citadel/server/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) 1998-2023 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 <assert.h>
  52 #include <libcitadel.h>
  53 #include "../../citadel_defs.h"
  54 #include "../../server.h"
  55 #include "../../citserver.h"
  56 #include "../../support.h"
  57 #include "../../config.h"
  58 #include "../../control.h"
  59 #include "../../user_ops.h"
  60 #include "../../room_ops.h"
  61 #include "../../database.h"
  62 #include "../../msgbase.h"
  63 #include "../../internet_addressing.h"
  64 #include "../../genstamp.h"
  65 #include "../../domain.h"
  66 #include "../../clientsocket.h"
  67 #include "../../locate_host.h"
  68 #include "../../citadel_dirs.h"
  69 #include "../../ctdl_module.h"
  70
  71 #include "smtp_util.h"
  72
  73 enum {                          // Command states for login authentication
  74         smtp_command,
  75         smtp_user,
  76         smtp_password,
  77         smtp_plain
  78 };
  79
  80 enum SMTP_FLAGS {
  81         HELO,
  82         EHLO,
  83         LHLO
  84 };
  85
  86
  87 // Here's where our SMTP session begins its happy day.
  88 void smtp_greeting(int is_msa) {
  89         char message_to_spammer[1024];
  90
  91         strcpy(CC->cs_clientname, "SMTP session");
  92         CC->internal_pgm = 1;
  93         CC->cs_flags |= CS_STEALTH;
  94         CC->session_specific_data = malloc(sizeof(struct citsmtp));
  95         memset(SMTP, 0, sizeof(struct citsmtp));
  96         SMTP->is_msa = is_msa;
  97         SMTP->Cmd = NewStrBufPlain(NULL, SIZ);
  98         SMTP->helo_node = NewStrBuf();
  99         SMTP->from = NewStrBufPlain(NULL, SIZ);
 100         SMTP->recipients = NewStrBufPlain(NULL, SIZ);
 101         SMTP->OneRcpt = NewStrBufPlain(NULL, SIZ);
 102         SMTP->preferred_sender_email = NULL;
 103         SMTP->preferred_sender_name = NULL;
 104
 105         // If this config option is set, reject connections from problem
 106         // addresses immediately instead of after they execute a RCPT
 107         if ( (CtdlGetConfigInt("c_rbl_at_greeting")) && (SMTP->is_msa == 0) ) {
 108                 if (rbl_check(CC->cs_addr, message_to_spammer)) {
 109                         if (server_shutting_down)
 110                                 cprintf("421 %s\r\n", message_to_spammer);
 111                         else
 112                                 cprintf("550 %s\r\n", message_to_spammer);
 113                         CC->kill_me = KILLME_SPAMMER;
 114                         // no need to free_recipients(valid), it's not allocated yet
 115                         return;
 116                 }
 117         }
 118
 119         // Otherwise we're either clean or we check later.
 120
 121         if (CC->nologin==1) {
 122                 cprintf("451 Too many connections are already open; please try again later.\r\n");
 123                 CC->kill_me = KILLME_MAX_SESSIONS_EXCEEDED;
 124                 // no need to free_recipients(valid), it's not allocated yet
 125                 return;
 126         }
 127
 128         // Note: the FQDN *must* appear as the first thing after the 220 code.
 129         // Some clients (including citmail.c) depend on it being there.
 130         cprintf("220 %s ESMTP Citadel server ready.\r\n", CtdlGetConfigStr("c_fqdn"));
 131 }
 132
 133
 134 // SMTPS is just like SMTP, except it goes crypto right away.
 135 void smtps_greeting(void) {
 136         CtdlModuleStartCryptoMsgs(NULL, NULL, NULL);
 137         if (!CC->redirect_ssl) {
 138                 CC->kill_me = KILLME_NO_CRYPTO;         // kill session if no crypto
 139         }
 140         smtp_greeting(0);
 141 }
 142
 143
 144 // SMTP MSA port requires authentication.
 145 void smtp_msa_greeting(void) {
 146         smtp_greeting(1);
 147 }
 148
 149
 150 // LMTP is like SMTP but with some extra bonus footage added.
 151 void lmtp_greeting(void) {
 152
 153         smtp_greeting(0);
 154         SMTP->is_lmtp = 1;
 155 }
 156
 157
 158 // Generic SMTP MTA greeting
 159 void smtp_mta_greeting(void) {
 160         smtp_greeting(0);
 161 }
 162
 163
 164 // We also have an unfiltered LMTP socket that bypasses spam filters.
 165 void lmtp_unfiltered_greeting(void) {
 166         smtp_greeting(0);
 167         SMTP->is_lmtp = 1;
 168         SMTP->is_unfiltered = 1;
 169 }
 170
 171
 172 // Login greeting common to all auth methods
 173 void smtp_auth_greeting(void) {
 174         cprintf("235 Hello, %s\r\n", CC->user.fullname);
 175         syslog(LOG_INFO, "serv_smtp: SMTP authenticated %s", CC->user.fullname);
 176         CC->internal_pgm = 0;
 177         CC->cs_flags &= ~CS_STEALTH;
 178 }
 179
 180
 181 // Implement HELO and EHLO commands.
