1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2016 */
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
73 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
74 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
75 # define EXIM_HAVE_OPENSSL_CHECKHOST
79 #if !defined(LIBRESSL_VERSION_NUMBER) \
80 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
81 # if !defined(OPENSSL_NO_ECDH)
82 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
83 # define EXIM_HAVE_ECDH
85 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
86 # if OPENSSL_VERSION_NUMBER < 0x10100000L
87 # define EXIM_HAVE_OPENSSL_ECDH_AUTO
89 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
94 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
95 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
99 /* Structure for collecting random data for seeding. */
101 typedef struct randstuff {
106 /* Local static variables */
108 static BOOL client_verify_callback_called = FALSE;
109 static BOOL server_verify_callback_called = FALSE;
110 static const uschar *sid_ctx = US"exim";
112 /* We have three different contexts to care about.
114 Simple case: client, `client_ctx`
115 As a client, we can be doing a callout or cut-through delivery while receiving
116 a message. So we have a client context, which should have options initialised
117 from the SMTP Transport.
120 There are two cases: with and without ServerNameIndication from the client.
121 Given TLS SNI, we can be using different keys, certs and various other
122 configuration settings, because they're re-expanded with $tls_sni set. This
123 allows vhosting with TLS. This SNI is sent in the handshake.
124 A client might not send SNI, so we need a fallback, and an initial setup too.
125 So as a server, we start out using `server_ctx`.
126 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
127 `server_sni` from `server_ctx` and then initialise settings by re-expanding
131 static SSL_CTX *client_ctx = NULL;
132 static SSL_CTX *server_ctx = NULL;
133 static SSL *client_ssl = NULL;
134 static SSL *server_ssl = NULL;
136 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
137 static SSL_CTX *server_sni = NULL;
140 static char ssl_errstring[256];
142 static int ssl_session_timeout = 200;
143 static BOOL client_verify_optional = FALSE;
144 static BOOL server_verify_optional = FALSE;
146 static BOOL reexpand_tls_files_for_sni = FALSE;
149 typedef struct tls_ext_ctx_cb {
154 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
158 uschar *file_expanded;
159 OCSP_RESPONSE *response;
162 X509_STORE *verify_store; /* non-null if status requested */
163 BOOL verify_required;
168 /* these are cached from first expand */
169 uschar *server_cipher_list;
170 /* only passed down to tls_error: */
172 const uschar * verify_cert_hostnames;
173 #ifndef DISABLE_EVENT
174 uschar * event_action;
178 /* should figure out a cleanup of API to handle state preserved per
179 implementation, for various reasons, which can be void * in the APIs.
180 For now, we hack around it. */
181 tls_ext_ctx_cb *client_static_cbinfo = NULL;
182 tls_ext_ctx_cb *server_static_cbinfo = NULL;
185 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
186 int (*cert_vfy_cb)(int, X509_STORE_CTX *) );
189 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
190 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
193 static int tls_server_stapling_cb(SSL *s, void *arg);
197 /*************************************************
199 *************************************************/
201 /* Called from lots of places when errors occur before actually starting to do
202 the TLS handshake, that is, while the session is still in clear. Always returns
203 DEFER for a server and FAIL for a client so that most calls can use "return
204 tls_error(...)" to do this processing and then give an appropriate return. A
205 single function is used for both server and client, because it is called from
206 some shared functions.
209 prefix text to include in the logged error
210 host NULL if setting up a server;
211 the connected host if setting up a client
212 msg error message or NULL if we should ask OpenSSL
214 Returns: OK/DEFER/FAIL
218 tls_error(uschar * prefix, const host_item * host, uschar * msg)
222 ERR_error_string(ERR_get_error(), ssl_errstring);
223 msg = (uschar *)ssl_errstring;
228 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection (%s): %s",
229 host->name, host->address, prefix, msg);
234 uschar *conn_info = smtp_get_connection_info();
235 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
237 /* I'd like to get separated H= here, but too hard for now */
238 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
239 conn_info, prefix, msg);
246 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
247 /*************************************************
248 * Callback to generate RSA key *
249 *************************************************/
257 Returns: pointer to generated key
261 rsa_callback(SSL *s, int export, int keylength)
264 #ifdef EXIM_HAVE_RSA_GENKEY_EX
265 BIGNUM *bn = BN_new();
268 export = export; /* Shut picky compilers up */
269 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
271 #ifdef EXIM_HAVE_RSA_GENKEY_EX
272 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
273 || !(rsa_key = RSA_new())
274 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
277 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
281 ERR_error_string(ERR_get_error(), ssl_errstring);
282 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
295 x509_store_dump_cert_s_names(X509_STORE * store)
297 STACK_OF(X509_OBJECT) * roots= store->objs;
299 static uschar name[256];
301 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
303 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
304 if(tmp_obj->type == X509_LU_X509)
306 X509 * current_cert= tmp_obj->data.x509;
307 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
308 name[sizeof(name)-1] = '\0';
309 debug_printf(" %s\n", name);
317 #ifndef DISABLE_EVENT
319 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
320 BOOL *calledp, const BOOL *optionalp, const uschar * what)
326 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
329 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
330 old_cert = tlsp->peercert;
331 tlsp->peercert = X509_dup(cert);
332 /* NB we do not bother setting peerdn */
333 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
335 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
336 "depth=%d cert=%s: %s",
337 tlsp == &tls_out ? deliver_host_address : sender_host_address,
338 what, depth, dn, yield);
342 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
343 return 1; /* reject (leaving peercert set) */
345 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
346 "(host in tls_try_verify_hosts)\n");
348 X509_free(tlsp->peercert);
349 tlsp->peercert = old_cert;
355 /*************************************************
356 * Callback for verification *
357 *************************************************/
359 /* The SSL library does certificate verification if set up to do so. This
360 callback has the current yes/no state is in "state". If verification succeeded,
361 we set the certificate-verified flag. If verification failed, what happens
362 depends on whether the client is required to present a verifiable certificate
365 If verification is optional, we change the state to yes, but still log the
366 verification error. For some reason (it really would help to have proper
367 documentation of OpenSSL), this callback function then gets called again, this
368 time with state = 1. We must take care not to set the private verified flag on
369 the second time through.
371 Note: this function is not called if the client fails to present a certificate
372 when asked. We get here only if a certificate has been received. Handling of
373 optional verification for this case is done when requesting SSL to verify, by
374 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
376 May be called multiple times for different issues with a certificate, even
377 for a given "depth" in the certificate chain.
380 preverify_ok current yes/no state as 1/0
381 x509ctx certificate information.
