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 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
517 if (rc != GNUTLS_E_SUCCESS)
520 exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real");
523 sz = write_to_fd_buf(fd, m.data, (size_t) m.size);
527 return tls_error(US"TLS cache write D-H params failed",
528 strerror(errno), NULL);
531 sz = write_to_fd_buf(fd, US"\n", 1);
533 return tls_error(US"TLS cache write D-H params final newline failed",
534 strerror(errno), NULL);
538 return tls_error(US"TLS cache write close() failed",
539 strerror(errno), NULL);
541 if (Urename(temp_fn, filename) < 0)
542 return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
543 temp_fn, filename), strerror(errno), NULL);
545 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
548 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
555 /*************************************************
556 * Variables re-expanded post-SNI *
557 *************************************************/
559 /* Called from both server and client code, via tls_init(), and also from
560 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
562 We can tell the two apart by state->received_sni being non-NULL in callback.
564 The callback should not call us unless state->trigger_sni_changes is true,
565 which we are responsible for setting on the first pass through.
568 state exim_gnutls_state_st *
570 Returns: OK/DEFER/FAIL
574 tls_expand_session_files(exim_gnutls_state_st *state)
578 const host_item *host = state->host; /* macro should be reconsidered? */
579 uschar *saved_tls_certificate = NULL;
580 uschar *saved_tls_privatekey = NULL;
581 uschar *saved_tls_verify_certificates = NULL;
582 uschar *saved_tls_crl = NULL;
585 /* We check for tls_sni *before* expansion. */
588 if (!state->received_sni)
590 if (state->tls_certificate && Ustrstr(state->tls_certificate, US"tls_sni"))
592 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
593 state->trigger_sni_changes = TRUE;
598 /* useful for debugging */
599 saved_tls_certificate = state->exp_tls_certificate;
600 saved_tls_privatekey = state->exp_tls_privatekey;
601 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
602 saved_tls_crl = state->exp_tls_crl;
606 rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
607 exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials");
609 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
610 state members, assuming consistent naming; and expand_check() returns
611 false if expansion failed, unless expansion was forced to fail. */
613 /* check if we at least have a certificate, before doing expensive
616 if (!expand_check_tlsvar(tls_certificate))
619 /* certificate is mandatory in server, optional in client */
621 if ((state->exp_tls_certificate == NULL) ||
622 (*state->exp_tls_certificate == '\0'))
624 if (state->host == NULL)
625 return tls_error(US"no TLS server certificate is specified", NULL, NULL);
627 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
630 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey))
633 /* tls_privatekey is optional, defaulting to same file as certificate */
635 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
637 state->tls_privatekey = state->tls_certificate;
638 state->exp_tls_privatekey = state->exp_tls_certificate;
642 if (state->exp_tls_certificate && *state->exp_tls_certificate)
644 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
645 state->exp_tls_certificate, state->exp_tls_privatekey);
647 if (state->received_sni)
649 if ((Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0) &&
650 (Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0))
652 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
656 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
660 rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
661 CS state->exp_tls_certificate, CS state->exp_tls_privatekey,
662 GNUTLS_X509_FMT_PEM);
663 exim_gnutls_err_check(
664 string_sprintf("cert/key setup: cert=%s key=%s",
665 state->exp_tls_certificate, state->exp_tls_privatekey));
666 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
667 } /* tls_certificate */
669 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
670 provided. Experiment shows that, if the certificate file is empty, an unhelpful
671 error message is provided. However, if we just refrain from setting anything up
672 in that case, certificate verification fails, which seems to be the correct
675 if (state->tls_verify_certificates && *state->tls_verify_certificates)
677 if (!expand_check_tlsvar(tls_verify_certificates))
679 if (state->tls_crl && *state->tls_crl)
680 if (!expand_check_tlsvar(tls_crl))
683 if (!(state->exp_tls_verify_certificates &&
684 *state->exp_tls_verify_certificates))
687 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
688 /* With no tls_verify_certificates, we ignore tls_crl too */
695 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
699 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
701 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
702 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
707 /* The test suite passes in /dev/null; we could check for that path explicitly,
708 but who knows if someone has some weird FIFO which always dumps some certs, or
709 other weirdness. The thing we really want to check is that it's not a
710 directory, since while OpenSSL supports that, GnuTLS does not.
