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
49 # define EXIM_HAVE_OPENSSL_DH_BITS
51 # define EXIM_HAVE_EPHEM_RSA_KEX
52 # define EXIM_HAVE_RAND_PSEUDO
54 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
55 # define EXIM_HAVE_SHA256
59 * X509_check_host provides sane certificate hostname checking, but was added
60 * to OpenSSL late, after other projects forked off the code-base. So in
61 * addition to guarding against the base version number, beware that LibreSSL
62 * does not (at this time) support this function.
64 * If LibreSSL gains a different API, perhaps via libtls, then we'll probably
65 * opt to disentangle and ask a LibreSSL user to provide glue for a third
66 * crypto provider for libtls instead of continuing to tie the OpenSSL glue
67 * into even twistier knots. If LibreSSL gains the same API, we can just
68 * change this guard and punt the issue for a while longer.
70 #ifndef LIBRESSL_VERSION_NUMBER
71 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
72 # define EXIM_HAVE_OPENSSL_CHECKHOST
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 /* Structure for collecting random data for seeding. */
99 typedef struct randstuff {
104 /* Local static variables */
106 static BOOL client_verify_callback_called = FALSE;
107 static BOOL server_verify_callback_called = FALSE;
108 static const uschar *sid_ctx = US"exim";
110 /* We have three different contexts to care about.
112 Simple case: client, `client_ctx`
113 As a client, we can be doing a callout or cut-through delivery while receiving
114 a message. So we have a client context, which should have options initialised
115 from the SMTP Transport.
118 There are two cases: with and without ServerNameIndication from the client.
119 Given TLS SNI, we can be using different keys, certs and various other
120 configuration settings, because they're re-expanded with $tls_sni set. This
121 allows vhosting with TLS. This SNI is sent in the handshake.
122 A client might not send SNI, so we need a fallback, and an initial setup too.
123 So as a server, we start out using `server_ctx`.
124 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
125 `server_sni` from `server_ctx` and then initialise settings by re-expanding
129 static SSL_CTX *client_ctx = NULL;
130 static SSL_CTX *server_ctx = NULL;
131 static SSL *client_ssl = NULL;
132 static SSL *server_ssl = NULL;
134 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
135 static SSL_CTX *server_sni = NULL;
138 static char ssl_errstring[256];
140 static int ssl_session_timeout = 200;
141 static BOOL client_verify_optional = FALSE;
142 static BOOL server_verify_optional = FALSE;
144 static BOOL reexpand_tls_files_for_sni = FALSE;
147 typedef struct tls_ext_ctx_cb {
152 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
156 uschar *file_expanded;
157 OCSP_RESPONSE *response;
160 X509_STORE *verify_store; /* non-null if status requested */
161 BOOL verify_required;
166 /* these are cached from first expand */
167 uschar *server_cipher_list;
168 /* only passed down to tls_error: */
170 const uschar * verify_cert_hostnames;
171 #ifndef DISABLE_EVENT
172 uschar * event_action;
176 /* should figure out a cleanup of API to handle state preserved per
177 implementation, for various reasons, which can be void * in the APIs.
178 For now, we hack around it. */
179 tls_ext_ctx_cb *client_static_cbinfo = NULL;
180 tls_ext_ctx_cb *server_static_cbinfo = NULL;
183 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
184 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
187 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
188 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
191 static int tls_server_stapling_cb(SSL *s, void *arg);
195 /*************************************************
197 *************************************************/
199 /* Called from lots of places when errors occur before actually starting to do
200 the TLS handshake, that is, while the session is still in clear. Always returns
201 DEFER for a server and FAIL for a client so that most calls can use "return
202 tls_error(...)" to do this processing and then give an appropriate return. A
203 single function is used for both server and client, because it is called from
204 some shared functions.
207 prefix text to include in the logged error
208 host NULL if setting up a server;
209 the connected host if setting up a client
210 msg error message or NULL if we should ask OpenSSL
211 errstr pointer to output error message
213 Returns: OK/DEFER/FAIL
217 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
221 ERR_error_string(ERR_get_error(), ssl_errstring);
222 msg = US ssl_errstring;
225 if (errstr) *errstr = string_sprintf("(%s): %s", prefix, msg);
226 return host ? FAIL : DEFER;
231 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
232 /*************************************************
233 * Callback to generate RSA key *
234 *************************************************/
242 Returns: pointer to generated key
246 rsa_callback(SSL *s, int export, int keylength)
249 #ifdef EXIM_HAVE_RSA_GENKEY_EX
250 BIGNUM *bn = BN_new();
253 export = export; /* Shut picky compilers up */
254 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
256 #ifdef EXIM_HAVE_RSA_GENKEY_EX
257 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
258 || !(rsa_key = RSA_new())
259 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
262 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
266 ERR_error_string(ERR_get_error(), ssl_errstring);
267 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
280 x509_store_dump_cert_s_names(X509_STORE * store)
282 STACK_OF(X509_OBJECT) * roots= store->objs;
284 static uschar name[256];
286 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
288 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
289 if(tmp_obj->type == X509_LU_X509)
291 X509 * current_cert= tmp_obj->data.x509;
292 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
293 name[sizeof(name)-1] = '\0';
294 debug_printf(" %s\n", name);
302 #ifndef DISABLE_EVENT
304 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
305 BOOL *calledp, const BOOL *optionalp, const uschar * what)
311 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
314 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
315 old_cert = tlsp->peercert;
316 tlsp->peercert = X509_dup(cert);
317 /* NB we do not bother setting peerdn */
318 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
320 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
321 "depth=%d cert=%s: %s",
322 tlsp == &tls_out ? deliver_host_address : sender_host_address,
323 what, depth, dn, yield);
327 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
328 return 1; /* reject (leaving peercert set) */
330 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
331 "(host in tls_try_verify_hosts)\n");
333 X509_free(tlsp->peercert);
334 tlsp->peercert = old_cert;
340 /*************************************************
341 * Callback for verification *
342 *************************************************/
344 /* The SSL library does certificate verification if set up to do so. This
345 callback has the current yes/no state is in "state". If verification succeeded,
346 we set the certificate-verified flag. If verification failed, what happens
347 depends on whether the client is required to present a verifiable certificate
350 If verification is optional, we change the state to yes, but still log the
351 verification error. For some reason (it really would help to have proper
352 documentation of OpenSSL), this callback function then gets called again, this
353 time with state = 1. We must take care not to set the private verified flag on
354 the second time through.
356 Note: this function is not called if the client fails to present a certificate
357 when asked. We get here only if a certificate has been received. Handling of
358 optional verification for this case is done when requesting SSL to verify, by
359 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
361 May be called multiple times for different issues with a certificate, even
362 for a given "depth" in the certificate chain.
365 preverify_ok current yes/no state as 1/0
366 x509ctx certificate information.
