#!/bin/bash
# file name 'utar.sh'
# coded by: Louis Casillas, e-mail: oxaric@gmail.com
# version 1.1
# How to use:
# In a linux shell or cygwin:
# ~/directory-containing-this-script$ sudo chmod +x utar.sh
# ~/directory-containing-this-script$ ./utar.sh
# This script will protect against tarbombs and allow you
# to choose the path to extract the tar file into.
# To know more type: ./utar.sh
TRUE=0
FALSE=1
ERROR=2
OFF=0
ON=1
NO=0
YES=1
SUCCEEDED=0
FAILED=1
file_name=""
optional_extraction_path=""
help_option=$OFF
force_option=$OFF
keep_root_option=$OFF
num_of_dirs_passed=0
is_a_tar_bomb=$NO
# the initial temporary directory name
temp_dir="this-is-my-directory-to-untar-in"
function display_help_and_exit
{
echo
echo "Usage: utar [[FILE]] [EXTRACT_PATH/] [-k] [-f]"
echo
echo "utar extracts a tar file while preventing tarbombs to explode"
echo "and allows the user to specify the tar extraction path"
echo
echo " [EXTRACT_PATH/] extract files in this path"
echo " which replaces the original root directories"
echo
echo " -k --keep-root-dir appends the [EXTRACT_PATH/] to the start of"
echo " the tar file's root directories"
echo " implies [EXTRACT_PATH/] is given"
echo
echo " -f --force force extraction"
echo " needed to force the extraction of a tarbomb"
echo
echo " -h --help display this help list"
echo
echo "Examples:"
echo " utar archive.tar # extracts all files from archive.tar"
echo " utar archive.tar foo/ # extracts the files into directory foo"
echo " utar -f archive.tar # forces an extraction even if"
echo " # archive.tar is a tarbomb"
echo
exit $SUCCEEDED
}
# receives the exit code of the last system command called
# if the command had an error then display an error message
# and exit
function system_command_error_exit
{
echo
echo "utar: An error occurred while trying to use a system command."
echo "utar: See the error message above."
echo "utar: Exiting..."
echo
exit $FAILED
}
function did_the_system_command_work
{
# $1 gives us the return result of the system command
if [ $1 -ne $SUCCEEDED ]; then
delete_the_temp_directory
system_command_error_exit
fi
}
function has_ending_forward_slash
{
# grab the last character of the string and test if it is a forward slash
if [[ "$(echo "$1" | tail --bytes=2 )" = "/" ]]; then
return $TRUE
else
return $FALSE
fi
}
function contains_a_forward_slash
{
# test if the string has a forward slash
# if true then this string is a directory
if [[ "$(echo "$1" | grep "/" )" != "" ]]; then
return $TRUE
else
return $FALSE
fi
}
# determines if the string is a proper option
function is_an_option
{
# must contain at least one hyphen at the beginning of the string
# to be considered an option
if [[ $(echo "$1" | head --bytes=1 | grep "\-" ) = "" ]]; then
return $FALSE
else
return $TRUE
fi
}
function evaluate_parameter
{
if is_an_option "$1"; then
# evaluate which option was used and set the necessary variables
# if it is an improper option then exit
case "$1" in
"--help")
help_option=$ON
;;
"-h")
help_option=$ON
;;
"--force")
force_option=$ON
;;
"-f")
force_option=$ON
;;
"--keep-root-dir")
keep_root_option=$ON
;;
"-k")
keep_root_option=$ON
;;
*)
echo "utar: invalid option: $1"
echo "Try 'utar --help' for more information."
echo
exit $FAILED
;;
esac # end of the case statement
else
num_of_dirs_passed=$(( $num_of_dirs_passed + 1 ))
# determine if the passed parameter is a directory path
# if it is then use it for the optional directory
# however if it is a name and no file name is specified
# then use this as the file name, otherwise it is
# used as the optional directory
if contains_a_forward_slash "$1"; then
optional_extraction_path="$1"
if ! has_ending_forward_slash "$1"; then
optional_extraction_path+="/"
fi
else
if [[ "$file_name" = "" ]]; then
file_name="$1"
else
# test to see if one of the parameters has ".tar" in the name
# if it does then switch the current file name with the
# optional extraction path to allow the tar file parameter
# to come after the extraction path
if [[ $(echo "$1" | grep ".tar" ) = "" ]]; then
optional_extraction_path="$1""/"
else
temp=$file_name
file_name="$1"
optional_extraction_path="$temp""/"
fi
fi
fi
# too many files or dirs passed
if [ $num_of_dirs_passed -eq 3 ]; then
echo "utar: an extra file or directory was passed: $1"
echo "utar only extracts one tar to one directory at a time"
echo "Try 'utar --help' for more information."
