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 the STARTTLS option...
 219                 if (    (!CC->redirect_ssl)                                                     // not if we're already TLS
 220                         && (    (SMTP->is_msa)                                                  // Always on port 587
 221                                 || (CtdlGetConfigInt("smtp_advertise_starttls") != 0)           // On port 25 only if enabled
 222                         )
 223                 ) {
 224                         cprintf("250-STARTTLS\r\n");
 225                 }
 226 #endif
 227
 228                 cprintf("250-AUTH LOGIN PLAIN\r\n"
 229                         "250-AUTH=LOGIN PLAIN\r\n"
 230                         "250 8BITMIME\r\n"
 231                 );
 232         }
 233 }
 234
 235
 236 // Backend function for smtp_webcit_preferences_hack().
 237 // Look at a message and determine if it's the preferences file.
 238 void smtp_webcit_preferences_hack_backend(long msgnum, void *userdata) {
 239         struct CtdlMessage *msg;
 240         char **webcit_conf = (char **) userdata;
 241
 242         if (*webcit_conf) {
 243                 return;         // already got it
 244         }
 245
 246         msg = CtdlFetchMessage(msgnum, 1);
 247         if (msg == NULL) {
 248                 return;
 249         }
 250
 251         if ( !CM_IsEmpty(msg, eMsgSubject) && (!strcasecmp(msg->cm_fields[eMsgSubject], "__ WebCit Preferences __"))) {
 252                 // This is it!  Change ownership of the message text so it doesn't get freed.
 253                 *webcit_conf = (char *)msg->cm_fields[eMessageText];
 254                 msg->cm_fields[eMessageText] = NULL;
 255         }
 256         CM_Free(msg);
 257 }
 258
 259
 260 // The configuration item for the user's preferred display name for outgoing email is, unfortunately,
 261 // stored in the account's WebCit configuration.  We have to fetch it now.
 262 void smtp_webcit_preferences_hack(void) {
 263         char config_roomname[ROOMNAMELEN];
 264         char *webcit_conf = NULL;
 265
 266         snprintf(config_roomname, sizeof config_roomname, "%010ld.%s", CC->user.usernum, USERCONFIGROOM);
 267         if (CtdlGetRoom(&CC->room, config_roomname) != 0) {
 268                 return;
 269         }
 270
 271         // Find the WebCit configuration message
 272         CtdlForEachMessage(MSGS_ALL, 1, NULL, NULL, NULL, smtp_webcit_preferences_hack_backend, (void *)&webcit_conf);
 273
 274         if (!webcit_conf) {
 275                 return;
 276         }
 277
 278         // Parse the webcit configuration and attempt to do something useful with it
 279         char *str = webcit_conf;
 280         char *saveptr = str;
 281         char *this_line = NULL;
 282         while (this_line = strtok_r(str, "\n", &saveptr), this_line != NULL) {
 283                 str = NULL;
 284                 if (!strncasecmp(this_line, "defaultfrom|", 12)) {
 285                         SMTP->preferred_sender_email = NewStrBufPlain(&this_line[12], -1);
 286                 }
 287                 if (!strncasecmp(this_line, "defaultname|", 12)) {
 288                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 289                 }
 290                 if ((!strncasecmp(this_line, "defaultname|", 12)) && (SMTP->preferred_sender_name == NULL)) {
 291                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 292                 }
 293
 294         }
 295         free(webcit_conf);
 296 }
 297
 298
 299 // Implement HELP command.
