OpenBSD-4.6/usr.sbin/ftp-proxy/ftp-proxy.c
/* $OpenBSD: ftp-proxy.c,v 1.19 2008/06/13 07:25:26 claudio Exp $ */
/*
* Copyright (c) 2004, 2005 Camiel Dobbelaar, <cd@sentia.nl>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/queue.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <net/if.h>
#include <net/pfvar.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <err.h>
#include <errno.h>
#include <event.h>
#include <fcntl.h>
#include <netdb.h>
#include <pwd.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <vis.h>
#include "filter.h"
#define CONNECT_TIMEOUT 30
#define MIN_PORT 1024
#define MAX_LINE 500
#define MAX_LOGLINE 300
#define NTOP_BUFS 3
#define TCP_BACKLOG 10
#define CHROOT_DIR "/var/empty"
#define NOPRIV_USER "proxy"
/* pfctl standard NAT range. */
#define PF_NAT_PROXY_PORT_LOW 50001
#define PF_NAT_PROXY_PORT_HIGH 65535
#define sstosa(ss) ((struct sockaddr *)(ss))
enum { CMD_NONE = 0, CMD_PORT, CMD_EPRT, CMD_PASV, CMD_EPSV };
struct session {
u_int32_t id;
struct sockaddr_storage client_ss;
struct sockaddr_storage proxy_ss;
struct sockaddr_storage server_ss;
struct sockaddr_storage orig_server_ss;
struct bufferevent *client_bufev;
struct bufferevent *server_bufev;
int client_fd;
int server_fd;
char cbuf[MAX_LINE];
size_t cbuf_valid;
char sbuf[MAX_LINE];
size_t sbuf_valid;
int cmd;
u_int16_t port;
u_int16_t proxy_port;
LIST_ENTRY(session) entry;
};
LIST_HEAD(, session) sessions = LIST_HEAD_INITIALIZER(sessions);
void client_error(struct bufferevent *, short, void *);
int client_parse(struct session *s);
int client_parse_anon(struct session *s);
int client_parse_cmd(struct session *s);
void client_read(struct bufferevent *, void *);
int drop_privs(void);
void end_session(struct session *);
void exit_daemon(void);
int getline(char *, size_t *);
void handle_connection(const int, short, void *);
void handle_signal(int, short, void *);
struct session * init_session(void);
void logmsg(int, const char *, ...);
u_int16_t parse_port(int);
u_int16_t pick_proxy_port(void);
void proxy_reply(int, struct sockaddr *, u_int16_t);
void server_error(struct bufferevent *, short, void *);
int server_parse(struct session *s);
int allow_data_connection(struct session *s);
void server_read(struct bufferevent *, void *);
const char *sock_ntop(struct sockaddr *);
void usage(void);
char linebuf[MAX_LINE + 1];
size_t linelen;
char ntop_buf[NTOP_BUFS][INET6_ADDRSTRLEN];
struct sockaddr_storage fixed_server_ss, fixed_proxy_ss;
char *fixed_server, *fixed_server_port, *fixed_proxy, *listen_ip, *listen_port,
*qname, *tagname;
int anonymous_only, daemonize, id_count, ipv6_mode, loglevel, max_sessions,
rfc_mode, session_count, timeout, verbose;
extern char *__progname;
void
client_error(struct bufferevent *bufev, short what, void *arg)
{
struct session *s = arg;
if (what & EVBUFFER_EOF)
logmsg(LOG_INFO, "#%d client close", s->id);
else if (what == (EVBUFFER_ERROR | EVBUFFER_READ))
logmsg(LOG_ERR, "#%d client reset connection", s->id);
else if (what & EVBUFFER_TIMEOUT)
logmsg(LOG_ERR, "#%d client timeout", s->id);
else if (what & EVBUFFER_WRITE)
logmsg(LOG_ERR, "#%d client write error: %d", s->id, what);
else
logmsg(LOG_ERR, "#%d abnormal client error: %d", s->id, what);
end_session(s);
}
int
client_parse(struct session *s)
{
/* Reset any previous command. */
s->cmd = CMD_NONE;
s->port = 0;
/* Commands we are looking for are at least 4 chars long. */
if (linelen < 4)
return (1);
if (linebuf[0] == 'P' || linebuf[0] == 'p' ||
linebuf[0] == 'E' || linebuf[0] == 'e') {
if (!client_parse_cmd(s))
return (0);
/*
* Allow active mode connections immediately, instead of
* waiting for a positive reply from the server. Some
* rare servers/proxies try to probe or setup the data
* connection before an actual transfer request.
