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 /* 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 /*************************************************
232 * Callback to generate RSA key *
233 *************************************************/
237 s SSL connection (not used)
241 Returns: pointer to generated key
245 rsa_callback(SSL *s, int export, int keylength)
248 #ifdef EXIM_HAVE_RSA_GENKEY_EX
249 BIGNUM *bn = BN_new();
252 export = export; /* Shut picky compilers up */
253 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
255 #ifdef EXIM_HAVE_RSA_GENKEY_EX
256 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
257 || !(rsa_key = RSA_new())
258 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
261 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
265 ERR_error_string(ERR_get_error(), ssl_errstring);
266 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
278 x509_store_dump_cert_s_names(X509_STORE * store)
280 STACK_OF(X509_OBJECT) * roots= store->objs;
282 static uschar name[256];
284 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
286 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
287 if(tmp_obj->type == X509_LU_X509)
289 X509 * current_cert= tmp_obj->data.x509;
290 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
291 name[sizeof(name)-1] = '\0';
292 debug_printf(" %s\n", name);
300 #ifndef DISABLE_EVENT
302 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
303 BOOL *calledp, const BOOL *optionalp, const uschar * what)
309 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
312 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
313 old_cert = tlsp->peercert;
314 tlsp->peercert = X509_dup(cert);
315 /* NB we do not bother setting peerdn */
316 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
318 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
319 "depth=%d cert=%s: %s",
320 tlsp == &tls_out ? deliver_host_address : sender_host_address,
321 what, depth, dn, yield);
325 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
326 return 1; /* reject (leaving peercert set) */
328 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
329 "(host in tls_try_verify_hosts)\n");
331 X509_free(tlsp->peercert);
332 tlsp->peercert = old_cert;
338 /*************************************************
339 * Callback for verification *
340 *************************************************/
342 /* The SSL library does certificate verification if set up to do so. This
343 callback has the current yes/no state is in "state". If verification succeeded,
344 we set the certificate-verified flag. If verification failed, what happens
345 depends on whether the client is required to present a verifiable certificate
348 If verification is optional, we change the state to yes, but still log the
349 verification error. For some reason (it really would help to have proper
350 documentation of OpenSSL), this callback function then gets called again, this
351 time with state = 1. We must take care not to set the private verified flag on
352 the second time through.
354 Note: this function is not called if the client fails to present a certificate
355 when asked. We get here only if a certificate has been received. Handling of
356 optional verification for this case is done when requesting SSL to verify, by
357 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
359 May be called multiple times for different issues with a certificate, even
360 for a given "depth" in the certificate chain.
363 preverify_ok current yes/no state as 1/0
364 x509ctx certificate information.
365 tlsp per-direction (client vs. server) support data
366 calledp has-been-called flag
367 optionalp verification-is-optional flag
369 Returns: 0 if verification should fail, otherwise 1
373 verify_callback(int preverify_ok, X509_STORE_CTX *x509ctx,
374 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
376 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
377 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
380 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
381 dn[sizeof(dn)-1] = '\0';
383 if (preverify_ok == 0)
385 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
386 *verify_mode, sender_host_address)
388 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
389 tlsp == &tls_out ? deliver_host_address : sender_host_address,
391 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
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 tlsp == &tls_out ? deliver_host_address : sender_host_address);
459 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
462 uschar * extra = verify_mode
463 ? string_sprintf(" (during %c-verify for [%s])",
464 *verify_mode, sender_host_address)
466 log_write(0, LOG_MAIN,
467 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
468 tlsp == &tls_out ? deliver_host_address : sender_host_address,
469 extra, dn, verify_cert_hostnames);
474 tlsp->peercert = X509_dup(cert); /* record failing cert */
475 return 0; /* reject */
477 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
478 "tls_try_verify_hosts)\n");
482 #ifndef DISABLE_EVENT
483 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
484 return 0; /* reject, with peercert set */
487 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
488 *calledp ? "" : " authenticated", dn);
489 if (!*calledp) tlsp->certificate_verified = TRUE;
493 return 1; /* accept, at least for this level */
497 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
499 return verify_callback(preverify_ok, x509ctx, &tls_out,
500 &client_verify_callback_called, &client_verify_optional);
504 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
506 return verify_callback(preverify_ok, x509ctx, &tls_in,
507 &server_verify_callback_called, &server_verify_optional);
511 #ifdef EXPERIMENTAL_DANE
513 /* This gets called *by* the dane library verify callback, which interposes
517 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
519 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
521 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
522 #ifndef DISABLE_EVENT
523 BOOL dummy_called, optional = FALSE;
526 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
527 dn[sizeof(dn)-1] = '\0';
529 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
530 preverify_ok ? "ok":"BAD", depth, dn);
532 #ifndef DISABLE_EVENT
533 if (verify_event(&tls_out, cert, depth, dn,
534 &dummy_called, &optional, US"DANE"))
535 return 0; /* reject, with peercert set */
538 if (preverify_ok == 1)
539 tls_out.dane_verified =
540 tls_out.certificate_verified = TRUE;
543 int err = X509_STORE_CTX_get_error(x509ctx);
545 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
546 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
552 #endif /*EXPERIMENTAL_DANE*/
555 /*************************************************
556 * Information callback *
557 *************************************************/
559 /* The SSL library functions call this from time to time to indicate what they
560 are doing. We copy the string to the debugging output when TLS debugging has
572 info_callback(SSL *s, int where, int ret)
576 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
581 /*************************************************
582 * Initialize for DH *
583 *************************************************/
585 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
588 sctx The current SSL CTX (inbound or outbound)
589 dhparam DH parameter file or fixed parameter identity string
590 host connected host, if client; NULL if server
591 errstr error string pointer
593 Returns: TRUE if OK (nothing to set up, or setup worked)
597 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
605 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
608 if (!dhexpanded || !*dhexpanded)
609 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
610 else if (dhexpanded[0] == '/')
612 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
614 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
615 host, US strerror(errno), errstr);
621 if (Ustrcmp(dhexpanded, "none") == 0)
623 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
627 if (!(pem = std_dh_prime_named(dhexpanded)))
629 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
630 host, US strerror(errno), errstr);
633 bio = BIO_new_mem_buf(CS pem, -1);
636 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
639 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
644 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
645 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
646 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
647 * If someone wants to dance at the edge, then they can raise the limit or use
648 * current libraries. */
649 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
650 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
651 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
652 dh_bitsize = DH_bits(dh);
654 dh_bitsize = 8 * DH_size(dh);
657 /* Even if it is larger, we silently return success rather than cause things
658 * to fail out, so that a too-large DH will not knock out all TLS; it's a
659 * debatable choice. */
660 if (dh_bitsize > tls_dh_max_bits)
663 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
664 dh_bitsize, tls_dh_max_bits);
668 SSL_CTX_set_tmp_dh(sctx, dh);
670 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
671 dhexpanded ? dhexpanded : US"default", dh_bitsize);
683 /*************************************************
684 * Initialize for ECDH *
685 *************************************************/
687 /* Load parameters for ECDH encryption.