711 So s/!S_ISREG/S_ISDIR/ and change some messsaging ... */
712 if (S_ISDIR(statbuf.st_mode))
715 debug_printf("verify certificates path is a dir: \"%s\"\n",
716 state->exp_tls_verify_certificates);
717 log_write(0, LOG_MAIN|LOG_PANIC,
718 "tls_verify_certificates \"%s\" is a directory",
719 state->exp_tls_verify_certificates);
723 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
724 state->exp_tls_verify_certificates, statbuf.st_size);
726 if (statbuf.st_size == 0)
729 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
733 cert_count = gnutls_certificate_set_x509_trust_file(state->x509_cred,
734 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
738 exim_gnutls_err_check(US"gnutls_certificate_set_x509_trust_file");
740 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);
742 if (state->tls_crl && *state->tls_crl &&
743 state->exp_tls_crl && *state->exp_tls_crl)
745 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
746 cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
747 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM);
751 exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file");
753 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
762 /*************************************************
763 * Set X.509 state variables *
764 *************************************************/
766 /* In GnuTLS, the registered cert/key are not replaced by a later
767 set of a cert/key, so for SNI support we need a whole new x509_cred
768 structure. Which means various other non-re-expanded pieces of state
769 need to be re-set in the new struct, so the setting logic is pulled
773 state exim_gnutls_state_st *
775 Returns: OK/DEFER/FAIL
779 tls_set_remaining_x509(exim_gnutls_state_st *state)
782 const host_item *host = state->host; /* macro should be reconsidered? */
784 /* Create D-H parameters, or read them from the cache file. This function does
785 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
786 client-side params. */
790 if (!dh_server_params)
792 rc = init_server_dh();
793 if (rc != OK) return rc;
795 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
798 /* Link the credentials to the session. */
800 rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred);
801 exim_gnutls_err_check(US"gnutls_credentials_set");
806 /*************************************************
807 * Initialize for GnuTLS *
808 *************************************************/
810 /* Called from both server and client code. In the case of a server, errors
811 before actual TLS negotiation return DEFER.
814 host connected host, if client; NULL if server
815 certificate certificate file
816 privatekey private key file
817 sni TLS SNI to send, sometimes when client; else NULL
820 require_ciphers tls_require_ciphers setting
822 Returns: OK/DEFER/FAIL
827 const host_item *host,
828 const uschar *certificate,
829 const uschar *privatekey,
833 const uschar *require_ciphers,
834 exim_gnutls_state_st **caller_state)
836 exim_gnutls_state_st *state;
841 BOOL want_default_priorities;
843 if (!exim_gnutls_base_init_done)
845 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
847 rc = gnutls_global_init();
848 exim_gnutls_err_check(US"gnutls_global_init");
850 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
853 gnutls_global_set_log_function(exim_gnutls_logger_cb);
854 /* arbitrarily chosen level; bump upto 9 for more */
855 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
859 exim_gnutls_base_init_done = TRUE;
864 state = &state_client;
865 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
866 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
867 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
871 state = &state_server;
872 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
873 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
874 rc = gnutls_init(&state->session, GNUTLS_SERVER);
876 exim_gnutls_err_check(US"gnutls_init");
880 state->tls_certificate = certificate;
881 state->tls_privatekey = privatekey;
