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0a49a7a4 | 1 | /* $Cambridge: exim/src/src/tls-openssl.c,v 1.22 2009/11/16 19:50:37 nm4 Exp $ */ |
059ec3d9 PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
0a49a7a4 | 7 | /* Copyright (c) University of Cambridge 1995 - 2009 */ |
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 { | |
9e3331ea TK |
29 | struct timeval tv; |
30 | pid_t p; | |
059ec3d9 PH |
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); | |
5ca6d115 | 76 | msg = (uschar *)ssl_errstring; |
7199e1ee TF |
77 | } |
78 | ||
059ec3d9 PH |
79 | if (host == NULL) |
80 | { | |
7199e1ee | 81 | uschar *conn_info = smtp_get_connection_info(); |
5ca6d115 | 82 | if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) |
7199e1ee TF |
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 | 255 | tls_error(string_sprintf("could not read dhparams file %s", dhexpanded), |
5ca6d115 | 256 | host, (uschar *)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 | ||
388d6564 | 308 | #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256) |
a0475b69 TK |
309 | /* SHA256 is becoming ever moar popular. This makes sure it gets added to the |
310 | list of available digests. */ | |
311 | EVP_add_digest(EVP_sha256()); | |
cf1ef1a9 | 312 | #endif |
a0475b69 | 313 | |
059ec3d9 PH |
314 | /* Create a context */ |
315 | ||
316 | ctx = SSL_CTX_new((host == NULL)? | |
317 | SSLv23_server_method() : SSLv23_client_method()); | |
318 | ||
7199e1ee | 319 | if (ctx == NULL) return tls_error(US"SSL_CTX_new", host, NULL); |
059ec3d9 PH |
320 | |
321 | /* It turns out that we need to seed the random number generator this early in | |
322 | order to get the full complement of ciphers to work. It took me roughly a day | |
323 | of work to discover this by experiment. | |
324 | ||
325 | On systems that have /dev/urandom, SSL may automatically seed itself from | |
326 | there. Otherwise, we have to make something up as best we can. Double check | |
327 | afterwards. */ | |
328 | ||
329 | if (!RAND_status()) | |
330 | { | |
331 | randstuff r; | |
9e3331ea | 332 | gettimeofday(&r.tv, NULL); |
059ec3d9 PH |
333 | r.p = getpid(); |
334 | ||
335 | RAND_seed((uschar *)(&r), sizeof(r)); | |
336 | RAND_seed((uschar *)big_buffer, big_buffer_size); | |
337 | if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr)); | |
338 | ||
339 | if (!RAND_status()) | |
7199e1ee | 340 | return tls_error(US"RAND_status", host, |
5ca6d115 | 341 | US"unable to seed random number generator"); |
059ec3d9 PH |
342 | } |
343 | ||
344 | /* Set up the information callback, which outputs if debugging is at a suitable | |
345 | level. */ | |
346 | ||
58c01c94 | 347 | SSL_CTX_set_info_callback(ctx, (void (*)())info_callback); |
059ec3d9 PH |
348 | |
349 | /* The following patch was supplied by Robert Roselius */ | |
350 | ||
351 | #if OPENSSL_VERSION_NUMBER > 0x00906040L | |
352 | /* Enable client-bug workaround. | |
353 | Versions of OpenSSL as of 0.9.6d include a "CBC countermeasure" feature, | |
354 | which causes problems with some clients (such as the Certicom SSL Plus | |
355 | library used by Eudora). This option, SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, | |
356 | disables the coutermeasure allowing Eudora to connect. | |
357 | Some poppers and MTAs use SSL_OP_ALL, which enables all such bug | |
358 | workarounds. */ | |
359 | /* XXX (Silently?) ignore failure here? XXX*/ | |
360 | ||
361 | if (!(SSL_CTX_set_options(ctx, SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS))) | |
7199e1ee | 362 | return tls_error(US"SSL_CTX_set_option", host, NULL); |
059ec3d9 PH |
363 | #endif |
364 | ||
365 | /* Initialize with DH parameters if supplied */ | |
366 | ||
7199e1ee | 367 | if (!init_dh(dhparam, host)) return DEFER; |
059ec3d9 PH |
368 | |
369 | /* Set up certificate and key */ | |
