Detailed explanation of php Bcrypt password encryption mechanism
这篇文章主要给大家介绍了关于PHP更安全的密码加密机制Bcrypt的相关资料,文中介绍的非常详细,对大家具有一定的参考学习价值,需要的朋友们下面来一起学习学习吧。
前言
我们常常为了避免在服务器受到攻击,数据库被拖库时,用户的明文密码不被泄露,一般会对密码进行单向不可逆加密——哈希。
常见的方式是:
哈希方式 | 加密密码 |
md5(‘123456') | e10adc3949ba59abbe56e057f20f883e |
md5(‘123456' . ($salt = ‘salt')) | 207acd61a3c1bd506d7e9a4535359f8a |
sha1(‘123456') | 40位密文 |
hash(‘sha256', ‘123456') | 64位密文 |
hash(‘sha512', ‘123456') | 128位密文 |
密文越长,在相同机器上,进行撞库消耗的时间越长,相对越安全。
比较常见的哈希方式是 md5 + 盐,避免用户设置简单密码,被轻松破解。
password_hash
但是,现在要推荐的是 password_hash()
函数,可以轻松对密码实现加盐加密,而且几乎不能破解。
$password = '123456'; var_dump(password_hash($password, PASSWORD_DEFAULT)); var_dump(password_hash($password, PASSWORD_DEFAULT));
password_hash
生成的哈希长度是 PASSWORD_BCRYPT —— 60位,PASSWORD_DEFAULT —— 60位 ~ 255位。PASSWORD_DEFAULT 取值跟 php 版本有关系,会等于其他值,但不影响使用。
每一次 password_hash
运行结果都不一样,因此需要使用 password_verify
函数进行验证。
$password = '123456'; $hash = password_hash($password, PASSWORD_DEFAULT); var_dump(password_verify($password, $hash));
password_hash
会把计算 hash 的所有参数都存储在 hash 结果中,可以使用 password_get_info
获取相关信息。
$password = '123456'; $hash = password_hash($password, PASSWORD_DEFAULT); var_dump(password_get_info($hash));
输出
array(3) { ["algo"]=> int(1) ["algoName"]=> string(6) "bcrypt" ["options"]=> array(1) { ["cost"]=> int(10) } }
注意:不包含 salt
可以看出我当前版本的 PHP 使用 PASSWORD_DEFAULT
实际是使用 PASSWORD_BCRYPT
。
password_hash($password, $algo, $options)
的第三个参数 $options
支持设置至少 22 位的 salt。但仍然强烈推荐使用 PHP 默认生成的 salt,不要主动设置 salt。
当要更新加密算法和加密选项时,可以通过 password_needs_rehash
判断是否需要重新加密,下面的代码是一段官方示例
$options = array('cost' => 11); // Verify stored hash against plain-text password if (password_verify($password, $hash)) { // Check if a newer hashing algorithm is available // or the cost has changed if (password_needs_rehash($hash, PASSWORD_DEFAULT, $options)) { // If so, create a new hash, and replace the old one $newHash = password_hash($password, PASSWORD_DEFAULT, $options); } // Log user in }
password_needs_rehash
可以理解为比较 $algo
+ $option
和 password_get_info($hash)
返回值。
password_hash 运算慢
password_hash
是出了名的运行慢,也就意味着在相同时间内,密码重试次数少,泄露风险降低。
$password = '123456'; var_dump(microtime(true)); var_dump(password_hash($password, PASSWORD_DEFAULT)); var_dump(microtime(true)); echo "\n"; var_dump(microtime(true)); var_dump(md5($password)); for ($i = 0; $i < 999; $i++) { md5($password); } var_dump(microtime(true));
输出
float(1495594920.7034) string(60) "$2y$10$9ZLvgzqmiZPEkYiIUchT6eUJqebekOAjFQO8/jW/Q6DMrmWNn0PDm" float(1495594920.7818) float(1495594920.7818) string(32) "e10adc3949ba59abbe56e057f20f883e" float(1495594920.7823)
password_hash
运行一次耗时 784 毫秒, md5 运行 1000 次耗时 5 毫秒。这是一个非常粗略的比较,跟运行机器有关,但也可以看出 password_hash
运行确实非常慢。
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