1 /* $NetBSD: smtp_sasl_glue.c,v 1.3 2020/03/18 19:05:20 christos Exp $ */
2
3 /*++
4 /* NAME
5 /* smtp_sasl_glue 3
6 /* SUMMARY
7 /* Postfix SASL interface for SMTP client
8 /* SYNOPSIS
9 /* #include smtp_sasl.h
10 /*
11 /* void smtp_sasl_initialize()
12 /*
13 /* void smtp_sasl_connect(session)
14 /* SMTP_SESSION *session;
15 /*
16 /* void smtp_sasl_start(session, sasl_opts_name, sasl_opts_val)
17 /* SMTP_SESSION *session;
18 /*
19 /* int smtp_sasl_passwd_lookup(session)
20 /* SMTP_SESSION *session;
21 /*
22 /* int smtp_sasl_authenticate(session, why)
23 /* SMTP_SESSION *session;
24 /* DSN_BUF *why;
25 /*
26 /* void smtp_sasl_cleanup(session)
27 /* SMTP_SESSION *session;
28 /*
29 /* void smtp_sasl_passivate(session, buf)
30 /* SMTP_SESSION *session;
31 /* VSTRING *buf;
32 /*
33 /* int smtp_sasl_activate(session, buf)
34 /* SMTP_SESSION *session;
35 /* char *buf;
36 /* DESCRIPTION
37 /* smtp_sasl_initialize() initializes the SASL library. This
38 /* routine must be called once at process startup, before any
39 /* chroot operations.
40 /*
41 /* smtp_sasl_connect() performs per-session initialization. This
42 /* routine must be called once at the start of each connection.
43 /*
44 /* smtp_sasl_start() performs per-session initialization. This
45 /* routine must be called once per session before doing any SASL
46 /* authentication. The sasl_opts_name and sasl_opts_val parameters are
47 /* the postfix configuration parameters setting the security
48 /* policy of the SASL authentication.
49 /*
50 /* smtp_sasl_passwd_lookup() looks up the username/password
51 /* for the current SMTP server. The result is zero in case
52 /* of failure, a long jump in case of error.
53 /*
54 /* smtp_sasl_authenticate() implements the SASL authentication
55 /* dialog. The result is < 0 in case of protocol failure, zero in
56 /* case of unsuccessful authentication, > 0 in case of success.
57 /* The why argument is updated with a reason for failure.
58 /* This routine must be called only when smtp_sasl_passwd_lookup()
59 /* succeeds.
60 /*
61 /* smtp_sasl_cleanup() cleans up. It must be called at the
62 /* end of every SMTP session that uses SASL authentication.
63 /* This routine is a noop for non-SASL sessions.
64 /*
65 /* smtp_sasl_passivate() appends flattened SASL attributes to the
66 /* specified buffer. The SASL attributes are not destroyed.
67 /*
68 /* smtp_sasl_activate() restores SASL attributes from the
69 /* specified buffer. The buffer is modified. A result < 0
70 /* means there was an error.
71 /*
72 /* Arguments:
73 /* .IP session
74 /* Session context.
75 /* .IP mech_list
76 /* String of SASL mechanisms (separated by blanks)
77 /* DIAGNOSTICS
78 /* All errors are fatal.
79 /* LICENSE
80 /* .ad
81 /* .fi
82 /* The Secure Mailer license must be distributed with this software.
83 /* AUTHOR(S)
84 /* Original author:
85 /* Till Franke
86 /* SuSE Rhein/Main AG
87 /* 65760 Eschborn, Germany
88 /*
89 /* Adopted by:
90 /* Wietse Venema
91 /* IBM T.J. Watson Research
92 /* P.O. Box 704
93 /* Yorktown Heights, NY 10598, USA
94 /*
95 /* Wietse Venema
96 /* Google, Inc.
97 /* 111 8th Avenue
98 /* New York, NY 10011, USA
99 /*--*/
100
101 /*
102 * System library.
