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) 1998-2022 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 // Here's where our SMTP session begins its happy day.
  87 void smtp_greeting(int is_msa) {
  88         char message_to_spammer[1024];
  89
  90         strcpy(CC->cs_clientname, "SMTP session");
  91         CC->internal_pgm = 1;
  92         CC->cs_flags |= CS_STEALTH;
  93         CC->session_specific_data = malloc(sizeof(struct citsmtp));
  94         memset(SMTP, 0, sizeof(struct citsmtp));
  95         SMTP->is_msa = is_msa;
  96         SMTP->Cmd = NewStrBufPlain(NULL, SIZ);
  97         SMTP->helo_node = NewStrBuf();
  98         SMTP->from = NewStrBufPlain(NULL, SIZ);
  99         SMTP->recipients = NewStrBufPlain(NULL, SIZ);
 100         SMTP->OneRcpt = NewStrBufPlain(NULL, SIZ);
 101         SMTP->preferred_sender_email = NULL;
 102         SMTP->preferred_sender_name = NULL;
 103
 104         // If this config option is set, reject connections from problem
 105         // addresses immediately instead of after they execute a RCPT
 106         if ( (CtdlGetConfigInt("c_rbl_at_greeting")) && (SMTP->is_msa == 0) ) {
 107                 if (rbl_check(CC->cs_addr, message_to_spammer)) {
 108                         if (server_shutting_down)
 109                                 cprintf("421 %s\r\n", message_to_spammer);
 110                         else
 111                                 cprintf("550 %s\r\n", message_to_spammer);
 112                         CC->kill_me = KILLME_SPAMMER;
 113                         /* no need to free_recipients(valid), it's not allocated yet */
 114                         return;
 115                 }
 116         }
 117
 118         // Otherwise we're either clean or we check later.
 119
 120         if (CC->nologin==1) {
 121                 cprintf("451 Too many connections are already open; please try again later.\r\n");
 122                 CC->kill_me = KILLME_MAX_SESSIONS_EXCEEDED;
 123                 // no need to free_recipients(valid), it's not allocated yet
 124                 return;
 125         }
 126
 127         // Note: the FQDN *must* appear as the first thing after the 220 code.
 128         // Some clients (including citmail.c) depend on it being there.
 129         cprintf("220 %s ESMTP Citadel server ready.\r\n", CtdlGetConfigStr("c_fqdn"));
 130 }
 131
 132
 133 // SMTPS is just like SMTP, except it goes crypto right away.
 134 void smtps_greeting(void) {
 135         CtdlModuleStartCryptoMsgs(NULL, NULL, NULL);
 136 #ifdef HAVE_OPENSSL
 137         if (!CC->redirect_ssl) CC->kill_me = KILLME_NO_CRYPTO;          // kill session if no crypto
 138 #endif
 139         smtp_greeting(0);
 140 }
 141
 142
 143 // SMTP MSA port requires authentication.
 144 void smtp_msa_greeting(void) {
 145         smtp_greeting(1);
 146 }
 147
 148
 149 // LMTP is like SMTP but with some extra bonus footage added.
 150 void lmtp_greeting(void) {
 151
 152         smtp_greeting(0);
 153         SMTP->is_lmtp = 1;
 154 }
 155
 156
 157 // Generic SMTP MTA greeting
 158 void smtp_mta_greeting(void) {
 159         smtp_greeting(0);
 160 }
 161
 162
 163 // We also have an unfiltered LMTP socket that bypasses spam filters.
 164 void lmtp_unfiltered_greeting(void) {
 165         smtp_greeting(0);
 166         SMTP->is_lmtp = 1;
 167         SMTP->is_unfiltered = 1;
 168 }
 169
 170
 171 // Login greeting common to all auth methods
 172 void smtp_auth_greeting(void) {
 173         cprintf("235 Hello, %s\r\n", CC->user.fullname);
 174         syslog(LOG_INFO, "serv_smtp: SMTP authenticated %s", CC->user.fullname);
 175         CC->internal_pgm = 0;
 176         CC->cs_flags &= ~CS_STEALTH;
 177 }
 178
 179
 180 // Implement HELO and EHLO commands.
