ftp-proxy.c revision 1.1.2.1
1 /* $NetBSD: ftp-proxy.c,v 1.1.2.1 2008/04/26 12:57:42 peter Exp $ */ 2 /* $OpenBSD: ftp-proxy.c,v 1.15 2007/08/15 15:18:02 camield Exp $ */ 3 4 /* 5 * Copyright (c) 2004, 2005 Camiel Dobbelaar, <cd (at) sentia.nl> 6 * 7 * Permission to use, copy, modify, and distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 18 */ 19 20 #include <sys/queue.h> 21 #include <sys/types.h> 22 #include <sys/time.h> 23 #include <sys/resource.h> 24 #include <sys/socket.h> 25 26 #include <net/if.h> 27 #include <net/pfvar.h> 28 #include <netinet/in.h> 29 #include <arpa/inet.h> 30 31 #include <err.h> 32 #include <errno.h> 33 #include <event.h> 34 #include <fcntl.h> 35 #include <netdb.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/chroot/ftp-proxy" 56 #define NOPRIV_USER "_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 #ifndef sstosa 63 #define sstosa(ss) ((struct sockaddr *)(ss)) 64 #endif /* sstosa */ 65 66 #ifndef IPPORT_HIFIRSTAUTO 67 #define IPPORT_HIFIRSTAUTO IPPORT_ANONMIN 68 #endif /* IPPORT_HIFIRSTAUTO */ 69 70 #ifndef IPPORT_HILASTAUTO 71 #define IPPORT_HILASTAUTO IPPORT_ANONMAX 72 #endif /* IPPORT_HILASTAUTO */ 73 74 enum { CMD_NONE = 0, CMD_PORT, CMD_EPRT, CMD_PASV, CMD_EPSV }; 75 76 struct session { 77 u_int32_t id; 78 struct sockaddr_storage client_ss; 79 struct sockaddr_storage proxy_ss; 80 struct sockaddr_storage server_ss; 81 struct sockaddr_storage orig_server_ss; 82 struct bufferevent *client_bufev; 83 struct bufferevent *server_bufev; 84 int client_fd; 85 int server_fd; 86 char cbuf[MAX_LINE]; 87 size_t cbuf_valid; 88 char sbuf[MAX_LINE]; 89 size_t sbuf_valid; 90 int cmd; 91 u_int16_t port; 92 u_int16_t proxy_port; 93 LIST_ENTRY(session) entry; 94 }; 95 96 LIST_HEAD(, session) sessions = LIST_HEAD_INITIALIZER(sessions); 97 98 void client_error(struct bufferevent *, short, void *); 99 int client_parse(struct session *s); 100 int client_parse_anon(struct session *s); 101 int client_parse_cmd(struct session *s); 102 void client_read(struct bufferevent *, void *); 103 int drop_privs(void); 104 void end_session(struct session *); 105 int exit_daemon(void); 106 int getline(char *, size_t *); 107 void handle_connection(const int, short, void *); 108 void handle_signal(int, short, void *); 109 struct session * init_session(void); 110 void logmsg(int, const char *, ...); 111 u_int16_t parse_port(int); 112 u_int16_t pick_proxy_port(void); 113 void proxy_reply(int, struct sockaddr *, u_int16_t); 114 void server_error(struct bufferevent *, short, void *); 115 int server_parse(struct session *s); 116 int allow_data_connection(struct session *s); 117 void server_read(struct bufferevent *, void *); 118 const char *sock_ntop(struct sockaddr *); 119 void usage(void); 120 121 char linebuf[MAX_LINE + 1]; 122 size_t linelen; 123 124 char ntop_buf[NTOP_BUFS][INET6_ADDRSTRLEN]; 125 126 struct sockaddr_storage fixed_server_ss, fixed_proxy_ss; 127 char *fixed_server, *fixed_server_port, *fixed_proxy, *listen_ip, *listen_port, 128 *qname, *tagname; 129 int anonymous_only, daemonize, id_count, ipv6_mode, loglevel, max_sessions, 130 rfc_mode, session_count, timeout, verbose; 131 extern char *__progname; 132 133 void 134 client_error(struct bufferevent *bufev, short what, void *arg) 135 { 136 struct session *s = arg; 137 138 if (what & EVBUFFER_EOF) 139 logmsg(LOG_INFO, "#%d client close", s->id); 140 else if (what == (EVBUFFER_ERROR | EVBUFFER_READ)) 141 logmsg(LOG_ERR, "#%d client reset connection", s->id); 142 else if (what & EVBUFFER_TIMEOUT) 143 logmsg(LOG_ERR, "#%d client timeout", s->id); 144 else if (what & EVBUFFER_WRITE) 145 logmsg(LOG_ERR, "#%d client write error: %d", s->id, what); 146 else 147 logmsg(LOG_ERR, "#%d abnormal client error: %d", s->id, what); 148 149 end_session(s); 150 } 151 152 int 153 client_parse(struct