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;
121 /* should figure out a cleanup of API to handle state preserved per
122 implementation, for various reasons, which can be void * in the APIs.
123 For now, we hack around it. */
124 tls_ext_ctx_cb *client_static_cbinfo = NULL;
125 tls_ext_ctx_cb *server_static_cbinfo = NULL;
128 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
129 int (*cert_vfy_cb)(int, X509_STORE_CTX *) );
132 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
133 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
136 static int tls_server_stapling_cb(SSL *s, void *arg);
140 /*************************************************
142 *************************************************/
144 /* Called from lots of places when errors occur before actually starting to do
145 the TLS handshake, that is, while the session is still in clear. Always returns
146 DEFER for a server and FAIL for a client so that most calls can use "return
147 tls_error(...)" to do this processing and then give an appropriate return. A
148 single function is used for both server and client, because it is called from
149 some shared functions.
152 prefix text to include in the logged error
153 host NULL if setting up a server;
154 the connected host if setting up a client
155 msg error message or NULL if we should ask OpenSSL
157 Returns: OK/DEFER/FAIL
161 tls_error(uschar *prefix, host_item *host, uschar *msg)
165 ERR_error_string(ERR_get_error(), ssl_errstring);
166 msg = (uschar *)ssl_errstring;
171 uschar *conn_info = smtp_get_connection_info();
172 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
174 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
175 conn_info, prefix, msg);
180 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
181 host->name, host->address, prefix, msg);
188 /*************************************************
189 * Callback to generate RSA key *
190 *************************************************/
198 Returns: pointer to generated key
202 rsa_callback(SSL *s, int export, int keylength)
205 export = export; /* Shut picky compilers up */
206 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
207 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
210 ERR_error_string(ERR_get_error(), ssl_errstring);
211 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
223 x509_store_dump_cert_s_names(X509_STORE * store)
225 STACK_OF(X509_OBJECT) * roots= store->objs;
227 static uschar name[256];
229 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
231 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
232 if(tmp_obj->type == X509_LU_X509)
234 X509 * current_cert= tmp_obj->data.x509;
235 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
236 debug_printf(" %s\n", name);
244 /*************************************************
245 * Callback for verification *
246 *************************************************/
248 /* The SSL library does certificate verification if set up to do so. This
249 callback has the current yes/no state is in "state". If verification succeeded,
250 we set up the tls_peerdn string. If verification failed, what happens depends
251 on whether the client is required to present a verifiable certificate or not.
253 If verification is optional, we change the state to yes, but still log the
254 verification error. For some reason (it really would help to have proper
255 documentation of OpenSSL), this callback function then gets called again, this
256 time with state = 1. In fact, that's useful, because we can set up the peerdn
257 value, but we must take care not to set the private verified flag on the second
260 Note: this function is not called if the client fails to present a certificate
261 when asked. We get here only if a certificate has been received. Handling of
262 optional verification for this case is done when requesting SSL to verify, by
263 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
266 state current yes/no state as 1/0
267 x509ctx certificate information.
268 client TRUE for client startup, FALSE for server startup
270 Returns: 1 if verified, 0 if not
274 verify_callback(int state, X509_STORE_CTX *x509ctx,
275 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
277 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
278 static uschar txt[256];
280 X509_NAME_oneline(X509_get_subject_name(cert), CS txt, sizeof(txt));
284 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
285 X509_STORE_CTX_get_error_depth(x509ctx),
286 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
288 tlsp->certificate_verified = FALSE;
292 tlsp->peercert = X509_dup(cert);
293 return 0; /* reject */
295 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
296 "tls_try_verify_hosts)\n");
299 else if (X509_STORE_CTX_get_error_depth(x509ctx) != 0)
301 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n",
302 X509_STORE_CTX_get_error_depth(x509ctx), txt);
304 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
305 { /* client, wanting stapling */
306 /* Add the server cert's signing chain as the one
307 for the verification of the OCSP stapled information. */
309 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
317 #ifdef EXPERIMENTAL_CERTNAMES
318 uschar * verify_cert_hostnames;
322 tlsp->peercert = X509_dup(cert);
324 #ifdef EXPERIMENTAL_CERTNAMES
325 if ( tlsp == &tls_out
326 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
327 /* client, wanting hostname check */
329 # if OPENSSL_VERSION_NUMBER >= 0x010100000L || OPENSSL_VERSION_NUMBER >= 0x010002000L
330 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
331 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
335 uschar * list = verify_cert_hostnames;
338 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
339 if ((rc = X509_check_host(cert, name, 0,
340 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS)))
344 log_write(0, LOG_MAIN, "SSL verify error: internal error\n");
351 log_write(0, LOG_MAIN,
352 "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
353 return 0; /* reject */
357 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
359 log_write(0, LOG_MAIN,
360 "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
361 return 0; /* reject */
366 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
367 *calledp ? "" : " authenticated", txt);
368 if (!*calledp) tlsp->certificate_verified = TRUE;
372 return 1; /* accept */
376 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
378 return verify_callback(state, x509ctx, &tls_out, &client_verify_callback_called, &client_verify_optional);
382 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
384 return verify_callback(state, x509ctx, &tls_in, &server_verify_callback_called, &server_verify_optional);
389 /*************************************************
390 * Information callback *
391 *************************************************/
393 /* The SSL library functions call this from time to time to indicate what they
394 are doing. We copy the string to the debugging output when TLS debugging has
406 info_callback(SSL *s, int where, int ret)
410 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
415 /*************************************************
416 * Initialize for DH *
417 *************************************************/
419 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
422 dhparam DH parameter file or fixed parameter identity string
423 host connected host, if client; NULL if server
425 Returns: TRUE if OK (nothing to set up, or setup worked)
429 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
436 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
439 if (dhexpanded == NULL || *dhexpanded == '\0')
441 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
443 else if (dhexpanded[0] == '/')
445 bio = BIO_new_file(CS dhexpanded, "r");
448 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
449 host, US strerror(errno));
455 if (Ustrcmp(dhexpanded, "none") == 0)
457 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
461 pem = std_dh_prime_named(dhexpanded);
464 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
465 host, US strerror(errno));
468 bio = BIO_new_mem_buf(CS pem, -1);
471 dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
475 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
480 /* Even if it is larger, we silently return success rather than cause things
481 * to fail out, so that a too-large DH will not knock out all TLS; it's a
482 * debatable choice. */
483 if ((8*DH_size(dh)) > tls_dh_max_bits)
486 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
487 8*DH_size(dh), tls_dh_max_bits);
491 SSL_CTX_set_tmp_dh(sctx, dh);
493 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
494 dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
507 /*************************************************
508 * Load OCSP information into state *
509 *************************************************/
511 /* Called to load the server OCSP response from the given file into memory, once