 181 // which_command:  0=HELO, 1=EHLO, 2=LHLO
 182 void smtp_hello(int which_command) {
 183
 184         if (StrLength(SMTP->Cmd) >= 6) {
 185                 FlushStrBuf(SMTP->helo_node);
 186                 StrBufAppendBuf(SMTP->helo_node, SMTP->Cmd, 5);
 187         }
 188
 189         if ( (which_command != LHLO) && (SMTP->is_lmtp) ) {
 190                 cprintf("500 Only LHLO is allowed when running LMTP\r\n");
 191                 return;
 192         }
 193
 194         if ( (which_command == LHLO) && (SMTP->is_lmtp == 0) ) {
 195                 cprintf("500 LHLO is only allowed when running LMTP\r\n");
 196                 return;
 197         }
 198
 199         if (which_command == HELO) {
 200                 cprintf("250 Hello %s (%s [%s])\r\n",
 201                         ChrPtr(SMTP->helo_node),
 202                         CC->cs_host,
 203                         CC->cs_addr
 204                 );
 205         }
 206         else {
 207                 if (which_command == EHLO) {
 208                         cprintf("250-Hello %s (%s [%s])\r\n",
 209                                 ChrPtr(SMTP->helo_node),
 210                                 CC->cs_host,
 211                                 CC->cs_addr
 212                         );
 213                 }
 214                 else {
 215                         cprintf("250-Greetings and joyous salutations.\r\n");
 216                 }
 217                 cprintf("250-HELP\r\n");
 218                 cprintf("250-SIZE %ld\r\n", CtdlGetConfigLong("c_maxmsglen"));
 219
 220 #ifdef HAVE_OPENSSL
 221                 // Offer TLS, but only if TLS is not already active.
 222                 // Furthermore, only offer TLS when running on
 223                 // the SMTP-MSA port, not on the SMTP-MTA port, due to
 224                 // questionable reliability of TLS in certain sending MTA's.
 225                 if ( (!CC->redirect_ssl) && (SMTP->is_msa) ) {
 226                         cprintf("250-STARTTLS\r\n");
 227                 }
 228 #endif
 229
 230                 cprintf("250-AUTH LOGIN PLAIN\r\n"
 231                         "250-AUTH=LOGIN PLAIN\r\n"
 232                         "250 8BITMIME\r\n"
 233                 );
 234         }
 235 }
 236
 237
 238 // Backend function for smtp_webcit_preferences_hack().
 239 // Look at a message and determine if it's the preferences file.
 240 void smtp_webcit_preferences_hack_backend(long msgnum, void *userdata) {
 241         struct CtdlMessage *msg;
 242         char **webcit_conf = (char **) userdata;
 243
 244         if (*webcit_conf) {
 245                 return;         // already got it
 246         }
 247
 248         msg = CtdlFetchMessage(msgnum, 1);
 249         if (msg == NULL) {
 250                 return;
 251         }
 252
 253         if ( !CM_IsEmpty(msg, eMsgSubject) && (!strcasecmp(msg->cm_fields[eMsgSubject], "__ WebCit Preferences __"))) {
 254                 // This is it!  Change ownership of the message text so it doesn't get freed.
 255                 *webcit_conf = (char *)msg->cm_fields[eMesageText];
 256                 msg->cm_fields[eMesageText] = NULL;
 257         }
 258         CM_Free(msg);
 259 }
 260
 261
 262 // The configuration item for the user's preferred display name for outgoing email is, unfortunately,
 263 // stored in the account's WebCit configuration.  We have to fetch it now.
 264 void smtp_webcit_preferences_hack(void) {
 265         char config_roomname[ROOMNAMELEN];
 266         char *webcit_conf = NULL;
 267
 268         snprintf(config_roomname, sizeof config_roomname, "%010ld.%s", CC->user.usernum, USERCONFIGROOM);
 269         if (CtdlGetRoom(&CC->room, config_roomname) != 0) {
 270                 return;
 271         }
 272
 273         // Find the WebCit configuration message
 274         CtdlForEachMessage(MSGS_ALL, 1, NULL, NULL, NULL, smtp_webcit_preferences_hack_backend, (void *)&webcit_conf);
 275
 276         if (!webcit_conf) {
 277                 return;
 278         }
 279
 280         // Parse the webcit configuration and attempt to do something useful with it
 281         char *str = webcit_conf;
 282         char *saveptr = str;
 283         char *this_line = NULL;
 284         while (this_line = strtok_r(str, "\n", &saveptr), this_line != NULL) {
 285                 str = NULL;
 286                 if (!strncasecmp(this_line, "defaultfrom|", 12)) {
 287                         SMTP->preferred_sender_email = NewStrBufPlain(&this_line[12], -1);
 288                 }
 289                 if (!strncasecmp(this_line, "defaultname|", 12)) {
 290                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 291                 }
 292                 if ((!strncasecmp(this_line, "defaultname|", 12)) && (SMTP->preferred_sender_name == NULL)) {
 293                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 294                 }
 295
 296         }
 297         free(webcit_conf);
 298 }
 299
 300
 301 // Implement HELP command.
