1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2012 */
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>
23 #ifdef EXPERIMENTAL_OCSP
24 #include <openssl/ocsp.h>
27 #ifdef EXPERIMENTAL_OCSP
28 #define EXIM_OCSP_SKEW_SECONDS (300L)
29 #define EXIM_OCSP_MAX_AGE (-1L)
32 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
33 #define EXIM_HAVE_OPENSSL_TLSEXT
36 /* Structure for collecting random data for seeding. */
38 typedef struct randstuff {
43 /* Local static variables */
45 static BOOL client_verify_callback_called = FALSE;
46 static BOOL server_verify_callback_called = FALSE;
47 static const uschar *sid_ctx = US"exim";
49 static SSL_CTX *client_ctx = NULL;
50 static SSL_CTX *server_ctx = NULL;
51 static SSL *client_ssl = NULL;
52 static SSL *server_ssl = NULL;
54 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
55 static SSL_CTX *client_sni = NULL;
56 static SSL_CTX *server_sni = NULL;
59 static char ssl_errstring[256];
61 static int ssl_session_timeout = 200;
62 static BOOL client_verify_optional = FALSE;
63 static BOOL server_verify_optional = FALSE;
65 static BOOL reexpand_tls_files_for_sni = FALSE;
68 typedef struct tls_ext_ctx_cb {
71 #ifdef EXPERIMENTAL_OCSP
73 uschar *ocsp_file_expanded;
74 OCSP_RESPONSE *ocsp_response;
77 /* these are cached from first expand */
78 uschar *server_cipher_list;
79 /* only passed down to tls_error: */
83 /* should figure out a cleanup of API to handle state preserved per
84 implementation, for various reasons, which can be void * in the APIs.
85 For now, we hack around it. */
86 tls_ext_ctx_cb *client_static_cbinfo = NULL;
87 tls_ext_ctx_cb *server_static_cbinfo = NULL;
90 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, BOOL client);
93 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
94 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
96 #ifdef EXPERIMENTAL_OCSP
97 static int tls_stapling_cb(SSL *s, void *arg);
101 /*************************************************
103 *************************************************/
105 /* Called from lots of places when errors occur before actually starting to do
106 the TLS handshake, that is, while the session is still in clear. Always returns
107 DEFER for a server and FAIL for a client so that most calls can use "return
108 tls_error(...)" to do this processing and then give an appropriate return. A
109 single function is used for both server and client, because it is called from
110 some shared functions.
113 prefix text to include in the logged error
114 host NULL if setting up a server;
115 the connected host if setting up a client
116 msg error message or NULL if we should ask OpenSSL
118 Returns: OK/DEFER/FAIL
122 tls_error(uschar *prefix, host_item *host, uschar *msg)
126 ERR_error_string(ERR_get_error(), ssl_errstring);
127 msg = (uschar *)ssl_errstring;
132 uschar *conn_info = smtp_get_connection_info();
133 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
135 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
136 conn_info, prefix, msg);
141 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
142 host->name, host->address, prefix, msg);
149 /*************************************************
150 * Callback to generate RSA key *
151 *************************************************/
159 Returns: pointer to generated key
163 rsa_callback(SSL *s, int export, int keylength)
166 export = export; /* Shut picky compilers up */
167 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
168 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
171 ERR_error_string(ERR_get_error(), ssl_errstring);
172 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
182 /*************************************************
183 * Callback for verification *
184 *************************************************/
186 /* The SSL library does certificate verification if set up to do so. This
187 callback has the current yes/no state is in "state". If verification succeeded,
188 we set up the tls_peerdn string. If verification failed, what happens depends
189 on whether the client is required to present a verifiable certificate or not.
191 If verification is optional, we change the state to yes, but still log the
192 verification error. For some reason (it really would help to have proper
193 documentation of OpenSSL), this callback function then gets called again, this
194 time with state = 1. In fact, that's useful, because we can set up the peerdn
195 value, but we must take care not to set the private verified flag on the second
198 Note: this function is not called if the client fails to present a certificate
199 when asked. We get here only if a certificate has been received. Handling of
200 optional verification for this case is done when requesting SSL to verify, by
201 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
204 state current yes/no state as 1/0
205 x509ctx certificate information.