512 caller has determined this is needed. Checks validity. Debugs a message
515 ASSUMES: single response, for single cert.
518 sctx the SSL_CTX* to update
519 cbinfo various parts of session state
520 expanded the filename putatively holding an OCSP response
525 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
529 OCSP_BASICRESP *basic_response;
530 OCSP_SINGLERESP *single_response;
531 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
533 unsigned long verify_flags;
534 int status, reason, i;
536 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
537 if (cbinfo->u_ocsp.server.response)
539 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
540 cbinfo->u_ocsp.server.response = NULL;
543 bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb");
546 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
547 cbinfo->u_ocsp.server.file_expanded);
551 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
555 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
559 status = OCSP_response_status(resp);
560 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
562 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
563 OCSP_response_status_str(status), status);
567 basic_response = OCSP_response_get1_basic(resp);
571 debug_printf("OCSP response parse error: unable to extract basic response.\n");
575 store = SSL_CTX_get_cert_store(sctx);
576 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
578 /* May need to expose ability to adjust those flags?
579 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
580 OCSP_TRUSTOTHER OCSP_NOINTERN */
582 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
586 ERR_error_string(ERR_get_error(), ssl_errstring);
587 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
592 /* Here's the simplifying assumption: there's only one response, for the
593 one certificate we use, and nothing for anything else in a chain. If this
594 proves false, we need to extract a cert id from our issued cert
595 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
596 right cert in the stack and then calls OCSP_single_get0_status()).
598 I'm hoping to avoid reworking a bunch more of how we handle state here. */
599 single_response = OCSP_resp_get0(basic_response, 0);
600 if (!single_response)
603 debug_printf("Unable to get first response from OCSP basic response.\n");
607 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
608 if (status != V_OCSP_CERTSTATUS_GOOD)
610 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
611 OCSP_cert_status_str(status), status,
612 OCSP_crl_reason_str(reason), reason);
616 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
618 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
623 cbinfo->u_ocsp.server.response = resp;
627 if (running_in_test_harness)
629 extern char ** environ;
631 for (p = USS environ; *p != NULL; p++)
632 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
634 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
635 goto supply_response;
640 #endif /*!DISABLE_OCSP*/
645 /*************************************************
646 * Expand key and cert file specs *
647 *************************************************/
649 /* Called once during tls_init and possibly again during TLS setup, for a
650 new context, if Server Name Indication was used and tls_sni was seen in
651 the certificate string.
654 sctx the SSL_CTX* to update
655 cbinfo various parts of session state
657 Returns: OK/DEFER/FAIL
661 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
665 if (cbinfo->certificate == NULL)
668 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
669 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
670 Ustrstr(cbinfo->certificate, US"tls_out_sni")
672 reexpand_tls_files_for_sni = TRUE;
674 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
677 if (expanded != NULL)
679 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
680 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
681 return tls_error(string_sprintf(
682 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
686 if (cbinfo->privatekey != NULL &&
687 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
690 /* If expansion was forced to fail, key_expanded will be NULL. If the result
691 of the expansion is an empty string, ignore it also, and assume the private
692 key is in the same file as the certificate. */
694 if (expanded != NULL && *expanded != 0)
696 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
697 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
698 return tls_error(string_sprintf(
699 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
703 if (cbinfo->is_server && cbinfo->u_ocsp.server.file != NULL)
705 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded))
708 if (expanded != NULL && *expanded != 0)
710 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
711 if (cbinfo->u_ocsp.server.file_expanded &&
712 (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
715 debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
717 ocsp_load_response(sctx, cbinfo, expanded);
729 /*************************************************
730 * Callback to handle SNI *
731 *************************************************/
733 /* Called when acting as server during the TLS session setup if a Server Name
734 Indication extension was sent by the client.
736 API documentation is OpenSSL s_server.c implementation.
739 s SSL* of the current session
740 ad unknown (part of OpenSSL API) (unused)
741 arg Callback of "our" registered data
743 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
746 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
748 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
750 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
751 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
753 int old_pool = store_pool;
756 return SSL_TLSEXT_ERR_OK;
758 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
759 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
761 /* Make the extension value available for expansion */
762 store_pool = POOL_PERM;
763 tls_in.sni = string_copy(US servername);
764 store_pool = old_pool;
766 if (!reexpand_tls_files_for_sni)
767 return SSL_TLSEXT_ERR_OK;
769 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
770 not confident that memcpy wouldn't break some internal reference counting.
