Commit | Line | Data |
---|---|---|
059ec3d9 PH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
17c76198 | 5 | /* Copyright (c) University of Cambridge 1995 - 2012 */ |
059ec3d9 PH |
6 | /* See the file NOTICE for conditions of use and distribution. */ |
7 | ||
17c76198 | 8 | /* Copyright (c) Phil Pennock 2012 */ |
059ec3d9 | 9 | |
17c76198 PP |
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. | |
059ec3d9 | 13 | |
17c76198 PP |
14 | The code herein is a revamp of GnuTLS integration using the current APIs; the |
15 | original tls-gnu.c was based on a patch which was contributed by Nikos | |
16 | Mavroyanopoulos. The revamp is partially a rewrite, partially cut&paste as | |
17 | appropriate. | |
059ec3d9 | 18 | |
17c76198 PP |
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). | |
059ec3d9 | 23 | |
17c76198 PP |
24 | Keeping client and server variables more split than before and is currently |
25 | the norm, in anticipation of TLS in ACL callouts. | |
059ec3d9 | 26 | |
17c76198 PP |
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. | |
059ec3d9 | 31 | |
17c76198 PP |
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 | */ | |
b5aea5e1 | 36 | |
17c76198 PP |
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> | |
059ec3d9 | 42 | |
17c76198 | 43 | /* GnuTLS 2 vs 3 |
059ec3d9 | 44 | |
17c76198 PP |
45 | GnuTLS 3 only: |
46 | gnutls_global_set_audit_log_function() | |
059ec3d9 | 47 | |
17c76198 PP |
48 | Changes: |
49 | gnutls_certificate_verify_peers2(): is new, drop the 2 for old version | |
50 | */ | |
059ec3d9 | 51 | |
17c76198 | 52 | /* Local static variables for GnuTLS */ |
059ec3d9 | 53 | |
17c76198 | 54 | /* Values for verify_requirement */ |
059ec3d9 | 55 | |
17c76198 | 56 | enum peer_verify_requirement { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED }; |
059ec3d9 | 57 | |
17c76198 PP |
58 | /* This holds most state for server or client; with this, we can set up an |
59 | outbound TLS-enabled connection in an ACL callout, while not stomping all | |
60 | over the TLS variables available for expansion. | |
059ec3d9 | 61 | |
17c76198 PP |
62 | Some of these correspond to variables in globals.c; those variables will |
63 | be set to point to content in one of these instances, as appropriate for | |
64 | the stage of the process lifetime. | |
059ec3d9 | 65 | |
17c76198 PP |
66 | Not handled here: globals tls_active, tls_bits, tls_cipher, tls_peerdn, |
67 | tls_certificate_verified, tls_channelbinding_b64, tls_sni. | |
68 | */ | |
059ec3d9 | 69 | |
17c76198 PP |
70 | typedef struct exim_gnutls_state { |
71 | gnutls_session_t session; | |
72 | gnutls_certificate_credentials_t x509_cred; | |
73 | gnutls_priority_t priority_cache; | |
74 | enum peer_verify_requirement verify_requirement; | |
75 | int fd_in; | |
76 | int fd_out; | |
77 | BOOL peer_cert_verified; | |
78 | BOOL trigger_sni_changes; | |
4fe99a6c | 79 | BOOL have_set_peerdn; |
17c76198 PP |
80 | const struct host_item *host; |
81 | uschar *peerdn; | |
75fe387d | 82 | uschar *ciphersuite; |
17c76198 PP |
83 | uschar *received_sni; |
84 | ||
85 | const uschar *tls_certificate; | |
86 | const uschar *tls_privatekey; | |
87 | const uschar *tls_sni; /* client send only, not received */ | |
88 | const uschar *tls_verify_certificates; | |
89 | const uschar *tls_crl; | |
90 | const uschar *tls_require_ciphers; | |
91 | uschar *exp_tls_certificate; | |
92 | uschar *exp_tls_privatekey; | |
93 | uschar *exp_tls_sni; | |
94 | uschar *exp_tls_verify_certificates; | |
95 | uschar *exp_tls_crl; | |
96 | uschar *exp_tls_require_ciphers; | |
97 | ||
98 | uschar *xfer_buffer; | |
99 | int xfer_buffer_lwm; | |
100 | int xfer_buffer_hwm; | |
101 | int xfer_eof; | |
102 | int xfer_error; | |
17c76198 PP |
103 | } exim_gnutls_state_st; |
104 | ||
105 | static const exim_gnutls_state_st exim_gnutls_state_init = { | |
4fe99a6c | 106 | NULL, NULL, NULL, VERIFY_NONE, -1, -1, FALSE, FALSE, FALSE, |
75fe387d | 107 | NULL, NULL, NULL, NULL, |
17c76198 PP |
108 | NULL, NULL, NULL, NULL, NULL, NULL, |
109 | NULL, NULL, NULL, NULL, NULL, NULL, | |
110 | NULL, 0, 0, 0, 0, | |
17c76198 | 111 | }; |
83da1223 | 112 | |
17c76198 PP |
113 | /* Not only do we have our own APIs which don't pass around state, assuming |
114 | it's held in globals, GnuTLS doesn't appear to let us register callback data | |
115 | for callbacks, or as part of the session, so we have to keep a "this is the | |
116 | context we're currently dealing with" pointer and rely upon being | |
117 | single-threaded to keep from processing data on an inbound TLS connection while | |
118 | talking to another TLS connection for an outbound check. This does mean that | |
119 | there's no way for heart-beats to be responded to, for the duration of the | |
120 | second connection. */ | |
059ec3d9 | 121 | |
17c76198 PP |
122 | static exim_gnutls_state_st state_server, state_client; |
123 | static exim_gnutls_state_st *current_global_tls_state; | |
059ec3d9 | 124 | |
17c76198 PP |
125 | /* dh_params are initialised once within the lifetime of a process using TLS; |
126 | if we used TLS in a long-lived daemon, we'd have to reconsider this. But we | |
127 | don't want to repeat this. */ | |
83da1223 | 128 | |
17c76198 | 129 | static gnutls_dh_params_t dh_server_params = NULL; |
059ec3d9 | 130 | |
17c76198 | 131 | /* No idea how this value was chosen; preserving it. Default is 3600. */ |
059ec3d9 | 132 | |
17c76198 | 133 | static const int ssl_session_timeout = 200; |
059ec3d9 | 134 | |
17c76198 | 135 | static const char * const exim_default_gnutls_priority = "NORMAL"; |
83da1223 | 136 | |
17c76198 | 137 | /* Guard library core initialisation */ |
83da1223 | 138 | |
17c76198 | 139 | static BOOL exim_gnutls_base_init_done = FALSE; |
059ec3d9 | 140 | |
059ec3d9 | 141 | |
17c76198 PP |
142 | /* ------------------------------------------------------------------------ */ |
143 | /* macros */ | |
83da1223 | 144 | |
17c76198 | 145 | #define MAX_HOST_LEN 255 |
83da1223 | 146 | |
17c76198 PP |
147 | /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup |
148 | the library logging; a value less than 0 disables the calls to set up logging | |
149 | callbacks. */ | |
2c17bb02 | 150 | #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL |
17c76198 | 151 | #define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1 |
2c17bb02 | 152 | #endif |
83da1223 | 153 | |
2c17bb02 | 154 | #ifndef EXIM_CLIENT_DH_MIN_BITS |
17c76198 | 155 | #define EXIM_CLIENT_DH_MIN_BITS 1024 |
2c17bb02 | 156 | #endif |
83da1223 | 157 | |
af3498d6 PP |
158 | /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we |
159 | can ask for a bit-strength. Without that, we stick to the constant we had | |
160 | before, for now. */ | |
2c17bb02 | 161 | #ifndef EXIM_SERVER_DH_BITS_PRE2_12 |
af3498d6 | 162 | #define EXIM_SERVER_DH_BITS_PRE2_12 1024 |
2c17bb02 | 163 | #endif |
af3498d6 | 164 | |
17c76198 PP |
165 | #define exim_gnutls_err_check(Label) do { \ |
166 | if (rc != GNUTLS_E_SUCCESS) { return tls_error((Label), gnutls_strerror(rc), host); } } while (0) | |
059ec3d9 | 167 | |
17c76198 | 168 | #define expand_check_tlsvar(Varname) expand_check(state->Varname, US #Varname, &state->exp_##Varname) |
83da1223 | 169 | |
17c76198 PP |
170 | #if GNUTLS_VERSION_NUMBER >= 0x020c00 |
171 | #define HAVE_GNUTLS_SESSION_CHANNEL_BINDING | |
af3498d6 PP |
172 | #define HAVE_GNUTLS_SEC_PARAM_CONSTANTS |
173 | #define HAVE_GNUTLS_RND | |
17c76198 | 174 | #endif |
83da1223 | 175 | |
af3498d6 PP |
176 | |
177 | ||
178 | ||
179 | /* ------------------------------------------------------------------------ */ | |
180 | /* Callback declarations */ | |
181 | ||
182 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 | |
183 | static void exim_gnutls_logger_cb(int level, const char *message); | |
184 | #endif | |
185 | ||
186 | static int exim_sni_handling_cb(gnutls_session_t session); | |
187 | ||
188 | ||
189 | ||
190 | ||
17c76198 PP |
191 | /* ------------------------------------------------------------------------ */ |
192 | /* Static functions */ | |
059ec3d9 PH |
193 | |
194 | /************************************************* | |
195 | * Handle TLS error * | |
196 | *************************************************/ | |
197 | ||
198 | /* Called from lots of places when errors occur before actually starting to do | |
199 | the TLS handshake, that is, while the session is still in clear. Always returns | |
200 | DEFER for a server and FAIL for a client so that most calls can use "return | |
201 | tls_error(...)" to do this processing and then give an appropriate return. A | |
202 | single function is used for both server and client, because it is called from | |
203 | some shared functions. | |
204 | ||
205 | Argument: | |
206 | prefix text to include in the logged error | |
7199e1ee TF |
207 | msg additional error string (may be NULL) |
208 | usually obtained from gnutls_strerror() | |
17c76198 PP |
209 | host NULL if setting up a server; |
210 | the connected host if setting up a client | |
059ec3d9 PH |
211 | |
212 | Returns: OK/DEFER/FAIL | |
213 | */ | |
214 | ||
215 | static int | |
17c76198 | 216 | tls_error(const uschar *prefix, const char *msg, const host_item *host) |
059ec3d9 | 217 | { |
17c76198 PP |
218 | if (host) |
219 | { | |
