Fix Debian Permissions after bad chown

From Mexico.purplecow.org

The Bad chown

At least once a year, somebody complains that they've managed to chown or chmod recursively from root and make a dog's breakfast of a system without proper backups or snapshots.

Oh, well.

At some point years ago, I found this script to fix it, so I'll mirror it here for good luck.

#!/bin/bash
# Restores file permissions for all files on a debian system for which .deb
# packages exist. 
#
# Author: Larry Kagan <me at larrykagan dot com>
# Since 2007-02-20

ARCHIVE_DIR=/var/cache/apt/archives/
PACKAGES=`ls $ARCHIVE_DIR`
cd /

function changePerms() {
    CHOWN="/bin/chown"
    CHMOD="/bin/chmod"
    PERMS=`echo $1 | sed -e 's/--x/1/g' -e 's/-w-/2/g' -e 's/-wx/3/g' -e 's/r--/4/g'  -e 's/r-x/5/g' -e 's/rw-/6/g' -e 's/rwx/7/g' -e 's/---/0/g'`
    PERMS=`echo ${PERMS:1}`
    OWN=`echo $2 | /usr/bin/tr '/' '.'`
    PATHNAME=$3
    PATHNAME=`echo ${PATHNAME:1}`

#    echo -e "CHMOD: $CHMOD $PERMS $PATHNAME"    

#    result=`$CHOWN $OWN $PATHNAME`
#    if [ $? -ne 0 ]; then
#   echo -e $result
#        exit 123;
#    fi

    echo -e "CHOWN: $CHMOD $PERMS $PATHNAME"
    result=`$CHMOD $PERMS $PATHNAME`
    if [ $? -ne 0 ]; then
    echo -e $result
    fi
}

for PACKAGE in $PACKAGES;
do
    if [ -d $PACKAGE ]; then
    continue;
    fi
    echo -e "Getting information for $PACKAGE\n"
    FILES=`/usr/bin/dpkg -c "${ARCHIVE_DIR}${PACKAGE}"`

    for FILE in "$FILES";
    do
        #FILE_DETAILS=`echo "$FILE" | awk '{print $1"\t"$2"\t"$6}'`
    echo "$FILE" | awk '{print $1"\t"$2"\t"$6}' | while read line;
        do
            changePerms $line
        done
        #changePerms $FILE_DETAILS
    done
done