1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2012 */
6 /* See the file NOTICE for conditions of use and distribution. */
8 /* 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 Mavroyanopoulos. 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>
46 gnutls_global_set_audit_log_function()
49 gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
52 /* Local static variables for GnuTLS */
54 /* Values for verify_requirement */
56 enum peer_verify_requirement { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED };
58 /* This holds most state for server or client; with this, we can set up an
59 outbound TLS-enabled connection in an ACL callout, while not stomping all
60 over the TLS variables available for expansion.
62 Some of these correspond to variables in globals.c; those variables will
63 be set to point to content in one of these instances, as appropriate for
64 the stage of the process lifetime.
66 Not handled here: globals tls_active, tls_bits, tls_cipher, tls_peerdn,
67 tls_certificate_verified, tls_channelbinding_b64, tls_sni.
70 typedef struct exim_gnutls_state {
71 gnutls_session_t session;
72 gnutls_certificate_credentials_t x509_cred;
73 gnutls_priority_t priority_cache;
74 enum peer_verify_requirement verify_requirement;
77 BOOL peer_cert_verified;
78 BOOL trigger_sni_changes;
80 const struct host_item *host;
85 const uschar *tls_certificate;
86 const uschar *tls_privatekey;
87 const uschar *tls_sni; /* client send only, not received */
88 const uschar *tls_verify_certificates;
89 const uschar *tls_crl;
90 const uschar *tls_require_ciphers;
91 uschar *exp_tls_certificate;
92 uschar *exp_tls_privatekey;
94 uschar *exp_tls_verify_certificates;
96 uschar *exp_tls_require_ciphers;
103 } exim_gnutls_state_st;
105 static const exim_gnutls_state_st exim_gnutls_state_init = {
106 NULL, NULL, NULL, VERIFY_NONE, -1, -1, FALSE, FALSE, FALSE,
107 NULL, NULL, NULL, NULL,
108 NULL, NULL, NULL, NULL, NULL, NULL,
109 NULL, NULL, NULL, NULL, NULL, NULL,
113 /* Not only do we have our own APIs which don't pass around state, assuming
114 it's held in globals, GnuTLS doesn't appear to let us register callback data
115 for callbacks, or as part of the session, so we have to keep a "this is the
116 context we're currently dealing with" pointer and rely upon being
117 single-threaded to keep from processing data on an inbound TLS connection while
118 talking to another TLS connection for an outbound check. This does mean that
119 there's no way for heart-beats to be responded to, for the duration of the
120 second connection. */
122 static exim_gnutls_state_st state_server, state_client;
123 static exim_gnutls_state_st *current_global_tls_state;
125 /* dh_params are initialised once within the lifetime of a process using TLS;
126 if we used TLS in a long-lived daemon, we'd have to reconsider this. But we
127 don't want to repeat this. */
129 static gnutls_dh_params_t dh_server_params = NULL;
131 /* No idea how this value was chosen; preserving it. Default is 3600. */
133 static const int ssl_session_timeout = 200;
135 static const char * const exim_default_gnutls_priority = "NORMAL";
137 /* Guard library core initialisation */
139 static BOOL exim_gnutls_base_init_done = FALSE;
142 /* ------------------------------------------------------------------------ */
145 #define MAX_HOST_LEN 255
147 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
148 the library logging; a value less than 0 disables the calls to set up logging
150 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
151 #define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
154 #ifndef EXIM_CLIENT_DH_MIN_BITS
155 #define EXIM_CLIENT_DH_MIN_BITS 1024
158 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
159 can ask for a bit-strength. Without that, we stick to the constant we had
161 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
162 #define EXIM_SERVER_DH_BITS_PRE2_12 1024
165 #define exim_gnutls_err_check(Label) do { \
166 if (rc != GNUTLS_E_SUCCESS) { return tls_error((Label), gnutls_strerror(rc), host); } } while (0)
168 #define expand_check_tlsvar(Varname) expand_check(state->Varname, US #Varname, &state->exp_##Varname)
170 #if GNUTLS_VERSION_NUMBER >= 0x020c00
171 #define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
172 #define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
173 #define HAVE_GNUTLS_RND
179 /* ------------------------------------------------------------------------ */
180 /* Callback declarations */
182 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
183 static void exim_gnutls_logger_cb(int level, const char *message);
186 static int exim_sni_handling_cb(gnutls_session_t session);
191 /* ------------------------------------------------------------------------ */
192 /* Static functions */
194 /*************************************************
196 *************************************************/
198 /* Called from lots of places when errors occur before actually starting to do
199 the TLS handshake, that is, while the session is still in clear. Always returns
200 DEFER for a server and FAIL for a client so that most calls can use "return
201 tls_error(...)" to do this processing and then give an appropriate return. A
202 single function is used for both server and client, because it is called from
203 some shared functions.
206 prefix text to include in the logged error
207 msg additional error string (may be NULL)
208 usually obtained from gnutls_strerror()
209 host NULL if setting up a server;
210 the connected host if setting up a client
212 Returns: OK/DEFER/FAIL
216 tls_error(const uschar *prefix, const char *msg, const host_item *host)
220 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s%s",
221 host->name, host->address, prefix, msg ? ": " : "", msg ? msg : "");
226 uschar *conn_info = smtp_get_connection_info();
227 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
229 log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s",
230 conn_info, prefix, msg ? ": " : "", msg ? msg : "");
238 /*************************************************
239 * Deal with logging errors during I/O *
240 *************************************************/
242 /* We have to get the identity of the peer from saved data.
