donglie1898
2011-03-17 18:35
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便携式(PHPass)密码哈希。 我应该使用它们吗?

I'm installing a user registration script (Tank Auth) for my website.

In the installation guide its says,

WARNING: By default the library generates strong system-specific password hashes that are not portable. It means that once created, user database cannot be dumped and exported to another server. This behavior can be changed in config-file as well.

This put me in a dilemma. In the future I may want to change servers but I don't want weak passwords either. Are portable password hashes a big risk? And more importantly, what do they mean by hashes? Is it the character length?

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我正在为我的网站安装用户注册脚本(Tank Auth)。

在安装指南中,

警告:默认情况下,库会生成强大的系统特定 密码哈希值,这些哈希值不可移植。 它表示 一旦创建,用户 数据库就无法转储并导出到另一台服务器。 此行为也可以在配置文件中更改。

这使我处于两难境地。 将来我可能想要更换服务器,但我也不想要弱密码。 便携式密码是否有很大的风险? 更重要的是,哈希是什么意思? 它是字符长度吗?

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  • doucuyu2259 2011-03-17 18:39
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    Task Auth uses PHPass for password hashing (an old version, that's not a good sign; you might want to update that in your install). PHPass has two modes, portable and bcrypt.

    Depending on the PHP version, you do not need to have portable hashes on. On PHP 5.3 and above, PHP supplies its own implementation of bcrypt if it isn't available on the system. If all your servers have PHP 5.3 and above, I highly recommend to turn portable hashes off. PHPass "portables hashes" exists because, depending of the version of PHP installed, bcrypt might not be available.

    That said, PHPass portable hashes does store the salt in its hash. That's why every run on the same password is different.

    Also, PHPass uses PHP_VERSION during the generation of those hashes* to check if the md5() function available with that version supports the $rawMode parameter. If it doesn't, pack() is use to transform the hexadecimal data into binary (note that this is considerably slower then simply using $rawMode, which is why the branch is made).

    Again, if all your servers are running PHP 5.3 and above, I highly recommend to turn off portable mode and let PHPass use bcrypt instead. Since PHP 5.3+ provides its own implementation when the system one isn't available, your hash will be checkable across OSes. Even if you do turn off portable mode, PHPass will still be smart enough to check your old hashes the proper way.

    * Line 131


    EDIT: For more explanation, here is how hashes in portable mode are generated (simplified, does not use actual variables found in PHPass, but accurate). Note that PHPass uses their own version of base64 encoding.

    1. $final = '$P$'

    2. $final .= encode64_int($rounds) (from constructor, minimum is 5 on PHP 5+, 3 other)

    3. $final .= genSalt() (Salt is 6 bytes... 8 bytes in "encode64" format).

    4. $hash = md5($salt . $password)

    5. For 2$rounds times, do $hash = md5($hash . $password)

    6. $final = encode64($hash)

    So the final hash essentially is this:

    $P$9IQRaTwmfeRo7ud9Fh4E2PdI0S3r.L0
    \__________/\____________________/
      \                   \
       \                   \ Actual Hash
        \
         \  $P$   9   IQRaTwmf
            \_/   \   \______/
             \     \      \
              \     \      \ Salt
               \     \ 
                \     \ # Rounds (not decimal representation, 9 is actually 11)
                 \
                  \ Hash Header
    
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