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
79 #if GNUTLS_VERSION_NUMBER >= 0x030600
80 # define GNUTLS_AUTO_DHPARAMS
82 #if GNUTLS_VERSION_NUMBER >= 0x030603
83 # define EXIM_HAVE_TLS1_3
84 # define SUPPORT_GNUTLS_EXT_RAW_PARSE
85 # define GNUTLS_OCSP_STATUS_REQUEST_GET2
89 # if GNUTLS_VERSION_NUMBER >= 0x030000
90 # define DANESSL_USAGE_DANE_TA 2
91 # define DANESSL_USAGE_DANE_EE 3
93 # error GnuTLS version too early for DANE
95 # if GNUTLS_VERSION_NUMBER < 0x999999
96 # define GNUTLS_BROKEN_DANE_VALIDATION
100 #ifdef EXPERIMENTAL_TLS_RESUME
101 # if GNUTLS_VERSION_NUMBER < 0x030603
102 # error GNUTLS version too early for session-resumption
107 # include <gnutls/ocsp.h>
110 # include <gnutls/dane.h>
113 #include "tls-cipher-stdname.c"
120 # ifdef EXPERIMENTAL_TLS_RESUME
121 builtin_macro_create_var(US"_RESUME_DECODE", RESUME_DECODE_STRING );
123 # ifdef EXIM_HAVE_TLS1_3
124 builtin_macro_create(US"_HAVE_TLS1_3");
133 gnutls_global_set_audit_log_function()
136 gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
139 /* Local static variables for GnuTLS */
141 /* Values for verify_requirement */
143 enum peer_verify_requirement
144 { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED, VERIFY_DANE };
146 /* This holds most state for server or client; with this, we can set up an
147 outbound TLS-enabled connection in an ACL callout, while not stomping all
148 over the TLS variables available for expansion.
150 Some of these correspond to variables in globals.c; those variables will
151 be set to point to content in one of these instances, as appropriate for
152 the stage of the process lifetime.
154 Not handled here: global tls_channelbinding_b64.
157 typedef struct exim_gnutls_state {
158 gnutls_session_t session;
159 gnutls_certificate_credentials_t x509_cred;
160 gnutls_priority_t priority_cache;
161 enum peer_verify_requirement verify_requirement;
164 BOOL peer_cert_verified;
165 BOOL peer_dane_verified;
166 BOOL trigger_sni_changes;
167 BOOL have_set_peerdn;
168 const struct host_item *host; /* NULL if server */
169 gnutls_x509_crt_t peercert;
172 uschar *received_sni;
174 const uschar *tls_certificate;
175 const uschar *tls_privatekey;
176 const uschar *tls_sni; /* client send only, not received */
177 const uschar *tls_verify_certificates;
178 const uschar *tls_crl;
179 const uschar *tls_require_ciphers;
181 uschar *exp_tls_certificate;
182 uschar *exp_tls_privatekey;
183 uschar *exp_tls_verify_certificates;
185 uschar *exp_tls_require_ciphers;
186 const uschar *exp_tls_verify_cert_hostnames;
187 #ifndef DISABLE_EVENT
188 uschar *event_action;
191 char * const * dane_data;
192 const int * dane_data_len;
195 tls_support *tlsp; /* set in tls_init() */
200 BOOL xfer_eof; /*XXX never gets set! */
202 } exim_gnutls_state_st;
204 static const exim_gnutls_state_st exim_gnutls_state_init = {
205 /* all elements not explicitly intialised here get 0/NULL/FALSE */
210 /* Not only do we have our own APIs which don't pass around state, assuming
211 it's held in globals, GnuTLS doesn't appear to let us register callback data
212 for callbacks, or as part of the session, so we have to keep a "this is the
213 context we're currently dealing with" pointer and rely upon being
214 single-threaded to keep from processing data on an inbound TLS connection while
215 talking to another TLS connection for an outbound check. This does mean that
216 there's no way for heart-beats to be responded to, for the duration of the
218 XXX But see gnutls_session_get_ptr()
221 static exim_gnutls_state_st state_server;
223 #ifndef GNUTLS_AUTO_DHPARAMS
224 /* dh_params are initialised once within the lifetime of a process using TLS;
225 if we used TLS in a long-lived daemon, we'd have to reconsider this. But we
226 don't want to repeat this. */
228 static gnutls_dh_params_t dh_server_params = NULL;
231 static int ssl_session_timeout = 7200; /* Two hours */
233 static const uschar * const exim_default_gnutls_priority = US"NORMAL";
235 /* Guard library core initialisation */
237 static BOOL exim_gnutls_base_init_done = FALSE;
240 static BOOL gnutls_buggy_ocsp = FALSE;
241 static BOOL exim_testharness_disable_ocsp_validity_check = FALSE;
244 #ifdef EXPERIMENTAL_TLS_RESUME
245 static gnutls_datum_t server_sessticket_key;
248 /* ------------------------------------------------------------------------ */
251 #define MAX_HOST_LEN 255
253 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
254 the library logging; a value less than 0 disables the calls to set up logging
255 callbacks. GNuTLS also looks for an environment variable - except not for
256 setuid binaries, making it useless - "GNUTLS_DEBUG_LEVEL".
257 Allegedly the testscript line "GNUTLS_DEBUG_LEVEL=9 sudo exim ..." would work,
258 but the env var must be added to /etc/sudoers too. */
259 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
260 # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
263 #ifndef EXIM_CLIENT_DH_MIN_BITS
264 # define EXIM_CLIENT_DH_MIN_BITS 1024
267 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
268 can ask for a bit-strength. Without that, we stick to the constant we had
270 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
271 # define EXIM_SERVER_DH_BITS_PRE2_12 1024
274 #define expand_check_tlsvar(Varname, errstr) \
275 expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr)
277 #if GNUTLS_VERSION_NUMBER >= 0x020c00
278 # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
279 # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
280 # define HAVE_GNUTLS_RND
281 /* The security fix we provide with the gnutls_allow_auto_pkcs11 option
282 * (4.82 PP/09) introduces a compatibility regression. The symbol simply
283 * isn't available sometimes, so this needs to become a conditional
284 * compilation; the sanest way to deal with this being a problem on
285 * older OSes is to block it in the Local/Makefile with this compiler
287 # ifndef AVOID_GNUTLS_PKCS11
288 # define HAVE_GNUTLS_PKCS11
289 # endif /* AVOID_GNUTLS_PKCS11 */
295 /* ------------------------------------------------------------------------ */
296 /* Callback declarations */
298 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
299 static void exim_gnutls_logger_cb(int level, const char *message);
302 static int exim_sni_handling_cb(gnutls_session_t session);
304 #ifdef EXPERIMENTAL_TLS_RESUME
306 tls_server_ticket_cb(gnutls_session_t sess, u_int htype, unsigned when,
307 unsigned incoming, const gnutls_datum_t * msg);
311 /* Daemon one-time initialisation */
313 tls_daemon_init(void)
315 #ifdef EXPERIMENTAL_TLS_RESUME
316 /* We are dependent on the GnuTLS implementation of the Session Ticket
317 encryption; both the strength and the key rotation period. We hope that
318 the strength at least matches that of the ciphersuite (but GnuTLS does not
321 static BOOL once = FALSE;
324 gnutls_session_ticket_key_generate(&server_sessticket_key); /* >= 2.10.0 */
325 if (f.running_in_test_harness) ssl_session_timeout = 6;
329 /* ------------------------------------------------------------------------ */
330 /* Static functions */
332 /*************************************************
334 *************************************************/
336 /* Called from lots of places when errors occur before actually starting to do
337 the TLS handshake, that is, while the session is still in clear. Always returns
338 DEFER for a server and FAIL for a client so that most calls can use "return
339 tls_error(...)" to do this processing and then give an appropriate return. A
340 single function is used for both server and client, because it is called from
341 some shared functions.
344 prefix text to include in the logged error
345 msg additional error string (may be NULL)
346 usually obtained from gnutls_strerror()
347 host NULL if setting up a server;
348 the connected host if setting up a client
349 errstr pointer to returned error string
351 Returns: OK/DEFER/FAIL
355 tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
359 *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
360 return host ? FAIL : DEFER;
365 tls_error_gnu(const uschar *prefix, int err, const host_item *host,
368 return tls_error(prefix, US gnutls_strerror(err), host, errstr);
372 tls_error_sys(const uschar *prefix, int err, const host_item *host,
375 return tls_error(prefix, US strerror(err), host, errstr);
379 /*************************************************
380 * Deal with logging errors during I/O *
381 *************************************************/
383 /* We have to get the identity of the peer from saved data.
386 state the current GnuTLS exim state container
387 rc the GnuTLS error code, or 0 if it's a local error
388 when text identifying read or write
389 text local error text when rc is 0
395 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
400 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
401 msg = string_sprintf("A TLS fatal alert has been received: %s",
402 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
404 msg = US gnutls_strerror(rc);
406 (void) tls_error(when, msg, state->host, &errstr);
409 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s",
410 state->host->name, state->host->address, errstr);
413 uschar * conn_info = smtp_get_connection_info();
414 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5;
415 /* I'd like to get separated H= here, but too hard for now */
416 log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr);
423 /*************************************************
424 * Set various Exim expansion vars *
425 *************************************************/
427 #define exim_gnutls_cert_err(Label) \
430 if (rc != GNUTLS_E_SUCCESS) \
432 DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \
433 (Label), gnutls_strerror(rc)); \
439 import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp)
443 rc = gnutls_x509_crt_init(crtp);
444 exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)");
446 rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER);
447 exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]");
452 #undef exim_gnutls_cert_err
455 /* We set various Exim global variables from the state, once a session has
456 been established. With TLS callouts, may need to change this to stack
457 variables, or just re-call it with the server state after client callout
460 Make sure anything set here is unset in tls_getc().
464 tls_bits strength indicator
465 tls_certificate_verified bool indicator
466 tls_channelbinding_b64 for some SASL mechanisms
468 tls_peercert pointer to library internal
470 tls_sni a (UTF-8) string
471 tls_ourcert pointer to library internal
474 state the relevant exim_gnutls_state_st *
478 extract_exim_vars_from_tls_state(exim_gnutls_state_st * state)
480 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
483 gnutls_datum_t channel;
485 tls_support * tlsp = state->tlsp;
487 tlsp->active.sock = state->fd_out;
488 tlsp->active.tls_ctx = state;
490 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
492 tlsp->certificate_verified = state->peer_cert_verified;
494 tlsp->dane_verified = state->peer_dane_verified;
497 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
498 only available for use for authenticators while this TLS session is running. */
500 tls_channelbinding_b64 = NULL;
501 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
504 if ((rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel)))
505 { DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); }
508 old_pool = store_pool;
509 store_pool = POOL_PERM;
510 tls_channelbinding_b64 = b64encode(CUS channel.data, (int)channel.size);
511 store_pool = old_pool;
512 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
516 /* peercert is set in peer_status() */
517 tlsp->peerdn = state->peerdn;
518 tlsp->sni = state->received_sni;
520 /* record our certificate */
522 const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session);
523 gnutls_x509_crt_t crt;
525 tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL;
532 #ifndef GNUTLS_AUTO_DHPARAMS
533 /*************************************************
534 * Setup up DH parameters *
535 *************************************************/
537 /* Generating the D-H parameters may take a long time. They only need to
538 be re-generated every so often, depending on security policy. What we do is to
539 keep these parameters in a file in the spool directory. If the file does not
540 exist, we generate them. This means that it is easy to cause a regeneration.
