fa8b731d494ddf98827c5d2e10bee83eb7e8e478
[citadel] / citadel / modules / smtp / serv_smtp.c
1 // This module is an SMTP and ESMTP server for the Citadel system.
2 // It is compliant with all of the following:
3 //
4 // RFC  821 - Simple Mail Transfer Protocol
5 // RFC  876 - Survey of SMTP Implementations
6 // RFC 1047 - Duplicate messages and SMTP
7 // RFC 1652 - 8 bit MIME
8 // RFC 1869 - Extended Simple Mail Transfer Protocol
9 // RFC 1870 - SMTP Service Extension for Message Size Declaration
10 // RFC 2033 - Local Mail Transfer Protocol
11 // RFC 2197 - SMTP Service Extension for Command Pipelining
12 // RFC 2476 - Message Submission
13 // RFC 2487 - SMTP Service Extension for Secure SMTP over TLS
14 // RFC 2554 - SMTP Service Extension for Authentication
15 // RFC 2821 - Simple Mail Transfer Protocol
16 // RFC 2822 - Internet Message Format
17 // RFC 2920 - SMTP Service Extension for Command Pipelining
18 //  
19 // The VRFY and EXPN commands have been removed from this implementation
20 // because nobody uses these commands anymore, except for spammers.
21 //
22 // Copyright (c) 1998-2021 by the citadel.org team
23 //
24 // This program is open source software; you can redistribute it and/or modify
25 // it under the terms of the GNU General Public License version 3.
26 //  
27 // This program is distributed in the hope that it will be useful,
28 // but WITHOUT ANY WARRANTY; without even the implied warranty of
29 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
30 // GNU General Public License for more details.
31
32 #include "sysdep.h"
33 #include <stdlib.h>
34 #include <unistd.h>
35 #include <stdio.h>
36 #include <termios.h>
37 #include <fcntl.h>
38 #include <signal.h>
39 #include <pwd.h>
40 #include <errno.h>
41 #include <sys/types.h>
42 #include <syslog.h>
43 #include <time.h>
44 #include <sys/wait.h>
45 #include <ctype.h>
46 #include <string.h>
47 #include <limits.h>
48 #include <sys/socket.h>
49 #include <netinet/in.h>
50 #include <arpa/inet.h>
51 #include <libcitadel.h>
52 #include "citadel.h"
53 #include "server.h"
54 #include "citserver.h"
55 #include "support.h"
56 #include "config.h"
57 #include "control.h"
58 #include "user_ops.h"
59 #include "room_ops.h"
60 #include "database.h"
61 #include "msgbase.h"
62 #include "internet_addressing.h"
63 #include "genstamp.h"
64 #include "domain.h"
65 #include "clientsocket.h"
66 #include "locate_host.h"
67 #include "citadel_dirs.h"
68 #include "ctdl_module.h"
69
70 #include "smtp_util.h"
71
72 enum {                          /* Command states for login authentication */
73         smtp_command,
74         smtp_user,
75         smtp_password,
76         smtp_plain
77 };
78
79 enum SMTP_FLAGS {
80         HELO,
81         EHLO,
82         LHLO
83 };
84
85
86 /*
87  * Here's where our SMTP session begins its happy day.
88  */
89 void smtp_greeting(int is_msa) {
90         char message_to_spammer[1024];
91
92         strcpy(CC->cs_clientname, "SMTP session");
93         CC->internal_pgm = 1;
94         CC->cs_flags |= CS_STEALTH;
95         CC->session_specific_data = malloc(sizeof(struct citsmtp));
96         memset(SMTP, 0, sizeof(struct citsmtp));
97         SMTP->is_msa = is_msa;
98         SMTP->Cmd = NewStrBufPlain(NULL, SIZ);
99         SMTP->helo_node = NewStrBuf();
100         SMTP->from = NewStrBufPlain(NULL, SIZ);
101         SMTP->recipients = NewStrBufPlain(NULL, SIZ);
102         SMTP->OneRcpt = NewStrBufPlain(NULL, SIZ);
103         SMTP->preferred_sender_email = NULL;
104         SMTP->preferred_sender_name = NULL;
105
106         /* If this config option is set, reject connections from problem
107          * addresses immediately instead of after they execute a RCPT
108          */
109         if ( (CtdlGetConfigInt("c_rbl_at_greeting")) && (SMTP->is_msa == 0) ) {
110                 if (rbl_check(CC->cs_addr, message_to_spammer)) {
111                         if (server_shutting_down)
112                                 cprintf("421 %s\r\n", message_to_spammer);
113                         else
114                                 cprintf("550 %s\r\n", message_to_spammer);
115                         CC->kill_me = KILLME_SPAMMER;
116                         /* no need to free_recipients(valid), it's not allocated yet */
117                         return;
118                 }
119         }
120
121         /* Otherwise we're either clean or we check later. */
122
123         if (CC->nologin==1) {
124                 cprintf("451 Too many connections are already open; please try again later.\r\n");
125                 CC->kill_me = KILLME_MAX_SESSIONS_EXCEEDED;
126                 /* no need to free_recipients(valid), it's not allocated yet */
127                 return;
128         }
129
130         /* Note: the FQDN *must* appear as the first thing after the 220 code.
