1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2012 */
6 /* See the file NOTICE for conditions of use and distribution. */
8 /* Copyright (c) Phil Pennock 2012 */
10 /* This file provides TLS/SSL support for Exim using the GnuTLS library,
11 one of the available supported implementations. This file is #included into
12 tls.c when USE_GNUTLS has been set.
14 The code herein is a revamp of GnuTLS integration using the current APIs; the
15 original tls-gnu.c was based on a patch which was contributed by Nikos
16 Mavroyanopoulos. The revamp is partially a rewrite, partially cut&paste as
19 APIs current as of GnuTLS 2.12.18; note that the GnuTLS manual is for GnuTLS 3,
20 which is not widely deployed by OS vendors. Will note issues below, which may
21 assist in updating the code in the future. Another sources of hints is
22 mod_gnutls for Apache (SNI callback registration and handling).
24 Keeping client and server variables more split than before and is currently
25 the norm, in anticipation of TLS in ACL callouts.
27 I wanted to switch to gnutls_certificate_set_verify_function() so that
28 certificate rejection could happen during handshake where it belongs, rather
29 than being dropped afterwards, but that was introduced in 2.10.0 and Debian
30 (6.0.5) is still on 2.8.6. So for now we have to stick with sub-par behaviour.
32 (I wasn't looking for libraries quite that old, when updating to get rid of
33 compiler warnings of deprecated APIs. If it turns out that a lot of the rest
34 require current GnuTLS, then we'll drop support for the ancient libraries).
37 #include <gnutls/gnutls.h>
38 /* needed for cert checks in verification and DN extraction: */
39 #include <gnutls/x509.h>
40 /* man-page is incorrect, gnutls_rnd() is not in gnutls.h: */
41 #include <gnutls/crypto.h>
46 gnutls_global_set_audit_log_function()
49 gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
52 /* Local static variables for GnuTLS */
54 /* Values for verify_requirement */
56 enum peer_verify_requirement { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED };
58 /* This holds most state for server or client; with this, we can set up an
59 outbound TLS-enabled connection in an ACL callout, while not stomping all
60 over the TLS variables available for expansion.
62 Some of these correspond to variables in globals.c; those variables will
63 be set to point to content in one of these instances, as appropriate for
64 the stage of the process lifetime.
66 Not handled here: globals tls_active, tls_bits, tls_cipher, tls_peerdn,
67 tls_certificate_verified, tls_channelbinding_b64, tls_sni.
70 typedef struct exim_gnutls_state {
71 gnutls_session_t session;
72 gnutls_certificate_credentials_t x509_cred;
73 gnutls_priority_t priority_cache;
74 enum peer_verify_requirement verify_requirement;
77 BOOL peer_cert_verified;
78 BOOL trigger_sni_changes;
80 const struct host_item *host;
85 const uschar *tls_certificate;
86 const uschar *tls_privatekey;
87 const uschar *tls_sni; /* client send only, not received */
88 const uschar *tls_verify_certificates;
89 const uschar *tls_crl;
90 const uschar *tls_require_ciphers;
91 uschar *exp_tls_certificate;
92 uschar *exp_tls_privatekey;
94 uschar *exp_tls_verify_certificates;
96 uschar *exp_tls_require_ciphers;
103 } exim_gnutls_state_st;
105 static const exim_gnutls_state_st exim_gnutls_state_init = {
106 NULL, NULL, NULL, VERIFY_NONE, -1, -1, FALSE, FALSE, FALSE,
107 NULL, NULL, NULL, NULL,
108 NULL, NULL, NULL, NULL, NULL, NULL,
109 NULL, NULL, NULL, NULL, NULL, NULL,
113 /* Not only do we have our own APIs which don't pass around state, assuming
114 it's held in globals, GnuTLS doesn't appear to let us register callback data
115 for callbacks, or as part of the session, so we have to keep a "this is the
116 context we're currently dealing with" pointer and rely upon being
117 single-threaded to keep from processing data on an inbound TLS connection while
118 talking to another TLS connection for an outbound check. This does mean that
119 there's no way for heart-beats to be responded to, for the duration of the
120 second connection. */
122 static exim_gnutls_state_st state_server, state_client;
123 static exim_gnutls_state_st *current_global_tls_state;
125 /* dh_params are initialised once within the lifetime of a process using TLS;
126 if we used TLS in a long-lived daemon, we'd have to reconsider this. But we
127 don't want to repeat this. */
129 static gnutls_dh_params_t dh_server_params = NULL;
131 /* No idea how this value was chosen; preserving it. Default is 3600. */
133 static const int ssl_session_timeout = 200;
135 static const char * const exim_default_gnutls_priority = "NORMAL";
137 /* Guard library core initialisation */
139 static BOOL exim_gnutls_base_init_done = FALSE;
142 /* ------------------------------------------------------------------------ */
145 #define MAX_HOST_LEN 255
147 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
148 the library logging; a value less than 0 disables the calls to set up logging
150 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
151 #define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
154 #ifndef EXIM_CLIENT_DH_MIN_BITS
155 #define EXIM_CLIENT_DH_MIN_BITS 1024
158 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
159 can ask for a bit-strength. Without that, we stick to the constant we had
161 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
162 #define EXIM_SERVER_DH_BITS_PRE2_12 1024
165 #define exim_gnutls_err_check(Label) do { \
166 if (rc != GNUTLS_E_SUCCESS) { return tls_error((Label), gnutls_strerror(rc), host); } } while (0)
168 #define expand_check_tlsvar(Varname) expand_check(state->Varname, US #Varname, &state->exp_##Varname)
170 #if GNUTLS_VERSION_NUMBER >= 0x020c00
171 #define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
172 #define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
173 #define HAVE_GNUTLS_RND
179 /* ------------------------------------------------------------------------ */
180 /* Callback declarations */
182 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
183 static void exim_gnutls_logger_cb(int level, const char *message);
186 static int exim_sni_handling_cb(gnutls_session_t session);
191 /* ------------------------------------------------------------------------ */
192 /* Static functions */
194 /*************************************************
196 *************************************************/
198 /* Called from lots of places when errors occur before actually starting to do
199 the TLS handshake, that is, while the session is still in clear. Always returns
200 DEFER for a server and FAIL for a client so that most calls can use "return
201 tls_error(...)" to do this processing and then give an appropriate return. A
202 single function is used for both server and client, because it is called from
203 some shared functions.
