1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2014 */
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>
26 # include <openssl/ocsp.h>
30 # define EXIM_OCSP_SKEW_SECONDS (300L)
31 # define EXIM_OCSP_MAX_AGE (-1L)
34 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
35 # define EXIM_HAVE_OPENSSL_TLSEXT
38 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
39 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
43 /* Structure for collecting random data for seeding. */
45 typedef struct randstuff {
50 /* Local static variables */
52 static BOOL client_verify_callback_called = FALSE;
53 static BOOL server_verify_callback_called = FALSE;
54 static const uschar *sid_ctx = US"exim";
56 /* We have three different contexts to care about.
58 Simple case: client, `client_ctx`
59 As a client, we can be doing a callout or cut-through delivery while receiving
60 a message. So we have a client context, which should have options initialised
61 from the SMTP Transport.
64 There are two cases: with and without ServerNameIndication from the client.
65 Given TLS SNI, we can be using different keys, certs and various other
66 configuration settings, because they're re-expanded with $tls_sni set. This
67 allows vhosting with TLS. This SNI is sent in the handshake.
68 A client might not send SNI, so we need a fallback, and an initial setup too.
69 So as a server, we start out using `server_ctx`.
70 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
71 `server_sni` from `server_ctx` and then initialise settings by re-expanding
75 static SSL_CTX *client_ctx = NULL;
76 static SSL_CTX *server_ctx = NULL;
77 static SSL *client_ssl = NULL;
78 static SSL *server_ssl = NULL;
80 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
81 static SSL_CTX *server_sni = NULL;
84 static char ssl_errstring[256];
86 static int ssl_session_timeout = 200;
87 static BOOL client_verify_optional = FALSE;
88 static BOOL server_verify_optional = FALSE;
90 static BOOL reexpand_tls_files_for_sni = FALSE;
93 typedef struct tls_ext_ctx_cb {
101 uschar *file_expanded;
102 OCSP_RESPONSE *response;
105 X509_STORE *verify_store; /* non-null if status requested */
106 BOOL verify_required;
111 /* these are cached from first expand */
112 uschar *server_cipher_list;
113 /* only passed down to tls_error: */
116 #ifdef EXPERIMENTAL_CERTNAMES
117 uschar * verify_cert_hostnames;
119 #ifdef EXPERIMENTAL_TPDA
120 uschar * event_action;
124 /* should figure out a cleanup of API to handle state preserved per
125 implementation, for various reasons, which can be void * in the APIs.
126 For now, we hack around it. */
127 tls_ext_ctx_cb *client_static_cbinfo = NULL;
128 tls_ext_ctx_cb *server_static_cbinfo = NULL;
131 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
132 int (*cert_vfy_cb)(int, X509_STORE_CTX *) );
135 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
136 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
139 static int tls_server_stapling_cb(SSL *s, void *arg);
143 /*************************************************
145 *************************************************/
147 /* Called from lots of places when errors occur before actually starting to do
148 the TLS handshake, that is, while the session is still in clear. Always returns
149 DEFER for a server and FAIL for a client so that most calls can use "return
150 tls_error(...)" to do this processing and then give an appropriate return. A
151 single function is used for both server and client, because it is called from
152 some shared functions.
155 prefix text to include in the logged error
156 host NULL if setting up a server;
157 the connected host if setting up a client
158 msg error message or NULL if we should ask OpenSSL
160 Returns: OK/DEFER/FAIL
164 tls_error(uschar *prefix, host_item *host, uschar *msg)
168 ERR_error_string(ERR_get_error(), ssl_errstring);
169 msg = (uschar *)ssl_errstring;
174 uschar *conn_info = smtp_get_connection_info();
175 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
177 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
178 conn_info, prefix, msg);
183 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
184 host->name, host->address, prefix, msg);
191 /*************************************************
192 * Callback to generate RSA key *
193 *************************************************/
201 Returns: pointer to generated key
205 rsa_callback(SSL *s, int export, int keylength)
208 export = export; /* Shut picky compilers up */
209 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
210 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
213 ERR_error_string(ERR_get_error(), ssl_errstring);
214 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
226 x509_store_dump_cert_s_names(X509_STORE * store)
228 STACK_OF(X509_OBJECT) * roots= store->objs;
230 static uschar name[256];
232 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
234 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
235 if(tmp_obj->type == X509_LU_X509)
237 X509 * current_cert= tmp_obj->data.x509;
238 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
239 debug_printf(" %s\n", name);
247 /*************************************************
248 * Callback for verification *
249 *************************************************/
251 /* The SSL library does certificate verification if set up to do so. This
252 callback has the current yes/no state is in "state". If verification succeeded,
253 we set up the tls_peerdn string. If verification failed, what happens depends
254 on whether the client is required to present a verifiable certificate or not.
256 If verification is optional, we change the state to yes, but still log the
257 verification error. For some reason (it really would help to have proper
258 documentation of OpenSSL), this callback function then gets called again, this
259 time with state = 1. In fact, that's useful, because we can set up the peerdn
260 value, but we must take care not to set the private verified flag on the second
263 Note: this function is not called if the client fails to present a certificate
264 when asked. We get here only if a certificate has been received. Handling of
265 optional verification for this case is done when requesting SSL to verify, by
266 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
268 May be called multiple times for different issues with a certificate, even
269 for a given "depth" in the certificate chain.
272 state current yes/no state as 1/0
273 x509ctx certificate information.
