Stack protection mechanisms in 4.0+/4.1.2?

Stack protection mechanisms in 4.0+/4.1.2?

[IceDane]

Hey there.

A course in my school involves exploitation of various vulnerabilities, 
such as buffer overflows and format string vulnerabilities and so on.

I'm currently running kbuntu, latest version, which comes with gcc 4.1.2 
stock. If I compile a vulnerable program(A simple strcpy of argv[1] to a 
small buffer) and then attempt to execute an exploit, no matter what  i 
do, it fails.

I realize that the ubuntu gcc 4.1.2 compiles with the -fstack-protector 
as default, however, even if I use -fno-stack-protector, the problem 
still prevails.

All kernels since 2.6 also come with virtual address space randomization 
as default, and I've disabled that.

Anyway, I found something that said if you installed gcc 3.3, you'd be 
fine. I try that, and voila, exploit executes accordingly.

Now, I ask - What is it, other than the -fstack-protector flag, which 
can disable buffer overflow exploits like that in gcc?

P.S. I just installed ubuntu to see if the problem prevailed here - I 
was using slack 12.0 just yesterday, with the same version of GCC, and I 
had the exact same problem.

All help greatly appreciated.

Re: Stack protection mechanisms in 4.0+/4.1.2?

[Andrew Haley]

IceDane writes:
 > Hey there.
 > 
 > A course in my school involves exploitation of various vulnerabilities, 
 > such as buffer overflows and format string vulnerabilities and so on.
 > 
 > I'm currently running kbuntu, latest version, which comes with gcc 4.1.2 
 > stock. If I compile a vulnerable program(A simple strcpy of argv[1] to a 
 > small buffer) and then attempt to execute an exploit, no matter what  i 
 > do, it fails.
 > 
 > I realize that the ubuntu gcc 4.1.2 compiles with the -fstack-protector 
 > as default, however, even if I use -fno-stack-protector, the problem 
 > still prevails.
 > 
 > All kernels since 2.6 also come with virtual address space randomization 
 > as default, and I've disabled that.
 > 
 > Anyway, I found something that said if you installed gcc 3.3, you'd be 
 > fine. I try that, and voila, exploit executes accordingly.
 > 
 > Now, I ask - What is it, other than the -fstack-protector flag, which 
 > can disable buffer overflow exploits like that in gcc?

I suspect that the stack layout has changed, and so your exploit no
longer works.  What happened whan you single-stepped through the
exploint injection in gdb?

Andrew.