771 Especially since there's a references struct member, which would be off. */
773 server_sni = SSL_CTX_new(SSLv23_server_method());
776 ERR_error_string(ERR_get_error(), ssl_errstring);
777 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
778 return SSL_TLSEXT_ERR_NOACK;
781 /* Not sure how many of these are actually needed, since SSL object
782 already exists. Might even need this selfsame callback, for reneg? */
784 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
785 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
786 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
787 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
788 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
789 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
790 if (cbinfo->server_cipher_list)
791 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
793 if (cbinfo->u_ocsp.server.file)
795 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
796 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
800 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server);
801 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
803 /* do this after setup_certs, because this can require the certs for verifying
805 rc = tls_expand_session_files(server_sni, cbinfo);
806 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
808 rc = init_dh(server_sni, cbinfo->dhparam, NULL);
809 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
811 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
812 SSL_set_SSL_CTX(s, server_sni);
814 return SSL_TLSEXT_ERR_OK;
816 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
823 /*************************************************
824 * Callback to handle OCSP Stapling *
825 *************************************************/
827 /* Called when acting as server during the TLS session setup if the client
828 requests OCSP information with a Certificate Status Request.
830 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
836 tls_server_stapling_cb(SSL *s, void *arg)
838 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
839 uschar *response_der;
840 int response_der_len;
843 debug_printf("Received TLS status request (OCSP stapling); %s response.",
844 cbinfo->u_ocsp.server.response ? "have" : "lack");
846 tls_in.ocsp = OCSP_NOT_RESP;
847 if (!cbinfo->u_ocsp.server.response)
848 return SSL_TLSEXT_ERR_NOACK;
851 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
853 if (response_der_len <= 0)
854 return SSL_TLSEXT_ERR_NOACK;
856 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
857 tls_in.ocsp = OCSP_VFIED;
858 return SSL_TLSEXT_ERR_OK;
863 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
865 BIO_printf(bp, "\t%s: ", str);
866 ASN1_GENERALIZEDTIME_print(bp, time);
871 tls_client_stapling_cb(SSL *s, void *arg)
873 tls_ext_ctx_cb * cbinfo = arg;
874 const unsigned char * p;
880 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
881 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
884 /* Expect this when we requested ocsp but got none */
885 if ( cbinfo->u_ocsp.client.verify_required
886 && log_extra_selector & LX_tls_cipher)
887 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
889 DEBUG(D_tls) debug_printf(" null\n");
890 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
893 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
895 tls_out.ocsp = OCSP_FAILED;
896 if (log_extra_selector & LX_tls_cipher)
897 log_write(0, LOG_MAIN, "Received TLS status response, parse error");
899 DEBUG(D_tls) debug_printf(" parse error\n");
903 if(!(bs = OCSP_response_get1_basic(rsp)))
905 tls_out.ocsp = OCSP_FAILED;
906 if (log_extra_selector & LX_tls_cipher)
907 log_write(0, LOG_MAIN, "Received TLS status response, error parsing response");
909 DEBUG(D_tls) debug_printf(" error parsing response\n");
910 OCSP_RESPONSE_free(rsp);
914 /* We'd check the nonce here if we'd put one in the request. */
915 /* However that would defeat cacheability on the server so we don't. */
917 /* This section of code reworked from OpenSSL apps source;
918 The OpenSSL Project retains copyright:
919 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
924 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
926 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
928 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
930 /* Use the chain that verified the server cert to verify the stapled info */
931 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
933 if ((i = OCSP_basic_verify(bs, NULL,
934 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
936 tls_out.ocsp = OCSP_FAILED;
937 BIO_printf(bp, "OCSP response verify failure\n");
938 ERR_print_errors(bp);
939 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
943 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
946 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
947 OCSP_SINGLERESP * single;
949 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
951 tls_out.ocsp = OCSP_FAILED;
952 log_write(0, LOG_MAIN, "OCSP stapling "
953 "with multiple responses not handled");
954 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
957 single = OCSP_resp_get0(bs, 0);
958 status = OCSP_single_get0_status(single, &reason, &rev,
962 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
963 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
964 if (!OCSP_check_validity(thisupd, nextupd,
965 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
967 tls_out.ocsp = OCSP_FAILED;
968 DEBUG(D_tls) ERR_print_errors(bp);
969 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
970 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
974 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
975 OCSP_cert_status_str(status));
978 case V_OCSP_CERTSTATUS_GOOD:
979 tls_out.ocsp = OCSP_VFIED;
982 case V_OCSP_CERTSTATUS_REVOKED:
983 tls_out.ocsp = OCSP_FAILED;
984 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
985 reason != -1 ? "; reason: " : "",
986 reason != -1 ? OCSP_crl_reason_str(reason) : "");
987 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
988 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
991 tls_out.ocsp = OCSP_FAILED;
992 log_write(0, LOG_MAIN,
993 "Server certificate status unknown, in OCSP stapling");
994 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1002 OCSP_RESPONSE_free(rsp);
1005 #endif /*!DISABLE_OCSP*/
1009 /*************************************************
1010 * Initialize for TLS *
1011 *************************************************/
1013 /* Called from both server and client code, to do preliminary initialization
1014 of the library. We allocate and return a context structure.