382 tlsp per-direction (client vs. server) support data
383 calledp has-been-called flag
384 optionalp verification-is-optional flag
386 Returns: 0 if verification should fail, otherwise 1
390 verify_callback(int preverify_ok, X509_STORE_CTX *x509ctx,
391 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
393 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
394 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
397 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
398 dn[sizeof(dn)-1] = '\0';
400 if (preverify_ok == 0)
402 log_write(0, LOG_MAIN, "[%s] SSL verify error: depth=%d error=%s cert=%s",
403 tlsp == &tls_out ? deliver_host_address : sender_host_address,
405 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
411 tlsp->peercert = X509_dup(cert); /* record failing cert */
412 return 0; /* reject */
414 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
415 "tls_try_verify_hosts)\n");
420 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
422 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
423 { /* client, wanting stapling */
424 /* Add the server cert's signing chain as the one
425 for the verification of the OCSP stapled information. */
427 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
430 sk_X509_push(client_static_cbinfo->verify_stack, cert);
433 #ifndef DISABLE_EVENT
434 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
435 return 0; /* reject, with peercert set */
440 const uschar * verify_cert_hostnames;
442 if ( tlsp == &tls_out
443 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
444 /* client, wanting hostname check */
447 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
448 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
449 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
451 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
452 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
455 const uschar * list = verify_cert_hostnames;
458 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
459 if ((rc = X509_check_host(cert, CCS name, 0,
460 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
461 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
466 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
467 tlsp == &tls_out ? deliver_host_address : sender_host_address);
474 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
477 log_write(0, LOG_MAIN,
478 "[%s] SSL verify error: certificate name mismatch: \"%s\"",
479 tlsp == &tls_out ? deliver_host_address : sender_host_address,
485 tlsp->peercert = X509_dup(cert); /* record failing cert */
486 return 0; /* reject */
488 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
489 "tls_try_verify_hosts)\n");
493 #ifndef DISABLE_EVENT
494 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
495 return 0; /* reject, with peercert set */
498 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
499 *calledp ? "" : " authenticated", dn);
500 if (!*calledp) tlsp->certificate_verified = TRUE;
504 return 1; /* accept, at least for this level */
508 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
510 return verify_callback(preverify_ok, x509ctx, &tls_out,
511 &client_verify_callback_called, &client_verify_optional);
515 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
517 return verify_callback(preverify_ok, x509ctx, &tls_in,
518 &server_verify_callback_called, &server_verify_optional);
522 #ifdef EXPERIMENTAL_DANE
524 /* This gets called *by* the dane library verify callback, which interposes
528 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
530 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
532 #ifndef DISABLE_EVENT
533 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
534 BOOL dummy_called, optional = FALSE;
537 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
538 dn[sizeof(dn)-1] = '\0';
540 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
541 preverify_ok ? "ok":"BAD", depth, dn);
543 #ifndef DISABLE_EVENT
544 if (verify_event(&tls_out, cert, depth, dn,
545 &dummy_called, &optional, US"DANE"))
546 return 0; /* reject, with peercert set */
549 if (preverify_ok == 1)
550 tls_out.dane_verified =
551 tls_out.certificate_verified = TRUE;
554 int err = X509_STORE_CTX_get_error(x509ctx);
556 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
557 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
563 #endif /*EXPERIMENTAL_DANE*/
566 /*************************************************
567 * Information callback *
568 *************************************************/
570 /* The SSL library functions call this from time to time to indicate what they
571 are doing. We copy the string to the debugging output when TLS debugging has
583 info_callback(SSL *s, int where, int ret)
587 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
592 /*************************************************
593 * Initialize for DH *
594 *************************************************/
596 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
599 sctx The current SSL CTX (inbound or outbound)
600 dhparam DH parameter file or fixed parameter identity string
601 host connected host, if client; NULL if server
603 Returns: TRUE if OK (nothing to set up, or setup worked)
607 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host)
614 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
617 if (!dhexpanded || !*dhexpanded)
618 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
619 else if (dhexpanded[0] == '/')
621 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
623 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
624 host, US strerror(errno));
630 if (Ustrcmp(dhexpanded, "none") == 0)
632 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
636 if (!(pem = std_dh_prime_named(dhexpanded)))
638 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
639 host, US strerror(errno));
642 bio = BIO_new_mem_buf(CS pem, -1);
645 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
648 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
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 ((8*DH_size(dh)) > tls_dh_max_bits)
659 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
660 8*DH_size(dh), 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", 8*DH_size(dh));
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
703 Returns: TRUE if OK (nothing to set up, or setup worked)
707 init_ecdh(SSL_CTX * sctx, host_item * host)
709 #ifdef OPENSSL_NO_ECDH
718 if (host) /* No ECDH setup for clients, only for servers */
721 # ifndef EXIM_HAVE_ECDH
723 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
727 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve))
729 if (!exp_curve || !*exp_curve)
732 # ifdef EXIM_HAVE_OPENSSL_ECDH_AUTO
733 /* check if new enough library to support auto ECDH temp key parameter selection */
734 if (Ustrcmp(exp_curve, "auto") == 0)
736 DEBUG(D_tls) debug_printf(
737 "ECDH temp key parameter settings: OpenSSL 1.2+ autoselection\n");
738 SSL_CTX_set_ecdh_auto(sctx, 1);
743 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
744 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
745 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
746 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
750 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'",
756 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
758 tls_error(US"Unable to create ec curve", host, NULL);
762 /* The "tmp" in the name here refers to setting a temporary key
763 not to the stability of the interface. */
765 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
766 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL);
768 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
773 # endif /*EXIM_HAVE_ECDH*/
774 #endif /*OPENSSL_NO_ECDH*/
781 /*************************************************
782 * Load OCSP information into state *
783 *************************************************/
784 /* Called to load the server OCSP response from the given file into memory, once
785 caller has determined this is needed. Checks validity. Debugs a message
788 ASSUMES: single response, for single cert.
791 sctx the SSL_CTX* to update
792 cbinfo various parts of session state
793 expanded the filename putatively holding an OCSP response
798 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
801 OCSP_RESPONSE * resp;
802 OCSP_BASICRESP * basic_response;
803 OCSP_SINGLERESP * single_response;
804 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
806 unsigned long verify_flags;
807 int status, reason, i;
809 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
810 if (cbinfo->u_ocsp.server.response)
812 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
813 cbinfo->u_ocsp.server.response = NULL;
816 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
818 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
819 cbinfo->u_ocsp.server.file_expanded);
823 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
827 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
831 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
833 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
834 OCSP_response_status_str(status), status);
838 if (!(basic_response = OCSP_response_get1_basic(resp)))
841 debug_printf("OCSP response parse error: unable to extract basic response.\n");
845 sk = cbinfo->verify_stack;
846 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
848 /* May need to expose ability to adjust those flags?
849 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
850 OCSP_TRUSTOTHER OCSP_NOINTERN */
852 /* This does a full verify on the OCSP proof before we load it for serviing
853 up; possibly overkill - just date-checks might be nice enough.
855 OCSP_basic_verify takes a "store" arg, but does not
856 use it for the chain verification, which is all we do
857 when OCSP_NOVERIFY is set. The content from the wire
858 "basic_response" and a cert-stack "sk" are all that is used.
860 We have a stack, loaded in setup_certs() if tls_verify_certificates
861 was a file (not a directory, or "system"). It is unfortunate we
862 cannot used the connection context store, as that would neatly
863 handle the "system" case too, but there seems to be no library
864 function for getting a stack from a store.
