blob: fc29274d219c29afca52be3ee9b431eb38eb1feb [file] [log] [blame]
/* Based on ipsvd utilities written by Gerrit Pape <>
* which are released into public domain by the author.
* Homepage:
* Copyright (C) 2007 Denis Vlasenko.
* Licensed under GPLv2, see file LICENSE in this tarball for details.
/* Based on ipsvd ipsvd-0.12.1. This tcpsvd accepts all options
* which are supported by one from ipsvd-0.12.1, but not all are
* functional. See help text at the end of this file for details.
* Code inside "#ifdef SSLSVD" is for sslsvd and is currently unused.
* Output of verbose mode matches original (modulo bugs and
* unimplemented stuff). Unnatural splitting of IP and PORT
* is retained (personally I prefer one-value "IP:PORT" notation -
* it is a natural string representation of struct sockaddr_XX).
* TCPORIGDST{IP,PORT} is busybox-specific addition
* udp server is hacked up by reusing TCP code. It has the following
* limitation inherent in Unix DGRAM sockets implementation:
* - local IP address is retrieved (using recvmsg voodoo) but
* child's socket is not bound to it (bind cannot be called on
* already bound socket). Thus it still can emit outgoing packets
* with wrong source IP...
* - don't know how to retrieve ORIGDST for udp.
#include <limits.h>
#include <linux/netfilter_ipv4.h> /* wants <limits.h> */
#include "libbb.h"
#include "ipsvd_perhost.h"
#ifdef SSLSVD
#include "matrixSsl.h"
#include "ssl_io.h"
struct globals {
unsigned verbose;
unsigned max_per_host;
unsigned cur_per_host;
unsigned cnum;
unsigned cmax;
#define G (*(struct globals*)&bb_common_bufsiz1)
#define verbose (G.verbose )
#define max_per_host (G.max_per_host)
#define cur_per_host (G.cur_per_host)
#define cnum (G.cnum )
#define cmax (G.cmax )
#define INIT_G() \
do { \
cmax = 30; \
} while (0)
static void xsetenv_proto(const char *proto, const char *n, const char *v)
putenv(xasprintf("%s%s=%s", proto, n, v));
static void sig_term_handler(int sig)
if (verbose)
printf("%s: info: sigterm received, exit\n", applet_name);
/* Little bloated, but tries to give accurate info how child exited.
* Makes easier to spot segfaulting children etc... */
static void print_waitstat(unsigned pid, int wstat)
unsigned e = 0;
const char *cause = "?exit";
if (WIFEXITED(wstat)) {
e = WEXITSTATUS(wstat);
} else if (WIFSIGNALED(wstat)) {
cause = "signal";
e = WTERMSIG(wstat);
printf("%s: info: end %d %s %d\n", applet_name, pid, cause, e);
/* Must match getopt32 in main! */
enum {
OPT_c = (1 << 0),
OPT_C = (1 << 1),
OPT_i = (1 << 2),
OPT_x = (1 << 3),
OPT_u = (1 << 4),
OPT_l = (1 << 5),
OPT_E = (1 << 6),
OPT_b = (1 << 7),
OPT_h = (1 << 8),
OPT_p = (1 << 9),
OPT_t = (1 << 10),
OPT_v = (1 << 11),
OPT_V = (1 << 12),
OPT_U = (1 << 13), /* from here: sslsvd only */
OPT_slash = (1 << 14),
OPT_Z = (1 << 15),
OPT_K = (1 << 16),
static void connection_status(void)
/* "only 1 client max" desn't need this */
if (cmax > 1)
printf("%s: info: status %u/%u\n", applet_name, cnum, cmax);
static void sig_child_handler(int sig)
int wstat;
int pid;
while ((pid = wait_nohang(&wstat)) > 0) {
if (max_per_host)
if (cnum)
if (verbose)
print_waitstat(pid, wstat);
if (verbose)
int tcpudpsvd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tcpudpsvd_main(int argc, char **argv)
char *str_c, *str_C, *str_b, *str_t;
char *user;
struct hcc *hccp;
const char *instructs;
char *msg_per_host = NULL;
unsigned len_per_host = len_per_host; /* gcc */
#ifndef SSLSVD
struct bb_uidgid_t ugid;
bool need_hostnames, need_remote_ip, tcp;
uint16_t local_port;
char *local_hostname = NULL;
char *remote_hostname = (char*)""; /* "" used if no -h */