542 The new file is written as a temporary file and renamed, so that an incomplete
543 file is never present. If two processes both compute some new parameters, you
544 waste a bit of effort, but it doesn't seem worth messing around with locking to
547 Returns: OK/DEFER/FAIL
551 init_server_dh(uschar ** errstr)
554 unsigned int dh_bits;
555 gnutls_datum_t m = {.data = NULL, .size = 0};
556 uschar filename_buf[PATH_MAX];
557 uschar *filename = NULL;
559 uschar *exp_tls_dhparam;
560 BOOL use_file_in_spool = FALSE;
561 host_item *host = NULL; /* dummy for macros */
563 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
565 if ((rc = gnutls_dh_params_init(&dh_server_params)))
566 return tls_error_gnu(US"gnutls_dh_params_init", rc, host, errstr);
568 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
571 if (!exp_tls_dhparam)
573 DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
574 m.data = US std_dh_prime_default();
575 m.size = Ustrlen(m.data);
577 else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
578 use_file_in_spool = TRUE;
579 else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
581 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
584 else if (exp_tls_dhparam[0] != '/')
586 if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
587 return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
588 m.size = Ustrlen(m.data);
591 filename = exp_tls_dhparam;
595 if ((rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM)))
596 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
597 DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
601 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
602 /* If you change this constant, also change dh_param_fn_ext so that we can use a
603 different filename and ensure we have sufficient bits. */
605 if (!(dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL)))
606 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr);
608 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
611 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
613 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
617 /* Some clients have hard-coded limits. */
618 if (dh_bits > tls_dh_max_bits)
621 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
623 dh_bits = tls_dh_max_bits;
626 if (use_file_in_spool)
628 if (!string_format(filename_buf, sizeof(filename_buf),
629 "%s/gnutls-params-%d", spool_directory, dh_bits))
630 return tls_error(US"overlong filename", NULL, NULL, errstr);
631 filename = filename_buf;
634 /* Open the cache file for reading and if successful, read it and set up the
637 if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
643 if (fstat(fd, &statbuf) < 0) /* EIO */
647 return tls_error_sys(US"TLS cache stat failed", saved_errno, NULL, errstr);
649 if (!S_ISREG(statbuf.st_mode))
652 return tls_error(US"TLS cache not a file", NULL, NULL, errstr);
654 if (!(fp = fdopen(fd, "rb")))
658 return tls_error_sys(US"fdopen(TLS cache stat fd) failed",
659 saved_errno, NULL, errstr);
662 m.size = statbuf.st_size;
663 if (!(m.data = store_malloc(m.size)))
666 return tls_error_sys(US"malloc failed", errno, NULL, errstr);
668 if (!(sz = fread(m.data, m.size, 1, fp)))
673 return tls_error_sys(US"fread failed", saved_errno, NULL, errstr);
677 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
680 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
681 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
684 /* If the file does not exist, fall through to compute new data and cache it.
685 If there was any other opening error, it is serious. */
687 else if (errno == ENOENT)
691 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
694 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
697 /* If ret < 0, either the cache file does not exist, or the data it contains
698 is not useful. One particular case of this is when upgrading from an older
699 release of Exim in which the data was stored in a different format. We don't
700 try to be clever and support both formats; we just regenerate new data in this
706 unsigned int dh_bits_gen = dh_bits;
708 if ((PATH_MAX - Ustrlen(filename)) < 10)
709 return tls_error(US"Filename too long to generate replacement",
710 filename, NULL, errstr);
712 temp_fn = string_copy(US"%s.XXXXXXX");
713 if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */
714 return tls_error_sys(US"Unable to open temp file", errno, NULL, errstr);
715 (void)exim_chown(temp_fn, exim_uid, exim_gid); /* Probably not necessary */
717 /* GnuTLS overshoots! If we ask for 2236, we might get 2237 or more. But
718 there's no way to ask GnuTLS how many bits there really are. We can ask
719 how many bits were used in a TLS session, but that's it! The prime itself
720 is hidden behind too much abstraction. So we ask for less, and proceed on
721 a wing and a prayer. First attempt, subtracted 3 for 2233 and got 2240. */
723 if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
725 dh_bits_gen = dh_bits - 10;
727 debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
732 debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
734 if ((rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen)))
735 return tls_error_gnu(US"gnutls_dh_params_generate2", rc, host, errstr);
737 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
738 and I confirmed that a NULL call to get the size first is how the GnuTLS
739 sample apps handle this. */
743 if ( (rc = gnutls_dh_params_export_pkcs3(dh_server_params,
744 GNUTLS_X509_FMT_PEM, m.data, &sz))
745 && rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
746 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3(NULL) sizing",
749 if (!(m.data = store_malloc(m.size)))
750 return tls_error_sys(US"memory allocation failed", errno, NULL, errstr);
752 /* this will return a size 1 less than the allocation size above */
753 if ((rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
757 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3() real", rc, host, errstr);
759 m.size = sz; /* shrink by 1, probably */
761 if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size)
764 return tls_error_sys(US"TLS cache write D-H params failed",
765 errno, NULL, errstr);
768 if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
769 return tls_error_sys(US"TLS cache write D-H params final newline failed",
770 errno, NULL, errstr);
772 if ((rc = close(fd)))
773 return tls_error_sys(US"TLS cache write close() failed", errno, NULL, errstr);
775 if (Urename(temp_fn, filename) < 0)
776 return tls_error_sys(string_sprintf("failed to rename \"%s\" as \"%s\"",
777 temp_fn, filename), errno, NULL, errstr);
779 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
782 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
790 /* Create and install a selfsigned certificate, for use in server mode */
793 tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr)
795 gnutls_x509_crt_t cert = NULL;
797 gnutls_x509_privkey_t pkey = NULL;
798 const uschar * where;
801 where = US"initialising pkey";
802 if ((rc = gnutls_x509_privkey_init(&pkey))) goto err;
804 where = US"initialising cert";
805 if ((rc = gnutls_x509_crt_init(&cert))) goto err;
807 where = US"generating pkey";
808 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
809 #ifdef SUPPORT_PARAM_TO_PK_BITS
810 # ifndef GNUTLS_SEC_PARAM_MEDIUM
811 # define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
813 gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
820 where = US"configuring cert";
822 if ( (rc = gnutls_x509_crt_set_version(cert, 3))
823 || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
824 || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
825 || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */
826 || (rc = gnutls_x509_crt_set_key(cert, pkey))
828 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
829 GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2))
830 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
831 GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15))
832 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
833 GNUTLS_OID_X520_COMMON_NAME, 0,
834 smtp_active_hostname, Ustrlen(smtp_active_hostname)))
838 where = US"signing cert";
839 if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err;
841 where = US"installing selfsign cert";
843 if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey)))
849 if (cert) gnutls_x509_crt_deinit(cert);
850 if (pkey) gnutls_x509_privkey_deinit(pkey);
854 rc = tls_error_gnu(where, rc, NULL, errstr);
861 /* Add certificate and key, from files.
864 Zero or negative: good. Negate value for certificate index if < 0.
865 Greater than zero: FAIL or DEFER code.
869 tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
870 uschar * certfile, uschar * keyfile, uschar ** errstr)
872 int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
873 CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
875 return tls_error_gnu(
876 string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
882 #if !defined(DISABLE_OCSP) && !defined(SUPPORT_GNUTLS_EXT_RAW_PARSE)
883 /* Load an OCSP proof from file for sending by the server. Called
884 on getting a status-request handshake message, for earlier versions
888 server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
889 gnutls_datum_t * ocsp_response)
892 DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr);
894 if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0)
896 DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n",
898 tls_in.ocsp = OCSP_NOT_RESP;
899 return GNUTLS_E_NO_CERTIFICATE_STATUS;
902 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
908 #ifdef SUPPORT_GNUTLS_EXT_RAW_PARSE
909 /* Make a note that we saw a status-request */
911 tls_server_clienthello_ext(void * ctx, unsigned tls_id,
912 const unsigned char *data, unsigned size)
914 /* https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml */
915 if (tls_id == 5) /* status_request */
917 DEBUG(D_tls) debug_printf("Seen status_request extension from client\n");
918 tls_in.ocsp = OCSP_NOT_RESP;
923 /* Callback for client-hello, on server, if we think we might serve stapled-OCSP */
925 tls_server_clienthello_cb(gnutls_session_t session, unsigned int htype,
926 unsigned when, unsigned int incoming, const gnutls_datum_t * msg)
928 /* Call fn for each extension seen. 3.6.3 onwards */
929 return gnutls_ext_raw_parse(NULL, tls_server_clienthello_ext, msg,
930 GNUTLS_EXT_RAW_FLAG_TLS_CLIENT_HELLO);
934 /* Make a note that we saw a status-response */
936 tls_server_servercerts_ext(void * ctx, unsigned tls_id,
937 const unsigned char *data, unsigned size)
939 /* debug_printf("%s %u\n", __FUNCTION__, tls_id); */
940 /* https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml */
941 if (FALSE && tls_id == 5) /* status_request */
943 DEBUG(D_tls) debug_printf("Seen status_request extension\n");
944 tls_in.ocsp = exim_testharness_disable_ocsp_validity_check
945 ? OCSP_VFY_NOT_TRIED : OCSP_VFIED; /* We know that GnuTLS verifies responses */
950 /* Callback for certificates packet, on server, if we think we might serve stapled-OCSP */
952 tls_server_servercerts_cb(gnutls_session_t session, unsigned int htype,
953 unsigned when, unsigned int incoming, const gnutls_datum_t * msg)
955 /* Call fn for each extension seen. 3.6.3 onwards */
958 return gnutls_ext_raw_parse(NULL, tls_server_servercerts_ext, msg, 0);
963 /*XXX in tls1.3 the cert-status travel as an extension next to the cert, in the
964 "Handshake Protocol: Certificate" record.
