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2e2a30b4 | 1 | /* $Cambridge: exim/src/src/tls-openssl.c,v 1.5 2005/05/03 14:20:01 ph10 Exp $ */ |
059ec3d9 PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
c988f1f4 | 7 | /* Copyright (c) University of Cambridge 1995 - 2005 */ |
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 | |
65 | ||
66 | Returns: OK/DEFER/FAIL | |
67 | */ | |
68 | ||
69 | static int | |
70 | tls_error(uschar *prefix, host_item *host) | |
71 | { | |
72 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
73 | if (host == NULL) | |
74 | { | |
75 | log_write(0, LOG_MAIN, "TLS error on connection from %s (%s): %s", | |
76 | (sender_fullhost != NULL)? sender_fullhost : US"local process", | |
77 | prefix, ssl_errstring); | |
78 | return DEFER; | |
79 | } | |
80 | else | |
81 | { | |
82 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s", | |
83 | host->name, host->address, prefix, ssl_errstring); | |
84 | return FAIL; | |
85 | } | |
86 | } | |
87 | ||
88 | ||
89 | ||
90 | /************************************************* | |
91 | * Callback to generate RSA key * | |
92 | *************************************************/ | |
93 | ||
94 | /* | |
95 | Arguments: | |
96 | s SSL connection | |
97 | export not used | |
98 | keylength keylength | |
99 | ||
100 | Returns: pointer to generated key | |
101 | */ | |
102 | ||
103 | static RSA * | |
104 | rsa_callback(SSL *s, int export, int keylength) | |
105 | { | |
106 | RSA *rsa_key; | |
107 | export = export; /* Shut picky compilers up */ | |
108 | DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength); | |
109 | rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL); | |
110 | if (rsa_key == NULL) | |
111 | { | |
112 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
113 | log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s", | |
114 | ssl_errstring); | |
115 | return NULL; | |
116 | } | |
117 | return rsa_key; | |
118 | } | |
119 | ||
120 | ||
121 | ||
122 | ||
123 | /************************************************* | |
124 | * Callback for verification * | |
125 | *************************************************/ | |
126 | ||
127 | /* The SSL library does certificate verification if set up to do so. This | |
128 | callback has the current yes/no state is in "state". If verification succeeded, | |
129 | we set up the tls_peerdn string. If verification failed, what happens depends | |
130 | on whether the client is required to present a verifiable certificate or not. | |
131 | ||
132 | If verification is optional, we change the state to yes, but still log the | |
133 | verification error. For some reason (it really would help to have proper | |
134 | documentation of OpenSSL), this callback function then gets called again, this | |
135 | time with state = 1. In fact, that's useful, because we can set up the peerdn | |
136 | value, but we must take care not to set the private verified flag on the second | |
137 | time through. | |
138 | ||
139 | Note: this function is not called if the client fails to present a certificate | |
140 | when asked. We get here only if a certificate has been received. Handling of | |
141 | optional verification for this case is done when requesting SSL to verify, by | |
142 | setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case. | |
143 | ||
144 | Arguments: | |
145 | state current yes/no state as 1/0 | |
146 | x509ctx certificate information. | |
147 | ||
148 | Returns: 1 if verified, 0 if not | |
149 | */ | |
150 | ||
151 | static int | |
152 | verify_callback(int state, X509_STORE_CTX *x509ctx) | |
153 | { | |
154 | static uschar txt[256]; | |
155 | ||
156 | X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert), | |
157 | CS txt, sizeof(txt)); | |
158 | ||
159 | if (state == 0) | |
160 | { | |
161 | log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s", | |
162 | x509ctx->error_depth, | |
163 | X509_verify_cert_error_string(x509ctx->error), | |
