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a0475b69 | 1 | /* $Cambridge: exim/src/src/tls-openssl.c,v 1.16 2009/10/16 08:34:50 tom Exp $ */ |
059ec3d9 PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
184e8823 | 7 | /* Copyright (c) University of Cambridge 1995 - 2007 */ |
059ec3d9 PH |
8 | /* See the file NOTICE for conditions of use and distribution. */ |
9 | ||
10 | /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL | |
11 | library. It is #included into the tls.c file when that library is used. The | |
12 | code herein is based on a patch that was originally contributed by Steve | |
13 | Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara. | |
14 | ||
15 | No cryptographic code is included in Exim. All this module does is to call | |
16 | functions from the OpenSSL library. */ | |
17 | ||
18 | ||
19 | /* Heading stuff */ | |
20 | ||
21 | #include <openssl/lhash.h> | |
22 | #include <openssl/ssl.h> | |
23 | #include <openssl/err.h> | |
24 | #include <openssl/rand.h> | |
25 | ||
26 | /* Structure for collecting random data for seeding. */ | |
27 | ||
28 | typedef struct randstuff { | |
29 | time_t t; | |
30 | pid_t p; | |
31 | } randstuff; | |
32 | ||
33 | /* Local static variables */ | |
34 | ||
35 | static BOOL verify_callback_called = FALSE; | |
36 | static const uschar *sid_ctx = US"exim"; | |
37 | ||
38 | static SSL_CTX *ctx = NULL; | |
39 | static SSL *ssl = NULL; | |
40 | ||
41 | static char ssl_errstring[256]; | |
42 | ||
43 | static int ssl_session_timeout = 200; | |
44 | static BOOL verify_optional = FALSE; | |
45 | ||
46 | ||
47 | ||
48 | ||
49 | ||
50 | /************************************************* | |
51 | * Handle TLS error * | |
52 | *************************************************/ | |
53 | ||
54 | /* Called from lots of places when errors occur before actually starting to do | |
55 | the TLS handshake, that is, while the session is still in clear. Always returns | |
56 | DEFER for a server and FAIL for a client so that most calls can use "return | |
57 | tls_error(...)" to do this processing and then give an appropriate return. A | |
58 | single function is used for both server and client, because it is called from | |
59 | some shared functions. | |
60 | ||
61 | Argument: | |
62 | prefix text to include in the logged error | |
63 | host NULL if setting up a server; | |
64 | the connected host if setting up a client | |
7199e1ee | 65 | msg error message or NULL if we should ask OpenSSL |
059ec3d9 PH |
66 | |
67 | Returns: OK/DEFER/FAIL | |
68 | */ | |
69 | ||
70 | static int | |
7199e1ee | 71 | tls_error(uschar *prefix, host_item *host, uschar *msg) |
059ec3d9 | 72 | { |
7199e1ee TF |
73 | if (msg == NULL) |
74 | { | |
75 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
76 | msg = ssl_errstring; | |
77 | } | |
78 | ||
059ec3d9 PH |
79 | if (host == NULL) |
80 | { | |
7199e1ee TF |
81 | uschar *conn_info = smtp_get_connection_info(); |
82 | if (strncmp(conn_info, "SMTP ", 5) == 0) | |
83 | conn_info += 5; | |
84 | log_write(0, LOG_MAIN, "TLS error on %s (%s): %s", | |
85 | conn_info, prefix, msg); | |
059ec3d9 PH |
86 | return DEFER; |
87 | } | |
88 | else | |
89 | { | |
90 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s", | |
7199e1ee | 91 | host->name, host->address, prefix, msg); |
059ec3d9 PH |
92 | return FAIL; |
93 | } | |
94 | } | |
95 | ||
96 | ||
97 | ||
98 | /************************************************* | |
99 | * Callback to generate RSA key * | |
100 | *************************************************/ | |
101 | ||
102 | /* | |
103 | Arguments: | |
104 | s SSL connection | |
105 | export not used | |
106 | keylength keylength | |
107 | ||
108 | Returns: pointer to generated key | |
109 | */ | |
110 | ||
111 | static RSA * | |
112 | rsa_callback(SSL *s, int export, int keylength) | |
113 | { | |
114 | RSA *rsa_key; | |
115 | export = export; /* Shut picky compilers up */ | |
116 | DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength); | |
117 | rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL); | |
118 | if (rsa_key == NULL) | |
119 | { | |
120 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
121 | log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s", | |
122 | ssl_errstring); | |
123 | return NULL; | |
124 | } | |
125 | return rsa_key; | |
126 | } | |
127 | ||
128 | ||
129 | ||
130 | ||
131 | /************************************************* | |
132 | * Callback for verification * | |
133 | *************************************************/ | |
134 | ||
135 | /* The SSL library does certificate verification if set up to do so. This | |
136 | callback has the current yes/no state is in "state". If verification succeeded, | |