882 state->tls_require_ciphers = require_ciphers;
883 state->tls_sni = sni;
884 state->tls_verify_certificates = cas;
885 state->tls_crl = crl;
887 /* This handles the variables that might get re-expanded after TLS SNI;
888 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
891 debug_printf("Expanding various TLS configuration options for session credentials.\n");
892 rc = tls_expand_session_files(state);
893 if (rc != OK) return rc;
895 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
896 requires a new structure afterwards. */
898 rc = tls_set_remaining_x509(state);
899 if (rc != OK) return rc;
901 /* set SNI in client, only */
904 if (!expand_check_tlsvar(tls_sni))
906 if (state->exp_tls_sni && *state->exp_tls_sni)
909 debug_printf("Setting TLS client SNI to \"%s\"\n", state->exp_tls_sni);
910 sz = Ustrlen(state->exp_tls_sni);
911 rc = gnutls_server_name_set(state->session,
912 GNUTLS_NAME_DNS, state->exp_tls_sni, sz);
913 exim_gnutls_err_check(US"gnutls_server_name_set");
916 else if (state->tls_sni)
917 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
918 "have an SNI set for a client [%s]\n", state->tls_sni);
920 /* This is the priority string support,
921 http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html
922 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
923 This was backwards incompatible, but means Exim no longer needs to track
924 all algorithms and provide string forms for them. */
926 want_default_priorities = TRUE;
928 if (state->tls_require_ciphers && *state->tls_require_ciphers)
930 if (!expand_check_tlsvar(tls_require_ciphers))
932 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
934 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n",
935 state->exp_tls_require_ciphers);
937 rc = gnutls_priority_init(&state->priority_cache,
938 CS state->exp_tls_require_ciphers, &errpos);
939 want_default_priorities = FALSE;
940 p = state->exp_tls_require_ciphers;
943 if (want_default_priorities)
946 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n",
947 exim_default_gnutls_priority);
948 rc = gnutls_priority_init(&state->priority_cache,
949 exim_default_gnutls_priority, &errpos);
950 p = US exim_default_gnutls_priority;
953 exim_gnutls_err_check(string_sprintf(
954 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
955 p, errpos - CS p, errpos));
957 rc = gnutls_priority_set(state->session, state->priority_cache);
958 exim_gnutls_err_check(US"gnutls_priority_set");
960 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
962 /* Reduce security in favour of increased compatibility, if the admin
963 decides to make that trade-off. */
964 if (gnutls_compat_mode)
966 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
967 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
968 gnutls_session_enable_compatibility_mode(state->session);
970 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
974 *caller_state = state;
975 /* needs to happen before callbacks during handshake */
976 current_global_tls_state = state;
983 /*************************************************
984 * Extract peer information *
985 *************************************************/
987 /* Called from both server and client code.
988 Only this is allowed to set state->peerdn and state->have_set_peerdn
989 and we use that to detect double-calls.
991 NOTE: the state blocks last while the TLS connection is up, which is fine
992 for logging in the server side, but for the client side, we log after teardown
993 in src/deliver.c. While the session is up, we can twist about states and
994 repoint tls_* globals, but those variables used for logging or other variable
995 expansion that happens _after_ delivery need to have a longer life-time.
997 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
998 doing this more than once per generation of a state context. We set them in
999 the state context, and repoint tls_* to them. After the state goes away, the
1000 tls_* copies of the pointers remain valid and client delivery logging is happy.