865 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
866 We do not free the stack since it could be needed a second time for
869 Seperately we might try to replace using OCSP_basic_verify() - which seems to not
870 be a public interface into the OpenSSL library (there's no manual entry) -
871 But what with? We also use OCSP_basic_verify in the client stapling callback.
872 And there we NEED it; we miust verify that status... unless the
873 library does it for us anyway? */
875 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
879 ERR_error_string(ERR_get_error(), ssl_errstring);
880 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
885 /* Here's the simplifying assumption: there's only one response, for the
886 one certificate we use, and nothing for anything else in a chain. If this
887 proves false, we need to extract a cert id from our issued cert
888 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
889 right cert in the stack and then calls OCSP_single_get0_status()).
891 I'm hoping to avoid reworking a bunch more of how we handle state here. */
893 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
896 debug_printf("Unable to get first response from OCSP basic response.\n");
900 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
901 if (status != V_OCSP_CERTSTATUS_GOOD)
903 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
904 OCSP_cert_status_str(status), status,
905 OCSP_crl_reason_str(reason), reason);
909 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
911 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
916 cbinfo->u_ocsp.server.response = resp;
920 if (running_in_test_harness)
922 extern char ** environ;
924 if (environ) for (p = USS environ; *p != NULL; p++)
925 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
927 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
928 goto supply_response;
933 #endif /*!DISABLE_OCSP*/
938 /* Create and install a selfsigned certificate, for use in server mode */
941 tls_install_selfsign(SSL_CTX * sctx)
949 where = US"allocating pkey";
950 if (!(pkey = EVP_PKEY_new()))
953 where = US"allocating cert";
954 if (!(x509 = X509_new()))
957 where = US"generating pkey";
958 /* deprecated, use RSA_generate_key_ex() */
959 if (!(rsa = RSA_generate_key(1024, RSA_F4, NULL, NULL)))
962 where = US"assiging pkey";
963 if (!EVP_PKEY_assign_RSA(pkey, rsa))
966 X509_set_version(x509, 2); /* N+1 - version 3 */
967 ASN1_INTEGER_set(X509_get_serialNumber(x509), 0);
968 X509_gmtime_adj(X509_get_notBefore(x509), 0);
969 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
970 X509_set_pubkey(x509, pkey);
972 name = X509_get_subject_name(x509);
973 X509_NAME_add_entry_by_txt(name, "C",
974 MBSTRING_ASC, CUS "UK", -1, -1, 0);
975 X509_NAME_add_entry_by_txt(name, "O",
976 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
977 X509_NAME_add_entry_by_txt(name, "CN",
978 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
979 X509_set_issuer_name(x509, name);
981 where = US"signing cert";
982 if (!X509_sign(x509, pkey, EVP_md5()))
985 where = US"installing selfsign cert";
986 if (!SSL_CTX_use_certificate(sctx, x509))
989 where = US"installing selfsign key";
990 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
996 (void) tls_error(where, NULL, NULL);
997 if (x509) X509_free(x509);
998 if (pkey) EVP_PKEY_free(pkey);
1005 /*************************************************
1006 * Expand key and cert file specs *
1007 *************************************************/
1009 /* Called once during tls_init and possibly again during TLS setup, for a
1010 new context, if Server Name Indication was used and tls_sni was seen in
1011 the certificate string.
1014 sctx the SSL_CTX* to update
1015 cbinfo various parts of session state
1017 Returns: OK/DEFER/FAIL
1021 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
1025 if (!cbinfo->certificate)
1027 if (cbinfo->host) /* client */
1030 if (tls_install_selfsign(sctx) != OK)
1035 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1036 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1037 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1039 reexpand_tls_files_for_sni = TRUE;
1041 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
1044 if (expanded != NULL)
1046 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
1047 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
1048 return tls_error(string_sprintf(
1049 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
1050 cbinfo->host, NULL);
1053 if (cbinfo->privatekey != NULL &&
1054 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
1057 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1058 of the expansion is an empty string, ignore it also, and assume the private
1059 key is in the same file as the certificate. */
1061 if (expanded && *expanded)
1063 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
1064 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
1065 return tls_error(string_sprintf(
1066 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
1070 #ifndef DISABLE_OCSP
1071 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1073 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded))
1076 if (expanded && *expanded)
1078 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1079 if ( cbinfo->u_ocsp.server.file_expanded
1080 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1082 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1085 ocsp_load_response(sctx, cbinfo, expanded);
1096 /*************************************************
1097 * Callback to handle SNI *
1098 *************************************************/
1100 /* Called when acting as server during the TLS session setup if a Server Name
1101 Indication extension was sent by the client.
1103 API documentation is OpenSSL s_server.c implementation.
1106 s SSL* of the current session
1107 ad unknown (part of OpenSSL API) (unused)
1108 arg Callback of "our" registered data
1110 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1113 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1115 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1117 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1118 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1120 int old_pool = store_pool;
1123 return SSL_TLSEXT_ERR_OK;
1125 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1126 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1128 /* Make the extension value available for expansion */
1129 store_pool = POOL_PERM;
1130 tls_in.sni = string_copy(US servername);
1131 store_pool = old_pool;
1133 if (!reexpand_tls_files_for_sni)
1134 return SSL_TLSEXT_ERR_OK;
1136 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1137 not confident that memcpy wouldn't break some internal reference counting.
1138 Especially since there's a references struct member, which would be off. */
1140 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1142 ERR_error_string(ERR_get_error(), ssl_errstring);
1143 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1144 return SSL_TLSEXT_ERR_NOACK;
1147 /* Not sure how many of these are actually needed, since SSL object
1148 already exists. Might even need this selfsame callback, for reneg? */
1150 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1151 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1152 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1153 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1154 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1155 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1157 if ( !init_dh(server_sni, cbinfo->dhparam, NULL)
1158 || !init_ecdh(server_sni, NULL)
1160 return SSL_TLSEXT_ERR_NOACK;
1162 if (cbinfo->server_cipher_list)
1163 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
1164 #ifndef DISABLE_OCSP
1165 if (cbinfo->u_ocsp.server.file)
1167 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1168 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1172 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1173 verify_callback_server)) != OK)
1174 return SSL_TLSEXT_ERR_NOACK;
1176 /* do this after setup_certs, because this can require the certs for verifying
1177 OCSP information. */
1178 if ((rc = tls_expand_session_files(server_sni, cbinfo)) != OK)
1179 return SSL_TLSEXT_ERR_NOACK;
1181 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1182 SSL_set_SSL_CTX(s, server_sni);
1184 return SSL_TLSEXT_ERR_OK;
1186 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1191 #ifndef DISABLE_OCSP
1193 /*************************************************
1194 * Callback to handle OCSP Stapling *
1195 *************************************************/
1197 /* Called when acting as server during the TLS session setup if the client
1198 requests OCSP information with a Certificate Status Request.
