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 >= 0x030500
74 # define SUPPORT_GNUTLS_KEYLOG
76 #if GNUTLS_VERSION_NUMBER >= 0x030506 && !defined(DISABLE_OCSP)
77 # define SUPPORT_SRV_OCSP_STACK
81 # if GNUTLS_VERSION_NUMBER >= 0x030000
82 # define DANESSL_USAGE_DANE_TA 2
83 # define DANESSL_USAGE_DANE_EE 3
85 # error GnuTLS version too early for DANE
87 # if GNUTLS_VERSION_NUMBER < 0x999999
88 # define GNUTLS_BROKEN_DANE_VALIDATION
93 # include <gnutls/ocsp.h>
96 # include <gnutls/dane.h>
102 gnutls_global_set_audit_log_function()
105 gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
108 /* Local static variables for GnuTLS */
110 /* Values for verify_requirement */
112 enum peer_verify_requirement
113 { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED, VERIFY_DANE };
115 /* This holds most state for server or client; with this, we can set up an
116 outbound TLS-enabled connection in an ACL callout, while not stomping all
117 over the TLS variables available for expansion.
119 Some of these correspond to variables in globals.c; those variables will
120 be set to point to content in one of these instances, as appropriate for
121 the stage of the process lifetime.
123 Not handled here: global tls_channelbinding_b64.
126 typedef struct exim_gnutls_state {
127 gnutls_session_t session;
128 gnutls_certificate_credentials_t x509_cred;
129 gnutls_priority_t priority_cache;
130 enum peer_verify_requirement verify_requirement;
133 BOOL peer_cert_verified;
134 BOOL peer_dane_verified;
135 BOOL trigger_sni_changes;
136 BOOL have_set_peerdn;
137 const struct host_item *host; /* NULL if server */
138 gnutls_x509_crt_t peercert;
141 uschar *received_sni;
143 const uschar *tls_certificate;
144 const uschar *tls_privatekey;
145 const uschar *tls_sni; /* client send only, not received */
146 const uschar *tls_verify_certificates;
147 const uschar *tls_crl;
148 const uschar *tls_require_ciphers;
150 uschar *exp_tls_certificate;
151 uschar *exp_tls_privatekey;
152 uschar *exp_tls_verify_certificates;
154 uschar *exp_tls_require_ciphers;
155 const uschar *exp_tls_verify_cert_hostnames;
156 #ifndef DISABLE_EVENT
157 uschar *event_action;
160 char * const * dane_data;
161 const int * dane_data_len;
164 tls_support *tlsp; /* set in tls_init() */
169 BOOL xfer_eof; /*XXX never gets set! */
171 } exim_gnutls_state_st;
173 static const exim_gnutls_state_st exim_gnutls_state_init = {
176 .priority_cache = NULL,
177 .verify_requirement = VERIFY_NONE,
180 .peer_cert_verified = FALSE,
181 .peer_dane_verified = FALSE,
182 .trigger_sni_changes =FALSE,
183 .have_set_peerdn = FALSE,
188 .received_sni = NULL,
190 .tls_certificate = NULL,
191 .tls_privatekey = NULL,
193 .tls_verify_certificates = NULL,
195 .tls_require_ciphers =NULL,
197 .exp_tls_certificate = NULL,
198 .exp_tls_privatekey = NULL,
199 .exp_tls_verify_certificates = NULL,
201 .exp_tls_require_ciphers = NULL,
202 .exp_tls_verify_cert_hostnames = NULL,
203 #ifndef DISABLE_EVENT
204 .event_action = NULL,
209 .xfer_buffer_lwm = 0,
210 .xfer_buffer_hwm = 0,
215 /* Not only do we have our own APIs which don't pass around state, assuming
216 it's held in globals, GnuTLS doesn't appear to let us register callback data
217 for callbacks, or as part of the session, so we have to keep a "this is the
218 context we're currently dealing with" pointer and rely upon being
219 single-threaded to keep from processing data on an inbound TLS connection while
220 talking to another TLS connection for an outbound check. This does mean that
221 there's no way for heart-beats to be responded to, for the duration of the
223 XXX But see gnutls_session_get_ptr()
226 static exim_gnutls_state_st state_server;
228 /* dh_params are initialised once within the lifetime of a process using TLS;
229 if we used TLS in a long-lived daemon, we'd have to reconsider this. But we
230 don't want to repeat this. */
232 static gnutls_dh_params_t dh_server_params = NULL;
234 /* No idea how this value was chosen; preserving it. Default is 3600. */
236 static const int ssl_session_timeout = 200;
238 static const char * const exim_default_gnutls_priority = "NORMAL";
240 /* Guard library core initialisation */
242 static BOOL exim_gnutls_base_init_done = FALSE;
245 static BOOL gnutls_buggy_ocsp = FALSE;
249 /* ------------------------------------------------------------------------ */
252 #define MAX_HOST_LEN 255
254 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
255 the library logging; a value less than 0 disables the calls to set up logging
256 callbacks. Possibly GNuTLS also looks for an environment variable
257 "GNUTLS_DEBUG_LEVEL". */
258 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
259 # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
262 #ifndef EXIM_CLIENT_DH_MIN_BITS
263 # define EXIM_CLIENT_DH_MIN_BITS 1024
266 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
267 can ask for a bit-strength. Without that, we stick to the constant we had
269 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
270 # define EXIM_SERVER_DH_BITS_PRE2_12 1024
273 #define exim_gnutls_err_check(rc, Label) do { \
274 if ((rc) != GNUTLS_E_SUCCESS) \
275 return tls_error((Label), US gnutls_strerror(rc), host, errstr); \
278 #define expand_check_tlsvar(Varname, errstr) \
279 expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr)
281 #if GNUTLS_VERSION_NUMBER >= 0x020c00
282 # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
283 # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
284 # define HAVE_GNUTLS_RND
285 /* The security fix we provide with the gnutls_allow_auto_pkcs11 option
286 * (4.82 PP/09) introduces a compatibility regression. The symbol simply
287 * isn't available sometimes, so this needs to become a conditional
288 * compilation; the sanest way to deal with this being a problem on
289 * older OSes is to block it in the Local/Makefile with this compiler
291 # ifndef AVOID_GNUTLS_PKCS11
292 # define HAVE_GNUTLS_PKCS11
293 # endif /* AVOID_GNUTLS_PKCS11 */
299 /* ------------------------------------------------------------------------ */
300 /* Callback declarations */
302 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
303 static void exim_gnutls_logger_cb(int level, const char *message);
306 static int exim_sni_handling_cb(gnutls_session_t session);
309 static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
310 gnutls_datum_t * ocsp_response);
315 /* ------------------------------------------------------------------------ */
316 /* Static functions */
318 /*************************************************
320 *************************************************/
322 /* Called from lots of places when errors occur before actually starting to do
323 the TLS handshake, that is, while the session is still in clear. Always returns
324 DEFER for a server and FAIL for a client so that most calls can use "return
325 tls_error(...)" to do this processing and then give an appropriate return. A
326 single function is used for both server and client, because it is called from
327 some shared functions.
330 prefix text to include in the logged error
331 msg additional error string (may be NULL)
332 usually obtained from gnutls_strerror()
333 host NULL if setting up a server;
334 the connected host if setting up a client
335 errstr pointer to returned error string
337 Returns: OK/DEFER/FAIL
341 tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
345 *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
346 return host ? FAIL : DEFER;
352 /*************************************************
353 * Deal with logging errors during I/O *
354 *************************************************/
356 /* We have to get the identity of the peer from saved data.
