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