#define VERSION "2.6" #define TRG "fakeidentd" #if 0 /* -*- mode: c; c-file-style: "gnu"; tab-width: 8; -*- # This program is easy to compile. For example the following ways: # $ sh identd.c # $ sh identd.c -g -DDEBUG # $ sh identd.c -s -DXXXMULTI # $ sh identd.c TRG=fake_identd -s -DBIND_ADDRESS=127.0.0.1 # $ sh identd.c CC=cc # $ sh identd.c CC=egcs -s -fomit-frame-pointer set -eu CC= TRG=`basename "$0" .c` OIFS=$IFS for arg in "$@" '' do case $arg in TRG=*) TRG=`echo "$arg" | sed 's/TRG=//'`; shift ;; CC=*) CC=`echo "$arg" | sed 's/CC=//'`; shift ;; clean) set -x; exec rm -f "$TRG" ;; readme) set -x; exec sed -n '1,/[e]nd/d;/\*\//q;s/..//p' "$0";; '') set 0 -s -O2; shift; break ;; *) break ;; esac; done case `uname` in SunOS) L='-lsocket -lnsl' ;; *) L= ;; esac WARN="-Wall -Wstrict-prototypes -pedantic -Wno-long-long" WARN="$WARN -Wcast-align -Wpointer-arith " # -Wfloat-equal #-Werror WARN="$WARN -W -Wwrite-strings -Wcast-qual -Wshadow" # -Wconversion VERSION=`sed -n '/^ [*] Version / { s/.*Version \([^ ]*\) *\([^ ]*\).*./\1 (\2)/p; q; }' "$0"` case $VERSION in '') echo Could not read version information. >&2; exit 1; esac TRGNAME=`basename "$TRG"` set -x; exec ${CC:-gcc} $WARN "$@" -DTRG="\"$TRGNAME\"" \ -DVERSION="\"$VERSION\"" -o "$TRG" "$0" $L exit 1 # */ #endif /* * identd.c 2.6 2012-05-31 20:37:27 UTC * * Author: Tomi Ollila -- too ät iki fi * * Created: Sat Nov 25 15:34:07 EET 1995 too * Last modified: Thu 31 May 2012 23:37:27 EEST too * * This program is standalone 'fake' ident daemon. This program does * not fork() but is configured to handle up to 20 concurrent connections. * Since one connection should not last long, if all 20 connections are * in use, the next connection will close the oldest connection data * has been read. This way this program is not very vulnerable to so * called `denial of service' attack, thus making this ideal "identd" * to be used in a firewall, IP masquerading hosts etc. * * Program takes one (or many) arguments, which if exist, determines the * `user' name(s) that is returned for successful ident query. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2, or (at your option) * any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * HISTORY * * Version 2.6 2012-05-31 20:37:27 UTC * Applied patches from the wl500g project, including IPv6 support, with * minor tweaks (patches provided by Daniel Gimpelevich. Thanks). * * Version 2.5 $Id: identd.c 862 2006-05-18 14:16:34Z too $ * Minor build and readme updates. * * Version 2.4 identd.c 568 2005-09-07 20:18:39Z too * More compilation warnings options set -- iov.base being non-const * gives warnings that are hard to avoid... * * Version 2.3 identd.c 564 2005-09-06 19:15:20Z too * Randident code from Matthias Jung tuned in. * * Version 2.2 identd.c 12 2004-09-08 21:46:54Z too * Fixed getservbyname() to look port for "auth" instead of "identd" * port. This "bug" also revealed port number byte order handling bug, * which was fixed. * Now this file is stored in subversion repository -- I entered * $ svn propset svn:keywords Id identd.c -- let's see how it works... * ... ``svn propset svn:keywords 'Id Rev' identd.c'' !!! * * Revision 2.1 2004/01/15 18:14:42 too * Made BIND_ADDRESS definable (in compiler command line). * Added some typecasts (using checked_cast() macro). * Thanks to Jeffrey D. Wheelhouse for his content. * * Revision 2.0 2003/05/05 15:21:01 too * Major update. Removed fdprintf(); replaced with use of * writev() and newly added outputstrings(). * Removed many now obsolete defines and converted one to * constant character string. * Added one assert() (and left room for more). Did some * relativily small other adjustments. * * Revision 1.7 2002/09/29 07:50:20 too * No longer chops up to IDSTR_MAX chars, but uses "%.