation which the clear fixed,
2019 * in some historic release.
2022 /* Set context and tell client to go ahead, except in the case of TLS startup
2023 on connection, where outputting anything now upsets the clients and tends to
2024 make them disconnect. We need to have an explicit fflush() here, to force out
2025 the response. Other smtp_printf() calls do not need it, because in non-TLS
2026 mode, the fflush() happens when smtp_getc() is called. */
2028 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2029 if (!tls_in.on_connect)
2031 smtp_printf("220 TLS go ahead\r\n", FALSE);
2035 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2036 that the OpenSSL library doesn't. */
2038 SSL_set_wfd(server_ssl, fileno(smtp_out));
2039 SSL_set_rfd(server_ssl, fileno(smtp_in));
2040 SSL_set_accept_state(server_ssl);
2042 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2044 sigalrm_seen = FALSE;
2045 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2046 rc = SSL_accept(server_ssl);
2051 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2055 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2057 /* TLS has been set up. Adjust the input functions to read via TLS,
2058 and initialize things. */
2060 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2062 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
2063 tls_in.cipher = cipherbuf;
2068 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
2069 debug_printf("Shared ciphers: %s\n", buf);
2072 /* Record the certificate we presented */
2074 X509 * crt = SSL_get_certificate(server_ssl);
2075 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2078 /* Only used by the server-side tls (tls_in), including tls_getc.
2079 Client-side (tls_out) reads (seem to?) go via
2080 smtp_read_response()/ip_recv().
2081 Hence no need to duplicate for _in and _out.
2083 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2084 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2085 ssl_xfer_eof = ssl_xfer_error = 0;
2087 receive_getc = tls_getc;
2088 receive_getbuf = tls_getbuf;
2089 receive_get_cache = tls_get_cache;
2090 receive_ungetc = tls_ungetc;
2091 receive_feof = tls_feof;
2092 receive_ferror = tls_ferror;
2093 receive_smtp_buffered = tls_smtp_buffered;
2095 tls_in.active = fileno(smtp_out);
2103 tls_client_basic_ctx_init(SSL_CTX * ctx,
2104 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2108 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2109 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2110 the specified host patterns if one of them is defined */
2112 if ( ( !ob->tls_verify_hosts
2113 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2115 || (verify_check_given_host(&ob->tls_verify_hosts, host) == OK)
2117 client_verify_optional = FALSE;
2118 else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK)
2119 client_verify_optional = TRUE;
2123 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2124 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2128 if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
2130 cbinfo->verify_cert_hostnames =
2132 string_domain_utf8_to_alabel(host->name, NULL);
2136 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2137 cbinfo->verify_cert_hostnames);
2143 #ifdef EXPERIMENTAL_DANE
2145 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2149 const char * hostnames[2] = { CS host->name, NULL };
2152 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2153 return tls_error(US"hostnames load", host, NULL, errstr);
2155 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
2157 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2158 ) if (rr->type == T_TLSA)
2160 const uschar * p = rr->data;
2161 uint8_t usage, selector, mtype;
2162 const char * mdname;
2166 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2167 if (usage != 2 && usage != 3) continue;
2174 default: continue; /* Only match-types 0, 1, 2 are supported */
2175 case 0: mdname = NULL; break;
2176 case 1: mdname = "sha256"; break;
2177 case 2: mdname = "sha512"; break;
2181 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2184 return tls_error(US"tlsa load", host, NULL, errstr);
2185 case 0: /* action not taken */
2189 tls_out.tlsa_usage |= 1<<usage;
2195 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2198 #endif /*EXPERIMENTAL_DANE*/
2202 /*************************************************
2203 * Start a TLS session in a client *
2204 *************************************************/
2206 /* Called from the smtp transport after STARTTLS has been accepted.