*/
if (s->cmd == CMD_PORT || s->cmd == CMD_EPRT)
return (allow_data_connection(s));
}
if (anonymous_only && (linebuf[0] == 'U' || linebuf[0] == 'u'))
return (client_parse_anon(s));
return (1);
}
int
client_parse_anon(struct session *s)
{
if (strcasecmp("USER ftp\r\n", linebuf) != 0 &&
strcasecmp("USER anonymous\r\n", linebuf) != 0) {
snprintf(linebuf, sizeof linebuf,
"500 Only anonymous FTP allowed\r\n");
logmsg(LOG_DEBUG, "#%d proxy: %s", s->id, linebuf);
/* Talk back to the client ourself. */
linelen = strlen(linebuf);
bufferevent_write(s->client_bufev, linebuf, linelen);
/* Clear buffer so it's not sent to the server. */
linebuf[0] = '\0';
linelen = 0;
}
return (1);
}
int
client_parse_cmd(struct session *s)
{
if (strncasecmp("PASV", linebuf, 4) == 0)
s->cmd = CMD_PASV;
else if (strncasecmp("PORT ", linebuf, 5) == 0)
s->cmd = CMD_PORT;
else if (strncasecmp("EPSV", linebuf, 4) == 0)
s->cmd = CMD_EPSV;
else if (strncasecmp("EPRT ", linebuf, 5) == 0)
s->cmd = CMD_EPRT;
else
return (1);
if (ipv6_mode && (s->cmd == CMD_PASV || s->cmd == CMD_PORT)) {
logmsg(LOG_CRIT, "PASV and PORT not allowed with IPv6");
return (0);
}
if (s->cmd == CMD_PORT || s->cmd == CMD_EPRT) {
s->port = parse_port(s->cmd);
if (s->port < MIN_PORT) {
logmsg(LOG_CRIT, "#%d bad port in '%s'", s->id,
linebuf);
return (0);
}
s->proxy_port = pick_proxy_port();
proxy_reply(s->cmd, sstosa(&s->proxy_ss), s->proxy_port);
logmsg(LOG_DEBUG, "#%d proxy: %s", s->id, linebuf);
}
return (1);
}
void
client_read(struct bufferevent *bufev, void *arg)
{
struct session *s = arg;
size_t buf_avail, read;
int n;
do {
buf_avail = sizeof s->cbuf - s->cbuf_valid;
read = bufferevent_read(bufev, s->cbuf + s->cbuf_valid,
buf_avail);
s->cbuf_valid += read;
while ((n = getline(s->cbuf, &s->cbuf_valid)) > 0) {
logmsg(LOG_DEBUG, "#%d client: %s", s->id, linebuf);
if (!client_parse(s)) {
end_session(s);
return;
}
bufferevent_write(s->server_bufev, linebuf, linelen);
}
if (n == -1) {
logmsg(LOG_ERR, "#%d client command too long or not"
" clean", s->id);
end_session(s);
return;
}
} while (read == buf_avail);
}
int
drop_privs(void)
{
struct passwd *pw;
pw = getpwnam(NOPRIV_USER);
if (pw == NULL)
return (0);
tzset();
if (chroot(CHROOT_DIR) != 0 || chdir("/") != 0 ||
setgroups(1, &pw->pw_gid) != 0 ||
setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0 ||
setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0)
return (0);
return (1);
}
void
end_session(struct session *s)
{
int err;
logmsg(LOG_INFO, "#%d ending session", s->id);
/* Flush output buffers. */
if (s->client_bufev && s->client_fd != -1)
evbuffer_write(s->client_bufev->output, s->client_fd);
if (s->server_bufev && s->server_fd != -1)
evbuffer_write(s->server_bufev->output, s->server_fd);
if (s->client_fd != -1)
close(s->client_fd);
if (s->server_fd != -1)
close(s->server_fd);
if (s->client_bufev)
bufferevent_free(s->client_bufev);
if (s->server_bufev)
bufferevent_free(s->server_bufev);
/* Remove rulesets by commiting empty ones. */
err = 0;
if (prepare_commit(s->id) == -1)