char *local_addr = local_addr; /* gcc */
char *remote_addr = remote_addr; /* gcc */
char *remote_ip = remote_addr; /* gcc */
len_and_sockaddr *lsa;
len_and_sockaddr local, remote;
socklen_t sa_len;
int pid;
int sock;
int conn;
unsigned backlog = 20;
tcp = (applet_name[0] == 't');
/* 3+ args, -i at most once, -p implies -h, -v is counter */
opt_complementary = "-3:i--i:ph:vv";
#ifdef SSLSVD
getopt32(argv, "+c:C:i:x:u:l:Eb:hpt:vU:/:Z:K:",
&str_c, &str_C, &instructs, &instructs, &user, &local_hostname,
&str_b, &str_t, &ssluser, &root, &cert, &key, &verbose
getopt32(argv, "+c:C:i:x:u:l:Eb:hpt:v",
&str_c, &str_C, &instructs, &instructs, &user, &local_hostname,
&str_b, &str_t, &verbose
if (option_mask32 & OPT_c)
cmax = xatou_range(str_c, 1, INT_MAX);
if (option_mask32 & OPT_C) { /* -C n[:message] */
max_per_host = bb_strtou(str_C, &str_C, 10);
if (str_C[0]) {
if (str_C[0] != ':')
msg_per_host = str_C + 1;
len_per_host = strlen(msg_per_host);
if (max_per_host > cmax)
max_per_host = cmax;
if (option_mask32 & OPT_u) {
if (!get_uidgid(&ugid, user, 1))
bb_error_msg_and_die("unknown user/group: %s", user);
if (option_mask32 & OPT_b)
backlog = xatou(str_b);
#ifdef SSLSVD
if (option_mask32 & OPT_U) ssluser = optarg;
if (option_mask32 & OPT_slash) root = optarg;
if (option_mask32 & OPT_Z) cert = optarg;
if (option_mask32 & OPT_K) key = optarg;
argv += optind;
if (!argv[0][0] || LONE_CHAR(argv[0], '0'))
argv[0] = (char*)"";
/* Per-IP flood protection is not thought-out for UDP */
if (!tcp)
max_per_host = 0;
/* stdout is used for logging, don't buffer */
bb_sanitize_stdio(); /* fd# 0,1,2 must be opened */
need_hostnames = verbose || !(option_mask32 & OPT_E);
need_remote_ip = max_per_host || need_hostnames;
#ifdef SSLSVD
sslser = user;
client = 0;
if ((getuid() == 0) && !(option_mask32 & OPT_u)) {
xfunc_exitcode = 100;
bb_error_msg_and_die("fatal: -U ssluser must be set when running as root");
if (option_mask32 & OPT_u)
if (!uidgid_get(&sslugid, ssluser, 1)) {
if (errno) {
bb_perror_msg_and_die("fatal: cannot get user/group: %s", ssluser);
bb_error_msg_and_die("fatal: unknown user/group '%s'", ssluser);
if (!cert) cert = "./cert.pem";
if (!key) key = cert;
if (matrixSslOpen() < 0)
fatal("cannot initialize ssl");
if (matrixSslReadKeys(&keys, cert, key, 0, ca) < 0) {
if (client)
fatal("cannot read cert, key, or ca file");
fatal("cannot read cert or key file");
if (matrixSslNewSession(&ssl, keys, 0, SSL_FLAGS_SERVER) < 0)
fatal("cannot create ssl session");
signal(SIGCHLD, sig_child_handler);
signal(SIGTERM, sig_term_handler);
if (max_per_host)
local_port = bb_lookup_port(argv[1], tcp ? "tcp" : "udp", 0);
lsa = xhost2sockaddr(argv[0], local_port);
sock = xsocket(lsa->sa.sa_family, tcp ? SOCK_STREAM : SOCK_DGRAM, 0);
sa_len = lsa->len; /* I presume sockaddr len stays the same */
xbind(sock, &lsa->sa, sa_len);
if (tcp)
xlisten(sock, backlog);
else /* udp: needed for recv_from_to to work: */
/* ndelay_off(sock); - it is the default I think? */
#ifndef SSLSVD
if (option_mask32 & OPT_u) {
/* drop permissions */
if (verbose) {
char *addr = xmalloc_sockaddr2dotted(&lsa->sa);
printf("%s: info: listening on %s", applet_name, addr);
#ifndef SSLSVD
if (option_mask32 & OPT_u)
printf(", uid %u, gid %u",
(unsigned)ugid.uid, (unsigned)ugid.gid);
puts(", starting");
/* Main accept() loop */
hccp = NULL;
while (cnum >= cmax)
sig_pause(); /* wait for any signal (expecting SIGCHLD) */
/* Accept a connection to fd #0 */
if (tcp) {
remote.len = sa_len;
conn = accept(sock, &, &remote.len);
} else {
/* In case recv_from_to won't be able to recover local addr.