359 state the current GnuTLS exim state container
360 rc the GnuTLS error code, or 0 if it's a local error
361 when text identifying read or write
362 text local error text when ec is 0
368 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
373 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
374 msg = string_sprintf("%s: %s", US gnutls_strerror(rc),
375 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
377 msg = US gnutls_strerror(rc);
379 (void) tls_error(when, msg, state->host, &errstr);
382 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s",
383 state->host->name, state->host->address, errstr);
386 uschar * conn_info = smtp_get_connection_info();
387 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5;
388 /* I'd like to get separated H= here, but too hard for now */
389 log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr);
396 /*************************************************
397 * Set various Exim expansion vars *
398 *************************************************/
400 #define exim_gnutls_cert_err(Label) \
403 if (rc != GNUTLS_E_SUCCESS) \
405 DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \
406 (Label), gnutls_strerror(rc)); \
412 import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp)
416 rc = gnutls_x509_crt_init(crtp);
417 exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)");
419 rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER);
420 exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]");
425 #undef exim_gnutls_cert_err
428 /* We set various Exim global variables from the state, once a session has
429 been established. With TLS callouts, may need to change this to stack
430 variables, or just re-call it with the server state after client callout
433 Make sure anything set here is unset in tls_getc().
437 tls_bits strength indicator
438 tls_certificate_verified bool indicator
439 tls_channelbinding_b64 for some SASL mechanisms
441 tls_peercert pointer to library internal
443 tls_sni a (UTF-8) string
444 tls_ourcert pointer to library internal
447 state the relevant exim_gnutls_state_st *
451 extract_exim_vars_from_tls_state(exim_gnutls_state_st * state)
453 gnutls_cipher_algorithm_t cipher;
454 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
457 gnutls_datum_t channel;
459 tls_support * tlsp = state->tlsp;
461 tlsp->active.sock = state->fd_out;
462 tlsp->active.tls_ctx = state;
464 cipher = gnutls_cipher_get(state->session);
465 /* returns size in "bytes" */
466 tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
468 tlsp->cipher = state->ciphersuite;
470 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
472 tlsp->certificate_verified = state->peer_cert_verified;
474 tlsp->dane_verified = state->peer_dane_verified;
477 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
478 only available for use for authenticators while this TLS session is running. */
480 tls_channelbinding_b64 = NULL;
481 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
484 if ((rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel)))
485 { DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); }
488 old_pool = store_pool;
489 store_pool = POOL_PERM;
490 tls_channelbinding_b64 = b64encode(CUS channel.data, (int)channel.size);
491 store_pool = old_pool;
492 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
496 /* peercert is set in peer_status() */
497 tlsp->peerdn = state->peerdn;
498 tlsp->sni = state->received_sni;
500 /* record our certificate */
502 const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session);
503 gnutls_x509_crt_t crt;
505 tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL;
512 /*************************************************
513 * Setup up DH parameters *
514 *************************************************/
516 /* Generating the D-H parameters may take a long time. They only need to
517 be re-generated every so often, depending on security policy. What we do is to
518 keep these parameters in a file in the spool directory. If the file does not
519 exist, we generate them. This means that it is easy to cause a regeneration.
521 The new file is written as a temporary file and renamed, so that an incomplete
522 file is never present. If two processes both compute some new parameters, you
523 waste a bit of effort, but it doesn't seem worth messing around with locking to
526 Returns: OK/DEFER/FAIL
530 init_server_dh(uschar ** errstr)
533 unsigned int dh_bits;
535 uschar filename_buf[PATH_MAX];
536 uschar *filename = NULL;
538 uschar *exp_tls_dhparam;
539 BOOL use_file_in_spool = FALSE;
540 BOOL use_fixed_file = FALSE;
541 host_item *host = NULL; /* dummy for macros */
543 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
545 rc = gnutls_dh_params_init(&dh_server_params);
546 exim_gnutls_err_check(rc, US"gnutls_dh_params_init");
551 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
554 if (!exp_tls_dhparam)
556 DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
557 m.data = US std_dh_prime_default();
558 m.size = Ustrlen(m.data);
560 else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
561 use_file_in_spool = TRUE;
562 else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
564 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
567 else if (exp_tls_dhparam[0] != '/')
569 if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
570 return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
571 m.size = Ustrlen(m.data);
575 use_fixed_file = TRUE;
576 filename = exp_tls_dhparam;
581 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
582 exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
583 DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
587 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
588 /* If you change this constant, also change dh_param_fn_ext so that we can use a
589 different filename and ensure we have sufficient bits. */
590 dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL);
592 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr);
594 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
597 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
599 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
603 /* Some clients have hard-coded limits. */
604 if (dh_bits > tls_dh_max_bits)
607 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
609 dh_bits = tls_dh_max_bits;
612 if (use_file_in_spool)
614 if (!string_format(filename_buf, sizeof(filename_buf),
615 "%s/gnutls-params-%d", spool_directory, dh_bits))
616 return tls_error(US"overlong filename", NULL, NULL, errstr);
617 filename = filename_buf;
620 /* Open the cache file for reading and if successful, read it and set up the
623 if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
629 if (fstat(fd, &statbuf) < 0) /* EIO */
633 return tls_error(US"TLS cache stat failed", US strerror(saved_errno), NULL, errstr);
635 if (!S_ISREG(statbuf.st_mode))
638 return tls_error(US"TLS cache not a file", NULL, NULL, errstr);
640 if (!(fp = fdopen(fd, "rb")))
644 return tls_error(US"fdopen(TLS cache stat fd) failed",
645 US strerror(saved_errno), NULL, errstr);
648 m.size = statbuf.st_size;
649 if (!(m.data = malloc(m.size)))
652 return tls_error(US"malloc failed", US strerror(errno), NULL, errstr);
654 if (!(sz = fread(m.data, m.size, 1, fp)))
659 return tls_error(US"fread failed", US strerror(saved_errno), NULL, errstr);
663 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
665 exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
666 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
669 /* If the file does not exist, fall through to compute new data and cache it.
670 If there was any other opening error, it is serious. */
672 else if (errno == ENOENT)
676 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
679 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
682 /* If ret < 0, either the cache file does not exist, or the data it contains
683 is not useful. One particular case of this is when upgrading from an older
684 release of Exim in which the data was stored in a different format. We don't
685 try to be clever and support both formats; we just regenerate new data in this
691 unsigned int dh_bits_gen = dh_bits;
693 if ((PATH_MAX - Ustrlen(filename)) < 10)
694 return tls_error(US"Filename too long to generate replacement",
695 filename, NULL, errstr);
697 temp_fn = string_copy(US"%s.XXXXXXX");
698 if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */
699 return tls_error(US"Unable to open temp file", US strerror(errno), NULL, errstr);
700 (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */
702 /* GnuTLS overshoots!
703 * If we ask for 2236, we might get 2237 or more.
704 * But there's no way to ask GnuTLS how many bits there really are.
705 * We can ask how many bits were used in a TLS session, but that's it!
706 * The prime itself is hidden behind too much abstraction.
707 * So we ask for less, and proceed on a wing and a prayer.
708 * First attempt, subtracted 3 for 2233 and got 2240.
710 if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
712 dh_bits_gen = dh_bits - 10;
714 debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
719 debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
721 rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen);
722 exim_gnutls_err_check(rc, US"gnutls_dh_params_generate2");
724 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
725 and I confirmed that a NULL call to get the size first is how the GnuTLS
726 sample apps handle this. */
730 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
732 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
733 exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3(NULL) sizing");
735 if (!(m.data = malloc(m.size)))
736 return tls_error(US"memory allocation failed", US strerror(errno), NULL, errstr);
738 /* this will return a size 1 less than the allocation size above */
739 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
741 if (rc != GNUTLS_E_SUCCESS)
744 exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3() real");
746 m.size = sz; /* shrink by 1, probably */
748 if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size)
751 return tls_error(US"TLS cache write D-H params failed",
752 US strerror(errno), NULL, errstr);
755 if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
756 return tls_error(US"TLS cache write D-H params final newline failed",
757 US strerror(errno), NULL, errstr);
759 if ((rc = close(fd)))
760 return tls_error(US"TLS cache write close() failed", US strerror(errno), NULL, errstr);
762 if (Urename(temp_fn, filename) < 0)
763 return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
764 temp_fn, filename), US strerror(errno), NULL, errstr);
766 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
769 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
776 /* Create and install a selfsigned certificate, for use in server mode */
779 tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr)
781 gnutls_x509_crt_t cert = NULL;
783 gnutls_x509_privkey_t pkey = NULL;
784 const uschar * where;
787 where = US"initialising pkey";
788 if ((rc = gnutls_x509_privkey_init(&pkey))) goto err;
790 where = US"initialising cert";
791 if ((rc = gnutls_x509_crt_init(&cert))) goto err;
793 where = US"generating pkey";
794 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
795 #ifdef SUPPORT_PARAM_TO_PK_BITS
796 # ifndef GNUTLS_SEC_PARAM_MEDIUM
797 # define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
799 gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
806 where = US"configuring cert";
808 if ( (rc = gnutls_x509_crt_set_version(cert, 3))
809 || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
810 || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
811 || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */
812 || (rc = gnutls_x509_crt_set_key(cert, pkey))
814 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
815 GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2))
816 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
817 GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15))
818 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
819 GNUTLS_OID_X520_COMMON_NAME, 0,
820 smtp_active_hostname, Ustrlen(smtp_active_hostname)))
824 where = US"signing cert";
825 if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err;
827 where = US"installing selfsign cert";
829 if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey)))
835 if (cert) gnutls_x509_crt_deinit(cert);
836 if (pkey) gnutls_x509_privkey_deinit(pkey);
840 rc = tls_error(where, US gnutls_strerror(rc), NULL, errstr);
847 /* Add certificate and key, from files.
