Add a wrapper script to run ansible in chroot

Script uses namespaces and overlayfs to be more robust.
Also it supports bind mounting to extend the chroot with
external files and directories.

Issue-ID: OOM-1551
Change-Id: I8c554e1b86fca86f86e6c0d0e1b106c97a08ef15
Signed-off-by: Petr Ospalý <p.ospaly@partner.samsung.com>

1 files changed, 465 insertions, 0 deletions

diff --git a/ansible/docker/run_chroot.sh b/ansible/docker/run_chroot.sh
new file mode 100755
index 00000000..b38c1295
--- /dev/null
+++ b/ansible/docker/run_chroot.sh
@@ -0,0 +1,465 @@
+#!/bin/sh
+
+#   COPYRIGHT NOTICE STARTS HERE
+
+#   Copyright 2018 © Samsung Electronics Co., Ltd.
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+
+#   COPYRIGHT NOTICE ENDS HERE
+
+
+set -e
+
+CMD=$(basename "$0")
+UMOUNT_TIMEOUT=120 # 2mins
+
+
+#
+# functions
+#
+
+help()
+{
+    echo "
+NAME:
+    ${CMD} - run command in chrooted directory
+
+DESCRIPTION:
+    It will do necessary steps to be able chroot, optional mounts and it will
+    run commands inside the requested chroot directory.
+
+    It does overlay mount so nothing inside the chroot is modified - if there
+    is no way to do overlay mount it will just do chroot directly - which means
+    that user has power to render chroot useless - beware...
+
+    The chroot is run in it's own namespace for better containerization.
+    Therefore the utility 'unshare' is necessary requirement.
+
+    After exiting the chroot all of those necessary steps are undone.
+
+USAGE:
+    ${CMD} [-h|--help|help]
+        This help
+
+    ${CMD} [OPTIONS] execute <chroot-directory> [<command with args>...]
+
+        It will do some necessary steps after which it will execute chroot
+        command and gives you prompt inside the chroot. When you leave the
+        prompt it will undo those steps.
+        On top of the ordinary chroot it will make overlay, so every change
+        inside the chroot is only temporary and chroot is kept stateless -
+        like inside a docker container. If there is no way to do overlay -
+        ordinary chroot is done.
+        Default command is: /bin/sh -l
+
+        OPTIONS:
+
+        --mount (ro|rw):<src-dir>:<inner-dir>
+            This option will mount 'src-dir' which is full path on the host
+            system into the relative path 'inner-dir' within the chroot
+            directory.
+            It can be mounted as read-only (ro) or read-write (rw).
+            Multiple usage of this argument can be used to create complex
+            hierarchy. Order is significant.
+            For example:
+                --mount ro:/scripts/ANSIBLE_DIR:/ansible \
+                --mount rw:/scripts/ANSIBLE_DIR/app:/ansible/app
+                This will mount directory ansible as read-only into chroot,
+                but it's subdirectory 'app' will be writeable.
+
+        --workdir <inner-dir>
+            This will set working directory (PWD) inside the chroot.
+
+EXAMPLE:
+    ${CMD} --mount ro:/scripts/ansible:ansible \
+        --mount rw:/scripts/ansible/app:ansible/app \
+        --workdir /ansible execute /tmp/ansible_chroot
+    # pwd
+    /ansible
+    # mount
+    overlay on / type overlay ...
+    /dev/disk on /ansible type ext4 (ro,relatime,errors=remount-ro)
+    /dev/disk on /ansible/application type ext4 (rw,relatime,errors=remount-ro)
+    none on /proc type proc (rw,relatime)
+    none on /sys type sysfs (rw,relatime)
+    none on /dev/shm type tmpfs (rw,relatime)
+
+    Directory /ansible inside the chroot is not writable but subdirectory
+    /ansible/app is.
+
+    Rest of the chroot is under overlay and all changes will be lost when
+    chroot command ends. Only changes in app directory persists bacause it
+    was bind mounted as read-write and is not part of overlay.