370 | ||
371 | if (certificate != NULL) | |
372 | { | |
373 | uschar *expanded; | |
374 | if (!expand_check(certificate, US"tls_certificate", &expanded)) | |
375 | return DEFER; | |
376 | ||
377 | if (expanded != NULL) | |
378 | { | |
379 | DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded); | |
380 | if (!SSL_CTX_use_certificate_chain_file(ctx, CS expanded)) | |
d6453af2 | 381 | return tls_error(string_sprintf( |
7199e1ee | 382 | "SSL_CTX_use_certificate_chain_file file=%s", expanded), host, NULL); |
059ec3d9 PH |
383 | } |
384 | ||
385 | if (privatekey != NULL && | |
386 | !expand_check(privatekey, US"tls_privatekey", &expanded)) | |
387 | return DEFER; | |
388 | ||
c91535f3 PH |
389 | /* If expansion was forced to fail, key_expanded will be NULL. If the result |
390 | of the expansion is an empty string, ignore it also, and assume the private | |
391 | key is in the same file as the certificate. */ | |
392 | ||
393 | if (expanded != NULL && *expanded != 0) | |
059ec3d9 PH |
394 | { |
395 | DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded); | |
396 | if (!SSL_CTX_use_PrivateKey_file(ctx, CS expanded, SSL_FILETYPE_PEM)) | |
d6453af2 | 397 | return tls_error(string_sprintf( |
7199e1ee | 398 | "SSL_CTX_use_PrivateKey_file file=%s", expanded), host, NULL); |
059ec3d9 PH |
399 | } |
400 | } | |
401 | ||
402 | /* Set up the RSA callback */ | |
403 | ||
404 | SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback); | |
405 | ||
406 | /* Finally, set the timeout, and we are done */ | |
407 | ||
408 | SSL_CTX_set_timeout(ctx, ssl_session_timeout); | |
409 | DEBUG(D_tls) debug_printf("Initialized TLS\n"); | |
410 | return OK; | |
411 | } | |
412 | ||
413 | ||
414 | ||
415 | ||
416 | /************************************************* | |
417 | * Get name of cipher in use * | |
418 | *************************************************/ | |
419 | ||
420 | /* The answer is left in a static buffer, and tls_cipher is set to point | |
421 | to it. | |
422 | ||
423 | Argument: pointer to an SSL structure for the connection | |
424 | Returns: nothing | |
425 | */ | |
426 | ||
427 | static void | |
428 | construct_cipher_name(SSL *ssl) | |
429 | { | |
430 | static uschar cipherbuf[256]; | |
431 | SSL_CIPHER *c; | |
432 | uschar *ver; | |
433 | int bits; | |
434 | ||
435 | switch (ssl->session->ssl_version) | |
436 | { | |
437 | case SSL2_VERSION: | |
438 | ver = US"SSLv2"; | |
439 | break; | |
440 | ||
441 | case SSL3_VERSION: | |
442 | ver = US"SSLv3"; | |
443 | break; | |
444 | ||
445 | case TLS1_VERSION: | |
446 | ver = US"TLSv1"; | |
447 | break; | |
448 | ||
449 | default: | |
450 | ver = US"UNKNOWN"; | |
451 | } | |
452 | ||
453 | c = SSL_get_current_cipher(ssl); | |
454 | SSL_CIPHER_get_bits(c, &bits); | |
455 | ||
456 | string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver, | |
457 | SSL_CIPHER_get_name(c), bits); | |
458 | tls_cipher = cipherbuf; | |
459 | ||
460 | DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf); | |
461 | } | |
462 | ||
463 | ||
464 | ||
465 | ||
466 | ||
467 | /************************************************* | |
468 | * Set up for verifying certificates * | |
469 | *************************************************/ | |
470 | ||
471 | /* Called by both client and server startup | |
472 | ||
473 | Arguments: | |
474 | certs certs file or NULL | |
475 | crl CRL file or NULL | |
476 | host NULL in a server; the remote host in a client | |
477 | optional TRUE if called from a server for a host in tls_try_verify_hosts; | |
478 | otherwise passed as FALSE | |
479 | ||
480 | Returns: OK/DEFER/FAIL | |
481 | */ | |
482 | ||
483 | static int | |
484 | setup_certs(uschar *certs, uschar *crl, host_item *host, BOOL optional) | |
485 | { | |
486 | uschar *expcerts, *expcrl; | |
487 | ||