err = errno;
else if (do_commit() == -1) {
err = errno;
do_rollback();
}
if (err)
logmsg(LOG_ERR, "#%d pf rule removal failed: %s", s->id,
strerror(err));
LIST_REMOVE(s, entry);
free(s);
session_count--;
}
void
exit_daemon(void)
{
struct session *s, *next;
for (s = LIST_FIRST(&sessions); s != LIST_END(&sessions); s = next) {
next = LIST_NEXT(s, entry);
end_session(s);
}
if (daemonize)
closelog();
exit(0);
}
int
getline(char *buf, size_t *valid)
{
size_t i;
if (*valid > MAX_LINE)
return (-1);
/* Copy to linebuf while searching for a newline. */
for (i = 0; i < *valid; i++) {
linebuf[i] = buf[i];
if (buf[i] == '\0')
return (-1);
if (buf[i] == '\n')
break;
}
if (i == *valid) {
/* No newline found. */
linebuf[0] = '\0';
linelen = 0;
if (i < MAX_LINE)
return (0);
return (-1);
}
linelen = i + 1;
linebuf[linelen] = '\0';
*valid -= linelen;
/* Move leftovers to the start. */
if (*valid != 0)
bcopy(buf + linelen, buf, *valid);
return ((int)linelen);
}
void
handle_connection(const int listen_fd, short event, void *ev)
{
struct sockaddr_storage tmp_ss;
struct sockaddr *client_sa, *server_sa, *fixed_server_sa;
struct sockaddr *client_to_proxy_sa, *proxy_to_server_sa;
struct session *s;
socklen_t len;
int client_fd, fc, on;
/*
* We _must_ accept the connection, otherwise libevent will keep
* coming back, and we will chew up all CPU.
*/
client_sa = sstosa(&tmp_ss);
len = sizeof(struct sockaddr_storage);
if ((client_fd = accept(listen_fd, client_sa, &len)) < 0) {
logmsg(LOG_CRIT, "accept failed: %s", strerror(errno));
return;
}
/* Refuse connection if the maximum is reached. */
if (session_count >= max_sessions) {
logmsg(LOG_ERR, "client limit (%d) reached, refusing "
"connection from %s", max_sessions, sock_ntop(client_sa));
close(client_fd);
return;
}
/* Allocate session and copy back the info from the accept(). */
s = init_session();
if (s == NULL) {
logmsg(LOG_CRIT, "init_session failed");
close(client_fd);
return;
}
s->client_fd = client_fd;
memcpy(sstosa(&s->client_ss), client_sa, client_sa->sa_len);
/* Cast it once, and be done with it. */
client_sa = sstosa(&s->client_ss);
server_sa = sstosa(&s->server_ss);
client_to_proxy_sa = sstosa(&tmp_ss);
proxy_to_server_sa = sstosa(&s->proxy_ss);
fixed_server_sa = sstosa(&fixed_server_ss);
/* Log id/client early to ease debugging. */
logmsg(LOG_DEBUG, "#%d accepted connection from %s", s->id,
sock_ntop(client_sa));
/*
* Find out the real server and port that the client wanted.
*/
len = sizeof(struct sockaddr_storage);
if ((getsockname(s->client_fd, client_to_proxy_sa, &len)) < 0) {
logmsg(LOG_CRIT, "#%d getsockname failed: %s", s->id,
strerror(errno));
goto fail;
}
if (server_lookup(client_sa, client_to_proxy_sa, server_sa) != 0) {
logmsg(LOG_CRIT, "#%d server lookup failed (no rdr?)", s->id);
goto fail;
}
if (fixed_server) {
memcpy(sstosa(&s->orig_server_ss), server_sa,
server_sa->sa_len);
memcpy(server_sa, fixed_server_sa, fixed_server_sa->sa_len);
}
/* XXX: check we are not connecting to ourself. */
/*
* Setup socket and connect to server.