137 | we set up the tls_peerdn string. If verification failed, what happens depends | |
138 | on whether the client is required to present a verifiable certificate or not. | |
139 | ||
140 | If verification is optional, we change the state to yes, but still log the | |
141 | verification error. For some reason (it really would help to have proper | |
142 | documentation of OpenSSL), this callback function then gets called again, this | |
143 | time with state = 1. In fact, that's useful, because we can set up the peerdn | |
144 | value, but we must take care not to set the private verified flag on the second | |
145 | time through. | |
146 | ||
147 | Note: this function is not called if the client fails to present a certificate | |
148 | when asked. We get here only if a certificate has been received. Handling of | |
149 | optional verification for this case is done when requesting SSL to verify, by | |
150 | setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case. | |
151 | ||
152 | Arguments: | |
153 | state current yes/no state as 1/0 | |
154 | x509ctx certificate information. | |
155 | ||
156 | Returns: 1 if verified, 0 if not | |
157 | */ | |
158 | ||
159 | static int | |
160 | verify_callback(int state, X509_STORE_CTX *x509ctx) | |
161 | { | |
162 | static uschar txt[256]; | |
163 | ||
164 | X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert), | |
165 | CS txt, sizeof(txt)); | |
166 | ||
167 | if (state == 0) | |
168 | { | |
169 | log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s", | |
170 | x509ctx->error_depth, | |
171 | X509_verify_cert_error_string(x509ctx->error), | |
172 | txt); | |
173 | tls_certificate_verified = FALSE; | |
174 | verify_callback_called = TRUE; | |
175 | if (!verify_optional) return 0; /* reject */ | |
176 | DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in " | |
177 | "tls_try_verify_hosts)\n"); | |
178 | return 1; /* accept */ | |
179 | } | |
180 | ||
181 | if (x509ctx->error_depth != 0) | |
182 | { | |
183 | DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n", | |
184 | x509ctx->error_depth, txt); | |
185 | } | |
186 | else | |
187 | { | |
188 | DEBUG(D_tls) debug_printf("SSL%s peer: %s\n", | |
189 | verify_callback_called? "" : " authenticated", txt); | |
190 | tls_peerdn = txt; | |
191 | } | |
192 | ||
059ec3d9 PH |
193 | if (!verify_callback_called) tls_certificate_verified = TRUE; |
194 | verify_callback_called = TRUE; | |
195 | ||
196 | return 1; /* accept */ | |
197 | } | |
198 | ||
199 | ||
200 | ||
201 | /************************************************* | |
202 | * Information callback * | |
203 | *************************************************/ | |
204 | ||
205 | /* The SSL library functions call this from time to time to indicate what they | |
206 | are doing. We copy the string to the debugging output when the level is high | |
207 | enough. | |
208 | ||
209 | Arguments: | |
210 | s the SSL connection | |
211 | where | |
212 | ret | |
213 | ||
214 | Returns: nothing | |
215 | */ | |
216 | ||
217 | static void | |
218 | info_callback(SSL *s, int where, int ret) | |
219 | { | |
220 | where = where; | |
221 | ret = ret; | |
222 | DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s)); | |
223 | } | |
224 | ||
225 | ||
226 | ||
227 | /************************************************* | |
228 | * Initialize for DH * | |
229 | *************************************************/ | |
230 | ||
231 | /* If dhparam is set, expand it, and load up the parameters for DH encryption. | |
232 | ||
233 | Arguments: | |
234 | dhparam DH parameter file | |
7199e1ee | 235 | host connected host, if client; NULL if server |
059ec3d9 PH |
236 | |
237 | Returns: TRUE if OK (nothing to set up, or setup worked) | |
238 | */ | |
239 | ||
240 | static BOOL | |
7199e1ee | 241 | init_dh(uschar *dhparam, host_item *host) |
059ec3d9 PH |
242 | { |
243 | BOOL yield = TRUE; | |
244 | BIO *bio; | |
245 | DH *dh; | |
246 | uschar *dhexpanded; | |
247 | ||
248 | if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded)) | |
249 | return FALSE; | |
250 | ||
251 | if (dhexpanded == NULL) return TRUE; | |
252 | ||
253 | if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL) | |
254 | { | |
7199e1ee TF |
255 | tls_error(string_sprintf("could not read dhparams file %s", dhexpanded), |
256 | host, strerror(errno)); | |
059ec3d9 PH |
257 | yield = FALSE; |
258 | } | |
259 | else | |
260 | { | |
261 | if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL) | |
262 | { | |
7199e1ee TF |
263 | tls_error(string_sprintf("could not read dhparams file %s", dhexpanded), |
264 | host, NULL); | |
059ec3d9 PH |
265 | yield = FALSE; |
266 | } | |