131          * Some clients (including citmail.c) depend on it being there.
132          */
133         cprintf("220 %s ESMTP Citadel server ready.\r\n", CtdlGetConfigStr("c_fqdn"));
134 }
135
136
137 /*
138  * SMTPS is just like SMTP, except it goes crypto right away.
139  */
140 void smtps_greeting(void) {
141         CtdlModuleStartCryptoMsgs(NULL, NULL, NULL);
142 #ifdef HAVE_OPENSSL
143         if (!CC->redirect_ssl) CC->kill_me = KILLME_NO_CRYPTO;          /* kill session if no crypto */
144 #endif
145         smtp_greeting(0);
146 }
147
148
149 /*
150  * SMTP MSA port requires authentication.
151  */
152 void smtp_msa_greeting(void) {
153         smtp_greeting(1);
154 }
155
156
157 /*
158  * LMTP is like SMTP but with some extra bonus footage added.
159  */
160 void lmtp_greeting(void) {
161
162         smtp_greeting(0);
163         SMTP->is_lmtp = 1;
164 }
165
166
167 /* 
168  * Generic SMTP MTA greeting
169  */
170 void smtp_mta_greeting(void) {
171         smtp_greeting(0);
172 }
173
174
175 /*
176  * We also have an unfiltered LMTP socket that bypasses spam filters.
177  */
178 void lmtp_unfiltered_greeting(void) {
179         smtp_greeting(0);
180         SMTP->is_lmtp = 1;
181         SMTP->is_unfiltered = 1;
182 }
183
184
185 /*
186  * Login greeting common to all auth methods
187  */
188 void smtp_auth_greeting(void) {
189         cprintf("235 Hello, %s\r\n", CC->user.fullname);
190         syslog(LOG_INFO, "serv_smtp: SMTP authenticated %s", CC->user.fullname);
191         CC->internal_pgm = 0;
192         CC->cs_flags &= ~CS_STEALTH;
193 }
194
195
196 /*
197  * Implement HELO and EHLO commands.
198  *
199  * which_command:  0=HELO, 1=EHLO, 2=LHLO
200  */
201 void smtp_hello(int which_command) {
202
203         if (StrLength(SMTP->Cmd) >= 6) {
204                 StrBufAppendBuf(SMTP->helo_node, SMTP->Cmd, 5);
205         }
206
207         if ( (which_command != LHLO) && (SMTP->is_lmtp) ) {
208                 cprintf("500 Only LHLO is allowed when running LMTP\r\n");
209                 return;
210         }
211
212         if ( (which_command == LHLO) && (SMTP->is_lmtp == 0) ) {
213                 cprintf("500 LHLO is only allowed when running LMTP\r\n");
214                 return;
215         }
216
217         if (which_command == HELO) {
218                 cprintf("250 Hello %s (%s [%s])\r\n",
219                         ChrPtr(SMTP->helo_node),
220                         CC->cs_host,
221                         CC->cs_addr
222                 );
223         }
224         else {
225                 if (which_command == EHLO) {
226                         cprintf("250-Hello %s (%s [%s])\r\n",
227                                 ChrPtr(SMTP->helo_node),
228                                 CC->cs_host,
229                                 CC->cs_addr
230                         );
231                 }
232                 else {
233                         cprintf("250-Greetings and joyous salutations.\r\n");
234                 }
235                 cprintf("250-HELP\r\n");
236                 cprintf("250-SIZE %ld\r\n", CtdlGetConfigLong("c_maxmsglen"));
237
238 #ifdef HAVE_OPENSSL
239                 /*
240                  * Offer TLS, but only if TLS is not already active.
241                  * Furthermore, only offer TLS when running on
242                  * the SMTP-MSA port, not on the SMTP-MTA port, due to
243                  * questionable reliability of TLS in certain sending MTA's.
244                  */
245                 if ( (!CC->redirect_ssl) && (SMTP->is_msa) ) {
246                         cprintf("250-STARTTLS\r\n");
247                 }
248 #endif  /* HAVE_OPENSSL */
249
250                 cprintf("250-AUTH LOGIN PLAIN\r\n"
251                         "250-AUTH=LOGIN PLAIN\r\n"
252                         "250 8BITMIME\r\n"
253                 );
254         }
255 }
256
257
258 /*
259  * Backend function for smtp_webcit_preferences_hack().
260  * Look at a message and determine if it's the preferences file.
261  */
262 void smtp_webcit_preferences_hack_backend(long msgnum, void *userdata) {
263         struct CtdlMessage *msg;
264         char **webcit_conf = (char **) userdata;
265
266         if (*webcit_conf) {
267                 return; // already got it
268         }
269
270         msg = CtdlFetchMessage(msgnum, 1);
271         if (msg == NULL) {
272                 return;
273         }
274
275         if ( !CM_IsEmpty(msg, eMsgSubject) && (!strcasecmp(msg->cm_fields[eMsgSubject], "__ WebCit Preferences __"))) {
276                 /* This is it!  Change ownership of the message text so it doesn't get freed. */
277                 *webcit_conf = (char *)msg->cm_fields[eMesageText];
278                 msg->cm_fields[eMesageText] = NULL;
279         }
280         CM_Free(msg);
281 }
282
283
284 /*
285  * The configuration item for the user's preferred display name for outgoing email is, unfortunately,
286  * stored in the account's WebCit configuration.  We have to fetch it now.
