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; I
516 originally used sz so as to avoid type compatibility errors, as gnutls_datum
517 uses "unsigned int" for the size field, but this call takes separate data
518 and size fields, with the latter being a size_t*. For now, we live with
519 the error as being safer than throwing away type information. */
520 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
522 if (rc != GNUTLS_E_SUCCESS)
525 exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real");
528 sz = write_to_fd_buf(fd, m.data, (size_t) m.size);
532 return tls_error(US"TLS cache write D-H params failed",
533 strerror(errno), NULL);
536 sz = write_to_fd_buf(fd, US"\n", 1);
538 return tls_error(US"TLS cache write D-H params final newline failed",
539 strerror(errno), NULL);
543 return tls_error(US"TLS cache write close() failed",
544 strerror(errno), NULL);
546 if (Urename(temp_fn, filename) < 0)
547 return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
548 temp_fn, filename), strerror(errno), NULL);
550 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
553 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
560 /*************************************************
561 * Variables re-expanded post-SNI *
562 *************************************************/
564 /* Called from both server and client code, via tls_init(), and also from
565 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
567 We can tell the two apart by state->received_sni being non-NULL in callback.
569 The callback should not call us unless state->trigger_sni_changes is true,
570 which we are responsible for setting on the first pass through.
573 state exim_gnutls_state_st *
575 Returns: OK/DEFER/FAIL
579 tls_expand_session_files(exim_gnutls_state_st *state)
583 const host_item *host = state->host; /* macro should be reconsidered? */
584 uschar *saved_tls_certificate = NULL;
585 uschar *saved_tls_privatekey = NULL;
586 uschar *saved_tls_verify_certificates = NULL;
587 uschar *saved_tls_crl = NULL;
590 /* We check for tls_sni *before* expansion. */
593 if (!state->received_sni)
595 if (state->tls_certificate && Ustrstr(state->tls_certificate, US"tls_sni"))
597 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
598 state->trigger_sni_changes = TRUE;
603 /* useful for debugging */
604 saved_tls_certificate = state->exp_tls_certificate;
605 saved_tls_privatekey = state->exp_tls_privatekey;
606 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
607 saved_tls_crl = state->exp_tls_crl;
611 rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
612 exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials");
614 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
615 state members, assuming consistent naming; and expand_check() returns
616 false if expansion failed, unless expansion was forced to fail. */
618 /* check if we at least have a certificate, before doing expensive
621 if (!expand_check_tlsvar(tls_certificate))
624 /* certificate is mandatory in server, optional in client */
626 if ((state->exp_tls_certificate == NULL) ||
627 (*state->exp_tls_certificate == '\0'))
629 if (state->host == NULL)
630 return tls_error(US"no TLS server certificate is specified", NULL, NULL);
632 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
635 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey))
638 /* tls_privatekey is optional, defaulting to same file as certificate */
640 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
642 state->tls_privatekey = state->tls_certificate;
643 state->exp_tls_privatekey = state->exp_tls_certificate;
647 if (state->exp_tls_certificate && *state->exp_tls_certificate)
649 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
650 state->exp_tls_certificate, state->exp_tls_privatekey);
652 if (state->received_sni)
654 if ((Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0) &&
655 (Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0))
657 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
661 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
665 rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
666 CS state->exp_tls_certificate, CS state->exp_tls_privatekey,
667 GNUTLS_X509_FMT_PEM);
668 exim_gnutls_err_check(
669 string_sprintf("cert/key setup: cert=%s key=%s",
670 state->exp_tls_certificate, state->exp_tls_privatekey));
671 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
672 } /* tls_certificate */
674 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
675 provided. Experiment shows that, if the certificate file is empty, an unhelpful
676 error message is provided. However, if we just refrain from setting anything up
677 in that case, certificate verification fails, which seems to be the correct
680 if (state->tls_verify_certificates && *state->tls_verify_certificates)
682 if (!expand_check_tlsvar(tls_verify_certificates))
684 if (state->tls_crl && *state->tls_crl)
685 if (!expand_check_tlsvar(tls_crl))
688 if (!(state->exp_tls_verify_certificates &&
689 *state->exp_tls_verify_certificates))
692 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
693 /* With no tls_verify_certificates, we ignore tls_crl too */
700 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
704 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
706 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
707 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
712 /* The test suite passes in /dev/null; we could check for that path explicitly,
713 but who knows if someone has some weird FIFO which always dumps some certs, or
714 other weirdness. The thing we really want to check is that it's not a
715 directory, since while OpenSSL supports that, GnuTLS does not.
