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         // This is a *preliminary* call to validate_recipients() to evaluate one recipient.
 685         valid = validate_recipients(
 686                 (char *)ChrPtr(SMTP->OneRcpt),
 687                 smtp_get_Recipients(),
 688                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 689         );
 690
 691         // Any type of error thrown by validate_recipients() will make the SMTP transaction fail at this point.
 692         if (valid->num_error != 0) {
 693                 cprintf("550 %s\r\n", valid->errormsg);
 694                 free_recipients(valid);
 695                 return;
 696         }
 697
 698         if (
 699                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 700                 && (CC->logged_in)                                              // ...and we're a logged-in user...
 701                 && (CtdlCheckInternetMailPermission(&CC->user)==0)              // ...who does not have Internet mail rights...
 702         ) {
 703                 cprintf("551 <%s> - you do not have permission to send Internet mail\r\n", ChrPtr(SMTP->OneRcpt));
 704                 free_recipients(valid);
 705                 return;
 706         }
 707
 708         if (
 709                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 710                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 711                 && (SMTP->is_lmtp == 0)                                         /// ...and didn't arrive via LMTP...
 712         ) {
 713                 cprintf("551 <%s> - relaying denied\r\n", ChrPtr(SMTP->OneRcpt));
 714                 free_recipients(valid);
 715                 return;
 716         }
 717
 718         if (
 719                 (valid->num_room > 0)                                           // If it's mail to a room (mailing list)...
 720                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 721                 && (is_email_subscribed_to_list((char *)ChrPtr(SMTP->from), valid->recp_room) == 0)     // ...and not a subscriber
 722         ) {
 723                 cprintf("551 <%s> - This mailing list only accepts messages from subscribers.\r\n", ChrPtr(SMTP->OneRcpt));
 724                 free_recipients(valid);
 725                 return;
 726         }
 727
 728         cprintf("250 RCPT ok <%s>\r\n", ChrPtr(SMTP->OneRcpt));
 729         if (StrLength(SMTP->recipients) > 0) {
 730                 StrBufAppendBufPlain(SMTP->recipients, HKEY(","), 0);
 731         }
 732         StrBufAppendBuf(SMTP->recipients, SMTP->OneRcpt, 0);
 733         SMTP->number_of_recipients ++;
 734         if (valid != NULL)  {
 735                 free_recipients(valid);
 736         }
 737 }
 738
 739
 740 /*
 741  * Implements the DATA command
 742  */
 743 void smtp_data(void) {
 744         StrBuf *body;
 745         StrBuf *defbody;
 746         struct CtdlMessage *msg = NULL;
 747         long msgnum = (-1L);
 748         char nowstamp[SIZ];
 749         struct recptypes *valid;
 750         int scan_errors;
 751         int i;
 752
 753         if (StrLength(SMTP->from) == 0) {
 754                 cprintf("503 Need MAIL command first.\r\n");
 755                 return;
 756         }
 757
 758         if (SMTP->number_of_recipients < 1) {
 759                 cprintf("503 Need RCPT command first.\r\n");
 760                 return;
 761         }
 762
 763         cprintf("354 Transmit message now - terminate with '.' by itself\r\n");
 764
 765         datestring(nowstamp, sizeof nowstamp, time(NULL), DATESTRING_RFC822);
 766         defbody = NewStrBufPlain(NULL, SIZ);
 767
 768         if (defbody != NULL) {
 769                 if (SMTP->is_lmtp && (CC->cs_UDSclientUID != -1)) {
 770                         StrBufPrintf(
 771                                 defbody,
 772                                 "Received: from %s (Citadel from userid %ld)\n"
 773                                 "       by %s; %s\n",
 774                                 ChrPtr(SMTP->helo_node),
 775                                 (long int) CC->cs_UDSclientUID,
 776                                 CtdlGetConfigStr("c_fqdn"),
 777                                 nowstamp);
 778                 }
 779                 else {
 780                         StrBufPrintf(
 781                                 defbody,
 782                                 "Received: from %s (%s [%s])\n"
 783                                 "       by %s; %s\n",
 784                                 ChrPtr(SMTP->helo_node),
 785                                 CC->cs_host,
 786                                 CC->cs_addr,
 787                                 CtdlGetConfigStr("c_fqdn"),
 788                                 nowstamp);
 789                 }
 790         }
 791         body = CtdlReadMessageBodyBuf(HKEY("."), CtdlGetConfigLong("c_maxmsglen"), defbody, 1);
 792         FreeStrBuf(&defbody);
 793         if (body == NULL) {
 794                 cprintf("550 Unable to save message: internal error.\r\n");
 795                 return;
 796         }
 797
 798         syslog(LOG_DEBUG, "serv_smtp: converting message...");
 799         msg = convert_internet_message_buf(&body);
 800
 801         /* If the user is locally authenticated, FORCE the From: header to
 802          * show up as the real sender.  Yes, this violates the RFC standard,
 803          * but IT MAKES SENSE.  If you prefer strict RFC adherence over
 804          * common sense, you can disable this in the configuration.