1002 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1006 state exim_gnutls_state_st *
1008 Returns: OK/DEFER/FAIL
1012 peer_status(exim_gnutls_state_st *state)
1014 uschar cipherbuf[256];
1015 const gnutls_datum *cert_list;
1017 unsigned int cert_list_size = 0;
1018 gnutls_protocol_t protocol;
1019 gnutls_cipher_algorithm_t cipher;
1020 gnutls_kx_algorithm_t kx;
1021 gnutls_mac_algorithm_t mac;
1022 gnutls_certificate_type_t ct;
1023 gnutls_x509_crt_t crt;
1027 if (state->have_set_peerdn)
1029 state->have_set_peerdn = TRUE;
1031 state->peerdn = NULL;
1034 cipher = gnutls_cipher_get(state->session);
1035 protocol = gnutls_protocol_get_version(state->session);
1036 mac = gnutls_mac_get(state->session);
1037 kx = gnutls_kx_get(state->session);
1039 string_format(cipherbuf, sizeof(cipherbuf),
1041 gnutls_protocol_get_name(protocol),
1042 gnutls_cipher_suite_get_name(kx, cipher, mac),
1043 (int) gnutls_cipher_get_key_size(cipher) * 8);
1045 /* I don't see a way that spaces could occur, in the current GnuTLS
1046 code base, but it was a concern in the old code and perhaps older GnuTLS
1047 releases did return "TLS 1.0"; play it safe, just in case. */
1048 for (p = cipherbuf; *p != '\0'; ++p)
1051 old_pool = store_pool;
1052 store_pool = POOL_PERM;
1053 state->ciphersuite = string_copy(cipherbuf);
1054 store_pool = old_pool;
1055 tls_cipher = state->ciphersuite;
1058 cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
1060 if (cert_list == NULL || cert_list_size == 0)
1062 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1063 cert_list, cert_list_size);
1064 if (state->verify_requirement == VERIFY_REQUIRED)
1065 return tls_error(US"certificate verification failed",
1066 "no certificate received from peer", state->host);
1070 ct = gnutls_certificate_type_get(state->session);
1071 if (ct != GNUTLS_CRT_X509)
1073 const char *ctn = gnutls_certificate_type_get_name(ct);
1075 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1076 if (state->verify_requirement == VERIFY_REQUIRED)
1077 return tls_error(US"certificate verification not possible, unhandled type",
1082 #define exim_gnutls_peer_err(Label) do { \
1083 if (rc != GNUTLS_E_SUCCESS) { \
1084 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", (Label), gnutls_strerror(rc)); \
1085 if (state->verify_requirement == VERIFY_REQUIRED) { return tls_error((Label), gnutls_strerror(rc), state->host); } \
1086 return OK; } } while (0)
1088 rc = gnutls_x509_crt_init(&crt);
1089 exim_gnutls_peer_err(US"gnutls_x509_crt_init (crt)");
1091 rc = gnutls_x509_crt_import(crt, &cert_list[0], GNUTLS_X509_FMT_DER);
1092 exim_gnutls_peer_err(US"failed to import certificate [gnutls_x509_crt_import(cert 0)]");
1094 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1095 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1097 exim_gnutls_peer_err(US"getting size for cert DN failed");
1098 return FAIL; /* should not happen */
1100 dn_buf = store_get_perm(sz);
1101 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1102 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1103 state->peerdn = dn_buf;
1106 #undef exim_gnutls_peer_err
1112 /*************************************************
1113 * Verify peer certificate *
1114 *************************************************/
1116 /* Called from both server and client code.
1117 *Should* be using a callback registered with
1118 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1119 the peer information, but that's too new for some OSes.
1122 state exim_gnutls_state_st *
1123 error where to put an error message
1126 FALSE if the session should be rejected
1127 TRUE if the cert is okay or we just don't care
1131 verify_certificate(exim_gnutls_state_st *state, const char **error)
1134 unsigned int verify;
1138 rc = peer_status(state);
1141 verify = GNUTLS_CERT_INVALID;
1142 *error = "not supplied";
1146 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1149 /* Handle the result of verification. INVALID seems to be set as well
1150 as REVOKED, but leave the test for both. */
1152 if ((rc < 0) || (verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0)
1154 state->peer_cert_verified = FALSE;
1156 *error = ((verify & GNUTLS_CERT_REVOKED) != 0) ? "revoked" : "invalid";
1159 debug_printf("TLS certificate verification failed (%s): peerdn=%s\n",
1160 *error, state->peerdn ? state->peerdn : US"<unset>");
1162 if (state->verify_requirement == VERIFY_REQUIRED)
1164 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1168 debug_printf("TLS verify failure overriden (host in tls_try_verify_hosts)\n");
1172 state->peer_cert_verified = TRUE;
1173 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n",
1174 state->peerdn ? state->peerdn : US"<unset>");
1177 tls_peerdn = state->peerdn;
1185 /* ------------------------------------------------------------------------ */
1188 /* Logging function which can be registered with
1189 * gnutls_global_set_log_function()
1190 * gnutls_global_set_log_level() 0..9
1192 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1194 exim_gnutls_logger_cb(int level, const char *message)
1196 size_t len = strlen(message);
1199 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1202 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1203 message[len-1] == '\n' ? "" : "\n");
1208 /* Called after client hello, should handle SNI work.
