From f9fdd76da8558747d4afb6b1563cccbc482301fd Mon Sep 17 00:00:00 2001
From: Jakub Filo <plantroon@plantroon.com>
Date: Tue, 7 Sep 2021 20:14:21 +0000
Subject: [PATCH] Add 'examples/shell/alpine/start-chroot.sh'

---
 examples/shell/alpine/start-chroot.sh | 108 ++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 examples/shell/alpine/start-chroot.sh

diff --git a/examples/shell/alpine/start-chroot.sh b/examples/shell/alpine/start-chroot.sh
new file mode 100644
index 0000000..8a352d8
--- /dev/null
+++ b/examples/shell/alpine/start-chroot.sh
@@ -0,0 +1,108 @@
+#!/bin/sh -e
+
+if [ 0 -ne `id -u` ]; then
+  echo "This script needs root access" >&2
+  exit 1
+fi
+
+if ! [ -d "$1" ] || [ x-h = x"$*" ] || [ x--help = x"$*" ]; then
+  echo "Usage: ${0##*/} <chroot_directory>" >&2
+  exit 1
+fi
+
+if [ x1 = x`sysctl -ne kernel.grsecurity.chroot_deny_chmod` ]; then
+  echo "Warning: can't suid/sgid inside chroot" >&2
+fi
+if [ x1 = x`sysctl -ne kernel.grsecurity.chroot_deny_mknod` ]; then
+  echo "Warning: can't mknod inside chroot" >&2
+fi
+if [ x1 = x`sysctl -ne kernel.grsecurity.chroot_deny_mount` ]; then
+  echo "Warning: can't mount inside chroot" >&2
+fi
+if [ x1 = x`sysctl -ne kernel.grsecurity.chroot_deny_chroot` ]; then
+  echo "Warning: can't chroot inside chroot" >&2
+fi
+
+cd "$1"
+if ! [ -d ./etc ]; then
+  echo "No etc directory inside $1" >&2
+  exit 1
+fi
+shift
+
+MOUNTED=
+umount_all() {
+  case $MOUNTED in
+  shm\ *) if [ -L ./dev/shm ]; then
+            umount ./`readlink ./dev/shm`
+          else
+            umount ./dev/shm
+          fi
+          MOUNTED=${MOUNTED#shm };;
+  esac
+  case $MOUNTED in
+  run\ *) umount ./run
+          MOUNTED=${MOUNTED#run };;
+  esac
+  case $MOUNTED in
+  tmp\ *) umount ./tmp
+          MOUNTED=${MOUNTED#tmp };;
+  esac
+  case $MOUNTED in
+  proc\ *) umount ./proc
+          MOUNTED=${MOUNTED#proc };;
+  esac
+  case $MOUNTED in
+  sys\ *) umount ./sys
+          MOUNTED=${MOUNTED#sys };;
+  esac
+  case $MOUNTED in
+  pts\ *) umount ./dev/pts
+          MOUNTED=${MOUNTED#pts };;
+  esac
+  case $MOUNTED in
+  dev\ *) umount ./dev
+          MOUNTED=${MOUNTED#dev };;
+  esac
+}
+trap 'umount_all' EXIT
+
+#mkdir -p ./etc ./dev/pts ./sys ./proc ./tmp ./run ./boot ./root
+
+cp -iL /etc/resolv.conf ./etc/ || true  # if ^C, will cancel script
+
+mount --bind /dev ./dev
+MOUNTED="dev $MOUNTED"
+
+mount -t devpts devpts ./dev/pts -o nosuid,noexec
+MOUNTED="pts $MOUNTED"
+
+mount -t sysfs sys ./sys -o nosuid,nodev,noexec,ro
+MOUNTED="sys $MOUNTED"
+
+mount -t proc proc ./proc -o nosuid,nodev,noexec
+MOUNTED="proc $MOUNTED"
+
+mount -t tmpfs tmp ./tmp -o mode=1777,nosuid,nodev,strictatime
+MOUNTED="tmp $MOUNTED"
+mount -t tmpfs run ./run -o mode=0755,nosuid,nodev
+MOUNTED="run $MOUNTED"
+if [ -L ./dev/shm ]; then
+  mkdir -p ./`readlink ./dev/shm`
+  mount -t tmpfs shm ./`readlink ./dev/shm` -o mode=1777,nosuid,nodev
+else
+  #mkdir -p ./dev/shm
+  mount -t tmpfs shm ./dev/shm -o mode=1777,nosuid,nodev
+fi
+MOUNTED="shm $MOUNTED"
+
+case $1 in
+  -l) shift;;
+  -l*) one=${1#-l}; shift; set -- -"$one" "$@";;
+esac
+chroot . /usr/bin/env -i SHELL=/bin/sh HOME=/root TERM="$TERM" \
+  PATH=/usr/sbin:/usr/bin:/sbin:/bin PS1='chroot # ' /bin/sh -l "$@"
+
+# FIXME
+# are USER and LOGNAME set automatically?
+# perhaps: source /etc/profile && export PS1="chroot $PS1"