689 For now, we stick to NIST P-256 because: it's simple and easy to configure;
690 it avoids any patent issues that might bite redistributors; despite events in
691 the news and concerns over curve choices, we're not cryptographers, we're not
692 pretending to be, and this is "good enough" to be better than no support,
693 protecting against most adversaries. Given another year or two, there might
694 be sufficient clarity about a "right" way forward to let us make an informed
695 decision, instead of a knee-jerk reaction.
697 Longer-term, we should look at supporting both various named curves and
698 external files generated with "openssl ecparam", much as we do for init_dh().
699 We should also support "none" as a value, to explicitly avoid initialisation.
704 sctx The current SSL CTX (inbound or outbound)
705 host connected host, if client; NULL if server
706 errstr error string pointer
708 Returns: TRUE if OK (nothing to set up, or setup worked)
712 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
714 #ifdef OPENSSL_NO_ECDH
723 if (host) /* No ECDH setup for clients, only for servers */
726 # ifndef EXIM_HAVE_ECDH
728 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
732 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
734 if (!exp_curve || !*exp_curve)
737 /* "auto" needs to be handled carefully.
738 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
739 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
740 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
741 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
742 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
744 if (Ustrcmp(exp_curve, "auto") == 0)
746 #if OPENSSL_VERSION_NUMBER < 0x10002000L
747 DEBUG(D_tls) debug_printf(
748 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
749 exp_curve = US"prime256v1";
751 # if defined SSL_CTRL_SET_ECDH_AUTO
752 DEBUG(D_tls) debug_printf(
753 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
754 SSL_CTX_set_ecdh_auto(sctx, 1);
757 DEBUG(D_tls) debug_printf(
758 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
764 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
765 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
766 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
767 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
771 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
776 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
778 tls_error(US"Unable to create ec curve", host, NULL, errstr);
782 /* The "tmp" in the name here refers to setting a temporary key
783 not to the stability of the interface. */
785 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
786 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
788 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
793 # endif /*EXIM_HAVE_ECDH*/
794 #endif /*OPENSSL_NO_ECDH*/
801 /*************************************************
802 * Load OCSP information into state *
803 *************************************************/
804 /* Called to load the server OCSP response from the given file into memory, once
805 caller has determined this is needed. Checks validity. Debugs a message
808 ASSUMES: single response, for single cert.
811 sctx the SSL_CTX* to update
812 cbinfo various parts of session state
813 expanded the filename putatively holding an OCSP response
818 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
821 OCSP_RESPONSE * resp;
822 OCSP_BASICRESP * basic_response;
823 OCSP_SINGLERESP * single_response;
824 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
826 unsigned long verify_flags;
827 int status, reason, i;
829 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
830 if (cbinfo->u_ocsp.server.response)
832 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
833 cbinfo->u_ocsp.server.response = NULL;
836 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
838 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
839 cbinfo->u_ocsp.server.file_expanded);
843 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
847 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
851 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
853 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
854 OCSP_response_status_str(status), status);
858 if (!(basic_response = OCSP_response_get1_basic(resp)))
861 debug_printf("OCSP response parse error: unable to extract basic response.\n");
865 sk = cbinfo->verify_stack;
866 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
868 /* May need to expose ability to adjust those flags?
869 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
870 OCSP_TRUSTOTHER OCSP_NOINTERN */
872 /* This does a full verify on the OCSP proof before we load it for serving
873 up; possibly overkill - just date-checks might be nice enough.
875 OCSP_basic_verify takes a "store" arg, but does not
876 use it for the chain verification, which is all we do
877 when OCSP_NOVERIFY is set. The content from the wire
878 "basic_response" and a cert-stack "sk" are all that is used.
880 We have a stack, loaded in setup_certs() if tls_verify_certificates
881 was a file (not a directory, or "system"). It is unfortunate we
882 cannot used the connection context store, as that would neatly
883 handle the "system" case too, but there seems to be no library
884 function for getting a stack from a store.
885 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
886 We do not free the stack since it could be needed a second time for
889 Separately we might try to replace using OCSP_basic_verify() - which seems to not
890 be a public interface into the OpenSSL library (there's no manual entry) -
891 But what with? We also use OCSP_basic_verify in the client stapling callback.
892 And there we NEED it; we must verify that status... unless the
893 library does it for us anyway? */
895 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
899 ERR_error_string(ERR_get_error(), ssl_errstring);
900 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
905 /* Here's the simplifying assumption: there's only one response, for the
906 one certificate we use, and nothing for anything else in a chain. If this
907 proves false, we need to extract a cert id from our issued cert
908 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
909 right cert in the stack and then calls OCSP_single_get0_status()).
911 I'm hoping to avoid reworking a bunch more of how we handle state here. */
913 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
916 debug_printf("Unable to get first response from OCSP basic response.\n");
920 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
921 if (status != V_OCSP_CERTSTATUS_GOOD)
923 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
924 OCSP_cert_status_str(status), status,
925 OCSP_crl_reason_str(reason), reason);
929 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
931 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
936 cbinfo->u_ocsp.server.response = resp;
940 if (running_in_test_harness)
942 extern char ** environ;
944 if (environ) for (p = USS environ; *p != NULL; p++)
945 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
947 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
948 goto supply_response;
953 #endif /*!DISABLE_OCSP*/
958 /* Create and install a selfsigned certificate, for use in server mode */
961 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
969 where = US"allocating pkey";
970 if (!(pkey = EVP_PKEY_new()))
973 where = US"allocating cert";
974 if (!(x509 = X509_new()))
977 where = US"generating pkey";
978 if (!(rsa = rsa_callback(NULL, 0, 1024)))
981 where = US"assigning pkey";
982 if (!EVP_PKEY_assign_RSA(pkey, rsa))
985 X509_set_version(x509, 2); /* N+1 - version 3 */
986 ASN1_INTEGER_set(X509_get_serialNumber(x509), 0);
987 X509_gmtime_adj(X509_get_notBefore(x509), 0);
988 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
989 X509_set_pubkey(x509, pkey);
991 name = X509_get_subject_name(x509);
992 X509_NAME_add_entry_by_txt(name, "C",
993 MBSTRING_ASC, CUS "UK", -1, -1, 0);
994 X509_NAME_add_entry_by_txt(name, "O",
995 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
996 X509_NAME_add_entry_by_txt(name, "CN",
997 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
998 X509_set_issuer_name(x509, name);
1000 where = US"signing cert";
1001 if (!X509_sign(x509, pkey, EVP_md5()))
1004 where = US"installing selfsign cert";
1005 if (!SSL_CTX_use_certificate(sctx, x509))
1008 where = US"installing selfsign key";
1009 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1015 (void) tls_error(where, NULL, NULL, errstr);
1016 if (x509) X509_free(x509);
1017 if (pkey) EVP_PKEY_free(pkey);
1025 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1028 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1029 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1030 return tls_error(string_sprintf(
1031 "SSL_CTX_use_certificate_chain_file file=%s", file),
1032 cbinfo->host, NULL, errstr);
1037 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1040 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1041 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1042 return tls_error(string_sprintf(
1043 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1048 /*************************************************
1049 * Expand key and cert file specs *
1050 *************************************************/
1052 /* Called once during tls_init and possibly again during TLS setup, for a
1053 new context, if Server Name Indication was used and tls_sni was seen in
1054 the certificate string.