 302 void smtp_help(void) {
 303         cprintf("214 RTFM http://www.ietf.org/rfc/rfc2821.txt\r\n");
 304 }
 305
 306
 307 void smtp_get_user(int offset) {
 308         char buf[SIZ];
 309
 310         StrBuf *UserName = NewStrBufDup(SMTP->Cmd);
 311         StrBufCutLeft(UserName, offset);
 312         StrBufDecodeBase64(UserName);
 313
 314         if (CtdlLoginExistingUser(ChrPtr(UserName)) == login_ok) {
 315                 size_t len = CtdlEncodeBase64(buf, "Password:", 9, 0);
 316
 317                 if (buf[len - 1] == '\n') {
 318                         buf[len - 1] = '\0';
 319                 }
 320                 cprintf("334 %s\r\n", buf);
 321                 SMTP->command_state = smtp_password;
 322         }
 323         else {
 324                 cprintf("500 No such user.\r\n");
 325                 SMTP->command_state = smtp_command;
 326         }
 327         FreeStrBuf(&UserName);
 328 }
 329
 330
 331 void smtp_get_pass(void) {
 332         char password[SIZ];
 333
 334         memset(password, 0, sizeof(password));
 335         StrBufDecodeBase64(SMTP->Cmd);
 336         syslog(LOG_DEBUG, "serv_smtp: trying <%s>", password);
 337         if (CtdlTryPassword(SKEY(SMTP->Cmd)) == pass_ok) {
 338                 smtp_auth_greeting();
 339         }
 340         else {
 341                 cprintf("535 Authentication failed.\r\n");
 342         }
 343         SMTP->command_state = smtp_command;
 344 }
 345
 346
 347 // Back end for PLAIN auth method (either inline or multistate)
 348 void smtp_try_plain(void) {
 349         const char*decoded_authstring;
 350         char ident[256] = "";
 351         char user[256] = "";
 352         char pass[256] = "";
 353         int result;
 354
 355         long decoded_len;
 356         long len = 0;
 357         long plen = 0;
 358
 359         memset(pass, 0, sizeof(pass));
 360         decoded_len = StrBufDecodeBase64(SMTP->Cmd);
 361
 362         if (decoded_len > 0) {
 363                 decoded_authstring = ChrPtr(SMTP->Cmd);
 364
 365                 len = safestrncpy(ident, decoded_authstring, sizeof ident);
 366
 367                 decoded_len -= len - 1;
 368                 decoded_authstring += len + 1;
 369
 370                 if (decoded_len > 0) {
 371                         len = safestrncpy(user, decoded_authstring, sizeof user);
 372
 373                         decoded_authstring += len + 1;
 374                         decoded_len -= len - 1;
 375                 }
 376
 377                 if (decoded_len > 0) {
 378                         plen = safestrncpy(pass, decoded_authstring, sizeof pass);
 379
 380                         if (plen < 0)
 381                                 plen = sizeof(pass) - 1;
 382                 }
 383         }
 384
 385         SMTP->command_state = smtp_command;
 386
 387         if (!IsEmptyStr(ident)) {
 388                 result = CtdlLoginExistingUser(ident);
 389         }
 390         else {
 391                 result = CtdlLoginExistingUser(user);
 392         }
 393
 394         if (result == login_ok) {
 395                 if (CtdlTryPassword(pass, plen) == pass_ok) {
 396                         smtp_webcit_preferences_hack();
 397                         smtp_auth_greeting();
 398                         return;
 399                 }
 400         }
 401         cprintf("504 Authentication failed.\r\n");
 402 }
 403
 404
 405 // Attempt to perform authenticated SMTP
 406 void smtp_auth(void) {
 407         char username_prompt[64];
 408         char method[64];
 409         char encoded_authstring[1024];
 410
 411         if (CC->logged_in) {
 412                 cprintf("504 Already logged in.\r\n");
 413                 return;
 414         }
 415
 416         if (StrLength(SMTP->Cmd) < 6) {
 417                 cprintf("501 Syntax error\r\n");
 418                 return;
 419         }
 420
 421         extract_token(method, ChrPtr(SMTP->Cmd) + 5, 0, ' ', sizeof method);
 422
 423         if (!strncasecmp(method, "login", 5) ) {
 424                 if (StrLength(SMTP->Cmd) >= 12) {
 425                         syslog(LOG_DEBUG, "serv_smtp: username <%s> supplied inline", ChrPtr(SMTP->Cmd)+11);
 426                         smtp_get_user(11);
 427                 }
 428                 else {
 429                         size_t len = CtdlEncodeBase64(username_prompt, "Username:", 9, 0);
 430                         if (username_prompt[len - 1] == '\n') {
 431                                 username_prompt[len - 1] = '\0';
 432                         }
 433                         cprintf("334 %s\r\n", username_prompt);
 434                         SMTP->command_state = smtp_user;
 435                 }
 436                 return;
 437         }
 438
 439         if (!strncasecmp(method, "plain", 5) ) {
 440                 long len;
 441                 if (num_tokens(ChrPtr(SMTP->Cmd) + 5, ' ') < 2) {
 442                         cprintf("334 \r\n");
 443                         SMTP->command_state = smtp_plain;
 444                         return;
 445                 }
 446
 447                 len = extract_token(encoded_authstring,
 448                                     ChrPtr(SMTP->Cmd) + 5,
 449                                     1, ' ',
 450                                     sizeof encoded_authstring);
 451                 StrBufPlain(SMTP->Cmd, encoded_authstring, len);
 452                 smtp_try_plain();
 453                 return;
 454         }
 455
 456         cprintf("504 Unknown authentication method.\r\n");
 457         return;
 458 }
 459
 460
 461 // Implements the RSET (reset state) command.
