1 /* $OpenBSD: ftp-proxy.c,v 1.35 2016/09/15 16:16:03 jca Exp $ */ 2 3 /* 4 * Copyright (c) 2004, 2005 Camiel Dobbelaar, <cd@sentia.nl> 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19 #include <sys/queue.h> 20 #include <sys/types.h> 21 #include <sys/time.h> 22 #include <sys/resource.h> 23 #include <sys/socket.h> 24 25 #include <netinet/in.h> 26 #include <arpa/inet.h> 27 #include <net/if.h> 28 #include <net/pfvar.h> 29 30 #include <err.h> 31 #include <errno.h> 32 #include <event.h> 33 #include <fcntl.h> 34 #include <netdb.h> 35 #include <paths.h> 36 #include <pwd.h> 37 #include <signal.h> 38 #include <stdarg.h> 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <string.h> 42 #include <syslog.h> 43 #include <unistd.h> 44 #include <vis.h> 45 46 #include "filter.h" 47 48 #define CONNECT_TIMEOUT 30 49 #define MIN_PORT 1024 50 #define MAX_LINE 500 51 #define MAX_LOGLINE 300 52 #define NTOP_BUFS 3 53 #define TCP_BACKLOG 10 54 55 #define CHROOT_DIR "/var/empty" 56 #define NOPRIV_USER "_ftp_proxy" 57 58 /* pfctl standard NAT range. */ 59 #define PF_NAT_PROXY_PORT_LOW 50001 60 #define PF_NAT_PROXY_PORT_HIGH 65535 61 62 #define sstosa(ss) ((struct sockaddr *)(ss)) 63 64 enum { CMD_NONE = 0, CMD_PORT, CMD_EPRT, CMD_PASV, CMD_EPSV }; 65 66 struct session { 67 u_int32_t id; 68 struct sockaddr_storage client_ss; 69 struct sockaddr_storage proxy_ss; 70 struct sockaddr_storage server_ss; 71 struct sockaddr_storage orig_server_ss; 72 struct bufferevent *client_bufev; 73 struct bufferevent *server_bufev; 74 int client_fd; 75 int server_fd; 76 char cbuf[MAX_LINE]; 77 size_t cbuf_valid; 78 char sbuf[MAX_LINE]; 79 size_t sbuf_valid; 80 int cmd; 81 int client_rd; 82 u_int16_t port; 83 u_int16_t proxy_port; 84 LIST_ENTRY(session) entry; 85 }; 86 87 LIST_HEAD(, session) sessions = LIST_HEAD_INITIALIZER(sessions); 88 89 void client_error(struct bufferevent *, short, void *); 90 int client_parse(struct session *s); 91 int client_parse_anon(struct session *s); 92 int client_parse_cmd(struct session *s); 93 void client_read(struct bufferevent *, void *); 94 int drop_privs(void); 95 void end_session(struct session *); 96 void exit_daemon(void); 97 int get_line(char *, size_t *); 98 void handle_connection(const int, short, void *); 99 void handle_signal(int, short, void *); 100 struct session * init_session(void); 101 void logmsg(int, const char *, ...); 102 u_int16_t parse_port(int); 103 u_int16_t pick_proxy_port(void); 104 void proxy_reply(int, struct sockaddr *, u_int16_t); 105 int rdaemon(int); 106 void server_error(struct bufferevent *, short, void *); 107 int server_parse(struct session *s); 108 int allow_data_connection(struct session *s); 109 void server_read(struct bufferevent *, void *); 110 const char *sock_ntop(struct sockaddr *); 111 void usage(void); 112 113 char linebuf[MAX_LINE + 1]; 114 size_t linelen; 115 116 char ntop_buf[NTOP_BUFS][INET6_ADDRSTRLEN]; 117 118 struct event listen_ev, pause_accept_ev; 119 struct sockaddr_storage fixed_server_ss, fixed_proxy_ss; 120 char *fixed_server, *fixed_server_port, *fixed_proxy, *listen_ip, *listen_port, 121 *qname, *tagname; 122 int anonymous_only, daemonize, id_count, ipv6_mode, loglevel, max_sessions, 123 rfc_mode, session_count, timeout, verbose; 124 extern char *__progname; 125 126 void 127 client_error(struct bufferevent *bufev, short what, void *arg) 128 { 129 struct session *s = arg; 130 131 if (what & EVBUFFER_EOF) 132 logmsg(LOG_INFO, "#%d client close", s->id); 133 else if (what == (EVBUFFER_ERROR | EVBUFFER_READ)) 134 logmsg(LOG_ERR, "#%d client reset connection", s->id); 135 else if (what & EVBUFFER_TIMEOUT) 136 logmsg(LOG_ERR, "#%d client timeout", s->id); 137 else if (what & EVBUFFER_WRITE) 138 logmsg(LOG_ERR, "#%d client write error: %d", s->id, what); 139 else 140 logmsg(LOG_ERR, "#%d abnormal client error: %d", s->id, what); 141 142 end_session(s); 143 } 144 145 int 146 