 182 // which_command:  0=HELO, 1=EHLO, 2=LHLO
 183 void smtp_hello(int which_command) {
 184
 185         if (StrLength(SMTP->Cmd) >= 6) {
 186                 FlushStrBuf(SMTP->helo_node);
 187                 StrBufAppendBuf(SMTP->helo_node, SMTP->Cmd, 5);
 188         }
 189
 190         if ( (which_command != LHLO) && (SMTP->is_lmtp) ) {
 191                 cprintf("500 Only LHLO is allowed when running LMTP\r\n");
 192                 return;
 193         }
 194
 195         if ( (which_command == LHLO) && (SMTP->is_lmtp == 0) ) {
 196                 cprintf("500 LHLO is only allowed when running LMTP\r\n");
 197                 return;
 198         }
 199
 200         if (which_command == HELO) {
 201                 cprintf("250 Hello %s (%s [%s])\r\n",
 202                         ChrPtr(SMTP->helo_node),
 203                         CC->cs_host,
 204                         CC->cs_addr
 205                 );
 206         }
 207         else {
 208                 if (which_command == EHLO) {
 209                         cprintf("250-Hello %s (%s [%s])\r\n", ChrPtr(SMTP->helo_node), CC->cs_host, CC->cs_addr);
 210                 }
 211                 else {
 212                         cprintf("250-Greetings and joyous salutations.\r\n");
 213                 }
 214                 cprintf("250-HELP\r\n");
 215                 cprintf("250-SIZE %ld\r\n", CtdlGetConfigLong("c_maxmsglen"));
 216
 217                 // Offer the STARTTLS option...
 218                 if (    (!CC->redirect_ssl)                                                     // not if we're already TLS
 219                         && (    (SMTP->is_msa)                                                  // Always on port 587
 220                                 || (CtdlGetConfigInt("smtp_advertise_starttls") != 0)           // On port 25 only if enabled
 221                         )
 222                 ) {
 223                         cprintf("250-STARTTLS\r\n");
 224                 }
 225
 226                 cprintf("250-AUTH LOGIN PLAIN\r\n"
 227                         "250-AUTH=LOGIN PLAIN\r\n"
 228                         "250 8BITMIME\r\n"
 229                 );
 230         }
 231 }
 232
 233
 234 // Backend function for smtp_webcit_preferences_hack().
 235 // Look at a message and determine if it's the preferences file.
 236 void smtp_webcit_preferences_hack_backend(long msgnum, void *userdata) {
 237         struct CtdlMessage *msg;
 238         char **webcit_conf = (char **) userdata;
 239
 240         if (*webcit_conf) {
 241                 return;         // already got it
 242         }
 243
 244         msg = CtdlFetchMessage(msgnum, 1);
 245         if (msg == NULL) {
 246                 return;
 247         }
 248
 249         if ( !CM_IsEmpty(msg, eMsgSubject) && (!strcasecmp(msg->cm_fields[eMsgSubject], "__ WebCit Preferences __"))) {
 250                 // This is it!  Change ownership of the message text so it doesn't get freed.
 251                 *webcit_conf = (char *)msg->cm_fields[eMessageText];
 252                 msg->cm_fields[eMessageText] = NULL;
 253         }
 254         CM_Free(msg);
 255 }
 256
 257
 258 // The configuration item for the user's preferred display name for outgoing email is, unfortunately,
 259 // stored in the account's WebCit configuration.  We have to fetch it now.
 260 void smtp_webcit_preferences_hack(void) {
 261         char config_roomname[ROOMNAMELEN];
 262         char *webcit_conf = NULL;
 263
 264         snprintf(config_roomname, sizeof config_roomname, "%010ld.%s", CC->user.usernum, USERCONFIGROOM);
 265         if (CtdlGetRoom(&CC->room, config_roomname) != 0) {
 266                 return;
 267         }
 268
 269         // Find the WebCit configuration message
 270         CtdlForEachMessage(MSGS_ALL, 1, NULL, NULL, NULL, smtp_webcit_preferences_hack_backend, (void *)&webcit_conf);
 271
 272         if (!webcit_conf) {
 273                 return;
 274         }
 275
 276         // Parse the webcit configuration and attempt to do something useful with it
 277         char *str = webcit_conf;
 278         char *saveptr = str;
 279         char *this_line = NULL;
 280         while (this_line = strtok_r(str, "\n", &saveptr), this_line != NULL) {
 281                 str = NULL;
 282                 if (!strncasecmp(this_line, "defaultfrom|", 12)) {
 283                         SMTP->preferred_sender_email = NewStrBufPlain(&this_line[12], -1);
 284                 }
 285                 if (!strncasecmp(this_line, "defaultname|", 12)) {
 286                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 287                 }
 288                 if ((!strncasecmp(this_line, "defaultname|", 12)) && (SMTP->preferred_sender_name == NULL)) {
 289                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 290                 }
 291
 292         }
 293         free(webcit_conf);
 294 }
 295
 296
 297 // Implement HELP command.
