hashboot/hashboot.sh

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#!/bin/bash
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#Hashes all files in /boot to check them during early boot
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#Exit codes: 0 = success, 1 = checksum mbr mismatch, 2 = checksum /boot mismatch,
#3 = checksum mbr/boot mismatch, 4 = not root, 5 = no hasher found, 6 = wrong usage,
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#7 = write error, 8 = dd error, 9 config file error
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VERSION="0.7.4"
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PATH="/bin:/usr/bin:/sbin:/usr/sbin:${PATH}"
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DIGEST_FILE="/var/lib/hashboot.digest"
LOG_FILE="/tmp/hashboot.log"
MBR_DEVICE=""
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MBR_TMP="/tmp/mbr"
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BACKUP_FILE="/var/cache/boot-backup.tar.gz"
HASHER=""
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BOOT_MOUNTED=0
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CONFIG_FILE="/etc/hashboot.cfg"
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#Umount /boot if we mounted it, exit with given exit code
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die ()
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{
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if [ ${BOOT_MOUNTED} -gt 0 ]
then
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umount /boot
fi
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[ -z "${2}" ] || echo "${2}" >&2
exit ${1}
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}
read_config ()
{
#Look for config file and set ${MBR_DEVICE}.
if [ -f ${CONFIG_FILE} ]
then
MBR_DEVICE=$(grep ^mbr_device ${CONFIG_FILE} | awk '{print $3}')
[ $? != 0 ] && die 9 "Error reading config file"
#If not found, create one and ask for ${MBR_DEVICE}
else
echo -n "Which device contains the MBR? [/dev/sda] "
read -r MBR_DEVICE
[ -z "${MBR_DEVICE}" ] && MBR_DEVICE="/dev/sda"
echo "#Device with the MBR on it" > ${CONFIG_FILE}
echo "mbr_device = ${MBR_DEVICE}" >> ${CONFIG_FILE}
fi
}
mbr_size ()
{
# Find out where the first partition starts returns(prints) size in KiB
sectorsize=$(LC_ALL=C fdisk -l /dev/sda | grep '^Units:' | awk '{print $8}')
startsector=$(LC_ALL=C fdisk -l /dev/sda | grep -A1 '^Device' | tail -n1 | awk '{print $3}')
expr ${sectorsize} \* ${startsector} / 1024
}
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#If we're not root: exit
if [ ${UID} -ne 0 ]
then
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die 4 "You have to be root"
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fi
#If /boot is in fstab but not mounted: mount, mark as mounted
if grep -q '/boot.*noauto' /etc/fstab && ! grep -q /boot /etc/mtab
then
mount /boot
BOOT_MOUNTED=1
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fi
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if [ "${1}" == "index" ]
then
#Try different hashers, use the most secure
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HASHER=$(/usr/bin/which sha512sum 2> /dev/null)
test -z "${HASHER}" && HASHER=$(/usr/bin/which sha384sum 2> /dev/null)
test -z "${HASHER}" && HASHER=$(/usr/bin/which sha256sum 2> /dev/null)
test -z "${HASHER}" && HASHER=$(/usr/bin/which sha224sum 2> /dev/null)
#It gets insecure below here, but better than nothing?
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test -z "${HASHER}" && HASHER=$(/usr/bin/which sha1sum 2> /dev/null)
test -z "${HASHER}" && HASHER=$(/usr/bin/which md5sum 2> /dev/null)
#If we found no hasher: exit
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[ -z "${HASHER}" ] && die 5 "No hash calculator found"
read_config
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#Write header
echo "#hashboot ${VERSION} - Algorithm: $(basename ${HASHER})" > ${DIGEST_FILE}
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#Write MBR of MBR_DEVICE to ${DIGEST_FILE}
dd if=${MBR_DEVICE} of=${MBR_TMP} bs=$(mbr_size)K count=1 status=noxfer || die 8
#Write hashes of all regular files to ${DIGEST_FILE}
${HASHER} ${MBR_TMP} >> ${DIGEST_FILE}
find /boot -type f -exec ${HASHER} --binary {} >> ${DIGEST_FILE} +
if [ $? == 0 ]
then
echo "List of hashes written to ${DIGEST_FILE}"
else
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die 7 "Error writing ${DIGEST_FILE}"
fi
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#Backup of good files
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tar -czpPf ${BACKUP_FILE} ${MBR_TMP} /boot ${DIGEST_FILE}
if [ $? == 0 ]
then
echo "Backup written to ${BACKUP_FILE}"
else
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die 7 "Error writing ${BACKUP_FILE}"
fi
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elif [ "${1}" == "check" ]
then
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COUNTER=0
HASHER=$(head -n1 ${DIGEST_FILE} | awk '{print $5}')
read_config
dd if=${MBR_DEVICE} of=${MBR_TMP} bs=$(mbr_size)K count=1 status=noxfer || die 8
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if ! $(grep ${MBR_TMP} ${DIGEST_FILE} | ${HASHER} --check --warn --quiet --strict > ${LOG_FILE})
then
echo " !! TIME TO PANIK: MBR WAS MODIFIED !!"
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COUNTER=$((COUNTER + 1))
fi
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if ! $(grep -v ${MBR_TMP} ${DIGEST_FILE} | ${HASHER} --check --warn --quiet --strict >> ${LOG_FILE})
then
echo " !! TIME TO PANIK: AT LEAST 1 FILE WAS MODIFIED !!"
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COUNTER=$((COUNTER + 2))
die $COUNTER
fi
elif [ "${1}" == "recover" ]
then
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echo "Restoring files from backup... (type yes or no for each file)"
#For each failed file: ask if it should be recovered from backup
for file in $(cut -d: -f1 ${LOG_FILE})
do
tar -xzpPvwf ${BACKUP_FILE} ${file}
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[ $? != 0 ] && echo "Error restoring ${file} from backup, continuing" >&2
#If the MBR is to be recovered, copy to ${MBR_DEVICE}
if [ "${file}" == ${MBR_TMP} ]
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then
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cp ${MBR_TMP} ${MBR_DEVICE}
[ $? != 0 ] && echo "Error restoring MBR from backup, continuing" >&2
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fi
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done
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else
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die 6 "Usage: ${0} index|check|recover"
fi
die 0