client_parse(struct session *s) 147 { 148 /* Reset any previous command. */ 149 s->cmd = CMD_NONE; 150 s->port = 0; 151 152 /* Commands we are looking for are at least 4 chars long. */ 153 if (linelen < 4) 154 return (1); 155 156 if (linebuf[0] == 'P' || linebuf[0] == 'p' || 157 linebuf[0] == 'E' || linebuf[0] == 'e') { 158 if (!client_parse_cmd(s)) 159 return (0); 160 161 /* 162 * Allow active mode connections immediately, instead of 163 * waiting for a positive reply from the server. Some 164 * rare servers/proxies try to probe or setup the data 165 * connection before an actual transfer request. 166 */ 167 if (s->cmd == CMD_PORT || s->cmd == CMD_EPRT) 168 return (allow_data_connection(s)); 169 } 170 171 if (anonymous_only && (linebuf[0] == 'U' || linebuf[0] == 'u')) 172 return (client_parse_anon(s)); 173 174 return (1); 175 } 176 177 int 178 client_parse_anon(struct session *s) 179 { 180 if (strcasecmp("USER ftp\r\n", linebuf) != 0 && 181 strcasecmp("USER anonymous\r\n", linebuf) != 0) { 182 snprintf(linebuf, sizeof linebuf, 183 "500 Only anonymous FTP allowed\r\n"); 184 logmsg(LOG_DEBUG, "#%d proxy: %s", s->id, linebuf); 185 186 /* Talk back to the client ourself. */ 187 linelen = strlen(linebuf); 188 bufferevent_write(s->client_bufev, linebuf, linelen); 189 190 /* Clear buffer so it's not sent to the server. */ 191 linebuf[0] = '\0'; 192 linelen = 0; 193 } 194 195 return (1); 196 } 197 198 int 199 client_parse_cmd(struct session *s) 200 { 201 if (strncasecmp("PASV", linebuf, 4) == 0) 202 s->cmd = CMD_PASV; 203 else if (strncasecmp("PORT ", linebuf, 5) == 0) 204 s->cmd = CMD_PORT; 205 else if (strncasecmp("EPSV", linebuf, 4) == 0) 206 s->cmd = CMD_EPSV; 207 else if (strncasecmp("EPRT ", linebuf, 5) == 0) 208 s->cmd = CMD_EPRT; 209 else 210 return (1); 211 212 if (ipv6_mode && (s->cmd == CMD_PASV || s->cmd == CMD_PORT)) { 213 logmsg(LOG_CRIT, "PASV and PORT not allowed with IPv6"); 214 return (0); 215 } 216 217 if (s->cmd == CMD_PORT || s->cmd == CMD_EPRT) { 218 s->port = parse_port(s->cmd); 219 if (s->port < MIN_PORT) { 220 logmsg(LOG_CRIT, "#%d bad port in '%s'", s->id, 221 linebuf); 222 return (0); 223 } 224 s->proxy_port = pick_proxy_port(); 225 proxy_reply(s->cmd, sstosa(&s->proxy_ss), s->proxy_port); 226 logmsg(LOG_DEBUG, "#%d proxy: %s", s->id, linebuf); 227 } 228 229 return (1); 230 } 231 232 void 233 client_read(struct bufferevent *bufev, void *arg) 234 { 235 struct session *s = arg; 236 size_t buf_avail, read; 237 int n; 238 239 do { 240 buf_avail = sizeof s->cbuf - s->cbuf_valid; 241 read = bufferevent_read(bufev, s->cbuf + s->cbuf_valid, 242 buf_avail); 243 s->cbuf_valid += read; 244 245 while ((n = get_line(s->cbuf, &s->cbuf_valid)) > 0) { 246 logmsg(LOG_DEBUG, "#%d client: %s", s->id, linebuf); 247 if (!client_parse(s)) { 248 end_session(s); 249 return; 250 } 251 bufferevent_write(s->server_bufev, linebuf, linelen); 252 } 253 254 if (n == -1) { 255 logmsg(LOG_ERR, "#%d client command too long or not" 256 " clean", s->id); 257 end_session(s); 258 return; 259 } 260 } while (read == buf_avail); 261 } 262 263 int 264 drop_privs(void) 265 { 266 struct passwd *pw; 267 268 pw = getpwnam(NOPRIV_USER); 269 if (pw == NULL) 270 return (0); 271 272 tzset(); 273 if (chroot(CHROOT_DIR) != 0 || chdir("/") != 0 || 274 setgroups(1, &pw->pw_gid) != 0 || 275 setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0 || 276 setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) 277 return (0); 278 279 return (1); 280 } 281 282 void 283 end_session(struct session *s) 284 { 285 int err; 286 287 logmsg(LOG_INFO, "#%d ending session", s->id); 288 289 /* Flush output buffers. */ 290 if (s->client_bufev && s->client_fd != -1) 291 evbuffer_write(s->client_bufev->output, s->client_fd); 292 if (s->server_bufev && s->server_fd != -1) 293 evbuffer_write(s->server_bufev->output, s->server_fd); 294 295 if (s->client_fd != -1) 296 