1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
6 /* See the file NOTICE for conditions of use and distribution. */
8 /* Copyright (c) Phil Pennock 2012 */
10 /* This file provides TLS/SSL support for Exim using the GnuTLS library,
11 one of the available supported implementations. This file is #included into
12 tls.c when USE_GNUTLS has been set.
14 The code herein is a revamp of GnuTLS integration using the current APIs; the
15 original tls-gnu.c was based on a patch which was contributed by Nikos
16 Mavrogiannopoulos. The revamp is partially a rewrite, partially cut&paste as
19 APIs current as of GnuTLS 2.12.18; note that the GnuTLS manual is for GnuTLS 3,
20 which is not widely deployed by OS vendors. Will note issues below, which may
21 assist in updating the code in the future. Another sources of hints is
22 mod_gnutls for Apache (SNI callback registration and handling).
24 Keeping client and server variables more split than before and is currently
25 the norm, in anticipation of TLS in ACL callouts.
27 I wanted to switch to gnutls_certificate_set_verify_function() so that
28 certificate rejection could happen during handshake where it belongs, rather
29 than being dropped afterwards, but that was introduced in 2.10.0 and Debian
30 (6.0.5) is still on 2.8.6. So for now we have to stick with sub-par behaviour.
32 (I wasn't looking for libraries quite that old, when updating to get rid of
33 compiler warnings of deprecated APIs. If it turns out that a lot of the rest
34 require current GnuTLS, then we'll drop support for the ancient libraries).
37 #include <gnutls/gnutls.h>
38 /* needed for cert checks in verification and DN extraction: */
39 #include <gnutls/x509.h>
40 /* man-page is incorrect, gnutls_rnd() is not in gnutls.h: */
41 #include <gnutls/crypto.h>
43 /* needed to disable PKCS11 autoload unless requested */
44 #if GNUTLS_VERSION_NUMBER >= 0x020c00
45 # include <gnutls/pkcs11.h>
46 # define SUPPORT_PARAM_TO_PK_BITS
48 #if GNUTLS_VERSION_NUMBER < 0x030103 && !defined(DISABLE_OCSP)
49 # warning "GnuTLS library version too old; define DISABLE_OCSP in Makefile"
52 #if GNUTLS_VERSION_NUMBER < 0x020a00 && !defined(DISABLE_EVENT)
53 # warning "GnuTLS library version too old; tls:cert event unsupported"
54 # define DISABLE_EVENT
56 #if GNUTLS_VERSION_NUMBER >= 0x030306
57 # define SUPPORT_CA_DIR
59 # undef SUPPORT_CA_DIR
61 #if GNUTLS_VERSION_NUMBER >= 0x030014
62 # define SUPPORT_SYSDEFAULT_CABUNDLE
64 #if GNUTLS_VERSION_NUMBER >= 0x030104
65 # define GNUTLS_CERT_VFY_STATUS_PRINT
67 #if GNUTLS_VERSION_NUMBER >= 0x030109
70 #if GNUTLS_VERSION_NUMBER >= 0x03010a
71 # define SUPPORT_GNUTLS_SESS_DESC
73 #if GNUTLS_VERSION_NUMBER >= 0x030506 && !defined(DISABLE_OCSP)
74 # define SUPPORT_SRV_OCSP_STACK
78 # if GNUTLS_VERSION_NUMBER >= 0x030000
79 # define DANESSL_USAGE_DANE_TA 2
80 # define DANESSL_USAGE_DANE_EE 3
82 # error GnuTLS version too early for DANE
84 # if GNUTLS_VERSION_NUMBER < 0x999999
85 # define GNUTLS_BROKEN_DANE_VALIDATION
90 # include <gnutls/ocsp.h>
93 # include <gnutls/dane.h>
99 gnutls_global_set_audit_log_function()
102 gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
105 /* Local static variables for GnuTLS */
107 /* Values for verify_requirement */
109 enum peer_verify_requirement
110 { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED, VERIFY_DANE };
112 /* This holds most state for server or client; with this, we can set up an
113 outbound TLS-enabled connection in an ACL callout, while not stomping all
114 over the TLS variables available for expansion.
116 Some of these correspond to variables in globals.c; those variables will
117 be set to point to content in one of these instances, as appropriate for
118 the stage of the process lifetime.
120 Not handled here: global tls_channelbinding_b64.
123 typedef struct exim_gnutls_state {
124 gnutls_session_t session;
125 gnutls_certificate_credentials_t x509_cred;
126 gnutls_priority_t priority_cache;
127 enum peer_verify_requirement verify_requirement;
130 BOOL peer_cert_verified;
131 BOOL peer_dane_verified;
132 BOOL trigger_sni_changes;
133 BOOL have_set_peerdn;
134 const struct host_item *host; /* NULL if server */
135 gnutls_x509_crt_t peercert;
138 uschar *received_sni;
140 const uschar *tls_certificate;
141 const uschar *tls_privatekey;
142 const uschar *tls_sni; /* client send only, not received */
143 const uschar *tls_verify_certificates;
144 const uschar *tls_crl;
145 const uschar *tls_require_ciphers;
147 uschar *exp_tls_certificate;
148 uschar *exp_tls_privatekey;
149 uschar *exp_tls_verify_certificates;
151 uschar *exp_tls_require_ciphers;
152 const uschar *exp_tls_verify_cert_hostnames;
153 #ifndef DISABLE_EVENT
154 uschar *event_action;
157 char * const * dane_data;
158 const int * dane_data_len;
161 tls_support *tlsp; /* set in tls_init() */
166 BOOL xfer_eof; /*XXX never gets set! */
168 } exim_gnutls_state_st;
170 static const exim_gnutls_state_st exim_gnutls_state_init = {
173 .priority_cache = NULL,
174 .verify_requirement = VERIFY_NONE,
177 .peer_cert_verified = FALSE,
178 .peer_dane_verified = FALSE,
179 .trigger_sni_changes =FALSE,
180 .have_set_peerdn = FALSE,
185 .received_sni = NULL,
187 .tls_certificate = NULL,
188 .tls_privatekey = NULL,
190 .tls_verify_certificates = NULL,
192 .tls_require_ciphers =NULL,
194 .exp_tls_certificate = NULL,
195 .exp_tls_privatekey = NULL,
196 .exp_tls_verify_certificates = NULL,
198 .exp_tls_require_ciphers = NULL,
199 .exp_tls_verify_cert_hostnames = NULL,
200 #ifndef DISABLE_EVENT
201 .event_action = NULL,
206 .xfer_buffer_lwm = 0,
207 .xfer_buffer_hwm = 0,
212 /* Not only do we have our own APIs which don't pass around state, assuming
213 it's held in globals, GnuTLS doesn't appear to let us register callback data
214 for callbacks, or as part of the session, so we have to keep a "this is the
215 context we're currently dealing with" pointer and rely upon being
216 single-threaded to keep from processing data on an inbound TLS connection while
217 talking to another TLS connection for an outbound check. This does mean that
218 there's no way for heart-beats to be responded to, for the duration of the
220 XXX But see gnutls_session_get_ptr()
223 static exim_gnutls_state_st state_server;
225 /* dh_params are initialised once within the lifetime of a process using TLS;
226 if we used TLS in a long-lived daemon, we'd have to reconsider this. But we
227 don't want to repeat this. */
229 static gnutls_dh_params_t dh_server_params = NULL;
231 /* No idea how this value was chosen; preserving it. Default is 3600. */
233 static const int ssl_session_timeout = 200;
235 static const uschar * const exim_default_gnutls_priority = US"NORMAL";
237 /* Guard library core initialisation */
239 static BOOL exim_gnutls_base_init_done = FALSE;
242 static BOOL gnutls_buggy_ocsp = FALSE;
246 /* ------------------------------------------------------------------------ */
249 #define MAX_HOST_LEN 255
251 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
252 the library logging; a value less than 0 disables the calls to set up logging
253 callbacks. Possibly GNuTLS also looks for an environment variable
254 "GNUTLS_DEBUG_LEVEL". */
255 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
256 # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
259 #ifndef EXIM_CLIENT_DH_MIN_BITS
260 # define EXIM_CLIENT_DH_MIN_BITS 1024
263 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
264 can ask for a bit-strength. Without that, we stick to the constant we had
266 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
267 # define EXIM_SERVER_DH_BITS_PRE2_12 1024
270 #define exim_gnutls_err_check(rc, Label) do { \
271 if ((rc) != GNUTLS_E_SUCCESS) \
272 return tls_error((Label), US gnutls_strerror(rc), host, errstr); \
275 #define expand_check_tlsvar(Varname, errstr) \
276 expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr)
278 #if GNUTLS_VERSION_NUMBER >= 0x020c00
279 # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
280 # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
281 # define HAVE_GNUTLS_RND
282 /* The security fix we provide with the gnutls_allow_auto_pkcs11 option
283 * (4.82 PP/09) introduces a compatibility regression. The symbol simply
284 * isn't available sometimes, so this needs to become a conditional
285 * compilation; the sanest way to deal with this being a problem on
286 * older OSes is to block it in the Local/Makefile with this compiler
288 # ifndef AVOID_GNUTLS_PKCS11
289 # define HAVE_GNUTLS_PKCS11
290 # endif /* AVOID_GNUTLS_PKCS11 */
296 /* ------------------------------------------------------------------------ */
297 /* Callback declarations */
299 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
300 static void exim_gnutls_logger_cb(int level, const char *message);
303 static int exim_sni_handling_cb(gnutls_session_t session);
306 static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
307 gnutls_datum_t * ocsp_response);
312 /* ------------------------------------------------------------------------ */
313 /* Static functions */
315 /*************************************************
317 *************************************************/
319 /* Called from lots of places when errors occur before actually starting to do
320 the TLS handshake, that is, while the session is still in clear. Always returns
321 DEFER for a server and FAIL for a client so that most calls can use "return
322 tls_error(...)" to do this processing and then give an appropriate return. A
323 single function is used for both server and client, because it is called from
324 some shared functions.
