ipsvd/udpsvd.c - codeaurora/busybox - Gitiles

 /* Based on ipsvd utilities written by Gerrit Pape <pape@smarden.org>
  * which are released into public domain by the author.
  * Homepage: http://smarden.sunsite.dk/ipsvd/
  *
  * 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 #if 0" is parts of original tcpsvd which are not implemented
  * for busyboxed version.
  *
  * 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).
  */

 #include "busybox.h"

 #include "udp_io.c"

 unsigned verbose;

 static void sig_term_handler(int sig)
 {
 	if (verbose)
 		printf("%s: info: sigterm received, exit\n", applet_name);
 	exit(0);
 }

 int udpsvd_main(int argc, char **argv);
 int udpsvd_main(int argc, char **argv)
 {
 	const char *instructs;
 	char *str_t, *user;
 	unsigned opt;

 	char *remote_hostname;
 	char *local_hostname = NULL;
 	char *remote_ip;
 	char *local_ip = local_ip; /* gcc */
 	uint16_t local_port, remote_port;
 	len_and_sockaddr remote;
 	len_and_sockaddr *localp;
 	int sock;
 	int wstat;
 	unsigned pid;
 	struct bb_uidgid_t ugid;

 	enum {
 		OPT_v = (1 << 0),
 		OPT_u = (1 << 1),
 		OPT_l = (1 << 2),
 		OPT_h = (1 << 3),
 		OPT_p = (1 << 4),
 		OPT_i = (1 << 5),
 		OPT_x = (1 << 6),
 		OPT_t = (1 << 7),
 	};

 	opt_complementary = "-3:ph:vv";
 	opt = getopt32(argc, argv, "vu:l:hpi:x:t:",
 			&user, &local_hostname, &instructs, &instructs, &str_t, &verbose);
 	//if (opt & OPT_x) iscdb =1;
 	//if (opt & OPT_t) timeout = xatou(str_t);
 	if (!(opt & OPT_h))
 		remote_hostname = (char *)"";
 	if (opt & OPT_u) {
 		if (!get_uidgid(&ugid, user, 1))
 			bb_error_msg_and_die("unknown user/group: %s", user);
 	}
 	argv += optind;
 	if (!argv[0][0] || LONE_CHAR(argv[0], '0'))
 		argv[0] = (char*)"0.0.0.0";

 	/* stdout is used for logging, don't buffer */
 	setlinebuf(stdout);
 	bb_sanitize_stdio(); /* fd# 1,2 must be opened */

 	signal(SIGTERM, sig_term_handler);
 	signal(SIGPIPE, SIG_IGN);

 	local_port = bb_lookup_port(argv[1], "udp", 0);
 	localp = xhost2sockaddr(argv[0], local_port);
 	sock = xsocket(localp->sa.sa_family, SOCK_DGRAM, 0);
 	xmove_fd(sock, 0); /* fd# 0 is the open UDP socket */
 	xbind(0, &localp->sa, localp->len);
 	socket_want_pktinfo(0);

 	if (opt & OPT_u) { /* drop permissions */
 		xsetgid(ugid.gid);
 		xsetuid(ugid.uid);
 	}

 	if (verbose) {
 		/* we do it only for ":port" cosmetics... oh well */
 		char *addr = xmalloc_sockaddr2dotted(&localp->sa, localp->len);
 		printf("%s: info: listening on %s", applet_name, addr);
 		free(addr);
 		if (option_mask32 & OPT_u)
 			printf(", uid %u, gid %u",
 				(unsigned)ugid.uid, (unsigned)ugid.gid);
 		puts(", starting");
 	}

  again:
 	/* if (recvfrom(0, NULL, 0, MSG_PEEK, &remote.sa, &localp->len) < 0) { */
 	if (recv_from_to(0, NULL, 0, MSG_PEEK, &remote.sa, &localp->sa, localp->len) < 0) {
 		bb_perror_msg("recvfrom");
 		goto again;
 	}

 	while ((pid = fork()) < 0) {
 		bb_perror_msg("fork failed, sleeping");
 		sleep(5);
 	}
 	if (pid > 0) { /* parent */
 		while (wait_pid(&wstat, pid) == -1)
 			bb_perror_msg("error waiting for child");
 		if (verbose)
 			printf("%s: info: end %u\n", applet_name, pid);
 		goto again;
 	}