2209 fd the fd of the connection
2210 host connected host (for messages)
2211 addr the first address
2212 tb transport (always smtp)
2213 tlsa_dnsa tlsa lookup, if DANE, else null
2214 errstr error string pointer
2216 Returns: OK on success
2217 FAIL otherwise - note that tls_error() will not give DEFER
2218 because this is not a server
2222 tls_client_start(int fd, host_item *host, address_item *addr,
2223 transport_instance * tb,
2224 #ifdef EXPERIMENTAL_DANE
2225 dns_answer * tlsa_dnsa,
2229 smtp_transport_options_block * ob =
2230 (smtp_transport_options_block *)tb->options_block;
2231 static uschar peerdn[256];
2232 uschar * expciphers;
2234 static uschar cipherbuf[256];
2236 #ifndef DISABLE_OCSP
2237 BOOL request_ocsp = FALSE;
2238 BOOL require_ocsp = FALSE;
2241 #ifdef EXPERIMENTAL_DANE
2242 tls_out.tlsa_usage = 0;
2245 #ifndef DISABLE_OCSP
2247 # ifdef EXPERIMENTAL_DANE
2249 && ob->hosts_request_ocsp[0] == '*'
2250 && ob->hosts_request_ocsp[1] == '\0'
2253 /* Unchanged from default. Use a safer one under DANE */
2254 request_ocsp = TRUE;
2255 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2256 " {= {4}{$tls_out_tlsa_usage}} } "
2262 verify_check_given_host(&ob->hosts_require_ocsp, host) == OK))
2263 request_ocsp = TRUE;
2265 # ifdef EXPERIMENTAL_DANE
2269 verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2273 rc = tls_init(&client_ctx, host, NULL,
2274 ob->tls_certificate, ob->tls_privatekey,
2275 #ifndef DISABLE_OCSP
2276 (void *)(long)request_ocsp,
2278 addr, &client_static_cbinfo, errstr);
2279 if (rc != OK) return rc;
2281 tls_out.certificate_verified = FALSE;
2282 client_verify_callback_called = FALSE;
2284 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2285 &expciphers, errstr))
2288 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2289 are separated by underscores. So that I can use either form in my tests, and
2290 also for general convenience, we turn underscores into hyphens here. */
2294 uschar *s = expciphers;
2295 while (*s) { if (*s == '_') *s = '-'; s++; }
2296 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2297 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
2298 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2301 #ifdef EXPERIMENTAL_DANE
2304 SSL_CTX_set_verify(client_ctx,
2305 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2306 verify_callback_client_dane);
2308 if (!DANESSL_library_init())
2309 return tls_error(US"library init", host, NULL, errstr);
2310 if (DANESSL_CTX_init(client_ctx) <= 0)
2311 return tls_error(US"context init", host, NULL, errstr);
2317 if ((rc = tls_client_basic_ctx_init(client_ctx, host, ob,
2318 client_static_cbinfo, errstr)) != OK)
2321 if ((client_ssl = SSL_new(client_ctx)) == NULL)
2322 return tls_error(US"SSL_new", host, NULL, errstr);
2323 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
2324 SSL_set_fd(client_ssl, fd);
2325 SSL_set_connect_state(client_ssl);
2329 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni, errstr))
2333 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2335 else if (!Ustrlen(tls_out.sni))
2339 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2340 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
2341 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
2343 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2349 #ifdef EXPERIMENTAL_DANE
2351 if ((rc = dane_tlsa_load(client_ssl, host, tlsa_dnsa, errstr)) != OK)
2355 #ifndef DISABLE_OCSP
2356 /* Request certificate status at connection-time. If the server
2357 does OCSP stapling we will get the callback (set in tls_init()) */
2358 # ifdef EXPERIMENTAL_DANE
2362 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2363 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2365 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2366 this means we avoid the OCSP request, we wasted the setup
2367 cost in tls_init(). */
2368 require_ocsp = verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
2369 request_ocsp = require_ocsp
2370 || verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2377 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
2378 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2379 tls_out.ocsp = OCSP_NOT_RESP;
2383 #ifndef DISABLE_EVENT
2384 client_static_cbinfo->event_action = tb->event_action;
2387 /* There doesn't seem to be a built-in timeout on connection. */
2389 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2390 sigalrm_seen = FALSE;
2391 alarm(ob->command_timeout);
2392 rc = SSL_connect(client_ssl);
2395 #ifdef EXPERIMENTAL_DANE
2397 DANESSL_cleanup(client_ssl);
2401 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL,
2404 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
2406 peer_cert(client_ssl, &tls_out, peerdn, sizeof(peerdn));
2408 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
2409 tls_out.cipher = cipherbuf;
2411 /* Record the certificate we presented */
2413 X509 * crt = SSL_get_certificate(client_ssl);
2414 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
2417 tls_out.active = fd;
2426 tls_refill(unsigned lim)
2431 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2432 ssl_xfer_buffer, ssl_xfer_buffer_size);