164 | txt); | |
165 | tls_certificate_verified = FALSE; | |
166 | verify_callback_called = TRUE; | |
167 | if (!verify_optional) return 0; /* reject */ | |
168 | DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in " | |
169 | "tls_try_verify_hosts)\n"); | |
170 | return 1; /* accept */ | |
171 | } | |
172 | ||
173 | if (x509ctx->error_depth != 0) | |
174 | { | |
175 | DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n", | |
176 | x509ctx->error_depth, txt); | |
177 | } | |
178 | else | |
179 | { | |
180 | DEBUG(D_tls) debug_printf("SSL%s peer: %s\n", | |
181 | verify_callback_called? "" : " authenticated", txt); | |
182 | tls_peerdn = txt; | |
183 | } | |
184 | ||
059ec3d9 PH |
185 | if (!verify_callback_called) tls_certificate_verified = TRUE; |
186 | verify_callback_called = TRUE; | |
187 | ||
188 | return 1; /* accept */ | |
189 | } | |
190 | ||
191 | ||
192 | ||
193 | /************************************************* | |
194 | * Information callback * | |
195 | *************************************************/ | |
196 | ||
197 | /* The SSL library functions call this from time to time to indicate what they | |
198 | are doing. We copy the string to the debugging output when the level is high | |
199 | enough. | |
200 | ||
201 | Arguments: | |
202 | s the SSL connection | |
203 | where | |
204 | ret | |
205 | ||
206 | Returns: nothing | |
207 | */ | |
208 | ||
209 | static void | |
210 | info_callback(SSL *s, int where, int ret) | |
211 | { | |
212 | where = where; | |
213 | ret = ret; | |
214 | DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s)); | |
215 | } | |
216 | ||
217 | ||
218 | ||
219 | /************************************************* | |
220 | * Initialize for DH * | |
221 | *************************************************/ | |
222 | ||
223 | /* If dhparam is set, expand it, and load up the parameters for DH encryption. | |
224 | ||
225 | Arguments: | |
226 | dhparam DH parameter file | |
227 | ||
228 | Returns: TRUE if OK (nothing to set up, or setup worked) | |
229 | */ | |
230 | ||
231 | static BOOL | |
232 | init_dh(uschar *dhparam) | |
233 | { | |
234 | BOOL yield = TRUE; | |
235 | BIO *bio; | |
236 | DH *dh; | |
237 | uschar *dhexpanded; | |
238 | ||
239 | if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded)) | |
240 | return FALSE; | |
241 | ||
242 | if (dhexpanded == NULL) return TRUE; | |
243 | ||
244 | if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL) | |
245 | { | |
246 | log_write(0, LOG_MAIN, "DH: could not read %s: %s", dhexpanded, | |
247 | strerror(errno)); | |
248 | yield = FALSE; | |
249 | } | |
250 | else | |
251 | { | |
252 | if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL) | |
253 | { | |
254 | log_write(0, LOG_MAIN, "DH: could not load params from %s", | |
255 | dhexpanded); | |
256 | yield = FALSE; | |
257 | } | |
258 | else | |
259 | { | |
260 | SSL_CTX_set_tmp_dh(ctx, dh); | |
261 | DEBUG(D_tls) | |
262 | debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n", | |
263 | dhexpanded, 8*DH_size(dh)); | |
264 | DH_free(dh); | |
265 | } | |
266 | BIO_free(bio); | |
267 | } | |
268 | ||
269 | return yield; | |
270 | } | |
271 | ||
272 | ||
273 | ||
274 | ||
275 | /************************************************* | |
276 | * Initialize for TLS * | |
277 | *************************************************/ | |
278 | ||
279 | /* Called from both server and client code, to do preliminary initialization of | |
280 | the library. | |
281 | ||
282 | Arguments: | |
283 | host connected host, if client; NULL if server | |
284 | dhparam DH parameter file | |
285 | certificate certificate file | |
286 | privatekey private key | |
287 | addr address if client; NULL if server (for some randomness) | |
288 | ||
289 | Returns: OK/DEFER/FAIL | |
290 | */ | |
291 | ||
292 | static int | |
293 | tls_init(host_item *host, uschar *dhparam, uschar *certificate, uschar *privatekey, | |
294 | address_item *addr) | |
295 | { | |