206 prefix text to include in the logged error
207 msg additional error string (may be NULL)
208 usually obtained from gnutls_strerror()
209 host NULL if setting up a server;
210 the connected host if setting up a client
212 Returns: OK/DEFER/FAIL
216 tls_error(const uschar *prefix, const char *msg, const host_item *host)
220 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s%s",
221 host->name, host->address, prefix, msg ? ": " : "", msg ? msg : "");
226 uschar *conn_info = smtp_get_connection_info();
227 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
229 log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s",
230 conn_info, prefix, msg ? ": " : "", msg ? msg : "");
238 /*************************************************
239 * Deal with logging errors during I/O *
240 *************************************************/
242 /* We have to get the identity of the peer from saved data.
245 state the current GnuTLS exim state container
246 rc the GnuTLS error code, or 0 if it's a local error
247 when text identifying read or write
248 text local error text when ec is 0
254 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
258 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
259 msg = CS string_sprintf("%s: %s", US gnutls_strerror(rc),
260 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
262 msg = gnutls_strerror(rc);
264 tls_error(when, msg, state->host);
270 /*************************************************
271 * Set various Exim expansion vars *
272 *************************************************/
274 /* We set various Exim global variables from the state, once a session has
275 been established. With TLS callouts, may need to change this to stack
276 variables, or just re-call it with the server state after client callout
279 Make sure anything set here is inset in tls_getc().
283 tls_bits strength indicator
284 tls_certificate_verified bool indicator
285 tls_channelbinding_b64 for some SASL mechanisms
288 tls_sni a (UTF-8) string
290 current_global_tls_state for API limitations
293 state the relevant exim_gnutls_state_st *
297 extract_exim_vars_from_tls_state(exim_gnutls_state_st *state)
299 gnutls_cipher_algorithm_t cipher;
300 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
303 gnutls_datum_t channel;
306 current_global_tls_state = state;
308 tls_active = state->fd_out;
310 cipher = gnutls_cipher_get(state->session);
311 /* returns size in "bytes" */
312 tls_bits = gnutls_cipher_get_key_size(cipher) * 8;
314 tls_cipher = state->ciphersuite;
316 DEBUG(D_tls) debug_printf("cipher: %s\n", tls_cipher);
318 tls_certificate_verified = state->peer_cert_verified;
320 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
321 only available for use for authenticators while this TLS session is running. */
323 tls_channelbinding_b64 = NULL;
324 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
327 rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel);
329 DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc));
331 old_pool = store_pool;
332 store_pool = POOL_PERM;
333 tls_channelbinding_b64 = auth_b64encode(channel.data, (int)channel.size);
334 store_pool = old_pool;
335 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
339 tls_peerdn = state->peerdn;
341 tls_sni = state->received_sni;
347 /*************************************************
348 * Setup up DH parameters *
349 *************************************************/
351 /* Generating the D-H parameters may take a long time. They only need to
352 be re-generated every so often, depending on security policy. What we do is to
353 keep these parameters in a file in the spool directory. If the file does not
354 exist, we generate them. This means that it is easy to cause a regeneration.
356 The new file is written as a temporary file and renamed, so that an incomplete
357 file is never present. If two processes both compute some new parameters, you
358 waste a bit of effort, but it doesn't seem worth messing around with locking to
362 host NULL for server, server for client (for error handling)
364 Returns: OK/DEFER/FAIL
371 unsigned int dh_bits;
373 uschar filename[PATH_MAX];
375 host_item *host = NULL; /* dummy for macros */
377 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
379 rc = gnutls_dh_params_init(&dh_server_params);
380 exim_gnutls_err_check(US"gnutls_dh_params_init");
382 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
383 /* If you change this constant, also change dh_param_fn_ext so that we can use a
384 different filename and ensure we have sufficient bits. */
385 dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL);
387 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL);
389 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
392 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
394 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
398 /* Some clients have hard-coded limits. */
399 if (dh_bits > tls_dh_max_bits)
402 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
404 dh_bits = tls_dh_max_bits;
407 if (!string_format(filename, sizeof(filename),
408 "%s/gnutls-params-%d", spool_directory, dh_bits))
409 return tls_error(US"overlong filename", NULL, NULL);
411 /* Open the cache file for reading and if successful, read it and set up the
414 fd = Uopen(filename, O_RDONLY, 0);
421 if (fstat(fd, &statbuf) < 0) /* EIO */
425 return tls_error(US"TLS cache stat failed", strerror(saved_errno), NULL);
427 if (!S_ISREG(statbuf.st_mode))
430 return tls_error(US"TLS cache not a file", NULL, NULL);
432 fp = fdopen(fd, "rb");
437 return tls_error(US"fdopen(TLS cache stat fd) failed",
438 strerror(saved_errno), NULL);
441 m.size = statbuf.st_size;
442 m.data = malloc(m.size);
446 return tls_error(US"malloc failed", strerror(errno), NULL);
448 sz = fread(m.data, m.size, 1, fp);
454 return tls_error(US"fread failed", strerror(saved_errno), NULL);
458 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
460 exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3");
461 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
464 /* If the file does not exist, fall through to compute new data and cache it.