327 prefix text to include in the logged error
328 msg additional error string (may be NULL)
329 usually obtained from gnutls_strerror()
330 host NULL if setting up a server;
331 the connected host if setting up a client
332 errstr pointer to returned error string
334 Returns: OK/DEFER/FAIL
338 tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
342 *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
343 return host ? FAIL : DEFER;
349 /*************************************************
350 * Deal with logging errors during I/O *
351 *************************************************/
353 /* We have to get the identity of the peer from saved data.
356 state the current GnuTLS exim state container
357 rc the GnuTLS error code, or 0 if it's a local error
358 when text identifying read or write
359 text local error text when ec is 0
365 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
370 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
371 msg = string_sprintf("%s: %s", US gnutls_strerror(rc),
372 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
374 msg = US gnutls_strerror(rc);
376 (void) tls_error(when, msg, state->host, &errstr);
379 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s",
380 state->host->name, state->host->address, errstr);
383 uschar * conn_info = smtp_get_connection_info();
384 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5;
385 /* I'd like to get separated H= here, but too hard for now */
386 log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr);
393 /*************************************************
394 * Set various Exim expansion vars *
395 *************************************************/
397 #define exim_gnutls_cert_err(Label) \
400 if (rc != GNUTLS_E_SUCCESS) \
402 DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \
403 (Label), gnutls_strerror(rc)); \
409 import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp)
413 rc = gnutls_x509_crt_init(crtp);
414 exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)");
416 rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER);
417 exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]");
422 #undef exim_gnutls_cert_err
425 /* We set various Exim global variables from the state, once a session has
426 been established. With TLS callouts, may need to change this to stack
427 variables, or just re-call it with the server state after client callout
430 Make sure anything set here is unset in tls_getc().
434 tls_bits strength indicator
435 tls_certificate_verified bool indicator
436 tls_channelbinding_b64 for some SASL mechanisms
438 tls_peercert pointer to library internal
440 tls_sni a (UTF-8) string
441 tls_ourcert pointer to library internal
444 state the relevant exim_gnutls_state_st *
448 extract_exim_vars_from_tls_state(exim_gnutls_state_st * state)
450 gnutls_cipher_algorithm_t cipher;
451 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
454 gnutls_datum_t channel;
456 tls_support * tlsp = state->tlsp;
458 tlsp->active.sock = state->fd_out;
459 tlsp->active.tls_ctx = state;
461 cipher = gnutls_cipher_get(state->session);
462 /* returns size in "bytes" */
463 tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
465 tlsp->cipher = state->ciphersuite;
467 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
469 tlsp->certificate_verified = state->peer_cert_verified;
471 tlsp->dane_verified = state->peer_dane_verified;
474 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
475 only available for use for authenticators while this TLS session is running. */
477 tls_channelbinding_b64 = NULL;
478 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
481 rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel);
483 DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc));
485 old_pool = store_pool;
486 store_pool = POOL_PERM;
487 tls_channelbinding_b64 = b64encode(channel.data, (int)channel.size);
488 store_pool = old_pool;
489 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
493 /* peercert is set in peer_status() */
494 tlsp->peerdn = state->peerdn;
495 tlsp->sni = state->received_sni;
497 /* record our certificate */
499 const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session);
500 gnutls_x509_crt_t crt;
502 tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL;
509 /*************************************************
510 * Setup up DH parameters *
511 *************************************************/
513 /* Generating the D-H parameters may take a long time. They only need to
514 be re-generated every so often, depending on security policy. What we do is to
515 keep these parameters in a file in the spool directory. If the file does not
516 exist, we generate them. This means that it is easy to cause a regeneration.
518 The new file is written as a temporary file and renamed, so that an incomplete
519 file is never present. If two processes both compute some new parameters, you
520 waste a bit of effort, but it doesn't seem worth messing around with locking to
523 Returns: OK/DEFER/FAIL
527 init_server_dh(uschar ** errstr)
530 unsigned int dh_bits;
532 uschar filename_buf[PATH_MAX];
533 uschar *filename = NULL;
535 uschar *exp_tls_dhparam;
536 BOOL use_file_in_spool = FALSE;
537 BOOL use_fixed_file = FALSE;
538 host_item *host = NULL; /* dummy for macros */
540 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
542 rc = gnutls_dh_params_init(&dh_server_params);
543 exim_gnutls_err_check(rc, US"gnutls_dh_params_init");
548 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
551 if (!exp_tls_dhparam)
553 DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
554 m.data = US std_dh_prime_default();
555 m.size = Ustrlen(m.data);
557 else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
558 use_file_in_spool = TRUE;
559 else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
561 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
564 else if (exp_tls_dhparam[0] != '/')
566 if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
567 return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
568 m.size = Ustrlen(m.data);
572 use_fixed_file = TRUE;
573 filename = exp_tls_dhparam;
578 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
579 exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
580 DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
584 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
585 /* If you change this constant, also change dh_param_fn_ext so that we can use a
586 different filename and ensure we have sufficient bits. */
587 dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL);
589 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr);
591 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
594 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
596 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
600 /* Some clients have hard-coded limits. */
601 if (dh_bits > tls_dh_max_bits)
604 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
606 dh_bits = tls_dh_max_bits;
609 if (use_file_in_spool)
611 if (!string_format(filename_buf, sizeof(filename_buf),
612 "%s/gnutls-params-%d", spool_directory, dh_bits))
613 return tls_error(US"overlong filename", NULL, NULL, errstr);
614 filename = filename_buf;
617 /* Open the cache file for reading and if successful, read it and set up the
620 if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
626 if (fstat(fd, &statbuf) < 0) /* EIO */
630 return tls_error(US"TLS cache stat failed", US strerror(saved_errno), NULL, errstr);
632 if (!S_ISREG(statbuf.st_mode))
635 return tls_error(US"TLS cache not a file", NULL, NULL, errstr);
637 if (!(fp = fdopen(fd, "rb")))
641 return tls_error(US"fdopen(TLS cache stat fd) failed",
642 US strerror(saved_errno), NULL, errstr);
645 m.size = statbuf.st_size;
646 if (!(m.data = malloc(m.size)))
649 return tls_error(US"malloc failed", US strerror(errno), NULL, errstr);
651 if (!(sz = fread(m.data, m.size, 1, fp)))
656 return tls_error(US"fread failed", US strerror(saved_errno), NULL, errstr);
660 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
662 exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
663 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
666 /* If the file does not exist, fall through to compute new data and cache it.
667 If there was any other opening error, it is serious. */
669 else if (errno == ENOENT)
673 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
676 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
679 /* If ret < 0, either the cache file does not exist, or the data it contains
680 is not useful. One particular case of this is when upgrading from an older
681 release of Exim in which the data was stored in a different format. We don't
682 try to be clever and support both formats; we just regenerate new data in this
688 unsigned int dh_bits_gen = dh_bits;
690 if ((PATH_MAX - Ustrlen(filename)) < 10)
691 return tls_error(US"Filename too long to generate replacement",
692 filename, NULL, errstr);
694 temp_fn = string_copy(US"%s.XXXXXXX");
695 if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */
696 return tls_error(US"Unable to open temp file", US strerror(errno), NULL, errstr);
697 (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */
699 /* GnuTLS overshoots!
700 * If we ask for 2236, we might get 2237 or more.
701 * But there's no way to ask GnuTLS how many bits there really are.
702 * We can ask how many bits were used in a TLS session, but that's it!