220 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s%s", | |
221 | host->name, host->address, prefix, msg ? ": " : "", msg ? msg : ""); | |
222 | return FAIL; | |
223 | } | |
224 | else | |
059ec3d9 | 225 | { |
7199e1ee | 226 | uschar *conn_info = smtp_get_connection_info(); |
17c76198 | 227 | if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) |
7199e1ee TF |
228 | conn_info += 5; |
229 | log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s", | |
17c76198 | 230 | conn_info, prefix, msg ? ": " : "", msg ? msg : ""); |
059ec3d9 PH |
231 | return DEFER; |
232 | } | |
059ec3d9 PH |
233 | } |
234 | ||
235 | ||
236 | ||
17c76198 | 237 | |
059ec3d9 | 238 | /************************************************* |
17c76198 | 239 | * Deal with logging errors during I/O * |
059ec3d9 PH |
240 | *************************************************/ |
241 | ||
17c76198 | 242 | /* We have to get the identity of the peer from saved data. |
059ec3d9 | 243 | |
17c76198 PP |
244 | Argument: |
245 | state the current GnuTLS exim state container | |
246 | rc the GnuTLS error code, or 0 if it's a local error | |
247 | when text identifying read or write | |
248 | text local error text when ec is 0 | |
059ec3d9 | 249 | |
17c76198 | 250 | Returns: nothing |
059ec3d9 PH |
251 | */ |
252 | ||
17c76198 PP |
253 | static void |
254 | record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text) | |
059ec3d9 | 255 | { |
17c76198 | 256 | const char *msg; |
059ec3d9 | 257 | |
17c76198 PP |
258 | if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED) |
259 | msg = CS string_sprintf("%s: %s", US gnutls_strerror(rc), | |
260 | US gnutls_alert_get_name(gnutls_alert_get(state->session))); | |
261 | else | |
262 | msg = gnutls_strerror(rc); | |
059ec3d9 | 263 | |
17c76198 PP |
264 | tls_error(when, msg, state->host); |
265 | } | |
059ec3d9 | 266 | |
059ec3d9 | 267 | |
059ec3d9 | 268 | |
059ec3d9 | 269 | |
17c76198 PP |
270 | /************************************************* |
271 | * Set various Exim expansion vars * | |
272 | *************************************************/ | |
059ec3d9 | 273 | |
17c76198 PP |
274 | /* We set various Exim global variables from the state, once a session has |
275 | been established. With TLS callouts, may need to change this to stack | |
276 | variables, or just re-call it with the server state after client callout | |
277 | has finished. | |
059ec3d9 | 278 | |
17c76198 PP |
279 | Make sure anything set here is inset in tls_getc(). |
280 | ||
281 | Sets: | |
282 | tls_active fd | |
283 | tls_bits strength indicator | |
284 | tls_certificate_verified bool indicator | |
285 | tls_channelbinding_b64 for some SASL mechanisms | |
286 | tls_cipher a string | |
287 | tls_peerdn a string | |
288 | tls_sni a (UTF-8) string | |
289 | Also: | |
290 | current_global_tls_state for API limitations | |
291 | ||
292 | Argument: | |
293 | state the relevant exim_gnutls_state_st * | |
294 | */ | |
295 | ||
296 | static void | |
297 | extract_exim_vars_from_tls_state(exim_gnutls_state_st *state) | |
298 | { | |
17c76198 | 299 | gnutls_cipher_algorithm_t cipher; |
17c76198 PP |
300 | #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING |
301 | int old_pool; | |
302 | int rc; | |
303 | gnutls_datum_t channel; | |
304 | #endif | |
305 | ||
306 | current_global_tls_state = state; | |
307 | ||
308 | tls_active = state->fd_out; | |
309 | ||
310 | cipher = gnutls_cipher_get(state->session); | |
311 | /* returns size in "bytes" */ | |
312 | tls_bits = gnutls_cipher_get_key_size(cipher) * 8; | |
313 | ||
75fe387d | 314 | tls_cipher = state->ciphersuite; |
17c76198 PP |
315 | |
316 | DEBUG(D_tls) debug_printf("cipher: %s\n", tls_cipher); | |
317 | ||
318 | tls_certificate_verified = state->peer_cert_verified; | |
059ec3d9 | 319 | |
17c76198 PP |
320 | /* note that tls_channelbinding_b64 is not saved to the spool file, since it's |
321 | only available for use for authenticators while this TLS session is running. */ | |
322 | ||
323 | tls_channelbinding_b64 = NULL; | |
324 | #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING | |
325 | channel.data = NULL; | |
326 | channel.size = 0; | |
327 | rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel); | |
328 | if (rc) { | |
329 | DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); | |
330 | } else { | |
331 | old_pool = store_pool; | |
332 | store_pool = POOL_PERM; | |
333 | tls_channelbinding_b64 = auth_b64encode(channel.data, (int)channel.size); | |
334 | store_pool = old_pool; | |
335 | DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n"); | |
336 | } | |
337 | #endif | |
338 | ||
339 | tls_peerdn = state->peerdn; | |
340 | ||
341 | tls_sni = state->received_sni; | |
059ec3d9 PH |
342 | } |
343 | ||
344 | ||
345 | ||
17c76198 | 346 | |
059ec3d9 | 347 | /************************************************* |
575643cd | 348 | * Setup up DH parameters * |
059ec3d9 PH |
349 | *************************************************/ |
350 | ||
575643cd | 351 | /* Generating the D-H parameters may take a long time. They only need to |
059ec3d9 PH |
352 | be re-generated every so often, depending on security policy. What we do is to |
353 | keep these parameters in a file in the spool directory. If the file does not | |
354 | exist, we generate them. This means that it is easy to cause a regeneration. | |
355 | ||
356 | The new file is written as a temporary file and renamed, so that an incomplete | |
357 | file is never present. If two processes both compute some new parameters, you | |
358 | waste a bit of effort, but it doesn't seem worth messing around with locking to | |
359 | prevent this. | |
360 | ||
361 | Argument: | |
362 | host NULL for server, server for client (for error handling) | |
363 | ||
364 | Returns: OK/DEFER/FAIL | |
365 | */ | |
366 | ||
367 | static int | |
17c76198 | 368 | init_server_dh(void) |
059ec3d9 | 369 | { |
17c76198 PP |
370 | int fd, rc; |
371 | unsigned int dh_bits; | |
b5aea5e1 | 372 | gnutls_datum m; |
17c76198 PP |
373 | uschar filename[PATH_MAX]; |
374 | size_t sz; | |
375 | host_item *host = NULL; /* dummy for macros */ | |
059ec3d9 | 376 | |
17c76198 | 377 | DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n"); |
059ec3d9 | 378 | |
17c76198 PP |
379 | rc = gnutls_dh_params_init(&dh_server_params); |
380 | exim_gnutls_err_check(US"gnutls_dh_params_init"); | |
059ec3d9 | 381 | |
af3498d6 PP |
382 | #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS |
383 | /* If you change this constant, also change dh_param_fn_ext so that we can use a | |
17c76198 PP |
384 | different filename and ensure we have sufficient bits. */ |
385 | dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL); | |
386 | if (!dh_bits) | |
387 | return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL); | |
af3498d6 | 388 | DEBUG(D_tls) |
b34fc30c | 389 | debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n", |
af3498d6 PP |
390 | dh_bits); |
391 | #else | |
392 | dh_bits = EXIM_SERVER_DH_BITS_PRE2_12; | |
393 | DEBUG(D_tls) | |
394 | debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n", | |
395 | dh_bits); | |
396 | #endif | |
059ec3d9 | 397 | |
17c76198 | 398 | if (!string_format(filename, sizeof(filename), |
af3498d6 | 399 | "%s/gnutls-params-%d", spool_directory, dh_bits)) |
17c76198 | 400 | return tls_error(US"overlong filename", NULL, NULL); |
059ec3d9 | 401 | |
b5aea5e1 | 402 | /* Open the cache file for reading and if successful, read it and set up the |
575643cd | 403 | parameters. */ |
059ec3d9 PH |
404 | |
405 | fd = Uopen(filename, O_RDONLY, 0); | |
b5aea5e1 | 406 | if (fd >= 0) |
059ec3d9 | 407 | { |
b5aea5e1 | 408 | struct stat statbuf; |
17c76198 PP |
409 | FILE *fp; |
410 | int saved_errno; | |
411 | ||
412 | if (fstat(fd, &statbuf) < 0) /* EIO */ | |
413 | { | |
414 | saved_errno = errno; | |
415 | (void)close(fd); | |
416 | return tls_error(US"TLS cache stat failed", strerror(saved_errno), NULL); | |
417 | } | |
418 | if (!S_ISREG(statbuf.st_mode)) | |
b5aea5e1 PH |
419 | { |
420 | (void)close(fd); | |
17c76198 PP |
421 | return tls_error(US"TLS cache not a file", NULL, NULL); |
422 | } | |
423 | fp = fdopen(fd, "rb"); | |
424 | if (!fp) | |
425 | { | |
426 | saved_errno = errno; | |
427 | (void)close(fd); | |
428 | return tls_error(US"fdopen(TLS cache stat fd) failed", | |
429 | strerror(saved_errno), NULL); | |
b5aea5e1 | 430 | } |
059ec3d9 | 431 | |
b5aea5e1 PH |
432 | m.size = statbuf.st_size; |
433 | m.data = malloc(m.size); | |
434 | if (m.data == NULL) | |
17c76198 PP |
435 | { |
436 | fclose(fp); | |
437 | return tls_error(US"malloc failed", strerror(errno), NULL); | |
438 | } | |
439 | sz = fread(m.data, m.size, 1, fp); | |
440 | if (!sz) | |
441 | { | |
442 | saved_errno = errno; | |
443 | fclose(fp); | |
444 | free(m.data); | |
445 | return tls_error(US"fread failed", strerror(saved_errno), NULL); | |
446 | } | |
447 | fclose(fp); | |
b5aea5e1 | 448 | |
17c76198 | 449 | rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM); |
b5aea5e1 | 450 | free(m.data); |
17c76198 PP |
451 | exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3"); |
452 | DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename); | |
b5aea5e1 PH |
453 | } |
454 | ||