1200 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1206 tls_server_stapling_cb(SSL *s, void *arg)
1208 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1209 uschar *response_der;
1210 int response_der_len;
1213 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1214 cbinfo->u_ocsp.server.response ? "have" : "lack");
1216 tls_in.ocsp = OCSP_NOT_RESP;
1217 if (!cbinfo->u_ocsp.server.response)
1218 return SSL_TLSEXT_ERR_NOACK;
1220 response_der = NULL;
1221 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
1223 if (response_der_len <= 0)
1224 return SSL_TLSEXT_ERR_NOACK;
1226 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1227 tls_in.ocsp = OCSP_VFIED;
1228 return SSL_TLSEXT_ERR_OK;
1233 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1235 BIO_printf(bp, "\t%s: ", str);
1236 ASN1_GENERALIZEDTIME_print(bp, time);
1241 tls_client_stapling_cb(SSL *s, void *arg)
1243 tls_ext_ctx_cb * cbinfo = arg;
1244 const unsigned char * p;
1246 OCSP_RESPONSE * rsp;
1247 OCSP_BASICRESP * bs;
1250 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1251 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1254 /* Expect this when we requested ocsp but got none */
1255 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1256 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1258 DEBUG(D_tls) debug_printf(" null\n");
1259 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1262 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1264 tls_out.ocsp = OCSP_FAILED;
1265 if (LOGGING(tls_cipher))
1266 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1268 DEBUG(D_tls) debug_printf(" parse error\n");
1272 if(!(bs = OCSP_response_get1_basic(rsp)))
1274 tls_out.ocsp = OCSP_FAILED;
1275 if (LOGGING(tls_cipher))
1276 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1278 DEBUG(D_tls) debug_printf(" error parsing response\n");
1279 OCSP_RESPONSE_free(rsp);
1283 /* We'd check the nonce here if we'd put one in the request. */
1284 /* However that would defeat cacheability on the server so we don't. */
1286 /* This section of code reworked from OpenSSL apps source;
1287 The OpenSSL Project retains copyright:
1288 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1293 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1295 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
1297 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1299 /* Use the chain that verified the server cert to verify the stapled info */
1300 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1302 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1303 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1305 tls_out.ocsp = OCSP_FAILED;
1306 if (LOGGING(tls_cipher))
1307 log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
1308 BIO_printf(bp, "OCSP response verify failure\n");
1309 ERR_print_errors(bp);
1313 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1315 /*XXX So we have a good stapled OCSP status. How do we know
1316 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1317 OCSP_resp_find_status() which matches on a cert id, which presumably
1318 we should use. Making an id needs OCSP_cert_id_new(), which takes
1319 issuerName, issuerKey, serialNumber. Are they all in the cert?
1321 For now, carry on blindly accepting the resp. */
1324 OCSP_SINGLERESP * single;
1326 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1327 if (OCSP_resp_count(bs) != 1)
1329 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1330 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1333 tls_out.ocsp = OCSP_FAILED;
1334 log_write(0, LOG_MAIN, "OCSP stapling "
1335 "with multiple responses not handled");
1338 single = OCSP_resp_get0(bs, 0);
1339 status = OCSP_single_get0_status(single, &reason, &rev,
1340 &thisupd, &nextupd);
1343 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1344 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1345 if (!OCSP_check_validity(thisupd, nextupd,
1346 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1348 tls_out.ocsp = OCSP_FAILED;
1349 DEBUG(D_tls) ERR_print_errors(bp);
1350 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1354 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1355 OCSP_cert_status_str(status));
1358 case V_OCSP_CERTSTATUS_GOOD:
1359 tls_out.ocsp = OCSP_VFIED;
1362 case V_OCSP_CERTSTATUS_REVOKED:
1363 tls_out.ocsp = OCSP_FAILED;
1364 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1365 reason != -1 ? "; reason: " : "",
1366 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1367 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1370 tls_out.ocsp = OCSP_FAILED;
1371 log_write(0, LOG_MAIN,
1372 "Server certificate status unknown, in OCSP stapling");
1377 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1382 OCSP_RESPONSE_free(rsp);
1385 #endif /*!DISABLE_OCSP*/
1388 /*************************************************
1389 * Initialize for TLS *
1390 *************************************************/
1392 /* Called from both server and client code, to do preliminary initialization
1393 of the library. We allocate and return a context structure.
1396 ctxp returned SSL context
1397 host connected host, if client; NULL if server
1398 dhparam DH parameter file
1399 certificate certificate file
1400 privatekey private key
1401 ocsp_file file of stapling info (server); flag for require ocsp (client)
1402 addr address if client; NULL if server (for some randomness)
1403 cbp place to put allocated callback context
1405 Returns: OK/DEFER/FAIL
1409 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1411 #ifndef DISABLE_OCSP
1414 address_item *addr, tls_ext_ctx_cb ** cbp)
1419 tls_ext_ctx_cb * cbinfo;
1421 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1422 cbinfo->certificate = certificate;
1423 cbinfo->privatekey = privatekey;
1424 #ifndef DISABLE_OCSP
1425 cbinfo->verify_stack = NULL;
1426 if ((cbinfo->is_server = host==NULL))
1428 cbinfo->u_ocsp.server.file = ocsp_file;
1429 cbinfo->u_ocsp.server.file_expanded = NULL;
1430 cbinfo->u_ocsp.server.response = NULL;
1433 cbinfo->u_ocsp.client.verify_store = NULL;
1435 cbinfo->dhparam = dhparam;
1436 cbinfo->server_cipher_list = NULL;
1437 cbinfo->host = host;
1438 #ifndef DISABLE_EVENT
1439 cbinfo->event_action = NULL;
1442 SSL_load_error_strings(); /* basic set up */
1443 OpenSSL_add_ssl_algorithms();
1445 #ifdef EXIM_HAVE_SHA256
1446 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1447 list of available digests. */
1448 EVP_add_digest(EVP_sha256());
1451 /* Create a context.
1452 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1453 negotiation in the different methods; as far as I can tell, the only
1454 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1455 when OpenSSL is built without SSLv2 support.
1456 By disabling with openssl_options, we can let admins re-enable with the
1459 *ctxp = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method());
1461 if (!*ctxp) return tls_error(US"SSL_CTX_new", host, NULL);
1463 /* It turns out that we need to seed the random number generator this early in
1464 order to get the full complement of ciphers to work. It took me roughly a day
1465 of work to discover this by experiment.
1467 On systems that have /dev/urandom, SSL may automatically seed itself from
1468 there. Otherwise, we have to make something up as best we can. Double check
1474 gettimeofday(&r.tv, NULL);
1477 RAND_seed((uschar *)(&r), sizeof(r));
1478 RAND_seed((uschar *)big_buffer, big_buffer_size);
1479 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1482 return tls_error(US"RAND_status", host,
1483 US"unable to seed random number generator");
1486 /* Set up the information callback, which outputs if debugging is at a suitable
1489 DEBUG(D_tls) SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1491 /* Automatically re-try reads/writes after renegotiation. */
1492 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1494 /* Apply administrator-supplied work-arounds.
1495 Historically we applied just one requested option,
1496 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1497 moved to an administrator-controlled list of options to specify and
1498 grandfathered in the first one as the default value for "openssl_options".