716 So s/!S_ISREG/S_ISDIR/ and change some messsaging ... */
717 if (S_ISDIR(statbuf.st_mode))
720 debug_printf("verify certificates path is a dir: \"%s\"\n",
721 state->exp_tls_verify_certificates);
722 log_write(0, LOG_MAIN|LOG_PANIC,
723 "tls_verify_certificates \"%s\" is a directory",
724 state->exp_tls_verify_certificates);
728 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
729 state->exp_tls_verify_certificates, statbuf.st_size);
731 if (statbuf.st_size == 0)
734 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
738 cert_count = gnutls_certificate_set_x509_trust_file(state->x509_cred,
739 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
743 exim_gnutls_err_check(US"gnutls_certificate_set_x509_trust_file");
745 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);
747 if (state->tls_crl && *state->tls_crl &&
748 state->exp_tls_crl && *state->exp_tls_crl)
750 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
751 cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
752 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM);
756 exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file");
758 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
767 /*************************************************
768 * Set X.509 state variables *
769 *************************************************/
771 /* In GnuTLS, the registered cert/key are not replaced by a later
772 set of a cert/key, so for SNI support we need a whole new x509_cred
773 structure. Which means various other non-re-expanded pieces of state
774 need to be re-set in the new struct, so the setting logic is pulled
778 state exim_gnutls_state_st *
780 Returns: OK/DEFER/FAIL
784 tls_set_remaining_x509(exim_gnutls_state_st *state)
787 const host_item *host = state->host; /* macro should be reconsidered? */
789 /* Create D-H parameters, or read them from the cache file. This function does
790 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
791 client-side params. */
795 if (!dh_server_params)
797 rc = init_server_dh();
798 if (rc != OK) return rc;
800 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
803 /* Link the credentials to the session. */
805 rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred);
806 exim_gnutls_err_check(US"gnutls_credentials_set");
811 /*************************************************
812 * Initialize for GnuTLS *
813 *************************************************/
815 /* Called from both server and client code. In the case of a server, errors
816 before actual TLS negotiation return DEFER.
819 host connected host, if client; NULL if server
820 certificate certificate file
821 privatekey private key file
822 sni TLS SNI to send, sometimes when client; else NULL
825 require_ciphers tls_require_ciphers setting
827 Returns: OK/DEFER/FAIL
832 const host_item *host,
833 const uschar *certificate,
834 const uschar *privatekey,
838 const uschar *require_ciphers,
839 exim_gnutls_state_st **caller_state)
841 exim_gnutls_state_st *state;
846 BOOL want_default_priorities;
848 if (!exim_gnutls_base_init_done)
850 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
852 rc = gnutls_global_init();
853 exim_gnutls_err_check(US"gnutls_global_init");
855 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
858 gnutls_global_set_log_function(exim_gnutls_logger_cb);
859 /* arbitrarily chosen level; bump upto 9 for more */
860 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
864 exim_gnutls_base_init_done = TRUE;
869 state = &state_client;
870 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
871 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
872 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
876 state = &state_server;
877 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
878 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
879 rc = gnutls_init(&state->session, GNUTLS_SERVER);
881 exim_gnutls_err_check(US"gnutls_init");
885 state->tls_certificate = certificate;
886 state->tls_privatekey = privatekey;