267 | else | |
268 | { | |
269 | SSL_CTX_set_tmp_dh(ctx, dh); | |
270 | DEBUG(D_tls) | |
271 | debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n", | |
272 | dhexpanded, 8*DH_size(dh)); | |
273 | DH_free(dh); | |
274 | } | |
275 | BIO_free(bio); | |
276 | } | |
277 | ||
278 | return yield; | |
279 | } | |
280 | ||
281 | ||
282 | ||
283 | ||
284 | /************************************************* | |
285 | * Initialize for TLS * | |
286 | *************************************************/ | |
287 | ||
288 | /* Called from both server and client code, to do preliminary initialization of | |
289 | the library. | |
290 | ||
291 | Arguments: | |
292 | host connected host, if client; NULL if server | |
293 | dhparam DH parameter file | |
294 | certificate certificate file | |
295 | privatekey private key | |
296 | addr address if client; NULL if server (for some randomness) | |
297 | ||
298 | Returns: OK/DEFER/FAIL | |
299 | */ | |
300 | ||
301 | static int | |
c91535f3 PH |
302 | tls_init(host_item *host, uschar *dhparam, uschar *certificate, |
303 | uschar *privatekey, address_item *addr) | |
059ec3d9 PH |
304 | { |
305 | SSL_load_error_strings(); /* basic set up */ | |
306 | OpenSSL_add_ssl_algorithms(); | |
307 | ||
a0475b69 TK |
308 | /* SHA256 is becoming ever moar popular. This makes sure it gets added to the |
309 | list of available digests. */ | |
310 | EVP_add_digest(EVP_sha256()); | |
311 | ||
059ec3d9 PH |
312 | /* Create a context */ |
313 | ||
314 | ctx = SSL_CTX_new((host == NULL)? | |
315 | SSLv23_server_method() : SSLv23_client_method()); | |
316 | ||
7199e1ee | 317 | if (ctx == NULL) return tls_error(US"SSL_CTX_new", host, NULL); |
059ec3d9 PH |
318 | |
319 | /* It turns out that we need to seed the random number generator this early in | |
320 | order to get the full complement of ciphers to work. It took me roughly a day | |
321 | of work to discover this by experiment. | |
322 | ||
323 | On systems that have /dev/urandom, SSL may automatically seed itself from | |
324 | there. Otherwise, we have to make something up as best we can. Double check | |
325 | afterwards. */ | |
326 | ||
327 | if (!RAND_status()) | |
328 | { | |
329 | randstuff r; | |
330 | r.t = time(NULL); | |
331 | r.p = getpid(); | |
332 | ||
333 | RAND_seed((uschar *)(&r), sizeof(r)); | |
334 | RAND_seed((uschar *)big_buffer, big_buffer_size); | |
335 | if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr)); | |
336 | ||
337 | if (!RAND_status()) | |
7199e1ee TF |
338 | return tls_error(US"RAND_status", host, |
339 | "unable to seed random number generator"); | |
059ec3d9 PH |
340 | } |
341 | ||
342 | /* Set up the information callback, which outputs if debugging is at a suitable | |
343 | level. */ | |
344 | ||
58c01c94 | 345 | SSL_CTX_set_info_callback(ctx, (void (*)())info_callback); |
059ec3d9 PH |
346 | |
347 | /* The following patch was supplied by Robert Roselius */ | |
348 | ||
349 | #if OPENSSL_VERSION_NUMBER > 0x00906040L | |
350 | /* Enable client-bug workaround. | |
351 | Versions of OpenSSL as of 0.9.6d include a "CBC countermeasure" feature, | |
352 | which causes problems with some clients (such as the Certicom SSL Plus | |
353 | library used by Eudora). This option, SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, | |
354 | disables the coutermeasure allowing Eudora to connect. | |
355 | Some poppers and MTAs use SSL_OP_ALL, which enables all such bug | |
356 | workarounds. */ | |
357 | /* XXX (Silently?) ignore failure here? XXX*/ | |
358 | ||
359 | if (!(SSL_CTX_set_options(ctx, SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS))) | |
7199e1ee | 360 | return tls_error(US"SSL_CTX_set_option", host, NULL); |
059ec3d9 PH |
361 | #endif |
362 | ||
363 | /* Initialize with DH parameters if supplied */ | |
364 | ||
7199e1ee | 365 | if (!init_dh(dhparam, host)) return DEFER; |
059ec3d9 PH |
366 | |
367 | /* Set up certificate and key */ | |
368 | ||
369 | if (certificate != NULL) | |
370 | { | |
371 | uschar *expanded; | |
372 | if (!expand_check(certificate, US"tls_certificate", &expanded)) | |
373 | return DEFER; | |
374 | ||
375 | if (expanded != NULL) | |
376 | { | |
377 | DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded); | |
378 | if (!SSL_CTX_use_certificate_chain_file(ctx, CS expanded)) | |
d6453af2 | 379 | return tls_error(string_sprintf( |
7199e1ee | 380 | "SSL_CTX_use_certificate_chain_file file=%s", expanded), host, NULL); |
059ec3d9 PH |
381 | } |
382 | ||
383 | if (privatekey != NULL && | |
384 | !expand_check(privatekey, US"tls_privatekey", &expanded)) | |
385 | return DEFER; | |
386 | ||
c91535f3 PH |
387 | /* If expansion was forced to fail, key_expanded will be NULL. If the result |