1500 No OpenSSL version number checks: the options we accept depend upon the
1501 availability of the option value macros from OpenSSL. */
1503 okay = tls_openssl_options_parse(openssl_options, &init_options);
1505 return tls_error(US"openssl_options parsing failed", host, NULL);
1509 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1510 if (!(SSL_CTX_set_options(*ctxp, init_options)))
1511 return tls_error(string_sprintf(
1512 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1515 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1517 /* Initialize with DH parameters if supplied */
1518 /* Initialize ECDH temp key parameter selection */
1520 if ( !init_dh(*ctxp, dhparam, host)
1521 || !init_ecdh(*ctxp, host)
1525 /* Set up certificate and key (and perhaps OCSP info) */
1527 if ((rc = tls_expand_session_files(*ctxp, cbinfo)) != OK)
1530 /* If we need to handle SNI or OCSP, do so */
1532 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1533 # ifndef DISABLE_OCSP
1534 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1536 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1541 if (host == NULL) /* server */
1543 # ifndef DISABLE_OCSP
1544 /* We check u_ocsp.server.file, not server.response, because we care about if
1545 the option exists, not what the current expansion might be, as SNI might
1546 change the certificate and OCSP file in use between now and the time the
1547 callback is invoked. */
1548 if (cbinfo->u_ocsp.server.file)
1550 SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1551 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1554 /* We always do this, so that $tls_sni is available even if not used in
1556 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1557 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1559 # ifndef DISABLE_OCSP
1561 if(ocsp_file) /* wanting stapling */
1563 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1565 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1568 SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1569 SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1574 cbinfo->verify_cert_hostnames = NULL;
1576 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1577 /* Set up the RSA callback */
1578 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1581 /* Finally, set the timeout, and we are done */
1583 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1584 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1594 /*************************************************
1595 * Get name of cipher in use *
1596 *************************************************/
1599 Argument: pointer to an SSL structure for the connection
1600 buffer to use for answer
1602 pointer to number of bits for cipher
1607 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1609 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1610 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1611 the accessor functions use const in the prototype. */
1612 const SSL_CIPHER *c;
1615 ver = (const uschar *)SSL_get_version(ssl);
1617 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1618 SSL_CIPHER_get_bits(c, bits);
1620 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1621 SSL_CIPHER_get_name(c), *bits);
1623 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1628 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned bsize)
1630 /*XXX we might consider a list-of-certs variable for the cert chain.
1631 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1632 in list-handling functions, also consider the difference between the entire
1633 chain and the elements sent by the peer. */
1635 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1636 if (!tlsp->peercert)
1637 tlsp->peercert = SSL_get_peer_certificate(ssl);
1638 /* Beware anonymous ciphers which lead to server_cert being NULL */
1641 X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, bsize);
1642 peerdn[bsize-1] = '\0';
1643 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1646 tlsp->peerdn = NULL;
1653 /*************************************************
1654 * Set up for verifying certificates *
1655 *************************************************/
1657 /* Load certs from file, return TRUE on success */
1660 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
1665 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
1666 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
1667 sk_X509_push(verify_stack, x);
1674 /* Called by both client and server startup
1677 sctx SSL_CTX* to initialise
1678 certs certs file or NULL
1679 crl CRL file or NULL
1680 host NULL in a server; the remote host in a client
1681 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1682 otherwise passed as FALSE
1683 cert_vfy_cb Callback function for certificate verification
1685 Returns: OK/DEFER/FAIL
1689 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1690 int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1692 uschar *expcerts, *expcrl;
1694 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1697 if (expcerts && *expcerts)
1699 /* Tell the library to use its compiled-in location for the system default
1700 CA bundle. Then add the ones specified in the config, if any. */
1702 if (!SSL_CTX_set_default_verify_paths(sctx))
1703 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1705 if (Ustrcmp(expcerts, "system") != 0)
1707 struct stat statbuf;
1709 if (Ustat(expcerts, &statbuf) < 0)
1711 log_write(0, LOG_MAIN|LOG_PANIC,
1712 "failed to stat %s for certificates", expcerts);
1718 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1719 { file = NULL; dir = expcerts; }
1722 file = expcerts; dir = NULL;
1723 #ifndef DISABLE_OCSP
1724 /* In the server if we will be offering an OCSP proof, load chain from
1725 file for verifying the OCSP proof at load time. */
1728 && statbuf.st_size > 0
1729 && server_static_cbinfo->u_ocsp.server.file
1730 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
1733 log_write(0, LOG_MAIN|LOG_PANIC,
1734 "failed to load cert hain from %s", file);
1740 /* If a certificate file is empty, the next function fails with an
1741 unhelpful error message. If we skip it, we get the correct behaviour (no
1742 certificates are recognized, but the error message is still misleading (it
1743 says no certificate was supplied). But this is better. */
1745 if ( (!file || statbuf.st_size > 0)
1746 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1747 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1749 /* Load the list of CAs for which we will accept certs, for sending
1750 to the client. This is only for the one-file tls_verify_certificates
1752 If a list isn't loaded into the server, but
1753 some verify locations are set, the server end appears to make
1754 a wildcard reqest for client certs.
1755 Meanwhile, the client library as default behaviour *ignores* the list
1756 we send over the wire - see man SSL_CTX_set_client_cert_cb.
1757 Because of this, and that the dir variant is likely only used for
1758 the public-CA bundle (not for a private CA), not worth fixing.
1762 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
1764 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
1765 sk_X509_NAME_num(names));
1766 SSL_CTX_set_client_CA_list(sctx, names);
1771 /* Handle a certificate revocation list. */
1773 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1775 /* This bit of code is now the version supplied by Lars Mainka. (I have
1776 merely reformatted it into the Exim code style.)
1778 "From here I changed the code to add support for multiple crl's
1779 in pem format in one file or to support hashed directory entries in
1780 pem format instead of a file. This method now uses the library function
1781 X509_STORE_load_locations to add the CRL location to the SSL context.
1782 OpenSSL will then handle the verify against CA certs and CRLs by
1783 itself in the verify callback." */
1785 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1786 if (expcrl && *expcrl)
1788 struct stat statbufcrl;
1789 if (Ustat(expcrl, &statbufcrl) < 0)
1791 log_write(0, LOG_MAIN|LOG_PANIC,
1792 "failed to stat %s for certificates revocation lists", expcrl);
1797 /* is it a file or directory? */
1799 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1800 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1804 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1810 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1812 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1813 return tls_error(US"X509_STORE_load_locations", host, NULL);
1815 /* setting the flags to check against the complete crl chain */
1817 X509_STORE_set_flags(cvstore,
1818 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1822 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1824 /* If verification is optional, don't fail if no certificate */
1826 SSL_CTX_set_verify(sctx,
1827 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1836 /*************************************************
1837 * Start a TLS session in a server *
1838 *************************************************/
1840 /* This is called when Exim is running as a server, after having received
1841 the STARTTLS command. It must respond to that command, and then negotiate
1845 require_ciphers allowed ciphers
1847 Returns: OK on success
1848 DEFER for errors before the start of the negotiation
1849 FAIL for errors during the negotation; the server can't
1854 tls_server_start(const uschar *require_ciphers)
1858 tls_ext_ctx_cb *cbinfo;
1859 static uschar peerdn[256];
1860 static uschar cipherbuf[256];
1862 /* Check for previous activation */
1864 if (tls_in.active >= 0)
1866 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1867 smtp_printf("554 Already in TLS\r\n");
1871 /* Initialize the SSL library. If it fails, it will already have logged
1874 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1875 #ifndef DISABLE_OCSP
1878 NULL, &server_static_cbinfo);
1879 if (rc != OK) return rc;
1880 cbinfo = server_static_cbinfo;
1882 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1885 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1886 were historically separated by underscores. So that I can use either form in my
1887 tests, and also for general convenience, we turn underscores into hyphens here.
