busybox/networking/fakeidentd.c

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/* 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"
/*
2006-01-25 05:38:53 +05:30
* 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 */