206 client TRUE for client startup, FALSE for server startup
208 Returns: 1 if verified, 0 if not
212 verify_callback(int state, X509_STORE_CTX *x509ctx, BOOL client)
214 static uschar txt[256];
222 calledp= &client_verify_callback_called;
223 optionalp= &client_verify_optional;
228 calledp= &server_verify_callback_called;
229 optionalp= &server_verify_optional;
232 X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert),
233 CS txt, sizeof(txt));
237 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
238 x509ctx->error_depth,
239 X509_verify_cert_error_string(x509ctx->error),
241 tlsp->certificate_verified = FALSE;
243 if (!*optionalp) return 0; /* reject */
244 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
245 "tls_try_verify_hosts)\n");
246 return 1; /* accept */
249 if (x509ctx->error_depth != 0)
251 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n",
252 x509ctx->error_depth, txt);
256 DEBUG(D_tls) debug_printf("SSL%s peer: %s\n",
257 *calledp ? "" : " authenticated", txt);
261 if (!*calledp) tlsp->certificate_verified = TRUE;
264 return 1; /* accept */
268 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
270 return verify_callback(state, x509ctx, TRUE);
274 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
276 return verify_callback(state, x509ctx, FALSE);
281 /*************************************************
282 * Information callback *
283 *************************************************/
285 /* The SSL library functions call this from time to time to indicate what they
286 are doing. We copy the string to the debugging output when TLS debugging has
298 info_callback(SSL *s, int where, int ret)
302 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
307 /*************************************************
308 * Initialize for DH *
309 *************************************************/
311 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
314 dhparam DH parameter file or fixed parameter identity string
315 host connected host, if client; NULL if server
317 Returns: TRUE if OK (nothing to set up, or setup worked)
321 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
328 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
331 if (dhexpanded == NULL || *dhexpanded == '\0')
333 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
335 else if (dhexpanded[0] == '/')
337 bio = BIO_new_file(CS dhexpanded, "r");
340 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
341 host, US strerror(errno));
347 if (Ustrcmp(dhexpanded, "none") == 0)
349 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
353 pem = std_dh_prime_named(dhexpanded);
356 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
357 host, US strerror(errno));
360 bio = BIO_new_mem_buf(CS pem, -1);
363 dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
367 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
372 /* Even if it is larger, we silently return success rather than cause things
373 * to fail out, so that a too-large DH will not knock out all TLS; it's a
374 * debatable choice. */
375 if ((8*DH_size(dh)) > tls_dh_max_bits)
378 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
379 8*DH_size(dh), tls_dh_max_bits);
383 SSL_CTX_set_tmp_dh(sctx, dh);
385 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
386 dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
398 #ifdef EXPERIMENTAL_OCSP
399 /*************************************************
400 * Load OCSP information into state *
401 *************************************************/
403 /* Called to load the OCSP response from the given file into memory, once
404 caller has determined this is needed. Checks validity. Debugs a message
407 ASSUMES: single response, for single cert.
410 sctx the SSL_CTX* to update
411 cbinfo various parts of session state
412 expanded the filename putatively holding an OCSP response
417 ocsp_load_response(SSL_CTX *sctx,
418 tls_ext_ctx_cb *cbinfo,
419 const uschar *expanded)
423 OCSP_BASICRESP *basic_response;
424 OCSP_SINGLERESP *single_response;
425 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
427 unsigned long verify_flags;
428 int status, reason, i;
430 cbinfo->ocsp_file_expanded = string_copy(expanded);
431 if (cbinfo->ocsp_response)
433 OCSP_RESPONSE_free(cbinfo->ocsp_response);
434 cbinfo->ocsp_response = NULL;
437 bio = BIO_new_file(CS cbinfo->ocsp_file_expanded, "rb");
440 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
441 cbinfo->ocsp_file_expanded);
445 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
449 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
453 status = OCSP_response_status(resp);
454 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
456 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
457 OCSP_response_status_str(status), status);
461 basic_response = OCSP_response_get1_basic(resp);
465 debug_printf("OCSP response parse error: unable to extract basic response.\n");
469 store = SSL_CTX_get_cert_store(sctx);
470 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
472 /* May need to expose ability to adjust those flags?
473 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
474 OCSP_TRUSTOTHER OCSP_NOINTERN */
476 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
480 ERR_error_string(ERR_get_error(), ssl_errstring);
481 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
486 /* Here's the simplifying assumption: there's only one response, for the
487 one certificate we use, and nothing for anything else in a chain. If this
488 proves false, we need to extract a cert id from our issued cert
489 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
490 right cert in the stack and then calls OCSP_single_get0_status()).
492 I'm hoping to avoid reworking a bunch more of how we handle state here. */
493 single_response = OCSP_resp_get0(basic_response, 0);
494 if (!single_response)
497 debug_printf("Unable to get first response from OCSP basic response.\n");
501 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
502 /* how does this status differ from the one above? */
503 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
505 DEBUG(D_tls) debug_printf("OCSP response not valid (take 2): %s (%d)\n",
506 OCSP_response_status_str(status), status);
510 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
512 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
516 cbinfo->ocsp_response = resp;
523 /*************************************************
524 * Expand key and cert file specs *
525 *************************************************/
527 /* Called once during tls_init and possibly againt during TLS setup, for a
528 new context, if Server Name Indication was used and tls_sni was seen in
529 the certificate string.
