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 #ifdef HAVE_OPENSSL
 138         if (!CC->redirect_ssl) CC->kill_me = KILLME_NO_CRYPTO;          // kill session if no crypto
 139 #endif
 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 #ifdef HAVE_OPENSSL
 218                 // Offer TLS, but only if TLS is not already active.
 219                 // Furthermore, only offer TLS when running on the SMTP-MSA port, not on the SMTP-MTA port,
 220                 // because if our server doesn't have a trusted certificate, some mailers will refuse to talk to it.
 221                 if ( (!CC->redirect_ssl) && (SMTP->is_msa) ) {
 222                         cprintf("250-STARTTLS\r\n");
 223                 }
 224 #endif
 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_get_Recipients(),
 611                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 612         );
 613
 614         // Any type of error thrown by validate_recipients() will make the SMTP transaction fail at this point.
 615         if (valid->num_error != 0) {
 616                 cprintf("550 %s\r\n", valid->errormsg);
 617                 free_recipients(valid);
 618                 return;
 619         }
 620
 621         if (
 622                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 623                 && (CC->logged_in)                                              // ...and we're a logged-in user...
 624                 && (CtdlCheckInternetMailPermission(&CC->user)==0)              // ...who does not have Internet mail rights...
 625         ) {
 626                 cprintf("551 <%s> - you do not have permission to send Internet mail\r\n", ChrPtr(SMTP->OneRcpt));
 627                 free_recipients(valid);
 628                 return;
 629         }
 630
 631         if (
 632                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 633                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 634                 && (SMTP->is_lmtp == 0)                                         /// ...and didn't arrive via LMTP...
 635         ) {
 636                 cprintf("551 <%s> - relaying denied\r\n", ChrPtr(SMTP->OneRcpt));
 637                 free_recipients(valid);
 638                 return;
 639         }
 640
 641         if (
 642                 (valid->num_room > 0)                                           // If it's mail to a room (mailing list)...
 643                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 644                 && (is_email_subscribed_to_list((char *)ChrPtr(SMTP->from), valid->recp_room) == 0)     // ...and not a subscriber
 645         ) {
 646                 cprintf("551 <%s> - The message is not from a list member\r\n", ChrPtr(SMTP->OneRcpt));
 647                 free_recipients(valid);
 648                 return;
 649         }
 650
 651         cprintf("250 RCPT ok <%s>\r\n", ChrPtr(SMTP->OneRcpt));
 652         if (StrLength(SMTP->recipients) > 0) {
 653                 StrBufAppendBufPlain(SMTP->recipients, HKEY(","), 0);
 654         }
 655         StrBufAppendBuf(SMTP->recipients, SMTP->OneRcpt, 0);
 656         SMTP->number_of_recipients ++;
 657         if (valid != NULL)  {
 658                 free_recipients(valid);
 659         }
 660 }
 661
 662
 663 // Implements the DATA command
 664 void smtp_data(void) {
 665         StrBuf *body;
 666         StrBuf *defbody;
 667         struct CtdlMessage *msg = NULL;
 668         long msgnum = (-1L);
 669         char nowstamp[SIZ];
 670         struct recptypes *valid;
 671         int scan_errors;
 672         int i;
 673
 674         if (StrLength(SMTP->from) == 0) {
 675                 cprintf("503 Need MAIL command first.\r\n");
 676                 return;
 677         }
 678
 679         if (SMTP->number_of_recipients < 1) {
 680                 cprintf("503 Need RCPT command first.\r\n");
 681                 return;
 682         }
 683
 684         cprintf("354 Transmit message now - terminate with '.' by itself\r\n");
 685
 686         datestring(nowstamp, sizeof nowstamp, time(NULL), DATESTRING_RFC822);
 687         defbody = NewStrBufPlain(NULL, SIZ);
 688
 689         if (defbody != NULL) {
 690                 if (SMTP->is_lmtp && (CC->cs_UDSclientUID != -1)) {
 691                         StrBufPrintf(
 692                                 defbody,
 693                                 "Received: from %s (Citadel from userid %ld)\n"
 694                                 "       by %s; %s\n",
 695                                 ChrPtr(SMTP->helo_node),
 696                                 (long int) CC->cs_UDSclientUID,
 697                                 CtdlGetConfigStr("c_fqdn"),
 698                                 nowstamp);
 699                 }
 700                 else {
 701                         StrBufPrintf(
 702                                 defbody,
 703                                 "Received: from %s (%s [%s])\n"
 704                                 "       by %s; %s\n",
 705                                 ChrPtr(SMTP->helo_node),
 706                                 CC->cs_host,
 707                                 CC->cs_addr,
 708                                 CtdlGetConfigStr("c_fqdn"),
 709                                 nowstamp);
 710                 }
 711         }
 712         body = CtdlReadMessageBodyBuf(HKEY("."), CtdlGetConfigLong("c_maxmsglen"), defbody, 1);
 713         FreeStrBuf(&defbody);
 714         if (body == NULL) {
 715                 cprintf("550 Unable to save message: internal error.\r\n");
 716                 return;
 717         }
 718
 719         syslog(LOG_DEBUG, "serv_smtp: converting message...");
 720         msg = convert_internet_message_buf(&body);
 721
 722         // If the user is locally authenticated, FORCE the From: header to
 723         // show up as the real sender.  Yes, this violates the RFC standard,
 724         // but IT MAKES SENSE.  If you prefer strict RFC adherence over
 725         // common sense, you can disable this in the configuration.