+
+    Note: as you can see app directory is mounted over itself but read-write.
+"
+}
+
+# arg: <directory>
+is_mounted()
+{
+    mountpoint=$(echo "$1" | sed 's#//*#/#g')
+
+    LANG=C mount | grep -q "^[^[:space:]]\+[[:space:]]\+on[[:space:]]\+${mountpoint}[[:space:]]\+type[[:space:]]\+"
+}
+
+# layers are right to left! First is on the right, top/last is on the left
+do_overlay_mount()
+{
+    if [ -d "$overlay" ] && is_mounted "$overlay" ; then
+        echo ERROR: "The overlay directory is already mounted: $overlay" >&2
+        echo ERROR: "Fix the issue - cannot proceed" >&2
+        exit 1
+    fi
+
+    # prepare dirs
+    rm -rf "$overlay" "$upperdir" "$workdir"
+    mkdir -p "$overlay"
+    mkdir -p "$upperdir"
+    mkdir -p "$workdir"
+
+    # finally overlay mount
+    if ! mount -t overlay --make-rprivate \
+        -o lowerdir="$lowerdir",upperdir="$upperdir",workdir="$workdir" \
+        overlay "$overlay" ;
+    then
+        echo ERROR: "Failed to do overlay mount!" >&2
+        echo ERROR: "Please check that your system supports overlay!" >&2
+        echo NOTE: "Continuing with the ordinary chroot without overlay!"
+
+        CHROOT_DIR="$lowerdir"
+        return 1
+    fi
+
+    CHROOT_DIR="$overlay"
+
+    return 0
+}
+
+cleanup()
+{
+    case "$OVERLAY_MOUNT" in
+        yes)
+            echo INFO: "Umounting overlay..." >&2
+            if ! umount_retry "$CHROOT_DIR" ; then
+                echo ERROR: "Cannot umount chroot: $CHROOT_DIR" >&2
+                return 1
+            fi
+
+            ;;
+        no)
+            echo INFO: "No overlay to umount" >&2
+            ;;
+    esac
+
+    if ! is_mounted "$overlay" ; then
+        echo INFO: "Deleting of temp directories..." >&2
+        rm -rf "$overlay" "$upperdir" "$workdir"
+    else
+        echo ERROR: "Overlay is still mounted: $CHROOT_DIR" >&2
+        echo ERROR: "Cannot delete: $overlay" >&2
+        echo ERROR: "Cannot delete: $upperdir" >&2
+        echo ERROR: "Cannot delete: $workdir" >&2
+        return 1
+    fi
+}
+
+check_external_mounts()
+{
+    echo "$EXTERNAL_MOUNTS" | sed '/^[[:space:]]*$/d' | while read -r mountexpr ; do
+        mount_type=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $1;}')
+        external=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $2;}')
+        internal=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $3;}' | sed -e 's#^/*##' -e 's#//*#/#g')
+
+        case "$mount_type" in
+            ro|rw)
+                :
+                ;;
+            *)
+                echo ERROR: "Wrong mount type (should be 'ro' or 'rw') in: ${mountexpr}" >&2
+                exit 1
+                ;;
+        esac
+
+        if ! [ -d "$external" ] ; then
+            echo ERROR: "Directory for mounting does not exist: ${external}" >&2
+            exit 1
+        fi
+
+        if echo "$internal" | grep -q '^/*$' ; then
+            echo ERROR: "Unacceptable internal path: ${internal}" >&2
+            exit 1
+        fi
+    done
+}
+
+do_external_mounts()
+{
+    echo INFO: "Bind mounting of external mounts..." >&2
+    echo "$EXTERNAL_MOUNTS" | sed '/^[[:space:]]*$/d' | while read -r mountexpr ; do
+        mount_type=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $1;}')
+        external=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $2;}')