850 Zero or negative: good. Negate value for certificate index if < 0.
851 Greater than zero: FAIL or DEFER code.
855 tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
856 uschar * certfile, uschar * keyfile, uschar ** errstr)
858 int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
859 CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
862 string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
863 US gnutls_strerror(rc), host, errstr);
868 /*************************************************
869 * Variables re-expanded post-SNI *
870 *************************************************/
872 /* Called from both server and client code, via tls_init(), and also from
873 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
875 We can tell the two apart by state->received_sni being non-NULL in callback.
877 The callback should not call us unless state->trigger_sni_changes is true,
878 which we are responsible for setting on the first pass through.
881 state exim_gnutls_state_st *
882 errstr error string pointer
884 Returns: OK/DEFER/FAIL
888 tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
892 const host_item *host = state->host; /* macro should be reconsidered? */
893 uschar *saved_tls_certificate = NULL;
894 uschar *saved_tls_privatekey = NULL;
895 uschar *saved_tls_verify_certificates = NULL;
896 uschar *saved_tls_crl = NULL;
899 /* We check for tls_sni *before* expansion. */
900 if (!host) /* server */
901 if (!state->received_sni)
903 if ( state->tls_certificate
904 && ( Ustrstr(state->tls_certificate, US"tls_sni")
905 || Ustrstr(state->tls_certificate, US"tls_in_sni")
906 || Ustrstr(state->tls_certificate, US"tls_out_sni")
909 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
910 state->trigger_sni_changes = TRUE;
915 /* useful for debugging */
916 saved_tls_certificate = state->exp_tls_certificate;
917 saved_tls_privatekey = state->exp_tls_privatekey;
918 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
919 saved_tls_crl = state->exp_tls_crl;
922 rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
923 exim_gnutls_err_check(rc, US"gnutls_certificate_allocate_credentials");
925 #ifdef SUPPORT_SRV_OCSP_STACK
926 gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
929 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
930 state members, assuming consistent naming; and expand_check() returns
931 false if expansion failed, unless expansion was forced to fail. */
933 /* check if we at least have a certificate, before doing expensive
936 if (!expand_check_tlsvar(tls_certificate, errstr))
939 /* certificate is mandatory in server, optional in client */
941 if ( !state->exp_tls_certificate
942 || !*state->exp_tls_certificate
945 return tls_install_selfsign(state, errstr);
947 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
949 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr))
952 /* tls_privatekey is optional, defaulting to same file as certificate */
954 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
956 state->tls_privatekey = state->tls_certificate;
957 state->exp_tls_privatekey = state->exp_tls_certificate;
961 if (state->exp_tls_certificate && *state->exp_tls_certificate)
963 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
964 state->exp_tls_certificate, state->exp_tls_privatekey);
966 if (state->received_sni)
967 if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0
968 && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0
971 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
975 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
978 if (!host) /* server */
980 const uschar * clist = state->exp_tls_certificate;
981 const uschar * klist = state->exp_tls_privatekey;
982 const uschar * olist;
983 int csep = 0, ksep = 0, osep = 0, cnt = 0;
984 uschar * cfile, * kfile, * ofile;
987 if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
992 while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
994 if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
995 return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
996 else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
1000 int gnutls_cert_index = -rc;
1001 DEBUG(D_tls) debug_printf("TLS: cert/key %s registered\n", cfile);
1003 /* Set the OCSP stapling server info */
1005 #ifndef DISABLE_OCSP
1007 if (gnutls_buggy_ocsp)
1010 debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
1012 else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1014 /* Use the full callback method for stapling just to get
1015 observability. More efficient would be to read the file once only,
1016 if it never changed (due to SNI). Would need restart on file update,
1017 or watch datestamp. */
1019 # ifdef SUPPORT_SRV_OCSP_STACK
1020 rc = gnutls_certificate_set_ocsp_status_request_function2(
1021 state->x509_cred, gnutls_cert_index,
1022 server_ocsp_stapling_cb, ofile);
1024 exim_gnutls_err_check(rc,
1025 US"gnutls_certificate_set_ocsp_status_request_function2");
1030 debug_printf("oops; multiple OCSP files not supported\n");
1033 gnutls_certificate_set_ocsp_status_request_function(
1034 state->x509_cred, server_ocsp_stapling_cb, ofile);
1037 DEBUG(D_tls) debug_printf("OCSP response file = %s\n", ofile);
1040 DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
1046 if (0 < (rc = tls_add_certfile(state, host,
1047 state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
1049 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
1052 } /* tls_certificate */
1055 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
1056 provided. Experiment shows that, if the certificate file is empty, an unhelpful
1057 error message is provided. However, if we just refrain from setting anything up
1058 in that case, certificate verification fails, which seems to be the correct
1061 if (state->tls_verify_certificates && *state->tls_verify_certificates)
1063 if (!expand_check_tlsvar(tls_verify_certificates, errstr))
1065 #ifndef SUPPORT_SYSDEFAULT_CABUNDLE
1066 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1067 state->exp_tls_verify_certificates = NULL;
1069 if (state->tls_crl && *state->tls_crl)
1070 if (!expand_check_tlsvar(tls_crl, errstr))
1073 if (!(state->exp_tls_verify_certificates &&
1074 *state->exp_tls_verify_certificates))
1077 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
1078 /* With no tls_verify_certificates, we ignore tls_crl too */
1085 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
1089 #ifdef SUPPORT_SYSDEFAULT_CABUNDLE
1090 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1091 cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred);
1095 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
1097 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
1098 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
1103 #ifndef SUPPORT_CA_DIR
1104 /* The test suite passes in /dev/null; we could check for that path explicitly,
1105 but who knows if someone has some weird FIFO which always dumps some certs, or
1106 other weirdness. The thing we really want to check is that it's not a
1107 directory, since while OpenSSL supports that, GnuTLS does not.
1108 So s/!S_ISREG/S_ISDIR/ and change some messaging ... */
1109 if (S_ISDIR(statbuf.st_mode))
1112 debug_printf("verify certificates path is a dir: \"%s\"\n",
1113 state->exp_tls_verify_certificates);
1114 log_write(0, LOG_MAIN|LOG_PANIC,
1115 "tls_verify_certificates \"%s\" is a directory",
1116 state->exp_tls_verify_certificates);
1121 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
1122 state->exp_tls_verify_certificates, statbuf.st_size);
1124 if (statbuf.st_size == 0)
1127 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
1133 #ifdef SUPPORT_CA_DIR
1134 (statbuf.st_mode & S_IFMT) == S_IFDIR
1136 gnutls_certificate_set_x509_trust_dir(state->x509_cred,
1137 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM)
1140 gnutls_certificate_set_x509_trust_file(state->x509_cred,
1141 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
1147 exim_gnutls_err_check(rc, US"setting certificate trust");
1149 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);
1151 if (state->tls_crl && *state->tls_crl &&
1152 state->exp_tls_crl && *state->exp_tls_crl)
1154 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
1155 cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
1156 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM);
1160 exim_gnutls_err_check(rc, US"gnutls_certificate_set_x509_crl_file");
1162 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
1171 /*************************************************
1172 * Set X.509 state variables *
1173 *************************************************/
1175 /* In GnuTLS, the registered cert/key are not replaced by a later
1176 set of a cert/key, so for SNI support we need a whole new x509_cred
1177 structure. Which means various other non-re-expanded pieces of state
1178 need to be re-set in the new struct, so the setting logic is pulled
1182 state exim_gnutls_state_st *
1183 errstr error string pointer
1185 Returns: OK/DEFER/FAIL
1189 tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
1192 const host_item *host = state->host; /* macro should be reconsidered? */
1194 /* Create D-H parameters, or read them from the cache file. This function does
1195 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
1196 client-side params. */
1200 if (!dh_server_params)
1202 rc = init_server_dh(errstr);
1203 if (rc != OK) return rc;
1205 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
1208 /* Link the credentials to the session. */
1210 rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred);
1211 exim_gnutls_err_check(rc, US"gnutls_credentials_set");
1216 /*************************************************
1217 * Initialize for GnuTLS *
1218 *************************************************/
1221 #ifndef DISABLE_OCSP
1224 tls_is_buggy_ocsp(void)
1227 uschar maj, mid, mic;
1229 s = CUS gnutls_check_version(NULL);
1233 while (*s && *s != '.') s++;
1234 mid = atoi(CCS ++s);
1241 while (*s && *s != '.') s++;
1242 mic = atoi(CCS ++s);
1243 return mic <= (mid == 3 ? 16 : 3);
1252 /* Called from both server and client code. In the case of a server, errors
1253 before actual TLS negotiation return DEFER.