 805          *
 806          * We also set the "message room name" ('O' field) to MAILROOM
 807          * (which is Mail> on most systems) to prevent it from getting set
 808          * to something ugly like "0000058008.Sent Items>" when the message
 809          * is read with a Citadel client.
 810          */
 811         if ( (CC->logged_in) && (CtdlGetConfigInt("c_rfc822_strict_from") != CFG_SMTP_FROM_NOFILTER) ) {
 812                 int validemail = 0;
 813
 814                 if (!CM_IsEmpty(msg, erFc822Addr)       &&
 815                     ((CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_CORRECT) ||
 816                      (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)    )  )
 817                 {
 818                         if (!IsEmptyStr(CC->cs_inet_email))
 819                                 validemail = strcmp(CC->cs_inet_email, msg->cm_fields[erFc822Addr]) == 0;
 820                         if ((!validemail) &&
 821                             (!IsEmptyStr(CC->cs_inet_other_emails)))
 822                         {
 823                                 int num_secondary_emails = 0;
 824                                 int i;
 825                                 num_secondary_emails = num_tokens(CC->cs_inet_other_emails, '|');
 826                                 for (i=0; i < num_secondary_emails && !validemail; ++i) {
 827                                         char buf[256];
 828                                         extract_token(buf, CC->cs_inet_other_emails,i,'|',sizeof CC->cs_inet_other_emails);
 829                                         validemail = strcmp(buf, msg->cm_fields[erFc822Addr]) == 0;
 830                                 }
 831                         }
 832                 }
 833
 834                 if (!validemail && (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)) {
 835                         syslog(LOG_ERR, "serv_smtp: invalid sender '%s' - rejecting this message", msg->cm_fields[erFc822Addr]);
 836                         cprintf("550 Invalid sender '%s' - rejecting this message.\r\n", msg->cm_fields[erFc822Addr]);
 837                         return;
 838                 }
 839
 840                 CM_SetField(msg, eOriginalRoom, HKEY(MAILROOM));
 841                 if (SMTP->preferred_sender_name != NULL)
 842                         CM_SetField(msg, eAuthor, SKEY(SMTP->preferred_sender_name));
 843                 else
 844                         CM_SetField(msg, eAuthor, CC->user.fullname, strlen(CC->user.fullname));
 845
 846                 if (!validemail) {
 847                         if (SMTP->preferred_sender_email != NULL) {
 848                                 CM_SetField(msg, erFc822Addr, SKEY(SMTP->preferred_sender_email));
 849                         }
 850                         else {
 851                                 CM_SetField(msg, erFc822Addr, CC->cs_inet_email, strlen(CC->cs_inet_email));
 852                         }
 853                 }
 854         }
 855
 856         /* Set the "envelope from" address */
 857         CM_SetField(msg, eMessagePath, SKEY(SMTP->from));
 858
 859         /* Set the "envelope to" address */
 860         CM_SetField(msg, eenVelopeTo, SKEY(SMTP->recipients));
 861
 862         /* Submit the message into the Citadel system. */
 863         valid = validate_recipients(
 864                 (char *)ChrPtr(SMTP->recipients),
 865                 smtp_get_Recipients(),
 866                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 867         );
 868
 869         /* If there are modules that want to scan this message before final
 870          * submission (such as virus checkers or spam filters), call them now
 871          * and give them an opportunity to reject the message.
 872          */
 873         if (SMTP->is_unfiltered) {
 874                 scan_errors = 0;
 875         }
 876         else {
 877                 scan_errors = PerformMessageHooks(msg, valid, EVT_SMTPSCAN);
 878         }
 879
 880         if (scan_errors > 0) {  /* We don't want this message! */
 881
 882                 if (CM_IsEmpty(msg, eErrorMsg)) {
 883                         CM_SetField(msg, eErrorMsg, HKEY("Message rejected by filter"));
 884                 }
 885
 886                 StrBufPrintf(SMTP->OneRcpt, "550 %s\r\n", msg->cm_fields[eErrorMsg]);
 887         }
 888
 889         else {                  /* Ok, we'll accept this message. */
 890                 msgnum = CtdlSubmitMsg(msg, valid, "");
 891                 if (msgnum > 0L) {
 892                         StrBufPrintf(SMTP->OneRcpt, "250 Message accepted.\r\n");
 893                 }
 894                 else {
 895                         StrBufPrintf(SMTP->OneRcpt, "550 Internal delivery error\r\n");
 896                 }
 897         }
 898
 899         /* For SMTP and ESMTP, just print the result message.  For LMTP, we
 900          * have to print one result message for each recipient.  Since there
 901          * is nothing in Citadel which would cause different recipients to
 902          * have different results, we can get away with just spitting out the
 903          * same message once for each recipient.