103 */
104 #include <sys_defs.h>
105 #include <stdlib.h>
106 #include <string.h>
107
108 /*
109 * Utility library
110 */
111 #include <msg.h>
112 #include <mymalloc.h>
113 #include <stringops.h>
114 #include <split_at.h>
115
116 /*
117 * Global library
118 */
119 #include <mail_params.h>
120 #include <string_list.h>
121 #include <maps.h>
122 #include <mail_addr_find.h>
123 #include <smtp_stream.h>
124
125 /*
126 * XSASL library.
127 */
128 #include <xsasl.h>
129
130 /*
131 * Application-specific
132 */
133 #include "smtp.h"
134 #include "smtp_sasl.h"
135 #include "smtp_sasl_auth_cache.h"
136
137 #ifdef USE_SASL_AUTH
138
139 /*
140 * Per-host login/password information.
141 */
142 static MAPS *smtp_sasl_passwd_map;
143
144 /*
145 * Supported SASL mechanisms.
146 */
147 STRING_LIST *smtp_sasl_mechs;
148
149 /*
150 * SASL implementation handle.
151 */
152 static XSASL_CLIENT_IMPL *smtp_sasl_impl;
153
154 /*
155 * The 535 SASL authentication failure cache.
156 */
157 #ifdef HAVE_SASL_AUTH_CACHE
158 static SMTP_SASL_AUTH_CACHE *smtp_sasl_auth_cache;
159
160 #endif
161
162 /* smtp_sasl_passwd_lookup - password lookup routine */
163
smtp_sasl_passwd_lookup(SMTP_SESSION * session)164 int smtp_sasl_passwd_lookup(SMTP_SESSION *session)
165 {
166 const char *myname = "smtp_sasl_passwd_lookup";
167 SMTP_STATE *state = session->state;
168 SMTP_ITERATOR *iter = session->iterator;
169 const char *value;
170 char *passwd;
171
172 /*
173 * Sanity check.
174 */
175 if (smtp_sasl_passwd_map == 0)
176 msg_panic("%s: passwd map not initialized", myname);
177
178 /*
179 * Look up the per-server password information. Try the hostname first,
180 * then try the destination.
181 *
182 * XXX Instead of using nexthop (the intended destination) we use dest
183 * (either the intended destination, or a fall-back destination).
184 *
185 * XXX SASL authentication currently depends on the host/domain but not on
186 * the TCP port. If the port is not :25, we should append it to the table
187 * lookup key. Code for this was briefly introduced into 2.2 snapshots,
188 * but didn't canonicalize the TCP port, and did not append the port to
189 * the MX hostname.
190 */
191 smtp_sasl_passwd_map->error = 0;
192 if ((smtp_mode
193 && var_smtp_sender_auth && state->request->sender[0]
194 && (value = mail_addr_find(smtp_sasl_passwd_map,
195 state->request->sender, (char **) 0)) != 0)
196 || (smtp_sasl_passwd_map->error == 0
197 && (value = maps_find(smtp_sasl_passwd_map,
198 STR(iter->host), 0)) != 0)
199 || (smtp_sasl_passwd_map->error == 0
200 && (value = maps_find(smtp_sasl_passwd_map,
201 STR(iter->dest), 0)) != 0)) {
202 if (session->sasl_username)
203 myfree(session->sasl_username);
204 session->sasl_username = mystrdup(value);
205 passwd = split_at(session->sasl_username, ':');
206 if (session->sasl_passwd)
207 myfree(session->sasl_passwd);
208 session->sasl_passwd = mystrdup(passwd ? passwd : "");
209 if (msg_verbose)
210 msg_info("%s: host `%s' user `%s' pass `%s'",
211 myname, STR(iter->host),
212 session->sasl_username, session->sasl_passwd);
213 return (1);
214 } else if (smtp_sasl_passwd_map->error) {
215 msg_warn("%s: %s lookup error",
216 state->request->queue_id, smtp_sasl_passwd_map->title);
217 vstream_longjmp(session->stream, SMTP_ERR_DATA);
218 } else {
219 if (msg_verbose)
220 msg_info("%s: no auth info found (sender=`%s', host=`%s')",
221 myname, state->request->sender, STR(iter->host));
222 return (0);
223 }
224 }
225
226 /* smtp_sasl_initialize - per-process initialization (pre jail) */
227
smtp_sasl_initialize(void)228 void smtp_sasl_initialize(void)
229 {
230
231 /*
232 * Sanity check.