 	/* Child */

 #if 0
 	/* I'd like to make it so that local addr is fixed to localp->sa,
 	 * but how? The below trick doesn't work... */
 	close(0);
 	set_nport(localp, htons(local_port));
 	xmove_fd(xsocket(localp->sa.sa_family, SOCK_DGRAM, 0), 0);
 	xbind(0, &localp->sa, localp->len);
 #endif

 	if (verbose) {
 		local_ip = xmalloc_sockaddr2dotted_noport(&localp->sa, localp->len);
 		if (!local_hostname) {
 			local_hostname = xmalloc_sockaddr2host_noport(&localp->sa, localp->len);
 			if (!local_hostname)
 				bb_error_msg_and_die("cannot look up local hostname for %s", local_ip);
 		}
 	}

 	remote_ip = xmalloc_sockaddr2dotted_noport(&remote.sa, localp->len);
 	remote_port = get_nport(&remote.sa);
 	remote_port = ntohs(remote_port);
 	if (verbose)
 		printf("%s: info: pid %u from %s\n", applet_name, pid, remote_ip);

 	if (opt & OPT_h) {
 		remote_hostname = xmalloc_sockaddr2host(&remote.sa, localp->len);
 		if (!remote_hostname) {
 			bb_error_msg("warning: cannot look up hostname for %s", remote_ip);
 			remote_hostname = (char*)"";
 		}
 	}

 #if 0
 	if (instructs) {
 		ac = ipsvd_check(iscdb, &inst, &match, (char*)instructs,
 				remote_ip, remote_hostname.s, timeout);
 		if (ac == -1) discard("unable to check inst", remote_ip);
 		if (ac == IPSVD_ERR) discard("unable to read", (char*)instructs);
 	} else
 		ac = IPSVD_DEFAULT;
 #endif

 	if (verbose) {
 #if 0
 		out("%s: info: ", applet_name);
 		switch(ac) {
 		case IPSVD_DENY: out("deny "); break;
 		case IPSVD_DEFAULT: case IPSVD_INSTRUCT: out("start "); break;
 		case IPSVD_EXEC: out("exec "); break;
 		}
 #endif
 		printf("%s: info: %u %s:%s :%s:%s:%u\n",
 				applet_name, pid, local_hostname, local_ip,
 				remote_hostname, remote_ip, remote_port);
 #if 0
 		if (instructs) {
 			out(" ");
 			if (iscdb) {
 				out((char*)instructs); out("/");
 			}
 			outfix(match.s);
 			if(inst.s && inst.len && (verbose > 1)) {
 				out(": "); outinst(&inst);
 			}
 		}
 #endif
 	}

 #if 0
 	if (ac == IPSVD_DENY) {
 		recv(0, 0, 0, 0);
 		_exit(100);
 	}
 	if (ac == IPSVD_EXEC) {
 		args[0] = "/bin/sh";
 		args[1] = "-c";
 		args[2] = inst.s;
 		args[3] = NULL;
 		run = args;
 	} else run = prog;
 #endif
 	/* Make plain write(1) work for the child by supplying default
 	 * destination address */
 	xconnect(0, &remote.sa, localp->len);
 	dup2(0, 1);

 	signal(SIGTERM, SIG_DFL);
 	signal(SIGPIPE, SIG_DFL);

 	argv += 2;
 	BB_EXECVP(argv[0], argv);
 	bb_perror_msg_and_die("exec '%s'", argv[0]);
 }

 /*
 udpsvd [-hpvv] [-u user] [-l name] [-i dir|-x cdb] [-t sec] host port prog

 udpsvd creates an UDP/IP socket, binds it to the address host:port,
 and listens on the socket for incoming datagrams.