296 | SSL_load_error_strings(); /* basic set up */ | |
297 | OpenSSL_add_ssl_algorithms(); | |
298 | ||
299 | /* Create a context */ | |
300 | ||
301 | ctx = SSL_CTX_new((host == NULL)? | |
302 | SSLv23_server_method() : SSLv23_client_method()); | |
303 | ||
304 | if (ctx == NULL) return tls_error(US"SSL_CTX_new", host); | |
305 | ||
306 | /* It turns out that we need to seed the random number generator this early in | |
307 | order to get the full complement of ciphers to work. It took me roughly a day | |
308 | of work to discover this by experiment. | |
309 | ||
310 | On systems that have /dev/urandom, SSL may automatically seed itself from | |
311 | there. Otherwise, we have to make something up as best we can. Double check | |
312 | afterwards. */ | |
313 | ||
314 | if (!RAND_status()) | |
315 | { | |
316 | randstuff r; | |
317 | r.t = time(NULL); | |
318 | r.p = getpid(); | |
319 | ||
320 | RAND_seed((uschar *)(&r), sizeof(r)); | |
321 | RAND_seed((uschar *)big_buffer, big_buffer_size); | |
322 | if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr)); | |
323 | ||
324 | if (!RAND_status()) | |
325 | { | |
326 | if (host == NULL) | |
327 | { | |
328 | log_write(0, LOG_MAIN, "TLS error on connection from %s: " | |
329 | "unable to seed random number generator", | |
330 | (sender_fullhost != NULL)? sender_fullhost : US"local process"); | |
331 | return DEFER; | |
332 | } | |
333 | else | |
334 | { | |
335 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s]: " | |
336 | "unable to seed random number generator", | |
337 | host->name, host->address); | |
338 | return FAIL; | |
339 | } | |
340 | } | |
341 | } | |
342 | ||
343 | /* Set up the information callback, which outputs if debugging is at a suitable | |
344 | level. */ | |
345 | ||
346 | if (!(SSL_CTX_set_info_callback(ctx, (void (*)())info_callback))) | |
347 | return tls_error(US"SSL_CTX_set_info_callback", host); | |
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))) | |
362 | return tls_error(US"SSL_CTX_set_option", host); | |
363 | #endif | |
364 | ||
365 | /* Initialize with DH parameters if supplied */ | |
366 | ||
367 | if (!init_dh(dhparam)) return DEFER; | |
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 PH |
381 | return tls_error(string_sprintf( |
382 | "SSL_CTX_use_certificate_chain_file file=%s", expanded), host); | |
059ec3d9 PH |
383 | } |
384 | ||
385 | if (privatekey != NULL && | |
386 | !expand_check(privatekey, US"tls_privatekey", &expanded)) | |
387 | return DEFER; | |
388 | ||
389 | if (expanded != NULL) | |
390 | { | |
391 | DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded); | |
392 | if (!SSL_CTX_use_PrivateKey_file(ctx, CS expanded, SSL_FILETYPE_PEM)) | |
d6453af2 PH |
393 | return tls_error(string_sprintf( |
394 | "SSL_CTX_use_PrivateKey_file file=%s", expanded), host); | |
059ec3d9 PH |
395 | } |
396 | } | |
397 | ||
398 | /* Set up the RSA callback */ | |
399 | ||
400 | SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback); | |
401 | ||
402 | /* Finally, set the timeout, and we are done */ | |
403 | ||
404 | SSL_CTX_set_timeout(ctx, ssl_session_timeout); | |
405 | DEBUG(D_tls) debug_printf("Initialized TLS\n"); | |
406 | return OK; | |
407 | } | |
408 | ||
409 | ||
410 | ||
411 | ||
412 | /************************************************* | |
413 | * Get name of cipher in use * | |
414 | *************************************************/ | |
415 | ||
416 | /* The answer is left in a static buffer, and tls_cipher is set to point | |
417 | to it. | |
418 | ||
419 | Argument: pointer to an SSL structure for the connection | |
420 | Returns: nothing | |
421 | */ | |
422 | ||
423 | static void | |
424 | construct_cipher_name(SSL *ssl) | |
425 | { | |
426 | static uschar cipherbuf[256]; | |
427 | SSL_CIPHER *c; | |
428 | uschar *ver; | |
429 | int bits; | |
430 | ||
431 | switch (ssl->session->ssl_version) | |
432 | { | |
433 | case SSL2_VERSION: | |
434 | ver = US"SSLv2"; | |
