citadel/modules/smtp/serv_smtp.c

   1 /*
   2  * This module is an SMTP and ESMTP server for the Citadel system.
   3  * It is compliant with all of the following:
   4  *
   5  * RFC  821 - Simple Mail Transfer Protocol
   6  * RFC  876 - Survey of SMTP Implementations
   7  * RFC 1047 - Duplicate messages and SMTP
   8  * RFC 1652 - 8 bit MIME
   9  * RFC 1869 - Extended Simple Mail Transfer Protocol
  10  * RFC 1870 - SMTP Service Extension for Message Size Declaration
  11  * RFC 2033 - Local Mail Transfer Protocol
  12  * RFC 2197 - SMTP Service Extension for Command Pipelining
  13  * RFC 2476 - Message Submission
  14  * RFC 2487 - SMTP Service Extension for Secure SMTP over TLS
  15  * RFC 2554 - SMTP Service Extension for Authentication
  16  * RFC 2821 - Simple Mail Transfer Protocol
  17  * RFC 2822 - Internet Message Format
  18  * RFC 2920 - SMTP Service Extension for Command Pipelining
  19  *
  20  * The VRFY and EXPN commands have been removed from this implementation
  21  * because nobody uses these commands anymore, except for spammers.
  22  *
  23  * Copyright (c) 1998-2021 by the citadel.org team
  24  *
  25  * This program is open source software; you can redistribute it and/or modify
  26  * it under the terms of the GNU General Public License version 3.
  27  *
  28  * This program is distributed in the hope that it will be useful,
  29  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  30  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  31  * GNU General Public License for more details.
  32  */
  33
  34 #include "sysdep.h"
  35 #include <stdlib.h>
  36 #include <unistd.h>
  37 #include <stdio.h>
  38 #include <termios.h>
  39 #include <fcntl.h>
  40 #include <signal.h>
  41 #include <pwd.h>
  42 #include <errno.h>
  43 #include <sys/types.h>
  44 #include <syslog.h>
  45 #include <time.h>
  46 #include <sys/wait.h>
  47 #include <ctype.h>
  48 #include <string.h>
  49 #include <limits.h>
  50 #include <sys/socket.h>
  51 #include <netinet/in.h>
  52 #include <arpa/inet.h>
  53 #include <libcitadel.h>
  54 #include "citadel.h"
  55 #include "server.h"
  56 #include "citserver.h"
  57 #include "support.h"
  58 #include "config.h"
  59 #include "control.h"
  60 #include "user_ops.h"
  61 #include "room_ops.h"
  62 #include "database.h"
  63 #include "msgbase.h"
  64 #include "internet_addressing.h"
  65 #include "genstamp.h"
  66 #include "domain.h"
  67 #include "clientsocket.h"
  68 #include "locate_host.h"
  69 #include "citadel_dirs.h"
  70 #include "ctdl_module.h"
  71
  72 #include "smtp_util.h"
  73
  74 enum {                          /* Command states for login authentication */
  75         smtp_command,
  76         smtp_user,
  77         smtp_password,
  78         smtp_plain
  79 };
  80
  81 enum SMTP_FLAGS {
  82         HELO,
  83         EHLO,
  84         LHLO
  85 };
  86
  87 typedef void (*smtp_handler)(long offest, long Flags);
  88
  89 typedef struct _smtp_handler_hook {
  90         smtp_handler h;
  91         int Flags;
  92 } smtp_handler_hook;
  93
  94 int EnableSMTPLog = 0;
  95
  96 HashList *SMTPCmds = NULL;
  97 #define MaxSMTPCmdLen 10
  98
  99 #define RegisterSmtpCMD(First, H, Flags) registerSmtpCMD(HKEY(First), H, Flags)
 100 void registerSmtpCMD(const char *First, long FLen, smtp_handler H, int Flags) {
 101         smtp_handler_hook *h;
 102
 103         if (FLen >= MaxSMTPCmdLen) {
 104                 abort();
 105         }
 106
 107         h = (smtp_handler_hook*) malloc(sizeof(smtp_handler_hook));
 108         memset(h, 0, sizeof(smtp_handler_hook));
 109
 110         h->Flags = Flags;
 111         h->h = H;
 112         Put(SMTPCmds, First, FLen, h, NULL);
 113 }
 114
 115
 116 /*
 117  * Here's where our SMTP session begins its happy day.
 118  */
 119 void smtp_greeting(int is_msa) {
 120         char message_to_spammer[1024];
 121
 122         strcpy(CC->cs_clientname, "SMTP session");
 123         CC->internal_pgm = 1;
 124         CC->cs_flags |= CS_STEALTH;
 125         CC->session_specific_data = malloc(sizeof(citsmtp));
 126         memset(SMTP, 0, sizeof(citsmtp));
 127         SMTP->is_msa = is_msa;
 128         SMTP->Cmd = NewStrBufPlain(NULL, SIZ);
 129         SMTP->helo_node = NewStrBuf();
 130         SMTP->from = NewStrBufPlain(NULL, SIZ);
 131         SMTP->recipients = NewStrBufPlain(NULL, SIZ);
 132         SMTP->OneRcpt = NewStrBufPlain(NULL, SIZ);
 133         SMTP->preferred_sender_email = NULL;
 134         SMTP->preferred_sender_name = NULL;
 135
 136         /* If this config option is set, reject connections from problem
 137          * addresses immediately instead of after they execute a RCPT
 138          */
 139         if ( (CtdlGetConfigInt("c_rbl_at_greeting")) && (SMTP->is_msa == 0) ) {
 140                 if (rbl_check(CC->cs_addr, message_to_spammer)) {
 141                         if (server_shutting_down)
 142                                 cprintf("421 %s\r\n", message_to_spammer);
 143                         else
 144                                 cprintf("550 %s\r\n", message_to_spammer);
 145                         CC->kill_me = KILLME_SPAMMER;
 146                         /* no need to free_recipients(valid), it's not allocated yet */
 147                         return;
 148                 }
 149         }
 150
 151         /* Otherwise we're either clean or we check later. */
 152
 153         if (CC->nologin==1) {
 154                 cprintf("451 Too many connections are already open; please try again later.\r\n");
 155                 CC->kill_me = KILLME_MAX_SESSIONS_EXCEEDED;
 156                 /* no need to free_recipients(valid), it's not allocated yet */
 157                 return;
 158         }
 159
 160         /* Note: the FQDN *must* appear as the first thing after the 220 code.