388 | of the expansion is an empty string, ignore it also, and assume the private | |
389 | key is in the same file as the certificate. */ | |
390 | ||
391 | if (expanded != NULL && *expanded != 0) | |
059ec3d9 PH |
392 | { |
393 | DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded); | |
394 | if (!SSL_CTX_use_PrivateKey_file(ctx, CS expanded, SSL_FILETYPE_PEM)) | |
d6453af2 | 395 | return tls_error(string_sprintf( |
7199e1ee | 396 | "SSL_CTX_use_PrivateKey_file file=%s", expanded), host, NULL); |
059ec3d9 PH |
397 | } |
398 | } | |
399 | ||
400 | /* Set up the RSA callback */ | |
401 | ||
402 | SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback); | |
403 | ||
404 | /* Finally, set the timeout, and we are done */ | |
405 | ||
406 | SSL_CTX_set_timeout(ctx, ssl_session_timeout); | |
407 | DEBUG(D_tls) debug_printf("Initialized TLS\n"); | |
408 | return OK; | |
409 | } | |
410 | ||
411 | ||
412 | ||
413 | ||
414 | /************************************************* | |
415 | * Get name of cipher in use * | |
416 | *************************************************/ | |
417 | ||
418 | /* The answer is left in a static buffer, and tls_cipher is set to point | |
419 | to it. | |
420 | ||
421 | Argument: pointer to an SSL structure for the connection | |
422 | Returns: nothing | |
423 | */ | |
424 | ||
425 | static void | |
426 | construct_cipher_name(SSL *ssl) | |
427 | { | |
428 | static uschar cipherbuf[256]; | |
429 | SSL_CIPHER *c; | |
430 | uschar *ver; | |
431 | int bits; | |
432 | ||
433 | switch (ssl->session->ssl_version) | |
434 | { | |
435 | case SSL2_VERSION: | |
436 | ver = US"SSLv2"; | |
437 | break; | |
438 | ||
439 | case SSL3_VERSION: | |
440 | ver = US"SSLv3"; | |
441 | break; | |
442 | ||
443 | case TLS1_VERSION: | |
444 | ver = US"TLSv1"; | |
445 | break; | |
446 | ||
447 | default: | |
448 | ver = US"UNKNOWN"; | |
449 | } | |
450 | ||
451 | c = SSL_get_current_cipher(ssl); | |
452 | SSL_CIPHER_get_bits(c, &bits); | |
453 | ||
454 | string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver, | |
455 | SSL_CIPHER_get_name(c), bits); | |
456 | tls_cipher = cipherbuf; | |
457 | ||
458 | DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf); | |
459 | } | |
460 | ||
461 | ||
462 | ||
463 | ||
464 | ||
465 | /************************************************* | |
466 | * Set up for verifying certificates * | |
467 | *************************************************/ | |
468 | ||
469 | /* Called by both client and server startup | |
470 | ||
471 | Arguments: | |
472 | certs certs file or NULL | |
473 | crl CRL file or NULL | |
474 | host NULL in a server; the remote host in a client | |
475 | optional TRUE if called from a server for a host in tls_try_verify_hosts; | |
476 | otherwise passed as FALSE | |
477 | ||
478 | Returns: OK/DEFER/FAIL | |
479 | */ | |
480 | ||
481 | static int | |
482 | setup_certs(uschar *certs, uschar *crl, host_item *host, BOOL optional) | |
483 | { | |
484 | uschar *expcerts, *expcrl; | |
485 | ||
486 | if (!expand_check(certs, US"tls_verify_certificates", &expcerts)) | |
487 | return DEFER; | |
488 | ||
489 | if (expcerts != NULL) | |
490 | { | |
491 | struct stat statbuf; | |
492 | if (!SSL_CTX_set_default_verify_paths(ctx)) | |
7199e1ee | 493 | return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL); |
059ec3d9 PH |
494 | |
495 | if (Ustat(expcerts, &statbuf) < 0) | |
496 | { | |
497 | log_write(0, LOG_MAIN|LOG_PANIC, | |
498 | "failed to stat %s for certificates", expcerts); | |
499 | return DEFER; | |
500 | } | |
501 | else | |
502 | { | |
503 | uschar *file, *dir; | |
504 | if ((statbuf.st_mode & S_IFMT) == S_IFDIR) | |
505 | { file = NULL; dir = expcerts; } | |
506 | else | |
507 | { file = expcerts; dir = NULL; } | |
508 | ||
509 | /* If a certificate file is empty, the next function fails with an | |
510 | unhelpful error message. If we skip it, we get the correct behaviour (no | |
511 | certificates are recognized, but the error message is still misleading (it | |
512 | says no certificate was supplied.) But this is better. */ | |
513 | ||
514 | if ((file == NULL || statbuf.st_size > 0) && | |
515 | !SSL_CTX_load_verify_locations(ctx, CS file, CS dir)) | |
7199e1ee | 516 | return tls_error(US"SSL_CTX_load_verify_locations", host, NULL); |
059ec3d9 PH |
517 | |
518 | if (file != NULL) | |
519 | { | |
520 | SSL_CTX_set_client_CA_list(ctx, SSL_load_client_CA_file(CS file)); | |
521 | } | |
522 | } | |
523 | ||
524 | /* Handle a certificate revocation list. */ | |
525 | ||
526 | #if OPENSSL_VERSION_NUMBER > 0x00907000L | |
527 | ||
8b417f2c PH |
528 | /* This bit of code is now the version supplied by Lars Mainka. (I have |
