networking/fakeidentd.c - busybox - Git at Google

 /* NB: this file is to be removed soon. See isrv_identd.c */

 /* vi: set sw=4 ts=4: */
 /*
  * A fake identd server
  *
  * Adapted to busybox by Thomas Lundquist <thomasez@zelow.no>
  * Original Author: Tomi Ollila <too@iki.fi>
  *                  http://www.guru-group.fi/~too/sw/
  *
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */

 /* Ident crash course
  *
  * Incoming requests are of form "6191, 23\r\n" - peer asks us
  * "which user connected from your port 6191 to my port 23?"
  * We should answer:
  * "6193, 23 : USERID : UNIX : username\r\n"
  * and close the connection.
  * We can also reply:
  * "6195, 23 : USERID : OTHER[,US-ASCII] : username\r\n"
  * "6195, 23 : ERROR : INVALID-PORT/NO-USER/HIDDEN-USER/UNKNOWN-ERROR\r\n"
  * but we probably will never want that.
  */

 #include "busybox.h"

 #define SANE_INETD_ONLY_VERSION

 #ifdef SANE_INETD_ONLY_VERSION

 int fakeidentd_main(int argc, char **argv)
 {
 	char buf[64];
 	const char *bogouser = "nobody";
 	char *cur = buf;
 	int rem = sizeof(buf)-1;

 	if (argv[1])
 		bogouser = argv[1];

 	alarm(30);
 	while (1) {
 		char *p;
 		int sz = safe_read(0, cur, rem);
 		if (sz < 0) return 1;
 		cur[sz] = '\0';
 		p = strpbrk(cur, "\r\n");
 		if (p) {
 			*p = '\0';
 			break;
 		}
 		cur += sz;
 		rem -= sz;
 		if (!rem || !sz)
 			break;
 	}
 	printf("%s : USERID : UNIX : %s\r\n", buf, bogouser);
 	return 0;
 }

 #else

 /* Welcome to the bloaty horrors */

 #include <sys/syslog.h>
 #include <sys/uio.h>

 #define MAXCONNS    20
 #define MAXIDLETIME 45

 static const char ident_substr[] = " : USERID : UNIX : ";
 enum { ident_substr_len = sizeof(ident_substr) - 1 };
 #define PIDFILE "/var/run/identd.pid"

 /*
  * We have to track the 'first connection socket' so that we
  * don't go around closing file descriptors for non-clients.
  *
  * descriptor setup normally
  *  0 = server socket
  *  1 = syslog fd (hopefully -- otherwise this won't work)
  *  2 = connection socket after detached from tty. standard error before that
  *  3 - 2 + MAXCONNS = rest connection sockets
  *
  * To try to make sure that syslog fd is what is "requested", the that fd
  * is closed before openlog() call.  It can only severely fail if fd 0
  * is initially closed.
  */
 #define FCS 2

 /*
  * FD of the connection is always the index of the connection structure
  * in `conns' array + FCS
  */
 static struct {
 	time_t lasttime;
 	int len;
 	char buf[20];
 } conns[MAXCONNS];

 /* When using global variables, bind those at least to a structure. */
 static struct {
 	const char *identuser;
 	fd_set readfds;
 	int conncnt;
 } G;

 static char *bind_ip_address;

 static int chmatch(char c, char *chars)
 {
 	for (; *chars; chars++)
 		if (c == *chars)
 			return 1;
 	return 0;
 }

 static int skipchars(char **p, char *chars)
 {
 	while (chmatch(**p, chars))
 		(*p)++;
 	if (**p == '\r' || **p == '\n')
 		return 0;
 	return 1;
 }

 static int parseAddrs(char *ptr, char **myaddr, char **heraddr)
 {
 	/* parse <port-on-server> , <port-on-client> */

 	if (!skipchars(&ptr, " \t"))
 		return -1;

 	*myaddr = ptr;

 	if (!skipchars(&ptr, "1234567890"))
 		return -1;

 	if (!chmatch(*ptr, " \t,"))
 		return -1;

 	*ptr++ = '\0';

 	if (!skipchars(&ptr, " \t,") )
 		return -1;

 	*heraddr = ptr;

 	skipchars(&ptr, "1234567890");

 	if (!chmatch(*ptr, " \n\r"))
 		return -1;