 161          * Some clients (including citmail.c) depend on it being there.
 162          */
 163         cprintf("220 %s ESMTP Citadel server ready.\r\n", CtdlGetConfigStr("c_fqdn"));
 164 }
 165
 166
 167 /*
 168  * SMTPS is just like SMTP, except it goes crypto right away.
 169  */
 170 void smtps_greeting(void) {
 171         CtdlModuleStartCryptoMsgs(NULL, NULL, NULL);
 172 #ifdef HAVE_OPENSSL
 173         if (!CC->redirect_ssl) CC->kill_me = KILLME_NO_CRYPTO;          /* kill session if no crypto */
 174 #endif
 175         smtp_greeting(0);
 176 }
 177
 178
 179 /*
 180  * SMTP MSA port requires authentication.
 181  */
 182 void smtp_msa_greeting(void) {
 183         smtp_greeting(1);
 184 }
 185
 186
 187 /*
 188  * LMTP is like SMTP but with some extra bonus footage added.
 189  */
 190 void lmtp_greeting(void) {
 191
 192         smtp_greeting(0);
 193         SMTP->is_lmtp = 1;
 194 }
 195
 196
 197 /*
 198  * Generic SMTP MTA greeting
 199  */
 200 void smtp_mta_greeting(void) {
 201         smtp_greeting(0);
 202 }
 203
 204
 205 /*
 206  * We also have an unfiltered LMTP socket that bypasses spam filters.
 207  */
 208 void lmtp_unfiltered_greeting(void) {
 209         smtp_greeting(0);
 210         SMTP->is_lmtp = 1;
 211         SMTP->is_unfiltered = 1;
 212 }
 213
 214
 215 /*
 216  * Login greeting common to all auth methods
 217  */
 218 void smtp_auth_greeting(long offset, long Flags) {
 219         cprintf("235 Hello, %s\r\n", CC->user.fullname);
 220         syslog(LOG_INFO, "serv_smtp: SMTP authenticated %s", CC->user.fullname);
 221         CC->internal_pgm = 0;
 222         CC->cs_flags &= ~CS_STEALTH;
 223 }
 224
 225
 226 /*
 227  * Implement HELO and EHLO commands.
 228  *
 229  * which_command:  0=HELO, 1=EHLO, 2=LHLO
 230  */
 231 void smtp_hello(long offset, long which_command) {
 232
 233         StrBufAppendBuf (SMTP->helo_node, SMTP->Cmd, offset);
 234
 235         if ( (which_command != LHLO) && (SMTP->is_lmtp) ) {
 236                 cprintf("500 Only LHLO is allowed when running LMTP\r\n");
 237                 return;
 238         }
 239
 240         if ( (which_command == LHLO) && (SMTP->is_lmtp == 0) ) {
 241                 cprintf("500 LHLO is only allowed when running LMTP\r\n");
 242                 return;
 243         }
 244
 245         if (which_command == HELO) {
 246                 cprintf("250 Hello %s (%s [%s])\r\n",
 247                         ChrPtr(SMTP->helo_node),
 248                         CC->cs_host,
 249                         CC->cs_addr
 250                 );
 251         }
 252         else {
 253                 if (which_command == EHLO) {
 254                         cprintf("250-Hello %s (%s [%s])\r\n",
 255                                 ChrPtr(SMTP->helo_node),
 256                                 CC->cs_host,
 257                                 CC->cs_addr
 258                         );
 259                 }
 260                 else {
 261                         cprintf("250-Greetings and joyous salutations.\r\n");
 262                 }
 263                 cprintf("250-HELP\r\n");
 264                 cprintf("250-SIZE %ld\r\n", CtdlGetConfigLong("c_maxmsglen"));
 265
 266 #ifdef HAVE_OPENSSL
 267                 /*
 268                  * Offer TLS, but only if TLS is not already active.
 269                  * Furthermore, only offer TLS when running on
 270                  * the SMTP-MSA port, not on the SMTP-MTA port, due to
 271                  * questionable reliability of TLS in certain sending MTA's.
 272                  */
 273                 if ( (!CC->redirect_ssl) && (SMTP->is_msa) ) {
 274                         cprintf("250-STARTTLS\r\n");
 275                 }
 276 #endif  /* HAVE_OPENSSL */
 277
 278                 cprintf("250-AUTH LOGIN PLAIN\r\n"
 279                         "250-AUTH=LOGIN PLAIN\r\n"
 280                         "250 8BITMIME\r\n"
 281                 );
 282         }
 283 }
 284
 285
 286 /*
 287  * Backend function for smtp_webcit_preferences_hack().
 288  * Look at a message and determine if it's the preferences file.