233 */
234 if (smtp_sasl_passwd_map || smtp_sasl_impl)
235 msg_panic("smtp_sasl_initialize: repeated call");
236 if (*var_smtp_sasl_passwd == 0)
237 msg_fatal("specify a password table via the `%s' configuration parameter",
238 VAR_LMTP_SMTP(SASL_PASSWD));
239
240 /*
241 * Open the per-host password table and initialize the SASL library. Use
242 * shared locks for reading, just in case someone updates the table.
243 */
244 smtp_sasl_passwd_map = maps_create(VAR_LMTP_SMTP(SASL_PASSWD),
245 var_smtp_sasl_passwd,
246 DICT_FLAG_LOCK | DICT_FLAG_FOLD_FIX
247 | DICT_FLAG_UTF8_REQUEST);
248 if ((smtp_sasl_impl = xsasl_client_init(var_smtp_sasl_type,
249 var_smtp_sasl_path)) == 0)
250 msg_fatal("SASL library initialization");
251
252 /*
253 * Initialize optional supported mechanism matchlist
254 */
255 if (*var_smtp_sasl_mechs)
256 smtp_sasl_mechs = string_list_init(VAR_SMTP_SASL_MECHS,
257 MATCH_FLAG_NONE,
258 var_smtp_sasl_mechs);
259
260 /*
261 * Initialize the 535 SASL authentication failure cache.
262 */
263 if (*var_smtp_sasl_auth_cache_name) {
264 #ifdef HAVE_SASL_AUTH_CACHE
265 smtp_sasl_auth_cache =
266 smtp_sasl_auth_cache_init(var_smtp_sasl_auth_cache_name,
267 var_smtp_sasl_auth_cache_time);
268 #else
269 msg_warn("not compiled with TLS support -- "
270 "ignoring the %s setting", VAR_LMTP_SMTP(SASL_AUTH_CACHE_NAME));
271 #endif
272 }
273 }
274
275 /* smtp_sasl_connect - per-session client initialization */
276
smtp_sasl_connect(SMTP_SESSION * session)277 void smtp_sasl_connect(SMTP_SESSION *session)
278 {
279
280 /*
281 * This initialization happens whenever we instantiate an SMTP session
282 * object. We don't instantiate a SASL client until we actually need one.
283 */
284 session->sasl_mechanism_list = 0;
285 session->sasl_username = 0;
286 session->sasl_passwd = 0;
287 session->sasl_client = 0;
288 session->sasl_reply = 0;
289 }
290
291 /* smtp_sasl_start - per-session SASL initialization */
292
smtp_sasl_start(SMTP_SESSION * session,const char * sasl_opts_name,const char * sasl_opts_val)293 void smtp_sasl_start(SMTP_SESSION *session, const char *sasl_opts_name,
294 const char *sasl_opts_val)
295 {
296 XSASL_CLIENT_CREATE_ARGS create_args;
297 SMTP_ITERATOR *iter = session->iterator;
298
299 if (msg_verbose)
300 msg_info("starting new SASL client");
301 if ((session->sasl_client =
302 XSASL_CLIENT_CREATE(smtp_sasl_impl, &create_args,
303 stream = session->stream,
304 service = var_procname,
305 server_name = STR(iter->host),
306 security_options = sasl_opts_val)) == 0)
307 msg_fatal("SASL per-connection initialization failed");
308 session->sasl_reply = vstring_alloc(20);
309 }
310
311 /* smtp_sasl_authenticate - run authentication protocol */
312
smtp_sasl_authenticate(SMTP_SESSION * session,DSN_BUF * why)313 int smtp_sasl_authenticate(SMTP_SESSION *session, DSN_BUF *why)
314 {
315 const char *myname = "smtp_sasl_authenticate";
316 SMTP_ITERATOR *iter = session->iterator;
317 SMTP_RESP *resp;
318 const char *mechanism;
319 int result;
320 char *line;
321 int steps = 0;
322
323 /*
324 * Sanity check.