435 | break; | |
436 | ||
437 | case SSL3_VERSION: | |
438 | ver = US"SSLv3"; | |
439 | break; | |
440 | ||
441 | case TLS1_VERSION: | |
442 | ver = US"TLSv1"; | |
443 | break; | |
444 | ||
445 | default: | |
446 | ver = US"UNKNOWN"; | |
447 | } | |
448 | ||
449 | c = SSL_get_current_cipher(ssl); | |
450 | SSL_CIPHER_get_bits(c, &bits); | |
451 | ||
452 | string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver, | |
453 | SSL_CIPHER_get_name(c), bits); | |
454 | tls_cipher = cipherbuf; | |
455 | ||
456 | DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf); | |
457 | } | |
458 | ||
459 | ||
460 | ||
461 | ||
462 | ||
463 | /************************************************* | |
464 | * Set up for verifying certificates * | |
465 | *************************************************/ | |
466 | ||
467 | /* Called by both client and server startup | |
468 | ||
469 | Arguments: | |
470 | certs certs file or NULL | |
471 | crl CRL file or NULL | |
472 | host NULL in a server; the remote host in a client | |
473 | optional TRUE if called from a server for a host in tls_try_verify_hosts; | |
474 | otherwise passed as FALSE | |
475 | ||
476 | Returns: OK/DEFER/FAIL | |
477 | */ | |
478 | ||
479 | static int | |
480 | setup_certs(uschar *certs, uschar *crl, host_item *host, BOOL optional) | |
481 | { | |
482 | uschar *expcerts, *expcrl; | |
483 | ||
484 | if (!expand_check(certs, US"tls_verify_certificates", &expcerts)) | |
485 | return DEFER; | |
486 | ||
487 | if (expcerts != NULL) | |
488 | { | |
489 | struct stat statbuf; | |
490 | if (!SSL_CTX_set_default_verify_paths(ctx)) | |
491 | return tls_error(US"SSL_CTX_set_default_verify_paths", host); | |
492 | ||
493 | if (Ustat(expcerts, &statbuf) < 0) | |
494 | { | |
495 | log_write(0, LOG_MAIN|LOG_PANIC, | |
496 | "failed to stat %s for certificates", expcerts); | |
497 | return DEFER; | |
498 | } | |
499 | else | |
500 | { | |
501 | uschar *file, *dir; | |
502 | if ((statbuf.st_mode & S_IFMT) == S_IFDIR) | |
503 | { file = NULL; dir = expcerts; } | |
504 | else | |
505 | { file = expcerts; dir = NULL; } | |
506 | ||
507 | /* If a certificate file is empty, the next function fails with an | |
508 | unhelpful error message. If we skip it, we get the correct behaviour (no | |
509 | certificates are recognized, but the error message is still misleading (it | |
510 | says no certificate was supplied.) But this is better. */ | |
511 | ||
512 | if ((file == NULL || statbuf.st_size > 0) && | |
513 | !SSL_CTX_load_verify_locations(ctx, CS file, CS dir)) | |
514 | return tls_error(US"SSL_CTX_load_verify_locations", host); | |
515 | ||
516 | if (file != NULL) | |
517 | { | |
518 | SSL_CTX_set_client_CA_list(ctx, SSL_load_client_CA_file(CS file)); | |
519 | } | |
520 | } | |
521 | ||
522 | /* Handle a certificate revocation list. */ | |
523 | ||
524 | #if OPENSSL_VERSION_NUMBER > 0x00907000L | |
525 | ||
8b417f2c PH |
526 | /* This bit of code is now the version supplied by Lars Mainka. (I have |
527 | * merely reformatted it into the Exim code style.) | |
528 | ||
529 | * "From here I changed the code to add support for multiple crl's | |
530 | * in pem format in one file or to support hashed directory entries in | |
531 | * pem format instead of a file. This method now uses the library function | |
532 | * X509_STORE_load_locations to add the CRL location to the SSL context. | |
533 | * OpenSSL will then handle the verify against CA certs and CRLs by | |
534 | * itself in the verify callback." */ | |
535 | ||
059ec3d9 PH |
536 | if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER; |
537 | if (expcrl != NULL && *expcrl != 0) | |
538 | { | |
8b417f2c PH |
539 | struct stat statbufcrl; |
540 | if (Ustat(expcrl, &statbufcrl) < 0) | |
541 | { | |
542 | log_write(0, LOG_MAIN|LOG_PANIC, | |
543 | "failed to stat %s for certificates revocation lists", expcrl); | |
544 | return DEFER; | |
545 | } | |
546 | else | |
059ec3d9 | 547 | { |
8b417f2c PH |