session *s) 154 { 155 /* Reset any previous command. */ 156 s->cmd = CMD_NONE; 157 s->port = 0; 158 159 /* Commands we are looking for are at least 4 chars long. */ 160 if (linelen < 4) 161 return (1); 162 163 if (linebuf[0] == 'P' || linebuf[0] == 'p' || 164 linebuf[0] == 'E' || linebuf[0] == 'e') { 165 if (!client_parse_cmd(s)) 166 return (0); 167 168 /* 169 * Allow active mode connections immediately, instead of 170 * waiting for a positive reply from the server. Some 171 * rare servers/proxies try to probe or setup the data 172 * connection before an actual transfer request. 173 */ 174 if (s->cmd == CMD_PORT || s->cmd == CMD_EPRT) 175 return (allow_data_connection(s)); 176 } 177 178 if (anonymous_only && (linebuf[0] == 'U' || linebuf[0] == 'u')) 179 return (client_parse_anon(s)); 180 181 return (1); 182 } 183 184 int 185 client_parse_anon(struct session *s) 186 { 187 if (strcasecmp("USER ftp\r\n", linebuf) != 0 && 188 strcasecmp("USER anonymous\r\n", linebuf) != 0) { 189 snprintf(linebuf, sizeof linebuf, 190 "500 Only anonymous FTP allowed\r\n"); 191 logmsg(LOG_DEBUG, "#%d proxy: %s", s->id, linebuf); 192 193 /* Talk back to the client ourself. */ 194 linelen = strlen(linebuf); 195 bufferevent_write(s->client_bufev, linebuf, linelen); 196 197 /* Clear buffer so it's not sent to the server. */ 198 linebuf[0] = '\0'; 199 linelen = 0; 200 } 201 202 return (1); 203 } 204 205 int 206 client_parse_cmd(struct session *s) 207 { 208 if (strncasecmp("PASV", linebuf, 4) == 0) 209 s->cmd = CMD_PASV; 210 else if (strncasecmp("PORT ", linebuf, 5) == 0) 211 s->cmd = CMD_PORT; 212 else if (strncasecmp("EPSV", linebuf, 4) == 0) 213 s->cmd = CMD_EPSV; 214 else if (strncasecmp("EPRT ", linebuf, 5) == 0) 215 s->cmd = CMD_EPRT; 216 else 217 return (1); 218 219 if (ipv6_mode && (s->cmd == CMD_PASV || s->cmd == CMD_PORT)) { 220 logmsg(LOG_CRIT, "PASV and PORT not allowed with IPv6"); 221 return (0); 222 } 223 224 if (s->cmd == CMD_PORT || s->cmd == CMD_EPRT) { 225 s->port = parse_port(s->cmd); 226 if (s->port < MIN_PORT) { 227 logmsg(LOG_CRIT, "#%d bad port in '%s'", s->id, 228 linebuf); 229 return (0); 230 } 231 s->proxy_port = pick_proxy_port(); 232 proxy_reply(s->cmd, sstosa(&s->proxy_ss), s->proxy_port); 233 logmsg(LOG_DEBUG, "#%d proxy: %s", s->id, linebuf); 234 } 235 236 return (1); 237 } 238 239 void 240 client_read(struct bufferevent *bufev, void *arg) 241 { 242 struct session *s = arg; 243 size_t buf_avail, read; 244 int n; 245 246 do { 247 buf_avail = sizeof s->cbuf - s->cbuf_valid; 248 read = bufferevent_read(bufev, s->cbuf + s->cbuf_valid, 249 buf_avail); 250 s->cbuf_valid += read; 251 252 while ((n = getline(s->cbuf, &s->cbuf_valid)) > 0) { 253 logmsg(LOG_DEBUG, "#%d client: %s", s->id, linebuf); 254 if (!client_parse(s)) { 255 end_session(s); 256 return; 257 } 258 bufferevent_write(s->server_bufev, linebuf, linelen); 259 } 260 261 if (n == -1) { 262 logmsg(LOG_ERR, "#%d client command too long or not" 263 " clean", s->id); 264 end_session(s); 265 return; 266 } 267 } while (read == buf_avail); 268 } 269 270 int 271 drop_privs(void) 272 { 273 struct passwd *pw; 274 275 pw = getpwnam(NOPRIV_USER); 276 if (pw == NULL) 277 return (0); 278 279 tzset(); 280 #ifdef __NetBSD__ 281 if (chroot(CHROOT_DIR) != 0 || chdir("/") != 0 || 282 setgroups(1, &pw->pw_gid) != 0 || 283 setgid(pw->pw_gid) != 0 || 284 setuid(pw->pw_uid) != 0) 285 return (0); 286 #else 287 if (chroot(CHROOT_DIR) != 0 || chdir("/") != 0 || 288 setgroups(1, &pw->pw_gid) != 0 || 289 setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0 || 290 setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) 291 return (0); 292 #endif /* !