325 */
326 if (session->sasl_mechanism_list == 0)
327 msg_panic("%s: no mechanism list", myname);
328
329 if (msg_verbose)
330 msg_info("%s: %s: SASL mechanisms %s",
331 myname, session->namaddrport, session->sasl_mechanism_list);
332
333 /*
334 * Avoid repeated login failures after a recent 535 error.
335 */
336 #ifdef HAVE_SASL_AUTH_CACHE
337 if (smtp_sasl_auth_cache
338 && smtp_sasl_auth_cache_find(smtp_sasl_auth_cache, session)) {
339 char *resp_dsn = smtp_sasl_auth_cache_dsn(smtp_sasl_auth_cache);
340 char *resp_str = smtp_sasl_auth_cache_text(smtp_sasl_auth_cache);
341
342 if (var_smtp_sasl_auth_soft_bounce && resp_dsn[0] == '5')
343 resp_dsn[0] = '4';
344 dsb_update(why, resp_dsn, DSB_DEF_ACTION, DSB_MTYPE_DNS,
345 STR(iter->host), var_procname, resp_str,
346 "SASL [CACHED] authentication failed; server %s said: %s",
347 STR(iter->host), resp_str);
348 return (0);
349 }
350 #endif
351
352 /*
353 * Start the client side authentication protocol.
354 */
355 result = xsasl_client_first(session->sasl_client,
356 session->sasl_mechanism_list,
357 session->sasl_username,
358 session->sasl_passwd,
359 &mechanism, session->sasl_reply);
360 if (result != XSASL_AUTH_OK) {
361 dsb_update(why, "4.7.0", DSB_DEF_ACTION, DSB_SKIP_RMTA,
362 DSB_DTYPE_SASL, STR(session->sasl_reply),
363 "SASL authentication failed; "
364 "cannot authenticate to server %s: %s",
365 session->namaddr, STR(session->sasl_reply));
366 return (-1);
367 }
368 /*-
369 * Send the AUTH command and the optional initial client response.
370 *
371 * https://tools.ietf.org/html/rfc4954#page-4
372 * Note that the AUTH command is still subject to the line length
373 * limitations defined in [SMTP]. If use of the initial response argument
374 * would cause the AUTH command to exceed this length, the client MUST NOT
375 * use the initial response parameter...
376 *
377 * https://tools.ietf.org/html/rfc5321#section-4.5.3.1.4
378 * The maximum total length of a command line including the command word
379 * and the <CRLF> is 512 octets.
380 *
381 * Defer the initial response if the resulting command exceeds the limit.
382 */
383 if (LEN(session->sasl_reply) > 0
384 && strlen(mechanism) + LEN(session->sasl_reply) + 8 <= 512) {
385 smtp_chat_cmd(session, "AUTH %s %s", mechanism,
386 STR(session->sasl_reply));
387 VSTRING_RESET(session->sasl_reply); /* no deferred initial reply */
388 } else {
389 smtp_chat_cmd(session, "AUTH %s", mechanism);
390 }
391
392 /*
393 * Step through the authentication protocol until the server tells us
394 * that we are done. If session->sasl_reply is non-empty we have a
395 * deferred initial reply and expect an empty initial challenge from the
396 * server. If the server's initial challenge is non-empty we have a SASL
397 * protocol violation with both sides wanting to go first.
398 */
399 while ((resp = smtp_chat_resp(session))->code / 100 == 3) {
400
401 /*
402 * Sanity check.
403 */
404 if (++steps > 100) {
405 dsb_simple(why, "4.3.0", "SASL authentication failed; "
406 "authentication protocol loop with server %s",
407 session->namaddr);
408 return (-1);
409 }
410
411 /*
412 * Process a server challenge.
