#!/bin/bash
#Hashes all files in /boot to check them during early boot
#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,
#7 = write error, 8 = dd error, 9 = file not found
#10 = bios mismatch, 11 == mbr&bios mismatch, 12 = files&bios mismatch
#13 = mbr&bios&files mismatch
###############################################################################
# "THE HUG-WARE LICENSE" (Revision 2):                                        #
# teldra <teldra@rotce.de> and tastytea <tastytea@tastytea.de> wrote this.    #
# As Long as you retain this notice you can do whatever you want with this.   #
# If we meet some day, and you think this is nice, you can give us a hug.     #
###############################################################################

# Disable warnings about $?.
# shellcheck disable=SC2181

VERSION="0.9.14"
PATH="/bin:/usr/bin:/sbin:/usr/sbin:${PATH}"
DIGEST_FILE=""
BACKUP_FILE=""
SAVEDIR=""
DIGEST_FILE_TMP="/tmp/hashboot.digesttmp"
LOG_FILE="/var/log/hashboot.log"
MBR_DEVICE="/dev/sda"
MBR_SIZE=1024
MBR_TMP="/tmp/mbr"
BIOS_TMP="/tmp/bios"
HASHER=""
BOOT_MOUNTED=0
CONFIG_FILE="/etc/hashboot.cfg"
COUNTER=0
DD_STATUS="none"
PROGRAMMER=${PROGRAMMER:=internal}
#bitmask:
# 001=mbr
# 010=files
# 100=bios
CKMODES=011

#Umount /boot if we mounted it, exit with given exit code
die ()
{
    if [ ${BOOT_MOUNTED} -gt 0 ]
    then
        umount /boot
    fi

    # Delete temporary files
    rm -f "${DIGEST_FILE_TMP}" "${MBR_TMP}" "${BIOS_TMP}"

    [ -z "${2}" ] || echo "${2}" >&2
    exit "${1}"
}

write_hashes ()
{
    local file="${1}"
    #Write header to ${file}
    echo "#hashboot ${VERSION} - Algorithm: $(basename ${HASHER})" > "${file}"

    if [ $((CKMODES & 001)) -ne 0 ]; then
        #copy mbr to file
        dd if=${MBR_DEVICE} of=${MBR_TMP} bs=${MBR_SIZE}K count=1 status=${DD_STATUS} || die 8
        #Write hash of MBR to ${file}
        ${HASHER} ${MBR_TMP} >> "${file}"
    fi
    if [ $((CKMODES & 010)) -ne 0 ]; then
        #Write hashes of all regular files to ${file}
        # shellcheck disable=SC2227
        find /boot -type f -exec ${HASHER} --binary {} >> "${file}" +
    fi
    if [ $((CKMODES & 100)) -ne 0 ]; then
        #read bios to file
        flashrom --programmer ${PROGRAMMER} -r ${BIOS_TMP} > /dev/null 2>&1
        #and write hashes of bios files to ${file}
        ${HASHER} ${BIOS_TMP} >> "${file}"

    fi
}


#If we're not root: exit
if [ ${UID} -ne 0 ]
then
    die 4 "You have to be root"
fi

#If /boot is in fstab but not mounted: mount, mark as mounted
if grep -q '/boot' /etc/fstab && ! grep -q /boot /etc/mtab
then
    mount /boot
    BOOT_MOUNTED=1
fi

# Debian < 8 check
if command -v lsb_release > /dev/null \
        && [ "$(lsb_release -si)" == "Debian" ] \
        && [ "$(lsb_release -sr | cut -d'.' -f1)" -lt 8 ]
then
    DD_STATUS="noxfer"
fi