 462 // Currently this just zeroes out the state buffer.  If pointers to data
 463 // allocated with malloc() are ever placed in the state buffer, we have to
 464 // be sure to free() them first!
 465 //
 466 // Set do_response to nonzero to output the SMTP RSET response code.
 467 void smtp_rset(int do_response) {
 468         FlushStrBuf(SMTP->Cmd);
 469         FlushStrBuf(SMTP->helo_node);
 470         FlushStrBuf(SMTP->from);
 471         FlushStrBuf(SMTP->recipients);
 472         FlushStrBuf(SMTP->OneRcpt);
 473
 474         SMTP->command_state = 0;
 475         SMTP->number_of_recipients = 0;
 476         SMTP->delivery_mode = 0;
 477         SMTP->message_originated_locally = 0;
 478         SMTP->is_msa = 0;
 479         // is_lmtp and is_unfiltered should not be cleared.
 480
 481         if (do_response) {
 482                 cprintf("250 Zap!\r\n");
 483         }
 484 }
 485
 486
 487 // Clear out the portions of the state buffer that need to be cleared out
 488 // after the DATA command finishes.
 489 void smtp_data_clear(void) {
 490         FlushStrBuf(SMTP->from);
 491         FlushStrBuf(SMTP->recipients);
 492         FlushStrBuf(SMTP->OneRcpt);
 493         SMTP->number_of_recipients = 0;
 494         SMTP->delivery_mode = 0;
 495         SMTP->message_originated_locally = 0;
 496 }
 497
 498
 499 // Implements the "MAIL FROM:" command
 500 void smtp_mail(void) {
 501         char user[SIZ];
 502         char node[SIZ];
 503         char name[SIZ];
 504
 505         if (StrLength(SMTP->from) > 0) {
 506                 cprintf("503 Only one sender permitted\r\n");
 507                 return;
 508         }
 509
 510         if (StrLength(SMTP->Cmd) < 6) {
 511                 cprintf("501 Syntax error\r\n");
 512                 return;
 513         }
 514
 515         if (strncasecmp(ChrPtr(SMTP->Cmd) + 5, "From:", 5)) {
 516                 cprintf("501 Syntax error\r\n");
 517                 return;
 518         }
 519
 520         StrBufAppendBuf(SMTP->from, SMTP->Cmd, 5);
 521         StrBufTrim(SMTP->from);
 522         if (strchr(ChrPtr(SMTP->from), '<') != NULL) {
 523                 StrBufStripAllBut(SMTP->from, '<', '>');
 524         }
 525
 526         // We used to reject empty sender names, until it was brought to our
 527         // attention that RFC1123 5.2.9 requires that this be allowed.  So now
 528         // we allow it, but replace the empty string with a fake
 529         // address so we don't have to contend with the empty string causing
 530         // other code to fail when it's expecting something there.
 531         if (StrLength(SMTP->from) == 0) {
 532                 StrBufPlain(SMTP->from, HKEY("someone@example.com"));
 533         }
 534
 535         // If this SMTP connection is from a logged-in user, force the 'from'
 536         // to be the user's Internet e-mail address as Citadel knows it.
 537         if (CC->logged_in) {
 538                 StrBufPlain(SMTP->from, CC->cs_inet_email, -1);
 539                 cprintf("250 Sender ok <%s>\r\n", ChrPtr(SMTP->from));
 540                 SMTP->message_originated_locally = 1;
 541                 return;
 542         }
 543
 544         else if (SMTP->is_lmtp) {
 545                 // Bypass forgery checking for LMTP
 546         }
 547
 548         // Otherwise, make sure outsiders aren't trying to forge mail from
 549         // this system (unless, of course, c_allow_spoofing is enabled)
 550         else if (CtdlGetConfigInt("c_allow_spoofing") == 0) {
 551                 process_rfc822_addr(ChrPtr(SMTP->from), user, node, name);
 552                 syslog(LOG_DEBUG, "serv_smtp: claimed envelope sender is '%s' == '%s' @ '%s' ('%s')",
 553                         ChrPtr(SMTP->from), user, node, name
 554                 );
 555                 if (CtdlHostAlias(node) != hostalias_nomatch) {
 556                         cprintf("550 You must log in to send mail from %s\r\n", node);
 557                         FlushStrBuf(SMTP->from);
 558                         syslog(LOG_DEBUG, "serv_smtp: rejecting unauthenticated mail from %s", node);
 559                         return;
 560                 }
 561         }
 562
 563         cprintf("250 Sender ok\r\n");
 564 }
 565
 566
 567 // Implements the "RCPT To:" command
 568 void smtp_rcpt(void) {
 569         char message_to_spammer[SIZ];
 570         struct recptypes *valid = NULL;
 571
 572         if (StrLength(SMTP->from) == 0) {
 573                 cprintf("503 Need MAIL before RCPT\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, "To:", 3)) {
 583                 cprintf("501 Syntax error\r\n");
 584                 return;
 585         }
 586
 587         if ( (SMTP->is_msa) && (!CC->logged_in) ) {
 588                 cprintf("550 You must log in to send mail on this port.\r\n");
 589                 FlushStrBuf(SMTP->from);
 590                 return;
 591         }
 592
 593         FlushStrBuf(SMTP->OneRcpt);
 594         StrBufAppendBuf(SMTP->OneRcpt, SMTP->Cmd, 8);
 595         StrBufTrim(SMTP->OneRcpt);
 596         StrBufStripAllBut(SMTP->OneRcpt, '<', '>');