1057 sctx the SSL_CTX* to update
1058 cbinfo various parts of session state
1059 errstr error string pointer
1061 Returns: OK/DEFER/FAIL
1065 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1070 if (!cbinfo->certificate)
1072 if (!cbinfo->is_server) /* client */
1075 if (tls_install_selfsign(sctx, errstr) != OK)
1082 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1083 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1084 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1086 reexpand_tls_files_for_sni = TRUE;
1088 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1092 if (cbinfo->is_server)
1094 const uschar * file_list = expanded;
1098 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1099 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1102 else /* would there ever be a need for multiple client certs? */
1103 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1106 if (cbinfo->privatekey != NULL &&
1107 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1110 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1111 of the expansion is an empty string, ignore it also, and assume the private
1112 key is in the same file as the certificate. */
1114 if (expanded && *expanded)
1115 if (cbinfo->is_server)
1117 const uschar * file_list = expanded;
1121 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1122 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1125 else /* would there ever be a need for multiple client certs? */
1126 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1130 #ifndef DISABLE_OCSP
1131 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1133 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1136 if (expanded && *expanded)
1138 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1139 if ( cbinfo->u_ocsp.server.file_expanded
1140 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1142 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1145 ocsp_load_response(sctx, cbinfo, expanded);
1156 /*************************************************
1157 * Callback to handle SNI *
1158 *************************************************/
1160 /* Called when acting as server during the TLS session setup if a Server Name
1161 Indication extension was sent by the client.
1163 API documentation is OpenSSL s_server.c implementation.
1166 s SSL* of the current session
1167 ad unknown (part of OpenSSL API) (unused)
1168 arg Callback of "our" registered data
1170 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1173 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1175 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1177 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1178 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1180 int old_pool = store_pool;
1181 uschar * dummy_errstr;
1184 return SSL_TLSEXT_ERR_OK;
1186 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1187 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1189 /* Make the extension value available for expansion */
1190 store_pool = POOL_PERM;
1191 tls_in.sni = string_copy(US servername);
1192 store_pool = old_pool;
1194 if (!reexpand_tls_files_for_sni)
1195 return SSL_TLSEXT_ERR_OK;
1197 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1198 not confident that memcpy wouldn't break some internal reference counting.
1199 Especially since there's a references struct member, which would be off. */
1201 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1203 ERR_error_string(ERR_get_error(), ssl_errstring);
1204 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1205 return SSL_TLSEXT_ERR_NOACK;
1208 /* Not sure how many of these are actually needed, since SSL object
1209 already exists. Might even need this selfsame callback, for reneg? */
1211 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1212 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1213 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1214 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1215 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1216 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1218 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1219 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1221 return SSL_TLSEXT_ERR_NOACK;
1223 if (cbinfo->server_cipher_list)
1224 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
1225 #ifndef DISABLE_OCSP
1226 if (cbinfo->u_ocsp.server.file)
1228 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1229 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1233 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1234 verify_callback_server, &dummy_errstr)) != OK)
1235 return SSL_TLSEXT_ERR_NOACK;
1237 /* do this after setup_certs, because this can require the certs for verifying
1238 OCSP information. */
1239 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1240 return SSL_TLSEXT_ERR_NOACK;
1242 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1243 SSL_set_SSL_CTX(s, server_sni);
1245 return SSL_TLSEXT_ERR_OK;
1247 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1252 #ifndef DISABLE_OCSP
1254 /*************************************************
1255 * Callback to handle OCSP Stapling *
1256 *************************************************/
1258 /* Called when acting as server during the TLS session setup if the client
1259 requests OCSP information with a Certificate Status Request.
1261 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1267 tls_server_stapling_cb(SSL *s, void *arg)
1269 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1270 uschar *response_der;
1271 int response_der_len;
1274 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1275 cbinfo->u_ocsp.server.response ? "have" : "lack");
1277 tls_in.ocsp = OCSP_NOT_RESP;
1278 if (!cbinfo->u_ocsp.server.response)
1279 return SSL_TLSEXT_ERR_NOACK;
1281 response_der = NULL;
1282 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
1284 if (response_der_len <= 0)
1285 return SSL_TLSEXT_ERR_NOACK;
1287 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1288 tls_in.ocsp = OCSP_VFIED;
1289 return SSL_TLSEXT_ERR_OK;
1294 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1296 BIO_printf(bp, "\t%s: ", str);
1297 ASN1_GENERALIZEDTIME_print(bp, time);
1302 tls_client_stapling_cb(SSL *s, void *arg)
1304 tls_ext_ctx_cb * cbinfo = arg;
1305 const unsigned char * p;
1307 OCSP_RESPONSE * rsp;
1308 OCSP_BASICRESP * bs;
1311 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1312 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1315 /* Expect this when we requested ocsp but got none */
1316 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1317 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1319 DEBUG(D_tls) debug_printf(" null\n");
1320 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1323 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1325 tls_out.ocsp = OCSP_FAILED;
1326 if (LOGGING(tls_cipher))
1327 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1329 DEBUG(D_tls) debug_printf(" parse error\n");
1333 if(!(bs = OCSP_response_get1_basic(rsp)))
1335 tls_out.ocsp = OCSP_FAILED;
1336 if (LOGGING(tls_cipher))
1337 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1339 DEBUG(D_tls) debug_printf(" error parsing response\n");
1340 OCSP_RESPONSE_free(rsp);
1344 /* We'd check the nonce here if we'd put one in the request. */
1345 /* However that would defeat cacheability on the server so we don't. */
1347 /* This section of code reworked from OpenSSL apps source;
1348 The OpenSSL Project retains copyright:
1349 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1354 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1356 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
1358 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1360 /* Use the chain that verified the server cert to verify the stapled info */
1361 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1363 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1364 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1366 tls_out.ocsp = OCSP_FAILED;
1367 if (LOGGING(tls_cipher))
1368 log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
1369 BIO_printf(bp, "OCSP response verify failure\n");
1370 ERR_print_errors(bp);
1374 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1376 /*XXX So we have a good stapled OCSP status. How do we know
1377 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1378 OCSP_resp_find_status() which matches on a cert id, which presumably
1379 we should use. Making an id needs OCSP_cert_id_new(), which takes
1380 issuerName, issuerKey, serialNumber. Are they all in the cert?