close(s->client_fd); 297 if (s->server_fd != -1) 298 close(s->server_fd); 299 300 if (s->client_bufev) 301 bufferevent_free(s->client_bufev); 302 if (s->server_bufev) 303 bufferevent_free(s->server_bufev); 304 305 /* Remove rulesets by committing empty ones. */ 306 err = 0; 307 if (prepare_commit(s->id) == -1) 308 err = errno; 309 else if (do_commit() == -1) { 310 err = errno; 311 do_rollback(); 312 } 313 if (err) 314 logmsg(LOG_ERR, "#%d pf rule removal failed: %s", s->id, 315 strerror(err)); 316 317 LIST_REMOVE(s, entry); 318 free(s); 319 session_count--; 320 } 321 322 void 323 exit_daemon(void) 324 { 325 struct session *s, *next; 326 327 for (s = LIST_FIRST(&sessions); s != NULL; s = next) { 328 next = LIST_NEXT(s, entry); 329 end_session(s); 330 } 331 332 if (daemonize) 333 closelog(); 334 335 exit(0); 336 } 337 338 int 339 get_line(char *buf, size_t *valid) 340 { 341 size_t i; 342 343 if (*valid > MAX_LINE) 344 return (-1); 345 346 /* Copy to linebuf while searching for a newline. */ 347 for (i = 0; i < *valid; i++) { 348 linebuf[i] = buf[i]; 349 if (buf[i] == '\0') 350 return (-1); 351 if (buf[i] == '\n') 352 break; 353 } 354 355 if (i == *valid) { 356 /* No newline found. */ 357 linebuf[0] = '\0'; 358 linelen = 0; 359 if (i < MAX_LINE) 360 return (0); 361 return (-1); 362 } 363 364 linelen = i + 1; 365 linebuf[linelen] = '\0'; 366 *valid -= linelen; 367 368 /* Move leftovers to the start. */ 369 if (*valid != 0) 370 bcopy(buf + linelen, buf, *valid); 371 372 return ((int)linelen); 373 } 374 375 void 376 handle_connection(const int listen_fd, short event, void *arg) 377 { 378 struct sockaddr_storage tmp_ss; 379 struct sockaddr *client_sa, *server_sa, *fixed_server_sa; 380 struct sockaddr *proxy_to_server_sa; 381 struct session *s; 382 socklen_t len; 383 int client_fd, fc, on; 384 385 event_add(&listen_ev, NULL); 386 387 if ((event & EV_TIMEOUT)) 388 /* accept() is no longer paused. */ 389 return; 390 391 /* 392 * We _must_ accept the connection, otherwise libevent will keep 393 * coming back, and we will chew up all CPU. 394 */ 395 client_sa = sstosa(&tmp_ss); 396 len = sizeof(struct sockaddr_storage); 397 if ((client_fd = accept(listen_fd, client_sa, &len)) < 0) { 398 logmsg(LOG_CRIT, "accept() failed: %s", strerror(errno)); 399 400 /* 401 * Pause accept if we are out of file descriptors, or 402 * libevent will haunt us here too. 403 */ 404 if (errno == ENFILE || errno == EMFILE) { 405 struct timeval pause = { 1, 0 }; 406 407 event_del(&listen_ev); 408 evtimer_add(&pause_accept_ev, &pause); 409 } else if (errno != EWOULDBLOCK && errno != EINTR && 410 errno != ECONNABORTED) 411 logmsg(LOG_CRIT, "accept() failed: %s", strerror(errno)); 412 return; 413 } 414 415 /* Refuse connection if the maximum is reached. */ 416 if (session_count >= max_sessions) { 417 logmsg(LOG_ERR, "client limit (%d) reached, refusing " 418 "connection from %s", max_sessions, sock_ntop(client_sa)); 419 close(client_fd); 420 return; 421 } 422 423 /* Allocate session and copy back the info from the accept(). */ 424 s = init_session(); 425 if (s == NULL) { 426 logmsg(LOG_CRIT, "init_session failed"); 427 close(client_fd); 428 return; 429 } 430 s->client_fd = client_fd; 431 memcpy(sstosa(&s->client_ss), client_sa, client_sa->sa_len); 432 433 /* Cast it once, and be done with it. */ 434 client_sa = sstosa(&s->client_ss); 435 server_sa = sstosa(&s->server_ss); 436 proxy_to_server_sa = sstosa(&s->proxy_ss); 437 fixed_server_sa = sstosa(&fixed_server_ss); 438 439 /* Log id/client early to ease debugging. */ 440 logmsg(LOG_DEBUG, "#%d accepted connection from %s", s->id, 441 sock_ntop(client_sa)); 442 443 /* 444 * Find out the real server and port that the client wanted. 