1 /* $Cambridge: exim/src/src/tls-openssl.c,v 1.23 2010/06/05 09:10:10 pdp Exp $ */
3 /*************************************************
4 * Exim - an Internet mail transport agent *
5 *************************************************/
7 /* Copyright (c) University of Cambridge 1995 - 2009 */
8 /* See the file NOTICE for conditions of use and distribution. */
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 /* Structure for collecting random data for seeding. */
28 typedef struct randstuff {
33 /* Local static variables */
35 static BOOL verify_callback_called = FALSE;
36 static const uschar *sid_ctx = US"exim";
38 static SSL_CTX *ctx = NULL;
39 static SSL *ssl = NULL;
41 static char ssl_errstring[256];
43 static int ssl_session_timeout = 200;
44 static BOOL verify_optional = FALSE;
50 /*************************************************
52 *************************************************/
54 /* Called from lots of places when errors occur before actually starting to do
55 the TLS handshake, that is, while the session is still in clear. Always returns
56 DEFER for a server and FAIL for a client so that most calls can use "return
57 tls_error(...)" to do this processing and then give an appropriate return. A
58 single function is used for both server and client, because it is called from
59 some shared functions.
62 prefix text to include in the logged error
63 host NULL if setting up a server;
64 the connected host if setting up a client
65 msg error message or NULL if we should ask OpenSSL
67 Returns: OK/DEFER/FAIL
71 tls_error(uschar *prefix, host_item *host, uschar *msg)
75 ERR_error_string(ERR_get_error(), ssl_errstring);
76 msg = (uschar *)ssl_errstring;
81 uschar *conn_info = smtp_get_connection_info();
82 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
84 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
85 conn_info, prefix, msg);
90 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
91 host->name, host->address, prefix, msg);
98 /*************************************************
99 * Callback to generate RSA key *
100 *************************************************/
108 Returns: pointer to generated key
112 rsa_callback(SSL *s, int export, int keylength)
115 export = export; /* Shut picky compilers up */
116 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
117 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
120 ERR_error_string(ERR_get_error(), ssl_errstring);
121 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
131 /*************************************************
132 * Callback for verification *
133 *************************************************/
135 /* The SSL library does certificate verification if set up to do so. This
136 callback has the current yes/no state is in "state". If verification succeeded,
137 we set up the tls_peerdn string. If verification failed, what happens depends
138 on whether the client is required to present a verifiable certificate or not.
140 If verification is optional, we change the state to yes, but still log the
141 verification error. For some reason (it really would help to have proper
142 documentation of OpenSSL), this callback function then gets called again, this
143 time with state = 1. In fact, that's useful, because we can set up the peerdn
144 value, but we must take care not to set the private verified flag on the second
147 Note: this function is not called if the client fails to present a certificate
148 when asked. We get here only if a certificate has been received. Handling of
149 optional verification for this case is done when requesting SSL to verify, by
150 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
153 state current yes/no state as 1/0
154 x509ctx certificate information.
156 Returns: 1 if verified, 0 if not
160 verify_callback(int state, X509_STORE_CTX *x509ctx)
162 static uschar txt[256];
164 X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert),
165 CS txt, sizeof(txt));
169 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
170 x509ctx->error_depth,
171 X509_verify_cert_error_string(x509ctx->error),
173 tls_certificate_verified = FALSE;
174 verify_callback_called = TRUE;
175 if (!verify_optional) return 0; /* reject */
176 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
177 "tls_try_verify_hosts)\n");
178 return 1; /* accept */
181 if (x509ctx->error_depth != 0)
183 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n",
184 x509ctx->error_depth, txt);
188 DEBUG(D_tls) debug_printf("SSL%s peer: %s\n",
189 verify_callback_called? "" : " authenticated", txt);
193 if (!verify_callback_called) tls_certificate_verified = TRUE;
194 verify_callback_called = TRUE;
196 return 1; /* accept */
201 /*************************************************
202 * Information callback *
203 *************************************************/
205 /* The SSL library functions call this from time to time to indicate what they
206 are doing. We copy the string to the debugging output when the level is high
218 info_callback(SSL *s, int where, int ret)
222 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
227 /*************************************************
228 * Initialize for DH *
229 *************************************************/
231 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
234 dhparam DH parameter file
235 host connected host, if client; NULL if server
237 Returns: TRUE if OK (nothing to set up, or setup worked)
241 init_dh(uschar *dhparam, host_item *host)
248 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
251 if (dhexpanded == NULL) return TRUE;
253 if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL)
255 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
256 host, (uschar *)strerror(errno));
261 if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL)
263 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
269 SSL_CTX_set_tmp_dh(ctx, dh);
271 debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n",
272 dhexpanded, 8*DH_size(dh));
284 /*************************************************
285 * Initialize for TLS *
286 *************************************************/
288 /* Called from both server and client code, to do preliminary initialization of
292 host connected host, if client; NULL if server
293 dhparam DH parameter file
294 certificate certificate file
295 privatekey private key
296 addr address if client; NULL if server (for some randomness)
298 Returns: OK/DEFER/FAIL
302 tls_init(host_item *host, uschar *dhparam, uschar *certificate,
303 uschar *privatekey, address_item *addr)
308 SSL_load_error_strings(); /* basic set up */
309 OpenSSL_add_ssl_algorithms();
311 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
312 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
313 list of available digests. */
314 EVP_add_digest(EVP_sha256());
317 /* Create a context */
319 ctx = SSL_CTX_new((host == NULL)?