1382 For now, carry on blindly accepting the resp. */
1385 OCSP_SINGLERESP * single;
1387 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1388 if (OCSP_resp_count(bs) != 1)
1390 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1391 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1394 tls_out.ocsp = OCSP_FAILED;
1395 log_write(0, LOG_MAIN, "OCSP stapling "
1396 "with multiple responses not handled");
1399 single = OCSP_resp_get0(bs, 0);
1400 status = OCSP_single_get0_status(single, &reason, &rev,
1401 &thisupd, &nextupd);
1404 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1405 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1406 if (!OCSP_check_validity(thisupd, nextupd,
1407 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1409 tls_out.ocsp = OCSP_FAILED;
1410 DEBUG(D_tls) ERR_print_errors(bp);
1411 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1415 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1416 OCSP_cert_status_str(status));
1419 case V_OCSP_CERTSTATUS_GOOD:
1420 tls_out.ocsp = OCSP_VFIED;
1423 case V_OCSP_CERTSTATUS_REVOKED:
1424 tls_out.ocsp = OCSP_FAILED;
1425 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1426 reason != -1 ? "; reason: " : "",
1427 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1428 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1431 tls_out.ocsp = OCSP_FAILED;
1432 log_write(0, LOG_MAIN,
1433 "Server certificate status unknown, in OCSP stapling");
1438 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1443 OCSP_RESPONSE_free(rsp);
1446 #endif /*!DISABLE_OCSP*/
1449 /*************************************************
1450 * Initialize for TLS *
1451 *************************************************/
1453 /* Called from both server and client code, to do preliminary initialization
1454 of the library. We allocate and return a context structure.
1457 ctxp returned SSL context
1458 host connected host, if client; NULL if server
1459 dhparam DH parameter file
1460 certificate certificate file
1461 privatekey private key
1462 ocsp_file file of stapling info (server); flag for require ocsp (client)
1463 addr address if client; NULL if server (for some randomness)
1464 cbp place to put allocated callback context
1465 errstr error string pointer
1467 Returns: OK/DEFER/FAIL
1471 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1473 #ifndef DISABLE_OCSP
1476 address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1481 tls_ext_ctx_cb * cbinfo;
1483 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1484 cbinfo->certificate = certificate;
1485 cbinfo->privatekey = privatekey;
1486 #ifndef DISABLE_OCSP
1487 cbinfo->verify_stack = NULL;
1488 if ((cbinfo->is_server = host==NULL))
1490 cbinfo->u_ocsp.server.file = ocsp_file;
1491 cbinfo->u_ocsp.server.file_expanded = NULL;
1492 cbinfo->u_ocsp.server.response = NULL;
1495 cbinfo->u_ocsp.client.verify_store = NULL;
1497 cbinfo->dhparam = dhparam;
1498 cbinfo->server_cipher_list = NULL;
1499 cbinfo->host = host;
1500 #ifndef DISABLE_EVENT
1501 cbinfo->event_action = NULL;
1504 SSL_load_error_strings(); /* basic set up */
1505 OpenSSL_add_ssl_algorithms();
1507 #ifdef EXIM_HAVE_SHA256
1508 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1509 list of available digests. */
1510 EVP_add_digest(EVP_sha256());
1513 /* Create a context.
1514 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1515 negotiation in the different methods; as far as I can tell, the only
1516 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1517 when OpenSSL is built without SSLv2 support.
1518 By disabling with openssl_options, we can let admins re-enable with the
1521 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1522 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1524 /* It turns out that we need to seed the random number generator this early in
1525 order to get the full complement of ciphers to work. It took me roughly a day
1526 of work to discover this by experiment.
1528 On systems that have /dev/urandom, SSL may automatically seed itself from
1529 there. Otherwise, we have to make something up as best we can. Double check
1535 gettimeofday(&r.tv, NULL);
1538 RAND_seed(US (&r), sizeof(r));
1539 RAND_seed(US big_buffer, big_buffer_size);
1540 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1543 return tls_error(US"RAND_status", host,
1544 US"unable to seed random number generator", errstr);
1547 /* Set up the information callback, which outputs if debugging is at a suitable
1550 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1552 /* Automatically re-try reads/writes after renegotiation. */
1553 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1555 /* Apply administrator-supplied work-arounds.
1556 Historically we applied just one requested option,
1557 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1558 moved to an administrator-controlled list of options to specify and
1559 grandfathered in the first one as the default value for "openssl_options".
1561 No OpenSSL version number checks: the options we accept depend upon the
1562 availability of the option value macros from OpenSSL. */
1564 if (!tls_openssl_options_parse(openssl_options, &init_options))
1565 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1569 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1570 if (!(SSL_CTX_set_options(ctx, init_options)))
1571 return tls_error(string_sprintf(
1572 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1575 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1577 /* Disable session cache unconditionally */
1579 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1581 /* Initialize with DH parameters if supplied */
1582 /* Initialize ECDH temp key parameter selection */
1584 if ( !init_dh(ctx, dhparam, host, errstr)
1585 || !init_ecdh(ctx, host, errstr)
1589 /* Set up certificate and key (and perhaps OCSP info) */
1591 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1594 /* If we need to handle SNI or OCSP, do so */
1596 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1597 # ifndef DISABLE_OCSP
1598 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1600 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1605 if (host == NULL) /* server */
1607 # ifndef DISABLE_OCSP
1608 /* We check u_ocsp.server.file, not server.response, because we care about if
1609 the option exists, not what the current expansion might be, as SNI might
1610 change the certificate and OCSP file in use between now and the time the
1611 callback is invoked. */
1612 if (cbinfo->u_ocsp.server.file)
1614 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1615 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1618 /* We always do this, so that $tls_sni is available even if not used in
1620 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1621 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1623 # ifndef DISABLE_OCSP
1625 if(ocsp_file) /* wanting stapling */
1627 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1629 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1632 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1633 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1638 cbinfo->verify_cert_hostnames = NULL;
1640 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1641 /* Set up the RSA callback */
1642 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1645 /* Finally, set the timeout, and we are done */
1647 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1648 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1659 /*************************************************
1660 * Get name of cipher in use *
1661 *************************************************/
1664 Argument: pointer to an SSL structure for the connection
1665 buffer to use for answer
1667 pointer to number of bits for cipher
1672 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1674 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1675 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1676 the accessor functions use const in the prototype. */
1677 const SSL_CIPHER *c;
1680 ver = (const uschar *)SSL_get_version(ssl);
1682 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1683 SSL_CIPHER_get_bits(c, bits);
1685 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1686 SSL_CIPHER_get_name(c), *bits);
1688 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1693 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned bsize)
1695 /*XXX we might consider a list-of-certs variable for the cert chain.