887 state->tls_require_ciphers = require_ciphers;
888 state->tls_sni = sni;
889 state->tls_verify_certificates = cas;
890 state->tls_crl = crl;
892 /* This handles the variables that might get re-expanded after TLS SNI;
893 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
896 debug_printf("Expanding various TLS configuration options for session credentials.\n");
897 rc = tls_expand_session_files(state);
898 if (rc != OK) return rc;
900 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
901 requires a new structure afterwards. */
903 rc = tls_set_remaining_x509(state);
904 if (rc != OK) return rc;
906 /* set SNI in client, only */
909 if (!expand_check_tlsvar(tls_sni))
911 if (state->exp_tls_sni && *state->exp_tls_sni)
914 debug_printf("Setting TLS client SNI to \"%s\"\n", state->exp_tls_sni);
915 sz = Ustrlen(state->exp_tls_sni);
916 rc = gnutls_server_name_set(state->session,
917 GNUTLS_NAME_DNS, state->exp_tls_sni, sz);
918 exim_gnutls_err_check(US"gnutls_server_name_set");
921 else if (state->tls_sni)
922 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
923 "have an SNI set for a client [%s]\n", state->tls_sni);
925 /* This is the priority string support,
926 http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html
927 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
928 This was backwards incompatible, but means Exim no longer needs to track
929 all algorithms and provide string forms for them. */
931 want_default_priorities = TRUE;
933 if (state->tls_require_ciphers && *state->tls_require_ciphers)
935 if (!expand_check_tlsvar(tls_require_ciphers))
937 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
939 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n",
940 state->exp_tls_require_ciphers);
942 rc = gnutls_priority_init(&state->priority_cache,
943 CS state->exp_tls_require_ciphers, &errpos);
944 want_default_priorities = FALSE;
945 p = state->exp_tls_require_ciphers;
948 if (want_default_priorities)
951 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n",
952 exim_default_gnutls_priority);
953 rc = gnutls_priority_init(&state->priority_cache,
954 exim_default_gnutls_priority, &errpos);
955 p = US exim_default_gnutls_priority;
958 exim_gnutls_err_check(string_sprintf(
959 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
960 p, errpos - CS p, errpos));
962 rc = gnutls_priority_set(state->session, state->priority_cache);
963 exim_gnutls_err_check(US"gnutls_priority_set");
965 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
967 /* Reduce security in favour of increased compatibility, if the admin
968 decides to make that trade-off. */
969 if (gnutls_compat_mode)
971 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
972 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
973 gnutls_session_enable_compatibility_mode(state->session);
975 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
979 *caller_state = state;
980 /* needs to happen before callbacks during handshake */
981 current_global_tls_state = state;
988 /*************************************************
989 * Extract peer information *
990 *************************************************/
992 /* Called from both server and client code.
993 Only this is allowed to set state->peerdn and state->have_set_peerdn
994 and we use that to detect double-calls.
996 NOTE: the state blocks last while the TLS connection is up, which is fine
997 for logging in the server side, but for the client side, we log after teardown
998 in src/deliver.c. While the session is up, we can twist about states and
999 repoint tls_* globals, but those variables used for logging or other variable
1000 expansion that happens _after_ delivery need to have a longer life-time.
1002 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1003 doing this more than once per generation of a state context. We set them in
1004 the state context, and repoint tls_* to them. After the state goes away, the
1005 tls_* copies of the pointers remain valid and client delivery logging is happy.