*/
if ((s->server_fd = socket(server_sa->sa_family, SOCK_STREAM,
IPPROTO_TCP)) < 0) {
logmsg(LOG_CRIT, "#%d server socket failed: %s", s->id,
strerror(errno));
goto fail;
}
if (fixed_proxy && bind(s->server_fd, sstosa(&fixed_proxy_ss),
fixed_proxy_ss.ss_len) != 0) {
logmsg(LOG_CRIT, "#%d cannot bind fixed proxy address: %s",
s->id, strerror(errno));
goto fail;
}
/* Use non-blocking connect(), see CONNECT_TIMEOUT below. */
if ((fc = fcntl(s->server_fd, F_GETFL)) == -1 ||
fcntl(s->server_fd, F_SETFL, fc | O_NONBLOCK) == -1) {
logmsg(LOG_CRIT, "#%d cannot mark socket non-blocking: %s",
s->id, strerror(errno));
goto fail;
}
if (connect(s->server_fd, server_sa, server_sa->sa_len) < 0 &&
errno != EINPROGRESS) {
logmsg(LOG_CRIT, "#%d proxy cannot connect to server %s: %s",
s->id, sock_ntop(server_sa), strerror(errno));
goto fail;
}
len = sizeof(struct sockaddr_storage);
if ((getsockname(s->server_fd, proxy_to_server_sa, &len)) < 0) {
logmsg(LOG_CRIT, "#%d getsockname failed: %s", s->id,
strerror(errno));
goto fail;
}
logmsg(LOG_INFO, "#%d FTP session %d/%d started: client %s to server "
"%s via proxy %s ", s->id, session_count, max_sessions,
sock_ntop(client_sa), sock_ntop(server_sa),
sock_ntop(proxy_to_server_sa));
/* Keepalive is nice, but don't care if it fails. */
on = 1;
setsockopt(s->client_fd, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
sizeof on);
setsockopt(s->server_fd, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
sizeof on);
/*
* Setup buffered events.
*/
s->client_bufev = bufferevent_new(s->client_fd, &client_read, NULL,
&client_error, s);
if (s->client_bufev == NULL) {
logmsg(LOG_CRIT, "#%d bufferevent_new client failed", s->id);
goto fail;
}
bufferevent_settimeout(s->client_bufev, timeout, 0);
bufferevent_enable(s->client_bufev, EV_READ | EV_TIMEOUT);
s->server_bufev = bufferevent_new(s->server_fd, &server_read, NULL,
&server_error, s);
if (s->server_bufev == NULL) {
logmsg(LOG_CRIT, "#%d bufferevent_new server failed", s->id);
goto fail;
}
bufferevent_settimeout(s->server_bufev, CONNECT_TIMEOUT, 0);
bufferevent_enable(s->server_bufev, EV_READ | EV_TIMEOUT);
return;
fail:
end_session(s);
}
void
handle_signal(int sig, short event, void *arg)
{
/*
* Signal handler rules don't apply, libevent decouples for us.
*/
logmsg(LOG_ERR, "exiting on signal %d", sig);
exit_daemon();
}
struct session *
init_session(void)
{
struct session *s;
s = calloc(1, sizeof(struct session));
if (s == NULL)
return (NULL);
s->id = id_count++;
s->client_fd = -1;
s->server_fd = -1;
s->cbuf[0] = '\0';
s->cbuf_valid = 0;
s->sbuf[0] = '\0';
s->sbuf_valid = 0;
s->client_bufev = NULL;
s->server_bufev = NULL;
s->cmd = CMD_NONE;
s->port = 0;
LIST_INSERT_HEAD(&sessions, s, entry);
session_count++;
return (s);
}
void
logmsg(int pri, const char *message, ...)