465 If there was any other opening error, it is serious. */
467 else if (errno == ENOENT)
471 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
474 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
477 /* If ret < 0, either the cache file does not exist, or the data it contains
478 is not useful. One particular case of this is when upgrading from an older
479 release of Exim in which the data was stored in a different format. We don't
480 try to be clever and support both formats; we just regenerate new data in this
487 if ((PATH_MAX - Ustrlen(filename)) < 10)
488 return tls_error(US"Filename too long to generate replacement",
491 temp_fn = string_copy(US "%s.XXXXXXX");
492 fd = mkstemp(CS temp_fn); /* modifies temp_fn */
494 return tls_error(US"Unable to open temp file", strerror(errno), NULL);
495 (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */
497 DEBUG(D_tls) debug_printf("generating %d bits Diffie-Hellman key ...\n", dh_bits);
498 rc = gnutls_dh_params_generate2(dh_server_params, dh_bits);
499 exim_gnutls_err_check(US"gnutls_dh_params_generate2");
501 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
502 and I confirmed that a NULL call to get the size first is how the GnuTLS
503 sample apps handle this. */
507 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
509 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
510 exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3(NULL) sizing");
512 m.data = malloc(m.size);
514 return tls_error(US"memory allocation failed", strerror(errno), NULL);
515 /* this will return a size 1 less than the allocation size above */
516 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
518 if (rc != GNUTLS_E_SUCCESS)
521 exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real");
524 sz = write_to_fd_buf(fd, m.data, (size_t) m.size);
528 return tls_error(US"TLS cache write D-H params failed",
529 strerror(errno), NULL);
532 sz = write_to_fd_buf(fd, US"\n", 1);
534 return tls_error(US"TLS cache write D-H params final newline failed",
535 strerror(errno), NULL);
539 return tls_error(US"TLS cache write close() failed",
540 strerror(errno), NULL);
542 if (Urename(temp_fn, filename) < 0)
543 return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
544 temp_fn, filename), strerror(errno), NULL);
546 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
549 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
556 /*************************************************
557 * Variables re-expanded post-SNI *
558 *************************************************/
560 /* Called from both server and client code, via tls_init(), and also from
561 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
563 We can tell the two apart by state->received_sni being non-NULL in callback.
565 The callback should not call us unless state->trigger_sni_changes is true,
566 which we are responsible for setting on the first pass through.
569 state exim_gnutls_state_st *
571 Returns: OK/DEFER/FAIL
575 tls_expand_session_files(exim_gnutls_state_st *state)
579 const host_item *host = state->host; /* macro should be reconsidered? */
580 uschar *saved_tls_certificate = NULL;
581 uschar *saved_tls_privatekey = NULL;
582 uschar *saved_tls_verify_certificates = NULL;
583 uschar *saved_tls_crl = NULL;
586 /* We check for tls_sni *before* expansion. */
589 if (!state->received_sni)
591 if (state->tls_certificate && Ustrstr(state->tls_certificate, US"tls_sni"))
593 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
594 state->trigger_sni_changes = TRUE;
599 /* useful for debugging */
600 saved_tls_certificate = state->exp_tls_certificate;
601 saved_tls_privatekey = state->exp_tls_privatekey;
602 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
603 saved_tls_crl = state->exp_tls_crl;
607 rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
608 exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials");
610 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
611 state members, assuming consistent naming; and expand_check() returns
612 false if expansion failed, unless expansion was forced to fail. */
614 /* check if we at least have a certificate, before doing expensive
617 if (!expand_check_tlsvar(tls_certificate))
620 /* certificate is mandatory in server, optional in client */
622 if ((state->exp_tls_certificate == NULL) ||
623 (*state->exp_tls_certificate == '\0'))
625 if (state->host == NULL)
626 return tls_error(US"no TLS server certificate is specified", NULL, NULL);
628 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
631 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey))
634 /* tls_privatekey is optional, defaulting to same file as certificate */
636 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
638 state->tls_privatekey = state->tls_certificate;
639 state->exp_tls_privatekey = state->exp_tls_certificate;
643 if (state->exp_tls_certificate && *state->exp_tls_certificate)
645 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
646 state->exp_tls_certificate, state->exp_tls_privatekey);
648 if (state->received_sni)
650 if ((Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0) &&
651 (Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0))
653 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
657 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
661 rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
662 CS state->exp_tls_certificate, CS state->exp_tls_privatekey,
663 GNUTLS_X509_FMT_PEM);
664 exim_gnutls_err_check(
665 string_sprintf("cert/key setup: cert=%s key=%s",
666 state->exp_tls_certificate, state->exp_tls_privatekey));
667 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
668 } /* tls_certificate */
670 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
671 provided. Experiment shows that, if the certificate file is empty, an unhelpful
672 error message is provided. However, if we just refrain from setting anything up
673 in that case, certificate verification fails, which seems to be the correct
676 if (state->tls_verify_certificates && *state->tls_verify_certificates)
678 if (!expand_check_tlsvar(tls_verify_certificates))
680 if (state->tls_crl && *state->tls_crl)
681 if (!expand_check_tlsvar(tls_crl))
684 if (!(state->exp_tls_verify_certificates &&
685 *state->exp_tls_verify_certificates))
688 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
689 /* With no tls_verify_certificates, we ignore tls_crl too */
696 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
700 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
702 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
703 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
708 /* The test suite passes in /dev/null; we could check for that path explicitly,
709 but who knows if someone has some weird FIFO which always dumps some certs, or
710 other weirdness. The thing we really want to check is that it's not a
711 directory, since while OpenSSL supports that, GnuTLS does not.