965 So we need to spot the Certificate handshake message, parse it and spot any status_request extension(s)
967 This is different to tls1.2 - where it is a separate record (wireshake term) / handshake message (gnutls term).
970 #if defined(EXPERIMENTAL_TLS_RESUME) || defined(SUPPORT_GNUTLS_EXT_RAW_PARSE)
971 /* Callback for certificate-status, on server. We sent stapled OCSP. */
973 tls_server_certstatus_cb(gnutls_session_t session, unsigned int htype,
974 unsigned when, unsigned int incoming, const gnutls_datum_t * msg)
976 DEBUG(D_tls) debug_printf("Sending certificate-status\n"); /*XXX we get this for tls1.2 but not for 1.3 */
977 #ifdef SUPPORT_SRV_OCSP_STACK
978 tls_in.ocsp = exim_testharness_disable_ocsp_validity_check
979 ? OCSP_VFY_NOT_TRIED : OCSP_VFIED; /* We know that GnuTLS verifies responses */
981 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
986 /* Callback for handshake messages, on server */
988 tls_server_hook_cb(gnutls_session_t sess, u_int htype, unsigned when,
989 unsigned incoming, const gnutls_datum_t * msg)
991 /* debug_printf("%s: htype %u\n", __FUNCTION__, htype); */
994 # ifdef SUPPORT_GNUTLS_EXT_RAW_PARSE
995 case GNUTLS_HANDSHAKE_CLIENT_HELLO:
996 return tls_server_clienthello_cb(sess, htype, when, incoming, msg);
997 case GNUTLS_HANDSHAKE_CERTIFICATE_PKT:
998 return tls_server_servercerts_cb(sess, htype, when, incoming, msg);
1000 case GNUTLS_HANDSHAKE_CERTIFICATE_STATUS:
1001 return tls_server_certstatus_cb(sess, htype, when, incoming, msg);
1002 # ifdef EXPERIMENTAL_TLS_RESUME
1003 case GNUTLS_HANDSHAKE_NEW_SESSION_TICKET:
1004 return tls_server_ticket_cb(sess, htype, when, incoming, msg);
1013 #if !defined(DISABLE_OCSP) && defined(SUPPORT_GNUTLS_EXT_RAW_PARSE)
1015 tls_server_testharness_ocsp_fiddle(void)
1017 extern char ** environ;
1018 if (environ) for (uschar ** p = USS environ; *p; p++)
1019 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1021 DEBUG(D_tls) debug_printf("Permitting known bad OCSP response\n");
1022 exim_testharness_disable_ocsp_validity_check = TRUE;
1027 /*************************************************
1028 * Variables re-expanded post-SNI *
1029 *************************************************/
1031 /* Called from both server and client code, via tls_init(), and also from
1032 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
1034 We can tell the two apart by state->received_sni being non-NULL in callback.
1036 The callback should not call us unless state->trigger_sni_changes is true,
1037 which we are responsible for setting on the first pass through.
1040 state exim_gnutls_state_st *
1041 errstr error string pointer
1043 Returns: OK/DEFER/FAIL
1047 tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
1049 struct stat statbuf;
1051 const host_item *host = state->host; /* macro should be reconsidered? */
1052 uschar *saved_tls_certificate = NULL;
1053 uschar *saved_tls_privatekey = NULL;
1054 uschar *saved_tls_verify_certificates = NULL;
1055 uschar *saved_tls_crl = NULL;
1058 /* We check for tls_sni *before* expansion. */
1059 if (!host) /* server */
1060 if (!state->received_sni)
1062 if ( state->tls_certificate
1063 && ( Ustrstr(state->tls_certificate, US"tls_sni")
1064 || Ustrstr(state->tls_certificate, US"tls_in_sni")
1065 || Ustrstr(state->tls_certificate, US"tls_out_sni")
1068 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
1069 state->trigger_sni_changes = TRUE;
1074 /* useful for debugging */
1075 saved_tls_certificate = state->exp_tls_certificate;
1076 saved_tls_privatekey = state->exp_tls_privatekey;
1077 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
1078 saved_tls_crl = state->exp_tls_crl;
1081 if ((rc = gnutls_certificate_allocate_credentials(&state->x509_cred)))
1082 return tls_error_gnu(US"gnutls_certificate_allocate_credentials",
1085 #ifdef SUPPORT_SRV_OCSP_STACK
1086 gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
1088 # if !defined(DISABLE_OCSP) && defined(SUPPORT_GNUTLS_EXT_RAW_PARSE)
1089 if (!host && tls_ocsp_file)
1091 if (f.running_in_test_harness)
1092 tls_server_testharness_ocsp_fiddle();
1094 if (exim_testharness_disable_ocsp_validity_check)
1095 gnutls_certificate_set_flags(state->x509_cred,
1096 GNUTLS_CERTIFICATE_API_V2 | GNUTLS_CERTIFICATE_SKIP_OCSP_RESPONSE_CHECK);
1101 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
1102 state members, assuming consistent naming; and expand_check() returns
1103 false if expansion failed, unless expansion was forced to fail. */
1105 /* check if we at least have a certificate, before doing expensive
1108 if (!expand_check_tlsvar(tls_certificate, errstr))
1111 /* certificate is mandatory in server, optional in client */
1113 if ( !state->exp_tls_certificate
1114 || !*state->exp_tls_certificate
1117 return tls_install_selfsign(state, errstr);
1119 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
1121 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr))
1124 /* tls_privatekey is optional, defaulting to same file as certificate */
1126 if (!state->tls_privatekey || !*state->tls_privatekey)
1128 state->tls_privatekey = state->tls_certificate;
1129 state->exp_tls_privatekey = state->exp_tls_certificate;
1133 if (state->exp_tls_certificate && *state->exp_tls_certificate)
1135 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
1136 state->exp_tls_certificate, state->exp_tls_privatekey);
1138 if (state->received_sni)
1139 if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0
1140 && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0
1143 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
1147 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
1150 if (!host) /* server */
1152 const uschar * clist = state->exp_tls_certificate;
1153 const uschar * klist = state->exp_tls_privatekey;
1154 const uschar * olist;
1155 int csep = 0, ksep = 0, osep = 0, cnt = 0;
1156 uschar * cfile, * kfile, * ofile;
1157 #ifndef DISABLE_OCSP
1158 # ifdef SUPPORT_GNUTLS_EXT_RAW_PARSE
1159 gnutls_x509_crt_fmt_t ocsp_fmt = GNUTLS_X509_FMT_DER;
1162 if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
1167 while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
1169 if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
1170 return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
1171 else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
1175 int gnutls_cert_index = -rc;
1176 DEBUG(D_tls) debug_printf("TLS: cert/key %d %s registered\n",
1177 gnutls_cert_index, cfile);
1179 #ifndef DISABLE_OCSP
1182 /* Set the OCSP stapling server info */
1183 if (gnutls_buggy_ocsp)
1186 debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
1188 else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1190 DEBUG(D_tls) debug_printf("OCSP response file %d = %s\n",
1191 gnutls_cert_index, ofile);
1192 # ifdef SUPPORT_GNUTLS_EXT_RAW_PARSE
1193 if (Ustrncmp(ofile, US"PEM ", 4) == 0)
1195 ocsp_fmt = GNUTLS_X509_FMT_PEM;
1198 else if (Ustrncmp(ofile, US"DER ", 4) == 0)
1200 ocsp_fmt = GNUTLS_X509_FMT_DER;
1204 if ((rc = gnutls_certificate_set_ocsp_status_request_file2(
1205 state->x509_cred, CCS ofile, gnutls_cert_index,
1207 return tls_error_gnu(
1208 US"gnutls_certificate_set_ocsp_status_request_file2",
1211 debug_printf(" %d response%s loaded\n", rc, rc>1 ? "s":"");
1213 /* Arrange callbacks for OCSP request observability */
1215 gnutls_handshake_set_hook_function(state->session,
1216 GNUTLS_HANDSHAKE_ANY, GNUTLS_HOOK_POST, tls_server_hook_cb);
1219 # if defined(SUPPORT_SRV_OCSP_STACK)
1220 if ((rc = gnutls_certificate_set_ocsp_status_request_function2(
1221 state->x509_cred, gnutls_cert_index,
1222 server_ocsp_stapling_cb, ofile)))
1223 return tls_error_gnu(
1224 US"gnutls_certificate_set_ocsp_status_request_function2",
1232 debug_printf("oops; multiple OCSP files not supported\n");
1235 gnutls_certificate_set_ocsp_status_request_function(
1236 state->x509_cred, server_ocsp_stapling_cb, ofile);
1238 # endif /* SUPPORT_GNUTLS_EXT_RAW_PARSE */
1241 DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
1243 #endif /* DISABLE_OCSP */
1248 if (0 < (rc = tls_add_certfile(state, host,
1249 state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
1251 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
1254 } /* tls_certificate */
1257 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
1258 provided. Experiment shows that, if the certificate file is empty, an unhelpful
1259 error message is provided. However, if we just refrain from setting anything up
1260 in that case, certificate verification fails, which seems to be the correct
1263 if (state->tls_verify_certificates && *state->tls_verify_certificates)
1265 if (!expand_check_tlsvar(tls_verify_certificates, errstr))
1267 #ifndef SUPPORT_SYSDEFAULT_CABUNDLE
1268 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1269 state->exp_tls_verify_certificates = NULL;
1271 if (state->tls_crl && *state->tls_crl)
1272 if (!expand_check_tlsvar(tls_crl, errstr))
1275 if (!(state->exp_tls_verify_certificates &&
1276 *state->exp_tls_verify_certificates))
1279 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
1280 /* With no tls_verify_certificates, we ignore tls_crl too */
1287 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
1291 #ifdef SUPPORT_SYSDEFAULT_CABUNDLE
1292 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1293 cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred);
1297 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
1299 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat '%s' "
1300 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
1305 #ifndef SUPPORT_CA_DIR
1306 /* The test suite passes in /dev/null; we could check for that path explicitly,
1307 but who knows if someone has some weird FIFO which always dumps some certs, or
1308 other weirdness. The thing we really want to check is that it's not a
1309 directory, since while OpenSSL supports that, GnuTLS does not.