1017 host connected host, if client; NULL if server
1018 dhparam DH parameter file
1019 certificate certificate file
1020 privatekey private key
1021 ocsp_file file of stapling info (server); flag for require ocsp (client)
1022 addr address if client; NULL if server (for some randomness)
1023 cbp place to put allocated context
1025 Returns: OK/DEFER/FAIL
1029 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1031 #ifndef DISABLE_OCSP
1034 address_item *addr, tls_ext_ctx_cb ** cbp)
1039 tls_ext_ctx_cb *cbinfo;
1041 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1042 cbinfo->certificate = certificate;
1043 cbinfo->privatekey = privatekey;
1044 #ifndef DISABLE_OCSP
1045 if ((cbinfo->is_server = host==NULL))
1047 cbinfo->u_ocsp.server.file = ocsp_file;
1048 cbinfo->u_ocsp.server.file_expanded = NULL;
1049 cbinfo->u_ocsp.server.response = NULL;
1052 cbinfo->u_ocsp.client.verify_store = NULL;
1054 cbinfo->dhparam = dhparam;
1055 cbinfo->host = host;
1057 SSL_load_error_strings(); /* basic set up */
1058 OpenSSL_add_ssl_algorithms();
1060 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1061 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1062 list of available digests. */
1063 EVP_add_digest(EVP_sha256());
1066 /* Create a context.
1067 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1068 negotiation in the different methods; as far as I can tell, the only
1069 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1070 when OpenSSL is built without SSLv2 support.
1071 By disabling with openssl_options, we can let admins re-enable with the
1074 *ctxp = SSL_CTX_new((host == NULL)?
1075 SSLv23_server_method() : SSLv23_client_method());
1077 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
1079 /* It turns out that we need to seed the random number generator this early in
1080 order to get the full complement of ciphers to work. It took me roughly a day
1081 of work to discover this by experiment.
1083 On systems that have /dev/urandom, SSL may automatically seed itself from
1084 there. Otherwise, we have to make something up as best we can. Double check
1090 gettimeofday(&r.tv, NULL);
1093 RAND_seed((uschar *)(&r), sizeof(r));
1094 RAND_seed((uschar *)big_buffer, big_buffer_size);
1095 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1098 return tls_error(US"RAND_status", host,
1099 US"unable to seed random number generator");
1102 /* Set up the information callback, which outputs if debugging is at a suitable
1105 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1107 /* Automatically re-try reads/writes after renegotiation. */
1108 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1110 /* Apply administrator-supplied work-arounds.
1111 Historically we applied just one requested option,
1112 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1113 moved to an administrator-controlled list of options to specify and
1114 grandfathered in the first one as the default value for "openssl_options".
1116 No OpenSSL version number checks: the options we accept depend upon the
1117 availability of the option value macros from OpenSSL. */
1119 okay = tls_openssl_options_parse(openssl_options, &init_options);
1121 return tls_error(US"openssl_options parsing failed", host, NULL);
1125 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1126 if (!(SSL_CTX_set_options(*ctxp, init_options)))
1127 return tls_error(string_sprintf(
1128 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1131 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1133 /* Initialize with DH parameters if supplied */
1135 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
1137 /* Set up certificate and key (and perhaps OCSP info) */
1139 rc = tls_expand_session_files(*ctxp, cbinfo);
1140 if (rc != OK) return rc;
1142 /* If we need to handle SNI, do so */
1143 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1144 if (host == NULL) /* server */
1146 # ifndef DISABLE_OCSP
1147 /* We check u_ocsp.server.file, not server.response, because we care about if
1148 the option exists, not what the current expansion might be, as SNI might
1149 change the certificate and OCSP file in use between now and the time the
1150 callback is invoked. */
1151 if (cbinfo->u_ocsp.server.file)
1153 SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1154 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1157 /* We always do this, so that $tls_sni is available even if not used in
1159 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1160 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1162 # ifndef DISABLE_OCSP
1164 if(ocsp_file) /* wanting stapling */
1166 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1168 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1171 SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1172 SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1177 #ifdef EXPERIMENTAL_CERTNAMES
1178 cbinfo->verify_cert_hostnames = NULL;
1181 /* Set up the RSA callback */
1183 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1185 /* Finally, set the timeout, and we are done */
1187 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1188 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1198 /*************************************************
1199 * Get name of cipher in use *
1200 *************************************************/
1203 Argument: pointer to an SSL structure for the connection
1204 buffer to use for answer
1206 pointer to number of bits for cipher
1211 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1213 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1214 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1215 the accessor functions use const in the prototype. */
1216 const SSL_CIPHER *c;
1219 ver = (const uschar *)SSL_get_version(ssl);
1221 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1222 SSL_CIPHER_get_bits(c, bits);
1224 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1225 SSL_CIPHER_get_name(c), *bits);
1227 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1234 /*************************************************
1235 * Set up for verifying certificates *
1236 *************************************************/
1238 /* Called by both client and server startup
1241 sctx SSL_CTX* to initialise
1242 certs certs file or NULL
1243 crl CRL file or NULL
1244 host NULL in a server; the remote host in a client
1245 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1246 otherwise passed as FALSE
1247 cert_vfy_cb Callback function for certificate verification
1249 Returns: OK/DEFER/FAIL
1253 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1254 int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1256 uschar *expcerts, *expcrl;
1258 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1261 if (expcerts != NULL && *expcerts != '\0')
1263 struct stat statbuf;
1264 if (!SSL_CTX_set_default_verify_paths(sctx))
1265 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1267 if (Ustat(expcerts, &statbuf) < 0)
1269 log_write(0, LOG_MAIN|LOG_PANIC,
1270 "failed to stat %s for certificates", expcerts);
1276 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1277 { file = NULL; dir = expcerts; }
1279 { file = expcerts; dir = NULL; }
1281 /* If a certificate file is empty, the next function fails with an
1282 unhelpful error message. If we skip it, we get the correct behaviour (no
1283 certificates are recognized, but the error message is still misleading (it
1284 says no certificate was supplied.) But this is better. */
1286 if ((file == NULL || statbuf.st_size > 0) &&
1287 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1288 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1292 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1296 /* Handle a certificate revocation list. */
1298 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1300 /* This bit of code is now the version supplied by Lars Mainka. (I have
1301 * merely reformatted it into the Exim code style.)