1256 host connected host, if client; NULL if server
1257 certificate certificate file
1258 privatekey private key file
1259 sni TLS SNI to send, sometimes when client; else NULL
1262 require_ciphers tls_require_ciphers setting
1263 caller_state returned state-info structure
1264 errstr error string pointer
1266 Returns: OK/DEFER/FAIL
1271 const host_item *host,
1272 const uschar *certificate,
1273 const uschar *privatekey,
1277 const uschar *require_ciphers,
1278 exim_gnutls_state_st **caller_state,
1282 exim_gnutls_state_st *state;
1287 BOOL want_default_priorities;
1289 if (!exim_gnutls_base_init_done)
1291 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
1293 #ifdef HAVE_GNUTLS_PKCS11
1294 /* By default, gnutls_global_init will init PKCS11 support in auto mode,
1295 which loads modules from a config file, which sounds good and may be wanted
1296 by some sysadmin, but also means in common configurations that GNOME keyring
1297 environment variables are used and so breaks for users calling mailq.
1298 To prevent this, we init PKCS11 first, which is the documented approach. */
1299 if (!gnutls_allow_auto_pkcs11)
1301 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
1302 exim_gnutls_err_check(rc, US"gnutls_pkcs11_init");
1306 rc = gnutls_global_init();
1307 exim_gnutls_err_check(rc, US"gnutls_global_init");
1309 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1312 gnutls_global_set_log_function(exim_gnutls_logger_cb);
1313 /* arbitrarily chosen level; bump upto 9 for more */
1314 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
1318 #ifndef DISABLE_OCSP
1319 if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp()))
1320 log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version");
1323 exim_gnutls_base_init_done = TRUE;
1328 /* For client-side sessions we allocate a context. This lets us run
1329 several in parallel. */
1330 int old_pool = store_pool;
1331 store_pool = POOL_PERM;
1332 state = store_get(sizeof(exim_gnutls_state_st));
1333 store_pool = old_pool;
1335 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1337 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
1338 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
1342 state = &state_server;
1343 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1345 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
1346 rc = gnutls_init(&state->session, GNUTLS_SERVER);
1348 exim_gnutls_err_check(rc, US"gnutls_init");
1352 state->tls_certificate = certificate;
1353 state->tls_privatekey = privatekey;
1354 state->tls_require_ciphers = require_ciphers;
1355 state->tls_sni = sni;
1356 state->tls_verify_certificates = cas;
1357 state->tls_crl = crl;
1359 /* This handles the variables that might get re-expanded after TLS SNI;
1360 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
1363 debug_printf("Expanding various TLS configuration options for session credentials.\n");
1364 if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc;
1366 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
1367 requires a new structure afterwards. */
1369 if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc;
1371 /* set SNI in client, only */
1374 if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr))
1376 if (state->tlsp->sni && *state->tlsp->sni)
1379 debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni);
1380 sz = Ustrlen(state->tlsp->sni);
1381 rc = gnutls_server_name_set(state->session,
1382 GNUTLS_NAME_DNS, state->tlsp->sni, sz);
1383 exim_gnutls_err_check(rc, US"gnutls_server_name_set");
1386 else if (state->tls_sni)
1387 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
1388 "have an SNI set for a server [%s]\n", state->tls_sni);
1390 /* This is the priority string support,
1391 http://www.gnutls.org/manual/html_node/Priority-Strings.html
1392 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
1393 This was backwards incompatible, but means Exim no longer needs to track
1394 all algorithms and provide string forms for them. */
1396 want_default_priorities = TRUE;
1398 if (state->tls_require_ciphers && *state->tls_require_ciphers)
1400 if (!expand_check_tlsvar(tls_require_ciphers, errstr))
1402 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
1404 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n",
1405 state->exp_tls_require_ciphers);
1407 rc = gnutls_priority_init(&state->priority_cache,
1408 CS state->exp_tls_require_ciphers, &errpos);
1409 want_default_priorities = FALSE;
1410 p = state->exp_tls_require_ciphers;
1413 if (want_default_priorities)
1416 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n",
1417 exim_default_gnutls_priority);
1418 rc = gnutls_priority_init(&state->priority_cache,
1419 exim_default_gnutls_priority, &errpos);
1420 p = US exim_default_gnutls_priority;
1423 exim_gnutls_err_check(rc, string_sprintf(
1424 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
1425 p, errpos - CS p, errpos));
1427 rc = gnutls_priority_set(state->session, state->priority_cache);
1428 exim_gnutls_err_check(rc, US"gnutls_priority_set");
1430 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
1432 /* Reduce security in favour of increased compatibility, if the admin
1433 decides to make that trade-off. */
1434 if (gnutls_compat_mode)
1436 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
1437 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
1438 gnutls_session_enable_compatibility_mode(state->session);
1440 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
1444 *caller_state = state;
1450 /*************************************************
1451 * Extract peer information *
1452 *************************************************/
1454 /* Called from both server and client code.
1455 Only this is allowed to set state->peerdn and state->have_set_peerdn
1456 and we use that to detect double-calls.
1458 NOTE: the state blocks last while the TLS connection is up, which is fine
1459 for logging in the server side, but for the client side, we log after teardown
1460 in src/deliver.c. While the session is up, we can twist about states and
1461 repoint tls_* globals, but those variables used for logging or other variable
1462 expansion that happens _after_ delivery need to have a longer life-time.
1464 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1465 doing this more than once per generation of a state context. We set them in
1466 the state context, and repoint tls_* to them. After the state goes away, the
1467 tls_* copies of the pointers remain valid and client delivery logging is happy.