320 SSLv23_server_method() : SSLv23_client_method());
322 if (ctx == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
324 /* It turns out that we need to seed the random number generator this early in
325 order to get the full complement of ciphers to work. It took me roughly a day
326 of work to discover this by experiment.
328 On systems that have /dev/urandom, SSL may automatically seed itself from
329 there. Otherwise, we have to make something up as best we can. Double check
335 gettimeofday(&r.tv, NULL);
338 RAND_seed((uschar *)(&r), sizeof(r));
339 RAND_seed((uschar *)big_buffer, big_buffer_size);
340 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
343 return tls_error(US"RAND_status", host,
344 US"unable to seed random number generator");
347 /* Set up the information callback, which outputs if debugging is at a suitable
350 SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
352 /* Apply administrator-supplied work-arounds.
353 Historically we applied just one requested option,
354 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
355 moved to an administrator-controlled list of options to specify and
356 grandfathered in the first one as the default value for "openssl_options".
358 No OpenSSL version number checks: the options we accept depend upon the
359 availability of the option value macros from OpenSSL. */
361 okay = tls_openssl_options_parse(openssl_options, &init_options);
363 return tls_error("openssl_options parsing failed", host, NULL);
367 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
368 if (!(SSL_CTX_set_options(ctx, init_options)))
369 return tls_error(string_sprintf(
370 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
373 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
375 /* Initialize with DH parameters if supplied */
377 if (!init_dh(dhparam, host)) return DEFER;
379 /* Set up certificate and key */
381 if (certificate != NULL)
384 if (!expand_check(certificate, US"tls_certificate", &expanded))
387 if (expanded != NULL)
389 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
390 if (!SSL_CTX_use_certificate_chain_file(ctx, CS expanded))
391 return tls_error(string_sprintf(
392 "SSL_CTX_use_certificate_chain_file file=%s", expanded), host, NULL);
395 if (privatekey != NULL &&
396 !expand_check(privatekey, US"tls_privatekey", &expanded))
399 /* If expansion was forced to fail, key_expanded will be NULL. If the result
400 of the expansion is an empty string, ignore it also, and assume the private
401 key is in the same file as the certificate. */
403 if (expanded != NULL && *expanded != 0)
405 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
406 if (!SSL_CTX_use_PrivateKey_file(ctx, CS expanded, SSL_FILETYPE_PEM))
407 return tls_error(string_sprintf(
408 "SSL_CTX_use_PrivateKey_file file=%s", expanded), host, NULL);
412 /* Set up the RSA callback */
414 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
416 /* Finally, set the timeout, and we are done */
418 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
419 DEBUG(D_tls) debug_printf("Initialized TLS\n");
426 /*************************************************
427 * Get name of cipher in use *
428 *************************************************/
430 /* The answer is left in a static buffer, and tls_cipher is set to point
433 Argument: pointer to an SSL structure for the connection
438 construct_cipher_name(SSL *ssl)
440 static uschar cipherbuf[256];
445 switch (ssl->session->ssl_version)
463 c = SSL_get_current_cipher(ssl);
464 SSL_CIPHER_get_bits(c, &bits);
466 string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver,
467 SSL_CIPHER_get_name(c), bits);
468 tls_cipher = cipherbuf;
470 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
477 /*************************************************
478 * Set up for verifying certificates *
479 *************************************************/
481 /* Called by both client and server startup
484 certs certs file or NULL
486 host NULL in a server; the remote host in a client
487 optional TRUE if called from a server for a host in tls_try_verify_hosts;
488 otherwise passed as FALSE
490 Returns: OK/DEFER/FAIL
494 setup_certs(uschar *certs, uschar *crl, host_item *host, BOOL optional)
496 uschar *expcerts, *expcrl;
498 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
501 if (expcerts != NULL)
504 if (!SSL_CTX_set_default_verify_paths(ctx))
505 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
507 if (Ustat(expcerts, &statbuf) < 0)
509 log_write(0, LOG_MAIN|LOG_PANIC,
510 "failed to stat %s for certificates", expcerts);
516 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
517 { file = NULL; dir = expcerts; }