455 | /* If the file does not exist, fall through to compute new data and cache it. | |
456 | If there was any other opening error, it is serious. */ | |
457 | ||
182ad5cf PH |
458 | else if (errno == ENOENT) |
459 | { | |
17c76198 | 460 | rc = -1; |
182ad5cf | 461 | DEBUG(D_tls) |
17c76198 | 462 | debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename); |
182ad5cf PH |
463 | } |
464 | else | |
17c76198 PP |
465 | return tls_error(string_open_failed(errno, "\"%s\" for reading", filename), |
466 | NULL, NULL); | |
b5aea5e1 PH |
467 | |
468 | /* If ret < 0, either the cache file does not exist, or the data it contains | |
469 | is not useful. One particular case of this is when upgrading from an older | |
470 | release of Exim in which the data was stored in a different format. We don't | |
471 | try to be clever and support both formats; we just regenerate new data in this | |
472 | case. */ | |
473 | ||
17c76198 | 474 | if (rc < 0) |
b5aea5e1 | 475 | { |
17c76198 | 476 | uschar *temp_fn; |
059ec3d9 | 477 | |
17c76198 PP |
478 | if ((PATH_MAX - Ustrlen(filename)) < 10) |
479 | return tls_error(US"Filename too long to generate replacement", | |
480 | CS filename, NULL); | |
059ec3d9 | 481 | |
17c76198 PP |
482 | temp_fn = string_copy(US "%s.XXXXXXX"); |
483 | fd = mkstemp(CS temp_fn); /* modifies temp_fn */ | |
059ec3d9 | 484 | if (fd < 0) |
17c76198 | 485 | return tls_error(US"Unable to open temp file", strerror(errno), NULL); |
059ec3d9 PH |
486 | (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */ |
487 | ||
17c76198 PP |
488 | DEBUG(D_tls) debug_printf("generating %d bits Diffie-Hellman key ...\n", dh_bits); |
489 | rc = gnutls_dh_params_generate2(dh_server_params, dh_bits); | |
490 | exim_gnutls_err_check(US"gnutls_dh_params_generate2"); | |
491 | ||
492 | /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time, | |
493 | and I confirmed that a NULL call to get the size first is how the GnuTLS | |
494 | sample apps handle this. */ | |
495 | ||
496 | sz = 0; | |
497 | m.data = NULL; | |
498 | rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, | |
499 | m.data, &sz); | |
500 | if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) | |
501 | exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3(NULL) sizing"); | |
502 | m.size = sz; | |
b5aea5e1 PH |
503 | m.data = malloc(m.size); |
504 | if (m.data == NULL) | |
17c76198 PP |
505 | return tls_error(US"memory allocation failed", strerror(errno), NULL); |
506 | rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, | |
507 | m.data, &sz); | |
508 | if (rc != GNUTLS_E_SUCCESS) | |
509 | { | |
510 | free(m.data); | |
511 | exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real"); | |
512 | } | |
059ec3d9 | 513 | |
17c76198 PP |
514 | sz = write_to_fd_buf(fd, m.data, (size_t) m.size); |
515 | if (sz != m.size) | |
516 | { | |
517 | free(m.data); | |
518 | return tls_error(US"TLS cache write D-H params failed", | |
519 | strerror(errno), NULL); | |
520 | } | |
b5aea5e1 | 521 | free(m.data); |
17c76198 PP |
522 | sz = write_to_fd_buf(fd, US"\n", 1); |
523 | if (sz != 1) | |
524 | return tls_error(US"TLS cache write D-H params final newline failed", | |
525 | strerror(errno), NULL); | |
526 | ||
527 | rc = close(fd); | |
528 | if (rc) | |
529 | return tls_error(US"TLS cache write close() failed", | |
530 | strerror(errno), NULL); | |
059ec3d9 | 531 | |
17c76198 PP |
532 | if (Urename(temp_fn, filename) < 0) |
533 | return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"", | |
534 | temp_fn, filename), strerror(errno), NULL); | |
059ec3d9 | 535 | |
17c76198 | 536 | DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename); |
059ec3d9 PH |
537 | } |
538 | ||
17c76198 | 539 | DEBUG(D_tls) debug_printf("initialized server D-H parameters\n"); |
059ec3d9 PH |
540 | return OK; |
541 | } | |
542 | ||
543 | ||
544 | ||
545 | ||
546 | /************************************************* | |
17c76198 | 547 | * Variables re-expanded post-SNI * |
059ec3d9 PH |
548 | *************************************************/ |
549 | ||
17c76198 PP |
550 | /* Called from both server and client code, via tls_init(), and also from |
551 | the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni". | |
552 | ||
553 | We can tell the two apart by state->received_sni being non-NULL in callback. | |
554 | ||
555 | The callback should not call us unless state->trigger_sni_changes is true, | |
556 | which we are responsible for setting on the first pass through. | |
059ec3d9 PH |
557 | |
558 | Arguments: | |
17c76198 | 559 | state exim_gnutls_state_st * |
059ec3d9 PH |
560 | |
561 | Returns: OK/DEFER/FAIL | |
562 | */ | |
563 | ||
564 | static int | |
17c76198 | 565 | tls_expand_session_files(exim_gnutls_state_st *state) |
059ec3d9 | 566 | { |
1365611d | 567 | struct stat statbuf; |
059ec3d9 | 568 | int rc; |
17c76198 PP |
569 | const host_item *host = state->host; /* macro should be reconsidered? */ |
570 | uschar *saved_tls_certificate = NULL; | |
571 | uschar *saved_tls_privatekey = NULL; | |
572 | uschar *saved_tls_verify_certificates = NULL; | |
573 | uschar *saved_tls_crl = NULL; | |
574 | int cert_count; | |
575 | ||
576 | /* We check for tls_sni *before* expansion. */ | |
577 | if (!state->host) | |
578 | { | |
579 | if (!state->received_sni) | |
580 | { | |
581 | if (Ustrstr(state->tls_certificate, US"tls_sni")) | |
582 | { | |
583 | DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n"); | |
584 | state->trigger_sni_changes = TRUE; | |
585 | } | |
586 | } | |
587 | else | |
588 | { | |
1365611d | 589 | /* useful for debugging */ |
17c76198 PP |
590 | saved_tls_certificate = state->exp_tls_certificate; |
591 | saved_tls_privatekey = state->exp_tls_privatekey; | |
592 | saved_tls_verify_certificates = state->exp_tls_verify_certificates; | |
593 | saved_tls_crl = state->exp_tls_crl; | |
594 | } | |
595 | } | |
059ec3d9 | 596 | |
1365611d PP |
597 | rc = gnutls_certificate_allocate_credentials(&state->x509_cred); |
598 | exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials"); | |
599 | ||
17c76198 PP |
600 | /* remember: expand_check_tlsvar() is expand_check() but fiddling with |
601 | state members, assuming consistent naming; and expand_check() returns | |
602 | false if expansion failed, unless expansion was forced to fail. */ | |
059ec3d9 | 603 | |
17c76198 PP |
604 | /* check if we at least have a certificate, before doing expensive |
605 | D-H generation. */ | |
059ec3d9 | 606 | |
17c76198 PP |
607 | if (!expand_check_tlsvar(tls_certificate)) |
608 | return DEFER; | |
059ec3d9 | 609 | |
17c76198 | 610 | /* certificate is mandatory in server, optional in client */ |
059ec3d9 | 611 | |
17c76198 PP |
612 | if ((state->exp_tls_certificate == NULL) || |
613 | (*state->exp_tls_certificate == '\0')) | |
614 | { | |
615 | if (state->host == NULL) | |
616 | return tls_error(US"no TLS server certificate is specified", NULL, NULL); | |
617 | else | |
618 | DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n"); | |
619 | } | |
059ec3d9 | 620 | |
17c76198 | 621 | if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey)) |
059ec3d9 PH |
622 | return DEFER; |
623 | ||
17c76198 PP |
624 | /* tls_privatekey is optional, defaulting to same file as certificate */ |
625 | ||
626 | if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0') | |
059ec3d9 | 627 | { |
17c76198 PP |
628 | state->tls_privatekey = state->tls_certificate; |
629 | state->exp_tls_privatekey = state->exp_tls_certificate; | |
059ec3d9 | 630 | } |
c91535f3 | 631 | |
059ec3d9 | 632 | |
17c76198 | 633 | if (state->exp_tls_certificate && *state->exp_tls_certificate) |
059ec3d9 PH |
634 | { |
635 | DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n", | |
17c76198 PP |
636 | state->exp_tls_certificate, state->exp_tls_privatekey); |
637 | ||
638 | if (state->received_sni) | |
de365ded | 639 | { |
17c76198 PP |
640 | if ((Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0) && |
641 | (Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0)) | |
642 | { | |
b34fc30c | 643 | DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n"); |
17c76198 PP |
644 | } |
645 | else | |
646 | { | |
b34fc30c | 647 | DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n"); |
17c76198 | 648 | } |
8e669ac1 | 649 | } |
059ec3d9 | 650 | |
1365611d PP |
651 | rc = gnutls_certificate_set_x509_key_file(state->x509_cred, |
652 | CS state->exp_tls_certificate, CS state->exp_tls_privatekey, | |
653 | GNUTLS_X509_FMT_PEM); | |
654 | exim_gnutls_err_check( | |
655 | string_sprintf("cert/key setup: cert=%s key=%s", | |
656 | state->exp_tls_certificate, state->exp_tls_privatekey)); | |
657 | DEBUG(D_tls) debug_printf("TLS: cert/key registered\n"); | |
b34fc30c | 658 | } /* tls_certificate */ |
059ec3d9 PH |
659 | |
660 | /* Set the trusted CAs file if one is provided, and then add the CRL if one is | |
661 | provided. Experiment shows that, if the certificate file is empty, an unhelpful | |
662 | error message is provided. However, if we just refrain from setting anything up | |
663 | in that case, certificate verification fails, which seems to be the correct | |
664 | behaviour. */ | |
665 | ||
17c76198 | 666 | if (state->tls_verify_certificates && *state->tls_verify_certificates) |
059ec3d9 | 667 | { |