703 * The prime itself is hidden behind too much abstraction.
704 * So we ask for less, and proceed on a wing and a prayer.
705 * First attempt, subtracted 3 for 2233 and got 2240.
707 if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
709 dh_bits_gen = dh_bits - 10;
711 debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
716 debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
718 rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen);
719 exim_gnutls_err_check(rc, US"gnutls_dh_params_generate2");
721 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
722 and I confirmed that a NULL call to get the size first is how the GnuTLS
723 sample apps handle this. */
727 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
729 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
730 exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3(NULL) sizing");
732 if (!(m.data = malloc(m.size)))
733 return tls_error(US"memory allocation failed", US strerror(errno), NULL, errstr);
735 /* this will return a size 1 less than the allocation size above */
736 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
738 if (rc != GNUTLS_E_SUCCESS)
741 exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3() real");
743 m.size = sz; /* shrink by 1, probably */
745 if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size)
748 return tls_error(US"TLS cache write D-H params failed",
749 US strerror(errno), NULL, errstr);
752 if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
753 return tls_error(US"TLS cache write D-H params final newline failed",
754 US strerror(errno), NULL, errstr);
756 if ((rc = close(fd)))
757 return tls_error(US"TLS cache write close() failed", US strerror(errno), NULL, errstr);
759 if (Urename(temp_fn, filename) < 0)
760 return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
761 temp_fn, filename), US strerror(errno), NULL, errstr);
763 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
766 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
773 /* Create and install a selfsigned certificate, for use in server mode */
776 tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr)
778 gnutls_x509_crt_t cert = NULL;
780 gnutls_x509_privkey_t pkey = NULL;
781 const uschar * where;
784 where = US"initialising pkey";
785 if ((rc = gnutls_x509_privkey_init(&pkey))) goto err;
787 where = US"initialising cert";
788 if ((rc = gnutls_x509_crt_init(&cert))) goto err;
790 where = US"generating pkey";
791 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
792 #ifdef SUPPORT_PARAM_TO_PK_BITS
793 # ifndef GNUTLS_SEC_PARAM_MEDIUM
794 # define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
796 gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
803 where = US"configuring cert";
805 if ( (rc = gnutls_x509_crt_set_version(cert, 3))
806 || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
807 || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
808 || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */
809 || (rc = gnutls_x509_crt_set_key(cert, pkey))
811 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
812 GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2))
813 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
814 GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15))
815 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
816 GNUTLS_OID_X520_COMMON_NAME, 0,
817 smtp_active_hostname, Ustrlen(smtp_active_hostname)))
821 where = US"signing cert";
822 if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err;
824 where = US"installing selfsign cert";
826 if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey)))
832 if (cert) gnutls_x509_crt_deinit(cert);
833 if (pkey) gnutls_x509_privkey_deinit(pkey);
837 rc = tls_error(where, US gnutls_strerror(rc), NULL, errstr);
844 /* Add certificate and key, from files.
847 Zero or negative: good. Negate value for certificate index if < 0.
848 Greater than zero: FAIL or DEFER code.
852 tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
853 uschar * certfile, uschar * keyfile, uschar ** errstr)
855 int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
856 CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
859 string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
860 US gnutls_strerror(rc), host, errstr);
865 /*************************************************
866 * Variables re-expanded post-SNI *
867 *************************************************/
869 /* Called from both server and client code, via tls_init(), and also from
870 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
872 We can tell the two apart by state->received_sni being non-NULL in callback.
874 The callback should not call us unless state->trigger_sni_changes is true,
875 which we are responsible for setting on the first pass through.
878 state exim_gnutls_state_st *
879 errstr error string pointer
881 Returns: OK/DEFER/FAIL
885 tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
889 const host_item *host = state->host; /* macro should be reconsidered? */
890 uschar *saved_tls_certificate = NULL;
891 uschar *saved_tls_privatekey = NULL;
892 uschar *saved_tls_verify_certificates = NULL;
893 uschar *saved_tls_crl = NULL;
896 /* We check for tls_sni *before* expansion. */
897 if (!host) /* server */
898 if (!state->received_sni)
900 if ( state->tls_certificate
901 && ( Ustrstr(state->tls_certificate, US"tls_sni")
902 || Ustrstr(state->tls_certificate, US"tls_in_sni")
903 || Ustrstr(state->tls_certificate, US"tls_out_sni")
906 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
907 state->trigger_sni_changes = TRUE;
912 /* useful for debugging */
913 saved_tls_certificate = state->exp_tls_certificate;
914 saved_tls_privatekey = state->exp_tls_privatekey;
915 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
916 saved_tls_crl = state->exp_tls_crl;
919 rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
920 exim_gnutls_err_check(rc, US"gnutls_certificate_allocate_credentials");
922 #ifdef SUPPORT_SRV_OCSP_STACK
923 gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
926 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
927 state members, assuming consistent naming; and expand_check() returns
928 false if expansion failed, unless expansion was forced to fail. */
930 /* check if we at least have a certificate, before doing expensive
933 if (!expand_check_tlsvar(tls_certificate, errstr))
936 /* certificate is mandatory in server, optional in client */
938 if ( !state->exp_tls_certificate
939 || !*state->exp_tls_certificate
942 return tls_install_selfsign(state, errstr);
944 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
946 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr))
949 /* tls_privatekey is optional, defaulting to same file as certificate */
951 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
953 state->tls_privatekey = state->tls_certificate;
954 state->exp_tls_privatekey = state->exp_tls_certificate;
958 if (state->exp_tls_certificate && *state->exp_tls_certificate)
960 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
961 state->exp_tls_certificate, state->exp_tls_privatekey);
963 if (state->received_sni)
964 if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0
965 && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0
968 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
972 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
975 if (!host) /* server */
977 const uschar * clist = state->exp_tls_certificate;
978 const uschar * klist = state->exp_tls_privatekey;
979 const uschar * olist;
980 int csep = 0, ksep = 0, osep = 0, cnt = 0;
981 uschar * cfile, * kfile, * ofile;
984 if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
989 while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
991 if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
992 return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
993 else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
997 int gnutls_cert_index = -rc;
998 DEBUG(D_tls) debug_printf("TLS: cert/key %s registered\n", cfile);
1000 /* Set the OCSP stapling server info */
1002 #ifndef DISABLE_OCSP
1004 if (gnutls_buggy_ocsp)
1007 debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
1009 else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1011 /* Use the full callback method for stapling just to get
1012 observability. More efficient would be to read the file once only,
1013 if it never changed (due to SNI). Would need restart on file update,
1014 or watch datestamp. */
1016 # ifdef SUPPORT_SRV_OCSP_STACK
1017 rc = gnutls_certificate_set_ocsp_status_request_function2(
1018 state->x509_cred, gnutls_cert_index,
1019 server_ocsp_stapling_cb, ofile);
1021 exim_gnutls_err_check(rc,
1022 US"gnutls_certificate_set_ocsp_status_request_function2");
1027 debug_printf("oops; multiple OCSP files not supported\n");
1030 gnutls_certificate_set_ocsp_status_request_function(
1031 state->x509_cred, server_ocsp_stapling_cb, ofile);
1034 DEBUG(D_tls) debug_printf("OCSP response file = %s\n", ofile);
1037 DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
1043 if (0 < (rc = tls_add_certfile(state, host,
1044 state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
1046 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
1049 } /* tls_certificate */
1052 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
1053 provided. Experiment shows that, if the certificate file is empty, an unhelpful
1054 error message is provided. However, if we just refrain from setting anything up
1055 in that case, certificate verification fails, which seems to be the correct
1058 if (state->tls_verify_certificates && *state->tls_verify_certificates)
1060 if (!expand_check_tlsvar(tls_verify_certificates, errstr))
1062 #ifndef SUPPORT_SYSDEFAULT_CABUNDLE
1063 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1064 state->exp_tls_verify_certificates = NULL;
1066 if (state->tls_crl && *state->tls_crl)
1067 if (!expand_check_tlsvar(tls_crl, errstr))
1070 if (!(state->exp_tls_verify_certificates &&
1071 *state->exp_tls_verify_certificates))
1074 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
1075 /* With no tls_verify_certificates, we ignore tls_crl too */
1082 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
1086 #ifdef SUPPORT_SYSDEFAULT_CABUNDLE
1087 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1088 cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred);
1092 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
1094 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
1095 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
1100 #ifndef SUPPORT_CA_DIR
1101 /* The test suite passes in /dev/null; we could check for that path explicitly,
1102 but who knows if someone has some weird FIFO which always dumps some certs, or
1103 other weirdness. The thing we really want to check is that it's not a
1104 directory, since while OpenSSL supports that, GnuTLS does not.