548 | /* is it a file or directory? */ |
549 | uschar *file, *dir; | |
550 | X509_STORE *cvstore = SSL_CTX_get_cert_store(ctx); | |
551 | if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR) | |
059ec3d9 | 552 | { |
8b417f2c PH |
553 | file = NULL; |
554 | dir = expcrl; | |
555 | DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir); | |
059ec3d9 PH |
556 | } |
557 | else | |
558 | { | |
8b417f2c PH |
559 | file = expcrl; |
560 | dir = NULL; | |
561 | DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file); | |
059ec3d9 | 562 | } |
8b417f2c PH |
563 | if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0) |
564 | return tls_error(US"X509_STORE_load_locations", host); | |
565 | ||
566 | /* setting the flags to check against the complete crl chain */ | |
567 | ||
568 | X509_STORE_set_flags(cvstore, | |
569 | X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL); | |
059ec3d9 | 570 | } |
059ec3d9 PH |
571 | } |
572 | ||
573 | #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */ | |
574 | ||
575 | /* If verification is optional, don't fail if no certificate */ | |
576 | ||
577 | SSL_CTX_set_verify(ctx, | |
578 | SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT), | |
579 | verify_callback); | |
580 | } | |
581 | ||
582 | return OK; | |
583 | } | |
584 | ||
585 | ||
586 | ||
587 | /************************************************* | |
588 | * Start a TLS session in a server * | |
589 | *************************************************/ | |
590 | ||
591 | /* This is called when Exim is running as a server, after having received | |
592 | the STARTTLS command. It must respond to that command, and then negotiate | |
593 | a TLS session. | |
594 | ||
595 | Arguments: | |
596 | require_ciphers allowed ciphers | |
597 | ||
598 | Returns: OK on success | |
599 | DEFER for errors before the start of the negotiation | |
600 | FAIL for errors during the negotation; the server can't | |
601 | continue running. | |
602 | */ | |
603 | ||
604 | int | |
605 | tls_server_start(uschar *require_ciphers) | |
606 | { | |
607 | int rc; | |
608 | uschar *expciphers; | |
609 | ||
610 | /* Check for previous activation */ | |
611 | ||
612 | if (tls_active >= 0) | |
613 | { | |
614 | log_write(0, LOG_MAIN, "STARTTLS received in already encrypted " | |
615 | "connection from %s", | |
616 | (sender_fullhost != NULL)? sender_fullhost : US"local process"); | |
617 | smtp_printf("554 Already in TLS\r\n"); | |
618 | return FAIL; | |
619 | } | |
620 | ||
621 | /* Initialize the SSL library. If it fails, it will already have logged | |
622 | the error. */ | |
623 | ||
624 | rc = tls_init(NULL, tls_dhparam, tls_certificate, tls_privatekey, NULL); | |
625 | if (rc != OK) return rc; | |
626 | ||
627 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) | |
628 | return FAIL; | |
629 | ||
630 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they | |
631 | are separated by underscores. So that I can use either form in my tests, and | |
632 | also for general convenience, we turn underscores into hyphens here. */ | |
633 | ||
634 | if (expciphers != NULL) | |
635 | { | |
636 | uschar *s = expciphers; | |
637 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } | |
638 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); | |
639 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) | |
640 | return tls_error(US"SSL_CTX_set_cipher_list", NULL); | |
641 | } | |
642 | ||
643 | /* If this is a host for which certificate verification is mandatory or | |
644 | optional, set up appropriately. */ | |
645 | ||
646 | tls_certificate_verified = FALSE; | |
647 | verify_callback_called = FALSE; | |
648 | ||
649 | if (verify_check_host(&tls_verify_hosts) == OK) | |
650 | { | |
651 | rc = setup_certs(tls_verify_certificates, tls_crl, NULL, FALSE); | |
652 | if (rc != OK) return rc; | |
653 | verify_optional = FALSE; | |
654 | } | |
655 | else if (verify_check_host(&tls_try_verify_hosts) == OK) | |
656 | { | |