529 | * merely reformatted it into the Exim code style.) | |
530 | ||
531 | * "From here I changed the code to add support for multiple crl's | |
532 | * in pem format in one file or to support hashed directory entries in | |
533 | * pem format instead of a file. This method now uses the library function | |
534 | * X509_STORE_load_locations to add the CRL location to the SSL context. | |
535 | * OpenSSL will then handle the verify against CA certs and CRLs by | |
536 | * itself in the verify callback." */ | |
537 | ||
059ec3d9 PH |
538 | if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER; |
539 | if (expcrl != NULL && *expcrl != 0) | |
540 | { | |
8b417f2c PH |
541 | struct stat statbufcrl; |
542 | if (Ustat(expcrl, &statbufcrl) < 0) | |
543 | { | |
544 | log_write(0, LOG_MAIN|LOG_PANIC, | |
545 | "failed to stat %s for certificates revocation lists", expcrl); | |
546 | return DEFER; | |
547 | } | |
548 | else | |
059ec3d9 | 549 | { |
8b417f2c PH |
550 | /* is it a file or directory? */ |
551 | uschar *file, *dir; | |
552 | X509_STORE *cvstore = SSL_CTX_get_cert_store(ctx); | |
553 | if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR) | |
059ec3d9 | 554 | { |
8b417f2c PH |
555 | file = NULL; |
556 | dir = expcrl; | |
557 | DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir); | |
059ec3d9 PH |
558 | } |
559 | else | |
560 | { | |
8b417f2c PH |
561 | file = expcrl; |
562 | dir = NULL; | |
563 | DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file); | |
059ec3d9 | 564 | } |
8b417f2c | 565 | if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0) |
7199e1ee | 566 | return tls_error(US"X509_STORE_load_locations", host, NULL); |
8b417f2c PH |
567 | |
568 | /* setting the flags to check against the complete crl chain */ | |
569 | ||
570 | X509_STORE_set_flags(cvstore, | |
571 | X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL); | |
059ec3d9 | 572 | } |
059ec3d9 PH |
573 | } |
574 | ||
575 | #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */ | |
576 | ||
577 | /* If verification is optional, don't fail if no certificate */ | |
578 | ||
579 | SSL_CTX_set_verify(ctx, | |
580 | SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT), | |
581 | verify_callback); | |
582 | } | |
583 | ||
584 | return OK; | |
585 | } | |
586 | ||
587 | ||
588 | ||
589 | /************************************************* | |
590 | * Start a TLS session in a server * | |
591 | *************************************************/ | |
592 | ||
593 | /* This is called when Exim is running as a server, after having received | |
594 | the STARTTLS command. It must respond to that command, and then negotiate | |
595 | a TLS session. | |
596 | ||
597 | Arguments: | |
598 | require_ciphers allowed ciphers | |
83da1223 PH |
599 | ------------------------------------------------------ |
600 | require_mac list of allowed MACs ) Not used | |
601 | require_kx list of allowed key_exchange methods ) for | |
602 | require_proto list of allowed protocols ) OpenSSL | |
603 | ------------------------------------------------------ | |
059ec3d9 PH |
604 | |
605 | Returns: OK on success | |
606 | DEFER for errors before the start of the negotiation | |
607 | FAIL for errors during the negotation; the server can't | |
608 | continue running. | |
609 | */ | |
610 | ||
611 | int | |
83da1223 PH |
612 | tls_server_start(uschar *require_ciphers, uschar *require_mac, |
613 | uschar *require_kx, uschar *require_proto) | |
059ec3d9 PH |
614 | { |
615 | int rc; | |
616 | uschar *expciphers; | |
617 | ||
618 | /* Check for previous activation */ | |
619 | ||
620 | if (tls_active >= 0) | |
621 | { | |
7199e1ee | 622 | tls_error("STARTTLS received after TLS started", NULL, ""); |
059ec3d9 PH |
623 | smtp_printf("554 Already in TLS\r\n"); |
624 | return FAIL; | |
625 | } | |
626 | ||
627 | /* Initialize the SSL library. If it fails, it will already have logged | |
628 | the error. */ | |
629 | ||
630 | rc = tls_init(NULL, tls_dhparam, tls_certificate, tls_privatekey, NULL); | |
631 | if (rc != OK) return rc; | |
632 | ||
633 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) | |
634 | return FAIL; | |
635 | ||
636 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they | |
637 | are separated by underscores. So that I can use either form in my tests, and | |
638 | also for general convenience, we turn underscores into hyphens here. */ | |
639 | ||
640 | if (expciphers != NULL) | |
641 | { | |
642 | uschar *s = expciphers; | |
643 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } | |
644 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); | |
645 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) | |