 If a datagram is available on the socket, udpsvd conditionally starts
 a program, with standard input reading from the socket, and standard
 output redirected to standard error, to handle this, and possibly
 more datagrams. udpsvd does not start the program if another program
 that it has started before still is running. If the program exits,
 udpsvd again listens to the socket until a new datagram is available.
 If there are still datagrams available on the socket, the program
 is restarted immediately.

 udpsvd optionally checks for special intructions depending on
 the IP address or hostname of the client sending the datagram which
 not yet was handled by a running program, see ipsvd-instruct(5)
 for details.

 Attention:
 UDP is a connectionless protocol. Most programs that handle user datagrams,
 such as talkd(8), keep running after receiving a datagram, and process
 subsequent datagrams sent to the socket until a timeout is reached.
 udpsvd only checks special instructions for a datagram that causes a startup
 of the program; not if a program handling datagrams already is running.
 It doesn't make much sense to restrict access through special instructions
 when using such a program.

 On the other hand, it makes perfectly sense with programs like tftpd(8),
 that fork to establish a separate connection to the client when receiving
 the datagram. In general it's adequate to set up special instructions for
 programs that support being run by tcpwrapper.
 Options

 host
     host either is a hostname, or a dotted-decimal IP address, or 0.
     If host is 0, udpsvd accepts datagrams to any local IP address.
 port
     udpsvd accepts datagrams to host:port. port may be a name from
     /etc/services or a number.
 prog
     prog consists of one or more arguments. udpsvd normally runs prog
     to handle a datagram, and possibly more, that is sent to the socket,
     if there is no program that was started before by udpsvd still running
     and handling datagrams.
 -i dir
     read instructions for handling new connections from the instructions
     directory dir. See ipsvd-instruct(5) for details.
 -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).
 -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; udpsvd 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.
 -l name
     local hostname. Do not look up the local hostname in DNS, but use name
     as hostname. By default udpsvd looks up the local hostname once at startup.
 -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.
 -h
     Look up the client's hostname in DNS.
 -p
     paranoid. After looking up the client's hostname in DNS, look up
     the IP addresses in DNS for that hostname, and forget 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.
 -v
     verbose. Print verbose messages to standard output.
 -vv
     more verbose. Print more verbose messages to standard output.
 */
	/* Based on ipsvd utilities written by Gerrit Pape <pape@smarden.org>
	* which are released into public domain by the author.
	* Homepage: http://smarden.sunsite.dk/ipsvd/
	*
	* 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 #if 0" is parts of original tcpsvd which are not implemented
	* for busyboxed version.
	*
	* 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).
	*/

	#include "busybox.h"

	#include "udp_io.c"

	unsigned verbose;

	static void sig_term_handler(int sig)
	{
	if (verbose)
	printf("%s: info: sigterm received, exit\n", applet_name);
	exit(0);
	}

	int udpsvd_main(int argc, char **argv);
	int udpsvd_main(int argc, char **argv)
	{
	const char *instructs;
	char str_t, user;
	unsigned opt;

	char *remote_hostname;
	char *local_hostname = NULL;
	char *remote_ip;
	char local_ip = local_ip; / gcc */
	uint16_t local_port, remote_port;
	len_and_sockaddr remote;
	len_and_sockaddr *localp;
	int sock;
	int wstat;
	unsigned pid;
	struct bb_uidgid_t ugid;

	enum {
	OPT_v = (1 << 0),
	OPT_u = (1 << 1),
	OPT_l = (1 << 2),
	OPT_h = (1 << 3),
	OPT_p = (1 << 4),
	OPT_i = (1 << 5),
	OPT_x = (1 << 6),
	OPT_t = (1 << 7),
	};

	opt_complementary = "-3:ph:vv";
	opt = getopt32(argc, argv, "vu:l:hpi:x:t:",
	&user, &local_hostname, &instructs, &instructs, &str_t, &verbose);
	//if (opt & OPT_x) iscdb =1;
	//if (opt & OPT_t) timeout = xatou(str_t);
	if (!(opt & OPT_h))
	remote_hostname = (char *)"";
	if (opt & OPT_u) {
	if (!get_uidgid(&ugid, user, 1))
	bb_error_msg_and_die("unknown user/group: %s", user);
	}
	argv += optind;
	if (!argv[0][0] \|\| LONE_CHAR(argv[0], '0'))
	argv[0] = (char*)"0.0.0.0";