532 sctx the SSL_CTX* to update
533 cbinfo various parts of session state
535 Returns: OK/DEFER/FAIL
539 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
543 if (cbinfo->certificate == NULL)
546 if (Ustrstr(cbinfo->certificate, US"tls_sni"))
547 reexpand_tls_files_for_sni = TRUE;
549 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
552 if (expanded != NULL)
554 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
555 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
556 return tls_error(string_sprintf(
557 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
561 if (cbinfo->privatekey != NULL &&
562 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
565 /* If expansion was forced to fail, key_expanded will be NULL. If the result
566 of the expansion is an empty string, ignore it also, and assume the private
567 key is in the same file as the certificate. */
569 if (expanded != NULL && *expanded != 0)
571 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
572 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
573 return tls_error(string_sprintf(
574 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
577 #ifdef EXPERIMENTAL_OCSP
578 if (cbinfo->ocsp_file != NULL)
580 if (!expand_check(cbinfo->ocsp_file, US"tls_ocsp_file", &expanded))
583 if (expanded != NULL && *expanded != 0)
585 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
586 if (cbinfo->ocsp_file_expanded &&
587 (Ustrcmp(expanded, cbinfo->ocsp_file_expanded) == 0))
590 debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
592 ocsp_load_response(sctx, cbinfo, expanded);
604 /*************************************************
605 * Callback to handle SNI *
606 *************************************************/
608 /* Called when acting as server during the TLS session setup if a Server Name
609 Indication extension was sent by the client.
611 API documentation is OpenSSL s_server.c implementation.
614 s SSL* of the current session
615 ad unknown (part of OpenSSL API) (unused)
616 arg Callback of "our" registered data
618 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
621 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
623 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
625 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
626 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
628 int old_pool = store_pool;
631 return SSL_TLSEXT_ERR_OK;
633 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
634 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
636 /* Make the extension value available for expansion */
637 store_pool = POOL_PERM;
638 tls_in.sni = string_copy(US servername);
639 store_pool = old_pool;
641 if (!reexpand_tls_files_for_sni)
642 return SSL_TLSEXT_ERR_OK;
644 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
645 not confident that memcpy wouldn't break some internal reference counting.
646 Especially since there's a references struct member, which would be off. */
648 server_sni = SSL_CTX_new(SSLv23_server_method());
651 ERR_error_string(ERR_get_error(), ssl_errstring);
652 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
653 return SSL_TLSEXT_ERR_NOACK;
656 /* Not sure how many of these are actually needed, since SSL object
657 already exists. Might even need this selfsame callback, for reneg? */
659 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
660 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
661 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
662 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
663 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
664 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
665 if (cbinfo->server_cipher_list)
666 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
667 #ifdef EXPERIMENTAL_OCSP
668 if (cbinfo->ocsp_file)
670 SSL_CTX_set_tlsext_status_cb(server_sni, tls_stapling_cb);
671 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
675 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, FALSE);
676 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
678 /* do this after setup_certs, because this can require the certs for verifying
680 rc = tls_expand_session_files(server_sni, cbinfo);
681 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
683 rc = init_dh(server_sni, cbinfo->dhparam, NULL);
684 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
686 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
687 SSL_set_SSL_CTX(s, server_sni);
689 return SSL_TLSEXT_ERR_OK;
691 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
696 #ifdef EXPERIMENTAL_OCSP
697 /*************************************************
698 * Callback to handle OCSP Stapling *
699 *************************************************/
701 /* Called when acting as server during the TLS session setup if the client
702 requests OCSP information with a Certificate Status Request.
704 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
710 tls_stapling_cb(SSL *s, void *arg)
712 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
713 uschar *response_der;
714 int response_der_len;
716 DEBUG(D_tls) debug_printf("Received TLS status request (OCSP stapling); %s response.\n",
717 cbinfo->ocsp_response ? "have" : "lack");
718 if (!cbinfo->ocsp_response)
719 return SSL_TLSEXT_ERR_NOACK;
722 response_der_len = i2d_OCSP_RESPONSE(cbinfo->ocsp_response, &response_der);
723 if (response_der_len <= 0)
724 return SSL_TLSEXT_ERR_NOACK;
726 SSL_set_tlsext_status_ocsp_resp(ssl, response_der, response_der_len);
727 return SSL_TLSEXT_ERR_OK;
730 #endif /* EXPERIMENTAL_OCSP */
735 /*************************************************
736 * Initialize for TLS *
737 *************************************************/
739 /* Called from both server and client code, to do preliminary initialization of
743 host connected host, if client; NULL if server
744 dhparam DH parameter file
745 certificate certificate file
746 privatekey private key
747 addr address if client; NULL if server (for some randomness)
749 Returns: OK/DEFER/FAIL
753 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
755 #ifdef EXPERIMENTAL_OCSP
758 address_item *addr, tls_ext_ctx_cb ** cbp)
763 tls_ext_ctx_cb *cbinfo;
765 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
766 cbinfo->certificate = certificate;
767 cbinfo->privatekey = privatekey;
768 #ifdef EXPERIMENTAL_OCSP
769 cbinfo->ocsp_file = ocsp_file;
771 cbinfo->dhparam = dhparam;
774 SSL_load_error_strings(); /* basic set up */
775 OpenSSL_add_ssl_algorithms();
777 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
778 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
779 list of available digests. */
780 EVP_add_digest(EVP_sha256());
784 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
785 negotiation in the different methods; as far as I can tell, the only
786 *_{server,client}_method which allows negotiation is SSLv23, which exists even
787 when OpenSSL is built without SSLv2 support.