7199e1ee | 646 | return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL); |
059ec3d9 PH |
647 | } |
648 | ||
649 | /* If this is a host for which certificate verification is mandatory or | |
650 | optional, set up appropriately. */ | |
651 | ||
652 | tls_certificate_verified = FALSE; | |
653 | verify_callback_called = FALSE; | |
654 | ||
655 | if (verify_check_host(&tls_verify_hosts) == OK) | |
656 | { | |
657 | rc = setup_certs(tls_verify_certificates, tls_crl, NULL, FALSE); | |
658 | if (rc != OK) return rc; | |
659 | verify_optional = FALSE; | |
660 | } | |
661 | else if (verify_check_host(&tls_try_verify_hosts) == OK) | |
662 | { | |
663 | rc = setup_certs(tls_verify_certificates, tls_crl, NULL, TRUE); | |
664 | if (rc != OK) return rc; | |
665 | verify_optional = TRUE; | |
666 | } | |
667 | ||
668 | /* Prepare for new connection */ | |
669 | ||
7199e1ee | 670 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL); |
059ec3d9 PH |
671 | SSL_clear(ssl); |
672 | ||
673 | /* Set context and tell client to go ahead, except in the case of TLS startup | |
674 | on connection, where outputting anything now upsets the clients and tends to | |
675 | make them disconnect. We need to have an explicit fflush() here, to force out | |
676 | the response. Other smtp_printf() calls do not need it, because in non-TLS | |
677 | mode, the fflush() happens when smtp_getc() is called. */ | |
678 | ||
679 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); | |
680 | if (!tls_on_connect) | |
681 | { | |
682 | smtp_printf("220 TLS go ahead\r\n"); | |
683 | fflush(smtp_out); | |
684 | } | |
685 | ||
686 | /* Now negotiate the TLS session. We put our own timer on it, since it seems | |
687 | that the OpenSSL library doesn't. */ | |
688 | ||
56f5d9bd PH |
689 | SSL_set_wfd(ssl, fileno(smtp_out)); |
690 | SSL_set_rfd(ssl, fileno(smtp_in)); | |
059ec3d9 PH |
691 | SSL_set_accept_state(ssl); |
692 | ||
693 | DEBUG(D_tls) debug_printf("Calling SSL_accept\n"); | |
694 | ||
695 | sigalrm_seen = FALSE; | |
696 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
697 | rc = SSL_accept(ssl); | |
698 | alarm(0); | |
699 | ||
700 | if (rc <= 0) | |
701 | { | |
7199e1ee | 702 | tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL); |
059ec3d9 PH |
703 | return FAIL; |
704 | } | |
705 | ||
706 | DEBUG(D_tls) debug_printf("SSL_accept was successful\n"); | |
707 | ||
708 | /* TLS has been set up. Adjust the input functions to read via TLS, | |
709 | and initialize things. */ | |
710 | ||
711 | construct_cipher_name(ssl); | |
712 | ||
713 | DEBUG(D_tls) | |
714 | { | |
715 | uschar buf[2048]; | |
716 | if (SSL_get_shared_ciphers(ssl, CS buf, sizeof(buf)) != NULL) | |
717 | debug_printf("Shared ciphers: %s\n", buf); | |
718 | } | |
719 | ||
720 | ||
721 | ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); | |
722 | ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; | |
723 | ssl_xfer_eof = ssl_xfer_error = 0; | |
724 | ||
725 | receive_getc = tls_getc; | |
726 | receive_ungetc = tls_ungetc; | |
727 | receive_feof = tls_feof; | |
728 | receive_ferror = tls_ferror; | |
58eb016e | 729 | receive_smtp_buffered = tls_smtp_buffered; |
059ec3d9 PH |
730 | |
731 | tls_active = fileno(smtp_out); | |
732 | return OK; | |
733 | } | |
734 | ||
735 | ||
736 | ||
737 | ||
738 | ||
739 | /************************************************* | |
740 | * Start a TLS session in a client * | |
741 | *************************************************/ | |
742 | ||
743 | /* Called from the smtp transport after STARTTLS has been accepted. | |
744 | ||
745 | Argument: | |
746 | fd the fd of the connection | |
747 | host connected host (for messages) | |
83da1223 | 748 | addr the first address |
059ec3d9 PH |
749 | dhparam DH parameter file |
750 | certificate certificate file | |
751 | privatekey private key file | |
752 | verify_certs file for certificate verify | |
753 | crl file containing CRL | |
754 | require_ciphers list of allowed ciphers | |
83da1223 PH |
755 | ------------------------------------------------------ |
756 | require_mac list of allowed MACs ) Not used | |
757 | require_kx list of allowed key_exchange methods ) for | |
758 | require_proto list of allowed protocols ) OpenSSL | |
759 | ------------------------------------------------------ | |
760 | timeout startup timeout | |
059ec3d9 PH |
761 | |
762 | Returns: OK on success | |
763 | FAIL otherwise - note that tls_error() will not give DEFER | |
764 | because this is not a server | |
765 | */ | |
766 | ||
767 | int | |
768 | tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam, | |
769 | uschar *certificate, uschar *privatekey, uschar *verify_certs, uschar *crl, | |