445 */ 446 len = sizeof(struct sockaddr_storage); 447 if (getsockname(s->client_fd, server_sa, &len) < 0) { 448 logmsg(LOG_CRIT, "#%d getsockname failed: %s", s->id, 449 strerror(errno)); 450 goto fail; 451 } 452 len = sizeof(s->client_rd); 453 if (getsockopt(s->client_fd, SOL_SOCKET, SO_RTABLE, &s->client_rd, 454 &len) && errno != ENOPROTOOPT) { 455 logmsg(LOG_CRIT, "#%d getsockopt failed: %s", s->id, 456 strerror(errno)); 457 goto fail; 458 } 459 if (fixed_server) { 460 memcpy(sstosa(&s->orig_server_ss), server_sa, 461 server_sa->sa_len); 462 memcpy(server_sa, fixed_server_sa, fixed_server_sa->sa_len); 463 } 464 465 /* XXX: check we are not connecting to ourself. */ 466 467 /* 468 * Setup socket and connect to server. 469 */ 470 if ((s->server_fd = socket(server_sa->sa_family, SOCK_STREAM, 471 IPPROTO_TCP)) < 0) { 472 logmsg(LOG_CRIT, "#%d server socket failed: %s", s->id, 473 strerror(errno)); 474 goto fail; 475 } 476 if (fixed_proxy && bind(s->server_fd, sstosa(&fixed_proxy_ss), 477 fixed_proxy_ss.ss_len) != 0) { 478 logmsg(LOG_CRIT, "#%d cannot bind fixed proxy address: %s", 479 s->id, strerror(errno)); 480 goto fail; 481 } 482 483 /* Use non-blocking connect(), see CONNECT_TIMEOUT below. */ 484 if ((fc = fcntl(s->server_fd, F_GETFL)) == -1 || 485 fcntl(s->server_fd, F_SETFL, fc | O_NONBLOCK) == -1) { 486 logmsg(LOG_CRIT, "#%d cannot mark socket non-blocking: %s", 487 s->id, strerror(errno)); 488 goto fail; 489 } 490 if (connect(s->server_fd, server_sa, server_sa->sa_len) < 0 && 491 errno != EINPROGRESS) { 492 logmsg(LOG_CRIT, "#%d proxy cannot connect to server %s: %s", 493 s->id, sock_ntop(server_sa), strerror(errno)); 494 goto fail; 495 } 496 497 len = sizeof(struct sockaddr_storage); 498 if ((getsockname(s->server_fd, proxy_to_server_sa, &len)) < 0) { 499 logmsg(LOG_CRIT, "#%d getsockname failed: %s", s->id, 500 strerror(errno)); 501 goto fail; 502 } 503 504 logmsg(LOG_INFO, "#%d FTP session %d/%d started: client %s to server " 505 "%s via proxy %s", s->id, session_count, max_sessions, 506 sock_ntop(client_sa), sock_ntop(server_sa), 507 sock_ntop(proxy_to_server_sa)); 508 509 /* Keepalive is nice, but don't care if it fails. */ 510 on = 1; 511 setsockopt(s->client_fd, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 512 sizeof on); 513 setsockopt(s->server_fd, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 514 sizeof on); 515 516 /* 517 * Setup buffered events. 518 */ 519 s->client_bufev = bufferevent_new(s->client_fd, &client_read, NULL, 520 &client_error, s); 521 if (s->client_bufev == NULL) { 522 logmsg(LOG_CRIT, "#%d bufferevent_new client failed", s->id); 523 goto fail; 524 } 525 bufferevent_settimeout(s->client_bufev, timeout, 0); 526 bufferevent_enable(s->client_bufev, EV_READ | EV_TIMEOUT); 527 528 s->server_bufev = bufferevent_new(s->server_fd, &server_read, NULL, 529 &server_error, s); 530 if (s->server_bufev == NULL) { 531 logmsg(LOG_CRIT, "#%d bufferevent_new server failed", s->id); 532 goto fail; 533 } 534 bufferevent_settimeout(s->server_bufev, CONNECT_TIMEOUT, 0); 535 bufferevent_enable(s->server_bufev, EV_READ | EV_TIMEOUT); 536 537 return; 538 539 fail: 540 end_session(s); 541 } 542 543 void 544 handle_signal(int sig, short event, void *arg) 545 { 546 /* 547 * Signal handler rules don't apply, libevent decouples for us. 548 */ 549 550 logmsg(LOG_ERR, "exiting on signal %d", sig); 551 552 exit_daemon(); 553 } 554 555 556 struct session * 557 init_session(void) 558 { 559 struct session *s; 560 561 s = calloc(1, sizeof(struct session)); 562 if (s == NULL) 563 return (NULL); 564 565 s->id = id_count++; 566 s->client_fd = -1; 567 s->server_fd = -1; 568 s->cbuf[0] = '\0'; 569 s->cbuf_valid = 0; 570 s->sbuf[0] = '\0'; 571 s->sbuf_valid = 0; 572 s->client_bufev = NULL; 573 s->server_bufev = NULL; 574 s->cmd = CMD_NONE; 575 s->port = 0; 576 577 LIST_INSERT_HEAD(&sessions, s, entry); 578 session_count++; 579 580 return (s); 581 } 582 583 void 584 logmsg(int pri, const char *message, ...) 