657 | rc = setup_certs(tls_verify_certificates, tls_crl, NULL, TRUE); | |
658 | if (rc != OK) return rc; | |
659 | verify_optional = TRUE; | |
660 | } | |
661 | ||
662 | /* Prepare for new connection */ | |
663 | ||
664 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", NULL); | |
665 | SSL_clear(ssl); | |
666 | ||
667 | /* Set context and tell client to go ahead, except in the case of TLS startup | |
668 | on connection, where outputting anything now upsets the clients and tends to | |
669 | make them disconnect. We need to have an explicit fflush() here, to force out | |
670 | the response. Other smtp_printf() calls do not need it, because in non-TLS | |
671 | mode, the fflush() happens when smtp_getc() is called. */ | |
672 | ||
673 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); | |
674 | if (!tls_on_connect) | |
675 | { | |
676 | smtp_printf("220 TLS go ahead\r\n"); | |
677 | fflush(smtp_out); | |
678 | } | |
679 | ||
680 | /* Now negotiate the TLS session. We put our own timer on it, since it seems | |
681 | that the OpenSSL library doesn't. */ | |
682 | ||
683 | SSL_set_fd(ssl, fileno(smtp_out)); | |
684 | SSL_set_accept_state(ssl); | |
685 | ||
686 | DEBUG(D_tls) debug_printf("Calling SSL_accept\n"); | |
687 | ||
688 | sigalrm_seen = FALSE; | |
689 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
690 | rc = SSL_accept(ssl); | |
691 | alarm(0); | |
692 | ||
693 | if (rc <= 0) | |
694 | { | |
695 | if (sigalrm_seen) Ustrcpy(ssl_errstring, "timed out"); | |
696 | else ERR_error_string(ERR_get_error(), ssl_errstring); | |
697 | log_write(0, LOG_MAIN, "TLS error on connection from %s (SSL_accept): %s", | |
698 | (sender_fullhost != NULL)? sender_fullhost : US"local process", | |
699 | ssl_errstring); | |
700 | return FAIL; | |
701 | } | |
702 | ||
703 | DEBUG(D_tls) debug_printf("SSL_accept was successful\n"); | |
704 | ||
705 | /* TLS has been set up. Adjust the input functions to read via TLS, | |
706 | and initialize things. */ | |
707 | ||
708 | construct_cipher_name(ssl); | |
709 | ||
710 | DEBUG(D_tls) | |
711 | { | |
712 | uschar buf[2048]; | |
713 | if (SSL_get_shared_ciphers(ssl, CS buf, sizeof(buf)) != NULL) | |
714 | debug_printf("Shared ciphers: %s\n", buf); | |
715 | } | |
716 | ||
717 | ||
718 | ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); | |
719 | ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; | |
720 | ssl_xfer_eof = ssl_xfer_error = 0; | |
721 | ||
722 | receive_getc = tls_getc; | |
723 | receive_ungetc = tls_ungetc; | |
724 | receive_feof = tls_feof; | |
725 | receive_ferror = tls_ferror; | |
726 | ||
727 | tls_active = fileno(smtp_out); | |
728 | return OK; | |
729 | } | |
730 | ||
731 | ||
732 | ||
733 | ||
734 | ||
735 | /************************************************* | |
736 | * Start a TLS session in a client * | |
737 | *************************************************/ | |
738 | ||
739 | /* Called from the smtp transport after STARTTLS has been accepted. | |
740 | ||
741 | Argument: | |
742 | fd the fd of the connection | |
743 | host connected host (for messages) | |
744 | dhparam DH parameter file | |
745 | certificate certificate file | |
746 | privatekey private key file | |
747 | verify_certs file for certificate verify | |
748 | crl file containing CRL | |
749 | require_ciphers list of allowed ciphers | |
750 | ||
751 | Returns: OK on success | |
752 | FAIL otherwise - note that tls_error() will not give DEFER | |
753 | because this is not a server | |
754 | */ | |
755 | ||
756 | int | |
757 | tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam, | |
758 | uschar *certificate, uschar *privatekey, uschar *verify_certs, uschar *crl, | |
759 | uschar *require_ciphers, int timeout) | |
760 | { | |
761 | static uschar txt[256]; | |
762 | uschar *expciphers; | |
763 | X509* server_cert; | |
764 | int rc; | |
765 | ||
766 | rc = tls_init(host, dhparam, certificate, privatekey, addr); | |
767 | if (rc != OK) return rc; | |