367 tlsp per-direction (client vs. server) support data
368 calledp has-been-called flag
369 optionalp verification-is-optional flag
371 Returns: 0 if verification should fail, otherwise 1
375 verify_callback(int preverify_ok, X509_STORE_CTX *x509ctx,
376 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
378 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
379 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
382 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
383 dn[sizeof(dn)-1] = '\0';
385 if (preverify_ok == 0)
387 log_write(0, LOG_MAIN, "[%s] SSL verify error: depth=%d error=%s cert=%s",
388 tlsp == &tls_out ? deliver_host_address : sender_host_address,
390 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
396 tlsp->peercert = X509_dup(cert); /* record failing cert */
397 return 0; /* reject */
399 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
400 "tls_try_verify_hosts)\n");
405 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
407 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
408 { /* client, wanting stapling */
409 /* Add the server cert's signing chain as the one
410 for the verification of the OCSP stapled information. */
412 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
415 sk_X509_push(client_static_cbinfo->verify_stack, cert);
418 #ifndef DISABLE_EVENT
419 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
420 return 0; /* reject, with peercert set */
425 const uschar * verify_cert_hostnames;
427 if ( tlsp == &tls_out
428 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
429 /* client, wanting hostname check */
432 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
433 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
434 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
436 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
437 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
440 const uschar * list = verify_cert_hostnames;
443 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
444 if ((rc = X509_check_host(cert, CCS name, 0,
445 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
446 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
451 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
452 deliver_host_address);
459 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
462 log_write(0, LOG_MAIN,
463 "[%s] SSL verify error: certificate name mismatch: "
464 "DN=\"%s\" H=\"%s\"",
465 deliver_host_address, dn, verify_cert_hostnames);
470 tlsp->peercert = X509_dup(cert); /* record failing cert */
471 return 0; /* reject */
473 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
474 "tls_try_verify_hosts)\n");
478 #ifndef DISABLE_EVENT
479 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
480 return 0; /* reject, with peercert set */
483 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
484 *calledp ? "" : " authenticated", dn);
485 if (!*calledp) tlsp->certificate_verified = TRUE;
489 return 1; /* accept, at least for this level */
493 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
495 return verify_callback(preverify_ok, x509ctx, &tls_out,
496 &client_verify_callback_called, &client_verify_optional);
500 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
502 return verify_callback(preverify_ok, x509ctx, &tls_in,
503 &server_verify_callback_called, &server_verify_optional);
507 #ifdef EXPERIMENTAL_DANE
509 /* This gets called *by* the dane library verify callback, which interposes
513 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
515 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
517 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
518 #ifndef DISABLE_EVENT
519 BOOL dummy_called, optional = FALSE;
522 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
523 dn[sizeof(dn)-1] = '\0';
525 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
526 preverify_ok ? "ok":"BAD", depth, dn);
528 #ifndef DISABLE_EVENT
529 if (verify_event(&tls_out, cert, depth, dn,
530 &dummy_called, &optional, US"DANE"))
531 return 0; /* reject, with peercert set */
534 if (preverify_ok == 1)
535 tls_out.dane_verified =
536 tls_out.certificate_verified = TRUE;
539 int err = X509_STORE_CTX_get_error(x509ctx);
541 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
542 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
548 #endif /*EXPERIMENTAL_DANE*/
551 /*************************************************
552 * Information callback *
553 *************************************************/
555 /* The SSL library functions call this from time to time to indicate what they
556 are doing. We copy the string to the debugging output when TLS debugging has
568 info_callback(SSL *s, int where, int ret)
572 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
577 /*************************************************
578 * Initialize for DH *
579 *************************************************/
581 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
584 sctx The current SSL CTX (inbound or outbound)
585 dhparam DH parameter file or fixed parameter identity string
586 host connected host, if client; NULL if server
587 errstr error string pointer
589 Returns: TRUE if OK (nothing to set up, or setup worked)
593 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
601 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
604 if (!dhexpanded || !*dhexpanded)
605 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
606 else if (dhexpanded[0] == '/')
608 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
610 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
611 host, US strerror(errno), errstr);
617 if (Ustrcmp(dhexpanded, "none") == 0)
619 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
623 if (!(pem = std_dh_prime_named(dhexpanded)))
625 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
626 host, US strerror(errno), errstr);
629 bio = BIO_new_mem_buf(CS pem, -1);
632 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
635 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
640 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
641 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
642 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
643 * If someone wants to dance at the edge, then they can raise the limit or use
644 * current libraries. */
645 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
646 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
647 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
648 dh_bitsize = DH_bits(dh);
650 dh_bitsize = 8 * DH_size(dh);
653 /* Even if it is larger, we silently return success rather than cause things
654 * to fail out, so that a too-large DH will not knock out all TLS; it's a
655 * debatable choice. */
656 if (dh_bitsize > tls_dh_max_bits)
659 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
660 dh_bitsize, tls_dh_max_bits);
664 SSL_CTX_set_tmp_dh(sctx, dh);
666 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
667 dhexpanded ? dhexpanded : US"default", dh_bitsize);
679 /*************************************************
680 * Initialize for ECDH *
681 *************************************************/
683 /* Load parameters for ECDH encryption.
685 For now, we stick to NIST P-256 because: it's simple and easy to configure;
686 it avoids any patent issues that might bite redistributors; despite events in
687 the news and concerns over curve choices, we're not cryptographers, we're not
688 pretending to be, and this is "good enough" to be better than no support,
689 protecting against most adversaries. Given another year or two, there might
690 be sufficient clarity about a "right" way forward to let us make an informed
691 decision, instead of a knee-jerk reaction.
693 Longer-term, we should look at supporting both various named curves and
694 external files generated with "openssl ecparam", much as we do for init_dh().
695 We should also support "none" as a value, to explicitly avoid initialisation.
700 sctx The current SSL CTX (inbound or outbound)
701 host connected host, if client; NULL if server
702 errstr error string pointer
704 Returns: TRUE if OK (nothing to set up, or setup worked)
708 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
710 #ifdef OPENSSL_NO_ECDH
719 if (host) /* No ECDH setup for clients, only for servers */
722 # ifndef EXIM_HAVE_ECDH
724 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
728 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
730 if (!exp_curve || !*exp_curve)
733 /* "auto" needs to be handled carefully.
734 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
735 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
736 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
737 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
738 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
740 if (Ustrcmp(exp_curve, "auto") == 0)
742 #if OPENSSL_VERSION_NUMBER < 0x10002000L
743 DEBUG(D_tls) debug_printf(
744 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
745 exp_curve = US"prime256v1";
747 # if defined SSL_CTRL_SET_ECDH_AUTO
748 DEBUG(D_tls) debug_printf(
749 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
750 SSL_CTX_set_ecdh_auto(sctx, 1);
753 DEBUG(D_tls) debug_printf(
754 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
760 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
761 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
762 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
763 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
767 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
772 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
774 tls_error(US"Unable to create ec curve", host, NULL, errstr);
778 /* The "tmp" in the name here refers to setting a temporary key
779 not to the stability of the interface. */
781 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
782 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
784 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
789 # endif /*EXIM_HAVE_ECDH*/
790 #endif /*OPENSSL_NO_ECDH*/
797 /*************************************************
798 * Load OCSP information into state *
799 *************************************************/
800 /* Called to load the server OCSP response from the given file into memory, once
801 caller has determined this is needed. Checks validity. Debugs a message
804 ASSUMES: single response, for single cert.
807 sctx the SSL_CTX* to update
808 cbinfo various parts of session state
809 expanded the filename putatively holding an OCSP response
814 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
817 OCSP_RESPONSE * resp;
818 OCSP_BASICRESP * basic_response;
819 OCSP_SINGLERESP * single_response;
820 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
822 unsigned long verify_flags;
823 int status, reason, i;
825 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
826 if (cbinfo->u_ocsp.server.response)
828 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
829 cbinfo->u_ocsp.server.response = NULL;
832 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
834 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
835 cbinfo->u_ocsp.server.file_expanded);
839 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
843 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
847 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
849 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
850 OCSP_response_status_str(status), status);
854 if (!(basic_response = OCSP_response_get1_basic(resp)))
857 debug_printf("OCSP response parse error: unable to extract basic response.\n");
861 sk = cbinfo->verify_stack;
862 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
864 /* May need to expose ability to adjust those flags?