 726         //
 727         // We also set the "message room name" ('O' field) to MAILROOM
 728         // (which is Mail> on most systems) to prevent it from getting set
 729         // to something ugly like "0000058008.Sent Items>" when the message
 730         // is read with a Citadel client.
 731
 732         if ( (CC->logged_in) && (CtdlGetConfigInt("c_rfc822_strict_from") != CFG_SMTP_FROM_NOFILTER) ) {
 733                 int validemail = 0;
 734
 735                 if (!CM_IsEmpty(msg, erFc822Addr)       &&
 736                     ((CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_CORRECT) ||
 737                      (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)    )  )
 738                 {
 739                         if (!IsEmptyStr(CC->cs_inet_email)) {
 740                                 validemail = strcmp(CC->cs_inet_email, msg->cm_fields[erFc822Addr]) == 0;
 741                         }
 742                         if ((!validemail) && (!IsEmptyStr(CC->cs_inet_other_emails))) {
 743                                 int num_secondary_emails = 0;
 744                                 int i;
 745                                 num_secondary_emails = num_tokens(CC->cs_inet_other_emails, '|');
 746                                 for (i=0; i < num_secondary_emails && !validemail; ++i) {
 747                                         char buf[256];
 748                                         extract_token(buf, CC->cs_inet_other_emails,i,'|',sizeof CC->cs_inet_other_emails);
 749                                         validemail = strcmp(buf, msg->cm_fields[erFc822Addr]) == 0;
 750                                 }
 751                         }
 752                 }
 753
 754                 if (!validemail && (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)) {
 755                         syslog(LOG_ERR, "serv_smtp: invalid sender '%s' - rejecting this message", msg->cm_fields[erFc822Addr]);
 756                         cprintf("550 Invalid sender '%s' - rejecting this message.\r\n", msg->cm_fields[erFc822Addr]);
 757                         return;
 758                 }
 759
 760                 CM_SetField(msg, eOriginalRoom, MAILROOM);
 761                 if (SMTP->preferred_sender_name != NULL)
 762                         CM_SetField(msg, eAuthor, ChrPtr(SMTP->preferred_sender_name));
 763                 else
 764                         CM_SetField(msg, eAuthor, CC->user.fullname);
 765
 766                 if (!validemail) {
 767                         if (SMTP->preferred_sender_email != NULL) {
 768                                 CM_SetField(msg, erFc822Addr, ChrPtr(SMTP->preferred_sender_email));
 769                         }
 770                         else {
 771                                 CM_SetField(msg, erFc822Addr, CC->cs_inet_email);
 772                         }
 773                 }
 774         }
 775
 776         // Set the "envelope from" address
 777         CM_SetField(msg, eMessagePath, ChrPtr(SMTP->from));
 778
 779         // Set the "envelope to" address
 780         CM_SetField(msg, eenVelopeTo, ChrPtr(SMTP->recipients));
 781
 782         // Submit the message into the Citadel system.
 783         valid = validate_recipients(
 784                 (char *)ChrPtr(SMTP->recipients),
 785                 smtp_get_Recipients(),
 786                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 787         );
 788
 789         // If there are modules that want to scan this message before final
 790         // submission (such as virus checkers or spam filters), call them now
 791         // and give them an opportunity to reject the message.
 792         if (SMTP->is_unfiltered) {
 793                 scan_errors = 0;
 794         }
 795         else {
 796                 scan_errors = PerformMessageHooks(msg, valid, EVT_SMTPSCAN);
 797         }
 798
 799         if (scan_errors > 0) {  // We don't want this message!
 800
 801                 if (CM_IsEmpty(msg, eErrorMsg)) {
 802                         CM_SetField(msg, eErrorMsg, "Message rejected by filter");
 803                 }
 804
 805                 StrBufPrintf(SMTP->OneRcpt, "550 %s\r\n", msg->cm_fields[eErrorMsg]);
 806         }
 807
 808         else {                  // Ok, we'll accept this message.