 289  */
 290 void smtp_webcit_preferences_hack_backend(long msgnum, void *userdata) {
 291         struct CtdlMessage *msg;
 292         char **webcit_conf = (char **) userdata;
 293
 294         if (*webcit_conf) {
 295                 return; // already got it
 296         }
 297
 298         msg = CtdlFetchMessage(msgnum, 1);
 299         if (msg == NULL) {
 300                 return;
 301         }
 302
 303         if ( !CM_IsEmpty(msg, eMsgSubject) &&
 304              (!strcasecmp(msg->cm_fields[eMsgSubject], "__ WebCit Preferences __")))
 305         {
 306                 /* This is it!  Change ownership of the message text so it doesn't get freed. */
 307                 *webcit_conf = (char *)msg->cm_fields[eMesageText];
 308                 msg->cm_fields[eMesageText] = NULL;
 309         }
 310         CM_Free(msg);
 311 }
 312
 313
 314 /*
 315  * The configuration item for the user's preferred display name for outgoing email is, unfortunately,
 316  * stored in the account's WebCit configuration.  We have to fetch it now.
 317  */
 318 void smtp_webcit_preferences_hack(void) {
 319         char config_roomname[ROOMNAMELEN];
 320         char *webcit_conf = NULL;
 321
 322         snprintf(config_roomname, sizeof config_roomname, "%010ld.%s", CC->user.usernum, USERCONFIGROOM);
 323         if (CtdlGetRoom(&CC->room, config_roomname) != 0) {
 324                 return;
 325         }
 326
 327         /*
 328          * Find the WebCit configuration message
 329          */
 330
 331         CtdlForEachMessage(MSGS_ALL, 1, NULL, NULL, NULL, smtp_webcit_preferences_hack_backend, (void *)&webcit_conf);
 332
 333         if (!webcit_conf) {
 334                 return;
 335         }
 336
 337         /* Parse the webcit configuration and attempt to do something useful with it */
 338         char *str = webcit_conf;
 339         char *saveptr = str;
 340         char *this_line = NULL;
 341         while (this_line = strtok_r(str, "\n", &saveptr), this_line != NULL) {
 342                 str = NULL;
 343                 if (!strncasecmp(this_line, "defaultfrom|", 12)) {
 344                         SMTP->preferred_sender_email = NewStrBufPlain(&this_line[12], -1);
 345                 }
 346                 if (!strncasecmp(this_line, "defaultname|", 12)) {
 347                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 348                 }
 349                 if ((!strncasecmp(this_line, "defaultname|", 12)) && (SMTP->preferred_sender_name == NULL)) {
 350                         SMTP->preferred_sender_name = NewStrBufPlain(&this_line[12], -1);
 351                 }
 352
 353         }
 354         free(webcit_conf);
 355 }
 356
 357
 358
 359 /*
 360  * Implement HELP command.
 361  */
 362 void smtp_help(long offset, long Flags) {
 363         cprintf("214 RTFM http://www.ietf.org/rfc/rfc2821.txt\r\n");
 364 }
 365
 366
 367 /*
 368  *
 369  */
 370 void smtp_get_user(long offset)
 371 {
 372         char buf[SIZ];
 373
 374         StrBufDecodeBase64(SMTP->Cmd);
 375
 376         if (CtdlLoginExistingUser(ChrPtr(SMTP->Cmd)) == login_ok) {
 377                 size_t len = CtdlEncodeBase64(buf, "Password:", 9, 0);
 378
 379                 if (buf[len - 1] == '\n') {
 380                         buf[len - 1] = '\0';
 381                 }
 382                 cprintf("334 %s\r\n", buf);
 383                 SMTP->command_state = smtp_password;
 384         }
 385         else {
 386                 cprintf("500 No such user.\r\n");
 387                 SMTP->command_state = smtp_command;
 388         }
 389 }
 390
 391
 392 /*
 393  *
 394  */
 395 void smtp_get_pass(long offset, long Flags)
 396 {
 397         char password[SIZ];
 398
 399         memset(password, 0, sizeof(password));
 400         StrBufDecodeBase64(SMTP->Cmd);
 401         syslog(LOG_DEBUG, "serv_smtp: trying <%s>", password);
 402         if (CtdlTryPassword(SKEY(SMTP->Cmd)) == pass_ok) {
 403                 smtp_auth_greeting(offset, Flags);
 404         }
 405         else {
 406                 cprintf("535 Authentication failed.\r\n");
 407         }
 408         SMTP->command_state = smtp_command;
 409 }
 410
 411
 412 /*
 413  * Back end for PLAIN auth method (either inline or multistate)
 414  */
 415 void smtp_try_plain(long offset, long Flags)
 416 {
 417         const char*decoded_authstring;
 418         char ident[256] = "";
 419         char user[256] = "";
 420         char pass[256] = "";
 421         int result;
 422
 423         long decoded_len;
 424         long len = 0;
 425         long plen = 0;
 426
 427         memset(pass, 0, sizeof(pass));
 428         decoded_len = StrBufDecodeBase64(SMTP->Cmd);
 429
 430         if (decoded_len > 0)
 431         {
 432                 decoded_authstring = ChrPtr(SMTP->Cmd);
 433
 434                 len = safestrncpy(ident, decoded_authstring, sizeof ident);
 435
 436                 decoded_len -= len - 1;
 437                 decoded_authstring += len + 1;
 438
 439                 if (decoded_len > 0)
 440                 {
 441                         len = safestrncpy(user, decoded_authstring, sizeof user);
 442
 443                         decoded_authstring += len + 1;
 444                         decoded_len -= len - 1;
 445                 }
 446
 447                 if (decoded_len > 0)
 448                 {
 449                         plen = safestrncpy(pass, decoded_authstring, sizeof pass);
 450
 451                         if (plen < 0)
 452                                 plen = sizeof(pass) - 1;
 453                 }
 454         }
 455
 456         SMTP->command_state = smtp_command;
 457
 458         if (!IsEmptyStr(ident)) {
 459                 result = CtdlLoginExistingUser(ident);
 460         }
 461         else {
 462                 result = CtdlLoginExistingUser(user);