1303 * "From here I changed the code to add support for multiple crl's
1304 * in pem format in one file or to support hashed directory entries in
1305 * pem format instead of a file. This method now uses the library function
1306 * X509_STORE_load_locations to add the CRL location to the SSL context.
1307 * OpenSSL will then handle the verify against CA certs and CRLs by
1308 * itself in the verify callback." */
1310 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1311 if (expcrl != NULL && *expcrl != 0)
1313 struct stat statbufcrl;
1314 if (Ustat(expcrl, &statbufcrl) < 0)
1316 log_write(0, LOG_MAIN|LOG_PANIC,
1317 "failed to stat %s for certificates revocation lists", expcrl);
1322 /* is it a file or directory? */
1324 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1325 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1329 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1335 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1337 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1338 return tls_error(US"X509_STORE_load_locations", host, NULL);
1340 /* setting the flags to check against the complete crl chain */
1342 X509_STORE_set_flags(cvstore,
1343 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1347 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1349 /* If verification is optional, don't fail if no certificate */
1351 SSL_CTX_set_verify(sctx,
1352 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1361 /*************************************************
1362 * Start a TLS session in a server *
1363 *************************************************/
1365 /* This is called when Exim is running as a server, after having received
1366 the STARTTLS command. It must respond to that command, and then negotiate
1370 require_ciphers allowed ciphers
1372 Returns: OK on success
1373 DEFER for errors before the start of the negotiation
1374 FAIL for errors during the negotation; the server can't
1379 tls_server_start(const uschar *require_ciphers)
1383 tls_ext_ctx_cb *cbinfo;
1384 static uschar cipherbuf[256];
1386 /* Check for previous activation */
1388 if (tls_in.active >= 0)
1390 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1391 smtp_printf("554 Already in TLS\r\n");
1395 /* Initialize the SSL library. If it fails, it will already have logged
1398 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1399 #ifndef DISABLE_OCSP
1402 NULL, &server_static_cbinfo);
1403 if (rc != OK) return rc;
1404 cbinfo = server_static_cbinfo;
1406 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1409 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1410 were historically separated by underscores. So that I can use either form in my
1411 tests, and also for general convenience, we turn underscores into hyphens here.
1414 if (expciphers != NULL)
1416 uschar *s = expciphers;
1417 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1418 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1419 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1420 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1421 cbinfo->server_cipher_list = expciphers;
1424 /* If this is a host for which certificate verification is mandatory or
1425 optional, set up appropriately. */
1427 tls_in.certificate_verified = FALSE;
1428 server_verify_callback_called = FALSE;
1430 if (verify_check_host(&tls_verify_hosts) == OK)
1432 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1433 FALSE, verify_callback_server);
1434 if (rc != OK) return rc;
1435 server_verify_optional = FALSE;
1437 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1439 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1440 TRUE, verify_callback_server);
1441 if (rc != OK) return rc;
1442 server_verify_optional = TRUE;
1445 /* Prepare for new connection */
1447 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1449 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1451 * With the SSL_clear(), we get strange interoperability bugs with
1452 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1453 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1455 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1456 * session shutdown. In this case, we have a brand new object and there's no
1457 * obvious reason to immediately clear it. I'm guessing that this was
1458 * originally added because of incomplete initialisation which the clear fixed,
1459 * in some historic release.
1462 /* Set context and tell client to go ahead, except in the case of TLS startup
1463 on connection, where outputting anything now upsets the clients and tends to
1464 make them disconnect. We need to have an explicit fflush() here, to force out
1465 the response. Other smtp_printf() calls do not need it, because in non-TLS
1466 mode, the fflush() happens when smtp_getc() is called. */
1468 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1469 if (!tls_in.on_connect)
1471 smtp_printf("220 TLS go ahead\r\n");
1475 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1476 that the OpenSSL library doesn't. */
1478 SSL_set_wfd(server_ssl, fileno(smtp_out));
1479 SSL_set_rfd(server_ssl, fileno(smtp_in));
1480 SSL_set_accept_state(server_ssl);
1482 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1484 sigalrm_seen = FALSE;
1485 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1486 rc = SSL_accept(server_ssl);
1491 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1492 if (ERR_get_error() == 0)
1493 log_write(0, LOG_MAIN,
1494 "TLS client disconnected cleanly (rejected our certificate?)");
1498 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1500 /* TLS has been set up. Adjust the input functions to read via TLS,
1501 and initialize things. */
1503 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1504 tls_in.cipher = cipherbuf;
1509 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1510 debug_printf("Shared ciphers: %s\n", buf);
1513 /* Record the certificate we presented */
1515 X509 * crt = SSL_get_certificate(server_ssl);
1516 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
1519 /* Only used by the server-side tls (tls_in), including tls_getc.