488 | if (!expand_check(certs, US"tls_verify_certificates", &expcerts)) | |
489 | return DEFER; | |
490 | ||
491 | if (expcerts != NULL) | |
492 | { | |
493 | struct stat statbuf; | |
494 | if (!SSL_CTX_set_default_verify_paths(ctx)) | |
7199e1ee | 495 | return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL); |
059ec3d9 PH |
496 | |
497 | if (Ustat(expcerts, &statbuf) < 0) | |
498 | { | |
499 | log_write(0, LOG_MAIN|LOG_PANIC, | |
500 | "failed to stat %s for certificates", expcerts); | |
501 | return DEFER; | |
502 | } | |
503 | else | |
504 | { | |
505 | uschar *file, *dir; | |
506 | if ((statbuf.st_mode & S_IFMT) == S_IFDIR) | |
507 | { file = NULL; dir = expcerts; } | |
508 | else | |
509 | { file = expcerts; dir = NULL; } | |
510 | ||
511 | /* If a certificate file is empty, the next function fails with an | |
512 | unhelpful error message. If we skip it, we get the correct behaviour (no | |
513 | certificates are recognized, but the error message is still misleading (it | |
514 | says no certificate was supplied.) But this is better. */ | |
515 | ||
516 | if ((file == NULL || statbuf.st_size > 0) && | |
517 | !SSL_CTX_load_verify_locations(ctx, CS file, CS dir)) | |
7199e1ee | 518 | return tls_error(US"SSL_CTX_load_verify_locations", host, NULL); |
059ec3d9 PH |
519 | |
520 | if (file != NULL) | |
521 | { | |
522 | SSL_CTX_set_client_CA_list(ctx, SSL_load_client_CA_file(CS file)); | |
523 | } | |
524 | } | |
525 | ||
526 | /* Handle a certificate revocation list. */ | |
527 | ||
528 | #if OPENSSL_VERSION_NUMBER > 0x00907000L | |
529 | ||
8b417f2c PH |
530 | /* This bit of code is now the version supplied by Lars Mainka. (I have |
531 | * merely reformatted it into the Exim code style.) | |
532 | ||
533 | * "From here I changed the code to add support for multiple crl's | |
534 | * in pem format in one file or to support hashed directory entries in | |
535 | * pem format instead of a file. This method now uses the library function | |
536 | * X509_STORE_load_locations to add the CRL location to the SSL context. | |
537 | * OpenSSL will then handle the verify against CA certs and CRLs by | |
538 | * itself in the verify callback." */ | |
539 | ||
059ec3d9 PH |
540 | if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER; |
541 | if (expcrl != NULL && *expcrl != 0) | |
542 | { | |
8b417f2c PH |
543 | struct stat statbufcrl; |
544 | if (Ustat(expcrl, &statbufcrl) < 0) | |
545 | { | |
546 | log_write(0, LOG_MAIN|LOG_PANIC, | |
547 | "failed to stat %s for certificates revocation lists", expcrl); | |
548 | return DEFER; | |
549 | } | |
550 | else | |
059ec3d9 | 551 | { |
8b417f2c PH |
552 | /* is it a file or directory? */ |
553 | uschar *file, *dir; | |
554 | X509_STORE *cvstore = SSL_CTX_get_cert_store(ctx); | |
555 | if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR) | |
059ec3d9 | 556 | { |
8b417f2c PH |
557 | file = NULL; |
558 | dir = expcrl; | |
559 | DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir); | |
059ec3d9 PH |
560 | } |
561 | else | |
562 | { | |
8b417f2c PH |
563 | file = expcrl; |
564 | dir = NULL; | |
565 | DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file); | |
059ec3d9 | 566 | } |
8b417f2c | 567 | if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0) |
7199e1ee | 568 | return tls_error(US"X509_STORE_load_locations", host, NULL); |
8b417f2c PH |
569 | |
570 | /* setting the flags to check against the complete crl chain */ | |
571 | ||
572 | X509_STORE_set_flags(cvstore, | |
573 | X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL); | |
059ec3d9 | 574 | } |
059ec3d9 PH |
575 | } |
576 | ||
577 | #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */ | |
578 | ||
579 | /* If verification is optional, don't fail if no certificate */ | |
580 | ||
581 | SSL_CTX_set_verify(ctx, | |
582 | SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT), | |