865 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
866 OCSP_TRUSTOTHER OCSP_NOINTERN */
868 /* This does a full verify on the OCSP proof before we load it for serving
869 up; possibly overkill - just date-checks might be nice enough.
871 OCSP_basic_verify takes a "store" arg, but does not
872 use it for the chain verification, which is all we do
873 when OCSP_NOVERIFY is set. The content from the wire
874 "basic_response" and a cert-stack "sk" are all that is used.
876 We have a stack, loaded in setup_certs() if tls_verify_certificates
877 was a file (not a directory, or "system"). It is unfortunate we
878 cannot used the connection context store, as that would neatly
879 handle the "system" case too, but there seems to be no library
880 function for getting a stack from a store.
881 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
882 We do not free the stack since it could be needed a second time for
885 Separately we might try to replace using OCSP_basic_verify() - which seems to not
886 be a public interface into the OpenSSL library (there's no manual entry) -
887 But what with? We also use OCSP_basic_verify in the client stapling callback.
888 And there we NEED it; we must verify that status... unless the
889 library does it for us anyway? */
891 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
895 ERR_error_string(ERR_get_error(), ssl_errstring);
896 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
901 /* Here's the simplifying assumption: there's only one response, for the
902 one certificate we use, and nothing for anything else in a chain. If this
903 proves false, we need to extract a cert id from our issued cert
904 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
905 right cert in the stack and then calls OCSP_single_get0_status()).
907 I'm hoping to avoid reworking a bunch more of how we handle state here. */
909 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
912 debug_printf("Unable to get first response from OCSP basic response.\n");
916 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
917 if (status != V_OCSP_CERTSTATUS_GOOD)
919 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
920 OCSP_cert_status_str(status), status,
921 OCSP_crl_reason_str(reason), reason);
925 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
927 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
932 cbinfo->u_ocsp.server.response = resp;
936 if (running_in_test_harness)
938 extern char ** environ;
940 if (environ) for (p = USS environ; *p != NULL; p++)
941 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
943 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
944 goto supply_response;
949 #endif /*!DISABLE_OCSP*/
954 /* Create and install a selfsigned certificate, for use in server mode */
957 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
965 where = US"allocating pkey";
966 if (!(pkey = EVP_PKEY_new()))
969 where = US"allocating cert";
970 if (!(x509 = X509_new()))
973 where = US"generating pkey";
974 /* deprecated, use RSA_generate_key_ex() */
975 if (!(rsa = RSA_generate_key(1024, RSA_F4, NULL, NULL)))
978 where = US"assigning pkey";
979 if (!EVP_PKEY_assign_RSA(pkey, rsa))
982 X509_set_version(x509, 2); /* N+1 - version 3 */
983 ASN1_INTEGER_set(X509_get_serialNumber(x509), 0);
984 X509_gmtime_adj(X509_get_notBefore(x509), 0);
985 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
986 X509_set_pubkey(x509, pkey);
988 name = X509_get_subject_name(x509);
989 X509_NAME_add_entry_by_txt(name, "C",
990 MBSTRING_ASC, CUS "UK", -1, -1, 0);
991 X509_NAME_add_entry_by_txt(name, "O",
992 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
993 X509_NAME_add_entry_by_txt(name, "CN",
994 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
995 X509_set_issuer_name(x509, name);
997 where = US"signing cert";
998 if (!X509_sign(x509, pkey, EVP_md5()))
1001 where = US"installing selfsign cert";
1002 if (!SSL_CTX_use_certificate(sctx, x509))
1005 where = US"installing selfsign key";
1006 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1012 (void) tls_error(where, NULL, NULL, errstr);
1013 if (x509) X509_free(x509);
1014 if (pkey) EVP_PKEY_free(pkey);
1021 /*************************************************
1022 * Expand key and cert file specs *
1023 *************************************************/
1025 /* Called once during tls_init and possibly again during TLS setup, for a
1026 new context, if Server Name Indication was used and tls_sni was seen in
1027 the certificate string.
1030 sctx the SSL_CTX* to update
1031 cbinfo various parts of session state
1032 errstr error string pointer
1034 Returns: OK/DEFER/FAIL
1038 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1043 if (!cbinfo->certificate)
1045 if (cbinfo->host) /* client */
1048 if (tls_install_selfsign(sctx, errstr) != OK)
1053 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1054 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1055 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1057 reexpand_tls_files_for_sni = TRUE;
1059 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1062 if (expanded != NULL)
1064 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
1065 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
1066 return tls_error(string_sprintf(
1067 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
1068 cbinfo->host, NULL, errstr);
1071 if (cbinfo->privatekey != NULL &&
1072 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1075 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1076 of the expansion is an empty string, ignore it also, and assume the private
1077 key is in the same file as the certificate. */
1079 if (expanded && *expanded)
1081 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
1082 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
1083 return tls_error(string_sprintf(
1084 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL, errstr);
1088 #ifndef DISABLE_OCSP
1089 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1091 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1094 if (expanded && *expanded)
1096 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1097 if ( cbinfo->u_ocsp.server.file_expanded
1098 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1100 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1103 ocsp_load_response(sctx, cbinfo, expanded);
1114 /*************************************************
1115 * Callback to handle SNI *
1116 *************************************************/
1118 /* Called when acting as server during the TLS session setup if a Server Name
1119 Indication extension was sent by the client.
1121 API documentation is OpenSSL s_server.c implementation.
1124 s SSL* of the current session
1125 ad unknown (part of OpenSSL API) (unused)
1126 arg Callback of "our" registered data
1128 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1131 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1133 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1135 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1136 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1138 int old_pool = store_pool;
1139 uschar * dummy_errstr;
1142 return SSL_TLSEXT_ERR_OK;
1144 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1145 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1147 /* Make the extension value available for expansion */
1148 store_pool = POOL_PERM;
1149 tls_in.sni = string_copy(US servername);
1150 store_pool = old_pool;
1152 if (!reexpand_tls_files_for_sni)
1153 return SSL_TLSEXT_ERR_OK;
1155 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1156 not confident that memcpy wouldn't break some internal reference counting.
1157 Especially since there's a references struct member, which would be off. */
1159 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1161 ERR_error_string(ERR_get_error(), ssl_errstring);
1162 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1163 return SSL_TLSEXT_ERR_NOACK;
1166 /* Not sure how many of these are actually needed, since SSL object
1167 already exists. Might even need this selfsame callback, for reneg? */
1169 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1170 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1171 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1172 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1173 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1174 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1176 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1177 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1179 return SSL_TLSEXT_ERR_NOACK;
1181 if (cbinfo->server_cipher_list)
1182 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
1183 #ifndef DISABLE_OCSP
1184 if (cbinfo->u_ocsp.server.file)
1186 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1187 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1191 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1192 verify_callback_server, &dummy_errstr)) != OK)
1193 return SSL_TLSEXT_ERR_NOACK;
1195 /* do this after setup_certs, because this can require the certs for verifying
1196 OCSP information. */
1197 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1198 return SSL_TLSEXT_ERR_NOACK;
1200 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1201 SSL_set_SSL_CTX(s, server_sni);
1203 return SSL_TLSEXT_ERR_OK;
1205 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1210 #ifndef DISABLE_OCSP
1212 /*************************************************
1213 * Callback to handle OCSP Stapling *
1214 *************************************************/
1216 /* Called when acting as server during the TLS session setup if the client
1217 requests OCSP information with a Certificate Status Request.