17c76198 | 668 | if (!expand_check_tlsvar(tls_verify_certificates)) |
059ec3d9 | 669 | return DEFER; |
17c76198 PP |
670 | if (state->tls_crl && *state->tls_crl) |
671 | if (!expand_check_tlsvar(tls_crl)) | |
672 | return DEFER; | |
059ec3d9 | 673 | |
1365611d PP |
674 | if (!(state->exp_tls_verify_certificates && |
675 | *state->exp_tls_verify_certificates)) | |
b34fc30c PP |
676 | { |
677 | DEBUG(D_tls) | |
1365611d PP |
678 | debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n"); |
679 | /* With no tls_verify_certificates, we ignore tls_crl too */ | |
17c76198 | 680 | return OK; |
b34fc30c | 681 | } |
1365611d | 682 | } |
83e2f8a2 PP |
683 | else |
684 | { | |
685 | DEBUG(D_tls) | |
686 | debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n"); | |
687 | return OK; | |
688 | } | |
17c76198 | 689 | |
1365611d PP |
690 | if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0) |
691 | { | |
692 | log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s " | |
693 | "(tls_verify_certificates): %s", state->exp_tls_verify_certificates, | |
694 | strerror(errno)); | |
695 | return DEFER; | |
696 | } | |
17c76198 | 697 | |
1365611d PP |
698 | if (!S_ISREG(statbuf.st_mode)) |
699 | { | |
700 | DEBUG(D_tls) | |
701 | debug_printf("verify certificates path is not a file: \"%s\"\n%s\n", | |
702 | state->exp_tls_verify_certificates, | |
703 | S_ISDIR(statbuf.st_mode) | |
704 | ? " it's a directory, that's OpenSSL, this is GnuTLS" | |
705 | : " (not a directory either)"); | |
706 | log_write(0, LOG_MAIN|LOG_PANIC, | |
707 | "tls_verify_certificates \"%s\" is not a file", | |
708 | state->exp_tls_verify_certificates); | |
709 | return DEFER; | |
710 | } | |
059ec3d9 | 711 | |
1365611d PP |
712 | DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n", |
713 | state->exp_tls_verify_certificates, statbuf.st_size); | |
059ec3d9 | 714 | |
1365611d PP |
715 | if (statbuf.st_size == 0) |
716 | { | |
717 | DEBUG(D_tls) | |
718 | debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n"); | |
719 | return OK; | |
720 | } | |
059ec3d9 | 721 | |
1365611d PP |
722 | cert_count = gnutls_certificate_set_x509_trust_file(state->x509_cred, |
723 | CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM); | |
724 | if (cert_count < 0) | |
725 | { | |
726 | rc = cert_count; | |
727 | exim_gnutls_err_check(US"gnutls_certificate_set_x509_trust_file"); | |
728 | } | |
729 | DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count); | |
059ec3d9 | 730 | |
5c8cda3a PP |
731 | if (state->tls_crl && *state->tls_crl && |
732 | state->exp_tls_crl && *state->exp_tls_crl) | |
1365611d | 733 | { |
5c8cda3a PP |
734 | DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl); |
735 | cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred, | |
736 | CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM); | |
737 | if (cert_count < 0) | |
1365611d | 738 | { |
5c8cda3a | 739 | rc = cert_count; |
1365611d PP |
740 | exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file"); |
741 | } | |
5c8cda3a | 742 | DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count); |
1365611d | 743 | } |
059ec3d9 | 744 | |
059ec3d9 PH |
745 | return OK; |
746 | } | |
747 | ||
748 | ||
749 | ||
750 | ||
1365611d PP |
751 | /************************************************* |
752 | * Set X.509 state variables * | |
753 | *************************************************/ | |
754 | ||
755 | /* In GnuTLS, the registered cert/key are not replaced by a later | |
756 | set of a cert/key, so for SNI support we need a whole new x509_cred | |
757 | structure. Which means various other non-re-expanded pieces of state | |
758 | need to be re-set in the new struct, so the setting logic is pulled | |
759 | out to this. | |
760 | ||
761 | Arguments: | |
762 | state exim_gnutls_state_st * | |
763 | ||
764 | Returns: OK/DEFER/FAIL | |
765 | */ | |
766 | ||
767 | static int | |
768 | tls_set_remaining_x509(exim_gnutls_state_st *state) | |
769 | { | |
770 | int rc; | |
771 | const host_item *host = state->host; /* macro should be reconsidered? */ | |
772 | ||
773 | /* Create D-H parameters, or read them from the cache file. This function does | |
774 | its own SMTP error messaging. This only happens for the server, TLS D-H ignores | |
775 | client-side params. */ | |
776 | ||
777 | if (!state->host) | |
778 | { | |
779 | if (!dh_server_params) | |
780 | { | |
781 | rc = init_server_dh(); | |
782 | if (rc != OK) return rc; | |
783 | } | |
784 | gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params); | |
785 | } | |
786 | ||
787 | /* Link the credentials to the session. */ | |
788 | ||
789 | rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred); | |
790 | exim_gnutls_err_check(US"gnutls_credentials_set"); | |
791 | ||
792 | return OK; | |
793 | } | |
794 | ||
059ec3d9 | 795 | /************************************************* |
17c76198 | 796 | * Initialize for GnuTLS * |
059ec3d9 PH |
797 | *************************************************/ |
798 | ||
17c76198 PP |
799 | /* Called from both server and client code. In the case of a server, errors |
800 | before actual TLS negotiation return DEFER. | |
059ec3d9 PH |
801 | |
802 | Arguments: | |
17c76198 PP |
803 | host connected host, if client; NULL if server |
804 | certificate certificate file | |
805 | privatekey private key file | |
806 | sni TLS SNI to send, sometimes when client; else NULL | |
807 | cas CA certs file | |
808 | crl CRL file | |
809 | require_ciphers tls_require_ciphers setting | |
059ec3d9 | 810 | |
17c76198 | 811 | Returns: OK/DEFER/FAIL |
059ec3d9 PH |
812 | */ |
813 | ||
17c76198 PP |
814 | static int |
815 | tls_init( | |
816 | const host_item *host, | |
817 | const uschar *certificate, | |
818 | const uschar *privatekey, | |
819 | const uschar *sni, | |
820 | const uschar *cas, | |
821 | const uschar *crl, | |
822 | const uschar *require_ciphers, | |
823 | exim_gnutls_state_st **caller_state) | |
059ec3d9 | 824 | { |
17c76198 PP |
825 | exim_gnutls_state_st *state; |
826 | int rc; | |
827 | size_t sz; | |
828 | const char *errpos; | |
829 | uschar *p; | |
830 | BOOL want_default_priorities; | |
831 | ||
832 | if (!exim_gnutls_base_init_done) | |
059ec3d9 | 833 | { |
17c76198 PP |
834 | DEBUG(D_tls) debug_printf("GnuTLS global init required.\n"); |
835 | ||
836 | rc = gnutls_global_init(); | |
837 | exim_gnutls_err_check(US"gnutls_global_init"); | |
838 | ||
839 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 | |
840 | DEBUG(D_tls) | |
059ec3d9 | 841 | { |
17c76198 PP |
842 | gnutls_global_set_log_function(exim_gnutls_logger_cb); |
843 | /* arbitrarily chosen level; bump upto 9 for more */ | |
844 | gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL); | |
059ec3d9 | 845 | } |
17c76198 PP |
846 | #endif |
847 | ||
848 | exim_gnutls_base_init_done = TRUE; | |
059ec3d9 | 849 | } |
059ec3d9 | 850 | |
17c76198 PP |
851 | if (host) |
852 | { | |
853 | state = &state_client; | |
854 | memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); | |
855 | DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n"); | |
856 | rc = gnutls_init(&state->session, GNUTLS_CLIENT); | |
857 | } | |
858 | else | |
859 | { | |
860 | state = &state_server; | |
861 | memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); | |
862 | DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n"); | |
863 | rc = gnutls_init(&state->session, GNUTLS_SERVER); | |
864 | } | |
865 | exim_gnutls_err_check(US"gnutls_init"); | |
059ec3d9 | 866 | |
17c76198 | 867 | state->host = host; |
059ec3d9 | 868 | |
17c76198 PP |
869 | state->tls_certificate = certificate; |
870 | state->tls_privatekey = privatekey; | |
871 | state->tls_sni = sni; | |
872 | state->tls_verify_certificates = cas; | |
873 | state->tls_crl = crl; | |
059ec3d9 | 874 | |
17c76198 PP |
875 | /* This handles the variables that might get re-expanded after TLS SNI; |
876 | that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */ | |
059ec3d9 | 877 | |
17c76198 PP |
878 | DEBUG(D_tls) |
879 | debug_printf("Expanding various TLS configuration options for session credentials.\n"); | |
880 | rc = tls_expand_session_files(state); | |
881 | if (rc != OK) return rc; | |
059ec3d9 | 882 | |
1365611d PP |
883 | /* These are all other parts of the x509_cred handling, since SNI in GnuTLS |
884 | requires a new structure afterwards. */ | |
83da1223 | 885 | |
1365611d PP |
886 | rc = tls_set_remaining_x509(state); |
887 | if (rc != OK) return rc; | |
83da1223 | 888 | |
17c76198 PP |
889 | /* set SNI in client, only */ |
890 | if (host) | |
891 | { | |
892 | if (!expand_check_tlsvar(tls_sni)) | |
893 | return DEFER; | |
894 | if (state->exp_tls_sni && *state->exp_tls_sni) | |
895 | { | |
896 | DEBUG(D_tls) | |
897 | debug_printf("Setting TLS client SNI to \"%s\"\n", state->exp_tls_sni); | |
898 | sz = Ustrlen(state->exp_tls_sni); | |
899 | rc = gnutls_server_name_set(state->session, | |
900 | GNUTLS_NAME_DNS, state->exp_tls_sni, sz); | |
901 | exim_gnutls_err_check(US"gnutls_server_name_set"); | |
902 | } | |
903 | } | |
904 | else if (state->tls_sni) | |
905 | DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \ | |
906 | "have an SNI set for a client [%s]\n", state->tls_sni); | |
83da1223 | 907 | |
17c76198 PP |
908 | /* This is the priority string support, |