1105 So s/!S_ISREG/S_ISDIR/ and change some messaging ... */
1106 if (S_ISDIR(statbuf.st_mode))
1109 debug_printf("verify certificates path is a dir: \"%s\"\n",
1110 state->exp_tls_verify_certificates);
1111 log_write(0, LOG_MAIN|LOG_PANIC,
1112 "tls_verify_certificates \"%s\" is a directory",
1113 state->exp_tls_verify_certificates);
1118 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
1119 state->exp_tls_verify_certificates, statbuf.st_size);
1121 if (statbuf.st_size == 0)
1124 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
1130 #ifdef SUPPORT_CA_DIR
1131 (statbuf.st_mode & S_IFMT) == S_IFDIR
1133 gnutls_certificate_set_x509_trust_dir(state->x509_cred,
1134 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM)
1137 gnutls_certificate_set_x509_trust_file(state->x509_cred,
1138 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
1140 #ifdef SUPPORT_CA_DIR
1141 /* Mimic the behaviour with OpenSSL of not advertising a usable-cert list
1142 when using the directory-of-certs config model. */
1144 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1145 gnutls_certificate_send_x509_rdn_sequence(state->session, 1);
1152 exim_gnutls_err_check(rc, US"setting certificate trust");
1154 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);
1156 if (state->tls_crl && *state->tls_crl &&
1157 state->exp_tls_crl && *state->exp_tls_crl)
1159 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
1160 cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
1161 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM);
1165 exim_gnutls_err_check(rc, US"gnutls_certificate_set_x509_crl_file");
1167 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
1176 /*************************************************
1177 * Set X.509 state variables *
1178 *************************************************/
1180 /* In GnuTLS, the registered cert/key are not replaced by a later
1181 set of a cert/key, so for SNI support we need a whole new x509_cred
1182 structure. Which means various other non-re-expanded pieces of state
1183 need to be re-set in the new struct, so the setting logic is pulled
1187 state exim_gnutls_state_st *
1188 errstr error string pointer
1190 Returns: OK/DEFER/FAIL
1194 tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
1197 const host_item *host = state->host; /* macro should be reconsidered? */
1199 /* Create D-H parameters, or read them from the cache file. This function does
1200 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
1201 client-side params. */
1205 if (!dh_server_params)
1207 rc = init_server_dh(errstr);
1208 if (rc != OK) return rc;
1210 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
1213 /* Link the credentials to the session. */
1215 rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred);
1216 exim_gnutls_err_check(rc, US"gnutls_credentials_set");
1221 /*************************************************
1222 * Initialize for GnuTLS *
1223 *************************************************/
1226 #ifndef DISABLE_OCSP
1229 tls_is_buggy_ocsp(void)
1232 uschar maj, mid, mic;
1234 s = CUS gnutls_check_version(NULL);
1238 while (*s && *s != '.') s++;
1239 mid = atoi(CCS ++s);
1246 while (*s && *s != '.') s++;
1247 mic = atoi(CCS ++s);
1248 return mic <= (mid == 3 ? 16 : 3);
1257 /* Called from both server and client code. In the case of a server, errors
1258 before actual TLS negotiation return DEFER.
1261 host connected host, if client; NULL if server
1262 certificate certificate file
1263 privatekey private key file
1264 sni TLS SNI to send, sometimes when client; else NULL
1267 require_ciphers tls_require_ciphers setting
1268 caller_state returned state-info structure
1269 errstr error string pointer
1271 Returns: OK/DEFER/FAIL
1276 const host_item *host,
1277 const uschar *certificate,
1278 const uschar *privatekey,
1282 const uschar *require_ciphers,
1283 exim_gnutls_state_st **caller_state,
1287 exim_gnutls_state_st *state;
1293 if (!exim_gnutls_base_init_done)
1295 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
1297 #ifdef HAVE_GNUTLS_PKCS11
1298 /* By default, gnutls_global_init will init PKCS11 support in auto mode,
1299 which loads modules from a config file, which sounds good and may be wanted
1300 by some sysadmin, but also means in common configurations that GNOME keyring
1301 environment variables are used and so breaks for users calling mailq.
1302 To prevent this, we init PKCS11 first, which is the documented approach. */
1303 if (!gnutls_allow_auto_pkcs11)
1305 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
1306 exim_gnutls_err_check(rc, US"gnutls_pkcs11_init");
1310 rc = gnutls_global_init();
1311 exim_gnutls_err_check(rc, US"gnutls_global_init");
1313 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1316 gnutls_global_set_log_function(exim_gnutls_logger_cb);
1317 /* arbitrarily chosen level; bump up to 9 for more */
1318 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
1322 #ifndef DISABLE_OCSP
1323 if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp()))
1324 log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version");
1327 exim_gnutls_base_init_done = TRUE;
1332 /* For client-side sessions we allocate a context. This lets us run
1333 several in parallel. */
1334 int old_pool = store_pool;
1335 store_pool = POOL_PERM;
1336 state = store_get(sizeof(exim_gnutls_state_st));
1337 store_pool = old_pool;
1339 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1341 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
1342 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
1346 state = &state_server;
1347 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1349 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
1350 rc = gnutls_init(&state->session, GNUTLS_SERVER);
1352 exim_gnutls_err_check(rc, US"gnutls_init");
1356 state->tls_certificate = certificate;
1357 state->tls_privatekey = privatekey;
1358 state->tls_require_ciphers = require_ciphers;
1359 state->tls_sni = sni;
1360 state->tls_verify_certificates = cas;
1361 state->tls_crl = crl;
1363 /* This handles the variables that might get re-expanded after TLS SNI;
1364 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
1367 debug_printf("Expanding various TLS configuration options for session credentials.\n");
1368 if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc;
1370 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
1371 requires a new structure afterwards. */
1373 if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc;
1375 /* set SNI in client, only */
1378 if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr))
1380 if (state->tlsp->sni && *state->tlsp->sni)
1383 debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni);
1384 sz = Ustrlen(state->tlsp->sni);
1385 rc = gnutls_server_name_set(state->session,
1386 GNUTLS_NAME_DNS, state->tlsp->sni, sz);
1387 exim_gnutls_err_check(rc, US"gnutls_server_name_set");
1390 else if (state->tls_sni)
1391 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
1392 "have an SNI set for a server [%s]\n", state->tls_sni);
1394 /* This is the priority string support,
1395 http://www.gnutls.org/manual/html_node/Priority-Strings.html
1396 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
1397 This was backwards incompatible, but means Exim no longer needs to track
1398 all algorithms and provide string forms for them. */
1401 if (state->tls_require_ciphers && *state->tls_require_ciphers)
1403 if (!expand_check_tlsvar(tls_require_ciphers, errstr))
1405 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
1407 p = state->exp_tls_require_ciphers;
1408 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", p);
1413 p = exim_default_gnutls_priority;
1415 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", p);
1417 rc = gnutls_priority_init(&state->priority_cache, CCS p, &errpos);
1419 exim_gnutls_err_check(rc, string_sprintf(
1420 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
1421 p, errpos - CS p, errpos));
1423 rc = gnutls_priority_set(state->session, state->priority_cache);
1424 exim_gnutls_err_check(rc, US"gnutls_priority_set");
1426 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
1428 /* Reduce security in favour of increased compatibility, if the admin
1429 decides to make that trade-off. */
1430 if (gnutls_compat_mode)
1432 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
1433 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
1434 gnutls_session_enable_compatibility_mode(state->session);
1436 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
1440 *caller_state = state;
1446 /*************************************************
1447 * Extract peer information *
1448 *************************************************/
1450 /* Called from both server and client code.
1451 Only this is allowed to set state->peerdn and state->have_set_peerdn
1452 and we use that to detect double-calls.
1454 NOTE: the state blocks last while the TLS connection is up, which is fine
1455 for logging in the server side, but for the client side, we log after teardown
1456 in src/deliver.c. While the session is up, we can twist about states and
1457 repoint tls_* globals, but those variables used for logging or other variable
1458 expansion that happens _after_ delivery need to have a longer life-time.
1460 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1461 doing this more than once per generation of a state context. We set them in
1462 the state context, and repoint tls_* to them. After the state goes away, the
1463 tls_* copies of the pointers remain valid and client delivery logging is happy.