1469 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1473 state exim_gnutls_state_st *
1474 errstr pointer to error string
1476 Returns: OK/DEFER/FAIL
1480 peer_status(exim_gnutls_state_st *state, uschar ** errstr)
1482 uschar cipherbuf[256];
1483 const gnutls_datum_t *cert_list;
1485 unsigned int cert_list_size = 0;
1486 gnutls_protocol_t protocol;
1487 gnutls_cipher_algorithm_t cipher;
1488 gnutls_kx_algorithm_t kx;
1489 gnutls_mac_algorithm_t mac;
1490 gnutls_certificate_type_t ct;
1491 gnutls_x509_crt_t crt;
1495 if (state->have_set_peerdn)
1497 state->have_set_peerdn = TRUE;
1499 state->peerdn = NULL;
1502 cipher = gnutls_cipher_get(state->session);
1503 protocol = gnutls_protocol_get_version(state->session);
1504 mac = gnutls_mac_get(state->session);
1505 kx = gnutls_kx_get(state->session);
1507 string_format(cipherbuf, sizeof(cipherbuf),
1509 gnutls_protocol_get_name(protocol),
1510 gnutls_cipher_suite_get_name(kx, cipher, mac),
1511 (int) gnutls_cipher_get_key_size(cipher) * 8);
1513 /* I don't see a way that spaces could occur, in the current GnuTLS
1514 code base, but it was a concern in the old code and perhaps older GnuTLS
1515 releases did return "TLS 1.0"; play it safe, just in case. */
1516 for (uschar * p = cipherbuf; *p != '\0'; ++p)
1519 old_pool = store_pool;
1520 store_pool = POOL_PERM;
1521 state->ciphersuite = string_copy(cipherbuf);
1522 store_pool = old_pool;
1523 state->tlsp->cipher = state->ciphersuite;
1526 cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
1528 if (cert_list == NULL || cert_list_size == 0)
1530 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1531 cert_list, cert_list_size);
1532 if (state->verify_requirement >= VERIFY_REQUIRED)
1533 return tls_error(US"certificate verification failed",
1534 US"no certificate received from peer", state->host, errstr);
1538 ct = gnutls_certificate_type_get(state->session);
1539 if (ct != GNUTLS_CRT_X509)
1541 const uschar *ctn = US gnutls_certificate_type_get_name(ct);
1543 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1544 if (state->verify_requirement >= VERIFY_REQUIRED)
1545 return tls_error(US"certificate verification not possible, unhandled type",
1546 ctn, state->host, errstr);
1550 #define exim_gnutls_peer_err(Label) \
1552 if (rc != GNUTLS_E_SUCCESS) \
1554 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \
1555 (Label), gnutls_strerror(rc)); \
1556 if (state->verify_requirement >= VERIFY_REQUIRED) \
1557 return tls_error((Label), US gnutls_strerror(rc), state->host, errstr); \
1562 rc = import_cert(&cert_list[0], &crt);
1563 exim_gnutls_peer_err(US"cert 0");
1565 state->tlsp->peercert = state->peercert = crt;
1568 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1569 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1571 exim_gnutls_peer_err(US"getting size for cert DN failed");
1572 return FAIL; /* should not happen */
1574 dn_buf = store_get_perm(sz);
1575 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1576 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1578 state->peerdn = dn_buf;
1581 #undef exim_gnutls_peer_err
1587 /*************************************************
1588 * Verify peer certificate *
1589 *************************************************/
1591 /* Called from both server and client code.
1592 *Should* be using a callback registered with
1593 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1594 the peer information, but that's too new for some OSes.
1597 state exim_gnutls_state_st *
1598 errstr where to put an error message
1601 FALSE if the session should be rejected
1602 TRUE if the cert is okay or we just don't care
1606 verify_certificate(exim_gnutls_state_st * state, uschar ** errstr)
1611 if (state->verify_requirement == VERIFY_NONE)
1614 DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n");
1617 if ((rc = peer_status(state, errstr)) != OK)
1619 verify = GNUTLS_CERT_INVALID;
1620 *errstr = US"certificate not supplied";
1626 if (state->verify_requirement == VERIFY_DANE && state->host)
1628 /* Using dane_verify_session_crt() would be easy, as it does it all for us
1629 including talking to a DNS resolver. But we want to do that bit ourselves
1630 as the testsuite intercepts and fakes its own DNS environment. */
1635 const gnutls_datum_t * certlist =
1636 gnutls_certificate_get_peers(state->session, &lsize);
1637 int usage = tls_out.tlsa_usage;
1639 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1640 /* Split the TLSA records into two sets, TA and EE selectors. Run the
1641 dane-verification separately so that we know which selector verified;
1642 then we know whether to do name-verification (needed for TA but not EE). */
1644 if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE)))
1645 { /* a mixed-usage bundle */
1650 for(nrec = 0; state->dane_data_len[nrec]; ) nrec++;
1653 dd = store_get(nrec * sizeof(uschar *));
1654 ddl = store_get(nrec * sizeof(int));
1657 if ((rc = dane_state_init(&s, 0)))
1660 for (usage = DANESSL_USAGE_DANE_EE;
1661 usage >= DANESSL_USAGE_DANE_TA; usage--)
1662 { /* take records with this usage */
1663 for (j = i = 0; i < nrec; i++)
1664 if (state->dane_data[i][0] == usage)
1666 dd[j] = state->dane_data[i];
1667 ddl[j++] = state->dane_data_len[i];
1674 if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0)))
1677 if ((rc = dane_verify_crt_raw(s, certlist, lsize,
1678 gnutls_certificate_type_get(state->session),
1680 usage == DANESSL_USAGE_DANE_EE
1681 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1685 debug_printf("TLSA record problem: %s\n", dane_strerror(rc));
1687 else if (verify == 0) /* verification passed */
1695 if (rc) goto tlsa_prob;
1700 if ( (rc = dane_state_init(&s, 0))
1701 || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len,
1703 || (rc = dane_verify_crt_raw(s, certlist, lsize,
1704 gnutls_certificate_type_get(state->session),
1706 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1707 usage == (1 << DANESSL_USAGE_DANE_EE)
1708 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1717 if (verify != 0) /* verification failed */
1720 (void) dane_verification_status_print(verify, &str, 0);
1721 *errstr = US str.data; /* don't bother to free */
1725 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1726 /* If a TA-mode TLSA record was used for verification we must additionally
1727 verify the cert name (but not the CA chain). For EE-mode, skip it. */
1729 if (usage & (1 << DANESSL_USAGE_DANE_EE))
1732 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1735 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1736 /* Assume that the name on the A-record is the one that should be matching
1737 the cert. An alternate view is that the domain part of the email address
1738 is also permissible. */
1740 if (gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1741 CS state->host->name))
1743 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1748 #endif /*SUPPORT_DANE*/
1750 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1753 /* Handle the result of verification. INVALID is set if any others are. */
1755 if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED))
1757 state->peer_cert_verified = FALSE;
1760 #ifdef GNUTLS_CERT_VFY_STATUS_PRINT
1765 if (gnutls_certificate_verification_status_print(verify,
1766 gnutls_certificate_type_get(state->session), &txt, 0)
1767 == GNUTLS_E_SUCCESS)
1769 debug_printf("%s\n", txt.data);
1770 gnutls_free(txt.data);
1774 *errstr = verify & GNUTLS_CERT_REVOKED
1775 ? US"certificate revoked" : US"certificate invalid";
1779 debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n",
1780 *errstr, state->peerdn ? state->peerdn : US"<unset>");
1782 if (state->verify_requirement >= VERIFY_REQUIRED)
1785 debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
1790 /* Client side, check the server's certificate name versus the name on the
1791 A-record for the connection we made. What to do for server side - what name
1792 to use for client? We document that there is no such checking for server
1795 if ( state->exp_tls_verify_cert_hostnames
1796 && !gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1797 CS state->exp_tls_verify_cert_hostnames)
1801 debug_printf("TLS certificate verification failed: cert name mismatch\n");
1802 if (state->verify_requirement >= VERIFY_REQUIRED)
1807 state->peer_cert_verified = TRUE;
1808 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n",
1809 state->peerdn ? state->peerdn : US"<unset>");
1813 state->tlsp->peerdn = state->peerdn;
1818 *errstr = string_sprintf("TLSA record problem: %s",
1819 rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc));
1823 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1830 /* ------------------------------------------------------------------------ */
1833 /* Logging function which can be registered with
1834 * gnutls_global_set_log_function()
1835 * gnutls_global_set_log_level() 0..9
1837 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1839 exim_gnutls_logger_cb(int level, const char *message)
1841 size_t len = strlen(message);
1844 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1847 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1848 message[len-1] == '\n' ? "" : "\n");
1853 /* Called after client hello, should handle SNI work.
1854 This will always set tls_sni (state->received_sni) if available,
1855 and may trigger presenting different certificates,
1856 if state->trigger_sni_changes is TRUE.