1209 This will always set tls_sni (state->received_sni) if available,
1210 and may trigger presenting different certificates,
1211 if state->trigger_sni_changes is TRUE.
1213 Should be registered with
1214 gnutls_handshake_set_post_client_hello_function()
1216 "This callback must return 0 on success or a gnutls error code to terminate the
1219 For inability to get SNI information, we return 0.
1220 We only return non-zero if re-setup failed.
1224 exim_sni_handling_cb(gnutls_session_t session)
1226 char sni_name[MAX_HOST_LEN];
1227 size_t data_len = MAX_HOST_LEN;
1228 exim_gnutls_state_st *state = current_global_tls_state;
1229 unsigned int sni_type;
1232 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
1233 if (rc != GNUTLS_E_SUCCESS)
1236 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
1237 debug_printf("TLS: no SNI presented in handshake.\n");
1239 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
1240 gnutls_strerror(rc), rc);
1245 if (sni_type != GNUTLS_NAME_DNS)
1247 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
1251 /* We now have a UTF-8 string in sni_name */
1252 old_pool = store_pool;
1253 store_pool = POOL_PERM;
1254 state->received_sni = string_copyn(US sni_name, data_len);
1255 store_pool = old_pool;
1257 /* We set this one now so that variable expansions below will work */
1258 tls_sni = state->received_sni;
1260 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
1261 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
1263 if (!state->trigger_sni_changes)
1266 rc = tls_expand_session_files(state);
1269 /* If the setup of certs/etc failed before handshake, TLS would not have
1270 been offered. The best we can do now is abort. */
1271 return GNUTLS_E_APPLICATION_ERROR_MIN;
1274 rc = tls_set_remaining_x509(state);
1275 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
1283 /* ------------------------------------------------------------------------ */
1284 /* Exported functions */
1289 /*************************************************
1290 * Start a TLS session in a server *
1291 *************************************************/
1293 /* This is called when Exim is running as a server, after having received
1294 the STARTTLS command. It must respond to that command, and then negotiate
1298 require_ciphers list of allowed ciphers or NULL
1300 Returns: OK on success
1301 DEFER for errors before the start of the negotiation
1302 FAIL for errors during the negotation; the server can't
1307 tls_server_start(const uschar *require_ciphers)
1311 exim_gnutls_state_st *state = NULL;
1313 /* Check for previous activation */
1314 /* nb: this will not be TLS callout safe, needs reworking as part of that. */
1316 if (tls_active >= 0)
1318 tls_error(US"STARTTLS received after TLS started", "", NULL);
1319 smtp_printf("554 Already in TLS\r\n");
1323 /* Initialize the library. If it fails, it will already have logged the error
1324 and sent an SMTP response. */
1326 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
1328 rc = tls_init(NULL, tls_certificate, tls_privatekey,
1329 NULL, tls_verify_certificates, tls_crl,
1330 require_ciphers, &state);
1331 if (rc != OK) return rc;
1333 /* If this is a host for which certificate verification is mandatory or
1334 optional, set up appropriately. */
1336 if (verify_check_host(&tls_verify_hosts) == OK)
1338 DEBUG(D_tls) debug_printf("TLS: a client certificate will be required.\n");