__NetBSD__ */ 293 294 return (1); 295 } 296 297 void 298 end_session(struct session *s) 299 { 300 int err; 301 302 logmsg(LOG_INFO, "#%d ending session", s->id); 303 304 if (s->client_fd != -1) 305 close(s->client_fd); 306 if (s->server_fd != -1) 307 close(s->server_fd); 308 309 if (s->client_bufev) 310 bufferevent_free(s->client_bufev); 311 if (s->server_bufev) 312 bufferevent_free(s->server_bufev); 313 314 /* Remove rulesets by commiting empty ones. */ 315 err = 0; 316 if (prepare_commit(s->id) == -1) 317 err = errno; 318 else if (do_commit() == -1) { 319 err = errno; 320 do_rollback(); 321 } 322 if (err) 323 logmsg(LOG_ERR, "#%d pf rule removal failed: %s", s->id, 324 strerror(err)); 325 326 LIST_REMOVE(s, entry); 327 free(s); 328 session_count--; 329 } 330 331 int 332 exit_daemon(void) 333 { 334 struct session *s, *next; 335 336 for (s = LIST_FIRST(&sessions); s != LIST_END(&sessions); s = next) { 337 next = LIST_NEXT(s, entry); 338 end_session(s); 339 } 340 341 if (daemonize) 342 closelog(); 343 344 exit(0); 345 346 /* NOTREACHED */ 347 return (-1); 348 } 349 350 int 351 getline(char *buf, size_t *valid) 352 { 353 size_t i; 354 355 if (*valid > MAX_LINE) 356 return (-1); 357 358 /* Copy to linebuf while searching for a newline. */ 359 for (i = 0; i < *valid; i++) { 360 linebuf[i] = buf[i]; 361 if (buf[i] == '\0') 362 return (-1); 363 if (buf[i] == '\n') 364 break; 365 } 366 367 if (i == *valid) { 368 /* No newline found. */ 369 linebuf[0] = '\0'; 370 linelen = 0; 371 if (i < MAX_LINE) 372 return (0); 373 return (-1); 374 } 375 376 linelen = i + 1; 377 linebuf[linelen] = '\0'; 378 *valid -= linelen; 379 380 /* Move leftovers to the start. */ 381 if (*valid != 0) 382 bcopy(buf + linelen, buf, *valid); 383 384 return ((int)linelen); 385 } 386 387 void 388 handle_connection(const int listen_fd, short event, void *ev) 389 { 390 struct sockaddr_storage tmp_ss; 391 struct sockaddr *client_sa, *server_sa, *fixed_server_sa; 392 struct sockaddr *client_to_proxy_sa, *proxy_to_server_sa; 393 struct session *s; 394 socklen_t len; 395 int client_fd, fc, on; 396 397 /* 398 * We _must_ accept the connection, otherwise libevent will keep 399 * coming back, and we will chew up all CPU. 400 */ 401 client_sa = sstosa(&tmp_ss); 402 len = sizeof(struct sockaddr_storage); 403 if ((client_fd = accept(listen_fd, client_sa, &len)) < 0) { 404 logmsg(LOG_CRIT, "accept failed: %s", strerror(errno)); 405 return; 406 } 407 408 /* Refuse connection if the maximum is reached. */ 409 if (session_count >= max_sessions) { 410 logmsg(LOG_ERR, "client limit (%d) reached, refusing " 411 "connection from %s", max_sessions, sock_ntop(client_sa)); 412 close(client_fd); 413 return; 414 } 415 416 /* Allocate session and copy back the info from the accept(). */ 417 s = init_session(); 418 if (s == NULL) { 419 logmsg(LOG_CRIT, "init_session failed"); 420 close(client_fd); 421 return; 422 } 423 s->client_fd = client_fd; 424 memcpy(sstosa(&s->client_ss), client_sa, client_sa->sa_len); 425 426 /* Cast it once, and be done with it. */ 427 client_sa = sstosa(&s->client_ss); 428 server_sa = sstosa(&s->server_ss); 429 client_to_proxy_sa = sstosa(&tmp_ss); 430 proxy_to_server_sa = sstosa(&s->proxy_ss); 431 fixed_server_sa = sstosa(&fixed_server_ss); 432 433 /* Log id/client early to ease debugging. */ 434 logmsg(LOG_DEBUG, "#%d accepted connection from %s", s->id, 435 sock_ntop(client_sa)); 436 437 /* 438 * Find out the real server and port that the client wanted. 439 */ 440 len = sizeof(struct sockaddr_storage); 441 if ((getsockname(s->client_fd, client_to_proxy_sa, &len)) < 0) { 442 logmsg(LOG_CRIT, "#%d getsockname failed: %s", s->id, 443 strerror(errno)); 444 goto fail; 445 } 446 if (server_lookup(client_sa, client_to_proxy_sa, server_sa) != 0) { 447 logmsg(LOG_CRIT, "#%d server lookup failed (no rdr?)", s->id); 448 goto fail; 449 } 450 if (fixed_server) { 451 memcpy(sstosa(&s->orig_server_ss), server_sa, 452 server_sa->sa_len); 453 memcpy(server_sa, fixed_server_sa, fixed_server_sa->sa_len); 454 } 455 456 /* XXX: check we are not connecting to ourself. */ 457 458 /* 459 * Setup socket and connect to server. 