1007 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1011 state exim_gnutls_state_st *
1013 Returns: OK/DEFER/FAIL
1017 peer_status(exim_gnutls_state_st *state)
1019 uschar cipherbuf[256];
1020 const gnutls_datum *cert_list;
1022 unsigned int cert_list_size = 0;
1023 gnutls_protocol_t protocol;
1024 gnutls_cipher_algorithm_t cipher;
1025 gnutls_kx_algorithm_t kx;
1026 gnutls_mac_algorithm_t mac;
1027 gnutls_certificate_type_t ct;
1028 gnutls_x509_crt_t crt;
1032 if (state->have_set_peerdn)
1034 state->have_set_peerdn = TRUE;
1036 state->peerdn = NULL;
1039 cipher = gnutls_cipher_get(state->session);
1040 protocol = gnutls_protocol_get_version(state->session);
1041 mac = gnutls_mac_get(state->session);
1042 kx = gnutls_kx_get(state->session);
1044 string_format(cipherbuf, sizeof(cipherbuf),
1046 gnutls_protocol_get_name(protocol),
1047 gnutls_cipher_suite_get_name(kx, cipher, mac),
1048 (int) gnutls_cipher_get_key_size(cipher) * 8);
1050 /* I don't see a way that spaces could occur, in the current GnuTLS
1051 code base, but it was a concern in the old code and perhaps older GnuTLS
1052 releases did return "TLS 1.0"; play it safe, just in case. */
1053 for (p = cipherbuf; *p != '\0'; ++p)
1056 old_pool = store_pool;
1057 store_pool = POOL_PERM;
1058 state->ciphersuite = string_copy(cipherbuf);
1059 store_pool = old_pool;
1060 tls_cipher = state->ciphersuite;
1063 cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
1065 if (cert_list == NULL || cert_list_size == 0)
1067 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1068 cert_list, cert_list_size);
1069 if (state->verify_requirement == VERIFY_REQUIRED)
1070 return tls_error(US"certificate verification failed",
1071 "no certificate received from peer", state->host);
1075 ct = gnutls_certificate_type_get(state->session);
1076 if (ct != GNUTLS_CRT_X509)
1078 const char *ctn = gnutls_certificate_type_get_name(ct);
1080 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1081 if (state->verify_requirement == VERIFY_REQUIRED)
1082 return tls_error(US"certificate verification not possible, unhandled type",
1087 #define exim_gnutls_peer_err(Label) do { \
1088 if (rc != GNUTLS_E_SUCCESS) { \
1089 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", (Label), gnutls_strerror(rc)); \
1090 if (state->verify_requirement == VERIFY_REQUIRED) { return tls_error((Label), gnutls_strerror(rc), state->host); } \
1091 return OK; } } while (0)
1093 rc = gnutls_x509_crt_init(&crt);
1094 exim_gnutls_peer_err(US"gnutls_x509_crt_init (crt)");
1096 rc = gnutls_x509_crt_import(crt, &cert_list[0], GNUTLS_X509_FMT_DER);
1097 exim_gnutls_peer_err(US"failed to import certificate [gnutls_x509_crt_import(cert 0)]");
1099 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1100 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1102 exim_gnutls_peer_err(US"getting size for cert DN failed");
1103 return FAIL; /* should not happen */
1105 dn_buf = store_get_perm(sz);
1106 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1107 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1108 state->peerdn = dn_buf;
1111 #undef exim_gnutls_peer_err
1117 /*************************************************
1118 * Verify peer certificate *
1119 *************************************************/
1121 /* Called from both server and client code.
1122 *Should* be using a callback registered with
1123 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1124 the peer information, but that's too new for some OSes.
1127 state exim_gnutls_state_st *
1128 error where to put an error message
1131 FALSE if the session should be rejected
1132 TRUE if the cert is okay or we just don't care
1136 verify_certificate(exim_gnutls_state_st *state, const char **error)
1139 unsigned int verify;
1143 rc = peer_status(state);
1146 verify = GNUTLS_CERT_INVALID;
1147 *error = "not supplied";
1151 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1154 /* Handle the result of verification. INVALID seems to be set as well
1155 as REVOKED, but leave the test for both. */
1157 if ((rc < 0) || (verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0)
1159 state->peer_cert_verified = FALSE;
1161 *error = ((verify & GNUTLS_CERT_REVOKED) != 0) ? "revoked" : "invalid";
1164 debug_printf("TLS certificate verification failed (%s): peerdn=%s\n",
1165 *error, state->peerdn ? state->peerdn : US"<unset>");
1167 if (state->verify_requirement == VERIFY_REQUIRED)
1169 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1173 debug_printf("TLS verify failure overriden (host in tls_try_verify_hosts)\n");
1177 state->peer_cert_verified = TRUE;
1178 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n",
1179 state->peerdn ? state->peerdn : US"<unset>");
1182 tls_peerdn = state->peerdn;
1190 /* ------------------------------------------------------------------------ */
1193 /* Logging function which can be registered with
1194 * gnutls_global_set_log_function()
1195 * gnutls_global_set_log_level() 0..9
1197 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1199 exim_gnutls_logger_cb(int level, const char *message)
1201 size_t len = strlen(message);
1204 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1207 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1208 message[len-1] == '\n' ? "" : "\n");
1213 /* Called after client hello, should handle SNI work.