1520 Client-side (tls_out) reads (seem to?) go via
1521 smtp_read_response()/ip_recv().
1522 Hence no need to duplicate for _in and _out.
1524 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1525 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1526 ssl_xfer_eof = ssl_xfer_error = 0;
1528 receive_getc = tls_getc;
1529 receive_ungetc = tls_ungetc;
1530 receive_feof = tls_feof;
1531 receive_ferror = tls_ferror;
1532 receive_smtp_buffered = tls_smtp_buffered;
1534 tls_in.active = fileno(smtp_out);
1542 /*************************************************
1543 * Start a TLS session in a client *
1544 *************************************************/
1546 /* Called from the smtp transport after STARTTLS has been accepted.
1549 fd the fd of the connection
1550 host connected host (for messages)
1551 addr the first address
1552 ob smtp transport options
1554 Returns: OK on success
1555 FAIL otherwise - note that tls_error() will not give DEFER
1556 because this is not a server
1560 tls_client_start(int fd, host_item *host, address_item *addr,
1563 smtp_transport_options_block * ob = v_ob;
1564 static uschar txt[256];
1568 static uschar cipherbuf[256];
1569 #ifndef DISABLE_OCSP
1570 BOOL require_ocsp = verify_check_this_host(&ob->hosts_require_ocsp,
1571 NULL, host->name, host->address, NULL) == OK;
1572 BOOL request_ocsp = require_ocsp ? TRUE
1573 : verify_check_this_host(&ob->hosts_request_ocsp,
1574 NULL, host->name, host->address, NULL) == OK;
1577 rc = tls_init(&client_ctx, host, NULL,
1578 ob->tls_certificate, ob->tls_privatekey,
1579 #ifndef DISABLE_OCSP
1580 (void *)(long)request_ocsp,
1582 addr, &client_static_cbinfo);
1583 if (rc != OK) return rc;
1585 tls_out.certificate_verified = FALSE;
1586 client_verify_callback_called = FALSE;
1588 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
1592 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1593 are separated by underscores. So that I can use either form in my tests, and
1594 also for general convenience, we turn underscores into hyphens here. */
1596 if (expciphers != NULL)
1598 uschar *s = expciphers;
1599 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1600 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1601 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1602 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1605 /* stick to the old behaviour for compatibility if tls_verify_certificates is
1606 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
1607 the specified host patterns if one of them is defined */
1609 if ((!ob->tls_verify_hosts && !ob->tls_try_verify_hosts) ||
1610 (verify_check_host(&ob->tls_verify_hosts) == OK))
1612 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1613 ob->tls_crl, host, FALSE, verify_callback_client)) != OK)
1615 client_verify_optional = FALSE;
1617 #ifdef EXPERIMENTAL_CERTNAMES
1618 if (ob->tls_verify_cert_hostnames)
1620 if (!expand_check(ob->tls_verify_cert_hostnames,
1621 US"tls_verify_cert_hostnames",
1622 &client_static_cbinfo->verify_cert_hostnames))
1624 if (client_static_cbinfo->verify_cert_hostnames)
1625 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
1626 client_static_cbinfo->verify_cert_hostnames);
1630 else if (verify_check_host(&ob->tls_try_verify_hosts) == OK)
1632 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1633 ob->tls_crl, host, TRUE, verify_callback_client)) != OK)
1635 client_verify_optional = TRUE;
1638 if ((client_ssl = SSL_new(client_ctx)) == NULL)
1639 return tls_error(US"SSL_new", host, NULL);
1640 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1641 SSL_set_fd(client_ssl, fd);
1642 SSL_set_connect_state(client_ssl);
1646 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
1648 if (tls_out.sni == NULL)
1650 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1652 else if (!Ustrlen(tls_out.sni))
1656 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1657 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1658 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1661 debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1667 #ifndef DISABLE_OCSP
1668 /* Request certificate status at connection-time. If the server
1669 does OCSP stapling we will get the callback (set in tls_init()) */
1672 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
1673 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
1674 tls_out.ocsp = OCSP_NOT_RESP;
1678 /* There doesn't seem to be a built-in timeout on connection. */
1680 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1681 sigalrm_seen = FALSE;
1682 alarm(ob->command_timeout);
1683 rc = SSL_connect(client_ssl);
1687 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1689 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1691 /* Beware anonymous ciphers which lead to server_cert being NULL */
1692 /*XXX server_cert is never freed... use X509_free() */
1693 server_cert = SSL_get_peer_certificate (client_ssl);
1696 tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1697 CS txt, sizeof(txt));
1698 tls_out.peerdn = txt; /*XXX a static buffer... */
1701 tls_out.peerdn = NULL;
1703 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1704 tls_out.cipher = cipherbuf;
1706 /* Record the certificate we presented */
1708 X509 * crt = SSL_get_certificate(client_ssl);
1709 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
1712 tls_out.active = fd;
1720 /*************************************************
1721 * TLS version of getc *
1722 *************************************************/
1724 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1725 it refills the buffer via the SSL reading function.