1310 So s/!S_ISREG/S_ISDIR/ and change some messaging ... */
1311 if (S_ISDIR(statbuf.st_mode))
1314 debug_printf("verify certificates path is a dir: \"%s\"\n",
1315 state->exp_tls_verify_certificates);
1316 log_write(0, LOG_MAIN|LOG_PANIC,
1317 "tls_verify_certificates \"%s\" is a directory",
1318 state->exp_tls_verify_certificates);
1323 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
1324 state->exp_tls_verify_certificates, statbuf.st_size);
1326 if (statbuf.st_size == 0)
1329 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
1335 #ifdef SUPPORT_CA_DIR
1336 (statbuf.st_mode & S_IFMT) == S_IFDIR
1338 gnutls_certificate_set_x509_trust_dir(state->x509_cred,
1339 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM)
1342 gnutls_certificate_set_x509_trust_file(state->x509_cred,
1343 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
1345 #ifdef SUPPORT_CA_DIR
1346 /* Mimic the behaviour with OpenSSL of not advertising a usable-cert list
1347 when using the directory-of-certs config model. */
1349 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1350 gnutls_certificate_send_x509_rdn_sequence(state->session, 1);
1355 return tls_error_gnu(US"setting certificate trust", cert_count, host, errstr);
1357 debug_printf("Added %d certificate authorities.\n", cert_count);
1359 if (state->tls_crl && *state->tls_crl &&
1360 state->exp_tls_crl && *state->exp_tls_crl)
1362 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
1363 if ((cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
1364 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM)) < 0)
1365 return tls_error_gnu(US"gnutls_certificate_set_x509_crl_file",
1366 cert_count, host, errstr);
1368 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
1377 /*************************************************
1378 * Set X.509 state variables *
1379 *************************************************/
1381 /* In GnuTLS, the registered cert/key are not replaced by a later
1382 set of a cert/key, so for SNI support we need a whole new x509_cred
1383 structure. Which means various other non-re-expanded pieces of state
1384 need to be re-set in the new struct, so the setting logic is pulled
1388 state exim_gnutls_state_st *
1389 errstr error string pointer
1391 Returns: OK/DEFER/FAIL
1395 tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
1398 const host_item *host = state->host; /* macro should be reconsidered? */
1400 #ifndef GNUTLS_AUTO_DHPARAMS
1401 /* Create D-H parameters, or read them from the cache file. This function does
1402 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
1403 client-side params. */
1407 if (!dh_server_params)
1408 if ((rc = init_server_dh(errstr)) != OK) return rc;
1410 /* Unnecessary & discouraged with 3.6.0 or later */
1411 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
1415 /* Link the credentials to the session. */
1417 if ((rc = gnutls_credentials_set(state->session,
1418 GNUTLS_CRD_CERTIFICATE, state->x509_cred)))
1419 return tls_error_gnu(US"gnutls_credentials_set", rc, host, errstr);
1424 /*************************************************
1425 * Initialize for GnuTLS *
1426 *************************************************/
1429 #ifndef DISABLE_OCSP
1432 tls_is_buggy_ocsp(void)
1435 uschar maj, mid, mic;
1437 s = CUS gnutls_check_version(NULL);
1441 while (*s && *s != '.') s++;
1442 mid = atoi(CCS ++s);
1449 while (*s && *s != '.') s++;
1450 mic = atoi(CCS ++s);
1451 return mic <= (mid == 3 ? 16 : 3);
1460 /* Called from both server and client code. In the case of a server, errors
1461 before actual TLS negotiation return DEFER.
1464 host connected host, if client; NULL if server
1465 certificate certificate file
1466 privatekey private key file
1467 sni TLS SNI to send, sometimes when client; else NULL
1470 require_ciphers tls_require_ciphers setting
1471 caller_state returned state-info structure
1472 errstr error string pointer
1474 Returns: OK/DEFER/FAIL
1479 const host_item *host,
1480 const uschar *certificate,
1481 const uschar *privatekey,
1485 const uschar *require_ciphers,
1486 exim_gnutls_state_st **caller_state,
1490 exim_gnutls_state_st * state;
1493 const char * errpos;
1496 if (!exim_gnutls_base_init_done)
1498 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
1500 #ifdef HAVE_GNUTLS_PKCS11
1501 /* By default, gnutls_global_init will init PKCS11 support in auto mode,
1502 which loads modules from a config file, which sounds good and may be wanted
1503 by some sysadmin, but also means in common configurations that GNOME keyring
1504 environment variables are used and so breaks for users calling mailq.
1505 To prevent this, we init PKCS11 first, which is the documented approach. */
1506 if (!gnutls_allow_auto_pkcs11)
1507 if ((rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL)))
1508 return tls_error_gnu(US"gnutls_pkcs11_init", rc, host, errstr);
1511 if ((rc = gnutls_global_init()))
1512 return tls_error_gnu(US"gnutls_global_init", rc, host, errstr);
1514 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1517 gnutls_global_set_log_function(exim_gnutls_logger_cb);
1518 /* arbitrarily chosen level; bump up to 9 for more */
1519 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
1523 #ifndef DISABLE_OCSP
1524 if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp()))
1525 log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version");
1528 exim_gnutls_base_init_done = TRUE;
1533 /* For client-side sessions we allocate a context. This lets us run
1534 several in parallel. */
1535 int old_pool = store_pool;
1536 store_pool = POOL_PERM;
1537 state = store_get(sizeof(exim_gnutls_state_st), FALSE);
1538 store_pool = old_pool;
1540 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1542 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
1543 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
1547 state = &state_server;
1548 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1550 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
1551 rc = gnutls_init(&state->session, GNUTLS_SERVER);
1554 return tls_error_gnu(US"gnutls_init", rc, host, errstr);
1558 state->tls_certificate = certificate;
1559 state->tls_privatekey = privatekey;
1560 state->tls_require_ciphers = require_ciphers;
1561 state->tls_sni = sni;
1562 state->tls_verify_certificates = cas;
1563 state->tls_crl = crl;
1565 /* This handles the variables that might get re-expanded after TLS SNI;
1566 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
1569 debug_printf("Expanding various TLS configuration options for session credentials.\n");
1570 if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc;
1572 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
1573 requires a new structure afterwards. */
1575 if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc;
1577 /* set SNI in client, only */
1580 if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr))
1582 if (state->tlsp->sni && *state->tlsp->sni)
1585 debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni);
1586 sz = Ustrlen(state->tlsp->sni);
1587 if ((rc = gnutls_server_name_set(state->session,
1588 GNUTLS_NAME_DNS, state->tlsp->sni, sz)))
1589 return tls_error_gnu(US"gnutls_server_name_set", rc, host, errstr);
1592 else if (state->tls_sni)
1593 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
1594 "have an SNI set for a server [%s]\n", state->tls_sni);
1596 /* This is the priority string support,
1597 http://www.gnutls.org/manual/html_node/Priority-Strings.html
1598 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
1599 This was backwards incompatible, but means Exim no longer needs to track
1600 all algorithms and provide string forms for them. */
1603 if (state->tls_require_ciphers && *state->tls_require_ciphers)
1605 if (!expand_check_tlsvar(tls_require_ciphers, errstr))
1607 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
1609 p = state->exp_tls_require_ciphers;
1610 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", p);
1615 p = exim_default_gnutls_priority;
1617 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", p);
1620 if ((rc = gnutls_priority_init(&state->priority_cache, CCS p, &errpos)))
1621 return tls_error_gnu(string_sprintf(
1622 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
1623 p, errpos - CS p, errpos),
1626 if ((rc = gnutls_priority_set(state->session, state->priority_cache)))
1627 return tls_error_gnu(US"gnutls_priority_set", rc, host, errstr);
1629 /* This also sets the server ticket expiration time to the same, and
1630 the STEK rotation time to 3x. */
1632 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
1634 /* Reduce security in favour of increased compatibility, if the admin
1635 decides to make that trade-off. */
1636 if (gnutls_compat_mode)
1638 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
1639 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
1640 gnutls_session_enable_compatibility_mode(state->session);
1642 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
1646 *caller_state = state;
1652 /*************************************************
1653 * Extract peer information *
1654 *************************************************/
1656 static const uschar *
1657 cipher_stdname_kcm(gnutls_kx_algorithm_t kx, gnutls_cipher_algorithm_t cipher,
1658 gnutls_mac_algorithm_t mac)
1661 gnutls_kx_algorithm_t kx_i;
1662 gnutls_cipher_algorithm_t cipher_i;
1663 gnutls_mac_algorithm_t mac_i;
1666 gnutls_cipher_suite_info(i, cs_id, &kx_i, &cipher_i, &mac_i, NULL);
1668 if (kx_i == kx && cipher_i == cipher && mac_i == mac)
1669 return cipher_stdname(cs_id[0], cs_id[1]);
1675 /* Called from both server and client code.
1676 Only this is allowed to set state->peerdn and state->have_set_peerdn
1677 and we use that to detect double-calls.
1679 NOTE: the state blocks last while the TLS connection is up, which is fine
1680 for logging in the server side, but for the client side, we log after teardown
1681 in src/deliver.c. While the session is up, we can twist about states and
1682 repoint tls_* globals, but those variables used for logging or other variable
1683 expansion that happens _after_ delivery need to have a longer life-time.
1685 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1686 doing this more than once per generation of a state context. We set them in
1687 the state context, and repoint tls_* to them. After the state goes away, the
1688 tls_* copies of the pointers remain valid and client delivery logging is happy.