1696 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1697 in list-handling functions, also consider the difference between the entire
1698 chain and the elements sent by the peer. */
1700 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1701 if (!tlsp->peercert)
1702 tlsp->peercert = SSL_get_peer_certificate(ssl);
1703 /* Beware anonymous ciphers which lead to server_cert being NULL */
1706 X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, bsize);
1707 peerdn[bsize-1] = '\0';
1708 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1711 tlsp->peerdn = NULL;
1718 /*************************************************
1719 * Set up for verifying certificates *
1720 *************************************************/
1722 /* Load certs from file, return TRUE on success */
1725 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
1730 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
1731 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
1732 sk_X509_push(verify_stack, x);
1739 /* Called by both client and server startup
1742 sctx SSL_CTX* to initialise
1743 certs certs file or NULL
1744 crl CRL file or NULL
1745 host NULL in a server; the remote host in a client
1746 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1747 otherwise passed as FALSE
1748 cert_vfy_cb Callback function for certificate verification
1749 errstr error string pointer
1751 Returns: OK/DEFER/FAIL
1755 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1756 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
1758 uschar *expcerts, *expcrl;
1760 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
1762 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
1764 if (expcerts && *expcerts)
1766 /* Tell the library to use its compiled-in location for the system default
1767 CA bundle. Then add the ones specified in the config, if any. */
1769 if (!SSL_CTX_set_default_verify_paths(sctx))
1770 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
1772 if (Ustrcmp(expcerts, "system") != 0)
1774 struct stat statbuf;
1776 if (Ustat(expcerts, &statbuf) < 0)
1778 log_write(0, LOG_MAIN|LOG_PANIC,
1779 "failed to stat %s for certificates", expcerts);
1785 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1786 { file = NULL; dir = expcerts; }
1789 file = expcerts; dir = NULL;
1790 #ifndef DISABLE_OCSP
1791 /* In the server if we will be offering an OCSP proof, load chain from
1792 file for verifying the OCSP proof at load time. */
1795 && statbuf.st_size > 0
1796 && server_static_cbinfo->u_ocsp.server.file
1797 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
1800 log_write(0, LOG_MAIN|LOG_PANIC,
1801 "failed to load cert hain from %s", file);
1807 /* If a certificate file is empty, the next function fails with an
1808 unhelpful error message. If we skip it, we get the correct behaviour (no
1809 certificates are recognized, but the error message is still misleading (it
1810 says no certificate was supplied). But this is better. */
1812 if ( (!file || statbuf.st_size > 0)
1813 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1814 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
1816 /* Load the list of CAs for which we will accept certs, for sending
1817 to the client. This is only for the one-file tls_verify_certificates
1819 If a list isn't loaded into the server, but
1820 some verify locations are set, the server end appears to make
1821 a wildcard request for client certs.
1822 Meanwhile, the client library as default behaviour *ignores* the list
1823 we send over the wire - see man SSL_CTX_set_client_cert_cb.
1824 Because of this, and that the dir variant is likely only used for
1825 the public-CA bundle (not for a private CA), not worth fixing.
1829 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
1831 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
1832 sk_X509_NAME_num(names));
1833 SSL_CTX_set_client_CA_list(sctx, names);
1838 /* Handle a certificate revocation list. */
1840 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1842 /* This bit of code is now the version supplied by Lars Mainka. (I have
1843 merely reformatted it into the Exim code style.)
1845 "From here I changed the code to add support for multiple crl's
1846 in pem format in one file or to support hashed directory entries in
1847 pem format instead of a file. This method now uses the library function
1848 X509_STORE_load_locations to add the CRL location to the SSL context.
1849 OpenSSL will then handle the verify against CA certs and CRLs by
1850 itself in the verify callback." */
1852 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
1853 if (expcrl && *expcrl)
1855 struct stat statbufcrl;
1856 if (Ustat(expcrl, &statbufcrl) < 0)
1858 log_write(0, LOG_MAIN|LOG_PANIC,
1859 "failed to stat %s for certificates revocation lists", expcrl);
1864 /* is it a file or directory? */
1866 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1867 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1871 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1877 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1879 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1880 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
1882 /* setting the flags to check against the complete crl chain */
1884 X509_STORE_set_flags(cvstore,
1885 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1889 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1891 /* If verification is optional, don't fail if no certificate */
1893 SSL_CTX_set_verify(sctx,
1894 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1903 /*************************************************
1904 * Start a TLS session in a server *
1905 *************************************************/
1907 /* This is called when Exim is running as a server, after having received
1908 the STARTTLS command. It must respond to that command, and then negotiate
1912 require_ciphers allowed ciphers
1913 errstr pointer to error message
1915 Returns: OK on success
1916 DEFER for errors before the start of the negotiation
1917 FAIL for errors during the negotiation; the server can't
1922 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
1925 uschar * expciphers;
1926 tls_ext_ctx_cb * cbinfo;
1927 static uschar peerdn[256];
1928 static uschar cipherbuf[256];
1930 /* Check for previous activation */
1932 if (tls_in.active >= 0)
1934 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
1935 smtp_printf("554 Already in TLS\r\n", FALSE);
1939 /* Initialize the SSL library. If it fails, it will already have logged
1942 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1943 #ifndef DISABLE_OCSP
1946 NULL, &server_static_cbinfo, errstr);
1947 if (rc != OK) return rc;
1948 cbinfo = server_static_cbinfo;
1950 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
1953 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1954 were historically separated by underscores. So that I can use either form in my
1955 tests, and also for general convenience, we turn underscores into hyphens here.
1960 uschar * s = expciphers;
1961 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1962 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1963 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1964 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
1965 cbinfo->server_cipher_list = expciphers;
1968 /* If this is a host for which certificate verification is mandatory or
1969 optional, set up appropriately. */
1971 tls_in.certificate_verified = FALSE;
1972 #ifdef EXPERIMENTAL_DANE
1973 tls_in.dane_verified = FALSE;
1975 server_verify_callback_called = FALSE;
1977 if (verify_check_host(&tls_verify_hosts) == OK)
1979 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1980 FALSE, verify_callback_server, errstr);
1981 if (rc != OK) return rc;
1982 server_verify_optional = FALSE;
1984 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1986 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1987 TRUE, verify_callback_server, errstr);
1988 if (rc != OK) return rc;
1989 server_verify_optional = TRUE;
1992 /* Prepare for new connection */
1994 if (!(server_ssl = SSL_new(server_ctx)))
1995 return tls_error(US"SSL_new", NULL, NULL, errstr);
1997 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1999 * With the SSL_clear(), we get strange interoperability bugs with
2000 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2001 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2003 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2004 * session shutdown. In this case, we have a brand new object and there's no
2005 * obvious reason to immediately clear it. I'm guessing that this was
2006 * originally added because of incomplete initialisation which the clear fixed,
2007 * in some historic release.