1214 This will always set tls_sni (state->received_sni) if available,
1215 and may trigger presenting different certificates,
1216 if state->trigger_sni_changes is TRUE.
1218 Should be registered with
1219 gnutls_handshake_set_post_client_hello_function()
1221 "This callback must return 0 on success or a gnutls error code to terminate the
1224 For inability to get SNI information, we return 0.
1225 We only return non-zero if re-setup failed.
1229 exim_sni_handling_cb(gnutls_session_t session)
1231 char sni_name[MAX_HOST_LEN];
1232 size_t data_len = MAX_HOST_LEN;
1233 exim_gnutls_state_st *state = current_global_tls_state;
1234 unsigned int sni_type;
1237 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
1238 if (rc != GNUTLS_E_SUCCESS)
1241 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
1242 debug_printf("TLS: no SNI presented in handshake.\n");
1244 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
1245 gnutls_strerror(rc), rc);
1250 if (sni_type != GNUTLS_NAME_DNS)
1252 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
1256 /* We now have a UTF-8 string in sni_name */
1257 old_pool = store_pool;
1258 store_pool = POOL_PERM;
1259 state->received_sni = string_copyn(US sni_name, data_len);
1260 store_pool = old_pool;
1262 /* We set this one now so that variable expansions below will work */
1263 tls_sni = state->received_sni;
1265 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
1266 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
1268 if (!state->trigger_sni_changes)
1271 rc = tls_expand_session_files(state);
1274 /* If the setup of certs/etc failed before handshake, TLS would not have
1275 been offered. The best we can do now is abort. */
1276 return GNUTLS_E_APPLICATION_ERROR_MIN;
1279 rc = tls_set_remaining_x509(state);
1280 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
1288 /* ------------------------------------------------------------------------ */
1289 /* Exported functions */
1294 /*************************************************
1295 * Start a TLS session in a server *
1296 *************************************************/
1298 /* This is called when Exim is running as a server, after having received
1299 the STARTTLS command. It must respond to that command, and then negotiate
1303 require_ciphers list of allowed ciphers or NULL
1305 Returns: OK on success
1306 DEFER for errors before the start of the negotiation
1307 FAIL for errors during the negotation; the server can't
1312 tls_server_start(const uschar *require_ciphers)
1316 exim_gnutls_state_st *state = NULL;
1318 /* Check for previous activation */
1319 /* nb: this will not be TLS callout safe, needs reworking as part of that. */
1321 if (tls_active >= 0)
1323 tls_error(US"STARTTLS received after TLS started", "", NULL);
1324 smtp_printf("554 Already in TLS\r\n");
1328 /* Initialize the library. If it fails, it will already have logged the error
1329 and sent an SMTP response. */
1331 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
1333 rc = tls_init(NULL, tls_certificate, tls_privatekey,
1334 NULL, tls_verify_certificates, tls_crl,
1335 require_ciphers, &state);
1336 if (rc != OK) return rc;
1338 /* If this is a host for which certificate verification is mandatory or
1339 optional, set up appropriately. */
1341 if (verify_check_host(&tls_verify_hosts) == OK)
1343 DEBUG(D_tls) debug_printf("TLS: a client certificate will be required.\n");
