WordPress password hashing

  • Resolved mtinsley

    (@mtinsley)


    14 years, 2 months ago

    So out of curiosity I went digging through the code today to figure out how wordpress was storing passwords. I was a little surprised to find that the underlying hash function used in the phpass class was md5.

    The reason given in the code is as follows:

    We’re kind of forced to use MD5 here since it’s the only cryptographic primitive available in all versions of PHP currently in use

    Keep in mind that this class was written in 2006 (according to the comments).

    The sha1 function was introduced in PHP 4.3 (in 2002), which is also the minimum version of PHP required by wordpress. I wonder if it is time to consider updating that code.

    To be honest I’m not certain of the issues that would arise from changing password storage method.

    If you look at the code there is a lot going on beyond md5, but I still wonder how much more collision resistant the resulting hash is compared to md5. From wikipedia:

    The security of the MD5 hash function is severely compromised. A collision attack exists that can find collisions within seconds on a computer with a 2.6Ghz Pentium4 processor (complexity of 2^24.1)

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  • Moderator James Huff

    (@macmanx)

    That’s a very interesting question. I recommend contacting [email protected] for more details.

    Thread Starter mtinsley

    (@mtinsley)

    Actually it looks like I jumped to conclusions. On closer inspection of the code it seems like md5 is used as a fallback. phpass will attempt to use blowfish and extended des before using md5 as a last resort.

    It seems very unlikely that wordpress would have to resort to md5. Support for blowfish doesn’t depend on PHP, but on the OS. I’m guessing most major OSs support either blowfish or extended des. In addition to this, as of version 5.3 PHP has its own implementation of both of those algos.

    Still, since the minimum PHP requirement is 4.3 and provided there won’t be too many side effects it might be a good idea to switch out md5 for sha1.

    I’m actually writing a 3rd party app that needs to authenticate against wordpress’ credentials. The app will not be running on wordpress’ container and is not written in Php (hence cannot use wp’s api). Is there any way to know for sure which algo is being used ?

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