abf2c25b8058f589f1d2366fcca6e178fe66669d
[exim.git] / src / src / tls-gnu.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
6 /* See the file NOTICE for conditions of use and distribution. */
7
8 /* Copyright (c) Phil Pennock 2012 */
9
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.
13
14 The code herein is a revamp of GnuTLS integration using the current APIs; the
15 original tls-gnu.c was based on a patch which was contributed by Nikos
16 Mavrogiannopoulos. The revamp is partially a rewrite, partially cut&paste as
17 appropriate.
18
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).
23
24 Keeping client and server variables more split than before and is currently
25 the norm, in anticipation of TLS in ACL callouts.
26
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.
31
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).
35 */
36
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>
42
43 /* needed to disable PKCS11 autoload unless requested */
44 #if GNUTLS_VERSION_NUMBER >= 0x020c00
45 # include <gnutls/pkcs11.h>
46 # define SUPPORT_PARAM_TO_PK_BITS
47 #endif
48 #if GNUTLS_VERSION_NUMBER < 0x030103 && !defined(DISABLE_OCSP)
49 # warning "GnuTLS library version too old; define DISABLE_OCSP in Makefile"
50 # define DISABLE_OCSP
51 #endif
52 #if GNUTLS_VERSION_NUMBER < 0x020a00 && !defined(DISABLE_EVENT)
53 # warning "GnuTLS library version too old; tls:cert event unsupported"
54 # define DISABLE_EVENT
55 #endif
56 #if GNUTLS_VERSION_NUMBER >= 0x030306
57 # define SUPPORT_CA_DIR
58 #else
59 # undef SUPPORT_CA_DIR
60 #endif
61 #if GNUTLS_VERSION_NUMBER >= 0x030014
62 # define SUPPORT_SYSDEFAULT_CABUNDLE
63 #endif
64 #if GNUTLS_VERSION_NUMBER >= 0x030104
65 # define GNUTLS_CERT_VFY_STATUS_PRINT
66 #endif
67 #if GNUTLS_VERSION_NUMBER >= 0x030109
68 # define SUPPORT_CORK
69 #endif
70 #if GNUTLS_VERSION_NUMBER >= 0x03010a
71 # define SUPPORT_GNUTLS_SESS_DESC
72 #endif
73 #if GNUTLS_VERSION_NUMBER >= 0x030500
74 # define SUPPORT_GNUTLS_KEYLOG
75 #endif
76 #if GNUTLS_VERSION_NUMBER >= 0x030506 && !defined(DISABLE_OCSP)
77 # define SUPPORT_SRV_OCSP_STACK
78 #endif
79
80 #ifdef SUPPORT_DANE
81 # if GNUTLS_VERSION_NUMBER >= 0x030000
82 # define DANESSL_USAGE_DANE_TA 2
83 # define DANESSL_USAGE_DANE_EE 3
84 # else
85 # error GnuTLS version too early for DANE
86 # endif
87 # if GNUTLS_VERSION_NUMBER < 0x999999
88 # define GNUTLS_BROKEN_DANE_VALIDATION
89 # endif
90 #endif
91
92 #ifndef DISABLE_OCSP
93 # include <gnutls/ocsp.h>
94 #endif
95 #ifdef SUPPORT_DANE
96 # include <gnutls/dane.h>
97 #endif
98
99 #include "tls-cipher-stdname.c"
100
101
102 /* GnuTLS 2 vs 3
103
104 GnuTLS 3 only:
105 gnutls_global_set_audit_log_function()
106
107 Changes:
108 gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
109 */
110
111 /* Local static variables for GnuTLS */
112
113 /* Values for verify_requirement */
114
115 enum peer_verify_requirement
116 { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED, VERIFY_DANE };
117
118 /* This holds most state for server or client; with this, we can set up an
119 outbound TLS-enabled connection in an ACL callout, while not stomping all
120 over the TLS variables available for expansion.
121
122 Some of these correspond to variables in globals.c; those variables will
123 be set to point to content in one of these instances, as appropriate for
124 the stage of the process lifetime.
125
126 Not handled here: global tls_channelbinding_b64.
127 */
128
129 typedef struct exim_gnutls_state {
130 gnutls_session_t session;
131 gnutls_certificate_credentials_t x509_cred;
132 gnutls_priority_t priority_cache;
133 enum peer_verify_requirement verify_requirement;
134 int fd_in;
135 int fd_out;
136 BOOL peer_cert_verified;
137 BOOL peer_dane_verified;
138 BOOL trigger_sni_changes;
139 BOOL have_set_peerdn;
140 const struct host_item *host; /* NULL if server */
141 gnutls_x509_crt_t peercert;
142 uschar *peerdn;
143 uschar *ciphersuite;
144 uschar *received_sni;
145
146 const uschar *tls_certificate;
147 const uschar *tls_privatekey;
148 const uschar *tls_sni; /* client send only, not received */
149 const uschar *tls_verify_certificates;
150 const uschar *tls_crl;
151 const uschar *tls_require_ciphers;
152
153 uschar *exp_tls_certificate;
154 uschar *exp_tls_privatekey;
155 uschar *exp_tls_verify_certificates;
156 uschar *exp_tls_crl;
157 uschar *exp_tls_require_ciphers;
158 const uschar *exp_tls_verify_cert_hostnames;
159 #ifndef DISABLE_EVENT
160 uschar *event_action;
161 #endif
162 #ifdef SUPPORT_DANE
163 char * const * dane_data;
164 const int * dane_data_len;
165 #endif
166
167 tls_support *tlsp; /* set in tls_init() */
168
169 uschar *xfer_buffer;
170 int xfer_buffer_lwm;
171 int xfer_buffer_hwm;
172 BOOL xfer_eof; /*XXX never gets set! */
173 BOOL xfer_error;
174 } exim_gnutls_state_st;
175
176 static const exim_gnutls_state_st exim_gnutls_state_init = {
177 .session = NULL,
178 .x509_cred = NULL,
179 .priority_cache = NULL,
180 .verify_requirement = VERIFY_NONE,
181 .fd_in = -1,
182 .fd_out = -1,
183 .peer_cert_verified = FALSE,
184 .peer_dane_verified = FALSE,
185 .trigger_sni_changes =FALSE,
186 .have_set_peerdn = FALSE,
187 .host = NULL,
188 .peercert = NULL,
189 .peerdn = NULL,
190 .ciphersuite = NULL,
191 .received_sni = NULL,
192
193 .tls_certificate = NULL,
194 .tls_privatekey = NULL,
195 .tls_sni = NULL,
196 .tls_verify_certificates = NULL,
197 .tls_crl = NULL,
198 .tls_require_ciphers =NULL,
199
200 .exp_tls_certificate = NULL,
201 .exp_tls_privatekey = NULL,
202 .exp_tls_verify_certificates = NULL,
203 .exp_tls_crl = NULL,
204 .exp_tls_require_ciphers = NULL,
205 .exp_tls_verify_cert_hostnames = NULL,
206 #ifndef DISABLE_EVENT
207 .event_action = NULL,
208 #endif
209 .tlsp = NULL,
210
211 .xfer_buffer = NULL,
212 .xfer_buffer_lwm = 0,
213 .xfer_buffer_hwm = 0,
214 .xfer_eof = FALSE,
215 .xfer_error = FALSE,
216 };
217
218 /* Not only do we have our own APIs which don't pass around state, assuming
219 it's held in globals, GnuTLS doesn't appear to let us register callback data
220 for callbacks, or as part of the session, so we have to keep a "this is the
221 context we're currently dealing with" pointer and rely upon being
222 single-threaded to keep from processing data on an inbound TLS connection while
223 talking to another TLS connection for an outbound check. This does mean that
224 there's no way for heart-beats to be responded to, for the duration of the
225 second connection.
226 XXX But see gnutls_session_get_ptr()
227 */
228
229 static exim_gnutls_state_st state_server;
230
231 /* dh_params are initialised once within the lifetime of a process using TLS;
232 if we used TLS in a long-lived daemon, we'd have to reconsider this. But we
233 don't want to repeat this. */
234
235 static gnutls_dh_params_t dh_server_params = NULL;
236
237 /* No idea how this value was chosen; preserving it. Default is 3600. */
238
239 static const int ssl_session_timeout = 200;
240
241 static const uschar * const exim_default_gnutls_priority = US"NORMAL";
242
243 /* Guard library core initialisation */
244
245 static BOOL exim_gnutls_base_init_done = FALSE;
246
247 #ifndef DISABLE_OCSP
248 static BOOL gnutls_buggy_ocsp = FALSE;
249 #endif
250
251
252 /* ------------------------------------------------------------------------ */
253 /* macros */
254
255 #define MAX_HOST_LEN 255
256
257 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
258 the library logging; a value less than 0 disables the calls to set up logging
259 callbacks. GNuTLS also looks for an environment variable - except not for
260 setuid binaries, making it useless - "GNUTLS_DEBUG_LEVEL".
261 Allegedly the testscript line "GNUTLS_DEBUG_LEVEL=9 sudo exim ..." would work,
262 but the env var must be added to /etc/sudoers too. */
263 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
264 # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
265 #endif
266
267 #ifndef EXIM_CLIENT_DH_MIN_BITS
268 # define EXIM_CLIENT_DH_MIN_BITS 1024
269 #endif
270
271 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
272 can ask for a bit-strength. Without that, we stick to the constant we had
273 before, for now. */
274 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
275 # define EXIM_SERVER_DH_BITS_PRE2_12 1024
276 #endif
277
278 #define expand_check_tlsvar(Varname, errstr) \
279 expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr)
280
281 #if GNUTLS_VERSION_NUMBER >= 0x020c00
282 # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
283 # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
284 # define HAVE_GNUTLS_RND
285 /* The security fix we provide with the gnutls_allow_auto_pkcs11 option
286 * (4.82 PP/09) introduces a compatibility regression. The symbol simply
287 * isn't available sometimes, so this needs to become a conditional
288 * compilation; the sanest way to deal with this being a problem on
289 * older OSes is to block it in the Local/Makefile with this compiler
290 * definition */
291 # ifndef AVOID_GNUTLS_PKCS11
292 # define HAVE_GNUTLS_PKCS11
293 # endif /* AVOID_GNUTLS_PKCS11 */
294 #endif
295
296
297
298
299 /* ------------------------------------------------------------------------ */
300 /* Callback declarations */
301
302 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
303 static void exim_gnutls_logger_cb(int level, const char *message);
304 #endif
305
306 static int exim_sni_handling_cb(gnutls_session_t session);
307
308 #ifndef DISABLE_OCSP
309 static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
310 gnutls_datum_t * ocsp_response);
311 #endif
312
313
314
315 /* ------------------------------------------------------------------------ */
316 /* Static functions */
317
318 /*************************************************
319 * Handle TLS error *
320 *************************************************/
321
322 /* Called from lots of places when errors occur before actually starting to do
323 the TLS handshake, that is, while the session is still in clear. Always returns
324 DEFER for a server and FAIL for a client so that most calls can use "return
325 tls_error(...)" to do this processing and then give an appropriate return. A
326 single function is used for both server and client, because it is called from
327 some shared functions.
328
329 Argument:
330 prefix text to include in the logged error
331 msg additional error string (may be NULL)
332 usually obtained from gnutls_strerror()
333 host NULL if setting up a server;
334 the connected host if setting up a client
335 errstr pointer to returned error string
336
337 Returns: OK/DEFER/FAIL
338 */
339
340 static int
341 tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
342 uschar ** errstr)
343 {
344 if (errstr)
345 *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
346 return host ? FAIL : DEFER;
347 }
348
349
350 static int
351 tls_error_gnu(const uschar *prefix, int err, const host_item *host,
352 uschar ** errstr)
353 {
354 return tls_error(prefix, US gnutls_strerror(err), host, errstr);
355 }
356
357 static int
358 tls_error_sys(const uschar *prefix, int err, const host_item *host,
359 uschar ** errstr)
360 {
361 return tls_error(prefix, US strerror(err), host, errstr);
362 }
363
364
365 /*************************************************
366 * Deal with logging errors during I/O *
367 *************************************************/
368
369 /* We have to get the identity of the peer from saved data.