287  */
288 void smtp_webcit_preferences_hack(void) {
289         char config_roomname[ROOMNAMELEN];
290         char *webcit_conf = NULL;
291
292         snprintf(config_roomname, sizeof config_roomname, "%010ld.%s", CC->user.usernum, USERCONFIGROOM);
293         if (CtdlGetRoom(&CC->room, config_roomname) != 0) {
294                 return;
295         }
296
297         /*
298          * Find the WebCit configuration message
299          */
300
301         CtdlForEachMessage(MSGS_ALL, 1, NULL, NULL, NULL, smtp_webcit_preferences_hack_backend, (void *)&webcit_conf);
302
303         if (!webcit_conf) {
304                 return;
305         }
306
307         /* Parse the webcit configuration and attempt to do something useful with it */
308         char *str = webcit_conf;
309         char *saveptr = str;
310         char *this_line = NULL;
311         while (this_line = strtok_r(str, "\n", &saveptr), this_line != NULL) {
312                 str = NULL;
313                 if (!strncasecmp(this_line, "defaultfrom|", 12)) {
314                         SMTP->preferred_sender_email = NewStrBufPlain(&this_line[12], -1);
315                 }
316                 if (!strncasecmp(this_line, "defaultname|", 12)) {
317                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
318                 }
319                 if ((!strncasecmp(this_line, "defaultname|", 12)) && (SMTP->preferred_sender_name == NULL)) {
320                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
321                 }
322
323         }
324         free(webcit_conf);
325 }
326
327
328 /*
329  * Implement HELP command.
330  */
331 void smtp_help(void) {
332         cprintf("214 RTFM http://www.ietf.org/rfc/rfc2821.txt\r\n");
333 }
334
335
336 /*
337  *
338  */
339 void smtp_get_user(int offset) {
340         char buf[SIZ];
341
342         StrBuf *UserName = NewStrBufDup(SMTP->Cmd);
343         StrBufCutLeft(UserName, offset);
344         StrBufDecodeBase64(UserName);
345
346         if (CtdlLoginExistingUser(ChrPtr(UserName)) == login_ok) {
347                 size_t len = CtdlEncodeBase64(buf, "Password:", 9, 0);
348
349                 if (buf[len - 1] == '\n') {
350                         buf[len - 1] = '\0';
351                 }
352                 cprintf("334 %s\r\n", buf);
353                 SMTP->command_state = smtp_password;
354         }
355         else {
356                 cprintf("500 No such user.\r\n");
357                 SMTP->command_state = smtp_command;
358         }
359         FreeStrBuf(&UserName);
360 }
361
362
363 /*
364  *
365  */
366 void smtp_get_pass(void)
367 {
368         char password[SIZ];
369
370         memset(password, 0, sizeof(password));
371         StrBufDecodeBase64(SMTP->Cmd);
372         syslog(LOG_DEBUG, "serv_smtp: trying <%s>", password);
373         if (CtdlTryPassword(SKEY(SMTP->Cmd)) == pass_ok) {
374                 smtp_auth_greeting();
375         }
376         else {
377                 cprintf("535 Authentication failed.\r\n");
378         }
379         SMTP->command_state = smtp_command;
380 }
381
382
383 /*
384  * Back end for PLAIN auth method (either inline or multistate)
385  */
386 void smtp_try_plain(void) {
387         const char*decoded_authstring;
388         char ident[256] = "";
389         char user[256] = "";
390         char pass[256] = "";
391         int result;
392
393         long decoded_len;
394         long len = 0;
395         long plen = 0;
396
397         memset(pass, 0, sizeof(pass));
398         decoded_len = StrBufDecodeBase64(SMTP->Cmd);
399
400         if (decoded_len > 0) {
401                 decoded_authstring = ChrPtr(SMTP->Cmd);
402
403                 len = safestrncpy(ident, decoded_authstring, sizeof ident);
404
405                 decoded_len -= len - 1;
406                 decoded_authstring += len + 1;
407
408                 if (decoded_len > 0) {
409                         len = safestrncpy(user, decoded_authstring, sizeof user);
410
411                         decoded_authstring += len + 1;
412                         decoded_len -= len - 1;
413                 }
414
415                 if (decoded_len > 0) {
416                         plen = safestrncpy(pass, decoded_authstring, sizeof pass);
417
418                         if (plen < 0)
419                                 plen = sizeof(pass) - 1;
420                 }
421         }
422
423         SMTP->command_state = smtp_command;
424
425         if (!IsEmptyStr(ident)) {
426                 result = CtdlLoginExistingUser(ident);
427         }
428         else {
429                 result = CtdlLoginExistingUser(user);
430         }
431
432         if (result == login_ok) {
433                 if (CtdlTryPassword(pass, plen) == pass_ok) {
434                         smtp_webcit_preferences_hack();
435                         smtp_auth_greeting();
436                         return;
437                 }
438         }
439         cprintf("504 Authentication failed.\r\n");
440 }
441
442
443 /*
444  * Attempt to perform authenticated SMTP
445  */
446 void smtp_auth(void) {
447         char username_prompt[64];
448         char method[64];
449         char encoded_authstring[1024];
450
451         if (CC->logged_in) {