1465 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1469 state exim_gnutls_state_st *
1470 errstr pointer to error string
1472 Returns: OK/DEFER/FAIL
1476 peer_status(exim_gnutls_state_st *state, uschar ** errstr)
1478 uschar cipherbuf[256];
1479 const gnutls_datum_t *cert_list;
1481 unsigned int cert_list_size = 0;
1482 gnutls_protocol_t protocol;
1483 gnutls_cipher_algorithm_t cipher;
1484 gnutls_kx_algorithm_t kx;
1485 gnutls_mac_algorithm_t mac;
1486 gnutls_certificate_type_t ct;
1487 gnutls_x509_crt_t crt;
1491 if (state->have_set_peerdn)
1493 state->have_set_peerdn = TRUE;
1495 state->peerdn = NULL;
1498 cipher = gnutls_cipher_get(state->session);
1499 protocol = gnutls_protocol_get_version(state->session);
1500 mac = gnutls_mac_get(state->session);
1502 #ifdef GNUTLS_TLS1_3
1503 protocol >= GNUTLS_TLS1_3 ? 0 :
1505 gnutls_kx_get(state->session);
1507 old_pool = store_pool;
1509 store_pool = POOL_PERM;
1511 #ifdef SUPPORT_GNUTLS_SESS_DESC
1514 uschar * s = US gnutls_session_get_desc(state->session), c;
1516 /* Nikos M suggests we use this by preference. It returns like:
1517 (TLS1.3)-(ECDHE-SECP256R1)-(RSA-PSS-RSAE-SHA256)-(AES-256-GCM)
1519 For partial back-compat, put a colon after the TLS version, replace the
1520 )-( grouping with __, replace in-group - with _ and append the :keysize. */
1522 /* debug_printf("peer_status: gnutls_session_get_desc %s\n", s); */
1524 for (s++; (c = *s) && c != ')'; s++) g = string_catn(g, s, 1);
1525 g = string_catn(g, US":", 1);
1526 if (*s) s++; /* now on _ between groups */
1529 for (*++s && ++s; (c = *s) && c != ')'; s++) g = string_catn(g, c == '-' ? US"_" : s, 1);
1530 /* now on ) closing group */
1531 if ((c = *s) && *++s == '-') g = string_catn(g, US"__", 2);
1532 /* now on _ between groups */
1534 g = string_catn(g, US":", 1);
1535 g = string_cat(g, string_sprintf("%d", (int) gnutls_cipher_get_key_size(cipher) * 8));
1536 state->ciphersuite = string_from_gstring(g);
1539 state->ciphersuite = string_sprintf("%s:%s:%d",
1540 gnutls_protocol_get_name(protocol),
1541 gnutls_cipher_suite_get_name(kx, cipher, mac),
1542 (int) gnutls_cipher_get_key_size(cipher) * 8);
1544 /* I don't see a way that spaces could occur, in the current GnuTLS
1545 code base, but it was a concern in the old code and perhaps older GnuTLS
1546 releases did return "TLS 1.0"; play it safe, just in case. */
1548 for (uschar * p = state->ciphersuite; *p; p++) if (isspace(*p)) *p = '-';
1551 /* debug_printf("peer_status: ciphersuite %s\n", state->ciphersuite); */
1553 state->tlsp->cipher = state->ciphersuite;
1554 state->tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
1556 store_pool = old_pool;
1557 state->tlsp->cipher = state->ciphersuite;
1560 cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
1562 if (cert_list == NULL || cert_list_size == 0)
1564 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1565 cert_list, cert_list_size);
1566 if (state->verify_requirement >= VERIFY_REQUIRED)
1567 return tls_error(US"certificate verification failed",
1568 US"no certificate received from peer", state->host, errstr);
1572 ct = gnutls_certificate_type_get(state->session);
1573 if (ct != GNUTLS_CRT_X509)
1575 const uschar *ctn = US gnutls_certificate_type_get_name(ct);
1577 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1578 if (state->verify_requirement >= VERIFY_REQUIRED)
1579 return tls_error(US"certificate verification not possible, unhandled type",
1580 ctn, state->host, errstr);
1584 #define exim_gnutls_peer_err(Label) \
1586 if (rc != GNUTLS_E_SUCCESS) \
1588 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \
1589 (Label), gnutls_strerror(rc)); \
1590 if (state->verify_requirement >= VERIFY_REQUIRED) \
1591 return tls_error((Label), US gnutls_strerror(rc), state->host, errstr); \
1596 rc = import_cert(&cert_list[0], &crt);
1597 exim_gnutls_peer_err(US"cert 0");
1599 state->tlsp->peercert = state->peercert = crt;
1602 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1603 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1605 exim_gnutls_peer_err(US"getting size for cert DN failed");
1606 return FAIL; /* should not happen */
1608 dn_buf = store_get_perm(sz);
1609 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1610 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1612 state->peerdn = dn_buf;
1615 #undef exim_gnutls_peer_err
1621 /*************************************************
1622 * Verify peer certificate *
1623 *************************************************/
1625 /* Called from both server and client code.
1626 *Should* be using a callback registered with
1627 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1628 the peer information, but that's too new for some OSes.
1631 state exim_gnutls_state_st *
1632 errstr where to put an error message
1635 FALSE if the session should be rejected
1636 TRUE if the cert is okay or we just don't care
1640 verify_certificate(exim_gnutls_state_st * state, uschar ** errstr)
1645 if (state->verify_requirement == VERIFY_NONE)
1648 DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n");
1651 if ((rc = peer_status(state, errstr)) != OK)
1653 verify = GNUTLS_CERT_INVALID;
1654 *errstr = US"certificate not supplied";
1660 if (state->verify_requirement == VERIFY_DANE && state->host)
1662 /* Using dane_verify_session_crt() would be easy, as it does it all for us
1663 including talking to a DNS resolver. But we want to do that bit ourselves
1664 as the testsuite intercepts and fakes its own DNS environment. */
1669 const gnutls_datum_t * certlist =
1670 gnutls_certificate_get_peers(state->session, &lsize);
1671 int usage = tls_out.tlsa_usage;
1673 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1674 /* Split the TLSA records into two sets, TA and EE selectors. Run the
1675 dane-verification separately so that we know which selector verified;
1676 then we know whether to do name-verification (needed for TA but not EE). */
1678 if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE)))
1679 { /* a mixed-usage bundle */
1684 for(nrec = 0; state->dane_data_len[nrec]; ) nrec++;
1687 dd = store_get(nrec * sizeof(uschar *));
1688 ddl = store_get(nrec * sizeof(int));
1691 if ((rc = dane_state_init(&s, 0)))
1694 for (usage = DANESSL_USAGE_DANE_EE;
1695 usage >= DANESSL_USAGE_DANE_TA; usage--)
1696 { /* take records with this usage */
1697 for (j = i = 0; i < nrec; i++)
1698 if (state->dane_data[i][0] == usage)
1700 dd[j] = state->dane_data[i];
1701 ddl[j++] = state->dane_data_len[i];
1708 if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0)))
1711 if ((rc = dane_verify_crt_raw(s, certlist, lsize,
1712 gnutls_certificate_type_get(state->session),
1714 usage == DANESSL_USAGE_DANE_EE
1715 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1719 debug_printf("TLSA record problem: %s\n", dane_strerror(rc));
1721 else if (verify == 0) /* verification passed */
1729 if (rc) goto tlsa_prob;
1734 if ( (rc = dane_state_init(&s, 0))
1735 || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len,
1737 || (rc = dane_verify_crt_raw(s, certlist, lsize,
1738 gnutls_certificate_type_get(state->session),
1740 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1741 usage == (1 << DANESSL_USAGE_DANE_EE)
1742 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1751 if (verify != 0) /* verification failed */
1754 (void) dane_verification_status_print(verify, &str, 0);
1755 *errstr = US str.data; /* don't bother to free */
1759 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1760 /* If a TA-mode TLSA record was used for verification we must additionally
1761 verify the cert name (but not the CA chain). For EE-mode, skip it. */
1763 if (usage & (1 << DANESSL_USAGE_DANE_EE))
1766 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1769 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1770 /* Assume that the name on the A-record is the one that should be matching
1771 the cert. An alternate view is that the domain part of the email address
1772 is also permissible. */
1774 if (gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1775 CS state->host->name))
1777 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1782 #endif /*SUPPORT_DANE*/
1784 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1787 /* Handle the result of verification. INVALID is set if any others are. */
1789 if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED))
1791 state->peer_cert_verified = FALSE;
1794 #ifdef GNUTLS_CERT_VFY_STATUS_PRINT
1799 if (gnutls_certificate_verification_status_print(verify,
1800 gnutls_certificate_type_get(state->session), &txt, 0)
1801 == GNUTLS_E_SUCCESS)
1803 debug_printf("%s\n", txt.data);
1804 gnutls_free(txt.data);
1808 *errstr = verify & GNUTLS_CERT_REVOKED
1809 ? US"certificate revoked" : US"certificate invalid";
1813 debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n",
1814 *errstr, state->peerdn ? state->peerdn : US"<unset>");
1816 if (state->verify_requirement >= VERIFY_REQUIRED)
1819 debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
1824 /* Client side, check the server's certificate name versus the name on the
1825 A-record for the connection we made. What to do for server side - what name
1826 to use for client? We document that there is no such checking for server
1829 if ( state->exp_tls_verify_cert_hostnames
1830 && !gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1831 CS state->exp_tls_verify_cert_hostnames)
1835 debug_printf("TLS certificate verification failed: cert name mismatch\n");
1836 if (state->verify_requirement >= VERIFY_REQUIRED)
1841 state->peer_cert_verified = TRUE;
1842 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n",
1843 state->peerdn ? state->peerdn : US"<unset>");
1847 state->tlsp->peerdn = state->peerdn;
1852 *errstr = string_sprintf("TLSA record problem: %s",
1853 rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc));
1857 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1864 /* ------------------------------------------------------------------------ */
1867 /* Logging function which can be registered with
1868 * gnutls_global_set_log_function()
1869 * gnutls_global_set_log_level() 0..9
1871 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1873 exim_gnutls_logger_cb(int level, const char *message)
1875 size_t len = strlen(message);
1878 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1881 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1882 message[len-1] == '\n' ? "" : "\n");
1887 /* Called after client hello, should handle SNI work.