712 So s/!S_ISREG/S_ISDIR/ and change some messsaging ... */
713 if (S_ISDIR(statbuf.st_mode))
716 debug_printf("verify certificates path is a dir: \"%s\"\n",
717 state->exp_tls_verify_certificates);
718 log_write(0, LOG_MAIN|LOG_PANIC,
719 "tls_verify_certificates \"%s\" is a directory",
720 state->exp_tls_verify_certificates);
724 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
725 state->exp_tls_verify_certificates, statbuf.st_size);
727 if (statbuf.st_size == 0)
730 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
734 cert_count = gnutls_certificate_set_x509_trust_file(state->x509_cred,
735 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
739 exim_gnutls_err_check(US"gnutls_certificate_set_x509_trust_file");
741 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);
743 if (state->tls_crl && *state->tls_crl &&
744 state->exp_tls_crl && *state->exp_tls_crl)
746 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
747 cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
748 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM);
752 exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file");
754 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
763 /*************************************************
764 * Set X.509 state variables *
765 *************************************************/
767 /* In GnuTLS, the registered cert/key are not replaced by a later
768 set of a cert/key, so for SNI support we need a whole new x509_cred
769 structure. Which means various other non-re-expanded pieces of state
770 need to be re-set in the new struct, so the setting logic is pulled
774 state exim_gnutls_state_st *
776 Returns: OK/DEFER/FAIL
780 tls_set_remaining_x509(exim_gnutls_state_st *state)
783 const host_item *host = state->host; /* macro should be reconsidered? */
785 /* Create D-H parameters, or read them from the cache file. This function does
786 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
787 client-side params. */
791 if (!dh_server_params)
793 rc = init_server_dh();
794 if (rc != OK) return rc;
796 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
799 /* Link the credentials to the session. */
801 rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred);
802 exim_gnutls_err_check(US"gnutls_credentials_set");
807 /*************************************************
808 * Initialize for GnuTLS *
809 *************************************************/
811 /* Called from both server and client code. In the case of a server, errors
812 before actual TLS negotiation return DEFER.
815 host connected host, if client; NULL if server
816 certificate certificate file
817 privatekey private key file
818 sni TLS SNI to send, sometimes when client; else NULL
821 require_ciphers tls_require_ciphers setting
823 Returns: OK/DEFER/FAIL
828 const host_item *host,
829 const uschar *certificate,
830 const uschar *privatekey,
834 const uschar *require_ciphers,
835 exim_gnutls_state_st **caller_state)
837 exim_gnutls_state_st *state;
842 BOOL want_default_priorities;
844 if (!exim_gnutls_base_init_done)
846 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
848 rc = gnutls_global_init();
849 exim_gnutls_err_check(US"gnutls_global_init");
851 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
854 gnutls_global_set_log_function(exim_gnutls_logger_cb);
855 /* arbitrarily chosen level; bump upto 9 for more */
856 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
860 exim_gnutls_base_init_done = TRUE;
865 state = &state_client;
866 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
867 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
868 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
872 state = &state_server;
873 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
874 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
875 rc = gnutls_init(&state->session, GNUTLS_SERVER);
877 exim_gnutls_err_check(US"gnutls_init");
881 state->tls_certificate = certificate;
882 state->tls_privatekey = privatekey;
883 state->tls_require_ciphers = require_ciphers;
884 state->tls_sni = sni;
885 state->tls_verify_certificates = cas;
886 state->tls_crl = crl;
888 /* This handles the variables that might get re-expanded after TLS SNI;
889 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
892 debug_printf("Expanding various TLS configuration options for session credentials.\n");
893 rc = tls_expand_session_files(state);
894 if (rc != OK) return rc;
896 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
897 requires a new structure afterwards. */
899 rc = tls_set_remaining_x509(state);
900 if (rc != OK) return rc;
902 /* set SNI in client, only */
905 if (!expand_check_tlsvar(tls_sni))
907 if (state->exp_tls_sni && *state->exp_tls_sni)
910 debug_printf("Setting TLS client SNI to \"%s\"\n", state->exp_tls_sni);
911 sz = Ustrlen(state->exp_tls_sni);
912 rc = gnutls_server_name_set(state->session,
913 GNUTLS_NAME_DNS, state->exp_tls_sni, sz);
914 exim_gnutls_err_check(US"gnutls_server_name_set");
917 else if (state->tls_sni)
918 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
919 "have an SNI set for a client [%s]\n", state->tls_sni);
921 /* This is the priority string support,
922 http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html
923 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
924 This was backwards incompatible, but means Exim no longer needs to track
925 all algorithms and provide string forms for them. */
927 want_default_priorities = TRUE;
929 if (state->tls_require_ciphers && *state->tls_require_ciphers)
931 if (!expand_check_tlsvar(tls_require_ciphers))
933 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
935 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n",
936 state->exp_tls_require_ciphers);
938 rc = gnutls_priority_init(&state->priority_cache,
939 CS state->exp_tls_require_ciphers, &errpos);
940 want_default_priorities = FALSE;
941 p = state->exp_tls_require_ciphers;
944 if (want_default_priorities)
947 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n",
948 exim_default_gnutls_priority);
949 rc = gnutls_priority_init(&state->priority_cache,
950 exim_default_gnutls_priority, &errpos);
951 p = US exim_default_gnutls_priority;
954 exim_gnutls_err_check(string_sprintf(
955 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
956 p, errpos - CS p, errpos));
958 rc = gnutls_priority_set(state->session, state->priority_cache);
959 exim_gnutls_err_check(US"gnutls_priority_set");
961 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
963 /* Reduce security in favour of increased compatibility, if the admin
964 decides to make that trade-off. */
965 if (gnutls_compat_mode)
967 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
968 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
969 gnutls_session_enable_compatibility_mode(state->session);
971 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
975 *caller_state = state;
976 /* needs to happen before callbacks during handshake */
977 current_global_tls_state = state;
984 /*************************************************
985 * Extract peer information *
986 *************************************************/
988 /* Called from both server and client code.
