Java.lang.securityexception: illegal url redirect

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Error: java.lang.SecurityException: Illegal URL redirect

The java.lang.SecurityException: Illegal URL redirect error occurs when there is an attempt to redirect the user to an unauthorized or illegal URL within a Java application.
This exception is thrown as a security measure to protect users from being redirected to potentially harmful or malicious websites.
In most cases, this error is encountered when using the java.net.URL or java.net.HttpURLConnection classes to handle URL redirections.

Causes

There are multiple reasons why this error can occur. Some of the common causes include:

  • Attempting to redirect to a URL that is not whitelisted or allowed by the application’s security policy.
  • Redirecting to an external URL that is considered unsafe or malicious.
  • Using a URL that violates the security restrictions set by the Java Security Manager.
  • Attempting to redirect to a URL that requires authentication or authorization, but the necessary credentials are not provided.

Examples

Let’s consider a few examples to better understand this error:

Example 1

Suppose you have a Java application with a login page. After successful authentication, the application redirects the user to a specific URL based on their role.
However, due to a misconfiguration or security policy, if the redirect URL is not whitelisted or allowed, the java.lang.SecurityException: Illegal URL redirect error will be thrown.
To resolve this, ensure that the redirect URL is valid and allowed by the application’s security settings. 


if (userRole.equals("admin")) {
    response.sendRedirect("/admin/dashboard"); // Incorrect redirect URL
} else if (userRole.equals("user")) {
    response.sendRedirect("/user/dashboard"); // Correct redirect URL
} else {
    response.sendRedirect("/login");
}

Example 2

Suppose you are making an HTTP request using java.net.HttpURLConnection and attempting to handle a redirect.
However, if the URL to which you are being redirected is considered unsafe or malicious, the java.lang.SecurityException: Illegal URL redirect error will be thrown to prevent the redirect.
To fix this, ensure that the target URL is trustworthy or modify your code to handle the redirect appropriately. 


URL url = new URL("http://example.com"); // Unsafe or malicious URL
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
int responseCode = connection.getResponseCode();

if (responseCode == HttpURLConnection.HTTP_MOVED_PERM || responseCode == HttpURLConnection.HTTP_MOVED_TEMP) {
    // Handle redirect
    String redirectUrl = connection.getHeaderField("Location");
    // ...
} else {
    // Handle other response codes
    // ...
}

Conclusion

The java.lang.SecurityException: Illegal URL redirect error typically occurs when there is an attempt to redirect the user to an unauthorized or unsafe URL within a Java application.
This error ensures the security of users by preventing them from being redirected to potentially harmful websites.
To resolve this error, ensure that the redirect URLs are valid, whitelisted, and adhere to the security policies set by the application.

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