245 state the current GnuTLS exim state container
246 rc the GnuTLS error code, or 0 if it's a local error
247 when text identifying read or write
248 text local error text when ec is 0
254 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
258 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
259 msg = CS string_sprintf("%s: %s", US gnutls_strerror(rc),
260 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
262 msg = gnutls_strerror(rc);
264 tls_error(when, msg, state->host);
270 /*************************************************
271 * Set various Exim expansion vars *
272 *************************************************/
274 /* We set various Exim global variables from the state, once a session has
275 been established. With TLS callouts, may need to change this to stack
276 variables, or just re-call it with the server state after client callout
279 Make sure anything set here is inset in tls_getc().
283 tls_bits strength indicator
284 tls_certificate_verified bool indicator
285 tls_channelbinding_b64 for some SASL mechanisms
288 tls_sni a (UTF-8) string
290 current_global_tls_state for API limitations
293 state the relevant exim_gnutls_state_st *
297 extract_exim_vars_from_tls_state(exim_gnutls_state_st *state)
299 gnutls_cipher_algorithm_t cipher;
300 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
303 gnutls_datum_t channel;
306 current_global_tls_state = state;
308 tls_active = state->fd_out;
310 cipher = gnutls_cipher_get(state->session);
311 /* returns size in "bytes" */
312 tls_bits = gnutls_cipher_get_key_size(cipher) * 8;
314 tls_cipher = state->ciphersuite;
316 DEBUG(D_tls) debug_printf("cipher: %s\n", tls_cipher);
318 tls_certificate_verified = state->peer_cert_verified;
320 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
321 only available for use for authenticators while this TLS session is running. */
323 tls_channelbinding_b64 = NULL;
324 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
327 rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel);
329 DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc));
331 old_pool = store_pool;
332 store_pool = POOL_PERM;
333 tls_channelbinding_b64 = auth_b64encode(channel.data, (int)channel.size);
334 store_pool = old_pool;
335 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
339 tls_peerdn = state->peerdn;
341 tls_sni = state->received_sni;
347 /*************************************************
348 * Setup up DH parameters *
349 *************************************************/
351 /* Generating the D-H parameters may take a long time. They only need to
352 be re-generated every so often, depending on security policy. What we do is to
353 keep these parameters in a file in the spool directory. If the file does not
354 exist, we generate them. This means that it is easy to cause a regeneration.
356 The new file is written as a temporary file and renamed, so that an incomplete
357 file is never present. If two processes both compute some new parameters, you
358 waste a bit of effort, but it doesn't seem worth messing around with locking to
362 host NULL for server, server for client (for error handling)
364 Returns: OK/DEFER/FAIL
371 unsigned int dh_bits;
373 uschar filename[PATH_MAX];
375 host_item *host = NULL; /* dummy for macros */
377 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
379 rc = gnutls_dh_params_init(&dh_server_params);
380 exim_gnutls_err_check(US"gnutls_dh_params_init");
382 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
383 /* If you change this constant, also change dh_param_fn_ext so that we can use a
384 different filename and ensure we have sufficient bits. */
385 dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL);
387 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL);
389 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
392 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
394 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
398 /* Some clients have hard-coded limits. */
399 if (dh_bits > tls_dh_max_bits)
402 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
404 dh_bits = tls_dh_max_bits;
407 if (!string_format(filename, sizeof(filename),
408 "%s/gnutls-params-%d", spool_directory, dh_bits))
409 return tls_error(US"overlong filename", NULL, NULL);
411 /* Open the cache file for reading and if successful, read it and set up the
414 fd = Uopen(filename, O_RDONLY, 0);
421 if (fstat(fd, &statbuf) < 0) /* EIO */
425 return tls_error(US"TLS cache stat failed", strerror(saved_errno), NULL);
427 if (!S_ISREG(statbuf.st_mode))
430 return tls_error(US"TLS cache not a file", NULL, NULL);
432 fp = fdopen(fd, "rb");
437 return tls_error(US"fdopen(TLS cache stat fd) failed",
438 strerror(saved_errno), NULL);
441 m.size = statbuf.st_size;
442 m.data = malloc(m.size);
446 return tls_error(US"malloc failed", strerror(errno), NULL);
448 sz = fread(m.data, m.size, 1, fp);
454 return tls_error(US"fread failed", strerror(saved_errno), NULL);
458 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
460 exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3");
461 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
464 /* If the file does not exist, fall through to compute new data and cache it.