 597
 598         if ( (StrLength(SMTP->OneRcpt) + StrLength(SMTP->recipients)) >= SIZ) {
 599                 cprintf("452 Too many recipients\r\n");
 600                 return;
 601         }
 602
 603         // RBL check
 604         if (
 605                 (!CC->logged_in)                                                // Don't RBL authenticated users
 606                 && (!SMTP->is_lmtp)                                             // Don't RBL LMTP clients
 607                 && (CtdlGetConfigInt("c_rbl_at_greeting") == 0)                 // Don't RBL if we did it at connection time
 608                 && (rbl_check(CC->cs_addr, message_to_spammer))
 609         ) {
 610                 cprintf("550 %s\r\n", message_to_spammer);
 611                 return;                                                         // no need to free_recipients(valid)
 612         }                                                                       // because it hasn't been allocated yet
 613
 614         // This is a *preliminary* call to validate_recipients() to evaluate one recipient.
 615         valid = validate_recipients(
 616                 (char *)ChrPtr(SMTP->OneRcpt),
 617                 smtp_get_Recipients(),
 618                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 619         );
 620
 621         // Any type of error thrown by validate_recipients() will make the SMTP transaction fail at this point.
 622         if (valid->num_error != 0) {
 623                 cprintf("550 %s\r\n", valid->errormsg);
 624                 free_recipients(valid);
 625                 return;
 626         }
 627
 628         if (
 629                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 630                 && (CC->logged_in)                                              // ...and we're a logged-in user...
 631                 && (CtdlCheckInternetMailPermission(&CC->user)==0)              // ...who does not have Internet mail rights...
 632         ) {
 633                 cprintf("551 <%s> - you do not have permission to send Internet mail\r\n", ChrPtr(SMTP->OneRcpt));
 634                 free_recipients(valid);
 635                 return;
 636         }
 637
 638         if (
 639                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 640                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 641                 && (SMTP->is_lmtp == 0)                                         /// ...and didn't arrive via LMTP...
 642         ) {
 643                 cprintf("551 <%s> - relaying denied\r\n", ChrPtr(SMTP->OneRcpt));
 644                 free_recipients(valid);
 645                 return;
 646         }
 647
 648         if (
 649                 (valid->num_room > 0)                                           // If it's mail to a room (mailing list)...
 650                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 651                 && (is_email_subscribed_to_list((char *)ChrPtr(SMTP->from), valid->recp_room) == 0)     // ...and not a subscriber
 652         ) {
 653                 cprintf("551 <%s> - The message is not from a list member\r\n", ChrPtr(SMTP->OneRcpt));
 654                 free_recipients(valid);
 655                 return;
 656         }
 657
 658         cprintf("250 RCPT ok <%s>\r\n", ChrPtr(SMTP->OneRcpt));
 659         if (StrLength(SMTP->recipients) > 0) {
 660                 StrBufAppendBufPlain(SMTP->recipients, HKEY(","), 0);
 661         }
 662         StrBufAppendBuf(SMTP->recipients, SMTP->OneRcpt, 0);
 663         SMTP->number_of_recipients ++;
 664         if (valid != NULL)  {
 665                 free_recipients(valid);
 666         }
 667 }
 668
 669
 670 // Implements the DATA command
 671 void smtp_data(void) {
 672         StrBuf *body;
 673         StrBuf *defbody;
 674         struct CtdlMessage *msg = NULL;
 675         long msgnum = (-1L);
 676         char nowstamp[SIZ];
 677         struct recptypes *valid;
 678         int scan_errors;
 679         int i;
 680
 681         if (StrLength(SMTP->from) == 0) {
 682                 cprintf("503 Need MAIL command first.\r\n");
 683                 return;
 684         }
 685
 686         if (SMTP->number_of_recipients < 1) {
 687                 cprintf("503 Need RCPT command first.\r\n");
 688                 return;
 689         }
 690
 691         cprintf("354 Transmit message now - terminate with '.' by itself\r\n");
 692
 693         datestring(nowstamp, sizeof nowstamp, time(NULL), DATESTRING_RFC822);
 694         defbody = NewStrBufPlain(NULL, SIZ);
 695
 696         if (defbody != NULL) {
 697                 if (SMTP->is_lmtp && (CC->cs_UDSclientUID != -1)) {
 698                         StrBufPrintf(
 699                                 defbody,
 700                                 "Received: from %s (Citadel from userid %ld)\n"
 701                                 "       by %s; %s\n",
 702                                 ChrPtr(SMTP->helo_node),
 703                                 (long int) CC->cs_UDSclientUID,
 704                                 CtdlGetConfigStr("c_fqdn"),