1339 state->verify_requirement = VERIFY_REQUIRED;
1340 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
1342 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1344 DEBUG(D_tls) debug_printf("TLS: a client certificate will be requested but not required.\n");
1345 state->verify_requirement = VERIFY_OPTIONAL;
1346 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
1350 DEBUG(D_tls) debug_printf("TLS: a client certificate will not be requested.\n");
1351 state->verify_requirement = VERIFY_NONE;
1352 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
1355 /* Register SNI handling; always, even if not in tls_certificate, so that the
1356 expansion variable $tls_sni is always available. */
1358 gnutls_handshake_set_post_client_hello_function(state->session,
1359 exim_sni_handling_cb);
1361 /* Set context and tell client to go ahead, except in the case of TLS startup
1362 on connection, where outputting anything now upsets the clients and tends to
1363 make them disconnect. We need to have an explicit fflush() here, to force out
1364 the response. Other smtp_printf() calls do not need it, because in non-TLS
1365 mode, the fflush() happens when smtp_getc() is called. */
1367 if (!tls_on_connect)
1369 smtp_printf("220 TLS go ahead\r\n");
1373 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1374 that the GnuTLS library doesn't. */
1376 gnutls_transport_set_ptr2(state->session,
1377 (gnutls_transport_ptr)fileno(smtp_in),
1378 (gnutls_transport_ptr)fileno(smtp_out));
1379 state->fd_in = fileno(smtp_in);
1380 state->fd_out = fileno(smtp_out);
1382 sigalrm_seen = FALSE;
1383 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1386 rc = gnutls_handshake(state->session);
1387 } while ((rc == GNUTLS_E_AGAIN) ||
1388 (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));
1391 if (rc != GNUTLS_E_SUCCESS)
1393 tls_error(US"gnutls_handshake",
1394 sigalrm_seen ? "timed out" : gnutls_strerror(rc), NULL);
1395 /* It seems that, except in the case of a timeout, we have to close the
1396 connection right here; otherwise if the other end is running OpenSSL it hangs
1397 until the server times out. */
1401 (void)fclose(smtp_out);
1402 (void)fclose(smtp_in);
1408 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
1410 /* Verify after the fact */
1412 if (state->verify_requirement != VERIFY_NONE)
1414 if (!verify_certificate(state, &error))
1416 if (state->verify_requirement == VERIFY_OPTIONAL)
1419 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
1424 tls_error(US"certificate verification failed", error, NULL);
1430 /* Figure out peer DN, and if authenticated, etc. */
1432 rc = peer_status(state);
1433 if (rc != OK) return rc;
1435 /* Sets various Exim expansion variables; always safe within server */
1437 extract_exim_vars_from_tls_state(state);
1439 /* TLS has been set up. Adjust the input functions to read via TLS,
1440 and initialize appropriately. */
1442 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1444 receive_getc = tls_getc;
1445 receive_ungetc = tls_ungetc;
1446 receive_feof = tls_feof;
1447 receive_ferror = tls_ferror;
1448 receive_smtp_buffered = tls_smtp_buffered;
1456 /*************************************************
1457 * Start a TLS session in a client *
1458 *************************************************/
1460 /* Called from the smtp transport after STARTTLS has been accepted.