465 If there was any other opening error, it is serious. */
467 else if (errno == ENOENT)
471 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
474 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
477 /* If ret < 0, either the cache file does not exist, or the data it contains
478 is not useful. One particular case of this is when upgrading from an older
479 release of Exim in which the data was stored in a different format. We don't
480 try to be clever and support both formats; we just regenerate new data in this
487 if ((PATH_MAX - Ustrlen(filename)) < 10)
488 return tls_error(US"Filename too long to generate replacement",
491 temp_fn = string_copy(US "%s.XXXXXXX");
492 fd = mkstemp(CS temp_fn); /* modifies temp_fn */
494 return tls_error(US"Unable to open temp file", strerror(errno), NULL);
495 (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */
497 DEBUG(D_tls) debug_printf("generating %d bits Diffie-Hellman key ...\n", dh_bits);
498 rc = gnutls_dh_params_generate2(dh_server_params, dh_bits);
499 exim_gnutls_err_check(US"gnutls_dh_params_generate2");
501 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
502 and I confirmed that a NULL call to get the size first is how the GnuTLS
503 sample apps handle this. */
507 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
509 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
510 exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3(NULL) sizing");
512 m.data = malloc(m.size);
514 return tls_error(US"memory allocation failed", strerror(errno), NULL);
515 /* this will return a size 1 less than the allocation size above */
516 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
518 if (rc != GNUTLS_E_SUCCESS)
521 exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real");
523 m.size = sz; /* shrink by 1, probably */
525 sz = write_to_fd_buf(fd, m.data, (size_t) m.size);
529 return tls_error(US"TLS cache write D-H params failed",
530 strerror(errno), NULL);
533 sz = write_to_fd_buf(fd, US"\n", 1);
535 return tls_error(US"TLS cache write D-H params final newline failed",
536 strerror(errno), NULL);
540 return tls_error(US"TLS cache write close() failed",
541 strerror(errno), NULL);
543 if (Urename(temp_fn, filename) < 0)
544 return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
545 temp_fn, filename), strerror(errno), NULL);
547 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
550 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
557 /*************************************************
558 * Variables re-expanded post-SNI *
559 *************************************************/
561 /* Called from both server and client code, via tls_init(), and also from
562 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
564 We can tell the two apart by state->received_sni being non-NULL in callback.
566 The callback should not call us unless state->trigger_sni_changes is true,
567 which we are responsible for setting on the first pass through.
570 state exim_gnutls_state_st *
572 Returns: OK/DEFER/FAIL
576 tls_expand_session_files(exim_gnutls_state_st *state)
580 const host_item *host = state->host; /* macro should be reconsidered? */
581 uschar *saved_tls_certificate = NULL;
582 uschar *saved_tls_privatekey = NULL;
583 uschar *saved_tls_verify_certificates = NULL;
584 uschar *saved_tls_crl = NULL;
587 /* We check for tls_sni *before* expansion. */
590 if (!state->received_sni)
592 if (state->tls_certificate && Ustrstr(state->tls_certificate, US"tls_sni"))
594 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
595 state->trigger_sni_changes = TRUE;
600 /* useful for debugging */
601 saved_tls_certificate = state->exp_tls_certificate;
602 saved_tls_privatekey = state->exp_tls_privatekey;
603 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
604 saved_tls_crl = state->exp_tls_crl;
608 rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
609 exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials");
611 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
612 state members, assuming consistent naming; and expand_check() returns
613 false if expansion failed, unless expansion was forced to fail. */
615 /* check if we at least have a certificate, before doing expensive
618 if (!expand_check_tlsvar(tls_certificate))
621 /* certificate is mandatory in server, optional in client */
623 if ((state->exp_tls_certificate == NULL) ||
624 (*state->exp_tls_certificate == '\0'))
626 if (state->host == NULL)
627 return tls_error(US"no TLS server certificate is specified", NULL, NULL);
629 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
632 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey))
635 /* tls_privatekey is optional, defaulting to same file as certificate */
637 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
639 state->tls_privatekey = state->tls_certificate;
640 state->exp_tls_privatekey = state->exp_tls_certificate;
644 if (state->exp_tls_certificate && *state->exp_tls_certificate)
646 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
647 state->exp_tls_certificate, state->exp_tls_privatekey);
649 if (state->received_sni)
651 if ((Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0) &&
652 (Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0))
654 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
658 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
662 rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
663 CS state->exp_tls_certificate, CS state->exp_tls_privatekey,
664 GNUTLS_X509_FMT_PEM);
665 exim_gnutls_err_check(
666 string_sprintf("cert/key setup: cert=%s key=%s",
667 state->exp_tls_certificate, state->exp_tls_privatekey));
668 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
669 } /* tls_certificate */
671 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
672 provided. Experiment shows that, if the certificate file is empty, an unhelpful
673 error message is provided. However, if we just refrain from setting anything up
674 in that case, certificate verification fails, which seems to be the correct
677 if (state->tls_verify_certificates && *state->tls_verify_certificates)
679 if (!expand_check_tlsvar(tls_verify_certificates))
681 if (state->tls_crl && *state->tls_crl)
682 if (!expand_check_tlsvar(tls_crl))
685 if (!(state->exp_tls_verify_certificates &&
686 *state->exp_tls_verify_certificates))
689 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
690 /* With no tls_verify_certificates, we ignore tls_crl too */
697 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
701 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
703 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
704 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
709 /* The test suite passes in /dev/null; we could check for that path explicitly,
710 but who knows if someone has some weird FIFO which always dumps some certs, or
711 other weirdness. The thing we really want to check is that it's not a
712 directory, since while OpenSSL supports that, GnuTLS does not.