274 client TRUE for client startup, FALSE for server startup
276 Returns: 1 if verified, 0 if not
280 verify_callback(int state, X509_STORE_CTX *x509ctx,
281 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
283 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
284 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
285 static uschar txt[256];
287 X509_NAME_oneline(X509_get_subject_name(cert), CS txt, sizeof(txt));
291 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
293 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
295 tlsp->certificate_verified = FALSE;
299 tlsp->peercert = X509_dup(cert);
300 return 0; /* reject */
302 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
303 "tls_try_verify_hosts)\n");
308 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, txt);
310 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
311 { /* client, wanting stapling */
312 /* Add the server cert's signing chain as the one
313 for the verification of the OCSP stapled information. */
315 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
320 #ifdef EXPERIMENTAL_TPDA
321 if (tlsp == &tls_out && client_static_cbinfo->event_action)
323 tlsp->peercert = X509_dup(cert);
324 if (tpda_raise_event(client_static_cbinfo->event_action,
325 US"tls:cert", string_sprintf("%d", depth)) == DEFER)
327 log_write(0, LOG_MAIN, "SSL verify denied by event-action: "
328 "depth=%d cert=%s", depth, txt);
329 tlsp->certificate_verified = FALSE;
331 return 0; /* reject */
333 X509_free(tlsp->peercert);
334 tlsp->peercert = NULL;
340 #ifdef EXPERIMENTAL_CERTNAMES
341 uschar * verify_cert_hostnames;
345 tlsp->peercert = X509_dup(cert);
347 #ifdef EXPERIMENTAL_CERTNAMES
348 if ( tlsp == &tls_out
349 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
350 /* client, wanting hostname check */
352 # if OPENSSL_VERSION_NUMBER >= 0x010100000L || OPENSSL_VERSION_NUMBER >= 0x010002000L
353 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
354 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
358 uschar * list = verify_cert_hostnames;
361 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
362 if ((rc = X509_check_host(cert, name, 0,
363 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS)))
367 log_write(0, LOG_MAIN, "SSL verify error: internal error\n");
374 log_write(0, LOG_MAIN,
375 "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
376 return 0; /* reject */
380 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
382 log_write(0, LOG_MAIN,
383 "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
384 return 0; /* reject */
387 #endif /*EXPERIMENTAL_CERTNAMES*/
389 #ifdef EXPERIMENTAL_TPDA
390 if (tlsp == &tls_out)
392 if (tpda_raise_event(client_static_cbinfo->event_action,
393 US"tls:cert", US"0") == DEFER)
395 log_write(0, LOG_MAIN, "SSL verify denied by event-action: "
396 "depth=0 cert=%s", txt);
397 tlsp->certificate_verified = FALSE;
399 return 0; /* reject */
404 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
405 *calledp ? "" : " authenticated", txt);
406 if (!*calledp) tlsp->certificate_verified = TRUE;
410 return 1; /* accept, at least for this level */
414 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
416 return verify_callback(state, x509ctx, &tls_out, &client_verify_callback_called, &client_verify_optional);
420 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
422 return verify_callback(state, x509ctx, &tls_in, &server_verify_callback_called, &server_verify_optional);
427 /*************************************************
428 * Information callback *
429 *************************************************/
431 /* The SSL library functions call this from time to time to indicate what they
432 are doing. We copy the string to the debugging output when TLS debugging has
444 info_callback(SSL *s, int where, int ret)
448 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
453 /*************************************************
454 * Initialize for DH *
455 *************************************************/
457 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
460 dhparam DH parameter file or fixed parameter identity string
461 host connected host, if client; NULL if server
463 Returns: TRUE if OK (nothing to set up, or setup worked)
467 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
474 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
477 if (!dhexpanded || !*dhexpanded)
478 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
479 else if (dhexpanded[0] == '/')
481 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
483 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
484 host, US strerror(errno));
490 if (Ustrcmp(dhexpanded, "none") == 0)
492 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
496 if (!(pem = std_dh_prime_named(dhexpanded)))
498 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
499 host, US strerror(errno));
502 bio = BIO_new_mem_buf(CS pem, -1);
505 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
508 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
513 /* Even if it is larger, we silently return success rather than cause things
514 * to fail out, so that a too-large DH will not knock out all TLS; it's a
515 * debatable choice. */
516 if ((8*DH_size(dh)) > tls_dh_max_bits)
519 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
520 8*DH_size(dh), tls_dh_max_bits);
524 SSL_CTX_set_tmp_dh(sctx, dh);
526 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
527 dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
540 /*************************************************
541 * Load OCSP information into state *
542 *************************************************/
544 /* Called to load the server OCSP response from the given file into memory, once
545 caller has determined this is needed. Checks validity. Debugs a message
548 ASSUMES: single response, for single cert.
551 sctx the SSL_CTX* to update
552 cbinfo various parts of session state
553 expanded the filename putatively holding an OCSP response
558 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
562 OCSP_BASICRESP *basic_response;
563 OCSP_SINGLERESP *single_response;
564 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
566 unsigned long verify_flags;
567 int status, reason, i;
569 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
570 if (cbinfo->u_ocsp.server.response)
572 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
573 cbinfo->u_ocsp.server.response = NULL;
576 bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb");
579 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
580 cbinfo->u_ocsp.server.file_expanded);
584 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
588 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
592 status = OCSP_response_status(resp);
593 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
595 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
596 OCSP_response_status_str(status), status);
600 basic_response = OCSP_response_get1_basic(resp);
604 debug_printf("OCSP response parse error: unable to extract basic response.\n");
608 store = SSL_CTX_get_cert_store(sctx);
609 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
611 /* May need to expose ability to adjust those flags?
612 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
613 OCSP_TRUSTOTHER OCSP_NOINTERN */
615 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
619 ERR_error_string(ERR_get_error(), ssl_errstring);
620 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
625 /* Here's the simplifying assumption: there's only one response, for the
626 one certificate we use, and nothing for anything else in a chain. If this
627 proves false, we need to extract a cert id from our issued cert
628 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
629 right cert in the stack and then calls OCSP_single_get0_status()).