788 By disabling with openssl_options, we can let admins re-enable with the
791 *ctxp = SSL_CTX_new((host == NULL)?
792 SSLv23_server_method() : SSLv23_client_method());
794 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
796 /* It turns out that we need to seed the random number generator this early in
797 order to get the full complement of ciphers to work. It took me roughly a day
798 of work to discover this by experiment.
800 On systems that have /dev/urandom, SSL may automatically seed itself from
801 there. Otherwise, we have to make something up as best we can. Double check
807 gettimeofday(&r.tv, NULL);
810 RAND_seed((uschar *)(&r), sizeof(r));
811 RAND_seed((uschar *)big_buffer, big_buffer_size);
812 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
815 return tls_error(US"RAND_status", host,
816 US"unable to seed random number generator");
819 /* Set up the information callback, which outputs if debugging is at a suitable
822 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
824 /* Automatically re-try reads/writes after renegotiation. */
825 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
827 /* Apply administrator-supplied work-arounds.
828 Historically we applied just one requested option,
829 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
830 moved to an administrator-controlled list of options to specify and
831 grandfathered in the first one as the default value for "openssl_options".
833 No OpenSSL version number checks: the options we accept depend upon the
834 availability of the option value macros from OpenSSL. */
836 okay = tls_openssl_options_parse(openssl_options, &init_options);
838 return tls_error(US"openssl_options parsing failed", host, NULL);
842 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
843 if (!(SSL_CTX_set_options(*ctxp, init_options)))
844 return tls_error(string_sprintf(
845 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
848 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
850 /* Initialize with DH parameters if supplied */
852 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
854 /* Set up certificate and key (and perhaps OCSP info) */
856 rc = tls_expand_session_files(*ctxp, cbinfo);
857 if (rc != OK) return rc;
859 /* If we need to handle SNI, do so */
860 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
863 #ifdef EXPERIMENTAL_OCSP
864 /* We check ocsp_file, not ocsp_response, because we care about if
865 the option exists, not what the current expansion might be, as SNI might
866 change the certificate and OCSP file in use between now and the time the
867 callback is invoked. */
868 if (cbinfo->ocsp_file)
870 SSL_CTX_set_tlsext_status_cb(ctx, tls_stapling_cb);
871 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
874 /* We always do this, so that $tls_sni is available even if not used in
876 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
877 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
881 /* Set up the RSA callback */
883 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
885 /* Finally, set the timeout, and we are done */
887 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
888 DEBUG(D_tls) debug_printf("Initialized TLS\n");
898 /*************************************************
899 * Get name of cipher in use *
900 *************************************************/
903 Argument: pointer to an SSL structure for the connection
904 buffer to use for answer
906 pointer to number of bits for cipher
911 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
913 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
914 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
915 the accessor functions use const in the prototype. */
919 switch (ssl->session->ssl_version)
933 #ifdef TLS1_1_VERSION
939 #ifdef TLS1_2_VERSION
949 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
950 SSL_CIPHER_get_bits(c, bits);
952 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
953 SSL_CIPHER_get_name(c), *bits);
955 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
962 /*************************************************
963 * Set up for verifying certificates *
964 *************************************************/
966 /* Called by both client and server startup
969 sctx SSL_CTX* to initialise
970 certs certs file or NULL
972 host NULL in a server; the remote host in a client
973 optional TRUE if called from a server for a host in tls_try_verify_hosts;
974 otherwise passed as FALSE
975 client TRUE if called for client startup, FALSE for server startup
977 Returns: OK/DEFER/FAIL
981 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, BOOL client)
983 uschar *expcerts, *expcrl;
985 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
988 if (expcerts != NULL)
991 if (!SSL_CTX_set_default_verify_paths(sctx))
992 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
994 if (Ustat(expcerts, &statbuf) < 0)
996 log_write(0, LOG_MAIN|LOG_PANIC,
997 "failed to stat %s for certificates", expcerts);
1003 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1004 { file = NULL; dir = expcerts; }
1006 { file = expcerts; dir = NULL; }
1008 /* If a certificate file is empty, the next function fails with an
1009 unhelpful error message. If we skip it, we get the correct behaviour (no
1010 certificates are recognized, but the error message is still misleading (it
1011 says no certificate was supplied.) But this is better. */
1013 if ((file == NULL || statbuf.st_size > 0) &&
1014 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1015 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1019 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1023 /* Handle a certificate revocation list. */
1025 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1027 /* This bit of code is now the version supplied by Lars Mainka. (I have
1028 * merely reformatted it into the Exim code style.)