 705                                 nowstamp);
 706                 }
 707                 else {
 708                         StrBufPrintf(
 709                                 defbody,
 710                                 "Received: from %s (%s [%s])\n"
 711                                 "       by %s; %s\n",
 712                                 ChrPtr(SMTP->helo_node),
 713                                 CC->cs_host,
 714                                 CC->cs_addr,
 715                                 CtdlGetConfigStr("c_fqdn"),
 716                                 nowstamp);
 717                 }
 718         }
 719         body = CtdlReadMessageBodyBuf(HKEY("."), CtdlGetConfigLong("c_maxmsglen"), defbody, 1);
 720         FreeStrBuf(&defbody);
 721         if (body == NULL) {
 722                 cprintf("550 Unable to save message: internal error.\r\n");
 723                 return;
 724         }
 725
 726         syslog(LOG_DEBUG, "serv_smtp: converting message...");
 727         msg = convert_internet_message_buf(&body);
 728
 729         // If the user is locally authenticated, FORCE the From: header to
 730         // show up as the real sender.  Yes, this violates the RFC standard,
 731         // but IT MAKES SENSE.  If you prefer strict RFC adherence over
 732         // common sense, you can disable this in the configuration.
 733         //
 734         // We also set the "message room name" ('O' field) to MAILROOM
 735         // (which is Mail> on most systems) to prevent it from getting set
 736         // to something ugly like "0000058008.Sent Items>" when the message
 737         // is read with a Citadel client.
 738
 739         if ( (CC->logged_in) && (CtdlGetConfigInt("c_rfc822_strict_from") != CFG_SMTP_FROM_NOFILTER) ) {
 740                 int validemail = 0;
 741
 742                 if (!CM_IsEmpty(msg, erFc822Addr)       &&
 743                     ((CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_CORRECT) ||
 744                      (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)    )  )
 745                 {
 746                         if (!IsEmptyStr(CC->cs_inet_email))
 747                                 validemail = strcmp(CC->cs_inet_email, msg->cm_fields[erFc822Addr]) == 0;
 748                         if ((!validemail) &&
 749                             (!IsEmptyStr(CC->cs_inet_other_emails)))
 750                         {
 751                                 int num_secondary_emails = 0;
 752                                 int i;
 753                                 num_secondary_emails = num_tokens(CC->cs_inet_other_emails, '|');
 754                                 for (i=0; i < num_secondary_emails && !validemail; ++i) {
 755                                         char buf[256];
 756                                         extract_token(buf, CC->cs_inet_other_emails,i,'|',sizeof CC->cs_inet_other_emails);
 757                                         validemail = strcmp(buf, msg->cm_fields[erFc822Addr]) == 0;
 758                                 }
 759                         }
 760                 }
 761
 762                 if (!validemail && (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)) {
 763                         syslog(LOG_ERR, "serv_smtp: invalid sender '%s' - rejecting this message", msg->cm_fields[erFc822Addr]);
 764                         cprintf("550 Invalid sender '%s' - rejecting this message.\r\n", msg->cm_fields[erFc822Addr]);
 765                         return;
 766                 }
 767
 768                 CM_SetField(msg, eOriginalRoom, HKEY(MAILROOM));
 769                 if (SMTP->preferred_sender_name != NULL)
 770                         CM_SetField(msg, eAuthor, SKEY(SMTP->preferred_sender_name));
 771                 else
 772                         CM_SetField(msg, eAuthor, CC->user.fullname, strlen(CC->user.fullname));
 773
 774                 if (!validemail) {
 775                         if (SMTP->preferred_sender_email != NULL) {
 776                                 CM_SetField(msg, erFc822Addr, SKEY(SMTP->preferred_sender_email));
 777                         }
 778                         else {
 779                                 CM_SetField(msg, erFc822Addr, CC->cs_inet_email, strlen(CC->cs_inet_email));
 780                         }
 781                 }
 782         }
 783
 784         // Set the "envelope from" address
 785         CM_SetField(msg, eMessagePath, SKEY(SMTP->from));
 786
 787         // Set the "envelope to" address
 788         CM_SetField(msg, eenVelopeTo, SKEY(SMTP->recipients));
 789
 790         // Submit the message into the Citadel system.
 791         valid = validate_recipients(
 792                 (char *)ChrPtr(SMTP->recipients),
 793                 smtp_get_Recipients(),
 794                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 795         );
 796
 797         // If there are modules that want to scan this message before final
 798         // submission (such as virus checkers or spam filters), call them now
 799         // and give them an opportunity to reject the message.