519 { file = expcerts; dir = NULL; }
521 /* If a certificate file is empty, the next function fails with an
522 unhelpful error message. If we skip it, we get the correct behaviour (no
523 certificates are recognized, but the error message is still misleading (it
524 says no certificate was supplied.) But this is better. */
526 if ((file == NULL || statbuf.st_size > 0) &&
527 !SSL_CTX_load_verify_locations(ctx, CS file, CS dir))
528 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
532 SSL_CTX_set_client_CA_list(ctx, SSL_load_client_CA_file(CS file));
536 /* Handle a certificate revocation list. */
538 #if OPENSSL_VERSION_NUMBER > 0x00907000L
540 /* This bit of code is now the version supplied by Lars Mainka. (I have
541 * merely reformatted it into the Exim code style.)
543 * "From here I changed the code to add support for multiple crl's
544 * in pem format in one file or to support hashed directory entries in
545 * pem format instead of a file. This method now uses the library function
546 * X509_STORE_load_locations to add the CRL location to the SSL context.
547 * OpenSSL will then handle the verify against CA certs and CRLs by
548 * itself in the verify callback." */
550 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
551 if (expcrl != NULL && *expcrl != 0)
553 struct stat statbufcrl;
554 if (Ustat(expcrl, &statbufcrl) < 0)
556 log_write(0, LOG_MAIN|LOG_PANIC,
557 "failed to stat %s for certificates revocation lists", expcrl);
562 /* is it a file or directory? */
564 X509_STORE *cvstore = SSL_CTX_get_cert_store(ctx);
565 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
569 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
575 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
577 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
578 return tls_error(US"X509_STORE_load_locations", host, NULL);
580 /* setting the flags to check against the complete crl chain */
582 X509_STORE_set_flags(cvstore,
583 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
587 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
589 /* If verification is optional, don't fail if no certificate */
591 SSL_CTX_set_verify(ctx,
592 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
601 /*************************************************
602 * Start a TLS session in a server *
603 *************************************************/
605 /* This is called when Exim is running as a server, after having received
606 the STARTTLS command. It must respond to that command, and then negotiate
610 require_ciphers allowed ciphers
611 ------------------------------------------------------
612 require_mac list of allowed MACs ) Not used
613 require_kx list of allowed key_exchange methods ) for
614 require_proto list of allowed protocols ) OpenSSL
615 ------------------------------------------------------
617 Returns: OK on success
618 DEFER for errors before the start of the negotiation
619 FAIL for errors during the negotation; the server can't
624 tls_server_start(uschar *require_ciphers, uschar *require_mac,
625 uschar *require_kx, uschar *require_proto)
630 /* Check for previous activation */
634 tls_error(US"STARTTLS received after TLS started", NULL, US"");
635 smtp_printf("554 Already in TLS\r\n");
639 /* Initialize the SSL library. If it fails, it will already have logged
642 rc = tls_init(NULL, tls_dhparam, tls_certificate, tls_privatekey, NULL);
643 if (rc != OK) return rc;
645 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
648 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
649 are separated by underscores. So that I can use either form in my tests, and
650 also for general convenience, we turn underscores into hyphens here. */
652 if (expciphers != NULL)
654 uschar *s = expciphers;
655 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
656 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
657 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
658 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
661 /* If this is a host for which certificate verification is mandatory or
662 optional, set up appropriately. */
664 tls_certificate_verified = FALSE;
665 verify_callback_called = FALSE;
667 if (verify_check_host(&tls_verify_hosts) == OK)
669 rc = setup_certs(tls_verify_certificates, tls_crl, NULL, FALSE);
670 if (rc != OK) return rc;
671 verify_optional = FALSE;
673 else if (verify_check_host(&tls_try_verify_hosts) == OK)
675 rc = setup_certs(tls_verify_certificates, tls_crl, NULL, TRUE);
676 if (rc != OK) return rc;
677 verify_optional = TRUE;
680 /* Prepare for new connection */
682 if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