713 So s/!S_ISREG/S_ISDIR/ and change some messsaging ... */
714 if (S_ISDIR(statbuf.st_mode))
717 debug_printf("verify certificates path is a dir: \"%s\"\n",
718 state->exp_tls_verify_certificates);
719 log_write(0, LOG_MAIN|LOG_PANIC,
720 "tls_verify_certificates \"%s\" is a directory",
721 state->exp_tls_verify_certificates);
725 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
726 state->exp_tls_verify_certificates, statbuf.st_size);
728 if (statbuf.st_size == 0)
731 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
735 cert_count = gnutls_certificate_set_x509_trust_file(state->x509_cred,
736 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
740 exim_gnutls_err_check(US"gnutls_certificate_set_x509_trust_file");
742 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);
744 if (state->tls_crl && *state->tls_crl &&
745 state->exp_tls_crl && *state->exp_tls_crl)
747 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
748 cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
749 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM);
753 exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file");
755 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
764 /*************************************************
765 * Set X.509 state variables *
766 *************************************************/
768 /* In GnuTLS, the registered cert/key are not replaced by a later
769 set of a cert/key, so for SNI support we need a whole new x509_cred
770 structure. Which means various other non-re-expanded pieces of state
771 need to be re-set in the new struct, so the setting logic is pulled
775 state exim_gnutls_state_st *
777 Returns: OK/DEFER/FAIL
781 tls_set_remaining_x509(exim_gnutls_state_st *state)
784 const host_item *host = state->host; /* macro should be reconsidered? */
786 /* Create D-H parameters, or read them from the cache file. This function does
787 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
788 client-side params. */
792 if (!dh_server_params)
794 rc = init_server_dh();
795 if (rc != OK) return rc;
797 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
800 /* Link the credentials to the session. */
802 rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred);
803 exim_gnutls_err_check(US"gnutls_credentials_set");
808 /*************************************************
809 * Initialize for GnuTLS *
810 *************************************************/
812 /* Called from both server and client code. In the case of a server, errors
813 before actual TLS negotiation return DEFER.
816 host connected host, if client; NULL if server
817 certificate certificate file
818 privatekey private key file
819 sni TLS SNI to send, sometimes when client; else NULL
822 require_ciphers tls_require_ciphers setting
824 Returns: OK/DEFER/FAIL
829 const host_item *host,
830 const uschar *certificate,
831 const uschar *privatekey,
835 const uschar *require_ciphers,
836 exim_gnutls_state_st **caller_state)
838 exim_gnutls_state_st *state;
843 BOOL want_default_priorities;
845 if (!exim_gnutls_base_init_done)
847 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
849 rc = gnutls_global_init();
850 exim_gnutls_err_check(US"gnutls_global_init");
852 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
855 gnutls_global_set_log_function(exim_gnutls_logger_cb);
856 /* arbitrarily chosen level; bump upto 9 for more */
857 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
861 exim_gnutls_base_init_done = TRUE;
866 state = &state_client;
867 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
868 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
869 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
873 state = &state_server;
874 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
875 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
876 rc = gnutls_init(&state->session, GNUTLS_SERVER);
878 exim_gnutls_err_check(US"gnutls_init");
882 state->tls_certificate = certificate;
883 state->tls_privatekey = privatekey;
884 state->tls_require_ciphers = require_ciphers;
885 state->tls_sni = sni;
886 state->tls_verify_certificates = cas;
887 state->tls_crl = crl;
889 /* This handles the variables that might get re-expanded after TLS SNI;
890 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
893 debug_printf("Expanding various TLS configuration options for session credentials.\n");
894 rc = tls_expand_session_files(state);
895 if (rc != OK) return rc;
897 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
898 requires a new structure afterwards. */
900 rc = tls_set_remaining_x509(state);
901 if (rc != OK) return rc;
903 /* set SNI in client, only */
906 if (!expand_check_tlsvar(tls_sni))
908 if (state->exp_tls_sni && *state->exp_tls_sni)
911 debug_printf("Setting TLS client SNI to \"%s\"\n", state->exp_tls_sni);
912 sz = Ustrlen(state->exp_tls_sni);
913 rc = gnutls_server_name_set(state->session,
914 GNUTLS_NAME_DNS, state->exp_tls_sni, sz);
915 exim_gnutls_err_check(US"gnutls_server_name_set");
918 else if (state->tls_sni)
919 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
920 "have an SNI set for a client [%s]\n", state->tls_sni);
922 /* This is the priority string support,
923 http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html
924 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
925 This was backwards incompatible, but means Exim no longer needs to track
926 all algorithms and provide string forms for them. */
928 want_default_priorities = TRUE;
930 if (state->tls_require_ciphers && *state->tls_require_ciphers)
932 if (!expand_check_tlsvar(tls_require_ciphers))
934 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
936 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n",
937 state->exp_tls_require_ciphers);
939 rc = gnutls_priority_init(&state->priority_cache,
940 CS state->exp_tls_require_ciphers, &errpos);
941 want_default_priorities = FALSE;
942 p = state->exp_tls_require_ciphers;
945 if (want_default_priorities)
948 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n",
949 exim_default_gnutls_priority);
950 rc = gnutls_priority_init(&state->priority_cache,
951 exim_default_gnutls_priority, &errpos);
952 p = US exim_default_gnutls_priority;
955 exim_gnutls_err_check(string_sprintf(
956 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
957 p, errpos - CS p, errpos));
959 rc = gnutls_priority_set(state->session, state->priority_cache);
960 exim_gnutls_err_check(US"gnutls_priority_set");
962 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
964 /* Reduce security in favour of increased compatibility, if the admin
965 decides to make that trade-off. */
966 if (gnutls_compat_mode)
968 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
969 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
970 gnutls_session_enable_compatibility_mode(state->session);
972 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
976 *caller_state = state;
977 /* needs to happen before callbacks during handshake */
978 current_global_tls_state = state;
985 /*************************************************
986 * Extract peer information *
987 *************************************************/
989 /* Called from both server and client code.
