password_needs_rehash

(PHP 5 >= 5.5.0, PHP 7, PHP 8)

password_needs_rehash — 检测散列值是否匹配指定的选项

说明

password_needs_rehash(string $hash, string|int|null $algo, array $options = []): bool

此函数检测指定的散列值是否实现了提供的算法和选项。如果没有，需要重新生成散列值。

参数

hash: 一个由 password_hash() 创建的散列值。
algo: 一个用来在散列密码时指示算法的密码算法常量。
options: 一个包含有选项的关联数组。详细的参数说明，请参考文档密码算法常数。

返回值

如果散列需要重新生成才能匹配指定的 algo 和 options，则返回 true，否则返回 false。

更新日志

版本	说明
7.4.0	现在 `algo` 参数可以支持 string 类型，但为了向后兼容性，同时支持 int 类型。

范例

示例 #1 password_needs_rehash()用法


<?php

$password = 'rasmuslerdorf';
$hash = '$2y$10$YCFsG6elYca568hBi2pZ0.3LDL5wjgxct1N8w/oLR/jfHsiQwCqTS';

// 当硬件性能得到改善时，cost 参数可以再修改
$options = array('cost' => 11);

// 根据明文密码验证储存的散列
if (password_verify($password, $hash)) {
    // 检测是否有更新的可用散列算法
    // 或者 cost 发生变化
    if (password_needs_rehash($hash, PASSWORD_DEFAULT, $options)) {
        // 如果是这样，则创建新散列，替换旧散列
        $newHash = password_hash($password, PASSWORD_DEFAULT, $options);
    }

    // 使用户登录
}
?>

add a note

User Contributed Notes 4 notes

down

php dot net at muer dot nl ¶

8 years ago


This function cannot check if a string is a MD5 or SHA1 hash. It can only tell you if a password, hashed using the password_hash function, needs to be put through the hashing function again to keep up to date with the new defaults.


The only time you can use this function is when your user logs in and you have already checked by means of password_verify that the password entered is actually correct. At that point, if password_needs_rehash returns true, you can put the plain text password through the password_hash function.

down

geekasylum at google mail ¶

4 years ago


This function can indeed be used to assist in transparently updating legacy passwords (those not using the password_hash() function - eg: perhaps something using MD5 or SHA1)

In legacy sites, when authenticating a user (during login) first check the password using password_verify(). If that fails it may simply be because the user's password hash was created long ago by a legacy or home-brew password algorithm.

You can then re-check the password against the site's legacy password algorithm.  If that fails too, then the login fails, since the supplied password did not authenticate against either the new, or the old password tests.

If any one of those two test was successfull, you know that the password is good so you would then call password_needs_rehash() on the stored hash, and it will properly indicate if the password hash needs to be re-computed, either because it's an unrecognised (legacy) hash or it's a modern hash created by password_hash(), which may just need its cost index updated.

Simply store the recomputed hash in the database and you now have a password_verify() compatible password for that user and the second test can be skipped in future logins (but still check if it needs rehashing).

down

admin at torntech dot com ¶

7 years ago


Some other use-cases for the password_needs_rehash function is when you have specified using the PASSWORD_DEFAULT algorithm for password_hash.
As mentioned on the Password Hashing Predefined Constants and password_hash pages, the algorithm used by PASSWORD_DEFAULT is subject to change as different versions of PHP are released.
Additionally password_needs_rehash would be used if you have changed the optional cost or static salt (DO NOT USE A STATIC SALT) requirements of your password_hash options.

Full example:

<?php

$new = [
    'options' => ['cost' => 11],
    'algo' => PASSWORD_DEFAULT,
    'hash' => null
];

$password = 'rasmuslerdorf';

//stored hash of password
$oldHash = '$2y$07$BCryptRequires22Chrcte/VlQH0piJtjXl.0t1XkA8pw9dMXTpOq';

//verify stored hash against plain-text password
if (true === password_verify($password, $oldHash)) {
    //verify legacy password to new password_hash options
    if (true === password_needs_rehash($oldHash, $new['algo'], $new['options'])) {
        //rehash/store plain-text password using new hash
        $newHash = password_hash($password, $new['algo'], $new['options']);
        echo $newHash;
    }
}
?>

The above example will output something similar to:
$2y$11$Wu5rN3u38.g/XWdUeA6Wj.PD.F0fLXXmZrMNFyzzg2UxkVmxlk41W

down

Daniel Hejduk ¶

5 months ago


Password need rehash also when its too strong. For example
<?php
$a = '123'; 
$hash = password_hash($a, PASSWORD_BCRYPT, ['cost'=>16]);
var_export(password_needs_rehash($hash,  PASSWORD_BCRYPT, ['cost'=>15])); //True

add a note

官方地址：https://www.php.net/manual/en/function.password-needs-rehash.php

有任何技术问题请点击这里网站运营推广招聘

IT PHP 编程语言 Linux 开发编程科技 Elasticsearch HTML/CSS/XML 网络数据库 JAVA 面试 NoSQL C/C++ Golang Git 算法操作系统正则表达式 Redis 互联网 MySql JavaScript 运维软件国际架构设计 Mac OS TCP/IP Excel Vim Windows Socket Oracle VR MongoDB Python 运营 MemCache 商业硬件电子娱乐设计 nginx 摄影游戏 WordPress HTTP 团建数码电器

php7 安装fileinfo扩展 preg_split — 通过一个正则表达式分隔字符串 php位值,解决 PHP 中 usort 在值相同时改变原始位置的问题 [PHP] inet_pton/inet_ntop IP地址转换函数 PHP 8.1 [鸟哥]PHP_INT_MIN 和 -9223372036854775808 adodb手册 ADORecordSet对象 opcache预加载 Composer的Packagist资源 array_multisort() 多字段排序 PHPMailer设置utf8 PHPMailer字符集CharSet PHP json解析（json_decode）页面工具 mysql面试题纯php实现DES以及TripleDES加密算法 php中几种注释规范两千行PHP学习笔记 php 修改图片大小支持php7的性能采集扩展利用PHP SOAP实现WEB SERVICE

略微加速

PHP官方手册 - 互联网笔记

password_needs_rehash

说明

参数

返回值

更新日志

范例

User Contributed Notes 4 notes