460 */ 461 if ((s->server_fd = socket(server_sa->sa_family, SOCK_STREAM, 462 IPPROTO_TCP)) < 0) { 463 logmsg(LOG_CRIT, "#%d server socket failed: %s", s->id, 464 strerror(errno)); 465 goto fail; 466 } 467 if (fixed_proxy && bind(s->server_fd, sstosa(&fixed_proxy_ss), 468 fixed_proxy_ss.ss_len) != 0) { 469 logmsg(LOG_CRIT, "#%d cannot bind fixed proxy address: %s", 470 s->id, strerror(errno)); 471 goto fail; 472 } 473 474 /* Use non-blocking connect(), see CONNECT_TIMEOUT below. */ 475 if ((fc = fcntl(s->server_fd, F_GETFL)) == -1 || 476 fcntl(s->server_fd, F_SETFL, fc | O_NONBLOCK) == -1) { 477 logmsg(LOG_CRIT, "#%d cannot mark socket non-blocking: %s", 478 s->id, strerror(errno)); 479 goto fail; 480 } 481 if (connect(s->server_fd, server_sa, server_sa->sa_len) < 0 && 482 errno != EINPROGRESS) { 483 logmsg(LOG_CRIT, "#%d proxy cannot connect to server %s: %s", 484 s->id, sock_ntop(server_sa), strerror(errno)); 485 goto fail; 486 } 487 488 len = sizeof(struct sockaddr_storage); 489 if ((getsockname(s->server_fd, proxy_to_server_sa, &len)) < 0) { 490 logmsg(LOG_CRIT, "#%d getsockname failed: %s", s->id, 491 strerror(errno)); 492 goto fail; 493 } 494 495 logmsg(LOG_INFO, "#%d FTP session %d/%d started: client %s to server " 496 "%s via proxy %s ", s->id, session_count, max_sessions, 497 sock_ntop(client_sa), sock_ntop(server_sa), 498 sock_ntop(proxy_to_server_sa)); 499 500 /* Keepalive is nice, but don't care if it fails. */ 501 on = 1; 502 setsockopt(s->client_fd, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 503 sizeof on); 504 setsockopt(s->server_fd, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 505 sizeof on); 506 507 /* 508 * Setup buffered events. 509 */ 510 s->client_bufev = bufferevent_new(s->client_fd, &client_read, NULL, 511 &client_error, s); 512 if (s->client_bufev == NULL) { 513 logmsg(LOG_CRIT, "#%d bufferevent_new client failed", s->id); 514 goto fail; 515 } 516 bufferevent_settimeout(s->client_bufev, timeout, 0); 517 bufferevent_enable(s->client_bufev, EV_READ | EV_TIMEOUT); 518 519 s->server_bufev = bufferevent_new(s->server_fd, &server_read, NULL, 520 &server_error, s); 521 if (s->server_bufev == NULL) { 522 logmsg(LOG_CRIT, "#%d bufferevent_new server failed", s->id); 523 goto fail; 524 } 525 bufferevent_settimeout(s->server_bufev, CONNECT_TIMEOUT, 0); 526 bufferevent_enable(s->server_bufev, EV_READ | EV_TIMEOUT); 527 528 return; 529 530 fail: 531 end_session(s); 532 } 533 534 void 535 handle_signal(int sig, short event, void *arg) 536 { 537 /* 538 * Signal handler rules don't apply, libevent decouples for us. 539 */ 540 541 logmsg(LOG_ERR, "%s exiting on signal %d", __progname, sig); 542 543 exit_daemon(); 544 } 545 546 547 struct session * 548 init_session(void) 549 { 550 struct session *s; 551 552 s = calloc(1, sizeof(struct session)); 553 if (s == NULL) 554 return (NULL); 555 556 s->id = id_count++; 557 s->client_fd = -1; 558 s->server_fd = -1; 559 s->cbuf[0] = '\0'; 560 s->cbuf_valid = 0; 561 s->sbuf[0] = '\0'; 562 s->sbuf_valid = 0; 563 s->client_bufev = NULL; 564 s->server_bufev = NULL; 565 s->cmd = CMD_NONE; 566 s->port = 0; 567 568 LIST_INSERT_HEAD(&sessions, s, entry); 569 session_count++; 570 571 return (s); 572 } 573 574 void 575 logmsg(int pri, const char *message, ...) 576 { 577 va_list ap; 578 579 if (pri > loglevel) 580 return; 581 582 va_start(ap, message); 583 584 if (daemonize) 585 /* syslog does its own vissing. */ 586 vsyslog(pri, message, ap); 587 else { 588 char buf[MAX_LOGLINE]; 589 char visbuf[2 * MAX_LOGLINE]; 590 591 /* We don't care about truncation. */ 592 vsnprintf(buf, sizeof buf, message, ap); 593 #ifdef __NetBSD__ 594 strvisx(visbuf, buf, sizeof visbuf, VIS_CSTYLE | VIS_NL); 595 #else 596 strnvis(visbuf, buf, sizeof visbuf, VIS_CSTYLE | VIS_NL); 597 #endif /* !