1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2009 */
6 /* See the file NOTICE for conditions of use and distribution. */
8 /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL
9 library. It is #included into the tls.c file when that library is used. The
10 code herein is based on a patch that was originally contributed by Steve
11 Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara.
13 No cryptographic code is included in Exim. All this module does is to call
14 functions from the OpenSSL library. */
19 #include <openssl/lhash.h>
20 #include <openssl/ssl.h>
21 #include <openssl/err.h>
22 #include <openssl/rand.h>
24 /* Structure for collecting random data for seeding. */
26 typedef struct randstuff {
31 /* Local static variables */
33 static BOOL verify_callback_called = FALSE;
34 static const uschar *sid_ctx = US"exim";
36 static SSL_CTX *ctx = NULL;
37 static SSL_CTX *ctx_sni = NULL;
38 static SSL *ssl = NULL;
40 static char ssl_errstring[256];
42 static int ssl_session_timeout = 200;
43 static BOOL verify_optional = FALSE;
45 static BOOL reexpand_tls_files_for_sni = FALSE;
48 typedef struct tls_ext_ctx_cb {
52 /* these are cached from first expand */
53 uschar *server_cipher_list;
54 /* only passed down to tls_error: */
58 /* should figure out a cleanup of API to handle state preserved per
59 implementation, for various reasons, which can be void * in the APIs.
60 For now, we hack around it. */
61 tls_ext_ctx_cb *static_cbinfo = NULL;
64 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional);
67 /*************************************************
69 *************************************************/
71 /* Called from lots of places when errors occur before actually starting to do
72 the TLS handshake, that is, while the session is still in clear. Always returns
73 DEFER for a server and FAIL for a client so that most calls can use "return
74 tls_error(...)" to do this processing and then give an appropriate return. A
75 single function is used for both server and client, because it is called from
76 some shared functions.
79 prefix text to include in the logged error
80 host NULL if setting up a server;
81 the connected host if setting up a client
82 msg error message or NULL if we should ask OpenSSL
84 Returns: OK/DEFER/FAIL
88 tls_error(uschar *prefix, host_item *host, uschar *msg)
92 ERR_error_string(ERR_get_error(), ssl_errstring);
93 msg = (uschar *)ssl_errstring;
98 uschar *conn_info = smtp_get_connection_info();
99 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
101 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
102 conn_info, prefix, msg);
107 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
108 host->name, host->address, prefix, msg);
115 /*************************************************
116 * Callback to generate RSA key *
117 *************************************************/
125 Returns: pointer to generated key
129 rsa_callback(SSL *s, int export, int keylength)
132 export = export; /* Shut picky compilers up */
133 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
134 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
137 ERR_error_string(ERR_get_error(), ssl_errstring);
138 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
148 /*************************************************
149 * Callback for verification *
150 *************************************************/
152 /* The SSL library does certificate verification if set up to do so. This
153 callback has the current yes/no state is in "state". If verification succeeded,
154 we set up the tls_peerdn string. If verification failed, what happens depends
155 on whether the client is required to present a verifiable certificate or not.
157 If verification is optional, we change the state to yes, but still log the
158 verification error. For some reason (it really would help to have proper
159 documentation of OpenSSL), this callback function then gets called again, this
160 time with state = 1. In fact, that's useful, because we can set up the peerdn
161 value, but we must take care not to set the private verified flag on the second
164 Note: this function is not called if the client fails to present a certificate
165 when asked. We get here only if a certificate has been received. Handling of
166 optional verification for this case is done when requesting SSL to verify, by
167 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
170 state current yes/no state as 1/0
171 x509ctx certificate information.