631 I'm hoping to avoid reworking a bunch more of how we handle state here. */
632 single_response = OCSP_resp_get0(basic_response, 0);
633 if (!single_response)
636 debug_printf("Unable to get first response from OCSP basic response.\n");
640 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
641 if (status != V_OCSP_CERTSTATUS_GOOD)
643 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
644 OCSP_cert_status_str(status), status,
645 OCSP_crl_reason_str(reason), reason);
649 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
651 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
656 cbinfo->u_ocsp.server.response = resp;
660 if (running_in_test_harness)
662 extern char ** environ;
664 for (p = USS environ; *p != NULL; p++)
665 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
667 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
668 goto supply_response;
673 #endif /*!DISABLE_OCSP*/
678 /*************************************************
679 * Expand key and cert file specs *
680 *************************************************/
682 /* Called once during tls_init and possibly again during TLS setup, for a
683 new context, if Server Name Indication was used and tls_sni was seen in
684 the certificate string.
687 sctx the SSL_CTX* to update
688 cbinfo various parts of session state
690 Returns: OK/DEFER/FAIL
694 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
698 if (cbinfo->certificate == NULL)
701 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
702 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
703 Ustrstr(cbinfo->certificate, US"tls_out_sni")
705 reexpand_tls_files_for_sni = TRUE;
707 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
710 if (expanded != NULL)
712 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
713 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
714 return tls_error(string_sprintf(
715 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
719 if (cbinfo->privatekey != NULL &&
720 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
723 /* If expansion was forced to fail, key_expanded will be NULL. If the result
724 of the expansion is an empty string, ignore it also, and assume the private
725 key is in the same file as the certificate. */
727 if (expanded != NULL && *expanded != 0)
729 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
730 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
731 return tls_error(string_sprintf(
732 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
736 if (cbinfo->is_server && cbinfo->u_ocsp.server.file != NULL)
738 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded))
741 if (expanded != NULL && *expanded != 0)
743 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
744 if (cbinfo->u_ocsp.server.file_expanded &&
745 (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
748 debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
750 ocsp_load_response(sctx, cbinfo, expanded);
762 /*************************************************
763 * Callback to handle SNI *
764 *************************************************/
766 /* Called when acting as server during the TLS session setup if a Server Name
767 Indication extension was sent by the client.
769 API documentation is OpenSSL s_server.c implementation.
772 s SSL* of the current session
773 ad unknown (part of OpenSSL API) (unused)
774 arg Callback of "our" registered data
776 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
779 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
781 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
783 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
784 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
786 int old_pool = store_pool;
789 return SSL_TLSEXT_ERR_OK;
791 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
792 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
794 /* Make the extension value available for expansion */
795 store_pool = POOL_PERM;
796 tls_in.sni = string_copy(US servername);
797 store_pool = old_pool;
799 if (!reexpand_tls_files_for_sni)
800 return SSL_TLSEXT_ERR_OK;
802 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
803 not confident that memcpy wouldn't break some internal reference counting.
804 Especially since there's a references struct member, which would be off. */
806 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
808 ERR_error_string(ERR_get_error(), ssl_errstring);
809 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
810 return SSL_TLSEXT_ERR_NOACK;
813 /* Not sure how many of these are actually needed, since SSL object
814 already exists. Might even need this selfsame callback, for reneg? */
816 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
817 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
818 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
819 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
820 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
821 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
822 if (cbinfo->server_cipher_list)
823 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
825 if (cbinfo->u_ocsp.server.file)
827 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
828 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
832 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server);
833 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
835 /* do this after setup_certs, because this can require the certs for verifying
837 rc = tls_expand_session_files(server_sni, cbinfo);
838 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
840 if (!init_dh(server_sni, cbinfo->dhparam, NULL))
841 return SSL_TLSEXT_ERR_NOACK;
843 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
844 SSL_set_SSL_CTX(s, server_sni);
846 return SSL_TLSEXT_ERR_OK;
848 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
855 /*************************************************
856 * Callback to handle OCSP Stapling *
857 *************************************************/
859 /* Called when acting as server during the TLS session setup if the client
860 requests OCSP information with a Certificate Status Request.
862 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
868 tls_server_stapling_cb(SSL *s, void *arg)
870 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
871 uschar *response_der;
872 int response_der_len;
875 debug_printf("Received TLS status request (OCSP stapling); %s response.",
876 cbinfo->u_ocsp.server.response ? "have" : "lack");
878 tls_in.ocsp = OCSP_NOT_RESP;
879 if (!cbinfo->u_ocsp.server.response)
880 return SSL_TLSEXT_ERR_NOACK;
883 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
885 if (response_der_len <= 0)
886 return SSL_TLSEXT_ERR_NOACK;
888 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
889 tls_in.ocsp = OCSP_VFIED;
890 return SSL_TLSEXT_ERR_OK;
895 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
897 BIO_printf(bp, "\t%s: ", str);
898 ASN1_GENERALIZEDTIME_print(bp, time);
903 tls_client_stapling_cb(SSL *s, void *arg)
