Show HN: PHP 8 disable_functions bypass PoC(github.com)
26 pointsby m0x41nos6 hours ago4 comments
  • turbert5 hours ago
    from a quick skim, it looks like the underlying bug is just not handling object resurrection[1] at all (FreeMe adds a reference to $array while its destructor is called).

    I'm not really familiar with PHP but this seems like a surprising oversight for a popular language. Does PHP just not care about memory corruption? The fact that it is this easy is far more surprising than it being used to circumvent a questionable security feature.

    [1] https://en.wikipedia.org/wiki/Object_resurrection

  • halb5 hours ago
    there was a php-only million-rows challenge that was posted here recently. This uaf offers the opportunity for the funniest solution.
  • altairprime5 hours ago
    Tell us more about how you searched for and uncovered this? Do you normally use PHP? What disclosure process did you use?
  • calvinmorrison5 hours ago
    That's a nice find. People rely a little heavily on this, and it only says in the manual "This directive allows certain functions to be disabled." but its not a security sandbox.

    I think PHP has in the past explicitly stated its not a security feature.

    There have been a few issues over the years with this.

    Anyway - good OS security is required anytime you run software!

    heres one from 6 years ago https://bugs.php.net/bug.php?id=76047

    • kadoban5 hours ago
      > I think PHP has in the past explicitly stated its not a security feature.

      I'm struggling to think what it's for then?

      • turbert5 hours ago
        likely intended more as a lint than a security feature, it's not unusual to want to exclude commonly misused features from your code and any libraries you use.

        Knowing the mess that is the php standard library, I imagine many applications would want to just straight up ban the really bad parts.

      • duskwuff5 hours ago
        > I'm struggling to think what it's for then?

        Placating some users - mainly shared web hosting providers - who still think that disabling functions like system() and exec() is an effective security measure.

      • calvinmorrison5 hours ago
        a lazy security feature that stops 90% of problems?