#!/bin/bash

# Check if the running kernel has the same version string as the on-disk
# kernel image.

# Copyright 2008,2009,2011,2012,2013,2014 Peter Palfrader
# Copyright 2009 Stephen Gran
# Copyright 2010,2012,2013 Uli Martens
# Copyright 2011 Alexander Reichle-Schmehl
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

OK=0;
WARNING=1;
CRITICAL=2;
UNKNOWN=3;

get_offset() {
  local file needle

  file="$1"
  needle="$2"

  perl -e '
    undef $/;
    $i = 0; $k=<>;
    while (($i = index($k, "'"$needle"'", $i)) >= 0) {
      print $i++,"\n";
    }; ' < "$file"
}

get_avail() {
  # This is wrong, but leaves room for when we have to care for machines running
  # myfirstunix-image-0.1-dsa-arm
  local prefix="$1"; shift

  local kervers=$(uname -r)

  local metavers=''

  # DSA uses kernel versions of the form 2.6.29.3-dsa-dl380-oldxeon, where
  # Debian uses versions of the form 2.6.29-2-amd64
  if [ "${kervers#2}" != "$kervers" ]; then
    if [ "${kervers//dsa}" != "$kervers" ]; then
      metavers=$(echo $kervers | sed -r -e 's/^2\.(4|6)\.[0-9]+([\.0-9]+?)-(.*)/2.\1-\3/')
    else
      metavers=$(echo $kervers | sed -r -e 's/^2\.(4|6)\.[0-9]+-[A-Za-z0-9\.]+-(.*)/2.\1-\2/')
    fi
  else
    metavers=$(echo $kervers | sed -r -e 's/^[0-9]+\.[0-9]+(\.[0-9])?+-[A-Za-z0-9\.]+-(.*)/\2/')
  fi

  # Attempt to track back to a metapackage failed.  bail
  if [ "$metavers" = "$kervers" ]; then
    return 2
  fi

  # We're just going to give up if we can't find a matching metapackage
  # I tried being strict once, and it just caused a lot of headaches.  We'll see how
  # being lax does for us

  local output=$(apt-cache policy ${prefix}-image-${metavers} 2>/dev/null)
  local metaavailvers=$(echo "$output" | grep '^  Candidate:' | awk '{print $2}')
  local metainstavers=$(echo "$output" | grep '^  Installed:' | awk '{print $2}')

  if [ -z "$metaavailvers" ] || [ "$metaavailvers" = '(none)' ]; then
    return 2
  fi
  if [ -z "$metainstavers" ] || [ "$metainstavers" = '(none)' ]; then
    return 2
  fi

  if [ "$metaavailvers" != "$metainstavers" ] ; then
    echo "${prefix}-image-${metavers} $metaavailvers available but $metainstavers installed"
    return 1
  fi

  local imagename=0
  # --no-all-versions show shows only the candidate
  # for vers in $(apt-cache --no-all-versions show ${prefix}-image-${metavers} | sed -n 's/^Depends: //p' | tr ',' '\n' | tr -d ' ' | grep ${prefix}-image | awk '{print $1}' | sort -u); do
  #   if dpkg --compare-versions "1.$vers" gt "1.$imagename"; then
  #     imagename=$vers
  #   fi
  # done

  if [ -z "$imagename" ] || [ "$imagename" = 0 ]; then
    return 2
  fi

  if [ "$imagename" != "${prefix}-image-${kervers}" ]; then
    if dpkg --compare-versions 1."$imagename" lt 1."${prefix}-image-${kervers}"; then
      return 2
    fi
    echo "$imagename" != "${prefix}-image-${kervers}"
    return 1
  fi

  local availvrs=$(apt-cache policy ${imagename} 2>/dev/null | grep '^  Candidate' | awk '{print $2}')
  local kernelversion
  for kernelversion in $(apt-cache policy ${prefix}-image-${kervers} ${prefix}-image-${kervers}-unsigned 2>/dev/null | grep '^  Installed:' | awk '{print $2}' | grep -F -v '(none)' ); do
    if [ "$availvrs" = "$kernelversion" ]; then
      return 0
    fi
  done

  echo "$kernelversion != $availvrs"
  return 1
}

cat_vmlinux() {
  local image header filter hdroff

  image="$1"
  header="$2"
  filter="$3"
  hdroff="$4"

  if ! which $filter >/dev/null; then
    echo "UNKNOWN: filter command '$filter' missing, perhaps install xz-utils?" >&2
    exit $UNKNOWN
  fi

  get_offset "$image" $header | head -n 5 | while read off; do
    (if [ "$off" != 0 ]; then
       dd ibs="$((off+hdroff))" skip=1 count=0
     fi &&
     dd bs=512k) < "$image"  2>/dev/null | $filter 2>/dev/null
  done
}

get_image_linux() {
  local image

  image="$1"
  # gzip compressed image
        cat_vmlinux "$image" "\x1f\x8b\x08\x00"      "zcat"   0
  cat_vmlinux "$image" "\x1f\x8b\x08\x08"      "zcat"   0
  # lzma compressed image
  cat_vmlinux "$image" "\x00\x00\x00\x02\xff"  "xzcat" -1
  cat_vmlinux "$image" "\x00\x00\x00\x04\xff"  "xzcat" -1
  # xz compressed image
  cat_vmlinux "$image" "\xfd\x37\x7a\x58\x5a " "xzcat"  0

  echo "ERROR: Unable to extract kernel image." 2>&1
  exit 1
}


freebsd_check_running_version() {
  local imagefile="$1"; shift

  local r="$(uname -r)"
  local v="$(uname -v| sed -e 's/^#[0-9]*/&:/')"

  local q='@(#)FreeBSD '"$r $v"

  if zcat "$imagefile" | $STRINGS | grep -F -q "$q"; then
    echo "OK"
  else
    echo "not OK"
  fi
}

