mardi 20 janvier 2015

Let's have (not) fun with afl

And that's a part two for an extreme exploitation of my previous bug found with afl. It was a crash in cabextract.

And it's a double fail.

1/ First fail
This crash is just a null pointer dereference. There is a lot of documentation in internet for it, and in that case, that's just not interesting at all. In order to be exploitable, you have to map an executable page at offset 0 and trigger the crash.

Here is a nice doc talking about null deref. Here is another blogspot explaining how to exploit null deref in linux kernel (now it's protected).

Short story short: "In the realm of userland applications, exploiting them usually requires being able to somehow control the target's allocations until you get page zero mapped, and this can be very hard."

2/ Second fail
This bug is known and corrected! You can see a nice explanation in debian bugtracker.

So,  nothing to do here, and moving for next target!


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