2434 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2435 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2436 MIN(ssl_xfer_buffer_size, lim));
2437 error = SSL_get_error(server_ssl, inbytes);
2440 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2441 closed down, not that the socket itself has been closed down. Revert to
2442 non-SSL handling. */
2444 if (error == SSL_ERROR_ZERO_RETURN)
2446 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2448 receive_getc = smtp_getc;
2449 receive_getbuf = smtp_getbuf;
2450 receive_get_cache = smtp_get_cache;
2451 receive_ungetc = smtp_ungetc;
2452 receive_feof = smtp_feof;
2453 receive_ferror = smtp_ferror;
2454 receive_smtp_buffered = smtp_buffered;
2456 SSL_free(server_ssl);
2460 tls_in.cipher = NULL;
2461 tls_in.peerdn = NULL;
2467 /* Handle genuine errors */
2469 else if (error == SSL_ERROR_SSL)
2471 ERR_error_string(ERR_get_error(), ssl_errstring);
2472 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2477 else if (error != SSL_ERROR_NONE)
2479 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2484 #ifndef DISABLE_DKIM
2485 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2487 ssl_xfer_buffer_hwm = inbytes;
2488 ssl_xfer_buffer_lwm = 0;
2493 /*************************************************
2494 * TLS version of getc *
2495 *************************************************/
2497 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2498 it refills the buffer via the SSL reading function.
2500 Arguments: lim Maximum amount to read/buffer
2501 Returns: the next character or EOF
2503 Only used by the server-side TLS.
2507 tls_getc(unsigned lim)
2509 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2510 if (!tls_refill(lim))
2511 return ssl_xfer_error ? EOF : smtp_getc(lim);
2513 /* Something in the buffer; return next uschar */
2515 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2519 tls_getbuf(unsigned * len)
2524 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2525 if (!tls_refill(*len))
2527 if (!ssl_xfer_error) return smtp_getbuf(len);
2532 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2534 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2535 ssl_xfer_buffer_lwm += size;
2544 #ifndef DISABLE_DKIM
2545 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2547 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2553 tls_could_read(void)
2555 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2559 /*************************************************
2560 * Read bytes from TLS channel *
2561 *************************************************/
2568 Returns: the number of bytes read
2569 -1 after a failed read
2571 Only used by the client-side TLS.
2575 tls_read(BOOL is_server, uschar *buff, size_t len)
2577 SSL *ssl = is_server ? server_ssl : client_ssl;
2581 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2582 buff, (unsigned int)len);
2584 inbytes = SSL_read(ssl, CS buff, len);
2585 error = SSL_get_error(ssl, inbytes);
2587 if (error == SSL_ERROR_ZERO_RETURN)
2589 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2592 else if (error != SSL_ERROR_NONE)
2602 /*************************************************
2603 * Write bytes down TLS channel *
2604 *************************************************/
2608 is_server channel specifier
2611 more further data expected soon
2613 Returns: the number of bytes after a successful write,
2614 -1 after a failed write
2616 Used by both server-side and client-side TLS.
2620 tls_write(BOOL is_server, const uschar *buff, size_t len, BOOL more)
2622 int outbytes, error, left;
2623 SSL *ssl = is_server ? server_ssl : client_ssl;
2624 static gstring * corked = NULL;
2626 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
2627 buff, (unsigned long)len, more ? ", more" : "");
2629 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2630 "more" is notified. This hack is only ok if small amounts are involved AND only
2631 one stream does it, in one context (i.e. no store reset). Currently it is used
2632 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. */
2634 if (is_server && (more || corked))
2636 corked = string_catn(corked, buff, len);
2639 buff = CUS corked->s;
2644 for (left = len; left > 0;)
2646 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
2647 outbytes = SSL_write(ssl, CS buff, left);
2648 error = SSL_get_error(ssl, outbytes);
2649 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2653 ERR_error_string(ERR_get_error(), ssl_errstring);
2654 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2657 case SSL_ERROR_NONE:
2662 case SSL_ERROR_ZERO_RETURN:
2663 log_write(0, LOG_MAIN, "SSL channel closed on write");
2666 case SSL_ERROR_SYSCALL:
2667 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
2668 sender_fullhost ? sender_fullhost : US"<unknown>",
2673 log_write(0, LOG_MAIN, "SSL_write error %d", error);
2682 /*************************************************
2683 * Close down a TLS session *
2684 *************************************************/
2686 /* This is also called from within a delivery subprocess forked from the
2687 daemon, to shut down the TLS library, without actually doing a shutdown (which
2688 would tamper with the SSL session in the parent process).