 298 void smtp_help(void) {
 299         cprintf("214 RTFM http://www.ietf.org/rfc/rfc2821.txt\r\n");
 300 }
 301
 302
 303 void smtp_get_user(int offset) {
 304         char buf[SIZ];
 305
 306         StrBuf *UserName = NewStrBufDup(SMTP->Cmd);
 307         StrBufCutLeft(UserName, offset);
 308         StrBufDecodeBase64(UserName);
 309
 310         if (CtdlLoginExistingUser(ChrPtr(UserName)) == login_ok) {
 311                 size_t len = CtdlEncodeBase64(buf, "Password:", 9, BASE64_NO_LINEBREAKS);
 312
 313                 if (buf[len - 1] == '\n') {
 314                         buf[len - 1] = '\0';
 315                 }
 316                 cprintf("334 %s\r\n", buf);
 317                 SMTP->command_state = smtp_password;
 318         }
 319         else {
 320                 cprintf("500 No such user.\r\n");
 321                 SMTP->command_state = smtp_command;
 322         }
 323         FreeStrBuf(&UserName);
 324 }
 325
 326
 327 void smtp_get_pass(void) {
 328         char password[SIZ];
 329
 330         memset(password, 0, sizeof(password));
 331         StrBufDecodeBase64(SMTP->Cmd);
 332         syslog(LOG_DEBUG, "serv_smtp: trying <%s>", password);
 333         if (CtdlTryPassword(SKEY(SMTP->Cmd)) == pass_ok) {
 334                 smtp_auth_greeting();
 335         }
 336         else {
 337                 cprintf("535 Authentication failed.\r\n");
 338         }
 339         SMTP->command_state = smtp_command;
 340 }
 341
 342
 343 // Back end for PLAIN auth method (either inline or multistate)
 344 void smtp_try_plain(void) {
 345         const char*decoded_authstring;
 346         char ident[256] = "";
 347         char user[256] = "";
 348         char pass[256] = "";
 349         int result;
 350
 351         long decoded_len;
 352         long len = 0;
 353         long plen = 0;
 354
 355         memset(pass, 0, sizeof(pass));
 356         decoded_len = StrBufDecodeBase64(SMTP->Cmd);
 357
 358         if (decoded_len > 0) {
 359                 decoded_authstring = ChrPtr(SMTP->Cmd);
 360
 361                 len = safestrncpy(ident, decoded_authstring, sizeof ident);
 362
 363                 decoded_len -= len - 1;
 364                 decoded_authstring += len + 1;
 365
 366                 if (decoded_len > 0) {
 367                         len = safestrncpy(user, decoded_authstring, sizeof user);
 368
 369                         decoded_authstring += len + 1;
 370                         decoded_len -= len - 1;
 371                 }
 372
 373                 if (decoded_len > 0) {
 374                         plen = safestrncpy(pass, decoded_authstring, sizeof pass);
 375
 376                         if (plen < 0)
 377                                 plen = sizeof(pass) - 1;
 378                 }
 379         }
 380
 381         SMTP->command_state = smtp_command;
 382
 383         if (!IsEmptyStr(ident)) {
 384                 result = CtdlLoginExistingUser(ident);
 385         }
 386         else {
 387                 result = CtdlLoginExistingUser(user);
 388         }
 389
 390         if (result == login_ok) {
 391                 if (CtdlTryPassword(pass, plen) == pass_ok) {
 392                         smtp_webcit_preferences_hack();
 393                         smtp_auth_greeting();
 394                         return;
 395                 }
 396         }
 397         cprintf("504 Authentication failed.\r\n");
 398 }
 399
 400
 401 // Attempt to perform authenticated SMTP
 402 void smtp_auth(void) {
 403         char username_prompt[64];
 404         char method[64];
 405         char encoded_authstring[1024];
 406
 407         if (CC->logged_in) {
 408                 cprintf("504 Already logged in.\r\n");
 409                 return;
 410         }
 411
 412         if (StrLength(SMTP->Cmd) < 6) {
 413                 cprintf("501 Syntax error\r\n");
 414                 return;
 415         }
 416
 417         extract_token(method, ChrPtr(SMTP->Cmd) + 5, 0, ' ', sizeof method);
 418
 419         if (!strncasecmp(method, "login", 5) ) {
 420                 if (StrLength(SMTP->Cmd) >= 12) {
 421                         syslog(LOG_DEBUG, "serv_smtp: username <%s> supplied inline", ChrPtr(SMTP->Cmd)+11);
 422                         smtp_get_user(11);
 423                 }
 424                 else {
 425                         size_t len = CtdlEncodeBase64(username_prompt, "Username:", 9, BASE64_NO_LINEBREAKS);
 426                         if (username_prompt[len - 1] == '\n') {
 427                                 username_prompt[len - 1] = '\0';
 428                         }
 429                         cprintf("334 %s\r\n", username_prompt);
 430                         SMTP->command_state = smtp_user;
 431                 }
 432                 return;
 433         }
 434
 435         if (!strncasecmp(method, "plain", 5) ) {
 436                 long len;
 437                 if (num_tokens(ChrPtr(SMTP->Cmd) + 5, ' ') < 2) {
 438                         cprintf("334 \r\n");
 439                         SMTP->command_state = smtp_plain;
 440                         return;
 441                 }
 442
 443                 len = extract_token(encoded_authstring, ChrPtr(SMTP->Cmd) + 5, 1, ' ', sizeof encoded_authstring);
 444                 StrBufPlain(SMTP->Cmd, encoded_authstring, len);
 445                 smtp_try_plain();
 446                 return;
 447         }
 448
 449         cprintf("504 Unknown authentication method.\r\n");
 450         return;
 451 }
 452
 453
 454 // Implements the RSET (reset state) command.