1728 Returns: the next character or EOF
1730 Only used by the server-side TLS.
1736 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1741 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1742 ssl_xfer_buffer, ssl_xfer_buffer_size);
1744 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1745 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1746 error = SSL_get_error(server_ssl, inbytes);
1749 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1750 closed down, not that the socket itself has been closed down. Revert to
1751 non-SSL handling. */
1753 if (error == SSL_ERROR_ZERO_RETURN)
1755 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1757 receive_getc = smtp_getc;
1758 receive_ungetc = smtp_ungetc;
1759 receive_feof = smtp_feof;
1760 receive_ferror = smtp_ferror;
1761 receive_smtp_buffered = smtp_buffered;
1763 SSL_free(server_ssl);
1767 tls_in.cipher = NULL;
1768 tls_in.peerdn = NULL;
1774 /* Handle genuine errors */
1776 else if (error == SSL_ERROR_SSL)
1778 ERR_error_string(ERR_get_error(), ssl_errstring);
1779 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1784 else if (error != SSL_ERROR_NONE)
1786 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1791 #ifndef DISABLE_DKIM
1792 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1794 ssl_xfer_buffer_hwm = inbytes;
1795 ssl_xfer_buffer_lwm = 0;
1798 /* Something in the buffer; return next uschar */
1800 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1805 /*************************************************
1806 * Read bytes from TLS channel *
1807 *************************************************/
1814 Returns: the number of bytes read
1815 -1 after a failed read
1817 Only used by the client-side TLS.
1821 tls_read(BOOL is_server, uschar *buff, size_t len)
1823 SSL *ssl = is_server ? server_ssl : client_ssl;
1827 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1828 buff, (unsigned int)len);
1830 inbytes = SSL_read(ssl, CS buff, len);
1831 error = SSL_get_error(ssl, inbytes);
1833 if (error == SSL_ERROR_ZERO_RETURN)
1835 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1838 else if (error != SSL_ERROR_NONE)
1850 /*************************************************
1851 * Write bytes down TLS channel *
1852 *************************************************/
1856 is_server channel specifier
1860 Returns: the number of bytes after a successful write,
1861 -1 after a failed write
1863 Used by both server-side and client-side TLS.
1867 tls_write(BOOL is_server, const uschar *buff, size_t len)
1872 SSL *ssl = is_server ? server_ssl : client_ssl;
1874 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1877 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1878 outbytes = SSL_write(ssl, CS buff, left);
1879 error = SSL_get_error(ssl, outbytes);
1880 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1884 ERR_error_string(ERR_get_error(), ssl_errstring);
1885 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1888 case SSL_ERROR_NONE:
1893 case SSL_ERROR_ZERO_RETURN:
1894 log_write(0, LOG_MAIN, "SSL channel closed on write");
1897 case SSL_ERROR_SYSCALL:
1898 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1899 sender_fullhost ? sender_fullhost : US"<unknown>",
1903 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1912 /*************************************************
1913 * Close down a TLS session *
1914 *************************************************/
1916 /* This is also called from within a delivery subprocess forked from the
1917 daemon, to shut down the TLS library, without actually doing a shutdown (which
1918 would tamper with the SSL session in the parent process).
1920 Arguments: TRUE if SSL_shutdown is to be called
1923 Used by both server-side and client-side TLS.
1927 tls_close(BOOL is_server, BOOL shutdown)
1929 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1930 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1932 if (*fdp < 0) return; /* TLS was not active */
1936 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1937 SSL_shutdown(*sslp);
1949 /*************************************************
1950 * Let tls_require_ciphers be checked at startup *
1951 *************************************************/
1953 /* The tls_require_ciphers option, if set, must be something which the
1956 Returns: NULL on success, or error message
1960 tls_validate_require_cipher(void)
1963 uschar *s, *expciphers, *err;
1965 /* this duplicates from tls_init(), we need a better "init just global
1966 state, for no specific purpose" singleton function of our own */
1968 SSL_load_error_strings();
1969 OpenSSL_add_ssl_algorithms();
1970 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1971 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1972 list of available digests. */
1973 EVP_add_digest(EVP_sha256());
1976 if (!(tls_require_ciphers && *tls_require_ciphers))
1979 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1980 return US"failed to expand tls_require_ciphers";
1982 if (!(expciphers && *expciphers))
1985 /* normalisation ripped from above */
1987 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1991 ctx = SSL_CTX_new(SSLv23_server_method());
1994 ERR_error_string(ERR_get_error(), ssl_errstring);
1995 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1999 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2001 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2003 ERR_error_string(ERR_get_error(), ssl_errstring);
2004 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
2015 /*************************************************
2016 * Report the library versions. *
2017 *************************************************/
2019 /* There have historically been some issues with binary compatibility in
2020 OpenSSL libraries; if Exim (like many other applications) is built against
2021 one version of OpenSSL but the run-time linker picks up another version,
2022 it can result in serious failures, including crashing with a SIGSEGV. So
2023 report the version found by the compiler and the run-time version.
2025 Note: some OS vendors backport security fixes without changing the version
2026 number/string, and the version date remains unchanged. The _build_ date
2027 will change, so we can more usefully assist with version diagnosis by also
2028 reporting the build date.