*s" to limit length; * now works also when XXXMULTI defined. * Back-hacked self-compilable trick, with more tricks to avoid compiler * warnings. * Removed own define of FD_SETSIZE altogether; * systems has it small to begin with. * Line '415' (or whatever that is now) fixed. () -> (void) in func def. * Some fine-tuning. * Thanks to Cristian for his patches. * * Revision 1.6.1 2002-09-28 12:30:29 +0200 cii * + added defines for IDSTR_MAX, IDENT_SUBSTR, IDSTR_BUFLEN and IDSTR_MAX * (length limit on the id-string) * + program arg 1 chopped after IDSTR_MAX characters (when applicable); * reason is: * - if the program is called with a relativelly long string as arg 1 * (tested with about 400 chars), a segfault occurs due to an internal * buffer overflow (buffer space reserved for id-string is 128 chars, * but never verified) * - it may trigger buffer overflows in clients * + put a proper comment at the top of the file * + sorted out FD_SETSIZE (on Linux it's already defined) * - moved it down below all the includes * + added time.h include * + added some short comments * + conditionals '{', '}' enclosed * + variable index -> idx in function closeOldest (killed a warning) * + splitted multiple statements on a singel line * + splitted long lines * + prototypes ending in '()' -> '(void)'; changed by protoize * + corrected most warnings, but "function declaration isn't a prototype" * which still occurs on line: 415 * + added IDENT_PORT * + added IDENT_SUBSTR * * Revision 1.6 2002/07/31 16:25:20 too * Now works when started as root (in Linux). Stupid me, tested * only starting as an ordinary loser. * * Revision 1.5 2002/07/29 14:02:42 too * Added possibility to have multible reply users, one (pseudo)randomly * chosen at each time. * * Revision 1.4 2001/02/09 08:45:42 too * Now GID is also changed to nobody/nogroup. * * Revision 1.3 2000/06/07 05:55:44 too * Fixed some Solaris compilation "bugs". * Changed LOG_PERROR to LOG_CONS * * Revision 1.2 1999/07/30 04:08:42 too * Added printing version string (and exit) with `-V' command line option. * * Revision 1.1 1999/04/21 17:23:20 too * - Writes process id to /var/run/identd.pid. * - Changes (effective) user id to `nobody' after initialization * (binding socket etc.). * - Ignores some signals (HUP and PIPE). * - Handles some signals that aborts by default. The handler function * tries to get rid of the pidfile. * * Revision 0.9b 1999/04/15 20:45:12 too * Not so much spaghetti anymore. Added documentation and more replies. * * Revision 0.9 1999/04/12 18:30:00 too * Version for unix systems. Standalone, supports 20 concurrent connections. * The code is quite a spaghetti. But that does not matter. */ #ifdef DEBUG #undef ndebug #else #define ndebug 1 #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if __BYTE_ORDER == __BIG_ENDIAN #define IPADDR(a,b,c,d) ((in_addr_t)((a << 24) + (b << 16) + (c << 8) + d)) #define IPPORT(v) ((in_port_t)v) #define A_x_256(a)((a<<8)) #elif __BYTE_ORDER == __LITTLE_ENDIAN #define IPADDR(a,b,c,d) (a + (b << 8) + (c << 16) + (d << 24)) #define IPPORT(v) ((in_port_t)((v >> 8) | (v << 8))) #define A_x_256(a) (a) #else #error unknown