 455 // Currently this just zeroes out the state buffer.  If pointers to data
 456 // allocated with malloc() are ever placed in the state buffer, we have to
 457 // be sure to free() them first!
 458 //
 459 // Set do_response to nonzero to output the SMTP RSET response code.
 460 void smtp_rset(int do_response) {
 461         FlushStrBuf(SMTP->Cmd);
 462         FlushStrBuf(SMTP->helo_node);
 463         FlushStrBuf(SMTP->from);
 464         FlushStrBuf(SMTP->recipients);
 465         FlushStrBuf(SMTP->OneRcpt);
 466
 467         SMTP->command_state = 0;
 468         SMTP->number_of_recipients = 0;
 469         SMTP->delivery_mode = 0;
 470         SMTP->message_originated_locally = 0;
 471         SMTP->is_msa = 0;
 472         // is_lmtp and is_unfiltered should not be cleared.
 473
 474         if (do_response) {
 475                 cprintf("250 Zap!\r\n");
 476         }
 477 }
 478
 479
 480 // Clear out the portions of the state buffer that need to be cleared out
 481 // after the DATA command finishes.
 482 void smtp_data_clear(void) {
 483         FlushStrBuf(SMTP->from);
 484         FlushStrBuf(SMTP->recipients);
 485         FlushStrBuf(SMTP->OneRcpt);
 486         SMTP->number_of_recipients = 0;
 487         SMTP->delivery_mode = 0;
 488         SMTP->message_originated_locally = 0;
 489 }
 490
 491
 492 // Implements the "MAIL FROM:" command
 493 void smtp_mail(void) {
 494         char user[SIZ];
 495         char node[SIZ];
 496         char name[SIZ];
 497
 498         if (StrLength(SMTP->from) > 0) {
 499                 cprintf("503 Only one sender permitted\r\n");
 500                 return;
 501         }
 502
 503         if (StrLength(SMTP->Cmd) < 6) {
 504                 cprintf("501 Syntax error\r\n");
 505                 return;
 506         }
 507
 508         if (strncasecmp(ChrPtr(SMTP->Cmd) + 5, "From:", 5)) {
 509                 cprintf("501 Syntax error\r\n");
 510                 return;
 511         }
 512
 513         StrBufAppendBuf(SMTP->from, SMTP->Cmd, 5);
 514         StrBufTrim(SMTP->from);
 515         if (strchr(ChrPtr(SMTP->from), '<') != NULL) {
 516                 StrBufStripAllBut(SMTP->from, '<', '>');
 517         }
 518
 519         // We used to reject empty sender names, until it was brought to our
 520         // attention that RFC1123 5.2.9 requires that this be allowed.  So now
 521         // we allow it, but replace the empty string with a fake
 522         // address so we don't have to contend with the empty string causing
 523         // other code to fail when it's expecting something there.
 524         if (StrLength(SMTP->from) == 0) {
 525                 StrBufPlain(SMTP->from, HKEY("someone@example.com"));
 526         }
 527
 528         // If this SMTP connection is from a logged-in user, force the 'from'
 529         // to be the user's Internet e-mail address as Citadel knows it.