* Also sets port - recv_from_to is unable to do it. */
local = *lsa;
conn = recv_from_to(sock, NULL, 0, MSG_PEEK, &, &, sa_len);
if (conn < 0) {
if (errno != EINTR)
bb_perror_msg(tcp ? "accept" : "recv");
goto again2;
xmove_fd(tcp ? conn : sock, 0);
if (max_per_host) {
/* Drop connection immediately if cur_per_host > max_per_host
* (minimizing load under SYN flood) */
remote_ip = xmalloc_sockaddr2dotted_noport(&;
cur_per_host = ipsvd_perhost_add(remote_ip, max_per_host, &hccp);
if (cur_per_host > max_per_host) {
/* ipsvd_perhost_add detected that max is exceeded
* (and did not store ip in connection table) */
if (msg_per_host) {
/* don't block or test for errors */
write(0, msg_per_host, len_per_host);
goto again1;
if (!tcp) {
/* Voodoo magic: making udp sockets each receive its own
* packets is not trivial, and I still not sure
* I do it 100% right.
* 1) we have to do it before fork()
* 2) order is important - is it right now? */
/* Make plain write/send work for this socket by supplying default
* destination address. This also restricts incoming packets
* to ones coming from this remote IP. */
xconnect(0, &, sa_len);
/* hole? at this point we have no wildcard udp socket...
* can this cause clients to get "port unreachable" icmp?
* Yup, time window is very small, but it exists (is it?) */
/* Open new non-connected UDP socket for further clients */
sock = xsocket(lsa->sa.sa_family, tcp ? SOCK_STREAM : SOCK_DGRAM, 0);
xbind(sock, &lsa->sa, sa_len);
/* Doesn't work:
* we cannot replace fd #0 - we will lose pending packet
* which is already buffered for us! And we cannot use fd #1
* instead - it will "intercept" all following packets, but child
* does not expect data coming *from fd #1*! */
#if 0
/* Make it so that local addr is fixed to localp->sa
* and we don't accidentally accept packets to other local IPs. */
/* NB: we possibly bind to the _very_ same_ address & port as the one
* already bound in parent! This seems to work in Linux.
* (otherwise we can move socket to fd #0 only if bind succeeds) */
set_nport(localp, htons(local_port));
xmove_fd(xsocket(localp->sa.sa_family, SOCK_DGRAM, 0), 0);
setsockopt_reuseaddr(0); /* crucial */
xbind(0, &localp->sa, localp->len);
pid = fork();
if (pid == -1) {
goto again;
if (pid != 0) {
/* parent */
if (verbose)
if (hccp)
hccp->pid = pid;
goto again;
/* Child: prepare env, log, and exec prog */
/* Closing tcp listening socket */
if (tcp)
if (need_remote_ip)
remote_addr = xmalloc_sockaddr2dotted(&;
if (need_hostnames) {
if (option_mask32 & OPT_h) {
remote_hostname = xmalloc_sockaddr2host_noport(&;
if (!remote_hostname) {
bb_error_msg("warning: cannot look up hostname for %s", remote_addr);
remote_hostname = (char*)"";
/* Find out local IP peer connected to.
* Errors ignored (I'm not paranoid enough to imagine kernel
* which doesn't know local IP). */
if (tcp) {
local.len = sa_len;
getsockname(0, &, &local.len);
local_addr = xmalloc_sockaddr2dotted(&;
if (!local_hostname) {
local_hostname = xmalloc_sockaddr2host_noport(&;
if (!local_hostname)
bb_error_msg_and_die("warning: cannot look up hostname for %s"+9, local_addr);
if (verbose) {
pid = getpid();
printf("%s: info: pid %u from %s\n", applet_name, pid, remote_addr);
if (max_per_host)
printf("%s: info: concurrency %u %s %u/%u\n",
applet_name, pid, remote_ip, cur_per_host, max_per_host);
printf("%s: info: start %u %s:%s :%s:%s\n",
applet_name, pid,
local_hostname, local_addr,
remote_hostname, remote_addr);
if (!(option_mask32 & OPT_E)) {
/* setup ucspi env */
const char *proto = tcp ? "TCP" : "UDP";
/* Extract "original" destination addr:port
* from Linux firewall. Useful when you redirect
* an outbond connection to local handler, and it needs
* to know where it originally tried to connect */
if (tcp && getsockopt(0, SOL_IP, SO_ORIGINAL_DST, &lsa->sa, &lsa->len) == 0) {
char *addr = xmalloc_sockaddr2dotted(&lsa->sa);
xsetenv("TCPORIGDSTADDR", addr);
xsetenv("PROTO", proto);
xsetenv_proto(proto, "LOCALADDR", local_addr);
xsetenv_proto(proto, "LOCALHOST", local_hostname);
xsetenv_proto(proto, "REMOTEADDR", remote_addr);
if (option_mask32 & OPT_h) {
xsetenv_proto(proto, "REMOTEHOST", remote_hostname);
xsetenv_proto(proto, "REMOTEINFO", "");
/* additional */
if (cur_per_host > 0) /* can not be true for udp */
xsetenv("TCPCONCURRENCY", utoa(cur_per_host));
dup2(0, 1);
argv += 2;
#ifdef SSLSVD
strcpy(id, utoa(pid);
ssl_io(0, argv);
BB_EXECVP(argv[0], argv);
bb_perror_msg_and_die("exec '%s'", argv[0]);
tcpsvd [-hpEvv] [-c n] [-C n:msg] [-b n] [-u user] [-l name]
[-i dir|-x cdb] [ -t sec] host port prog
tcpsvd creates a TCP/IP socket, binds it to the address host:port,
and listens on the socket for incoming connections.