1888 This will always set tls_sni (state->received_sni) if available,
1889 and may trigger presenting different certificates,
1890 if state->trigger_sni_changes is TRUE.
1892 Should be registered with
1893 gnutls_handshake_set_post_client_hello_function()
1895 "This callback must return 0 on success or a gnutls error code to terminate the
1898 For inability to get SNI information, we return 0.
1899 We only return non-zero if re-setup failed.
1900 Only used for server-side TLS.
1904 exim_sni_handling_cb(gnutls_session_t session)
1906 char sni_name[MAX_HOST_LEN];
1907 size_t data_len = MAX_HOST_LEN;
1908 exim_gnutls_state_st *state = &state_server;
1909 unsigned int sni_type;
1911 uschar * dummy_errstr;
1913 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
1914 if (rc != GNUTLS_E_SUCCESS)
1917 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
1918 debug_printf("TLS: no SNI presented in handshake.\n");
1920 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
1921 gnutls_strerror(rc), rc);
1926 if (sni_type != GNUTLS_NAME_DNS)
1928 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
1932 /* We now have a UTF-8 string in sni_name */
1933 old_pool = store_pool;
1934 store_pool = POOL_PERM;
1935 state->received_sni = string_copyn(US sni_name, data_len);
1936 store_pool = old_pool;
1938 /* We set this one now so that variable expansions below will work */
1939 state->tlsp->sni = state->received_sni;
1941 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
1942 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
1944 if (!state->trigger_sni_changes)
1947 if ((rc = tls_expand_session_files(state, &dummy_errstr)) != OK)
1949 /* If the setup of certs/etc failed before handshake, TLS would not have
1950 been offered. The best we can do now is abort. */
1951 return GNUTLS_E_APPLICATION_ERROR_MIN;
1954 rc = tls_set_remaining_x509(state, &dummy_errstr);
1955 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
1962 #ifndef DISABLE_OCSP
1965 server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
1966 gnutls_datum_t * ocsp_response)
1969 DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr);
1971 if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0)
1973 DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n",
1975 tls_in.ocsp = OCSP_NOT_RESP;
1976 return GNUTLS_E_NO_CERTIFICATE_STATUS;
1979 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
1986 #ifndef DISABLE_EVENT
1988 We use this callback to get observability and detail-level control
1989 for an exim TLS connection (either direction), raising a tls:cert event
1990 for each cert in the chain presented by the peer. Any event
1991 can deny verification.
1993 Return 0 for the handshake to continue or non-zero to terminate.
1997 verify_cb(gnutls_session_t session)
1999 const gnutls_datum_t * cert_list;
2000 unsigned int cert_list_size = 0;
2001 gnutls_x509_crt_t crt;
2004 exim_gnutls_state_st * state = gnutls_session_get_ptr(session);
2006 if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size)))
2007 while (cert_list_size--)
2009 if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS)
2011 DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n",
2012 cert_list_size, gnutls_strerror(rc));
2016 state->tlsp->peercert = crt;
2017 if ((yield = event_raise(state->event_action,
2018 US"tls:cert", string_sprintf("%d", cert_list_size))))
2020 log_write(0, LOG_MAIN,
2021 "SSL verify denied by event-action: depth=%d: %s",
2022 cert_list_size, yield);
2023 return 1; /* reject */
2025 state->tlsp->peercert = NULL;
2035 /* ------------------------------------------------------------------------ */
2036 /* Exported functions */
2041 /*************************************************
2042 * Start a TLS session in a server *
2043 *************************************************/
2045 /* This is called when Exim is running as a server, after having received
2046 the STARTTLS command. It must respond to that command, and then negotiate
2050 require_ciphers list of allowed ciphers or NULL
2051 errstr pointer to error string
2053 Returns: OK on success
2054 DEFER for errors before the start of the negotiation
2055 FAIL for errors during the negotiation; the server can't
2060 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2063 exim_gnutls_state_st * state = NULL;
2065 /* Check for previous activation */
2066 if (tls_in.active.sock >= 0)
2068 tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr);
2069 smtp_printf("554 Already in TLS\r\n", FALSE);
2073 /* Initialize the library. If it fails, it will already have logged the error
2074 and sent an SMTP response. */
2076 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
2078 if ((rc = tls_init(NULL, tls_certificate, tls_privatekey,
2079 NULL, tls_verify_certificates, tls_crl,
2080 require_ciphers, &state, &tls_in, errstr)) != OK) return rc;
2082 /* If this is a host for which certificate verification is mandatory or
2083 optional, set up appropriately. */
2085 if (verify_check_host(&tls_verify_hosts) == OK)
2088 debug_printf("TLS: a client certificate will be required.\n");
2089 state->verify_requirement = VERIFY_REQUIRED;
2090 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2092 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2095 debug_printf("TLS: a client certificate will be requested but not required.\n");
2096 state->verify_requirement = VERIFY_OPTIONAL;
2097 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2102 debug_printf("TLS: a client certificate will not be requested.\n");
2103 state->verify_requirement = VERIFY_NONE;
2104 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2107 #ifndef DISABLE_EVENT
2110 state->event_action = event_action;
2111 gnutls_session_set_ptr(state->session, state);
2112 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2116 /* Register SNI handling; always, even if not in tls_certificate, so that the
2117 expansion variable $tls_sni is always available. */
2119 gnutls_handshake_set_post_client_hello_function(state->session,
2120 exim_sni_handling_cb);
2122 /* Set context and tell client to go ahead, except in the case of TLS startup
2123 on connection, where outputting anything now upsets the clients and tends to
2124 make them disconnect. We need to have an explicit fflush() here, to force out
2125 the response. Other smtp_printf() calls do not need it, because in non-TLS
2126 mode, the fflush() happens when smtp_getc() is called. */
2128 if (!state->tlsp->on_connect)
2130 smtp_printf("220 TLS go ahead\r\n", FALSE);
2134 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2135 that the GnuTLS library doesn't.
2136 From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you
2137 to set (and clear down afterwards) up a pull-timeout callback function that does
2138 a select, so we're no better off unless avoiding signals becomes an issue. */
2140 gnutls_transport_set_ptr2(state->session,
2141 (gnutls_transport_ptr_t)(long) fileno(smtp_in),
2142 (gnutls_transport_ptr_t)(long) fileno(smtp_out));
2143 state->fd_in = fileno(smtp_in);
2144 state->fd_out = fileno(smtp_out);
2146 sigalrm_seen = FALSE;
2147 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2149 rc = gnutls_handshake(state->session);
2150 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2153 if (rc != GNUTLS_E_SUCCESS)
2155 /* It seems that, except in the case of a timeout, we have to close the
2156 connection right here; otherwise if the other end is running OpenSSL it hangs
2157 until the server times out. */
2161 tls_error(US"gnutls_handshake", US"timed out", NULL, errstr);
2162 gnutls_db_remove_session(state->session);
2166 tls_error(US"gnutls_handshake", US gnutls_strerror(rc), NULL, errstr);
2167 (void) gnutls_alert_send_appropriate(state->session, rc);
2168 gnutls_deinit(state->session);
2169 gnutls_certificate_free_credentials(state->x509_cred);
2171 shutdown(state->fd_out, SHUT_WR);
2172 for (rc = 1024; fgetc(smtp_in) != EOF && rc > 0; ) rc--; /* drain skt */
2173 (void)fclose(smtp_out);
2174 (void)fclose(smtp_in);
2175 smtp_out = smtp_in = NULL;
2181 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
2183 /* Verify after the fact */
2185 if (!verify_certificate(state, errstr))
2187 if (state->verify_requirement != VERIFY_OPTIONAL)
2189 (void) tls_error(US"certificate verification failed", *errstr, NULL, errstr);
2193 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
2197 /* Figure out peer DN, and if authenticated, etc. */
2199 if ((rc = peer_status(state, NULL)) != OK) return rc;
2201 /* Sets various Exim expansion variables; always safe within server */
2203 extract_exim_vars_from_tls_state(state);
2205 /* TLS has been set up. Adjust the input functions to read via TLS,
2206 and initialize appropriately. */
2208 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2210 receive_getc = tls_getc;
2211 receive_getbuf = tls_getbuf;
2212 receive_get_cache = tls_get_cache;
2213 receive_ungetc = tls_ungetc;
2214 receive_feof = tls_feof;
2215 receive_ferror = tls_ferror;
2216 receive_smtp_buffered = tls_smtp_buffered;
2225 tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state,
2226 smtp_transport_options_block * ob)
2228 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2230 state->exp_tls_verify_cert_hostnames =
2232 string_domain_utf8_to_alabel(host->name, NULL);
2237 debug_printf("TLS: server cert verification includes hostname: \"%s\".\n",
2238 state->exp_tls_verify_cert_hostnames);
2246 /* Given our list of RRs from the TLSA lookup, build a lookup block in
2247 GnuTLS-DANE's preferred format. Hang it on the state str for later
2248 use in DANE verification.