 530         if (CC->logged_in) {
 531                 StrBufPlain(SMTP->from, CC->cs_inet_email, -1);
 532                 cprintf("250 Sender ok <%s>\r\n", ChrPtr(SMTP->from));
 533                 SMTP->message_originated_locally = 1;
 534                 return;
 535         }
 536
 537         else if (SMTP->is_lmtp) {
 538                 // Bypass forgery checking for LMTP
 539         }
 540
 541         // Otherwise, make sure outsiders aren't trying to forge mail from
 542         // this system (unless, of course, c_allow_spoofing is enabled)
 543         else if (CtdlGetConfigInt("c_allow_spoofing") == 0) {
 544                 process_rfc822_addr(ChrPtr(SMTP->from), user, node, name);
 545                 syslog(LOG_DEBUG, "serv_smtp: claimed envelope sender is '%s' == '%s' @ '%s' ('%s')",
 546                         ChrPtr(SMTP->from), user, node, name
 547                 );
 548                 if (CtdlHostAlias(node) != hostalias_nomatch) {
 549                         cprintf("550 You must log in to send mail from %s\r\n", node);
 550                         FlushStrBuf(SMTP->from);
 551                         syslog(LOG_DEBUG, "serv_smtp: rejecting unauthenticated mail from %s", node);
 552                         return;
 553                 }
 554         }
 555
 556         cprintf("250 Sender ok\r\n");
 557 }
 558
 559
 560 // Implements the "RCPT To:" command
 561 void smtp_rcpt(void) {
 562         char message_to_spammer[SIZ];
 563         struct recptypes *valid = NULL;
 564
 565         if (StrLength(SMTP->from) == 0) {
 566                 cprintf("503 Need MAIL before RCPT\r\n");
 567                 return;
 568         }
 569
 570         if (StrLength(SMTP->Cmd) < 6) {
 571                 cprintf("501 Syntax error\r\n");
 572                 return;
 573         }
 574
 575         if (strncasecmp(ChrPtr(SMTP->Cmd) + 5, "To:", 3)) {
 576                 cprintf("501 Syntax error\r\n");
 577                 return;
 578         }
 579
 580         if ( (SMTP->is_msa) && (!CC->logged_in) ) {
 581                 cprintf("550 You must log in to send mail on this port.\r\n");
 582                 FlushStrBuf(SMTP->from);
 583                 return;
 584         }
 585
 586         FlushStrBuf(SMTP->OneRcpt);
 587         StrBufAppendBuf(SMTP->OneRcpt, SMTP->Cmd, 8);
 588         StrBufTrim(SMTP->OneRcpt);
 589         StrBufStripAllBut(SMTP->OneRcpt, '<', '>');
 590
 591         if ( (StrLength(SMTP->OneRcpt) + StrLength(SMTP->recipients)) >= SIZ) {
 592                 cprintf("452 Too many recipients\r\n");
 593                 return;
 594         }
 595
 596         // RBL check
 597         if (
 598                 (!CC->logged_in)                                                // Don't RBL authenticated users
 599                 && (!SMTP->is_lmtp)                                             // Don't RBL LMTP clients
 600                 && (CtdlGetConfigInt("c_rbl_at_greeting") == 0)                 // Don't RBL if we did it at connection time
 601                 && (rbl_check(CC->cs_addr, message_to_spammer))
 602         ) {
 603                 cprintf("550 %s\r\n", message_to_spammer);
 604                 return;                                                         // no need to free_recipients(valid)
 605         }                                                                       // because it hasn't been allocated yet
 606
 607         // This is a *preliminary* call to validate_recipients() to evaluate one recipient.
 608         valid = validate_recipients(
 609                 (char *)ChrPtr(SMTP->OneRcpt),
 610                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 611         );
 612
 613         // Any type of error thrown by validate_recipients() will make the SMTP transaction fail at this point.
 614         if (valid->num_error != 0) {
 615                 cprintf("550 %s\r\n", valid->errormsg);
 616                 free_recipients(valid);
 617                 return;
 618         }
 619
 620         if (
 621                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 622                 && (CC->logged_in)                                              // ...and we're a logged-in user...
 623                 && (CtdlCheckInternetMailPermission(&CC->user)==0)              // ...who does not have Internet mail rights...
 624         ) {
 625                 cprintf("551 <%s> - you do not have permission to send Internet mail\r\n", ChrPtr(SMTP->OneRcpt));
 626                 free_recipients(valid);
 627                 return;
 628         }
 629
 630         if (
 631                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 632                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 633                 && (SMTP->is_lmtp == 0)                                         /// ...and didn't arrive via LMTP...
 634         ) {
 635                 cprintf("551 <%s> - relaying denied\r\n", ChrPtr(SMTP->OneRcpt));
 636                 free_recipients(valid);
 637                 return;
 638         }
 639
 640         if (
 641                 (valid->num_room > 0)                                           // If it's mail to a room (mailing list)...