 	*ptr = '\0';

 	return 0;
 }

 static void replyError(int s, char *buf)
 {
 	struct iovec iv[3];
 	iv[0].iov_base = "0, 0 : ERROR : ";   iv[0].iov_len = 15;
 	iv[1].iov_base = buf;                 iv[1].iov_len = strlen(buf);
 	iv[2].iov_base = "\r\n";              iv[2].iov_len = 2;
 	writev(s, iv, 3);
 }

 static void reply(int s, char *buf)
 {
 	char *myaddr, *heraddr;

 	myaddr = heraddr = NULL;

 	if (parseAddrs(buf, &myaddr, &heraddr))
 		replyError(s, "X-INVALID-REQUEST");
 	else {
 		struct iovec iv[6];
 		iv[0].iov_base = myaddr;               iv[0].iov_len = strlen(myaddr);
 		iv[1].iov_base = ", ";                 iv[1].iov_len = 2;
 		iv[2].iov_base = heraddr;              iv[2].iov_len = strlen(heraddr);
 		iv[3].iov_base = (void *)ident_substr; iv[3].iov_len = ident_substr_len;
 		iv[4].iov_base = (void *)G.identuser;  iv[4].iov_len = strlen(G.identuser);
 		iv[5].iov_base = "\r\n";               iv[5].iov_len = 2;
 		writev(s, iv, 6);
 	}
 }

 static void movefd(int from, int to)
 {
 	if (from != to) {
 		dup2(from, to);
 		close(from);
 	}
 }

 static void deleteConn(int s)
 {
 	int i = s - FCS;

 	close(s);

 	G.conncnt--;

 	/*
 	 * Most of the time there is 0 connections. Most often that there
 	 * is connections, there is just one connection. When this one connection
 	 * closes, i == G.conncnt = 0 -> no copying.
 	 * When there is more than one connection, the oldest connections closes
 	 * earlier on average. When this happens, the code below starts copying
 	 * the connection structure w/ highest index to the place which which is
 	 * just deleted. This means that the connection structures are no longer
 	 * in chronological order. I'd quess this means that when there is more
 	 * than 1 connection, on average every other connection structure needs
 	 * to be copied over the time all these connections are deleted.
 	 */
 	if (i != G.conncnt) {
 		memcpy(&conns[i], &conns[G.conncnt], sizeof(conns[0]));
 		movefd(G.conncnt + FCS, s);
 	}

 	FD_CLR(G.conncnt + FCS, &G.readfds);
 }

 static int closeOldest(void)
 {
 	time_t min = conns[0].lasttime;
 	int idx = 0;
 	int i;

 	for (i = 1; i < MAXCONNS; i++)
 		if (conns[i].lasttime < min)
 			idx = i;

 	replyError(idx + FCS, "X-SERVER-TOO-BUSY");
 	close(idx + FCS);

 	return idx;
 }

 static int checkInput(char *buf, int len, int l)
 {
 	int i;
 	for (i = len; i < len + l; ++i)
 		if (buf[i] == '\n')
 			return 1;
 	return 0;
 }

 /* May succeed. If not, won't care. */
 static const char *to_unlink;
 static void writepid(void)
 {
 	int fd = open(PIDFILE, O_WRONLY|O_CREAT|O_TRUNC, 0664);
 	if (fd < 0)
 		return;
 	to_unlink = PIDFILE;
 	fdprintf(fd, "%d\n", getpid());
 	close(fd);
 }

 static void handlexitsigs(int signum)
 {
 	if (to_unlink)
 		if (unlink(to_unlink) < 0)
 			close(open(to_unlink, O_WRONLY|O_CREAT|O_TRUNC, 0644));
 	exit(0);
 }

 int fakeidentd_main(int argc, char **argv)
 {
 	int fd;
 	pid_t pid;

 	/* FD_ZERO(&G.readfds); - in bss, already zeroed */
 	FD_SET(0, &G.readfds);

 	/* handle -b <ip> parameter */
 	getopt32(argc, argv, "b:", &bind_ip_address);
 	/* handle optional REPLY STRING */
 	if (optind < argc)
 		G.identuser = argv[optind];
 	else
 		G.identuser = "nobody";

 	writepid();
 	signal(SIGTERM, handlexitsigs);
 	signal(SIGINT,  handlexitsigs);
 	signal(SIGQUIT, handlexitsigs);
 	signal(SIGHUP, SIG_IGN);
 	signal(SIGPIPE, SIG_IGN); /* ignore closed connections when writing */

 	fd = create_and_bind_stream_or_die(bind_ip_address, bb_lookup_port("identd", "tcp", 113));
 	xlisten(fd, 5);

 	pid = fork();
 	if (pid < 0)
 		bb_perror_msg_and_die("fork");
 	if (pid != 0) /* parent */
 		exit(0);
 	/* child */
 	setsid();
 	movefd(fd, 0);
 	while (fd)
 		close(fd--);
 	openlog(applet_name, 0, LOG_DAEMON);
 	logmode = LOGMODE_SYSLOG;