905 tls_ext_ctx_cb * cbinfo = arg;
906 const unsigned char * p;
912 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
913 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
916 /* Expect this when we requested ocsp but got none */
917 if ( cbinfo->u_ocsp.client.verify_required
918 && log_extra_selector & LX_tls_cipher)
919 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
921 DEBUG(D_tls) debug_printf(" null\n");
922 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
925 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
927 tls_out.ocsp = OCSP_FAILED;
928 if (log_extra_selector & LX_tls_cipher)
929 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
931 DEBUG(D_tls) debug_printf(" parse error\n");
935 if(!(bs = OCSP_response_get1_basic(rsp)))
937 tls_out.ocsp = OCSP_FAILED;
938 if (log_extra_selector & LX_tls_cipher)
939 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
941 DEBUG(D_tls) debug_printf(" error parsing response\n");
942 OCSP_RESPONSE_free(rsp);
946 /* We'd check the nonce here if we'd put one in the request. */
947 /* However that would defeat cacheability on the server so we don't. */
949 /* This section of code reworked from OpenSSL apps source;
950 The OpenSSL Project retains copyright:
951 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
956 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
958 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
960 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
962 /* Use the chain that verified the server cert to verify the stapled info */
963 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
965 if ((i = OCSP_basic_verify(bs, NULL,
966 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
968 tls_out.ocsp = OCSP_FAILED;
969 if (log_extra_selector & LX_tls_cipher)
970 log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
971 BIO_printf(bp, "OCSP response verify failure\n");
972 ERR_print_errors(bp);
973 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
977 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
980 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
981 OCSP_SINGLERESP * single;
983 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
985 tls_out.ocsp = OCSP_FAILED;
986 log_write(0, LOG_MAIN, "OCSP stapling "
987 "with multiple responses not handled");
988 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
991 single = OCSP_resp_get0(bs, 0);
992 status = OCSP_single_get0_status(single, &reason, &rev,
996 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
997 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
998 if (!OCSP_check_validity(thisupd, nextupd,
999 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1001 tls_out.ocsp = OCSP_FAILED;
1002 DEBUG(D_tls) ERR_print_errors(bp);
1003 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1004 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1008 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1009 OCSP_cert_status_str(status));
1012 case V_OCSP_CERTSTATUS_GOOD:
1013 tls_out.ocsp = OCSP_VFIED;
1016 case V_OCSP_CERTSTATUS_REVOKED:
1017 tls_out.ocsp = OCSP_FAILED;
1018 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1019 reason != -1 ? "; reason: " : "",
1020 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1021 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1022 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1025 tls_out.ocsp = OCSP_FAILED;
1026 log_write(0, LOG_MAIN,
1027 "Server certificate status unknown, in OCSP stapling");
1028 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1036 OCSP_RESPONSE_free(rsp);
1039 #endif /*!DISABLE_OCSP*/
1043 /*************************************************
1044 * Initialize for TLS *
1045 *************************************************/
1047 /* Called from both server and client code, to do preliminary initialization
1048 of the library. We allocate and return a context structure.
1051 host connected host, if client; NULL if server
1052 dhparam DH parameter file
1053 certificate certificate file
1054 privatekey private key
1055 ocsp_file file of stapling info (server); flag for require ocsp (client)
1056 addr address if client; NULL if server (for some randomness)
1057 cbp place to put allocated context
1059 Returns: OK/DEFER/FAIL
1063 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1065 #ifndef DISABLE_OCSP
1068 address_item *addr, tls_ext_ctx_cb ** cbp)
1073 tls_ext_ctx_cb * cbinfo;
1075 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1076 cbinfo->certificate = certificate;
1077 cbinfo->privatekey = privatekey;
1078 #ifndef DISABLE_OCSP
1079 if ((cbinfo->is_server = host==NULL))
1081 cbinfo->u_ocsp.server.file = ocsp_file;
1082 cbinfo->u_ocsp.server.file_expanded = NULL;
1083 cbinfo->u_ocsp.server.response = NULL;
1086 cbinfo->u_ocsp.client.verify_store = NULL;
1088 cbinfo->dhparam = dhparam;
1089 cbinfo->server_cipher_list = NULL;
1090 cbinfo->host = host;
1091 #ifdef EXPERIMENTAL_TPDA
1092 cbinfo->event_action = NULL;
1095 SSL_load_error_strings(); /* basic set up */
1096 OpenSSL_add_ssl_algorithms();
1098 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1099 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1100 list of available digests. */
1101 EVP_add_digest(EVP_sha256());
1104 /* Create a context.
1105 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1106 negotiation in the different methods; as far as I can tell, the only
1107 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1108 when OpenSSL is built without SSLv2 support.
1109 By disabling with openssl_options, we can let admins re-enable with the
1112 *ctxp = SSL_CTX_new((host == NULL)?
1113 SSLv23_server_method() : SSLv23_client_method());
1115 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
1117 /* It turns out that we need to seed the random number generator this early in
1118 order to get the full complement of ciphers to work. It took me roughly a day
1119 of work to discover this by experiment.
1121 On systems that have /dev/urandom, SSL may automatically seed itself from
1122 there. Otherwise, we have to make something up as best we can. Double check
1128 gettimeofday(&r.tv, NULL);
1131 RAND_seed((uschar *)(&r), sizeof(r));
1132 RAND_seed((uschar *)big_buffer, big_buffer_size);
1133 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1136 return tls_error(US"RAND_status", host,
1137 US"unable to seed random number generator");
1140 /* Set up the information callback, which outputs if debugging is at a suitable
1143 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1145 /* Automatically re-try reads/writes after renegotiation. */
1146 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1148 /* Apply administrator-supplied work-arounds.
1149 Historically we applied just one requested option,
1150 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1151 moved to an administrator-controlled list of options to specify and
1152 grandfathered in the first one as the default value for "openssl_options".