909 | http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html | |
910 | and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols. | |
911 | This was backwards incompatible, but means Exim no longer needs to track | |
912 | all algorithms and provide string forms for them. */ | |
83da1223 | 913 | |
17c76198 | 914 | want_default_priorities = TRUE; |
83da1223 | 915 | |
17c76198 | 916 | if (state->tls_require_ciphers && *state->tls_require_ciphers) |
83da1223 | 917 | { |
17c76198 PP |
918 | if (!expand_check_tlsvar(tls_require_ciphers)) |
919 | return DEFER; | |
920 | if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers) | |
83da1223 | 921 | { |
17c76198 PP |
922 | DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", |
923 | state->exp_tls_require_ciphers); | |
924 | ||
925 | rc = gnutls_priority_init(&state->priority_cache, | |
926 | CS state->exp_tls_require_ciphers, &errpos); | |
927 | want_default_priorities = FALSE; | |
928 | p = state->exp_tls_require_ciphers; | |
83da1223 PH |
929 | } |
930 | } | |
17c76198 PP |
931 | if (want_default_priorities) |
932 | { | |
83e2f8a2 PP |
933 | DEBUG(D_tls) |
934 | debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", | |
935 | exim_default_gnutls_priority); | |
17c76198 PP |
936 | rc = gnutls_priority_init(&state->priority_cache, |
937 | exim_default_gnutls_priority, &errpos); | |
938 | p = US exim_default_gnutls_priority; | |
939 | } | |
83da1223 | 940 | |
17c76198 PP |
941 | exim_gnutls_err_check(string_sprintf( |
942 | "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"", | |
943 | p, errpos - CS p, errpos)); | |
944 | ||
945 | rc = gnutls_priority_set(state->session, state->priority_cache); | |
946 | exim_gnutls_err_check(US"gnutls_priority_set"); | |
947 | ||
948 | gnutls_db_set_cache_expiration(state->session, ssl_session_timeout); | |
949 | ||
950 | /* Reduce security in favour of increased compatibility, if the admin | |
951 | decides to make that trade-off. */ | |
952 | if (gnutls_compat_mode) | |
83da1223 | 953 | { |
17c76198 PP |
954 | #if LIBGNUTLS_VERSION_NUMBER >= 0x020104 |
955 | DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n"); | |
956 | gnutls_session_enable_compatibility_mode(state->session); | |
957 | #else | |
958 | DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n"); | |
959 | #endif | |
83da1223 PH |
960 | } |
961 | ||
17c76198 PP |
962 | *caller_state = state; |
963 | /* needs to happen before callbacks during handshake */ | |
964 | current_global_tls_state = state; | |
965 | return OK; | |
83da1223 PH |
966 | } |
967 | ||
968 | ||
969 | ||
970 | ||
059ec3d9 | 971 | /************************************************* |
17c76198 | 972 | * Extract peer information * |
059ec3d9 PH |
973 | *************************************************/ |
974 | ||
17c76198 | 975 | /* Called from both server and client code. |
4fe99a6c PP |
976 | Only this is allowed to set state->peerdn and state->have_set_peerdn |
977 | and we use that to detect double-calls. | |
059ec3d9 | 978 | |
75fe387d PP |
979 | NOTE: the state blocks last while the TLS connection is up, which is fine |
980 | for logging in the server side, but for the client side, we log after teardown | |
981 | in src/deliver.c. While the session is up, we can twist about states and | |
982 | repoint tls_* globals, but those variables used for logging or other variable | |
983 | expansion that happens _after_ delivery need to have a longer life-time. | |
984 | ||
985 | So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from | |
986 | doing this more than once per generation of a state context. We set them in | |
987 | the state context, and repoint tls_* to them. After the state goes away, the | |
988 | tls_* copies of the pointers remain valid and client delivery logging is happy. | |
989 | ||
990 | tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues | |
991 | don't apply. | |
992 | ||
059ec3d9 | 993 | Arguments: |
17c76198 | 994 | state exim_gnutls_state_st * |
059ec3d9 | 995 | |
17c76198 | 996 | Returns: OK/DEFER/FAIL |
059ec3d9 PH |
997 | */ |
998 | ||
17c76198 PP |
999 | static int |
1000 | peer_status(exim_gnutls_state_st *state) | |
059ec3d9 | 1001 | { |
75fe387d | 1002 | uschar cipherbuf[256]; |
17c76198 | 1003 | const gnutls_datum *cert_list; |
75fe387d | 1004 | int old_pool, rc; |
17c76198 | 1005 | unsigned int cert_list_size = 0; |
4fe99a6c PP |
1006 | gnutls_protocol_t protocol; |
1007 | gnutls_cipher_algorithm_t cipher; | |
1008 | gnutls_kx_algorithm_t kx; | |
1009 | gnutls_mac_algorithm_t mac; | |
17c76198 PP |
1010 | gnutls_certificate_type_t ct; |
1011 | gnutls_x509_crt_t crt; | |
4fe99a6c | 1012 | uschar *p, *dn_buf; |
17c76198 | 1013 | size_t sz; |
059ec3d9 | 1014 | |
4fe99a6c | 1015 | if (state->have_set_peerdn) |
17c76198 | 1016 | return OK; |
4fe99a6c | 1017 | state->have_set_peerdn = TRUE; |
059ec3d9 | 1018 | |
4fe99a6c | 1019 | state->peerdn = NULL; |
059ec3d9 | 1020 | |
4fe99a6c PP |
1021 | /* tls_cipher */ |
1022 | cipher = gnutls_cipher_get(state->session); | |
1023 | protocol = gnutls_protocol_get_version(state->session); | |
1024 | mac = gnutls_mac_get(state->session); | |
1025 | kx = gnutls_kx_get(state->session); | |
1026 | ||
75fe387d | 1027 | string_format(cipherbuf, sizeof(cipherbuf), |
4fe99a6c PP |
1028 | "%s:%s:%d", |
1029 | gnutls_protocol_get_name(protocol), | |
1030 | gnutls_cipher_suite_get_name(kx, cipher, mac), | |
1031 | (int) gnutls_cipher_get_key_size(cipher) * 8); | |
1032 | ||
1033 | /* I don't see a way that spaces could occur, in the current GnuTLS | |
1034 | code base, but it was a concern in the old code and perhaps older GnuTLS | |
1035 | releases did return "TLS 1.0"; play it safe, just in case. */ | |
75fe387d | 1036 | for (p = cipherbuf; *p != '\0'; ++p) |
4fe99a6c PP |
1037 | if (isspace(*p)) |
1038 | *p = '-'; | |
75fe387d PP |
1039 | old_pool = store_pool; |
1040 | store_pool = POOL_PERM; | |
1041 | state->ciphersuite = string_copy(cipherbuf); | |
1042 | store_pool = old_pool; | |
1043 | tls_cipher = state->ciphersuite; | |
4fe99a6c PP |
1044 | |
1045 | /* tls_peerdn */ | |
17c76198 | 1046 | cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size); |
83da1223 | 1047 | |
17c76198 PP |
1048 | if (cert_list == NULL || cert_list_size == 0) |
1049 | { | |
17c76198 PP |
1050 | DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n", |
1051 | cert_list, cert_list_size); | |
1052 | if (state->verify_requirement == VERIFY_REQUIRED) | |
1053 | return tls_error(US"certificate verification failed", | |
1054 | "no certificate received from peer", state->host); | |
1055 | return OK; | |
1056 | } | |
059ec3d9 | 1057 | |
17c76198 PP |
1058 | ct = gnutls_certificate_type_get(state->session); |
1059 | if (ct != GNUTLS_CRT_X509) | |
059ec3d9 | 1060 | { |
17c76198 | 1061 | const char *ctn = gnutls_certificate_type_get_name(ct); |
17c76198 PP |
1062 | DEBUG(D_tls) |
1063 | debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn); | |
1064 | if (state->verify_requirement == VERIFY_REQUIRED) | |
1065 | return tls_error(US"certificate verification not possible, unhandled type", | |
1066 | ctn, state->host); | |
1067 | return OK; | |
83da1223 | 1068 | } |
059ec3d9 | 1069 | |
17c76198 PP |
1070 | #define exim_gnutls_peer_err(Label) do { \ |
1071 | if (rc != GNUTLS_E_SUCCESS) { \ | |
1072 | DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", (Label), gnutls_strerror(rc)); \ | |
1073 | if (state->verify_requirement == VERIFY_REQUIRED) { return tls_error((Label), gnutls_strerror(rc), state->host); } \ | |
1074 | return OK; } } while (0) | |
1075 | ||
1076 | rc = gnutls_x509_crt_init(&crt); | |
1077 | exim_gnutls_peer_err(US"gnutls_x509_crt_init (crt)"); | |
1078 | ||
1079 | rc = gnutls_x509_crt_import(crt, &cert_list[0], GNUTLS_X509_FMT_DER); | |
1080 | exim_gnutls_peer_err(US"failed to import certificate [gnutls_x509_crt_import(cert 0)]"); | |
1081 | sz = 0; | |
1082 | rc = gnutls_x509_crt_get_dn(crt, NULL, &sz); | |
1083 | if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) | |
83da1223 | 1084 | { |
17c76198 PP |
1085 | exim_gnutls_peer_err(US"getting size for cert DN failed"); |
1086 | return FAIL; /* should not happen */ | |
059ec3d9 | 1087 | } |
17c76198 PP |
1088 | dn_buf = store_get_perm(sz); |
1089 | rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz); | |
1090 | exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]"); | |
1091 | state->peerdn = dn_buf; | |
1092 | ||
1093 | return OK; | |
1094 | #undef exim_gnutls_peer_err | |
1095 | } | |
059ec3d9 | 1096 | |
059ec3d9 | 1097 | |
059ec3d9 | 1098 | |
059ec3d9 | 1099 | |
17c76198 PP |
1100 | /************************************************* |
1101 | * Verify peer certificate * | |
1102 | *************************************************/ | |
059ec3d9 | 1103 | |
17c76198 PP |
1104 | /* Called from both server and client code. |
1105 | *Should* be using a callback registered with | |
1106 | gnutls_certificate_set_verify_function() to fail the handshake if we dislike | |
1107 | the peer information, but that's too new for some OSes. | |
059ec3d9 | 1108 | |
17c76198 PP |
1109 | Arguments: |
1110 | state exim_gnutls_state_st * | |
1111 | error where to put an error message | |
059ec3d9 | 1112 | |
17c76198 PP |
1113 | Returns: |