1858 Should be registered with
1859 gnutls_handshake_set_post_client_hello_function()
1861 "This callback must return 0 on success or a gnutls error code to terminate the
1864 For inability to get SNI information, we return 0.
1865 We only return non-zero if re-setup failed.
1866 Only used for server-side TLS.
1870 exim_sni_handling_cb(gnutls_session_t session)
1872 char sni_name[MAX_HOST_LEN];
1873 size_t data_len = MAX_HOST_LEN;
1874 exim_gnutls_state_st *state = &state_server;
1875 unsigned int sni_type;
1877 uschar * dummy_errstr;
1879 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
1880 if (rc != GNUTLS_E_SUCCESS)
1883 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
1884 debug_printf("TLS: no SNI presented in handshake.\n");
1886 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
1887 gnutls_strerror(rc), rc);
1892 if (sni_type != GNUTLS_NAME_DNS)
1894 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
1898 /* We now have a UTF-8 string in sni_name */
1899 old_pool = store_pool;
1900 store_pool = POOL_PERM;
1901 state->received_sni = string_copyn(US sni_name, data_len);
1902 store_pool = old_pool;
1904 /* We set this one now so that variable expansions below will work */
1905 state->tlsp->sni = state->received_sni;
1907 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
1908 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
1910 if (!state->trigger_sni_changes)
1913 if ((rc = tls_expand_session_files(state, &dummy_errstr)) != OK)
1915 /* If the setup of certs/etc failed before handshake, TLS would not have
1916 been offered. The best we can do now is abort. */
1917 return GNUTLS_E_APPLICATION_ERROR_MIN;
1920 rc = tls_set_remaining_x509(state, &dummy_errstr);
1921 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
1928 #ifndef DISABLE_OCSP
1931 server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
1932 gnutls_datum_t * ocsp_response)
1935 DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr);
1937 if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0)
1939 DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n",
1941 tls_in.ocsp = OCSP_NOT_RESP;
1942 return GNUTLS_E_NO_CERTIFICATE_STATUS;
1945 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
1952 #ifndef DISABLE_EVENT
1954 We use this callback to get observability and detail-level control
1955 for an exim TLS connection (either direction), raising a tls:cert event
1956 for each cert in the chain presented by the peer. Any event
1957 can deny verification.
1959 Return 0 for the handshake to continue or non-zero to terminate.
1963 verify_cb(gnutls_session_t session)
1965 const gnutls_datum_t * cert_list;
1966 unsigned int cert_list_size = 0;
1967 gnutls_x509_crt_t crt;
1970 exim_gnutls_state_st * state = gnutls_session_get_ptr(session);
1972 if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size)))
1973 while (cert_list_size--)
1975 if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS)
1977 DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n",
1978 cert_list_size, gnutls_strerror(rc));
1982 state->tlsp->peercert = crt;
1983 if ((yield = event_raise(state->event_action,
1984 US"tls:cert", string_sprintf("%d", cert_list_size))))
1986 log_write(0, LOG_MAIN,
1987 "SSL verify denied by event-action: depth=%d: %s",
1988 cert_list_size, yield);
1989 return 1; /* reject */
1991 state->tlsp->peercert = NULL;
2001 ddump(gnutls_datum_t * d)
2003 gstring * g = string_get((d->size+1) * 2);
2004 uschar * s = d->data;
2005 for (unsigned i = d->size; i > 0; i--, s++)
2007 g = string_catn(g, US "0123456789abcdef" + (*s >> 4), 1);
2008 g = string_catn(g, US "0123456789abcdef" + (*s & 0xf), 1);
2013 /* ------------------------------------------------------------------------ */
2014 /* Exported functions */
2019 /*************************************************
2020 * Start a TLS session in a server *
2021 *************************************************/
2023 /* This is called when Exim is running as a server, after having received
2024 the STARTTLS command. It must respond to that command, and then negotiate
2028 require_ciphers list of allowed ciphers or NULL
2029 errstr pointer to error string
2031 Returns: OK on success
2032 DEFER for errors before the start of the negotiation
2033 FAIL for errors during the negotiation; the server can't
2038 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2041 exim_gnutls_state_st * state = NULL;
2043 /* Check for previous activation */
2044 if (tls_in.active.sock >= 0)
2046 tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr);
2047 smtp_printf("554 Already in TLS\r\n", FALSE);
2051 /* Initialize the library. If it fails, it will already have logged the error
2052 and sent an SMTP response. */
2054 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
2056 if ((rc = tls_init(NULL, tls_certificate, tls_privatekey,
2057 NULL, tls_verify_certificates, tls_crl,
2058 require_ciphers, &state, &tls_in, errstr)) != OK) return rc;
2060 /* If this is a host for which certificate verification is mandatory or
2061 optional, set up appropriately. */
2063 if (verify_check_host(&tls_verify_hosts) == OK)
2066 debug_printf("TLS: a client certificate will be required.\n");
2067 state->verify_requirement = VERIFY_REQUIRED;
2068 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2070 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2073 debug_printf("TLS: a client certificate will be requested but not required.\n");
2074 state->verify_requirement = VERIFY_OPTIONAL;
2075 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2080 debug_printf("TLS: a client certificate will not be requested.\n");
2081 state->verify_requirement = VERIFY_NONE;
2082 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2085 #ifndef DISABLE_EVENT
2088 state->event_action = event_action;
2089 gnutls_session_set_ptr(state->session, state);
2090 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2094 /* Register SNI handling; always, even if not in tls_certificate, so that the
2095 expansion variable $tls_sni is always available. */
2097 gnutls_handshake_set_post_client_hello_function(state->session,
2098 exim_sni_handling_cb);
2100 /* Set context and tell client to go ahead, except in the case of TLS startup
2101 on connection, where outputting anything now upsets the clients and tends to
2102 make them disconnect. We need to have an explicit fflush() here, to force out
2103 the response. Other smtp_printf() calls do not need it, because in non-TLS
2104 mode, the fflush() happens when smtp_getc() is called. */
2106 if (!state->tlsp->on_connect)
2108 smtp_printf("220 TLS go ahead\r\n", FALSE);
2112 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2113 that the GnuTLS library doesn't.
2114 From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you
2115 to set (and clear down afterwards) up a pull-timeout callback function that does
2116 a select, so we're no better off unless avoiding signals becomes an issue. */
2118 gnutls_transport_set_ptr2(state->session,
2119 (gnutls_transport_ptr_t)(long) fileno(smtp_in),
2120 (gnutls_transport_ptr_t)(long) fileno(smtp_out));
2121 state->fd_in = fileno(smtp_in);
2122 state->fd_out = fileno(smtp_out);
2124 sigalrm_seen = FALSE;
2125 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2127 rc = gnutls_handshake(state->session);
2128 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2131 if (rc != GNUTLS_E_SUCCESS)
2133 /* It seems that, except in the case of a timeout, we have to close the
2134 connection right here; otherwise if the other end is running OpenSSL it hangs
2135 until the server times out. */
2139 tls_error(US"gnutls_handshake", US"timed out", NULL, errstr);
2140 gnutls_db_remove_session(state->session);
2144 tls_error(US"gnutls_handshake", US gnutls_strerror(rc), NULL, errstr);
2145 (void) gnutls_alert_send_appropriate(state->session, rc);
2146 gnutls_deinit(state->session);
2147 gnutls_certificate_free_credentials(state->x509_cred);
2149 shutdown(state->fd_out, SHUT_WR);
2150 for (int i = 1024; fgetc(smtp_in) != EOF && i > 0; ) i--; /* drain skt */
2151 (void)fclose(smtp_out);
2152 (void)fclose(smtp_in);
2153 smtp_out = smtp_in = NULL;
2161 debug_printf("gnutls_handshake was successful\n");
2162 #ifdef SUPPORT_GNUTLS_SESS_DESC
2163 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2165 #ifdef SUPPORT_GNUTLS_KEYLOG
2167 gnutls_datum_t c, s;
2169 gnutls_session_get_random(state->session, &c, &s);
2170 gnutls_session_get_master_secret(state->session, &s);
2173 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2178 /* Verify after the fact */
2180 if (!verify_certificate(state, errstr))
2182 if (state->verify_requirement != VERIFY_OPTIONAL)
2184 (void) tls_error(US"certificate verification failed", *errstr, NULL, errstr);
2188 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
2192 /* Figure out peer DN, and if authenticated, etc. */
2194 if ((rc = peer_status(state, NULL)) != OK) return rc;
2196 /* Sets various Exim expansion variables; always safe within server */
2198 extract_exim_vars_from_tls_state(state);
2200 /* TLS has been set up. Adjust the input functions to read via TLS,
2201 and initialize appropriately. */
2203 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2205 receive_getc = tls_getc;
2206 receive_getbuf = tls_getbuf;
2207 receive_get_cache = tls_get_cache;
2208 receive_ungetc = tls_ungetc;
2209 receive_feof = tls_feof;
2210 receive_ferror = tls_ferror;
2211 receive_smtp_buffered = tls_smtp_buffered;
2220 tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state,
2221 smtp_transport_options_block * ob)
2223 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2225 state->exp_tls_verify_cert_hostnames =
2227 string_domain_utf8_to_alabel(host->name, NULL);
2232 debug_printf("TLS: server cert verification includes hostname: \"%s\".\n",
2233 state->exp_tls_verify_cert_hostnames);
2241 /* Given our list of RRs from the TLSA lookup, build a lookup block in
2242 GnuTLS-DANE's preferred format. Hang it on the state str for later
2243 use in DANE verification.