STRINGS="";
if [ -x "$(which strings)" ]; then
  STRINGS="$(which strings)"
elif [ -x "$(which busybox)" -a "$( echo foobar | $(which busybox) strings 2>/dev/null)" = "foobar" ]; then
  STRINGS="$(which busybox) strings"
fi

searched=""
for on_disk in \
  $([ -f "/boot/vmlinuz-$(uname -r)" ] && find /boot/ -name 'vmlinuz*' -and -name "vmlinuz-$(uname -r)" -or -name 'vmlinuz*' -and -newer "/boot/vmlinuz-$(uname -r)" 2>/dev/null | sort) \
  $([ -f "/boot/kfreebsd-$(uname -r).gz" ] && find /boot/ -name 'kfreebsd*' -and -name "kfreebsd-$(uname -r).gz" -or -name 'kfreebsd*' -and -newer "/boot/kfreebsd-$(uname -r).gz" 2>/dev/null | sort); do

  if [ -e "$on_disk" ]; then
    if [ -z "$STRINGS" ]; then
      echo "UNKNOWN: 'strings' command missing, perhaps install binutils or busybox?"
      exit $UNKNOWN
    fi
    if [ "${on_disk/vmlinu}" != "$on_disk" ]; then
      on_disk_version="`get_image_linux $on_disk | $STRINGS | grep 'Linux version' | head -n1`"
      if [ -x /usr/bin/lsb_release ] ; then
        vendor=$(lsb_release -i -s)
        if [ -n "$vendor" ] && [ "xDebian" != "x$vendor" ] ; then
          on_disk_version=$( echo $on_disk_version|sed -e "s/ ($vendor [[:alnum:]\.-]\+ [[:alnum:]\.-]\+)//")
        fi
      fi
      [ -z "$on_disk_version" ] || continue
      on_disk_version="`cat "$on_disk" | $STRINGS | grep 'Linux version' | head -n1`"
      [ -z "$on_disk_version" ] || continue

      # TRW-2020-05-13 - start:fix for PVE - uses different version string
      on_disk_version="`file -bL "$on_disk" | $STRINGS | grep 'version' | head -n1 | perl -pe 's/^.* SMP PVE ([\.-\d]+) .*$/\1/'`"
      [ -z "$on_disk_version" ] || continue
      # TRW-2020-05-13 - end:fix for PVE - uses different version string

      echo "UNKNOWN: Failed to get a version string from image $on_disk"
      exit $UNKNOWN
    else
      on_disk_version="$(zcat $on_disk | $STRINGS | grep Debian | head -n 1 | sed -e 's/Debian [[:alnum:]]\+ (\(.*\))/\1/')"
    fi
  fi
  searched="$searched $on_disk"
done

if ! [ -e "$on_disk" ]; then
  echo "WARNING: Did not find a kernel image (checked$searched) - I have no idea which kernel I am running"
  exit $WARNING
fi

if [ "$(uname -s)" = "Linux" ]; then
  running_version="`cat /proc/version`"
  if [ -z "$running_version" ] ; then
    echo "UNKNOWN: Failed to get a version string from running system"
    exit $UNKNOWN
  fi

  if [[ $running_version == *"pve"* ]]; then
    running_version=`cat /proc/version | perl -pe 's/^.* SMP PVE ([\.-\d]+) .*$/\1/'`
  fi

  if [ "$running_version" != "$on_disk_version" ]; then
    echo "WARNING: Running kernel [$running_version] does not match on-disk kernel image: [$on_disk_version]"
    exit $WARNING
  fi

  ret="$(get_avail linux)"
  if [ $? = 1 ]; then
    echo "WARNING: Kernel needs upgrade [$ret]"
    exit $WARNING
  fi
else
  image_current=$(freebsd_check_running_version $on_disk)
  running_version="`uname -s` `uname -r` `uname -v`"
  if [ "$image_current" != "OK" ]; then
    approx_time="$(date -d "@`stat -c '%Y' "$on_disk"`" +"%Y-%m-%d %H:%M:%S")"
    echo "WARNING: Currently running kernel ($running_version) does not match on disk image (~ $approx_time)"
    exit $WARNING;
  fi

  ret="$(get_avail linux)"
  if [ $? = 1 ]; then
    echo "WARNING: Kernel needs upgrade [$ret]"
    exit $WARNING
  fi
fi

echo "OK: Running kernel matches on disk image: [$running_version]"
exit $OK