1690 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1694 state exim_gnutls_state_st *
1695 errstr pointer to error string
1697 Returns: OK/DEFER/FAIL
1701 peer_status(exim_gnutls_state_st * state, uschar ** errstr)
1703 gnutls_session_t session = state->session;
1704 const gnutls_datum_t * cert_list;
1706 unsigned int cert_list_size = 0;
1707 gnutls_protocol_t protocol;
1708 gnutls_cipher_algorithm_t cipher;
1709 gnutls_kx_algorithm_t kx;
1710 gnutls_mac_algorithm_t mac;
1711 gnutls_certificate_type_t ct;
1712 gnutls_x509_crt_t crt;
1716 if (state->have_set_peerdn)
1718 state->have_set_peerdn = TRUE;
1720 state->peerdn = NULL;
1723 cipher = gnutls_cipher_get(session);
1724 protocol = gnutls_protocol_get_version(session);
1725 mac = gnutls_mac_get(session);
1727 #ifdef GNUTLS_TLS1_3
1728 protocol >= GNUTLS_TLS1_3 ? 0 :
1730 gnutls_kx_get(session);
1732 old_pool = store_pool;
1734 tls_support * tlsp = state->tlsp;
1735 store_pool = POOL_PERM;
1737 #ifdef SUPPORT_GNUTLS_SESS_DESC
1740 uschar * s = US gnutls_session_get_desc(session), c;
1742 /* Nikos M suggests we use this by preference. It returns like:
1743 (TLS1.3)-(ECDHE-SECP256R1)-(RSA-PSS-RSAE-SHA256)-(AES-256-GCM)
1745 For partial back-compat, put a colon after the TLS version, replace the
1746 )-( grouping with __, replace in-group - with _ and append the :keysize. */
1748 /* debug_printf("peer_status: gnutls_session_get_desc %s\n", s); */
1750 for (s++; (c = *s) && c != ')'; s++) g = string_catn(g, s, 1);
1751 g = string_catn(g, US":", 1);
1752 if (*s) s++; /* now on _ between groups */
1755 for (*++s && ++s; (c = *s) && c != ')'; s++) g = string_catn(g, c == '-' ? US"_" : s, 1);
1756 /* now on ) closing group */
1757 if ((c = *s) && *++s == '-') g = string_catn(g, US"__", 2);
1758 /* now on _ between groups */
1760 g = string_catn(g, US":", 1);
1761 g = string_cat(g, string_sprintf("%d", (int) gnutls_cipher_get_key_size(cipher) * 8));
1762 state->ciphersuite = string_from_gstring(g);
1765 state->ciphersuite = string_sprintf("%s:%s:%d",
1766 gnutls_protocol_get_name(protocol),
1767 gnutls_cipher_suite_get_name(kx, cipher, mac),
1768 (int) gnutls_cipher_get_key_size(cipher) * 8);
1770 /* I don't see a way that spaces could occur, in the current GnuTLS
1771 code base, but it was a concern in the old code and perhaps older GnuTLS
1772 releases did return "TLS 1.0"; play it safe, just in case. */
1774 for (uschar * p = state->ciphersuite; *p; p++) if (isspace(*p)) *p = '-';
1777 /* debug_printf("peer_status: ciphersuite %s\n", state->ciphersuite); */
1779 tlsp->cipher = state->ciphersuite;
1780 tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
1782 tlsp->cipher_stdname = cipher_stdname_kcm(kx, cipher, mac);
1784 store_pool = old_pool;
1787 cert_list = gnutls_certificate_get_peers(session, &cert_list_size);
1789 if (!cert_list || cert_list_size == 0)
1791 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1792 cert_list, cert_list_size);
1793 if (state->verify_requirement >= VERIFY_REQUIRED)
1794 return tls_error(US"certificate verification failed",
1795 US"no certificate received from peer", state->host, errstr);
1799 if ((ct = gnutls_certificate_type_get(session)) != GNUTLS_CRT_X509)
1801 const uschar * ctn = US gnutls_certificate_type_get_name(ct);
1803 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1804 if (state->verify_requirement >= VERIFY_REQUIRED)
1805 return tls_error(US"certificate verification not possible, unhandled type",
1806 ctn, state->host, errstr);
1810 #define exim_gnutls_peer_err(Label) \
1812 if (rc != GNUTLS_E_SUCCESS) \
1814 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \
1815 (Label), gnutls_strerror(rc)); \
1816 if (state->verify_requirement >= VERIFY_REQUIRED) \
1817 return tls_error_gnu((Label), rc, state->host, errstr); \
1822 rc = import_cert(&cert_list[0], &crt);
1823 exim_gnutls_peer_err(US"cert 0");
1825 state->tlsp->peercert = state->peercert = crt;
1828 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1829 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1831 exim_gnutls_peer_err(US"getting size for cert DN failed");
1832 return FAIL; /* should not happen */
1834 dn_buf = store_get_perm(sz, TRUE); /* tainted */
1835 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1836 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1838 state->peerdn = dn_buf;
1841 #undef exim_gnutls_peer_err
1847 /*************************************************
1848 * Verify peer certificate *
1849 *************************************************/
1851 /* Called from both server and client code.
1852 *Should* be using a callback registered with
1853 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1854 the peer information, but that's too new for some OSes.
1857 state exim_gnutls_state_st *
1858 errstr where to put an error message
1861 FALSE if the session should be rejected
1862 TRUE if the cert is okay or we just don't care
1866 verify_certificate(exim_gnutls_state_st * state, uschar ** errstr)
1871 DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n");
1873 rc = peer_status(state, errstr);
1875 if (state->verify_requirement == VERIFY_NONE)
1878 if (rc != OK || !state->peerdn)
1880 verify = GNUTLS_CERT_INVALID;
1881 *errstr = US"certificate not supplied";
1887 if (state->verify_requirement == VERIFY_DANE && state->host)
1889 /* Using dane_verify_session_crt() would be easy, as it does it all for us
1890 including talking to a DNS resolver. But we want to do that bit ourselves
1891 as the testsuite intercepts and fakes its own DNS environment. */
1896 const gnutls_datum_t * certlist =
1897 gnutls_certificate_get_peers(state->session, &lsize);
1898 int usage = tls_out.tlsa_usage;
1900 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1901 /* Split the TLSA records into two sets, TA and EE selectors. Run the
1902 dane-verification separately so that we know which selector verified;
1903 then we know whether to do name-verification (needed for TA but not EE). */
1905 if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE)))
1906 { /* a mixed-usage bundle */
1911 for(nrec = 0; state->dane_data_len[nrec]; ) nrec++;
1914 dd = store_get(nrec * sizeof(uschar *), FALSE);
1915 ddl = store_get(nrec * sizeof(int), FALSE);
1918 if ((rc = dane_state_init(&s, 0)))
1921 for (usage = DANESSL_USAGE_DANE_EE;
1922 usage >= DANESSL_USAGE_DANE_TA; usage--)
1923 { /* take records with this usage */
1924 for (j = i = 0; i < nrec; i++)
1925 if (state->dane_data[i][0] == usage)
1927 dd[j] = state->dane_data[i];
1928 ddl[j++] = state->dane_data_len[i];
1935 if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0)))
1938 if ((rc = dane_verify_crt_raw(s, certlist, lsize,
1939 gnutls_certificate_type_get(state->session),
1941 usage == DANESSL_USAGE_DANE_EE
1942 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1946 debug_printf("TLSA record problem: %s\n", dane_strerror(rc));
1948 else if (verify == 0) /* verification passed */
1956 if (rc) goto tlsa_prob;
1961 if ( (rc = dane_state_init(&s, 0))
1962 || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len,
1964 || (rc = dane_verify_crt_raw(s, certlist, lsize,
1965 gnutls_certificate_type_get(state->session),
1967 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1968 usage == (1 << DANESSL_USAGE_DANE_EE)
1969 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1978 if (verify != 0) /* verification failed */
1981 (void) dane_verification_status_print(verify, &str, 0);
1982 *errstr = US str.data; /* don't bother to free */
1986 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1987 /* If a TA-mode TLSA record was used for verification we must additionally
1988 verify the cert name (but not the CA chain). For EE-mode, skip it. */
1990 if (usage & (1 << DANESSL_USAGE_DANE_EE))
1993 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1996 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1997 /* Assume that the name on the A-record is the one that should be matching
1998 the cert. An alternate view is that the domain part of the email address
1999 is also permissible. */
2001 if (gnutls_x509_crt_check_hostname(state->tlsp->peercert,
2002 CS state->host->name))
2004 state->peer_dane_verified = state->peer_cert_verified = TRUE;
2009 #endif /*SUPPORT_DANE*/
2011 rc = gnutls_certificate_verify_peers2(state->session, &verify);
2014 /* Handle the result of verification. INVALID is set if any others are. */
2016 if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED))
2018 state->peer_cert_verified = FALSE;
2021 #ifdef GNUTLS_CERT_VFY_STATUS_PRINT
2026 if (gnutls_certificate_verification_status_print(verify,
2027 gnutls_certificate_type_get(state->session), &txt, 0)
2028 == GNUTLS_E_SUCCESS)
2030 debug_printf("%s\n", txt.data);
2031 gnutls_free(txt.data);
2035 *errstr = verify & GNUTLS_CERT_REVOKED
2036 ? US"certificate revoked" : US"certificate invalid";
2040 debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n",
2041 *errstr, state->peerdn ? state->peerdn : US"<unset>");
2043 if (state->verify_requirement >= VERIFY_REQUIRED)
2046 debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
2051 /* Client side, check the server's certificate name versus the name on the
2052 A-record for the connection we made. What to do for server side - what name
2053 to use for client? We document that there is no such checking for server
2056 if ( state->exp_tls_verify_cert_hostnames
2057 && !gnutls_x509_crt_check_hostname(state->tlsp->peercert,
2058 CS state->exp_tls_verify_cert_hostnames)
2062 debug_printf("TLS certificate verification failed: cert name mismatch\n");
2063 if (state->verify_requirement >= VERIFY_REQUIRED)
2068 state->peer_cert_verified = TRUE;
2069 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n",
2070 state->peerdn ? state->peerdn : US"<unset>");
2074 state->tlsp->peerdn = state->peerdn;
2079 *errstr = string_sprintf("TLSA record problem: %s",
2080 rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc));
2084 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
2091 /* ------------------------------------------------------------------------ */
2094 /* Logging function which can be registered with
2095 * gnutls_global_set_log_function()
2096 * gnutls_global_set_log_level() 0..9
2098 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
2100 exim_gnutls_logger_cb(int level, const char *message)
2102 size_t len = strlen(message);
2105 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
2108 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
2109 message[len-1] == '\n' ? "" : "\n");
2114 /* Called after client hello, should handle SNI work.
2115 This will always set tls_sni (state->received_sni) if available,
2116 and may trigger presenting different certificates,
2117 if state->trigger_sni_changes is TRUE.
2119 Should be registered with
2120 gnutls_handshake_set_post_client_hello_function()
2122 "This callback must return 0 on success or a gnutls error code to terminate the
2125 For inability to get SNI information, we return 0.
2126 We only return non-zero if re-setup failed.
2127 Only used for server-side TLS.
2131 exim_sni_handling_cb(gnutls_session_t session)
2133 char sni_name[MAX_HOST_LEN];
2134 size_t data_len = MAX_HOST_LEN;
2135 exim_gnutls_state_st *state = &state_server;
2136 unsigned int sni_type;
2138 uschar * dummy_errstr;
2140 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
2141 if (rc != GNUTLS_E_SUCCESS)
2144 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
2145 debug_printf("TLS: no SNI presented in handshake.\n");
2147 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
2148 gnutls_strerror(rc), rc);
2152 if (sni_type != GNUTLS_NAME_DNS)
2154 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
2158 /* We now have a UTF-8 string in sni_name */
2159 old_pool = store_pool;
2160 store_pool = POOL_PERM;
2161 state->received_sni = string_copy_taint(US sni_name, TRUE);
2162 store_pool = old_pool;
2164 /* We set this one now so that variable expansions below will work */
2165 state->tlsp->sni = state->received_sni;
2167 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
2168 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
2170 if (!state->trigger_sni_changes)
2173 if ((rc = tls_expand_session_files(state, &dummy_errstr)) != OK)
2175 /* If the setup of certs/etc failed before handshake, TLS would not have
2176 been offered. The best we can do now is abort. */
2177 return GNUTLS_E_APPLICATION_ERROR_MIN;
2180 rc = tls_set_remaining_x509(state, &dummy_errstr);
2181 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
2188 #ifndef DISABLE_EVENT
2190 We use this callback to get observability and detail-level control
2191 for an exim TLS connection (either direction), raising a tls:cert event
2192 for each cert in the chain presented by the peer. Any event
2193 can deny verification.