1892 uschar * s = expciphers;
1893 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1894 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1895 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1896 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1897 cbinfo->server_cipher_list = expciphers;
1900 /* If this is a host for which certificate verification is mandatory or
1901 optional, set up appropriately. */
1903 tls_in.certificate_verified = FALSE;
1904 #ifdef EXPERIMENTAL_DANE
1905 tls_in.dane_verified = FALSE;
1907 server_verify_callback_called = FALSE;
1909 if (verify_check_host(&tls_verify_hosts) == OK)
1911 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1912 FALSE, verify_callback_server);
1913 if (rc != OK) return rc;
1914 server_verify_optional = FALSE;
1916 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1918 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1919 TRUE, verify_callback_server);
1920 if (rc != OK) return rc;
1921 server_verify_optional = TRUE;
1924 /* Prepare for new connection */
1926 if (!(server_ssl = SSL_new(server_ctx))) return tls_error(US"SSL_new", NULL, NULL);
1928 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1930 * With the SSL_clear(), we get strange interoperability bugs with
1931 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1932 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1934 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1935 * session shutdown. In this case, we have a brand new object and there's no
1936 * obvious reason to immediately clear it. I'm guessing that this was
1937 * originally added because of incomplete initialisation which the clear fixed,
1938 * in some historic release.
1941 /* Set context and tell client to go ahead, except in the case of TLS startup
1942 on connection, where outputting anything now upsets the clients and tends to
1943 make them disconnect. We need to have an explicit fflush() here, to force out
1944 the response. Other smtp_printf() calls do not need it, because in non-TLS
1945 mode, the fflush() happens when smtp_getc() is called. */
1947 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1948 if (!tls_in.on_connect)
1950 smtp_printf("220 TLS go ahead\r\n");
1954 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1955 that the OpenSSL library doesn't. */
1957 SSL_set_wfd(server_ssl, fileno(smtp_out));
1958 SSL_set_rfd(server_ssl, fileno(smtp_in));
1959 SSL_set_accept_state(server_ssl);
1961 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1963 sigalrm_seen = FALSE;
1964 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1965 rc = SSL_accept(server_ssl);
1970 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1971 if (ERR_get_error() == 0)
1972 log_write(0, LOG_MAIN,
1973 "TLS client disconnected cleanly (rejected our certificate?)");
1977 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1979 /* TLS has been set up. Adjust the input functions to read via TLS,
1980 and initialize things. */
1982 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
1984 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1985 tls_in.cipher = cipherbuf;
1990 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1991 debug_printf("Shared ciphers: %s\n", buf);
1994 /* Record the certificate we presented */
1996 X509 * crt = SSL_get_certificate(server_ssl);
1997 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2000 /* Only used by the server-side tls (tls_in), including tls_getc.
2001 Client-side (tls_out) reads (seem to?) go via
2002 smtp_read_response()/ip_recv().
2003 Hence no need to duplicate for _in and _out.
2005 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2006 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2007 ssl_xfer_eof = ssl_xfer_error = 0;
2009 receive_getc = tls_getc;
2010 receive_get_cache = tls_get_cache;
2011 receive_ungetc = tls_ungetc;
2012 receive_feof = tls_feof;
2013 receive_ferror = tls_ferror;
2014 receive_smtp_buffered = tls_smtp_buffered;
2016 tls_in.active = fileno(smtp_out);
2024 tls_client_basic_ctx_init(SSL_CTX * ctx,
2025 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo
2029 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2030 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2031 the specified host patterns if one of them is defined */
2033 if ( ( !ob->tls_verify_hosts
2034 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2036 || (verify_check_given_host(&ob->tls_verify_hosts, host) == OK)
2038 client_verify_optional = FALSE;
2039 else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK)
2040 client_verify_optional = TRUE;
2044 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2045 ob->tls_crl, host, client_verify_optional, verify_callback_client)) != OK)
2048 if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
2050 cbinfo->verify_cert_hostnames =
2052 string_domain_utf8_to_alabel(host->name, NULL);
2056 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2057 cbinfo->verify_cert_hostnames);
2063 #ifdef EXPERIMENTAL_DANE
2065 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa)
2069 const char * hostnames[2] = { CS host->name, NULL };
2072 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2073 return tls_error(US"hostnames load", host, NULL);
2075 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
2077 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2078 ) if (rr->type == T_TLSA)
2080 const uschar * p = rr->data;
2081 uint8_t usage, selector, mtype;
2082 const char * mdname;
2086 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2087 if (usage != 2 && usage != 3) continue;
2094 default: continue; /* Only match-types 0, 1, 2 are supported */
2095 case 0: mdname = NULL; break;
2096 case 1: mdname = "sha256"; break;
2097 case 2: mdname = "sha512"; break;
2101 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2104 return tls_error(US"tlsa load", host, NULL);
2105 case 0: /* action not taken */
2109 tls_out.tlsa_usage |= 1<<usage;
2115 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2118 #endif /*EXPERIMENTAL_DANE*/
2122 /*************************************************
2123 * Start a TLS session in a client *
2124 *************************************************/
2126 /* Called from the smtp transport after STARTTLS has been accepted.