 463         }
 464
 465         if (result == login_ok) {
 466                 if (CtdlTryPassword(pass, plen) == pass_ok) {
 467                         smtp_webcit_preferences_hack();
 468                         smtp_auth_greeting(offset, Flags);
 469                         return;
 470                 }
 471         }
 472         cprintf("504 Authentication failed.\r\n");
 473 }
 474
 475
 476 /*
 477  * Attempt to perform authenticated SMTP
 478  */
 479 void smtp_auth(long offset, long Flags)
 480 {
 481         char username_prompt[64];
 482         char method[64];
 483         char encoded_authstring[1024];
 484
 485         if (CC->logged_in) {
 486                 cprintf("504 Already logged in.\r\n");
 487                 return;
 488         }
 489
 490         extract_token(method, ChrPtr(SMTP->Cmd) + offset, 0, ' ', sizeof method);
 491
 492         if (!strncasecmp(method, "login", 5) ) {
 493                 if (StrLength(SMTP->Cmd) - offset >= 7) {
 494                         smtp_get_user(6);
 495                 }
 496                 else {
 497                         size_t len = CtdlEncodeBase64(username_prompt, "Username:", 9, 0);
 498                         if (username_prompt[len - 1] == '\n') {
 499                                 username_prompt[len - 1] = '\0';
 500                         }
 501                         cprintf("334 %s\r\n", username_prompt);
 502                         SMTP->command_state = smtp_user;
 503                 }
 504                 return;
 505         }
 506
 507         if (!strncasecmp(method, "plain", 5) ) {
 508                 long len;
 509                 if (num_tokens(ChrPtr(SMTP->Cmd) + offset, ' ') < 2) {
 510                         cprintf("334 \r\n");
 511                         SMTP->command_state = smtp_plain;
 512                         return;
 513                 }
 514
 515                 len = extract_token(encoded_authstring,
 516                                     ChrPtr(SMTP->Cmd) + offset,
 517                                     1, ' ',
 518                                     sizeof encoded_authstring);
 519                 StrBufPlain(SMTP->Cmd, encoded_authstring, len);
 520                 smtp_try_plain(0, Flags);
 521                 return;
 522         }
 523
 524         if (strncasecmp(method, "login", 5) ) {
 525                 cprintf("504 Unknown authentication method.\r\n");
 526                 return;
 527         }
 528
 529 }
 530
 531
 532 /*
 533  * Implements the RSET (reset state) command.
 534  * Currently this just zeroes out the state buffer.  If pointers to data
 535  * allocated with malloc() are ever placed in the state buffer, we have to
 536  * be sure to free() them first!
 537  *
 538  * Set do_response to nonzero to output the SMTP RSET response code.
 539  */
 540 void smtp_rset(long offset, long do_response) {
 541         /*
 542          * Our entire SMTP state is discarded when a RSET command is issued,
 543          * but we need to preserve this one little piece of information, so
 544          * we save it for later.
 545          */
 546
 547         FlushStrBuf(SMTP->Cmd);
 548         FlushStrBuf(SMTP->helo_node);
 549         FlushStrBuf(SMTP->from);
 550         FlushStrBuf(SMTP->recipients);
 551         FlushStrBuf(SMTP->OneRcpt);
 552
 553         SMTP->command_state = 0;
 554         SMTP->number_of_recipients = 0;
 555         SMTP->delivery_mode = 0;
 556         SMTP->message_originated_locally = 0;
 557         SMTP->is_msa = 0;
 558         /*
 559          * we must remember is_lmtp & is_unfiltered.
 560          */
 561
 562         /*
 563          * It is somewhat ambiguous whether we want to log out when a RSET
 564          * command is issued.  Here's the code to do it.  It is commented out
 565          * because some clients (such as Pine) issue RSET commands before
 566          * each message, but still expect to be logged in.
 567          *
 568          * if (CC->logged_in) {
 569          *      logout(CC);
 570          * }
 571          */
 572
 573         if (do_response) {
 574                 cprintf("250 Zap!\r\n");
 575         }
 576 }
 577
 578 /*
 579  * Clear out the portions of the state buffer that need to be cleared out
 580  * after the DATA command finishes.
 581  */
 582 void smtp_data_clear(long offset, long flags)
 583 {
 584         FlushStrBuf(SMTP->from);
 585         FlushStrBuf(SMTP->recipients);
 586         FlushStrBuf(SMTP->OneRcpt);
 587         SMTP->number_of_recipients = 0;
 588         SMTP->delivery_mode = 0;
 589         SMTP->message_originated_locally = 0;
 590 }
 591
 592 /*
 593  * Implements the "MAIL FROM:" command
 594  */
 595 void smtp_mail(long offset, long flags) {
 596         char user[SIZ];
 597         char node[SIZ];
 598         char name[SIZ];
 599
 600         if (StrLength(SMTP->from) > 0) {
 601                 cprintf("503 Only one sender permitted\r\n");
 602                 return;
 603         }
 604
 605         if (strncasecmp(ChrPtr(SMTP->Cmd) + offset, "From:", 5)) {
 606                 cprintf("501 Syntax error\r\n");
 607                 return;
 608         }
 609
 610         StrBufAppendBuf(SMTP->from, SMTP->Cmd, offset);
 611         StrBufTrim(SMTP->from);
 612         if (strchr(ChrPtr(SMTP->from), '<') != NULL) {
 613                 StrBufStripAllBut(SMTP->from, '<', '>');
 614         }
 615
 616         /* We used to reject empty sender names, until it was brought to our
 617          * attention that RFC1123 5.2.9 requires that this be allowed.  So now
 618          * we allow it, but replace the empty string with a fake
 619          * address so we don't have to contend with the empty string causing
 620          * other code to fail when it's expecting something there.
