#!/usr/bin/env bash
# Copyright 2026 Emile Clark-Boman
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

set -euo pipefail

USAGE="${BOLD}${UNDERLINE}${RED}Usage${RESET}
	${BOLD}${GREEN}$THIS new password [option...]${RESET}

${BOLD}${UNDERLINE}${RED}Description${RESET}
	Generates a new password hash in libxcrypt format with secure defaults.
	For more advanced usage run the ${BOLD}${MAGENTA}\`mkpasswd\`${RESET} utility directly.

${BOLD}${UNDERLINE}${RED}Options${RESET}
	${BOLD}${MAGENTA}-h, --help${RESET}               Show this message (^_^)
	${BOLD}${MAGENTA}-o, --out${RESET}                Private key file name to write to (the public key is named identically but ends with ${BOLD}${CYAN}.pub${RESET})
	${BOLD}${MAGENTA}-j, --json${RESET}               Output in JSON format
	${BOLD}${MAGENTA}-i, --stdin${RESET}              Read the password to hash from stdin ${BOLD}$CYAN(single line only)${RESET}
	${BOLD}${MAGENTA}-t, --type${RESET}               The hash algorithm to use: ${BOLD}${MAGENTA}yescrypt, scrypt, bcrypt ${CYAN}(default: yescrypt)${RESET}
	${BOLD}${MAGENTA}-r, --rounds${RESET}             The number of KDF to apply ${BOLD}${MAGENTA}(format: ^[0-9]+\$) ${CYAN}(defaults: yescrypt=11, scrypt=10, bcrypt=14)${RESET}
	${BOLD}${MAGENTA}-s, --salt${RESET}               Specify the hash's salt directly ${BOLD}${RED}(not recommended)${RESET} ${BOLD}${CYAN}(default: libxcrypt secure default)${RESET}"

# ==== Argument Values ====
TYPE='yescrypt'
ROUNDS=''
SALTED=false
OUT=''
JSON=false
STDIN=false
EXTRA=''
# ==== Argument Values ====

# parse all args
while [[ $# -gt 0 ]]; do
	ARG="$1"
	case "$ARG" in
		-h|--help)
			throw-usage 0
			;;
		-o|--out)
			shift
			OUT="$1"; shift
			;;
		-j|--json)
			shift
			JSON=true
			;;
		-i|--stdin)
			shift
			STDIN=true
			;;
		-t|--type)
			shift
			TYPE="$1"; shift
			;;
		-r|--rounds)
			shift
			ROUNDS="$1"; shift
			;;
		-s|--salt)
			shift
			if [[ "$SALTED" == false ]]; then
				SALTED=true
				EXTRA="$EXTRA --salt=\'$1\'"
			fi
			shift
			;;
		-*)
			throw-badflag 1 "$ARG"
			;;
		*)
			throw-badarg 1 "$ARG"
		  ;;
	esac
done; unset -v ARG

# NOTE: Available password hashing methods for /etc/passwd & /etc/shadow
# NOTE: Read the manual pages via `man 3 crypt` and `man 5 crypt` (if available)
# NOTE: Available online via https://man.archlinux.org/man/crypt.5
# WARNING: Due to modern developments in cryptography most of these methods
# WARNING: are no longer recommended however some distrobutions still use them.
# WARNING: Cerulean intentionally restricts access to only secure algorithms.
# $ mkpasswd -m help
## Available methods:
## yescrypt        Yescrypt
## gost-yescrypt   GOST Yescrypt
## scrypt          scrypt
## bcrypt          bcrypt
## bcrypt-a        bcrypt (obsolete $2a$ version)
## sha512crypt     SHA-512
## sha256crypt     SHA-256
## sunmd5          SunMD5
## md5crypt        MD5
## bsdicrypt       BSDI extended DES-based crypt(3)
## descrypt        standard 56 bit DES-based crypt(3)
## nt              NT-Hash
function perr-unsupportedhash {
	local ALGO="$1"
	echo -e "${BOLD}${CYAN}$THIS${RED} does not support the ${MAGENTA}$ALGO${RED} hashing algorithm${RESET}" >&2
}
function perr-forbiddenhash {
	local ALGO="$1"
	echo -e "${BOLD}${CYAN}Cerulean${RED} intentionally forbids ${MAGENTA}$ALGO-based${RED} hashes.${RESET}" >&2
}
function perr-recommendhash {
	local ALGO="$1"	
	echo -e "${BOLD}${CYAN}Cerulean${WHITE} recommends the ${MAGENTA}$ALGO${WHITE} algorithm ${GREEN}(embrace modernity loser)${RESET}" >&2
}

# ensure $TYPE is a valid hash algorithm
case "$TYPE" in
	# ========= PERMITTED HASH ALGORITHMS =========
	yescrypt)
		if [[ -z "$ROUNDS" ]]; then
			ROUNDS='11'
		fi
		;;
	scrypt)
		if [[ -z "$ROUNDS" ]]; then
			ROUNDS='10'
		fi
		;;
	bcrypt)
		if [[ -z "$ROUNDS" ]]; then
			ROUNDS='14'
		fi
		;;
	