583 | verify_callback); | |
584 | } | |
585 | ||
586 | return OK; | |
587 | } | |
588 | ||
589 | ||
590 | ||
591 | /************************************************* | |
592 | * Start a TLS session in a server * | |
593 | *************************************************/ | |
594 | ||
595 | /* This is called when Exim is running as a server, after having received | |
596 | the STARTTLS command. It must respond to that command, and then negotiate | |
597 | a TLS session. | |
598 | ||
599 | Arguments: | |
600 | require_ciphers allowed ciphers | |
83da1223 PH |
601 | ------------------------------------------------------ |
602 | require_mac list of allowed MACs ) Not used | |
603 | require_kx list of allowed key_exchange methods ) for | |
604 | require_proto list of allowed protocols ) OpenSSL | |
605 | ------------------------------------------------------ | |
059ec3d9 PH |
606 | |
607 | Returns: OK on success | |
608 | DEFER for errors before the start of the negotiation | |
609 | FAIL for errors during the negotation; the server can't | |
610 | continue running. | |
611 | */ | |
612 | ||
613 | int | |
83da1223 PH |
614 | tls_server_start(uschar *require_ciphers, uschar *require_mac, |
615 | uschar *require_kx, uschar *require_proto) | |
059ec3d9 PH |
616 | { |
617 | int rc; | |
618 | uschar *expciphers; | |
619 | ||
620 | /* Check for previous activation */ | |
621 | ||
622 | if (tls_active >= 0) | |
623 | { | |
5ca6d115 | 624 | tls_error(US"STARTTLS received after TLS started", NULL, US""); |
059ec3d9 PH |
625 | smtp_printf("554 Already in TLS\r\n"); |
626 | return FAIL; | |
627 | } | |
628 | ||
629 | /* Initialize the SSL library. If it fails, it will already have logged | |
630 | the error. */ | |
631 | ||
632 | rc = tls_init(NULL, tls_dhparam, tls_certificate, tls_privatekey, NULL); | |
633 | if (rc != OK) return rc; | |
634 | ||
635 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) | |
636 | return FAIL; | |
637 | ||
638 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they | |
639 | are separated by underscores. So that I can use either form in my tests, and | |
640 | also for general convenience, we turn underscores into hyphens here. */ | |
641 | ||
642 | if (expciphers != NULL) | |
643 | { | |
644 | uschar *s = expciphers; | |
645 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } | |
646 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); | |
647 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) | |
7199e1ee | 648 | return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL); |
059ec3d9 PH |
649 | } |
650 | ||
651 | /* If this is a host for which certificate verification is mandatory or | |
652 | optional, set up appropriately. */ | |
653 | ||
654 | tls_certificate_verified = FALSE; | |
655 | verify_callback_called = FALSE; | |
656 | ||
657 | if (verify_check_host(&tls_verify_hosts) == OK) | |
658 | { | |
659 | rc = setup_certs(tls_verify_certificates, tls_crl, NULL, FALSE); | |
660 | if (rc != OK) return rc; | |
661 | verify_optional = FALSE; | |
662 | } | |
663 | else if (verify_check_host(&tls_try_verify_hosts) == OK) | |
664 | { | |
665 | rc = setup_certs(tls_verify_certificates, tls_crl, NULL, TRUE); | |
666 | if (rc != OK) return rc; | |
667 | verify_optional = TRUE; | |
668 | } | |
669 | ||
670 | /* Prepare for new connection */ | |
671 | ||
7199e1ee | 672 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL); |
059ec3d9 PH |
673 | SSL_clear(ssl); |
674 | ||
675 | /* Set context and tell client to go ahead, except in the case of TLS startup | |
676 | on connection, where outputting anything now upsets the clients and tends to | |
677 | make them disconnect. We need to have an explicit fflush() here, to force out | |
678 | the response. Other smtp_printf() calls do not need it, because in non-TLS | |