{
va_list ap;
if (pri > loglevel)
return;
va_start(ap, message);
if (daemonize)
/* syslog does its own vissing. */
vsyslog(pri, message, ap);
else {
char buf[MAX_LOGLINE];
char visbuf[2 * MAX_LOGLINE];
/* We don't care about truncation. */
vsnprintf(buf, sizeof buf, message, ap);
strnvis(visbuf, buf, sizeof visbuf, VIS_CSTYLE | VIS_NL);
fprintf(stderr, "%s\n", visbuf);
}
va_end(ap);
}
int
main(int argc, char *argv[])
{
struct rlimit rlp;
struct addrinfo hints, *res;
struct event ev, ev_sighup, ev_sigint, ev_sigterm;
int ch, error, listenfd, on;
const char *errstr;
/* Defaults. */
anonymous_only = 0;
daemonize = 1;
fixed_proxy = NULL;
fixed_server = NULL;
fixed_server_port = "21";
ipv6_mode = 0;
listen_ip = NULL;
listen_port = "8021";
loglevel = LOG_NOTICE;
max_sessions = 100;
qname = NULL;
rfc_mode = 0;
tagname = NULL;
timeout = 24 * 3600;
verbose = 0;
/* Other initialization. */
id_count = 1;
session_count = 0;
while ((ch = getopt(argc, argv, "6Aa:b:D:dm:P:p:q:R:rT:t:v")) != -1) {
switch (ch) {
case '6':
ipv6_mode = 1;
break;
case 'A':
anonymous_only = 1;
break;
case 'a':
fixed_proxy = optarg;
break;
case 'b':
listen_ip = optarg;
break;
case 'D':
loglevel = strtonum(optarg, LOG_EMERG, LOG_DEBUG,
&errstr);
if (errstr)
errx(1, "loglevel %s", errstr);
break;
case 'd':
daemonize = 0;
break;
case 'm':
max_sessions = strtonum(optarg, 1, 500, &errstr);
if (errstr)
errx(1, "max sessions %s", errstr);
break;
case 'P':
fixed_server_port = optarg;
break;
case 'p':
listen_port = optarg;
break;
case 'q':
if (strlen(optarg) >= PF_QNAME_SIZE)
errx(1, "queuename too long");
qname = optarg;
break;
case 'R':
fixed_server = optarg;
break;
case 'r':
rfc_mode = 1;
break;
case 'T':
if (strlen(optarg) >= PF_TAG_NAME_SIZE)
errx(1, "tagname too long");
tagname = optarg;
break;
case 't':
timeout = strtonum(optarg, 0, 86400, &errstr);
if (errstr)
errx(1, "timeout %s", errstr);
break;
case 'v':
verbose++;
if (verbose > 2)
usage();
break;
default:
usage();
}
}
if (listen_ip == NULL)
listen_ip = ipv6_mode ? "::1" : "127.0.0.1";
/* Check for root to save the user from cryptic failure messages. */
if (getuid() != 0)
errx(1, "needs to start as root");
/* Raise max. open files limit to satisfy max. sessions. */
rlp.rlim_cur = rlp.rlim_max = (2 * max_sessions) + 10;
if (setrlimit(RLIMIT_NOFILE, &rlp) == -1)
err(1, "setrlimit");
if (fixed_proxy) {
memset(&hints, 0, sizeof hints);
hints.ai_flags = AI_NUMERICHOST;
hints.ai_family = ipv6_mode ? AF_INET6 : AF_INET;
hints.ai_socktype = SOCK_STREAM;
error = getaddrinfo(fixed_proxy, NULL, &hints, &res);
if (error)
errx(1, "getaddrinfo fixed proxy address failed: %s",
gai_strerror(error));
memcpy(&fixed_proxy_ss, res->ai_addr, res->ai_addrlen);
logmsg(LOG_INFO, "using %s to connect to servers",
sock_ntop(sstosa(&fixed_proxy_ss)));
freeaddrinfo(res);
}
if (fixed_server) {
memset(&hints, 0, sizeof hints);
hints.ai_family = ipv6_mode ? AF_INET6 : AF_INET;
hints.ai_socktype = SOCK_STREAM;
error = getaddrinfo(fixed_server, fixed_server_port, &hints,
&res);
if (error)
errx(1, "getaddrinfo fixed server address failed: %s",
gai_strerror(error));
memcpy(&fixed_server_ss, res->ai_addr, res->ai_addrlen);
logmsg(LOG_INFO, "using fixed server %s",
sock_ntop(sstosa(&fixed_server_ss)));
freeaddrinfo(res);
}
/* Setup listener. */
memset(&hints, 0, sizeof hints);
hints.ai_flags = AI_NUMERICHOST | AI_PASSIVE;
hints.ai_family = ipv6_mode ? AF_INET6 : AF_INET;
hints.ai_socktype = SOCK_STREAM;
error = getaddrinfo(listen_ip, listen_port, &hints, &res);
if (error)
errx(1, "getaddrinfo listen address failed: %s",
gai_strerror(error));
if ((listenfd = socket(res->ai_family, SOCK_STREAM, IPPROTO_TCP)) == -1)