2250 We point at the dnsa data not copy it, so it must remain valid until
2251 after verification is done.*/
2254 dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa)
2259 const char ** dane_data;
2260 int * dane_data_len;
2262 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS), i = 1;
2264 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2265 ) if (rr->type == T_TLSA) i++;
2267 dane_data = store_get(i * sizeof(uschar *));
2268 dane_data_len = store_get(i * sizeof(int));
2270 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS), i = 0;
2272 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2273 ) if (rr->type == T_TLSA && rr->size > 3)
2275 const uschar * p = rr->data;
2276 uint8_t usage = p[0], sel = p[1], type = p[2];
2279 debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size);
2281 if ( (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE)
2282 || (sel != 0 && sel != 1)
2287 case 0: /* Full: cannot check at present */
2289 case 1: if (rr->size != 3 + 256/8) continue; /* sha2-256 */
2291 case 2: if (rr->size != 3 + 512/8) continue; /* sha2-512 */
2296 tls_out.tlsa_usage |= 1<<usage;
2297 dane_data[i] = CS p;
2298 dane_data_len[i++] = rr->size;
2301 if (!i) return FALSE;
2303 dane_data[i] = NULL;
2304 dane_data_len[i] = 0;
2306 state->dane_data = (char * const *)dane_data;
2307 state->dane_data_len = dane_data_len;
2314 /*************************************************
2315 * Start a TLS session in a client *
2316 *************************************************/
2318 /* Called from the smtp transport after STARTTLS has been accepted.
2321 fd the fd of the connection
2322 host connected host (for messages and option-tests)
2323 addr the first address (not used)
2324 tb transport (always smtp)
2325 tlsa_dnsa non-NULL, either request or require dane for this host, and
2326 a TLSA record found. Therefore, dane verify required.
2327 Which implies cert must be requested and supplied, dane
2328 verify must pass, and cert verify irrelevant (incl.
2329 hostnames), and (caller handled) require_tls
2330 tlsp record details of channel configuration
2331 errstr error string pointer
2333 Returns: Pointer to TLS session context, or NULL on error
2337 tls_client_start(int fd, host_item *host,
2338 address_item *addr ARG_UNUSED,
2339 transport_instance * tb,
2341 dns_answer * tlsa_dnsa,
2343 tls_support * tlsp, uschar ** errstr)
2345 smtp_transport_options_block *ob = tb
2346 ? (smtp_transport_options_block *)tb->options_block
2347 : &smtp_transport_option_defaults;
2349 exim_gnutls_state_st * state = NULL;
2350 uschar *cipher_list = NULL;
2352 #ifndef DISABLE_OCSP
2354 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2355 BOOL request_ocsp = require_ocsp ? TRUE
2356 : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2359 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);
2362 if (tlsa_dnsa && ob->dane_require_tls_ciphers)
2364 /* not using expand_check_tlsvar because not yet in state */
2365 if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2366 &cipher_list, errstr))
2368 cipher_list = cipher_list && *cipher_list
2369 ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
2374 cipher_list = ob->tls_require_ciphers;
2376 if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
2377 ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
2378 cipher_list, &state, tlsp, errstr) != OK)
2382 int dh_min_bits = ob->tls_dh_min_bits;
2383 if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
2386 debug_printf("WARNING: tls_dh_min_bits far too low,"
2387 " clamping %d up to %d\n",
2388 dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
2389 dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
2392 DEBUG(D_tls) debug_printf("Setting D-H prime minimum"
2393 " acceptable bits to %d\n",
2395 gnutls_dh_set_prime_bits(state->session, dh_min_bits);
2398 /* Stick to the old behaviour for compatibility if tls_verify_certificates is
2399 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
2400 the specified host patterns if one of them is defined */
2403 if (tlsa_dnsa && dane_tlsa_load(state, tlsa_dnsa))
2406 debug_printf("TLS: server certificate DANE required.\n");
2407 state->verify_requirement = VERIFY_DANE;
2408 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2412 if ( ( state->exp_tls_verify_certificates
2413 && !ob->tls_verify_hosts
2414 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2416 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2419 tls_client_setup_hostname_checks(host, state, ob);
2421 debug_printf("TLS: server certificate verification required.\n");
2422 state->verify_requirement = VERIFY_REQUIRED;
2423 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2425 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2427 tls_client_setup_hostname_checks(host, state, ob);
2429 debug_printf("TLS: server certificate verification optional.\n");
2430 state->verify_requirement = VERIFY_OPTIONAL;
2431 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2436 debug_printf("TLS: server certificate verification not required.\n");
2437 state->verify_requirement = VERIFY_NONE;
2438 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2441 #ifndef DISABLE_OCSP
2442 /* supported since GnuTLS 3.1.3 */
2445 DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
2446 if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
2447 NULL, 0, NULL)) != OK)
2449 tls_error(US"cert-status-req", US gnutls_strerror(rc), state->host, errstr);
2452 tlsp->ocsp = OCSP_NOT_RESP;
2456 #ifndef DISABLE_EVENT
2457 if (tb && tb->event_action)
2459 state->event_action = tb->event_action;
2460 gnutls_session_set_ptr(state->session, state);
2461 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2465 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) fd);
2469 DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
2470 /* There doesn't seem to be a built-in timeout on connection. */
2472 sigalrm_seen = FALSE;
2473 ALARM(ob->command_timeout);
2475 rc = gnutls_handshake(state->session);
2476 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2479 if (rc != GNUTLS_E_SUCCESS)
2483 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
2484 tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
2487 tls_error(US"gnutls_handshake", US gnutls_strerror(rc), state->host, errstr);
2491 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
2495 if (!verify_certificate(state, errstr))
2497 tls_error(US"certificate verification failed", *errstr, state->host, errstr);
2501 #ifndef DISABLE_OCSP
2506 gnutls_datum_t stapling;
2507 gnutls_ocsp_resp_t resp;
2508 gnutls_datum_t printed;
2509 if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0
2510 && (rc= gnutls_ocsp_resp_init(&resp)) == 0
2511 && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0
2512 && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0
2515 debug_printf("%.4096s", printed.data);
2516 gnutls_free(printed.data);
2519 (void) tls_error(US"ocsp decode", US gnutls_strerror(rc), state->host, errstr);
2522 if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
2524 tlsp->ocsp = OCSP_FAILED;
2525 tls_error(US"certificate status check failed", NULL, state->host, errstr);
2531 DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
2532 tlsp->ocsp = OCSP_VFIED;
2537 /* Figure out peer DN, and if authenticated, etc. */
2539 if (peer_status(state, errstr) != OK)
2542 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
2544 extract_exim_vars_from_tls_state(state);
2552 /*************************************************
2553 * Close down a TLS session *
2554 *************************************************/
2556 /* This is also called from within a delivery subprocess forked from the
2557 daemon, to shut down the TLS library, without actually doing a shutdown (which
2558 would tamper with the TLS session in the parent process).