1219 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1225 tls_server_stapling_cb(SSL *s, void *arg)
1227 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1228 uschar *response_der;
1229 int response_der_len;
1232 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1233 cbinfo->u_ocsp.server.response ? "have" : "lack");
1235 tls_in.ocsp = OCSP_NOT_RESP;
1236 if (!cbinfo->u_ocsp.server.response)
1237 return SSL_TLSEXT_ERR_NOACK;
1239 response_der = NULL;
1240 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
1242 if (response_der_len <= 0)
1243 return SSL_TLSEXT_ERR_NOACK;
1245 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1246 tls_in.ocsp = OCSP_VFIED;
1247 return SSL_TLSEXT_ERR_OK;
1252 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1254 BIO_printf(bp, "\t%s: ", str);
1255 ASN1_GENERALIZEDTIME_print(bp, time);
1260 tls_client_stapling_cb(SSL *s, void *arg)
1262 tls_ext_ctx_cb * cbinfo = arg;
1263 const unsigned char * p;
1265 OCSP_RESPONSE * rsp;
1266 OCSP_BASICRESP * bs;
1269 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1270 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1273 /* Expect this when we requested ocsp but got none */
1274 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1275 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1277 DEBUG(D_tls) debug_printf(" null\n");
1278 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1281 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1283 tls_out.ocsp = OCSP_FAILED;
1284 if (LOGGING(tls_cipher))
1285 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1287 DEBUG(D_tls) debug_printf(" parse error\n");
1291 if(!(bs = OCSP_response_get1_basic(rsp)))
1293 tls_out.ocsp = OCSP_FAILED;
1294 if (LOGGING(tls_cipher))
1295 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1297 DEBUG(D_tls) debug_printf(" error parsing response\n");
1298 OCSP_RESPONSE_free(rsp);
1302 /* We'd check the nonce here if we'd put one in the request. */
1303 /* However that would defeat cacheability on the server so we don't. */
1305 /* This section of code reworked from OpenSSL apps source;
1306 The OpenSSL Project retains copyright:
1307 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1312 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1314 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
1316 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1318 /* Use the chain that verified the server cert to verify the stapled info */
1319 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1321 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1322 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1324 tls_out.ocsp = OCSP_FAILED;
1325 if (LOGGING(tls_cipher))
1326 log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
1327 BIO_printf(bp, "OCSP response verify failure\n");
1328 ERR_print_errors(bp);
1332 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1334 /*XXX So we have a good stapled OCSP status. How do we know
1335 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1336 OCSP_resp_find_status() which matches on a cert id, which presumably
1337 we should use. Making an id needs OCSP_cert_id_new(), which takes
1338 issuerName, issuerKey, serialNumber. Are they all in the cert?
1340 For now, carry on blindly accepting the resp. */
1343 OCSP_SINGLERESP * single;
1345 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1346 if (OCSP_resp_count(bs) != 1)
1348 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1349 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1352 tls_out.ocsp = OCSP_FAILED;
1353 log_write(0, LOG_MAIN, "OCSP stapling "
1354 "with multiple responses not handled");
1357 single = OCSP_resp_get0(bs, 0);
1358 status = OCSP_single_get0_status(single, &reason, &rev,
1359 &thisupd, &nextupd);
1362 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1363 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1364 if (!OCSP_check_validity(thisupd, nextupd,
1365 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1367 tls_out.ocsp = OCSP_FAILED;
1368 DEBUG(D_tls) ERR_print_errors(bp);
1369 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1373 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1374 OCSP_cert_status_str(status));
1377 case V_OCSP_CERTSTATUS_GOOD:
1378 tls_out.ocsp = OCSP_VFIED;
1381 case V_OCSP_CERTSTATUS_REVOKED:
1382 tls_out.ocsp = OCSP_FAILED;
1383 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1384 reason != -1 ? "; reason: " : "",
1385 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1386 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1389 tls_out.ocsp = OCSP_FAILED;
1390 log_write(0, LOG_MAIN,
1391 "Server certificate status unknown, in OCSP stapling");
1396 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1401 OCSP_RESPONSE_free(rsp);
1404 #endif /*!DISABLE_OCSP*/
1407 /*************************************************
1408 * Initialize for TLS *
1409 *************************************************/
1411 /* Called from both server and client code, to do preliminary initialization
1412 of the library. We allocate and return a context structure.
1415 ctxp returned SSL context
1416 host connected host, if client; NULL if server
1417 dhparam DH parameter file
1418 certificate certificate file
1419 privatekey private key
1420 ocsp_file file of stapling info (server); flag for require ocsp (client)
1421 addr address if client; NULL if server (for some randomness)
1422 cbp place to put allocated callback context
1423 errstr error string pointer
1425 Returns: OK/DEFER/FAIL
1429 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1431 #ifndef DISABLE_OCSP
1434 address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1439 tls_ext_ctx_cb * cbinfo;
1441 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1442 cbinfo->certificate = certificate;
1443 cbinfo->privatekey = privatekey;
1444 #ifndef DISABLE_OCSP
1445 cbinfo->verify_stack = NULL;
1446 if ((cbinfo->is_server = host==NULL))
1448 cbinfo->u_ocsp.server.file = ocsp_file;
1449 cbinfo->u_ocsp.server.file_expanded = NULL;
1450 cbinfo->u_ocsp.server.response = NULL;
1453 cbinfo->u_ocsp.client.verify_store = NULL;
1455 cbinfo->dhparam = dhparam;
1456 cbinfo->server_cipher_list = NULL;
1457 cbinfo->host = host;
1458 #ifndef DISABLE_EVENT
1459 cbinfo->event_action = NULL;
1462 SSL_load_error_strings(); /* basic set up */
1463 OpenSSL_add_ssl_algorithms();
1465 #ifdef EXIM_HAVE_SHA256
1466 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1467 list of available digests. */
1468 EVP_add_digest(EVP_sha256());
1471 /* Create a context.
1472 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1473 negotiation in the different methods; as far as I can tell, the only
1474 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1475 when OpenSSL is built without SSLv2 support.
1476 By disabling with openssl_options, we can let admins re-enable with the
1479 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1480 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1482 /* It turns out that we need to seed the random number generator this early in
1483 order to get the full complement of ciphers to work. It took me roughly a day
1484 of work to discover this by experiment.
1486 On systems that have /dev/urandom, SSL may automatically seed itself from
1487 there. Otherwise, we have to make something up as best we can. Double check
1493 gettimeofday(&r.tv, NULL);
1496 RAND_seed((uschar *)(&r), sizeof(r));
1497 RAND_seed((uschar *)big_buffer, big_buffer_size);
1498 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1501 return tls_error(US"RAND_status", host,
1502 US"unable to seed random number generator", errstr);
1505 /* Set up the information callback, which outputs if debugging is at a suitable
1508 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1510 /* Automatically re-try reads/writes after renegotiation. */
1511 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1513 /* Apply administrator-supplied work-arounds.
1514 Historically we applied just one requested option,
1515 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1516 moved to an administrator-controlled list of options to specify and
1517 grandfathered in the first one as the default value for "openssl_options".