173 Returns: 1 if verified, 0 if not
177 verify_callback(int state, X509_STORE_CTX *x509ctx)
179 static uschar txt[256];
181 X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert),
182 CS txt, sizeof(txt));
186 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
187 x509ctx->error_depth,
188 X509_verify_cert_error_string(x509ctx->error),
190 tls_certificate_verified = FALSE;
191 verify_callback_called = TRUE;
192 if (!verify_optional) return 0; /* reject */
193 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
194 "tls_try_verify_hosts)\n");
195 return 1; /* accept */
198 if (x509ctx->error_depth != 0)
200 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n",
201 x509ctx->error_depth, txt);
205 DEBUG(D_tls) debug_printf("SSL%s peer: %s\n",
206 verify_callback_called? "" : " authenticated", txt);
210 if (!verify_callback_called) tls_certificate_verified = TRUE;
211 verify_callback_called = TRUE;
213 return 1; /* accept */
218 /*************************************************
219 * Information callback *
220 *************************************************/
222 /* The SSL library functions call this from time to time to indicate what they
223 are doing. We copy the string to the debugging output when TLS debugging has
235 info_callback(SSL *s, int where, int ret)
239 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
244 /*************************************************
245 * Initialize for DH *
246 *************************************************/
248 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
251 dhparam DH parameter file
252 host connected host, if client; NULL if server
254 Returns: TRUE if OK (nothing to set up, or setup worked)
258 init_dh(uschar *dhparam, host_item *host)
265 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
268 if (dhexpanded == NULL) return TRUE;
270 if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL)
272 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
273 host, (uschar *)strerror(errno));
278 if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL)
280 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
286 SSL_CTX_set_tmp_dh(ctx, dh);
288 debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n",
289 dhexpanded, 8*DH_size(dh));
301 /*************************************************
302 * Expand key and cert file specs *
303 *************************************************/
305 /* Called once during tls_init and possibly againt during TLS setup, for a
306 new context, if Server Name Indication was used and tls_sni was seen in
307 the certificate string.
310 sctx the SSL_CTX* to update
311 cbinfo various parts of session state
313 Returns: OK/DEFER/FAIL
317 tls_expand_session_files(SSL_CTX *sctx, const tls_ext_ctx_cb *cbinfo)
321 if (cbinfo->certificate == NULL)
324 if (Ustrstr(cbinfo->certificate, US"tls_sni"))
325 reexpand_tls_files_for_sni = TRUE;
327 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
330 if (expanded != NULL)
332 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
333 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
334 return tls_error(string_sprintf(
335 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
339 if (cbinfo->privatekey != NULL &&
340 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
343 /* If expansion was forced to fail, key_expanded will be NULL. If the result
344 of the expansion is an empty string, ignore it also, and assume the private
345 key is in the same file as the certificate. */
347 if (expanded != NULL && *expanded != 0)
349 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
350 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
351 return tls_error(string_sprintf(
352 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
361 /*************************************************
362 * Callback to handle SNI *
363 *************************************************/
365 /* Called when acting as server during the TLS session setup if a Server Name
366 Indication extension was sent by the client.
368 API documentation is OpenSSL s_server.c implementation.
371 s SSL* of the current session
372 ad unknown (part of OpenSSL API) (unused)
373 arg Callback of "our" registered data
375 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
379 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
380 /* pre-declared for SSL_CTX_set_tlsext_servername_callback call within func */
383 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
385 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
386 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
388 int old_pool = store_pool;
391 return SSL_TLSEXT_ERR_OK;
393 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
394 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
396 /* Make the extension value available for expansion */
397 store_pool = POOL_PERM;
398 tls_sni = string_copy(US servername);
399 store_pool = old_pool;
401 if (!reexpand_tls_files_for_sni)
402 return SSL_TLSEXT_ERR_OK;
404 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
405 not confident that memcpy wouldn't break some internal reference counting.