errx(1, "socket failed");
on = 1;
if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, (void *)&on,
sizeof on) != 0)
err(1, "setsockopt failed");
if (bind(listenfd, (struct sockaddr *)res->ai_addr,
(socklen_t)res->ai_addrlen) != 0)
err(1, "bind failed");
if (listen(listenfd, TCP_BACKLOG) != 0)
err(1, "listen failed");
freeaddrinfo(res);
/* Initialize pf. */
init_filter(qname, tagname, verbose);
if (daemonize) {
if (daemon(0, 0) == -1)
err(1, "cannot daemonize");
openlog(__progname, LOG_PID | LOG_NDELAY, LOG_DAEMON);
}
/* Use logmsg for output from here on. */
if (!drop_privs()) {
logmsg(LOG_ERR, "cannot drop privileges: %s", strerror(errno));
exit(1);
}
event_init();
/* Setup signal handler. */
signal(SIGPIPE, SIG_IGN);
signal_set(&ev_sighup, SIGHUP, handle_signal, NULL);
signal_set(&ev_sigint, SIGINT, handle_signal, NULL);
signal_set(&ev_sigterm, SIGTERM, handle_signal, NULL);
signal_add(&ev_sighup, NULL);
signal_add(&ev_sigint, NULL);
signal_add(&ev_sigterm, NULL);
event_set(&ev, listenfd, EV_READ | EV_PERSIST, handle_connection, &ev);
event_add(&ev, NULL);
logmsg(LOG_NOTICE, "listening on %s port %s", listen_ip, listen_port);
/* Vroom, vroom. */
event_dispatch();
logmsg(LOG_ERR, "event_dispatch error: %s", strerror(errno));
exit_daemon();
/* NOTREACHED */
return (1);
}
u_int16_t
parse_port(int mode)
{
unsigned int port, v[6];
int n;
char *p;
/* Find the last space or left-parenthesis. */
for (p = linebuf + linelen; p > linebuf; p--)
if (*p == ' ' || *p == '(')
break;
if (p == linebuf)
return (0);
switch (mode) {
case CMD_PORT:
n = sscanf(p, " %u,%u,%u,%u,%u,%u", &v[0], &v[1], &v[2],
&v[3], &v[4], &v[5]);
if (n == 6 && v[0] < 256 && v[1] < 256 && v[2] < 256 &&
v[3] < 256 && v[4] < 256 && v[5] < 256)
return ((v[4] << 8) | v[5]);
break;
case CMD_PASV:
n = sscanf(p, "(%u,%u,%u,%u,%u,%u)", &v[0], &v[1], &v[2],
&v[3], &v[4], &v[5]);
if (n == 6 && v[0] < 256 && v[1] < 256 && v[2] < 256 &&
v[3] < 256 && v[4] < 256 && v[5] < 256)
return ((v[4] << 8) | v[5]);
break;
case CMD_EPSV:
n = sscanf(p, "(|||%u|)", &port);
if (n == 1 && port < 65536)
return (port);
break;
case CMD_EPRT:
n = sscanf(p, " |1|%u.%u.%u.%u|%u|", &v[0], &v[1], &v[2],
&v[3], &port);
if (n == 5 && v[0] < 256 && v[1] < 256 && v[2] < 256 &&
v[3] < 256 && port < 65536)
return (port);
n = sscanf(p, " |2|%*[a-fA-F0-9:]|%u|", &port);
if (n == 1 && port < 65536)
return (port);
break;
default:
return (0);
}
return (0);
}
u_int16_t
pick_proxy_port(void)
{
/* Random should be good enough for avoiding port collisions. */
return (IPPORT_HIFIRSTAUTO +
arc4random_uniform(IPPORT_HILASTAUTO - IPPORT_HIFIRSTAUTO));
}
void
proxy_reply(int cmd, struct sockaddr *sa, u_int16_t port)
{
int i, r;
switch (cmd) {
case CMD_PORT:
r = snprintf(linebuf, sizeof linebuf,
"PORT %s,%u,%u\r\n", sock_ntop(sa), port / 256,
port % 256);
break;
case CMD_PASV:
r = snprintf(linebuf, sizeof linebuf,
"227 Entering Passive Mode (%s,%u,%u)\r\n", sock_ntop(sa),
port / 256, port % 256);
break;
case CMD_EPRT:
if (sa->sa_family == AF_INET)
r = snprintf(linebuf, sizeof linebuf,
"EPRT |1|%s|%u|\r\n", sock_ntop(sa), port);
else if (sa->sa_family == AF_INET6)
r = snprintf(linebuf, sizeof linebuf,
"EPRT |2|%s|%u|\r\n", sock_ntop(sa), port);
break;
case CMD_EPSV:
r = snprintf(linebuf, sizeof linebuf,
"229 Entering Extended Passive Mode (|||%u|)\r\n", port);
break;
}
if (r < 0 || r >= sizeof linebuf) {
logmsg(LOG_ERR, "proxy_reply failed: %d", r);
linebuf[0] = '\0';
linelen = 0;
return;
}
linelen = (size_t)r;
if (cmd == CMD_PORT || cmd == CMD_PASV) {
/* Replace dots in IP address with commas. */
for (i = 0; i < linelen; i++)
if (linebuf[i] == '.')