585 { 586 va_list ap; 587 588 if (pri > loglevel) 589 return; 590 591 va_start(ap, message); 592 593 if (daemonize) 594 /* syslog does its own vissing. */ 595 vsyslog(pri, message, ap); 596 else { 597 char buf[MAX_LOGLINE]; 598 char visbuf[2 * MAX_LOGLINE]; 599 600 /* We don't care about truncation. */ 601 vsnprintf(buf, sizeof buf, message, ap); 602 strnvis(visbuf, buf, sizeof visbuf, VIS_CSTYLE | VIS_NL); 603 fprintf(stderr, "%s\n", visbuf); 604 } 605 606 va_end(ap); 607 } 608 609 int 610 main(int argc, char *argv[]) 611 { 612 struct rlimit rlp; 613 struct addrinfo hints, *res; 614 struct event ev_sighup, ev_sigint, ev_sigterm; 615 int ch, devnull, error, listenfd, on; 616 const char *errstr; 617 618 /* Defaults. */ 619 anonymous_only = 0; 620 daemonize = 1; 621 fixed_proxy = NULL; 622 fixed_server = NULL; 623 fixed_server_port = "21"; 624 ipv6_mode = 0; 625 listen_ip = NULL; 626 listen_port = "8021"; 627 loglevel = LOG_NOTICE; 628 max_sessions = 100; 629 qname = NULL; 630 rfc_mode = 0; 631 tagname = NULL; 632 timeout = 24 * 3600; 633 verbose = 0; 634 635 /* Other initialization. */ 636 id_count = 1; 637 session_count = 0; 638 639 while ((ch = getopt(argc, argv, "6Aa:b:D:dm:P:p:q:R:rT:t:v")) != -1) { 640 switch (ch) { 641 case '6': 642 ipv6_mode = 1; 643 break; 644 case 'A': 645 anonymous_only = 1; 646 break; 647 case 'a': 648 fixed_proxy = optarg; 649 break; 650 case 'b': 651 listen_ip = optarg; 652 break; 653 case 'D': 654 loglevel = strtonum(optarg, LOG_EMERG, LOG_DEBUG, 655 &errstr); 656 if (errstr) 657 errx(1, "loglevel %s", errstr); 658 break; 659 case 'd': 660 daemonize = 0; 661 break; 662 case 'm': 663 max_sessions = strtonum(optarg, 1, 500, &errstr); 664 if (errstr) 665 errx(1, "max sessions %s", errstr); 666 break; 667 case 'P': 668 fixed_server_port = optarg; 669 break; 670 case 'p': 671 listen_port = optarg; 672 break; 673 case 'q': 674 if (strlen(optarg) >= PF_QNAME_SIZE) 675 errx(1, "queuename too long"); 676 qname = optarg; 677 break; 678 case 'R': 679 fixed_server = optarg; 680 break; 681 case 'r': 682 rfc_mode = 1; 683 break; 684 case 'T': 685 if (strlen(optarg) >= PF_TAG_NAME_SIZE) 686 errx(1, "tagname too long"); 687 tagname = optarg; 688 break; 689 case 't': 690 timeout = strtonum(optarg, 0, 86400, &errstr); 691 if (errstr) 692 errx(1, "timeout %s", errstr); 693 break; 694 case 'v': 695 verbose++; 696 if (verbose > 2) 697 usage(); 698 break; 699 default: 700 usage(); 701 } 702 } 703 704 if (listen_ip == NULL) 705 listen_ip = ipv6_mode ? "::1" : "127.0.0.1"; 706 707 /* Check for root to save the user from cryptic failure messages. */ 708 if (getuid() != 0) 709 errx(1, "needs to start as root"); 710 711 if (getpwnam(NOPRIV_USER) == NULL) 712 errx(1, "unknown user %s", NOPRIV_USER); 713 714 /* Raise max. open files limit to satisfy max. sessions. */ 715 rlp.rlim_cur = rlp.rlim_max = (2 * max_sessions) + 10; 716 if (setrlimit(RLIMIT_NOFILE, &rlp) == -1) 717 err(1, "setrlimit"); 718 719 if (fixed_proxy) { 720 memset(&hints, 0, sizeof hints); 721 hints.ai_flags = AI_NUMERICHOST; 722 hints.ai_family = ipv6_mode ? AF_INET6 : AF_INET; 723 hints.ai_socktype = SOCK_STREAM; 724 error = getaddrinfo(fixed_proxy, NULL, &hints, &res); 725 if (error) 726 errx(1, "getaddrinfo fixed proxy address failed: %s", 727 gai_strerror(error)); 728 memcpy(&fixed_proxy_ss, res->ai_addr, res->ai_addrlen); 729 logmsg(LOG_INFO, "using %s to connect to servers", 730 sock_ntop(sstosa(&fixed_proxy_ss))); 731 freeaddrinfo(res); 732 } 733 734 if (fixed_server) { 735 memset(&hints, 0, sizeof hints); 736 hints.ai_family = ipv6_mode ? AF_INET6 : AF_INET; 737 hints.ai_socktype = SOCK_STREAM; 738 error = getaddrinfo(fixed_server, fixed_server_port, &hints, 739 &res); 740 if (error) 741 errx(1, "getaddrinfo fixed server address failed: %s", 742 gai_strerror(error)); 743 memcpy(&fixed_server_ss, res->ai_addr, res->ai_addrlen); 744 logmsg(LOG_INFO, "using fixed server %s", 745 sock_ntop(sstosa(&fixed_server_ss))); 746 freeaddrinfo(res); 747 } 