helper.c.orig

/*
 *  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);
}