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 var/tmp
  39
  40 has_files()
  41 {
  42         for _f; do
  43                 test -f "$_f" || return 1
  44         done
  45         return 0
  46 }
  47
  48 # Bring in basic libraries:
  49 rm -f lib/*
  50
  51 # ld.so:
  52 [ -d /lib ] && has_files /lib/ld-linux*.so* && cp -p -t lib /lib/ld-linux*.so*
  53 [ -d /lib64 ] && has_files /lib64/ld-linux*64.so* && cp -p -t lib /lib64/ld-linux*64.so*
  54 has_files lib/ld-linux*.so* || {
  55         echo "ERROR: could not find any ld-linux*.so* file" >&2
  56         exit 1
  57 }
  58
  59 # Besides '=>' libs, attempt to pick up absolute path libs and create a symlink for upto one level deep
  60 extract_libs() {
  61         ldd "$1" | grep -v -e linux-gate -e linux-vdso -e ld-linux | awk '{print $1 " " $2 " " $3}' | \
  62         while read -r _f1 _f2 _f3; do
  63                 case "$_f2" in
  64                         "=>")
  65                                 echo "$_f3"
  66                                 ;;
  67                         "(0x"*)
  68                                 case "$_f1" in /*.so*)
  69                                         _basedir="$(dirname "$_f1")"
  70                                         _basedir="${_basedir#/}"
  71                                         _basedir="${_basedir#usr/}"
  72                                         case "$_basedir" in
  73                                                 lib)
  74                                                         echo "$_f1"
  75                                                         ;;
  76                                                 lib/?*)
  77                                                         _basedir="${_basedir#lib/}"
  78                                                         case "$_basedir" in */*) :;; *)
  79                                                                 if [ ! -e "lib/$_basedir" ]; then
  80                                                                         ln -s . "lib/$_basedir"
  81                                                                 fi
  82                                                                 echo "$_f1"
  83                                                         esac
  84                                         esac
  85                                 esac
  86                 esac
  87         done
  88 }
  89
  90 pull_in_lib() {
  91         [ -f "$1" ] || return
  92         dst="${2%/}/$(basename "$1")"
  93         if [ ! -e "$dst" ] || [ "$1" -nt "$dst" ]; then
  94                 cp -p -t "$2" "$1"
  95                 for llib in $(extract_libs "$1"); do
  96                         (pull_in_lib "$llib" lib)
  97                 done
  98         fi
  99         case "$(basename "$1")" in libc.*)
 100                 # grab libnss_compat.so* from libc location
 101                 for nlib in "$(dirname "$1")/libnss_compat."so*; do
 102                         (pull_in_lib "$nlib" "$2")
 103                 done
 104         esac
 105 }
 106
 107 # pull_in_bin takes two arguments:
 108 # 1: the full path to a binary to pull in (together with any library dependencies)
 109 # 2: the destination directory relative to the current directory to copy it to which
 110 # MUST already exist with optional alternate name if the name in the chroot should be different
 111 # 3: optional name of binary that if already in $2 and the same as $1 hard link to instead
 112 # for example, "pull_in_bin /bin/sh bin" will install the shell into the chroot bin directory
 113 # for example, "pull_in_bin /bin/bash bin/sh" will install bash as the chroot bin/sh
 114 # IMPORTANT: argument 1 must be a machine binary, NOT a shell script or other interpreted text
 115 # IMPORTANT: text scripts can simply be copied in or installed as they don't have libraries to copy
 116 # NOTE: it's expected that calling this function on a running chroot may cause temporary disruption
 117 # In order to avoid a busy error while replacing binaries we first copy the binary to the
 118 # var/tmp directory and then force move it into place after the libs have been brought in.
 119 pull_in_bin() {
 120         bin="$1"; bdst="$2"
 121         if [ -d "${bdst%/}" ]; then
 122                 bnam="$(basename "$bin")"
 123                 bdst="${bdst%/}"
 124         else
 125                 bnam="$(basename "$bdst")"
 126                 bdst="${bdst%/*}"
 127         fi
 128         if [ -n "$3" ] && [ "$3" != "$bnam" ] && \
 129            [ -r "$bdst/$3" -a -x "$bdst/$3" ] && cmp -s "$bin" "$bdst/$3"; then
 130                 ln -f "$bdst/$3" "$bdst/$bnam"
 131                 return 0
 132         fi
 133         cp -p -t var/tmp "$bin"
 134         # ...and all the dependencies.
 135         for lib in $(extract_libs "$bin"); do
 136                 pull_in_lib "$lib" lib
 137         done
 138         mv -f "var/tmp/$(basename "$bin")" "$bdst/$bnam"
 139 }
 140
 141 # A catch all that needs to be called after everything's been pulled in
 142 chroot_update_permissions() {
 143         rm -rf var/tmp
 144         chown -R 0:0 bin dev lib sbin var
 145 }
 146
 147 # nothing special here, the nc.openbsd compatible utility is nc.openbsd
 148 pull_in_bin /bin/nc.openbsd bin