+        internal=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $3;}' | sed -e 's#^/*##' -e 's#//*#/#g')
+
+        if is_mounted "${CHROOT_DIR}/${internal}" ; then
+            echo ERROR: "Mountpoint is already mounted: ${CHROOT_DIR}/${internal}" >&2
+            echo ERROR: "Fix the issue - cannot proceed" >&2
+            exit 1
+        fi
+
+        if ! mkdir -p "${CHROOT_DIR}/${internal}" ; then
+            echo ERROR: "Cannot create mountpoint: ${CHROOT_DIR}/${internal}" >&2
+            exit 1
+        fi
+
+        if ! mount --make-rprivate -o bind,${mount_type} "$external" "${CHROOT_DIR}/${internal}" ; then
+            echo ERROR: "Failed to mount: ${external} -> ${internal}" >&2
+            exit 1
+        else
+            echo INFO: "Mount: ${external} -> ${internal}" >&2
+        fi
+    done
+}
+
+# arg: <mountpoint>
+umount_retry()
+{
+    mountpoint=$(echo "$1" | sed 's#//*#/#g')
+    timeout=${UMOUNT_TIMEOUT}
+
+    umount "$mountpoint" 2>/dev/null
+    while is_mounted "$mountpoint" && [ $timeout -gt 0 ] ; do
+        umount "$mountpoint" 2>/dev/null
+        sleep 1
+        timeout=$(( timeout - 1 ))
+    done
+
+    if ! is_mounted "$mountpoint" ; then
+        return 0
+    fi
+
+    return 1
+}
+
+undo_external_mounts()
+{
+    echo INFO: "Umount external mount points..." >&2
+    echo "$EXTERNAL_MOUNTS" | tac | sed '/^[[:space:]]*$/d' | while read -r mountexpr ; do
+        mount_type=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $1;}')
+        external=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $2;}')
+        internal=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $3;}' | sed -e 's#^/*##' -e 's#//*#/#g')
+        if umount_retry "${CHROOT_DIR}/${internal}" ; then
+            echo INFO: "Unmounted: ${CHROOT_DIR}/${internal}" >&2
+        else
+            echo ERROR: "Failed to umount: ${CHROOT_DIR}/${internal}" >&2
+        fi
+    done
+}
+
+install_wrapper()
+{
+    cat > "$CHROOT_DIR"/usr/local/bin/fakeshell.sh <<EOF
+#!/bin/sh
+
+PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+export PATH
+
+gid_tty=\$(getent group | sed -n '/^tty:/p' | cut -d: -f 3)
+
+mount -t proc proc /proc
+mount -t sysfs none /sys
+mount -t tmpfs none /dev
+
+mkdir -p /dev/shm
+mkdir -p /dev/pts
+mount -t devpts -o gid=\${gid_tty},mode=620 none /dev/pts
+
+[ -e /dev/full ] || mknod -m 666 /dev/full c 1 7
+[ -e /dev/ptmx ] || mknod -m 666 /dev/ptmx c 5 2
+[ -e /dev/random ] || mknod -m 644 /dev/random c 1 8
+[ -e /dev/urandom ] || mknod -m 644 /dev/urandom c 1 9
+[ -e /dev/zero ] || mknod -m 666 /dev/zero c 1 5
+[ -e /dev/tty ] || mknod -m 666 /dev/tty c 5 0
+[ -e /dev/console ] || mknod -m 622 /dev/console c 5 1
+[ -e /dev/null ] || mknod -m 666 /dev/null c 1 3
+
+chown root:tty /dev/console
+chown root:tty /dev/ptmx
+chown root:tty /dev/tty
+
+mkdir -p "\$1" || exit 1
+cd "\$1" || exit 1
+shift
+
+exec "\$@"
+
+EOF
+    chmod +x "$CHROOT_DIR"/usr/local/bin/fakeshell.sh
+}
+
+on_exit()
+{
+    set +e
+    echo
+
+    if [ -n "$OVERLAY_MOUNT" ] ; then
+        undo_external_mounts
+    fi
+    cleanup
+}
+
+
+#
+# parse arguments
+#
+
+state=nil
+action=nil
+EXTERNAL_MOUNTS=''
+CHROOT_WORKDIR=''
+CHROOT_METADIR=''
+CHROOT_DIR=''
+COMMAND=''
+while [ -n "$1" ] ; do
+    case "$state" in
+        nil)
+            case "$1" in
+                ''|-h|--help|help)
+                    help
+                    exit 0
+                    ;;
+                --mount)