679 | mode, the fflush() happens when smtp_getc() is called. */ | |
680 | ||
681 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); | |
682 | if (!tls_on_connect) | |
683 | { | |
684 | smtp_printf("220 TLS go ahead\r\n"); | |
685 | fflush(smtp_out); | |
686 | } | |
687 | ||
688 | /* Now negotiate the TLS session. We put our own timer on it, since it seems | |
689 | that the OpenSSL library doesn't. */ | |
690 | ||
56f5d9bd PH |
691 | SSL_set_wfd(ssl, fileno(smtp_out)); |
692 | SSL_set_rfd(ssl, fileno(smtp_in)); | |
059ec3d9 PH |
693 | SSL_set_accept_state(ssl); |
694 | ||
695 | DEBUG(D_tls) debug_printf("Calling SSL_accept\n"); | |
696 | ||
697 | sigalrm_seen = FALSE; | |
698 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
699 | rc = SSL_accept(ssl); | |
700 | alarm(0); | |
701 | ||
702 | if (rc <= 0) | |
703 | { | |
7199e1ee | 704 | tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL); |
059ec3d9 PH |
705 | return FAIL; |
706 | } | |
707 | ||
708 | DEBUG(D_tls) debug_printf("SSL_accept was successful\n"); | |
709 | ||
710 | /* TLS has been set up. Adjust the input functions to read via TLS, | |
711 | and initialize things. */ | |
712 | ||
713 | construct_cipher_name(ssl); | |
714 | ||
715 | DEBUG(D_tls) | |
716 | { | |
717 | uschar buf[2048]; | |
718 | if (SSL_get_shared_ciphers(ssl, CS buf, sizeof(buf)) != NULL) | |
719 | debug_printf("Shared ciphers: %s\n", buf); | |
720 | } | |
721 | ||
722 | ||
723 | ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); | |
724 | ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; | |
725 | ssl_xfer_eof = ssl_xfer_error = 0; | |
726 | ||
727 | receive_getc = tls_getc; | |
728 | receive_ungetc = tls_ungetc; | |
729 | receive_feof = tls_feof; | |
730 | receive_ferror = tls_ferror; | |
58eb016e | 731 | receive_smtp_buffered = tls_smtp_buffered; |
059ec3d9 PH |
732 | |
733 | tls_active = fileno(smtp_out); | |
734 | return OK; | |
735 | } | |
736 | ||
737 | ||
738 | ||
739 | ||
740 | ||
741 | /************************************************* | |
742 | * Start a TLS session in a client * | |
743 | *************************************************/ | |
744 | ||
745 | /* Called from the smtp transport after STARTTLS has been accepted. | |
746 | ||
747 | Argument: | |
748 | fd the fd of the connection | |
749 | host connected host (for messages) | |
83da1223 | 750 | addr the first address |
059ec3d9 PH |
751 | dhparam DH parameter file |
752 | certificate certificate file | |
753 | privatekey private key file | |
754 | verify_certs file for certificate verify | |
755 | crl file containing CRL | |
756 | require_ciphers list of allowed ciphers | |
83da1223 PH |
757 | ------------------------------------------------------ |
758 | require_mac list of allowed MACs ) Not used | |
759 | require_kx list of allowed key_exchange methods ) for | |
760 | require_proto list of allowed protocols ) OpenSSL | |
761 | ------------------------------------------------------ | |
762 | timeout startup timeout | |
059ec3d9 PH |
763 | |
764 | Returns: OK on success | |
765 | FAIL otherwise - note that tls_error() will not give DEFER | |
766 | because this is not a server | |
767 | */ | |
768 | ||
769 | int | |
770 | tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam, | |
771 | uschar *certificate, uschar *privatekey, uschar *verify_certs, uschar *crl, | |
83da1223 PH |
772 | uschar *require_ciphers, uschar *require_mac, uschar *require_kx, |
773 | uschar *require_proto, int timeout) | |
059ec3d9 PH |
774 | { |
775 | static uschar txt[256]; | |
776 | uschar *expciphers; | |
777 | X509* server_cert; | |
778 | int rc; | |
779 | ||
780 | rc = tls_init(host, dhparam, certificate, privatekey, addr); | |
781 | if (rc != OK) return rc; | |
782 | ||
783 | tls_certificate_verified = FALSE; | |
784 | verify_callback_called = FALSE; | |