2129 fd the fd of the connection
2130 host connected host (for messages)
2131 addr the first address
2132 tb transport (always smtp)
2133 tlsa_dnsa tlsa lookup, if DANE, else null
2135 Returns: OK on success
2136 FAIL otherwise - note that tls_error() will not give DEFER
2137 because this is not a server
2141 tls_client_start(int fd, host_item *host, address_item *addr,
2142 transport_instance *tb
2143 #ifdef EXPERIMENTAL_DANE
2144 , dns_answer * tlsa_dnsa
2148 smtp_transport_options_block * ob =
2149 (smtp_transport_options_block *)tb->options_block;
2150 static uschar peerdn[256];
2151 uschar * expciphers;
2153 static uschar cipherbuf[256];
2155 #ifndef DISABLE_OCSP
2156 BOOL request_ocsp = FALSE;
2157 BOOL require_ocsp = FALSE;
2160 #ifdef EXPERIMENTAL_DANE
2161 tls_out.tlsa_usage = 0;
2164 #ifndef DISABLE_OCSP
2166 # ifdef EXPERIMENTAL_DANE
2168 && ob->hosts_request_ocsp[0] == '*'
2169 && ob->hosts_request_ocsp[1] == '\0'
2172 /* Unchanged from default. Use a safer one under DANE */
2173 request_ocsp = TRUE;
2174 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2175 " {= {4}{$tls_out_tlsa_usage}} } "
2181 verify_check_given_host(&ob->hosts_require_ocsp, host) == OK))
2182 request_ocsp = TRUE;
2184 # ifdef EXPERIMENTAL_DANE
2188 verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2192 rc = tls_init(&client_ctx, host, NULL,
2193 ob->tls_certificate, ob->tls_privatekey,
2194 #ifndef DISABLE_OCSP
2195 (void *)(long)request_ocsp,
2197 addr, &client_static_cbinfo);
2198 if (rc != OK) return rc;
2200 tls_out.certificate_verified = FALSE;
2201 client_verify_callback_called = FALSE;
2203 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2207 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2208 are separated by underscores. So that I can use either form in my tests, and
2209 also for general convenience, we turn underscores into hyphens here. */
2211 if (expciphers != NULL)
2213 uschar *s = expciphers;
2214 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2215 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2216 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
2217 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
2220 #ifdef EXPERIMENTAL_DANE
2223 SSL_CTX_set_verify(client_ctx,
2224 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2225 verify_callback_client_dane);
2227 if (!DANESSL_library_init())
2228 return tls_error(US"library init", host, NULL);
2229 if (DANESSL_CTX_init(client_ctx) <= 0)
2230 return tls_error(US"context init", host, NULL);
2236 if ((rc = tls_client_basic_ctx_init(client_ctx, host, ob, client_static_cbinfo))
2240 if ((client_ssl = SSL_new(client_ctx)) == NULL)
2241 return tls_error(US"SSL_new", host, NULL);
2242 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
2243 SSL_set_fd(client_ssl, fd);
2244 SSL_set_connect_state(client_ssl);
2248 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
2250 if (tls_out.sni == NULL)
2252 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2254 else if (!Ustrlen(tls_out.sni))
2258 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2259 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
2260 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
2262 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2268 #ifdef EXPERIMENTAL_DANE
2270 if ((rc = dane_tlsa_load(client_ssl, host, tlsa_dnsa)) != OK)
2274 #ifndef DISABLE_OCSP
2275 /* Request certificate status at connection-time. If the server
2276 does OCSP stapling we will get the callback (set in tls_init()) */
2277 # ifdef EXPERIMENTAL_DANE
2281 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2282 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2284 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2285 this means we avoid the OCSP request, we wasted the setup
2286 cost in tls_init(). */
2287 require_ocsp = verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
2288 request_ocsp = require_ocsp
2289 || verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2296 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
2297 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2298 tls_out.ocsp = OCSP_NOT_RESP;
2302 #ifndef DISABLE_EVENT
2303 client_static_cbinfo->event_action = tb->event_action;
2306 /* There doesn't seem to be a built-in timeout on connection. */
2308 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2309 sigalrm_seen = FALSE;
2310 alarm(ob->command_timeout);
2311 rc = SSL_connect(client_ssl);
2314 #ifdef EXPERIMENTAL_DANE
2316 DANESSL_cleanup(client_ssl);
2320 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
2322 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
2324 peer_cert(client_ssl, &tls_out, peerdn, sizeof(peerdn));
2326 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
2327 tls_out.cipher = cipherbuf;
2329 /* Record the certificate we presented */
2331 X509 * crt = SSL_get_certificate(client_ssl);
2332 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
2335 tls_out.active = fd;
2343 /*************************************************
2344 * TLS version of getc *
2345 *************************************************/
2347 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2348 it refills the buffer via the SSL reading function.
2351 Returns: the next character or EOF
2353 Only used by the server-side TLS.
2359 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2364 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2365 ssl_xfer_buffer, ssl_xfer_buffer_size);
2367 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2368 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
2369 error = SSL_get_error(server_ssl, inbytes);
2372 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2373 closed down, not that the socket itself has been closed down. Revert to
2374 non-SSL handling. */
2376 if (error == SSL_ERROR_ZERO_RETURN)
2378 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2380 receive_getc = smtp_getc;
2381 receive_get_cache = smtp_get_cache;
2382 receive_ungetc = smtp_ungetc;
2383 receive_feof = smtp_feof;
2384 receive_ferror = smtp_ferror;
2385 receive_smtp_buffered = smtp_buffered;
2387 SSL_free(server_ssl);
2391 tls_in.cipher = NULL;
2392 tls_in.peerdn = NULL;
2398 /* Handle genuine errors */
2400 else if (error == SSL_ERROR_SSL)
2402 ERR_error_string(ERR_get_error(), ssl_errstring);
2403 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2408 else if (error != SSL_ERROR_NONE)
2410 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2415 #ifndef DISABLE_DKIM
2416 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2418 ssl_xfer_buffer_hwm = inbytes;
2419 ssl_xfer_buffer_lwm = 0;
2422 /* Something in the buffer; return next uschar */
2424 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2430 #ifndef DISABLE_DKIM
2431 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2433 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2439 /*************************************************
2440 * Read bytes from TLS channel *
2441 *************************************************/
2448 Returns: the number of bytes read
2449 -1 after a failed read
2451 Only used by the client-side TLS.
2455 tls_read(BOOL is_server, uschar *buff, size_t len)
2457 SSL *ssl = is_server ? server_ssl : client_ssl;
2461 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2462 buff, (unsigned int)len);
2464 inbytes = SSL_read(ssl, CS buff, len);
2465 error = SSL_get_error(ssl, inbytes);
2467 if (error == SSL_ERROR_ZERO_RETURN)
2469 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2472 else if (error != SSL_ERROR_NONE)
2484 /*************************************************
2485 * Write bytes down TLS channel *
2486 *************************************************/
2490 is_server channel specifier
2494 Returns: the number of bytes after a successful write,
2495 -1 after a failed write
2497 Used by both server-side and client-side TLS.
2501 tls_write(BOOL is_server, const uschar *buff, size_t len)
2506 SSL *ssl = is_server ? server_ssl : client_ssl;
2508 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
2511 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
2512 outbytes = SSL_write(ssl, CS buff, left);
2513 error = SSL_get_error(ssl, outbytes);
2514 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2518 ERR_error_string(ERR_get_error(), ssl_errstring);
2519 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2522 case SSL_ERROR_NONE:
2527 case SSL_ERROR_ZERO_RETURN:
2528 log_write(0, LOG_MAIN, "SSL channel closed on write");
2531 case SSL_ERROR_SYSCALL:
2532 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
2533 sender_fullhost ? sender_fullhost : US"<unknown>",
2538 log_write(0, LOG_MAIN, "SSL_write error %d", error);
2547 /*************************************************
2548 * Close down a TLS session *
2549 *************************************************/
2551 /* This is also called from within a delivery subprocess forked from the
2552 daemon, to shut down the TLS library, without actually doing a shutdown (which
2553 would tamper with the SSL session in the parent process).