2010 /* Set context and tell client to go ahead, except in the case of TLS startup
2011 on connection, where outputting anything now upsets the clients and tends to
2012 make them disconnect. We need to have an explicit fflush() here, to force out
2013 the response. Other smtp_printf() calls do not need it, because in non-TLS
2014 mode, the fflush() happens when smtp_getc() is called. */
2016 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2017 if (!tls_in.on_connect)
2019 smtp_printf("220 TLS go ahead\r\n", FALSE);
2023 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2024 that the OpenSSL library doesn't. */
2026 SSL_set_wfd(server_ssl, fileno(smtp_out));
2027 SSL_set_rfd(server_ssl, fileno(smtp_in));
2028 SSL_set_accept_state(server_ssl);
2030 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2032 sigalrm_seen = FALSE;
2033 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2034 rc = SSL_accept(server_ssl);
2039 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2043 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2045 /* TLS has been set up. Adjust the input functions to read via TLS,
2046 and initialize things. */
2048 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2050 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
2051 tls_in.cipher = cipherbuf;
2056 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
2057 debug_printf("Shared ciphers: %s\n", buf);
2060 /* Record the certificate we presented */
2062 X509 * crt = SSL_get_certificate(server_ssl);
2063 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2066 /* Only used by the server-side tls (tls_in), including tls_getc.
2067 Client-side (tls_out) reads (seem to?) go via
2068 smtp_read_response()/ip_recv().
2069 Hence no need to duplicate for _in and _out.
2071 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2072 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2073 ssl_xfer_eof = ssl_xfer_error = 0;
2075 receive_getc = tls_getc;
2076 receive_getbuf = tls_getbuf;
2077 receive_get_cache = tls_get_cache;
2078 receive_ungetc = tls_ungetc;
2079 receive_feof = tls_feof;
2080 receive_ferror = tls_ferror;
2081 receive_smtp_buffered = tls_smtp_buffered;
2083 tls_in.active = fileno(smtp_out);
2091 tls_client_basic_ctx_init(SSL_CTX * ctx,
2092 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2096 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2097 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2098 the specified host patterns if one of them is defined */
2100 if ( ( !ob->tls_verify_hosts
2101 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2103 || (verify_check_given_host(&ob->tls_verify_hosts, host) == OK)
2105 client_verify_optional = FALSE;
2106 else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK)
2107 client_verify_optional = TRUE;
2111 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2112 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2116 if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
2118 cbinfo->verify_cert_hostnames =
2120 string_domain_utf8_to_alabel(host->name, NULL);
2124 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2125 cbinfo->verify_cert_hostnames);
2131 #ifdef EXPERIMENTAL_DANE
2133 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2137 const char * hostnames[2] = { CS host->name, NULL };
2140 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2141 return tls_error(US"hostnames load", host, NULL, errstr);
2143 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
2145 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2146 ) if (rr->type == T_TLSA)
2148 const uschar * p = rr->data;
2149 uint8_t usage, selector, mtype;
2150 const char * mdname;
2154 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2155 if (usage != 2 && usage != 3) continue;
2162 default: continue; /* Only match-types 0, 1, 2 are supported */
2163 case 0: mdname = NULL; break;
2164 case 1: mdname = "sha256"; break;
2165 case 2: mdname = "sha512"; break;
2169 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2172 return tls_error(US"tlsa load", host, NULL, errstr);
2173 case 0: /* action not taken */
2177 tls_out.tlsa_usage |= 1<<usage;
2183 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2186 #endif /*EXPERIMENTAL_DANE*/
2190 /*************************************************
2191 * Start a TLS session in a client *
2192 *************************************************/
2194 /* Called from the smtp transport after STARTTLS has been accepted.
2197 fd the fd of the connection
2198 host connected host (for messages)
2199 addr the first address
2200 tb transport (always smtp)
2201 tlsa_dnsa tlsa lookup, if DANE, else null
2202 errstr error string pointer
2204 Returns: OK on success
2205 FAIL otherwise - note that tls_error() will not give DEFER
2206 because this is not a server
2210 tls_client_start(int fd, host_item *host, address_item *addr,
2211 transport_instance * tb,
2212 #ifdef EXPERIMENTAL_DANE
2213 dns_answer * tlsa_dnsa,
2217 smtp_transport_options_block * ob =
2218 (smtp_transport_options_block *)tb->options_block;
2219 static uschar peerdn[256];
2220 uschar * expciphers;
2222 static uschar cipherbuf[256];
2224 #ifndef DISABLE_OCSP
2225 BOOL request_ocsp = FALSE;
2226 BOOL require_ocsp = FALSE;
2229 #ifdef EXPERIMENTAL_DANE
2230 tls_out.tlsa_usage = 0;
2233 #ifndef DISABLE_OCSP
2235 # ifdef EXPERIMENTAL_DANE
2237 && ob->hosts_request_ocsp[0] == '*'
2238 && ob->hosts_request_ocsp[1] == '\0'
2241 /* Unchanged from default. Use a safer one under DANE */
2242 request_ocsp = TRUE;
2243 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2244 " {= {4}{$tls_out_tlsa_usage}} } "
2250 verify_check_given_host(&ob->hosts_require_ocsp, host) == OK))
2251 request_ocsp = TRUE;
2253 # ifdef EXPERIMENTAL_DANE
2257 verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2261 rc = tls_init(&client_ctx, host, NULL,
2262 ob->tls_certificate, ob->tls_privatekey,
2263 #ifndef DISABLE_OCSP
2264 (void *)(long)request_ocsp,
2266 addr, &client_static_cbinfo, errstr);
2267 if (rc != OK) return rc;
2269 tls_out.certificate_verified = FALSE;
2270 client_verify_callback_called = FALSE;
2272 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2273 &expciphers, errstr))
2276 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2277 are separated by underscores. So that I can use either form in my tests, and
2278 also for general convenience, we turn underscores into hyphens here. */
2282 uschar *s = expciphers;
2283 while (*s) { if (*s == '_') *s = '-'; s++; }
2284 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2285 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
2286 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2289 #ifdef EXPERIMENTAL_DANE
2292 SSL_CTX_set_verify(client_ctx,
2293 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2294 verify_callback_client_dane);
2296 if (!DANESSL_library_init())
2297 return tls_error(US"library init", host, NULL, errstr);
2298 if (DANESSL_CTX_init(client_ctx) <= 0)
2299 return tls_error(US"context init", host, NULL, errstr);
2305 if ((rc = tls_client_basic_ctx_init(client_ctx, host, ob,
2306 client_static_cbinfo, errstr)) != OK)
2309 if ((client_ssl = SSL_new(client_ctx)) == NULL)
2310 return tls_error(US"SSL_new", host, NULL, errstr);
2311 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
2312 SSL_set_fd(client_ssl, fd);
2313 SSL_set_connect_state(client_ssl);
2317 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni, errstr))
2321 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2323 else if (!Ustrlen(tls_out.sni))
2327 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2328 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
2329 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
2331 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2337 #ifdef EXPERIMENTAL_DANE
2339 if ((rc = dane_tlsa_load(client_ssl, host, tlsa_dnsa, errstr)) != OK)
2343 #ifndef DISABLE_OCSP
2344 /* Request certificate status at connection-time. If the server
2345 does OCSP stapling we will get the callback (set in tls_init()) */
2346 # ifdef EXPERIMENTAL_DANE
2350 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2351 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2353 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2354 this means we avoid the OCSP request, we wasted the setup
2355 cost in tls_init(). */
2356 require_ocsp = verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
2357 request_ocsp = require_ocsp
2358 || verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2365 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
2366 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2367 tls_out.ocsp = OCSP_NOT_RESP;