785 | ||
786 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) | |
787 | return FAIL; | |
788 | ||
789 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they | |
790 | are separated by underscores. So that I can use either form in my tests, and | |
791 | also for general convenience, we turn underscores into hyphens here. */ | |
792 | ||
793 | if (expciphers != NULL) | |
794 | { | |
795 | uschar *s = expciphers; | |
796 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } | |
797 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); | |
798 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) | |
7199e1ee | 799 | return tls_error(US"SSL_CTX_set_cipher_list", host, NULL); |
059ec3d9 PH |
800 | } |
801 | ||
802 | rc = setup_certs(verify_certs, crl, host, FALSE); | |
803 | if (rc != OK) return rc; | |
804 | ||
7199e1ee | 805 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", host, NULL); |
059ec3d9 PH |
806 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); |
807 | SSL_set_fd(ssl, fd); | |
808 | SSL_set_connect_state(ssl); | |
809 | ||
810 | /* There doesn't seem to be a built-in timeout on connection. */ | |
811 | ||
812 | DEBUG(D_tls) debug_printf("Calling SSL_connect\n"); | |
813 | sigalrm_seen = FALSE; | |
814 | alarm(timeout); | |
815 | rc = SSL_connect(ssl); | |
816 | alarm(0); | |
817 | ||
818 | if (rc <= 0) | |
7199e1ee | 819 | return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL); |
059ec3d9 PH |
820 | |
821 | DEBUG(D_tls) debug_printf("SSL_connect succeeded\n"); | |
822 | ||
823 | server_cert = SSL_get_peer_certificate (ssl); | |
824 | tls_peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert), | |
825 | CS txt, sizeof(txt)); | |
826 | tls_peerdn = txt; | |
827 | ||
828 | construct_cipher_name(ssl); /* Sets tls_cipher */ | |
829 | ||
830 | tls_active = fd; | |
831 | return OK; | |
832 | } | |
833 | ||
834 | ||
835 | ||
836 | ||
837 | ||
838 | /************************************************* | |
839 | * TLS version of getc * | |
840 | *************************************************/ | |
841 | ||
842 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, | |
843 | it refills the buffer via the SSL reading function. | |
844 | ||
845 | Arguments: none | |
846 | Returns: the next character or EOF | |
847 | */ | |
848 | ||
849 | int | |
850 | tls_getc(void) | |
851 | { | |
852 | if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) | |
853 | { | |
854 | int error; | |
855 | int inbytes; | |
856 | ||
857 | DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl, | |
858 | (long)ssl_xfer_buffer, ssl_xfer_buffer_size); | |
859 | ||
860 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
861 | inbytes = SSL_read(ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size); | |
862 | error = SSL_get_error(ssl, inbytes); | |
863 | alarm(0); | |
864 | ||
865 | /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been | |
866 | closed down, not that the socket itself has been closed down. Revert to | |
867 | non-SSL handling. */ | |
868 | ||
869 | if (error == SSL_ERROR_ZERO_RETURN) | |
870 | { | |
871 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); | |
872 | ||
873 | receive_getc = smtp_getc; | |
874 | receive_ungetc = smtp_ungetc; | |
875 | receive_feof = smtp_feof; | |
876 | receive_ferror = smtp_ferror; | |
58eb016e | 877 | receive_smtp_buffered = smtp_buffered; |
059ec3d9 PH |
878 | |
879 | SSL_free(ssl); | |
880 | ssl = NULL; | |
881 | tls_active = -1; | |
882 | tls_cipher = NULL; | |
883 | tls_peerdn = NULL; | |
884 | ||
885 | return smtp_getc(); | |
886 | } | |
887 | ||
888 | /* Handle genuine errors */ | |
889 | ||
890 | else if (error != SSL_ERROR_NONE) | |
891 | { | |
892 | DEBUG(D_tls) debug_printf("Got SSL error %d\n", error); | |
893 | ssl_xfer_error = 1; | |
894 | return EOF; | |
895 | } | |