83da1223 PH |
770 | uschar *require_ciphers, uschar *require_mac, uschar *require_kx, |
771 | uschar *require_proto, int timeout) | |
059ec3d9 PH |
772 | { |
773 | static uschar txt[256]; | |
774 | uschar *expciphers; | |
775 | X509* server_cert; | |
776 | int rc; | |
777 | ||
778 | rc = tls_init(host, dhparam, certificate, privatekey, addr); | |
779 | if (rc != OK) return rc; | |
780 | ||
781 | tls_certificate_verified = FALSE; | |
782 | verify_callback_called = FALSE; | |
783 | ||
784 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) | |
785 | return FAIL; | |
786 | ||
787 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they | |
788 | are separated by underscores. So that I can use either form in my tests, and | |
789 | also for general convenience, we turn underscores into hyphens here. */ | |
790 | ||
791 | if (expciphers != NULL) | |
792 | { | |
793 | uschar *s = expciphers; | |
794 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } | |
795 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); | |
796 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) | |
7199e1ee | 797 | return tls_error(US"SSL_CTX_set_cipher_list", host, NULL); |
059ec3d9 PH |
798 | } |
799 | ||
800 | rc = setup_certs(verify_certs, crl, host, FALSE); | |
801 | if (rc != OK) return rc; | |
802 | ||
7199e1ee | 803 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", host, NULL); |
059ec3d9 PH |
804 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); |
805 | SSL_set_fd(ssl, fd); | |
806 | SSL_set_connect_state(ssl); | |
807 | ||
808 | /* There doesn't seem to be a built-in timeout on connection. */ | |
809 | ||
810 | DEBUG(D_tls) debug_printf("Calling SSL_connect\n"); | |
811 | sigalrm_seen = FALSE; | |
812 | alarm(timeout); | |
813 | rc = SSL_connect(ssl); | |
814 | alarm(0); | |
815 | ||
816 | if (rc <= 0) | |
7199e1ee | 817 | return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL); |
059ec3d9 PH |
818 | |
819 | DEBUG(D_tls) debug_printf("SSL_connect succeeded\n"); | |
820 | ||
821 | server_cert = SSL_get_peer_certificate (ssl); | |
822 | tls_peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert), | |
823 | CS txt, sizeof(txt)); | |
824 | tls_peerdn = txt; | |
825 | ||
826 | construct_cipher_name(ssl); /* Sets tls_cipher */ | |
827 | ||
828 | tls_active = fd; | |
829 | return OK; | |
830 | } | |
831 | ||
832 | ||
833 | ||
834 | ||
835 | ||
836 | /************************************************* | |
837 | * TLS version of getc * | |
838 | *************************************************/ | |
839 | ||
840 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, | |
841 | it refills the buffer via the SSL reading function. | |
842 | ||
843 | Arguments: none | |
844 | Returns: the next character or EOF | |
845 | */ | |
846 | ||
847 | int | |
848 | tls_getc(void) | |
849 | { | |
850 | if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) | |
851 | { | |
852 | int error; | |
853 | int inbytes; | |
854 | ||
855 | DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl, | |
856 | (long)ssl_xfer_buffer, ssl_xfer_buffer_size); | |
857 | ||
858 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
859 | inbytes = SSL_read(ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size); | |
860 | error = SSL_get_error(ssl, inbytes); | |
861 | alarm(0); | |
862 | ||
863 | /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been | |
864 | closed down, not that the socket itself has been closed down. Revert to | |
865 | non-SSL handling. */ | |
866 | ||
867 | if (error == SSL_ERROR_ZERO_RETURN) | |
868 | { | |
869 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); | |
870 | ||
871 | receive_getc = smtp_getc; | |
872 | receive_ungetc = smtp_ungetc; | |
873 | receive_feof = smtp_feof; | |
874 | receive_ferror = smtp_ferror; | |
58eb016e | 875 | receive_smtp_buffered = smtp_buffered; |
059ec3d9 PH |
876 | |
877 | SSL_free(ssl); | |
878 | ssl = NULL; | |
879 | tls_active = -1; | |
880 | tls_cipher = NULL; | |
881 | tls_peerdn = NULL; | |
882 | ||
883 | return smtp_getc(); | |
884 | } | |
885 | ||
886 | /* Handle genuine errors */ | |
887 | ||
888 | else if (error != SSL_ERROR_NONE) | |
889 | { | |
890 | DEBUG(D_tls) debug_printf("Got SSL error %d\n", error); | |
891 | ssl_xfer_error = 1; | |
892 | return EOF; | |
893 | } | |
80a47a2c TK |
894 | #ifndef DISABLE_DKIM |
895 | dkim_exim_verify_feed(ssl_xfer_buffer, inbytes); | |
896 | #endif | |
059ec3d9 PH |
897 | ssl_xfer_buffer_hwm = inbytes; |
898 | ssl_xfer_buffer_lwm = 0; | |
899 | } | |
900 | ||
901 | /* Something in the buffer; return next uschar */ | |
902 | ||
903 | return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; | |
904 | } | |