#Look for config file and set ${MBR_DEVICE}.
if [ -f ${CONFIG_FILE} ]
then
    # shellcheck source=/dev/null
    source ${CONFIG_FILE} || die 9 "Error reading config file"
    #compatibility to old cfg format
    if [ -n "${BACKUP_FILE}" ]; then
        SAVEDIR="/var/lib/hashboot"
        echo "SAVEDIR=${SAVEDIR}" >> ${CONFIG_FILE}
        mkdir -p ${SAVEDIR}
        mv ${BACKUP_FILE} ${SAVEDIR}
        mv /var/lib/hashboot.digest ${SAVEDIR}
        ln -s "${SAVEDIR}/boot-backup.tar" "${BACKUP_FILE}"
        ln -s "${SAVEDIR}/hashboot.digest" "/var/lib/hashboot.digest"
        sed -i '/BACKUP_FILE/d' ${CONFIG_FILE}
        echo "The backup und the digests have been moved to ${SAVEDIR}"
    fi
    # here we extrapolate paths from savedir.
    DIGEST_FILE="${SAVEDIR}/hashboot.digest"
    BACKUP_FILE="${SAVEDIR}/boot-backup.tar"
#If not found, create one and ask for ${MBR_DEVICE}
else
    #Create ${CONFIG_FILE} with defaults if noninterctive
    if [ -t "0" ]
    then
        echo -n "Where should backup file and digestfile be stored? [/var/lib/hashboot] "
        read -r SAVEDIR
        [ -z "${SAVEDIR}" ] && SAVEDIR="/var/lib/hashboot"
        echo "#Where the Backup files are stored" > ${CONFIG_FILE}
        echo "SAVEDIR=${SAVEDIR}" >> ${CONFIG_FILE}
        DIGEST_FILE="${SAVEDIR}/hashboot.digest"
        BACKUP_FILE="${SAVEDIR}/boot-backup.tar"
        mkdir -p ${SAVEDIR}

        echo "What do we check?"
        echo "001=mbr"
        echo "010=files"
        echo "100=core-/libreboot bios"
        echo "eg. 101 for mbr and bios: "
        read -r CKMODES
        echo "#001=mbr,010=files,100=bios" >> ${CONFIG_FILE}
        echo "CKMODES=$CKMODES" >> ${CONFIG_FILE}

        if [ $((CKMODES & 001)) -ne 0 ]; then
            echo -n "Which device contains the MBR? [/dev/sda] "
            read -r MBR_DEVICE
            [ -z "${MBR_DEVICE}" ] && MBR_DEVICE="/dev/sda"
            echo "#Device with the MBR on it" >> ${CONFIG_FILE}
            echo "MBR_DEVICE=${MBR_DEVICE}" >> ${CONFIG_FILE}
        fi

        if [ $((CKMODES & 100)) -ne 0 ]; then
            if ! command -v flashrom > /dev/null; then
                echo "You need to have flashrom installed!"
                echo "Currently it is not installed, don't reboot"
                echo "If you need another programmer than internal"
                echo "use the variable PROGRAMMER in ${CONFIG_FILE}!"
            fi
        fi

    else
        die 9 "No config file found. Run hashboot interactively to generate one."
    fi
fi

if [ $((CKMODES & 001)) -ne 0 ]; then
    # Find out where the first partition starts and set ${MBR_SIZE} in KiB
    sectorsize=$(LC_ALL=C fdisk -l ${MBR_DEVICE} | grep '^Units' | awk '{print $8}' )
    if [ "${sectorsize}" == "=" ] # Older versions of util-linux
    then
        sectorsize=$(LC_ALL=C fdisk -l ${MBR_DEVICE} | grep '^Units' | awk '{print $9}' )
    fi
        startsector=$(LC_ALL=C fdisk -l ${MBR_DEVICE} | grep -A1 'Device' | tail -n1 | awk '{print $2}' )
    if [ "${startsector}" == "*" ] # If partition is marked as boot, read next field
    then
        startsector=$(LC_ALL=C fdisk -l ${MBR_DEVICE} | grep -A1 'Device' | tail -n1 | awk '{print $3}' )
    fi

    MBR_SIZE=$((sectorsize * startsector / 1024))

    if [ ${?} != 0 ]
    then
        echo "Something went wrong. Most likely your partition table is corrupt." >&2
        die 1 "You have to recover the MBR manually by copying the mbr from ${BACKUP_FILE}"
    fi
fi

if [ "${1}" == "index" ]
then
    #Try different hashers, use the most secure
    HASHER=$(command -v sha512sum)
    test -z "${HASHER}" && HASHER=$(command -v sha384sum)
    test -z "${HASHER}" && HASHER=$(command -v sha256sum)
    test -z "${HASHER}" && HASHER=$(command -v sha224sum)
    #If we found no hasher: exit
    [ -z "${HASHER}" ] && die 5 "No hash calculator found"

    #Exists ${DIGEST_FILE}, if true run do magic, else write ${DIGEST_FILE}
    if [ -f ${DIGEST_FILE} ]
    then

        #Collect mbr and /boot hashes and write to $DIGEST_FILE_TMP
        write_hashes $DIGEST_FILE_TMP