990 Only this is allowed to set state->peerdn and state->have_set_peerdn
991 and we use that to detect double-calls.
993 NOTE: the state blocks last while the TLS connection is up, which is fine
994 for logging in the server side, but for the client side, we log after teardown
995 in src/deliver.c. While the session is up, we can twist about states and
996 repoint tls_* globals, but those variables used for logging or other variable
997 expansion that happens _after_ delivery need to have a longer life-time.
999 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1000 doing this more than once per generation of a state context. We set them in
1001 the state context, and repoint tls_* to them. After the state goes away, the
1002 tls_* copies of the pointers remain valid and client delivery logging is happy.
1004 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1008 state exim_gnutls_state_st *
1010 Returns: OK/DEFER/FAIL
1014 peer_status(exim_gnutls_state_st *state)
1016 uschar cipherbuf[256];
1017 const gnutls_datum *cert_list;
1019 unsigned int cert_list_size = 0;
1020 gnutls_protocol_t protocol;
1021 gnutls_cipher_algorithm_t cipher;
1022 gnutls_kx_algorithm_t kx;
1023 gnutls_mac_algorithm_t mac;
1024 gnutls_certificate_type_t ct;
1025 gnutls_x509_crt_t crt;
1029 if (state->have_set_peerdn)
1031 state->have_set_peerdn = TRUE;
1033 state->peerdn = NULL;
1036 cipher = gnutls_cipher_get(state->session);
1037 protocol = gnutls_protocol_get_version(state->session);
1038 mac = gnutls_mac_get(state->session);
1039 kx = gnutls_kx_get(state->session);
1041 string_format(cipherbuf, sizeof(cipherbuf),
1043 gnutls_protocol_get_name(protocol),
1044 gnutls_cipher_suite_get_name(kx, cipher, mac),
1045 (int) gnutls_cipher_get_key_size(cipher) * 8);
1047 /* I don't see a way that spaces could occur, in the current GnuTLS
1048 code base, but it was a concern in the old code and perhaps older GnuTLS
1049 releases did return "TLS 1.0"; play it safe, just in case. */
1050 for (p = cipherbuf; *p != '\0'; ++p)
1053 old_pool = store_pool;
1054 store_pool = POOL_PERM;
1055 state->ciphersuite = string_copy(cipherbuf);
1056 store_pool = old_pool;
1057 tls_cipher = state->ciphersuite;
1060 cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
1062 if (cert_list == NULL || cert_list_size == 0)
1064 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1065 cert_list, cert_list_size);
1066 if (state->verify_requirement == VERIFY_REQUIRED)
1067 return tls_error(US"certificate verification failed",
1068 "no certificate received from peer", state->host);
1072 ct = gnutls_certificate_type_get(state->session);
1073 if (ct != GNUTLS_CRT_X509)
1075 const char *ctn = gnutls_certificate_type_get_name(ct);
1077 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1078 if (state->verify_requirement == VERIFY_REQUIRED)
1079 return tls_error(US"certificate verification not possible, unhandled type",
1084 #define exim_gnutls_peer_err(Label) do { \
1085 if (rc != GNUTLS_E_SUCCESS) { \
1086 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", (Label), gnutls_strerror(rc)); \
1087 if (state->verify_requirement == VERIFY_REQUIRED) { return tls_error((Label), gnutls_strerror(rc), state->host); } \
1088 return OK; } } while (0)
1090 rc = gnutls_x509_crt_init(&crt);
1091 exim_gnutls_peer_err(US"gnutls_x509_crt_init (crt)");
1093 rc = gnutls_x509_crt_import(crt, &cert_list[0], GNUTLS_X509_FMT_DER);
1094 exim_gnutls_peer_err(US"failed to import certificate [gnutls_x509_crt_import(cert 0)]");
1096 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1097 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1099 exim_gnutls_peer_err(US"getting size for cert DN failed");
1100 return FAIL; /* should not happen */
1102 dn_buf = store_get_perm(sz);
1103 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1104 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1105 state->peerdn = dn_buf;
1108 #undef exim_gnutls_peer_err
1114 /*************************************************
1115 * Verify peer certificate *
1116 *************************************************/
1118 /* Called from both server and client code.
1119 *Should* be using a callback registered with
1120 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1121 the peer information, but that's too new for some OSes.
1124 state exim_gnutls_state_st *
1125 error where to put an error message
1128 FALSE if the session should be rejected
1129 TRUE if the cert is okay or we just don't care
1133 verify_certificate(exim_gnutls_state_st *state, const char **error)
1136 unsigned int verify;
1140 rc = peer_status(state);
1143 verify = GNUTLS_CERT_INVALID;
1144 *error = "not supplied";
1148 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1151 /* Handle the result of verification. INVALID seems to be set as well
1152 as REVOKED, but leave the test for both. */
1154 if ((rc < 0) || (verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0)
1156 state->peer_cert_verified = FALSE;
1158 *error = ((verify & GNUTLS_CERT_REVOKED) != 0) ? "revoked" : "invalid";
1161 debug_printf("TLS certificate verification failed (%s): peerdn=%s\n",
1162 *error, state->peerdn ? state->peerdn : US"<unset>");
1164 if (state->verify_requirement == VERIFY_REQUIRED)
1166 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1170 debug_printf("TLS verify failure overriden (host in tls_try_verify_hosts)\n");
1174 state->peer_cert_verified = TRUE;
1175 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n",
1176 state->peerdn ? state->peerdn : US"<unset>");
1179 tls_peerdn = state->peerdn;
1187 /* ------------------------------------------------------------------------ */
1190 /* Logging function which can be registered with
1191 * gnutls_global_set_log_function()
1192 * gnutls_global_set_log_level() 0..9
1194 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1196 exim_gnutls_logger_cb(int level, const char *message)
1198 size_t len = strlen(message);
1201 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1204 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1205 message[len-1] == '\n' ? "" : "\n");
1210 /* Called after client hello, should handle SNI work.