 300 void smtp_help(void) {
 301         cprintf("214 RTFM http://www.ietf.org/rfc/rfc2821.txt\r\n");
 302 }
 303
 304
 305 void smtp_get_user(int offset) {
 306         char buf[SIZ];
 307
 308         StrBuf *UserName = NewStrBufDup(SMTP->Cmd);
 309         StrBufCutLeft(UserName, offset);
 310         StrBufDecodeBase64(UserName);
 311
 312         if (CtdlLoginExistingUser(ChrPtr(UserName)) == login_ok) {
 313                 size_t len = CtdlEncodeBase64(buf, "Password:", 9, BASE64_NO_LINEBREAKS);
 314
 315                 if (buf[len - 1] == '\n') {
 316                         buf[len - 1] = '\0';
 317                 }
 318                 cprintf("334 %s\r\n", buf);
 319                 SMTP->command_state = smtp_password;
 320         }
 321         else {
 322                 cprintf("500 No such user.\r\n");
 323                 SMTP->command_state = smtp_command;
 324         }
 325         FreeStrBuf(&UserName);
 326 }
 327
 328
 329 void smtp_get_pass(void) {
 330         char password[SIZ];
 331
 332         memset(password, 0, sizeof(password));
 333         StrBufDecodeBase64(SMTP->Cmd);
 334         syslog(LOG_DEBUG, "serv_smtp: trying <%s>", password);
 335         if (CtdlTryPassword(SKEY(SMTP->Cmd)) == pass_ok) {
 336                 smtp_auth_greeting();
 337         }
 338         else {
 339                 cprintf("535 Authentication failed.\r\n");
 340         }
 341         SMTP->command_state = smtp_command;
 342 }
 343
 344
 345 // Back end for PLAIN auth method (either inline or multistate)
 346 void smtp_try_plain(void) {
 347         const char*decoded_authstring;
 348         char ident[256] = "";
 349         char user[256] = "";
 350         char pass[256] = "";
 351         int result;
 352
 353         long decoded_len;
 354         long len = 0;
 355         long plen = 0;
 356
 357         memset(pass, 0, sizeof(pass));
 358         decoded_len = StrBufDecodeBase64(SMTP->Cmd);
 359
 360         if (decoded_len > 0) {
 361                 decoded_authstring = ChrPtr(SMTP->Cmd);
 362
 363                 len = safestrncpy(ident, decoded_authstring, sizeof ident);
 364
 365                 decoded_len -= len - 1;
 366                 decoded_authstring += len + 1;
 367
 368                 if (decoded_len > 0) {
 369                         len = safestrncpy(user, decoded_authstring, sizeof user);
 370
 371                         decoded_authstring += len + 1;
 372                         decoded_len -= len - 1;
 373                 }
 374
 375                 if (decoded_len > 0) {
 376                         plen = safestrncpy(pass, decoded_authstring, sizeof pass);
 377
 378                         if (plen < 0)
 379                                 plen = sizeof(pass) - 1;
 380                 }
 381         }
 382
 383         SMTP->command_state = smtp_command;
 384
 385         if (!IsEmptyStr(ident)) {
 386                 result = CtdlLoginExistingUser(ident);
 387         }
 388         else {
 389                 result = CtdlLoginExistingUser(user);
 390         }
 391
 392         if (result == login_ok) {
 393                 if (CtdlTryPassword(pass, plen) == pass_ok) {
 394                         smtp_webcit_preferences_hack();
 395                         smtp_auth_greeting();
 396                         return;
 397                 }
 398         }
 399         cprintf("504 Authentication failed.\r\n");
 400 }
 401
 402
 403 // Attempt to perform authenticated SMTP
 404 void smtp_auth(void) {
 405         char username_prompt[64];
 406         char method[64];
 407         char encoded_authstring[1024];
 408
 409         if (CC->logged_in) {
 410                 cprintf("504 Already logged in.\r\n");
 411                 return;
 412         }
 413
 414         if (StrLength(SMTP->Cmd) < 6) {
 415                 cprintf("501 Syntax error\r\n");
 416                 return;
 417         }
 418
 419         extract_token(method, ChrPtr(SMTP->Cmd) + 5, 0, ' ', sizeof method);
 420
 421         if (!strncasecmp(method, "login", 5) ) {
 422                 if (StrLength(SMTP->Cmd) >= 12) {
 423                         syslog(LOG_DEBUG, "serv_smtp: username <%s> supplied inline", ChrPtr(SMTP->Cmd)+11);
 424                         smtp_get_user(11);
 425                 }
 426                 else {
 427                         size_t len = CtdlEncodeBase64(username_prompt, "Username:", 9, BASE64_NO_LINEBREAKS);
 428                         if (username_prompt[len - 1] == '\n') {
 429                                 username_prompt[len - 1] = '\0';
 430                         }
 431                         cprintf("334 %s\r\n", username_prompt);
 432                         SMTP->command_state = smtp_user;
 433                 }
 434                 return;
 435         }
 436
 437         if (!strncasecmp(method, "plain", 5) ) {
 438                 long len;
 439                 if (num_tokens(ChrPtr(SMTP->Cmd) + 5, ' ') < 2) {
 440                         cprintf("334 \r\n");
 441                         SMTP->command_state = smtp_plain;
 442                         return;
 443                 }
 444
 445                 len = extract_token(encoded_authstring, ChrPtr(SMTP->Cmd) + 5, 1, ' ', sizeof encoded_authstring);
 446                 StrBufPlain(SMTP->Cmd, encoded_authstring, len);
 447                 smtp_try_plain();
 448                 return;
 449         }
 450
 451         cprintf("504 Unknown authentication method.\r\n");
 452         return;
 453 }
 454
 455
 456 // Implements the RSET (reset state) command.
