/* 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. */ #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <stdarg.h> #include <string.h> #include <fcntl.h> #include <signal.h> #include <sys/syslog.h> #include <pwd.h> #include <netdb.h> #include <sys/syslog.h> #include <sys/types.h> #include <time.h> #include <sys/socket.h> #include <netinet/in.h> #include <errno.h> #include <arpa/inet.h> #include <sys/uio.h> #include "busybox.h" #define IDENT_PORT 113 #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 { char buf[20]; int len; time_t lasttime; } conns[MAXCONNS]; /* When using global variables, bind those at least to a structure. */ static struct { const char *identuser; fd_set readfds; int conncnt; } G; /* * Prototypes */ static void reply(int s, char *buf); static void replyError(int s, char *buf); static const char *nobodystr = "nobody"; /* this needs to be declared like this */ static char *bind_ip_address = "0.0.0.0"; static inline void movefd(int from, int to) { if (from != to) { dup2(from, to); close(from); } } static void inetbind(void) { int s, port; struct sockaddr_in addr; int len = sizeof(addr); int one = 1; struct servent *se; if ((se = getservbyname("identd", "tcp")) == NULL) port = IDENT_PORT; else port = se->s_port; s = bb_xsocket(AF_INET, SOCK_STREAM, 0); setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)); memset(&addr, 0, sizeof(addr)); addr.sin_addr.s_addr = inet_addr(bind_ip_address); addr.sin_family = AF_INET; addr.sin_port = htons(port); if (bind(s, (struct sockaddr *)&addr, len) < 0) /* bb_xbind? */ bb_perror_msg_and_die("Cannot bind() port %i", IDENT_PORT); if (listen(s, 5) < 0) /* bb_xlisten? */ bb_perror_msg_and_die("Cannot listen() on port %i", IDENT_PORT); movefd(s, 0); } static void handlexitsigs(int signum) { if (unlink(PIDFILE) < 0) close(open(PIDFILE, O_WRONLY|O_CREAT|O_TRUNC, 0644)); exit(0); } /* May succeed. If not, won't care. */ static inline void writepid(uid_t nobody, uid_t nogrp) { char buf[24]; int fd = open(PIDFILE, O_WRONLY|O_CREAT|O_TRUNC, 0664); if (fd < 0) return; snprintf(buf, 23, "%d\n", getpid()); write(fd, buf, strlen(buf)); fchown(fd, nobody, nogrp); close(fd); /* should this handle ILL, ... (see signal(7)) */ signal(SIGTERM, handlexitsigs); signal(SIGINT, handlexitsigs); signal(SIGQUIT, handlexitsigs); } /* return 0 as parent, 1 as child */ static int godaemon(void) { uid_t nobody, nogrp; struct passwd *pw; switch (fork()) { case -1: bb_perror_msg_and_die("Could not fork"); case 0: pw = getpwnam(nobodystr); if (pw == NULL) bb_error_msg_and_die("Cannot find uid/gid of user '%s'", nobodystr); nobody = pw->pw_uid; nogrp = pw->pw_gid; writepid(nobody, nogrp); close(0); inetbind(); if (setgid(nogrp)) bb_error_msg_and_die("Could not setgid()"); if (setuid(nobody)) bb_error_msg_and_die("Could not setuid()"); close(1); close(2); signal(SIGHUP, SIG_IGN); signal(SIGPIPE, SIG_IGN); /* connection closed when writing (raises ???) */ setsid(); openlog(bb_applet_name, 0, LOG_DAEMON); return 1; } return 0; } 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; } int fakeidentd_main(int argc, char **argv) { memset(conns, 0, sizeof(conns)); memset(&G, 0, sizeof(G)); FD_ZERO(&G.readfds); FD_SET(0, &G.readfds); /* handle -b <ip> parameter */ bb_getopt_ulflags(argc, argv, "b:", &bind_ip_address); /* handle optional REPLY STRING */ if (optind < argc) G.identuser = argv[optind]; else G.identuser = nobodystr; /* daemonize and have the parent return */ if (godaemon() == 0) return 0; /* 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 int len = conns[i].len; unsigned int l; if ((l = read(s, buf + len, sizeof(conns[0].buf) - len)) > 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) /* EINTR */ syslog(LOG_ERR, "accept: %s", strerror(errno)); } 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; } static int parseAddrs(char *ptr, char **myaddr, char **heraddr); 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 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 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; }