1344 state->verify_requirement = VERIFY_REQUIRED;
1345 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
1347 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1349 DEBUG(D_tls) debug_printf("TLS: a client certificate will be requested but not required.\n");
1350 state->verify_requirement = VERIFY_OPTIONAL;
1351 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
1355 DEBUG(D_tls) debug_printf("TLS: a client certificate will not be requested.\n");
1356 state->verify_requirement = VERIFY_NONE;
1357 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
1360 /* Register SNI handling; always, even if not in tls_certificate, so that the
1361 expansion variable $tls_sni is always available. */
1363 gnutls_handshake_set_post_client_hello_function(state->session,
1364 exim_sni_handling_cb);
1366 /* Set context and tell client to go ahead, except in the case of TLS startup
1367 on connection, where outputting anything now upsets the clients and tends to
1368 make them disconnect. We need to have an explicit fflush() here, to force out
1369 the response. Other smtp_printf() calls do not need it, because in non-TLS
1370 mode, the fflush() happens when smtp_getc() is called. */
1372 if (!tls_on_connect)
1374 smtp_printf("220 TLS go ahead\r\n");
1378 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1379 that the GnuTLS library doesn't. */
1381 gnutls_transport_set_ptr2(state->session,
1382 (gnutls_transport_ptr)fileno(smtp_in),
1383 (gnutls_transport_ptr)fileno(smtp_out));
1384 state->fd_in = fileno(smtp_in);
1385 state->fd_out = fileno(smtp_out);
1387 sigalrm_seen = FALSE;
1388 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1391 rc = gnutls_handshake(state->session);
1392 } while ((rc == GNUTLS_E_AGAIN) ||
1393 (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));
1396 if (rc != GNUTLS_E_SUCCESS)
1398 tls_error(US"gnutls_handshake",
1399 sigalrm_seen ? "timed out" : gnutls_strerror(rc), NULL);
1400 /* It seems that, except in the case of a timeout, we have to close the
1401 connection right here; otherwise if the other end is running OpenSSL it hangs
1402 until the server times out. */
1406 (void)fclose(smtp_out);
1407 (void)fclose(smtp_in);
1413 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
1415 /* Verify after the fact */
1417 if (state->verify_requirement != VERIFY_NONE)
1419 if (!verify_certificate(state, &error))
1421 if (state->verify_requirement == VERIFY_OPTIONAL)
1424 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
1429 tls_error(US"certificate verification failed", error, NULL);
1435 /* Figure out peer DN, and if authenticated, etc. */
1437 rc = peer_status(state);
1438 if (rc != OK) return rc;
1440 /* Sets various Exim expansion variables; always safe within server */
1442 extract_exim_vars_from_tls_state(state);
1444 /* TLS has been set up. Adjust the input functions to read via TLS,
1445 and initialize appropriately. */
1447 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1449 receive_getc = tls_getc;
1450 receive_ungetc = tls_ungetc;
1451 receive_feof = tls_feof;
1452 receive_ferror = tls_ferror;
1453 receive_smtp_buffered = tls_smtp_buffered;
1461 /*************************************************
1462 * Start a TLS session in a client *
1463 *************************************************/
1465 /* Called from the smtp transport after STARTTLS has been accepted.