685 /* Set context and tell client to go ahead, except in the case of TLS startup
686 on connection, where outputting anything now upsets the clients and tends to
687 make them disconnect. We need to have an explicit fflush() here, to force out
688 the response. Other smtp_printf() calls do not need it, because in non-TLS
689 mode, the fflush() happens when smtp_getc() is called. */
691 SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx));
694 smtp_printf("220 TLS go ahead\r\n");
698 /* Now negotiate the TLS session. We put our own timer on it, since it seems
699 that the OpenSSL library doesn't. */
701 SSL_set_wfd(ssl, fileno(smtp_out));
702 SSL_set_rfd(ssl, fileno(smtp_in));
703 SSL_set_accept_state(ssl);
705 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
707 sigalrm_seen = FALSE;
708 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
709 rc = SSL_accept(ssl);
714 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
715 if (ERR_get_error() == 0)
716 log_write(0, LOG_MAIN,
717 " => client disconnected cleanly (rejected our certificate?)\n");
721 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
723 /* TLS has been set up. Adjust the input functions to read via TLS,
724 and initialize things. */
726 construct_cipher_name(ssl);
731 if (SSL_get_shared_ciphers(ssl, CS buf, sizeof(buf)) != NULL)
732 debug_printf("Shared ciphers: %s\n", buf);
736 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
737 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
738 ssl_xfer_eof = ssl_xfer_error = 0;
740 receive_getc = tls_getc;
741 receive_ungetc = tls_ungetc;
742 receive_feof = tls_feof;
743 receive_ferror = tls_ferror;
744 receive_smtp_buffered = tls_smtp_buffered;
746 tls_active = fileno(smtp_out);
754 /*************************************************
755 * Start a TLS session in a client *
756 *************************************************/
758 /* Called from the smtp transport after STARTTLS has been accepted.
761 fd the fd of the connection
762 host connected host (for messages)
763 addr the first address
764 dhparam DH parameter file
765 certificate certificate file
766 privatekey private key file
767 verify_certs file for certificate verify
768 crl file containing CRL
769 require_ciphers list of allowed ciphers
770 ------------------------------------------------------
771 require_mac list of allowed MACs ) Not used
772 require_kx list of allowed key_exchange methods ) for
773 require_proto list of allowed protocols ) OpenSSL
774 ------------------------------------------------------
775 timeout startup timeout
777 Returns: OK on success
778 FAIL otherwise - note that tls_error() will not give DEFER
779 because this is not a server
783 tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam,
784 uschar *certificate, uschar *privatekey, uschar *verify_certs, uschar *crl,
785 uschar *require_ciphers, uschar *require_mac, uschar *require_kx,
786 uschar *require_proto, int timeout)
788 static uschar txt[256];
793 rc = tls_init(host, dhparam, certificate, privatekey, addr);
794 if (rc != OK) return rc;
796 tls_certificate_verified = FALSE;
797 verify_callback_called = FALSE;
799 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
802 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
803 are separated by underscores. So that I can use either form in my tests, and
804 also for general convenience, we turn underscores into hyphens here. */
806 if (expciphers != NULL)
808 uschar *s = expciphers;
809 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
810 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
811 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
812 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
815 rc = setup_certs(verify_certs, crl, host, FALSE);
816 if (rc != OK) return rc;
818 if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", host, NULL);
819 SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx));
821 SSL_set_connect_state(ssl);
823 /* There doesn't seem to be a built-in timeout on connection. */
825 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
826 sigalrm_seen = FALSE;
828 rc = SSL_connect(ssl);
832 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
834 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
836 server_cert = SSL_get_peer_certificate (ssl);
837 tls_peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
838 CS txt, sizeof(txt));
841 construct_cipher_name(ssl); /* Sets tls_cipher */
851 /*************************************************
852 * TLS version of getc *
853 *************************************************/
855 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
856 it refills the buffer via the SSL reading function.