370
371 Argument:
372 state the current GnuTLS exim state container
373 rc the GnuTLS error code, or 0 if it's a local error
374 when text identifying read or write
375 text local error text when rc is 0
376
377 Returns: nothing
378 */
379
380 static void
381 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
382 {
383 const uschar * msg;
384 uschar * errstr;
385
386 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
387 msg = string_sprintf("A TLS fatal alert has been received: %s",
388 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
389 else
390 msg = US gnutls_strerror(rc);
391
392 (void) tls_error(when, msg, state->host, &errstr);
393
394 if (state->host)
395 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s",
396 state->host->name, state->host->address, errstr);
397 else
398 {
399 uschar * conn_info = smtp_get_connection_info();
400 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5;
401 /* I'd like to get separated H= here, but too hard for now */
402 log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr);
403 }
404 }
405
406
407
408
409 /*************************************************
410 * Set various Exim expansion vars *
411 *************************************************/
412
413 #define exim_gnutls_cert_err(Label) \
414 do \
415 { \
416 if (rc != GNUTLS_E_SUCCESS) \
417 { \
418 DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \
419 (Label), gnutls_strerror(rc)); \
420 return rc; \
421 } \
422 } while (0)
423
424 static int
425 import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp)
426 {
427 int rc;
428
429 rc = gnutls_x509_crt_init(crtp);
430 exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)");
431
432 rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER);
433 exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]");
434
435 return rc;
436 }
437
438 #undef exim_gnutls_cert_err
439
440
441 /* We set various Exim global variables from the state, once a session has
442 been established. With TLS callouts, may need to change this to stack
443 variables, or just re-call it with the server state after client callout
444 has finished.
445
446 Make sure anything set here is unset in tls_getc().
447
448 Sets:
449 tls_active fd
450 tls_bits strength indicator
451 tls_certificate_verified bool indicator
452 tls_channelbinding_b64 for some SASL mechanisms
453 tls_cipher a string
454 tls_peercert pointer to library internal
455 tls_peerdn a string
456 tls_sni a (UTF-8) string
457 tls_ourcert pointer to library internal
458
459 Argument:
460 state the relevant exim_gnutls_state_st *
461 */
462
463 static void
464 extract_exim_vars_from_tls_state(exim_gnutls_state_st * state)
465 {
466 gnutls_cipher_algorithm_t cipher;
467 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
468 int old_pool;
469 int rc;
470 gnutls_datum_t channel;
471 #endif
472 tls_support * tlsp = state->tlsp;
473
474 tlsp->active.sock = state->fd_out;
475 tlsp->active.tls_ctx = state;
476
477 cipher = gnutls_cipher_get(state->session);
478 /* returns size in "bytes" */
479 tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
480
481 tlsp->cipher = state->ciphersuite;
482
483 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
484
485 tlsp->certificate_verified = state->peer_cert_verified;
486 #ifdef SUPPORT_DANE
487 tlsp->dane_verified = state->peer_dane_verified;
488 #endif
489
490 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
491 only available for use for authenticators while this TLS session is running. */
492
493 tls_channelbinding_b64 = NULL;
494 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
495 channel.data = NULL;
496 channel.size = 0;
497 if ((rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel)))
498 { DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); }
499 else
500 {
501 old_pool = store_pool;
502 store_pool = POOL_PERM;
503 tls_channelbinding_b64 = b64encode(CUS channel.data, (int)channel.size);
504 store_pool = old_pool;
505 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
506 }
507 #endif
508
509 /* peercert is set in peer_status() */
510 tlsp->peerdn = state->peerdn;
511 tlsp->sni = state->received_sni;
512
513 /* record our certificate */
514 {
515 const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session);
516 gnutls_x509_crt_t crt;
517
518 tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL;
519 }
520 }
521
522
523
524
525 /*************************************************
526 * Setup up DH parameters *
527 *************************************************/
528
529 /* Generating the D-H parameters may take a long time. They only need to
530 be re-generated every so often, depending on security policy. What we do is to
531 keep these parameters in a file in the spool directory. If the file does not
532 exist, we generate them. This means that it is easy to cause a regeneration.
533
534 The new file is written as a temporary file and renamed, so that an incomplete
535 file is never present. If two processes both compute some new parameters, you
536 waste a bit of effort, but it doesn't seem worth messing around with locking to
537 prevent this.
538
539 Returns: OK/DEFER/FAIL
540 */
541
542 static int
543 init_server_dh(uschar ** errstr)
544 {
545 int fd, rc;
546 unsigned int dh_bits;
547 gnutls_datum_t m;
548 uschar filename_buf[PATH_MAX];
549 uschar *filename = NULL;
550 size_t sz;
551 uschar *exp_tls_dhparam;
552 BOOL use_file_in_spool = FALSE;
553 host_item *host = NULL; /* dummy for macros */
554
555 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
556
557 if ((rc = gnutls_dh_params_init(&dh_server_params)))
558 return tls_error_gnu(US"gnutls_dh_params_init", rc, host, errstr);
559
560 m.data = NULL;
561 m.size = 0;
562
563 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
564 return DEFER;
565
566 if (!exp_tls_dhparam)
567 {
568 DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
569 m.data = US std_dh_prime_default();
570 m.size = Ustrlen(m.data);
571 }
572 else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
573 use_file_in_spool = TRUE;
574 else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
575 {
576 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
577 return OK;
578 }
579 else if (exp_tls_dhparam[0] != '/')
580 {
581 if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
582 return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
583 m.size = Ustrlen(m.data);
584 }
585 else
586 filename = exp_tls_dhparam;
587
588 if (m.data)
589 {
590 if ((rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM)))
591 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
592 DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
593 return OK;
594 }
595
596 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
597 /* If you change this constant, also change dh_param_fn_ext so that we can use a
598 different filename and ensure we have sufficient bits. */
599
600 if (!(dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL)))
601 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr);
602 DEBUG(D_tls)
603 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
604 dh_bits);
605 #else
606 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
607 DEBUG(D_tls)
608 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
609 dh_bits);
610 #endif
611
612 /* Some clients have hard-coded limits. */
613 if (dh_bits > tls_dh_max_bits)
614 {
615 DEBUG(D_tls)
616 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
617 tls_dh_max_bits);
618 dh_bits = tls_dh_max_bits;
619 }
620
621 if (use_file_in_spool)
622 {
623 if (!string_format(filename_buf, sizeof(filename_buf),
624 "%s/gnutls-params-%d", spool_directory, dh_bits))
625 return tls_error(US"overlong filename", NULL, NULL, errstr);
626 filename = filename_buf;
627 }
628
629 /* Open the cache file for reading and if successful, read it and set up the
630 parameters. */
631
632 if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
633 {
634 struct stat statbuf;
635 FILE *fp;
636 int saved_errno;
637
638 if (fstat(fd, &statbuf) < 0) /* EIO */
639 {
640 saved_errno = errno;
641 (void)close(fd);
642 return tls_error_sys(US"TLS cache stat failed", saved_errno, NULL, errstr);
643 }
644 if (!S_ISREG(statbuf.st_mode))
645 {
646 (void)close(fd);
647 return tls_error(US"TLS cache not a file", NULL, NULL, errstr);
648 }
649 if (!(fp = fdopen(fd, "rb")))
650 {
651 saved_errno = errno;
652 (void)close(fd);
653 return tls_error_sys(US"fdopen(TLS cache stat fd) failed",
654 saved_errno, NULL, errstr);
655 }
656
657 m.size = statbuf.st_size;
658 if (!(m.data = malloc(m.size)))
659 {
660 fclose(fp);
661 return tls_error_sys(US"malloc failed", errno, NULL, errstr);
662 }
663 if (!(sz = fread(m.data, m.size, 1, fp)))
664 {
665 saved_errno = errno;
666 fclose(fp);
667 free(m.data);
668 return tls_error_sys(US"fread failed", saved_errno, NULL, errstr);
669 }
670 fclose(fp);
671
672 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
673 free(m.data);
674 if (rc)
675 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
676 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
677 }
678
679 /* If the file does not exist, fall through to compute new data and cache it.
680 If there was any other opening error, it is serious. */
681
682 else if (errno == ENOENT)
683 {
684 rc = -1;
685 DEBUG(D_tls)
686 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
687 }
688 else
689 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
690 NULL, NULL, errstr);
691
692 /* If ret < 0, either the cache file does not exist, or the data it contains
693 is not useful. One particular case of this is when upgrading from an older
694 release of Exim in which the data was stored in a different format. We don't
695 try to be clever and support both formats; we just regenerate new data in this
696 case. */
697
698 if (rc < 0)
699 {
700 uschar *temp_fn;
701 unsigned int dh_bits_gen = dh_bits;
702
703 if ((PATH_MAX - Ustrlen(filename)) < 10)
704 return tls_error(US"Filename too long to generate replacement",
705 filename, NULL, errstr);
706
707 temp_fn = string_copy(US"%s.XXXXXXX");
708 if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */
709 return tls_error_sys(US"Unable to open temp file", errno, NULL, errstr);
710 (void)exim_chown(temp_fn, exim_uid, exim_gid); /* Probably not necessary */
711
712 /* GnuTLS overshoots!
713 * If we ask for 2236, we might get 2237 or more.
714 * But there's no way to ask GnuTLS how many bits there really are.
715 * We can ask how many bits were used in a TLS session, but that's it!
716 * The prime itself is hidden behind too much abstraction.
717 * So we ask for less, and proceed on a wing and a prayer.
718 * First attempt, subtracted 3 for 2233 and got 2240.
