Earlier, I was playing with some code from Jon Erickson’s book which exploited stack overflow bugs, on an older Linux system. When it came time to bring that code over to OS X though, the overflow protection would kill the process before it got a chance to do anything nasty.
Here’s the incantation required to disable it:
gcc -fno-stack-protector -D_FORTIFY_SOURCE=0 -g -o overflow overflow.c
Before:
› ./overflow 1234567890
[BEFORE] second_buffer is at 0x7fff52d22868 and contains 'two'
[BEFORE] first_buffer is at 0x7fff52d22870 and contains 'one'
[BEFORE] value is at 0x7fff52d22854 and contains 5 (0x00000005)
Copying 10 bytes into second_buffer
zsh: abort ./overflow 1234567890
After:
› ./overflow 1234567890
[BEFORE] second_buffer is at 0x7fff5e14e85c and contains 'two'
[BEFORE] first_buffer is at 0x7fff5e14e864 and contains 'one'
[BEFORE] value is at 0x7fff5e14e86c and contains 5 (0x00000005)
Copying 10 bytes into second_buffer
[AFTER] second_buffer is at 0x7fff5e14e85c and contains '1234567890'
[AFTER] first_buffer is at 0x7fff5e14e864 and contains '90'
[AFTER] value is at 0x7fff5e14e86c and contains 5 (0x00000005)