 457 // Currently this just zeroes out the state buffer.  If pointers to data
 458 // allocated with malloc() are ever placed in the state buffer, we have to
 459 // be sure to free() them first!
 460 //
 461 // Set do_response to nonzero to output the SMTP RSET response code.
 462 void smtp_rset(int do_response) {
 463         FlushStrBuf(SMTP->Cmd);
 464         FlushStrBuf(SMTP->helo_node);
 465         FlushStrBuf(SMTP->from);
 466         FlushStrBuf(SMTP->recipients);
 467         FlushStrBuf(SMTP->OneRcpt);
 468
 469         SMTP->command_state = 0;
 470         SMTP->number_of_recipients = 0;
 471         SMTP->delivery_mode = 0;
 472         SMTP->message_originated_locally = 0;
 473         SMTP->is_msa = 0;
 474         // is_lmtp and is_unfiltered should not be cleared.
 475
 476         if (do_response) {
 477                 cprintf("250 Zap!\r\n");
 478         }
 479 }
 480
 481
 482 // Clear out the portions of the state buffer that need to be cleared out
 483 // after the DATA command finishes.
 484 void smtp_data_clear(void) {
 485         FlushStrBuf(SMTP->from);
 486         FlushStrBuf(SMTP->recipients);
 487         FlushStrBuf(SMTP->OneRcpt);
 488         SMTP->number_of_recipients = 0;
 489         SMTP->delivery_mode = 0;
 490         SMTP->message_originated_locally = 0;
 491 }
 492
 493
 494 // Implements the "MAIL FROM:" command
 495 void smtp_mail(void) {
 496         char user[SIZ];
 497         char node[SIZ];
 498         char name[SIZ];
 499
 500         if (StrLength(SMTP->from) > 0) {
 501                 cprintf("503 Only one sender permitted\r\n");
 502                 return;
 503         }
 504
 505         if (StrLength(SMTP->Cmd) < 6) {
 506                 cprintf("501 Syntax error\r\n");
 507                 return;
 508         }
 509
 510         if (strncasecmp(ChrPtr(SMTP->Cmd) + 5, "From:", 5)) {
 511                 cprintf("501 Syntax error\r\n");
 512                 return;
 513         }
 514
 515         StrBufAppendBuf(SMTP->from, SMTP->Cmd, 5);
 516         StrBufTrim(SMTP->from);
 517         if (strchr(ChrPtr(SMTP->from), '<') != NULL) {
 518                 StrBufStripAllBut(SMTP->from, '<', '>');
 519         }
 520
 521         // We used to reject empty sender names, until it was brought to our
 522         // attention that RFC1123 5.2.9 requires that this be allowed.  So now
 523         // we allow it, but replace the empty string with a fake
 524         // address so we don't have to contend with the empty string causing
 525         // other code to fail when it's expecting something there.
 526         if (StrLength(SMTP->from) == 0) {
 527                 StrBufPlain(SMTP->from, HKEY("someone@example.com"));
 528         }
 529
 530         // If this SMTP connection is from a logged-in user, force the 'from'
 531         // to be the user's Internet e-mail address as Citadel knows it.