80a47a2c TK |
896 | #ifndef DISABLE_DKIM |
897 | dkim_exim_verify_feed(ssl_xfer_buffer, inbytes); | |
898 | #endif | |
059ec3d9 PH |
899 | ssl_xfer_buffer_hwm = inbytes; |
900 | ssl_xfer_buffer_lwm = 0; | |
901 | } | |
902 | ||
903 | /* Something in the buffer; return next uschar */ | |
904 | ||
905 | return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; | |
906 | } | |
907 | ||
908 | ||
909 | ||
910 | /************************************************* | |
911 | * Read bytes from TLS channel * | |
912 | *************************************************/ | |
913 | ||
914 | /* | |
915 | Arguments: | |
916 | buff buffer of data | |
917 | len size of buffer | |
918 | ||
919 | Returns: the number of bytes read | |
920 | -1 after a failed read | |
921 | */ | |
922 | ||
923 | int | |
924 | tls_read(uschar *buff, size_t len) | |
925 | { | |
926 | int inbytes; | |
927 | int error; | |
928 | ||
929 | DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl, | |
930 | (long)buff, (unsigned int)len); | |
931 | ||
932 | inbytes = SSL_read(ssl, CS buff, len); | |
933 | error = SSL_get_error(ssl, inbytes); | |
934 | ||
935 | if (error == SSL_ERROR_ZERO_RETURN) | |
936 | { | |
937 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); | |
938 | return -1; | |
939 | } | |
940 | else if (error != SSL_ERROR_NONE) | |
941 | { | |
942 | return -1; | |
943 | } | |
944 | ||
945 | return inbytes; | |
946 | } | |
947 | ||
948 | ||
949 | ||
950 | ||
951 | ||
952 | /************************************************* | |
953 | * Write bytes down TLS channel * | |
954 | *************************************************/ | |
955 | ||
956 | /* | |
957 | Arguments: | |
958 | buff buffer of data | |
959 | len number of bytes | |
960 | ||
961 | Returns: the number of bytes after a successful write, | |
962 | -1 after a failed write | |
963 | */ | |
964 | ||
965 | int | |
966 | tls_write(const uschar *buff, size_t len) | |
967 | { | |
968 | int outbytes; | |
969 | int error; | |
970 | int left = len; | |
971 | ||
972 | DEBUG(D_tls) debug_printf("tls_do_write(%lx, %d)\n", (long)buff, left); | |
973 | while (left > 0) | |
974 | { | |
975 | DEBUG(D_tls) debug_printf("SSL_write(SSL, %lx, %d)\n", (long)buff, left); | |
976 | outbytes = SSL_write(ssl, CS buff, left); | |
977 | error = SSL_get_error(ssl, outbytes); | |
978 | DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error); | |
979 | switch (error) | |
980 | { | |
981 | case SSL_ERROR_SSL: | |
982 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
983 | log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring); | |
984 | return -1; | |
985 | ||
986 | case SSL_ERROR_NONE: | |
987 | left -= outbytes; | |
988 | buff += outbytes; | |
989 | break; | |
990 | ||
991 | case SSL_ERROR_ZERO_RETURN: | |
992 | log_write(0, LOG_MAIN, "SSL channel closed on write"); | |
993 | return -1; | |
994 | ||
995 | default: | |
996 | log_write(0, LOG_MAIN, "SSL_write error %d", error); | |
997 | return -1; | |
998 | } | |
999 | } | |
1000 | return len; | |
1001 | } | |
1002 | ||
1003 | ||
1004 | ||
1005 | /************************************************* | |
1006 | * Close down a TLS session * | |
1007 | *************************************************/ | |
1008 | ||
1009 | /* This is also called from within a delivery subprocess forked from the | |
1010 | daemon, to shut down the TLS library, without actually doing a shutdown (which | |
1011 | would tamper with the SSL session in the parent process). | |
1012 | ||
1013 | Arguments: TRUE if SSL_shutdown is to be called | |
1014 | Returns: nothing | |
1015 | */ | |
1016 | ||
1017 | void | |
1018 | tls_close(BOOL shutdown) | |
1019 | { | |
1020 | if (tls_active < 0) return; /* TLS was not active */ | |
1021 | ||
1022 | if (shutdown) | |
1023 | { | |
1024 | DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n"); | |