1154 No OpenSSL version number checks: the options we accept depend upon the
1155 availability of the option value macros from OpenSSL. */
1157 okay = tls_openssl_options_parse(openssl_options, &init_options);
1159 return tls_error(US"openssl_options parsing failed", host, NULL);
1163 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1164 if (!(SSL_CTX_set_options(*ctxp, init_options)))
1165 return tls_error(string_sprintf(
1166 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1169 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1171 /* Initialize with DH parameters if supplied */
1173 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
1175 /* Set up certificate and key (and perhaps OCSP info) */
1177 rc = tls_expand_session_files(*ctxp, cbinfo);
1178 if (rc != OK) return rc;
1180 /* If we need to handle SNI, do so */
1181 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1182 if (host == NULL) /* server */
1184 # ifndef DISABLE_OCSP
1185 /* We check u_ocsp.server.file, not server.response, because we care about if
1186 the option exists, not what the current expansion might be, as SNI might
1187 change the certificate and OCSP file in use between now and the time the
1188 callback is invoked. */
1189 if (cbinfo->u_ocsp.server.file)
1191 SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1192 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1195 /* We always do this, so that $tls_sni is available even if not used in
1197 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1198 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1200 # ifndef DISABLE_OCSP
1202 if(ocsp_file) /* wanting stapling */
1204 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1206 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1209 SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1210 SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1215 #ifdef EXPERIMENTAL_CERTNAMES
1216 cbinfo->verify_cert_hostnames = NULL;
1219 /* Set up the RSA callback */
1221 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1223 /* Finally, set the timeout, and we are done */
1225 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1226 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1236 /*************************************************
1237 * Get name of cipher in use *
1238 *************************************************/
1241 Argument: pointer to an SSL structure for the connection
1242 buffer to use for answer
1244 pointer to number of bits for cipher
1249 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1251 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1252 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1253 the accessor functions use const in the prototype. */
1254 const SSL_CIPHER *c;
1257 ver = (const uschar *)SSL_get_version(ssl);
1259 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1260 SSL_CIPHER_get_bits(c, bits);
1262 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1263 SSL_CIPHER_get_name(c), *bits);
1265 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1272 /*************************************************
1273 * Set up for verifying certificates *
1274 *************************************************/
1276 /* Called by both client and server startup
1279 sctx SSL_CTX* to initialise
1280 certs certs file or NULL
1281 crl CRL file or NULL
1282 host NULL in a server; the remote host in a client
1283 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1284 otherwise passed as FALSE
1285 cert_vfy_cb Callback function for certificate verification
1287 Returns: OK/DEFER/FAIL
1291 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1292 int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1294 uschar *expcerts, *expcrl;
1296 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1299 if (expcerts != NULL && *expcerts != '\0')
1301 struct stat statbuf;
1302 if (!SSL_CTX_set_default_verify_paths(sctx))
1303 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1305 if (Ustat(expcerts, &statbuf) < 0)
1307 log_write(0, LOG_MAIN|LOG_PANIC,
1308 "failed to stat %s for certificates", expcerts);
1314 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1315 { file = NULL; dir = expcerts; }
1317 { file = expcerts; dir = NULL; }
1319 /* If a certificate file is empty, the next function fails with an
1320 unhelpful error message. If we skip it, we get the correct behaviour (no
1321 certificates are recognized, but the error message is still misleading (it
1322 says no certificate was supplied.) But this is better. */
1324 if ((file == NULL || statbuf.st_size > 0) &&
1325 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1326 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1330 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1334 /* Handle a certificate revocation list. */
1336 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1338 /* This bit of code is now the version supplied by Lars Mainka. (I have
1339 * merely reformatted it into the Exim code style.)
1341 * "From here I changed the code to add support for multiple crl's
1342 * in pem format in one file or to support hashed directory entries in
1343 * pem format instead of a file. This method now uses the library function
1344 * X509_STORE_load_locations to add the CRL location to the SSL context.
1345 * OpenSSL will then handle the verify against CA certs and CRLs by
1346 * itself in the verify callback." */
1348 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1349 if (expcrl != NULL && *expcrl != 0)
1351 struct stat statbufcrl;
1352 if (Ustat(expcrl, &statbufcrl) < 0)
1354 log_write(0, LOG_MAIN|LOG_PANIC,
1355 "failed to stat %s for certificates revocation lists", expcrl);
1360 /* is it a file or directory? */
1362 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1363 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1367 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1373 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1375 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1376 return tls_error(US"X509_STORE_load_locations", host, NULL);
1378 /* setting the flags to check against the complete crl chain */
1380 X509_STORE_set_flags(cvstore,
1381 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1385 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1387 /* If verification is optional, don't fail if no certificate */
1389 SSL_CTX_set_verify(sctx,
1390 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1399 /*************************************************
1400 * Start a TLS session in a server *
1401 *************************************************/
1403 /* This is called when Exim is running as a server, after having received
1404 the STARTTLS command. It must respond to that command, and then negotiate
1408 require_ciphers allowed ciphers
1410 Returns: OK on success
1411 DEFER for errors before the start of the negotiation
1412 FAIL for errors during the negotation; the server can't
1417 tls_server_start(const uschar *require_ciphers)
1421 tls_ext_ctx_cb *cbinfo;
1422 static uschar cipherbuf[256];
1424 /* Check for previous activation */
1426 if (tls_in.active >= 0)
1428 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1429 smtp_printf("554 Already in TLS\r\n");
1433 /* Initialize the SSL library. If it fails, it will already have logged
1436 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1437 #ifndef DISABLE_OCSP
1440 NULL, &server_static_cbinfo);
1441 if (rc != OK) return rc;
1442 cbinfo = server_static_cbinfo;
1444 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1447 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1448 were historically separated by underscores. So that I can use either form in my
1449 tests, and also for general convenience, we turn underscores into hyphens here.
1452 if (expciphers != NULL)
1454 uschar *s = expciphers;
1455 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1456 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1457 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1458 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1459 cbinfo->server_cipher_list = expciphers;
1462 /* If this is a host for which certificate verification is mandatory or
1463 optional, set up appropriately. */
1465 tls_in.certificate_verified = FALSE;
1466 server_verify_callback_called = FALSE;
1468 if (verify_check_host(&tls_verify_hosts) == OK)
1470 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1471 FALSE, verify_callback_server);
1472 if (rc != OK) return rc;
1473 server_verify_optional = FALSE;
1475 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1477 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1478 TRUE, verify_callback_server);
1479 if (rc != OK) return rc;
1480 server_verify_optional = TRUE;
1483 /* Prepare for new connection */
1485 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1487 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1489 * With the SSL_clear(), we get strange interoperability bugs with
1490 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1491 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1493 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1494 * session shutdown. In this case, we have a brand new object and there's no
1495 * obvious reason to immediately clear it. I'm guessing that this was
1496 * originally added because of incomplete initialisation which the clear fixed,
1497 * in some historic release.
