[Full-disclosure] ShortNotes : Stack Smashing with GCC4

[Marcus Meissner]

> The classic example (Gera's Law): 
> 
[File : abo1.c ]

After fixing your code (adding a missing #include <string.h>)

> $ gcc -o abo1 abo1.c

Which is just not how to compile your code. 
If you pass the right options:

$ gcc -O2 -D_FORTIFY_SOURCE=2 xx.c -o xx
$ ./xx `perl -e "print 'a' x 1024;"`
*** buffer overflow detected ***: ./xx terminated
======= Backtrace: =========
/lib/power4/libc.so.6(__chk_fail+0x68)[0xff7db68]
/lib/power4/libc.so.6(__strcpy_chk+0x60)[0xff7c820]
./xx[0x1000056c]
/lib/power4/libc.so.6[0xfea3f70]
/lib/power4/libc.so.6[0xfea41cc]
...


gcc -O2 -fstack-protector xx.c -o xx
./xx `perl -e "print 'a' x 1024;"`
Input : aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
*** stack smashing detected ***: ./xx terminated


Perhaps you should read the manpages of the compiler first to find the
correct options to enable.

Ciao, Marcus