989 Only this is allowed to set state->peerdn and state->have_set_peerdn
990 and we use that to detect double-calls.
992 NOTE: the state blocks last while the TLS connection is up, which is fine
993 for logging in the server side, but for the client side, we log after teardown
994 in src/deliver.c. While the session is up, we can twist about states and
995 repoint tls_* globals, but those variables used for logging or other variable
996 expansion that happens _after_ delivery need to have a longer life-time.
998 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
999 doing this more than once per generation of a state context. We set them in
1000 the state context, and repoint tls_* to them. After the state goes away, the
1001 tls_* copies of the pointers remain valid and client delivery logging is happy.
1003 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1007 state exim_gnutls_state_st *
1009 Returns: OK/DEFER/FAIL
1013 peer_status(exim_gnutls_state_st *state)
1015 uschar cipherbuf[256];
1016 const gnutls_datum *cert_list;
1018 unsigned int cert_list_size = 0;
1019 gnutls_protocol_t protocol;
1020 gnutls_cipher_algorithm_t cipher;
1021 gnutls_kx_algorithm_t kx;
1022 gnutls_mac_algorithm_t mac;
1023 gnutls_certificate_type_t ct;
1024 gnutls_x509_crt_t crt;
1028 if (state->have_set_peerdn)
1030 state->have_set_peerdn = TRUE;
1032 state->peerdn = NULL;
1035 cipher = gnutls_cipher_get(state->session);
1036 protocol = gnutls_protocol_get_version(state->session);
1037 mac = gnutls_mac_get(state->session);
1038 kx = gnutls_kx_get(state->session);
1040 string_format(cipherbuf, sizeof(cipherbuf),
1042 gnutls_protocol_get_name(protocol),
1043 gnutls_cipher_suite_get_name(kx, cipher, mac),
1044 (int) gnutls_cipher_get_key_size(cipher) * 8);
1046 /* I don't see a way that spaces could occur, in the current GnuTLS
1047 code base, but it was a concern in the old code and perhaps older GnuTLS
1048 releases did return "TLS 1.0"; play it safe, just in case. */
1049 for (p = cipherbuf; *p != '\0'; ++p)
1052 old_pool = store_pool;
1053 store_pool = POOL_PERM;
1054 state->ciphersuite = string_copy(cipherbuf);
1055 store_pool = old_pool;
1056 tls_cipher = state->ciphersuite;
1059 cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
1061 if (cert_list == NULL || cert_list_size == 0)
1063 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1064 cert_list, cert_list_size);
1065 if (state->verify_requirement == VERIFY_REQUIRED)
1066 return tls_error(US"certificate verification failed",
1067 "no certificate received from peer", state->host);
1071 ct = gnutls_certificate_type_get(state->session);
1072 if (ct != GNUTLS_CRT_X509)
1074 const char *ctn = gnutls_certificate_type_get_name(ct);
1076 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1077 if (state->verify_requirement == VERIFY_REQUIRED)
1078 return tls_error(US"certificate verification not possible, unhandled type",
1083 #define exim_gnutls_peer_err(Label) do { \
1084 if (rc != GNUTLS_E_SUCCESS) { \
1085 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", (Label), gnutls_strerror(rc)); \
1086 if (state->verify_requirement == VERIFY_REQUIRED) { return tls_error((Label), gnutls_strerror(rc), state->host); } \
1087 return OK; } } while (0)
1089 rc = gnutls_x509_crt_init(&crt);
1090 exim_gnutls_peer_err(US"gnutls_x509_crt_init (crt)");
1092 rc = gnutls_x509_crt_import(crt, &cert_list[0], GNUTLS_X509_FMT_DER);
1093 exim_gnutls_peer_err(US"failed to import certificate [gnutls_x509_crt_import(cert 0)]");
1095 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1096 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1098 exim_gnutls_peer_err(US"getting size for cert DN failed");
1099 return FAIL; /* should not happen */
1101 dn_buf = store_get_perm(sz);
1102 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1103 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1104 state->peerdn = dn_buf;
1107 #undef exim_gnutls_peer_err
1113 /*************************************************
1114 * Verify peer certificate *
1115 *************************************************/
1117 /* Called from both server and client code.
1118 *Should* be using a callback registered with
1119 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1120 the peer information, but that's too new for some OSes.
