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--;
}
int
main(int argc, char *argv[])
{
int c, fd = 0, on = 1, out_fd = 0, peer, reqsize = 0;
int transwait = DEFTRANSWAIT;
char *p;
struct tftphdr *tp;
struct passwd *pw;
size_t cbuflen;
char *cbuf;
char req[PKTSIZE];
struct cmsghdr *cmsg;
struct msghdr msg;
struct iovec iov;
struct sockaddr_storage from, proxy, server, proxy_to_server, s_in;
struct sockaddr_in sock_out;
socklen_t j;
in_port_t bindport;
openlog(__progname, LOG_PID | LOG_NDELAY, LOG_DAEMON);
while ((c = getopt(argc, argv, "vw:")) != -1)
switch (c) {
case 'v':
verbose++;
break;
case 'w':
transwait = strtoll(optarg, &p, 10);
if (transwait < 1) {
syslog(LOG_ERR, "invalid -w value");
exit(1);
}
break;
default:
usage();
break;
}
/* open /dev/pf */
init_filter(NULL, verbose);
tzset();
pw = getpwnam(NOPRIV_USER);
if (!pw) {
syslog(LOG_ERR, "no such user %s: %m", NOPRIV_USER);
exit(1);
}
if (chroot(CHROOT_DIR) || chdir("/")) {
syslog(LOG_ERR, "chroot %s: %m", CHROOT_DIR);
exit(1);
}
#ifdef __NetBSD__
if (setgroups(1, &pw->pw_gid) ||
setgid(pw->pw_gid) ||
setuid(pw->pw_uid)) {
syslog(LOG_ERR, "can't revoke privs: %m");
exit(1);
}
#else
if (setgroups(1, &pw->pw_gid) ||
setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid)) {
syslog(LOG_ERR, "can't revoke privs: %m");
exit(1);
}
#endif /* !__NetBSD__ */
/* non-blocking io */
if (ioctl(fd, FIONBIO, &on) < 0) {
syslog(LOG_ERR, "ioctl(FIONBIO): %m");
exit(1);
}
if (setsockopt(fd, IPPROTO_IP, IP_RECVDSTADDR, &on, sizeof(on)) == -1) {
syslog(LOG_ERR, "setsockopt(IP_RECVDSTADDR): %m");
exit(1);
}
j = sizeof(s_in);
if (getsockname(fd, (struct sockaddr *)&s_in, &j) == -1) {
syslog(LOG_ERR, "getsockname: %m");
exit(1);
}
bindport = ((struct sockaddr_in *)&s_in)->sin_port;
/* req will be pushed back out at the end, unchanged */
j = sizeof(from);
if ((reqsize = recvfrom(fd, req, sizeof(req), MSG_PEEK,
(struct sockaddr *)&from, &j)) < 0) {
syslog(LOG_ERR, "recvfrom: %m");
exit(1);
}
bzero(&msg, sizeof(msg));
iov.iov_base = req;
iov.iov_len = sizeof(req);
msg.msg_name = &from;
msg.msg_namelen = sizeof(from);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
cbuflen = CMSG_SPACE(sizeof(struct sockaddr_storage));
if ((cbuf = malloc(cbuflen)) == NULL) {
syslog(LOG_ERR, "malloc: %m");
exit(1);
}
msg.msg_control = cbuf;
msg.msg_controllen = cbuflen;
if (recvmsg(fd, &msg, 0) < 0) {
syslog(LOG_ERR, "recvmsg: %m");
exit(1);
}
close(fd);
close(1);
peer = socket(from.ss_family, SOCK_DGRAM, 0);
if (peer < 0) {
syslog(LOG_ERR, "socket: %m");
exit(1);
}
memset(&s_in, 0, sizeof(s_in));
s_in.ss_family = from.ss_family;
s_in.ss_len = from.ss_len;
/* get local address if possible */
for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
cmsg = CMSG_NXTHDR(&msg, cmsg)) {
if (cmsg->cmsg_level == IPPROTO_IP &&
cmsg->cmsg_type == IP_RECVDSTADDR) {
memcpy(&((struct sockaddr_in *)&s_in)->sin_addr,
CMSG_DATA(cmsg), sizeof(struct in_addr));
break;
}
}
if (bind(peer, (struct sockaddr *)&s_in, s_in.ss_len) < 0) {
syslog(LOG_ERR, "bind: %m");
exit(1);
}
if (connect(peer, (struct sockaddr *)&from, from.ss_len) < 0) {
syslog(LOG_ERR, "connect: %m");
exit(1);
}
tp = (struct tftphdr *)req;
if (!(ntohs(tp->th_opcode) == RRQ || ntohs(tp->th_opcode) == WRQ)) {
/* not a tftp request, bail */
if (verbose) {
syslog(LOG_WARNING, "not a valid tftp request");
exit(1);
} else
/* exit 0 so inetd doesn't log anything */
exit(0);
}
j = sizeof(struct sockaddr_storage);
if (getsockname(fd, (struct sockaddr *)&proxy, &j) == -1) {
syslog(LOG_ERR, "getsockname: %m");
exit(1);
}
((struct sockaddr_in *)&proxy)->sin_port = bindport;
/* find the un-rdr'd server and port the client wanted */
if (server_lookup((struct sockaddr *)&from,
(struct sockaddr *)&proxy, (struct sockaddr *)&server,
IPPROTO_UDP) != 0) {
syslog(LOG_ERR, "pf connection lookup failed (no rdr?)");
exit(1);
}
/* establish a new outbound connection to the remote server */
if ((out_fd = socket(((struct sockaddr *)&from)->sa_family,