 800         if (SMTP->is_unfiltered) {
 801                 scan_errors = 0;
 802         }
 803         else {
 804                 scan_errors = PerformMessageHooks(msg, valid, EVT_SMTPSCAN);
 805         }
 806
 807         if (scan_errors > 0) {  // We don't want this message!
 808
 809                 if (CM_IsEmpty(msg, eErrorMsg)) {
 810                         CM_SetField(msg, eErrorMsg, HKEY("Message rejected by filter"));
 811                 }
 812
 813                 StrBufPrintf(SMTP->OneRcpt, "550 %s\r\n", msg->cm_fields[eErrorMsg]);
 814         }
 815
 816         else {                  // Ok, we'll accept this message.
 817                 msgnum = CtdlSubmitMsg(msg, valid, "");
 818                 if (msgnum > 0L) {
 819                         StrBufPrintf(SMTP->OneRcpt, "250 Message accepted.\r\n");
 820                 }
 821                 else {
 822                         StrBufPrintf(SMTP->OneRcpt, "550 Internal delivery error\r\n");
 823                 }
 824         }
 825
 826         // For SMTP and ESMTP, just print the result message.  For LMTP, we
 827         // have to print one result message for each recipient.  Since there
 828         // is nothing in Citadel which would cause different recipients to
 829         // have different results, we can get away with just spitting out the
 830         // same message once for each recipient.
 831         if (SMTP->is_lmtp) {
 832                 for (i=0; i<SMTP->number_of_recipients; ++i) {
 833                         cputbuf(SMTP->OneRcpt);
 834                 }
 835         }
 836         else {
 837                 cputbuf(SMTP->OneRcpt);
 838         }
 839
 840         // Write something to the syslog(which may or may not be where the
 841         // rest of the Citadel logs are going; some sysadmins want LOG_MAIL).
 842         syslog((LOG_MAIL | LOG_INFO),
 843                     "%ld: from=<%s>, nrcpts=%d, relay=%s [%s], stat=%s",
 844                     msgnum,
 845                     ChrPtr(SMTP->from),
 846                     SMTP->number_of_recipients,
 847                     CC->cs_host,
 848                     CC->cs_addr,
 849                     ChrPtr(SMTP->OneRcpt)
 850         );
 851
 852         // Clean up
 853         CM_Free(msg);
 854         free_recipients(valid);
 855         smtp_data_clear();      // clear out the buffers now
 856 }
 857
 858
 859 // Implements the STARTTLS command
 860 void smtp_starttls(void) {
 861         char ok_response[SIZ];
 862         char nosup_response[SIZ];
 863         char error_response[SIZ];
 864
 865         sprintf(ok_response, "220 Begin TLS negotiation now\r\n");
 866         sprintf(nosup_response, "554 TLS not supported here\r\n");
 867         sprintf(error_response, "554 Internal error\r\n");
 868         CtdlModuleStartCryptoMsgs(ok_response, nosup_response, error_response);
 869         smtp_rset(0);
 870 }
 871
 872
 873 // Implements the NOOP (NO OPeration) command
 874 void smtp_noop(void) {
 875         cprintf("250 NOOP\r\n");
 876 }
 877
 878
 879 // Implements the QUIT command
 880 void smtp_quit(void) {
 881         cprintf("221 Goodbye...\r\n");
 882         CC->kill_me = KILLME_CLIENT_LOGGED_OUT;
 883 }
 884
 885
 886 // Main command loop for SMTP server sessions.
 887 void smtp_command_loop(void) {
 888         static const ConstStr AuthPlainStr = {HKEY("AUTH PLAIN")};
 889
 890         if (SMTP == NULL) {
 891                 syslog(LOG_ERR, "serv_smtp: Session SMTP data is null.  WTF?  We will crash now.");
 892                 abort();
 893         }
 894
 895         time(&CC->lastcmd);
 896         if (CtdlClientGetLine(SMTP->Cmd) < 1) {
 897                 syslog(LOG_INFO, "SMTP: client disconnected: ending session.");
 898                 CC->kill_me = KILLME_CLIENT_DISCONNECTED;
 899                 return;
 900         }
 901
 902         if (SMTP->command_state == smtp_user) {
 903                 if (!strncmp(ChrPtr(SMTP->Cmd), AuthPlainStr.Key, AuthPlainStr.len)) {
 904                         smtp_try_plain();
 905                 }
 906                 else {
 907                         smtp_get_user(0);
 908                 }
 909                 return;
 910         }
 911
 912         else if (SMTP->command_state == smtp_password) {
 913                 smtp_get_pass();
 914                 return;
 915         }
 916
 917         else if (SMTP->command_state == smtp_plain) {
 918                 smtp_try_plain();
 919                 return;
 920         }
 921
 922         syslog(LOG_DEBUG, "serv_smtp: client sent command <%s>", ChrPtr(SMTP->Cmd));
 923
 924         if (!strncasecmp(ChrPtr(SMTP->Cmd), "NOOP", 4)) {
 925                 smtp_noop();
 926                 return;
 927         }
 928
 929         if (!strncasecmp(ChrPtr(SMTP->Cmd), "QUIT", 4)) {
 930                 smtp_quit();
 931                 return;
 932         }
 933
 934         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELO", 4)) {
 935                 smtp_hello(HELO);
 936                 return;
 937         }