linebuf[i] = ',';
}
}
void
server_error(struct bufferevent *bufev, short what, void *arg)
{
struct session *s = arg;
if (what & EVBUFFER_EOF)
logmsg(LOG_INFO, "#%d server close", s->id);
else if (what == (EVBUFFER_ERROR | EVBUFFER_READ))
logmsg(LOG_ERR, "#%d server refused connection", s->id);
else if (what & EVBUFFER_WRITE)
logmsg(LOG_ERR, "#%d server write error: %d", s->id, what);
else if (what & EVBUFFER_TIMEOUT)
logmsg(LOG_NOTICE, "#%d server timeout", s->id);
else
logmsg(LOG_ERR, "#%d abnormal server error: %d", s->id, what);
end_session(s);
}
int
server_parse(struct session *s)
{
if (s->cmd == CMD_NONE || linelen < 4 || linebuf[0] != '2')
goto out;
if ((s->cmd == CMD_PASV && strncmp("227 ", linebuf, 4) == 0) ||
(s->cmd == CMD_EPSV && strncmp("229 ", linebuf, 4) == 0))
return (allow_data_connection(s));
out:
s->cmd = CMD_NONE;
s->port = 0;
return (1);
}
int
allow_data_connection(struct session *s)
{
struct sockaddr *client_sa, *orig_sa, *proxy_sa, *server_sa;
int prepared = 0;
/*
* The pf rules below do quite some NAT rewriting, to keep up
* appearances. Points to keep in mind:
* 1) The client must think it's talking to the real server,
* for both control and data connections. Transparently.
* 2) The server must think that the proxy is the client.
* 3) Source and destination ports are rewritten to minimize
* port collisions, to aid security (some systems pick weak
* ports) or to satisfy RFC requirements (source port 20).
*/
/* Cast this once, to make code below it more readable. */
client_sa = sstosa(&s->client_ss);
server_sa = sstosa(&s->server_ss);
proxy_sa = sstosa(&s->proxy_ss);
if (fixed_server)
/* Fixed server: data connections must appear to come
from / go to the original server, not the fixed one. */
orig_sa = sstosa(&s->orig_server_ss);
else
/* Server not fixed: orig_server == server. */
orig_sa = sstosa(&s->server_ss);
/* Passive modes. */
if (s->cmd == CMD_PASV || s->cmd == CMD_EPSV) {
s->port = parse_port(s->cmd);
if (s->port < MIN_PORT) {
logmsg(LOG_CRIT, "#%d bad port in '%s'", s->id,
linebuf);
return (0);
}
s->proxy_port = pick_proxy_port();
logmsg(LOG_INFO, "#%d passive: client to server port %d"
" via port %d", s->id, s->port, s->proxy_port);
if (prepare_commit(s->id) == -1)
goto fail;
prepared = 1;
proxy_reply(s->cmd, orig_sa, s->proxy_port);
logmsg(LOG_DEBUG, "#%d proxy: %s", s->id, linebuf);
/* rdr from $client to $orig_server port $proxy_port -> $server
port $port */
if (add_rdr(s->id, client_sa, orig_sa, s->proxy_port,
server_sa, s->port) == -1)
goto fail;
/* nat from $client to $server port $port -> $proxy */
if (add_nat(s->id, client_sa, server_sa, s->port, proxy_sa,
PF_NAT_PROXY_PORT_LOW, PF_NAT_PROXY_PORT_HIGH) == -1)
goto fail;
/* pass in from $client to $server port $port */
if (add_filter(s->id, PF_IN, client_sa, server_sa,
s->port) == -1)
goto fail;
/* pass out from $proxy to $server port $port */