1030 * "From here I changed the code to add support for multiple crl's
1031 * in pem format in one file or to support hashed directory entries in
1032 * pem format instead of a file. This method now uses the library function
1033 * X509_STORE_load_locations to add the CRL location to the SSL context.
1034 * OpenSSL will then handle the verify against CA certs and CRLs by
1035 * itself in the verify callback." */
1037 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1038 if (expcrl != NULL && *expcrl != 0)
1040 struct stat statbufcrl;
1041 if (Ustat(expcrl, &statbufcrl) < 0)
1043 log_write(0, LOG_MAIN|LOG_PANIC,
1044 "failed to stat %s for certificates revocation lists", expcrl);
1049 /* is it a file or directory? */
1051 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1052 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1056 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1062 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1064 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1065 return tls_error(US"X509_STORE_load_locations", host, NULL);
1067 /* setting the flags to check against the complete crl chain */
1069 X509_STORE_set_flags(cvstore,
1070 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1074 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1076 /* If verification is optional, don't fail if no certificate */
1078 SSL_CTX_set_verify(sctx,
1079 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1080 client ? verify_callback_client : verify_callback_server);
1088 /*************************************************
1089 * Start a TLS session in a server *
1090 *************************************************/
1092 /* This is called when Exim is running as a server, after having received
1093 the STARTTLS command. It must respond to that command, and then negotiate
1097 require_ciphers allowed ciphers
1099 Returns: OK on success
1100 DEFER for errors before the start of the negotiation
1101 FAIL for errors during the negotation; the server can't
1106 tls_server_start(const uschar *require_ciphers)
1110 tls_ext_ctx_cb *cbinfo;
1111 static uschar cipherbuf[256];
1113 /* Check for previous activation */
1115 if (tls_in.active >= 0)
1117 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1118 smtp_printf("554 Already in TLS\r\n");
1122 /* Initialize the SSL library. If it fails, it will already have logged
1125 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1126 #ifdef EXPERIMENTAL_OCSP
1129 NULL, &server_static_cbinfo);
1130 if (rc != OK) return rc;
1131 cbinfo = server_static_cbinfo;
1133 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1136 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1137 were historically separated by underscores. So that I can use either form in my
1138 tests, and also for general convenience, we turn underscores into hyphens here.
1141 if (expciphers != NULL)
1143 uschar *s = expciphers;
1144 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1145 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1146 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1147 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1148 cbinfo->server_cipher_list = expciphers;
1151 /* If this is a host for which certificate verification is mandatory or
1152 optional, set up appropriately. */
1154 tls_in.certificate_verified = FALSE;
1155 server_verify_callback_called = FALSE;
1157 if (verify_check_host(&tls_verify_hosts) == OK)
1159 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, FALSE, FALSE);
1160 if (rc != OK) return rc;
1161 server_verify_optional = FALSE;
1163 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1165 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, TRUE, FALSE);
1166 if (rc != OK) return rc;
1167 server_verify_optional = TRUE;
1170 /* Prepare for new connection */
1172 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1174 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1176 * With the SSL_clear(), we get strange interoperability bugs with
1177 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1178 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1180 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1181 * session shutdown. In this case, we have a brand new object and there's no
1182 * obvious reason to immediately clear it. I'm guessing that this was
1183 * originally added because of incomplete initialisation which the clear fixed,
1184 * in some historic release.
1187 /* Set context and tell client to go ahead, except in the case of TLS startup
1188 on connection, where outputting anything now upsets the clients and tends to
1189 make them disconnect. We need to have an explicit fflush() here, to force out
1190 the response. Other smtp_printf() calls do not need it, because in non-TLS
1191 mode, the fflush() happens when smtp_getc() is called. */
1193 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1194 if (!tls_in.on_connect)
1196 smtp_printf("220 TLS go ahead\r\n");
1200 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1201 that the OpenSSL library doesn't. */
1203 SSL_set_wfd(server_ssl, fileno(smtp_out));
1204 SSL_set_rfd(server_ssl, fileno(smtp_in));
1205 SSL_set_accept_state(server_ssl);
1207 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1209 sigalrm_seen = FALSE;
1210 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1211 rc = SSL_accept(server_ssl);
1216 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1217 if (ERR_get_error() == 0)
1218 log_write(0, LOG_MAIN,
1219 "TLS client disconnected cleanly (rejected our certificate?)");
1223 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1225 /* TLS has been set up. Adjust the input functions to read via TLS,
1226 and initialize things. */
1228 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1229 tls_in.cipher = cipherbuf;
1234 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1235 debug_printf("Shared ciphers: %s\n", buf);
1239 /* Only used by the server-side tls (tls_in), including tls_getc.