2245 We point at the dnsa data not copy it, so it must remain valid until
2246 after verification is done.*/
2249 dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa)
2253 const char ** dane_data;
2254 int * dane_data_len;
2257 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2258 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2259 ) if (rr->type == T_TLSA) i++;
2261 dane_data = store_get(i * sizeof(uschar *));
2262 dane_data_len = store_get(i * sizeof(int));
2265 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2266 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2267 ) if (rr->type == T_TLSA && rr->size > 3)
2269 const uschar * p = rr->data;
2270 uint8_t usage = p[0], sel = p[1], type = p[2];
2273 debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size);
2275 if ( (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE)
2276 || (sel != 0 && sel != 1)
2281 case 0: /* Full: cannot check at present */
2283 case 1: if (rr->size != 3 + 256/8) continue; /* sha2-256 */
2285 case 2: if (rr->size != 3 + 512/8) continue; /* sha2-512 */
2290 tls_out.tlsa_usage |= 1<<usage;
2291 dane_data[i] = CS p;
2292 dane_data_len[i++] = rr->size;
2295 if (!i) return FALSE;
2297 dane_data[i] = NULL;
2298 dane_data_len[i] = 0;
2300 state->dane_data = (char * const *)dane_data;
2301 state->dane_data_len = dane_data_len;
2308 /*************************************************
2309 * Start a TLS session in a client *
2310 *************************************************/
2312 /* Called from the smtp transport after STARTTLS has been accepted.
2315 fd the fd of the connection
2316 host connected host (for messages and option-tests)
2317 addr the first address (not used)
2318 tb transport (always smtp)
2319 tlsa_dnsa non-NULL, either request or require dane for this host, and
2320 a TLSA record found. Therefore, dane verify required.
2321 Which implies cert must be requested and supplied, dane
2322 verify must pass, and cert verify irrelevant (incl.
2323 hostnames), and (caller handled) require_tls
2324 tlsp record details of channel configuration
2325 errstr error string pointer
2327 Returns: Pointer to TLS session context, or NULL on error
2331 tls_client_start(int fd, host_item *host,
2332 address_item *addr ARG_UNUSED,
2333 transport_instance * tb,
2335 dns_answer * tlsa_dnsa,
2337 tls_support * tlsp, uschar ** errstr)
2339 smtp_transport_options_block *ob = tb
2340 ? (smtp_transport_options_block *)tb->options_block
2341 : &smtp_transport_option_defaults;
2343 exim_gnutls_state_st * state = NULL;
2344 uschar *cipher_list = NULL;
2346 #ifndef DISABLE_OCSP
2348 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2349 BOOL request_ocsp = require_ocsp ? TRUE
2350 : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2353 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);
2356 if (tlsa_dnsa && ob->dane_require_tls_ciphers)
2358 /* not using expand_check_tlsvar because not yet in state */
2359 if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2360 &cipher_list, errstr))
2362 cipher_list = cipher_list && *cipher_list
2363 ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
2368 cipher_list = ob->tls_require_ciphers;
2370 if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
2371 ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
2372 cipher_list, &state, tlsp, errstr) != OK)
2376 int dh_min_bits = ob->tls_dh_min_bits;
2377 if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
2380 debug_printf("WARNING: tls_dh_min_bits far too low,"
2381 " clamping %d up to %d\n",
2382 dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
2383 dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
2386 DEBUG(D_tls) debug_printf("Setting D-H prime minimum"
2387 " acceptable bits to %d\n",
2389 gnutls_dh_set_prime_bits(state->session, dh_min_bits);
2392 /* Stick to the old behaviour for compatibility if tls_verify_certificates is
2393 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
2394 the specified host patterns if one of them is defined */
2397 if (tlsa_dnsa && dane_tlsa_load(state, tlsa_dnsa))
2400 debug_printf("TLS: server certificate DANE required.\n");
2401 state->verify_requirement = VERIFY_DANE;
2402 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2406 if ( ( state->exp_tls_verify_certificates
2407 && !ob->tls_verify_hosts
2408 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2410 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2413 tls_client_setup_hostname_checks(host, state, ob);
2415 debug_printf("TLS: server certificate verification required.\n");
2416 state->verify_requirement = VERIFY_REQUIRED;
2417 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2419 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2421 tls_client_setup_hostname_checks(host, state, ob);
2423 debug_printf("TLS: server certificate verification optional.\n");
2424 state->verify_requirement = VERIFY_OPTIONAL;
2425 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2430 debug_printf("TLS: server certificate verification not required.\n");
2431 state->verify_requirement = VERIFY_NONE;
2432 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2435 #ifndef DISABLE_OCSP
2436 /* supported since GnuTLS 3.1.3 */
2439 DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
2440 if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
2441 NULL, 0, NULL)) != OK)
2443 tls_error(US"cert-status-req", US gnutls_strerror(rc), state->host, errstr);
2446 tlsp->ocsp = OCSP_NOT_RESP;
2450 #ifndef DISABLE_EVENT
2451 if (tb && tb->event_action)
2453 state->event_action = tb->event_action;
2454 gnutls_session_set_ptr(state->session, state);
2455 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2459 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) fd);
2463 DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
2464 /* There doesn't seem to be a built-in timeout on connection. */
2466 sigalrm_seen = FALSE;
2467 ALARM(ob->command_timeout);
2469 rc = gnutls_handshake(state->session);
2470 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2473 if (rc != GNUTLS_E_SUCCESS)
2477 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
2478 tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
2481 tls_error(US"gnutls_handshake", US gnutls_strerror(rc), state->host, errstr);
2487 debug_printf("gnutls_handshake was successful\n");
2488 #ifdef SUPPORT_GNUTLS_SESS_DESC
2489 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2491 #ifdef SUPPORT_GNUTLS_KEYLOG
2493 gnutls_datum_t c, s;
2495 gnutls_session_get_random(state->session, &c, &s);
2496 gnutls_session_get_master_secret(state->session, &s);
2499 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2506 if (!verify_certificate(state, errstr))
2508 tls_error(US"certificate verification failed", *errstr, state->host, errstr);
2512 #ifndef DISABLE_OCSP
2517 gnutls_datum_t stapling;
2518 gnutls_ocsp_resp_t resp;
2519 gnutls_datum_t printed;
2520 if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0
2521 && (rc= gnutls_ocsp_resp_init(&resp)) == 0
2522 && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0
2523 && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0
2526 debug_printf("%.4096s", printed.data);
2527 gnutls_free(printed.data);
2530 (void) tls_error(US"ocsp decode", US gnutls_strerror(rc), state->host, errstr);
2533 if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
2535 tlsp->ocsp = OCSP_FAILED;
2536 tls_error(US"certificate status check failed", NULL, state->host, errstr);
2539 DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
2540 tlsp->ocsp = OCSP_VFIED;
2544 /* Figure out peer DN, and if authenticated, etc. */
2546 if (peer_status(state, errstr) != OK)
2549 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
2551 extract_exim_vars_from_tls_state(state);
2559 /*************************************************
2560 * Close down a TLS session *
2561 *************************************************/
2563 /* This is also called from within a delivery subprocess forked from the
2564 daemon, to shut down the TLS library, without actually doing a shutdown (which
2565 would tamper with the TLS session in the parent process).