452                 cprintf("504 Already logged in.\r\n");
453                 return;
454         }
455
456         if (StrLength(SMTP->Cmd) < 6) {
457                 cprintf("501 Syntax error\r\n");
458                 return;
459         }
460
461         extract_token(method, ChrPtr(SMTP->Cmd) + 5, 0, ' ', sizeof method);
462
463         if (!strncasecmp(method, "login", 5) ) {
464                 if (StrLength(SMTP->Cmd) >= 12) {
465                         syslog(LOG_DEBUG, "serv_smtp: username <%s> supplied inline", ChrPtr(SMTP->Cmd)+11);
466                         smtp_get_user(11);
467                 }
468                 else {
469                         size_t len = CtdlEncodeBase64(username_prompt, "Username:", 9, 0);
470                         if (username_prompt[len - 1] == '\n') {
471                                 username_prompt[len - 1] = '\0';
472                         }
473                         cprintf("334 %s\r\n", username_prompt);
474                         SMTP->command_state = smtp_user;
475                 }
476                 return;
477         }
478
479         if (!strncasecmp(method, "plain", 5) ) {
480                 long len;
481                 if (num_tokens(ChrPtr(SMTP->Cmd) + 5, ' ') < 2) {
482                         cprintf("334 \r\n");
483                         SMTP->command_state = smtp_plain;
484                         return;
485                 }
486
487                 len = extract_token(encoded_authstring, 
488                                     ChrPtr(SMTP->Cmd) + 5,
489                                     1, ' ',
490                                     sizeof encoded_authstring);
491                 StrBufPlain(SMTP->Cmd, encoded_authstring, len);
492                 smtp_try_plain();
493                 return;
494         }
495
496         cprintf("504 Unknown authentication method.\r\n");
497         return;
498 }
499
500
501 /*
502  * Implements the RSET (reset state) command.
503  * Currently this just zeroes out the state buffer.  If pointers to data
504  * allocated with malloc() are ever placed in the state buffer, we have to
505  * be sure to free() them first!
506  *
507  * Set do_response to nonzero to output the SMTP RSET response code.
508  */
509 void smtp_rset(int do_response) {
510         /*
511          * Our entire SMTP state is discarded when a RSET command is issued,
512          * but we need to preserve this one little piece of information, so
513          * we save it for later.
514          */
515
516         FlushStrBuf(SMTP->Cmd);
517         FlushStrBuf(SMTP->helo_node);
518         FlushStrBuf(SMTP->from);
519         FlushStrBuf(SMTP->recipients);
520         FlushStrBuf(SMTP->OneRcpt);
521
522         SMTP->command_state = 0;
523         SMTP->number_of_recipients = 0;
524         SMTP->delivery_mode = 0;
525         SMTP->message_originated_locally = 0;
526         SMTP->is_msa = 0;
527         /*
528          * we must remember is_lmtp & is_unfiltered.
529          */
530
531         /*
532          * It is somewhat ambiguous whether we want to log out when a RSET
533          * command is issued.  Here's the code to do it.  It is commented out
534          * because some clients (such as Pine) issue RSET commands before
535          * each message, but still expect to be logged in.
536          *
537          * if (CC->logged_in) {
538          *      logout(CC);
539          * }
540          */
541
542         if (do_response) {
543                 cprintf("250 Zap!\r\n");
544         }
545 }
546
547
548 /*
549  * Clear out the portions of the state buffer that need to be cleared out
550  * after the DATA command finishes.
551  */
552 void smtp_data_clear(void) {
553         FlushStrBuf(SMTP->from);
554         FlushStrBuf(SMTP->recipients);
555         FlushStrBuf(SMTP->OneRcpt);
556         SMTP->number_of_recipients = 0;
557         SMTP->delivery_mode = 0;
558         SMTP->message_originated_locally = 0;
559 }
560
561
562 /*
563  * Implements the "MAIL FROM:" command
564  */
565 void smtp_mail(void) {
566         char user[SIZ];
567         char node[SIZ];
568         char name[SIZ];
569
570         if (StrLength(SMTP->from) > 0) {
571                 cprintf("503 Only one sender permitted\r\n");
572                 return;
573         }
574
575         if (StrLength(SMTP->Cmd) < 6) {
576                 cprintf("501 Syntax error\r\n");
577                 return;
578         }
579
580         if (strncasecmp(ChrPtr(SMTP->Cmd) + 5, "From:", 5)) {
581                 cprintf("501 Syntax error\r\n");
582                 return;
583         }
584
585         StrBufAppendBuf(SMTP->from, SMTP->Cmd, 5);
586         StrBufTrim(SMTP->from);
587         if (strchr(ChrPtr(SMTP->from), '<') != NULL) {
588                 StrBufStripAllBut(SMTP->from, '<', '>');
589         }
590
591         /* We used to reject empty sender names, until it was brought to our
592          * attention that RFC1123 5.2.9 requires that this be allowed.  So now
593          * we allow it, but replace the empty string with a fake
594          * address so we don't have to contend with the empty string causing
595          * other code to fail when it's expecting something there.