1240 Client-side (tls_out) reads (seem to?) go via
1241 smtp_read_response()/ip_recv().
1242 Hence no need to duplicate for _in and _out.
1244 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1245 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1246 ssl_xfer_eof = ssl_xfer_error = 0;
1248 receive_getc = tls_getc;
1249 receive_ungetc = tls_ungetc;
1250 receive_feof = tls_feof;
1251 receive_ferror = tls_ferror;
1252 receive_smtp_buffered = tls_smtp_buffered;
1254 tls_in.active = fileno(smtp_out);
1262 /*************************************************
1263 * Start a TLS session in a client *
1264 *************************************************/
1266 /* Called from the smtp transport after STARTTLS has been accepted.
1269 fd the fd of the connection
1270 host connected host (for messages)
1271 addr the first address
1272 dhparam DH parameter file
1273 certificate certificate file
1274 privatekey private key file
1275 sni TLS SNI to send to remote host
1276 verify_certs file for certificate verify
1277 crl file containing CRL
1278 require_ciphers list of allowed ciphers
1279 dh_min_bits minimum number of bits acceptable in server's DH prime
1281 timeout startup timeout
1283 Returns: OK on success
1284 FAIL otherwise - note that tls_error() will not give DEFER
1285 because this is not a server
1289 tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam,
1290 uschar *certificate, uschar *privatekey, uschar *sni,
1291 uschar *verify_certs, uschar *crl,
1292 uschar *require_ciphers, int dh_min_bits ARG_UNUSED, int timeout)
1294 static uschar txt[256];
1298 static uschar cipherbuf[256];
1300 rc = tls_init(&client_ctx, host, dhparam, certificate, privatekey,
1301 #ifdef EXPERIMENTAL_OCSP
1304 addr, &client_static_cbinfo);
1305 if (rc != OK) return rc;
1307 tls_out.certificate_verified = FALSE;
1308 client_verify_callback_called = FALSE;
1310 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1313 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1314 are separated by underscores. So that I can use either form in my tests, and
1315 also for general convenience, we turn underscores into hyphens here. */
1317 if (expciphers != NULL)
1319 uschar *s = expciphers;
1320 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1321 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1322 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1323 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1326 rc = setup_certs(client_ctx, verify_certs, crl, host, FALSE, TRUE);
1327 if (rc != OK) return rc;
1329 if ((client_ssl = SSL_new(client_ctx)) == NULL) return tls_error(US"SSL_new", host, NULL);
1330 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1331 SSL_set_fd(client_ssl, fd);
1332 SSL_set_connect_state(client_ssl);
1336 if (!expand_check(sni, US"tls_sni", &tls_out.sni))
1338 if (!Ustrlen(tls_out.sni))
1342 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1343 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1344 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1347 debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1353 /* There doesn't seem to be a built-in timeout on connection. */
1355 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1356 sigalrm_seen = FALSE;
1358 rc = SSL_connect(client_ssl);
1362 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1364 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1366 /* Beware anonymous ciphers which lead to server_cert being NULL */
1367 server_cert = SSL_get_peer_certificate (client_ssl);
1370 tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1371 CS txt, sizeof(txt));
1372 tls_out.peerdn = txt;
1375 tls_out.peerdn = NULL;
1377 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1378 tls_out.cipher = cipherbuf;
1380 tls_out.active = fd;
1388 /*************************************************
1389 * TLS version of getc *
1390 *************************************************/
1392 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1393 it refills the buffer via the SSL reading function.
1396 Returns: the next character or EOF
1398 Only used by the server-side TLS.
1404 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1409 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1410 ssl_xfer_buffer, ssl_xfer_buffer_size);
1412 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1413 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1414 error = SSL_get_error(server_ssl, inbytes);
1417 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1418 closed down, not that the socket itself has been closed down. Revert to
1419 non-SSL handling. */
1421 if (error == SSL_ERROR_ZERO_RETURN)
1423 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1425 receive_getc = smtp_getc;
1426 receive_ungetc = smtp_ungetc;
1427 receive_feof = smtp_feof;
1428 receive_ferror = smtp_ferror;
1429 receive_smtp_buffered = smtp_buffered;
1431 SSL_free(server_ssl);
1435 tls_in.cipher = NULL;
1436 tls_in.peerdn = NULL;
1442 /* Handle genuine errors */
1444 else if (error == SSL_ERROR_SSL)
1446 ERR_error_string(ERR_get_error(), ssl_errstring);
1447 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1452 else if (error != SSL_ERROR_NONE)
1454 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1459 #ifndef DISABLE_DKIM
1460 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1462 ssl_xfer_buffer_hwm = inbytes;
1463 ssl_xfer_buffer_lwm = 0;
1466 /* Something in the buffer; return next uschar */
1468 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1473 /*************************************************