748 749 /* Setup listener. */ 750 memset(&hints, 0, sizeof hints); 751 hints.ai_flags = AI_NUMERICHOST | AI_PASSIVE; 752 hints.ai_family = ipv6_mode ? AF_INET6 : AF_INET; 753 hints.ai_socktype = SOCK_STREAM; 754 error = getaddrinfo(listen_ip, listen_port, &hints, &res); 755 if (error) 756 errx(1, "getaddrinfo listen address failed: %s", 757 gai_strerror(error)); 758 if ((listenfd = socket(res->ai_family, SOCK_STREAM, IPPROTO_TCP)) == -1) 759 errx(1, "socket failed"); 760 on = 1; 761 if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, (void *)&on, 762 sizeof on) != 0) 763 err(1, "setsockopt failed"); 764 if (bind(listenfd, (struct sockaddr *)res->ai_addr, 765 (socklen_t)res->ai_addrlen) != 0) 766 err(1, "bind failed"); 767 if (listen(listenfd, TCP_BACKLOG) != 0) 768 err(1, "listen failed"); 769 freeaddrinfo(res); 770 771 /* Initialize pf. */ 772 init_filter(qname, tagname, verbose); 773 774 if (daemonize) { 775 devnull = open(_PATH_DEVNULL, O_RDWR, 0); 776 if (devnull == -1) 777 err(1, "open(%s)", _PATH_DEVNULL); 778 } 779 780 if (!drop_privs()) 781 err(1, "cannot drop privileges"); 782 783 if (daemonize) { 784 if (rdaemon(devnull) == -1) 785 err(1, "cannot daemonize"); 786 openlog(__progname, LOG_PID | LOG_NDELAY, LOG_DAEMON); 787 } 788 789 /* Use logmsg for output from here on. */ 790 791 event_init(); 792 793 /* Setup signal handler. */ 794 signal(SIGPIPE, SIG_IGN); 795 signal_set(&ev_sighup, SIGHUP, handle_signal, NULL); 796 signal_set(&ev_sigint, SIGINT, handle_signal, NULL); 797 signal_set(&ev_sigterm, SIGTERM, handle_signal, NULL); 798 signal_add(&ev_sighup, NULL); 799 signal_add(&ev_sigint, NULL); 800 signal_add(&ev_sigterm, NULL); 801 802 event_set(&listen_ev, listenfd, EV_READ, handle_connection, NULL); 803 event_add(&listen_ev, NULL); 804 evtimer_set(&pause_accept_ev, handle_connection, NULL); 805 806 logmsg(LOG_NOTICE, "listening on %s port %s", listen_ip, listen_port); 807 808 /* Vroom, vroom. */ 809 event_dispatch(); 810 811 logmsg(LOG_ERR, "event_dispatch error: %s", strerror(errno)); 812 exit_daemon(); 813 814 /* NOTREACHED */ 815 return (1); 816 } 817 818 u_int16_t 819 parse_port(int mode) 820 { 821 unsigned int port, v[6]; 822 int n; 823 char *p; 824 825 /* Find the last space or left-parenthesis. */ 826 for (p = linebuf + linelen; p > linebuf; p--) 827 if (*p == ' ' || *p == '(') 828 break; 829 if (p == linebuf) 830 return (0); 831 832 switch (mode) { 833 case CMD_PORT: 834 n = sscanf(p, " %u,%u,%u,%u,%u,%u", &v[0], &v[1], &v[2], 835 &v[3], &v[4], &v[5]); 836 if (n == 6 && v[0] < 256 && v[1] < 256 && v[2] < 256 && 837 v[3] < 256 && v[4] < 256 && v[5] < 256) 838 return ((v[4] << 8) | v[5]); 839 break; 840 case CMD_PASV: 841 n = sscanf(p, "(%u,%u,%u,%u,%u,%u)", &v[0], &v[1], &v[2], 842 &v[3], &v[4], &v[5]); 843 if (n == 6 && v[0] < 256 && v[1] < 256 && v[2] < 256 && 844 v[3] < 256 && v[4] < 256 && v[5] < 256) 845 return ((v[4] << 8) | v[5]); 846 break; 847 case CMD_EPSV: 848 n = sscanf(p, "(|||%u|)", &port); 849 if (n == 1 && port < 65536) 850 return (port); 851 break; 852 case CMD_EPRT: 853 n = sscanf(p, " |1|%u.%u.%u.%u|%u|", &v[0], &v[1], &v[2], 854 &v[3], &port); 855 if (n == 5 && v[0] < 256 && v[1] < 256 && v[2] < 256 && 856 v[3] < 256 && port < 65536) 857 return (port); 858 n = sscanf(p, " |2|%*[a-fA-F0-9:]|%u|", &port); 859 if (n == 1 && port < 65536) 860 return (port); 861 break; 862 default: 863 return (0); 864 } 865 866 return (0); 867 } 868 869 u_int16_t 870 pick_proxy_port(void) 871 { 872 /* Random should be good enough for avoiding port collisions. */ 873 return (IPPORT_HIFIRSTAUTO + 874 arc4random_uniform(IPPORT_HILASTAUTO - IPPORT_HIFIRSTAUTO)); 875 } 876 877 void 878 proxy_reply(int cmd, struct sockaddr *sa, u_int16_t port) 879 { 880 int i, r; 881 882 switch (cmd) { 883 case CMD_PORT: 884 r = snprintf(linebuf, sizeof linebuf, 885 "PORT %s,%u,%u\r\n", sock_ntop(sa), port / 256, 886 port % 