2568 ct_ctx client context pointer, or NULL for the one global server context
2569 shutdown 1 if TLS close-alert is to be sent,
2570 2 if also response to be waited for
2576 tls_close(void * ct_ctx, int shutdown)
2578 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2580 if (!state->tlsp || state->tlsp->active.sock < 0) return; /* TLS was not active */
2584 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
2585 shutdown > 1 ? " (with response-wait)" : "");
2588 gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
2592 gnutls_deinit(state->session);
2593 gnutls_certificate_free_credentials(state->x509_cred);
2596 state->tlsp->active.sock = -1;
2597 state->tlsp->active.tls_ctx = NULL;
2598 if (state->xfer_buffer) store_free(state->xfer_buffer);
2599 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
2606 tls_refill(unsigned lim)
2608 exim_gnutls_state_st * state = &state_server;
2611 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
2612 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
2614 sigalrm_seen = FALSE;
2615 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2618 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
2619 MIN(ssl_xfer_buffer_size, lim));
2620 while (inbytes == GNUTLS_E_AGAIN);
2622 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2624 if (had_command_timeout) /* set by signal handler */
2625 smtp_command_timeout_exit(); /* does not return */
2626 if (had_command_sigterm)
2627 smtp_command_sigterm_exit();
2628 if (had_data_timeout)
2629 smtp_data_timeout_exit();
2630 if (had_data_sigint)
2631 smtp_data_sigint_exit();
2633 /* Timeouts do not get this far. A zero-byte return appears to mean that the
2634 TLS session has been closed down, not that the socket itself has been closed
2635 down. Revert to non-TLS handling. */
2639 DEBUG(D_tls) debug_printf("Got tls read timeout\n");
2640 state->xfer_error = TRUE;
2644 else if (inbytes == 0)
2646 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2648 receive_getc = smtp_getc;
2649 receive_getbuf = smtp_getbuf;
2650 receive_get_cache = smtp_get_cache;
2651 receive_ungetc = smtp_ungetc;
2652 receive_feof = smtp_feof;
2653 receive_ferror = smtp_ferror;
2654 receive_smtp_buffered = smtp_buffered;
2656 gnutls_deinit(state->session);
2657 gnutls_certificate_free_credentials(state->x509_cred);
2659 state->session = NULL;
2660 state->tlsp->active.sock = -1;
2661 state->tlsp->active.tls_ctx = NULL;
2662 state->tlsp->bits = 0;
2663 state->tlsp->certificate_verified = FALSE;
2664 tls_channelbinding_b64 = NULL;
2665 state->tlsp->cipher = NULL;
2666 state->tlsp->peercert = NULL;
2667 state->tlsp->peerdn = NULL;
2672 /* Handle genuine errors */
2674 else if (inbytes < 0)
2676 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__);
2677 record_io_error(state, (int) inbytes, US"recv", NULL);
2678 state->xfer_error = TRUE;
2681 #ifndef DISABLE_DKIM
2682 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
2684 state->xfer_buffer_hwm = (int) inbytes;
2685 state->xfer_buffer_lwm = 0;
2689 /*************************************************
2690 * TLS version of getc *
2691 *************************************************/
2693 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2694 it refills the buffer via the GnuTLS reading function.
2695 Only used by the server-side TLS.
2697 This feeds DKIM and should be used for all message-body reads.
2699 Arguments: lim Maximum amount to read/bufffer
2700 Returns: the next character or EOF
2704 tls_getc(unsigned lim)
2706 exim_gnutls_state_st * state = &state_server;
2708 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2709 if (!tls_refill(lim))
2710 return state->xfer_error ? EOF : smtp_getc(lim);
2712 /* Something in the buffer; return next uschar */
2714 return state->xfer_buffer[state->xfer_buffer_lwm++];
2718 tls_getbuf(unsigned * len)
2720 exim_gnutls_state_st * state = &state_server;
2724 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2725 if (!tls_refill(*len))
2727 if (!state->xfer_error) return smtp_getbuf(len);
2732 if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
2734 buf = &state->xfer_buffer[state->xfer_buffer_lwm];
2735 state->xfer_buffer_lwm += size;
2744 #ifndef DISABLE_DKIM
2745 exim_gnutls_state_st * state = &state_server;
2746 int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm;
2748 dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n);
2754 tls_could_read(void)
2756 return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
2757 || gnutls_record_check_pending(state_server.session) > 0;
2763 /*************************************************
2764 * Read bytes from TLS channel *
2765 *************************************************/
2767 /* This does not feed DKIM, so if the caller uses this for reading message body,
2768 then the caller must feed DKIM.
2771 ct_ctx client context pointer, or NULL for the one global server context
2775 Returns: the number of bytes read
2776 -1 after a failed read, including EOF
2780 tls_read(void * ct_ctx, uschar *buff, size_t len)
2782 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2788 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
2790 debug_printf("*** PROBABLY A BUG *** " \
2791 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
2792 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
2795 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
2796 state->session, buff, len);
2799 inbytes = gnutls_record_recv(state->session, buff, len);
2800 while (inbytes == GNUTLS_E_AGAIN);
2802 if (inbytes > 0) return inbytes;
2805 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2809 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__);
2810 record_io_error(state, (int)inbytes, US"recv", NULL);
2819 /*************************************************
2820 * Write bytes down TLS channel *
2821 *************************************************/
2825 ct_ctx client context pointer, or NULL for the one global server context
2828 more more data expected soon
2830 Returns: the number of bytes after a successful write,
2831 -1 after a failed write
2835 tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
2839 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2841 static BOOL corked = FALSE;
2843 if (more && !corked) gnutls_record_cork(state->session);
2846 DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
2847 buff, left, more ? ", more" : "");
2851 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
2855 outbytes = gnutls_record_send(state->session, buff, left);
2856 while (outbytes == GNUTLS_E_AGAIN);
2858 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
2861 DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
2862 record_io_error(state, outbytes, US"send", NULL);
2867 record_io_error(state, 0, US"send", US"TLS channel closed on write");
2878 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
2886 if (!more) (void) gnutls_record_uncork(state->session, 0);
2897 /*************************************************
2898 * Random number generation *
2899 *************************************************/
2901 /* Pseudo-random number generation. The result is not expected to be
2902 cryptographically strong but not so weak that someone will shoot themselves
2903 in the foot using it as a nonce in input in some email header scheme or
2904 whatever weirdness they'll twist this into. The result should handle fork()
2905 and avoid repeating sequences. OpenSSL handles that for us.
2909 Returns a random number in range [0, max-1]
2912 #ifdef HAVE_GNUTLS_RND
2914 vaguely_random_number(int max)
2918 uschar smallbuf[sizeof(r)];
2923 needed_len = sizeof(r);
2924 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2925 asked for a number less than 10. */
2927 for (r = max, i = 0; r; ++i)
2933 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
2936 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
2937 return vaguely_random_number_fallback(max);
2940 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
2943 /* We don't particularly care about weighted results; if someone wants
2944 * smooth distribution and cares enough then they should submit a patch then. */
2947 #else /* HAVE_GNUTLS_RND */
2949 vaguely_random_number(int max)
2951 return vaguely_random_number_fallback(max);
2953 #endif /* HAVE_GNUTLS_RND */
2958 /*************************************************
2959 * Let tls_require_ciphers be checked at startup *
2960 *************************************************/
2962 /* The tls_require_ciphers option, if set, must be something which the
2965 Returns: NULL on success, or error message
2969 tls_validate_require_cipher(void)
2972 uschar *expciphers = NULL;
2973 gnutls_priority_t priority_cache;
2975 uschar * dummy_errstr;
2977 #define validate_check_rc(Label) do { \
2978 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
2979 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
2980 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
2982 if (exim_gnutls_base_init_done)
2983 log_write(0, LOG_MAIN|LOG_PANIC,
2984 "already initialised GnuTLS, Exim developer bug");
2986 #ifdef HAVE_GNUTLS_PKCS11
2987 if (!gnutls_allow_auto_pkcs11)
2989 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
2990 validate_check_rc(US"gnutls_pkcs11_init");
2993 rc = gnutls_global_init();
2994 validate_check_rc(US"gnutls_global_init()");
2995 exim_gnutls_base_init_done = TRUE;
2997 if (!(tls_require_ciphers && *tls_require_ciphers))
2998 return_deinit(NULL);
3000 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3002 return_deinit(US"failed to expand tls_require_ciphers");
3004 if (!(expciphers && *expciphers))
3005 return_deinit(NULL);
3008 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3010 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
3011 validate_check_rc(string_sprintf(
3012 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
3013 expciphers, errpos - CS expciphers, errpos));
3015 #undef return_deinit
3016 #undef validate_check_rc
3017 gnutls_global_deinit();
3025 /*************************************************
3026 * Report the library versions. *
3027 *************************************************/
3029 /* See a description in tls-openssl.c for an explanation of why this exists.
3031 Arguments: a FILE* to print the results to
3036 tls_version_report(FILE *f)
3038 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
3041 gnutls_check_version(NULL));
3046 /* End of tls-gnu.c */