__NetBSD__ */ 598 fprintf(stderr, "%s\n", visbuf); 599 } 600 601 va_end(ap); 602 } 603 604 int 605 main(int argc, char *argv[]) 606 { 607 struct rlimit rlp; 608 struct addrinfo hints, *res; 609 struct event ev, ev_sighup, ev_sigint, ev_sigterm; 610 int ch, error, listenfd, on; 611 const char *errstr = NULL; /* XXX gcc */ 612 613 /* Defaults. */ 614 anonymous_only = 0; 615 daemonize = 1; 616 fixed_proxy = NULL; 617 fixed_server = NULL; 618 fixed_server_port = "21"; 619 ipv6_mode = 0; 620 listen_ip = NULL; 621 listen_port = "8021"; 622 loglevel = LOG_NOTICE; 623 max_sessions = 100; 624 qname = NULL; 625 rfc_mode = 0; 626 tagname = NULL; 627 timeout = 24 * 3600; 628 verbose = 0; 629 630 /* Other initialization. */ 631 id_count = 1; 632 session_count = 0; 633 634 while ((ch = getopt(argc, argv, "6Aa:b:D:dm:P:p:q:R:rT:t:v")) != -1) { 635 switch (ch) { 636 case '6': 637 ipv6_mode = 1; 638 break; 639 case 'A': 640 anonymous_only = 1; 641 break; 642 case 'a': 643 fixed_proxy = optarg; 644 break; 645 case 'b': 646 listen_ip = optarg; 647 break; 648 case 'D': 649 loglevel = strtonum(optarg, LOG_EMERG, LOG_DEBUG, 650 &errstr); 651 if (errstr) 652 errx(1, "loglevel %s", errstr); 653 break; 654 case 'd': 655 daemonize = 0; 656 break; 657 case 'm': 658 max_sessions = strtonum(optarg, 1, 500, &errstr); 659 if (errstr) 660 errx(1, "max sessions %s", errstr); 661 break; 662 case 'P': 663 fixed_server_port = optarg; 664 break; 665 case 'p': 666 listen_port = optarg; 667 break; 668 case 'q': 669 if (strlen(optarg) >= PF_QNAME_SIZE) 670 errx(1, "queuename too long"); 671 qname = optarg; 672 break; 673 case 'R': 674 fixed_server = optarg; 675 break; 676 case 'r': 677 rfc_mode = 1; 678 break; 679 case 'T': 680 if (strlen(optarg) >= PF_TAG_NAME_SIZE) 681 errx(1, "tagname too long"); 682 tagname = optarg; 683 break; 684 case 't': 685 timeout = strtonum(optarg, 0, 86400, &errstr); 686 if (errstr) 687 errx(1, "timeout %s", errstr); 688 break; 689 case 'v': 690 verbose++; 691 if (verbose > 2) 692 usage(); 693 break; 694 default: 695 usage(); 696 } 697 } 698 699 if (listen_ip == NULL) 700 listen_ip = ipv6_mode ? "::1" : "127.0.0.1"; 701 702 /* Check for root to save the user from cryptic failure messages. */ 703 if (getuid() != 0) 704 errx(1, "needs to start as root"); 705 706 /* Raise max. open files limit to satisfy max. sessions. */ 707 rlp.rlim_cur = rlp.rlim_max = (2 * max_sessions) + 10; 708 if (setrlimit(RLIMIT_NOFILE, &rlp) == -1) 709 err(1, "setrlimit"); 710 711 if (fixed_proxy) { 712 memset(&hints, 0, sizeof hints); 713 hints.ai_flags = AI_NUMERICHOST; 714 hints.ai_family = ipv6_mode ? AF_INET6 : AF_INET; 715 hints.ai_socktype = SOCK_STREAM; 716 error = getaddrinfo(fixed_proxy, NULL, &hints, &res); 717 if (error) 718 errx(1, "getaddrinfo fixed proxy address failed: %s", 719 gai_strerror(error)); 720 memcpy(&fixed_proxy_ss, res->ai_addr, res->ai_addrlen); 721 logmsg(LOG_INFO, "using %s to connect to servers", 722 sock_ntop(sstosa(&fixed_proxy_ss))); 723 freeaddrinfo(res); 724 } 725 726 if (fixed_server) { 727 memset(&hints, 0, sizeof hints); 728 hints.ai_family = ipv6_mode ? AF_INET6 : AF_INET; 729 hints.ai_socktype = SOCK_STREAM; 730 error = getaddrinfo(fixed_server, fixed_server_port, &hints, 731 &res); 732 if (error) 733 errx(1, "getaddrinfo fixed server address failed: %s", 734 gai_strerror(error)); 735 memcpy(&fixed_server_ss, res->ai_addr, res->ai_addrlen); 736 logmsg(LOG_INFO, "using fixed server %s", 737 sock_ntop(sstosa(&fixed_server_ss))); 738 freeaddrinfo(res); 739 } 740 741 /* Setup listener. */ 742 memset(&hints, 0, sizeof hints); 743 hints.ai_flags = AI_NUMERICHOST | AI_PASSIVE; 744 hints.ai_family = ipv6_mode ? AF_INET6 : AF_INET; 745 hints.ai_socktype = SOCK_STREAM; 746 error = getaddrinfo(listen_ip, listen_port, &hints, &res); 747 if (error) 748 errx(1, "getaddrinfo listen address failed: %s", 749 gai_strerror(error)); 750 if ((listenfd = socket(res->ai_family, SOCK_STREAM, IPPROTO_TCP)) == -1) 751 errx(1, "socket failed"); 752 on = 1; 753 if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, (void *)&on, 754 sizeof on) != 0) 755 err(1, "setsockopt failed"); 756 if (bind(listenfd, (struct sockaddr *)res->ai_addr, 757 (socklen_t)res->ai_addrlen) != 0) 758 err(1, "bind failed"); 759 if (listen(listenfd, TCP_BACKLOG) != 0) 760 err(1, "listen failed"); 761 freeaddrinfo(res); 762 763 /* Initialize pf. */ 764 init_filter(qname, tagname, verbose); 765 766 if (daemonize) { 767 if (daemon(0, 0) == -1) 768 err(1, "cannot daemonize"); 769 openlog(__progname, LOG_PID | LOG_NDELAY, LOG_DAEMON); 770 } 771 772 /* Use logmsg for output from here on. */ 773 774 if (!drop_privs()) { 775 logmsg(LOG_ERR, "cannot drop privileges: %s", strerror(errno)); 776 exit(1); 777 } 778 779 event_init(); 780 781 /* Setup signal handler. */ 782 signal(SIGPIPE, SIG_IGN); 783 signal_set(&ev_sighup, SIGHUP, handle_signal, NULL); 784 signal_set(&ev_sigint, SIGINT, handle_signal, NULL); 785 signal_set(&ev_sigterm, SIGTERM, handle_signal, NULL); 786 signal_add(&ev_sighup, NULL); 787 signal_add(&ev_sigint, NULL); 788 signal_add(&ev_sigterm, NULL); 789 790 event_set(&ev, listenfd, EV_READ | EV_PERSIST, handle_connection, &ev); 791 event_add(&ev, NULL); 792 793 logmsg(LOG_NOTICE, "listening on %s port %s", listen_ip, listen_port); 794 795 /* Vroom, vroom. */ 796 event_dispatch(); 797 798 logmsg(LOG_ERR, "event_dispatch error: %s", strerror(errno)); 799 exit_daemon(); 800 801 /* NOTREACHED */ 802 return (1); 803 } 804 805 u_int16_t 806 parse_port(int mode) 807 { 808 unsigned int port, v[6]; 809 int n; 810 char *p; 811 812 /* Find the last space or left-parenthesis. */ 813 for (p = linebuf + linelen; p > linebuf; p--) 814 if (*p == ' ' || *p == '(') 815 break; 816 if (p == linebuf) 817 return (0); 818 819 switch (mode) { 820 case CMD_PORT: 821 n = sscanf(p, " %u,%u,%u,%u,%u,%u", &v[0], &v[1], &v[2], 822 &v[3], &v[4], &v[5]); 823 if (n == 6 && v[0] < 256 && v[1] < 256 && v[2] < 256 && 824 v[3] < 256 && v[4] < 256 && v[5] < 256) 825 return ((v[4] << 8) | v[5]); 826 break; 827 case CMD_PASV: 828 n = sscanf(p, "(%u,%u,%u,%u,%u,%u)", &v[0], &v[1], &v[2], 829 &v[3], &v[4], &v[5]); 830 if (n == 6 && v[0] < 256 && v[1] < 256 && v[2] < 256 && 831 v[3] < 256 && v[4] < 256 && v[5] < 256) 832 return ((v[4] << 8) | v[5]); 833 break; 834 case CMD_EPSV: 835 n = sscanf(p, "(|||%u|)", &port); 836 if (n == 1 && port < 65536) 837 return (port); 838 break; 839 case CMD_EPRT: 840 n = sscanf(p, " |1|%u.%u.%u.%u|%u|", &v[0], &v[1], &v[2], 841 &v[3], &port); 842 if (n == 5 && v[0] < 256 && v[1] < 256 && v[2] < 256 && 843 v[3] < 256 && port < 65536) 844 return (port); 845 n = sscanf(p, " |2|%*[a-fA-F0-9:]|%u|", &port); 846 if (n == 1 && port < 65536) 847 return (port); 848 break; 849 default: 850 return (0); 851 } 852 853 return (0); 854 } 855 856 u_int16_t 857 pick_proxy_port(void) 858 { 859 /* Random should be good enough for avoiding port collisions. */ 860 return (IPPORT_HIFIRSTAUTO + (arc4random() % 861 (IPPORT_HILASTAUTO - IPPORT_HIFIRSTAUTO))); 862 } 863 864 void 865 proxy_reply(int cmd, struct sockaddr *sa, u_int16_t port) 866 { 867 int i, r = -1; 868 869 switch (cmd) { 870 case CMD_PORT: 871 r = snprintf(linebuf, sizeof linebuf, 872 "PORT %s,%u,%u\r\n", sock_ntop(sa), port / 256, 873 port % 256); 874 break; 875 case CMD_PASV: 876 r = snprintf(linebuf, sizeof linebuf, 877 "227 Entering Passive Mode (%s,%u,%u)\r\n", sock_ntop(sa), 878 port / 256, port % 256); 879 break; 880 case CMD_EPRT: 881 if (sa->sa_family == AF_INET) 