406 Especially since there's a references struct member, which would be off. */
408 ctx_sni = SSL_CTX_new(SSLv23_server_method());
411 ERR_error_string(ERR_get_error(), ssl_errstring);
412 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
413 return SSL_TLSEXT_ERR_NOACK;
416 /* Not sure how many of these are actually needed, since SSL object
417 already exists. Might even need this selfsame callback, for reneg? */
419 SSL_CTX_set_info_callback(ctx_sni, SSL_CTX_get_info_callback(ctx));
420 SSL_CTX_set_mode(ctx_sni, SSL_CTX_get_mode(ctx));
421 SSL_CTX_set_options(ctx_sni, SSL_CTX_get_options(ctx));
422 SSL_CTX_set_timeout(ctx_sni, SSL_CTX_get_timeout(ctx));
423 SSL_CTX_set_tlsext_servername_callback(ctx_sni, tls_servername_cb);
424 SSL_CTX_set_tlsext_servername_arg(ctx_sni, cbinfo);
425 if (cbinfo->server_cipher_list)
426 SSL_CTX_set_cipher_list(ctx_sni, CS cbinfo->server_cipher_list);
428 rc = tls_expand_session_files(ctx_sni, cbinfo);
429 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
431 rc = setup_certs(ctx_sni, tls_verify_certificates, tls_crl, NULL, FALSE);
432 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
434 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
435 SSL_set_SSL_CTX(s, ctx_sni);
437 return SSL_TLSEXT_ERR_OK;
443 /*************************************************
444 * Initialize for TLS *
445 *************************************************/
447 /* Called from both server and client code, to do preliminary initialization of
451 host connected host, if client; NULL if server
452 dhparam DH parameter file
453 certificate certificate file
454 privatekey private key
455 addr address if client; NULL if server (for some randomness)
457 Returns: OK/DEFER/FAIL
461 tls_init(host_item *host, uschar *dhparam, uschar *certificate,
462 uschar *privatekey, address_item *addr)
467 tls_ext_ctx_cb *cbinfo;
469 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
470 cbinfo->certificate = certificate;
471 cbinfo->privatekey = privatekey;
472 cbinfo->dhparam = dhparam;
475 SSL_load_error_strings(); /* basic set up */
476 OpenSSL_add_ssl_algorithms();
478 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
479 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
480 list of available digests. */
481 EVP_add_digest(EVP_sha256());
484 /* Create a context */
486 ctx = SSL_CTX_new((host == NULL)?
487 SSLv23_server_method() : SSLv23_client_method());
489 if (ctx == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
491 /* It turns out that we need to seed the random number generator this early in
492 order to get the full complement of ciphers to work. It took me roughly a day
493 of work to discover this by experiment.
495 On systems that have /dev/urandom, SSL may automatically seed itself from
496 there. Otherwise, we have to make something up as best we can. Double check
502 gettimeofday(&r.tv, NULL);
505 RAND_seed((uschar *)(&r), sizeof(r));
506 RAND_seed((uschar *)big_buffer, big_buffer_size);
507 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
510 return tls_error(US"RAND_status", host,
511 US"unable to seed random number generator");
514 /* Set up the information callback, which outputs if debugging is at a suitable
517 SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
519 /* Automatically re-try reads/writes after renegotiation. */
520 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
522 /* Apply administrator-supplied work-arounds.
523 Historically we applied just one requested option,
524 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
525 moved to an administrator-controlled list of options to specify and
526 grandfathered in the first one as the default value for "openssl_options".
528 No OpenSSL version number checks: the options we accept depend upon the
529 availability of the option value macros from OpenSSL. */
531 okay = tls_openssl_options_parse(openssl_options, &init_options);
533 return tls_error(US"openssl_options parsing failed", host, NULL);
537 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
538 if (!(SSL_CTX_set_options(ctx, init_options)))
539 return tls_error(string_sprintf(
540 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
543 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
545 /* Initialize with DH parameters if supplied */
547 if (!init_dh(dhparam, host)) return DEFER;
549 /* Set up certificate and key */
551 rc = tls_expand_session_files(ctx, cbinfo);
552 if (rc != OK) return rc;
554 /* If we need to handle SNI, do so */
555 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
558 /* We always do this, so that $tls_sni is available even if not used in
560 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
561 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
565 /* Set up the RSA callback */
567 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
569 /* Finally, set the timeout, and we are done */
571 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
572 DEBUG(D_tls) debug_printf("Initialized TLS\n");
574 static_cbinfo = cbinfo;
582 /*************************************************
583 * Get name of cipher in use *
584 *************************************************/
586 /* The answer is left in a static buffer, and tls_cipher is set to point
589 Argument: pointer to an SSL structure for the connection
594 construct_cipher_name(SSL *ssl)
596 static uschar cipherbuf[256];
597 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
598 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
599 the accessor functions use const in the prototype. */
603 switch (ssl->session->ssl_version)
617 #ifdef TLS1_1_VERSION
623 #ifdef TLS1_2_VERSION
633 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
634 SSL_CIPHER_get_bits(c, &tls_bits);
636 string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver,
637 SSL_CIPHER_get_name(c), tls_bits);
638 tls_cipher = cipherbuf;
640 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
647 /*************************************************
648 * Set up for verifying certificates *
649 *************************************************/
651 /* Called by both client and server startup
654 sctx SSL_CTX* to initialise
655 certs certs file or NULL
657 host NULL in a server; the remote host in a client
658 optional TRUE if called from a server for a host in tls_try_verify_hosts;
659 otherwise passed as FALSE
661 Returns: OK/DEFER/FAIL
665 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional)
667 uschar *expcerts, *expcrl;
669 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
672 if (expcerts != NULL)
675 if (!SSL_CTX_set_default_verify_paths(sctx))
676 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
678 if (Ustat(expcerts, &statbuf) < 0)
680 log_write(0, LOG_MAIN|LOG_PANIC,
681 "failed to stat %s for certificates", expcerts);
687 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
688 { file = NULL; dir = expcerts; }
690 { file = expcerts; dir = NULL; }
692 /* If a certificate file is empty, the next function fails with an
693 unhelpful error message. If we skip it, we get the correct behaviour (no
694 certificates are recognized, but the error message is still misleading (it
695 says no certificate was supplied.) But this is better. */
697 if ((file == NULL || statbuf.st_size > 0) &&
698 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
699 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
703 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
707 /* Handle a certificate revocation list. */
709 #if OPENSSL_VERSION_NUMBER > 0x00907000L
711 /* This bit of code is now the version supplied by Lars Mainka. (I have
712 * merely reformatted it into the Exim code style.)