	/* stdout is used for logging, don't buffer */
	setlinebuf(stdout);
	bb_sanitize_stdio(); /* fd# 1,2 must be opened */

	signal(SIGTERM, sig_term_handler);
	signal(SIGPIPE, SIG_IGN);

	local_port = bb_lookup_port(argv[1], "udp", 0);
	localp = xhost2sockaddr(argv[0], local_port);
	sock = xsocket(localp->sa.sa_family, SOCK_DGRAM, 0);
	xmove_fd(sock, 0); /* fd# 0 is the open UDP socket */
	xbind(0, &localp->sa, localp->len);
	socket_want_pktinfo(0);

	if (opt & OPT_u) { /* drop permissions */
	xsetgid(ugid.gid);
	xsetuid(ugid.uid);
	}

	if (verbose) {
	/* we do it only for ":port" cosmetics... oh well */
	char *addr = xmalloc_sockaddr2dotted(&localp->sa, localp->len);
	printf("%s: info: listening on %s", applet_name, addr);
	free(addr);
	if (option_mask32 & OPT_u)
	printf(", uid %u, gid %u",
	(unsigned)ugid.uid, (unsigned)ugid.gid);
	puts(", starting");
	}

	again:
	/* if (recvfrom(0, NULL, 0, MSG_PEEK, &remote.sa, &localp->len) < 0) { */
	if (recv_from_to(0, NULL, 0, MSG_PEEK, &remote.sa, &localp->sa, localp->len) < 0) {
	bb_perror_msg("recvfrom");
	goto again;
	}

	while ((pid = fork()) < 0) {
	bb_perror_msg("fork failed, sleeping");
	sleep(5);
	}
	if (pid > 0) { /* parent */
	while (wait_pid(&wstat, pid) == -1)
	bb_perror_msg("error waiting for child");
	if (verbose)
	printf("%s: info: end %u\n", applet_name, pid);
	goto again;
	}

	/* Child */

	#if 0
	/* I'd like to make it so that local addr is fixed to localp->sa,
	* but how? The below trick doesn't work... */
	close(0);
	set_nport(localp, htons(local_port));
	xmove_fd(xsocket(localp->sa.sa_family, SOCK_DGRAM, 0), 0);
	xbind(0, &localp->sa, localp->len);
	#endif

	if (verbose) {
	local_ip = xmalloc_sockaddr2dotted_noport(&localp->sa, localp->len);
	if (!local_hostname) {
	local_hostname = xmalloc_sockaddr2host_noport(&localp->sa, localp->len);
	if (!local_hostname)
	bb_error_msg_and_die("cannot look up local hostname for %s", local_ip);
	}
	}

	remote_ip = xmalloc_sockaddr2dotted_noport(&remote.sa, localp->len);
	remote_port = get_nport(&remote.sa);
	remote_port = ntohs(remote_port);
	if (verbose)
	printf("%s: info: pid %u from %s\n", applet_name, pid, remote_ip);

	if (opt & OPT_h) {
	remote_hostname = xmalloc_sockaddr2host(&remote.sa, localp->len);
	if (!remote_hostname) {
	bb_error_msg("warning: cannot look up hostname for %s", remote_ip);
	remote_hostname = (char*)"";
	}
	}