	# ========= FORBIDDEN HASH ALGORITHMS =========
	gost-yescrypt)
		perr-unsupportedhash "$TYPE"
		perr-recommendhash 'yescrypt'
		echo -e "┏
┃	Dear Comrade,
┃   It is with a heavy heart I must inform you that \"GOST Algorithms
┃   Considered Harmful\" - Edsger Wybe Dijkstra (probably). Alas
┃	  GOST is considered broken... It is no longer 1970, please grow up :(
┃	Слава Родине! - Glory to the Motherland!
┗" >&2
		exit 1
		;;
	bcrypt-a)
		perr-unsupportedhash "$TYPE"
		perr-recommendhash 'bcrypt'
		echo -e "┏
┃ The alternative prefix \"\$2y$\" is equivalent to \"\$2b$\".
┃	It exists for historical reasons only. The alternative prefixes
┃	\"\$2a$\" and \"\$2x$\" provide bug-compatibility with
┃	crypt_blowfish 1.0.4 and earlier, which incorrectly processed
┃	characters with the 8th bit set.
┗" >&2
		exit 1
		;;
	sha512crypt|sha256crypt)
		perr-unsupportedhash "$TYPE"
		perr-forbiddenhash 'SHA'
		echo -e "┏
┃ SHA-based hashes are considered outdated and generally insecure
┃	due to their vulnerabilit to brute-force and collision attacks.
┃	Modern algorithms such as yescrypt, scrypt, and bcrypt are recommended.
┗" >&2
		exit 1
		;;
	sunmd5|md5crypt)
		perr-unsupportedhash "$TYPE"
		perr-forbiddenhash 'MD5'
		echo -e "┏
┃ Not as weak as the DES-based hashes, but MD5 is so cheap
┃	on modern hardware that it should not be used for new hashes.
┗" >&2
		exit 1
		;;
	bsdicrypt|descrypt)
		perr-unsupportedhash "$TYPE"
		perr-forbiddenhash 'DES'
		echo -e "┏
┃ The DES block cipher is cheap on modern hardware. Because there are only
┃ 4096 possible salts and 2**56 distinct passphrases, which it
┃ truncates to 8 characters, it is feasible to discover any passphrase
┃ hashed with this method. It should only be used if you absolutely have to
┃ generate hashes that will work on an old operating system that supports nothing else.
┗" >&2
		exit 1
		;;
	nt)
		perr-unsupportedhash "$TYPE"
		echo -e "${BOLD}Please ${RED}repent${WHITE} for your filthy sins ${RED}you disgusting human...${RESET}" >&2
		echo -e "┏
┃ Available for cross-compatibility's sake on FreeBSD. Based on MD4.
┃	Has no salt or tunable cost parameter. It is so weak that
┃	almost any human-chosen passphrase hashed with this method is guessable.
┃	It should only be used if you absolutely have to generate hashes that
┃	will work on an old operating system that supports nothing else. 
┗" >&2
		exit 1
		;;
	*)
		echo -e "${BOLD}${RED}Unrecognised hash algorithm ${MAGENTA}\"$TYPE\"${RESET}" >&2
		echo -e "${BOLD}${GREEN}Supported algorithms: ${MAGENTA}yescrypt, scrypt, bcrypt${RESET}" >&2
		exit 1
		;;
esac
unset -f perr-unsupportedhash perr-forbiddenhash perr-recommendhash

# ensure $ROUNDS is a valid numeric
if ! isnumeric "$ROUNDS"; then
	throw-badval 1 "$ROUNDS" '-r|--rounds'
fi

# Acquire password from stdin
if [[ "$STDIN" == true ]]; then
	read -s PASS
else
	read -sp "$(echo -e "${BOLD}${GREEN}Password:${RESET} ")" PASS
	echo # \n
	read -sp "$(echo -e "${BOLD}${GREEN}Retype Password:${RESET} ")" PASS2
	echo # \n
	if [[ "$PASS" != "$PASS2" ]]; then
		echo -e "${BOLD}${RED}Sorry, passwords do not match${RESET}" >&2
		exit 1
	fi
	unset -v PASS2
fi

# Compute hash of password
RESULT=$(mkpasswd -sm "$TYPE" -R "$ROUNDS" $EXTRA <<<"$PASS")
unset -v PASS
# Format as JSON if necessary
if [[ "$JSON" == true ]]; then
	RESULT="{
  \"type\": \"${TYPE}\",
  \"rounds\": ${ROUNDS},
  \"hash\": \"${RESULT}\"
}"
fi

# Display hash result
if [[ -n "$OUT" ]]; then
	echo "$RESULT" > "$OUT"
elif [[ "$JSON" == true ]]; then
	echo "$RESULT"
else
	echo -e "${BOLD}${GREEN}Hash:${WHITE} $RESULT${RESET}"
fi
unset -v RESULT

unset -v TYPE ROUNDS SALTED OUT JSON STDIN EXTRA