1474 * Read bytes from TLS channel *
1475 *************************************************/
1482 Returns: the number of bytes read
1483 -1 after a failed read
1485 Only used by the client-side TLS.
1489 tls_read(BOOL is_server, uschar *buff, size_t len)
1491 SSL *ssl = is_server ? server_ssl : client_ssl;
1495 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1496 buff, (unsigned int)len);
1498 inbytes = SSL_read(ssl, CS buff, len);
1499 error = SSL_get_error(ssl, inbytes);
1501 if (error == SSL_ERROR_ZERO_RETURN)
1503 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1506 else if (error != SSL_ERROR_NONE)
1518 /*************************************************
1519 * Write bytes down TLS channel *
1520 *************************************************/
1524 is_server channel specifier
1528 Returns: the number of bytes after a successful write,
1529 -1 after a failed write
1531 Used by both server-side and client-side TLS.
1535 tls_write(BOOL is_server, const uschar *buff, size_t len)
1540 SSL *ssl = is_server ? server_ssl : client_ssl;
1542 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1545 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1546 outbytes = SSL_write(ssl, CS buff, left);
1547 error = SSL_get_error(ssl, outbytes);
1548 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1552 ERR_error_string(ERR_get_error(), ssl_errstring);
1553 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1556 case SSL_ERROR_NONE:
1561 case SSL_ERROR_ZERO_RETURN:
1562 log_write(0, LOG_MAIN, "SSL channel closed on write");
1565 case SSL_ERROR_SYSCALL:
1566 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1567 sender_fullhost ? sender_fullhost : US"<unknown>",
1571 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1580 /*************************************************
1581 * Close down a TLS session *
1582 *************************************************/
1584 /* This is also called from within a delivery subprocess forked from the
1585 daemon, to shut down the TLS library, without actually doing a shutdown (which
1586 would tamper with the SSL session in the parent process).
1588 Arguments: TRUE if SSL_shutdown is to be called
1591 Used by both server-side and client-side TLS.
1595 tls_close(BOOL is_server, BOOL shutdown)
1597 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1598 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1600 if (*fdp < 0) return; /* TLS was not active */
1604 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1605 SSL_shutdown(*sslp);
1617 /*************************************************
1618 * Let tls_require_ciphers be checked at startup *
1619 *************************************************/
1621 /* The tls_require_ciphers option, if set, must be something which the
1624 Returns: NULL on success, or error message
1628 tls_validate_require_cipher(void)
1631 uschar *s, *expciphers, *err;
1633 /* this duplicates from tls_init(), we need a better "init just global
1634 state, for no specific purpose" singleton function of our own */
1636 SSL_load_error_strings();
1637 OpenSSL_add_ssl_algorithms();
1638 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1639 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1640 list of available digests. */
1641 EVP_add_digest(EVP_sha256());
1644 if (!(tls_require_ciphers && *tls_require_ciphers))
1647 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1648 return US"failed to expand tls_require_ciphers";
1650 if (!(expciphers && *expciphers))
1653 /* normalisation ripped from above */
1655 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1659 ctx = SSL_CTX_new(SSLv23_server_method());
1662 ERR_error_string(ERR_get_error(), ssl_errstring);
1663 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1667 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1669 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1671 ERR_error_string(ERR_get_error(), ssl_errstring);
1672 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
1683 /*************************************************
1684 * Report the library versions. *
1685 *************************************************/
1687 /* There have historically been some issues with binary compatibility in
1688 OpenSSL libraries; if Exim (like many other applications) is built against
1689 one version of OpenSSL but the run-time linker picks up another version,
1690 it can result in serious failures, including crashing with a SIGSEGV. So
1691 report the version found by the compiler and the run-time version.
1693 Arguments: a FILE* to print the results to
1698 tls_version_report(FILE *f)
1700 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
1702 OPENSSL_VERSION_TEXT,
1703 SSLeay_version(SSLEAY_VERSION));
1709 /*************************************************
1710 * Random number generation *
1711 *************************************************/
1713 /* Pseudo-random number generation. The result is not expected to be
1714 cryptographically strong but not so weak that someone will shoot themselves
1715 in the foot using it as a nonce in input in some email header scheme or
1716 whatever weirdness they'll twist this into. The result should handle fork()
1717 and avoid repeating sequences. OpenSSL handles that for us.