719 */
720 if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
721 {
722 dh_bits_gen = dh_bits - 10;
723 DEBUG(D_tls)
724 debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
725 dh_bits_gen);
726 }
727
728 DEBUG(D_tls)
729 debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
730 dh_bits_gen);
731 if ((rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen)))
732 return tls_error_gnu(US"gnutls_dh_params_generate2", rc, host, errstr);
733
734 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
735 and I confirmed that a NULL call to get the size first is how the GnuTLS
736 sample apps handle this. */
737
738 sz = 0;
739 m.data = NULL;
740 if ( (rc = gnutls_dh_params_export_pkcs3(dh_server_params,
741 GNUTLS_X509_FMT_PEM, m.data, &sz))
742 && rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
743 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3(NULL) sizing",
744 rc, host, errstr);
745 m.size = sz;
746 if (!(m.data = malloc(m.size)))
747 return tls_error_sys(US"memory allocation failed", errno, NULL, errstr);
748
749 /* this will return a size 1 less than the allocation size above */
750 if ((rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
751 m.data, &sz)))
752 {
753 free(m.data);
754 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3() real", rc, host, errstr);
755 }
756 m.size = sz; /* shrink by 1, probably */
757
758 if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size)
759 {
760 free(m.data);
761 return tls_error_sys(US"TLS cache write D-H params failed",
762 errno, NULL, errstr);
763 }
764 free(m.data);
765 if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
766 return tls_error_sys(US"TLS cache write D-H params final newline failed",
767 errno, NULL, errstr);
768
769 if ((rc = close(fd)))
770 return tls_error_sys(US"TLS cache write close() failed", errno, NULL, errstr);
771
772 if (Urename(temp_fn, filename) < 0)
773 return tls_error_sys(string_sprintf("failed to rename \"%s\" as \"%s\"",
774 temp_fn, filename), errno, NULL, errstr);
775
776 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
777 }
778
779 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
780 return OK;
781 }
782
783
784
785
786 /* Create and install a selfsigned certificate, for use in server mode */
787
788 static int
789 tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr)
790 {
791 gnutls_x509_crt_t cert = NULL;
792 time_t now;
793 gnutls_x509_privkey_t pkey = NULL;
794 const uschar * where;
795 int rc;
796
797 where = US"initialising pkey";
798 if ((rc = gnutls_x509_privkey_init(&pkey))) goto err;
799
800 where = US"initialising cert";
801 if ((rc = gnutls_x509_crt_init(&cert))) goto err;
802
803 where = US"generating pkey";
804 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
805 #ifdef SUPPORT_PARAM_TO_PK_BITS
806 # ifndef GNUTLS_SEC_PARAM_MEDIUM
807 # define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
808 # endif
809 gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
810 #else
811 2048,
812 #endif
813 0)))
814 goto err;
815
816 where = US"configuring cert";
817 now = 1;
818 if ( (rc = gnutls_x509_crt_set_version(cert, 3))
819 || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
820 || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
821 || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */
822 || (rc = gnutls_x509_crt_set_key(cert, pkey))
823
824 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
825 GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2))
826 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
827 GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15))
828 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
829 GNUTLS_OID_X520_COMMON_NAME, 0,
830 smtp_active_hostname, Ustrlen(smtp_active_hostname)))
831 )
832 goto err;
833
834 where = US"signing cert";
835 if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err;
836
837 where = US"installing selfsign cert";
838 /* Since: 2.4.0 */
839 if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey)))
840 goto err;
841
842 rc = OK;
843
844 out:
845 if (cert) gnutls_x509_crt_deinit(cert);
846 if (pkey) gnutls_x509_privkey_deinit(pkey);
847 return rc;
848
849 err:
850 rc = tls_error_gnu(where, rc, NULL, errstr);
851 goto out;
852 }
853
854
855
856
857 /* Add certificate and key, from files.
858
859 Return:
860 Zero or negative: good. Negate value for certificate index if < 0.
861 Greater than zero: FAIL or DEFER code.
862 */
863
864 static int
865 tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
866 uschar * certfile, uschar * keyfile, uschar ** errstr)
867 {
868 int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
869 CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
870 if (rc < 0)
871 return tls_error_gnu(
872 string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
873 rc, host, errstr);
874 return -rc;
875 }
876
877
878 /*************************************************
879 * Variables re-expanded post-SNI *
880 *************************************************/
881
882 /* Called from both server and client code, via tls_init(), and also from
883 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
884
885 We can tell the two apart by state->received_sni being non-NULL in callback.
886
887 The callback should not call us unless state->trigger_sni_changes is true,
888 which we are responsible for setting on the first pass through.
889
890 Arguments:
891 state exim_gnutls_state_st *
892 errstr error string pointer
893
894 Returns: OK/DEFER/FAIL
895 */
896
897 static int
898 tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
899 {
900 struct stat statbuf;
901 int rc;
902 const host_item *host = state->host; /* macro should be reconsidered? */
903 uschar *saved_tls_certificate = NULL;
904 uschar *saved_tls_privatekey = NULL;
905 uschar *saved_tls_verify_certificates = NULL;
906 uschar *saved_tls_crl = NULL;
907 int cert_count;
908
909 /* We check for tls_sni *before* expansion. */
910 if (!host) /* server */
911 if (!state->received_sni)
912 {
913 if ( state->tls_certificate
914 && ( Ustrstr(state->tls_certificate, US"tls_sni")
915 || Ustrstr(state->tls_certificate, US"tls_in_sni")
916 || Ustrstr(state->tls_certificate, US"tls_out_sni")
917 ) )
918 {
919 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
920 state->trigger_sni_changes = TRUE;
921 }
922 }
923 else
924 {
925 /* useful for debugging */
926 saved_tls_certificate = state->exp_tls_certificate;
927 saved_tls_privatekey = state->exp_tls_privatekey;
928 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
929 saved_tls_crl = state->exp_tls_crl;
930 }
931
932 if ((rc = gnutls_certificate_allocate_credentials(&state->x509_cred)))
933 return tls_error_gnu(US"gnutls_certificate_allocate_credentials",
934 rc, host, errstr);
935
936 #ifdef SUPPORT_SRV_OCSP_STACK
937 gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
938 #endif
939
940 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
941 state members, assuming consistent naming; and expand_check() returns
942 false if expansion failed, unless expansion was forced to fail. */
943
944 /* check if we at least have a certificate, before doing expensive
945 D-H generation. */
946
947 if (!expand_check_tlsvar(tls_certificate, errstr))
948 return DEFER;
949
950 /* certificate is mandatory in server, optional in client */
951
952 if ( !state->exp_tls_certificate
953 || !*state->exp_tls_certificate
954 )
955 if (!host)
956 return tls_install_selfsign(state, errstr);
957 else
958 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
959
960 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr))
961 return DEFER;
962
963 /* tls_privatekey is optional, defaulting to same file as certificate */
964
965 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
966 {
967 state->tls_privatekey = state->tls_certificate;
968 state->exp_tls_privatekey = state->exp_tls_certificate;
969 }
970
971
972 if (state->exp_tls_certificate && *state->exp_tls_certificate)
973 {
974 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
975 state->exp_tls_certificate, state->exp_tls_privatekey);
976
977 if (state->received_sni)
978 if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0
979 && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0
980 )
981 {
982 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
983 }
984 else
985 {
986 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
987 }
988
989 if (!host) /* server */
990 {
991 const uschar * clist = state->exp_tls_certificate;
992 const uschar * klist = state->exp_tls_privatekey;
993 const uschar * olist;
994 int csep = 0, ksep = 0, osep = 0, cnt = 0;
995 uschar * cfile, * kfile, * ofile;
996
997 #ifndef DISABLE_OCSP
998 if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
999 return DEFER;
1000 olist = ofile;
1001 #endif
1002
1003 while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
1004
1005 if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
1006 return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
1007 else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
1008 return rc;
1009 else
1010 {
1011 int gnutls_cert_index = -rc;
1012 DEBUG(D_tls) debug_printf("TLS: cert/key %s registered\n", cfile);
1013
1014 /* Set the OCSP stapling server info */
1015
1016 #ifndef DISABLE_OCSP
1017 if (tls_ocsp_file)
1018 if (gnutls_buggy_ocsp)
1019 {
1020 DEBUG(D_tls)
1021 debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
1022 }
1023 else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1024 {
1025 /* Use the full callback method for stapling just to get
1026 observability. More efficient would be to read the file once only,
1027 if it never changed (due to SNI). Would need restart on file update,
1028 or watch datestamp. */
1029
1030 # ifdef SUPPORT_SRV_OCSP_STACK
1031 if ((rc = gnutls_certificate_set_ocsp_status_request_function2(
1032 state->x509_cred, gnutls_cert_index,
1033 server_ocsp_stapling_cb, ofile)))
1034 return tls_error_gnu(
1035 US"gnutls_certificate_set_ocsp_status_request_function2",
1036 rc, host, errstr);
1037 # else
1038 if (cnt++ > 0)
1039 {
1040 DEBUG(D_tls)
1041 debug_printf("oops; multiple OCSP files not supported\n");
1042 break;
1043 }
1044 gnutls_certificate_set_ocsp_status_request_function(
1045 state->x509_cred, server_ocsp_stapling_cb, ofile);
1046 # endif
1047
1048 DEBUG(D_tls) debug_printf("OCSP response file = %s\n", ofile);
1049 }
1050 else
1051 DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
1052 #endif
1053 }
1054 }
1055 else
1056 {
1057 if (0 < (rc = tls_add_certfile(state, host,
1058 state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
1059 return rc;
1060 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
1061 }
1062
1063 } /* tls_certificate */
1064
1065
1066 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
1067 provided. Experiment shows that, if the certificate file is empty, an unhelpful
1068 error message is provided. However, if we just refrain from setting anything up
1069 in that case, certificate verification fails, which seems to be the correct
1070 behaviour. */
1071
1072 if (state->tls_verify_certificates && *state->tls_verify_certificates)
1073 {
1074 if (!expand_check_tlsvar(tls_verify_certificates, errstr))
1075 return DEFER;
1076 #ifndef SUPPORT_SYSDEFAULT_CABUNDLE
1077 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1078 state->exp_tls_verify_certificates = NULL;
1079 #endif
1080 if (state->tls_crl && *state->tls_crl)
1081 if (!expand_check_tlsvar(tls_crl, errstr))
1082 return DEFER;
1083
1084 if (!(state->exp_tls_verify_certificates &&
1085 *state->exp_tls_verify_certificates))
1086 {
1087 DEBUG(D_tls)
1088 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
1089 /* With no tls_verify_certificates, we ignore tls_crl too */
1090 return OK;
1091 }
1092 }
1093 else
1094 {
1095 DEBUG(D_tls)
1096 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
1097 return OK;
1098 }
1099
1100 #ifdef SUPPORT_SYSDEFAULT_CABUNDLE
1101 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1102 cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred);
1103 else
1104 #endif
1105 {
1106 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
1107 {
1108 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
1109 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
1110 strerror(errno));
1111 return DEFER;
1112 }
1113
1114 #ifndef SUPPORT_CA_DIR
1115 /* The test suite passes in /dev/null; we could check for that path explicitly,
1116 but who knows if someone has some weird FIFO which always dumps some certs, or
1117 other weirdness. The thing we really want to check is that it's not a
1118 directory, since while OpenSSL supports that, GnuTLS does not.
1119 So s/!S_ISREG/S_ISDIR/ and change some messaging ... */
1120 if (S_ISDIR(statbuf.st_mode))
1121 {
1122 DEBUG(D_tls)
1123 debug_printf("verify certificates path is a dir: \"%s\"\n",
1124 state->exp_tls_verify_certificates);
1125 log_write(0, LOG_MAIN|LOG_PANIC,
1126 "tls_verify_certificates \"%s\" is a directory",
1127 state->exp_tls_verify_certificates);
1128 return DEFER;
1129 }
1130 #endif
1131
1132 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
1133 state->exp_tls_verify_certificates, statbuf.st_size);
1134
1135 if (statbuf.st_size == 0)
1136 {
1137 DEBUG(D_tls)
1138 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
1139 return OK;
1140 }
1141
1142 cert_count =
1143
1144 #ifdef SUPPORT_CA_DIR
1145 (statbuf.st_mode & S_IFMT) == S_IFDIR
1146 ?
1147 gnutls_certificate_set_x509_trust_dir(state->x509_cred,
1148 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM)
1149 :
1150 #endif
1151 gnutls_certificate_set_x509_trust_file(state->x509_cred,
1152 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
1153 }
1154
1155 if (cert_count < 0)
1156 return tls_error_gnu(US"setting certificate trust", cert_count, host, errstr);
1157 DEBUG(D_tls)
1158 debug_printf("Added %d certificate authorities.\n", cert_count);
1159
1160 if (state->tls_crl && *state->tls_crl &&
1161 state->exp_tls_crl && *state->exp_tls_crl)
1162 {
1163 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
1164 if ((cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
1165 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM)) < 0)
1166 return tls_error_gnu(US"gnutls_certificate_set_x509_crl_file",
1167 cert_count, host, errstr);
1168
1169 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
1170 }
1171
1172 return OK;
1173 }
1174
1175
1176
1177
1178 /*************************************************
1179 * Set X.509 state variables *
1180 *************************************************/
1181
1182 /* In GnuTLS, the registered cert/key are not replaced by a later
1183 set of a cert/key, so for SNI support we need a whole new x509_cred
1184 structure. Which means various other non-re-expanded pieces of state
1185 need to be re-set in the new struct, so the setting logic is pulled
1186 out to this.
