citadel/modules/smtp/serv_smtp.c

   1 /*
   2  * This module is an SMTP and ESMTP server for the Citadel system.
   3  * It is compliant with all of the following:
   4  *
   5  * RFC  821 - Simple Mail Transfer Protocol
   6  * RFC  876 - Survey of SMTP Implementations
   7  * RFC 1047 - Duplicate messages and SMTP
   8  * RFC 1652 - 8 bit MIME
   9  * RFC 1869 - Extended Simple Mail Transfer Protocol
  10  * RFC 1870 - SMTP Service Extension for Message Size Declaration
  11  * RFC 2033 - Local Mail Transfer Protocol
  12  * RFC 2197 - SMTP Service Extension for Command Pipelining
  13  * RFC 2476 - Message Submission
  14  * RFC 2487 - SMTP Service Extension for Secure SMTP over TLS
  15  * RFC 2554 - SMTP Service Extension for Authentication
  16  * RFC 2821 - Simple Mail Transfer Protocol
  17  * RFC 2822 - Internet Message Format
  18  * RFC 2920 - SMTP Service Extension for Command Pipelining
  19  *
  20  * The VRFY and EXPN commands have been removed from this implementation
  21  * because nobody uses these commands anymore, except for spammers.
  22  *
  23  * Copyright (c) 1998-2021 by the citadel.org team
  24  *
  25  * This program is open source software; you can redistribute it and/or modify
  26  * it under the terms of the GNU General Public License version 3.
  27  *
  28  * This program is distributed in the hope that it will be useful,
  29  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  30  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  31  * GNU General Public License for more details.
  32  */
  33
  34 #include "sysdep.h"
  35 #include <stdlib.h>
  36 #include <unistd.h>
  37 #include <stdio.h>
  38 #include <termios.h>
  39 #include <fcntl.h>
  40 #include <signal.h>
  41 #include <pwd.h>
  42 #include <errno.h>
  43 #include <sys/types.h>
  44 #include <syslog.h>
  45 #include <time.h>
  46 #include <sys/wait.h>
  47 #include <ctype.h>
  48 #include <string.h>
  49 #include <limits.h>
  50 #include <sys/socket.h>
  51 #include <netinet/in.h>
  52 #include <arpa/inet.h>
  53 #include <libcitadel.h>
  54 #include "citadel.h"
  55 #include "server.h"
  56 #include "citserver.h"
  57 #include "support.h"
  58 #include "config.h"
  59 #include "control.h"
  60 #include "user_ops.h"
  61 #include "room_ops.h"
  62 #include "database.h"
  63 #include "msgbase.h"
  64 #include "internet_addressing.h"
  65 #include "genstamp.h"
  66 #include "domain.h"
  67 #include "clientsocket.h"
  68 #include "locate_host.h"
  69 #include "citadel_dirs.h"
  70 #include "ctdl_module.h"
  71
  72 #include "smtp_util.h"
  73
  74 enum {                          /* Command states for login authentication */
  75         smtp_command,
  76         smtp_user,
  77         smtp_password,
  78         smtp_plain
  79 };
  80
  81 enum SMTP_FLAGS {
  82         HELO,
  83         EHLO,
  84         LHLO
  85 };
  86
  87
  88 /*
  89  * Here's where our SMTP session begins its happy day.
  90  */
  91 void smtp_greeting(int is_msa) {
  92         char message_to_spammer[1024];
  93
  94         strcpy(CC->cs_clientname, "SMTP session");
  95         CC->internal_pgm = 1;
  96         CC->cs_flags |= CS_STEALTH;
  97         CC->session_specific_data = malloc(sizeof(struct citsmtp));
  98         memset(SMTP, 0, sizeof(struct citsmtp));
  99         SMTP->is_msa = is_msa;
 100         SMTP->Cmd = NewStrBufPlain(NULL, SIZ);
 101         SMTP->helo_node = NewStrBuf();
 102         SMTP->from = NewStrBufPlain(NULL, SIZ);
 103         SMTP->recipients = NewStrBufPlain(NULL, SIZ);
 104         SMTP->OneRcpt = NewStrBufPlain(NULL, SIZ);
 105         SMTP->preferred_sender_email = NULL;
 106         SMTP->preferred_sender_name = NULL;
 107
 108         /* If this config option is set, reject connections from problem
 109          * addresses immediately instead of after they execute a RCPT
 110          */
 111         if ( (CtdlGetConfigInt("c_rbl_at_greeting")) && (SMTP->is_msa == 0) ) {
 112                 if (rbl_check(CC->cs_addr, message_to_spammer)) {
 113                         if (server_shutting_down)
 114                                 cprintf("421 %s\r\n", message_to_spammer);
 115                         else
 116                                 cprintf("550 %s\r\n", message_to_spammer);
 117                         CC->kill_me = KILLME_SPAMMER;
 118                         /* no need to free_recipients(valid), it's not allocated yet */
 119                         return;
 120                 }
 121         }
 122
 123         /* Otherwise we're either clean or we check later. */
 124
 125         if (CC->nologin==1) {
 126                 cprintf("451 Too many connections are already open; please try again later.\r\n");
 127                 CC->kill_me = KILLME_MAX_SESSIONS_EXCEEDED;
 128                 /* no need to free_recipients(valid), it's not allocated yet */
 129                 return;
 130         }
 131
 132         /* Note: the FQDN *must* appear as the first thing after the 220 code.
 133          * Some clients (including citmail.c) depend on it being there.