 809                 msgnum = CtdlSubmitMsg(msg, valid, "");
 810                 if (msgnum > 0L) {
 811                         StrBufPrintf(SMTP->OneRcpt, "250 Message accepted.\r\n");
 812                 }
 813                 else {
 814                         StrBufPrintf(SMTP->OneRcpt, "550 Internal delivery error\r\n");
 815                 }
 816         }
 817
 818         // For SMTP and ESMTP, just print the result message.  For LMTP, we
 819         // have to print one result message for each recipient.  Since there
 820         // is nothing in Citadel which would cause different recipients to
 821         // have different results, we can get away with just spitting out the
 822         // same message once for each recipient.
 823         if (SMTP->is_lmtp) {
 824                 for (i=0; i<SMTP->number_of_recipients; ++i) {
 825                         cputbuf(SMTP->OneRcpt);
 826                 }
 827         }
 828         else {
 829                 cputbuf(SMTP->OneRcpt);
 830         }
 831
 832         // Write something to the syslog(which may or may not be where the
 833         // rest of the Citadel logs are going; some sysadmins want LOG_MAIL).
 834         syslog((LOG_MAIL | LOG_INFO),
 835                     "%ld: from=<%s>, nrcpts=%d, relay=%s [%s], stat=%s",
 836                     msgnum,
 837                     ChrPtr(SMTP->from),
 838                     SMTP->number_of_recipients,
 839                     CC->cs_host,
 840                     CC->cs_addr,
 841                     ChrPtr(SMTP->OneRcpt)
 842         );
 843
 844         // Clean up
 845         CM_Free(msg);
 846         free_recipients(valid);
 847         smtp_data_clear();      // clear out the buffers now
 848 }
 849
 850
 851 // Implements the STARTTLS command
 852 void smtp_starttls(void) {
 853         char ok_response[SIZ];
 854         char nosup_response[SIZ];
 855         char error_response[SIZ];
 856
 857         sprintf(ok_response, "220 Begin TLS negotiation now\r\n");
 858         sprintf(nosup_response, "554 TLS not supported here\r\n");
 859         sprintf(error_response, "554 Internal error\r\n");
 860         CtdlModuleStartCryptoMsgs(ok_response, nosup_response, error_response);
 861         smtp_rset(0);
 862 }
 863
 864
 865 // Implements the NOOP (NO OPeration) command
 866 void smtp_noop(void) {
 867         cprintf("250 NOOP\r\n");
 868 }
 869
 870
 871 // Implements the QUIT command
 872 void smtp_quit(void) {
 873         cprintf("221 Goodbye...\r\n");
 874         CC->kill_me = KILLME_CLIENT_LOGGED_OUT;
 875 }
 876
 877
 878 // Main command loop for SMTP server sessions.
 879 void smtp_command_loop(void) {
 880         static const ConstStr AuthPlainStr = {HKEY("AUTH PLAIN")};
 881
 882         assert(SMTP != NULL);
 883
 884         time(&CC->lastcmd);
 885         if (CtdlClientGetLine(SMTP->Cmd) < 1) {
 886                 syslog(LOG_INFO, "SMTP: client disconnected: ending session.");
 887                 CC->kill_me = KILLME_CLIENT_DISCONNECTED;
 888                 return;
 889         }
 890
 891         if (SMTP->command_state == smtp_user) {
 892                 if (!strncmp(ChrPtr(SMTP->Cmd), AuthPlainStr.Key, AuthPlainStr.len)) {
 893                         smtp_try_plain();
 894                 }
 895                 else {
 896                         smtp_get_user(0);
 897                 }
 898                 return;
 899         }
 900
 901         else if (SMTP->command_state == smtp_password) {
 902                 smtp_get_pass();
 903                 return;
 904         }
 905
 906         else if (SMTP->command_state == smtp_plain) {
 907                 smtp_try_plain();
 908                 return;
 909         }
 910
 911         syslog(LOG_DEBUG, "serv_smtp: client sent command <%s>", ChrPtr(SMTP->Cmd));
 912
 913         if (!strncasecmp(ChrPtr(SMTP->Cmd), "NOOP", 4)) {
 914                 smtp_noop();
 915                 return;
 916         }
 917
 918         if (!strncasecmp(ChrPtr(SMTP->Cmd), "QUIT", 4)) {
 919                 smtp_quit();
 920                 return;
 921         }
 922
 923         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELO", 4)) {
 924                 smtp_hello(HELO);
 925                 return;
 926         }
 927
 928         if (!strncasecmp(ChrPtr(SMTP->Cmd), "EHLO", 4)) {
 929                 smtp_hello(EHLO);
 930                 return;
 931         }
 932
 933         if (!strncasecmp(ChrPtr(SMTP->Cmd), "LHLO", 4)) {
 934                 smtp_hello(LHLO);
 935                 return;
 936         }
 937
 938         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RSET", 4)) {
 939                 smtp_rset(1);
 940                 return;