 642                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 643                 && (is_email_subscribed_to_list((char *)ChrPtr(SMTP->from), valid->recp_room) == 0)     // ...and not a subscriber
 644         ) {
 645                 cprintf("551 <%s> - The message is not from a list member\r\n", ChrPtr(SMTP->OneRcpt));
 646                 free_recipients(valid);
 647                 return;
 648         }
 649
 650         cprintf("250 RCPT ok <%s>\r\n", ChrPtr(SMTP->OneRcpt));
 651         if (StrLength(SMTP->recipients) > 0) {
 652                 StrBufAppendBufPlain(SMTP->recipients, HKEY(","), 0);
 653         }
 654         StrBufAppendBuf(SMTP->recipients, SMTP->OneRcpt, 0);
 655         SMTP->number_of_recipients ++;
 656         if (valid != NULL)  {
 657                 free_recipients(valid);
 658         }
 659 }
 660
 661
 662 // Implements the DATA command
 663 void smtp_data(void) {
 664         StrBuf *body;
 665         StrBuf *defbody;
 666         struct CtdlMessage *msg = NULL;
 667         long msgnum = (-1L);
 668         char nowstamp[SIZ];
 669         struct recptypes *valid;
 670         int scan_errors;
 671         int i;
 672
 673         if (StrLength(SMTP->from) == 0) {
 674                 cprintf("503 Need MAIL command first.\r\n");
 675                 return;
 676         }
 677
 678         if (SMTP->number_of_recipients < 1) {
 679                 cprintf("503 Need RCPT command first.\r\n");
 680                 return;
 681         }
 682
 683         cprintf("354 Transmit message now - terminate with '.' by itself\r\n");
 684
 685         datestring(nowstamp, sizeof nowstamp, time(NULL), DATESTRING_RFC822);
 686         defbody = NewStrBufPlain(NULL, SIZ);
 687
 688         if (defbody != NULL) {
 689                 if (SMTP->is_lmtp && (CC->cs_UDSclientUID != -1)) {
 690                         StrBufPrintf(
 691                                 defbody,
 692                                 "Received: from %s (Citadel from userid %ld)\n"
 693                                 "       by %s; %s\n",
 694                                 ChrPtr(SMTP->helo_node),
 695                                 (long int) CC->cs_UDSclientUID,
 696                                 CtdlGetConfigStr("c_fqdn"),
 697                                 nowstamp);
 698                 }
 699                 else {
 700                         StrBufPrintf(
 701                                 defbody,
 702                                 "Received: from %s (%s [%s])\n"
 703                                 "       by %s; %s\n",
 704                                 ChrPtr(SMTP->helo_node),
 705                                 CC->cs_host,
 706                                 CC->cs_addr,
 707                                 CtdlGetConfigStr("c_fqdn"),
 708                                 nowstamp);
 709                 }
 710         }
 711         body = CtdlReadMessageBodyBuf(HKEY("."), CtdlGetConfigLong("c_maxmsglen"), defbody, 1);
 712         FreeStrBuf(&defbody);
 713         if (body == NULL) {
 714                 cprintf("550 Unable to save message: internal error.\r\n");
 715                 return;
 716         }
 717
 718         syslog(LOG_DEBUG, "serv_smtp: converting message...");
 719         msg = convert_internet_message_buf(&body);
 720
 721         // If the user is locally authenticated, FORCE the From: header to
 722         // show up as the real sender.  Yes, this violates the RFC standard,
 723         // but IT MAKES SENSE.  If you prefer strict RFC adherence over
 724         // common sense, you can disable this in the configuration.
 725         //
 726         // We also set the "message room name" ('O' field) to MAILROOM
 727         // (which is Mail> on most systems) to prevent it from getting set
 728         // to something ugly like "0000058008.Sent Items>" when the message
 729         // is read with a Citadel client.
 730
 731         if ( (CC->logged_in) && (CtdlGetConfigInt("c_rfc822_strict_from") != CFG_SMTP_FROM_NOFILTER) ) {
 732                 int validemail = 0;
 733
 734                 if (!CM_IsEmpty(msg, erFc822Addr)       &&
 735                     ((CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_CORRECT) ||
 736                      (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)    )  )
 737                 {
 738                         if (!IsEmptyStr(CC->cs_inet_email)) {
 739                                 validemail = strcmp(CC->cs_inet_email, msg->cm_fields[erFc822Addr]) == 0;
 740                         }
 741                         if ((!validemail) && (!IsEmptyStr(CC->cs_inet_other_emails))) {
 742                                 int num_secondary_emails = 0;
 743                                 int i;
 744                                 num_secondary_emails = num_tokens(CC->cs_inet_other_emails, '|');
 745                                 for (i=0; i < num_secondary_emails && !validemail; ++i) {
 746                                         char buf[256];
 747                                         extract_token(buf, CC->cs_inet_other_emails,i,'|',sizeof CC->cs_inet_other_emails);
 748                                         validemail = strcmp(buf, msg->cm_fields[erFc822Addr]) == 0;
 749                                 }
 750                         }
 751                 }
 752
 753                 if (!validemail && (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)) {
 754                         syslog(LOG_ERR, "serv_smtp: invalid sender '%s' - rejecting this message", msg->cm_fields[erFc822Addr]);
 755                         cprintf("550 Invalid sender '%s' - rejecting this message.\r\n", msg->cm_fields[erFc822Addr]);
 756                         return;
 757                 }
 758
 759                 CM_SetField(msg, eOriginalRoom, MAILROOM);
 760                 if (SMTP->preferred_sender_name != NULL)
 761                         CM_SetField(msg, eAuthor, ChrPtr(SMTP->preferred_sender_name));
 762                 else
 763                         CM_SetField(msg, eAuthor, CC->user.fullname);
 764
 765                 if (!validemail) {
 766                         if (SMTP->preferred_sender_email != NULL) {
 767                                 CM_SetField(msg, erFc822Addr, ChrPtr(SMTP->preferred_sender_email));
 768                         }
 769                         else {
 770                                 CM_SetField(msg, erFc822Addr, CC->cs_inet_email);
 771                         }
 772                 }
 773         }
 774
 775         // Set the "envelope from" address
 776         CM_SetField(msg, eMessagePath, ChrPtr(SMTP->from));
 777
 778         // Set the "envelope to" address
 779         CM_SetField(msg, eenVelopeTo, ChrPtr(SMTP->recipients));
 780
 781         // Submit the message into the Citadel system.