 	/* main loop where we process all events and never exit */
 	while (1) {
 		fd_set rfds = G.readfds;
 		struct timeval tv = { 15, 0 };
 		int i;
 		int tim = time(NULL);

 		select(G.conncnt + FCS, &rfds, NULL, NULL, G.conncnt? &tv: NULL);

 		for (i = G.conncnt - 1; i >= 0; i--) {
 			int s = i + FCS;

 			if (FD_ISSET(s, &rfds)) {
 				char *buf = conns[i].buf;
 				unsigned len = conns[i].len;
 				unsigned l;

 				l = read(s, buf + len, sizeof(conns[0].buf) - len);
 				if (l > 0) {
 					if (checkInput(buf, len, l)) {
 						reply(s, buf);
 						goto deleteconn;
 					} else if (len + l >= sizeof(conns[0].buf)) {
 						replyError(s, "X-INVALID-REQUEST");
 						goto deleteconn;
 					} else {
 						conns[i].len += l;
 					}
 				} else {
 					goto deleteconn;
 				}
 				conns[i].lasttime = tim;
 				continue;
 deleteconn:
 				deleteConn(s);
 			} else {
 				/* implement as time_after() in linux kernel sources ... */
 				if (conns[i].lasttime + MAXIDLETIME <= tim) {
 					replyError(s, "X-TIMEOUT");
 					deleteConn(s);
 				}
 			}
 		}

 		if (FD_ISSET(0, &rfds)) {
 			int s = accept(0, NULL, 0);

 			if (s < 0) {
 				if (errno != EINTR)
 					bb_perror_msg("accept");
 			} else {
 				if (G.conncnt == MAXCONNS)
 					i = closeOldest();
 				else
 					i = G.conncnt++;

 				movefd(s, i + FCS); /* move if not already there */
 				FD_SET(i + FCS, &G.readfds);
 				conns[i].len = 0;
 				conns[i].lasttime = time(NULL);
 			}
 		}
 	} /* end of while (1) */

 	return 0;
 }

 #endif /* !SANE_INETD_ONLY_VERSION */
	/* NB: this file is to be removed soon. See isrv_identd.c */

	/* vi: set sw=4 ts=4: */
	/*
	* A fake identd server
	*
	* Adapted to busybox by Thomas Lundquist <thomasez@zelow.no>
	* Original Author: Tomi Ollila <too@iki.fi>
	* http://www.guru-group.fi/~too/sw/
	*
	* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
	*/

	/* Ident crash course
	*
	* Incoming requests are of form "6191, 23\r\n" - peer asks us
	* "which user connected from your port 6191 to my port 23?"
	* We should answer:
	* "6193, 23 : USERID : UNIX : username\r\n"
	* and close the connection.
	* We can also reply:
	* "6195, 23 : USERID : OTHER[,US-ASCII] : username\r\n"
	* "6195, 23 : ERROR : INVALID-PORT/NO-USER/HIDDEN-USER/UNKNOWN-ERROR\r\n"
	* but we probably will never want that.
	*/

	#include "busybox.h"

	#define SANE_INETD_ONLY_VERSION

	#ifdef SANE_INETD_ONLY_VERSION

	int fakeidentd_main(int argc, char **argv)
	{
	char buf[64];
	const char *bogouser = "nobody";
	char *cur = buf;
	int rem = sizeof(buf)-1;

	if (argv[1])
	bogouser = argv[1];

	alarm(30);
	while (1) {
	char *p;
	int sz = safe_read(0, cur, rem);
	if (sz < 0) return 1;
	cur[sz] = '\0';
	p = strpbrk(cur, "\r\n");
	if (p) {
	*p = '\0';
	break;
	}
	cur += sz;
	rem -= sz;
	if (!rem \|\| !sz)
	break;
	}
	printf("%s : USERID : UNIX : %s\r\n", buf, bogouser);
	return 0;
	}