 621          */
 622         if (StrLength(SMTP->from) == 0) {
 623                 StrBufPlain(SMTP->from, HKEY("someone@example.com"));
 624         }
 625
 626         /* If this SMTP connection is from a logged-in user, force the 'from'
 627          * to be the user's Internet e-mail address as Citadel knows it.
 628          */
 629         if (CC->logged_in) {
 630                 StrBufPlain(SMTP->from, CC->cs_inet_email, -1);
 631                 cprintf("250 Sender ok <%s>\r\n", ChrPtr(SMTP->from));
 632                 SMTP->message_originated_locally = 1;
 633                 return;
 634         }
 635
 636         else if (SMTP->is_lmtp) {
 637                 /* Bypass forgery checking for LMTP */
 638         }
 639
 640         /* Otherwise, make sure outsiders aren't trying to forge mail from
 641          * this system (unless, of course, c_allow_spoofing is enabled)
 642          */
 643         else if (CtdlGetConfigInt("c_allow_spoofing") == 0) {
 644                 process_rfc822_addr(ChrPtr(SMTP->from), user, node, name);
 645                 syslog(LOG_DEBUG, "serv_smtp: claimed envelope sender is '%s' == '%s' @ '%s' ('%s')",
 646                         ChrPtr(SMTP->from), user, node, name
 647                 );
 648                 if (CtdlHostAlias(node) != hostalias_nomatch) {
 649                         cprintf("550 You must log in to send mail from %s\r\n", node);
 650                         FlushStrBuf(SMTP->from);
 651                         syslog(LOG_DEBUG, "serv_smtp: rejecting unauthenticated mail from %s", node);
 652                         return;
 653                 }
 654         }
 655
 656         cprintf("250 Sender ok\r\n");
 657 }
 658
 659
 660
 661 /*
 662  * Implements the "RCPT To:" command
 663  */
 664 void smtp_rcpt(long offset, long flags)
 665 {
 666         char message_to_spammer[SIZ];
 667         struct recptypes *valid = NULL;
 668
 669         if (StrLength(SMTP->from) == 0) {
 670                 cprintf("503 Need MAIL before RCPT\r\n");
 671                 return;
 672         }
 673
 674         if (strncasecmp(ChrPtr(SMTP->Cmd) + offset, "To:", 3)) {
 675                 cprintf("501 Syntax error\r\n");
 676                 return;
 677         }
 678
 679         if ( (SMTP->is_msa) && (!CC->logged_in) ) {
 680                 cprintf("550 You must log in to send mail on this port.\r\n");
 681                 FlushStrBuf(SMTP->from);
 682                 return;
 683         }
 684         FlushStrBuf(SMTP->OneRcpt);
 685         StrBufAppendBuf(SMTP->OneRcpt, SMTP->Cmd, offset + 3);
 686         StrBufTrim(SMTP->OneRcpt);
 687         StrBufStripAllBut(SMTP->OneRcpt, '<', '>');
 688
 689         if ( (StrLength(SMTP->OneRcpt) + StrLength(SMTP->recipients)) >= SIZ) {
 690                 cprintf("452 Too many recipients\r\n");
 691                 return;
 692         }
 693
 694         /* RBL check */
 695         if ( (!CC->logged_in)   /* Don't RBL authenticated users */
 696            && (!SMTP->is_lmtp) ) {      /* Don't RBL LMTP clients */
 697                 if (CtdlGetConfigInt("c_rbl_at_greeting") == 0) {       /* Don't RBL again if we already did it */
 698                         if (rbl_check(CC->cs_addr, message_to_spammer)) {
 699                                 if (server_shutting_down)
 700                                         cprintf("421 %s\r\n", message_to_spammer);
 701                                 else
 702                                         cprintf("550 %s\r\n", message_to_spammer);
 703                                 /* no need to free_recipients(valid), it's not allocated yet */
 704                                 return;
 705                         }
 706                 }
 707         }
 708
 709         valid = validate_recipients(
 710                 ChrPtr(SMTP->OneRcpt),
 711                 smtp_get_Recipients(),
 712                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 713         );
 714         if (valid->num_error != 0) {
 715                 cprintf("550 %s\r\n", valid->errormsg);
 716                 free_recipients(valid);
 717                 return;
 718         }
 719
 720         if (valid->num_internet > 0) {
 721                 if (CC->logged_in) {
 722                         if (CtdlCheckInternetMailPermission(&CC->user)==0) {
 723                                 cprintf("551 <%s> - you do not have permission to send Internet mail\r\n",
 724                                         ChrPtr(SMTP->OneRcpt));
 725                                 free_recipients(valid);
 726                                 return;
 727                         }
 728                 }
 729         }
 730
 731         if (valid->num_internet > 0) {
 732                 if ( (SMTP->message_originated_locally == 0)
 733                    && (SMTP->is_lmtp == 0) ) {
 734                         cprintf("551 <%s> - relaying denied\r\n", ChrPtr(SMTP->OneRcpt));
 735                         free_recipients(valid);
 736                         return;
 737                 }
 738         }
 739
 740         cprintf("250 RCPT ok <%s>\r\n", ChrPtr(SMTP->OneRcpt));
 741         if (StrLength(SMTP->recipients) > 0) {
 742                 StrBufAppendBufPlain(SMTP->recipients, HKEY(","), 0);
 743         }
 744         StrBufAppendBuf(SMTP->recipients, SMTP->OneRcpt, 0);
 745         SMTP->number_of_recipients ++;
 746         if (valid != NULL)  {
 747                 free_recipients(valid);
 748         }
 749 }
 750
 751
 752
 753
 754 /*
 755  * Implements the DATA command
 756  */
 757 void smtp_data(long offset, long flags)
 758 {
 759         StrBuf *body;
 760         StrBuf *defbody;
 761         struct CtdlMessage *msg = NULL;
 762         long msgnum = (-1L);
 763         char nowstamp[SIZ];
 764         struct recptypes *valid;
 765         int scan_errors;
 766         int i;
 767
 768         if (StrLength(SMTP->from) == 0) {
 769                 cprintf("503 Need MAIL command first.\r\n");
 770                 return;
 771         }
 772
