chrootsetup_linux.sh

   1 # chrootsetup_linux.sh
   2
   3 # This file SHOULD NOT be executable!  It is sourced by jailsetup.sh and
   4 # SHOULD NOT be executed directly!
   5
   6 # On entry the current directory will be set to the top of the chroot
   7 # This script must perform platform-specific chroot setup which includes
   8 # creating any dev device entries, setting up proc (if needed), setting
   9 # up lib64 (if needed) as well as installing a basic set of whatever libraries
  10 # are needed for a chroot to function on this platform.
  11
  12 # This script must also define a pull_in_bin function that may be called to
  13 # install an executable together with any libraries it depends on into the
  14 # chroot.
  15
  16 # Finally this script must install a suitable nc.openbsd compatible version of
  17 # netcat into the chroot jail that's available as nc.openbsd and which supports
  18 # connects to unix sockets.
  19
  20 # We are designed to set up the chroot based on binaries from
  21 # amd64 Debian lenny; some things may need slight modifications if
  22 # being run on a different distribution.
  23
  24 mkdir -p dev proc selinux
  25 chown 0:0 proc selinux
  26 rm -f lib64
  27 ln -s lib lib64
  28
  29 # Seed up /dev:
  30 rm -f dev/null dev/zero dev/random dev/urandom
  31 mknod dev/null c 1 3
  32 mknod dev/zero c 1 5
  33 mknod dev/random c 1 8
  34 mknod dev/urandom c 1 9
  35 chmod a+rw dev/null dev/zero dev/random dev/urandom
  36
  37 # Extra directories
  38 mkdir -p var/run/sshd
  39
  40 # Bring in basic libraries:
  41 rm -f lib/*
  42 # ld.so:
  43 cp -p -t lib /lib/ld-linux*.so*
  44 [ ! -d /lib64 ] || cp -p -t lib /lib64/ld-linux*64.so*
  45
  46 # Besides '=>' libs, attempt to pick up absolute path libs and create a symlink for upto one level deep
  47 extract_libs() {
  48         ldd "$1" | grep -v -e linux-gate -e linux-vdso -e ld-linux | awk '{print $1 " " $2 " " $3}' | \
  49         while read -r _f1 _f2 _f3; do
  50                 case "$_f2" in
  51                         "=>")
  52                                 echo "$_f3"
  53                                 ;;
  54                         "(0x"*)
  55                                 case "$_f1" in /*.so*)
  56                                         _basedir="$(dirname "$_f1")"
  57                                         _basedir="${_basedir#/}"
  58                                         _basedir="${_basedir#usr/}"
  59                                         case "$_basedir" in
  60                                                 lib)
  61                                                         echo "$_f1"
  62                                                         ;;
  63                                                 lib/?*)
  64                                                         _basedir="${_basedir#lib/}"
  65                                                         case "$_basedir" in */*) :;; *)
  66                                                                 if [ ! -e "lib/$_basedir" ]; then
  67                                                                         ln -s . "lib/$_basedir"
  68                                                                 fi
  69                                                                 echo "$_f1"
  70                                                         esac
  71                                         esac
  72                                 esac
  73                 esac
  74         done
  75 }
  76
  77 pull_in_lib() {
  78         [ -f "$1" ] || return
  79         dst="${2%/}/$(basename "$1")"
  80         if [ ! -e "$dst" ] || [ "$1" -nt "$dst" ]; then
  81                 cp -p -t "$2" "$1"
  82                 for llib in $(extract_libs "$1"); do
  83                         (pull_in_lib "$llib" lib)
  84                 done
  85         fi
  86         case "$(basename "$1")" in libc.*)
  87                 # grab libnss_compat.so* from libc location
  88                 for nlib in "$(dirname "$1")/libnss_compat."so*; do
  89                         (pull_in_lib "$nlib" "$2")
  90                 done
  91         esac
  92 }
  93
  94 # pull_in_bin takes two arguments:
  95 # 1: the full path to a binary to pull in (together with any library dependencies)
  96 # 2: the destination directory relative to the current directory to copy it to
  97 # for example, "pull_in_bin /bin/sh bin" will install the shell into the chroot bin directory
  98 # IMPORTANT: argument 1 must be a machine binary, NOT a shell script or other interpreted text
  99 # IMPORTANT: text scripts can simply be copied in or installed as they don't have libraries to copy
 100 # NOTE: it's expected that calling this function on a running chroot may cause temporary disruption
 101 pull_in_bin() {
 102         bin="$1"; dst="$2"
 103         cp -p -t "$dst" "$bin"
 104         # ...and all the dependencies.
 105         for lib in $(extract_libs "$bin"); do
 106                 pull_in_lib "$lib" lib
 107         done
 108 }
 109
 110 # A catch all that needs to be called after everything's been pulled in
 111 chroot_update_permissions() {
 112         chown -R 0:0 bin dev lib sbin var
 113 }
 114
 115 # nothing special here, the nc.openbsd compatible utility is nc.openbsd
 116 pull_in_bin /bin/nc.openbsd bin