1500 /* Set context and tell client to go ahead, except in the case of TLS startup
1501 on connection, where outputting anything now upsets the clients and tends to
1502 make them disconnect. We need to have an explicit fflush() here, to force out
1503 the response. Other smtp_printf() calls do not need it, because in non-TLS
1504 mode, the fflush() happens when smtp_getc() is called. */
1506 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1507 if (!tls_in.on_connect)
1509 smtp_printf("220 TLS go ahead\r\n");
1513 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1514 that the OpenSSL library doesn't. */
1516 SSL_set_wfd(server_ssl, fileno(smtp_out));
1517 SSL_set_rfd(server_ssl, fileno(smtp_in));
1518 SSL_set_accept_state(server_ssl);
1520 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1522 sigalrm_seen = FALSE;
1523 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1524 rc = SSL_accept(server_ssl);
1529 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1530 if (ERR_get_error() == 0)
1531 log_write(0, LOG_MAIN,
1532 "TLS client disconnected cleanly (rejected our certificate?)");
1536 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1538 /* TLS has been set up. Adjust the input functions to read via TLS,
1539 and initialize things. */
1541 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1542 tls_in.cipher = cipherbuf;
1547 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1548 debug_printf("Shared ciphers: %s\n", buf);
1551 /* Record the certificate we presented */
1553 X509 * crt = SSL_get_certificate(server_ssl);
1554 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
1557 /* Only used by the server-side tls (tls_in), including tls_getc.
1558 Client-side (tls_out) reads (seem to?) go via
1559 smtp_read_response()/ip_recv().
1560 Hence no need to duplicate for _in and _out.
1562 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1563 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1564 ssl_xfer_eof = ssl_xfer_error = 0;
1566 receive_getc = tls_getc;
1567 receive_ungetc = tls_ungetc;
1568 receive_feof = tls_feof;
1569 receive_ferror = tls_ferror;
1570 receive_smtp_buffered = tls_smtp_buffered;
1572 tls_in.active = fileno(smtp_out);
1580 /*************************************************
1581 * Start a TLS session in a client *
1582 *************************************************/
1584 /* Called from the smtp transport after STARTTLS has been accepted.
1587 fd the fd of the connection
1588 host connected host (for messages)
1589 addr the first address
1590 tb transport (always smtp)
1592 Returns: OK on success
1593 FAIL otherwise - note that tls_error() will not give DEFER
1594 because this is not a server
1598 tls_client_start(int fd, host_item *host, address_item *addr,
1599 transport_instance *tb)
1601 smtp_transport_options_block * ob =
1602 (smtp_transport_options_block *)tb->options_block;
1603 static uschar txt[256];
1607 static uschar cipherbuf[256];
1608 #ifndef DISABLE_OCSP
1609 BOOL require_ocsp = verify_check_this_host(&ob->hosts_require_ocsp,
1610 NULL, host->name, host->address, NULL) == OK;
1611 BOOL request_ocsp = require_ocsp ? TRUE
1612 : verify_check_this_host(&ob->hosts_request_ocsp,
1613 NULL, host->name, host->address, NULL) == OK;
1616 rc = tls_init(&client_ctx, host, NULL,
1617 ob->tls_certificate, ob->tls_privatekey,
1618 #ifndef DISABLE_OCSP
1619 (void *)(long)request_ocsp,
1621 addr, &client_static_cbinfo);
1622 if (rc != OK) return rc;
1624 tls_out.certificate_verified = FALSE;
1625 client_verify_callback_called = FALSE;
1627 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
1631 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1632 are separated by underscores. So that I can use either form in my tests, and
1633 also for general convenience, we turn underscores into hyphens here. */
1635 if (expciphers != NULL)
1637 uschar *s = expciphers;
1638 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1639 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1640 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1641 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1644 /* stick to the old behaviour for compatibility if tls_verify_certificates is
1645 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
1646 the specified host patterns if one of them is defined */
1648 if ((!ob->tls_verify_hosts && !ob->tls_try_verify_hosts) ||
1649 (verify_check_host(&ob->tls_verify_hosts) == OK))
1651 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1652 ob->tls_crl, host, FALSE, verify_callback_client)) != OK)
1654 client_verify_optional = FALSE;
1656 #ifdef EXPERIMENTAL_CERTNAMES
1657 if (ob->tls_verify_cert_hostnames)
1659 if (!expand_check(ob->tls_verify_cert_hostnames,
1660 US"tls_verify_cert_hostnames",
1661 &client_static_cbinfo->verify_cert_hostnames))
1663 if (client_static_cbinfo->verify_cert_hostnames)
1664 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
1665 client_static_cbinfo->verify_cert_hostnames);
1669 else if (verify_check_host(&ob->tls_try_verify_hosts) == OK)
1671 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1672 ob->tls_crl, host, TRUE, verify_callback_client)) != OK)
1674 client_verify_optional = TRUE;
1677 if ((client_ssl = SSL_new(client_ctx)) == NULL)
1678 return tls_error(US"SSL_new", host, NULL);
1679 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1680 SSL_set_fd(client_ssl, fd);
1681 SSL_set_connect_state(client_ssl);
1685 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
1687 if (tls_out.sni == NULL)
1689 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1691 else if (!Ustrlen(tls_out.sni))
1695 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1696 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1697 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1700 debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1706 #ifndef DISABLE_OCSP
1707 /* Request certificate status at connection-time. If the server
1708 does OCSP stapling we will get the callback (set in tls_init()) */
1711 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
1712 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
1713 tls_out.ocsp = OCSP_NOT_RESP;
1717 #ifdef EXPERIMENTAL_TPDA
1718 client_static_cbinfo->event_action = tb->tpda_event_action;
1721 /* There doesn't seem to be a built-in timeout on connection. */
1723 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1724 sigalrm_seen = FALSE;
1725 alarm(ob->command_timeout);
1726 rc = SSL_connect(client_ssl);
1730 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1732 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1734 /* Beware anonymous ciphers which lead to server_cert being NULL */
1735 /*XXX server_cert is never freed... use X509_free() */
1736 server_cert = SSL_get_peer_certificate (client_ssl);
1739 tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1740 CS txt, sizeof(txt));
1741 tls_out.peerdn = txt; /*XXX a static buffer... */
1744 tls_out.peerdn = NULL;
1746 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1747 tls_out.cipher = cipherbuf;
1749 /* Record the certificate we presented */
1751 X509 * crt = SSL_get_certificate(client_ssl);
1752 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
1755 tls_out.active = fd;
1763 /*************************************************
1764 * TLS version of getc *
1765 *************************************************/
1767 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1768 it refills the buffer via the SSL reading function.