 532         if (CC->logged_in) {
 533                 StrBufPlain(SMTP->from, CC->cs_inet_email, -1);
 534                 cprintf("250 Sender ok <%s>\r\n", ChrPtr(SMTP->from));
 535                 SMTP->message_originated_locally = 1;
 536                 return;
 537         }
 538
 539         else if (SMTP->is_lmtp) {
 540                 // Bypass forgery checking for LMTP
 541         }
 542
 543         // Otherwise, make sure outsiders aren't trying to forge mail from
 544         // this system (unless, of course, c_allow_spoofing is enabled)
 545         else if (CtdlGetConfigInt("c_allow_spoofing") == 0) {
 546                 process_rfc822_addr(ChrPtr(SMTP->from), user, node, name);
 547                 syslog(LOG_DEBUG, "serv_smtp: claimed envelope sender is '%s' == '%s' @ '%s' ('%s')",
 548                         ChrPtr(SMTP->from), user, node, name
 549                 );
 550                 if (CtdlHostAlias(node) != hostalias_nomatch) {
 551                         cprintf("550 You must log in to send mail from %s\r\n", node);
 552                         FlushStrBuf(SMTP->from);
 553                         syslog(LOG_DEBUG, "serv_smtp: rejecting unauthenticated mail from %s", node);
 554                         return;
 555                 }
 556         }
 557
 558         cprintf("250 Sender ok\r\n");
 559 }
 560
 561
 562 // Implements the "RCPT To:" command
 563 void smtp_rcpt(void) {
 564         char message_to_spammer[SIZ];
 565         struct recptypes *valid = NULL;
 566
 567         if (StrLength(SMTP->from) == 0) {
 568                 cprintf("503 Need MAIL before RCPT\r\n");
 569                 return;
 570         }
 571
 572         if (StrLength(SMTP->Cmd) < 6) {
 573                 cprintf("501 Syntax error\r\n");
 574                 return;
 575         }
 576
 577         if (strncasecmp(ChrPtr(SMTP->Cmd) + 5, "To:", 3)) {
 578                 cprintf("501 Syntax error\r\n");
 579                 return;
 580         }
 581
 582         if ( (SMTP->is_msa) && (!CC->logged_in) ) {
 583                 cprintf("550 You must log in to send mail on this port.\r\n");
 584                 FlushStrBuf(SMTP->from);
 585                 return;
 586         }
 587
 588         FlushStrBuf(SMTP->OneRcpt);
 589         StrBufAppendBuf(SMTP->OneRcpt, SMTP->Cmd, 8);
 590         StrBufTrim(SMTP->OneRcpt);
 591         StrBufStripAllBut(SMTP->OneRcpt, '<', '>');
 592
 593         if ( (StrLength(SMTP->OneRcpt) + StrLength(SMTP->recipients)) >= SIZ) {
 594                 cprintf("452 Too many recipients\r\n");
 595                 return;
 596         }
 597
 598         // RBL check
 599         if (
 600                 (!CC->logged_in)                                                // Don't RBL authenticated users
 601                 && (!SMTP->is_lmtp)                                             // Don't RBL LMTP clients
 602                 && (CtdlGetConfigInt("c_rbl_at_greeting") == 0)                 // Don't RBL if we did it at connection time
 603                 && (rbl_check(CC->cs_addr, message_to_spammer))
 604         ) {
 605                 cprintf("550 %s\r\n", message_to_spammer);
 606                 return;                                                         // no need to free_recipients(valid)
 607         }                                                                       // because it hasn't been allocated yet
 608
 609         // This is a *preliminary* call to validate_recipients() to evaluate one recipient.
 610         valid = validate_recipients(
 611                 (char *)ChrPtr(SMTP->OneRcpt),
 612                 smtp_get_Recipients(),
 613                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 614         );
 615
 616         // Any type of error thrown by validate_recipients() will make the SMTP transaction fail at this point.
 617         if (valid->num_error != 0) {
 618                 cprintf("550 %s\r\n", valid->errormsg);
 619                 free_recipients(valid);
 620                 return;
 621         }
 622
 623         if (
 624                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 625                 && (CC->logged_in)                                              // ...and we're a logged-in user...
 626                 && (CtdlCheckInternetMailPermission(&CC->user)==0)              // ...who does not have Internet mail rights...
 627         ) {
 628                 cprintf("551 <%s> - you do not have permission to send Internet mail\r\n", ChrPtr(SMTP->OneRcpt));
 629                 free_recipients(valid);
 630                 return;
 631         }
 632
 633         if (
 634                 (valid->num_internet > 0)                                       // If it's outbound Internet mail...
 635                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 636                 && (SMTP->is_lmtp == 0)                                         /// ...and didn't arrive via LMTP...