256); 887 break; 888 case CMD_PASV: 889 r = snprintf(linebuf, sizeof linebuf, 890 "227 Entering Passive Mode (%s,%u,%u)\r\n", sock_ntop(sa), 891 port / 256, port % 256); 892 break; 893 case CMD_EPRT: 894 if (sa->sa_family == AF_INET) 895 r = snprintf(linebuf, sizeof linebuf, 896 "EPRT |1|%s|%u|\r\n", sock_ntop(sa), port); 897 else if (sa->sa_family == AF_INET6) 898 r = snprintf(linebuf, sizeof linebuf, 899 "EPRT |2|%s|%u|\r\n", sock_ntop(sa), port); 900 break; 901 case CMD_EPSV: 902 r = snprintf(linebuf, sizeof linebuf, 903 "229 Entering Extended Passive Mode (|||%u|)\r\n", port); 904 break; 905 } 906 907 if (r < 0 || r >= sizeof linebuf) { 908 logmsg(LOG_ERR, "proxy_reply failed: %d", r); 909 linebuf[0] = '\0'; 910 linelen = 0; 911 return; 912 } 913 linelen = (size_t)r; 914 915 if (cmd == CMD_PORT || cmd == CMD_PASV) { 916 /* Replace dots in IP address with commas. */ 917 for (i = 0; i < linelen; i++) 918 if (linebuf[i] == '.') 919 linebuf[i] = ','; 920 } 921 } 922 923 void 924 server_error(struct bufferevent *bufev, short what, void *arg) 925 { 926 struct session *s = arg; 927 928 if (what & EVBUFFER_EOF) 929 logmsg(LOG_INFO, "#%d server close", s->id); 930 else if (what == (EVBUFFER_ERROR | EVBUFFER_READ)) 931 logmsg(LOG_ERR, "#%d server refused connection", s->id); 932 else if (what & EVBUFFER_WRITE) 933 logmsg(LOG_ERR, "#%d server write error: %d", s->id, what); 934 else if (what & EVBUFFER_TIMEOUT) 935 logmsg(LOG_NOTICE, "#%d server timeout", s->id); 936 else 937 logmsg(LOG_ERR, "#%d abnormal server error: %d", s->id, what); 938 939 end_session(s); 940 } 941 942 int 943 server_parse(struct session *s) 944 { 945 if (s->cmd == CMD_NONE || linelen < 4 || linebuf[0] != '2') 946 goto out; 947 948 if ((s->cmd == CMD_PASV && strncmp("227 ", linebuf, 4) == 0) || 949 (s->cmd == CMD_EPSV && strncmp("229 ", linebuf, 4) == 0)) 950 return (allow_data_connection(s)); 951 952 out: 953 s->cmd = CMD_NONE; 954 s->port = 0; 955 956 return (1); 957 } 958 959 int 960 allow_data_connection(struct session *s) 961 { 962 struct sockaddr *client_sa, *orig_sa, *proxy_sa, *server_sa; 963 int prepared = 0; 964 965 /* 966 * The pf rules below do quite some NAT rewriting, to keep up 967 * appearances. Points to keep in mind: 968 * 1) The client must think it's talking to the real server, 969 * for both control and data connections. Transparently. 970 * 2) The server must think that the proxy is the client. 971 * 3) Source and destination ports are rewritten to minimize 972 * port collisions, to aid security (some systems pick weak 973 * ports) or to satisfy RFC requirements (source port 20). 974 */ 975 976 /* Cast this once, to make code below it more readable. */ 977 client_sa = sstosa(&s->client_ss); 978 server_sa = sstosa(&s->server_ss); 979 proxy_sa = sstosa(&s->proxy_ss); 980 if (fixed_server) 981 /* Fixed server: data connections must appear to come 982 from / go to the original server, not the fixed one. */ 983 orig_sa = sstosa(&s->orig_server_ss); 984 else 985 /* Server not fixed: orig_server == server. */ 986 orig_sa = sstosa(&s->server_ss); 987 988 /* Passive modes. */ 989 if (s->cmd == CMD_PASV || s->cmd == CMD_EPSV) { 990 s->port = parse_port(s->cmd); 991 if (s->port < MIN_PORT) { 992 logmsg(LOG_CRIT, "#%d bad port in '%s'", s->id, 993 linebuf); 994 return (0); 995 } 996 s->proxy_port = pick_proxy_port(); 997 logmsg(LOG_INFO, "#%d passive: client to server port %d" 998 " via port %d", s->id, s->port, s->proxy_port); 999 1000 if (prepare_commit(s->id) == -1) 1001 goto fail; 1002 prepared = 1; 1003 1004 proxy_reply(s->cmd, orig_sa, s->proxy_port); 1005 logmsg(LOG_DEBUG, "#%d proxy: %s", s->id, linebuf); 1006 1007 /* pass in from $client to $orig_server port $proxy_port 1008 rdr-to $server port $port */ 1009 if (add_rdr(s->id, client_sa, s->client_rd, orig_sa, 1010 s->proxy_port, server_sa, s->port, getrtable()) == -1) 1011 goto fail; 1012 