882 r = snprintf(linebuf, sizeof linebuf, 883 "EPRT |1|%s|%u|\r\n", sock_ntop(sa), port); 884 else if (sa->sa_family == AF_INET6) 885 r = snprintf(linebuf, sizeof linebuf, 886 "EPRT |2|%s|%u|\r\n", sock_ntop(sa), port); 887 break; 888 case CMD_EPSV: 889 r = snprintf(linebuf, sizeof linebuf, 890 "229 Entering Extended Passive Mode (|||%u|)\r\n", port); 891 break; 892 } 893 894 if (r < 0 || r >= sizeof linebuf) { 895 logmsg(LOG_ERR, "proxy_reply failed: %d", r); 896 linebuf[0] = '\0'; 897 linelen = 0; 898 return; 899 } 900 linelen = (size_t)r; 901 902 if (cmd == CMD_PORT || cmd == CMD_PASV) { 903 /* Replace dots in IP address with commas. */ 904 for (i = 0; i < linelen; i++) 905 if (linebuf[i] == '.') 906 linebuf[i] = ','; 907 } 908 } 909 910 void 911 server_error(struct bufferevent *bufev, short what, void *arg) 912 { 913 struct session *s = arg; 914 915 if (what & EVBUFFER_EOF) 916 logmsg(LOG_INFO, "#%d server close", s->id); 917 else if (what == (EVBUFFER_ERROR | EVBUFFER_READ)) 918 logmsg(LOG_ERR, "#%d server refused connection", s->id); 919 else if (what & EVBUFFER_WRITE) 920 logmsg(LOG_ERR, "#%d server write error: %d", s->id, what); 921 else if (what & EVBUFFER_TIMEOUT) 922 logmsg(LOG_NOTICE, "#%d server timeout", s->id); 923 else 924 logmsg(LOG_ERR, "#%d abnormal server error: %d", s->id, what); 925 926 end_session(s); 927 } 928 929 int 930 server_parse(struct session *s) 931 { 932 if (s->cmd == CMD_NONE || linelen < 4 || linebuf[0] != '2') 933 goto out; 934 935 if ((s->cmd == CMD_PASV && strncmp("227 ", linebuf, 4) == 0) || 936 (s->cmd == CMD_EPSV && strncmp("229 ", linebuf, 4) == 0)) 937 return (allow_data_connection(s)); 938 939 out: 940 s->cmd = CMD_NONE; 941 s->port = 0; 942 943 return (1); 944 } 945 946 int 947 allow_data_connection(struct session *s) 948 { 949 struct sockaddr *client_sa, *orig_sa, *proxy_sa, *server_sa; 950 int prepared = 0; 951 952 /* 953 * The pf rules below do quite some NAT rewriting, to keep up 954 * appearances. Points to keep in mind: 955 * 1) The client must think it's talking to the real server, 956 * for both control and data connections. Transparently. 957 * 2) The server must think that the proxy is the client. 958 * 3) Source and destination ports are rewritten to minimize 959 * port collisions, to aid security (some systems pick weak 960 * ports) or to satisfy RFC requirements (source port 20). 961 */ 962 963 /* Cast this once, to make code below it more readable. */ 964 client_sa = sstosa(&s->client_ss); 965 server_sa = sstosa(&s->server_ss); 966 proxy_sa = sstosa(&s->proxy_ss); 967 if (fixed_server) 968 /* Fixed server: data connections must appear to come 969 from / go to the original server, not the fixed one. */ 970 orig_sa = sstosa(&s->orig_server_ss); 971 else 972 /* Server not fixed: orig_server == server. */ 973 orig_sa = sstosa(&s->server_ss); 974 975 /* Passive modes. */ 976 if (s->cmd == CMD_PASV || s->cmd == CMD_EPSV) { 977 s->port = parse_port(s->cmd); 978 if (s->port < MIN_PORT) { 979 logmsg(LOG_CRIT, "#%d bad port in '%s'", s->id, 980 linebuf); 981 return (0); 982 } 983 s->proxy_port = pick_proxy_port(); 984 logmsg(LOG_INFO, "#%d passive: client to server port %d" 985 " via port %d", s->id, s->port, s->proxy_port); 986 987 if (prepare_commit(s->id) == -1) 988 goto fail; 989 prepared = 1; 990 991 proxy_reply(s->cmd, orig_sa, s->proxy_port); 992 logmsg(LOG_DEBUG, "#%d proxy: %s", s->id, linebuf); 993 994 /* rdr from $client to $orig_server port $proxy_port -> $server 995 port $port */ 996 if (add_rdr(s->id, client_sa, orig_sa, s->proxy_port, 997 server_sa, s->port) == -1) 998 goto fail; 999 1000 /* nat from $client to $server port $port -> $proxy */ 1001 if (add_nat(s->id, client_sa, server_sa, s->port, proxy_sa, 1002 PF_NAT_PROXY_PORT_LOW, PF_NAT_PROXY_PORT_HIGH) == -1) 1003 goto fail; 