if (add_filter(s->id, PF_OUT, proxy_sa, server_sa,
s->port) == -1)
goto fail;
}
/* Active modes. */
if (s->cmd == CMD_PORT || s->cmd == CMD_EPRT) {
logmsg(LOG_INFO, "#%d active: server to client port %d"
" via port %d", s->id, s->port, s->proxy_port);
if (prepare_commit(s->id) == -1)
goto fail;
prepared = 1;
/* rdr from $server to $proxy port $proxy_port -> $client port
$port */
if (add_rdr(s->id, server_sa, proxy_sa, s->proxy_port,
client_sa, s->port) == -1)
goto fail;
/* nat from $server to $client port $port -> $orig_server port
$natport */
if (rfc_mode && s->cmd == CMD_PORT) {
/* Rewrite sourceport to RFC mandated 20. */
if (add_nat(s->id, server_sa, client_sa, s->port,
orig_sa, 20, 20) == -1)
goto fail;
} else {
/* Let pf pick a source port from the standard range. */
if (add_nat(s->id, server_sa, client_sa, s->port,
orig_sa, PF_NAT_PROXY_PORT_LOW,
PF_NAT_PROXY_PORT_HIGH) == -1)
goto fail;
}
/* pass in from $server to $client port $port */
if (add_filter(s->id, PF_IN, server_sa, client_sa, s->port) ==
-1)
goto fail;
/* pass out from $orig_server to $client port $port */
if (add_filter(s->id, PF_OUT, orig_sa, client_sa, s->port) ==
-1)
goto fail;
}
/* Commit rules if they were prepared. */
if (prepared && (do_commit() == -1)) {
if (errno != EBUSY)
goto fail;
/* One more try if busy. */
usleep(5000);
if (do_commit() == -1)
goto fail;
}
s->cmd = CMD_NONE;
s->port = 0;
return (1);
fail:
logmsg(LOG_CRIT, "#%d pf operation failed: %s", s->id, strerror(errno));
if (prepared)
do_rollback();
return (0);
}
void
server_read(struct bufferevent *bufev, void *arg)
{
struct session *s = arg;
size_t buf_avail, read;
int n;
bufferevent_settimeout(bufev, timeout, 0);
do {
buf_avail = sizeof s->sbuf - s->sbuf_valid;
read = bufferevent_read(bufev, s->sbuf + s->sbuf_valid,
buf_avail);
s->sbuf_valid += read;
while ((n = getline(s->sbuf, &s->sbuf_valid)) > 0) {
logmsg(LOG_DEBUG, "#%d server: %s", s->id, linebuf);
if (!server_parse(s)) {
end_session(s);
return;
}
bufferevent_write(s->client_bufev, linebuf, linelen);
}
if (n == -1) {
logmsg(LOG_ERR, "#%d server reply too long or not"
" clean", s->id);
end_session(s);
return;
}
} while (read == buf_avail);
}
const char *
sock_ntop(struct sockaddr *sa)
{
static int n = 0;
/* Cycle to next buffer. */
n = (n + 1) % NTOP_BUFS;
ntop_buf[n][0] = '\0';
if (sa->sa_family == AF_INET) {
struct sockaddr_in *sin = (struct sockaddr_in *)sa;
return (inet_ntop(AF_INET, &sin->sin_addr, ntop_buf[n],
sizeof ntop_buf[0]));
}
if (sa->sa_family == AF_INET6) {
struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa;
return (inet_ntop(AF_INET6, &sin6->sin6_addr, ntop_buf[n],
sizeof ntop_buf[0]));
}
return (NULL);
}
void
usage(void)
{
fprintf(stderr, "usage: %s [-6Adrv] [-a address] [-b address]"
" [-D level] [-m maxsessions]\n [-P port]"
" [-p port] [-q queue] [-R address] [-T tag]\n"
" [-t timeout]\n", __progname);
exit(1);
}