905 | ||
906 | ||
907 | ||
908 | /************************************************* | |
909 | * Read bytes from TLS channel * | |
910 | *************************************************/ | |
911 | ||
912 | /* | |
913 | Arguments: | |
914 | buff buffer of data | |
915 | len size of buffer | |
916 | ||
917 | Returns: the number of bytes read | |
918 | -1 after a failed read | |
919 | */ | |
920 | ||
921 | int | |
922 | tls_read(uschar *buff, size_t len) | |
923 | { | |
924 | int inbytes; | |
925 | int error; | |
926 | ||
927 | DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl, | |
928 | (long)buff, (unsigned int)len); | |
929 | ||
930 | inbytes = SSL_read(ssl, CS buff, len); | |
931 | error = SSL_get_error(ssl, inbytes); | |
932 | ||
933 | if (error == SSL_ERROR_ZERO_RETURN) | |
934 | { | |
935 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); | |
936 | return -1; | |
937 | } | |
938 | else if (error != SSL_ERROR_NONE) | |
939 | { | |
940 | return -1; | |
941 | } | |
942 | ||
943 | return inbytes; | |
944 | } | |
945 | ||
946 | ||
947 | ||
948 | ||
949 | ||
950 | /************************************************* | |
951 | * Write bytes down TLS channel * | |
952 | *************************************************/ | |
953 | ||
954 | /* | |
955 | Arguments: | |
956 | buff buffer of data | |
957 | len number of bytes | |
958 | ||
959 | Returns: the number of bytes after a successful write, | |
960 | -1 after a failed write | |
961 | */ | |
962 | ||
963 | int | |
964 | tls_write(const uschar *buff, size_t len) | |
965 | { | |
966 | int outbytes; | |
967 | int error; | |
968 | int left = len; | |
969 | ||
970 | DEBUG(D_tls) debug_printf("tls_do_write(%lx, %d)\n", (long)buff, left); | |
971 | while (left > 0) | |
972 | { | |
973 | DEBUG(D_tls) debug_printf("SSL_write(SSL, %lx, %d)\n", (long)buff, left); | |
974 | outbytes = SSL_write(ssl, CS buff, left); | |
975 | error = SSL_get_error(ssl, outbytes); | |
976 | DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error); | |
977 | switch (error) | |
978 | { | |
979 | case SSL_ERROR_SSL: | |
980 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
981 | log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring); | |
982 | return -1; | |
983 | ||
984 | case SSL_ERROR_NONE: | |
985 | left -= outbytes; | |
986 | buff += outbytes; | |
987 | break; | |
988 | ||
989 | case SSL_ERROR_ZERO_RETURN: | |
990 | log_write(0, LOG_MAIN, "SSL channel closed on write"); | |
991 | return -1; | |
992 | ||
993 | default: | |
994 | log_write(0, LOG_MAIN, "SSL_write error %d", error); | |
995 | return -1; | |
996 | } | |
997 | } | |
998 | return len; | |
999 | } | |
1000 | ||
1001 | ||
1002 | ||
1003 | /************************************************* | |
1004 | * Close down a TLS session * | |
1005 | *************************************************/ | |
1006 | ||
1007 | /* This is also called from within a delivery subprocess forked from the | |
1008 | daemon, to shut down the TLS library, without actually doing a shutdown (which | |
1009 | would tamper with the SSL session in the parent process). | |
1010 | ||
1011 | Arguments: TRUE if SSL_shutdown is to be called | |
1012 | Returns: nothing | |
1013 | */ | |
1014 | ||
1015 | void | |
1016 | tls_close(BOOL shutdown) | |
1017 | { | |
1018 | if (tls_active < 0) return; /* TLS was not active */ | |
1019 | ||
1020 | if (shutdown) | |
1021 | { | |
1022 | DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n"); | |
1023 | SSL_shutdown(ssl); | |
1024 | } | |
1025 | ||
1026 | SSL_free(ssl); | |
1027 | ssl = NULL; | |
1028 | ||
1029 | tls_active = -1; | |
1030 | } | |
1031 | ||
36f12725 NM |
1032 | |
1033 | ||
1034 | ||
1035 | /************************************************* | |
1036 | * Report the library versions. * | |
1037 | *************************************************/ | |
1038 | ||
1039 | /* There have historically been some issues with binary compatibility in | |
1040 | OpenSSL libraries; if Exim (like many other applications) is built against | |
1041 | one version of OpenSSL but the run-time linker picks up another version, | |
1042 | it can result in serious failures, including crashing with a SIGSEGV. So | |
1043 | report the version found by the compiler and the run-time version. | |
1044 | ||
1045 | Arguments: a FILE* to print the results to | |
1046 | Returns: nothing | |
1047 | */ | |
1048 | ||
1049 | void | |
1050 | tls_version_report(FILE *f) | |
1051 | { | |
1052 | fprintf(f, "OpenSSL compile-time version: %s\n", OPENSSL_VERSION_TEXT); | |
1053 | fprintf(f, "OpenSSL runtime version: %s\n", SSLeay_version(SSLEAY_VERSION)); | |
1054 | } | |
1055 | ||
059ec3d9 | 1056 | /* End of tls-openssl.c */ |