        #Compare $DIGEST_FILE_TMP against ${DIGEST_FILE} and exit, when fine. Otherwise do magic.
        if diff -q --ignore-matching-lines='#hashboot' ${DIGEST_FILE} ${DIGEST_FILE_TMP} ;
        then
            die 0
        else
            for file in $(diff ${DIGEST_FILE} ${DIGEST_FILE_TMP} | grep -v '#hashboot' | grep '<' | cut -d'*' -f2 | sed 's/\ /\\ /g' );
            do
                #delete from tar
                tar --delete -v -P -f ${BACKUP_FILE} "${file}"
            done
            for file in $(diff ${DIGEST_FILE} ${DIGEST_FILE_TMP} | grep -v '#hashboot' | grep '>' | cut -d'*' -f2 | sed 's/\ /\\ /g' );
            do
                tar -r -v -P -f $BACKUP_FILE "${file}"
            done
        fi
    #nur, wenn das updaten des Backups geklappt hat. *im Hinterkopf behalt*
    mv ${DIGEST_FILE_TMP} ${DIGEST_FILE}
    else
        write_hashes $DIGEST_FILE
        INCLUDE_FILES=""
        if [ -f "${MBR_TMP}" ]; then
            INCLUDE_FILES="${INCLUDE_FILES} ${MBR_TMP}"
        fi
        if [ -f "${BIOS_TMP}" ]; then
            INCLUDE_FILES="${BIOS_TMP}"
        fi
        tar -cpPf "${BACKUP_FILE}" ${INCLUDE_FILES} /boot ${DIGEST_FILE} || die 7 "Error writing ${BACKUP_FILE}"
        echo "Backup written to ${BACKUP_FILE}"
    fi

elif [ "${1}" == "check" ]
then
    [ -f ${DIGEST_FILE} ] || die 9 "No digestfile"
    HASHER=$(head -n1 ${DIGEST_FILE} | awk '{print $5}')
    if [ $((CKMODES & 001)) != 0 ]; then
        dd if=${MBR_DEVICE} of=${MBR_TMP} bs=${MBR_SIZE}K count=1 status=${DD_STATUS} || die 8
        grep ${MBR_TMP} ${DIGEST_FILE} | ${HASHER} --check --warn --quiet --strict | tee ${LOG_FILE}
        if [ "${PIPESTATUS[2]}" -ne 0 ]
        then
            echo "    !! TIME TO PANIK: MBR WAS MODIFIED !!"
            COUNTER=$((COUNTER + 1))
        fi
    fi
    if [ $((CKMODES & 010)) -ne 0 ]; then
        grep -v ${MBR_TMP} ${DIGEST_FILE} | grep -v ${BIOS_TMP} | ${HASHER} --check --warn --quiet --strict | tee -a ${LOG_FILE}
        if [ "${PIPESTATUS[2]}" -ne 0 ]
        then
            echo "    !! TIME TO PANIK: AT LEAST 1 FILE WAS MODIFIED !!"
            COUNTER=$((COUNTER + 2))
        fi
    fi
    if [ $((CKMODES & 100)) -ne 0 ]; then
        flashrom --programmer ${PROGRAMMER} -r ${BIOS_TMP} > /dev/null 2>&1
        #if we set an programmer chip in config, find line with hash for bios and compare. if smthg wrong, panic
        grep ${BIOS_TMP} ${DIGEST_FILE} | ${HASHER} --check --warn --quiet --strict | tee -a ${LOG_FILE}
        if [ "${PIPESTATUS[2]}" -ne 0 ]
        then
            echo "    !! TIME TO PANIK: BIOS WAS MODIFIED !!"
            COUNTER=$((COUNTER + 10))
        fi

    fi

    if [ ${COUNTER} -gt 0 ]; then
        die ${COUNTER}
    fi
elif [ "${1}" == "recover" ]
then
    echo "Restoring files from backup... (type yes or no for each file)"

    #For each failed file: ask if it should be recovered from backup
    # shellcheck disable=2013
    for file in $(cut -d: -f1 ${LOG_FILE})
    do
        tar -xpPvwf ${BACKUP_FILE} "${file}"
        [ ${?} != 0 ] && echo "Error restoring ${file} from backup, continuing" >&2
        #If the MBR is to be recovered, copy to ${MBR_DEVICE}
        if [ "${file}" == ${MBR_TMP} ]
        then
            cp ${MBR_TMP} ${MBR_DEVICE}
            [ ${?} != 0 ] && echo "Error restoring MBR from backup, continuing" >&2
        fi
    done
else
    die 6 "Usage: ${0} index|check|recover"
fi

die 0