Cross-Site Request Forgery is done with attacker tricking a victim into making a request he did not intend to do. As in above diagram attacker manipulate the trust application has on victims browser.
To do this attack there have to be 2 requirments fulfilled.
1.The victim should be logged in to the targeted website (have an active session)
2. The site should be vulnerable to cross-site scripting forgery
The attack is against authenticated web application using a cookie.
Synchronizer token patterns is a method to prevent this from happening. This article discusses on how it works.
- First I have created my login page. This is where the user enters the credentials to log in to a certain website.
- The session starts on the client side and a cookie is created using the session id.
- At the same time, the server side randomly generates a key and use it to generate the CSRF token. CSRF token is saved in a session variable for future use.
- Then the loadDoc function is created in java script to request the token that created from the client side and to place it in the html tag.
- The loadDoc function should be called with the method, server-side URL and the HTML tag for the form.
- This is the HTML form for credentials. Here you can see a hidden field with the id = Token. This hidden file stores the token and send it to the server by POST method.
- In the server side, the data that was sent from the post method are assigned as parameters for loginvalidate function.
- By comparison from the credentials are validated and the Tokens and session ids are compared.
- If all 4 matches access granted. Else an error message will be displayed.
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