1114 | FALSE if the session should be rejected | |
1115 | TRUE if the cert is okay or we just don't care | |
1116 | */ | |
059ec3d9 | 1117 | |
17c76198 PP |
1118 | static BOOL |
1119 | verify_certificate(exim_gnutls_state_st *state, const char **error) | |
1120 | { | |
1121 | int rc; | |
1122 | unsigned int verify; | |
1123 | ||
1124 | *error = NULL; | |
1125 | ||
1126 | rc = peer_status(state); | |
1127 | if (rc != OK) | |
e6060e2c | 1128 | { |
17c76198 PP |
1129 | verify = GNUTLS_CERT_INVALID; |
1130 | *error = "not supplied"; | |
1131 | } | |
1132 | else | |
1133 | { | |
1134 | rc = gnutls_certificate_verify_peers2(state->session, &verify); | |
e6060e2c NM |
1135 | } |
1136 | ||
17c76198 PP |
1137 | /* Handle the result of verification. INVALID seems to be set as well |
1138 | as REVOKED, but leave the test for both. */ | |
059ec3d9 | 1139 | |
17c76198 PP |
1140 | if ((rc < 0) || (verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0) |
1141 | { | |
1142 | state->peer_cert_verified = FALSE; | |
1143 | if (*error == NULL) | |
1144 | *error = ((verify & GNUTLS_CERT_REVOKED) != 0) ? "revoked" : "invalid"; | |
059ec3d9 | 1145 | |
17c76198 PP |
1146 | DEBUG(D_tls) |
1147 | debug_printf("TLS certificate verification failed (%s): peerdn=%s\n", | |
4fe99a6c | 1148 | *error, state->peerdn ? state->peerdn : US"<unset>"); |
059ec3d9 | 1149 | |
17c76198 PP |
1150 | if (state->verify_requirement == VERIFY_REQUIRED) |
1151 | { | |
1152 | gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE); | |
1153 | return FALSE; | |
1154 | } | |
1155 | DEBUG(D_tls) | |
1156 | debug_printf("TLS verify failure overriden (host in tls_try_verify_hosts)\n"); | |
1157 | } | |
1158 | else | |
1159 | { | |
1160 | state->peer_cert_verified = TRUE; | |
4fe99a6c PP |
1161 | DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n", |
1162 | state->peerdn ? state->peerdn : US"<unset>"); | |
17c76198 | 1163 | } |
059ec3d9 | 1164 | |
17c76198 | 1165 | tls_peerdn = state->peerdn; |
059ec3d9 | 1166 | |
17c76198 PP |
1167 | return TRUE; |
1168 | } | |
059ec3d9 | 1169 | |
17c76198 PP |
1170 | |
1171 | ||
1172 | ||
1173 | /* ------------------------------------------------------------------------ */ | |
1174 | /* Callbacks */ | |
1175 | ||
1176 | /* Logging function which can be registered with | |
1177 | * gnutls_global_set_log_function() | |
1178 | * gnutls_global_set_log_level() 0..9 | |
1179 | */ | |
af3498d6 | 1180 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 |
059ec3d9 | 1181 | static void |
17c76198 | 1182 | exim_gnutls_logger_cb(int level, const char *message) |
059ec3d9 | 1183 | { |
17c76198 PP |
1184 | DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s\n", level, message); |
1185 | } | |
af3498d6 | 1186 | #endif |
059ec3d9 | 1187 | |
059ec3d9 | 1188 | |
17c76198 PP |
1189 | /* Called after client hello, should handle SNI work. |
1190 | This will always set tls_sni (state->received_sni) if available, | |
1191 | and may trigger presenting different certificates, | |
1192 | if state->trigger_sni_changes is TRUE. | |
059ec3d9 | 1193 | |
17c76198 PP |
1194 | Should be registered with |
1195 | gnutls_handshake_set_post_client_hello_function() | |
059ec3d9 | 1196 | |
17c76198 PP |
1197 | "This callback must return 0 on success or a gnutls error code to terminate the |
1198 | handshake.". | |
059ec3d9 | 1199 | |
17c76198 PP |
1200 | For inability to get SNI information, we return 0. |
1201 | We only return non-zero if re-setup failed. | |
1202 | */ | |
44bbabb5 | 1203 | |
17c76198 PP |
1204 | static int |
1205 | exim_sni_handling_cb(gnutls_session_t session) | |
1206 | { | |
1207 | char sni_name[MAX_HOST_LEN]; | |
1208 | size_t data_len = MAX_HOST_LEN; | |
1209 | exim_gnutls_state_st *state = current_global_tls_state; | |
1210 | unsigned int sni_type; | |
1211 | int rc, old_pool; | |
1212 | ||
1213 | rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0); | |
b34fc30c PP |
1214 | if (rc != GNUTLS_E_SUCCESS) |
1215 | { | |
1216 | DEBUG(D_tls) { | |
1217 | if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) | |
1218 | debug_printf("TLS: no SNI presented in handshake.\n"); | |
1219 | else | |
1220 | debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n", | |
1221 | gnutls_strerror(rc), rc); | |
1222 | }; | |
1223 | return 0; | |
1224 | } | |
1225 | ||
17c76198 PP |
1226 | if (sni_type != GNUTLS_NAME_DNS) |
1227 | { | |
1228 | DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type); | |
1229 | return 0; | |
1230 | } | |
44bbabb5 | 1231 | |
17c76198 PP |
1232 | /* We now have a UTF-8 string in sni_name */ |
1233 | old_pool = store_pool; | |
1234 | store_pool = POOL_PERM; | |
1235 | state->received_sni = string_copyn(US sni_name, data_len); | |
1236 | store_pool = old_pool; | |
1237 | ||
1238 | /* We set this one now so that variable expansions below will work */ | |
1239 | tls_sni = state->received_sni; | |
1240 | ||
1241 | DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name, | |
1242 | state->trigger_sni_changes ? "" : " (unused for certificate selection)"); | |
1243 | ||
1244 | if (!state->trigger_sni_changes) | |
1245 | return 0; | |
1246 | ||
1247 | rc = tls_expand_session_files(state); | |
1248 | if (rc != OK) | |
1249 | { | |
1250 | /* If the setup of certs/etc failed before handshake, TLS would not have | |
1251 | been offered. The best we can do now is abort. */ | |
1252 | return GNUTLS_E_APPLICATION_ERROR_MIN; | |
1253 | } | |
1254 | ||
1365611d PP |
1255 | rc = tls_set_remaining_x509(state); |
1256 | if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN; | |
1257 | ||
1258 | return 0; | |
059ec3d9 PH |
1259 | } |
1260 | ||
1261 | ||
1262 | ||
17c76198 PP |
1263 | |
1264 | /* ------------------------------------------------------------------------ */ | |
1265 | /* Exported functions */ | |
1266 | ||
1267 | ||
1268 | ||
1269 | ||
059ec3d9 PH |
1270 | /************************************************* |
1271 | * Start a TLS session in a server * | |
1272 | *************************************************/ | |
1273 | ||
1274 | /* This is called when Exim is running as a server, after having received | |
1275 | the STARTTLS command. It must respond to that command, and then negotiate | |
1276 | a TLS session. | |
1277 | ||
1278 | Arguments: | |
83da1223 | 1279 | require_ciphers list of allowed ciphers or NULL |
059ec3d9 PH |
1280 | |
1281 | Returns: OK on success | |
1282 | DEFER for errors before the start of the negotiation | |
1283 | FAIL for errors during the negotation; the server can't | |
1284 | continue running. | |
1285 | */ | |
1286 | ||
1287 | int | |
17c76198 | 1288 | tls_server_start(const uschar *require_ciphers) |
059ec3d9 PH |
1289 | { |
1290 | int rc; | |
7199e1ee | 1291 | const char *error; |
17c76198 | 1292 | exim_gnutls_state_st *state = NULL; |
059ec3d9 PH |
1293 | |
1294 | /* Check for previous activation */ | |
17c76198 | 1295 | /* nb: this will not be TLS callout safe, needs reworking as part of that. */ |
059ec3d9 PH |
1296 | |
1297 | if (tls_active >= 0) | |
1298 | { | |
17c76198 | 1299 | tls_error(US"STARTTLS received after TLS started", "", NULL); |
059ec3d9 PH |
1300 | smtp_printf("554 Already in TLS\r\n"); |
1301 | return FAIL; | |
1302 | } | |
1303 | ||
1304 | /* Initialize the library. If it fails, it will already have logged the error | |
1305 | and sent an SMTP response. */ | |
1306 | ||
17c76198 | 1307 | DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n"); |
059ec3d9 | 1308 | |
17c76198 PP |
1309 | rc = tls_init(NULL, tls_certificate, tls_privatekey, |
1310 | NULL, tls_verify_certificates, tls_crl, | |
1311 | require_ciphers, &state); | |
059ec3d9 PH |
1312 | if (rc != OK) return rc; |
1313 | ||
059ec3d9 PH |
1314 | /* If this is a host for which certificate verification is mandatory or |
1315 | optional, set up appropriately. */ | |
1316 | ||
059ec3d9 | 1317 | if (verify_check_host(&tls_verify_hosts) == OK) |
17c76198 PP |
1318 | { |
1319 | DEBUG(D_tls) debug_printf("TLS: a client certificate will be required.\n"); | |
1320 | state->verify_requirement = VERIFY_REQUIRED; | |
1321 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); | |
1322 | } | |
059ec3d9 | 1323 | else if (verify_check_host(&tls_try_verify_hosts) == OK) |
17c76198 PP |
1324 | { |
1325 | DEBUG(D_tls) debug_printf("TLS: a client certificate will be requested but not required.\n"); | |
1326 | state->verify_requirement = VERIFY_OPTIONAL; | |
1327 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); | |
1328 | } | |
1329 | else | |
1330 | { | |
1331 | DEBUG(D_tls) debug_printf("TLS: a client certificate will not be requested.\n"); | |
1332 | state->verify_requirement = VERIFY_NONE; | |
1333 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE); | |
1334 | } | |
059ec3d9 | 1335 | |
17c76198 PP |
1336 | /* Register SNI handling; always, even if not in tls_certificate, so that the |
1337 | expansion variable $tls_sni is always available. */ | |
059ec3d9 | 1338 | |
17c76198 PP |
1339 | gnutls_handshake_set_post_client_hello_function(state->session, |
1340 | exim_sni_handling_cb); | |
059ec3d9 PH |
1341 | |
1342 | /* Set context and tell client to go ahead, except in the case of TLS startup | |
1343 | on connection, where outputting anything now upsets the clients and tends to | |