 938
 939         if (!strncasecmp(ChrPtr(SMTP->Cmd), "EHLO", 4)) {
 940                 smtp_hello(EHLO);
 941                 return;
 942         }
 943
 944         if (!strncasecmp(ChrPtr(SMTP->Cmd), "LHLO", 4)) {
 945                 smtp_hello(LHLO);
 946                 return;
 947         }
 948
 949         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RSET", 4)) {
 950                 smtp_rset(1);
 951                 return;
 952         }
 953
 954         if (!strncasecmp(ChrPtr(SMTP->Cmd), "AUTH", 4)) {
 955                 smtp_auth();
 956                 return;
 957         }
 958
 959         if (!strncasecmp(ChrPtr(SMTP->Cmd), "DATA", 4)) {
 960                 smtp_data();
 961                 return;
 962         }
 963
 964         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELP", 4)) {
 965                 smtp_help();
 966                 return;
 967         }
 968
 969         if (!strncasecmp(ChrPtr(SMTP->Cmd), "MAIL", 4)) {
 970                 smtp_mail();
 971                 return;
 972         }
 973
 974         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RCPT", 4)) {
 975                 smtp_rcpt();
 976                 return;
 977         }
 978 #ifdef HAVE_OPENSSL
 979         if (!strncasecmp(ChrPtr(SMTP->Cmd), "STARTTLS", 8)) {
 980                 smtp_starttls();
 981                 return;
 982         }
 983 #endif
 984
 985         cprintf("502 I'm afraid I can't do that.\r\n");
 986 }
 987
 988
 989 /*****************************************************************************/
 990 /*                      MODULE INITIALIZATION STUFF                          */
 991 /*****************************************************************************/
 992 /*
 993  * This cleanup function blows away the temporary memory used by
 994  * the SMTP server.
 995  */
 996 void smtp_cleanup_function(void)
 997 {
 998         /* Don't do this stuff if this is not an SMTP session! */
 999         if (CC->h_command_function != smtp_command_loop) return;
1000
1001         syslog(LOG_DEBUG, "Performing SMTP cleanup hook");
1002
1003         FreeStrBuf(&SMTP->Cmd);
1004         FreeStrBuf(&SMTP->helo_node);
1005         FreeStrBuf(&SMTP->from);
1006         FreeStrBuf(&SMTP->recipients);
1007         FreeStrBuf(&SMTP->OneRcpt);
1008         FreeStrBuf(&SMTP->preferred_sender_email);
1009         FreeStrBuf(&SMTP->preferred_sender_name);
1010
1011         free(SMTP);
1012 }
1013
1014 const char *CitadelServiceSMTP_MTA="SMTP-MTA";
1015 const char *CitadelServiceSMTPS_MTA="SMTPs-MTA";
1016 const char *CitadelServiceSMTP_MSA="SMTP-MSA";
1017 const char *CitadelServiceSMTP_LMTP="LMTP";
1018 const char *CitadelServiceSMTP_LMTP_UNF="LMTP-UnF";
1019
1020
1021 CTDL_MODULE_INIT(smtp)
1022 {
1023         if (!threading) {
1024                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtp_port"),        /* SMTP MTA */
1025                                         NULL,
1026                                         smtp_mta_greeting,
1027                                         smtp_command_loop,
1028                                         NULL,
1029                                         CitadelServiceSMTP_MTA);
1030
1031 #ifdef HAVE_OPENSSL
1032                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtps_port"),       /* SMTPS MTA */
1033                                         NULL,
1034                                         smtps_greeting,
1035                                         smtp_command_loop,
1036                                         NULL,
1037                                         CitadelServiceSMTPS_MTA);
1038 #endif
1039
1040                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_msa_port"),         /* SMTP MSA */
1041                                         NULL,
1042                                         smtp_msa_greeting,
1043                                         smtp_command_loop,
1044                                         NULL,
1045                                         CitadelServiceSMTP_MSA);
1046
1047                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1048                                         file_lmtp_socket,
1049                                         lmtp_greeting,
1050                                         smtp_command_loop,
1051                                         NULL,
1052                                         CitadelServiceSMTP_LMTP);
1053
1054                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1055                                         file_lmtp_unfiltered_socket,
1056                                         lmtp_unfiltered_greeting,
1057                                         smtp_command_loop,
1058                                         NULL,
1059                                         CitadelServiceSMTP_LMTP_UNF);
1060
1061                 CtdlRegisterSessionHook(smtp_cleanup_function, EVT_STOP, PRIO_STOP + 250);
1062         }
1063
1064         /* return our module name for the log */
1065         return "smtp";
1066 }