1721 Returns a random number in range [0, max-1]
1725 vaguely_random_number(int max)
1730 uschar smallbuf[sizeof(r)];
1735 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
1739 gettimeofday(&r.tv, NULL);
1742 RAND_seed((uschar *)(&r), sizeof(r));
1744 /* We're after pseudo-random, not random; if we still don't have enough data
1745 in the internal PRNG then our options are limited. We could sleep and hope
1746 for entropy to come along (prayer technique) but if the system is so depleted
1747 in the first place then something is likely to just keep taking it. Instead,
1748 we'll just take whatever little bit of pseudo-random we can still manage to
1751 needed_len = sizeof(r);
1752 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1753 asked for a number less than 10. */
1754 for (r = max, i = 0; r; ++i)
1760 /* We do not care if crypto-strong */
1761 i = RAND_pseudo_bytes(smallbuf, needed_len);
1765 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
1766 return vaguely_random_number_fallback(max);
1770 for (p = smallbuf; needed_len; --needed_len, ++p)
1776 /* We don't particularly care about weighted results; if someone wants
1777 smooth distribution and cares enough then they should submit a patch then. */
1784 /*************************************************
1785 * OpenSSL option parse *
1786 *************************************************/
1788 /* Parse one option for tls_openssl_options_parse below
1791 name one option name
1792 value place to store a value for it
1793 Returns success or failure in parsing
1796 struct exim_openssl_option {
1800 /* We could use a macro to expand, but we need the ifdef and not all the
1801 options document which version they were introduced in. Policylet: include
1802 all options unless explicitly for DTLS, let the administrator choose which
1805 This list is current as of:
1807 static struct exim_openssl_option exim_openssl_options[] = {
1808 /* KEEP SORTED ALPHABETICALLY! */
1810 { US"all", SSL_OP_ALL },
1812 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
1813 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
1815 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
1816 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
1818 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
1819 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
1821 #ifdef SSL_OP_EPHEMERAL_RSA
1822 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
1824 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
1825 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
1827 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
1828 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
1830 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
1831 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
1833 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
1834 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
1836 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
1837 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
1839 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
1840 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
1842 #ifdef SSL_OP_NO_COMPRESSION
1843 { US"no_compression", SSL_OP_NO_COMPRESSION },
1845 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
1846 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
1848 #ifdef SSL_OP_NO_SSLv2
1849 { US"no_sslv2", SSL_OP_NO_SSLv2 },
1851 #ifdef SSL_OP_NO_SSLv3
1852 { US"no_sslv3", SSL_OP_NO_SSLv3 },
1854 #ifdef SSL_OP_NO_TICKET
1855 { US"no_ticket", SSL_OP_NO_TICKET },
1857 #ifdef SSL_OP_NO_TLSv1
1858 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
1860 #ifdef SSL_OP_NO_TLSv1_1
1861 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
1862 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
1863 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
1865 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
1868 #ifdef SSL_OP_NO_TLSv1_2
1869 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
1871 #ifdef SSL_OP_SINGLE_DH_USE
1872 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
1874 #ifdef SSL_OP_SINGLE_ECDH_USE
1875 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
1877 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
1878 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
1880 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
1881 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
1883 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
1884 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
1886 #ifdef SSL_OP_TLS_D5_BUG
1887 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
1889 #ifdef SSL_OP_TLS_ROLLBACK_BUG
1890 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
1893 static int exim_openssl_options_size =
1894 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
1898 tls_openssl_one_option_parse(uschar *name, long *value)
1901 int last = exim_openssl_options_size;
1902 while (last > first)
1904 int middle = (first + last)/2;
1905 int c = Ustrcmp(name, exim_openssl_options[middle].name);
1908 *value = exim_openssl_options[middle].value;
1922 /*************************************************
1923 * OpenSSL option parsing logic *
1924 *************************************************/
1926 /* OpenSSL has a number of compatibility options which an administrator might
1927 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
1928 we look like log_selector.
1931 option_spec the administrator-supplied string of options
1932 results ptr to long storage for the options bitmap
1933 Returns success or failure
1937 tls_openssl_options_parse(uschar *option_spec, long *results)
1942 BOOL adding, item_parsed;
1945 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
1946 * from default because it increases BEAST susceptibility. */
1947 #ifdef SSL_OP_NO_SSLv2
1948 result |= SSL_OP_NO_SSLv2;
1951 if (option_spec == NULL)
1957 for (s=option_spec; *s != '\0'; /**/)
1959 while (isspace(*s)) ++s;
1962 if (*s != '+' && *s != '-')
1964 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
1965 "+ or - expected but found \"%s\"\n", s);
1968 adding = *s++ == '+';
1969 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
1972 item_parsed = tls_openssl_one_option_parse(s, &item);
1975 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
1978 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
1979 adding ? "adding" : "removing", result, item, s);
1992 /* End of tls-openssl.c */