2371 #ifndef DISABLE_EVENT
2372 client_static_cbinfo->event_action = tb->event_action;
2375 /* There doesn't seem to be a built-in timeout on connection. */
2377 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2378 sigalrm_seen = FALSE;
2379 alarm(ob->command_timeout);
2380 rc = SSL_connect(client_ssl);
2383 #ifdef EXPERIMENTAL_DANE
2385 DANESSL_cleanup(client_ssl);
2389 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL,
2392 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
2394 peer_cert(client_ssl, &tls_out, peerdn, sizeof(peerdn));
2396 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
2397 tls_out.cipher = cipherbuf;
2399 /* Record the certificate we presented */
2401 X509 * crt = SSL_get_certificate(client_ssl);
2402 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
2405 tls_out.active = fd;
2414 tls_refill(unsigned lim)
2419 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2420 ssl_xfer_buffer, ssl_xfer_buffer_size);
2422 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2423 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2424 MIN(ssl_xfer_buffer_size, lim));
2425 error = SSL_get_error(server_ssl, inbytes);
2428 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2429 closed down, not that the socket itself has been closed down. Revert to
2430 non-SSL handling. */
2432 if (error == SSL_ERROR_ZERO_RETURN)
2434 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2436 receive_getc = smtp_getc;
2437 receive_getbuf = smtp_getbuf;
2438 receive_get_cache = smtp_get_cache;
2439 receive_ungetc = smtp_ungetc;
2440 receive_feof = smtp_feof;
2441 receive_ferror = smtp_ferror;
2442 receive_smtp_buffered = smtp_buffered;
2444 SSL_free(server_ssl);
2448 tls_in.cipher = NULL;
2449 tls_in.peerdn = NULL;
2455 /* Handle genuine errors */
2457 else if (error == SSL_ERROR_SSL)
2459 ERR_error_string(ERR_get_error(), ssl_errstring);
2460 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2465 else if (error != SSL_ERROR_NONE)
2467 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2472 #ifndef DISABLE_DKIM
2473 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2475 ssl_xfer_buffer_hwm = inbytes;
2476 ssl_xfer_buffer_lwm = 0;
2481 /*************************************************
2482 * TLS version of getc *
2483 *************************************************/
2485 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2486 it refills the buffer via the SSL reading function.
2488 Arguments: lim Maximum amount to read/buffer
2489 Returns: the next character or EOF
2491 Only used by the server-side TLS.
2495 tls_getc(unsigned lim)
2497 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2498 if (!tls_refill(lim))
2499 return ssl_xfer_error ? EOF : smtp_getc(lim);
2501 /* Something in the buffer; return next uschar */
2503 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2507 tls_getbuf(unsigned * len)
2512 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2513 if (!tls_refill(*len))
2515 if (!ssl_xfer_error) return smtp_getbuf(len);
2520 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2522 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2523 ssl_xfer_buffer_lwm += size;
2532 #ifndef DISABLE_DKIM
2533 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2535 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2541 tls_could_read(void)
2543 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2547 /*************************************************
2548 * Read bytes from TLS channel *
2549 *************************************************/
2556 Returns: the number of bytes read
2557 -1 after a failed read
2559 Only used by the client-side TLS.
2563 tls_read(BOOL is_server, uschar *buff, size_t len)
2565 SSL *ssl = is_server ? server_ssl : client_ssl;
2569 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2570 buff, (unsigned int)len);
2572 inbytes = SSL_read(ssl, CS buff, len);
2573 error = SSL_get_error(ssl, inbytes);
2575 if (error == SSL_ERROR_ZERO_RETURN)
2577 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2580 else if (error != SSL_ERROR_NONE)
2590 /*************************************************
2591 * Write bytes down TLS channel *
2592 *************************************************/
2596 is_server channel specifier
2599 more further data expected soon
2601 Returns: the number of bytes after a successful write,
2602 -1 after a failed write
2604 Used by both server-side and client-side TLS.
2608 tls_write(BOOL is_server, const uschar *buff, size_t len, BOOL more)
2610 int outbytes, error, left;
2611 SSL *ssl = is_server ? server_ssl : client_ssl;
2612 static gstring * corked = NULL;
2614 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
2615 buff, (unsigned long)len, more ? ", more" : "");
2617 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2618 "more" is notified. This hack is only ok if small amounts are involved AND only
2619 one stream does it, in one context (i.e. no store reset). Currently it is used
2620 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. */
2622 if (is_server && (more || corked))
2624 corked = string_catn(corked, buff, len);
2627 buff = CUS corked->s;
2632 for (left = len; left > 0;)
2634 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
2635 outbytes = SSL_write(ssl, CS buff, left);
2636 error = SSL_get_error(ssl, outbytes);
2637 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2641 ERR_error_string(ERR_get_error(), ssl_errstring);
2642 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2645 case SSL_ERROR_NONE:
2650 case SSL_ERROR_ZERO_RETURN:
2651 log_write(0, LOG_MAIN, "SSL channel closed on write");
2654 case SSL_ERROR_SYSCALL:
2655 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
2656 sender_fullhost ? sender_fullhost : US"<unknown>",
2661 log_write(0, LOG_MAIN, "SSL_write error %d", error);
2670 /*************************************************
2671 * Close down a TLS session *
2672 *************************************************/
2674 /* This is also called from within a delivery subprocess forked from the
2675 daemon, to shut down the TLS library, without actually doing a shutdown (which
2676 would tamper with the SSL session in the parent process).
2678 Arguments: TRUE if SSL_shutdown is to be called
2681 Used by both server-side and client-side TLS.
2685 tls_close(BOOL is_server, BOOL shutdown)
2687 SSL **sslp = is_server ? &server_ssl : &client_ssl;
2688 int *fdp = is_server ? &tls_in.active : &tls_out.active;
2690 if (*fdp < 0) return; /* TLS was not active */
2694 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
2695 SSL_shutdown(*sslp);
2707 /*************************************************
2708 * Let tls_require_ciphers be checked at startup *
2709 *************************************************/
2711 /* The tls_require_ciphers option, if set, must be something which the
2714 Returns: NULL on success, or error message
2718 tls_validate_require_cipher(void)
2721 uschar *s, *expciphers, *err;
2723 /* this duplicates from tls_init(), we need a better "init just global
2724 state, for no specific purpose" singleton function of our own */
2726 SSL_load_error_strings();
2727 OpenSSL_add_ssl_algorithms();
2728 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2729 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2730 list of available digests. */
2731 EVP_add_digest(EVP_sha256());
2734 if (!(tls_require_ciphers && *tls_require_ciphers))
2737 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
2739 return US"failed to expand tls_require_ciphers";
2741 if (!(expciphers && *expciphers))
2744 /* normalisation ripped from above */
2746 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2750 ctx = SSL_CTX_new(SSLv23_server_method());
2753 ERR_error_string(ERR_get_error(), ssl_errstring);
2754 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2758 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2760 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2762 ERR_error_string(ERR_get_error(), ssl_errstring);
2763 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
2764 expciphers, ssl_errstring);
2775 /*************************************************
2776 * Report the library versions. *
2777 *************************************************/
2779 /* There have historically been some issues with binary compatibility in
2780 OpenSSL libraries; if Exim (like many other applications) is built against
2781 one version of OpenSSL but the run-time linker picks up another version,
2782 it can result in serious failures, including crashing with a SIGSEGV. So
2783 report the version found by the compiler and the run-time version.
