The session fixation attack is a class of Session Hijacking, which steals the established session between the client and the Web Server after the user logs in. Instead, the Session Fixation attack fixes an established session on the victim's browser, so the attack starts before the user logs in.
There are several techniques to execute the attack; it depends on how the Web application deals with session tokens. Below are some of the most common techniques:
• Session token in the URL argument: The Session ID is sent to the victim in a hyperlink and the victim accesses the site through the malicious URL.
• Session token in a hidden form field:In this method, the victim must be tricked to authenticate in the target Web Server, using a login form developed for the attacker. The form could be hosted in the evil web server or directly in html formatted e-mail.
• Session ID in a cookie:
o Client-side script
Most browsers support the execution of client-side scripting. In this case, the aggressor could use attacks of code injection as the XSS (Cross-site scripting) attack to insert a malicious code in the hyperlink sent to the victim and fix a Session ID in its cookie. Using the function document.cookie, the browser which executes the command becomes capable of fixing values inside of the cookie that it will use to keep a session between the client and the Web Application.
o tag
tag also is considered a code injection attack, however, different from the XSS attack where undesirable scripts can be disabled, or the execution can be denied. The attack using this method becomes much more efficient because it's impossible to disable the processing of these tags in the browsers.
o HTTP header response
This method explores the server response to fix the Session ID in the victim's browser. Including the parameter Set-Cookie in the HTTP header response, the attacker is able to insert the value of Session ID in the cookie and sends it to the victim's browser.






Client-side scripting


The processes for the attack using the execution of scripts in the victim's browser are very similar to example 1, however, in this case, the Session ID does not appear as an argument of the URL, but inside of the cookie. To fix the value of the Session ID in the victim's cookie, the attacker could insert a JavaScript code in the URL that will be executed in the victim's browser.


Example 3

<META> tag

As well as client-side scripting, the code injection must be made in the URL that will be sent to the victim.

http://website.kon/<meta http-equiv=Set-Cookie content=”sessionid=abcd”>


Example 4

HTTP header response
The insertion of the value of the SessionID into the cookie manipulating the server response can be made, intercepting the packages exchanged between the client and the Web Application inserting the Set-Cookie parameter.

How to Solve ?

1. when ever the client request a page [ generate a brand new session id]
2. once he input login credentials [ check and generate a new brand session id to track ]
3. once he logout his/her session [ make session.invalidate() and create a new session again ]

Note : adding Token is very good and more safer also..