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/*
* helper.c - setuid helper program for authbind
*
* authbind is Copyright (C) 1998 Ian Jackson
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
*/
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <assert.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#ifndef CONFIGDIR
# define CONFIGDIR "/etc/authbind"
#endif
static const char *rcsid="$Id: helper.c,v 1.5 1998-08-30 19:52:38 ian Exp $";
static void exiterrno(int e) {
exit(e>0 && e<128 ? e : ENOSYS);
}
static void perrorfail(const char *m) {
int e;
e= errno;
fprintf(stderr,"libauthbind's helper: %s: %s\n",m,strerror(e));
exiterrno(e);
}
static void badusage(void) {
fprintf(stderr,"libauthbind's helper: bad usage\n (%s)\n",rcsid);
exit(ENOSYS);
}
static struct sockaddr_in saddr;
static void authorised(void) {
if (bind(0,&saddr,sizeof(saddr))) exiterrno(errno);
else _exit(0);
}
int main(int argc, const char *const *argv) {
uid_t uid;
char fnbuf[100];
char *ep;
const char *np;
unsigned long addr, port, haddr, thaddr, thmask;
unsigned int hport, a1,a2,a3,a4, alen,pmin,pmax;
int nchar;
FILE *file;
if (argc != 3) badusage();
addr= strtoul(argv[1],&ep,16); if (*ep || addr&~0x0ffffffffUL) badusage();
port= strtoul(argv[2],&ep,16); if (*ep || port&~0x0ffffUL) badusage();
hport= htons(port);
if (hport >= IPPORT_RESERVED/2) _exit(EPERM);
if (chdir(CONFIGDIR)) perrorfail("chdir " CONFIGDIR);
fnbuf[sizeof(fnbuf)-1]= 0;
memset(&saddr,0,sizeof(saddr));
saddr.sin_family= AF_INET;
saddr.sin_port= port;
saddr.sin_addr.s_addr= addr;
snprintf(fnbuf,sizeof(fnbuf)-1,"byport/%u",hport);
if (!access(fnbuf,X_OK)) authorised();
if (errno != ENOENT) exiterrno(errno);
np= inet_ntoa(saddr.sin_addr); assert(np);
snprintf(fnbuf,sizeof(fnbuf)-1,"byaddr/%s:%u",np,hport);
if (!access(fnbuf,X_OK)) authorised();
if (errno != ENOENT) exiterrno(errno);
uid= getuid(); if (uid==(uid_t)-1) perrorfail("getuid");
snprintf(fnbuf,sizeof(fnbuf)-1,"byuid/%lu",(unsigned long)uid);
file= fopen(fnbuf,"r");
if (!file) exiterrno(errno==ENOENT ? EPERM : errno);
haddr= ntohl(addr);
while (fgets(fnbuf,sizeof(fnbuf)-1,file)) {
nchar= -1;
sscanf(fnbuf," %u.%u.%u.%u/%u:%u,%u %n",
&a1,&a2,&a3,&a4,&alen,&pmin,&pmax,&nchar);
if (nchar != strlen(fnbuf) ||
alen>32 || pmin&~0x0ffff || pmax&~0x0ffff ||
a1&~0x0ff || a2&~0xff || a3&~0x0ff || a4&~0x0ff)
continue;
if (hport<pmin || hport>pmax) continue;
thaddr= (a1<<24)|(a2<<16)|(a3<<8)|(a4);
thmask= 0x0ffffffffUL<<(32-alen);
if ((haddr&thmask) != thaddr) continue;
authorised();
}
if (ferror(file)) perrorfail("read per-uid file");
_exit(ENOENT);
}