What's the algorithm that Linux uses to hash users' passwords? How can I implement that algorithm in PHP?
2条回答 默认 最新
- dscizpq790832708 2011-06-16 05:45关注
You might need to know some background information on Linux password storage formats - especially on shadowed password configuration before you can actually implement your own.
On Linux distributions using glibc2, the hash function has a 'magic bit' and salt prefixed to it.
The magic bit starts off with '$x$' and is used to determined the hash function that was used:
- $1$ for MD5
- $2$ for Blowfish,
- $5$ for SHA-256 and
- $6$ for SHA-512
(Other unix systems like NetBSD might have different values for this).
The magic bit then followed by 8 bits that constitutes the salt and optionally is terminated by another "$". Between this and the next "$", you will find the actual password hash.
Almost all modern Linux systems these days do NOT store the passwords in the world-readable
/etc/passwd
. Instead the passwords are shadowed in/etc/shadow
where only root is allowed read permission. If the shadowed password scheme in use, the/etc/passwd
file shows a character such as '*', or 'x' instead of the password.The format of a typical password in
/etc/shadow
would looks like this:$a:$b:$c:$e:$f:$g:$h:$i
Where:
$a: username
$b: salt and hashed password (as explained above). If this is "NP" or "!" or null then it means that the account has no password. "LK" or "*" means the account is locked and the user will be unable to log-in. "!!" means that the password has expired
$c: Days since epoch of last password change
$d: Days until change allowed
$e: Days before change required
$f: Days warning for expiration
$g: Days before account inactive
$h: Days since epoch when account expires
$i: Reserved for future use.
An example of a shadowed password file could be found at: http://configuration.logfish.net/index.php/etc/shadow
References:
本回答被题主选为最佳回答 , 对您是否有帮助呢?解决 无用评论 打赏 举报
悬赏问题
- ¥15 如何在scanpy上做差异基因和通路富集?
- ¥20 关于#硬件工程#的问题,请各位专家解答!
- ¥15 关于#matlab#的问题:期望的系统闭环传递函数为G(s)=wn^2/s^2+2¢wn+wn^2阻尼系数¢=0.707,使系统具有较小的超调量
- ¥15 FLUENT如何实现在堆积颗粒的上表面加载高斯热源
- ¥30 截图中的mathematics程序转换成matlab
- ¥15 动力学代码报错,维度不匹配
- ¥15 Power query添加列问题
- ¥50 Kubernetes&Fission&Eleasticsearch
- ¥15 報錯:Person is not mapped,如何解決?
- ¥15 c++头文件不能识别CDialog