 782         valid = validate_recipients(
 783                 (char *)ChrPtr(SMTP->recipients),
 784                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 785         );
 786
 787         // If there are modules that want to scan this message before final
 788         // submission (such as virus checkers or spam filters), call them now
 789         // and give them an opportunity to reject the message.
 790         if (SMTP->is_unfiltered) {
 791                 scan_errors = 0;
 792         }
 793         else {
 794                 scan_errors = PerformMessageHooks(msg, valid, EVT_SMTPSCAN);
 795         }
 796
 797         if (scan_errors > 0) {  // We don't want this message!
 798
 799                 if (CM_IsEmpty(msg, eErrorMsg)) {
 800                         CM_SetField(msg, eErrorMsg, "Message rejected by filter");
 801                 }
 802
 803                 StrBufPrintf(SMTP->OneRcpt, "550 %s\r\n", msg->cm_fields[eErrorMsg]);
 804         }
 805
 806         else {                  // Ok, we'll accept this message.
 807                 msgnum = CtdlSubmitMsg(msg, valid, "");
 808                 if (msgnum > 0L) {
 809                         StrBufPrintf(SMTP->OneRcpt, "250 Message accepted.\r\n");
 810                 }
 811                 else {
 812                         StrBufPrintf(SMTP->OneRcpt, "550 Internal delivery error\r\n");
 813                 }
 814         }
 815
 816         // For SMTP and ESMTP, just print the result message.  For LMTP, we
 817         // have to print one result message for each recipient.  Since there
 818         // is nothing in Citadel which would cause different recipients to
 819         // have different results, we can get away with just spitting out the
 820         // same message once for each recipient.
 821         if (SMTP->is_lmtp) {
 822                 for (i=0; i<SMTP->number_of_recipients; ++i) {
 823                         cputbuf(SMTP->OneRcpt);
 824                 }
 825         }
 826         else {
 827                 cputbuf(SMTP->OneRcpt);
 828         }
 829
 830         // Write something to the syslog(which may or may not be where the
 831         // rest of the Citadel logs are going; some sysadmins want LOG_MAIL).
 832         syslog((LOG_MAIL | LOG_INFO),
 833                     "%ld: from=<%s>, nrcpts=%d, relay=%s [%s], stat=%s",
 834                     msgnum,
 835                     ChrPtr(SMTP->from),
 836                     SMTP->number_of_recipients,
 837                     CC->cs_host,
 838                     CC->cs_addr,
 839                     ChrPtr(SMTP->OneRcpt)
 840         );
 841
 842         // Clean up
 843         CM_Free(msg);
 844         free_recipients(valid);
 845         smtp_data_clear();      // clear out the buffers now
 846 }
 847
 848
 849 // Implements the STARTTLS command
 850 void smtp_starttls(void) {
 851         char ok_response[SIZ];
 852         char nosup_response[SIZ];
 853         char error_response[SIZ];
 854
 855         sprintf(ok_response, "220 Begin TLS negotiation now\r\n");
 856         sprintf(nosup_response, "554 TLS not supported here\r\n");
 857         sprintf(error_response, "554 Internal error\r\n");
 858         CtdlModuleStartCryptoMsgs(ok_response, nosup_response, error_response);
 859         smtp_rset(0);
 860 }
 861
 862
 863 // Implements the NOOP (NO OPeration) command
 864 void smtp_noop(void) {
 865         cprintf("250 NOOP\r\n");
 866 }
 867
 868
 869 // Implements the QUIT command
 870 void smtp_quit(void) {
 871         cprintf("221 Goodbye...\r\n");
 872         CC->kill_me = KILLME_CLIENT_LOGGED_OUT;
 873 }
 874
 875
 876 // Main command loop for SMTP server sessions.
