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 # connections 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 chroot_dir="$(pwd)"
  25
  26 mkdir -p dev proc selinux
  27 chown 0:0 proc selinux
  28 rm -f lib64
  29 ln -s lib lib64
  30
  31 # Seed up /dev:
  32 rm -f dev/null dev/zero dev/random dev/urandom
  33 mknod dev/null c 1 3
  34 mknod dev/zero c 1 5
  35 mknod dev/random c 1 8
  36 mknod dev/urandom c 1 9
  37 chmod a+rw dev/null dev/zero dev/random dev/urandom
  38
  39 # Extra directories
  40 mkdir -p var/run/sshd var/tmp
  41
  42 has_files()
  43 {
  44         for _f in "$@"; do
  45                 test -f "$_f" || return 1
  46         done
  47         return 0
  48 }
  49
  50 # Bring in basic libraries:
  51 rm -f lib/*
  52
  53 # ld.so:
  54 ! [ -d /lib ] || ! has_files /lib/ld-linux*.so* || cp -p -t lib /lib/ld-linux*.so*
  55 ! [ -d /lib64 ] || ! has_files /lib64/ld-linux*64.so* || cp -p -t lib /lib64/ld-linux*64.so*
  56 has_files lib/ld-linux*.so* || {
  57         echo "ERROR: could not find any ld-linux*.so* file" >&2
  58         exit 1
  59 }
  60
  61 # Besides '=>' libs, attempt to pick up absolute path libs and create a symlink for upto one level deep
  62 extract_libs() {
  63         ldd "$1" | grep -v -e linux-gate -e linux-vdso -e ld-linux | awk '{print $1 " " $2 " " $3}' |
  64         while read -r _f1 _f2 _f3; do
  65                 case "$_f2" in
  66                         "=>")
  67                                 echo "$_f3"
  68                                 ;;
  69                         "(0x"*)
  70                                 case "$_f1" in /*.so*)
  71                                         _basedir="$(dirname "$_f1")"
  72                                         _basedir="${_basedir#/}"
  73                                         _basedir="${_basedir#usr/}"
  74                                         case "$_basedir" in
  75                                                 lib)
  76                                                         echo "$_f1"
  77                                                         ;;
  78                                                 lib/?*)
  79                                                         _basedir="${_basedir#lib/}"
  80                                                         case "$_basedir" in */*) :;; *)
  81                                                                 if [ ! -e "lib/$_basedir" ]; then
  82                                                                         ln -s . "lib/$_basedir"
  83                                                                 fi
  84                                                                 echo "$_f1"
  85                                                         esac
  86                                         esac
  87                                 esac
  88                 esac
  89         done
  90         test $? -eq 0
  91 }
  92
  93 pull_in_lib() {
  94         [ -f "$1" ] || return
  95         dst="${2%/}/$(basename "$1")"
  96         if [ ! -e "$dst" ] || [ "$1" -nt "$dst" ]; then
  97                 cp -p -t "$2" "$1"
  98                 for llib in $(extract_libs "$1"); do
  99                         (pull_in_lib "$llib" lib)
 100                         test $? -eq 0
 101                 done
 102         fi
 103         case "$(basename "$1")" in libc.*)
 104                 # grab libnss_compat.so* from libc location
 105                 ! has_files "$(dirname "$1")/libnss_compat."so* ||
 106                 for nlib in "$(dirname "$1")/libnss_compat."so*; do
 107                         (pull_in_lib "$nlib" "$2")
 108                         test $? -eq 0
 109                 done
 110         esac
 111 }
 112
 113 # pull_in_bin takes two arguments:
 114 # 1: the full path to a binary to pull in (together with any library dependencies)
 115 # 2: the destination directory relative to the current directory to copy it to which
 116 # MUST already exist with optional alternate name if the name in the chroot should be different
 117 # 3: optional name of binary that if already in $2 and the same as $1 hard link to instead
 118 # for example, "pull_in_bin /bin/sh bin" will install the shell into the chroot bin directory
 119 # for example, "pull_in_bin /bin/bash bin/sh" will install bash as the chroot bin/sh
 120 # IMPORTANT: argument 1 must be a machine binary, NOT a shell script or other interpreted text
 121 # IMPORTANT: text scripts can simply be copied in or installed as they don't have libraries to copy
 122 # NOTE: it's expected that calling this function on a running chroot may cause temporary disruption
 123 # In order to avoid a busy error while replacing binaries we first copy the binary to the
 124 # var/tmp directory and then force move it into place after the libs have been brought in.
 125 pull_in_bin() {
 126         bin="$1"; bdst="$2"
 127         if [ -d "${bdst%/}" ]; then
 128                 bnam="$(basename "$bin")"
 129                 bdst="${bdst%/}"
 130         else
 131                 bnam="$(basename "$bdst")"
 132                 bdst="${bdst%/*}"
 133         fi
 134         if [ -n "$3" ] && [ "$3" != "$bnam" ] &&
 135            [ -r "$bdst/$3" ] && [ -x "$bdst/$3" ] && cmp -s "$bin" "$bdst/$3"; then
 136                 ln -f "$bdst/$3" "$bdst/$bnam"
 137                 return 0
 138         fi
 139         cp -p -t var/tmp "$bin"
 140         # ...and all the dependencies.
 141         for lib in $(extract_libs "$bin"); do
 142                 pull_in_lib "$lib" lib
 143         done
 144         mv -f "var/tmp/$(basename "$bin")" "$bdst/$bnam"
 145 }
 146
 147 # A catch all that needs to be called after everything's been pulled in
 148 chroot_update_permissions() {
 149         # Be paranoid
 150         [ -n "$chroot_dir" ] && [ "$chroot_dir" != "/" ] || { echo bad '$chroot_dir' >&2; exit 2; }
 151         cd "$chroot_dir" || { echo bad '$chroot_dir' >&2; exit 2; }
 152         rm -rf var/tmp
 153         chown -R 0:0 bin dev lib sbin var
 154 }
 155
 156 # the nc.openbsd compatible utility is available as $var_nc_openbsd_bin
 157 pull_in_bin "$var_nc_openbsd_bin" bin/nc.openbsd