 134          */
 135         cprintf("220 %s ESMTP Citadel server ready.\r\n", CtdlGetConfigStr("c_fqdn"));
 136 }
 137
 138
 139 /*
 140  * SMTPS is just like SMTP, except it goes crypto right away.
 141  */
 142 void smtps_greeting(void) {
 143         CtdlModuleStartCryptoMsgs(NULL, NULL, NULL);
 144 #ifdef HAVE_OPENSSL
 145         if (!CC->redirect_ssl) CC->kill_me = KILLME_NO_CRYPTO;          /* kill session if no crypto */
 146 #endif
 147         smtp_greeting(0);
 148 }
 149
 150
 151 /*
 152  * SMTP MSA port requires authentication.
 153  */
 154 void smtp_msa_greeting(void) {
 155         smtp_greeting(1);
 156 }
 157
 158
 159 /*
 160  * LMTP is like SMTP but with some extra bonus footage added.
 161  */
 162 void lmtp_greeting(void) {
 163
 164         smtp_greeting(0);
 165         SMTP->is_lmtp = 1;
 166 }
 167
 168
 169 /*
 170  * Generic SMTP MTA greeting
 171  */
 172 void smtp_mta_greeting(void) {
 173         smtp_greeting(0);
 174 }
 175
 176
 177 /*
 178  * We also have an unfiltered LMTP socket that bypasses spam filters.
 179  */
 180 void lmtp_unfiltered_greeting(void) {
 181         smtp_greeting(0);
 182         SMTP->is_lmtp = 1;
 183         SMTP->is_unfiltered = 1;
 184 }
 185
 186
 187 /*
 188  * Login greeting common to all auth methods
 189  */
 190 void smtp_auth_greeting(void) {
 191         cprintf("235 Hello, %s\r\n", CC->user.fullname);
 192         syslog(LOG_INFO, "serv_smtp: SMTP authenticated %s", CC->user.fullname);
 193         CC->internal_pgm = 0;
 194         CC->cs_flags &= ~CS_STEALTH;
 195 }
 196
 197
 198 /*
 199  * Implement HELO and EHLO commands.
 200  *
 201  * which_command:  0=HELO, 1=EHLO, 2=LHLO
 202  */
 203 void smtp_hello(int which_command) {
 204
 205         if (StrLength(SMTP->Cmd) >= 6) {
 206                 StrBufAppendBuf(SMTP->helo_node, SMTP->Cmd, 5);
 207         }
 208
 209         if ( (which_command != LHLO) && (SMTP->is_lmtp) ) {
 210                 cprintf("500 Only LHLO is allowed when running LMTP\r\n");
 211                 return;
 212         }
 213
 214         if ( (which_command == LHLO) && (SMTP->is_lmtp == 0) ) {
 215                 cprintf("500 LHLO is only allowed when running LMTP\r\n");
 216                 return;
 217         }
 218
 219         if (which_command == HELO) {
 220                 cprintf("250 Hello %s (%s [%s])\r\n",
 221                         ChrPtr(SMTP->helo_node),
 222                         CC->cs_host,
 223                         CC->cs_addr
 224                 );
 225         }
 226         else {
 227                 if (which_command == EHLO) {
 228                         cprintf("250-Hello %s (%s [%s])\r\n",
 229                                 ChrPtr(SMTP->helo_node),
 230                                 CC->cs_host,
 231                                 CC->cs_addr
 232                         );
 233                 }
 234                 else {
 235                         cprintf("250-Greetings and joyous salutations.\r\n");
 236                 }
 237                 cprintf("250-HELP\r\n");
 238                 cprintf("250-SIZE %ld\r\n", CtdlGetConfigLong("c_maxmsglen"));
 239
 240 #ifdef HAVE_OPENSSL
 241                 /*
 242                  * Offer TLS, but only if TLS is not already active.
 243                  * Furthermore, only offer TLS when running on
 244                  * the SMTP-MSA port, not on the SMTP-MTA port, due to
 245                  * questionable reliability of TLS in certain sending MTA's.
 246                  */
 247                 if ( (!CC->redirect_ssl) && (SMTP->is_msa) ) {
 248                         cprintf("250-STARTTLS\r\n");
 249                 }
 250 #endif  /* HAVE_OPENSSL */
 251
 252                 cprintf("250-AUTH LOGIN PLAIN\r\n"
 253                         "250-AUTH=LOGIN PLAIN\r\n"
 254                         "250 8BITMIME\r\n"
 255                 );
 256         }
 257 }
 258
 259
 260 /*
 261  * Backend function for smtp_webcit_preferences_hack().
 262  * Look at a message and determine if it's the preferences file.
 263  */
 264 void smtp_webcit_preferences_hack_backend(long msgnum, void *userdata) {
 265         struct CtdlMessage *msg;
 266         char **webcit_conf = (char **) userdata;
 267
 268         if (*webcit_conf) {
 269                 return; // already got it
 270         }
 271
 272         msg = CtdlFetchMessage(msgnum, 1);
 273         if (msg == NULL) {
 274                 return;
 275         }
 276
 277         if ( !CM_IsEmpty(msg, eMsgSubject) && (!strcasecmp(msg->cm_fields[eMsgSubject], "__ WebCit Preferences __"))) {
 278                 /* This is it!  Change ownership of the message text so it doesn't get freed. */
 279                 *webcit_conf = (char *)msg->cm_fields[eMesageText];
 280                 msg->cm_fields[eMesageText] = NULL;
 281         }
 282         CM_Free(msg);
 283 }
 284
 285
 286 /*
 287  * The configuration item for the user's preferred display name for outgoing email is, unfortunately,
 288  * stored in the account's WebCit configuration.  We have to fetch it now.