	#else

	/* Welcome to the bloaty horrors */

	#include <sys/syslog.h>
	#include <sys/uio.h>

	#define MAXCONNS 20
	#define MAXIDLETIME 45

	static const char ident_substr[] = " : USERID : UNIX : ";
	enum { ident_substr_len = sizeof(ident_substr) - 1 };
	#define PIDFILE "/var/run/identd.pid"

	/*
	* We have to track the 'first connection socket' so that we
	* don't go around closing file descriptors for non-clients.
	*
	* descriptor setup normally
	* 0 = server socket
	* 1 = syslog fd (hopefully -- otherwise this won't work)
	* 2 = connection socket after detached from tty. standard error before that
	* 3 - 2 + MAXCONNS = rest connection sockets
	*
	* To try to make sure that syslog fd is what is "requested", the that fd
	* is closed before openlog() call. It can only severely fail if fd 0
	* is initially closed.
	*/
	#define FCS 2

	/*
	* FD of the connection is always the index of the connection structure
	* in `conns' array + FCS
	*/
	static struct {
	time_t lasttime;
	int len;
	char buf[20];
	} conns[MAXCONNS];

	/* When using global variables, bind those at least to a structure. */
	static struct {
	const char *identuser;
	fd_set readfds;
	int conncnt;
	} G;

	static char *bind_ip_address;

	static int chmatch(char c, char *chars)
	{
	for (; *chars; chars++)
	if (c == *chars)
	return 1;
	return 0;
	}

	static int skipchars(char *p, char chars)
	{
	while (chmatch(**p, chars))
	(*p)++;
	if (p == '\r' \|\| p == '\n')
	return 0;
	return 1;
	}

	static int parseAddrs(char ptr, char myaddr, char *heraddr)
	{
	/* parse <port-on-server> , <port-on-client> */

	if (!skipchars(&ptr, " \t"))
	return -1;

	*myaddr = ptr;

	if (!skipchars(&ptr, "1234567890"))
	return -1;

	if (!chmatch(*ptr, " \t,"))
	return -1;

	*ptr++ = '\0';

	if (!skipchars(&ptr, " \t,") )
	return -1;

	*heraddr = ptr;

	skipchars(&ptr, "1234567890");

	if (!chmatch(*ptr, " \n\r"))
	return -1;

	*ptr = '\0';

	return 0;
	}

	static void replyError(int s, char *buf)
	{
	struct iovec iv[3];
	iv[0].iov_base = "0, 0 : ERROR : "; iv[0].iov_len = 15;
	iv[1].iov_base = buf; iv[1].iov_len = strlen(buf);
	iv[2].iov_base = "\r\n"; iv[2].iov_len = 2;
	writev(s, iv, 3);
	}

	static void reply(int s, char *buf)
	{
	char myaddr, heraddr;

	myaddr = heraddr = NULL;

	if (parseAddrs(buf, &myaddr, &heraddr))
	replyError(s, "X-INVALID-REQUEST");
	else {
	struct iovec iv[6];
	iv[0].iov_base = myaddr; iv[0].iov_len = strlen(myaddr);
	iv[1].iov_base = ", "; iv[1].iov_len = 2;
	iv[2].iov_base = heraddr; iv[2].iov_len = strlen(heraddr);
	iv[3].iov_base = (void *)ident_substr; iv[3].iov_len = ident_substr_len;
	iv[4].iov_base = (void *)G.identuser; iv[4].iov_len = strlen(G.identuser);
	iv[5].iov_base = "\r\n"; iv[5].iov_len = 2;
	writev(s, iv, 6);
	}
	}

	static void movefd(int from, int to)
	{
	if (from != to) {
	dup2(from, to);
	close(from);
	}
	}

	static void deleteConn(int s)
	{
	int i = s - FCS;

	close(s);

	G.conncnt--;

	/*
	* Most of the time there is 0 connections. Most often that there
	* is connections, there is just one connection. When this one connection
	* closes, i == G.conncnt = 0 -> no copying.
	* When there is more than one connection, the oldest connections closes
	* earlier on average. When this happens, the code below starts copying
	* the connection structure w/ highest index to the place which which is
	* just deleted. This means that the connection structures are no longer
	* in chronological order. I'd quess this means that when there is more
	* than 1 connection, on average every other connection structure needs
	* to be copied over the time all these connections are deleted.
	*/
	if (i != G.conncnt) {
	memcpy(&conns[i], &conns[G.conncnt], sizeof(conns[0]));
	movefd(G.conncnt + FCS, s);
	}