1123 state exim_gnutls_state_st *
1124 error where to put an error message
1127 FALSE if the session should be rejected
1128 TRUE if the cert is okay or we just don't care
1132 verify_certificate(exim_gnutls_state_st *state, const char **error)
1135 unsigned int verify;
1139 rc = peer_status(state);
1142 verify = GNUTLS_CERT_INVALID;
1143 *error = "not supplied";
1147 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1150 /* Handle the result of verification. INVALID seems to be set as well
1151 as REVOKED, but leave the test for both. */
1153 if ((rc < 0) || (verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0)
1155 state->peer_cert_verified = FALSE;
1157 *error = ((verify & GNUTLS_CERT_REVOKED) != 0) ? "revoked" : "invalid";
1160 debug_printf("TLS certificate verification failed (%s): peerdn=%s\n",
1161 *error, state->peerdn ? state->peerdn : US"<unset>");
1163 if (state->verify_requirement == VERIFY_REQUIRED)
1165 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1169 debug_printf("TLS verify failure overriden (host in tls_try_verify_hosts)\n");
1173 state->peer_cert_verified = TRUE;
1174 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n",
1175 state->peerdn ? state->peerdn : US"<unset>");
1178 tls_peerdn = state->peerdn;
1186 /* ------------------------------------------------------------------------ */
1189 /* Logging function which can be registered with
1190 * gnutls_global_set_log_function()
1191 * gnutls_global_set_log_level() 0..9
1193 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1195 exim_gnutls_logger_cb(int level, const char *message)
1197 size_t len = strlen(message);
1200 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1203 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1204 message[len-1] == '\n' ? "" : "\n");
1209 /* Called after client hello, should handle SNI work.
1210 This will always set tls_sni (state->received_sni) if available,
1211 and may trigger presenting different certificates,
1212 if state->trigger_sni_changes is TRUE.
1214 Should be registered with
1215 gnutls_handshake_set_post_client_hello_function()
1217 "This callback must return 0 on success or a gnutls error code to terminate the
1220 For inability to get SNI information, we return 0.
1221 We only return non-zero if re-setup failed.
1225 exim_sni_handling_cb(gnutls_session_t session)
1227 char sni_name[MAX_HOST_LEN];
1228 size_t data_len = MAX_HOST_LEN;
1229 exim_gnutls_state_st *state = current_global_tls_state;
1230 unsigned int sni_type;
1233 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
1234 if (rc != GNUTLS_E_SUCCESS)
1237 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
1238 debug_printf("TLS: no SNI presented in handshake.\n");
1240 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
1241 gnutls_strerror(rc), rc);
1246 if (sni_type != GNUTLS_NAME_DNS)
1248 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
1252 /* We now have a UTF-8 string in sni_name */
1253 old_pool = store_pool;
1254 store_pool = POOL_PERM;
1255 state->received_sni = string_copyn(US sni_name, data_len);
1256 store_pool = old_pool;
1258 /* We set this one now so that variable expansions below will work */
1259 tls_sni = state->received_sni;
1261 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
1262 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
1264 if (!state->trigger_sni_changes)
1267 rc = tls_expand_session_files(state);
1270 /* If the setup of certs/etc failed before handshake, TLS would not have
1271 been offered. The best we can do now is abort. */
1272 return GNUTLS_E_APPLICATION_ERROR_MIN;
1275 rc = tls_set_remaining_x509(state);
1276 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
1284 /* ------------------------------------------------------------------------ */
1285 /* Exported functions */
1290 /*************************************************
1291 * Start a TLS session in a server *
1292 *************************************************/
1294 /* This is called when Exim is running as a server, after having received
1295 the STARTTLS command. It must respond to that command, and then negotiate
1299 require_ciphers list of allowed ciphers or NULL
1301 Returns: OK on success
1302 DEFER for errors before the start of the negotiation
1303 FAIL for errors during the negotation; the server can't
1308 tls_server_start(const uschar *require_ciphers)
1312 exim_gnutls_state_st *state = NULL;
1314 /* Check for previous activation */
1315 /* nb: this will not be TLS callout safe, needs reworking as part of that. */
1317 if (tls_active >= 0)
1319 tls_error(US"STARTTLS received after TLS started", "", NULL);
1320 smtp_printf("554 Already in TLS\r\n");
1324 /* Initialize the library. If it fails, it will already have logged the error
1325 and sent an SMTP response. */
1327 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
1329 rc = tls_init(NULL, tls_certificate, tls_privatekey,
1330 NULL, tls_verify_certificates, tls_crl,
1331 require_ciphers, &state);
1332 if (rc != OK) return rc;
1334 /* If this is a host for which certificate verification is mandatory or
1335 optional, set up appropriately. */
1337 if (verify_check_host(&tls_verify_hosts) == OK)
1339 DEBUG(D_tls) debug_printf("TLS: a client certificate will be required.\n");
1340 state->verify_requirement = VERIFY_REQUIRED;
1341 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
1343 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1345 DEBUG(D_tls) debug_printf("TLS: a client certificate will be requested but not required.\n");
1346 state->verify_requirement = VERIFY_OPTIONAL;
1347 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
1351 DEBUG(D_tls) debug_printf("TLS: a client certificate will not be requested.\n");
1352 state->verify_requirement = VERIFY_NONE;
1353 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
1356 /* Register SNI handling; always, even if not in tls_certificate, so that the
1357 expansion variable $tls_sni is always available. */
1359 gnutls_handshake_set_post_client_hello_function(state->session,
1360 exim_sni_handling_cb);
1362 /* Set context and tell client to go ahead, except in the case of TLS startup