596          */
597         if (StrLength(SMTP->from) == 0) {
598                 StrBufPlain(SMTP->from, HKEY("someone@example.com"));
599         }
600
601         /* If this SMTP connection is from a logged-in user, force the 'from'
602          * to be the user's Internet e-mail address as Citadel knows it.
603          */
604         if (CC->logged_in) {
605                 StrBufPlain(SMTP->from, CC->cs_inet_email, -1);
606                 cprintf("250 Sender ok <%s>\r\n", ChrPtr(SMTP->from));
607                 SMTP->message_originated_locally = 1;
608                 return;
609         }
610
611         else if (SMTP->is_lmtp) {
612                 /* Bypass forgery checking for LMTP */
613         }
614
615         /* Otherwise, make sure outsiders aren't trying to forge mail from
616          * this system (unless, of course, c_allow_spoofing is enabled)
617          */
618         else if (CtdlGetConfigInt("c_allow_spoofing") == 0) {
619                 process_rfc822_addr(ChrPtr(SMTP->from), user, node, name);
620                 syslog(LOG_DEBUG, "serv_smtp: claimed envelope sender is '%s' == '%s' @ '%s' ('%s')",
621                         ChrPtr(SMTP->from), user, node, name
622                 );
623                 if (CtdlHostAlias(node) != hostalias_nomatch) {
624                         cprintf("550 You must log in to send mail from %s\r\n", node);
625                         FlushStrBuf(SMTP->from);
626                         syslog(LOG_DEBUG, "serv_smtp: rejecting unauthenticated mail from %s", node);
627                         return;
628                 }
629         }
630
631         cprintf("250 Sender ok\r\n");
632 }
633
634
635 /*
636  * Implements the "RCPT To:" command
637  */
638 void smtp_rcpt(void) {
639         char message_to_spammer[SIZ];
640         struct recptypes *valid = NULL;
641
642         if (StrLength(SMTP->from) == 0) {
643                 cprintf("503 Need MAIL before RCPT\r\n");
644                 return;
645         }
646         
647         if (StrLength(SMTP->Cmd) < 6) {
648                 cprintf("501 Syntax error\r\n");
649                 return;
650         }
651
652         if (strncasecmp(ChrPtr(SMTP->Cmd) + 5, "To:", 3)) {
653                 cprintf("501 Syntax error\r\n");
654                 return;
655         }
656
657         if ( (SMTP->is_msa) && (!CC->logged_in) ) {
658                 cprintf("550 You must log in to send mail on this port.\r\n");
659                 FlushStrBuf(SMTP->from);
660                 return;
661         }
662
663         FlushStrBuf(SMTP->OneRcpt);
664         StrBufAppendBuf(SMTP->OneRcpt, SMTP->Cmd, 8);
665         StrBufTrim(SMTP->OneRcpt);
666         StrBufStripAllBut(SMTP->OneRcpt, '<', '>');
667
668         if ( (StrLength(SMTP->OneRcpt) + StrLength(SMTP->recipients)) >= SIZ) {
669                 cprintf("452 Too many recipients\r\n");
670                 return;
671         }
672
673         // RBL check
674         if (
675                 (!CC->logged_in)                                                // Don't RBL authenticated users
676                 && (!SMTP->is_lmtp)                                             // Don't RBL LMTP clients
677                 && (CtdlGetConfigInt("c_rbl_at_greeting") == 0)                 // Don't RBL if we did it at connection time
678                 && (rbl_check(CC->cs_addr, message_to_spammer))
679         ) {
680                 cprintf("550 %s\r\n", message_to_spammer);
681                 return;                                                         // no need to free_recipients(valid)
682         }                                                                       // because it hasn't been allocated yet
683
684         valid = validate_recipients(
685                 (char *)ChrPtr(SMTP->OneRcpt), 
686                 smtp_get_Recipients(),
687                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
688         );
689         if (valid->num_error != 0) {
690                 cprintf("550 %s\r\n", valid->errormsg);
691                 free_recipients(valid);
692                 return;
693         }
694
695         if (valid->num_internet > 0) {
696                 if (CC->logged_in) {
697                         if (CtdlCheckInternetMailPermission(&CC->user)==0) {
698                                 cprintf("551 <%s> - you do not have permission to send Internet mail\r\n", 
699                                         ChrPtr(SMTP->OneRcpt));
700                                 free_recipients(valid);
701                                 return;
702                         }
703                 }
704         }
705
706         if (valid->num_internet > 0) {
707                 if ( (SMTP->message_originated_locally == 0)
708                    && (SMTP->is_lmtp == 0) ) {
709                         cprintf("551 <%s> - relaying denied\r\n", ChrPtr(SMTP->OneRcpt));
710                         free_recipients(valid);
711                         return;
712                 }
713         }
714
715         cprintf("250 RCPT ok <%s>\r\n", ChrPtr(SMTP->OneRcpt));
716         if (StrLength(SMTP->recipients) > 0) {
717                 StrBufAppendBufPlain(SMTP->recipients, HKEY(","), 0);
718         }
719         StrBufAppendBuf(SMTP->recipients, SMTP->OneRcpt, 0);
720         SMTP->number_of_recipients ++;
721         if (valid != NULL)  {
722                 free_recipients(valid);
723         }
724 }
725
726
727 /*
728  * Implements the DATA command
729  */
730 void smtp_data(void) {
731         StrBuf *body;
732         StrBuf *defbody; 
733         struct CtdlMessage *msg = NULL;
734         long msgnum = (-1L);
735         char nowstamp[SIZ];
736         struct recptypes *valid;
737         int scan_errors;
738         int i;
739
740         if (StrLength(SMTP->from) == 0) {
741                 cprintf("503 Need MAIL command first.\r\n");
742                 return;
743         }
744
745         if (SMTP->number_of_recipients < 1) {