	#if 0
	if (instructs) {
	ac = ipsvd_check(iscdb, &inst, &match, (char*)instructs,
	remote_ip, remote_hostname.s, timeout);
	if (ac == -1) discard("unable to check inst", remote_ip);
	if (ac == IPSVD_ERR) discard("unable to read", (char*)instructs);
	} else
	ac = IPSVD_DEFAULT;
	#endif

	if (verbose) {
	#if 0
	out("%s: info: ", applet_name);
	switch(ac) {
	case IPSVD_DENY: out("deny "); break;
	case IPSVD_DEFAULT: case IPSVD_INSTRUCT: out("start "); break;
	case IPSVD_EXEC: out("exec "); break;
	}
	#endif
	printf("%s: info: %u %s:%s :%s:%s:%u\n",
	applet_name, pid, local_hostname, local_ip,
	remote_hostname, remote_ip, remote_port);
	#if 0
	if (instructs) {
	out(" ");
	if (iscdb) {
	out((char*)instructs); out("/");
	}
	outfix(match.s);
	if(inst.s && inst.len && (verbose > 1)) {
	out(": "); outinst(&inst);
	}
	}
	#endif
	}

	#if 0
	if (ac == IPSVD_DENY) {
	recv(0, 0, 0, 0);
	_exit(100);
	}
	if (ac == IPSVD_EXEC) {
	args[0] = "/bin/sh";
	args[1] = "-c";
	args[2] = inst.s;
	args[3] = NULL;
	run = args;
	} else run = prog;
	#endif
	/* Make plain write(1) work for the child by supplying default
	* destination address */
	xconnect(0, &remote.sa, localp->len);
	dup2(0, 1);

	signal(SIGTERM, SIG_DFL);
	signal(SIGPIPE, SIG_DFL);

	argv += 2;
	BB_EXECVP(argv[0], argv);
	bb_perror_msg_and_die("exec '%s'", argv[0]);
	}

	/*
	udpsvd [-hpvv] [-u user] [-l name] [-i dir\|-x cdb] [-t sec] host port prog

	udpsvd creates an UDP/IP socket, binds it to the address host:port,
	and listens on the socket for incoming datagrams.

	If a datagram is available on the socket, udpsvd conditionally starts
	a program, with standard input reading from the socket, and standard
	output redirected to standard error, to handle this, and possibly
	more datagrams. udpsvd does not start the program if another program
	that it has started before still is running. If the program exits,
	udpsvd again listens to the socket until a new datagram is available.
	If there are still datagrams available on the socket, the program
	is restarted immediately.

	udpsvd optionally checks for special intructions depending on
	the IP address or hostname of the client sending the datagram which
	not yet was handled by a running program, see ipsvd-instruct(5)
	for details.

	Attention:
	UDP is a connectionless protocol. Most programs that handle user datagrams,
	such as talkd(8), keep running after receiving a datagram, and process
	subsequent datagrams sent to the socket until a timeout is reached.
	udpsvd only checks special instructions for a datagram that causes a startup
	of the program; not if a program handling datagrams already is running.
	It doesn't make much sense to restrict access through special instructions
	when using such a program.

	On the other hand, it makes perfectly sense with programs like tftpd(8),
	that fork to establish a separate connection to the client when receiving
	the datagram. In general it's adequate to set up special instructions for
	programs that support being run by tcpwrapper.
	Options

	host
	host either is a hostname, or a dotted-decimal IP address, or 0.
	If host is 0, udpsvd accepts datagrams to any local IP address.
	port
	udpsvd accepts datagrams to host:port. port may be a name from
	/etc/services or a number.
	prog
	prog consists of one or more arguments. udpsvd normally runs prog
	to handle a datagram, and possibly more, that is sent to the socket,
	if there is no program that was started before by udpsvd still running
	and handling datagrams.
	-i dir
	read instructions for handling new connections from the instructions
	directory dir. See ipsvd-instruct(5) for details.
	-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).
	-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; udpsvd 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.
	-l name
	local hostname. Do not look up the local hostname in DNS, but use name
	as hostname. By default udpsvd looks up the local hostname once at startup.
	-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.
	-h
	Look up the client's hostname in DNS.
	-p
	paranoid. After looking up the client's hostname in DNS, look up
	the IP addresses in DNS for that hostname, and forget 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.
	-v
	verbose. Print verbose messages to standard output.
	-vv
	more verbose. Print more verbose messages to standard output.
	*/