2690 Arguments: TRUE if SSL_shutdown is to be called
2693 Used by both server-side and client-side TLS.
2697 tls_close(BOOL is_server, BOOL shutdown)
2699 SSL **sslp = is_server ? &server_ssl : &client_ssl;
2700 int *fdp = is_server ? &tls_in.active : &tls_out.active;
2702 if (*fdp < 0) return; /* TLS was not active */
2706 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
2707 SSL_shutdown(*sslp);
2719 /*************************************************
2720 * Let tls_require_ciphers be checked at startup *
2721 *************************************************/
2723 /* The tls_require_ciphers option, if set, must be something which the
2726 Returns: NULL on success, or error message
2730 tls_validate_require_cipher(void)
2733 uschar *s, *expciphers, *err;
2735 /* this duplicates from tls_init(), we need a better "init just global
2736 state, for no specific purpose" singleton function of our own */
2738 SSL_load_error_strings();
2739 OpenSSL_add_ssl_algorithms();
2740 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2741 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2742 list of available digests. */
2743 EVP_add_digest(EVP_sha256());
2746 if (!(tls_require_ciphers && *tls_require_ciphers))
2749 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
2751 return US"failed to expand tls_require_ciphers";
2753 if (!(expciphers && *expciphers))
2756 /* normalisation ripped from above */
2758 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2762 ctx = SSL_CTX_new(SSLv23_server_method());
2765 ERR_error_string(ERR_get_error(), ssl_errstring);
2766 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2770 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2772 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2774 ERR_error_string(ERR_get_error(), ssl_errstring);
2775 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
2776 expciphers, ssl_errstring);
2787 /*************************************************
2788 * Report the library versions. *
2789 *************************************************/
2791 /* There have historically been some issues with binary compatibility in
2792 OpenSSL libraries; if Exim (like many other applications) is built against
2793 one version of OpenSSL but the run-time linker picks up another version,
2794 it can result in serious failures, including crashing with a SIGSEGV. So
2795 report the version found by the compiler and the run-time version.
2797 Note: some OS vendors backport security fixes without changing the version
2798 number/string, and the version date remains unchanged. The _build_ date
2799 will change, so we can more usefully assist with version diagnosis by also
2800 reporting the build date.
2802 Arguments: a FILE* to print the results to
2807 tls_version_report(FILE *f)
2809 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2812 OPENSSL_VERSION_TEXT,
2813 SSLeay_version(SSLEAY_VERSION),
2814 SSLeay_version(SSLEAY_BUILT_ON));
2815 /* third line is 38 characters for the %s and the line is 73 chars long;
2816 the OpenSSL output includes a "built on: " prefix already. */
2822 /*************************************************
2823 * Random number generation *
2824 *************************************************/
2826 /* Pseudo-random number generation. The result is not expected to be
2827 cryptographically strong but not so weak that someone will shoot themselves
2828 in the foot using it as a nonce in input in some email header scheme or
2829 whatever weirdness they'll twist this into. The result should handle fork()
2830 and avoid repeating sequences. OpenSSL handles that for us.
2834 Returns a random number in range [0, max-1]
2838 vaguely_random_number(int max)
2842 static pid_t pidlast = 0;
2845 uschar smallbuf[sizeof(r)];
2851 if (pidnow != pidlast)
2853 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2854 is unique for each thread", this doesn't apparently apply across processes,
2855 so our own warning from vaguely_random_number_fallback() applies here too.