746                 cprintf("503 Need RCPT command first.\r\n");
747                 return;
748         }
749
750         cprintf("354 Transmit message now - terminate with '.' by itself\r\n");
751         
752         datestring(nowstamp, sizeof nowstamp, time(NULL), DATESTRING_RFC822);
753         defbody = NewStrBufPlain(NULL, SIZ);
754
755         if (defbody != NULL) {
756                 if (SMTP->is_lmtp && (CC->cs_UDSclientUID != -1)) {
757                         StrBufPrintf(
758                                 defbody,
759                                 "Received: from %s (Citadel from userid %ld)\n"
760                                 "       by %s; %s\n",
761                                 ChrPtr(SMTP->helo_node),
762                                 (long int) CC->cs_UDSclientUID,
763                                 CtdlGetConfigStr("c_fqdn"),
764                                 nowstamp);
765                 }
766                 else {
767                         StrBufPrintf(
768                                 defbody,
769                                 "Received: from %s (%s [%s])\n"
770                                 "       by %s; %s\n",
771                                 ChrPtr(SMTP->helo_node),
772                                 CC->cs_host,
773                                 CC->cs_addr,
774                                 CtdlGetConfigStr("c_fqdn"),
775                                 nowstamp);
776                 }
777         }
778         body = CtdlReadMessageBodyBuf(HKEY("."), CtdlGetConfigLong("c_maxmsglen"), defbody, 1);
779         FreeStrBuf(&defbody);
780         if (body == NULL) {
781                 cprintf("550 Unable to save message: internal error.\r\n");
782                 return;
783         }
784
785         syslog(LOG_DEBUG, "serv_smtp: converting message...");
786         msg = convert_internet_message_buf(&body);
787
788         /* If the user is locally authenticated, FORCE the From: header to
789          * show up as the real sender.  Yes, this violates the RFC standard,
790          * but IT MAKES SENSE.  If you prefer strict RFC adherence over
791          * common sense, you can disable this in the configuration.
792          *
793          * We also set the "message room name" ('O' field) to MAILROOM
794          * (which is Mail> on most systems) to prevent it from getting set
795          * to something ugly like "0000058008.Sent Items>" when the message
796          * is read with a Citadel client.
797          */
798         if ( (CC->logged_in) && (CtdlGetConfigInt("c_rfc822_strict_from") != CFG_SMTP_FROM_NOFILTER) ) {
799                 int validemail = 0;
800                 
801                 if (!CM_IsEmpty(msg, erFc822Addr)       &&
802                     ((CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_CORRECT) || 
803                      (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)    )  )
804                 {
805                         if (!IsEmptyStr(CC->cs_inet_email))
806                                 validemail = strcmp(CC->cs_inet_email, msg->cm_fields[erFc822Addr]) == 0;
807                         if ((!validemail) && 
808                             (!IsEmptyStr(CC->cs_inet_other_emails)))
809                         {
810                                 int num_secondary_emails = 0;
811                                 int i;
812                                 num_secondary_emails = num_tokens(CC->cs_inet_other_emails, '|');
813                                 for (i=0; i < num_secondary_emails && !validemail; ++i) {
814                                         char buf[256];
815                                         extract_token(buf, CC->cs_inet_other_emails,i,'|',sizeof CC->cs_inet_other_emails);
816                                         validemail = strcmp(buf, msg->cm_fields[erFc822Addr]) == 0;
817                                 }
818                         }
819                 }
820
821                 if (!validemail && (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)) {
822                         syslog(LOG_ERR, "serv_smtp: invalid sender '%s' - rejecting this message", msg->cm_fields[erFc822Addr]);
823                         cprintf("550 Invalid sender '%s' - rejecting this message.\r\n", msg->cm_fields[erFc822Addr]);
824                         return;
825                 }
826
827                 CM_SetField(msg, eOriginalRoom, HKEY(MAILROOM));
828                 if (SMTP->preferred_sender_name != NULL)
829                         CM_SetField(msg, eAuthor, SKEY(SMTP->preferred_sender_name));
830                 else 
831                         CM_SetField(msg, eAuthor, CC->user.fullname, strlen(CC->user.fullname));
832
833                 if (!validemail) {
834                         if (SMTP->preferred_sender_email != NULL) {
835                                 CM_SetField(msg, erFc822Addr, SKEY(SMTP->preferred_sender_email));
836                         }
837                         else {
838                                 CM_SetField(msg, erFc822Addr, CC->cs_inet_email, strlen(CC->cs_inet_email));
839                         }
840                 }
841         }
842
843         /* Set the "envelope from" address */
844         CM_SetField(msg, eMessagePath, SKEY(SMTP->from));
845
846         /* Set the "envelope to" address */
847         CM_SetField(msg, eenVelopeTo, SKEY(SMTP->recipients));
848
849         /* Submit the message into the Citadel system. */
850         valid = validate_recipients(
851                 (char *)ChrPtr(SMTP->recipients),
852                 smtp_get_Recipients(),
853                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
854         );
855
856         /* If there are modules that want to scan this message before final
857          * submission (such as virus checkers or spam filters), call them now
858          * and give them an opportunity to reject the message.