 773         if (SMTP->number_of_recipients < 1) {
 774                 cprintf("503 Need RCPT command first.\r\n");
 775                 return;
 776         }
 777
 778         cprintf("354 Transmit message now - terminate with '.' by itself\r\n");
 779
 780         datestring(nowstamp, sizeof nowstamp, time(NULL), DATESTRING_RFC822);
 781         defbody = NewStrBufPlain(NULL, SIZ);
 782
 783         if (defbody != NULL) {
 784                 if (SMTP->is_lmtp && (CC->cs_UDSclientUID != -1)) {
 785                         StrBufPrintf(
 786                                 defbody,
 787                                 "Received: from %s (Citadel from userid %ld)\n"
 788                                 "       by %s; %s\n",
 789                                 ChrPtr(SMTP->helo_node),
 790                                 (long int) CC->cs_UDSclientUID,
 791                                 CtdlGetConfigStr("c_fqdn"),
 792                                 nowstamp);
 793                 }
 794                 else {
 795                         StrBufPrintf(
 796                                 defbody,
 797                                 "Received: from %s (%s [%s])\n"
 798                                 "       by %s; %s\n",
 799                                 ChrPtr(SMTP->helo_node),
 800                                 CC->cs_host,
 801                                 CC->cs_addr,
 802                                 CtdlGetConfigStr("c_fqdn"),
 803                                 nowstamp);
 804                 }
 805         }
 806         body = CtdlReadMessageBodyBuf(HKEY("."), CtdlGetConfigLong("c_maxmsglen"), defbody, 1);
 807         FreeStrBuf(&defbody);
 808         if (body == NULL) {
 809                 cprintf("550 Unable to save message: internal error.\r\n");
 810                 return;
 811         }
 812
 813         syslog(LOG_DEBUG, "serv_smtp: converting message...");
 814         msg = convert_internet_message_buf(&body);
 815
 816         /* If the user is locally authenticated, FORCE the From: header to
 817          * show up as the real sender.  Yes, this violates the RFC standard,
 818          * but IT MAKES SENSE.  If you prefer strict RFC adherence over
 819          * common sense, you can disable this in the configuration.
 820          *
 821          * We also set the "message room name" ('O' field) to MAILROOM
 822          * (which is Mail> on most systems) to prevent it from getting set
 823          * to something ugly like "0000058008.Sent Items>" when the message
 824          * is read with a Citadel client.
 825          */
 826         if ( (CC->logged_in) && (CtdlGetConfigInt("c_rfc822_strict_from") != CFG_SMTP_FROM_NOFILTER) ) {
 827                 int validemail = 0;
 828
 829                 if (!CM_IsEmpty(msg, erFc822Addr)       &&
 830                     ((CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_CORRECT) ||
 831                      (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)    )  )
 832                 {
 833                         if (!IsEmptyStr(CC->cs_inet_email))
 834                                 validemail = strcmp(CC->cs_inet_email, msg->cm_fields[erFc822Addr]) == 0;
 835                         if ((!validemail) &&
 836                             (!IsEmptyStr(CC->cs_inet_other_emails)))
 837                         {
 838                                 int num_secondary_emails = 0;
 839                                 int i;
 840                                 num_secondary_emails = num_tokens(CC->cs_inet_other_emails, '|');
 841                                 for (i=0; i < num_secondary_emails && !validemail; ++i) {
 842                                         char buf[256];
 843                                         extract_token(buf, CC->cs_inet_other_emails,i,'|',sizeof CC->cs_inet_other_emails);
 844                                         validemail = strcmp(buf, msg->cm_fields[erFc822Addr]) == 0;
 845                                 }
 846                         }
 847                 }
 848
 849                 if (!validemail && (CtdlGetConfigInt("c_rfc822_strict_from") == CFG_SMTP_FROM_REJECT)) {
 850                         syslog(LOG_ERR, "serv_smtp: invalid sender '%s' - rejecting this message", msg->cm_fields[erFc822Addr]);
 851                         cprintf("550 Invalid sender '%s' - rejecting this message.\r\n", msg->cm_fields[erFc822Addr]);
 852                         return;
 853                 }
 854
 855                 CM_SetField(msg, eOriginalRoom, HKEY(MAILROOM));
 856                 if (SMTP->preferred_sender_name != NULL)
 857                         CM_SetField(msg, eAuthor, SKEY(SMTP->preferred_sender_name));
 858                 else
 859                         CM_SetField(msg, eAuthor, CC->user.fullname, strlen(CC->user.fullname));
 860
 861                 if (!validemail) {
 862                         if (SMTP->preferred_sender_email != NULL) {
 863                                 CM_SetField(msg, erFc822Addr, SKEY(SMTP->preferred_sender_email));
 864                         }
 865                         else {
 866                                 CM_SetField(msg, erFc822Addr, CC->cs_inet_email, strlen(CC->cs_inet_email));
 867                         }
 868                 }
 869         }
 870
 871         /* Set the "envelope from" address */
 872         CM_SetField(msg, eMessagePath, SKEY(SMTP->from));
 873
 874         /* Set the "envelope to" address */
 875         CM_SetField(msg, eenVelopeTo, SKEY(SMTP->recipients));
 876
 877         /* Submit the message into the Citadel system. */
 878         valid = validate_recipients(
 879                 ChrPtr(SMTP->recipients),
 880                 smtp_get_Recipients(),
 881                 (SMTP->is_lmtp)? POST_LMTP: (CC->logged_in)? POST_LOGGED_IN: POST_EXTERNAL
 882         );
 883
 884         /* If there are modules that want to scan this message before final
 885          * submission (such as virus checkers or spam filters), call them now
 886          * and give them an opportunity to reject the message.