768 | ||
769 | tls_certificate_verified = FALSE; | |
770 | verify_callback_called = FALSE; | |
771 | ||
772 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) | |
773 | return FAIL; | |
774 | ||
775 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they | |
776 | are separated by underscores. So that I can use either form in my tests, and | |
777 | also for general convenience, we turn underscores into hyphens here. */ | |
778 | ||
779 | if (expciphers != NULL) | |
780 | { | |
781 | uschar *s = expciphers; | |
782 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } | |
783 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); | |
784 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) | |
785 | return tls_error(US"SSL_CTX_set_cipher_list", host); | |
786 | } | |
787 | ||
788 | rc = setup_certs(verify_certs, crl, host, FALSE); | |
789 | if (rc != OK) return rc; | |
790 | ||
791 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", host); | |
792 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); | |
793 | SSL_set_fd(ssl, fd); | |
794 | SSL_set_connect_state(ssl); | |
795 | ||
796 | /* There doesn't seem to be a built-in timeout on connection. */ | |
797 | ||
798 | DEBUG(D_tls) debug_printf("Calling SSL_connect\n"); | |
799 | sigalrm_seen = FALSE; | |
800 | alarm(timeout); | |
801 | rc = SSL_connect(ssl); | |
802 | alarm(0); | |
803 | ||
804 | if (rc <= 0) | |
805 | { | |
806 | if (sigalrm_seen) | |
807 | { | |
808 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s]: " | |
809 | "SSL_connect timed out", host->name, host->address); | |
810 | return FAIL; | |
811 | } | |
812 | else return tls_error(US"SSL_connect", host); | |
813 | } | |
814 | ||
815 | DEBUG(D_tls) debug_printf("SSL_connect succeeded\n"); | |
816 | ||
817 | server_cert = SSL_get_peer_certificate (ssl); | |
818 | tls_peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert), | |
819 | CS txt, sizeof(txt)); | |
820 | tls_peerdn = txt; | |
821 | ||
822 | construct_cipher_name(ssl); /* Sets tls_cipher */ | |
823 | ||
824 | tls_active = fd; | |
825 | return OK; | |
826 | } | |
827 | ||
828 | ||
829 | ||
830 | ||
831 | ||
832 | /************************************************* | |
833 | * TLS version of getc * | |
834 | *************************************************/ | |
835 | ||
836 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, | |
837 | it refills the buffer via the SSL reading function. | |
838 | ||
839 | Arguments: none | |
840 | Returns: the next character or EOF | |
841 | */ | |
842 | ||
843 | int | |
844 | tls_getc(void) | |
845 | { | |
846 | if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) | |
847 | { | |
848 | int error; | |
849 | int inbytes; | |
850 | ||
851 | DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl, | |
852 | (long)ssl_xfer_buffer, ssl_xfer_buffer_size); | |
853 | ||
854 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); | |
855 | inbytes = SSL_read(ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size); | |
856 | error = SSL_get_error(ssl, inbytes); | |
857 | alarm(0); | |
858 | ||
859 | /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been | |
860 | closed down, not that the socket itself has been closed down. Revert to | |
861 | non-SSL handling. */ | |
862 | ||
863 | if (error == SSL_ERROR_ZERO_RETURN) | |
864 | { | |
865 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); | |
866 | ||
867 | receive_getc = smtp_getc; | |
868 | receive_ungetc = smtp_ungetc; | |
869 | receive_feof = smtp_feof; | |
870 | receive_ferror = smtp_ferror; | |
871 | ||
872 | SSL_free(ssl); | |
873 | ssl = NULL; | |
874 | tls_active = -1; | |
875 | tls_cipher = NULL; | |
876 | tls_peerdn = NULL; | |
877 | ||
878 | return smtp_getc(); | |
879 | } | |
880 | ||
881 | /* Handle genuine errors */ | |
882 | ||
883 | else if (error != SSL_ERROR_NONE) | |
884 | { | |
885 | DEBUG(D_tls) debug_printf("Got SSL error %d\n", error); | |
886 | ssl_xfer_error = 1; | |
