De-obfuscates macOS /etc/kcpassword file used for automatic login

kcpasswordDecode.sh

#!/bin/bash
#kcpasswordDecode (20220729) Copyright (c) 2021 Joel Bruner (https://github.com/brunerd)
#Licensed under the MIT License

#specify file as input
#kcpasswordDecode.sh /etc/kcpassword

#given a filepath XOR to the it back and truncate padding
function kcpasswordDecode() (
	filepath="${1}"
	#no file
	if [ -z "${filepath}" ]; then
		[ ! -t '0' ] && echo "Redirected input no longer supported" >/dev/stderr
		echo "Please specify a file path" >/dev/stderr
		exit 1
	#bad file
	elif [ ! -f "${filepath}" ]; then
		echo "$(basename "$0"): ${filepath}: No such file" >/dev/stderr
		exit 1
	#file
	else
		#test for type of data
		case "$(file -b "${filepath}")" in
			#in some cases the kcpassword may be a hex representation in ASCII (10.10+)
			"ASCII text")
				#just space out the ASCII data into 2 byte couplets
				thisStringHex_array=( $(sed 's/../& /g' "${filepath}") )
				;;
			#otherwise treat as binary data
			*)
				#convert to hex representation with spaces
				thisStringHex_array=( $(xxd -p -u "${filepath}" | sed 's/../& /g') )
			;;
		esac
	fi

	#macOS cipher hex ascii representation array
	cipherHex_array=( 7D 89 52 23 D2 BC DD EA A3 B9 1F )	

	for ((i=0; i < ${#thisStringHex_array[@]}; i++)); do
		#use modulus to loop through the cipher array elements
		charHex_cipher=${cipherHex_array[$(( $i % 11 ))]}

		#get the current hex representation element
		charHex=${thisStringHex_array[$i]}
	
		#use $(( shell Aritmethic )) to ^ XOR the two 0x## values (extra padding is 0x00) 
		#take decimal value and printf convert to two char hex value
		#use xxd to convert hex to ascii representation
		decodedCharacter=$(printf "%02X" "$((0x${charHex_cipher} ^ 0x${charHex:-00}))")		

		if [[ "${decodedCharacter}" = "00" ]]; then
			break
		else
			printf "%02X" "$(( 0x${charHex_cipher} ^ 0x${charHex:-00} ))" | xxd -r -p > /dev/stdout
		fi
	done
)

kcpasswordDecode "$@"

macOS Ventura changes the encoding in kcpassword to be an ASCII representation of hex data. While file can easily determine the type of data, it doesn't work so well if piped input or file redirection is used. To simplify things, only files are used as input sources now.