echo
exit $FAILED
fi
fi
}
# sorts out the 6 parameters passed and makes sure they are proper
function deal_with_the_parameters
{
if [[ "$1" != "" ]]; then
evaluate_parameter "$1"
else
# exit if no parameters were passed
echo "utar: You must specify a tar file"
echo "Try 'utar --help' for more information."
echo
exit $FAILED
fi
if [[ "$2" != "" ]]; then
evaluate_parameter "$2"
fi
if [[ "$3" != "" ]]; then
evaluate_parameter "$3"
fi
if [[ "$4" != "" ]]; then
evaluate_parameter "$4"
fi
if [[ "$5" != "" ]]; then
evaluate_parameter "$5"
fi
# test if there are more options than is possible
if [[ "$6" != "" ]]; then
echo "utar: invalid command: $6"
echo "Try 'utar --help' for more information."
echo
exit $FAILED
fi
if [ $help_option -eq $ON ]; then
display_help_and_exit
fi
###
# uncomment these lines if you want the extraction of a tarbomb
# to be automatically forced if an extraction path is specified
# except when the path is the current directory
#
# if [[ "$optional_extraction_path" != "" ]]; then
# if [[ "$optional_extraction_path" != "." ]]; then
# if [[ "$optional_extraction_path" != "./" ]]; then
# force_option="$ON"
# fi
# fi
# fi
###
}
function create_the_temp_directory
{
# if in some rare chance the temporary directory already exists
# then append a random number to the end of the directory and
# test again.
# repeats until a non-existant directory is found.
while [ -d "$temp_dir" ]
do
# grab a random number between 0 and 9
temp_num=$(( $RANDOM % 10 ))
temp_dir+="$temp_num"
done
temp_dir+="/"
# make the temporary directory
mkdir "$temp_dir"
did_the_system_command_work $?
}
function delete_the_temp_directory
{
# remove the temp directory
rm -rf "$temp_dir"
# $? gives us the return result of the system command
if [ $? -ne $SUCCEEDED ]; then
system_command_error_exit
fi
}
function remove_dirs_from_the_temp_directory
{
# grab a list of the files and directories in the temp directory
temp="$(ls $temp_dir -A --file-type)"
did_the_system_command_work $?
# test if there any directories in the temp directory
temp="$(echo "$temp" | grep /)"
# if there are directories in the mpt directory then
# delete them
if [[ "$temp" != "" ]]; then
# output list of dirs to file temp.txt
echo "$temp" > "$temp_dir""temp.txt"
did_the_system_command_work $?
exec<"$temp_dir""temp.txt"
# delete all directories inside the temp directory
# if any files are left in the temp directory this
# signifies the files would have normally been extracted
# into the current directory which means the tar file is a 'tarbomb'
while read line
do
rm -rf "$temp_dir""$line"
did_the_system_command_work $?
done
# this does not exactly need to be removed at this point because
# later on the whole temp directory should be removed however
# I left it in just in case there is some kind of error before
# the temp directory is deleted. Gotta hide the details! :)
rm "$temp_dir""temp.txt"
did_the_system_command_work $?
fi
}
function test_for_being_a_tar_bomb
{
create_the_temp_directory
# extract the tar to temporary directory
tar -xf "$file_name" -C "$temp_dir"
did_the_system_command_work $?
remove_dirs_from_the_temp_directory
temp="$(ls $temp_dir)"
did_the_system_command_work $?