 941         }
 942
 943         if (!strncasecmp(ChrPtr(SMTP->Cmd), "AUTH", 4)) {
 944                 smtp_auth();
 945                 return;
 946         }
 947
 948         if (!strncasecmp(ChrPtr(SMTP->Cmd), "DATA", 4)) {
 949                 smtp_data();
 950                 return;
 951         }
 952
 953         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELP", 4)) {
 954                 smtp_help();
 955                 return;
 956         }
 957
 958         if (!strncasecmp(ChrPtr(SMTP->Cmd), "MAIL", 4)) {
 959                 smtp_mail();
 960                 return;
 961         }
 962
 963         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RCPT", 4)) {
 964                 smtp_rcpt();
 965                 return;
 966         }
 967 #ifdef HAVE_OPENSSL
 968         if (!strncasecmp(ChrPtr(SMTP->Cmd), "STARTTLS", 8)) {
 969                 smtp_starttls();
 970                 return;
 971         }
 972 #endif
 973
 974         cprintf("502 I'm afraid I can't do that.\r\n");
 975 }
 976
 977
 978 // *****************************************************************************
 979 // *                      MODULE INITIALIZATION STUFF                          *
 980 // *****************************************************************************
 981
 982 // This cleanup function blows away the temporary memory used by
 983 // the SMTP server.
 984 void smtp_cleanup_function(void) {
 985         // Don't do this stuff if this is not an SMTP session!
 986         if (CC->h_command_function != smtp_command_loop) return;
 987
 988         syslog(LOG_DEBUG, "Performing SMTP cleanup hook");
 989
 990         FreeStrBuf(&SMTP->Cmd);
 991         FreeStrBuf(&SMTP->helo_node);
 992         FreeStrBuf(&SMTP->from);
 993         FreeStrBuf(&SMTP->recipients);
 994         FreeStrBuf(&SMTP->OneRcpt);
 995         FreeStrBuf(&SMTP->preferred_sender_email);
 996         FreeStrBuf(&SMTP->preferred_sender_name);
 997
 998         free(SMTP);
 999 }
1000
1001 const char *CitadelServiceSMTP_MTA="SMTP-MTA";
1002 const char *CitadelServiceSMTPS_MTA="SMTPs-MTA";
1003 const char *CitadelServiceSMTP_MSA="SMTP-MSA";
1004 const char *CitadelServiceSMTP_LMTP="LMTP";
1005 const char *CitadelServiceSMTP_LMTP_UNF="LMTP-UnF";
1006
1007
1008 // Initialization function, called from modules_init.c
1009 char *ctdl_module_init_smtp(void) {
1010         if (!threading) {
1011                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtp_port"),        // SMTP MTA
1012                                         NULL,
1013                                         smtp_mta_greeting,
1014                                         smtp_command_loop,
1015                                         NULL,
1016                                         CitadelServiceSMTP_MTA);
1017
1018 #ifdef HAVE_OPENSSL
1019                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtps_port"),       // SMTPS MTA
1020                                         NULL,
1021                                         smtps_greeting,
1022                                         smtp_command_loop,
1023                                         NULL,
1024                                         CitadelServiceSMTPS_MTA);
1025 #endif
1026
1027                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_msa_port"),         // SMTP MSA
1028                                         NULL,
1029                                         smtp_msa_greeting,
1030                                         smtp_command_loop,
1031                                         NULL,
1032                                         CitadelServiceSMTP_MSA);
1033
1034                 CtdlRegisterServiceHook(0,                                      // local LMTP
1035                                         file_lmtp_socket,
1036                                         lmtp_greeting,
1037                                         smtp_command_loop,
1038                                         NULL,
1039                                         CitadelServiceSMTP_LMTP);
1040
1041                 CtdlRegisterServiceHook(0,                                      // local LMTP
1042                                         file_lmtp_unfiltered_socket,
1043                                         lmtp_unfiltered_greeting,
1044                                         smtp_command_loop,
1045                                         NULL,
1046                                         CitadelServiceSMTP_LMTP_UNF);
1047
1048                 CtdlRegisterSessionHook(smtp_cleanup_function, EVT_STOP, PRIO_STOP + 250);
1049         }
1050
1051         // return our module name for the log
1052         return "smtp";
1053 }