2856 Fix per PostgreSQL. */
2862 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2866 gettimeofday(&r.tv, NULL);
2869 RAND_seed(US (&r), sizeof(r));
2871 /* We're after pseudo-random, not random; if we still don't have enough data
2872 in the internal PRNG then our options are limited. We could sleep and hope
2873 for entropy to come along (prayer technique) but if the system is so depleted
2874 in the first place then something is likely to just keep taking it. Instead,
2875 we'll just take whatever little bit of pseudo-random we can still manage to
2878 needed_len = sizeof(r);
2879 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2880 asked for a number less than 10. */
2881 for (r = max, i = 0; r; ++i)
2887 #ifdef EXIM_HAVE_RAND_PSEUDO
2888 /* We do not care if crypto-strong */
2889 i = RAND_pseudo_bytes(smallbuf, needed_len);
2891 i = RAND_bytes(smallbuf, needed_len);
2897 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2898 return vaguely_random_number_fallback(max);
2902 for (p = smallbuf; needed_len; --needed_len, ++p)
2908 /* We don't particularly care about weighted results; if someone wants
2909 smooth distribution and cares enough then they should submit a patch then. */
2916 /*************************************************
2917 * OpenSSL option parse *
2918 *************************************************/
2920 /* Parse one option for tls_openssl_options_parse below
2923 name one option name
2924 value place to store a value for it
2925 Returns success or failure in parsing
2928 struct exim_openssl_option {
2932 /* We could use a macro to expand, but we need the ifdef and not all the
2933 options document which version they were introduced in. Policylet: include
2934 all options unless explicitly for DTLS, let the administrator choose which
2937 This list is current as of:
2939 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2941 static struct exim_openssl_option exim_openssl_options[] = {
2942 /* KEEP SORTED ALPHABETICALLY! */
2944 { US"all", SSL_OP_ALL },
2946 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2947 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2949 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2950 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2952 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2953 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2955 #ifdef SSL_OP_EPHEMERAL_RSA
2956 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2958 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2959 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2961 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2962 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2964 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2965 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2967 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2968 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2970 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2971 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2973 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2974 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2976 #ifdef SSL_OP_NO_COMPRESSION
2977 { US"no_compression", SSL_OP_NO_COMPRESSION },
2979 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2980 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2982 #ifdef SSL_OP_NO_SSLv2
2983 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2985 #ifdef SSL_OP_NO_SSLv3
2986 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2988 #ifdef SSL_OP_NO_TICKET
2989 { US"no_ticket", SSL_OP_NO_TICKET },
2991 #ifdef SSL_OP_NO_TLSv1
2992 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2994 #ifdef SSL_OP_NO_TLSv1_1
2995 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2996 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2997 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2999 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
3002 #ifdef SSL_OP_NO_TLSv1_2
3003 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
3005 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
3006 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
3008 #ifdef SSL_OP_SINGLE_DH_USE
3009 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
3011 #ifdef SSL_OP_SINGLE_ECDH_USE
3012 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
3014 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
3015 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
3017 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
3018 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
3020 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
3021 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
3023 #ifdef SSL_OP_TLS_D5_BUG
3024 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
3026 #ifdef SSL_OP_TLS_ROLLBACK_BUG
3027 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
3030 static int exim_openssl_options_size =
3031 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
3035 tls_openssl_one_option_parse(uschar *name, long *value)
3038 int last = exim_openssl_options_size;
3039 while (last > first)
3041 int middle = (first + last)/2;
3042 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3045 *value = exim_openssl_options[middle].value;
3059 /*************************************************
3060 * OpenSSL option parsing logic *
3061 *************************************************/
3063 /* OpenSSL has a number of compatibility options which an administrator might
3064 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3065 we look like log_selector.
3068 option_spec the administrator-supplied string of options
3069 results ptr to long storage for the options bitmap
3070 Returns success or failure
3074 tls_openssl_options_parse(uschar *option_spec, long *results)
3079 BOOL adding, item_parsed;
3081 result = SSL_OP_NO_TICKET;
3082 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3083 * from default because it increases BEAST susceptibility. */
3084 #ifdef SSL_OP_NO_SSLv2
3085 result |= SSL_OP_NO_SSLv2;
3087 #ifdef SSL_OP_SINGLE_DH_USE
3088 result |= SSL_OP_SINGLE_DH_USE;
3097 for (s=option_spec; *s != '\0'; /**/)
3099 while (isspace(*s)) ++s;
3102 if (*s != '+' && *s != '-')
3104 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3105 "+ or - expected but found \"%s\"\n", s);
3108 adding = *s++ == '+';
3109 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3112 item_parsed = tls_openssl_one_option_parse(s, &item);
3116 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3119 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
3120 adding ? "adding" : "removing", result, item, s);
3134 /* End of tls-openssl.c */