2195 Return 0 for the handshake to continue or non-zero to terminate.
2199 verify_cb(gnutls_session_t session)
2201 const gnutls_datum_t * cert_list;
2202 unsigned int cert_list_size = 0;
2203 gnutls_x509_crt_t crt;
2206 exim_gnutls_state_st * state = gnutls_session_get_ptr(session);
2208 if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size)))
2209 while (cert_list_size--)
2211 if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS)
2213 DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n",
2214 cert_list_size, gnutls_strerror(rc));
2218 state->tlsp->peercert = crt;
2219 if ((yield = event_raise(state->event_action,
2220 US"tls:cert", string_sprintf("%d", cert_list_size))))
2222 log_write(0, LOG_MAIN,
2223 "SSL verify denied by event-action: depth=%d: %s",
2224 cert_list_size, yield);
2225 return 1; /* reject */
2227 state->tlsp->peercert = NULL;
2237 ddump(gnutls_datum_t * d)
2239 gstring * g = string_get((d->size+1) * 2);
2240 uschar * s = d->data;
2241 for (unsigned i = d->size; i > 0; i--, s++)
2243 g = string_catn(g, US "0123456789abcdef" + (*s >> 4), 1);
2244 g = string_catn(g, US "0123456789abcdef" + (*s & 0xf), 1);
2250 post_handshake_debug(exim_gnutls_state_st * state)
2252 #ifdef SUPPORT_GNUTLS_SESS_DESC
2253 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2255 #ifdef SUPPORT_GNUTLS_KEYLOG
2257 # ifdef EXIM_HAVE_TLS1_3
2258 if (gnutls_protocol_get_version(state->session) < GNUTLS_TLS1_3)
2263 gnutls_datum_t c, s;
2265 /* we only want the client random and the master secret */
2266 gnutls_session_get_random(state->session, &c, &s);
2267 gnutls_session_get_master_secret(state->session, &s);
2270 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2273 debug_printf("To get keying info for TLS1.3 is hard:\n"
2274 " set environment variable SSLKEYLOGFILE to a filename writable by uid exim\n"
2275 " add SSLKEYLOGFILE to keep_environment in the exim config\n"
2276 " run exim as root\n"
2277 " if using sudo, add SSLKEYLOGFILE to env_keep in /etc/sudoers\n"
2278 " (works for TLS1.2 also, and saves cut-paste into file)\n");
2283 #ifdef EXPERIMENTAL_TLS_RESUME
2285 tls_server_ticket_cb(gnutls_session_t sess, u_int htype, unsigned when,
2286 unsigned incoming, const gnutls_datum_t * msg)
2288 DEBUG(D_tls) debug_printf("newticket cb\n");
2289 tls_in.resumption |= RESUME_CLIENT_REQUESTED;
2294 tls_server_resume_prehandshake(exim_gnutls_state_st * state)
2296 /* Should the server offer session resumption? */
2297 tls_in.resumption = RESUME_SUPPORTED;
2298 if (verify_check_host(&tls_resumption_hosts) == OK)
2301 /* GnuTLS appears to not do ticket overlap, but does emit a fresh ticket when
2302 an offered resumption is unacceptable. We lose one resumption per ticket
2303 lifetime, and sessions cannot be indefinitely re-used. There seems to be no
2304 way (3.6.7) of changing the default number of 2 TLS1.3 tickets issued, but at
2305 least they go out in a single packet. */
2307 if (!(rc = gnutls_session_ticket_enable_server(state->session,
2308 &server_sessticket_key)))
2309 tls_in.resumption |= RESUME_SERVER_TICKET;
2312 debug_printf("enabling session tickets: %s\n", US gnutls_strerror(rc));
2314 /* Try to tell if we see a ticket request */
2315 gnutls_handshake_set_hook_function(state->session,
2316 GNUTLS_HANDSHAKE_ANY, GNUTLS_HOOK_POST, tls_server_hook_cb);
2321 tls_server_resume_posthandshake(exim_gnutls_state_st * state)
2323 if (gnutls_session_resumption_requested(state->session))
2325 /* This tells us the client sent a full ticket. We use a
2326 callback on session-ticket request, elsewhere, to tell
2327 if a client asked for a ticket. */
2329 tls_in.resumption |= RESUME_CLIENT_SUGGESTED;
2330 DEBUG(D_tls) debug_printf("client requested resumption\n");
2332 if (gnutls_session_is_resumed(state->session))
2334 tls_in.resumption |= RESUME_USED;
2335 DEBUG(D_tls) debug_printf("Session resumed\n");
2339 /* ------------------------------------------------------------------------ */
2340 /* Exported functions */
2345 /*************************************************
2346 * Start a TLS session in a server *
2347 *************************************************/
2349 /* This is called when Exim is running as a server, after having received
2350 the STARTTLS command. It must respond to that command, and then negotiate
2354 require_ciphers list of allowed ciphers or NULL
2355 errstr pointer to error string
2357 Returns: OK on success
2358 DEFER for errors before the start of the negotiation
2359 FAIL for errors during the negotiation; the server can't
2364 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2367 exim_gnutls_state_st * state = NULL;
2369 /* Check for previous activation */
2370 if (tls_in.active.sock >= 0)
2372 tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr);
2373 smtp_printf("554 Already in TLS\r\n", FALSE);
2377 /* Initialize the library. If it fails, it will already have logged the error
2378 and sent an SMTP response. */
2380 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
2382 if ((rc = tls_init(NULL, tls_certificate, tls_privatekey,
2383 NULL, tls_verify_certificates, tls_crl,
2384 require_ciphers, &state, &tls_in, errstr)) != OK) return rc;
2386 #ifdef EXPERIMENTAL_TLS_RESUME
2387 tls_server_resume_prehandshake(state);
2390 /* If this is a host for which certificate verification is mandatory or
2391 optional, set up appropriately. */
2393 if (verify_check_host(&tls_verify_hosts) == OK)
2396 debug_printf("TLS: a client certificate will be required.\n");
2397 state->verify_requirement = VERIFY_REQUIRED;
2398 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2400 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2403 debug_printf("TLS: a client certificate will be requested but not required.\n");
2404 state->verify_requirement = VERIFY_OPTIONAL;
2405 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2410 debug_printf("TLS: a client certificate will not be requested.\n");
2411 state->verify_requirement = VERIFY_NONE;
2412 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2415 #ifndef DISABLE_EVENT
2418 state->event_action = event_action;
2419 gnutls_session_set_ptr(state->session, state);
2420 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2424 /* Register SNI handling; always, even if not in tls_certificate, so that the
2425 expansion variable $tls_sni is always available. */
2427 gnutls_handshake_set_post_client_hello_function(state->session,
2428 exim_sni_handling_cb);
2430 /* Set context and tell client to go ahead, except in the case of TLS startup
2431 on connection, where outputting anything now upsets the clients and tends to
2432 make them disconnect. We need to have an explicit fflush() here, to force out
2433 the response. Other smtp_printf() calls do not need it, because in non-TLS
2434 mode, the fflush() happens when smtp_getc() is called. */
2436 if (!state->tlsp->on_connect)
2438 smtp_printf("220 TLS go ahead\r\n", FALSE);
2442 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2443 that the GnuTLS library doesn't.
2444 From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you
2445 to set (and clear down afterwards) up a pull-timeout callback function that does
2446 a select, so we're no better off unless avoiding signals becomes an issue. */
2448 gnutls_transport_set_ptr2(state->session,
2449 (gnutls_transport_ptr_t)(long) fileno(smtp_in),
2450 (gnutls_transport_ptr_t)(long) fileno(smtp_out));
2451 state->fd_in = fileno(smtp_in);
2452 state->fd_out = fileno(smtp_out);
2454 sigalrm_seen = FALSE;
2455 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2457 rc = gnutls_handshake(state->session);
2458 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2461 if (rc != GNUTLS_E_SUCCESS)
2463 /* It seems that, except in the case of a timeout, we have to close the
2464 connection right here; otherwise if the other end is running OpenSSL it hangs
2465 until the server times out. */
2469 tls_error(US"gnutls_handshake", US"timed out", NULL, errstr);
2470 gnutls_db_remove_session(state->session);
2474 tls_error_gnu(US"gnutls_handshake", rc, NULL, errstr);
2475 (void) gnutls_alert_send_appropriate(state->session, rc);
2476 gnutls_deinit(state->session);
2477 gnutls_certificate_free_credentials(state->x509_cred);
2479 shutdown(state->fd_out, SHUT_WR);
2480 for (int i = 1024; fgetc(smtp_in) != EOF && i > 0; ) i--; /* drain skt */
2481 (void)fclose(smtp_out);
2482 (void)fclose(smtp_in);
2483 smtp_out = smtp_in = NULL;
2489 #ifdef EXPERIMENTAL_TLS_RESUME
2490 tls_server_resume_posthandshake(state);
2493 DEBUG(D_tls) post_handshake_debug(state);
2495 /* Verify after the fact */
2497 if (!verify_certificate(state, errstr))
2499 if (state->verify_requirement != VERIFY_OPTIONAL)
2501 (void) tls_error(US"certificate verification failed", *errstr, NULL, errstr);
2505 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
2509 /* Sets various Exim expansion variables; always safe within server */
2511 extract_exim_vars_from_tls_state(state);
2513 /* TLS has been set up. Adjust the input functions to read via TLS,
2514 and initialize appropriately. */
2516 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2518 receive_getc = tls_getc;
2519 receive_getbuf = tls_getbuf;
2520 receive_get_cache = tls_get_cache;
2521 receive_ungetc = tls_ungetc;
2522 receive_feof = tls_feof;
2523 receive_ferror = tls_ferror;
2524 receive_smtp_buffered = tls_smtp_buffered;
2533 tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state,
2534 smtp_transport_options_block * ob)
2536 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2538 state->exp_tls_verify_cert_hostnames =
2540 string_domain_utf8_to_alabel(host->name, NULL);
2545 debug_printf("TLS: server cert verification includes hostname: \"%s\".\n",
2546 state->exp_tls_verify_cert_hostnames);
2554 /* Given our list of RRs from the TLSA lookup, build a lookup block in
2555 GnuTLS-DANE's preferred format. Hang it on the state str for later
2556 use in DANE verification.