1211 This will always set tls_sni (state->received_sni) if available,
1212 and may trigger presenting different certificates,
1213 if state->trigger_sni_changes is TRUE.
1215 Should be registered with
1216 gnutls_handshake_set_post_client_hello_function()
1218 "This callback must return 0 on success or a gnutls error code to terminate the
1221 For inability to get SNI information, we return 0.
1222 We only return non-zero if re-setup failed.
1226 exim_sni_handling_cb(gnutls_session_t session)
1228 char sni_name[MAX_HOST_LEN];
1229 size_t data_len = MAX_HOST_LEN;
1230 exim_gnutls_state_st *state = current_global_tls_state;
1231 unsigned int sni_type;
1234 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
1235 if (rc != GNUTLS_E_SUCCESS)
1238 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
1239 debug_printf("TLS: no SNI presented in handshake.\n");
1241 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
1242 gnutls_strerror(rc), rc);
1247 if (sni_type != GNUTLS_NAME_DNS)
1249 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
1253 /* We now have a UTF-8 string in sni_name */
1254 old_pool = store_pool;
1255 store_pool = POOL_PERM;
1256 state->received_sni = string_copyn(US sni_name, data_len);
1257 store_pool = old_pool;
1259 /* We set this one now so that variable expansions below will work */
1260 tls_sni = state->received_sni;
1262 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
1263 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
1265 if (!state->trigger_sni_changes)
1268 rc = tls_expand_session_files(state);
1271 /* If the setup of certs/etc failed before handshake, TLS would not have
1272 been offered. The best we can do now is abort. */
1273 return GNUTLS_E_APPLICATION_ERROR_MIN;
1276 rc = tls_set_remaining_x509(state);
1277 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
1285 /* ------------------------------------------------------------------------ */
1286 /* Exported functions */
1291 /*************************************************
1292 * Start a TLS session in a server *
1293 *************************************************/
1295 /* This is called when Exim is running as a server, after having received
1296 the STARTTLS command. It must respond to that command, and then negotiate
1300 require_ciphers list of allowed ciphers or NULL
1302 Returns: OK on success
1303 DEFER for errors before the start of the negotiation
1304 FAIL for errors during the negotation; the server can't
1309 tls_server_start(const uschar *require_ciphers)
1313 exim_gnutls_state_st *state = NULL;
1315 /* Check for previous activation */
1316 /* nb: this will not be TLS callout safe, needs reworking as part of that. */
1318 if (tls_active >= 0)
1320 tls_error(US"STARTTLS received after TLS started", "", NULL);
1321 smtp_printf("554 Already in TLS\r\n");
1325 /* Initialize the library. If it fails, it will already have logged the error
1326 and sent an SMTP response. */
1328 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
1330 rc = tls_init(NULL, tls_certificate, tls_privatekey,
1331 NULL, tls_verify_certificates, tls_crl,
1332 require_ciphers, &state);
1333 if (rc != OK) return rc;
1335 /* If this is a host for which certificate verification is mandatory or
1336 optional, set up appropriately. */
1338 if (verify_check_host(&tls_verify_hosts) == OK)
1340 DEBUG(D_tls) debug_printf("TLS: a client certificate will be required.\n");
1341 state->verify_requirement = VERIFY_REQUIRED;
1342 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
1344 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1346 DEBUG(D_tls) debug_printf("TLS: a client certificate will be requested but not required.\n");
1347 state->verify_requirement = VERIFY_OPTIONAL;
1348 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
1352 DEBUG(D_tls) debug_printf("TLS: a client certificate will not be requested.\n");
1353 state->verify_requirement = VERIFY_NONE;
1354 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
1357 /* Register SNI handling; always, even if not in tls_certificate, so that the
1358 expansion variable $tls_sni is always available. */
1360 gnutls_handshake_set_post_client_hello_function(state->session,
1361 exim_sni_handling_cb);
1363 /* Set context and tell client to go ahead, except in the case of TLS startup
1364 on connection, where outputting anything now upsets the clients and tends to
1365 make them disconnect. We need to have an explicit fflush() here, to force out
1366 the response. Other smtp_printf() calls do not need it, because in non-TLS
1367 mode, the fflush() happens when smtp_getc() is called. */
1369 if (!tls_on_connect)
1371 smtp_printf("220 TLS go ahead\r\n");
1375 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1376 that the GnuTLS library doesn't. */
1378 gnutls_transport_set_ptr2(state->session,
1379 (gnutls_transport_ptr)fileno(smtp_in),
1380 (gnutls_transport_ptr)fileno(smtp_out));
1381 state->fd_in = fileno(smtp_in);
1382 state->fd_out = fileno(smtp_out);
1384 sigalrm_seen = FALSE;
1385 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1388 rc = gnutls_handshake(state->session);
1389 } while ((rc == GNUTLS_E_AGAIN) ||
1390 (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));