1344 | make them disconnect. We need to have an explicit fflush() here, to force out | |
1345 | the response. Other smtp_printf() calls do not need it, because in non-TLS | |
1346 | mode, the fflush() happens when smtp_getc() is called. */ | |
1347 | ||
1348 | if (!tls_on_connect) | |
1349 | { | |
1350 | smtp_printf("220 TLS go ahead\r\n"); | |
1351 | fflush(smtp_out); | |
1352 | } | |
1353 | ||
1354 | /* Now negotiate the TLS session. We put our own timer on it, since it seems | |
1355 | that the GnuTLS library doesn't. */ | |
1356 | ||
17c76198 PP |
1357 | gnutls_transport_set_ptr2(state->session, |
1358 | (gnutls_transport_ptr)fileno(smtp_in), | |
1359 | (gnutls_transport_ptr)fileno(smtp_out)); | |
1360 | state->fd_in = fileno(smtp_in); | |
1361 | state->fd_out = fileno(smtp_out); | |
059ec3d9 PH |
1362 | |
1363 | sigalrm_seen = FALSE; | |
1364 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
17c76198 PP |
1365 | do |
1366 | { | |
1367 | rc = gnutls_handshake(state->session); | |
1368 | } while ((rc == GNUTLS_E_AGAIN) || (rc == GNUTLS_E_INTERRUPTED)); | |
059ec3d9 PH |
1369 | alarm(0); |
1370 | ||
17c76198 | 1371 | if (rc != GNUTLS_E_SUCCESS) |
059ec3d9 | 1372 | { |
17c76198 PP |
1373 | tls_error(US"gnutls_handshake", |
1374 | sigalrm_seen ? "timed out" : gnutls_strerror(rc), NULL); | |
059ec3d9 PH |
1375 | /* It seems that, except in the case of a timeout, we have to close the |
1376 | connection right here; otherwise if the other end is running OpenSSL it hangs | |
1377 | until the server times out. */ | |
1378 | ||
1379 | if (!sigalrm_seen) | |
1380 | { | |
f1e894f3 PH |
1381 | (void)fclose(smtp_out); |
1382 | (void)fclose(smtp_in); | |
059ec3d9 PH |
1383 | } |
1384 | ||
1385 | return FAIL; | |
1386 | } | |
1387 | ||
1388 | DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); | |
1389 | ||
17c76198 PP |
1390 | /* Verify after the fact */ |
1391 | ||
1392 | if (state->verify_requirement != VERIFY_NONE) | |
059ec3d9 | 1393 | { |
17c76198 PP |
1394 | if (!verify_certificate(state, &error)) |
1395 | { | |
1396 | if (state->verify_requirement == VERIFY_OPTIONAL) | |
1397 | { | |
1398 | DEBUG(D_tls) | |
1399 | debug_printf("TLS: continuing on only because verification was optional, after: %s\n", | |
1400 | error); | |
1401 | } | |
1402 | else | |
1403 | { | |
1404 | tls_error(US"certificate verification failed", error, NULL); | |
1405 | return FAIL; | |
1406 | } | |
1407 | } | |
059ec3d9 PH |
1408 | } |
1409 | ||
17c76198 PP |
1410 | /* Figure out peer DN, and if authenticated, etc. */ |
1411 | ||
1412 | rc = peer_status(state); | |
1413 | if (rc != OK) return rc; | |
1414 | ||
1415 | /* Sets various Exim expansion variables; always safe within server */ | |
1416 | ||
1417 | extract_exim_vars_from_tls_state(state); | |
059ec3d9 PH |
1418 | |
1419 | /* TLS has been set up. Adjust the input functions to read via TLS, | |
1420 | and initialize appropriately. */ | |
1421 | ||
17c76198 | 1422 | state->xfer_buffer = store_malloc(ssl_xfer_buffer_size); |
059ec3d9 PH |
1423 | |
1424 | receive_getc = tls_getc; | |
1425 | receive_ungetc = tls_ungetc; | |
1426 | receive_feof = tls_feof; | |
1427 | receive_ferror = tls_ferror; | |
58eb016e | 1428 | receive_smtp_buffered = tls_smtp_buffered; |
059ec3d9 | 1429 | |
059ec3d9 PH |
1430 | return OK; |
1431 | } | |
1432 | ||
1433 | ||
1434 | ||
1435 | ||
1436 | /************************************************* | |
1437 | * Start a TLS session in a client * | |
1438 | *************************************************/ | |
1439 | ||
1440 | /* Called from the smtp transport after STARTTLS has been accepted. | |
1441 | ||
1442 | Arguments: | |
1443 | fd the fd of the connection | |
1444 | host connected host (for messages) | |
83da1223 | 1445 | addr the first address (not used) |
17c76198 | 1446 | dhparam DH parameter file (ignored, we're a client) |
059ec3d9 PH |
1447 | certificate certificate file |
1448 | privatekey private key file | |
3f0945ff | 1449 | sni TLS SNI to send to remote host |
059ec3d9 PH |
1450 | verify_certs file for certificate verify |
1451 | verify_crl CRL for verify | |
83da1223 | 1452 | require_ciphers list of allowed ciphers or NULL |
059ec3d9 PH |
1453 | timeout startup timeout |
1454 | ||
1455 | Returns: OK/DEFER/FAIL (because using common functions), | |
1456 | but for a client, DEFER and FAIL have the same meaning | |
1457 | */ | |
1458 | ||
1459 | int | |
17c76198 PP |
1460 | tls_client_start(int fd, host_item *host, |
1461 | address_item *addr ARG_UNUSED, uschar *dhparam ARG_UNUSED, | |
1462 | uschar *certificate, uschar *privatekey, uschar *sni, | |
1463 | uschar *verify_certs, uschar *verify_crl, | |
1464 | uschar *require_ciphers, int timeout) | |
059ec3d9 | 1465 | { |
059ec3d9 | 1466 | int rc; |
17c76198 PP |
1467 | const char *error; |
1468 | exim_gnutls_state_st *state = NULL; | |
059ec3d9 | 1469 | |
17c76198 | 1470 | DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd); |
059ec3d9 | 1471 | |
17c76198 PP |
1472 | rc = tls_init(host, certificate, privatekey, |
1473 | sni, verify_certs, verify_crl, require_ciphers, &state); | |
059ec3d9 PH |
1474 | if (rc != OK) return rc; |
1475 | ||
17c76198 | 1476 | gnutls_dh_set_prime_bits(state->session, EXIM_CLIENT_DH_MIN_BITS); |
83da1223 | 1477 | |
17c76198 PP |
1478 | if (verify_certs == NULL) |
1479 | { | |
1480 | DEBUG(D_tls) debug_printf("TLS: server certificate verification not required\n"); | |
1481 | state->verify_requirement = VERIFY_NONE; | |
1482 | /* we still ask for it, to log it, etc */ | |
1483 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); | |
1484 | } | |
1485 | else | |
1486 | { | |
1487 | DEBUG(D_tls) debug_printf("TLS: server certificate verification required\n"); | |
1488 | state->verify_requirement = VERIFY_REQUIRED; | |
1489 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); | |
1490 | } | |
059ec3d9 | 1491 | |
17c76198 PP |
1492 | gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr)fd); |
1493 | state->fd_in = fd; | |
1494 | state->fd_out = fd; | |
059ec3d9 PH |
1495 | |
1496 | /* There doesn't seem to be a built-in timeout on connection. */ | |
1497 | ||
1498 | sigalrm_seen = FALSE; | |
1499 | alarm(timeout); | |
17c76198 PP |
1500 | do |
1501 | { | |
1502 | rc = gnutls_handshake(state->session); | |
1503 | } while ((rc == GNUTLS_E_AGAIN) || (rc == GNUTLS_E_INTERRUPTED)); | |
059ec3d9 PH |
1504 | alarm(0); |
1505 | ||
4fe99a6c PP |
1506 | if (rc != GNUTLS_E_SUCCESS) |
1507 | return tls_error(US"gnutls_handshake", | |
1508 | sigalrm_seen ? "timed out" : gnutls_strerror(rc), state->host); | |
1509 | ||
17c76198 | 1510 | DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); |
059ec3d9 | 1511 | |
17c76198 | 1512 | /* Verify late */ |
059ec3d9 | 1513 | |
17c76198 PP |
1514 | if (state->verify_requirement != VERIFY_NONE && |
1515 | !verify_certificate(state, &error)) | |
1516 | return tls_error(US"certificate verification failed", error, state->host); | |
059ec3d9 | 1517 | |
17c76198 | 1518 | /* Figure out peer DN, and if authenticated, etc. */ |
059ec3d9 | 1519 | |
17c76198 PP |
1520 | rc = peer_status(state); |
1521 | if (rc != OK) return rc; | |
059ec3d9 | 1522 | |
4fe99a6c | 1523 | /* Sets various Exim expansion variables; may need to adjust for ACL callouts */ |
059ec3d9 | 1524 | |
17c76198 | 1525 | extract_exim_vars_from_tls_state(state); |
059ec3d9 | 1526 | |
059ec3d9 PH |
1527 | return OK; |
1528 | } | |
1529 | ||
1530 | ||
1531 | ||
17c76198 | 1532 | |
059ec3d9 | 1533 | /************************************************* |
17c76198 | 1534 | * Close down a TLS session * |
059ec3d9 PH |
1535 | *************************************************/ |
1536 | ||
17c76198 PP |
1537 | /* This is also called from within a delivery subprocess forked from the |
1538 | daemon, to shut down the TLS library, without actually doing a shutdown (which | |
1539 | would tamper with the TLS session in the parent process). | |
059ec3d9 | 1540 | |
17c76198 PP |
1541 | Arguments: TRUE if gnutls_bye is to be called |
1542 | Returns: nothing | |
059ec3d9 PH |
1543 | */ |
1544 | ||
17c76198 PP |
1545 | void |
1546 | tls_close(BOOL shutdown) | |
059ec3d9 | 1547 | { |
17c76198 | 1548 | exim_gnutls_state_st *state = current_global_tls_state; |
059ec3d9 | 1549 | |
17c76198 PP |
1550 | if (tls_active < 0) return; /* TLS was not active */ |
1551 | ||
1552 | if (shutdown) | |
1553 | { | |
1554 | DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n"); | |
1555 | gnutls_bye(state->session, GNUTLS_SHUT_WR); | |
1556 | } | |
1557 | ||
1558 | gnutls_deinit(state->session); | |
1559 | ||
1560 | memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); | |
1561 | ||
1562 | if ((state_server.session == NULL) && (state_client.session == NULL)) | |
1563 | { | |
1564 | gnutls_global_deinit(); | |
1565 | exim_gnutls_base_init_done = FALSE; | |
1566 | } | |
7199e1ee | 1567 | |
17c76198 | 1568 | tls_active = -1; |
059ec3d9 PH |
1569 | } |
1570 | ||
1571 | ||
1572 | ||
17c76198 | 1573 | |
059ec3d9 PH |
1574 | /************************************************* |
1575 | * TLS version of getc * | |
1576 | *************************************************/ | |
1577 | ||
1578 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, | |
1579 | it refills the buffer via the GnuTLS reading function. | |