2785 Note: some OS vendors backport security fixes without changing the version
2786 number/string, and the version date remains unchanged. The _build_ date
2787 will change, so we can more usefully assist with version diagnosis by also
2788 reporting the build date.
2790 Arguments: a FILE* to print the results to
2795 tls_version_report(FILE *f)
2797 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2800 OPENSSL_VERSION_TEXT,
2801 SSLeay_version(SSLEAY_VERSION),
2802 SSLeay_version(SSLEAY_BUILT_ON));
2803 /* third line is 38 characters for the %s and the line is 73 chars long;
2804 the OpenSSL output includes a "built on: " prefix already. */
2810 /*************************************************
2811 * Random number generation *
2812 *************************************************/
2814 /* Pseudo-random number generation. The result is not expected to be
2815 cryptographically strong but not so weak that someone will shoot themselves
2816 in the foot using it as a nonce in input in some email header scheme or
2817 whatever weirdness they'll twist this into. The result should handle fork()
2818 and avoid repeating sequences. OpenSSL handles that for us.
2822 Returns a random number in range [0, max-1]
2826 vaguely_random_number(int max)
2830 static pid_t pidlast = 0;
2833 uschar smallbuf[sizeof(r)];
2839 if (pidnow != pidlast)
2841 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2842 is unique for each thread", this doesn't apparently apply across processes,
2843 so our own warning from vaguely_random_number_fallback() applies here too.
2844 Fix per PostgreSQL. */
2850 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2854 gettimeofday(&r.tv, NULL);
2857 RAND_seed(US (&r), sizeof(r));
2859 /* We're after pseudo-random, not random; if we still don't have enough data
2860 in the internal PRNG then our options are limited. We could sleep and hope
2861 for entropy to come along (prayer technique) but if the system is so depleted
2862 in the first place then something is likely to just keep taking it. Instead,
2863 we'll just take whatever little bit of pseudo-random we can still manage to
2866 needed_len = sizeof(r);
2867 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2868 asked for a number less than 10. */
2869 for (r = max, i = 0; r; ++i)
2875 #ifdef EXIM_HAVE_RAND_PSEUDO
2876 /* We do not care if crypto-strong */
2877 i = RAND_pseudo_bytes(smallbuf, needed_len);
2879 i = RAND_bytes(smallbuf, needed_len);
2885 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2886 return vaguely_random_number_fallback(max);
2890 for (p = smallbuf; needed_len; --needed_len, ++p)
2896 /* We don't particularly care about weighted results; if someone wants
2897 smooth distribution and cares enough then they should submit a patch then. */
2904 /*************************************************
2905 * OpenSSL option parse *
2906 *************************************************/
2908 /* Parse one option for tls_openssl_options_parse below
2911 name one option name
2912 value place to store a value for it
2913 Returns success or failure in parsing
2916 struct exim_openssl_option {
2920 /* We could use a macro to expand, but we need the ifdef and not all the
2921 options document which version they were introduced in. Policylet: include
2922 all options unless explicitly for DTLS, let the administrator choose which
2925 This list is current as of:
2927 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2929 static struct exim_openssl_option exim_openssl_options[] = {
2930 /* KEEP SORTED ALPHABETICALLY! */
2932 { US"all", SSL_OP_ALL },
2934 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2935 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2937 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2938 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2940 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2941 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2943 #ifdef SSL_OP_EPHEMERAL_RSA
2944 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2946 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2947 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2949 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2950 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2952 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2953 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2955 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2956 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2958 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2959 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2961 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2962 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2964 #ifdef SSL_OP_NO_COMPRESSION
2965 { US"no_compression", SSL_OP_NO_COMPRESSION },
2967 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2968 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2970 #ifdef SSL_OP_NO_SSLv2
2971 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2973 #ifdef SSL_OP_NO_SSLv3
2974 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2976 #ifdef SSL_OP_NO_TICKET
2977 { US"no_ticket", SSL_OP_NO_TICKET },
2979 #ifdef SSL_OP_NO_TLSv1
2980 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2982 #ifdef SSL_OP_NO_TLSv1_1
2983 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2984 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2985 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2987 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2990 #ifdef SSL_OP_NO_TLSv1_2
2991 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2993 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2994 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2996 #ifdef SSL_OP_SINGLE_DH_USE
2997 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2999 #ifdef SSL_OP_SINGLE_ECDH_USE
3000 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
3002 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
3003 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
3005 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
3006 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
3008 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
3009 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
3011 #ifdef SSL_OP_TLS_D5_BUG
3012 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
3014 #ifdef SSL_OP_TLS_ROLLBACK_BUG
3015 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
3018 static int exim_openssl_options_size =
3019 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
3023 tls_openssl_one_option_parse(uschar *name, long *value)
3026 int last = exim_openssl_options_size;
3027 while (last > first)
3029 int middle = (first + last)/2;
3030 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3033 *value = exim_openssl_options[middle].value;
3047 /*************************************************
3048 * OpenSSL option parsing logic *
3049 *************************************************/
3051 /* OpenSSL has a number of compatibility options which an administrator might
3052 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3053 we look like log_selector.
3056 option_spec the administrator-supplied string of options
3057 results ptr to long storage for the options bitmap
3058 Returns success or failure
3062 tls_openssl_options_parse(uschar *option_spec, long *results)
3067 BOOL adding, item_parsed;
3069 result = SSL_OP_NO_TICKET;
3070 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3071 * from default because it increases BEAST susceptibility. */
3072 #ifdef SSL_OP_NO_SSLv2
3073 result |= SSL_OP_NO_SSLv2;
3075 #ifdef SSL_OP_SINGLE_DH_USE
3076 result |= SSL_OP_SINGLE_DH_USE;
3085 for (s=option_spec; *s != '\0'; /**/)
3087 while (isspace(*s)) ++s;
3090 if (*s != '+' && *s != '-')
3092 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3093 "+ or - expected but found \"%s\"\n", s);
3096 adding = *s++ == '+';
3097 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3100 item_parsed = tls_openssl_one_option_parse(s, &item);
3104 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3107 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
3108 adding ? "adding" : "removing", result, item, s);
3122 /* End of tls-openssl.c */