 637         ) {
 638                 cprintf("551 <%s> - relaying denied\r\n", ChrPtr(SMTP->OneRcpt));
 639                 free_recipients(valid);
 640                 return;
 641         }
 642
 643         if (
 644                 (valid->num_room > 0)                                           // If it's mail to a room (mailing list)...
 645                 && (SMTP->message_originated_locally == 0)                      // ...and also inbound Internet mail...
 646                 && (is_email_subscribed_to_list((char *)ChrPtr(SMTP->from), valid->recp_room) == 0)     // ...and not a subscriber
 647         ) {
 648                 cprintf("551 <%s> - The message is not from a list member\r\n", ChrPtr(SMTP->OneRcpt));
 649                 free_recipients(valid);
 650                 return;
 651         }
 652
 653         cprintf("250 RCPT ok <%s>\r\n", ChrPtr(SMTP->OneRcpt));
 654         if (StrLength(SMTP->recipients) > 0) {
 655                 StrBufAppendBufPlain(SMTP->recipients, HKEY(","), 0);
 656         }
 657         StrBufAppendBuf(SMTP->recipients, SMTP->OneRcpt, 0);
 658         SMTP->number_of_recipients ++;
 659         if (valid != NULL)  {
 660                 free_recipients(valid);
 661         }
 662 }
 663
 664
 665 // Implements the DATA command
 666 void smtp_data(void) {
 667         StrBuf *body;
 668         StrBuf *defbody;
 669         struct CtdlMessage *msg = NULL;
 670         long msgnum = (-1L);
 671         char nowstamp[SIZ];
 672         struct recptypes *valid;
 673         int scan_errors;
 674         int i;
 675
 676         if (StrLength(SMTP->from) == 0) {
 677                 cprintf("503 Need MAIL command first.\r\n");
 678                 return;
 679         }
 680
 681         if (SMTP->number_of_recipients < 1) {
 682                 cprintf("503 Need RCPT command first.\r\n");
 683                 return;
 684         }
 685
 686         cprintf("354 Transmit message now - terminate with '.' by itself\r\n");
 687
 688         datestring(nowstamp, sizeof nowstamp, time(NULL), DATESTRING_RFC822);
 689         defbody = NewStrBufPlain(NULL, SIZ);
 690
 691         if (defbody != NULL) {
 692                 if (SMTP->is_lmtp && (CC->cs_UDSclientUID != -1)) {
 693                         StrBufPrintf(
 694                                 defbody,
 695                                 "Received: from %s (Citadel from userid %ld)\n"
 696                                 "       by %s; %s\n",
 697                                 ChrPtr(SMTP->helo_node),
 698                                 (long int) CC->cs_UDSclientUID,
 699                                 CtdlGetConfigStr("c_fqdn"),
 700                                 nowstamp);
 701                 }
 702                 else {
 703                         StrBufPrintf(
 704                                 defbody,
 705                                 "Received: from %s (%s [%s])\n"
 706                                 "       by %s; %s\n",
 707                                 ChrPtr(SMTP->helo_node),
 708                                 CC->cs_host,
 709                                 CC->cs_addr,
 710                                 CtdlGetConfigStr("c_fqdn"),
 711                                 nowstamp);
 712                 }
 713         }
 714         body = CtdlReadMessageBodyBuf(HKEY("."), CtdlGetConfigLong("c_maxmsglen"), defbody, 1);
 715         FreeStrBuf(&defbody);
 716         if (body == NULL) {
 717                 cprintf("550 Unable to save message: internal error.\r\n");
 718                 return;
 719         }
 720
 721         syslog(LOG_DEBUG, "serv_smtp: converting message...");
 722         msg = convert_internet_message_buf(&body);
 723
 724         // If the user is locally authenticated, FORCE the From: header to
 725         // show up as the real sender.  Yes, this violates the RFC standard,
 726         // but IT MAKES SENSE.  If you prefer strict RFC adherence over
 727         // common sense, you can disable this in the configuration.
 728         //
 729         // We also set the "message room name" ('O' field) to MAILROOM
 730         // (which is Mail> on most systems) to prevent it from getting set
 731         // to something ugly like "0000058008.Sent Items>" when the message
 732         // is read with a Citadel client.
