用Python代码编写的SHA 512 crypt输出与mkpasswd不同

问题描述

运行mkpasswd -m sha-512 -S salt1234 password会导致以下结果:

$6$salt1234$Zr07alHmuONZlfKILiGKKULQZaBG6Qmf5smHCNH35KnciTapZ7dItwaCv5SKZ1xH9ydG59SCgkdtsTqVWGhk81

我有一段我认为可以输出相同内容的Python代码，但事实并非如此:

I have this snippet of Python code that I thought would output the same, but isn't:

import hashlib, base64
print(base64.b64encode(hashlib.sha512('password' + 'salt1234').digest()))

相反，它导致:

nOkBUt6l7zlKAfjtk1EfB0TmckXfDiA4FPLcpywOLORZ1PWQK4+PZVEiT4+9rFjqR3xnaruZBiRjDGcDpxxTig==

不确定我做错了什么.

我的另一个问题是，如何告诉sha512函数进行自定义回合.似乎只需要一个参数.

Another question I have is, how do I tell sha512 function to do custom rounds. It seems to take only 1 argument.

推荐答案

mkpasswd是 crypt()函数.我不认为这是简单的SHA512哈希.

mkpasswd is a front-end to the crypt() function. I don't think it is a straight-forward SHA512 hash here.

一些研究指出了SHA256-crypt和SHA512-crypt的规范，显示默认应用哈希5000次.您可以使用-R切换到mkpasswd来指定不同的回合数. -R 5000确实为您提供了相同的输出:

A little research points to the specification for SHA256-crypt and SHA512-crypt, which shows the hash is applied a default 5000 times. You can specify a different number of rounds using the -R switch to mkpasswd; -R 5000 indeed gives you the same output:

$ mkpasswd -m sha-512 -S salt1234 -R 5000 password
$6$rounds=5000$salt1234$Zr07alHmuONZlfKILiGKKULQZaBG6Qmf5smHCNH35KnciTapZ7dItwaCv5SKZ1xH9ydG59SCgkdtsTqVWGhk81

命令行工具提供的最小回合数为1000:

The minimum number of rounds offered by the command-line tool is 1000:

$ mkpasswd -m sha-512 -S salt1234 -R 999 password
$6$rounds=1000$salt1234$SVDFHbJXYrzjGi2fA1k3ws01/D9q0ZTAh1KfRF5.ehgjVBqfHUaKqfynXefJ4DxIWxkMAITYq9mmcBl938YQ//
$ mkpasswd -m sha-512 -S salt1234 -R 1 password
$6$rounds=1000$salt1234$SVDFHbJXYrzjGi2fA1k3ws01/D9q0ZTAh1KfRF5.ehgjVBqfHUaKqfynXefJ4DxIWxkMAITYq9mmcBl938YQ//

该算法涉及更多，需要您创建多个摘要.您可以可以通过 crypt.crypt()函数，并以与mkpasswd命令行相同的方式驱动它.

The algorithm is a bit more involved, requiring you to create several digests. You could instead access the C crypt() function through the crypt.crypt() function, and drive it the same way the mkpasswd commandline does.

SHA512-crypt方法是否可用取决于您的平台； crypt模块的Python 3版本提供了 crypt.methods列表告诉您平台支持的方法.由于此库使用与mkpasswd完全相同的库，因此您的操作系统显然支持SHA512-crypt，并且Python也将具有访问权限.

It depends on your platform if the SHA512-crypt method is available; the Python 3 version of the crypt module offers a crypt.methods list that tells you what methods your platform supports. Since this use the exact same library mkpasswd uses, your OS obviously does support SHA512-crypt and Python will have access too.

您需要在盐之前加上'$6$来指定其他方法.您可以通过在'$6$'字符串和盐之间添加'rounds=<N>$'字符串来指定轮数:

You need to prefix the salt with '$6$ to specify the different method. You can specify the number of rounds by adding a 'rounds=<N>$' string between the '$6$' string and your salt:

import crypt
import os
import string

try:  # 3.6 or above
    from secrets import choice as randchoice
except ImportError:
    from random import SystemRandom
    randchoice = SystemRandom().choice

def sha512_crypt(password, salt=None, rounds=None):
    if salt is None:
        salt = ''.join([randchoice(string.ascii_letters + string.digits)
                        for _ in range(8)])

    prefix = '$6$'
    if rounds is not None:
        rounds = max(1000, min(999999999, rounds or 5000))
        prefix += 'rounds={0}$'.format(rounds)
    return crypt.crypt(password, prefix + salt)

然后产生与mkpasswd命令行相同的输出:

This then produces the same output as the mkpasswd command line:

>>> sha512_crypt('password', 'salt1234')
'$6$salt1234$Zr07alHmuONZlfKILiGKKULQZaBG6Qmf5smHCNH35KnciTapZ7dItwaCv5SKZ1xH9ydG59SCgkdtsTqVWGhk81'
>>> sha512_crypt('password', 'salt1234', rounds=1000)
'$6$rounds=1000$salt1234$SVDFHbJXYrzjGi2fA1k3ws01/D9q0ZTAh1KfRF5.ehgjVBqfHUaKqfynXefJ4DxIWxkMAITYq9mmcBl938YQ//'

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