1187
1188 Arguments:
1189 state exim_gnutls_state_st *
1190 errstr error string pointer
1191
1192 Returns: OK/DEFER/FAIL
1193 */
1194
1195 static int
1196 tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
1197 {
1198 int rc;
1199 const host_item *host = state->host; /* macro should be reconsidered? */
1200
1201 /* Create D-H parameters, or read them from the cache file. This function does
1202 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
1203 client-side params. */
1204
1205 if (!state->host)
1206 {
1207 if (!dh_server_params)
1208 if ((rc = init_server_dh(errstr)) != OK) return rc;
1209 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
1210 }
1211
1212 /* Link the credentials to the session. */
1213
1214 if ((rc = gnutls_credentials_set(state->session,
1215 GNUTLS_CRD_CERTIFICATE, state->x509_cred)))
1216 return tls_error_gnu(US"gnutls_credentials_set", rc, host, errstr);
1217
1218 return OK;
1219 }
1220
1221 /*************************************************
1222 * Initialize for GnuTLS *
1223 *************************************************/
1224
1225
1226 #ifndef DISABLE_OCSP
1227
1228 static BOOL
1229 tls_is_buggy_ocsp(void)
1230 {
1231 const uschar * s;
1232 uschar maj, mid, mic;
1233
1234 s = CUS gnutls_check_version(NULL);
1235 maj = atoi(CCS s);
1236 if (maj == 3)
1237 {
1238 while (*s && *s != '.') s++;
1239 mid = atoi(CCS ++s);
1240 if (mid <= 2)
1241 return TRUE;
1242 else if (mid >= 5)
1243 return FALSE;
1244 else
1245 {
1246 while (*s && *s != '.') s++;
1247 mic = atoi(CCS ++s);
1248 return mic <= (mid == 3 ? 16 : 3);
1249 }
1250 }
1251 return FALSE;
1252 }
1253
1254 #endif
1255
1256
1257 /* Called from both server and client code. In the case of a server, errors
1258 before actual TLS negotiation return DEFER.
1259
1260 Arguments:
1261 host connected host, if client; NULL if server
1262 certificate certificate file
1263 privatekey private key file
1264 sni TLS SNI to send, sometimes when client; else NULL
1265 cas CA certs file
1266 crl CRL file
1267 require_ciphers tls_require_ciphers setting
1268 caller_state returned state-info structure
1269 errstr error string pointer
1270
1271 Returns: OK/DEFER/FAIL
1272 */
1273
1274 static int
1275 tls_init(
1276 const host_item *host,
1277 const uschar *certificate,
1278 const uschar *privatekey,
1279 const uschar *sni,
1280 const uschar *cas,
1281 const uschar *crl,
1282 const uschar *require_ciphers,
1283 exim_gnutls_state_st **caller_state,
1284 tls_support * tlsp,
1285 uschar ** errstr)
1286 {
1287 exim_gnutls_state_st * state;
1288 int rc;
1289 size_t sz;
1290 const char * errpos;
1291 const uschar * p;
1292
1293 if (!exim_gnutls_base_init_done)
1294 {
1295 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
1296
1297 #ifdef HAVE_GNUTLS_PKCS11
1298 /* By default, gnutls_global_init will init PKCS11 support in auto mode,
1299 which loads modules from a config file, which sounds good and may be wanted
1300 by some sysadmin, but also means in common configurations that GNOME keyring
1301 environment variables are used and so breaks for users calling mailq.
1302 To prevent this, we init PKCS11 first, which is the documented approach. */
1303 if (!gnutls_allow_auto_pkcs11)
1304 if ((rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL)))
1305 return tls_error_gnu(US"gnutls_pkcs11_init", rc, host, errstr);
1306 #endif
1307
1308 if ((rc = gnutls_global_init()))
1309 return tls_error_gnu(US"gnutls_global_init", rc, host, errstr);
1310
1311 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1312 DEBUG(D_tls)
1313 {
1314 gnutls_global_set_log_function(exim_gnutls_logger_cb);
1315 /* arbitrarily chosen level; bump up to 9 for more */
1316 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
1317 }
1318 #endif
1319
1320 #ifndef DISABLE_OCSP
1321 if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp()))
1322 log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version");
1323 #endif
1324
1325 exim_gnutls_base_init_done = TRUE;
1326 }
1327
1328 if (host)
1329 {
1330 /* For client-side sessions we allocate a context. This lets us run
1331 several in parallel. */
1332 int old_pool = store_pool;
1333 store_pool = POOL_PERM;
1334 state = store_get(sizeof(exim_gnutls_state_st));
1335 store_pool = old_pool;
1336
1337 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1338 state->tlsp = tlsp;
1339 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
1340 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
1341 }
1342 else
1343 {
1344 state = &state_server;
1345 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1346 state->tlsp = tlsp;
1347 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
1348 rc = gnutls_init(&state->session, GNUTLS_SERVER);
1349 }
1350 if (rc)
1351 return tls_error_gnu(US"gnutls_init", rc, host, errstr);
1352
1353 state->host = host;
1354
1355 state->tls_certificate = certificate;
1356 state->tls_privatekey = privatekey;
1357 state->tls_require_ciphers = require_ciphers;
1358 state->tls_sni = sni;
1359 state->tls_verify_certificates = cas;
1360 state->tls_crl = crl;
1361
1362 /* This handles the variables that might get re-expanded after TLS SNI;
1363 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
1364
1365 DEBUG(D_tls)
1366 debug_printf("Expanding various TLS configuration options for session credentials.\n");
1367 if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc;
1368
1369 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
1370 requires a new structure afterwards. */
1371
1372 if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc;
1373
1374 /* set SNI in client, only */
1375 if (host)
1376 {
1377 if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr))
1378 return DEFER;
1379 if (state->tlsp->sni && *state->tlsp->sni)
1380 {
1381 DEBUG(D_tls)
1382 debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni);
1383 sz = Ustrlen(state->tlsp->sni);
1384 if ((rc = gnutls_server_name_set(state->session,
1385 GNUTLS_NAME_DNS, state->tlsp->sni, sz)))
1386 return tls_error_gnu(US"gnutls_server_name_set", rc, host, errstr);
1387 }
1388 }
1389 else if (state->tls_sni)
1390 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
1391 "have an SNI set for a server [%s]\n", state->tls_sni);
1392
1393 /* This is the priority string support,
1394 http://www.gnutls.org/manual/html_node/Priority-Strings.html
1395 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
1396 This was backwards incompatible, but means Exim no longer needs to track
1397 all algorithms and provide string forms for them. */
1398
1399 p = NULL;
1400 if (state->tls_require_ciphers && *state->tls_require_ciphers)
1401 {
1402 if (!expand_check_tlsvar(tls_require_ciphers, errstr))
1403 return DEFER;
1404 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
1405 {
1406 p = state->exp_tls_require_ciphers;
1407 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", p);
1408 }
1409 }
1410 if (!p)
1411 {
1412 p = exim_default_gnutls_priority;
1413 DEBUG(D_tls)
1414 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", p);
1415 }
1416
1417 if ((rc = gnutls_priority_init(&state->priority_cache, CCS p, &errpos)))
1418 return tls_error_gnu(string_sprintf(
1419 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
1420 p, errpos - CS p, errpos),
1421 rc, host, errstr);
1422
1423 if ((rc = gnutls_priority_set(state->session, state->priority_cache)))
1424 return tls_error_gnu(US"gnutls_priority_set", rc, host, errstr);
1425
1426 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
1427
1428 /* Reduce security in favour of increased compatibility, if the admin
1429 decides to make that trade-off. */
1430 if (gnutls_compat_mode)
1431 {
1432 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
1433 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
1434 gnutls_session_enable_compatibility_mode(state->session);
1435 #else
1436 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
1437 #endif
1438 }
1439
1440 *caller_state = state;
1441 return OK;
1442 }
1443
1444
1445
1446 /*************************************************
1447 * Extract peer information *
1448 *************************************************/
1449
1450 static const uschar *
1451 cipher_stdname_kcm(gnutls_kx_algorithm_t kx, gnutls_cipher_algorithm_t cipher,
1452 gnutls_mac_algorithm_t mac)
1453 {
1454 uschar cs_id[2];
1455 gnutls_kx_algorithm_t kx_i;
1456 gnutls_cipher_algorithm_t cipher_i;
1457 gnutls_mac_algorithm_t mac_i;
1458
1459 for (size_t i = 0;
1460 gnutls_cipher_suite_info(i, cs_id, &kx_i, &cipher_i, &mac_i, NULL);
1461 i++)
1462 if (kx_i == kx && cipher_i == cipher && mac_i == mac)
1463 return cipher_stdname(cs_id[0], cs_id[1]);
1464 return NULL;
1465 }
1466
1467
1468
1469 /* Called from both server and client code.
1470 Only this is allowed to set state->peerdn and state->have_set_peerdn
1471 and we use that to detect double-calls.
1472
1473 NOTE: the state blocks last while the TLS connection is up, which is fine
1474 for logging in the server side, but for the client side, we log after teardown
1475 in src/deliver.c. While the session is up, we can twist about states and
1476 repoint tls_* globals, but those variables used for logging or other variable
1477 expansion that happens _after_ delivery need to have a longer life-time.
1478
1479 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1480 doing this more than once per generation of a state context. We set them in
1481 the state context, and repoint tls_* to them. After the state goes away, the
1482 tls_* copies of the pointers remain valid and client delivery logging is happy.
1483
1484 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1485 don't apply.