1519 No OpenSSL version number checks: the options we accept depend upon the
1520 availability of the option value macros from OpenSSL. */
1522 if (!tls_openssl_options_parse(openssl_options, &init_options))
1523 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1527 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1528 if (!(SSL_CTX_set_options(ctx, init_options)))
1529 return tls_error(string_sprintf(
1530 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1533 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1535 /* Disable session cache unconditionally */
1537 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1539 /* Initialize with DH parameters if supplied */
1540 /* Initialize ECDH temp key parameter selection */
1542 if ( !init_dh(ctx, dhparam, host, errstr)
1543 || !init_ecdh(ctx, host, errstr)
1547 /* Set up certificate and key (and perhaps OCSP info) */
1549 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1552 /* If we need to handle SNI or OCSP, do so */
1554 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1555 # ifndef DISABLE_OCSP
1556 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1558 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1563 if (host == NULL) /* server */
1565 # ifndef DISABLE_OCSP
1566 /* We check u_ocsp.server.file, not server.response, because we care about if
1567 the option exists, not what the current expansion might be, as SNI might
1568 change the certificate and OCSP file in use between now and the time the
1569 callback is invoked. */
1570 if (cbinfo->u_ocsp.server.file)
1572 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1573 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1576 /* We always do this, so that $tls_sni is available even if not used in
1578 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1579 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1581 # ifndef DISABLE_OCSP
1583 if(ocsp_file) /* wanting stapling */
1585 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1587 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1590 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1591 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1596 cbinfo->verify_cert_hostnames = NULL;
1598 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1599 /* Set up the RSA callback */
1600 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1603 /* Finally, set the timeout, and we are done */
1605 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1606 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1617 /*************************************************
1618 * Get name of cipher in use *
1619 *************************************************/
1622 Argument: pointer to an SSL structure for the connection
1623 buffer to use for answer
1625 pointer to number of bits for cipher
1630 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1632 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1633 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1634 the accessor functions use const in the prototype. */
1635 const SSL_CIPHER *c;
1638 ver = (const uschar *)SSL_get_version(ssl);
1640 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1641 SSL_CIPHER_get_bits(c, bits);
1643 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1644 SSL_CIPHER_get_name(c), *bits);
1646 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1651 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned bsize)
1653 /*XXX we might consider a list-of-certs variable for the cert chain.
1654 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1655 in list-handling functions, also consider the difference between the entire
1656 chain and the elements sent by the peer. */
1658 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1659 if (!tlsp->peercert)
1660 tlsp->peercert = SSL_get_peer_certificate(ssl);
1661 /* Beware anonymous ciphers which lead to server_cert being NULL */
1664 X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, bsize);
1665 peerdn[bsize-1] = '\0';
1666 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1669 tlsp->peerdn = NULL;
1676 /*************************************************
1677 * Set up for verifying certificates *
1678 *************************************************/
1680 /* Load certs from file, return TRUE on success */
1683 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
1688 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
1689 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
1690 sk_X509_push(verify_stack, x);
1697 /* Called by both client and server startup
1700 sctx SSL_CTX* to initialise
1701 certs certs file or NULL
1702 crl CRL file or NULL
1703 host NULL in a server; the remote host in a client
1704 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1705 otherwise passed as FALSE
1706 cert_vfy_cb Callback function for certificate verification
1707 errstr error string pointer
1709 Returns: OK/DEFER/FAIL
1713 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1714 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
1716 uschar *expcerts, *expcrl;
1718 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
1720 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
1722 if (expcerts && *expcerts)
1724 /* Tell the library to use its compiled-in location for the system default
1725 CA bundle. Then add the ones specified in the config, if any. */
1727 if (!SSL_CTX_set_default_verify_paths(sctx))
1728 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
1730 if (Ustrcmp(expcerts, "system") != 0)
1732 struct stat statbuf;
1734 if (Ustat(expcerts, &statbuf) < 0)
1736 log_write(0, LOG_MAIN|LOG_PANIC,
1737 "failed to stat %s for certificates", expcerts);
1743 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1744 { file = NULL; dir = expcerts; }
1747 file = expcerts; dir = NULL;
1748 #ifndef DISABLE_OCSP
1749 /* In the server if we will be offering an OCSP proof, load chain from
1750 file for verifying the OCSP proof at load time. */
1753 && statbuf.st_size > 0
1754 && server_static_cbinfo->u_ocsp.server.file
1755 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
1758 log_write(0, LOG_MAIN|LOG_PANIC,
1759 "failed to load cert hain from %s", file);
1765 /* If a certificate file is empty, the next function fails with an
1766 unhelpful error message. If we skip it, we get the correct behaviour (no
1767 certificates are recognized, but the error message is still misleading (it
1768 says no certificate was supplied). But this is better. */
1770 if ( (!file || statbuf.st_size > 0)
1771 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1772 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
1774 /* Load the list of CAs for which we will accept certs, for sending
1775 to the client. This is only for the one-file tls_verify_certificates
1777 If a list isn't loaded into the server, but
1778 some verify locations are set, the server end appears to make
1779 a wildcard request for client certs.
1780 Meanwhile, the client library as default behaviour *ignores* the list
1781 we send over the wire - see man SSL_CTX_set_client_cert_cb.
1782 Because of this, and that the dir variant is likely only used for
1783 the public-CA bundle (not for a private CA), not worth fixing.
1787 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
1789 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
1790 sk_X509_NAME_num(names));
1791 SSL_CTX_set_client_CA_list(sctx, names);
1796 /* Handle a certificate revocation list. */
1798 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1800 /* This bit of code is now the version supplied by Lars Mainka. (I have
1801 merely reformatted it into the Exim code style.)
1803 "From here I changed the code to add support for multiple crl's
1804 in pem format in one file or to support hashed directory entries in
1805 pem format instead of a file. This method now uses the library function
1806 X509_STORE_load_locations to add the CRL location to the SSL context.
1807 OpenSSL will then handle the verify against CA certs and CRLs by
1808 itself in the verify callback." */
1810 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
1811 if (expcrl && *expcrl)
1813 struct stat statbufcrl;
1814 if (Ustat(expcrl, &statbufcrl) < 0)
1816 log_write(0, LOG_MAIN|LOG_PANIC,
1817 "failed to stat %s for certificates revocation lists", expcrl);
1822 /* is it a file or directory? */
1824 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1825 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1829 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1835 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1837 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1838 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
1840 /* setting the flags to check against the complete crl chain */
1842 X509_STORE_set_flags(cvstore,
1843 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1847 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1849 /* If verification is optional, don't fail if no certificate */
1851 SSL_CTX_set_verify(sctx,
1852 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1861 /*************************************************
1862 * Start a TLS session in a server *
1863 *************************************************/
1865 /* This is called when Exim is running as a server, after having received
1866 the STARTTLS command. It must respond to that command, and then negotiate
1870 require_ciphers allowed ciphers
1871 errstr pointer to error message
1873 Returns: OK on success
1874 DEFER for errors before the start of the negotiation
1875 FAIL for errors during the negotiation; the server can't
1880 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
1883 uschar * expciphers;
1884 tls_ext_ctx_cb * cbinfo;
1885 static uschar peerdn[256];
1886 static uschar cipherbuf[256];
1888 /* Check for previous activation */
1890 if (tls_in.active >= 0)
1892 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
1893 smtp_printf("554 Already in TLS\r\n", FALSE);
1897 /* Initialize the SSL library. If it fails, it will already have logged
1900 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1901 #ifndef DISABLE_OCSP
1904 NULL, &server_static_cbinfo, errstr);
1905 if (rc != OK) return rc;
1906 cbinfo = server_static_cbinfo;
1908 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
1911 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1912 were historically separated by underscores. So that I can use either form in my
1913 tests, and also for general convenience, we turn underscores into hyphens here.