859 Returns: the next character or EOF
865 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
870 DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl,
871 (long)ssl_xfer_buffer, ssl_xfer_buffer_size);
873 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
874 inbytes = SSL_read(ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
875 error = SSL_get_error(ssl, inbytes);
878 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
879 closed down, not that the socket itself has been closed down. Revert to
882 if (error == SSL_ERROR_ZERO_RETURN)
884 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
886 receive_getc = smtp_getc;
887 receive_ungetc = smtp_ungetc;
888 receive_feof = smtp_feof;
889 receive_ferror = smtp_ferror;
890 receive_smtp_buffered = smtp_buffered;
901 /* Handle genuine errors */
903 else if (error != SSL_ERROR_NONE)
905 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
910 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
912 ssl_xfer_buffer_hwm = inbytes;
913 ssl_xfer_buffer_lwm = 0;
916 /* Something in the buffer; return next uschar */
918 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
923 /*************************************************
924 * Read bytes from TLS channel *
925 *************************************************/
932 Returns: the number of bytes read
933 -1 after a failed read
937 tls_read(uschar *buff, size_t len)
942 DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl,
943 (long)buff, (unsigned int)len);
945 inbytes = SSL_read(ssl, CS buff, len);
946 error = SSL_get_error(ssl, inbytes);
948 if (error == SSL_ERROR_ZERO_RETURN)
950 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
953 else if (error != SSL_ERROR_NONE)
965 /*************************************************
966 * Write bytes down TLS channel *
967 *************************************************/
974 Returns: the number of bytes after a successful write,
975 -1 after a failed write
979 tls_write(const uschar *buff, size_t len)
985 DEBUG(D_tls) debug_printf("tls_do_write(%lx, %d)\n", (long)buff, left);
988 DEBUG(D_tls) debug_printf("SSL_write(SSL, %lx, %d)\n", (long)buff, left);
989 outbytes = SSL_write(ssl, CS buff, left);
990 error = SSL_get_error(ssl, outbytes);
991 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
995 ERR_error_string(ERR_get_error(), ssl_errstring);
996 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1004 case SSL_ERROR_ZERO_RETURN:
1005 log_write(0, LOG_MAIN, "SSL channel closed on write");
1009 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1018 /*************************************************
1019 * Close down a TLS session *
1020 *************************************************/
1022 /* This is also called from within a delivery subprocess forked from the
1023 daemon, to shut down the TLS library, without actually doing a shutdown (which
1024 would tamper with the SSL session in the parent process).
1026 Arguments: TRUE if SSL_shutdown is to be called
1031 tls_close(BOOL shutdown)
1033 if (tls_active < 0) return; /* TLS was not active */
1037 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1050 /*************************************************
1051 * Report the library versions. *
1052 *************************************************/
1054 /* There have historically been some issues with binary compatibility in
1055 OpenSSL libraries; if Exim (like many other applications) is built against
1056 one version of OpenSSL but the run-time linker picks up another version,
1057 it can result in serious failures, including crashing with a SIGSEGV. So
1058 report the version found by the compiler and the run-time version.
1060 Arguments: a FILE* to print the results to
1065 tls_version_report(FILE *f)
1067 fprintf(f, "OpenSSL compile-time version: %s\n", OPENSSL_VERSION_TEXT);
1068 fprintf(f, "OpenSSL runtime version: %s\n", SSLeay_version(SSLEAY_VERSION));
1074 /*************************************************
1075 * Pseudo-random number generation *
1076 *************************************************/
1078 /* Pseudo-random number generation. The result is not expected to be
1079 cryptographically strong but not so weak that someone will shoot themselves
1080 in the foot using it as a nonce in input in some email header scheme or
1081 whatever weirdness they'll twist this into. The result should handle fork()
1082 and avoid repeating sequences. OpenSSL handles that for us.