1463 fd the fd of the connection
1464 host connected host (for messages)
1465 addr the first address (not used)
1466 dhparam DH parameter file (ignored, we're a client)
1467 certificate certificate file
1468 privatekey private key file
1469 sni TLS SNI to send to remote host
1470 verify_certs file for certificate verify
1471 verify_crl CRL for verify
1472 require_ciphers list of allowed ciphers or NULL
1473 timeout startup timeout
1475 Returns: OK/DEFER/FAIL (because using common functions),
1476 but for a client, DEFER and FAIL have the same meaning
1480 tls_client_start(int fd, host_item *host,
1481 address_item *addr ARG_UNUSED, uschar *dhparam ARG_UNUSED,
1482 uschar *certificate, uschar *privatekey, uschar *sni,
1483 uschar *verify_certs, uschar *verify_crl,
1484 uschar *require_ciphers, int timeout)
1488 exim_gnutls_state_st *state = NULL;
1490 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);
1492 rc = tls_init(host, certificate, privatekey,
1493 sni, verify_certs, verify_crl, require_ciphers, &state);
1494 if (rc != OK) return rc;
1496 gnutls_dh_set_prime_bits(state->session, EXIM_CLIENT_DH_MIN_BITS);
1498 if (verify_certs == NULL)
1500 DEBUG(D_tls) debug_printf("TLS: server certificate verification not required\n");
1501 state->verify_requirement = VERIFY_NONE;
1502 /* we still ask for it, to log it, etc */
1503 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
1507 DEBUG(D_tls) debug_printf("TLS: server certificate verification required\n");
1508 state->verify_requirement = VERIFY_REQUIRED;
1509 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
1512 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr)fd);
1516 /* There doesn't seem to be a built-in timeout on connection. */
1518 sigalrm_seen = FALSE;
1522 rc = gnutls_handshake(state->session);
1523 } while ((rc == GNUTLS_E_AGAIN) ||
1524 (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));
1527 if (rc != GNUTLS_E_SUCCESS)
1528 return tls_error(US"gnutls_handshake",
1529 sigalrm_seen ? "timed out" : gnutls_strerror(rc), state->host);
1531 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
1535 if (state->verify_requirement != VERIFY_NONE &&
1536 !verify_certificate(state, &error))
1537 return tls_error(US"certificate verification failed", error, state->host);
1539 /* Figure out peer DN, and if authenticated, etc. */
1541 rc = peer_status(state);
1542 if (rc != OK) return rc;
1544 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
1546 extract_exim_vars_from_tls_state(state);
1554 /*************************************************
1555 * Close down a TLS session *
1556 *************************************************/
1558 /* This is also called from within a delivery subprocess forked from the
1559 daemon, to shut down the TLS library, without actually doing a shutdown (which
1560 would tamper with the TLS session in the parent process).
1562 Arguments: TRUE if gnutls_bye is to be called
1567 tls_close(BOOL shutdown)
1569 exim_gnutls_state_st *state = current_global_tls_state;
1571 if (tls_active < 0) return; /* TLS was not active */
1575 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n");
1576 gnutls_bye(state->session, GNUTLS_SHUT_WR);
1579 gnutls_deinit(state->session);
1581 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1583 if ((state_server.session == NULL) && (state_client.session == NULL))
1585 gnutls_global_deinit();
1586 exim_gnutls_base_init_done = FALSE;
1595 /*************************************************
1596 * TLS version of getc *
1597 *************************************************/
1599 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1600 it refills the buffer via the GnuTLS reading function.
1602 This feeds DKIM and should be used for all message-body reads.
1605 Returns: the next character or EOF
1611 exim_gnutls_state_st *state = current_global_tls_state;
1612 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
1616 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
1617 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
1619 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1620 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
1621 ssl_xfer_buffer_size);
1624 /* A zero-byte return appears to mean that the TLS session has been
1625 closed down, not that the socket itself has been closed down. Revert to
1626 non-TLS handling. */
1630 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1632 receive_getc = smtp_getc;
1633 receive_ungetc = smtp_ungetc;
1634 receive_feof = smtp_feof;
1635 receive_ferror = smtp_ferror;
1636 receive_smtp_buffered = smtp_buffered;
1638 gnutls_deinit(state->session);
1639 state->session = NULL;
1642 tls_certificate_verified = FALSE;
1643 tls_channelbinding_b64 = NULL;
1650 /* Handle genuine errors */
1652 else if (inbytes < 0)
1654 record_io_error(state, (int) inbytes, US"recv", NULL);
1655 state->xfer_error = 1;
1658 #ifndef DISABLE_DKIM
1659 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
1661 state->xfer_buffer_hwm = (int) inbytes;
1662 state->xfer_buffer_lwm = 0;
1665 /* Something in the buffer; return next uschar */
1667 return state->xfer_buffer[state->xfer_buffer_lwm++];
1673 /*************************************************
1674 * Read bytes from TLS channel *
1675 *************************************************/
1677 /* This does not feed DKIM, so if the caller uses this for reading message body,
1678 then the caller must feed DKIM.