ENDIAN #endif #ifndef __STRING #define __STRING(x) #x #endif /* Let's see how long-lived this is... */ #define __STRINGIFY_MACRO(x) __STRING(x) #ifndef BIND_ADDRESS #define BIND_ADDRESS 0.0.0.0 #endif #ifndef BIND_ADDRESS6 #define BIND_ADDRESS6 :: #endif #define IDENT_PORT 113 #define MAXCONNS 20 #define MAXIDLETIME 45 #ifndef USE_UNIX_OS static const char ident_substr[] = " : USERID : OTHER : "; #else static const char ident_substr[] = " : USERID : UNIX : "; #endif static const int ident_substr_len = sizeof ident_substr - 1; #if !defined __cplusplus typedef enum { false = 0, true = 1 } bool; #endif #if (__GNUC__ >= 3) #define GCCATTR_UNUSED __attribute ((unused)) #define from_type(ft, v) \ __builtin_choose_expr (__builtin_types_compatible_p (typeof (v), ft), \ (v), (void)0) #define checked_cast(ft, tt, v) \ __builtin_choose_expr (__builtin_types_compatible_p (typeof (v), ft), \ ((tt)(v)), (void)0) #else #define GCCATTR_UNUSED #define from_type(ft, v) (v) #define checked_cast(ft, tt, v) ((tt)(v)) #endif /* ... */ #define CVP (const void *) #ifndef DEBUG #define FCS 2 /* First Connection Socket */ #define TRACE(x, y); #else #define FCS 4 #define TRACE(x, y) if (x) printf y #endif /* descriptors when debugging: * 0 = server socket * 1 = standard output (debugging output) * 2 = standard error * 3 = syslog fd (hopefully -- otherwise may work a bit wierdly) * 4 - 4 + MAXCONNS = connection sockets * * descriptors when not debugging * 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. */ /* * FD of the connection is always the index of the connection structure * in `conns' array + FCS */ struct { char buf[20]; int len; time_t lasttime; } conns[MAXCONNS]; /* * To support multible usernames that can be replied by this fake identd * define `XXXMULTI' in compilation command line. This doesn't look guite * pretty, but alternatives looks even uglier. * XXX NOTE: multi currently only slightly tested XXXX. */ #ifdef XXXMULTI #define IU_IN_STRUCT const char * const * identuserlist; int identusers #define SET_IU(s, c) do { G.identuserlist = &(s); G.identusers = c; } while (0) #define IU_IN_USAGESTR "[identuser [identuser2...]]" #else #define IU_IN_STRUCT const char * identuser #define SET_IU(s, c) G.identuser = (s) #define IU_IN_USAGESTR "[identuser]" #endif /* When using global variables, bind those at least to a structure. */ struct { IU_IN_STRUCT; fd_set readfds; int conncnt; bool randident; } G; /* * Prototypes */ static void reply(int s, char * buf); static void replyError(int s, const char * buf); static const char * strerrno(void); static const int one = 1; static const char * const nobodystr = "nobody"; static const char * alphanum = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; static inline void movefd(int from, int to) { TRACE(1, ("movefd(from = %d, to = %d)\n", from, to)); if (from != to) { dup2(from, to); close(from); } } /* * inetbind() must always return 0 or value < 0. * ... i.e. this version -- saves need for storage of the return value. */ #if 0 /* unused */ static int inetbind(int port) { return inetbind(htons(port)); } #endif static int inetbind(int ipport) { int s, len; union { struct sockaddr_in sin4; struct sockaddr_in6 sin6; } addr; close(0); memset(&addr, 0, sizeof addr); if ((s = socket(AF_INET6, SOCK_STREAM, 0)) >= 0) { len = sizeof addr.sin6; inet_pton(AF_INET6, __STRINGIFY_MACRO(BIND_ADDRESS6), &addr.sin6.sin6_addr); addr.sin6.sin6_family = AF_INET6; addr.sin6.sin6_port = ipport; } else