1918 uschar * s = expciphers;
1919 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1920 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1921 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1922 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
1923 cbinfo->server_cipher_list = expciphers;
1926 /* If this is a host for which certificate verification is mandatory or
1927 optional, set up appropriately. */
1929 tls_in.certificate_verified = FALSE;
1930 #ifdef EXPERIMENTAL_DANE
1931 tls_in.dane_verified = FALSE;
1933 server_verify_callback_called = FALSE;
1935 if (verify_check_host(&tls_verify_hosts) == OK)
1937 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1938 FALSE, verify_callback_server, errstr);
1939 if (rc != OK) return rc;
1940 server_verify_optional = FALSE;
1942 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1944 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1945 TRUE, verify_callback_server, errstr);
1946 if (rc != OK) return rc;
1947 server_verify_optional = TRUE;
1950 /* Prepare for new connection */
1952 if (!(server_ssl = SSL_new(server_ctx)))
1953 return tls_error(US"SSL_new", NULL, NULL, errstr);
1955 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1957 * With the SSL_clear(), we get strange interoperability bugs with
1958 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1959 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1961 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1962 * session shutdown. In this case, we have a brand new object and there's no
1963 * obvious reason to immediately clear it. I'm guessing that this was
1964 * originally added because of incomplete initialisation which the clear fixed,
1965 * in some historic release.
1968 /* Set context and tell client to go ahead, except in the case of TLS startup
1969 on connection, where outputting anything now upsets the clients and tends to
1970 make them disconnect. We need to have an explicit fflush() here, to force out
1971 the response. Other smtp_printf() calls do not need it, because in non-TLS
1972 mode, the fflush() happens when smtp_getc() is called. */
1974 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1975 if (!tls_in.on_connect)
1977 smtp_printf("220 TLS go ahead\r\n", FALSE);
1981 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1982 that the OpenSSL library doesn't. */
1984 SSL_set_wfd(server_ssl, fileno(smtp_out));
1985 SSL_set_rfd(server_ssl, fileno(smtp_in));
1986 SSL_set_accept_state(server_ssl);
1988 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1990 sigalrm_seen = FALSE;
1991 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1992 rc = SSL_accept(server_ssl);
1997 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2001 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2003 /* TLS has been set up. Adjust the input functions to read via TLS,
2004 and initialize things. */
2006 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2008 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
2009 tls_in.cipher = cipherbuf;
2014 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
2015 debug_printf("Shared ciphers: %s\n", buf);
2018 /* Record the certificate we presented */
2020 X509 * crt = SSL_get_certificate(server_ssl);
2021 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2024 /* Only used by the server-side tls (tls_in), including tls_getc.
2025 Client-side (tls_out) reads (seem to?) go via
2026 smtp_read_response()/ip_recv().
2027 Hence no need to duplicate for _in and _out.
2029 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2030 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2031 ssl_xfer_eof = ssl_xfer_error = 0;
2033 receive_getc = tls_getc;
2034 receive_getbuf = tls_getbuf;
2035 receive_get_cache = tls_get_cache;
2036 receive_ungetc = tls_ungetc;
2037 receive_feof = tls_feof;
2038 receive_ferror = tls_ferror;
2039 receive_smtp_buffered = tls_smtp_buffered;
2041 tls_in.active = fileno(smtp_out);
2049 tls_client_basic_ctx_init(SSL_CTX * ctx,
2050 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2054 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2055 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2056 the specified host patterns if one of them is defined */
2058 if ( ( !ob->tls_verify_hosts
2059 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2061 || (verify_check_given_host(&ob->tls_verify_hosts, host) == OK)
2063 client_verify_optional = FALSE;
2064 else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK)
2065 client_verify_optional = TRUE;
2069 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2070 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2074 if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
2076 cbinfo->verify_cert_hostnames =
2078 string_domain_utf8_to_alabel(host->name, NULL);
2082 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2083 cbinfo->verify_cert_hostnames);
2089 #ifdef EXPERIMENTAL_DANE
2091 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2095 const char * hostnames[2] = { CS host->name, NULL };
2098 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2099 return tls_error(US"hostnames load", host, NULL, errstr);
2101 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
2103 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2104 ) if (rr->type == T_TLSA)
2106 const uschar * p = rr->data;
2107 uint8_t usage, selector, mtype;
2108 const char * mdname;
2112 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2113 if (usage != 2 && usage != 3) continue;
2120 default: continue; /* Only match-types 0, 1, 2 are supported */
2121 case 0: mdname = NULL; break;
2122 case 1: mdname = "sha256"; break;
2123 case 2: mdname = "sha512"; break;
2127 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2130 return tls_error(US"tlsa load", host, NULL, errstr);
2131 case 0: /* action not taken */
2135 tls_out.tlsa_usage |= 1<<usage;
2141 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2144 #endif /*EXPERIMENTAL_DANE*/
2148 /*************************************************
2149 * Start a TLS session in a client *
2150 *************************************************/
2152 /* Called from the smtp transport after STARTTLS has been accepted.
2155 fd the fd of the connection
2156 host connected host (for messages)
2157 addr the first address
2158 tb transport (always smtp)
2159 tlsa_dnsa tlsa lookup, if DANE, else null
2160 errstr error string pointer
2162 Returns: OK on success
2163 FAIL otherwise - note that tls_error() will not give DEFER
2164 because this is not a server
2168 tls_client_start(int fd, host_item *host, address_item *addr,
2169 transport_instance * tb,
2170 #ifdef EXPERIMENTAL_DANE
2171 dns_answer * tlsa_dnsa,
2175 smtp_transport_options_block * ob =
2176 (smtp_transport_options_block *)tb->options_block;
2177 static uschar peerdn[256];
2178 uschar * expciphers;
2180 static uschar cipherbuf[256];
2182 #ifndef DISABLE_OCSP
2183 BOOL request_ocsp = FALSE;
2184 BOOL require_ocsp = FALSE;
2187 #ifdef EXPERIMENTAL_DANE
2188 tls_out.tlsa_usage = 0;
2191 #ifndef DISABLE_OCSP
2193 # ifdef EXPERIMENTAL_DANE
2195 && ob->hosts_request_ocsp[0] == '*'
2196 && ob->hosts_request_ocsp[1] == '\0'
2199 /* Unchanged from default. Use a safer one under DANE */
2200 request_ocsp = TRUE;
2201 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2202 " {= {4}{$tls_out_tlsa_usage}} } "
2208 verify_check_given_host(&ob->hosts_require_ocsp, host) == OK))
2209 request_ocsp = TRUE;
2211 # ifdef EXPERIMENTAL_DANE
2215 verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2219 rc = tls_init(&client_ctx, host, NULL,
2220 ob->tls_certificate, ob->tls_privatekey,
2221 #ifndef DISABLE_OCSP
2222 (void *)(long)request_ocsp,
2224 addr, &client_static_cbinfo, errstr);
2225 if (rc != OK) return rc;
2227 tls_out.certificate_verified = FALSE;
2228 client_verify_callback_called = FALSE;
2230 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2231 &expciphers, errstr))
2234 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2235 are separated by underscores. So that I can use either form in my tests, and
2236 also for general convenience, we turn underscores into hyphens here. */
2240 uschar *s = expciphers;
2241 while (*s) { if (*s == '_') *s = '-'; s++; }
2242 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2243 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