 289  */
 290 void smtp_webcit_preferences_hack(void) {
 291         char config_roomname[ROOMNAMELEN];
 292         char *webcit_conf = NULL;
 293
 294         snprintf(config_roomname, sizeof config_roomname, "%010ld.%s", CC->user.usernum, USERCONFIGROOM);
 295         if (CtdlGetRoom(&CC->room, config_roomname) != 0) {
 296                 return;
 297         }
 298
 299         /*
 300          * Find the WebCit configuration message
 301          */
 302
 303         CtdlForEachMessage(MSGS_ALL, 1, NULL, NULL, NULL, smtp_webcit_preferences_hack_backend, (void *)&webcit_conf);
 304
 305         if (!webcit_conf) {
 306                 return;
 307         }
 308
 309         /* Parse the webcit configuration and attempt to do something useful with it */
 310         char *str = webcit_conf;
 311         char *saveptr = str;
 312         char *this_line = NULL;
 313         while (this_line = strtok_r(str, "\n", &saveptr), this_line != NULL) {
 314                 str = NULL;
 315                 if (!strncasecmp(this_line, "defaultfrom|", 12)) {
 316                         SMTP->preferred_sender_email = NewStrBufPlain(&this_line[12], -1);
 317                 }
 318                 if (!strncasecmp(this_line, "defaultname|", 12)) {
 319                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 320                 }
 321                 if ((!strncasecmp(this_line, "defaultname|", 12)) && (SMTP->preferred_sender_name == NULL)) {
 322                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 323                 }
 324
 325         }
 326         free(webcit_conf);
 327 }
 328
 329
 330 /*
 331  * Implement HELP command.
 332  */
 333 void smtp_help(void) {
 334         cprintf("214 RTFM http://www.ietf.org/rfc/rfc2821.txt\r\n");
 335 }
 336
 337
 338 /*
 339  *
 340  */
 341 void smtp_get_user(int offset) {
 342         char buf[SIZ];
 343
 344         StrBuf *UserName = NewStrBufDup(SMTP->Cmd);
 345         StrBufCutLeft(UserName, offset);
 346         StrBufDecodeBase64(UserName);
 347
 348         if (CtdlLoginExistingUser(ChrPtr(UserName)) == login_ok) {
 349                 size_t len = CtdlEncodeBase64(buf, "Password:", 9, 0);
 350
 351                 if (buf[len - 1] == '\n') {
 352                         buf[len - 1] = '\0';
 353                 }
 354                 cprintf("334 %s\r\n", buf);
 355                 SMTP->command_state = smtp_password;
 356         }
 357         else {
 358                 cprintf("500 No such user.\r\n");
 359                 SMTP->command_state = smtp_command;
 360         }
 361         FreeStrBuf(&UserName);
 362 }
 363
 364
 365 /*
 366  *
 367  */
 368 void smtp_get_pass(void)
 369 {
 370         char password[SIZ];
 371
 372         memset(password, 0, sizeof(password));
 373         StrBufDecodeBase64(SMTP->Cmd);
 374         syslog(LOG_DEBUG, "serv_smtp: trying <%s>", password);
 375         if (CtdlTryPassword(SKEY(SMTP->Cmd)) == pass_ok) {
 376                 smtp_auth_greeting();
 377         }
 378         else {
 379                 cprintf("535 Authentication failed.\r\n");
 380         }
 381         SMTP->command_state = smtp_command;
 382 }
 383
 384
 385 /*
 386  * Back end for PLAIN auth method (either inline or multistate)
 387  */
 388 void smtp_try_plain(void) {
 389         const char*decoded_authstring;
 390         char ident[256] = "";
 391         char user[256] = "";
 392         char pass[256] = "";
 393         int result;
 394
 395         long decoded_len;
 396         long len = 0;
 397         long plen = 0;
 398
 399         memset(pass, 0, sizeof(pass));
 400         decoded_len = StrBufDecodeBase64(SMTP->Cmd);
 401
 402         if (decoded_len > 0) {
 403                 decoded_authstring = ChrPtr(SMTP->Cmd);
 404
 405                 len = safestrncpy(ident, decoded_authstring, sizeof ident);
 406
 407                 decoded_len -= len - 1;
 408                 decoded_authstring += len + 1;
 409
 410                 if (decoded_len > 0) {
 411                         len = safestrncpy(user, decoded_authstring, sizeof user);
 412
 413                         decoded_authstring += len + 1;
 414                         decoded_len -= len - 1;
 415                 }
 416
 417                 if (decoded_len > 0) {
 418                         plen = safestrncpy(pass, decoded_authstring, sizeof pass);
 419
 420                         if (plen < 0)
 421                                 plen = sizeof(pass) - 1;
 422                 }
 423         }
 424
 425         SMTP->command_state = smtp_command;
 426
 427         if (!IsEmptyStr(ident)) {
 428                 result = CtdlLoginExistingUser(ident);
 429         }
 430         else {
 431                 result = CtdlLoginExistingUser(user);
 432         }
 433
 434         if (result == login_ok) {
 435                 if (CtdlTryPassword(pass, plen) == pass_ok) {
 436                         smtp_webcit_preferences_hack();
 437                         smtp_auth_greeting();
 438                         return;
 439                 }
 440         }
 441         cprintf("504 Authentication failed.\r\n");
 442 }
 443
 444
 445 /*
 446  * Attempt to perform authenticated SMTP
 447  */
 448 void smtp_auth(void) {
 449         char username_prompt[64];
 450         char method[64];
 451         char encoded_authstring[1024];
 452
 453         if (CC->logged_in) {