if ((s = socket(AF_INET, SOCK_STREAM, 0)) >= 0) { len = sizeof addr.sin4; addr.sin4.sin_addr.s_addr = inet_addr(__STRINGIFY_MACRO(BIND_ADDRESS)); addr.sin4.sin_family = AF_INET; addr.sin4.sin_port = ipport; } else { syslog(LOG_CRIT, "Can not create server socket: %s.", strerrno()); return -1; } setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &one, sizeof one); if (bind(s, (struct sockaddr *)&addr, len) < 0) { syslog(LOG_CRIT, "Can not bind() server socket: %s.", strerrno()); return -1; } if (listen(s, 5) < 0) { syslog(LOG_CRIT, "Can not listen() server socket: %s.", strerrno()); return -1; } movefd(s, 0); return 0; } static void deleteConn(int s) { int i = s - FCS; TRACE(1, ("deleteConn(): socket %d, conncnt %d\n", s, G.conncnt)); 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); } TRACE(1, ("Clearing fd %d, readfds now 0x%x\n\n", G.conncnt + FCS, *(int *)&G.readfds)); 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; TRACE(1, ("closeOldest(): index %d, socket %d\n", idx, idx + FCS)); 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; } static int getport(void) { struct servent * se; if ((se = getservbyname("auth", "tcp")) == NULL) return IPPORT(IDENT_PORT); else return se->s_port; } static const char * strerrno() { #if 1 return strerror(errno); #else extern char * sys_errlist[]; return sys_errlist[errno]; #endif } #define WriteCS(f, s) write(f, s, sizeof s - 1) static void writestrings(int fd, const char * str, ...) { va_list ap; va_start(ap, str); while (str) { write(fd, str, strlen(str)); str = va_arg(ap, const char *); } va_end(ap); } #ifndef DEBUG static void godaemon(void) { switch(fork()) { case -1: exit(-1); case 0: close(1); close(2); setsid(); break; default: exit(0); } } #endif #ifdef TRG #define PIDFILE "/var/run/" TRG ".pid" #else #define PIDFILE "/var/run/identd.pid" #endif static void delpidfile(void) { /* * Usually nobody has no write/delete access to directory /var/run/ * therefore if file cannot be deleted, it is truncated */ if (unlink(PIDFILE) < 0) close(open(PIDFILE, O_WRONLY|O_CREAT|O_TRUNC, 0644)); } static void handlexitsigs(void) { delpidfile(); exit(0); } static void writepid(uid_t nobody, uid_t nogrp) /* May succeed. If not, won't care. */ { int fd = open(PIDFILE, O_WRONLY|O_CREAT|O_TRUNC, 0664); char buf[24]; if (fd < 0) return; /* we don't use snprintf() here since it is not so portable...*/ /* Anyway, 64-bit integer is at max 20 characters long. */ sprintf(buf, "%d\n", getpid()); buf[23] = '\0'; write(fd, buf, strlen(buf)); fchown(fd, nobody, nogrp); close(fd); signal(SIGTERM, (void(*)(int))handlexitsigs); signal(SIGINT, (void(*)(int))handlexitsigs); signal(SIGQUIT, (void(*)(int))handlexitsigs); /* should this handle ILL, ... (see signal(7)) */ } static void printversion(void) { struct iovec iv[4]; iv[0].iov_base = TRG; iv[0].iov_len = sizeof TRG - 1; iv[1].iov_base = " "; iv[1].iov_len = 1; iv[2].iov_base = VERSION; iv[2].iov_len = sizeof VERSION - 1; iv[3].iov_base = ".\n"; iv[3].iov_len = 2; writev(1, iv, 4); } int main(int argc GCCATTR_UNUSED, const char * argv[]) { uid_t nobody, nogrp; memset(conns, 0, sizeof conns); memset(&G, 0, sizeof G); FD_ZERO(&G.readfds); FD_SET(0, &G.readfds); TRACE(1, ("s: `%s', l = %d\n", ident_substr, ident_substr_len)); if (argv[1]) if (argv[1][0] == '-') { if (argv[1][1] == 'V') { printversion(); return 0; } else { if (argv[1][1] == 'r') { G.randident = true; srand(time(0)); } else { char b[2]; b[0] = argv[1][1]; b[1]= '\0'; writestrings(2, argv[0], ": invalid option -- ", b, ".