1468 fd the fd of the connection
1469 host connected host (for messages)
1470 addr the first address (not used)
1471 dhparam DH parameter file (ignored, we're a client)
1472 certificate certificate file
1473 privatekey private key file
1474 sni TLS SNI to send to remote host
1475 verify_certs file for certificate verify
1476 verify_crl CRL for verify
1477 require_ciphers list of allowed ciphers or NULL
1478 timeout startup timeout
1480 Returns: OK/DEFER/FAIL (because using common functions),
1481 but for a client, DEFER and FAIL have the same meaning
1485 tls_client_start(int fd, host_item *host,
1486 address_item *addr ARG_UNUSED, uschar *dhparam ARG_UNUSED,
1487 uschar *certificate, uschar *privatekey, uschar *sni,
1488 uschar *verify_certs, uschar *verify_crl,
1489 uschar *require_ciphers, int timeout)
1493 exim_gnutls_state_st *state = NULL;
1495 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);
1497 rc = tls_init(host, certificate, privatekey,
1498 sni, verify_certs, verify_crl, require_ciphers, &state);
1499 if (rc != OK) return rc;
1501 gnutls_dh_set_prime_bits(state->session, EXIM_CLIENT_DH_MIN_BITS);
1503 if (verify_certs == NULL)
1505 DEBUG(D_tls) debug_printf("TLS: server certificate verification not required\n");
1506 state->verify_requirement = VERIFY_NONE;
1507 /* we still ask for it, to log it, etc */
1508 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
1512 DEBUG(D_tls) debug_printf("TLS: server certificate verification required\n");
1513 state->verify_requirement = VERIFY_REQUIRED;
1514 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
1517 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr)fd);
1521 /* There doesn't seem to be a built-in timeout on connection. */
1523 sigalrm_seen = FALSE;
1527 rc = gnutls_handshake(state->session);
1528 } while ((rc == GNUTLS_E_AGAIN) ||
1529 (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));
1532 if (rc != GNUTLS_E_SUCCESS)
1533 return tls_error(US"gnutls_handshake",
1534 sigalrm_seen ? "timed out" : gnutls_strerror(rc), state->host);
1536 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
1540 if (state->verify_requirement != VERIFY_NONE &&
1541 !verify_certificate(state, &error))
1542 return tls_error(US"certificate verification failed", error, state->host);
1544 /* Figure out peer DN, and if authenticated, etc. */
1546 rc = peer_status(state);
1547 if (rc != OK) return rc;
1549 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
1551 extract_exim_vars_from_tls_state(state);
1559 /*************************************************
1560 * Close down a TLS session *
1561 *************************************************/
1563 /* This is also called from within a delivery subprocess forked from the
1564 daemon, to shut down the TLS library, without actually doing a shutdown (which
1565 would tamper with the TLS session in the parent process).
1567 Arguments: TRUE if gnutls_bye is to be called
1572 tls_close(BOOL shutdown)
1574 exim_gnutls_state_st *state = current_global_tls_state;
1576 if (tls_active < 0) return; /* TLS was not active */
1580 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n");
1581 gnutls_bye(state->session, GNUTLS_SHUT_WR);
1584 gnutls_deinit(state->session);
1586 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1588 if ((state_server.session == NULL) && (state_client.session == NULL))
1590 gnutls_global_deinit();
1591 exim_gnutls_base_init_done = FALSE;
1600 /*************************************************
1601 * TLS version of getc *
1602 *************************************************/
1604 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1605 it refills the buffer via the GnuTLS reading function.
1607 This feeds DKIM and should be used for all message-body reads.
1610 Returns: the next character or EOF
1616 exim_gnutls_state_st *state = current_global_tls_state;
1617 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
1621 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
1622 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
1624 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1625 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
1626 ssl_xfer_buffer_size);
1629 /* A zero-byte return appears to mean that the TLS session has been
1630 closed down, not that the socket itself has been closed down. Revert to
1631 non-TLS handling. */
1635 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1637 receive_getc = smtp_getc;
1638 receive_ungetc = smtp_ungetc;
1639 receive_feof = smtp_feof;
1640 receive_ferror = smtp_ferror;
1641 receive_smtp_buffered = smtp_buffered;
1643 gnutls_deinit(state->session);
1644 state->session = NULL;
1647 tls_certificate_verified = FALSE;
1648 tls_channelbinding_b64 = NULL;
1655 /* Handle genuine errors */
1657 else if (inbytes < 0)
1659 record_io_error(state, (int) inbytes, US"recv", NULL);
1660 state->xfer_error = 1;
1663 #ifndef DISABLE_DKIM
1664 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
1666 state->xfer_buffer_hwm = (int) inbytes;
1667 state->xfer_buffer_lwm = 0;
1670 /* Something in the buffer; return next uschar */
1672 return state->xfer_buffer[state->xfer_buffer_lwm++];
1678 /*************************************************
1679 * Read bytes from TLS channel *
1680 *************************************************/
1682 /* This does not feed DKIM, so if the caller uses this for reading message body,
1683 then the caller must feed DKIM.