1683 Returns: the number of bytes read
1684 -1 after a failed read
1688 tls_read(uschar *buff, size_t len)
1690 exim_gnutls_state_st *state = current_global_tls_state;
1696 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
1698 debug_printf("*** PROBABLY A BUG *** " \
1699 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
1700 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
1703 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
1704 state->session, buff, len);
1706 inbytes = gnutls_record_recv(state->session, buff, len);
1707 if (inbytes > 0) return inbytes;
1710 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1712 else record_io_error(state, (int)inbytes, US"recv", NULL);
1720 /*************************************************
1721 * Write bytes down TLS channel *
1722 *************************************************/
1729 Returns: the number of bytes after a successful write,
1730 -1 after a failed write
1734 tls_write(const uschar *buff, size_t len)
1738 exim_gnutls_state_st *state = current_global_tls_state;
1740 DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left);
1743 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
1745 outbytes = gnutls_record_send(state->session, buff, left);
1747 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
1750 record_io_error(state, outbytes, US"send", NULL);
1755 record_io_error(state, 0, US"send", US"TLS channel closed on write");
1766 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
1777 /*************************************************
1778 * Random number generation *
1779 *************************************************/
1781 /* Pseudo-random number generation. The result is not expected to be
1782 cryptographically strong but not so weak that someone will shoot themselves
1783 in the foot using it as a nonce in input in some email header scheme or
1784 whatever weirdness they'll twist this into. The result should handle fork()
1785 and avoid repeating sequences. OpenSSL handles that for us.
1789 Returns a random number in range [0, max-1]
1792 #ifdef HAVE_GNUTLS_RND
1794 vaguely_random_number(int max)
1799 uschar smallbuf[sizeof(r)];
1804 needed_len = sizeof(r);
1805 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1806 * asked for a number less than 10. */
1807 for (r = max, i = 0; r; ++i)
1813 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
1816 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
1817 return vaguely_random_number_fallback(max);
1820 for (p = smallbuf; needed_len; --needed_len, ++p)
1826 /* We don't particularly care about weighted results; if someone wants
1827 * smooth distribution and cares enough then they should submit a patch then. */
1830 #else /* HAVE_GNUTLS_RND */
1832 vaguely_random_number(int max)
1834 return vaguely_random_number_fallback(max);
1836 #endif /* HAVE_GNUTLS_RND */
1841 /*************************************************
1842 * Let tls_require_ciphers be checked at startup *
1843 *************************************************/
1845 /* The tls_require_ciphers option, if set, must be something which the
1848 Returns: NULL on success, or error message
1852 tls_validate_require_cipher(void)
1855 uschar *expciphers = NULL;
1856 gnutls_priority_t priority_cache;
1859 #define validate_check_rc(Label) do { \
1860 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
1861 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
1862 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
1864 if (exim_gnutls_base_init_done)
1865 log_write(0, LOG_MAIN|LOG_PANIC,
1866 "already initialised GnuTLS, Exim developer bug");
1868 rc = gnutls_global_init();
1869 validate_check_rc(US"gnutls_global_init()");
1870 exim_gnutls_base_init_done = TRUE;
1872 if (!(tls_require_ciphers && *tls_require_ciphers))
1873 return_deinit(NULL);
1875 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1876 return_deinit(US"failed to expand tls_require_ciphers");
1878 if (!(expciphers && *expciphers))
1879 return_deinit(NULL);
1882 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1884 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
1885 validate_check_rc(string_sprintf(
1886 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
1887 expciphers, errpos - CS expciphers, errpos));
1889 #undef return_deinit
1890 #undef validate_check_rc
1891 gnutls_global_deinit();
1899 /*************************************************
1900 * Report the library versions. *
1901 *************************************************/
1903 /* See a description in tls-openssl.c for an explanation of why this exists.
1905 Arguments: a FILE* to print the results to
1910 tls_version_report(FILE *f)
1912 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
1915 gnutls_check_version(NULL));
1918 /* End of tls-gnu.c */