 454                 cprintf("504 Already logged in.\r\n");
 455                 return;
 456         }
 457
 458         if (StrLength(SMTP->Cmd) < 6) {
 459                 cprintf("501 Syntax error\r\n");
 460                 return;
 461         }
 462
 463         extract_token(method, ChrPtr(SMTP->Cmd) + 5, 0, ' ', sizeof method);
 464
 465         if (!strncasecmp(method, "login", 5) ) {
 466                 if (StrLength(SMTP->Cmd) >= 12) {
 467                         syslog(LOG_DEBUG, "serv_smtp: username <%s> supplied inline", ChrPtr(SMTP->Cmd)+11);
 468                         smtp_get_user(11);
 469                 }
 470                 else {
 471                         size_t len = CtdlEncodeBase64(username_prompt, "Username:", 9, 0);
 472                         if (username_prompt[len - 1] == '\n') {
 473                                 username_prompt[len - 1] = '\0';
 474                         }
 475                         cprintf("334 %s\r\n", username_prompt);
 476                         SMTP->command_state = smtp_user;
 477                 }
 478                 return;
 479         }
 480
 481         if (!strncasecmp(method, "plain", 5) ) {
 482                 long len;
 483                 if (num_tokens(ChrPtr(SMTP->Cmd) + 5, ' ') < 2) {
 484                         cprintf("334 \r\n");
 485                         SMTP->command_state = smtp_plain;
 486                         return;
 487                 }
 488
 489                 len = extract_token(encoded_authstring,
 490                                     ChrPtr(SMTP->Cmd) + 5,
 491                                     1, ' ',
 492                                     sizeof encoded_authstring);
 493                 StrBufPlain(SMTP->Cmd, encoded_authstring, len);
 494                 smtp_try_plain();
 495                 return;
 496         }
 497
 498         cprintf("504 Unknown authentication method.\r\n");
 499         return;
 500 }
 501
 502
 503 /*
 504  * Implements the RSET (reset state) command.
 505  * Currently this just zeroes out the state buffer.  If pointers to data
 506  * allocated with malloc() are ever placed in the state buffer, we have to
 507  * be sure to free() them first!
 508  *
 509  * Set do_response to nonzero to output the SMTP RSET response code.
 510  */
 511 void smtp_rset(int do_response) {
 512         /*
 513          * Our entire SMTP state is discarded when a RSET command is issued,
 514          * but we need to preserve this one little piece of information, so
 515          * we save it for later.
 516          */
 517
 518         FlushStrBuf(SMTP->Cmd);
 519         FlushStrBuf(SMTP->helo_node);
 520         FlushStrBuf(SMTP->from);
 521         FlushStrBuf(SMTP->recipients);
 522         FlushStrBuf(SMTP->OneRcpt);
 523
 524         SMTP->command_state = 0;
 525         SMTP->number_of_recipients = 0;
 526         SMTP->delivery_mode = 0;
 527         SMTP->message_originated_locally = 0;
 528         SMTP->is_msa = 0;
 529         /*
 530          * we must remember is_lmtp & is_unfiltered.
 531          */
 532
 533         /*
 534          * It is somewhat ambiguous whether we want to log out when a RSET
 535          * command is issued.  Here's the code to do it.  It is commented out
 536          * because some clients (such as Pine) issue RSET commands before
 537          * each message, but still expect to be logged in.
 538          *
 539          * if (CC->logged_in) {
 540          *      logout(CC);
 541          * }
 542          */
 543
 544         if (do_response) {
 545                 cprintf("250 Zap!\r\n");
 546         }
 547 }
 548
 549
 550 /*
 551  * Clear out the portions of the state buffer that need to be cleared out
 552  * after the DATA command finishes.
 553  */
 554 void smtp_data_clear(void) {
 555         FlushStrBuf(SMTP->from);
 556         FlushStrBuf(SMTP->recipients);
 557         FlushStrBuf(SMTP->OneRcpt);
 558         SMTP->number_of_recipients = 0;
 559         SMTP->delivery_mode = 0;
 560         SMTP->message_originated_locally = 0;
 561 }
 562
 563
 564 /*
 565  * Implements the "MAIL FROM:" command
 566  */
 567 void smtp_mail(void) {
 568         char user[SIZ];
 569         char node[SIZ];
 570         char name[SIZ];
 571
 572         if (StrLength(SMTP->from) > 0) {
 573                 cprintf("503 Only one sender permitted\r\n");
 574                 return;
 575         }
 576
 577         if (StrLength(SMTP->Cmd) < 6) {
 578                 cprintf("501 Syntax error\r\n");
 579                 return;
 580         }
 581
 582         if (strncasecmp(ChrPtr(SMTP->Cmd) + 5, "From:", 5)) {
 583                 cprintf("501 Syntax error\r\n");
 584                 return;
 585         }
 586
 587         StrBufAppendBuf(SMTP->from, SMTP->Cmd, 5);
 588         StrBufTrim(SMTP->from);
 589         if (strchr(ChrPtr(SMTP->from), '<') != NULL) {
 590                 StrBufStripAllBut(SMTP->from, '<', '>');
 591         }
 592
 593         /* We used to reject empty sender names, until it was brought to our
 594          * attention that RFC1123 5.2.9 requires that this be allowed.  So now
 595          * we allow it, but replace the empty string with a fake
 596          * address so we don't have to contend with the empty string causing
 597          * other code to fail when it's expecting something there.