 887          */
 888         if (SMTP->is_unfiltered) {
 889                 scan_errors = 0;
 890         }
 891         else {
 892                 scan_errors = PerformMessageHooks(msg, valid, EVT_SMTPSCAN);
 893         }
 894
 895         if (scan_errors > 0) {  /* We don't want this message! */
 896
 897                 if (CM_IsEmpty(msg, eErrorMsg)) {
 898                         CM_SetField(msg, eErrorMsg, HKEY("Message rejected by filter"));
 899                 }
 900
 901                 StrBufPrintf(SMTP->OneRcpt, "550 %s\r\n", msg->cm_fields[eErrorMsg]);
 902         }
 903
 904         else {                  /* Ok, we'll accept this message. */
 905                 msgnum = CtdlSubmitMsg(msg, valid, "");
 906                 if (msgnum > 0L) {
 907                         StrBufPrintf(SMTP->OneRcpt, "250 Message accepted.\r\n");
 908                 }
 909                 else {
 910                         StrBufPrintf(SMTP->OneRcpt, "550 Internal delivery error\r\n");
 911                 }
 912         }
 913
 914         /* For SMTP and ESMTP, just print the result message.  For LMTP, we
 915          * have to print one result message for each recipient.  Since there
 916          * is nothing in Citadel which would cause different recipients to
 917          * have different results, we can get away with just spitting out the
 918          * same message once for each recipient.
 919          */
 920         if (SMTP->is_lmtp) {
 921                 for (i=0; i<SMTP->number_of_recipients; ++i) {
 922                         cputbuf(SMTP->OneRcpt);
 923                 }
 924         }
 925         else {
 926                 cputbuf(SMTP->OneRcpt);
 927         }
 928
 929         /* Write something to the syslog(which may or may not be where the
 930          * rest of the Citadel logs are going; some sysadmins want LOG_MAIL).
 931          */
 932         syslog((LOG_MAIL | LOG_INFO),
 933                     "%ld: from=<%s>, nrcpts=%d, relay=%s [%s], stat=%s",
 934                     msgnum,
 935                     ChrPtr(SMTP->from),
 936                     SMTP->number_of_recipients,
 937                     CC->cs_host,
 938                     CC->cs_addr,
 939                     ChrPtr(SMTP->OneRcpt)
 940         );
 941
 942         /* Clean up */
 943         CM_Free(msg);
 944         free_recipients(valid);
 945         smtp_data_clear(0, 0);  /* clear out the buffers now */
 946 }
 947
 948
 949 /*
 950  * implements the STARTTLS command
 951  */
 952 void smtp_starttls(long offset, long flags)
 953 {
 954         char ok_response[SIZ];
 955         char nosup_response[SIZ];
 956         char error_response[SIZ];
 957
 958         sprintf(ok_response, "220 Begin TLS negotiation now\r\n");
 959         sprintf(nosup_response, "554 TLS not supported here\r\n");
 960         sprintf(error_response, "554 Internal error\r\n");
 961         CtdlModuleStartCryptoMsgs(ok_response, nosup_response, error_response);
 962         smtp_rset(0, 0);
 963 }
 964
 965
 966 /*
 967  * Main command loop for SMTP server sessions.