SOCK_DGRAM, IPPROTO_UDP)) < 0) {
syslog(LOG_ERR, "couldn't create new socket");
exit(1);
}
bzero((char *)&sock_out, sizeof(sock_out));
sock_out.sin_family = from.ss_family;
sock_out.sin_port = htons(pick_proxy_port());
if (bind(out_fd, (struct sockaddr *)&sock_out, sizeof(sock_out)) < 0) {
syslog(LOG_ERR, "couldn't bind to new socket: %m");
exit(1);
}
if (connect(out_fd, (struct sockaddr *)&server,
((struct sockaddr *)&server)->sa_len) < 0 && errno != EINPROGRESS) {
syslog(LOG_ERR, "couldn't connect to remote server: %m");
exit(1);
}
j = sizeof(struct sockaddr_storage);
if ((getsockname(out_fd, (struct sockaddr *)&proxy_to_server,
&j)) < 0) {
syslog(LOG_ERR, "getsockname: %m");
exit(1);
}
if (verbose)
syslog(LOG_INFO, "%s:%d -> %s:%d/%s:%d -> %s:%d \"%s %s\"",
sock_ntop((struct sockaddr *)&from),
ntohs(((struct sockaddr_in *)&from)->sin_port),
sock_ntop((struct sockaddr *)&proxy),
ntohs(((struct sockaddr_in *)&proxy)->sin_port),
sock_ntop((struct sockaddr *)&proxy_to_server),
ntohs(((struct sockaddr_in *)&proxy_to_server)->sin_port),
sock_ntop((struct sockaddr *)&server),
ntohs(((struct sockaddr_in *)&server)->sin_port),
opcode(ntohs(tp->th_opcode)),
tp->th_stuff);
/* get ready to add rdr and pass rules */
if (prepare_commit(1) == -1) {
syslog(LOG_ERR, "couldn't prepare pf commit");
exit(1);
}
/* rdr from server to us on our random port -> client on its port */
if (add_rdr(1, (struct sockaddr *)&server,
(struct sockaddr *)&proxy_to_server, ntohs(sock_out.sin_port),
(struct sockaddr *)&from,
ntohs(((struct sockaddr_in *)&from)->sin_port),
IPPROTO_UDP) == -1) {
syslog(LOG_ERR, "couldn't add rdr");
exit(1);
}
/* explicitly allow the packets to return back to the client (which pf
* will see post-rdr) */
if (add_filter(1, PF_IN, (struct sockaddr *)&server,
(struct sockaddr *)&from,
ntohs(((struct sockaddr_in *)&from)->sin_port),
IPPROTO_UDP) == -1) {
syslog(LOG_ERR, "couldn't add pass in");
exit(1);
}
if (add_filter(1, PF_OUT, (struct sockaddr *)&server,
(struct sockaddr *)&from,
ntohs(((struct sockaddr_in *)&from)->sin_port),
IPPROTO_UDP) == -1) {
syslog(LOG_ERR, "couldn't add pass out");
exit(1);
}
/* and just in case, to pass out from us to the server */
if (add_filter(1, PF_OUT, (struct sockaddr *)&proxy_to_server,
(struct sockaddr *)&server,
ntohs(((struct sockaddr_in *)&server)->sin_port),
IPPROTO_UDP) == -1) {
syslog(LOG_ERR, "couldn't add pass out");
exit(1);
}
if (do_commit() == -1) {
syslog(LOG_ERR, "couldn't commit pf rules");
exit(1);
}
/* forward the initial tftp request and start the insanity */
if (send(out_fd, tp, reqsize, 0) < 0) {
syslog(LOG_ERR, "couldn't forward tftp packet: %m");
exit(1);
}
/* allow the transfer to start to establish a state */
sleep(transwait);
/* delete our rdr rule and clean up */
prepare_commit(1);
do_commit();
return(0);
}
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);
/* pass in from $client to $orig_server port $proxy_port
rdr-to $server port $port */
if (add_rdr(s->id, client_sa, s->client_rd, orig_sa,
s->proxy_port, server_sa, s->port, getrtable()) == -1)
goto fail;
/* pass out from $client to $server port $port nat-to $proxy */
if (add_nat(s->id, client_sa, getrtable(), server_sa,
s->port, proxy_sa, PF_NAT_PROXY_PORT_LOW,
PF_NAT_PROXY_PORT_HIGH) == -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;
/* pass in from $server to $proxy port $proxy_port
rdr-to $client port $port */
if (add_rdr(s->id, server_sa, getrtable(), proxy_sa,
s->proxy_port, client_sa, s->port, s->client_rd) == -1)
goto fail;
/* pass out from $server to $client port $port
nat-to $orig_server port $natport */
if (rfc_mode && s->cmd == CMD_PORT) {
/* Rewrite sourceport to RFC mandated 20. */
if (add_nat(s->id, server_sa, s->client_rd, 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, s->client_rd, client_sa,
s->port, orig_sa, PF_NAT_PROXY_PORT_LOW,
PF_NAT_PROXY_PORT_HIGH) == -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);
}
