util-vserver/src/capchroot.c

   1 // $Id$
   2
   3 // Copyright (C) 2003 Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de>
   4 // based on capchroot.cc by Jacques Gelinas
   5 //
   6 // This program is free software; you can redistribute it and/or modify
   7 // it under the terms of the GNU General Public License as published by
   8 // the Free Software Foundation; either version 2, or (at your option)
   9 // any later version.
  10 //
  11 // This program is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15 //
  16 // You should have received a copy of the GNU General Public License
  17 // along with this program; if not, write to the Free Software
  18 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19
  20 /*
  21         This chroot command does very little. Once the chroot
  22         system call is executed, it (option) remove the CAP_SYS_CHROOT
  23         capability. Then it executes its argument
  24 */
  25
  26 #ifdef HAVE_CONFIG_H
  27 #  include <config.h>
  28 #endif
  29 #include "compat.h"
  30
  31 #include <stdio.h>
  32 #include <string.h>
  33 #include <pwd.h>
  34 #include <grp.h>
  35 #include <errno.h>
  36 #include <unistd.h>
  37 #include <stdbool.h>
  38 #include <stdlib.h>
  39
  40 #include "vserver.h"
  41
  42 int main (int argc, char *argv[])
  43 {
  44         if (argc < 3){
  45                 fprintf (stderr,"capchroot version %s\n",VERSION);
  46                 fprintf (stderr
  47                         ,"capchroot --nochroot directory [ --suid user ] command argument\n"
  48                          "\n"
  49                          "--nochroot remove the CAP_SYS_CHROOT capability\n"
  50                          "           after the chroot system call.\n"
  51                          "--suid switch to a different user (in the vserver context)\n"
  52                          "       before executing the command.\n");
  53         }else{
  54                 const char *uid = NULL;
  55                 bool nochroot = false;
  56                 int dir;
  57                 for (dir=1; dir<argc; dir++){
  58                         const char *arg = argv[dir];
  59                         if (arg[0] != '-' && arg[1] != '-'){
  60                                 break;
  61                         }else if (strcmp(arg,"--nochroot")==0){
  62                                 nochroot = true;
  63                         }else if (strcmp(arg,"--suid")==0){
  64                                 dir++;
  65                                 uid = argv[dir];
  66                         }
  67
  68                 }
  69                 // We resolve the UID before doing the chroot.
  70                 // If we do the getpwnam after the chroot, we will end
  71                 // up loading shared object from the vserver.
  72                 // This is causing two kind of problem: Incompatibilities
  73                 // and also a security flaw. The shared objects in the vserver
  74                 // may be tweaked to get control of the root server ...
  75                 getpwnam ("root");
  76                 if (chroot(argv[dir]) == -1){
  77                         fprintf (stderr,"Can't chroot to directory %s (%s)\n",argv[dir]
  78                                 ,strerror(errno));
  79                 }else{
  80                         struct passwd *p = NULL;
  81                         int cmd          = dir + 1;
  82
  83                         if (nochroot){
  84                                 vc_new_s_context (-2,1<<VC_CAP_SYS_CHROOT,0);
  85                         }
  86
  87                         if (uid != NULL && strcmp(uid,"root")!=0){
  88                                 p = getpwnam(uid);
  89                                 if (p == NULL){
  90                                         fprintf (stderr,"User not found: %s\n",uid);
  91                                         exit (-1);
  92                                 }
  93                         }
  94                         if (p != NULL) {
  95                                 setgroups (0,NULL);
  96                                 setgid(p->pw_gid);
  97                                 setuid(p->pw_uid);
  98                         }
  99                         if (cmd >= argc){
 100                                 fprintf (stderr,"capchroot: No command to execute, do nothing\n");
 101                         }else{
 102                                 execvp (argv[cmd],argv+cmd);
 103                                 fprintf (stderr,"Can't execute %s (%s)\n",argv[cmd]
 104                                         ,strerror(errno));
 105                         }
 106                 }
 107         }
 108         return -1;
 109 }
 110
 111