1393 if (rc != GNUTLS_E_SUCCESS)
1395 tls_error(US"gnutls_handshake",
1396 sigalrm_seen ? "timed out" : gnutls_strerror(rc), NULL);
1397 /* It seems that, except in the case of a timeout, we have to close the
1398 connection right here; otherwise if the other end is running OpenSSL it hangs
1399 until the server times out. */
1403 (void)fclose(smtp_out);
1404 (void)fclose(smtp_in);
1410 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
1412 /* Verify after the fact */
1414 if (state->verify_requirement != VERIFY_NONE)
1416 if (!verify_certificate(state, &error))
1418 if (state->verify_requirement == VERIFY_OPTIONAL)
1421 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
1426 tls_error(US"certificate verification failed", error, NULL);
1432 /* Figure out peer DN, and if authenticated, etc. */
1434 rc = peer_status(state);
1435 if (rc != OK) return rc;
1437 /* Sets various Exim expansion variables; always safe within server */
1439 extract_exim_vars_from_tls_state(state);
1441 /* TLS has been set up. Adjust the input functions to read via TLS,
1442 and initialize appropriately. */
1444 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1446 receive_getc = tls_getc;
1447 receive_ungetc = tls_ungetc;
1448 receive_feof = tls_feof;
1449 receive_ferror = tls_ferror;
1450 receive_smtp_buffered = tls_smtp_buffered;
1458 /*************************************************
1459 * Start a TLS session in a client *
1460 *************************************************/
1462 /* Called from the smtp transport after STARTTLS has been accepted.
1465 fd the fd of the connection
1466 host connected host (for messages)
1467 addr the first address (not used)
1468 dhparam DH parameter file (ignored, we're a client)
1469 certificate certificate file
1470 privatekey private key file
1471 sni TLS SNI to send to remote host
1472 verify_certs file for certificate verify
1473 verify_crl CRL for verify
1474 require_ciphers list of allowed ciphers or NULL
1475 timeout startup timeout
1477 Returns: OK/DEFER/FAIL (because using common functions),
1478 but for a client, DEFER and FAIL have the same meaning
1482 tls_client_start(int fd, host_item *host,
1483 address_item *addr ARG_UNUSED, uschar *dhparam ARG_UNUSED,
1484 uschar *certificate, uschar *privatekey, uschar *sni,
1485 uschar *verify_certs, uschar *verify_crl,
1486 uschar *require_ciphers, int timeout)
1490 exim_gnutls_state_st *state = NULL;
1492 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);
1494 rc = tls_init(host, certificate, privatekey,
1495 sni, verify_certs, verify_crl, require_ciphers, &state);
1496 if (rc != OK) return rc;
1498 gnutls_dh_set_prime_bits(state->session, EXIM_CLIENT_DH_MIN_BITS);
1500 if (verify_certs == NULL)
1502 DEBUG(D_tls) debug_printf("TLS: server certificate verification not required\n");
1503 state->verify_requirement = VERIFY_NONE;
1504 /* we still ask for it, to log it, etc */
1505 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
1509 DEBUG(D_tls) debug_printf("TLS: server certificate verification required\n");
1510 state->verify_requirement = VERIFY_REQUIRED;
1511 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
1514 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr)fd);
1518 /* There doesn't seem to be a built-in timeout on connection. */
1520 sigalrm_seen = FALSE;
1524 rc = gnutls_handshake(state->session);
1525 } while ((rc == GNUTLS_E_AGAIN) ||
1526 (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));
1529 if (rc != GNUTLS_E_SUCCESS)
1530 return tls_error(US"gnutls_handshake",
1531 sigalrm_seen ? "timed out" : gnutls_strerror(rc), state->host);
1533 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
1537 if (state->verify_requirement != VERIFY_NONE &&
1538 !verify_certificate(state, &error))
1539 return tls_error(US"certificate verification failed", error, state->host);
1541 /* Figure out peer DN, and if authenticated, etc. */
1543 rc = peer_status(state);
1544 if (rc != OK) return rc;
1546 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
1548 extract_exim_vars_from_tls_state(state);
1556 /*************************************************
1557 * Close down a TLS session *
1558 *************************************************/
1560 /* This is also called from within a delivery subprocess forked from the
1561 daemon, to shut down the TLS library, without actually doing a shutdown (which
1562 would tamper with the TLS session in the parent process).
1564 Arguments: TRUE if gnutls_bye is to be called
1569 tls_close(BOOL shutdown)
1571 exim_gnutls_state_st *state = current_global_tls_state;
1573 if (tls_active < 0) return; /* TLS was not active */
1577 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n");
1578 gnutls_bye(state->session, GNUTLS_SHUT_WR);
1581 gnutls_deinit(state->session);
1583 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1585 if ((state_server.session == NULL) && (state_client.session == NULL))
1587 gnutls_global_deinit();
1588 exim_gnutls_base_init_done = FALSE;
1597 /*************************************************
1598 * TLS version of getc *
1599 *************************************************/
1601 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1602 it refills the buffer via the GnuTLS reading function.