 598          */
 599         if (StrLength(SMTP->from) == 0) {
 600                 StrBufPlain(SMTP->from, HKEY("someone@example.com"));
 601         }
 602
 603         /* If this SMTP connection is from a logged-in user, force the 'from'
 604          * to be the user's Internet e-mail address as Citadel knows it.
 605          */
 606         if (CC->logged_in) {
 607                 StrBufPlain(SMTP->from, CC->cs_inet_email, -1);
 608                 cprintf("250 Sender ok <%s>\r\n", ChrPtr(SMTP->from));
 609                 SMTP->message_originated_locally = 1;
 610                 return;
 611         }
 612
 613         else if (SMTP->is_lmtp) {
 614                 /* Bypass forgery checking for LMTP */
 615         }
 616
 617         /* Otherwise, make sure outsiders aren't trying to forge mail from
 618          * this system (unless, of course, c_allow_spoofing is enabled)
 619          */
 620         else if (CtdlGetConfigInt("c_allow_spoofing") == 0) {
 621                 process_rfc822_addr(ChrPtr(SMTP->from), user, node, name);
 622                 syslog(LOG_DEBUG, "serv_smtp: claimed envelope sender is '%s' == '%s' @ '%s' ('%s')",
 623                         ChrPtr(SMTP->from), user, node, name
 624                 );
 625                 if (CtdlHostAlias(node) != hostalias_nomatch) {
 626                         cprintf("550 You must log in to send mail from %s\r\n", node);
 627                         FlushStrBuf(SMTP->from);
 628                         syslog(LOG_DEBUG, "serv_smtp: rejecting unauthenticated mail from %s", node);
 629                         return;
 630                 }
 631         }
 632
 633         cprintf("250 Sender ok\r\n");
 634 }
 635
 636
 637 /*
 638  * Implements the "RCPT To:" command
 639  */
 640 void smtp_rcpt(void) {
 641         char message_to_spammer[SIZ];
 642         struct recptypes *valid = NULL;
 643
 644         if (StrLength(SMTP->from) == 0) {
 645                 cprintf("503 Need MAIL before RCPT\r\n");
 646                 return;
 647         }
 648
 649         if (StrLength(SMTP->Cmd) < 6) {
 650                 cprintf("501 Syntax error\r\n");
 651                 return;
 652         }
 653
 654         if (strncasecmp(ChrPtr(SMTP->Cmd) + 5, "To:", 3)) {
 655                 cprintf("501 Syntax error\r\n");
 656                 return;
 657         }
 658
 659         if ( (SMTP->is_msa) && (!CC->logged_in) ) {
 660                 cprintf("550 You must log in to send mail on this port.\r\n");
 661                 FlushStrBuf(SMTP->from);
 662                 return;
 663         }
 664
 665         FlushStrBuf(SMTP->OneRcpt);
 666         StrBufAppendBuf(SMTP->OneRcpt, SMTP->Cmd, 8);
 667         StrBufTrim(SMTP->OneRcpt);
 668         StrBufStripAllBut(SMTP->OneRcpt, '<', '>');
 669
 670         if ( (StrLength(SMTP->OneRcpt) + StrLength(SMTP->recipients)) >= SIZ) {
 671                 cprintf("452 Too many recipients\r\n");
 672                 return;
 673         }
 674
 675         /* RBL check */
 676         if ( (!CC->logged_in)   /* Don't RBL authenticated users */
 677            && (!SMTP->is_lmtp) ) {      /* Don't RBL LMTP clients */
 678                 if (CtdlGetConfigInt("c_rbl_at_greeting") == 0) {       /* Don't RBL again if we already did it */
 679                         if (rbl_check(CC->cs_addr, message_to_spammer)) {
 680                                 if (server_shutting_down)
 681                                         cprintf("421 %s\r\n", message_to_spammer);
 682                                 else
 683                                         cprintf("550 %s\r\n", message_to_spammer);
 684                                 /* no need to free_recipients(valid), it's not allocated yet */
 685                                 return;
 686                         }
 687                 }
 688         }
 689
 690         valid = validate_recipients(
 691                 ChrPtr(SMTP->OneRcpt),
 692                 smtp_get_Recipients(),
 693                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 694         );
 695         if (valid->num_error != 0) {
 696                 cprintf("550 %s\r\n", valid->errormsg);
 697                 free_recipients(valid);
 698                 return;
 699         }
 700
 701         if (valid->num_internet > 0) {
 702                 if (CC->logged_in) {
 703                         if (CtdlCheckInternetMailPermission(&CC->user)==0) {
 704                                 cprintf("551 <%s> - you do not have permission to send Internet mail\r\n",
 705                                         ChrPtr(SMTP->OneRcpt));
 706                                 free_recipients(valid);
 707                                 return;
 708                         }
 709                 }
 710         }
 711
 712         if (valid->num_internet > 0) {
 713                 if ( (SMTP->message_originated_locally == 0)
 714                    && (SMTP->is_lmtp == 0) ) {
 715                         cprintf("551 <%s> - relaying denied\r\n", ChrPtr(SMTP->OneRcpt));
 716                         free_recipients(valid);
 717                         return;
 718                 }
 719         }
 720
 721         cprintf("250 RCPT ok <%s>\r\n", ChrPtr(SMTP->OneRcpt));
 722         if (StrLength(SMTP->recipients) > 0) {
 723                 StrBufAppendBufPlain(SMTP->recipients, HKEY(","), 0);
 724         }
 725         StrBufAppendBuf(SMTP->recipients, SMTP->OneRcpt, 0);
 726         SMTP->number_of_recipients ++;
 727         if (valid != NULL)  {
 728                 free_recipients(valid);
 729         }
 730 }
 731
 732
 733 /*
 734  * Implements the DATA command
 735  */
 736 void smtp_data(void) {
 737         StrBuf *body;
 738         StrBuf *defbody;
 739         struct CtdlMessage *msg = NULL;
 740         long msgnum = (-1L);
 741         char nowstamp[SIZ];
 742         struct recptypes *valid;
 743         int scan_errors;
 744         int i;
 745
 746         if (StrLength(SMTP->from) == 0) {
 747                 cprintf("503 Need MAIL command first.\r\n");