859          */
860         if (SMTP->is_unfiltered) {
861                 scan_errors = 0;
862         }
863         else {
864                 scan_errors = PerformMessageHooks(msg, valid, EVT_SMTPSCAN);
865         }
866
867         if (scan_errors > 0) {  /* We don't want this message! */
868
869                 if (CM_IsEmpty(msg, eErrorMsg)) {
870                         CM_SetField(msg, eErrorMsg, HKEY("Message rejected by filter"));
871                 }
872
873                 StrBufPrintf(SMTP->OneRcpt, "550 %s\r\n", msg->cm_fields[eErrorMsg]);
874         }
875         
876         else {                  /* Ok, we'll accept this message. */
877                 msgnum = CtdlSubmitMsg(msg, valid, "");
878                 if (msgnum > 0L) {
879                         StrBufPrintf(SMTP->OneRcpt, "250 Message accepted.\r\n");
880                 }
881                 else {
882                         StrBufPrintf(SMTP->OneRcpt, "550 Internal delivery error\r\n");
883                 }
884         }
885
886         /* For SMTP and ESMTP, just print the result message.  For LMTP, we
887          * have to print one result message for each recipient.  Since there
888          * is nothing in Citadel which would cause different recipients to
889          * have different results, we can get away with just spitting out the
890          * same message once for each recipient.
891          */
892         if (SMTP->is_lmtp) {
893                 for (i=0; i<SMTP->number_of_recipients; ++i) {
894                         cputbuf(SMTP->OneRcpt);
895                 }
896         }
897         else {
898                 cputbuf(SMTP->OneRcpt);
899         }
900
901         /* Write something to the syslog(which may or may not be where the
902          * rest of the Citadel logs are going; some sysadmins want LOG_MAIL).
903          */
904         syslog((LOG_MAIL | LOG_INFO),
905                     "%ld: from=<%s>, nrcpts=%d, relay=%s [%s], stat=%s",
906                     msgnum,
907                     ChrPtr(SMTP->from),
908                     SMTP->number_of_recipients,
909                     CC->cs_host,
910                     CC->cs_addr,
911                     ChrPtr(SMTP->OneRcpt)
912         );
913
914         /* Clean up */
915         CM_Free(msg);
916         free_recipients(valid);
917         smtp_data_clear();      /* clear out the buffers now */
918 }
919
920
921 /*
922  * Implements the STARTTLS command
923  */
924 void smtp_starttls(void) {
925         char ok_response[SIZ];
926         char nosup_response[SIZ];
927         char error_response[SIZ];
928
929         sprintf(ok_response, "220 Begin TLS negotiation now\r\n");
930         sprintf(nosup_response, "554 TLS not supported here\r\n");
931         sprintf(error_response, "554 Internal error\r\n");
932         CtdlModuleStartCryptoMsgs(ok_response, nosup_response, error_response);
933         smtp_rset(0);
934 }
935
936
937 /*
938  * Implements the NOOP (NO OPeration) command
939  */
940 void smtp_noop(void) {
941         cprintf("250 NOOP\r\n");
942 }
943
944
945 /*
946  * Implements the QUIT command
947  */
948 void smtp_quit(void) {
949         cprintf("221 Goodbye...\r\n");
950         CC->kill_me = KILLME_CLIENT_LOGGED_OUT;
951 }
952
953
954 /* 
955  * Main command loop for SMTP server sessions.