 904          */
 905         if (SMTP->is_lmtp) {
 906                 for (i=0; i<SMTP->number_of_recipients; ++i) {
 907                         cputbuf(SMTP->OneRcpt);
 908                 }
 909         }
 910         else {
 911                 cputbuf(SMTP->OneRcpt);
 912         }
 913
 914         /* Write something to the syslog(which may or may not be where the
 915          * rest of the Citadel logs are going; some sysadmins want LOG_MAIL).
 916          */
 917         syslog((LOG_MAIL | LOG_INFO),
 918                     "%ld: from=<%s>, nrcpts=%d, relay=%s [%s], stat=%s",
 919                     msgnum,
 920                     ChrPtr(SMTP->from),
 921                     SMTP->number_of_recipients,
 922                     CC->cs_host,
 923                     CC->cs_addr,
 924                     ChrPtr(SMTP->OneRcpt)
 925         );
 926
 927         /* Clean up */
 928         CM_Free(msg);
 929         free_recipients(valid);
 930         smtp_data_clear();      /* clear out the buffers now */
 931 }
 932
 933
 934 /*
 935  * Implements the STARTTLS command
 936  */
 937 void smtp_starttls(void) {
 938         char ok_response[SIZ];
 939         char nosup_response[SIZ];
 940         char error_response[SIZ];
 941
 942         sprintf(ok_response, "220 Begin TLS negotiation now\r\n");
 943         sprintf(nosup_response, "554 TLS not supported here\r\n");
 944         sprintf(error_response, "554 Internal error\r\n");
 945         CtdlModuleStartCryptoMsgs(ok_response, nosup_response, error_response);
 946         smtp_rset(0);
 947 }
 948
 949
 950 /*
 951  * Implements the NOOP (NO OPeration) command
 952  */
 953 void smtp_noop(void) {
 954         cprintf("250 NOOP\r\n");
 955 }
 956
 957
 958 /*
 959  * Implements the QUIT command
 960  */
 961 void smtp_quit(void) {
 962         cprintf("221 Goodbye...\r\n");
 963         CC->kill_me = KILLME_CLIENT_LOGGED_OUT;
 964 }
 965
 966
 967 /*
 968  * Main command loop for SMTP server sessions.
 969  */
 970 void smtp_command_loop(void) {
 971         static const ConstStr AuthPlainStr = {HKEY("AUTH PLAIN")};
 972
 973         if (SMTP == NULL) {
 974                 syslog(LOG_ERR, "serv_smtp: Session SMTP data is null.  WTF?  We will crash now.");
 975                 abort();
 976         }
 977
 978         time(&CC->lastcmd);
 979         if (CtdlClientGetLine(SMTP->Cmd) < 1) {
 980                 syslog(LOG_INFO, "SMTP: client disconnected: ending session.");
 981                 CC->kill_me = KILLME_CLIENT_DISCONNECTED;
 982                 return;
 983         }
 984
 985         if (SMTP->command_state == smtp_user) {
 986                 if (!strncmp(ChrPtr(SMTP->Cmd), AuthPlainStr.Key, AuthPlainStr.len)) {
 987                         smtp_try_plain();
 988                 }
 989                 else {
 990                         smtp_get_user(0);
 991                 }
 992                 return;
 993         }
 994
 995         else if (SMTP->command_state == smtp_password) {
 996                 smtp_get_pass();
 997                 return;
 998         }
 999
1000         else if (SMTP->command_state == smtp_plain) {
1001                 smtp_try_plain();
1002                 return;
1003         }
1004
1005         syslog(LOG_DEBUG, "serv_smtp: client sent command <%s>", ChrPtr(SMTP->Cmd));
1006
1007         if (!strncasecmp(ChrPtr(SMTP->Cmd), "NOOP", 4)) {
1008                 smtp_noop();
1009                 return;
1010         }
1011
1012         if (!strncasecmp(ChrPtr(SMTP->Cmd), "QUIT", 4)) {
1013                 smtp_quit();
1014                 return;
1015         }
1016
1017         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELO", 4)) {
1018                 smtp_hello(HELO);
1019                 return;
1020         }
1021
1022         if (!strncasecmp(ChrPtr(SMTP->Cmd), "EHLO", 4)) {
1023                 smtp_hello(EHLO);
1024                 return;
1025         }
1026
1027         if (!strncasecmp(ChrPtr(SMTP->Cmd), "LHLO", 4)) {
1028                 smtp_hello(LHLO);
1029                 return;
1030         }
1031
1032         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RSET", 4)) {
1033                 smtp_rset(1);
1034                 return;
1035         }
1036
1037         if (!strncasecmp(ChrPtr(SMTP->Cmd), "AUTH", 4)) {
1038                 smtp_auth();
1039                 return;
1040         }
1041