1486
1487 Arguments:
1488 state exim_gnutls_state_st *
1489 errstr pointer to error string
1490
1491 Returns: OK/DEFER/FAIL
1492 */
1493
1494 static int
1495 peer_status(exim_gnutls_state_st *state, uschar ** errstr)
1496 {
1497 const gnutls_datum_t *cert_list;
1498 int old_pool, rc;
1499 unsigned int cert_list_size = 0;
1500 gnutls_protocol_t protocol;
1501 gnutls_cipher_algorithm_t cipher;
1502 gnutls_kx_algorithm_t kx;
1503 gnutls_mac_algorithm_t mac;
1504 gnutls_certificate_type_t ct;
1505 gnutls_x509_crt_t crt;
1506 uschar *dn_buf;
1507 size_t sz;
1508
1509 if (state->have_set_peerdn)
1510 return OK;
1511 state->have_set_peerdn = TRUE;
1512
1513 state->peerdn = NULL;
1514
1515 /* tls_cipher */
1516 cipher = gnutls_cipher_get(state->session);
1517 protocol = gnutls_protocol_get_version(state->session);
1518 mac = gnutls_mac_get(state->session);
1519 kx = protocol < GNUTLS_TLS1_3 ? gnutls_kx_get(state->session) : 0;
1520
1521 old_pool = store_pool;
1522 {
1523 store_pool = POOL_PERM;
1524
1525 #ifdef SUPPORT_GNUTLS_SESS_DESC
1526 {
1527 gstring * g = NULL;
1528 uschar * s = US gnutls_session_get_desc(state->session), c;
1529
1530 /* Nikos M suggests we use this by preference. It returns like:
1531 (TLS1.3)-(ECDHE-SECP256R1)-(RSA-PSS-RSAE-SHA256)-(AES-256-GCM)
1532
1533 For partial back-compat, put a colon after the TLS version, replace the
1534 )-( grouping with __, replace in-group - with _ and append the :keysize. */
1535
1536 /* debug_printf("peer_status: gnutls_session_get_desc %s\n", s); */
1537
1538 for (s++; (c = *s) && c != ')'; s++) g = string_catn(g, s, 1);
1539 g = string_catn(g, US":", 1);
1540 if (*s) s++; /* now on _ between groups */
1541 while ((c = *s))
1542 {
1543 for (*++s && ++s; (c = *s) && c != ')'; s++) g = string_catn(g, c == '-' ? US"_" : s, 1);
1544 /* now on ) closing group */
1545 if ((c = *s) && *++s == '-') g = string_catn(g, US"__", 2);
1546 /* now on _ between groups */
1547 }
1548 g = string_catn(g, US":", 1);
1549 g = string_cat(g, string_sprintf("%d", (int) gnutls_cipher_get_key_size(cipher) * 8));
1550 state->ciphersuite = string_from_gstring(g);
1551 }
1552 #else
1553 state->ciphersuite = string_sprintf("%s:%s:%d",
1554 gnutls_protocol_get_name(protocol),
1555 gnutls_cipher_suite_get_name(kx, cipher, mac),
1556 (int) gnutls_cipher_get_key_size(cipher) * 8);
1557
1558 /* I don't see a way that spaces could occur, in the current GnuTLS
1559 code base, but it was a concern in the old code and perhaps older GnuTLS
1560 releases did return "TLS 1.0"; play it safe, just in case. */
1561
1562 for (uschar * p = state->ciphersuite; *p; p++) if (isspace(*p)) *p = '-';
1563 #endif
1564
1565 /* debug_printf("peer_status: ciphersuite %s\n", state->ciphersuite); */
1566
1567 state->tlsp->cipher = state->ciphersuite;
1568 state->tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
1569
1570 state->tlsp->cipher_stdname = cipher_stdname_kcm(kx, cipher, mac);
1571 }
1572 store_pool = old_pool;
1573
1574 /* tls_peerdn */
1575 cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
1576
1577 if (!cert_list || cert_list_size == 0)
1578 {
1579 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1580 cert_list, cert_list_size);
1581 if (state->verify_requirement >= VERIFY_REQUIRED)
1582 return tls_error(US"certificate verification failed",
1583 US"no certificate received from peer", state->host, errstr);
1584 return OK;
1585 }
1586
1587 if ((ct = gnutls_certificate_type_get(state->session)) != GNUTLS_CRT_X509)
1588 {
1589 const uschar * ctn = US gnutls_certificate_type_get_name(ct);
1590 DEBUG(D_tls)
1591 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1592 if (state->verify_requirement >= VERIFY_REQUIRED)
1593 return tls_error(US"certificate verification not possible, unhandled type",
1594 ctn, state->host, errstr);
1595 return OK;
1596 }
1597
1598 #define exim_gnutls_peer_err(Label) \
1599 do { \
1600 if (rc != GNUTLS_E_SUCCESS) \
1601 { \
1602 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \
1603 (Label), gnutls_strerror(rc)); \
1604 if (state->verify_requirement >= VERIFY_REQUIRED) \
1605 return tls_error_gnu((Label), rc, state->host, errstr); \
1606 return OK; \
1607 } \
1608 } while (0)
1609
1610 rc = import_cert(&cert_list[0], &crt);
1611 exim_gnutls_peer_err(US"cert 0");
1612
1613 state->tlsp->peercert = state->peercert = crt;
1614
1615 sz = 0;
1616 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1617 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1618 {
1619 exim_gnutls_peer_err(US"getting size for cert DN failed");
1620 return FAIL; /* should not happen */
1621 }
1622 dn_buf = store_get_perm(sz);
1623 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1624 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1625
1626 state->peerdn = dn_buf;
1627
1628 return OK;
1629 #undef exim_gnutls_peer_err
1630 }
1631
1632
1633
1634
1635 /*************************************************
1636 * Verify peer certificate *
1637 *************************************************/
1638
1639 /* Called from both server and client code.
1640 *Should* be using a callback registered with
1641 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1642 the peer information, but that's too new for some OSes.
1643
1644 Arguments:
1645 state exim_gnutls_state_st *
1646 errstr where to put an error message
1647
1648 Returns:
1649 FALSE if the session should be rejected
1650 TRUE if the cert is okay or we just don't care
1651 */
1652
1653 static BOOL
1654 verify_certificate(exim_gnutls_state_st * state, uschar ** errstr)
1655 {
1656 int rc;
1657 uint verify;
1658
1659 if (state->verify_requirement == VERIFY_NONE)
1660 return TRUE;
1661
1662 DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n");
1663 *errstr = NULL;
1664
1665 if ((rc = peer_status(state, errstr)) != OK || !state->peerdn)
1666 {
1667 verify = GNUTLS_CERT_INVALID;
1668 *errstr = US"certificate not supplied";
1669 }
1670 else
1671
1672 {
1673 #ifdef SUPPORT_DANE
1674 if (state->verify_requirement == VERIFY_DANE && state->host)
1675 {
1676 /* Using dane_verify_session_crt() would be easy, as it does it all for us
1677 including talking to a DNS resolver. But we want to do that bit ourselves
1678 as the testsuite intercepts and fakes its own DNS environment. */
1679
1680 dane_state_t s;
1681 dane_query_t r;
1682 uint lsize;
1683 const gnutls_datum_t * certlist =
1684 gnutls_certificate_get_peers(state->session, &lsize);
1685 int usage = tls_out.tlsa_usage;
1686
1687 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1688 /* Split the TLSA records into two sets, TA and EE selectors. Run the
1689 dane-verification separately so that we know which selector verified;
1690 then we know whether to do name-verification (needed for TA but not EE). */
1691
1692 if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE)))
1693 { /* a mixed-usage bundle */
1694 int i, j, nrec;
1695 const char ** dd;
1696 int * ddl;
1697
1698 for(nrec = 0; state->dane_data_len[nrec]; ) nrec++;
1699 nrec++;
1700
1701 dd = store_get(nrec * sizeof(uschar *));
1702 ddl = store_get(nrec * sizeof(int));
1703 nrec--;
1704
1705 if ((rc = dane_state_init(&s, 0)))
1706 goto tlsa_prob;
1707
1708 for (usage = DANESSL_USAGE_DANE_EE;
1709 usage >= DANESSL_USAGE_DANE_TA; usage--)
1710 { /* take records with this usage */
1711 for (j = i = 0; i < nrec; i++)
1712 if (state->dane_data[i][0] == usage)
1713 {
1714 dd[j] = state->dane_data[i];
1715 ddl[j++] = state->dane_data_len[i];
1716 }
1717 if (j)
1718 {
1719 dd[j] = NULL;
1720 ddl[j] = 0;
1721
1722 if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0)))
1723 goto tlsa_prob;
1724
1725 if ((rc = dane_verify_crt_raw(s, certlist, lsize,
1726 gnutls_certificate_type_get(state->session),
1727 r, 0,
1728 usage == DANESSL_USAGE_DANE_EE
1729 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1730 &verify)))
1731 {
1732 DEBUG(D_tls)
1733 debug_printf("TLSA record problem: %s\n", dane_strerror(rc));
1734 }
1735 else if (verify == 0) /* verification passed */
1736 {
1737 usage = 1 << usage;
1738 break;
1739 }
1740 }
1741 }
1742
1743 if (rc) goto tlsa_prob;
1744 }
1745 else
1746 # endif
1747 {
1748 if ( (rc = dane_state_init(&s, 0))
1749 || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len,
1750 1, 0))
1751 || (rc = dane_verify_crt_raw(s, certlist, lsize,
1752 gnutls_certificate_type_get(state->session),
1753 r, 0,
1754 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1755 usage == (1 << DANESSL_USAGE_DANE_EE)
1756 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1757 # else
1758 0,
1759 # endif
1760 &verify))
1761 )
1762 goto tlsa_prob;
1763 }
1764
1765 if (verify != 0) /* verification failed */
1766 {
1767 gnutls_datum_t str;
1768 (void) dane_verification_status_print(verify, &str, 0);
1769 *errstr = US str.data; /* don't bother to free */
1770 goto badcert;
1771 }
1772
1773 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1774 /* If a TA-mode TLSA record was used for verification we must additionally
1775 verify the cert name (but not the CA chain). For EE-mode, skip it. */
1776
1777 if (usage & (1 << DANESSL_USAGE_DANE_EE))
1778 # endif
1779 {
1780 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1781 goto goodcert;
1782 }
1783 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1784 /* Assume that the name on the A-record is the one that should be matching
1785 the cert. An alternate view is that the domain part of the email address
1786 is also permissible. */
1787
1788 if (gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1789 CS state->host->name))
1790 {
1791 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1792 goto goodcert;
1793 }
1794 # endif
1795 }
1796 #endif /*SUPPORT_DANE*/
1797
1798 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1799 }
1800
1801 /* Handle the result of verification. INVALID is set if any others are. */
1802
1803 if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED))
1804 {
1805 state->peer_cert_verified = FALSE;
1806 if (!*errstr)
1807 {
1808 #ifdef GNUTLS_CERT_VFY_STATUS_PRINT
1809 DEBUG(D_tls)
1810 {
1811 gnutls_datum_t txt;
1812
1813 if (gnutls_certificate_verification_status_print(verify,
1814 gnutls_certificate_type_get(state->session), &txt, 0)
1815 == GNUTLS_E_SUCCESS)
1816 {
1817 debug_printf("%s\n", txt.data);
1818 gnutls_free(txt.data);
1819 }
1820 }
1821 #endif
1822 *errstr = verify & GNUTLS_CERT_REVOKED
1823 ? US"certificate revoked" : US"certificate invalid";
1824 }
1825
1826 DEBUG(D_tls)
1827 debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n",
1828 *errstr, state->peerdn ? state->peerdn : US"<unset>");
1829
1830 if (state->verify_requirement >= VERIFY_REQUIRED)
1831 goto badcert;
1832 DEBUG(D_tls)
1833 debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
1834 }
1835
1836 else
1837 {
1838 /* Client side, check the server's certificate name versus the name on the
1839 A-record for the connection we made. What to do for server side - what name
1840 to use for client? We document that there is no such checking for server
1841 side. */
1842
1843 if ( state->exp_tls_verify_cert_hostnames
1844 && !gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1845 CS state->exp_tls_verify_cert_hostnames)
1846 )
1847 {
1848 DEBUG(D_tls)
1849 debug_printf("TLS certificate verification failed: cert name mismatch\n");
1850 if (state->verify_requirement >= VERIFY_REQUIRED)
1851 goto badcert;
1852 return TRUE;
1853 }
1854
1855 state->peer_cert_verified = TRUE;
1856 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n",
1857 state->peerdn ? state->peerdn : US"<unset>");
1858 }
1859
1860 goodcert:
1861 state->tlsp->peerdn = state->peerdn;
1862 return TRUE;
1863
1864 #ifdef SUPPORT_DANE
1865 tlsa_prob:
1866 *errstr = string_sprintf("TLSA record problem: %s",
1867 rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc));
1868 #endif
1869
1870 badcert:
1871 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1872 return FALSE;
1873 }
1874
1875
1876
1877
1878 /* ------------------------------------------------------------------------ */
1879 /* Callbacks */
1880
1881 /* Logging function which can be registered with
1882 * gnutls_global_set_log_function()
1883 * gnutls_global_set_log_level() 0..9
1884 */
1885 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1886 static void
1887 exim_gnutls_logger_cb(int level, const char *message)
1888 {
1889 size_t len = strlen(message);
1890 if (len < 1)
1891 {
1892 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1893 return;
1894 }
1895 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1896 message[len-1] == '\n' ? "" : "\n");
1897 }
1898 #endif
1899
1900
1901 /* Called after client hello, should handle SNI work.
