An attacker can successfully launch a phishing scam and steal user credentials from the victim users by modifying the untrusted URL input to a malicious site.
This redirection attack is possible because the server’s name of the original site is identical to the destination site. As the malicious site is almost identical to the original site, the phishing attempts may have a more trustworthy appearance.
The attacker misuses the unvalidated redirect vulnerability to create a maliciously crafted URL to pass the application’s access control check and then forward the attacker to privileged functions that they would normally not be able to access.
This vulnerability occurs when an application accepts untrusted input that contains a URL value without sanitizing it. The attacker can use the URL value to redirect the user to another page controlled by the attacker.
Example
response.sendRedirect(request.getParameter("http://example.beaglesecurity.com"));
What is insecure redirection?
Insecure redirection, also known as open redirection, is a web application security vulnerability that occurs when a web application redirects users to an untrusted or potentially malicious website without properly validating or sanitizing the redirect destination.
This vulnerability can be exploited by attackers to conduct phishing attacks or to trick users into visiting malicious sites. Here’s how insecure redirection typically works:
The web application accepts user-provided input, often through a query parameter in the URL or as part of a form submission, which specifies the destination URL for a redirect.
Instead of validating or sanitizing the input to ensure that it points to a safe and trusted location, the application directly uses this input to construct the redirection URL.
An attacker can manipulate this input by providing a malicious URL or script as the parameter value.
When an unsuspecting user clicks on a link or takes an action that triggers the redirect, they are redirected to the attacker’s specified URL, potentially leading to a phishing site or other malicious destination.
What are the impacts of insecure redirection?
The impacts of indirect redirection in a web application can vary depending on how it is implemented and for what purpose.
Indirect redirection, which involves routing user requests through an intermediary or middleman before reaching the destination, can have severe impacts:
1. Latency
Adding an intermediary step can introduce latency into the user experience, especially if the intermediary server performs resource-intensive operations or has network latency.
2. Complexity
Implementing indirect redirection adds complexity to the application’s architecture and can make it more challenging to maintain and troubleshoot.
3. User confusion
Users may find the redirection process confusing, especially if they are presented with multiple intermediary pages or if the redirection logic is not well-explained.
4. Privacy concerns
Collecting user data and tracking user interactions through intermediary servers may raise privacy concerns, especially if users are not informed about the data collection practices.
5. Single point of failure
The intermediary server becomes a single point of failure in the redirection process. If it goes down or becomes compromised, it can disrupt user access to external resources.
6. Phishing scams
Poorly implemented indirect redirection can introduce security risks if the intermediary server does not properly validate and sanitize input. This can lead to open redirection vulnerabilities and phishing attacks.
In short, the impacts of indirect redirection depend on how it is implemented and for what purpose. When used with careful consideration and proper security measures, it can provide benefits such as improved security and analytics.
However, it should be implemented thoughtfully to avoid negative impacts on user experience and potential security risks.
How can you prevent/mitigate indirect redirection vulnerabilities?
Preventing indirect redirection vulnerabilities involves ensuring that any redirections, whether direct or indirect, are implemented securely.
Here are some steps you can take to prevent indirect redirection vulnerabilities in your web application:
1. Validate and sanitize input
Always validate and sanitize any user-provided input used in redirection, including input that determines intermediary destinations. Ensure that it adheres to a whitelist of trusted domains or URLs.
2. Use whitelists
Maintain a whitelist of trusted intermediary destinations. Only allow redirection to URLs that are explicitly on the whitelist.
3. Encode output
When including user-generated input in a URL, make sure to properly URL-encode it to prevent any injection attacks.
4. Avoid user input for redirection
Whenever possible, avoid using user-supplied input for redirection. Construct URLs and redirection logic based on trusted sources within your application rather than relying on user-provided data.
5. Implement a secure intermediary
If you do use an intermediary in your redirection process, ensure that it is secure. It should validate and sanitize input, perform necessary security checks, and not introduce security vulnerabilities of its own.
6. Logging and monitoring
Implement logging and monitoring to detect and respond to any suspicious or unexpected redirection behavior. Set up alerts for unusual access patterns.
7. User awareness
If intermediary pages are presented to users before redirection, provide clear and informative messages explaining why they are being redirected and what to expect on the destination site.
This can help prevent user confusion and reduce the risk of phishing.
8. Regular security testing
Conduct security testing, including penetration testing using a platform like Beagle Security and code reviews, to identify and fix indirect redirection vulnerabilities in your application.
9. Security headers
Implement security headers, such as Content Security Policy (CSP) and X-Content-Type-Options, to mitigate various web vulnerabilities, including redirection issues.
10. Keep software updated
Keep all software components (frameworks, libraries, and the application itself) up to date to patch known security vulnerabilities.
By following these best practices and ensuring that your application’s redirection logic is secure and well-audited, you can significantly reduce the risk of indirect redirection vulnerabilities and enhance the overall security of your web application.
