For example, the "Back" button browser capability is often hindered as the previous page may contain a token that is no longer valid. However, this may result in usability concerns. Per-request tokens are more secure than per-session tokens as the time range for an attacker to exploit the stolen tokens is minimal. They can be generated once per user session or for each request. Synchronizer Token Pattern ¶ĬSRF tokens should be generated on the server-side. You are responsible for proper configuration (such as key management and token management) before using these built-in CSRF protections that generate tokens to guard CSRF vulnerable resources. NET has built-in protection that adds a token to CSRF vulnerable resources. It is strongly recommended to research if the framework you are using has an option to achieve CSRF protection by default before trying to build your custom token generating system. Synchronizer token defenses have been built into many frameworks. Use Built-In Or Existing CSRF Implementations for CSRF Protection ¶ The synchronizer token pattern is one of the most popular and recommended methods to mitigate CSRF. If for any reason you do it, protect those resources against CSRF.Do not use GET requests for state changing operations.See the OWASP XSS Prevention Cheat Sheet for detailed guidance on how to prevent XSS flaws.Remember that any Cross-Site Scripting (XSS) can be used to defeat all CSRF mitigation techniques!.Consider verifying the origin with standard headers. Consider implementing user interaction based protection for highly sensitive operations.This is particularly an issue when a subdomain has a CNAME to domains not in your control. Consider SameSite Cookie Attribute for session cookies but be careful to NOT set a cookie specifically for a domain as that would introduce a security vulnerability that all subdomains of that domain share the cookie.Implement at least one mitigation from Defense in Depth Mitigations section.For API-driven sites that don't use tags, consider using custom request headers.For stateless software use double submit cookies.For stateful software use the synchronizer token pattern.If framework does not have built-in CSRF protection, add CSRF tokens to all state changing requests (requests that cause actions on the site) and validate them on the backend.Check if your framework has built-in CSRF protection and use it.In short, the following principles should be followed to defend against CSRF: In effect, CSRF attacks are used by an attacker to make a target system perform a function via the victim's browser, without the victim's knowledge, at least until the unauthorized transaction has been committed. For example, this attack could result in a transfer of funds, changing a password, or making a purchase with the user's credentials. The impact of a successful CSRF attack is limited to the capabilities exposed by the vulnerable application and privileges of the user. This attack is thwarted when proper Authorization is used, which implies that a challenge-response mechanism is required that verifies the identity and authority of the requester. Therefore, if the user is authenticated to the site, the site cannot distinguish between legitimate authorized requests and forged authenticated requests. A CSRF attack works because browser requests automatically include all cookies including session cookies. Insecure Direct Object Reference PreventionĬross-Site Request Forgery Prevention Cheat Sheet ¶ Introduction ¶Ĭross-Site Request Forgery (CSRF) is a type of attack that occurs when a malicious web site, email, blog, instant message, or program causes a user's web browser to perform an unwanted action on a trusted site when the user is authenticated. JavaScript Guidance for Auto-inclusion of CSRF tokens as an AJAX Request header Identifying Source Origin (via Origin/Referer header) Use Built-In Or Existing CSRF Implementations for CSRF Protection
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