714 * "From here I changed the code to add support for multiple crl's
715 * in pem format in one file or to support hashed directory entries in
716 * pem format instead of a file. This method now uses the library function
717 * X509_STORE_load_locations to add the CRL location to the SSL context.
718 * OpenSSL will then handle the verify against CA certs and CRLs by
719 * itself in the verify callback." */
721 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
722 if (expcrl != NULL && *expcrl != 0)
724 struct stat statbufcrl;
725 if (Ustat(expcrl, &statbufcrl) < 0)
727 log_write(0, LOG_MAIN|LOG_PANIC,
728 "failed to stat %s for certificates revocation lists", expcrl);
733 /* is it a file or directory? */
735 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
736 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
740 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
746 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
748 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
749 return tls_error(US"X509_STORE_load_locations", host, NULL);
751 /* setting the flags to check against the complete crl chain */
753 X509_STORE_set_flags(cvstore,
754 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
758 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
760 /* If verification is optional, don't fail if no certificate */
762 SSL_CTX_set_verify(sctx,
763 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
772 /*************************************************
773 * Start a TLS session in a server *
774 *************************************************/
776 /* This is called when Exim is running as a server, after having received
777 the STARTTLS command. It must respond to that command, and then negotiate
781 require_ciphers allowed ciphers
783 Returns: OK on success
784 DEFER for errors before the start of the negotiation
785 FAIL for errors during the negotation; the server can't
790 tls_server_start(const uschar *require_ciphers)
794 tls_ext_ctx_cb *cbinfo;
796 /* Check for previous activation */
800 tls_error(US"STARTTLS received after TLS started", NULL, US"");
801 smtp_printf("554 Already in TLS\r\n");
805 /* Initialize the SSL library. If it fails, it will already have logged
808 rc = tls_init(NULL, tls_dhparam, tls_certificate, tls_privatekey, NULL);
809 if (rc != OK) return rc;
810 cbinfo = static_cbinfo;
812 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
815 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
816 were historically separated by underscores. So that I can use either form in my
817 tests, and also for general convenience, we turn underscores into hyphens here.
820 if (expciphers != NULL)
822 uschar *s = expciphers;
823 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
824 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
825 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
826 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
827 cbinfo->server_cipher_list = expciphers;
830 /* If this is a host for which certificate verification is mandatory or
831 optional, set up appropriately. */
833 tls_certificate_verified = FALSE;
834 verify_callback_called = FALSE;
836 if (verify_check_host(&tls_verify_hosts) == OK)
838 rc = setup_certs(ctx, tls_verify_certificates, tls_crl, NULL, FALSE);
839 if (rc != OK) return rc;
840 verify_optional = FALSE;
842 else if (verify_check_host(&tls_try_verify_hosts) == OK)
844 rc = setup_certs(ctx, tls_verify_certificates, tls_crl, NULL, TRUE);
845 if (rc != OK) return rc;
846 verify_optional = TRUE;
849 /* Prepare for new connection */
851 if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
853 /* Warning: we used to SSL_clear(ssl) here, it was removed.