 968  */
 969 void smtp_command_loop(void) {
 970         static const ConstStr AuthPlainStr = {HKEY("AUTH PLAIN")};
 971         const char *pch, *pchs;
 972         long i;
 973         char CMD[MaxSMTPCmdLen + 1];
 974
 975         if (SMTP == NULL) {
 976                 syslog(LOG_ERR, "serv_smtp: Session SMTP data is null.  WTF?  We will crash now.");
 977                 abort();
 978         }
 979
 980         time(&CC->lastcmd);
 981         if (CtdlClientGetLine(SMTP->Cmd) < 1) {
 982                 syslog(LOG_INFO, "SMTP: client disconnected: ending session.");
 983                 CC->kill_me = KILLME_CLIENT_DISCONNECTED;
 984                 return;
 985         }
 986         syslog(LOG_DEBUG, "serv_smtp: %s", ChrPtr(SMTP->Cmd));
 987
 988         if (SMTP->command_state == smtp_user) {
 989                 if (!strncmp(ChrPtr(SMTP->Cmd), AuthPlainStr.Key, AuthPlainStr.len)) {
 990                         smtp_try_plain(0, 0);
 991                 }
 992                 else {
 993                         smtp_get_user(0);
 994                 }
 995                 return;
 996         }
 997
 998         else if (SMTP->command_state == smtp_password) {
 999                 smtp_get_pass(0, 0);
1000                 return;
1001         }
1002
1003         else if (SMTP->command_state == smtp_plain) {
1004                 smtp_try_plain(0, 0);
1005                 return;
1006         }
1007
1008         pchs = pch = ChrPtr(SMTP->Cmd);
1009         i = 0;
1010         while ((*pch != '\0') &&
1011                (!isblank(*pch)) &&
1012                (pch - pchs <= MaxSMTPCmdLen))
1013         {
1014                 CMD[i] = toupper(*pch);
1015                 pch ++;
1016                 i++;
1017         }
1018         CMD[i] = '\0';
1019
1020         if ((*pch == '\0') ||
1021             (isblank(*pch)))
1022         {
1023                 void *v;
1024
1025                 if (GetHash(SMTPCmds, CMD, i, &v) &&
1026                     (v != NULL))
1027                 {
1028                         smtp_handler_hook *h = (smtp_handler_hook*) v;
1029
1030                         if (isblank(pchs[i]))
1031                                 i++;
1032
1033                         h->h(i, h->Flags);
1034
1035                         return;
1036                 }
1037         }
1038         cprintf("502 I'm afraid I can't do that.\r\n");
1039 }
1040
1041 void smtp_noop(long offest, long Flags)
1042 {
1043         cprintf("250 NOOP\r\n");
1044 }
1045
1046 void smtp_quit(long offest, long Flags)
1047 {
1048         cprintf("221 Goodbye...\r\n");
1049         CC->kill_me = KILLME_CLIENT_LOGGED_OUT;
1050 }
1051
1052 /*****************************************************************************/
1053 /*                      MODULE INITIALIZATION STUFF                          */
1054 /*****************************************************************************/
1055 /*
1056  * This cleanup function blows away the temporary memory used by
1057  * the SMTP server.
1058  */
1059 void smtp_cleanup_function(void)
1060 {
1061         /* Don't do this stuff if this is not an SMTP session! */
1062         if (CC->h_command_function != smtp_command_loop) return;
1063
1064         syslog(LOG_DEBUG, "Performing SMTP cleanup hook");
1065
1066         FreeStrBuf(&SMTP->Cmd);
1067         FreeStrBuf(&SMTP->helo_node);
1068         FreeStrBuf(&SMTP->from);
1069         FreeStrBuf(&SMTP->recipients);
1070         FreeStrBuf(&SMTP->OneRcpt);
1071         FreeStrBuf(&SMTP->preferred_sender_email);
1072         FreeStrBuf(&SMTP->preferred_sender_name);
1073
1074         free(SMTP);
1075 }
1076
1077 const char *CitadelServiceSMTP_MTA="SMTP-MTA";
1078 const char *CitadelServiceSMTPS_MTA="SMTPs-MTA";
1079 const char *CitadelServiceSMTP_MSA="SMTP-MSA";
1080 const char *CitadelServiceSMTP_LMTP="LMTP";
1081 const char *CitadelServiceSMTP_LMTP_UNF="LMTP-UnF";
1082
1083
1084 CTDL_MODULE_INIT(smtp)
1085 {
1086         if (!threading) {
1087                 SMTPCmds = NewHash(1, NULL);
1088
1089                 RegisterSmtpCMD("AUTH", smtp_auth, 0);
1090                 RegisterSmtpCMD("DATA", smtp_data, 0);
1091                 RegisterSmtpCMD("HELO", smtp_hello, HELO);
1092                 RegisterSmtpCMD("EHLO", smtp_hello, EHLO);
1093                 RegisterSmtpCMD("LHLO", smtp_hello, LHLO);
1094                 RegisterSmtpCMD("HELP", smtp_help, 0);
1095                 RegisterSmtpCMD("MAIL", smtp_mail, 0);
1096                 RegisterSmtpCMD("NOOP", smtp_noop, 0);
1097                 RegisterSmtpCMD("QUIT", smtp_quit, 0);
1098                 RegisterSmtpCMD("RCPT", smtp_rcpt, 0);
1099                 RegisterSmtpCMD("RSET", smtp_rset, 1);
1100 #ifdef HAVE_OPENSSL
1101                 RegisterSmtpCMD("STARTTLS", smtp_starttls, 0);
1102 #endif
1103
1104
1105                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtp_port"),        /* SMTP MTA */
1106                                         NULL,
1107                                         smtp_mta_greeting,
1108                                         smtp_command_loop,
1109                                         NULL,
1110                                         CitadelServiceSMTP_MTA);
1111
1112 #ifdef HAVE_OPENSSL
1113                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_smtps_port"),       /* SMTPS MTA */
1114                                         NULL,
1115                                         smtps_greeting,
1116                                         smtp_command_loop,
1117                                         NULL,
1118                                         CitadelServiceSMTPS_MTA);
1119 #endif
1120
1121                 CtdlRegisterServiceHook(CtdlGetConfigInt("c_msa_port"),         /* SMTP MSA */
1122                                         NULL,
1123                                         smtp_msa_greeting,
1124                                         smtp_command_loop,
1125                                         NULL,
1126                                         CitadelServiceSMTP_MSA);
1127
1128                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1129                                         file_lmtp_socket,
1130                                         lmtp_greeting,
1131                                         smtp_command_loop,
1132                                         NULL,
1133                                         CitadelServiceSMTP_LMTP);
1134
1135                 CtdlRegisterServiceHook(0,                      /* local LMTP */
1136                                         file_lmtp_unfiltered_socket,
1137                                         lmtp_unfiltered_greeting,
1138                                         smtp_command_loop,
1139                                         NULL,
1140                                         CitadelServiceSMTP_LMTP_UNF);
1141
1142                 CtdlRegisterSessionHook(smtp_cleanup_function, EVT_STOP, PRIO_STOP + 250);
1143         }
1144
1145         /* return our module name for the log */
1146         return "smtp";
1147 }