1902 This will always set tls_sni (state->received_sni) if available,
1903 and may trigger presenting different certificates,
1904 if state->trigger_sni_changes is TRUE.
1905
1906 Should be registered with
1907 gnutls_handshake_set_post_client_hello_function()
1908
1909 "This callback must return 0 on success or a gnutls error code to terminate the
1910 handshake.".
1911
1912 For inability to get SNI information, we return 0.
1913 We only return non-zero if re-setup failed.
1914 Only used for server-side TLS.
1915 */
1916
1917 static int
1918 exim_sni_handling_cb(gnutls_session_t session)
1919 {
1920 char sni_name[MAX_HOST_LEN];
1921 size_t data_len = MAX_HOST_LEN;
1922 exim_gnutls_state_st *state = &state_server;
1923 unsigned int sni_type;
1924 int rc, old_pool;
1925 uschar * dummy_errstr;
1926
1927 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
1928 if (rc != GNUTLS_E_SUCCESS)
1929 {
1930 DEBUG(D_tls) {
1931 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
1932 debug_printf("TLS: no SNI presented in handshake.\n");
1933 else
1934 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
1935 gnutls_strerror(rc), rc);
1936 }
1937 return 0;
1938 }
1939
1940 if (sni_type != GNUTLS_NAME_DNS)
1941 {
1942 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
1943 return 0;
1944 }
1945
1946 /* We now have a UTF-8 string in sni_name */
1947 old_pool = store_pool;
1948 store_pool = POOL_PERM;
1949 state->received_sni = string_copyn(US sni_name, data_len);
1950 store_pool = old_pool;
1951
1952 /* We set this one now so that variable expansions below will work */
1953 state->tlsp->sni = state->received_sni;
1954
1955 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
1956 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
1957
1958 if (!state->trigger_sni_changes)
1959 return 0;
1960
1961 if ((rc = tls_expand_session_files(state, &dummy_errstr)) != OK)
1962 {
1963 /* If the setup of certs/etc failed before handshake, TLS would not have
1964 been offered. The best we can do now is abort. */
1965 return GNUTLS_E_APPLICATION_ERROR_MIN;
1966 }
1967
1968 rc = tls_set_remaining_x509(state, &dummy_errstr);
1969 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
1970
1971 return 0;
1972 }
1973
1974
1975
1976 #ifndef DISABLE_OCSP
1977
1978 static int
1979 server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
1980 gnutls_datum_t * ocsp_response)
1981 {
1982 int ret;
1983 DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr);
1984
1985 if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0)
1986 {
1987 DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n",
1988 CS ptr);
1989 tls_in.ocsp = OCSP_NOT_RESP;
1990 return GNUTLS_E_NO_CERTIFICATE_STATUS;
1991 }
1992
1993 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
1994 return 0;
1995 }
1996
1997 #endif
1998
1999
2000 #ifndef DISABLE_EVENT
2001 /*
2002 We use this callback to get observability and detail-level control
2003 for an exim TLS connection (either direction), raising a tls:cert event
2004 for each cert in the chain presented by the peer. Any event
2005 can deny verification.
2006
2007 Return 0 for the handshake to continue or non-zero to terminate.
2008 */
2009
2010 static int
2011 verify_cb(gnutls_session_t session)
2012 {
2013 const gnutls_datum_t * cert_list;
2014 unsigned int cert_list_size = 0;
2015 gnutls_x509_crt_t crt;
2016 int rc;
2017 uschar * yield;
2018 exim_gnutls_state_st * state = gnutls_session_get_ptr(session);
2019
2020 if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size)))
2021 while (cert_list_size--)
2022 {
2023 if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS)
2024 {
2025 DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n",
2026 cert_list_size, gnutls_strerror(rc));
2027 break;
2028 }
2029
2030 state->tlsp->peercert = crt;
2031 if ((yield = event_raise(state->event_action,
2032 US"tls:cert", string_sprintf("%d", cert_list_size))))
2033 {
2034 log_write(0, LOG_MAIN,
2035 "SSL verify denied by event-action: depth=%d: %s",
2036 cert_list_size, yield);
2037 return 1; /* reject */
2038 }
2039 state->tlsp->peercert = NULL;
2040 }
2041
2042 return 0;
2043 }
2044
2045 #endif
2046
2047
2048 static gstring *
2049 ddump(gnutls_datum_t * d)
2050 {
2051 gstring * g = string_get((d->size+1) * 2);
2052 uschar * s = d->data;
2053 for (unsigned i = d->size; i > 0; i--, s++)
2054 {
2055 g = string_catn(g, US "0123456789abcdef" + (*s >> 4), 1);
2056 g = string_catn(g, US "0123456789abcdef" + (*s & 0xf), 1);
2057 }
2058 return g;
2059 }
2060
2061 static void
2062 post_handshake_debug(exim_gnutls_state_st * state)
2063 {
2064 debug_printf("gnutls_handshake was successful\n");
2065 #ifdef SUPPORT_GNUTLS_SESS_DESC
2066 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2067 #endif
2068 #ifdef SUPPORT_GNUTLS_KEYLOG
2069 if (gnutls_protocol_get_version(state->session) < GNUTLS_TLS1_3)
2070 {
2071 gnutls_datum_t c, s;
2072 gstring * gc, * gs;
2073 /* we only want the client random and the master secret */
2074 gnutls_session_get_random(state->session, &c, &s);
2075 gnutls_session_get_master_secret(state->session, &s);
2076 gc = ddump(&c);
2077 gs = ddump(&s);
2078 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2079 }
2080 else
2081 debug_printf("To get keying info for TLS1.3 is hard:\n"
2082 " set environment variable SSLKEYLOGFILE to a filename writable by uid exim\n"
2083 " add SSLKEYLOGFILE to keep_environment in the exim config\n"
2084 " run exim as root\n"
2085 " if using sudo, add SSLKEYLOGFILE to env_keep in /etc/sudoers\n");
2086 #endif
2087 }
2088
2089 /* ------------------------------------------------------------------------ */
2090 /* Exported functions */
2091
2092
2093
2094
2095 /*************************************************
2096 * Start a TLS session in a server *
2097 *************************************************/
2098
2099 /* This is called when Exim is running as a server, after having received
2100 the STARTTLS command. It must respond to that command, and then negotiate
2101 a TLS session.
2102
2103 Arguments:
2104 require_ciphers list of allowed ciphers or NULL
2105 errstr pointer to error string
2106
2107 Returns: OK on success
2108 DEFER for errors before the start of the negotiation
2109 FAIL for errors during the negotiation; the server can't
2110 continue running.
2111 */
2112
2113 int
2114 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2115 {
2116 int rc;
2117 exim_gnutls_state_st * state = NULL;
2118
2119 /* Check for previous activation */
2120 if (tls_in.active.sock >= 0)
2121 {
2122 tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr);
2123 smtp_printf("554 Already in TLS\r\n", FALSE);
2124 return FAIL;
2125 }
2126
2127 /* Initialize the library. If it fails, it will already have logged the error
2128 and sent an SMTP response. */
2129
2130 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
2131
2132 if ((rc = tls_init(NULL, tls_certificate, tls_privatekey,
2133 NULL, tls_verify_certificates, tls_crl,
2134 require_ciphers, &state, &tls_in, errstr)) != OK) return rc;
2135
2136 /* If this is a host for which certificate verification is mandatory or
2137 optional, set up appropriately. */
2138
2139 if (verify_check_host(&tls_verify_hosts) == OK)
2140 {
2141 DEBUG(D_tls)
2142 debug_printf("TLS: a client certificate will be required.\n");
2143 state->verify_requirement = VERIFY_REQUIRED;
2144 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2145 }
2146 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2147 {
2148 DEBUG(D_tls)
2149 debug_printf("TLS: a client certificate will be requested but not required.\n");
2150 state->verify_requirement = VERIFY_OPTIONAL;
2151 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2152 }
2153 else
2154 {
2155 DEBUG(D_tls)
2156 debug_printf("TLS: a client certificate will not be requested.\n");
2157 state->verify_requirement = VERIFY_NONE;
2158 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2159 }
2160
2161 #ifndef DISABLE_EVENT
2162 if (event_action)
2163 {
2164 state->event_action = event_action;
2165 gnutls_session_set_ptr(state->session, state);
2166 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2167 }
2168 #endif
2169
2170 /* Register SNI handling; always, even if not in tls_certificate, so that the
2171 expansion variable $tls_sni is always available. */
2172
2173 gnutls_handshake_set_post_client_hello_function(state->session,
2174 exim_sni_handling_cb);
2175
2176 /* Set context and tell client to go ahead, except in the case of TLS startup
2177 on connection, where outputting anything now upsets the clients and tends to
2178 make them disconnect. We need to have an explicit fflush() here, to force out
2179 the response. Other smtp_printf() calls do not need it, because in non-TLS
2180 mode, the fflush() happens when smtp_getc() is called. */
2181
2182 if (!state->tlsp->on_connect)
2183 {
2184 smtp_printf("220 TLS go ahead\r\n", FALSE);
2185 fflush(smtp_out);
2186 }
2187
2188 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2189 that the GnuTLS library doesn't.
2190 From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you
2191 to set (and clear down afterwards) up a pull-timeout callback function that does
2192 a select, so we're no better off unless avoiding signals becomes an issue. */
2193
2194 gnutls_transport_set_ptr2(state->session,
2195 (gnutls_transport_ptr_t)(long) fileno(smtp_in),
2196 (gnutls_transport_ptr_t)(long) fileno(smtp_out));
2197 state->fd_in = fileno(smtp_in);
2198 state->fd_out = fileno(smtp_out);
2199
2200 sigalrm_seen = FALSE;
2201 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2202 do
2203 rc = gnutls_handshake(state->session);
2204 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2205 ALARM_CLR(0);
2206
2207 if (rc != GNUTLS_E_SUCCESS)
2208 {
2209 /* It seems that, except in the case of a timeout, we have to close the
2210 connection right here; otherwise if the other end is running OpenSSL it hangs
2211 until the server times out. */
2212
2213 if (sigalrm_seen)
2214 {
2215 tls_error(US"gnutls_handshake", US"timed out", NULL, errstr);
2216 gnutls_db_remove_session(state->session);
2217 }
2218 else
2219 {
2220 tls_error_gnu(US"gnutls_handshake", rc, NULL, errstr);
2221 (void) gnutls_alert_send_appropriate(state->session, rc);
2222 gnutls_deinit(state->session);
2223 gnutls_certificate_free_credentials(state->x509_cred);
2224 millisleep(500);
2225 shutdown(state->fd_out, SHUT_WR);
2226 for (int i = 1024; fgetc(smtp_in) != EOF && i > 0; ) i--; /* drain skt */
2227 (void)fclose(smtp_out);
2228 (void)fclose(smtp_in);
2229 smtp_out = smtp_in = NULL;
2230 }
2231
2232 return FAIL;
2233 }
2234
2235 DEBUG(D_tls) post_handshake_debug(state);
2236
2237 /* Verify after the fact */
2238
2239 if (!verify_certificate(state, errstr))
2240 {
2241 if (state->verify_requirement != VERIFY_OPTIONAL)
2242 {
2243 (void) tls_error(US"certificate verification failed", *errstr, NULL, errstr);
2244 return FAIL;
2245 }
2246 DEBUG(D_tls)
2247 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
2248 *errstr);
2249 }
2250
2251 /* Figure out peer DN, and if authenticated, etc. */
2252
2253 if ((rc = peer_status(state, NULL)) != OK) return rc;
2254
2255 /* Sets various Exim expansion variables; always safe within server */
2256
2257 extract_exim_vars_from_tls_state(state);
2258
2259 /* TLS has been set up. Adjust the input functions to read via TLS,
2260 and initialize appropriately. */
2261
2262 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2263
2264 receive_getc = tls_getc;
2265 receive_getbuf = tls_getbuf;
2266 receive_get_cache = tls_get_cache;
2267 receive_ungetc = tls_ungetc;
2268 receive_feof = tls_feof;
2269 receive_ferror = tls_ferror;
2270 receive_smtp_buffered = tls_smtp_buffered;
2271
2272 return OK;
2273 }
2274
2275
2276
2277
2278 static void
2279 tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state,
2280 smtp_transport_options_block * ob)
2281 {
2282 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2283 {
2284 state->exp_tls_verify_cert_hostnames =
2285 #ifdef SUPPORT_I18N
2286 string_domain_utf8_to_alabel(host->name, NULL);
2287 #else
2288 host->name;
2289 #endif
2290 DEBUG(D_tls)
2291 debug_printf("TLS: server cert verification includes hostname: \"%s\".\n",
2292 state->exp_tls_verify_cert_hostnames);
2293 }
2294 }
2295
2296
2297
2298
2299 #ifdef SUPPORT_DANE
2300 /* Given our list of RRs from the TLSA lookup, build a lookup block in
2301 GnuTLS-DANE's preferred format. Hang it on the state str for later
2302 use in DANE verification.