1086 Returns a random number in range [0, max-1]
1090 pseudo_random_number(int max)
1095 uschar smallbuf[sizeof(r)];
1100 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
1104 gettimeofday(&r.tv, NULL);
1107 RAND_seed((uschar *)(&r), sizeof(r));
1109 /* We're after pseudo-random, not random; if we still don't have enough data
1110 in the internal PRNG then our options are limited. We could sleep and hope
1111 for entropy to come along (prayer technique) but if the system is so depleted
1112 in the first place then something is likely to just keep taking it. Instead,
1113 we'll just take whatever little bit of pseudo-random we can still manage to
1116 needed_len = sizeof(r);
1117 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1118 asked for a number less than 10. */
1119 for (r = max, i = 0; r; ++i)
1125 /* We do not care if crypto-strong */
1126 (void) RAND_pseudo_bytes(smallbuf, needed_len);
1128 for (p = smallbuf; needed_len; --needed_len, ++p)
1134 /* We don't particularly care about weighted results; if someone wants
1135 smooth distribution and cares enough then they should submit a patch then. */
1142 /*************************************************
1143 * OpenSSL option parse *
1144 *************************************************/
1146 /* Parse one option for tls_openssl_options_parse below
1149 name one option name
1150 value place to store a value for it
1151 Returns success or failure in parsing
1154 struct exim_openssl_option {
1158 /* We could use a macro to expand, but we need the ifdef and not all the
1159 options document which version they were introduced in. Policylet: include
1160 all options unless explicitly for DTLS, let the administrator choose which
1163 This list is current as of:
1165 static struct exim_openssl_option exim_openssl_options[] = {
1166 /* KEEP SORTED ALPHABETICALLY! */
1168 { "all", SSL_OP_ALL },
1170 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
1171 { "allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
1173 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
1174 { "cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
1176 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
1177 { "dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
1179 #ifdef SSL_OP_EPHEMERAL_RSA
1180 { "ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
1182 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
1183 { "legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
1185 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
1186 { "microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
1188 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
1189 { "microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
1191 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
1192 { "msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
1194 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
1195 { "netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
1197 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
1198 { "netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
1200 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
1201 { "no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
1203 #ifdef SSL_OP_SINGLE_DH_USE
1204 { "single_dh_use", SSL_OP_SINGLE_DH_USE },
1206 #ifdef SSL_OP_SINGLE_ECDH_USE
1207 { "single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
1209 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
1210 { "ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
1212 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
1213 { "sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
1215 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
1216 { "tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
1218 #ifdef SSL_OP_TLS_D5_BUG
1219 { "tls_d5_bug", SSL_OP_TLS_D5_BUG },
1221 #ifdef SSL_OP_TLS_ROLLBACK_BUG
1222 { "tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
1225 static int exim_openssl_options_size =
1226 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
1229 tls_openssl_one_option_parse(uschar *name, long *value)
1232 int last = exim_openssl_options_size;
1233 while (last > first)
1235 int middle = (first + last)/2;
1236 int c = Ustrcmp(name, exim_openssl_options[middle].name);
1239 *value = exim_openssl_options[middle].value;
1253 /*************************************************
1254 * OpenSSL option parsing logic *
1255 *************************************************/
1257 /* OpenSSL has a number of compatibility options which an administrator might
1258 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
1259 we look like log_selector.
1262 option_spec the administrator-supplied string of options
1263 results ptr to long storage for the options bitmap
1264 Returns success or failure
1268 tls_openssl_options_parse(uschar *option_spec, long *results)
1273 BOOL adding, item_parsed;
1275 /* We grandfather in as default the one option which we used to set always. */
1276 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
1277 result = SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
1282 if (option_spec == NULL)
1288 for (s=option_spec; *s != '\0'; /**/)
1290 while (isspace(*s)) ++s;
1293 if (*s != '+' && *s != '-')
1295 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
1296 "+ or - expected but found \"%s\"", s);
1299 adding = *s++ == '+';
1300 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
1303 item_parsed = tls_openssl_one_option_parse(s, &item);
1306 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"", s);
1309 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
1310 adding ? "adding" : "removing", result, item, s);
1323 /* End of tls-openssl.c */