855 * With the SSL_clear(), we get strange interoperability bugs with
856 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
857 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
859 * The SSL_clear() call is to let an existing SSL* be reused, typically after
860 * session shutdown. In this case, we have a brand new object and there's no
861 * obvious reason to immediately clear it. I'm guessing that this was
862 * originally added because of incomplete initialisation which the clear fixed,
863 * in some historic release.
866 /* Set context and tell client to go ahead, except in the case of TLS startup
867 on connection, where outputting anything now upsets the clients and tends to
868 make them disconnect. We need to have an explicit fflush() here, to force out
869 the response. Other smtp_printf() calls do not need it, because in non-TLS
870 mode, the fflush() happens when smtp_getc() is called. */
872 SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx));
875 smtp_printf("220 TLS go ahead\r\n");
879 /* Now negotiate the TLS session. We put our own timer on it, since it seems
880 that the OpenSSL library doesn't. */
882 SSL_set_wfd(ssl, fileno(smtp_out));
883 SSL_set_rfd(ssl, fileno(smtp_in));
884 SSL_set_accept_state(ssl);
886 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
888 sigalrm_seen = FALSE;
889 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
890 rc = SSL_accept(ssl);
895 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
896 if (ERR_get_error() == 0)
897 log_write(0, LOG_MAIN,
898 "TLS client disconnected cleanly (rejected our certificate?)");
902 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
904 /* TLS has been set up. Adjust the input functions to read via TLS,
905 and initialize things. */
907 construct_cipher_name(ssl);
912 if (SSL_get_shared_ciphers(ssl, CS buf, sizeof(buf)) != NULL)
913 debug_printf("Shared ciphers: %s\n", buf);
917 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
918 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
919 ssl_xfer_eof = ssl_xfer_error = 0;
921 receive_getc = tls_getc;
922 receive_ungetc = tls_ungetc;
923 receive_feof = tls_feof;
924 receive_ferror = tls_ferror;
925 receive_smtp_buffered = tls_smtp_buffered;
927 tls_active = fileno(smtp_out);
935 /*************************************************
936 * Start a TLS session in a client *
937 *************************************************/
939 /* Called from the smtp transport after STARTTLS has been accepted.
942 fd the fd of the connection
943 host connected host (for messages)
944 addr the first address
945 dhparam DH parameter file
946 certificate certificate file
947 privatekey private key file
948 sni TLS SNI to send to remote host
949 verify_certs file for certificate verify
950 crl file containing CRL
951 require_ciphers list of allowed ciphers
952 timeout startup timeout
954 Returns: OK on success
955 FAIL otherwise - note that tls_error() will not give DEFER
956 because this is not a server
960 tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam,
961 uschar *certificate, uschar *privatekey, uschar *sni,
962 uschar *verify_certs, uschar *crl,
963 uschar *require_ciphers, int timeout)
965 static uschar txt[256];
970 rc = tls_init(host, dhparam, certificate, privatekey, addr);
971 if (rc != OK) return rc;
973 tls_certificate_verified = FALSE;
974 verify_callback_called = FALSE;
976 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
979 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
980 are separated by underscores. So that I can use either form in my tests, and
981 also for general convenience, we turn underscores into hyphens here. */
983 if (expciphers != NULL)
985 uschar *s = expciphers;
986 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
987 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
988 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
989 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
992 rc = setup_certs(ctx, verify_certs, crl, host, FALSE);
993 if (rc != OK) return rc;
995 if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", host, NULL);
996 SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx));
998 SSL_set_connect_state(ssl);
1002 if (!expand_check(sni, US"tls_sni", &tls_sni))
1004 if (!Ustrlen(tls_sni))
1008 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_sni);
1009 SSL_set_tlsext_host_name(ssl, tls_sni);
1013 /* There doesn't seem to be a built-in timeout on connection. */
1015 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1016 sigalrm_seen = FALSE;
1018 rc = SSL_connect(ssl);
1022 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1024 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1026 /* Beware anonymous ciphers which lead to server_cert being NULL */
1027 server_cert = SSL_get_peer_certificate (ssl);
1030 tls_peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1031 CS txt, sizeof(txt));
1037 construct_cipher_name(ssl); /* Sets tls_cipher */
1047 /*************************************************
1048 * TLS version of getc *
1049 *************************************************/
1051 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1052 it refills the buffer via the SSL reading function.