2303
2304 We point at the dnsa data not copy it, so it must remain valid until
2305 after verification is done.*/
2306
2307 static BOOL
2308 dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa)
2309 {
2310 dns_scan dnss;
2311 int i;
2312 const char ** dane_data;
2313 int * dane_data_len;
2314
2315 i = 1;
2316 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2317 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2318 ) if (rr->type == T_TLSA) i++;
2319
2320 dane_data = store_get(i * sizeof(uschar *));
2321 dane_data_len = store_get(i * sizeof(int));
2322
2323 i = 0;
2324 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2325 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2326 ) if (rr->type == T_TLSA && rr->size > 3)
2327 {
2328 const uschar * p = rr->data;
2329 uint8_t usage = p[0], sel = p[1], type = p[2];
2330
2331 DEBUG(D_tls)
2332 debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size);
2333
2334 if ( (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE)
2335 || (sel != 0 && sel != 1)
2336 )
2337 continue;
2338 switch(type)
2339 {
2340 case 0: /* Full: cannot check at present */
2341 break;
2342 case 1: if (rr->size != 3 + 256/8) continue; /* sha2-256 */
2343 break;
2344 case 2: if (rr->size != 3 + 512/8) continue; /* sha2-512 */
2345 break;
2346 default: continue;
2347 }
2348
2349 tls_out.tlsa_usage |= 1<<usage;
2350 dane_data[i] = CS p;
2351 dane_data_len[i++] = rr->size;
2352 }
2353
2354 if (!i) return FALSE;
2355
2356 dane_data[i] = NULL;
2357 dane_data_len[i] = 0;
2358
2359 state->dane_data = (char * const *)dane_data;
2360 state->dane_data_len = dane_data_len;
2361 return TRUE;
2362 }
2363 #endif
2364
2365
2366
2367 /*************************************************
2368 * Start a TLS session in a client *
2369 *************************************************/
2370
2371 /* Called from the smtp transport after STARTTLS has been accepted.
2372
2373 Arguments:
2374 cctx connection context
2375 conn_args connection details
2376 cookie datum for randomness (not used)
2377 tlsp record details of channel configuration here; must be non-NULL
2378 errstr error string pointer
2379
2380 Returns: TRUE for success with TLS session context set in smtp context,
2381 FALSE on error
2382 */
2383
2384 BOOL
2385 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
2386 void * cookie ARG_UNUSED,
2387 tls_support * tlsp, uschar ** errstr)
2388 {
2389 host_item * host = conn_args->host; /* for msgs and option-tests */
2390 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
2391 smtp_transport_options_block * ob = tb
2392 ? (smtp_transport_options_block *)tb->options_block
2393 : &smtp_transport_option_defaults;
2394 int rc;
2395 exim_gnutls_state_st * state = NULL;
2396 uschar * cipher_list = NULL;
2397
2398 #ifndef DISABLE_OCSP
2399 BOOL require_ocsp =
2400 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2401 BOOL request_ocsp = require_ocsp ? TRUE
2402 : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2403 #endif
2404
2405 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", cctx->sock);
2406
2407 #ifdef SUPPORT_DANE
2408 /* If dane is flagged, have either request or require dane for this host, and
2409 a TLSA record found. Therefore, dane verify required. Which implies cert must
2410 be requested and supplied, dane verify must pass, and cert verify irrelevant
2411 (incl. hostnames), and (caller handled) require_tls */
2412
2413 if (conn_args->dane && ob->dane_require_tls_ciphers)
2414 {
2415 /* not using expand_check_tlsvar because not yet in state */
2416 if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2417 &cipher_list, errstr))
2418 return FALSE;
2419 cipher_list = cipher_list && *cipher_list
2420 ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
2421 }
2422 #endif
2423
2424 if (!cipher_list)
2425 cipher_list = ob->tls_require_ciphers;
2426
2427 if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
2428 ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
2429 cipher_list, &state, tlsp, errstr) != OK)
2430 return FALSE;
2431
2432 {
2433 int dh_min_bits = ob->tls_dh_min_bits;
2434 if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
2435 {
2436 DEBUG(D_tls)
2437 debug_printf("WARNING: tls_dh_min_bits far too low,"
2438 " clamping %d up to %d\n",
2439 dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
2440 dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
2441 }
2442
2443 DEBUG(D_tls) debug_printf("Setting D-H prime minimum"
2444 " acceptable bits to %d\n",
2445 dh_min_bits);
2446 gnutls_dh_set_prime_bits(state->session, dh_min_bits);
2447 }
2448
2449 /* Stick to the old behaviour for compatibility if tls_verify_certificates is
2450 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
2451 the specified host patterns if one of them is defined */
2452
2453 #ifdef SUPPORT_DANE
2454 if (conn_args->dane && dane_tlsa_load(state, &conn_args->tlsa_dnsa))
2455 {
2456 DEBUG(D_tls)
2457 debug_printf("TLS: server certificate DANE required.\n");
2458 state->verify_requirement = VERIFY_DANE;
2459 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2460 }
2461 else
2462 #endif
2463 if ( ( state->exp_tls_verify_certificates
2464 && !ob->tls_verify_hosts
2465 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2466 )
2467 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2468 )
2469 {
2470 tls_client_setup_hostname_checks(host, state, ob);
2471 DEBUG(D_tls)
2472 debug_printf("TLS: server certificate verification required.\n");
2473 state->verify_requirement = VERIFY_REQUIRED;
2474 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2475 }
2476 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2477 {
2478 tls_client_setup_hostname_checks(host, state, ob);
2479 DEBUG(D_tls)
2480 debug_printf("TLS: server certificate verification optional.\n");
2481 state->verify_requirement = VERIFY_OPTIONAL;
2482 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2483 }
2484 else
2485 {
2486 DEBUG(D_tls)
2487 debug_printf("TLS: server certificate verification not required.\n");
2488 state->verify_requirement = VERIFY_NONE;
2489 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2490 }
2491
2492 #ifndef DISABLE_OCSP
2493 /* supported since GnuTLS 3.1.3 */
2494 if (request_ocsp)
2495 {
2496 DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
2497 if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
2498 NULL, 0, NULL)) != OK)
2499 {
2500 tls_error_gnu(US"cert-status-req", rc, state->host, errstr);
2501 return FALSE;
2502 }
2503 tlsp->ocsp = OCSP_NOT_RESP;
2504 }
2505 #endif
2506
2507 #ifndef DISABLE_EVENT
2508 if (tb && tb->event_action)
2509 {
2510 state->event_action = tb->event_action;
2511 gnutls_session_set_ptr(state->session, state);
2512 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2513 }
2514 #endif
2515
2516 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) cctx->sock);
2517 state->fd_in = cctx->sock;
2518 state->fd_out = cctx->sock;
2519
2520 DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
2521 /* There doesn't seem to be a built-in timeout on connection. */
2522
2523 sigalrm_seen = FALSE;
2524 ALARM(ob->command_timeout);
2525 do
2526 rc = gnutls_handshake(state->session);
2527 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2528 ALARM_CLR(0);
2529
2530 if (rc != GNUTLS_E_SUCCESS)
2531 {
2532 if (sigalrm_seen)
2533 {
2534 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
2535 tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
2536 }
2537 else
2538 tls_error_gnu(US"gnutls_handshake", rc, state->host, errstr);
2539 return FALSE;
2540 }
2541
2542 DEBUG(D_tls) post_handshake_debug(state);
2543
2544 /* Verify late */
2545
2546 if (!verify_certificate(state, errstr))
2547 {
2548 tls_error(US"certificate verification failed", *errstr, state->host, errstr);
2549 return FALSE;
2550 }
2551
2552 #ifndef DISABLE_OCSP
2553 if (require_ocsp)
2554 {
2555 DEBUG(D_tls)
2556 {
2557 gnutls_datum_t stapling;
2558 gnutls_ocsp_resp_t resp;
2559 gnutls_datum_t printed;
2560 if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0
2561 && (rc= gnutls_ocsp_resp_init(&resp)) == 0
2562 && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0
2563 && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0
2564 )
2565 {
2566 debug_printf("%.4096s", printed.data);
2567 gnutls_free(printed.data);
2568 }
2569 else
2570 (void) tls_error_gnu(US"ocsp decode", rc, state->host, errstr);
2571 }
2572
2573 if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
2574 {
2575 tlsp->ocsp = OCSP_FAILED;
2576 tls_error(US"certificate status check failed", NULL, state->host, errstr);
2577 return FALSE;
2578 }
2579 DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
2580 tlsp->ocsp = OCSP_VFIED;
2581 }
2582 #endif
2583
2584 /* Figure out peer DN, and if authenticated, etc. */
2585
2586 if (peer_status(state, errstr) != OK)
2587 return FALSE;
2588
2589 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
2590
2591 extract_exim_vars_from_tls_state(state);
2592
2593 cctx->tls_ctx = state;
2594 return TRUE;
2595 }
2596
2597
2598
2599
2600 /*************************************************
2601 * Close down a TLS session *
2602 *************************************************/
2603
2604 /* This is also called from within a delivery subprocess forked from the
2605 daemon, to shut down the TLS library, without actually doing a shutdown (which
2606 would tamper with the TLS session in the parent process).