2244 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2247 #ifdef EXPERIMENTAL_DANE
2250 SSL_CTX_set_verify(client_ctx,
2251 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2252 verify_callback_client_dane);
2254 if (!DANESSL_library_init())
2255 return tls_error(US"library init", host, NULL, errstr);
2256 if (DANESSL_CTX_init(client_ctx) <= 0)
2257 return tls_error(US"context init", host, NULL, errstr);
2263 if ((rc = tls_client_basic_ctx_init(client_ctx, host, ob,
2264 client_static_cbinfo, errstr)) != OK)
2267 if ((client_ssl = SSL_new(client_ctx)) == NULL)
2268 return tls_error(US"SSL_new", host, NULL, errstr);
2269 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
2270 SSL_set_fd(client_ssl, fd);
2271 SSL_set_connect_state(client_ssl);
2275 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni, errstr))
2279 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2281 else if (!Ustrlen(tls_out.sni))
2285 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2286 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
2287 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
2289 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2295 #ifdef EXPERIMENTAL_DANE
2297 if ((rc = dane_tlsa_load(client_ssl, host, tlsa_dnsa, errstr)) != OK)
2301 #ifndef DISABLE_OCSP
2302 /* Request certificate status at connection-time. If the server
2303 does OCSP stapling we will get the callback (set in tls_init()) */
2304 # ifdef EXPERIMENTAL_DANE
2308 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2309 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2311 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2312 this means we avoid the OCSP request, we wasted the setup
2313 cost in tls_init(). */
2314 require_ocsp = verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
2315 request_ocsp = require_ocsp
2316 || verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2323 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
2324 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2325 tls_out.ocsp = OCSP_NOT_RESP;
2329 #ifndef DISABLE_EVENT
2330 client_static_cbinfo->event_action = tb->event_action;
2333 /* There doesn't seem to be a built-in timeout on connection. */
2335 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2336 sigalrm_seen = FALSE;
2337 alarm(ob->command_timeout);
2338 rc = SSL_connect(client_ssl);
2341 #ifdef EXPERIMENTAL_DANE
2343 DANESSL_cleanup(client_ssl);
2347 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL,
2350 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
2352 peer_cert(client_ssl, &tls_out, peerdn, sizeof(peerdn));
2354 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
2355 tls_out.cipher = cipherbuf;
2357 /* Record the certificate we presented */
2359 X509 * crt = SSL_get_certificate(client_ssl);
2360 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
2363 tls_out.active = fd;
2372 tls_refill(unsigned lim)
2377 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2378 ssl_xfer_buffer, ssl_xfer_buffer_size);
2380 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2381 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2382 MIN(ssl_xfer_buffer_size, lim));
2383 error = SSL_get_error(server_ssl, inbytes);
2386 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2387 closed down, not that the socket itself has been closed down. Revert to
2388 non-SSL handling. */
2390 if (error == SSL_ERROR_ZERO_RETURN)
2392 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2394 receive_getc = smtp_getc;
2395 receive_getbuf = smtp_getbuf;
2396 receive_get_cache = smtp_get_cache;
2397 receive_ungetc = smtp_ungetc;
2398 receive_feof = smtp_feof;
2399 receive_ferror = smtp_ferror;
2400 receive_smtp_buffered = smtp_buffered;
2402 SSL_free(server_ssl);
2406 tls_in.cipher = NULL;
2407 tls_in.peerdn = NULL;
2413 /* Handle genuine errors */
2415 else if (error == SSL_ERROR_SSL)
2417 ERR_error_string(ERR_get_error(), ssl_errstring);
2418 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2423 else if (error != SSL_ERROR_NONE)
2425 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2430 #ifndef DISABLE_DKIM
2431 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2433 ssl_xfer_buffer_hwm = inbytes;
2434 ssl_xfer_buffer_lwm = 0;
2439 /*************************************************
2440 * TLS version of getc *
2441 *************************************************/
2443 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2444 it refills the buffer via the SSL reading function.
2446 Arguments: lim Maximum amount to read/buffer
2447 Returns: the next character or EOF
2449 Only used by the server-side TLS.
2453 tls_getc(unsigned lim)
2455 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2456 if (!tls_refill(lim))
2457 return ssl_xfer_error ? EOF : smtp_getc(lim);
2459 /* Something in the buffer; return next uschar */
2461 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2465 tls_getbuf(unsigned * len)
2470 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2471 if (!tls_refill(*len))
2473 if (!ssl_xfer_error) return smtp_getbuf(len);
2478 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2480 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2481 ssl_xfer_buffer_lwm += size;
2490 #ifndef DISABLE_DKIM
2491 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2493 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2499 tls_could_read(void)
2501 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2505 /*************************************************
2506 * Read bytes from TLS channel *
2507 *************************************************/
2514 Returns: the number of bytes read
2515 -1 after a failed read
2517 Only used by the client-side TLS.
2521 tls_read(BOOL is_server, uschar *buff, size_t len)
2523 SSL *ssl = is_server ? server_ssl : client_ssl;
2527 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2528 buff, (unsigned int)len);
2530 inbytes = SSL_read(ssl, CS buff, len);
2531 error = SSL_get_error(ssl, inbytes);
2533 if (error == SSL_ERROR_ZERO_RETURN)
2535 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2538 else if (error != SSL_ERROR_NONE)
2548 /*************************************************
2549 * Write bytes down TLS channel *
2550 *************************************************/
2554 is_server channel specifier
2557 more further data expected soon
2559 Returns: the number of bytes after a successful write,
2560 -1 after a failed write
2562 Used by both server-side and client-side TLS.
2566 tls_write(BOOL is_server, const uschar *buff, size_t len, BOOL more)
2568 int outbytes, error, left;
2569 SSL *ssl = is_server ? server_ssl : client_ssl;
2570 static uschar * corked = NULL;
2571 static int c_size = 0, c_len = 0;
2573 DEBUG(D_tls) debug_printf("%s(%p, %d%s)\n", __FUNCTION__,
2574 buff, left, more ? ", more" : "");
2576 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2577 "more" is notified. This hack is only ok if small amounts are involved AND only
2578 one stream does it, in one context (i.e. no store reset). Currently it is used
2579 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. */
2581 if (is_server && (more || corked))
2583 corked = string_catn(corked, &c_size, &c_len, buff, len);
2588 corked = NULL; c_size = c_len = 0;
2591 for (left = len; left > 0;)
2593 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
2594 outbytes = SSL_write(ssl, CS buff, left);
2595 error = SSL_get_error(ssl, outbytes);
2596 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2600 ERR_error_string(ERR_get_error(), ssl_errstring);
2601 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2604 case SSL_ERROR_NONE:
2609 case SSL_ERROR_ZERO_RETURN:
2610 log_write(0, LOG_MAIN, "SSL channel closed on write");
2613 case SSL_ERROR_SYSCALL:
2614 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
2615 sender_fullhost ? sender_fullhost : US"<unknown>",
2620 log_write(0, LOG_MAIN, "SSL_write error %d", error);
2629 /*************************************************
2630 * Close down a TLS session *
2631 *************************************************/
2633 /* This is also called from within a delivery subprocess forked from the
2634 daemon, to shut down the TLS library, without actually doing a shutdown (which
2635 would tamper with the SSL session in the parent process).