1363 on connection, where outputting anything now upsets the clients and tends to
1364 make them disconnect. We need to have an explicit fflush() here, to force out
1365 the response. Other smtp_printf() calls do not need it, because in non-TLS
1366 mode, the fflush() happens when smtp_getc() is called. */
1368 if (!tls_on_connect)
1370 smtp_printf("220 TLS go ahead\r\n");
1374 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1375 that the GnuTLS library doesn't. */
1377 gnutls_transport_set_ptr2(state->session,
1378 (gnutls_transport_ptr)fileno(smtp_in),
1379 (gnutls_transport_ptr)fileno(smtp_out));
1380 state->fd_in = fileno(smtp_in);
1381 state->fd_out = fileno(smtp_out);
1383 sigalrm_seen = FALSE;
1384 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1387 rc = gnutls_handshake(state->session);
1388 } while ((rc == GNUTLS_E_AGAIN) ||
1389 (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));
1392 if (rc != GNUTLS_E_SUCCESS)
1394 tls_error(US"gnutls_handshake",
1395 sigalrm_seen ? "timed out" : gnutls_strerror(rc), NULL);
1396 /* It seems that, except in the case of a timeout, we have to close the
1397 connection right here; otherwise if the other end is running OpenSSL it hangs
1398 until the server times out. */
1402 (void)fclose(smtp_out);
1403 (void)fclose(smtp_in);
1409 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
1411 /* Verify after the fact */
1413 if (state->verify_requirement != VERIFY_NONE)
1415 if (!verify_certificate(state, &error))
1417 if (state->verify_requirement == VERIFY_OPTIONAL)
1420 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
1425 tls_error(US"certificate verification failed", error, NULL);
1431 /* Figure out peer DN, and if authenticated, etc. */
1433 rc = peer_status(state);
1434 if (rc != OK) return rc;
1436 /* Sets various Exim expansion variables; always safe within server */
1438 extract_exim_vars_from_tls_state(state);
1440 /* TLS has been set up. Adjust the input functions to read via TLS,
1441 and initialize appropriately. */
1443 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1445 receive_getc = tls_getc;
1446 receive_ungetc = tls_ungetc;
1447 receive_feof = tls_feof;
1448 receive_ferror = tls_ferror;
1449 receive_smtp_buffered = tls_smtp_buffered;
1457 /*************************************************
1458 * Start a TLS session in a client *
1459 *************************************************/
1461 /* Called from the smtp transport after STARTTLS has been accepted.
1464 fd the fd of the connection
1465 host connected host (for messages)
1466 addr the first address (not used)
1467 dhparam DH parameter file (ignored, we're a client)
1468 certificate certificate file
1469 privatekey private key file
1470 sni TLS SNI to send to remote host
1471 verify_certs file for certificate verify
1472 verify_crl CRL for verify
1473 require_ciphers list of allowed ciphers or NULL
1474 timeout startup timeout
1476 Returns: OK/DEFER/FAIL (because using common functions),
1477 but for a client, DEFER and FAIL have the same meaning
1481 tls_client_start(int fd, host_item *host,
1482 address_item *addr ARG_UNUSED, uschar *dhparam ARG_UNUSED,
1483 uschar *certificate, uschar *privatekey, uschar *sni,
1484 uschar *verify_certs, uschar *verify_crl,
1485 uschar *require_ciphers, int timeout)
1489 exim_gnutls_state_st *state = NULL;
1491 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);
1493 rc = tls_init(host, certificate, privatekey,
1494 sni, verify_certs, verify_crl, require_ciphers, &state);
1495 if (rc != OK) return rc;
1497 gnutls_dh_set_prime_bits(state->session, EXIM_CLIENT_DH_MIN_BITS);
1499 if (verify_certs == NULL)
1501 DEBUG(D_tls) debug_printf("TLS: server certificate verification not required\n");
1502 state->verify_requirement = VERIFY_NONE;
1503 /* we still ask for it, to log it, etc */
1504 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
1508 DEBUG(D_tls) debug_printf("TLS: server certificate verification required\n");
1509 state->verify_requirement = VERIFY_REQUIRED;
1510 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
1513 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr)fd);
1517 /* There doesn't seem to be a built-in timeout on connection. */
1519 sigalrm_seen = FALSE;
1523 rc = gnutls_handshake(state->session);
1524 } while ((rc == GNUTLS_E_AGAIN) ||
1525 (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));
1528 if (rc != GNUTLS_E_SUCCESS)
1529 return tls_error(US"gnutls_handshake",
1530 sigalrm_seen ? "timed out" : gnutls_strerror(rc), state->host);
1532 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
1536 if (state->verify_requirement != VERIFY_NONE &&
1537 !verify_certificate(state, &error))
1538 return tls_error(US"certificate verification failed", error, state->host);
1540 /* Figure out peer DN, and if authenticated, etc. */
1542 rc = peer_status(state);
1543 if (rc != OK) return rc;
1545 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
1547 extract_exim_vars_from_tls_state(state);
1555 /*************************************************
1556 * Close down a TLS session *
1557 *************************************************/
1559 /* This is also called from within a delivery subprocess forked from the
1560 daemon, to shut down the TLS library, without actually doing a shutdown (which
1561 would tamper with the TLS session in the parent process).
1563 Arguments: TRUE if gnutls_bye is to be called
1568 tls_close(BOOL shutdown)
1570 exim_gnutls_state_st *state = current_global_tls_state;
1572 if (tls_active < 0) return; /* TLS was not active */
1576 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n");
1577 gnutls_bye(state->session, GNUTLS_SHUT_WR);
1580 gnutls_deinit(state->session);
1582 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1584 if ((state_server.session == NULL) && (state_client.session == NULL))
1586 gnutls_global_deinit();
1587 exim_gnutls_base_init_done = FALSE;
1596 /*************************************************
1597 * TLS version of getc *
1598 *************************************************/
1600 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1601 it refills the buffer via the GnuTLS reading function.