 733
 734         if ( (CC->logged_in) && (CtdlGetConfigInt("c_rfc822_strict_from") != CFG_SMTP_FROM_NOFILTER) ) {
 735                 int validemail = 0;
 736
 737                 if (!CM_IsEmpty(msg, erFc822Addr)       &&
 738                     ((CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_CORRECT) ||
 739                      (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)    )  )
 740                 {
 741                         if (!IsEmptyStr(CC->cs_inet_email)) {
 742                                 validemail = strcmp(CC->cs_inet_email, msg->cm_fields[erFc822Addr]) == 0;
 743                         }
 744                         if ((!validemail) && (!IsEmptyStr(CC->cs_inet_other_emails))) {
 745                                 int num_secondary_emails = 0;
 746                                 int i;
 747                                 num_secondary_emails = num_tokens(CC->cs_inet_other_emails, '|');
 748                                 for (i=0; i < num_secondary_emails && !validemail; ++i) {
 749                                         char buf[256];
 750                                         extract_token(buf, CC->cs_inet_other_emails,i,'|',sizeof CC->cs_inet_other_emails);
 751                                         validemail = strcmp(buf, msg->cm_fields[erFc822Addr]) == 0;
 752                                 }
 753                         }
 754                 }
 755
 756                 if (!validemail && (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)) {
 757                         syslog(LOG_ERR, "serv_smtp: invalid sender '%s' - rejecting this message", msg->cm_fields[erFc822Addr]);
 758                         cprintf("550 Invalid sender '%s' - rejecting this message.\r\n", msg->cm_fields[erFc822Addr]);
 759                         return;
 760                 }
 761
 762                 CM_SetField(msg, eOriginalRoom, MAILROOM);
 763                 if (SMTP->preferred_sender_name != NULL)
 764                         CM_SetField(msg, eAuthor, ChrPtr(SMTP->preferred_sender_name));
 765                 else
 766                         CM_SetField(msg, eAuthor, CC->user.fullname);
 767
 768                 if (!validemail) {
 769                         if (SMTP->preferred_sender_email != NULL) {
 770                                 CM_SetField(msg, erFc822Addr, ChrPtr(SMTP->preferred_sender_email));
 771                         }
 772                         else {
 773                                 CM_SetField(msg, erFc822Addr, CC->cs_inet_email);
 774                         }
 775                 }
 776         }
 777
 778         // Set the "envelope from" address
 779         CM_SetField(msg, eMessagePath, ChrPtr(SMTP->from));
 780
 781         // Set the "envelope to" address
 782         CM_SetField(msg, eenVelopeTo, ChrPtr(SMTP->recipients));
 783
 784         // Submit the message into the Citadel system.
 785         valid = validate_recipients(
 786                 (char *)ChrPtr(SMTP->recipients),
 787                 smtp_get_Recipients(),
 788                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 789         );
 790
 791         // If there are modules that want to scan this message before final
 792         // submission (such as virus checkers or spam filters), call them now
 793         // and give them an opportunity to reject the message.
 794         if (SMTP->is_unfiltered) {
 795                 scan_errors = 0;
 796         }
 797         else {
 798                 scan_errors = PerformMessageHooks(msg, valid, EVT_SMTPSCAN);
 799         }
 800
 801         if (scan_errors > 0) {  // We don't want this message!
 802
 803                 if (CM_IsEmpty(msg, eErrorMsg)) {
 804                         CM_SetField(msg, eErrorMsg, "Message rejected by filter");
 805                 }
 806
 807                 StrBufPrintf(SMTP->OneRcpt, "550 %s\r\n", msg->cm_fields[eErrorMsg]);
 808         }
 809
 810         else {                  // Ok, we'll accept this message.
 811                 msgnum = CtdlSubmitMsg(msg, valid, "");
 812                 if (msgnum > 0L) {
 813                         StrBufPrintf(SMTP->OneRcpt, "250 Message accepted.\r\n");
 814                 }
 815                 else {
 816                         StrBufPrintf(SMTP->OneRcpt, "550 Internal delivery error\r\n");
 817                 }
 818         }
 819
 820         // For SMTP and ESMTP, just print the result message.  For LMTP, we
 821         // have to print one result message for each recipient.  Since there
 822         // is nothing in Citadel which would cause different recipients to
 823         // have different results, we can get away with just spitting out the
 824         // same message once for each recipient.