1604 This feeds DKIM and should be used for all message-body reads.
1607 Returns: the next character or EOF
1613 exim_gnutls_state_st *state = current_global_tls_state;
1614 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
1618 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
1619 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
1621 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1622 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
1623 ssl_xfer_buffer_size);
1626 /* A zero-byte return appears to mean that the TLS session has been
1627 closed down, not that the socket itself has been closed down. Revert to
1628 non-TLS handling. */
1632 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1634 receive_getc = smtp_getc;
1635 receive_ungetc = smtp_ungetc;
1636 receive_feof = smtp_feof;
1637 receive_ferror = smtp_ferror;
1638 receive_smtp_buffered = smtp_buffered;
1640 gnutls_deinit(state->session);
1641 state->session = NULL;
1644 tls_certificate_verified = FALSE;
1645 tls_channelbinding_b64 = NULL;
1652 /* Handle genuine errors */
1654 else if (inbytes < 0)
1656 record_io_error(state, (int) inbytes, US"recv", NULL);
1657 state->xfer_error = 1;
1660 #ifndef DISABLE_DKIM
1661 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
1663 state->xfer_buffer_hwm = (int) inbytes;
1664 state->xfer_buffer_lwm = 0;
1667 /* Something in the buffer; return next uschar */
1669 return state->xfer_buffer[state->xfer_buffer_lwm++];
1675 /*************************************************
1676 * Read bytes from TLS channel *
1677 *************************************************/
1679 /* This does not feed DKIM, so if the caller uses this for reading message body,
1680 then the caller must feed DKIM.
1685 Returns: the number of bytes read
1686 -1 after a failed read
1690 tls_read(uschar *buff, size_t len)
1692 exim_gnutls_state_st *state = current_global_tls_state;
1698 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
1700 debug_printf("*** PROBABLY A BUG *** " \
1701 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
1702 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
1705 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
1706 state->session, buff, len);
1708 inbytes = gnutls_record_recv(state->session, buff, len);
1709 if (inbytes > 0) return inbytes;
1712 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1714 else record_io_error(state, (int)inbytes, US"recv", NULL);
1722 /*************************************************
1723 * Write bytes down TLS channel *
1724 *************************************************/
1731 Returns: the number of bytes after a successful write,
1732 -1 after a failed write
1736 tls_write(const uschar *buff, size_t len)
1740 exim_gnutls_state_st *state = current_global_tls_state;
1742 DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left);
1745 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
1747 outbytes = gnutls_record_send(state->session, buff, left);
1749 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
1752 record_io_error(state, outbytes, US"send", NULL);
1757 record_io_error(state, 0, US"send", US"TLS channel closed on write");
1768 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
1779 /*************************************************
1780 * Random number generation *
1781 *************************************************/
1783 /* Pseudo-random number generation. The result is not expected to be
1784 cryptographically strong but not so weak that someone will shoot themselves
1785 in the foot using it as a nonce in input in some email header scheme or
1786 whatever weirdness they'll twist this into. The result should handle fork()
1787 and avoid repeating sequences. OpenSSL handles that for us.
1791 Returns a random number in range [0, max-1]
1794 #ifdef HAVE_GNUTLS_RND
1796 vaguely_random_number(int max)
1801 uschar smallbuf[sizeof(r)];
1806 needed_len = sizeof(r);
1807 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1808 * asked for a number less than 10. */
1809 for (r = max, i = 0; r; ++i)
1815 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
1818 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
1819 return vaguely_random_number_fallback(max);
1822 for (p = smallbuf; needed_len; --needed_len, ++p)
1828 /* We don't particularly care about weighted results; if someone wants
1829 * smooth distribution and cares enough then they should submit a patch then. */
1832 #else /* HAVE_GNUTLS_RND */
1834 vaguely_random_number(int max)
1836 return vaguely_random_number_fallback(max);
1838 #endif /* HAVE_GNUTLS_RND */
1843 /*************************************************
1844 * Let tls_require_ciphers be checked at startup *
1845 *************************************************/
1847 /* The tls_require_ciphers option, if set, must be something which the
1850 Returns: NULL on success, or error message
1854 tls_validate_require_cipher(void)
1857 uschar *expciphers = NULL;
1858 gnutls_priority_t priority_cache;
1861 #define validate_check_rc(Label) do { \
1862 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
1863 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
1864 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
1866 if (exim_gnutls_base_init_done)
1867 log_write(0, LOG_MAIN|LOG_PANIC,
1868 "already initialised GnuTLS, Exim developer bug");
1870 rc = gnutls_global_init();
1871 validate_check_rc(US"gnutls_global_init()");
1872 exim_gnutls_base_init_done = TRUE;
1874 if (!(tls_require_ciphers && *tls_require_ciphers))
1875 return_deinit(NULL);
1877 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1878 return_deinit(US"failed to expand tls_require_ciphers");
1880 if (!(expciphers && *expciphers))
1881 return_deinit(NULL);
1884 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1886 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
1887 validate_check_rc(string_sprintf(
1888 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
1889 expciphers, errpos - CS expciphers, errpos));
1891 #undef return_deinit
1892 #undef validate_check_rc
1893 gnutls_global_deinit();
1901 /*************************************************
1902 * Report the library versions. *
1903 *************************************************/
1905 /* See a description in tls-openssl.c for an explanation of why this exists.
1907 Arguments: a FILE* to print the results to
1912 tls_version_report(FILE *f)
1914 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
1917 gnutls_check_version(NULL));
1920 /* End of tls-gnu.c */