1688 Returns: the number of bytes read
1689 -1 after a failed read
1693 tls_read(uschar *buff, size_t len)
1695 exim_gnutls_state_st *state = current_global_tls_state;
1701 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
1703 debug_printf("*** PROBABLY A BUG *** " \
1704 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
1705 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
1708 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
1709 state->session, buff, len);
1711 inbytes = gnutls_record_recv(state->session, buff, len);
1712 if (inbytes > 0) return inbytes;
1715 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1717 else record_io_error(state, (int)inbytes, US"recv", NULL);
1725 /*************************************************
1726 * Write bytes down TLS channel *
1727 *************************************************/
1734 Returns: the number of bytes after a successful write,
1735 -1 after a failed write
1739 tls_write(const uschar *buff, size_t len)
1743 exim_gnutls_state_st *state = current_global_tls_state;
1745 DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left);
1748 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
1750 outbytes = gnutls_record_send(state->session, buff, left);
1752 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
1755 record_io_error(state, outbytes, US"send", NULL);
1760 record_io_error(state, 0, US"send", US"TLS channel closed on write");
1771 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
1782 /*************************************************
1783 * Random number generation *
1784 *************************************************/
1786 /* Pseudo-random number generation. The result is not expected to be
1787 cryptographically strong but not so weak that someone will shoot themselves
1788 in the foot using it as a nonce in input in some email header scheme or
1789 whatever weirdness they'll twist this into. The result should handle fork()
1790 and avoid repeating sequences. OpenSSL handles that for us.
1794 Returns a random number in range [0, max-1]
1797 #ifdef HAVE_GNUTLS_RND
1799 vaguely_random_number(int max)
1804 uschar smallbuf[sizeof(r)];
1809 needed_len = sizeof(r);
1810 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1811 * asked for a number less than 10. */
1812 for (r = max, i = 0; r; ++i)
1818 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
1821 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
1822 return vaguely_random_number_fallback(max);
1825 for (p = smallbuf; needed_len; --needed_len, ++p)
1831 /* We don't particularly care about weighted results; if someone wants
1832 * smooth distribution and cares enough then they should submit a patch then. */
1835 #else /* HAVE_GNUTLS_RND */
1837 vaguely_random_number(int max)
1839 return vaguely_random_number_fallback(max);
1841 #endif /* HAVE_GNUTLS_RND */
1846 /*************************************************
1847 * Let tls_require_ciphers be checked at startup *
1848 *************************************************/
1850 /* The tls_require_ciphers option, if set, must be something which the
1853 Returns: NULL on success, or error message
1857 tls_validate_require_cipher(void)
1860 uschar *expciphers = NULL;
1861 gnutls_priority_t priority_cache;
1864 #define validate_check_rc(Label) do { \
1865 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
1866 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
1867 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
1869 if (exim_gnutls_base_init_done)
1870 log_write(0, LOG_MAIN|LOG_PANIC,
1871 "already initialised GnuTLS, Exim developer bug");
1873 rc = gnutls_global_init();
1874 validate_check_rc(US"gnutls_global_init()");
1875 exim_gnutls_base_init_done = TRUE;
1877 if (!(tls_require_ciphers && *tls_require_ciphers))
1878 return_deinit(NULL);
1880 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1881 return_deinit(US"failed to expand tls_require_ciphers");
1883 if (!(expciphers && *expciphers))
1884 return_deinit(NULL);
1887 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1889 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
1890 validate_check_rc(string_sprintf(
1891 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
1892 expciphers, errpos - CS expciphers, errpos));
1894 #undef return_deinit
1895 #undef validate_check_rc
1896 gnutls_global_deinit();
1904 /*************************************************
1905 * Report the library versions. *
1906 *************************************************/
1908 /* See a description in tls-openssl.c for an explanation of why this exists.
1910 Arguments: a FILE* to print the results to
1915 tls_version_report(FILE *f)
1917 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
1920 gnutls_check_version(NULL));
1923 /* End of tls-gnu.c */