2558 We point at the dnsa data not copy it, so it must remain valid until
2559 after verification is done.*/
2562 dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa)
2566 const char ** dane_data;
2567 int * dane_data_len;
2570 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2571 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2572 ) if (rr->type == T_TLSA) i++;
2574 dane_data = store_get(i * sizeof(uschar *), FALSE);
2575 dane_data_len = store_get(i * sizeof(int), FALSE);
2578 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2579 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2580 ) if (rr->type == T_TLSA && rr->size > 3)
2582 const uschar * p = rr->data;
2583 /*XXX need somehow to mark rr and its data as tainted. Doues this mean copying it? */
2584 uint8_t usage = p[0], sel = p[1], type = p[2];
2587 debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size);
2589 if ( (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE)
2590 || (sel != 0 && sel != 1)
2595 case 0: /* Full: cannot check at present */
2597 case 1: if (rr->size != 3 + 256/8) continue; /* sha2-256 */
2599 case 2: if (rr->size != 3 + 512/8) continue; /* sha2-512 */
2604 tls_out.tlsa_usage |= 1<<usage;
2605 dane_data[i] = CS p;
2606 dane_data_len[i++] = rr->size;
2609 if (!i) return FALSE;
2611 dane_data[i] = NULL;
2612 dane_data_len[i] = 0;
2614 state->dane_data = (char * const *)dane_data;
2615 state->dane_data_len = dane_data_len;
2622 #ifdef EXPERIMENTAL_TLS_RESUME
2623 /* On the client, get any stashed session for the given IP from hints db
2624 and apply it to the ssl-connection for attempted resumption. Although
2625 there is a gnutls_session_ticket_enable_client() interface it is
2626 documented as unnecessary (as of 3.6.7) as "session tickets are emabled
2627 by deafult". There seems to be no way to disable them, so even hosts not
2628 enabled by the transport option will be sent a ticket request. We will
2629 however avoid storing and retrieving session information. */
2632 tls_retrieve_session(tls_support * tlsp, gnutls_session_t session,
2633 host_item * host, smtp_transport_options_block * ob)
2635 tlsp->resumption = RESUME_SUPPORTED;
2636 if (verify_check_given_host(CUSS &ob->tls_resumption_hosts, host) == OK)
2638 dbdata_tls_session * dt;
2640 open_db dbblock, * dbm_file;
2643 debug_printf("check for resumable session for %s\n", host->address);
2644 tlsp->host_resumable = TRUE;
2645 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
2646 if ((dbm_file = dbfn_open(US"tls", O_RDONLY, &dbblock, FALSE, FALSE)))
2648 /* Key for the db is the IP. We'd like to filter the retrieved session
2649 for ticket advisory expiry, but 3.6.1 seems to give no access to that */
2651 if ((dt = dbfn_read_with_length(dbm_file, host->address, &len)))
2652 if (!(rc = gnutls_session_set_data(session,
2653 CUS dt->session, (size_t)len - sizeof(dbdata_tls_session))))
2655 DEBUG(D_tls) debug_printf("good session\n");
2656 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
2658 else DEBUG(D_tls) debug_printf("setting session resumption data: %s\n",
2659 US gnutls_strerror(rc));
2660 dbfn_close(dbm_file);
2667 tls_save_session(tls_support * tlsp, gnutls_session_t session, const host_item * host)
2669 /* TLS 1.2 - we get both the callback and the direct posthandshake call,
2670 but this flag is not set until the second. TLS 1.3 it's the other way about.
2671 Keep both calls as the session data cannot be extracted before handshake
2674 if (gnutls_session_get_flags(session) & GNUTLS_SFLAGS_SESSION_TICKET)
2679 DEBUG(D_tls) debug_printf("server offered session ticket\n");
2680 tlsp->ticket_received = TRUE;
2681 tlsp->resumption |= RESUME_SERVER_TICKET;
2683 if (tlsp->host_resumable)
2684 if (!(rc = gnutls_session_get_data2(session, &tkt)))
2686 open_db dbblock, * dbm_file;
2687 int dlen = sizeof(dbdata_tls_session) + tkt.size;
2688 dbdata_tls_session * dt = store_get(dlen, TRUE);
2690 DEBUG(D_tls) debug_printf("session data size %u\n", (unsigned)tkt.size);
2691 memcpy(dt->session, tkt.data, tkt.size);
2692 gnutls_free(tkt.data);
2694 if ((dbm_file = dbfn_open(US"tls", O_RDWR, &dbblock, FALSE, FALSE)))
2696 /* key for the db is the IP */
2697 dbfn_delete(dbm_file, host->address);
2698 dbfn_write(dbm_file, host->address, dt, dlen);
2699 dbfn_close(dbm_file);
2702 debug_printf("wrote session db (len %u)\n", (unsigned)dlen);
2706 debug_printf("extract session data: %s\n", US gnutls_strerror(rc));
2711 /* With a TLS1.3 session, the ticket(s) are not seen until
2712 the first data read is attempted. And there's often two of them.
2713 Pick them up with this callback. We are also called for 1.2
2717 tls_client_ticket_cb(gnutls_session_t sess, u_int htype, unsigned when,
2718 unsigned incoming, const gnutls_datum_t * msg)
2720 exim_gnutls_state_st * state = gnutls_session_get_ptr(sess);
2721 tls_support * tlsp = state->tlsp;
2723 DEBUG(D_tls) debug_printf("newticket cb\n");
2725 if (!tlsp->ticket_received)
2726 tls_save_session(tlsp, sess, state->host);
2732 tls_client_resume_prehandshake(exim_gnutls_state_st * state,
2733 tls_support * tlsp, host_item * host,
2734 smtp_transport_options_block * ob)
2736 gnutls_session_set_ptr(state->session, state);
2737 gnutls_handshake_set_hook_function(state->session,
2738 GNUTLS_HANDSHAKE_NEW_SESSION_TICKET, GNUTLS_HOOK_POST, tls_client_ticket_cb);
2740 tls_retrieve_session(tlsp, state->session, host, ob);
2744 tls_client_resume_posthandshake(exim_gnutls_state_st * state,
2745 tls_support * tlsp, host_item * host)
2747 if (gnutls_session_is_resumed(state->session))
2749 DEBUG(D_tls) debug_printf("Session resumed\n");
2750 tlsp->resumption |= RESUME_USED;
2753 tls_save_session(tlsp, state->session, host);
2755 #endif /* EXPERIMENTAL_TLS_RESUME */
2758 /*************************************************
2759 * Start a TLS session in a client *
2760 *************************************************/
2762 /* Called from the smtp transport after STARTTLS has been accepted.
2765 cctx connection context
2766 conn_args connection details
2767 cookie datum for randomness (not used)
2768 tlsp record details of channel configuration here; must be non-NULL
2769 errstr error string pointer
2771 Returns: TRUE for success with TLS session context set in smtp context,
2776 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
2777 void * cookie ARG_UNUSED,
2778 tls_support * tlsp, uschar ** errstr)
2780 host_item * host = conn_args->host; /* for msgs and option-tests */
2781 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
2782 smtp_transport_options_block * ob = tb
2783 ? (smtp_transport_options_block *)tb->options_block
2784 : &smtp_transport_option_defaults;
2786 exim_gnutls_state_st * state = NULL;
2787 uschar * cipher_list = NULL;
2789 #ifndef DISABLE_OCSP
2791 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2792 BOOL request_ocsp = require_ocsp ? TRUE
2793 : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2796 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", cctx->sock);
2799 /* If dane is flagged, have either request or require dane for this host, and
2800 a TLSA record found. Therefore, dane verify required. Which implies cert must
2801 be requested and supplied, dane verify must pass, and cert verify irrelevant
2802 (incl. hostnames), and (caller handled) require_tls */
2804 if (conn_args->dane && ob->dane_require_tls_ciphers)
2806 /* not using expand_check_tlsvar because not yet in state */
2807 if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2808 &cipher_list, errstr))
2810 cipher_list = cipher_list && *cipher_list
2811 ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
2816 cipher_list = ob->tls_require_ciphers;
2818 if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
2819 ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
2820 cipher_list, &state, tlsp, errstr) != OK)
2824 int dh_min_bits = ob->tls_dh_min_bits;
2825 if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
2828 debug_printf("WARNING: tls_dh_min_bits far too low,"
2829 " clamping %d up to %d\n",
2830 dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
2831 dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
2834 DEBUG(D_tls) debug_printf("Setting D-H prime minimum"
2835 " acceptable bits to %d\n",
2837 gnutls_dh_set_prime_bits(state->session, dh_min_bits);
2840 /* Stick to the old behaviour for compatibility if tls_verify_certificates is
2841 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
2842 the specified host patterns if one of them is defined */
2845 if (conn_args->dane && dane_tlsa_load(state, &conn_args->tlsa_dnsa))
2848 debug_printf("TLS: server certificate DANE required.\n");
2849 state->verify_requirement = VERIFY_DANE;
2850 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2854 if ( ( state->exp_tls_verify_certificates
2855 && !ob->tls_verify_hosts
2856 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2858 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2861 tls_client_setup_hostname_checks(host, state, ob);
2863 debug_printf("TLS: server certificate verification required.\n");
2864 state->verify_requirement = VERIFY_REQUIRED;
2865 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2867 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2869 tls_client_setup_hostname_checks(host, state, ob);
2871 debug_printf("TLS: server certificate verification optional.\n");
2872 state->verify_requirement = VERIFY_OPTIONAL;
2873 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2878 debug_printf("TLS: server certificate verification not required.\n");
2879 state->verify_requirement = VERIFY_NONE;
2880 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2883 #ifndef DISABLE_OCSP
2884 /* supported since GnuTLS 3.1.3 */
2887 DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
2888 if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
2889 NULL, 0, NULL)) != OK)
2891 tls_error_gnu(US"cert-status-req", rc, state->host, errstr);
2894 tlsp->ocsp = OCSP_NOT_RESP;
2898 #ifdef EXPERIMENTAL_TLS_RESUME
2899 tls_client_resume_prehandshake(state, tlsp, host, ob);
2902 #ifndef DISABLE_EVENT
2903 if (tb && tb->event_action)
2905 state->event_action = tb->event_action;
2906 gnutls_session_set_ptr(state->session, state);
2907 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2911 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) cctx->sock);
2912 state->fd_in = cctx->sock;
2913 state->fd_out = cctx->sock;
2915 DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
2916 /* There doesn't seem to be a built-in timeout on connection. */
2918 sigalrm_seen = FALSE;
2919 ALARM(ob->command_timeout);
2921 rc = gnutls_handshake(state->session);
2922 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2925 if (rc != GNUTLS_E_SUCCESS)
2929 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
2930 tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
2933 tls_error_gnu(US"gnutls_handshake", rc, state->host, errstr);
2937 DEBUG(D_tls) post_handshake_debug(state);
2941 if (!verify_certificate(state, errstr))
2943 tls_error(US"certificate verification failed", *errstr, state->host, errstr);
2947 #ifndef DISABLE_OCSP
2952 gnutls_datum_t stapling;
2953 gnutls_ocsp_resp_t resp;
2954 gnutls_datum_t printed;
2958 # ifdef GNUTLS_OCSP_STATUS_REQUEST_GET2
2959 (rc = gnutls_ocsp_status_request_get2(state->session, idx, &stapling)) == 0;
2961 (rc = gnutls_ocsp_status_request_get(state->session, &stapling)) == 0;
2964 if ( (rc= gnutls_ocsp_resp_init(&resp)) == 0
2965 && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0
2966 && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_COMPACT, &printed)) == 0
2969 debug_printf("%.4096s", printed.data);
2970 gnutls_free(printed.data);
2973 (void) tls_error_gnu(US"ocsp decode", rc, state->host, errstr);
2975 (void) tls_error_gnu(US"ocsp decode", rc, state->host, errstr);
2978 if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
2980 tlsp->ocsp = OCSP_FAILED;
2981 tls_error(US"certificate status check failed", NULL, state->host, errstr);
2987 DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
2988 tlsp->ocsp = OCSP_VFIED;
2993 #ifdef EXPERIMENTAL_TLS_RESUME
2994 tls_client_resume_posthandshake(state, tlsp, host);
2997 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
2999 extract_exim_vars_from_tls_state(state);
3001 cctx->tls_ctx = state;
3008 /*************************************************
3009 * Close down a TLS session *
3010 *************************************************/
3012 /* This is also called from within a delivery subprocess forked from the
3013 daemon, to shut down the TLS library, without actually doing a shutdown (which
3014 would tamper with the TLS session in the parent process).