1771 Returns: the next character or EOF
1773 Only used by the server-side TLS.
1779 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1784 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1785 ssl_xfer_buffer, ssl_xfer_buffer_size);
1787 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1788 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1789 error = SSL_get_error(server_ssl, inbytes);
1792 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1793 closed down, not that the socket itself has been closed down. Revert to
1794 non-SSL handling. */
1796 if (error == SSL_ERROR_ZERO_RETURN)
1798 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1800 receive_getc = smtp_getc;
1801 receive_ungetc = smtp_ungetc;
1802 receive_feof = smtp_feof;
1803 receive_ferror = smtp_ferror;
1804 receive_smtp_buffered = smtp_buffered;
1806 SSL_free(server_ssl);
1810 tls_in.cipher = NULL;
1811 tls_in.peerdn = NULL;
1817 /* Handle genuine errors */
1819 else if (error == SSL_ERROR_SSL)
1821 ERR_error_string(ERR_get_error(), ssl_errstring);
1822 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1827 else if (error != SSL_ERROR_NONE)
1829 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1834 #ifndef DISABLE_DKIM
1835 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1837 ssl_xfer_buffer_hwm = inbytes;
1838 ssl_xfer_buffer_lwm = 0;
1841 /* Something in the buffer; return next uschar */
1843 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1848 /*************************************************
1849 * Read bytes from TLS channel *
1850 *************************************************/
1857 Returns: the number of bytes read
1858 -1 after a failed read
1860 Only used by the client-side TLS.
1864 tls_read(BOOL is_server, uschar *buff, size_t len)
1866 SSL *ssl = is_server ? server_ssl : client_ssl;
1870 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1871 buff, (unsigned int)len);
1873 inbytes = SSL_read(ssl, CS buff, len);
1874 error = SSL_get_error(ssl, inbytes);
1876 if (error == SSL_ERROR_ZERO_RETURN)
1878 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1881 else if (error != SSL_ERROR_NONE)
1893 /*************************************************
1894 * Write bytes down TLS channel *
1895 *************************************************/
1899 is_server channel specifier
1903 Returns: the number of bytes after a successful write,
1904 -1 after a failed write
1906 Used by both server-side and client-side TLS.
1910 tls_write(BOOL is_server, const uschar *buff, size_t len)
1915 SSL *ssl = is_server ? server_ssl : client_ssl;
1917 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1920 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1921 outbytes = SSL_write(ssl, CS buff, left);
1922 error = SSL_get_error(ssl, outbytes);
1923 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1927 ERR_error_string(ERR_get_error(), ssl_errstring);
1928 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1931 case SSL_ERROR_NONE:
1936 case SSL_ERROR_ZERO_RETURN:
1937 log_write(0, LOG_MAIN, "SSL channel closed on write");
1940 case SSL_ERROR_SYSCALL:
1941 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1942 sender_fullhost ? sender_fullhost : US"<unknown>",
1946 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1955 /*************************************************
1956 * Close down a TLS session *
1957 *************************************************/
1959 /* This is also called from within a delivery subprocess forked from the
1960 daemon, to shut down the TLS library, without actually doing a shutdown (which
1961 would tamper with the SSL session in the parent process).
1963 Arguments: TRUE if SSL_shutdown is to be called
1966 Used by both server-side and client-side TLS.
1970 tls_close(BOOL is_server, BOOL shutdown)
1972 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1973 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1975 if (*fdp < 0) return; /* TLS was not active */
1979 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1980 SSL_shutdown(*sslp);
1992 /*************************************************
1993 * Let tls_require_ciphers be checked at startup *
1994 *************************************************/
1996 /* The tls_require_ciphers option, if set, must be something which the
1999 Returns: NULL on success, or error message
2003 tls_validate_require_cipher(void)
2006 uschar *s, *expciphers, *err;
2008 /* this duplicates from tls_init(), we need a better "init just global
2009 state, for no specific purpose" singleton function of our own */
2011 SSL_load_error_strings();
2012 OpenSSL_add_ssl_algorithms();
2013 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2014 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2015 list of available digests. */
2016 EVP_add_digest(EVP_sha256());
2019 if (!(tls_require_ciphers && *tls_require_ciphers))
2022 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
2023 return US"failed to expand tls_require_ciphers";
2025 if (!(expciphers && *expciphers))
2028 /* normalisation ripped from above */
2030 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2034 ctx = SSL_CTX_new(SSLv23_server_method());
2037 ERR_error_string(ERR_get_error(), ssl_errstring);
2038 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2042 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2044 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2046 ERR_error_string(ERR_get_error(), ssl_errstring);
2047 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
2058 /*************************************************
2059 * Report the library versions. *
2060 *************************************************/
2062 /* There have historically been some issues with binary compatibility in
2063 OpenSSL libraries; if Exim (like many other applications) is built against
2064 one version of OpenSSL but the run-time linker picks up another version,
2065 it can result in serious failures, including crashing with a SIGSEGV. So
2066 report the version found by the compiler and the run-time version.