887 | return EOF; | |
888 | } | |
889 | ||
890 | ssl_xfer_buffer_hwm = inbytes; | |
891 | ssl_xfer_buffer_lwm = 0; | |
892 | } | |
893 | ||
894 | /* Something in the buffer; return next uschar */ | |
895 | ||
896 | return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; | |
897 | } | |
898 | ||
899 | ||
900 | ||
901 | /************************************************* | |
902 | * Read bytes from TLS channel * | |
903 | *************************************************/ | |
904 | ||
905 | /* | |
906 | Arguments: | |
907 | buff buffer of data | |
908 | len size of buffer | |
909 | ||
910 | Returns: the number of bytes read | |
911 | -1 after a failed read | |
912 | */ | |
913 | ||
914 | int | |
915 | tls_read(uschar *buff, size_t len) | |
916 | { | |
917 | int inbytes; | |
918 | int error; | |
919 | ||
920 | DEBUG(D_tls) debug_printf("Calling SSL_read(%lx, %lx, %u)\n", (long)ssl, | |
921 | (long)buff, (unsigned int)len); | |
922 | ||
923 | inbytes = SSL_read(ssl, CS buff, len); | |
924 | error = SSL_get_error(ssl, inbytes); | |
925 | ||
926 | if (error == SSL_ERROR_ZERO_RETURN) | |
927 | { | |
928 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); | |
929 | return -1; | |
930 | } | |
931 | else if (error != SSL_ERROR_NONE) | |
932 | { | |
933 | return -1; | |
934 | } | |
935 | ||
936 | return inbytes; | |
937 | } | |
938 | ||
939 | ||
940 | ||
941 | ||
942 | ||
943 | /************************************************* | |
944 | * Write bytes down TLS channel * | |
945 | *************************************************/ | |
946 | ||
947 | /* | |
948 | Arguments: | |
949 | buff buffer of data | |
950 | len number of bytes | |
951 | ||
952 | Returns: the number of bytes after a successful write, | |
953 | -1 after a failed write | |
954 | */ | |
955 | ||
956 | int | |
957 | tls_write(const uschar *buff, size_t len) | |
958 | { | |
959 | int outbytes; | |
960 | int error; | |
961 | int left = len; | |
962 | ||
963 | DEBUG(D_tls) debug_printf("tls_do_write(%lx, %d)\n", (long)buff, left); | |
964 | while (left > 0) | |
965 | { | |
966 | DEBUG(D_tls) debug_printf("SSL_write(SSL, %lx, %d)\n", (long)buff, left); | |
967 | outbytes = SSL_write(ssl, CS buff, left); | |
968 | error = SSL_get_error(ssl, outbytes); | |
969 | DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error); | |
970 | switch (error) | |
971 | { | |
972 | case SSL_ERROR_SSL: | |
973 | ERR_error_string(ERR_get_error(), ssl_errstring); | |
974 | log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring); | |
975 | return -1; | |
976 | ||
977 | case SSL_ERROR_NONE: | |
978 | left -= outbytes; | |
979 | buff += outbytes; | |
980 | break; | |
981 | ||
982 | case SSL_ERROR_ZERO_RETURN: | |
983 | log_write(0, LOG_MAIN, "SSL channel closed on write"); | |
984 | return -1; | |
985 | ||
986 | default: | |
987 | log_write(0, LOG_MAIN, "SSL_write error %d", error); | |
988 | return -1; | |
989 | } | |
990 | } | |
991 | return len; | |
992 | } | |
993 | ||
994 | ||
995 | ||
996 | /************************************************* | |
997 | * Close down a TLS session * | |
998 | *************************************************/ | |
999 | ||
1000 | /* This is also called from within a delivery subprocess forked from the | |
1001 | daemon, to shut down the TLS library, without actually doing a shutdown (which | |
1002 | would tamper with the SSL session in the parent process). | |
1003 | ||
1004 | Arguments: TRUE if SSL_shutdown is to be called | |
1005 | Returns: nothing | |
1006 | */ | |
1007 | ||
1008 | void | |
1009 | tls_close(BOOL shutdown) | |
1010 | { | |
1011 | if (tls_active < 0) return; /* TLS was not active */ | |
1012 | ||
1013 | if (shutdown) | |
1014 | { | |
1015 | DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n"); | |
1016 | SSL_shutdown(ssl); | |
1017 | } | |
1018 | ||
1019 | SSL_free(ssl); | |
1020 | ssl = NULL; | |
1021 | ||
1022 | tls_active = -1; | |
1023 | } | |
1024 | ||
1025 | /* End of tls-openssl.c */ |