1042         if (!strncasecmp(ChrPtr(SMTP->Cmd), "DATA", 4)) {
1043                 smtp_data();
1044                 return;
1045         }
1046
1047         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELP", 4)) {
1048                 smtp_help();
1049                 return;
1050         }
1051
1052         if (!strncasecmp(ChrPtr(SMTP->Cmd), "MAIL", 4)) {
1053                 smtp_mail();
1054                 return;
1055         }
1056
1057         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RCPT", 4)) {
1058                 smtp_rcpt();
1059                 return;
1060         }
1061 #ifdef HAVE_OPENSSL
1062         if (!strncasecmp(ChrPtr(SMTP->Cmd), "STARTTLS", 8)) {
1063                 smtp_starttls();
1064                 return;
1065         }
1066 #endif
1067
1068         cprintf("502 I'm afraid I can't do that.\r\n");
1069 }
1070
1071
1072 /*****************************************************************************/
1073 /*                      MODULE INITIALIZATION STUFF                          */
1074 /*****************************************************************************/
1075 /*
1076  * This cleanup function blows away the temporary memory used by
1077  * the SMTP server.
1078  */
1079 void smtp_cleanup_function(void)
1080 {
1081         /* Don't do this stuff if this is not an SMTP session! */
1082         if (CC->h_command_function != smtp_command_loop) return;
1083
1084         syslog(LOG_DEBUG, "Performing SMTP cleanup hook");
1085
1086         FreeStrBuf(&SMTP->Cmd);
1087         FreeStrBuf(&SMTP->helo_node);
1088         FreeStrBuf(&SMTP->from);
1089         FreeStrBuf(&SMTP->recipients);
1090         FreeStrBuf(&SMTP->OneRcpt);
1091         FreeStrBuf(&SMTP->preferred_sender_email);
1092         FreeStrBuf(&SMTP->preferred_sender_name);
1093
1094         free(SMTP);
1095 }
1096
1097 const char *CitadelServiceSMTP_MTA="SMTP-MTA";
1098 const char *CitadelServiceSMTPS_MTA="SMTPs-MTA";
1099 const char *CitadelServiceSMTP_MSA="SMTP-MSA";
1100 const char *CitadelServiceSMTP_LMTP="LMTP";
1101 const char *CitadelServiceSMTP_LMTP_UNF="LMTP-UnF";
1102
1103
1104 CTDL_MODULE_INIT(smtp)
1105 {
1106         if (!threading) {
1107                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtp_port"),        /* SMTP MTA */
1108                                         NULL,
1109                                         smtp_mta_greeting,
1110                                         smtp_command_loop,
1111                                         NULL,
1112                                         CitadelServiceSMTP_MTA);
1113
1114 #ifdef HAVE_OPENSSL
1115                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtps_port"),       /* SMTPS MTA */
1116                                         NULL,
1117                                         smtps_greeting,
1118                                         smtp_command_loop,
1119                                         NULL,
1120                                         CitadelServiceSMTPS_MTA);
1121 #endif
1122
1123                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_msa_port"),         /* SMTP MSA */
1124                                         NULL,
1125                                         smtp_msa_greeting,
1126                                         smtp_command_loop,
1127                                         NULL,
1128                                         CitadelServiceSMTP_MSA);
1129
1130                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1131                                         file_lmtp_socket,
1132                                         lmtp_greeting,
1133                                         smtp_command_loop,
1134                                         NULL,
1135                                         CitadelServiceSMTP_LMTP);
1136
1137                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1138                                         file_lmtp_unfiltered_socket,
1139                                         lmtp_unfiltered_greeting,
1140                                         smtp_command_loop,
1141                                         NULL,
1142                                         CitadelServiceSMTP_LMTP_UNF);
1143
1144                 CtdlRegisterSessionHook(smtp_cleanup_function, EVT_STOP, PRIO_STOP + 250);
1145         }
1146
1147         /* return our module name for the log */
1148         return "smtp";
1149 }