 825         if (SMTP->is_lmtp) {
 826                 for (i=0; i<SMTP->number_of_recipients; ++i) {
 827                         cputbuf(SMTP->OneRcpt);
 828                 }
 829         }
 830         else {
 831                 cputbuf(SMTP->OneRcpt);
 832         }
 833
 834         // Write something to the syslog(which may or may not be where the
 835         // rest of the Citadel logs are going; some sysadmins want LOG_MAIL).
 836         syslog((LOG_MAIL | LOG_INFO),
 837                     "%ld: from=<%s>, nrcpts=%d, relay=%s [%s], stat=%s",
 838                     msgnum,
 839                     ChrPtr(SMTP->from),
 840                     SMTP->number_of_recipients,
 841                     CC->cs_host,
 842                     CC->cs_addr,
 843                     ChrPtr(SMTP->OneRcpt)
 844         );
 845
 846         // Clean up
 847         CM_Free(msg);
 848         free_recipients(valid);
 849         smtp_data_clear();      // clear out the buffers now
 850 }
 851
 852
 853 // Implements the STARTTLS command
 854 void smtp_starttls(void) {
 855         char ok_response[SIZ];
 856         char nosup_response[SIZ];
 857         char error_response[SIZ];
 858
 859         sprintf(ok_response, "220 Begin TLS negotiation now\r\n");
 860         sprintf(nosup_response, "554 TLS not supported here\r\n");
 861         sprintf(error_response, "554 Internal error\r\n");
 862         CtdlModuleStartCryptoMsgs(ok_response, nosup_response, error_response);
 863         smtp_rset(0);
 864 }
 865
 866
 867 // Implements the NOOP (NO OPeration) command
 868 void smtp_noop(void) {
 869         cprintf("250 NOOP\r\n");
 870 }
 871
 872
 873 // Implements the QUIT command
 874 void smtp_quit(void) {
 875         cprintf("221 Goodbye...\r\n");
 876         CC->kill_me = KILLME_CLIENT_LOGGED_OUT;
 877 }
 878
 879
 880 // Main command loop for SMTP server sessions.
 881 void smtp_command_loop(void) {
 882         static const ConstStr AuthPlainStr = {HKEY("AUTH PLAIN")};
 883
 884         assert(SMTP != NULL);
 885
 886         time(&CC->lastcmd);
 887         if (CtdlClientGetLine(SMTP->Cmd) < 1) {
 888                 syslog(LOG_INFO, "SMTP: client disconnected: ending session.");
 889                 CC->kill_me = KILLME_CLIENT_DISCONNECTED;
 890                 return;
 891         }
 892
 893         if (SMTP->command_state == smtp_user) {
 894                 if (!strncmp(ChrPtr(SMTP->Cmd), AuthPlainStr.Key, AuthPlainStr.len)) {
 895                         smtp_try_plain();
 896                 }
 897                 else {
 898                         smtp_get_user(0);
 899                 }
 900                 return;
 901         }
 902
 903         else if (SMTP->command_state == smtp_password) {
 904                 smtp_get_pass();
 905                 return;
 906         }
 907
 908         else if (SMTP->command_state == smtp_plain) {
 909                 smtp_try_plain();
 910                 return;
 911         }
 912
 913         syslog(LOG_DEBUG, "serv_smtp: client sent command <%s>", ChrPtr(SMTP->Cmd));
 914
 915         if (!strncasecmp(ChrPtr(SMTP->Cmd), "NOOP", 4)) {
 916                 smtp_noop();
 917                 return;
 918         }
 919
 920         if (!strncasecmp(ChrPtr(SMTP->Cmd), "QUIT", 4)) {
 921                 smtp_quit();
 922                 return;
 923         }
 924
 925         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELO", 4)) {
 926                 smtp_hello(HELO);
 927                 return;
 928         }
 929
 930         if (!strncasecmp(ChrPtr(SMTP->Cmd), "EHLO", 4)) {
 931                 smtp_hello(EHLO);
 932                 return;
 933         }
 934
 935         if (!strncasecmp(ChrPtr(SMTP->Cmd), "LHLO", 4)) {
 936                 smtp_hello(LHLO);
 937                 return;
 938         }
 939
 940         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RSET", 4)) {
 941                 smtp_rset(1);
 942                 return;
 943         }
 944
 945         if (!strncasecmp(ChrPtr(SMTP->Cmd), "AUTH", 4)) {
 946                 smtp_auth();
 947                 return;
 948         }
 949
 950         if (!strncasecmp(ChrPtr(SMTP->Cmd), "DATA", 4)) {
 951                 smtp_data();
 952                 return;
 953         }
 954
 955         if (!strncasecmp(ChrPtr(SMTP->Cmd), "HELP", 4)) {