	FD_CLR(G.conncnt + FCS, &G.readfds);
	}

	static int closeOldest(void)
	{
	time_t min = conns[0].lasttime;
	int idx = 0;
	int i;

	for (i = 1; i < MAXCONNS; i++)
	if (conns[i].lasttime < min)
	idx = i;

	replyError(idx + FCS, "X-SERVER-TOO-BUSY");
	close(idx + FCS);

	return idx;
	}

	static int checkInput(char *buf, int len, int l)
	{
	int i;
	for (i = len; i < len + l; ++i)
	if (buf[i] == '\n')
	return 1;
	return 0;
	}

	/* May succeed. If not, won't care. */
	static const char *to_unlink;
	static void writepid(void)
	{
	int fd = open(PIDFILE, O_WRONLY\|O_CREAT\|O_TRUNC, 0664);
	if (fd < 0)
	return;
	to_unlink = PIDFILE;
	fdprintf(fd, "%d\n", getpid());
	close(fd);
	}

	static void handlexitsigs(int signum)
	{
	if (to_unlink)
	if (unlink(to_unlink) < 0)
	close(open(to_unlink, O_WRONLY\|O_CREAT\|O_TRUNC, 0644));
	exit(0);
	}

	int fakeidentd_main(int argc, char **argv)
	{
	int fd;
	pid_t pid;

	/* FD_ZERO(&G.readfds); - in bss, already zeroed */
	FD_SET(0, &G.readfds);

	/* handle -b <ip> parameter */
	getopt32(argc, argv, "b:", &bind_ip_address);
	/* handle optional REPLY STRING */
	if (optind < argc)
	G.identuser = argv[optind];
	else
	G.identuser = "nobody";

	writepid();
	signal(SIGTERM, handlexitsigs);
	signal(SIGINT, handlexitsigs);
	signal(SIGQUIT, handlexitsigs);
	signal(SIGHUP, SIG_IGN);
	signal(SIGPIPE, SIG_IGN); /* ignore closed connections when writing */

	fd = create_and_bind_stream_or_die(bind_ip_address, bb_lookup_port("identd", "tcp", 113));
	xlisten(fd, 5);

	pid = fork();
	if (pid < 0)
	bb_perror_msg_and_die("fork");
	if (pid != 0) /* parent */
	exit(0);
	/* child */
	setsid();
	movefd(fd, 0);
	while (fd)
	close(fd--);
	openlog(applet_name, 0, LOG_DAEMON);
	logmode = LOGMODE_SYSLOG;

	/* main loop where we process all events and never exit */
	while (1) {
	fd_set rfds = G.readfds;
	struct timeval tv = { 15, 0 };
	int i;
	int tim = time(NULL);

	select(G.conncnt + FCS, &rfds, NULL, NULL, G.conncnt? &tv: NULL);

	for (i = G.conncnt - 1; i >= 0; i--) {
	int s = i + FCS;

	if (FD_ISSET(s, &rfds)) {
	char *buf = conns[i].buf;
	unsigned len = conns[i].len;
	unsigned l;

	l = read(s, buf + len, sizeof(conns[0].buf) - len);
	if (l > 0) {
	if (checkInput(buf, len, l)) {
	reply(s, buf);
	goto deleteconn;
	} else if (len + l >= sizeof(conns[0].buf)) {
	replyError(s, "X-INVALID-REQUEST");
	goto deleteconn;
	} else {
	conns[i].len += l;
	}
	} else {
	goto deleteconn;
	}
	conns[i].lasttime = tim;
	continue;
	deleteconn:
	deleteConn(s);
	} else {
	/* implement as time_after() in linux kernel sources ... */
	if (conns[i].lasttime + MAXIDLETIME <= tim) {
	replyError(s, "X-TIMEOUT");
	deleteConn(s);
	}
	}
	}

	if (FD_ISSET(0, &rfds)) {
	int s = accept(0, NULL, 0);

	if (s < 0) {
	if (errno != EINTR)
	bb_perror_msg("accept");
	} else {
	if (G.conncnt == MAXCONNS)
	i = closeOldest();
	else
	i = G.conncnt++;

	movefd(s, i + FCS); /* move if not already there */
	FD_SET(i + FCS, &G.readfds);
	conns[i].len = 0;
	conns[i].lasttime = time(NULL);
	}
	}
	} /* end of while (1) */

	return 0;
	}

	#endif /* !SANE_INETD_ONLY_VERSION */