956  */
957 void smtp_command_loop(void) {
958         static const ConstStr AuthPlainStr = {HKEY("AUTH PLAIN")};
959
960         if (SMTP == NULL) {
961                 syslog(LOG_ERR, "serv_smtp: Session SMTP data is null.  WTF?  We will crash now.");
962                 abort();
963         }
964
965         time(&CC->lastcmd);
966         if (CtdlClientGetLine(SMTP->Cmd) < 1) {
967                 syslog(LOG_INFO, "SMTP: client disconnected: ending session.");
968                 CC->kill_me = KILLME_CLIENT_DISCONNECTED;
969                 return;
970         }
971
972         if (SMTP->command_state == smtp_user) {
973                 if (!strncmp(ChrPtr(SMTP->Cmd), AuthPlainStr.Key, AuthPlainStr.len)) {
974                         smtp_try_plain();
975                 }
976                 else {
977                         smtp_get_user(0);
978                 }
979                 return;
980         }
981
982         else if (SMTP->command_state == smtp_password) {
983                 smtp_get_pass();
984                 return;
985         }
986
987         else if (SMTP->command_state == smtp_plain) {
988                 smtp_try_plain();
989                 return;
990         }
991
992         syslog(LOG_DEBUG, "serv_smtp: client sent command <%s>", ChrPtr(SMTP->Cmd));
993
994         if (!strncasecmp(ChrPtr(SMTP->Cmd), "NOOP", 4)) {
995                 smtp_noop();
996                 return;
997         }
998
999         if (!strncasecmp(ChrPtr(SMTP->Cmd), "QUIT", 4)) {
1000                 smtp_quit();
1001                 return;
1002         }
1003
1004         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELO", 4)) {
1005                 smtp_hello(HELO);
1006                 return;
1007         }
1008
1009         if (!strncasecmp(ChrPtr(SMTP->Cmd), "EHLO", 4)) {
1010                 smtp_hello(EHLO);
1011                 return;
1012         }
1013
1014         if (!strncasecmp(ChrPtr(SMTP->Cmd), "LHLO", 4)) {
1015                 smtp_hello(LHLO);
1016                 return;
1017         }
1018
1019         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RSET", 4)) {
1020                 smtp_rset(1);
1021                 return;
1022         }
1023
1024         if (!strncasecmp(ChrPtr(SMTP->Cmd), "AUTH", 4)) {
1025                 smtp_auth();
1026                 return;
1027         }
1028
1029         if (!strncasecmp(ChrPtr(SMTP->Cmd), "DATA", 4)) {
1030                 smtp_data();
1031                 return;
1032         }
1033
1034         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELP", 4)) {
1035                 smtp_help();
1036                 return;
1037         }
1038
1039         if (!strncasecmp(ChrPtr(SMTP->Cmd), "MAIL", 4)) {
1040                 smtp_mail();
1041                 return;
1042         }
1043         
1044         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RCPT", 4)) {
1045                 smtp_rcpt();
1046                 return;
1047         }
1048 #ifdef HAVE_OPENSSL
1049         if (!strncasecmp(ChrPtr(SMTP->Cmd), "STARTTLS", 8)) {
1050                 smtp_starttls();
1051                 return;
1052         }
1053 #endif
1054
1055         cprintf("502 I'm afraid I can't do that.\r\n");
1056 }
1057
1058
1059 /*****************************************************************************/
1060 /*                      MODULE INITIALIZATION STUFF                          */
1061 /*****************************************************************************/
1062 /*
1063  * This cleanup function blows away the temporary memory used by
1064  * the SMTP server.
1065  */
1066 void smtp_cleanup_function(void)
1067 {
1068         /* Don't do this stuff if this is not an SMTP session! */
1069         if (CC->h_command_function != smtp_command_loop) return;
1070
1071         syslog(LOG_DEBUG, "Performing SMTP cleanup hook");
1072
1073         FreeStrBuf(&SMTP->Cmd);
1074         FreeStrBuf(&SMTP->helo_node);
1075         FreeStrBuf(&SMTP->from);
1076         FreeStrBuf(&SMTP->recipients);
1077         FreeStrBuf(&SMTP->OneRcpt);
1078         FreeStrBuf(&SMTP->preferred_sender_email);
1079         FreeStrBuf(&SMTP->preferred_sender_name);
1080
1081         free(SMTP);
1082 }
1083
1084 const char *CitadelServiceSMTP_MTA="SMTP-MTA";
1085 const char *CitadelServiceSMTPS_MTA="SMTPs-MTA";
1086 const char *CitadelServiceSMTP_MSA="SMTP-MSA";
1087 const char *CitadelServiceSMTP_LMTP="LMTP";
1088 const char *CitadelServiceSMTP_LMTP_UNF="LMTP-UnF";
1089
1090
1091 CTDL_MODULE_INIT(smtp)
1092 {
1093         if (!threading) {
1094                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtp_port"),        /* SMTP MTA */
1095                                         NULL,
1096                                         smtp_mta_greeting,
1097                                         smtp_command_loop,
1098                                         NULL, 
1099                                         CitadelServiceSMTP_MTA);
1100
1101 #ifdef HAVE_OPENSSL
1102                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtps_port"),       /* SMTPS MTA */
1103                                         NULL,
1104                                         smtps_greeting,
1105                                         smtp_command_loop,
1106                                         NULL,
1107                                         CitadelServiceSMTPS_MTA);
1108 #endif
1109
1110                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_msa_port"),         /* SMTP MSA */
1111                                         NULL,
1112                                         smtp_msa_greeting,
1113                                         smtp_command_loop,
1114                                         NULL,
1115                                         CitadelServiceSMTP_MSA);
1116
1117                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1118                                         file_lmtp_socket,
1119                                         lmtp_greeting,
1120                                         smtp_command_loop,
1121                                         NULL,
1122                                         CitadelServiceSMTP_LMTP);
1123
1124                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1125                                         file_lmtp_unfiltered_socket,
1126                                         lmtp_unfiltered_greeting,
1127                                         smtp_command_loop,
1128                                         NULL,
1129                                         CitadelServiceSMTP_LMTP_UNF);
1130
1131                 CtdlRegisterSessionHook(smtp_cleanup_function, EVT_STOP, PRIO_STOP + 250);
1132         }
1133         
1134         /* return our module name for the log */
1135         return "smtp";
1136 }