3017 ct_ctx client context pointer, or NULL for the one global server context
3018 shutdown 1 if TLS close-alert is to be sent,
3019 2 if also response to be waited for
3025 tls_close(void * ct_ctx, int shutdown)
3027 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
3028 tls_support * tlsp = state->tlsp;
3030 if (!tlsp || tlsp->active.sock < 0) return; /* TLS was not active */
3034 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
3035 shutdown > 1 ? " (with response-wait)" : "");
3038 gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
3042 if (!ct_ctx) /* server */
3044 receive_getc = smtp_getc;
3045 receive_getbuf = smtp_getbuf;
3046 receive_get_cache = smtp_get_cache;
3047 receive_ungetc = smtp_ungetc;
3048 receive_feof = smtp_feof;
3049 receive_ferror = smtp_ferror;
3050 receive_smtp_buffered = smtp_buffered;
3053 gnutls_deinit(state->session);
3054 gnutls_certificate_free_credentials(state->x509_cred);
3056 tlsp->active.sock = -1;
3057 tlsp->active.tls_ctx = NULL;
3058 /* Leave bits, peercert, cipher, peerdn, certificate_verified set, for logging */
3059 tls_channelbinding_b64 = NULL;
3062 if (state->xfer_buffer) store_free(state->xfer_buffer);
3063 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
3070 tls_refill(unsigned lim)
3072 exim_gnutls_state_st * state = &state_server;
3075 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
3076 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
3078 sigalrm_seen = FALSE;
3079 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
3082 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
3083 MIN(ssl_xfer_buffer_size, lim));
3084 while (inbytes == GNUTLS_E_AGAIN);
3086 if (smtp_receive_timeout > 0) ALARM_CLR(0);
3088 if (had_command_timeout) /* set by signal handler */
3089 smtp_command_timeout_exit(); /* does not return */
3090 if (had_command_sigterm)
3091 smtp_command_sigterm_exit();
3092 if (had_data_timeout)
3093 smtp_data_timeout_exit();
3094 if (had_data_sigint)
3095 smtp_data_sigint_exit();
3097 /* Timeouts do not get this far. A zero-byte return appears to mean that the
3098 TLS session has been closed down, not that the socket itself has been closed
3099 down. Revert to non-TLS handling. */
3103 DEBUG(D_tls) debug_printf("Got tls read timeout\n");
3104 state->xfer_error = TRUE;
3108 else if (inbytes == 0)
3110 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
3111 tls_close(NULL, TLS_NO_SHUTDOWN);
3115 /* Handle genuine errors */
3117 else if (inbytes < 0)
3119 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
3120 record_io_error(state, (int) inbytes, US"recv", NULL);
3121 state->xfer_error = TRUE;
3124 #ifndef DISABLE_DKIM
3125 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
3127 state->xfer_buffer_hwm = (int) inbytes;
3128 state->xfer_buffer_lwm = 0;
3132 /*************************************************
3133 * TLS version of getc *
3134 *************************************************/
3136 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
3137 it refills the buffer via the GnuTLS reading function.
3138 Only used by the server-side TLS.
3140 This feeds DKIM and should be used for all message-body reads.
3142 Arguments: lim Maximum amount to read/buffer
3143 Returns: the next character or EOF
3147 tls_getc(unsigned lim)
3149 exim_gnutls_state_st * state = &state_server;
3151 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
3152 if (!tls_refill(lim))
3153 return state->xfer_error ? EOF : smtp_getc(lim);
3155 /* Something in the buffer; return next uschar */
3157 return state->xfer_buffer[state->xfer_buffer_lwm++];
3161 tls_getbuf(unsigned * len)
3163 exim_gnutls_state_st * state = &state_server;
3167 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
3168 if (!tls_refill(*len))
3170 if (!state->xfer_error) return smtp_getbuf(len);
3175 if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
3177 buf = &state->xfer_buffer[state->xfer_buffer_lwm];
3178 state->xfer_buffer_lwm += size;
3187 #ifndef DISABLE_DKIM
3188 exim_gnutls_state_st * state = &state_server;
3189 int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm;
3191 dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n);
3197 tls_could_read(void)
3199 return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
3200 || gnutls_record_check_pending(state_server.session) > 0;
3206 /*************************************************
3207 * Read bytes from TLS channel *
3208 *************************************************/
3210 /* This does not feed DKIM, so if the caller uses this for reading message body,
3211 then the caller must feed DKIM.
3214 ct_ctx client context pointer, or NULL for the one global server context
3218 Returns: the number of bytes read
3219 -1 after a failed read, including EOF
3223 tls_read(void * ct_ctx, uschar *buff, size_t len)
3225 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
3231 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
3233 debug_printf("*** PROBABLY A BUG *** " \
3234 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
3235 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
3238 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
3239 state->session, buff, len);
3242 inbytes = gnutls_record_recv(state->session, buff, len);
3243 while (inbytes == GNUTLS_E_AGAIN);
3245 if (inbytes > 0) return inbytes;
3248 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
3252 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
3253 record_io_error(state, (int)inbytes, US"recv", NULL);
3262 /*************************************************
3263 * Write bytes down TLS channel *
3264 *************************************************/
3268 ct_ctx client context pointer, or NULL for the one global server context
3271 more more data expected soon
3273 Returns: the number of bytes after a successful write,
3274 -1 after a failed write
3278 tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
3282 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
3284 static BOOL corked = FALSE;
3286 if (more && !corked) gnutls_record_cork(state->session);
3289 DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
3290 buff, left, more ? ", more" : "");
3294 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
3298 outbytes = gnutls_record_send(state->session, buff, left);
3299 while (outbytes == GNUTLS_E_AGAIN);
3301 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
3304 DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
3305 record_io_error(state, outbytes, US"send", NULL);
3310 record_io_error(state, 0, US"send", US"TLS channel closed on write");
3321 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
3329 if (!more) (void) gnutls_record_uncork(state->session, 0);
3340 /*************************************************
3341 * Random number generation *
3342 *************************************************/
3344 /* Pseudo-random number generation. The result is not expected to be
3345 cryptographically strong but not so weak that someone will shoot themselves
3346 in the foot using it as a nonce in input in some email header scheme or
3347 whatever weirdness they'll twist this into. The result should handle fork()
3348 and avoid repeating sequences. OpenSSL handles that for us.
3352 Returns a random number in range [0, max-1]
3355 #ifdef HAVE_GNUTLS_RND
3357 vaguely_random_number(int max)
3361 uschar smallbuf[sizeof(r)];
3366 needed_len = sizeof(r);
3367 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
3368 asked for a number less than 10. */
3370 for (r = max, i = 0; r; ++i)
3376 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
3379 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
3380 return vaguely_random_number_fallback(max);
3383 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
3386 /* We don't particularly care about weighted results; if someone wants
3387 * smooth distribution and cares enough then they should submit a patch then. */
3390 #else /* HAVE_GNUTLS_RND */
3392 vaguely_random_number(int max)
3394 return vaguely_random_number_fallback(max);
3396 #endif /* HAVE_GNUTLS_RND */
3401 /*************************************************
3402 * Let tls_require_ciphers be checked at startup *
3403 *************************************************/
3405 /* The tls_require_ciphers option, if set, must be something which the
3408 Returns: NULL on success, or error message
3412 tls_validate_require_cipher(void)
3415 uschar *expciphers = NULL;
3416 gnutls_priority_t priority_cache;
3418 uschar * dummy_errstr;
3420 #define validate_check_rc(Label) do { \
3421 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
3422 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
3423 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
3425 if (exim_gnutls_base_init_done)
3426 log_write(0, LOG_MAIN|LOG_PANIC,
3427 "already initialised GnuTLS, Exim developer bug");
3429 #ifdef HAVE_GNUTLS_PKCS11
3430 if (!gnutls_allow_auto_pkcs11)
3432 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
3433 validate_check_rc(US"gnutls_pkcs11_init");
3436 rc = gnutls_global_init();
3437 validate_check_rc(US"gnutls_global_init()");
3438 exim_gnutls_base_init_done = TRUE;
3440 if (!(tls_require_ciphers && *tls_require_ciphers))
3441 return_deinit(NULL);
3443 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3445 return_deinit(US"failed to expand tls_require_ciphers");
3447 if (!(expciphers && *expciphers))
3448 return_deinit(NULL);
3451 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3453 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
3454 validate_check_rc(string_sprintf(
3455 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
3456 expciphers, errpos - CS expciphers, errpos));
3458 #undef return_deinit
3459 #undef validate_check_rc
3460 gnutls_global_deinit();
3468 /*************************************************
3469 * Report the library versions. *
3470 *************************************************/
3472 /* See a description in tls-openssl.c for an explanation of why this exists.
3474 Arguments: a FILE* to print the results to
3479 tls_version_report(FILE *f)
3481 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
3484 gnutls_check_version(NULL));
3487 #endif /*!MACRO_PREDEF*/
3490 /* End of tls-gnu.c */