1004 1005 /* pass in from $client to $server port $port */ 1006 if (add_filter(s->id, PF_IN, client_sa, server_sa, 1007 s->port) == -1) 1008 goto fail; 1009 1010 /* pass out from $proxy to $server port $port */ 1011 if (add_filter(s->id, PF_OUT, proxy_sa, server_sa, 1012 s->port) == -1) 1013 goto fail; 1014 } 1015 1016 /* Active modes. */ 1017 if (s->cmd == CMD_PORT || s->cmd == CMD_EPRT) { 1018 logmsg(LOG_INFO, "#%d active: server to client port %d" 1019 " via port %d", s->id, s->port, s->proxy_port); 1020 1021 if (prepare_commit(s->id) == -1) 1022 goto fail; 1023 prepared = 1; 1024 1025 /* rdr from $server to $proxy port $proxy_port -> $client port 1026 $port */ 1027 if (add_rdr(s->id, server_sa, proxy_sa, s->proxy_port, 1028 client_sa, s->port) == -1) 1029 goto fail; 1030 1031 /* nat from $server to $client port $port -> $orig_server port 1032 $natport */ 1033 if (rfc_mode && s->cmd == CMD_PORT) { 1034 /* Rewrite sourceport to RFC mandated 20. */ 1035 if (add_nat(s->id, server_sa, client_sa, s->port, 1036 orig_sa, 20, 20) == -1) 1037 goto fail; 1038 } else { 1039 /* Let pf pick a source port from the standard range. */ 1040 if (add_nat(s->id, server_sa, client_sa, s->port, 1041 orig_sa, PF_NAT_PROXY_PORT_LOW, 1042 PF_NAT_PROXY_PORT_HIGH) == -1) 1043 goto fail; 1044 } 1045 1046 /* pass in from $server to $client port $port */ 1047 if (add_filter(s->id, PF_IN, server_sa, client_sa, s->port) == 1048 -1) 1049 goto fail; 1050 1051 /* pass out from $orig_server to $client port $port */ 1052 if (add_filter(s->id, PF_OUT, orig_sa, client_sa, s->port) == 1053 -1) 1054 goto fail; 1055 } 1056 1057 /* Commit rules if they were prepared. */ 1058 if (prepared && (do_commit() == -1)) { 1059 if (errno != EBUSY) 1060 goto fail; 1061 /* One more try if busy. */ 1062 usleep(5000); 1063 if (do_commit() == -1) 1064 goto fail; 1065 } 1066 1067 s->cmd = CMD_NONE; 1068 s->port = 0; 1069 1070 return (1); 1071 1072 fail: 1073 logmsg(LOG_CRIT, "#%d pf operation failed: %s", s->id, strerror(errno)); 1074 if (prepared) 1075 do_rollback(); 1076 return (0); 1077 } 1078 1079 void 1080 server_read(struct bufferevent *bufev, void *arg) 1081 { 1082 struct session *s = arg; 1083 size_t buf_avail, read; 1084 int n; 1085 1086 bufferevent_settimeout(bufev, timeout, 0); 1087 1088 do { 1089 buf_avail = sizeof s->sbuf - s->sbuf_valid; 1090 read = bufferevent_read(bufev, s->sbuf + s->sbuf_valid, 1091 buf_avail); 1092 s->sbuf_valid += read; 1093 1094 while ((n = getline(s->sbuf, &s->sbuf_valid)) > 0) { 1095 logmsg(LOG_DEBUG, "#%d server: %s", s->id, linebuf); 1096 if (!server_parse(s)) { 1097 end_session(s); 1098 return; 1099 } 1100 bufferevent_write(s->client_bufev, linebuf, linelen); 1101 } 1102 1103 if (n == -1) { 1104 logmsg(LOG_ERR, "#%d server reply too long or not" 1105 " clean", s->id); 1106 end_session(s); 1107 return; 1108 } 1109 } while (read == buf_avail); 1110 } 1111 1112 const char * 1113 sock_ntop(struct sockaddr *sa) 1114 { 1115 static int n = 0; 1116 1117 /* Cycle to next buffer. */ 1118 n = (n + 1) % NTOP_BUFS; 1119 ntop_buf[n][0] = '\0'; 1120 1121 if (sa->sa_family == AF_INET) { 1122 struct sockaddr_in *sin = (struct sockaddr_in *)sa; 1123 1124 return (inet_ntop(AF_INET, &sin->sin_addr, ntop_buf[n], 1125 sizeof ntop_buf[0])); 1126 } 1127 1128 if (sa->sa_family == AF_INET6) { 1129 struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa; 1130 1131 return (inet_ntop(AF_INET6, &sin6->sin6_addr, ntop_buf[n], 1132 sizeof ntop_buf[0])); 1133 } 1134 1135 return (NULL); 1136 } 1137 1138 void 1139 usage(void) 1140 { 1141 fprintf(stderr, "usage: %s [-6Adrv] [-a address] [-b address]" 1142 " [-D level] [-m maxsessions]\n [-P port]" 1143 " [-p port] [-q queue] [-R address] [-T tag] [-t timeout]\n", __progname); 1144 exit(1); 1145 } 1146
Indexes created Tue Sep 30 17:09:57 GMT 2025