Frame pointer overwriting and FreeBSD

Hi,

Been trying some frame pointer overwriting techniques and it doesn't seem to be working like i'd expect on a FreeBSD (x86) system, wondering if the more familiar could clarify?

I'm basically doing a frame pointer overwrite by 1 byte exploit.

Stepping through the code in GDB i can make eip run into my NOPs, and then my shellcode, however, using (multiple) standard execve /bin/sh shellcodes written for FreeBSD, causes the vulnerable program to die with numerous errors like SIGFPE, SIGILL, etc (strangely enough, looking at what eip was in the core dump, it was usually in the string "/bin/sh").

Is it correct that since i've altered ebp's value, and as BSD passes it's arguments on the stack, i wont be able to get it working?

I'm taking a guess that it works on Linux because it's syscall arguments get passed via registers?

Cheers,

Chris. Received on Wed Jun 4 14:12:21 2003

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