1603 This feeds DKIM and should be used for all message-body reads.
1606 Returns: the next character or EOF
1612 exim_gnutls_state_st *state = current_global_tls_state;
1613 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
1617 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
1618 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
1620 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1621 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
1622 ssl_xfer_buffer_size);
1625 /* A zero-byte return appears to mean that the TLS session has been
1626 closed down, not that the socket itself has been closed down. Revert to
1627 non-TLS handling. */
1631 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1633 receive_getc = smtp_getc;
1634 receive_ungetc = smtp_ungetc;
1635 receive_feof = smtp_feof;
1636 receive_ferror = smtp_ferror;
1637 receive_smtp_buffered = smtp_buffered;
1639 gnutls_deinit(state->session);
1640 state->session = NULL;
1643 tls_certificate_verified = FALSE;
1644 tls_channelbinding_b64 = NULL;
1651 /* Handle genuine errors */
1653 else if (inbytes < 0)
1655 record_io_error(state, (int) inbytes, US"recv", NULL);
1656 state->xfer_error = 1;
1659 #ifndef DISABLE_DKIM
1660 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
1662 state->xfer_buffer_hwm = (int) inbytes;
1663 state->xfer_buffer_lwm = 0;
1666 /* Something in the buffer; return next uschar */
1668 return state->xfer_buffer[state->xfer_buffer_lwm++];
1674 /*************************************************
1675 * Read bytes from TLS channel *
1676 *************************************************/
1678 /* This does not feed DKIM, so if the caller uses this for reading message body,
1679 then the caller must feed DKIM.
1684 Returns: the number of bytes read
1685 -1 after a failed read
1689 tls_read(uschar *buff, size_t len)
1691 exim_gnutls_state_st *state = current_global_tls_state;
1697 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
1699 debug_printf("*** PROBABLY A BUG *** " \
1700 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
1701 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
1704 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
1705 state->session, buff, len);
1707 inbytes = gnutls_record_recv(state->session, buff, len);
1708 if (inbytes > 0) return inbytes;
1711 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1713 else record_io_error(state, (int)inbytes, US"recv", NULL);
1721 /*************************************************
1722 * Write bytes down TLS channel *
1723 *************************************************/
1730 Returns: the number of bytes after a successful write,
1731 -1 after a failed write
1735 tls_write(const uschar *buff, size_t len)
1739 exim_gnutls_state_st *state = current_global_tls_state;
1741 DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left);
1744 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
1746 outbytes = gnutls_record_send(state->session, buff, left);
1748 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
1751 record_io_error(state, outbytes, US"send", NULL);
1756 record_io_error(state, 0, US"send", US"TLS channel closed on write");
1767 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
1778 /*************************************************
1779 * Random number generation *
1780 *************************************************/
1782 /* Pseudo-random number generation. The result is not expected to be
1783 cryptographically strong but not so weak that someone will shoot themselves
1784 in the foot using it as a nonce in input in some email header scheme or
1785 whatever weirdness they'll twist this into. The result should handle fork()
1786 and avoid repeating sequences. OpenSSL handles that for us.
1790 Returns a random number in range [0, max-1]
1793 #ifdef HAVE_GNUTLS_RND
1795 vaguely_random_number(int max)
1800 uschar smallbuf[sizeof(r)];
1805 needed_len = sizeof(r);
1806 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1807 * asked for a number less than 10. */
1808 for (r = max, i = 0; r; ++i)
1814 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
1817 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
1818 return vaguely_random_number_fallback(max);
1821 for (p = smallbuf; needed_len; --needed_len, ++p)
1827 /* We don't particularly care about weighted results; if someone wants
1828 * smooth distribution and cares enough then they should submit a patch then. */
1831 #else /* HAVE_GNUTLS_RND */
1833 vaguely_random_number(int max)
1835 return vaguely_random_number_fallback(max);
1837 #endif /* HAVE_GNUTLS_RND */
1842 /*************************************************
1843 * Let tls_require_ciphers be checked at startup *
1844 *************************************************/
1846 /* The tls_require_ciphers option, if set, must be something which the
1849 Returns: NULL on success, or error message
1853 tls_validate_require_cipher(void)
1856 uschar *expciphers = NULL;
1857 gnutls_priority_t priority_cache;
1860 #define validate_check_rc(Label) do { \
1861 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
1862 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
1863 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
1865 if (exim_gnutls_base_init_done)
1866 log_write(0, LOG_MAIN|LOG_PANIC,
1867 "already initialised GnuTLS, Exim developer bug");
1869 rc = gnutls_global_init();
1870 validate_check_rc(US"gnutls_global_init()");
1871 exim_gnutls_base_init_done = TRUE;
1873 if (!(tls_require_ciphers && *tls_require_ciphers))
1874 return_deinit(NULL);
1876 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1877 return_deinit(US"failed to expand tls_require_ciphers");
1879 if (!(expciphers && *expciphers))
1880 return_deinit(NULL);
1883 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1885 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
1886 validate_check_rc(string_sprintf(
1887 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
1888 expciphers, errpos - CS expciphers, errpos));
1890 #undef return_deinit
1891 #undef validate_check_rc
1892 gnutls_global_deinit();
1900 /*************************************************
1901 * Report the library versions. *
1902 *************************************************/
1904 /* See a description in tls-openssl.c for an explanation of why this exists.
1906 Arguments: a FILE* to print the results to
1911 tls_version_report(FILE *f)
1913 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
1916 gnutls_check_version(NULL));
1919 /* End of tls-gnu.c */