# test for any leftover files in the temp directory
# if there are leftover files this tells us the tar
# is a tarbomb
if [[ "$temp" != "" ]]; then
echo "Warning! A tarbomb was detected!"
is_a_tar_bomb=$YES
# remove all leftover files in the temp directory
rm -rf "$temp_dir"*
did_the_system_command_work $?
if [ $force_option -eq $ON ]; then
echo "Forcing the extraction..."
echo
else
delete_the_temp_directory
echo "Exiting..."
echo
exit $FAILED
fi
fi
}
# check if the tar file exists
# if it does not exit
function check_for_tar_file
{
if [ -f "$file_name" ]; then
return
else
echo "utar: The specified file '$file_name' does not exist..."
echo
exit $FAILED
fi
}
function create_specified_extract_path_if_needed
{
# check to see if an optional extract path was given
if [[ "$optional_extraction_path" != "" ]]; then
# if the specified extract path does not exist then create it
if [ ! -d "$optional_extraction_path" ]; then
mkdir -p "$optional_extraction_path"
did_the_system_command_work $?
fi
fi
}
function try_normal_extraction
{
# test if no optional extract path was given
# if none is given then perform a normal extraction
if [[ "$optional_extraction_path" = "" ]]; then
tar -xf "$file_name"
did_the_system_command_work $?
delete_the_temp_directory
exit $SUCCEEDED
fi
}
function try_maintaining_the_root_directory_extraction
{
# if the -k or --keep-root-dir option was passed perform a normal
# extraction into the specified directory
if [ $keep_root_option -eq $ON ]; then
tar -xf "$file_name" -C "$optional_extraction_path"
did_the_system_command_work $?
delete_the_temp_directory
exit $SUCCEEDED
fi
}
function extract_the_tar_bomb
{
# extract the tar to the specified directory while
# stripping the root directory
tar -xf "$file_name" -C "$optional_extraction_path" --strip-components=1
did_the_system_command_work $?
# now take care of any files from a tarbomb
# extract the tar to temporary directory
tar -xf "$file_name" -C "$temp_dir"
did_the_system_command_work $?
# grab a list of the files and directories in the temp directory
temp="$(ls $temp_dir -A --file-type)"
did_the_system_command_work $?
remove_dirs_from_the_temp_directory
# output list of left over files to file temp.txt
ls_results=$(ls "$temp_dir")
did_the_system_command_work $?
echo "$ls_results" > "$temp_dir""temp.txt"
did_the_system_command_work $?
exec<"$temp_dir""temp.txt"
# go through the list of leftover files and
# before moving them make sure they do not
# have the same file name as any files in the
# specified directory. if they do then append
# a hyphen and a number i.e. duplicate-file-1
# increase the number until an untaken file name is found
while read line
do
i=1
# test to see if the file exists
if [ -f "$optional_extraction_path""$line" ]; then
while [ -f "$optional_extraction_path""$line""-""$i" ]
do
i=$(( $i + 1 ))
done
echo "Found a duplicate file: ""'$line':"" renaming it to ""'$line""-""$i'"
# move the files back to the specified directory
mv "$temp_dir""$line" "$optional_extraction_path""$line""-""$i"
did_the_system_command_work $?
else
# move the files back to the specified directory
mv "$temp_dir""$line" "$optional_extraction_path"
did_the_system_command_work $?
fi
done
delete_the_temp_directory
exit $SUCCEEDED
}
function extract_to_the_specified_path
{
tar -xf "$file_name" -C "$optional_extraction_path" --strip-components=1
did_the_system_command_work $?
delete_the_temp_directory
exit $SUCCEEDED
}
### HERE STARTS THE CODE EXECUTION
deal_with_the_parameters "$1" "$2" "$3" "$4" "$5" "$6"
# makes sure the specified tar file exists
check_for_tar_file
# tests the tar for being a tarbomb
# creates a temporary directory
test_for_being_a_tar_bomb
# runs and exits if no specified extract path was given
try_normal_extraction
# if the extract path does not exist then create it
create_specified_extract_path_if_needed
# runs and exits if a specified extract path was given
# and the -k or --keep-root-dir option was passed
try_maintaining_the_root_directory_extraction
if [ $is_a_tar_bomb -eq $YES ]; then
# runs and exits after extracting the tarbomb to the path given
extract_the_tar_bomb
else
# runs and exits after extracting to the path given
extract_to_the_specified_path
fi
|