2607
2608 Arguments:
2609 ct_ctx client context pointer, or NULL for the one global server context
2610 shutdown 1 if TLS close-alert is to be sent,
2611 2 if also response to be waited for
2612
2613 Returns: nothing
2614 */
2615
2616 void
2617 tls_close(void * ct_ctx, int shutdown)
2618 {
2619 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2620
2621 if (!state->tlsp || state->tlsp->active.sock < 0) return; /* TLS was not active */
2622
2623 if (shutdown)
2624 {
2625 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
2626 shutdown > 1 ? " (with response-wait)" : "");
2627
2628 ALARM(2);
2629 gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
2630 ALARM_CLR(0);
2631 }
2632
2633 gnutls_deinit(state->session);
2634 gnutls_certificate_free_credentials(state->x509_cred);
2635
2636
2637 state->tlsp->active.sock = -1;
2638 state->tlsp->active.tls_ctx = NULL;
2639 if (state->xfer_buffer) store_free(state->xfer_buffer);
2640 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
2641 }
2642
2643
2644
2645
2646 static BOOL
2647 tls_refill(unsigned lim)
2648 {
2649 exim_gnutls_state_st * state = &state_server;
2650 ssize_t inbytes;
2651
2652 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
2653 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
2654
2655 sigalrm_seen = FALSE;
2656 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2657
2658 do
2659 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
2660 MIN(ssl_xfer_buffer_size, lim));
2661 while (inbytes == GNUTLS_E_AGAIN);
2662
2663 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2664
2665 if (had_command_timeout) /* set by signal handler */
2666 smtp_command_timeout_exit(); /* does not return */
2667 if (had_command_sigterm)
2668 smtp_command_sigterm_exit();
2669 if (had_data_timeout)
2670 smtp_data_timeout_exit();
2671 if (had_data_sigint)
2672 smtp_data_sigint_exit();
2673
2674 /* Timeouts do not get this far. A zero-byte return appears to mean that the
2675 TLS session has been closed down, not that the socket itself has been closed
2676 down. Revert to non-TLS handling. */
2677
2678 if (sigalrm_seen)
2679 {
2680 DEBUG(D_tls) debug_printf("Got tls read timeout\n");
2681 state->xfer_error = TRUE;
2682 return FALSE;
2683 }
2684
2685 else if (inbytes == 0)
2686 {
2687 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2688
2689 receive_getc = smtp_getc;
2690 receive_getbuf = smtp_getbuf;
2691 receive_get_cache = smtp_get_cache;
2692 receive_ungetc = smtp_ungetc;
2693 receive_feof = smtp_feof;
2694 receive_ferror = smtp_ferror;
2695 receive_smtp_buffered = smtp_buffered;
2696
2697 gnutls_deinit(state->session);
2698 gnutls_certificate_free_credentials(state->x509_cred);
2699
2700 state->session = NULL;
2701 state->tlsp->active.sock = -1;
2702 state->tlsp->active.tls_ctx = NULL;
2703 state->tlsp->bits = 0;
2704 state->tlsp->certificate_verified = FALSE;
2705 tls_channelbinding_b64 = NULL;
2706 state->tlsp->cipher = NULL;
2707 state->tlsp->peercert = NULL;
2708 state->tlsp->peerdn = NULL;
2709
2710 return FALSE;
2711 }
2712
2713 /* Handle genuine errors */
2714
2715 else if (inbytes < 0)
2716 {
2717 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
2718 record_io_error(state, (int) inbytes, US"recv", NULL);
2719 state->xfer_error = TRUE;
2720 return FALSE;
2721 }
2722 #ifndef DISABLE_DKIM
2723 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
2724 #endif
2725 state->xfer_buffer_hwm = (int) inbytes;
2726 state->xfer_buffer_lwm = 0;
2727 return TRUE;
2728 }
2729
2730 /*************************************************
2731 * TLS version of getc *
2732 *************************************************/
2733
2734 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2735 it refills the buffer via the GnuTLS reading function.
2736 Only used by the server-side TLS.
2737
2738 This feeds DKIM and should be used for all message-body reads.
2739
2740 Arguments: lim Maximum amount to read/buffer
2741 Returns: the next character or EOF
2742 */
2743
2744 int
2745 tls_getc(unsigned lim)
2746 {
2747 exim_gnutls_state_st * state = &state_server;
2748
2749 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2750 if (!tls_refill(lim))
2751 return state->xfer_error ? EOF : smtp_getc(lim);
2752
2753 /* Something in the buffer; return next uschar */
2754
2755 return state->xfer_buffer[state->xfer_buffer_lwm++];
2756 }
2757
2758 uschar *
2759 tls_getbuf(unsigned * len)
2760 {
2761 exim_gnutls_state_st * state = &state_server;
2762 unsigned size;
2763 uschar * buf;
2764
2765 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2766 if (!tls_refill(*len))
2767 {
2768 if (!state->xfer_error) return smtp_getbuf(len);
2769 *len = 0;
2770 return NULL;
2771 }
2772
2773 if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
2774 size = *len;
2775 buf = &state->xfer_buffer[state->xfer_buffer_lwm];
2776 state->xfer_buffer_lwm += size;
2777 *len = size;
2778 return buf;
2779 }
2780
2781
2782 void
2783 tls_get_cache()
2784 {
2785 #ifndef DISABLE_DKIM
2786 exim_gnutls_state_st * state = &state_server;
2787 int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm;
2788 if (n > 0)
2789 dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n);
2790 #endif
2791 }
2792
2793
2794 BOOL
2795 tls_could_read(void)
2796 {
2797 return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
2798 || gnutls_record_check_pending(state_server.session) > 0;
2799 }
2800
2801
2802
2803
2804 /*************************************************
2805 * Read bytes from TLS channel *
2806 *************************************************/
2807
2808 /* This does not feed DKIM, so if the caller uses this for reading message body,
2809 then the caller must feed DKIM.
2810
2811 Arguments:
2812 ct_ctx client context pointer, or NULL for the one global server context
2813 buff buffer of data
2814 len size of buffer
2815
2816 Returns: the number of bytes read
2817 -1 after a failed read, including EOF
2818 */
2819
2820 int
2821 tls_read(void * ct_ctx, uschar *buff, size_t len)
2822 {
2823 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2824 ssize_t inbytes;
2825
2826 if (len > INT_MAX)
2827 len = INT_MAX;
2828
2829 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
2830 DEBUG(D_tls)
2831 debug_printf("*** PROBABLY A BUG *** " \
2832 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
2833 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
2834
2835 DEBUG(D_tls)
2836 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
2837 state->session, buff, len);
2838
2839 do
2840 inbytes = gnutls_record_recv(state->session, buff, len);
2841 while (inbytes == GNUTLS_E_AGAIN);
2842
2843 if (inbytes > 0) return inbytes;
2844 if (inbytes == 0)
2845 {
2846 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2847 }
2848 else
2849 {
2850 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
2851 record_io_error(state, (int)inbytes, US"recv", NULL);
2852 }
2853
2854 return -1;
2855 }
2856
2857
2858
2859
2860 /*************************************************
2861 * Write bytes down TLS channel *
2862 *************************************************/
2863
2864 /*
2865 Arguments:
2866 ct_ctx client context pointer, or NULL for the one global server context
2867 buff buffer of data
2868 len number of bytes
2869 more more data expected soon
2870
2871 Returns: the number of bytes after a successful write,
2872 -1 after a failed write
2873 */
2874
2875 int
2876 tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
2877 {
2878 ssize_t outbytes;
2879 size_t left = len;
2880 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2881 #ifdef SUPPORT_CORK
2882 static BOOL corked = FALSE;
2883
2884 if (more && !corked) gnutls_record_cork(state->session);
2885 #endif
2886
2887 DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
2888 buff, left, more ? ", more" : "");
2889
2890 while (left > 0)
2891 {
2892 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
2893 buff, left);
2894
2895 do
2896 outbytes = gnutls_record_send(state->session, buff, left);
2897 while (outbytes == GNUTLS_E_AGAIN);
2898
2899 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
2900 if (outbytes < 0)
2901 {
2902 DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
2903 record_io_error(state, outbytes, US"send", NULL);
2904 return -1;
2905 }
2906 if (outbytes == 0)
2907 {
2908 record_io_error(state, 0, US"send", US"TLS channel closed on write");
2909 return -1;
2910 }
2911
2912 left -= outbytes;
2913 buff += outbytes;
2914 }
2915
2916 if (len > INT_MAX)
2917 {
2918 DEBUG(D_tls)
2919 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
2920 len);
2921 len = INT_MAX;
2922 }
2923
2924 #ifdef SUPPORT_CORK
2925 if (more != corked)
2926 {
2927 if (!more) (void) gnutls_record_uncork(state->session, 0);
2928 corked = more;
2929 }
2930 #endif
2931
2932 return (int) len;
2933 }
2934
2935
2936
2937
2938 /*************************************************
2939 * Random number generation *
2940 *************************************************/
2941
2942 /* Pseudo-random number generation. The result is not expected to be
2943 cryptographically strong but not so weak that someone will shoot themselves
2944 in the foot using it as a nonce in input in some email header scheme or
2945 whatever weirdness they'll twist this into. The result should handle fork()
2946 and avoid repeating sequences. OpenSSL handles that for us.
2947
2948 Arguments:
2949 max range maximum
2950 Returns a random number in range [0, max-1]
2951 */
2952
2953 #ifdef HAVE_GNUTLS_RND
2954 int
2955 vaguely_random_number(int max)
2956 {
2957 unsigned int r;
2958 int i, needed_len;
2959 uschar smallbuf[sizeof(r)];
2960
2961 if (max <= 1)
2962 return 0;
2963
2964 needed_len = sizeof(r);
2965 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2966 asked for a number less than 10. */
2967
2968 for (r = max, i = 0; r; ++i)
2969 r >>= 1;
2970 i = (i + 7) / 8;
2971 if (i < needed_len)
2972 needed_len = i;
2973
2974 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
2975 if (i < 0)
2976 {
2977 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
2978 return vaguely_random_number_fallback(max);
2979 }
2980 r = 0;
2981 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
2982 r = r * 256 + *p;
2983
2984 /* We don't particularly care about weighted results; if someone wants
2985 * smooth distribution and cares enough then they should submit a patch then. */
2986 return r % max;
2987 }
2988 #else /* HAVE_GNUTLS_RND */
2989 int
2990 vaguely_random_number(int max)
2991 {
2992 return vaguely_random_number_fallback(max);
2993 }
2994 #endif /* HAVE_GNUTLS_RND */
2995
2996
2997
2998
2999 /*************************************************
3000 * Let tls_require_ciphers be checked at startup *
3001 *************************************************/
3002
3003 /* The tls_require_ciphers option, if set, must be something which the
3004 library can parse.
3005
3006 Returns: NULL on success, or error message
3007 */
3008
3009 uschar *
3010 tls_validate_require_cipher(void)
3011 {
3012 int rc;
3013 uschar *expciphers = NULL;
3014 gnutls_priority_t priority_cache;
3015 const char *errpos;
3016 uschar * dummy_errstr;
3017
3018 #define validate_check_rc(Label) do { \
3019 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
3020 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
3021 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
3022
3023 if (exim_gnutls_base_init_done)
3024 log_write(0, LOG_MAIN|LOG_PANIC,
3025 "already initialised GnuTLS, Exim developer bug");
3026
3027 #ifdef HAVE_GNUTLS_PKCS11
3028 if (!gnutls_allow_auto_pkcs11)
3029 {
3030 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
3031 validate_check_rc(US"gnutls_pkcs11_init");
3032 }
3033 #endif
3034 rc = gnutls_global_init();
3035 validate_check_rc(US"gnutls_global_init()");
3036 exim_gnutls_base_init_done = TRUE;
3037
3038 if (!(tls_require_ciphers && *tls_require_ciphers))
3039 return_deinit(NULL);
3040
3041 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3042 &dummy_errstr))
3043 return_deinit(US"failed to expand tls_require_ciphers");
3044
3045 if (!(expciphers && *expciphers))
3046 return_deinit(NULL);
3047
3048 DEBUG(D_tls)
3049 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3050
3051 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
3052 validate_check_rc(string_sprintf(
3053 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
3054 expciphers, errpos - CS expciphers, errpos));
3055
3056 #undef return_deinit
3057 #undef validate_check_rc
3058 gnutls_global_deinit();
3059
3060 return NULL;
3061 }
3062
3063
3064
3065
3066 /*************************************************
3067 * Report the library versions. *
3068 *************************************************/
3069
3070 /* See a description in tls-openssl.c for an explanation of why this exists.
3071
3072 Arguments: a FILE* to print the results to
3073 Returns: nothing
3074 */
3075
3076 void
3077 tls_version_report(FILE *f)
3078 {
3079 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
3080 " Runtime: %s\n",
3081 LIBGNUTLS_VERSION,
3082 gnutls_check_version(NULL));
3083 }
3084
3085 /* vi: aw ai sw=2
3086 */
3087 /* End of tls-gnu.c */