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PHP如何给密码加密(实例详解)

Jun 21, 2016 am 08:56 AM
php Password encryption

很多用户多个网站使用一个密码,当一个密码丢失其他也遭殃,本篇文章介绍了PHP中的密码加密的解决方案总结,有需要的朋友可以了解一下。

层出不穷的类似事件对用户会造成巨大的影响,因为人们往往习惯在不同网站使用相同的密码,一家“暴库”,全部遭殃

一般的解决方案。

1、将明文密码做单向hash

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$password = md5($_POST["password"]);

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2、密码+salt后做单向hash,PHP内置了hash()函数,你只需要将加密方式传给hash()函数就好了。你可以直接指明sha256, sha512, md5, sha1等加密方式

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<?php

function generateHashWithSalt($password) {

 $intermediateSalt = md5(uniqid(rand(), true));

 $salt = substr($intermediateSalt, 0, 6);

 return hash("sha256", $password . $salt);

}

?>

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单向哈希算法有一个特性,无法通过哈希后的摘要(digest)恢复原始数据,常用的单向哈希算法包括SHA-256,SHA-1,MD5等。例如,对密码“passwordhunter”进 行SHA-256哈希后的摘要(digest)如下:
“bbed833d2c7805c4bf039b140bec7e7452125a04efa9e0b296395a9b95c2d44c”

注意:攻击者可以将所有密码的常见组合进行单向哈希,得到一个摘要组合,然后与数据库中的摘要进行比对即可获得对应的密码。这个摘要组合也被称为rainbow table。更糟糕的是,一个攻击者只要建立上述的rainbow table,可以匹配所有的密码数据库。仍然等同于一家“暴库”,全部遭殃

比较好的解决方案

Bcrypt

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<?php

function generateHash($password) {

 if (defined("CRYPT_BLOWFISH") && CRYPT_BLOWFISH) {

  $salt = &#39;$2y$11$&#39; . substr(md5(uniqid(rand(), true)), 0, 22);

  return crypt($password, $salt);

 }

}

?>

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Bcrypt 其实就是Blowfish和crypt()函数的结合,我们这里通过CRYPT_BLOWFISH判断Blowfish是否可用,然后像上面一样生成一个盐值,不过这里需要注意的是,crypt()的盐值必须以2a2a或者2y2y开头。

Password Hashing API

Password Hashing API是PHP 5.5之后才有的新特性,它主要是提供下面几个函数供我们使用

password_hash() – 对密码加密.

password_verify() – 验证已经加密的密码,检验其hash字串是否一致.

password_needs_rehash() – 给密码重新加密.

password_get_info() – 返回加密算法的名称和一些相关信息.

虽然说crypt()函数在使用上已足够,但是password_hash()不仅可以使我们的代码更加简短,而且还在安全方面给了我们更好的保障,所以,现在PHP的官方都是推荐这种方式来加密用户的密码,很多流行的框架比如Laravel就是用的这种加密方式

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<?php

$hash = password_hash($passwod, PASSWORD_DEFAULT);?>

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PASSWORD_DEFAULT目前使用的就是Bcrypt,最好的还是Password Hashing API。这里需要注意的是,如果你代码使用的都是PASSWORD_DEFAULT加密方式,那么在数据库的表中,password字段就得设置超过60个字符长度,你也可以使用PASSWORD_BCRYPT,这个时候,加密后字串总是60个字符长度。

这里使用password_hash()你完全可以不提供盐值(salt)和 消耗值 (cost),你可以将后者理解为一种性能的消耗值,cost越大,加密算法越复杂,消耗的内存也就越大。当然,如果你需要指定对应的盐值和消耗值,你可以这样写

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<?php

function custom_function_for_salt(){

 return $salt = &#39;$2y$11$&#39; . substr(md5(uniqid(rand(), true)), 0, 22);

}

  

$password =123456;

  

$options = [

 &#39;salt&#39; => custom_function_for_salt(), //write your own code to generate a suitable salt

 &#39;cost&#39; => 12 // the default cost is 10

];

$hash = password_hash($password, PASSWORD_DEFAULT, $options);

echo $hash;

?>

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密码加密过后,我们需要对密码进行验证,以此来判断用户输入的密码是否正确

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<?php

if (password_verify($password, $hash)) {

 // Pass

}

else {

 // Invalid

}

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直接使用password_verify就可以对我们之前加密过的字符串(存在数据库中)进行验证了

如果有时候我们需要更改我们的加密方式,如某一天我们突然想更换一下盐值或者提高一下消耗值,我们这时候就要使用到password_needs_rehash()函数了

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<?php

if (password_needs_rehash($hash, PASSWORD_DEFAULT, [&#39;cost&#39; => 12])) {

 // cost change to 12

 $hash = password_hash($password, PASSWORD_DEFAULT, [&#39;cost&#39; => 12]);

  

 // don&#39;t forget to store the new hash!

}

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只有这样,PHP的Password Hashing API才会知道我们重现更换了加密方式,这样的主要目的就是为了后面的密码验证,password_get_info(),这个函数一般可以看到下面三个信息

algo – 算法实例
algoName – 算法名字
options – 加密时候的可选参数

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持脚本之家。

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