1580 | ||
17c76198 PP |
1581 | This feeds DKIM and should be used for all message-body reads. |
1582 | ||
059ec3d9 PH |
1583 | Arguments: none |
1584 | Returns: the next character or EOF | |
1585 | */ | |
1586 | ||
1587 | int | |
1588 | tls_getc(void) | |
1589 | { | |
17c76198 PP |
1590 | exim_gnutls_state_st *state = current_global_tls_state; |
1591 | if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm) | |
059ec3d9 | 1592 | { |
17c76198 | 1593 | ssize_t inbytes; |
059ec3d9 | 1594 | |
17c76198 PP |
1595 | DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n", |
1596 | state->session, state->xfer_buffer, ssl_xfer_buffer_size); | |
059ec3d9 PH |
1597 | |
1598 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
17c76198 | 1599 | inbytes = gnutls_record_recv(state->session, state->xfer_buffer, |
059ec3d9 PH |
1600 | ssl_xfer_buffer_size); |
1601 | alarm(0); | |
1602 | ||
1603 | /* A zero-byte return appears to mean that the TLS session has been | |
1604 | closed down, not that the socket itself has been closed down. Revert to | |
1605 | non-TLS handling. */ | |
1606 | ||
1607 | if (inbytes == 0) | |
1608 | { | |
1609 | DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); | |
1610 | ||
1611 | receive_getc = smtp_getc; | |
1612 | receive_ungetc = smtp_ungetc; | |
1613 | receive_feof = smtp_feof; | |
1614 | receive_ferror = smtp_ferror; | |
58eb016e | 1615 | receive_smtp_buffered = smtp_buffered; |
059ec3d9 | 1616 | |
17c76198 PP |
1617 | gnutls_deinit(state->session); |
1618 | state->session = NULL; | |
059ec3d9 | 1619 | tls_active = -1; |
17c76198 PP |
1620 | tls_bits = 0; |
1621 | tls_certificate_verified = FALSE; | |
1622 | tls_channelbinding_b64 = NULL; | |
059ec3d9 PH |
1623 | tls_cipher = NULL; |
1624 | tls_peerdn = NULL; | |
1625 | ||
1626 | return smtp_getc(); | |
1627 | } | |
1628 | ||
1629 | /* Handle genuine errors */ | |
1630 | ||
1631 | else if (inbytes < 0) | |
1632 | { | |
17c76198 PP |
1633 | record_io_error(state, (int) inbytes, US"recv", NULL); |
1634 | state->xfer_error = 1; | |
059ec3d9 PH |
1635 | return EOF; |
1636 | } | |
80a47a2c | 1637 | #ifndef DISABLE_DKIM |
17c76198 | 1638 | dkim_exim_verify_feed(state->xfer_buffer, inbytes); |
80a47a2c | 1639 | #endif |
17c76198 PP |
1640 | state->xfer_buffer_hwm = (int) inbytes; |
1641 | state->xfer_buffer_lwm = 0; | |
059ec3d9 PH |
1642 | } |
1643 | ||
059ec3d9 PH |
1644 | /* Something in the buffer; return next uschar */ |
1645 | ||
17c76198 | 1646 | return state->xfer_buffer[state->xfer_buffer_lwm++]; |
059ec3d9 PH |
1647 | } |
1648 | ||
1649 | ||
1650 | ||
17c76198 | 1651 | |
059ec3d9 PH |
1652 | /************************************************* |
1653 | * Read bytes from TLS channel * | |
1654 | *************************************************/ | |
1655 | ||
17c76198 PP |
1656 | /* This does not feed DKIM, so if the caller uses this for reading message body, |
1657 | then the caller must feed DKIM. | |
059ec3d9 PH |
1658 | Arguments: |
1659 | buff buffer of data | |
1660 | len size of buffer | |
1661 | ||
1662 | Returns: the number of bytes read | |
1663 | -1 after a failed read | |
1664 | */ | |
1665 | ||
1666 | int | |
1667 | tls_read(uschar *buff, size_t len) | |
1668 | { | |
17c76198 PP |
1669 | exim_gnutls_state_st *state = current_global_tls_state; |
1670 | ssize_t inbytes; | |
059ec3d9 | 1671 | |
17c76198 PP |
1672 | if (len > INT_MAX) |
1673 | len = INT_MAX; | |
059ec3d9 | 1674 | |
17c76198 PP |
1675 | if (state->xfer_buffer_lwm < state->xfer_buffer_hwm) |
1676 | DEBUG(D_tls) | |
1677 | debug_printf("*** PROBABLY A BUG *** " \ | |
1678 | "tls_read() called with data in the tls_getc() buffer, %d ignored\n", | |
1679 | state->xfer_buffer_hwm - state->xfer_buffer_lwm); | |
1680 | ||
1681 | DEBUG(D_tls) | |
1682 | debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n", | |
1683 | state->session, buff, len); | |
1684 | ||
1685 | inbytes = gnutls_record_recv(state->session, buff, len); | |
059ec3d9 PH |
1686 | if (inbytes > 0) return inbytes; |
1687 | if (inbytes == 0) | |
1688 | { | |
1689 | DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); | |
1690 | } | |
17c76198 | 1691 | else record_io_error(state, (int)inbytes, US"recv", NULL); |
059ec3d9 PH |
1692 | |
1693 | return -1; | |
1694 | } | |
1695 | ||
1696 | ||
1697 | ||
17c76198 | 1698 | |
059ec3d9 PH |
1699 | /************************************************* |
1700 | * Write bytes down TLS channel * | |
1701 | *************************************************/ | |
1702 | ||
1703 | /* | |
1704 | Arguments: | |
1705 | buff buffer of data | |
1706 | len number of bytes | |
1707 | ||
1708 | Returns: the number of bytes after a successful write, | |
1709 | -1 after a failed write | |
1710 | */ | |
1711 | ||
1712 | int | |
1713 | tls_write(const uschar *buff, size_t len) | |
1714 | { | |
17c76198 PP |
1715 | ssize_t outbytes; |
1716 | size_t left = len; | |
1717 | exim_gnutls_state_st *state = current_global_tls_state; | |
059ec3d9 | 1718 | |
17c76198 | 1719 | DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left); |
059ec3d9 PH |
1720 | while (left > 0) |
1721 | { | |
17c76198 PP |
1722 | DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n", |
1723 | buff, left); | |
1724 | outbytes = gnutls_record_send(state->session, buff, left); | |
059ec3d9 | 1725 | |
17c76198 | 1726 | DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes); |
059ec3d9 PH |
1727 | if (outbytes < 0) |
1728 | { | |
17c76198 | 1729 | record_io_error(state, outbytes, US"send", NULL); |
059ec3d9 PH |
1730 | return -1; |
1731 | } | |
1732 | if (outbytes == 0) | |
1733 | { | |
17c76198 | 1734 | record_io_error(state, 0, US"send", US"TLS channel closed on write"); |
059ec3d9 PH |
1735 | return -1; |
1736 | } | |
1737 | ||
1738 | left -= outbytes; | |
1739 | buff += outbytes; | |
1740 | } | |
1741 | ||
17c76198 PP |
1742 | if (len > INT_MAX) |
1743 | { | |
1744 | DEBUG(D_tls) | |
1745 | debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n", | |
1746 | len); | |
1747 | len = INT_MAX; | |
1748 | } | |
1749 | ||
1750 | return (int) len; | |
059ec3d9 PH |
1751 | } |
1752 | ||
1753 | ||
1754 | ||
17c76198 | 1755 | |
059ec3d9 | 1756 | /************************************************* |
17c76198 | 1757 | * Random number generation * |
059ec3d9 PH |
1758 | *************************************************/ |
1759 | ||
17c76198 PP |
1760 | /* Pseudo-random number generation. The result is not expected to be |
1761 | cryptographically strong but not so weak that someone will shoot themselves | |
1762 | in the foot using it as a nonce in input in some email header scheme or | |
1763 | whatever weirdness they'll twist this into. The result should handle fork() | |
1764 | and avoid repeating sequences. OpenSSL handles that for us. | |
059ec3d9 | 1765 | |
17c76198 PP |
1766 | Arguments: |
1767 | max range maximum | |
1768 | Returns a random number in range [0, max-1] | |
059ec3d9 PH |
1769 | */ |
1770 | ||
af3498d6 | 1771 | #ifdef HAVE_GNUTLS_RND |
17c76198 PP |
1772 | int |
1773 | vaguely_random_number(int max) | |
059ec3d9 | 1774 | { |
17c76198 PP |
1775 | unsigned int r; |
1776 | int i, needed_len; | |
1777 | uschar *p; | |
1778 | uschar smallbuf[sizeof(r)]; | |
1779 | ||
1780 | if (max <= 1) | |
1781 | return 0; | |
1782 | ||
1783 | needed_len = sizeof(r); | |
1784 | /* Don't take 8 times more entropy than needed if int is 8 octets and we were | |
1785 | * asked for a number less than 10. */ | |
1786 | for (r = max, i = 0; r; ++i) | |
1787 | r >>= 1; | |
1788 | i = (i + 7) / 8; | |
1789 | if (i < needed_len) | |
1790 | needed_len = i; | |
1791 | ||
1792 | i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len); | |
1793 | if (i < 0) | |
059ec3d9 | 1794 | { |
17c76198 PP |
1795 | DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n"); |
1796 | return vaguely_random_number_fallback(max); | |
1797 | } | |
1798 | r = 0; | |
1799 | for (p = smallbuf; needed_len; --needed_len, ++p) | |
1800 | { | |
1801 | r *= 256; | |
1802 | r += *p; | |
059ec3d9 PH |
1803 | } |
1804 | ||
17c76198 PP |
1805 | /* We don't particularly care about weighted results; if someone wants |
1806 | * smooth distribution and cares enough then they should submit a patch then. */ | |
1807 | return r % max; | |
059ec3d9 | 1808 | } |
af3498d6 PP |
1809 | #else /* HAVE_GNUTLS_RND */ |
1810 | int | |
1811 | vaguely_random_number(int max) | |
1812 | { | |
1813 | return vaguely_random_number_fallback(max); | |
1814 | } | |
1815 | #endif /* HAVE_GNUTLS_RND */ | |
059ec3d9 | 1816 | |
36f12725 NM |
1817 | |
1818 | ||
1819 | ||
1820 | /************************************************* | |
1821 | * Report the library versions. * | |
1822 | *************************************************/ | |
1823 | ||
1824 | /* See a description in tls-openssl.c for an explanation of why this exists. | |
1825 | ||
1826 | Arguments: a FILE* to print the results to | |
1827 | Returns: nothing | |
1828 | */ | |
1829 | ||
1830 | void | |
1831 | tls_version_report(FILE *f) | |
1832 | { | |
754a0503 PP |
1833 | fprintf(f, "Library version: GnuTLS: Compile: %s\n" |
1834 | " Runtime: %s\n", | |
1835 | LIBGNUTLS_VERSION, | |
1836 | gnutls_check_version(NULL)); | |
36f12725 NM |
1837 | } |
1838 | ||
059ec3d9 | 1839 | /* End of tls-gnu.c */ |