2555 Arguments: TRUE if SSL_shutdown is to be called
2558 Used by both server-side and client-side TLS.
2562 tls_close(BOOL is_server, BOOL shutdown)
2564 SSL **sslp = is_server ? &server_ssl : &client_ssl;
2565 int *fdp = is_server ? &tls_in.active : &tls_out.active;
2567 if (*fdp < 0) return; /* TLS was not active */
2571 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
2572 SSL_shutdown(*sslp);
2584 /*************************************************
2585 * Let tls_require_ciphers be checked at startup *
2586 *************************************************/
2588 /* The tls_require_ciphers option, if set, must be something which the
2591 Returns: NULL on success, or error message
2595 tls_validate_require_cipher(void)
2598 uschar *s, *expciphers, *err;
2600 /* this duplicates from tls_init(), we need a better "init just global
2601 state, for no specific purpose" singleton function of our own */
2603 SSL_load_error_strings();
2604 OpenSSL_add_ssl_algorithms();
2605 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2606 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2607 list of available digests. */
2608 EVP_add_digest(EVP_sha256());
2611 if (!(tls_require_ciphers && *tls_require_ciphers))
2614 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
2615 return US"failed to expand tls_require_ciphers";
2617 if (!(expciphers && *expciphers))
2620 /* normalisation ripped from above */
2622 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2626 ctx = SSL_CTX_new(SSLv23_server_method());
2629 ERR_error_string(ERR_get_error(), ssl_errstring);
2630 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2634 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2636 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2638 ERR_error_string(ERR_get_error(), ssl_errstring);
2639 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
2650 /*************************************************
2651 * Report the library versions. *
2652 *************************************************/
2654 /* There have historically been some issues with binary compatibility in
2655 OpenSSL libraries; if Exim (like many other applications) is built against
2656 one version of OpenSSL but the run-time linker picks up another version,
2657 it can result in serious failures, including crashing with a SIGSEGV. So
2658 report the version found by the compiler and the run-time version.
2660 Note: some OS vendors backport security fixes without changing the version
2661 number/string, and the version date remains unchanged. The _build_ date
2662 will change, so we can more usefully assist with version diagnosis by also
2663 reporting the build date.
2665 Arguments: a FILE* to print the results to
2670 tls_version_report(FILE *f)
2672 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2675 OPENSSL_VERSION_TEXT,
2676 SSLeay_version(SSLEAY_VERSION),
2677 SSLeay_version(SSLEAY_BUILT_ON));
2678 /* third line is 38 characters for the %s and the line is 73 chars long;
2679 the OpenSSL output includes a "built on: " prefix already. */
2685 /*************************************************
2686 * Random number generation *
2687 *************************************************/
2689 /* Pseudo-random number generation. The result is not expected to be
2690 cryptographically strong but not so weak that someone will shoot themselves
2691 in the foot using it as a nonce in input in some email header scheme or
2692 whatever weirdness they'll twist this into. The result should handle fork()
2693 and avoid repeating sequences. OpenSSL handles that for us.
2697 Returns a random number in range [0, max-1]
2701 vaguely_random_number(int max)
2705 static pid_t pidlast = 0;
2708 uschar smallbuf[sizeof(r)];
2714 if (pidnow != pidlast)
2716 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2717 is unique for each thread", this doesn't apparently apply across processes,
2718 so our own warning from vaguely_random_number_fallback() applies here too.
2719 Fix per PostgreSQL. */
2725 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2729 gettimeofday(&r.tv, NULL);
2732 RAND_seed((uschar *)(&r), sizeof(r));
2734 /* We're after pseudo-random, not random; if we still don't have enough data
2735 in the internal PRNG then our options are limited. We could sleep and hope
2736 for entropy to come along (prayer technique) but if the system is so depleted
2737 in the first place then something is likely to just keep taking it. Instead,
2738 we'll just take whatever little bit of pseudo-random we can still manage to
2741 needed_len = sizeof(r);
2742 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2743 asked for a number less than 10. */
2744 for (r = max, i = 0; r; ++i)
2750 #ifdef EXIM_HAVE_RAND_PSEUDO
2751 /* We do not care if crypto-strong */
2752 i = RAND_pseudo_bytes(smallbuf, needed_len);
2754 i = RAND_bytes(smallbuf, needed_len);
2760 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2761 return vaguely_random_number_fallback(max);
2765 for (p = smallbuf; needed_len; --needed_len, ++p)
2771 /* We don't particularly care about weighted results; if someone wants
2772 smooth distribution and cares enough then they should submit a patch then. */
2779 /*************************************************
2780 * OpenSSL option parse *
2781 *************************************************/
2783 /* Parse one option for tls_openssl_options_parse below
2786 name one option name
2787 value place to store a value for it
2788 Returns success or failure in parsing
2791 struct exim_openssl_option {
2795 /* We could use a macro to expand, but we need the ifdef and not all the
2796 options document which version they were introduced in. Policylet: include
2797 all options unless explicitly for DTLS, let the administrator choose which
2800 This list is current as of:
2802 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2804 static struct exim_openssl_option exim_openssl_options[] = {
2805 /* KEEP SORTED ALPHABETICALLY! */
2807 { US"all", SSL_OP_ALL },
2809 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2810 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2812 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2813 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2815 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2816 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2818 #ifdef SSL_OP_EPHEMERAL_RSA
2819 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2821 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2822 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2824 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2825 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2827 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2828 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2830 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2831 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2833 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2834 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2836 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2837 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2839 #ifdef SSL_OP_NO_COMPRESSION
2840 { US"no_compression", SSL_OP_NO_COMPRESSION },
2842 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2843 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2845 #ifdef SSL_OP_NO_SSLv2
2846 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2848 #ifdef SSL_OP_NO_SSLv3
2849 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2851 #ifdef SSL_OP_NO_TICKET
2852 { US"no_ticket", SSL_OP_NO_TICKET },
2854 #ifdef SSL_OP_NO_TLSv1
2855 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2857 #ifdef SSL_OP_NO_TLSv1_1
2858 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2859 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2860 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2862 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2865 #ifdef SSL_OP_NO_TLSv1_2
2866 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2868 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2869 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2871 #ifdef SSL_OP_SINGLE_DH_USE
2872 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2874 #ifdef SSL_OP_SINGLE_ECDH_USE
2875 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2877 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2878 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2880 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2881 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2883 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2884 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2886 #ifdef SSL_OP_TLS_D5_BUG
2887 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2889 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2890 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2893 static int exim_openssl_options_size =
2894 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2898 tls_openssl_one_option_parse(uschar *name, long *value)
2901 int last = exim_openssl_options_size;
2902 while (last > first)
2904 int middle = (first + last)/2;
2905 int c = Ustrcmp(name, exim_openssl_options[middle].name);
2908 *value = exim_openssl_options[middle].value;
2922 /*************************************************
2923 * OpenSSL option parsing logic *
2924 *************************************************/
2926 /* OpenSSL has a number of compatibility options which an administrator might
2927 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
2928 we look like log_selector.
2931 option_spec the administrator-supplied string of options
2932 results ptr to long storage for the options bitmap
2933 Returns success or failure
2937 tls_openssl_options_parse(uschar *option_spec, long *results)
2942 BOOL adding, item_parsed;
2945 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2946 * from default because it increases BEAST susceptibility. */
2947 #ifdef SSL_OP_NO_SSLv2
2948 result |= SSL_OP_NO_SSLv2;
2950 #ifdef SSL_OP_SINGLE_DH_USE
2951 result |= SSL_OP_SINGLE_DH_USE;
2954 if (option_spec == NULL)
2960 for (s=option_spec; *s != '\0'; /**/)
2962 while (isspace(*s)) ++s;
2965 if (*s != '+' && *s != '-')
2967 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2968 "+ or - expected but found \"%s\"\n", s);
2971 adding = *s++ == '+';
2972 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2975 item_parsed = tls_openssl_one_option_parse(s, &item);
2979 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2982 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2983 adding ? "adding" : "removing", result, item, s);
2997 /* End of tls-openssl.c */