 748                 return;
 749         }
 750
 751         if (SMTP->number_of_recipients < 1) {
 752                 cprintf("503 Need RCPT command first.\r\n");
 753                 return;
 754         }
 755
 756         cprintf("354 Transmit message now - terminate with '.' by itself\r\n");
 757
 758         datestring(nowstamp, sizeof nowstamp, time(NULL), DATESTRING_RFC822);
 759         defbody = NewStrBufPlain(NULL, SIZ);
 760
 761         if (defbody != NULL) {
 762                 if (SMTP->is_lmtp && (CC->cs_UDSclientUID != -1)) {
 763                         StrBufPrintf(
 764                                 defbody,
 765                                 "Received: from %s (Citadel from userid %ld)\n"
 766                                 "       by %s; %s\n",
 767                                 ChrPtr(SMTP->helo_node),
 768                                 (long int) CC->cs_UDSclientUID,
 769                                 CtdlGetConfigStr("c_fqdn"),
 770                                 nowstamp);
 771                 }
 772                 else {
 773                         StrBufPrintf(
 774                                 defbody,
 775                                 "Received: from %s (%s [%s])\n"
 776                                 "       by %s; %s\n",
 777                                 ChrPtr(SMTP->helo_node),
 778                                 CC->cs_host,
 779                                 CC->cs_addr,
 780                                 CtdlGetConfigStr("c_fqdn"),
 781                                 nowstamp);
 782                 }
 783         }
 784         body = CtdlReadMessageBodyBuf(HKEY("."), CtdlGetConfigLong("c_maxmsglen"), defbody, 1);
 785         FreeStrBuf(&defbody);
 786         if (body == NULL) {
 787                 cprintf("550 Unable to save message: internal error.\r\n");
 788                 return;
 789         }
 790
 791         syslog(LOG_DEBUG, "serv_smtp: converting message...");
 792         msg = convert_internet_message_buf(&body);
 793
 794         /* If the user is locally authenticated, FORCE the From: header to
 795          * show up as the real sender.  Yes, this violates the RFC standard,
 796          * but IT MAKES SENSE.  If you prefer strict RFC adherence over
 797          * common sense, you can disable this in the configuration.
 798          *
 799          * We also set the "message room name" ('O' field) to MAILROOM
 800          * (which is Mail> on most systems) to prevent it from getting set
 801          * to something ugly like "0000058008.Sent Items>" when the message
 802          * is read with a Citadel client.
 803          */
 804         if ( (CC->logged_in) && (CtdlGetConfigInt("c_rfc822_strict_from") != CFG_SMTP_FROM_NOFILTER) ) {
 805                 int validemail = 0;
 806
 807                 if (!CM_IsEmpty(msg, erFc822Addr)       &&
 808                     ((CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_CORRECT) ||
 809                      (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)    )  )
 810                 {
 811                         if (!IsEmptyStr(CC->cs_inet_email))
 812                                 validemail = strcmp(CC->cs_inet_email, msg->cm_fields[erFc822Addr]) == 0;
 813                         if ((!validemail) &&
 814                             (!IsEmptyStr(CC->cs_inet_other_emails)))
 815                         {
 816                                 int num_secondary_emails = 0;
 817                                 int i;
 818                                 num_secondary_emails = num_tokens(CC->cs_inet_other_emails, '|');
 819                                 for (i=0; i < num_secondary_emails && !validemail; ++i) {
 820                                         char buf[256];
 821                                         extract_token(buf, CC->cs_inet_other_emails,i,'|',sizeof CC->cs_inet_other_emails);
 822                                         validemail = strcmp(buf, msg->cm_fields[erFc822Addr]) == 0;
 823                                 }
 824                         }
 825                 }
 826
 827                 if (!validemail && (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)) {
 828                         syslog(LOG_ERR, "serv_smtp: invalid sender '%s' - rejecting this message", msg->cm_fields[erFc822Addr]);
 829                         cprintf("550 Invalid sender '%s' - rejecting this message.\r\n", msg->cm_fields[erFc822Addr]);
 830                         return;
 831                 }
 832
 833                 CM_SetField(msg, eOriginalRoom, HKEY(MAILROOM));
 834                 if (SMTP->preferred_sender_name != NULL)
 835                         CM_SetField(msg, eAuthor, SKEY(SMTP->preferred_sender_name));
 836                 else
 837                         CM_SetField(msg, eAuthor, CC->user.fullname, strlen(CC->user.fullname));
 838
 839                 if (!validemail) {
 840                         if (SMTP->preferred_sender_email != NULL) {
 841                                 CM_SetField(msg, erFc822Addr, SKEY(SMTP->preferred_sender_email));
 842                         }
 843                         else {
 844                                 CM_SetField(msg, erFc822Addr, CC->cs_inet_email, strlen(CC->cs_inet_email));
 845                         }
 846                 }
 847         }
 848
 849         /* Set the "envelope from" address */
 850         CM_SetField(msg, eMessagePath, SKEY(SMTP->from));
 851
 852         /* Set the "envelope to" address */
 853         CM_SetField(msg, eenVelopeTo, SKEY(SMTP->recipients));
 854
 855         /* Submit the message into the Citadel system. */
 856         valid = validate_recipients(
 857                 ChrPtr(SMTP->recipients),
 858                 smtp_get_Recipients(),
 859                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 860         );
 861
 862         /* If there are modules that want to scan this message before final
 863          * submission (such as virus checkers or spam filters), call them now
 864          * and give them an opportunity to reject the message.