+                    EXTERNAL_MOUNTS=$(printf "%s\n%s\n" "$EXTERNAL_MOUNTS" "${2}")
+                    state=next
+                    ;;
+                --workdir)
+                    if [ -z "$CHROOT_WORKDIR" ] ; then
+                        CHROOT_WORKDIR="$2"
+                        state=next
+                    else
+                        echo ERROR: "Multiple working directory argument" >&2
+                        help >&2
+                        exit 1
+                    fi
+                    ;;
+                execute)
+                    action=execute
+                    state=execute
+                    ;;
+                *)
+                    echo ERROR: "Bad usage" >&2
+                    help >&2
+                    exit 1
+                    ;;
+            esac
+            ;;
+        next)
+            state=nil
+            ;;
+        execute)
+            CHROOT_METADIR="$1"
+            shift
+            break
+            ;;
+    esac
+    shift
+done
+
+
+case "$action" in
+    ''|nil)
+        echo ERROR: "Nothing to do - missing command" >&2
+        help >&2
+        exit 1
+        ;;
+    execute)
+        # firstly do sanity checking ...
+
+        if [ -z "$CHROOT_METADIR" ] ; then
+            echo ERROR: "Missing argument" >&2
+            help >&2
+            exit 1
+        fi
+
+        # making sure that CHROOT_METADIR is absolute path
+        CHROOT_METADIR=$(readlink -f "$CHROOT_METADIR")
+
+        if ! [ -d "$CHROOT_METADIR"/chroot ] ; then
+            echo ERROR: "Filepath does not exist: ${CHROOT_METADIR}/chroot" >&2
+            exit 1
+        fi
+
+        # check external mounts if there are any
+        check_external_mounts
+
+        # check workdir
+        if [ -n "$CHROOT_WORKDIR" ] ; then
+            CHROOT_WORKDIR=$(echo "$CHROOT_WORKDIR" | sed -e 's#^/*##' -e 's#//*#/#g')
+        fi
+
+        # we must be root
+        if [ "$(id -u)" -ne 0 ] ; then
+            echo ERROR: "Need to be root and you are not: $(id -nu)" >&2
+            exit 1
+        fi
+
+        if ! which unshare >/dev/null 2>/dev/null ; then
+            echo ERROR: "'unshare' system command is missing - ABORT" >&2
+            echo INFO: "Try to install 'util-linux' package" >&2
+            exit 1
+        fi
+
+        # ... sanity checking done
+
+        # setup paths
+        lowerdir="$CHROOT_METADIR"/chroot
+        upperdir="$CHROOT_METADIR"/.overlay
+        workdir="$CHROOT_METADIR"/.workdir
+        overlay="$CHROOT_METADIR"/.merged
+
+        # set trap
+        trap on_exit QUIT TERM EXIT
+
+        # mount overlay
+        OVERLAY_MOUNT=''
+        if do_overlay_mount ; then
+            # overlay chroot
+            OVERLAY_MOUNT=yes
+        else
+            # non overlay mount
+            OVERLAY_MOUNT=no
+        fi
+
+        # do the user-specific mounts
+        do_external_mounts
+
+        # I need this wrapper to do some setup inside the chroot...
+        install_wrapper
+
+        # execute chroot
+        # copy resolv.conf
+        cp -a /etc/resolv.conf "$CHROOT_DIR"/etc/resolv.conf
+
+        if [ -n "$1" ] ; then
+            :
+        else
+            set -- /bin/sh -l
+        fi
+        unshare -mfpi --propagation private \
+            chroot "$CHROOT_DIR" /usr/local/bin/fakeshell.sh "${CHROOT_WORKDIR:-/}" "$@"
+        ;;
+esac
+
+exit 0
+