2068 Note: some OS vendors backport security fixes without changing the version
2069 number/string, and the version date remains unchanged. The _build_ date
2070 will change, so we can more usefully assist with version diagnosis by also
2071 reporting the build date.
2073 Arguments: a FILE* to print the results to
2078 tls_version_report(FILE *f)
2080 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2083 OPENSSL_VERSION_TEXT,
2084 SSLeay_version(SSLEAY_VERSION),
2085 SSLeay_version(SSLEAY_BUILT_ON));
2086 /* third line is 38 characters for the %s and the line is 73 chars long;
2087 the OpenSSL output includes a "built on: " prefix already. */
2093 /*************************************************
2094 * Random number generation *
2095 *************************************************/
2097 /* Pseudo-random number generation. The result is not expected to be
2098 cryptographically strong but not so weak that someone will shoot themselves
2099 in the foot using it as a nonce in input in some email header scheme or
2100 whatever weirdness they'll twist this into. The result should handle fork()
2101 and avoid repeating sequences. OpenSSL handles that for us.
2105 Returns a random number in range [0, max-1]
2109 vaguely_random_number(int max)
2113 static pid_t pidlast = 0;
2116 uschar smallbuf[sizeof(r)];
2122 if (pidnow != pidlast)
2124 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2125 is unique for each thread", this doesn't apparently apply across processes,
2126 so our own warning from vaguely_random_number_fallback() applies here too.
2127 Fix per PostgreSQL. */
2133 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2137 gettimeofday(&r.tv, NULL);
2140 RAND_seed((uschar *)(&r), sizeof(r));
2142 /* We're after pseudo-random, not random; if we still don't have enough data
2143 in the internal PRNG then our options are limited. We could sleep and hope
2144 for entropy to come along (prayer technique) but if the system is so depleted
2145 in the first place then something is likely to just keep taking it. Instead,
2146 we'll just take whatever little bit of pseudo-random we can still manage to
2149 needed_len = sizeof(r);
2150 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2151 asked for a number less than 10. */
2152 for (r = max, i = 0; r; ++i)
2158 /* We do not care if crypto-strong */
2159 i = RAND_pseudo_bytes(smallbuf, needed_len);
2163 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2164 return vaguely_random_number_fallback(max);
2168 for (p = smallbuf; needed_len; --needed_len, ++p)
2174 /* We don't particularly care about weighted results; if someone wants
2175 smooth distribution and cares enough then they should submit a patch then. */
2182 /*************************************************
2183 * OpenSSL option parse *
2184 *************************************************/
2186 /* Parse one option for tls_openssl_options_parse below
2189 name one option name
2190 value place to store a value for it
2191 Returns success or failure in parsing
2194 struct exim_openssl_option {
2198 /* We could use a macro to expand, but we need the ifdef and not all the
2199 options document which version they were introduced in. Policylet: include
2200 all options unless explicitly for DTLS, let the administrator choose which
2203 This list is current as of:
2205 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2207 static struct exim_openssl_option exim_openssl_options[] = {
2208 /* KEEP SORTED ALPHABETICALLY! */
2210 { US"all", SSL_OP_ALL },
2212 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2213 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2215 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2216 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2218 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2219 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2221 #ifdef SSL_OP_EPHEMERAL_RSA
2222 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2224 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2225 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2227 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2228 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2230 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2231 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2233 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2234 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2236 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2237 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2239 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2240 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2242 #ifdef SSL_OP_NO_COMPRESSION
2243 { US"no_compression", SSL_OP_NO_COMPRESSION },
2245 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2246 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2248 #ifdef SSL_OP_NO_SSLv2
2249 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2251 #ifdef SSL_OP_NO_SSLv3
2252 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2254 #ifdef SSL_OP_NO_TICKET
2255 { US"no_ticket", SSL_OP_NO_TICKET },
2257 #ifdef SSL_OP_NO_TLSv1
2258 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2260 #ifdef SSL_OP_NO_TLSv1_1
2261 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2262 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2263 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2265 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2268 #ifdef SSL_OP_NO_TLSv1_2
2269 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2271 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2272 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2274 #ifdef SSL_OP_SINGLE_DH_USE
2275 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2277 #ifdef SSL_OP_SINGLE_ECDH_USE
2278 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2280 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2281 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2283 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2284 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2286 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2287 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2289 #ifdef SSL_OP_TLS_D5_BUG
2290 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2292 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2293 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2296 static int exim_openssl_options_size =
2297 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2301 tls_openssl_one_option_parse(uschar *name, long *value)
2304 int last = exim_openssl_options_size;
2305 while (last > first)
2307 int middle = (first + last)/2;
2308 int c = Ustrcmp(name, exim_openssl_options[middle].name);
2311 *value = exim_openssl_options[middle].value;
2325 /*************************************************
2326 * OpenSSL option parsing logic *
2327 *************************************************/
2329 /* OpenSSL has a number of compatibility options which an administrator might
2330 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
2331 we look like log_selector.
2334 option_spec the administrator-supplied string of options
2335 results ptr to long storage for the options bitmap
2336 Returns success or failure
2340 tls_openssl_options_parse(uschar *option_spec, long *results)
2345 BOOL adding, item_parsed;
2348 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2349 * from default because it increases BEAST susceptibility. */
2350 #ifdef SSL_OP_NO_SSLv2
2351 result |= SSL_OP_NO_SSLv2;
2354 if (option_spec == NULL)
2360 for (s=option_spec; *s != '\0'; /**/)
2362 while (isspace(*s)) ++s;
2365 if (*s != '+' && *s != '-')
2367 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2368 "+ or - expected but found \"%s\"\n", s);
2371 adding = *s++ == '+';
2372 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2375 item_parsed = tls_openssl_one_option_parse(s, &item);
2378 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2381 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2382 adding ? "adding" : "removing", result, item, s);
2397 /* End of tls-openssl.c */