1013 /* pass out from $client to $server port $port nat-to $proxy */ 1014 if (add_nat(s->id, client_sa, getrtable(), server_sa, 1015 s->port, proxy_sa, PF_NAT_PROXY_PORT_LOW, 1016 PF_NAT_PROXY_PORT_HIGH) == -1) 1017 goto fail; 1018 } 1019 1020 /* Active modes. */ 1021 if (s->cmd == CMD_PORT || s->cmd == CMD_EPRT) { 1022 logmsg(LOG_INFO, "#%d active: server to client port %d" 1023 " via port %d", s->id, s->port, s->proxy_port); 1024 1025 if (prepare_commit(s->id) == -1) 1026 goto fail; 1027 prepared = 1; 1028 1029 /* pass in from $server to $proxy port $proxy_port 1030 rdr-to $client port $port */ 1031 if (add_rdr(s->id, server_sa, getrtable(), proxy_sa, 1032 s->proxy_port, client_sa, s->port, s->client_rd) == -1) 1033 goto fail; 1034 1035 /* pass out from $server to $client port $port 1036 nat-to $orig_server port $natport */ 1037 if (rfc_mode && s->cmd == CMD_PORT) { 1038 /* Rewrite sourceport to RFC mandated 20. */ 1039 if (add_nat(s->id, server_sa, s->client_rd, client_sa, 1040 s->port, orig_sa, 20, 20) == -1) 1041 goto fail; 1042 } else { 1043 /* Let pf pick a source port from the standard range. */ 1044 if (add_nat(s->id, server_sa, s->client_rd, client_sa, 1045 s->port, orig_sa, PF_NAT_PROXY_PORT_LOW, 1046 PF_NAT_PROXY_PORT_HIGH) == -1) 1047 goto fail; 1048 } 1049 } 1050 1051 /* Commit rules if they were prepared. */ 1052 if (prepared && (do_commit() == -1)) { 1053 if (errno != EBUSY) 1054 goto fail; 1055 /* One more try if busy. */ 1056 usleep(5000); 1057 if (do_commit() == -1) 1058 goto fail; 1059 } 1060 1061 s->cmd = CMD_NONE; 1062 s->port = 0; 1063 1064 return (1); 1065 1066 fail: 1067 logmsg(LOG_CRIT, "#%d pf operation failed: %s", s->id, strerror(errno)); 1068 if (prepared) 1069 do_rollback(); 1070 return (0); 1071 } 1072 1073 void 1074 server_read(struct bufferevent *bufev, void *arg) 1075 { 1076 struct session *s = arg; 1077 size_t buf_avail, read; 1078 int n; 1079 1080 bufferevent_settimeout(bufev, timeout, 0); 1081 1082 do { 1083 buf_avail = sizeof s->sbuf - s->sbuf_valid; 1084 read = bufferevent_read(bufev, s->sbuf + s->sbuf_valid, 1085 buf_avail); 1086 s->sbuf_valid += read; 1087 1088 while ((n = get_line(s->sbuf, &s->sbuf_valid)) > 0) { 1089 logmsg(LOG_DEBUG, "#%d server: %s", s->id, linebuf); 1090 if (!server_parse(s)) { 1091 end_session(s); 1092 return; 1093 } 1094 bufferevent_write(s->client_bufev, linebuf, linelen); 1095 } 1096 1097 if (n == -1) { 1098 logmsg(LOG_ERR, "#%d server reply too long or not" 1099 " clean", s->id); 1100 end_session(s); 1101 return; 1102 } 1103 } while (read == buf_avail); 1104 } 1105 1106 const char * 1107 sock_ntop(struct sockaddr *sa) 1108 { 1109 static int n = 0; 1110 1111 /* Cycle to next buffer. */ 1112 n = (n + 1) % NTOP_BUFS; 1113 ntop_buf[n][0] = '\0'; 1114 1115 if (sa->sa_family == AF_INET) { 1116 struct sockaddr_in *sin = (struct sockaddr_in *)sa; 1117 1118 return (inet_ntop(AF_INET, &sin->sin_addr, ntop_buf[n], 1119 sizeof ntop_buf[0])); 1120 } 1121 1122 if (sa->sa_family == AF_INET6) { 1123 struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa; 1124 1125 return (inet_ntop(AF_INET6, &sin6->sin6_addr, ntop_buf[n], 1126 sizeof ntop_buf[0])); 1127 } 1128 1129 return (NULL); 1130 } 1131 1132 void 1133 usage(void) 1134 { 1135 fprintf(stderr, "usage: %s [-6Adrv] [-a address] [-b address]" 1136 " [-D level] [-m maxsessions]\n [-P port]" 1137 " [-p port] [-q queue] [-R address] [-T tag]\n" 1138 " [-t timeout]\n", __progname); 1139 exit(1); 1140 } 1141 1142 int 1143 rdaemon(int devnull) 1144 { 1145 1146 switch (fork()) { 1147 case -1: 1148 return (-1); 1149 case 0: 1150 break; 1151 default: 1152 _exit(0); 1153 } 1154 1155 if (setsid() == -1) 1156 return (-1); 1157 1158 (void)dup2(devnull, STDIN_FILENO); 1159 (void)dup2(devnull, STDOUT_FILENO); 1160 (void)dup2(devnull, STDERR_FILENO); 1161 if (devnull > 2) 1162 (void)close(devnull); 1163 1164 return (0); 1165 } 1166