1055 Returns: the next character or EOF
1061 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1066 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1067 ssl_xfer_buffer, ssl_xfer_buffer_size);
1069 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1070 inbytes = SSL_read(ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1071 error = SSL_get_error(ssl, inbytes);
1074 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1075 closed down, not that the socket itself has been closed down. Revert to
1076 non-SSL handling. */
1078 if (error == SSL_ERROR_ZERO_RETURN)
1080 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1082 receive_getc = smtp_getc;
1083 receive_ungetc = smtp_ungetc;
1084 receive_feof = smtp_feof;
1085 receive_ferror = smtp_ferror;
1086 receive_smtp_buffered = smtp_buffered;
1099 /* Handle genuine errors */
1101 else if (error == SSL_ERROR_SSL)
1103 ERR_error_string(ERR_get_error(), ssl_errstring);
1104 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1109 else if (error != SSL_ERROR_NONE)
1111 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1116 #ifndef DISABLE_DKIM
1117 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1119 ssl_xfer_buffer_hwm = inbytes;
1120 ssl_xfer_buffer_lwm = 0;
1123 /* Something in the buffer; return next uschar */
1125 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1130 /*************************************************
1131 * Read bytes from TLS channel *
1132 *************************************************/
1139 Returns: the number of bytes read
1140 -1 after a failed read
1144 tls_read(uschar *buff, size_t len)
1149 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1150 buff, (unsigned int)len);
1152 inbytes = SSL_read(ssl, CS buff, len);
1153 error = SSL_get_error(ssl, inbytes);
1155 if (error == SSL_ERROR_ZERO_RETURN)
1157 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1160 else if (error != SSL_ERROR_NONE)
1172 /*************************************************
1173 * Write bytes down TLS channel *
1174 *************************************************/
1181 Returns: the number of bytes after a successful write,
1182 -1 after a failed write
1186 tls_write(const uschar *buff, size_t len)
1192 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1195 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1196 outbytes = SSL_write(ssl, CS buff, left);
1197 error = SSL_get_error(ssl, outbytes);
1198 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1202 ERR_error_string(ERR_get_error(), ssl_errstring);
1203 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1206 case SSL_ERROR_NONE:
1211 case SSL_ERROR_ZERO_RETURN:
1212 log_write(0, LOG_MAIN, "SSL channel closed on write");
1216 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1225 /*************************************************
1226 * Close down a TLS session *
1227 *************************************************/
1229 /* This is also called from within a delivery subprocess forked from the
1230 daemon, to shut down the TLS library, without actually doing a shutdown (which
1231 would tamper with the SSL session in the parent process).
1233 Arguments: TRUE if SSL_shutdown is to be called
1238 tls_close(BOOL shutdown)
1240 if (tls_active < 0) return; /* TLS was not active */
1244 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1257 /*************************************************
1258 * Report the library versions. *
1259 *************************************************/
1261 /* There have historically been some issues with binary compatibility in
1262 OpenSSL libraries; if Exim (like many other applications) is built against
1263 one version of OpenSSL but the run-time linker picks up another version,
1264 it can result in serious failures, including crashing with a SIGSEGV. So
1265 report the version found by the compiler and the run-time version.
1267 Arguments: a FILE* to print the results to
1272 tls_version_report(FILE *f)
1274 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
1276 OPENSSL_VERSION_TEXT,
1277 SSLeay_version(SSLEAY_VERSION));
1283 /*************************************************
1284 * Random number generation *
1285 *************************************************/
1287 /* Pseudo-random number generation. The result is not expected to be
1288 cryptographically strong but not so weak that someone will shoot themselves
1289 in the foot using it as a nonce in input in some email header scheme or
1290 whatever weirdness they'll twist this into. The result should handle fork()
1291 and avoid repeating sequences. OpenSSL handles that for us.