413 */
414 line = resp->str;
415 (void) mystrtok(&line, "- \t\n"); /* skip over result code */
416
417 if (LEN(session->sasl_reply) > 0) {
418
419 /*
420 * Deferred initial response, the server challenge must be empty.
421 * Cleared after actual transmission to the server.
422 */
423 if (*line) {
424 dsb_update(why, "4.7.0", DSB_DEF_ACTION,
425 DSB_SKIP_RMTA, DSB_DTYPE_SASL, "protocol error",
426 "SASL authentication failed; non-empty initial "
427 "%s challenge from server %s: %s", mechanism,
428 session->namaddr, STR(session->sasl_reply));
429 return (-1);
430 }
431 } else {
432 result = xsasl_client_next(session->sasl_client, line,
433 session->sasl_reply);
434 if (result != XSASL_AUTH_OK) {
435 dsb_update(why, "4.7.0", DSB_DEF_ACTION, /* Fix 200512 */
436 DSB_SKIP_RMTA, DSB_DTYPE_SASL, STR(session->sasl_reply),
437 "SASL authentication failed; "
438 "cannot authenticate to server %s: %s",
439 session->namaddr, STR(session->sasl_reply));
440 return (-1); /* Fix 200512 */
441 }
442 }
443
444 /*
445 * Send a client response.
446 */
447 smtp_chat_cmd(session, "%s", STR(session->sasl_reply));
448 VSTRING_RESET(session->sasl_reply); /* clear initial reply */
449 }
450
451 /*
452 * We completed the authentication protocol.
453 */
454 if (resp->code / 100 != 2) {
455 #ifdef HAVE_SASL_AUTH_CACHE
456 /* Update the 535 authentication failure cache. */
457 if (smtp_sasl_auth_cache && resp->code == 535)
458 smtp_sasl_auth_cache_store(smtp_sasl_auth_cache, session, resp);
459 #endif
460 if (var_smtp_sasl_auth_soft_bounce && resp->code / 100 == 5)
461 STR(resp->dsn_buf)[0] = '4';
462 dsb_update(why, resp->dsn, DSB_DEF_ACTION,
463 DSB_MTYPE_DNS, STR(iter->host),
464 var_procname, resp->str,
465 "SASL authentication failed; server %s said: %s",
466 session->namaddr, resp->str);
467 return (0);
468 }
469 return (1);
470 }
471
472 /* smtp_sasl_cleanup - per-session cleanup */
473
smtp_sasl_cleanup(SMTP_SESSION * session)474 void smtp_sasl_cleanup(SMTP_SESSION *session)
475 {
476 if (session->sasl_username) {
477 myfree(session->sasl_username);
478 session->sasl_username = 0;
479 }
480 if (session->sasl_passwd) {
481 myfree(session->sasl_passwd);
482 session->sasl_passwd = 0;
483 }
484 if (session->sasl_mechanism_list) {
485 /* allocated in smtp_sasl_helo_auth */
486 myfree(session->sasl_mechanism_list);
487 session->sasl_mechanism_list = 0;
488 }
489 if (session->sasl_client) {
490 if (msg_verbose)
491 msg_info("disposing SASL state information");
492 xsasl_client_free(session->sasl_client);
493 session->sasl_client = 0;
494 }
495 if (session->sasl_reply) {
496 vstring_free(session->sasl_reply);
497 session->sasl_reply = 0;
498 }
499 }
500
501 /* smtp_sasl_passivate - append serialized SASL attributes */
502
smtp_sasl_passivate(SMTP_SESSION * session,VSTRING * buf)503 void smtp_sasl_passivate(SMTP_SESSION *session, VSTRING *buf)
504 {
505 }
506
507 /* smtp_sasl_activate - de-serialize SASL attributes */
508
smtp_sasl_activate(SMTP_SESSION * session,char * buf)509 int smtp_sasl_activate(SMTP_SESSION *session, char *buf)
510 {
511 return (0);
512 }
513
514 #endif
515