2561 ct_ctx client context pointer, or NULL for the one global server context
2562 shutdown 1 if TLS close-alert is to be sent,
2563 2 if also response to be waited for
2569 tls_close(void * ct_ctx, int shutdown)
2571 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2573 if (!state->tlsp || state->tlsp->active.sock < 0) return; /* TLS was not active */
2577 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
2578 shutdown > 1 ? " (with response-wait)" : "");
2581 gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
2585 gnutls_deinit(state->session);
2586 gnutls_certificate_free_credentials(state->x509_cred);
2589 state->tlsp->active.sock = -1;
2590 state->tlsp->active.tls_ctx = NULL;
2591 if (state->xfer_buffer) store_free(state->xfer_buffer);
2592 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
2599 tls_refill(unsigned lim)
2601 exim_gnutls_state_st * state = &state_server;
2604 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
2605 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
2607 sigalrm_seen = FALSE;
2608 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2611 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
2612 MIN(ssl_xfer_buffer_size, lim));
2613 while (inbytes == GNUTLS_E_AGAIN);
2615 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2617 if (had_command_timeout) /* set by signal handler */
2618 smtp_command_timeout_exit(); /* does not return */
2619 if (had_command_sigterm)
2620 smtp_command_sigterm_exit();
2621 if (had_data_timeout)
2622 smtp_data_timeout_exit();
2623 if (had_data_sigint)
2624 smtp_data_sigint_exit();
2626 /* Timeouts do not get this far. A zero-byte return appears to mean that the
2627 TLS session has been closed down, not that the socket itself has been closed
2628 down. Revert to non-TLS handling. */
2632 DEBUG(D_tls) debug_printf("Got tls read timeout\n");
2633 state->xfer_error = TRUE;
2637 else if (inbytes == 0)
2639 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2641 receive_getc = smtp_getc;
2642 receive_getbuf = smtp_getbuf;
2643 receive_get_cache = smtp_get_cache;
2644 receive_ungetc = smtp_ungetc;
2645 receive_feof = smtp_feof;
2646 receive_ferror = smtp_ferror;
2647 receive_smtp_buffered = smtp_buffered;
2649 gnutls_deinit(state->session);
2650 gnutls_certificate_free_credentials(state->x509_cred);
2652 state->session = NULL;
2653 state->tlsp->active.sock = -1;
2654 state->tlsp->active.tls_ctx = NULL;
2655 state->tlsp->bits = 0;
2656 state->tlsp->certificate_verified = FALSE;
2657 tls_channelbinding_b64 = NULL;
2658 state->tlsp->cipher = NULL;
2659 state->tlsp->peercert = NULL;
2660 state->tlsp->peerdn = NULL;
2665 /* Handle genuine errors */
2667 else if (inbytes < 0)
2669 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__);
2670 record_io_error(state, (int) inbytes, US"recv", NULL);
2671 state->xfer_error = TRUE;
2674 #ifndef DISABLE_DKIM
2675 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
2677 state->xfer_buffer_hwm = (int) inbytes;
2678 state->xfer_buffer_lwm = 0;
2682 /*************************************************
2683 * TLS version of getc *
2684 *************************************************/
2686 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2687 it refills the buffer via the GnuTLS reading function.
2688 Only used by the server-side TLS.
2690 This feeds DKIM and should be used for all message-body reads.
2692 Arguments: lim Maximum amount to read/buffer
2693 Returns: the next character or EOF
2697 tls_getc(unsigned lim)
2699 exim_gnutls_state_st * state = &state_server;
2701 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2702 if (!tls_refill(lim))
2703 return state->xfer_error ? EOF : smtp_getc(lim);
2705 /* Something in the buffer; return next uschar */
2707 return state->xfer_buffer[state->xfer_buffer_lwm++];
2711 tls_getbuf(unsigned * len)
2713 exim_gnutls_state_st * state = &state_server;
2717 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2718 if (!tls_refill(*len))
2720 if (!state->xfer_error) return smtp_getbuf(len);
2725 if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
2727 buf = &state->xfer_buffer[state->xfer_buffer_lwm];
2728 state->xfer_buffer_lwm += size;
2737 #ifndef DISABLE_DKIM
2738 exim_gnutls_state_st * state = &state_server;
2739 int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm;
2741 dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n);
2747 tls_could_read(void)
2749 return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
2750 || gnutls_record_check_pending(state_server.session) > 0;
2756 /*************************************************
2757 * Read bytes from TLS channel *
2758 *************************************************/
2760 /* This does not feed DKIM, so if the caller uses this for reading message body,
2761 then the caller must feed DKIM.
2764 ct_ctx client context pointer, or NULL for the one global server context
2768 Returns: the number of bytes read
2769 -1 after a failed read, including EOF
2773 tls_read(void * ct_ctx, uschar *buff, size_t len)
2775 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2781 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
2783 debug_printf("*** PROBABLY A BUG *** " \
2784 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
2785 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
2788 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
2789 state->session, buff, len);
2792 inbytes = gnutls_record_recv(state->session, buff, len);
2793 while (inbytes == GNUTLS_E_AGAIN);
2795 if (inbytes > 0) return inbytes;
2798 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2802 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__);
2803 record_io_error(state, (int)inbytes, US"recv", NULL);
2812 /*************************************************
2813 * Write bytes down TLS channel *
2814 *************************************************/
2818 ct_ctx client context pointer, or NULL for the one global server context
2821 more more data expected soon
2823 Returns: the number of bytes after a successful write,
2824 -1 after a failed write
2828 tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
2832 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2834 static BOOL corked = FALSE;
2836 if (more && !corked) gnutls_record_cork(state->session);
2839 DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
2840 buff, left, more ? ", more" : "");
2844 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
2848 outbytes = gnutls_record_send(state->session, buff, left);
2849 while (outbytes == GNUTLS_E_AGAIN);
2851 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
2854 DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
2855 record_io_error(state, outbytes, US"send", NULL);
2860 record_io_error(state, 0, US"send", US"TLS channel closed on write");
2871 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
2879 if (!more) (void) gnutls_record_uncork(state->session, 0);
2890 /*************************************************
2891 * Random number generation *
2892 *************************************************/
2894 /* Pseudo-random number generation. The result is not expected to be
2895 cryptographically strong but not so weak that someone will shoot themselves
2896 in the foot using it as a nonce in input in some email header scheme or
2897 whatever weirdness they'll twist this into. The result should handle fork()
2898 and avoid repeating sequences. OpenSSL handles that for us.
2902 Returns a random number in range [0, max-1]
2905 #ifdef HAVE_GNUTLS_RND
2907 vaguely_random_number(int max)
2912 uschar smallbuf[sizeof(r)];
2917 needed_len = sizeof(r);
2918 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2919 * asked for a number less than 10. */
2920 for (r = max, i = 0; r; ++i)
2926 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
2929 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
2930 return vaguely_random_number_fallback(max);
2933 for (p = smallbuf; needed_len; --needed_len, ++p)
2939 /* We don't particularly care about weighted results; if someone wants
2940 * smooth distribution and cares enough then they should submit a patch then. */
2943 #else /* HAVE_GNUTLS_RND */
2945 vaguely_random_number(int max)
2947 return vaguely_random_number_fallback(max);
2949 #endif /* HAVE_GNUTLS_RND */
2954 /*************************************************
2955 * Let tls_require_ciphers be checked at startup *
2956 *************************************************/
2958 /* The tls_require_ciphers option, if set, must be something which the
2961 Returns: NULL on success, or error message
2965 tls_validate_require_cipher(void)
2968 uschar *expciphers = NULL;
2969 gnutls_priority_t priority_cache;
2971 uschar * dummy_errstr;
2973 #define validate_check_rc(Label) do { \
2974 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
2975 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
2976 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
2978 if (exim_gnutls_base_init_done)
2979 log_write(0, LOG_MAIN|LOG_PANIC,
2980 "already initialised GnuTLS, Exim developer bug");
2982 #ifdef HAVE_GNUTLS_PKCS11
2983 if (!gnutls_allow_auto_pkcs11)
2985 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
2986 validate_check_rc(US"gnutls_pkcs11_init");
2989 rc = gnutls_global_init();
2990 validate_check_rc(US"gnutls_global_init()");
2991 exim_gnutls_base_init_done = TRUE;
2993 if (!(tls_require_ciphers && *tls_require_ciphers))
2994 return_deinit(NULL);
2996 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
2998 return_deinit(US"failed to expand tls_require_ciphers");
3000 if (!(expciphers && *expciphers))
3001 return_deinit(NULL);
3004 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3006 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
3007 validate_check_rc(string_sprintf(
3008 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
3009 expciphers, errpos - CS expciphers, errpos));
3011 #undef return_deinit
3012 #undef validate_check_rc
3013 gnutls_global_deinit();
3021 /*************************************************
3022 * Report the library versions. *
3023 *************************************************/
3025 /* See a description in tls-openssl.c for an explanation of why this exists.
3027 Arguments: a FILE* to print the results to
3032 tls_version_report(FILE *f)
3034 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
3037 gnutls_check_version(NULL));
3042 /* End of tls-gnu.c */