2030 Arguments: a FILE* to print the results to
2035 tls_version_report(FILE *f)
2037 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2040 OPENSSL_VERSION_TEXT,
2041 SSLeay_version(SSLEAY_VERSION),
2042 SSLeay_version(SSLEAY_BUILT_ON));
2043 /* third line is 38 characters for the %s and the line is 73 chars long;
2044 the OpenSSL output includes a "built on: " prefix already. */
2050 /*************************************************
2051 * Random number generation *
2052 *************************************************/
2054 /* Pseudo-random number generation. The result is not expected to be
2055 cryptographically strong but not so weak that someone will shoot themselves
2056 in the foot using it as a nonce in input in some email header scheme or
2057 whatever weirdness they'll twist this into. The result should handle fork()
2058 and avoid repeating sequences. OpenSSL handles that for us.
2062 Returns a random number in range [0, max-1]
2066 vaguely_random_number(int max)
2070 static pid_t pidlast = 0;
2073 uschar smallbuf[sizeof(r)];
2079 if (pidnow != pidlast)
2081 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2082 is unique for each thread", this doesn't apparently apply across processes,
2083 so our own warning from vaguely_random_number_fallback() applies here too.
2084 Fix per PostgreSQL. */
2090 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2094 gettimeofday(&r.tv, NULL);
2097 RAND_seed((uschar *)(&r), sizeof(r));
2099 /* We're after pseudo-random, not random; if we still don't have enough data
2100 in the internal PRNG then our options are limited. We could sleep and hope
2101 for entropy to come along (prayer technique) but if the system is so depleted
2102 in the first place then something is likely to just keep taking it. Instead,
2103 we'll just take whatever little bit of pseudo-random we can still manage to
2106 needed_len = sizeof(r);
2107 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2108 asked for a number less than 10. */
2109 for (r = max, i = 0; r; ++i)
2115 /* We do not care if crypto-strong */
2116 i = RAND_pseudo_bytes(smallbuf, needed_len);
2120 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2121 return vaguely_random_number_fallback(max);
2125 for (p = smallbuf; needed_len; --needed_len, ++p)
2131 /* We don't particularly care about weighted results; if someone wants
2132 smooth distribution and cares enough then they should submit a patch then. */
2139 /*************************************************
2140 * OpenSSL option parse *
2141 *************************************************/
2143 /* Parse one option for tls_openssl_options_parse below
2146 name one option name
2147 value place to store a value for it
2148 Returns success or failure in parsing
2151 struct exim_openssl_option {
2155 /* We could use a macro to expand, but we need the ifdef and not all the
2156 options document which version they were introduced in. Policylet: include
2157 all options unless explicitly for DTLS, let the administrator choose which
2160 This list is current as of:
2162 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2164 static struct exim_openssl_option exim_openssl_options[] = {
2165 /* KEEP SORTED ALPHABETICALLY! */
2167 { US"all", SSL_OP_ALL },
2169 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2170 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2172 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2173 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2175 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2176 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2178 #ifdef SSL_OP_EPHEMERAL_RSA
2179 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2181 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2182 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2184 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2185 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2187 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2188 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2190 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2191 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2193 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2194 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2196 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2197 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2199 #ifdef SSL_OP_NO_COMPRESSION
2200 { US"no_compression", SSL_OP_NO_COMPRESSION },
2202 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2203 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2205 #ifdef SSL_OP_NO_SSLv2
2206 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2208 #ifdef SSL_OP_NO_SSLv3
2209 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2211 #ifdef SSL_OP_NO_TICKET
2212 { US"no_ticket", SSL_OP_NO_TICKET },
2214 #ifdef SSL_OP_NO_TLSv1
2215 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2217 #ifdef SSL_OP_NO_TLSv1_1
2218 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2219 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2220 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2222 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2225 #ifdef SSL_OP_NO_TLSv1_2
2226 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2228 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2229 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2231 #ifdef SSL_OP_SINGLE_DH_USE
2232 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2234 #ifdef SSL_OP_SINGLE_ECDH_USE
2235 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2237 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2238 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2240 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2241 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2243 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2244 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2246 #ifdef SSL_OP_TLS_D5_BUG
2247 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2249 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2250 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2253 static int exim_openssl_options_size =
2254 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2258 tls_openssl_one_option_parse(uschar *name, long *value)
2261 int last = exim_openssl_options_size;
2262 while (last > first)
2264 int middle = (first + last)/2;
2265 int c = Ustrcmp(name, exim_openssl_options[middle].name);
2268 *value = exim_openssl_options[middle].value;
2282 /*************************************************
2283 * OpenSSL option parsing logic *
2284 *************************************************/
2286 /* OpenSSL has a number of compatibility options which an administrator might
2287 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
2288 we look like log_selector.
2291 option_spec the administrator-supplied string of options
2292 results ptr to long storage for the options bitmap
2293 Returns success or failure
2297 tls_openssl_options_parse(uschar *option_spec, long *results)
2302 BOOL adding, item_parsed;
2305 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2306 * from default because it increases BEAST susceptibility. */
2307 #ifdef SSL_OP_NO_SSLv2
2308 result |= SSL_OP_NO_SSLv2;
2311 if (option_spec == NULL)
2317 for (s=option_spec; *s != '\0'; /**/)
2319 while (isspace(*s)) ++s;
2322 if (*s != '+' && *s != '-')
2324 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2325 "+ or - expected but found \"%s\"\n", s);
2328 adding = *s++ == '+';
2329 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2332 item_parsed = tls_openssl_one_option_parse(s, &item);
2335 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2338 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2339 adding ? "adding" : "removing", result, item, s);
2354 /* End of tls-openssl.c */