 877 void smtp_command_loop(void) {
 878         static const ConstStr AuthPlainStr = {HKEY("AUTH PLAIN")};
 879
 880         assert(SMTP != NULL);
 881
 882         time(&CC->lastcmd);
 883         if (CtdlClientGetLine(SMTP->Cmd) < 1) {
 884                 syslog(LOG_INFO, "SMTP: client disconnected: ending session.");
 885                 CC->kill_me = KILLME_CLIENT_DISCONNECTED;
 886                 return;
 887         }
 888
 889         if (SMTP->command_state == smtp_user) {
 890                 if (!strncmp(ChrPtr(SMTP->Cmd), AuthPlainStr.Key, AuthPlainStr.len)) {
 891                         smtp_try_plain();
 892                 }
 893                 else {
 894                         smtp_get_user(0);
 895                 }
 896                 return;
 897         }
 898
 899         else if (SMTP->command_state == smtp_password) {
 900                 smtp_get_pass();
 901                 return;
 902         }
 903
 904         else if (SMTP->command_state == smtp_plain) {
 905                 smtp_try_plain();
 906                 return;
 907         }
 908
 909         syslog(LOG_DEBUG, "serv_smtp: client sent command <%s>", ChrPtr(SMTP->Cmd));
 910
 911         if (!strncasecmp(ChrPtr(SMTP->Cmd), "NOOP", 4)) {
 912                 smtp_noop();
 913                 return;
 914         }
 915
 916         if (!strncasecmp(ChrPtr(SMTP->Cmd), "QUIT", 4)) {
 917                 smtp_quit();
 918                 return;
 919         }
 920
 921         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELO", 4)) {
 922                 smtp_hello(HELO);
 923                 return;
 924         }
 925
 926         if (!strncasecmp(ChrPtr(SMTP->Cmd), "EHLO", 4)) {
 927                 smtp_hello(EHLO);
 928                 return;
 929         }
 930
 931         if (!strncasecmp(ChrPtr(SMTP->Cmd), "LHLO", 4)) {
 932                 smtp_hello(LHLO);
 933                 return;
 934         }
 935
 936         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RSET", 4)) {
 937                 smtp_rset(1);
 938                 return;
 939         }
 940
 941         if (!strncasecmp(ChrPtr(SMTP->Cmd), "AUTH", 4)) {
 942                 smtp_auth();
 943                 return;
 944         }
 945
 946         if (!strncasecmp(ChrPtr(SMTP->Cmd), "DATA", 4)) {
 947                 smtp_data();
 948                 return;
 949         }
 950
 951         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELP", 4)) {
 952                 smtp_help();
 953                 return;
 954         }
 955
 956         if (!strncasecmp(ChrPtr(SMTP->Cmd), "MAIL", 4)) {
 957                 smtp_mail();
 958                 return;
 959         }
 960
 961         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RCPT", 4)) {
 962                 smtp_rcpt();
 963                 return;
 964         }
 965         if (!strncasecmp(ChrPtr(SMTP->Cmd), "STARTTLS", 8)) {
 966                 smtp_starttls();
 967                 return;
 968         }
 969
 970         cprintf("502 I'm afraid I can't do that.\r\n");
 971 }
 972
 973
 974 // *****************************************************************************
 975 // *                      MODULE INITIALIZATION STUFF                          *
 976 // *****************************************************************************
 977
 978 // This cleanup function blows away the temporary memory used by
 979 // the SMTP server.
 980 void smtp_cleanup_function(void) {
 981         // Don't do this stuff if this is not an SMTP session!
 982         if (CC->h_command_function != smtp_command_loop) return;
 983
 984         syslog(LOG_DEBUG, "Performing SMTP cleanup hook");
 985
 986         FreeStrBuf(&SMTP->Cmd);
 987         FreeStrBuf(&SMTP->helo_node);
 988         FreeStrBuf(&SMTP->from);
 989         FreeStrBuf(&SMTP->recipients);
 990         FreeStrBuf(&SMTP->OneRcpt);
 991         FreeStrBuf(&SMTP->preferred_sender_email);
 992         FreeStrBuf(&SMTP->preferred_sender_name);
 993
 994         free(SMTP);
 995 }
 996
 997 const char *CitadelServiceSMTP_MTA="SMTP-MTA";
 998 const char *CitadelServiceSMTPS_MTA="SMTPs-MTA";
 999 const char *CitadelServiceSMTP_MSA="SMTP-MSA";
1000 const char *CitadelServiceSMTP_LMTP="LMTP";
1001 const char *CitadelServiceSMTP_LMTP_UNF="LMTP-UnF";
1002
1003
1004 // Initialization function, called from modules_init.c
1005 char *ctdl_module_init_smtp(void) {
1006         if (!threading) {
1007                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtp_port"),        // SMTP MTA
1008                                         NULL,
1009                                         smtp_mta_greeting,
1010                                         smtp_command_loop,
1011                                         NULL,
1012                                         CitadelServiceSMTP_MTA);
1013
1014                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtps_port"),       // SMTPS MTA
1015                                         NULL,
1016                                         smtps_greeting,
1017                                         smtp_command_loop,
1018                                         NULL,
1019                                         CitadelServiceSMTPS_MTA);
1020
1021                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_msa_port"),         // SMTP MSA
1022                                         NULL,
1023                                         smtp_msa_greeting,
1024                                         smtp_command_loop,
1025                                         NULL,
1026                                         CitadelServiceSMTP_MSA);
1027
1028                 CtdlRegisterServiceHook(0,                                      // local LMTP
1029                                         file_lmtp_socket,
1030                                         lmtp_greeting,
1031                                         smtp_command_loop,
1032                                         NULL,
1033                                         CitadelServiceSMTP_LMTP);
1034
1035                 CtdlRegisterServiceHook(0,                                      // local LMTP
1036                                         file_lmtp_unfiltered_socket,
1037                                         lmtp_unfiltered_greeting,
1038                                         smtp_command_loop,
1039                                         NULL,
1040                                         CitadelServiceSMTP_LMTP_UNF);
1041
1042                 CtdlRegisterSessionHook(smtp_cleanup_function, EVT_STOP, PRIO_STOP + 250);
1043         }
1044
1045         // return our module name for the log
1046         return "smtp";
1047 }