On each incoming connection, tcpsvd conditionally runs a program,
with standard input reading from the socket, and standard output
writing to the socket, to handle this connection. tcpsvd keeps
listening on the socket for new connections, and can handle
multiple connections simultaneously.
tcpsvd optionally checks for special instructions depending
on the IP address or hostname of the client that initiated
the connection, see ipsvd-instruct(5).
host either is a hostname, or a dotted-decimal IP address,
or 0. If host is 0, tcpsvd accepts connections to any local
IP address.
* busybox accepts IPv6 addresses and host:port pairs too
In this case second parameter is ignored
tcpsvd accepts connections to host:port. port may be a name
from /etc/services or a number.
prog consists of one or more arguments. For each connection,
tcpsvd normally runs prog, with file descriptor 0 reading from
the network, and file descriptor 1 writing to the network.
By default it also sets up TCP-related environment variables,
see tcp-environ(5)
-i dir
read instructions for handling new connections from the instructions
directory dir. See ipsvd-instruct(5) for details.
* ignored by busyboxed version
-x cdb
read instructions for handling new connections from the constant database
cdb. The constant database normally is created from an instructions
directory by running ipsvd-cdb(8).
* ignored by busyboxed version
-t sec
timeout. This option only takes effect if the -i option is given.
While checking the instructions directory, check the time of last access
of the file that matches the clients address or hostname if any, discard
and remove the file if it wasn't accessed within the last sec seconds;
tcpsvd does not discard or remove a file if the user's write permission
is not set, for those files the timeout is disabled. Default is 0,
which means that the timeout is disabled.
* ignored by busyboxed version
-l name
local hostname. Do not look up the local hostname in DNS, but use name
as hostname. This option must be set if tcpsvd listens on port 53
to avoid loops.
-u user[:group]
drop permissions. Switch user ID to user's UID, and group ID to user's
primary GID after creating and binding to the socket. If user is followed
by a colon and a group name, the group ID is switched to the GID of group
instead. All supplementary groups are removed.
-c n
concurrency. Handle up to n connections simultaneously. Default is 30.
If there are n connections active, tcpsvd defers acceptance of a new
connection until an active connection is closed.
-C n[:msg]
per host concurrency. Allow only up to n connections from the same IP
address simultaneously. If there are n active connections from one IP
address, new incoming connections from this IP address are closed
immediately. If n is followed by :msg, the message msg is written
to the client if possible, before closing the connection. By default
msg is empty. See ipsvd-instruct(5) for supported escape sequences in msg.
For each accepted connection, the current per host concurrency is
available through the environment variable TCPCONCURRENCY. n and msg
can be overwritten by ipsvd(7) instructions, see ipsvd-instruct(5).
By default tcpsvd doesn't keep track of connections.
Look up the client's hostname in DNS.
paranoid. After looking up the client's hostname in DNS, look up the IP
addresses in DNS for that hostname, and forget about the hostname
if none of the addresses match the client's IP address. You should
set this option if you use hostname based instructions. The -p option
implies the -h option.
* ignored by busyboxed version
-b n
backlog. Allow a backlog of approximately n TCP SYNs. On some systems n
is silently limited. Default is 20.
no special environment. Do not set up TCP-related environment variables.
verbose. Print verbose messsages to standard output.
more verbose. Print more verbose messages to standard output.
* no difference between -v and -vv in busyboxed version