 865          */
 866         if (SMTP->is_unfiltered) {
 867                 scan_errors = 0;
 868         }
 869         else {
 870                 scan_errors = PerformMessageHooks(msg, valid, EVT_SMTPSCAN);
 871         }
 872
 873         if (scan_errors > 0) {  /* We don't want this message! */
 874
 875                 if (CM_IsEmpty(msg, eErrorMsg)) {
 876                         CM_SetField(msg, eErrorMsg, HKEY("Message rejected by filter"));
 877                 }
 878
 879                 StrBufPrintf(SMTP->OneRcpt, "550 %s\r\n", msg->cm_fields[eErrorMsg]);
 880         }
 881
 882         else {                  /* Ok, we'll accept this message. */
 883                 msgnum = CtdlSubmitMsg(msg, valid, "");
 884                 if (msgnum > 0L) {
 885                         StrBufPrintf(SMTP->OneRcpt, "250 Message accepted.\r\n");
 886                 }
 887                 else {
 888                         StrBufPrintf(SMTP->OneRcpt, "550 Internal delivery error\r\n");
 889                 }
 890         }
 891
 892         /* For SMTP and ESMTP, just print the result message.  For LMTP, we
 893          * have to print one result message for each recipient.  Since there
 894          * is nothing in Citadel which would cause different recipients to
 895          * have different results, we can get away with just spitting out the
 896          * same message once for each recipient.
 897          */
 898         if (SMTP->is_lmtp) {
 899                 for (i=0; i<SMTP->number_of_recipients; ++i) {
 900                         cputbuf(SMTP->OneRcpt);
 901                 }
 902         }
 903         else {
 904                 cputbuf(SMTP->OneRcpt);
 905         }
 906
 907         /* Write something to the syslog(which may or may not be where the
 908          * rest of the Citadel logs are going; some sysadmins want LOG_MAIL).
 909          */
 910         syslog((LOG_MAIL | LOG_INFO),
 911                     "%ld: from=<%s>, nrcpts=%d, relay=%s [%s], stat=%s",
 912                     msgnum,
 913                     ChrPtr(SMTP->from),
 914                     SMTP->number_of_recipients,
 915                     CC->cs_host,
 916                     CC->cs_addr,
 917                     ChrPtr(SMTP->OneRcpt)
 918         );
 919
 920         /* Clean up */
 921         CM_Free(msg);
 922         free_recipients(valid);
 923         smtp_data_clear();      /* clear out the buffers now */
 924 }
 925
 926
 927 /*
 928  * Implements the STARTTLS command
 929  */
 930 void smtp_starttls(void) {
 931         char ok_response[SIZ];
 932         char nosup_response[SIZ];
 933         char error_response[SIZ];
 934
 935         sprintf(ok_response, "220 Begin TLS negotiation now\r\n");
 936         sprintf(nosup_response, "554 TLS not supported here\r\n");
 937         sprintf(error_response, "554 Internal error\r\n");
 938         CtdlModuleStartCryptoMsgs(ok_response, nosup_response, error_response);
 939         smtp_rset(0);
 940 }
 941
 942
 943 /*
 944  * Implements the NOOP (NO OPeration) command
 945  */
 946 void smtp_noop(void) {
 947         cprintf("250 NOOP\r\n");
 948 }
 949
 950
 951 /*
 952  * Implements the QUIT command
 953  */
 954 void smtp_quit(void) {
 955         cprintf("221 Goodbye...\r\n");
 956         CC->kill_me = KILLME_CLIENT_LOGGED_OUT;
 957 }
 958
 959
 960 /*
 961  * Main command loop for SMTP server sessions.