1295 Returns a random number in range [0, max-1]
1299 vaguely_random_number(int max)
1304 uschar smallbuf[sizeof(r)];
1309 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
1313 gettimeofday(&r.tv, NULL);
1316 RAND_seed((uschar *)(&r), sizeof(r));
1318 /* We're after pseudo-random, not random; if we still don't have enough data
1319 in the internal PRNG then our options are limited. We could sleep and hope
1320 for entropy to come along (prayer technique) but if the system is so depleted
1321 in the first place then something is likely to just keep taking it. Instead,
1322 we'll just take whatever little bit of pseudo-random we can still manage to
1325 needed_len = sizeof(r);
1326 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1327 asked for a number less than 10. */
1328 for (r = max, i = 0; r; ++i)
1334 /* We do not care if crypto-strong */
1335 i = RAND_pseudo_bytes(smallbuf, needed_len);
1339 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
1340 return vaguely_random_number_fallback(max);
1344 for (p = smallbuf; needed_len; --needed_len, ++p)
1350 /* We don't particularly care about weighted results; if someone wants
1351 smooth distribution and cares enough then they should submit a patch then. */
1358 /*************************************************
1359 * OpenSSL option parse *
1360 *************************************************/
1362 /* Parse one option for tls_openssl_options_parse below
1365 name one option name
1366 value place to store a value for it
1367 Returns success or failure in parsing
1370 struct exim_openssl_option {
1374 /* We could use a macro to expand, but we need the ifdef and not all the
1375 options document which version they were introduced in. Policylet: include
1376 all options unless explicitly for DTLS, let the administrator choose which
1379 This list is current as of:
1381 static struct exim_openssl_option exim_openssl_options[] = {
1382 /* KEEP SORTED ALPHABETICALLY! */
1384 { US"all", SSL_OP_ALL },
1386 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
1387 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
1389 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
1390 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
1392 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
1393 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
1395 #ifdef SSL_OP_EPHEMERAL_RSA
1396 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
1398 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
1399 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
1401 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
1402 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
1404 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
1405 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
1407 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
1408 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
1410 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
1411 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
1413 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
1414 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
1416 #ifdef SSL_OP_NO_COMPRESSION
1417 { US"no_compression", SSL_OP_NO_COMPRESSION },
1419 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
1420 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
1422 #ifdef SSL_OP_NO_SSLv2
1423 { US"no_sslv2", SSL_OP_NO_SSLv2 },
1425 #ifdef SSL_OP_NO_SSLv3
1426 { US"no_sslv3", SSL_OP_NO_SSLv3 },
1428 #ifdef SSL_OP_NO_TICKET
1429 { US"no_ticket", SSL_OP_NO_TICKET },
1431 #ifdef SSL_OP_NO_TLSv1
1432 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
1434 #ifdef SSL_OP_NO_TLSv1_1
1435 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
1436 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
1437 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
1439 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
1442 #ifdef SSL_OP_NO_TLSv1_2
1443 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
1445 #ifdef SSL_OP_SINGLE_DH_USE
1446 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
1448 #ifdef SSL_OP_SINGLE_ECDH_USE
1449 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
1451 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
1452 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
1454 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
1455 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
1457 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
1458 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
1460 #ifdef SSL_OP_TLS_D5_BUG
1461 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
1463 #ifdef SSL_OP_TLS_ROLLBACK_BUG
1464 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
1467 static int exim_openssl_options_size =
1468 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
1472 tls_openssl_one_option_parse(uschar *name, long *value)
1475 int last = exim_openssl_options_size;
1476 while (last > first)
1478 int middle = (first + last)/2;
1479 int c = Ustrcmp(name, exim_openssl_options[middle].name);
1482 *value = exim_openssl_options[middle].value;
1496 /*************************************************
1497 * OpenSSL option parsing logic *
1498 *************************************************/
1500 /* OpenSSL has a number of compatibility options which an administrator might
1501 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
1502 we look like log_selector.
1505 option_spec the administrator-supplied string of options
1506 results ptr to long storage for the options bitmap
1507 Returns success or failure
1511 tls_openssl_options_parse(uschar *option_spec, long *results)
1516 BOOL adding, item_parsed;
1519 /* Prior to 4.78 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
1520 * from default because it increases BEAST susceptibility. */
1522 if (option_spec == NULL)
1528 for (s=option_spec; *s != '\0'; /**/)
1530 while (isspace(*s)) ++s;
1533 if (*s != '+' && *s != '-')
1535 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
1536 "+ or - expected but found \"%s\"\n", s);
1539 adding = *s++ == '+';
1540 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
1543 item_parsed = tls_openssl_one_option_parse(s, &item);
1546 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
1549 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
1550 adding ? "adding" : "removing", result, item, s);
1563 /* End of tls-openssl.c */