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e087c9af2f
This enables support for passwords with more than 72 bytes (or more than 18-72 characters) and for passwords containing null bytes
97 lines
3.5 KiB
PHP
97 lines
3.5 KiB
PHP
<?php
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/*
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* PHP-Auth (https://github.com/delight-im/PHP-Auth)
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* Copyright (c) delight.im (https://www.delight.im/)
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* Licensed under the MIT License (https://opensource.org/licenses/MIT)
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*/
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namespace Delight\Auth;
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final class PasswordHash {
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const HASH_ALGORITHM_IDENTIFIER = \PASSWORD_DEFAULT;
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const PEPPER_HMAC_SHA_512_PREHASH = 'bec95beffb3afd078df7cbfd4c4617ba214ac4641a157c1ca64106e7544c9fb4cef6e99b0a8f0b63e96328c09943ce96b9b8899ff54fa7ea57b622675442dbbf';
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const PREFIX_BCRYPT_WITH_HMAC_SHA_512_PREHASH = '$pa01';
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const PREFIX_LENGTH = 5;
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/**
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* Creates a computationally expensive hash from a password
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*
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* @param string $passwordText
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* @return string|bool
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*/
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public static function from($passwordText) {
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// if the bcrypt algorithm will be used for computationally expensive hashing
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if (self::HASH_ALGORITHM_IDENTIFIER === \PASSWORD_BCRYPT || self::HASH_ALGORITHM_IDENTIFIER === null) {
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// pre-hash the password to support passwords with more than 72 bytes (i.e. more than 18-72 characters) and passwords containing null bytes
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$passwordText = self::prehash($passwordText);
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// use 72 out of the ~88 bytes from the prehash in bcrypt later and denote this in a custom hash prefix
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$outputPrefix = self::PREFIX_BCRYPT_WITH_HMAC_SHA_512_PREHASH;
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}
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else {
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$outputPrefix = '';
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}
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return $outputPrefix . \password_hash($passwordText, self::HASH_ALGORITHM_IDENTIFIER);
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}
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/**
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* Verifies whether a password matches a computationally expensive hash
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*
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* @param string $passwordText
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* @param string $expectedHash
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* @return bool
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*/
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public static function verify($passwordText, $expectedHash) {
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// if the expected hash has a custom prefix that indicates a prehash has been used
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if (\substr($expectedHash, 0, self::PREFIX_LENGTH) === self::PREFIX_BCRYPT_WITH_HMAC_SHA_512_PREHASH) {
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// pre-hash the password here as well to allow for a possible match
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$passwordText = self::prehash($passwordText);
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// and drop the custom prefix from the expected hash
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$expectedHash = \substr($expectedHash, self::PREFIX_LENGTH);
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}
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return \password_verify($passwordText, $expectedHash);
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}
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/**
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* Checks whether a computationally expensive hash needs to be updated to match a desired algorithm and set of options
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*
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* @param string $existingHash
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* @return bool
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*/
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public static function needsRehash($existingHash) {
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// if the existing hash has a custom prefix indicating that a prehash has been used
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if (\substr($existingHash, 0, self::PREFIX_LENGTH) === self::PREFIX_BCRYPT_WITH_HMAC_SHA_512_PREHASH) {
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// drop that custom prefix from the existing hash
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$existingHash = \substr($existingHash, self::PREFIX_LENGTH);
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}
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/*// if the existing hash has no custom prefix denoting a prehash
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else {
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// if the existing hash used the bcrypt algorithm
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if (\preg_match('/^\$2[abxy]?\$/', $existingHash) === 1) {
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// the prehash needs to be applied
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return true;
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}
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}*/
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return \password_needs_rehash($existingHash, self::HASH_ALGORITHM_IDENTIFIER);
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}
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private static function prehash($passwordText) {
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$pepperBinary = \hex2bin(self::PEPPER_HMAC_SHA_512_PREHASH);
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// do not just use SHA-512 but apply an HMAC with a (semi-public) pepper to avoid breach correlation or "password shucking"
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$hmacBinary = \hash_hmac('sha512', $passwordText, $pepperBinary, true);
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if (empty($hmacBinary)) {
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throw new AuthError('Could not generate HMAC');
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}
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// encode the prehash using Base64 to avoid passing null bytes to the main hash function later (which could truncate the input)
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return \base64_encode($hmacBinary);
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}
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}
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