 956                 smtp_help();
 957                 return;
 958         }
 959
 960         if (!strncasecmp(ChrPtr(SMTP->Cmd), "MAIL", 4)) {
 961                 smtp_mail();
 962                 return;
 963         }
 964
 965         if (!strncasecmp(ChrPtr(SMTP->Cmd), "RCPT", 4)) {
 966                 smtp_rcpt();
 967                 return;
 968         }
 969 #ifdef HAVE_OPENSSL
 970         if (!strncasecmp(ChrPtr(SMTP->Cmd), "STARTTLS", 8)) {
 971                 smtp_starttls();
 972                 return;
 973         }
 974 #endif
 975
 976         cprintf("502 I'm afraid I can't do that.\r\n");
 977 }
 978
 979
 980 // *****************************************************************************
 981 // *                      MODULE INITIALIZATION STUFF                          *
 982 // *****************************************************************************
 983
 984 // This cleanup function blows away the temporary memory used by
 985 // the SMTP server.
 986 void smtp_cleanup_function(void) {
 987         // Don't do this stuff if this is not an SMTP session!
 988         if (CC->h_command_function != smtp_command_loop) return;
 989
 990         syslog(LOG_DEBUG, "Performing SMTP cleanup hook");
 991
 992         FreeStrBuf(&SMTP->Cmd);
 993         FreeStrBuf(&SMTP->helo_node);
 994         FreeStrBuf(&SMTP->from);
 995         FreeStrBuf(&SMTP->recipients);
 996         FreeStrBuf(&SMTP->OneRcpt);
 997         FreeStrBuf(&SMTP->preferred_sender_email);
 998         FreeStrBuf(&SMTP->preferred_sender_name);
 999
1000         free(SMTP);
1001 }
1002
1003 const char *CitadelServiceSMTP_MTA="SMTP-MTA";
1004 const char *CitadelServiceSMTPS_MTA="SMTPs-MTA";
1005 const char *CitadelServiceSMTP_MSA="SMTP-MSA";
1006 const char *CitadelServiceSMTP_LMTP="LMTP";
1007 const char *CitadelServiceSMTP_LMTP_UNF="LMTP-UnF";
1008
1009
1010 // Initialization function, called from modules_init.c
1011 char *ctdl_module_init_smtp(void) {
1012         if (!threading) {
1013                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtp_port"),        // SMTP MTA
1014                                         NULL,
1015                                         smtp_mta_greeting,
1016                                         smtp_command_loop,
1017                                         NULL,
1018                                         CitadelServiceSMTP_MTA);
1019
1020 #ifdef HAVE_OPENSSL
1021                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtps_port"),       // SMTPS MTA
1022                                         NULL,
1023                                         smtps_greeting,
1024                                         smtp_command_loop,
1025                                         NULL,
1026                                         CitadelServiceSMTPS_MTA);
1027 #endif
1028
1029                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_msa_port"),         // SMTP MSA
1030                                         NULL,
1031                                         smtp_msa_greeting,
1032                                         smtp_command_loop,
1033                                         NULL,
1034                                         CitadelServiceSMTP_MSA);
1035
1036                 CtdlRegisterServiceHook(0,                                      // local LMTP
1037                                         file_lmtp_socket,
1038                                         lmtp_greeting,
1039                                         smtp_command_loop,
1040                                         NULL,
1041                                         CitadelServiceSMTP_LMTP);
1042
1043                 CtdlRegisterServiceHook(0,                                      // local LMTP
1044                                         file_lmtp_unfiltered_socket,
1045                                         lmtp_unfiltered_greeting,
1046                                         smtp_command_loop,
1047                                         NULL,
1048                                         CitadelServiceSMTP_LMTP_UNF);
1049
1050                 CtdlRegisterSessionHook(smtp_cleanup_function, EVT_STOP, PRIO_STOP + 250);
1051         }
1052
1053         // return our module name for the log
1054         return "smtp";
1055 }