\n", "Usage: ", argv[0], " [-rV] ", IU_IN_USAGESTR "\n", NULL); return 1; } }} else SET_IU(argv[1], argc - 1); else SET_IU(nobodystr, 1); #ifndef DEBUG close(1); /* not debugging, openlog() hopefully uses fd 1. */ #else close(3); /* debugging, TRACE uses fd 1, openlog() hopefully fd 3 */ #endif openlog("identd", LOG_CONS, LOG_DAEMON); { struct passwd * pw = getpwnam(nobodystr); if (pw) { nobody = pw->pw_uid; nogrp = pw->pw_gid; } else { syslog(LOG_CRIT, "Can not find user `nobody': %s,", strerrno()); return -1; } } if (inetbind(getport()) < 0) return -1; /* */ { int i; for (i = FCS; i < MAXCONNS + FCS; i++) close(i); } #ifdef DEBUG #ifndef LOG_PERROR #define LOG_PERROR 0 #endif openlog("identd", LOG_PERROR, LOG_DAEMON); #else /* not DEBUG */ godaemon(); openlog("identd", 0, LOG_DAEMON); close(2); signal(SIGHUP, SIG_IGN); #endif /* DEBUG */ signal(SIGPIPE, SIG_IGN); /* connection closed when writing (raises ???) */ writepid(nobody, nogrp); setegid(nogrp); setgid(nogrp); setuid(nobody); seteuid(nobody); { int i; for (i = 0; i < 4; i++) { const char * id = NULL; unsigned int rv = 0; switch (i) { case 0: rv = (unsigned int)getegid(); id = "egid"; break; case 1: rv = (unsigned int)getgid(); id = "gid"; break; case 2: rv = (unsigned int)geteuid(); id = "euid"; break; case 3: rv = (unsigned int)getuid(); id = "uid"; break; } if (rv == 0) { syslog(LOG_ERR, "Can not drop all root privileges (%s) !!! %s !!!", id, strerrno()); delpidfile(); return -1; } } } while (2) { fd_set rfds = G.readfds; struct timeval tv = { 15, 0 }; int i; int tim = time(NULL); TRACE(1, ("calling select(): n = %d, rfds = 0x%x\n\n", G.conncnt + FCS, *(int *)&rfds)); 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; TRACE(1, ("data socket fd_isset %d\n", s)); if ((int)(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); TRACE(1, ("server socket fd_isset, %d accepted\n", s)); if (s < 0) { if (errno != EINTR) /* EINTR */ syslog(LOG_ERR, "accept: %s", strerrno()); } 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); } } } } static int parseAddrs(char * ptr, char ** myaddr, char ** heraddr); static void replyError(int s, const 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]; #ifdef XXXMULTI const char * iul = G.identuserlist[random() % G.identusers]; #endif 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 = checked_cast(const char[], void *, ident_substr); iv[3].iov_len = ident_substr_len; #ifdef XXXMULTI iv[4].iov_base = checked_cast(const char *, void *, iul); iv[4].iov_len = strlen(iul); #else if (G.randident) { /* generate random string as reply: */ int i; char randomstring[8]; int randlen = (random() % 6) + 3; /* random string length 3-8 */ /* have first char letter... */ randomstring[0] = alphanum[10 + random() % 52]; for (i = 1; i < randlen; i++) randomstring[i] = alphanum[random() % 62]; iv[4].iov_base = checked_cast(char [], void *, randomstring); iv[4].iov_len = randlen; } else { /* use usual behaviour */ iv[4].iov_base = checked_cast(const char *, void *, G.identuser); iv[4].iov_len = strlen(G.identuser); } #endif iv[5].iov_base = "\r\n"; iv[5].iov_len = 2; writev(s, iv, 6); } } static int chmatch(char c, const char * chars) { for (; *chars; chars++) if (c == *chars) return 1; return 0; } static int skipchars(char ** p, const 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 , */ 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; } /* EOF */