2637 Arguments: TRUE if SSL_shutdown is to be called
2640 Used by both server-side and client-side TLS.
2644 tls_close(BOOL is_server, BOOL shutdown)
2646 SSL **sslp = is_server ? &server_ssl : &client_ssl;
2647 int *fdp = is_server ? &tls_in.active : &tls_out.active;
2649 if (*fdp < 0) return; /* TLS was not active */
2653 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
2654 SSL_shutdown(*sslp);
2666 /*************************************************
2667 * Let tls_require_ciphers be checked at startup *
2668 *************************************************/
2670 /* The tls_require_ciphers option, if set, must be something which the
2673 Returns: NULL on success, or error message
2677 tls_validate_require_cipher(void)
2680 uschar *s, *expciphers, *err;
2682 /* this duplicates from tls_init(), we need a better "init just global
2683 state, for no specific purpose" singleton function of our own */
2685 SSL_load_error_strings();
2686 OpenSSL_add_ssl_algorithms();
2687 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2688 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2689 list of available digests. */
2690 EVP_add_digest(EVP_sha256());
2693 if (!(tls_require_ciphers && *tls_require_ciphers))
2696 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
2698 return US"failed to expand tls_require_ciphers";
2700 if (!(expciphers && *expciphers))
2703 /* normalisation ripped from above */
2705 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2709 ctx = SSL_CTX_new(SSLv23_server_method());
2712 ERR_error_string(ERR_get_error(), ssl_errstring);
2713 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2717 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2719 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2721 ERR_error_string(ERR_get_error(), ssl_errstring);
2722 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
2723 expciphers, ssl_errstring);
2734 /*************************************************
2735 * Report the library versions. *
2736 *************************************************/
2738 /* There have historically been some issues with binary compatibility in
2739 OpenSSL libraries; if Exim (like many other applications) is built against
2740 one version of OpenSSL but the run-time linker picks up another version,
2741 it can result in serious failures, including crashing with a SIGSEGV. So
2742 report the version found by the compiler and the run-time version.
2744 Note: some OS vendors backport security fixes without changing the version
2745 number/string, and the version date remains unchanged. The _build_ date
2746 will change, so we can more usefully assist with version diagnosis by also
2747 reporting the build date.
2749 Arguments: a FILE* to print the results to
2754 tls_version_report(FILE *f)
2756 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2759 OPENSSL_VERSION_TEXT,
2760 SSLeay_version(SSLEAY_VERSION),
2761 SSLeay_version(SSLEAY_BUILT_ON));
2762 /* third line is 38 characters for the %s and the line is 73 chars long;
2763 the OpenSSL output includes a "built on: " prefix already. */
2769 /*************************************************
2770 * Random number generation *
2771 *************************************************/
2773 /* Pseudo-random number generation. The result is not expected to be
2774 cryptographically strong but not so weak that someone will shoot themselves
2775 in the foot using it as a nonce in input in some email header scheme or
2776 whatever weirdness they'll twist this into. The result should handle fork()
2777 and avoid repeating sequences. OpenSSL handles that for us.
2781 Returns a random number in range [0, max-1]
2785 vaguely_random_number(int max)
2789 static pid_t pidlast = 0;
2792 uschar smallbuf[sizeof(r)];
2798 if (pidnow != pidlast)
2800 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2801 is unique for each thread", this doesn't apparently apply across processes,
2802 so our own warning from vaguely_random_number_fallback() applies here too.
2803 Fix per PostgreSQL. */
2809 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2813 gettimeofday(&r.tv, NULL);
2816 RAND_seed((uschar *)(&r), sizeof(r));
2818 /* We're after pseudo-random, not random; if we still don't have enough data
2819 in the internal PRNG then our options are limited. We could sleep and hope
2820 for entropy to come along (prayer technique) but if the system is so depleted
2821 in the first place then something is likely to just keep taking it. Instead,
2822 we'll just take whatever little bit of pseudo-random we can still manage to
2825 needed_len = sizeof(r);
2826 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2827 asked for a number less than 10. */
2828 for (r = max, i = 0; r; ++i)
2834 #ifdef EXIM_HAVE_RAND_PSEUDO
2835 /* We do not care if crypto-strong */
2836 i = RAND_pseudo_bytes(smallbuf, needed_len);
2838 i = RAND_bytes(smallbuf, needed_len);
2844 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2845 return vaguely_random_number_fallback(max);
2849 for (p = smallbuf; needed_len; --needed_len, ++p)
2855 /* We don't particularly care about weighted results; if someone wants
2856 smooth distribution and cares enough then they should submit a patch then. */
2863 /*************************************************
2864 * OpenSSL option parse *
2865 *************************************************/
2867 /* Parse one option for tls_openssl_options_parse below
2870 name one option name
2871 value place to store a value for it
2872 Returns success or failure in parsing
2875 struct exim_openssl_option {
2879 /* We could use a macro to expand, but we need the ifdef and not all the
2880 options document which version they were introduced in. Policylet: include
2881 all options unless explicitly for DTLS, let the administrator choose which
2884 This list is current as of:
2886 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2888 static struct exim_openssl_option exim_openssl_options[] = {
2889 /* KEEP SORTED ALPHABETICALLY! */
2891 { US"all", SSL_OP_ALL },
2893 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2894 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2896 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2897 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2899 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2900 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2902 #ifdef SSL_OP_EPHEMERAL_RSA
2903 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2905 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2906 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2908 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2909 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2911 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2912 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2914 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2915 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2917 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2918 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2920 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2921 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2923 #ifdef SSL_OP_NO_COMPRESSION
2924 { US"no_compression", SSL_OP_NO_COMPRESSION },
2926 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2927 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2929 #ifdef SSL_OP_NO_SSLv2
2930 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2932 #ifdef SSL_OP_NO_SSLv3
2933 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2935 #ifdef SSL_OP_NO_TICKET
2936 { US"no_ticket", SSL_OP_NO_TICKET },
2938 #ifdef SSL_OP_NO_TLSv1
2939 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2941 #ifdef SSL_OP_NO_TLSv1_1
2942 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2943 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2944 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2946 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2949 #ifdef SSL_OP_NO_TLSv1_2
2950 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2952 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2953 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2955 #ifdef SSL_OP_SINGLE_DH_USE
2956 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2958 #ifdef SSL_OP_SINGLE_ECDH_USE
2959 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2961 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2962 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2964 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2965 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2967 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2968 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2970 #ifdef SSL_OP_TLS_D5_BUG
2971 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2973 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2974 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2977 static int exim_openssl_options_size =
2978 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2982 tls_openssl_one_option_parse(uschar *name, long *value)
2985 int last = exim_openssl_options_size;
2986 while (last > first)
2988 int middle = (first + last)/2;
2989 int c = Ustrcmp(name, exim_openssl_options[middle].name);
2992 *value = exim_openssl_options[middle].value;
3006 /*************************************************
3007 * OpenSSL option parsing logic *
3008 *************************************************/
3010 /* OpenSSL has a number of compatibility options which an administrator might
3011 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3012 we look like log_selector.
3015 option_spec the administrator-supplied string of options
3016 results ptr to long storage for the options bitmap
3017 Returns success or failure
3021 tls_openssl_options_parse(uschar *option_spec, long *results)
3026 BOOL adding, item_parsed;
3028 result = SSL_OP_NO_TICKET;
3029 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3030 * from default because it increases BEAST susceptibility. */
3031 #ifdef SSL_OP_NO_SSLv2
3032 result |= SSL_OP_NO_SSLv2;
3034 #ifdef SSL_OP_SINGLE_DH_USE
3035 result |= SSL_OP_SINGLE_DH_USE;
3044 for (s=option_spec; *s != '\0'; /**/)
3046 while (isspace(*s)) ++s;
3049 if (*s != '+' && *s != '-')
3051 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3052 "+ or - expected but found \"%s\"\n", s);
3055 adding = *s++ == '+';
3056 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3059 item_parsed = tls_openssl_one_option_parse(s, &item);
3063 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3066 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
3067 adding ? "adding" : "removing", result, item, s);
3081 /* End of tls-openssl.c */