1025 | SSL_shutdown(ssl); | |
1026 | } | |
1027 | ||
1028 | SSL_free(ssl); | |
1029 | ssl = NULL; | |
1030 | ||
1031 | tls_active = -1; | |
1032 | } | |
1033 | ||
36f12725 NM |
1034 | |
1035 | ||
1036 | ||
1037 | /************************************************* | |
1038 | * Report the library versions. * | |
1039 | *************************************************/ | |
1040 | ||
1041 | /* There have historically been some issues with binary compatibility in | |
1042 | OpenSSL libraries; if Exim (like many other applications) is built against | |
1043 | one version of OpenSSL but the run-time linker picks up another version, | |
1044 | it can result in serious failures, including crashing with a SIGSEGV. So | |
1045 | report the version found by the compiler and the run-time version. | |
1046 | ||
1047 | Arguments: a FILE* to print the results to | |
1048 | Returns: nothing | |
1049 | */ | |
1050 | ||
1051 | void | |
1052 | tls_version_report(FILE *f) | |
1053 | { | |
1054 | fprintf(f, "OpenSSL compile-time version: %s\n", OPENSSL_VERSION_TEXT); | |
1055 | fprintf(f, "OpenSSL runtime version: %s\n", SSLeay_version(SSLEAY_VERSION)); | |
1056 | } | |
1057 | ||
9e3331ea TK |
1058 | |
1059 | ||
1060 | ||
1061 | /************************************************* | |
1062 | * Pseudo-random number generation * | |
1063 | *************************************************/ | |
1064 | ||
1065 | /* Pseudo-random number generation. The result is not expected to be | |
1066 | cryptographically strong but not so weak that someone will shoot themselves | |
1067 | in the foot using it as a nonce in input in some email header scheme or | |
1068 | whatever weirdness they'll twist this into. The result should handle fork() | |
1069 | and avoid repeating sequences. OpenSSL handles that for us. | |
1070 | ||
1071 | Arguments: | |
1072 | max range maximum | |
1073 | Returns a random number in range [0, max-1] | |
1074 | */ | |
1075 | ||
1076 | int | |
1077 | pseudo_random_number(int max) | |
1078 | { | |
1079 | unsigned int r; | |
1080 | int i, needed_len; | |
1081 | uschar *p; | |
1082 | uschar smallbuf[sizeof(r)]; | |
1083 | ||
1084 | if (max <= 1) | |
1085 | return 0; | |
1086 | ||
1087 | /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */ | |
1088 | if (!RAND_status()) | |
1089 | { | |
1090 | randstuff r; | |
1091 | gettimeofday(&r.tv, NULL); | |
1092 | r.p = getpid(); | |
1093 | ||
1094 | RAND_seed((uschar *)(&r), sizeof(r)); | |
1095 | } | |
1096 | /* We're after pseudo-random, not random; if we still don't have enough data | |
1097 | in the internal PRNG then our options are limited. We could sleep and hope | |
1098 | for entropy to come along (prayer technique) but if the system is so depleted | |
1099 | in the first place then something is likely to just keep taking it. Instead, | |
1100 | we'll just take whatever little bit of pseudo-random we can still manage to | |
1101 | get. */ | |
1102 | ||
1103 | needed_len = sizeof(r); | |
1104 | /* Don't take 8 times more entropy than needed if int is 8 octets and we were | |
1105 | asked for a number less than 10. */ | |
1106 | for (r = max, i = 0; r; ++i) | |
1107 | r >>= 1; | |
1108 | i = (i + 7) / 8; | |
1109 | if (i < needed_len) | |
1110 | needed_len = i; | |
1111 | ||
1112 | /* We do not care if crypto-strong */ | |
1113 | (void) RAND_pseudo_bytes(smallbuf, needed_len); | |
1114 | r = 0; | |
1115 | for (p = smallbuf; needed_len; --needed_len, ++p) | |
1116 | { | |
1117 | r *= 256; | |
1118 | r += *p; | |
1119 | } | |
1120 | ||
1121 | /* We don't particularly care about weighted results; if someone wants | |
1122 | smooth distribution and cares enough then they should submit a patch then. */ | |
1123 | return r % max; | |
1124 | } | |
1125 | ||
059ec3d9 | 1126 | /* End of tls-openssl.c */ |