 962  */
 963 void smtp_command_loop(void) {
 964         static const ConstStr AuthPlainStr = {HKEY("AUTH PLAIN")};
 965
 966         if (SMTP == NULL) {
 967                 syslog(LOG_ERR, "serv_smtp: Session SMTP data is null.  WTF?  We will crash now.");
 968                 abort();
 969         }
 970
 971         time(&CC->lastcmd);
 972         if (CtdlClientGetLine(SMTP->Cmd) < 1) {
 973                 syslog(LOG_INFO, "SMTP: client disconnected: ending session.");
 974                 CC->kill_me = KILLME_CLIENT_DISCONNECTED;
 975                 return;
 976         }
 977
 978         if (SMTP->command_state == smtp_user) {
 979                 if (!strncmp(ChrPtr(SMTP->Cmd), AuthPlainStr.Key, AuthPlainStr.len)) {
 980                         smtp_try_plain();
 981                 }
 982                 else {
 983                         smtp_get_user(5);
 984                 }
 985                 return;
 986         }
 987
 988         else if (SMTP->command_state == smtp_password) {
 989                 smtp_get_pass();
 990                 return;
 991         }
 992
 993         else if (SMTP->command_state == smtp_plain) {
 994                 smtp_try_plain();
 995                 return;
 996         }
 997
 998         syslog(LOG_DEBUG, "serv_smtp: client sent command <%s>", ChrPtr(SMTP->Cmd));
 999
1000         if (!strncasecmp(ChrPtr(SMTP->Cmd), "NOOP", 4)) {
1001                 smtp_noop();
1002                 return;
1003         }
1004
1005         if (!strncasecmp(ChrPtr(SMTP->Cmd), "QUIT", 4)) {
1006                 smtp_quit();
1007                 return;
1008         }
1009
1010         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELO", 4)) {
1011                 smtp_hello(HELO);
1012                 return;
1013         }
1014
1015         if (!strncasecmp(ChrPtr(SMTP->Cmd), "EHLO", 4)) {
1016                 smtp_hello(EHLO);
1017                 return;
1018         }
1019
1020         if (!strncasecmp(ChrPtr(SMTP->Cmd), "LHLO", 4)) {
1021                 smtp_hello(LHLO);
1022                 return;
1023         }
1024
1025         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RSET", 4)) {
1026                 smtp_rset(1);
1027                 return;
1028         }
1029
1030         if (!strncasecmp(ChrPtr(SMTP->Cmd), "AUTH", 4)) {
1031                 smtp_auth();
1032                 return;
1033         }
1034
1035         if (!strncasecmp(ChrPtr(SMTP->Cmd), "DATA", 4)) {
1036                 smtp_data();
1037                 return;
1038         }
1039
1040         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELP", 4)) {
1041                 smtp_help();
1042                 return;
1043         }
1044
1045         if (!strncasecmp(ChrPtr(SMTP->Cmd), "MAIL", 4)) {
1046                 smtp_mail();
1047                 return;
1048         }
1049
1050         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RCPT", 4)) {
1051                 smtp_rcpt();
1052                 return;
1053         }
1054 #ifdef HAVE_OPENSSL
1055         if (!strncasecmp(ChrPtr(SMTP->Cmd), "STARTTLS", 8)) {
1056                 smtp_starttls();
1057                 return;
1058         }
1059 #endif
1060
1061         cprintf("502 I'm afraid I can't do that.\r\n");
1062 }
1063
1064
1065 /*****************************************************************************/
1066 /*                      MODULE INITIALIZATION STUFF                          */
1067 /*****************************************************************************/
1068 /*
1069  * This cleanup function blows away the temporary memory used by
1070  * the SMTP server.
1071  */
1072 void smtp_cleanup_function(void)
1073 {
1074         /* Don't do this stuff if this is not an SMTP session! */
1075         if (CC->h_command_function != smtp_command_loop) return;
1076
1077         syslog(LOG_DEBUG, "Performing SMTP cleanup hook");
1078
1079         FreeStrBuf(&SMTP->Cmd);
1080         FreeStrBuf(&SMTP->helo_node);
1081         FreeStrBuf(&SMTP->from);
1082         FreeStrBuf(&SMTP->recipients);
1083         FreeStrBuf(&SMTP->OneRcpt);
1084         FreeStrBuf(&SMTP->preferred_sender_email);
1085         FreeStrBuf(&SMTP->preferred_sender_name);
1086
1087         free(SMTP);
1088 }
1089
1090 const char *CitadelServiceSMTP_MTA="SMTP-MTA";
1091 const char *CitadelServiceSMTPS_MTA="SMTPs-MTA";
1092 const char *CitadelServiceSMTP_MSA="SMTP-MSA";
1093 const char *CitadelServiceSMTP_LMTP="LMTP";
1094 const char *CitadelServiceSMTP_LMTP_UNF="LMTP-UnF";
1095
1096
1097 CTDL_MODULE_INIT(smtp)
1098 {
1099         if (!threading) {
1100                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtp_port"),        /* SMTP MTA */
1101                                         NULL,
1102                                         smtp_mta_greeting,
1103                                         smtp_command_loop,
1104                                         NULL,
1105                                         CitadelServiceSMTP_MTA);
1106
1107 #ifdef HAVE_OPENSSL
1108                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtps_port"),       /* SMTPS MTA */
1109                                         NULL,
1110                                         smtps_greeting,
1111                                         smtp_command_loop,
1112                                         NULL,
1113                                         CitadelServiceSMTPS_MTA);
1114 #endif
1115
1116                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_msa_port"),         /* SMTP MSA */
1117                                         NULL,
1118                                         smtp_msa_greeting,
1119                                         smtp_command_loop,
1120                                         NULL,
1121                                         CitadelServiceSMTP_MSA);
1122
1123                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1124                                         file_lmtp_socket,
1125                                         lmtp_greeting,
1126                                         smtp_command_loop,
1127                                         NULL,
1128                                         CitadelServiceSMTP_LMTP);
1129
1130                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1131                                         file_lmtp_unfiltered_socket,
1132                                         lmtp_unfiltered_greeting,
1133                                         smtp_command_loop,
1134                                         NULL,
1135                                         CitadelServiceSMTP_LMTP_UNF);
1136
1137                 CtdlRegisterSessionHook(smtp_cleanup_function, EVT_STOP, PRIO_STOP + 250);
1138         }
1139
1140         /* return our module name for the log */
1141         return "smtp";
1142 }