CWE-103: Struts: Incomplete validate() Method Definition

What is Struts: Incomplete validate() Method Definition?

• Overview: This vulnerability occurs in Java applications using the Struts framework, where the validate() method in a validator form is either not defined or defined without calling super.validate(), leading to the disabling of the validation framework for that form.

• Exploitation Methods:

• Attackers can exploit this vulnerability by submitting malicious or malformed data through form inputs that bypass validation checks.
• Common attack patterns include injection attacks, such as SQL injection or script injection, due to unvalidated input fields.

• Security Impact:

• Direct consequences of successful exploitation include unauthorized access, data corruption, or application malfunction due to invalid input processing.
• Potential cascading effects include increased risk of broader application compromise and data breaches.
• Business impact could involve loss of customer trust, legal liabilities, and financial losses due to data breaches or application downtime.

• Prevention Guidelines:

• Ensure that the validate() method is implemented for all validator forms and that it always calls super.validate() to enable the validation framework.
• Follow security best practices by validating and sanitizing all input data, even if internal validation is expected.
• Use recommended tools and frameworks like OWASP’s ESAPI for additional input validation and protection against injection attacks.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Java

Affected Technologies: Not specified

The Struts Validator uses a form's validate() method to check the contents of the form properties against the constraints specified in the associated validation form. That means the following classes have a validate() method that is part of the validation framework: ValidatorForm, ValidatorActionForm, DynaValidatorForm, and DynaValidatorActionForm. If the code creates a class that extends one of these classes, and if that class implements custom validation logic by overriding the validate() method, the code must call super.validate() in the validate() implementation.

Vulnerable Code Example

// This code defines a Struts form without a proper validate() method.
// The lack of a validate() method means user inputs are not checked for correctness or security,
// leading to potential data integrity issues and security vulnerabilities.
public class UserForm extends ActionForm {
    private String username;
    private String email;

    // Missing validate() method
    // Without validation, user inputs could be malicious or incorrect, leading to potential issues.
}

How to fix Struts: Incomplete validate() Method Definition?

To fix this vulnerability, it's essential to implement a validate() method within the Struts form class. This method should override the validate() method from the ActionForm class and call super.validate() to ensure that any superclass validations are executed. Additionally, implement custom validation logic tailored to the application's security and data integrity needs. This practice prevents malicious or incorrect data from being processed by the system, reducing the risk of injection attacks and maintaining data consistency.

Fixed Code Example

// Fixed code with a properly defined validate() method that includes a call to super.validate()
public class UserForm extends ActionForm {
    private String username;
    private String email;

    @Override
    public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) {
        // Initialize an ActionErrors object to collect validation errors
        ActionErrors errors = new ActionErrors();

        // Custom validation logic for the username field
        if (username == null || username.trim().isEmpty()) {
            errors.add("username", new ActionMessage("error.username.required"));
        }

        // Custom validation logic for the email field
        if (email == null || !email.matches("[a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,4}")) {
            errors.add("email", new ActionMessage("error.email.invalid"));
        }

        // Ensure superclass validations are also executed
        errors.add(super.validate(mapping, request));

        return errors;
    }
}

In this fixed version, we've properly overridden the validate() method, ensuring that any validations from ActionForm are performed by calling super.validate(). We also added custom validation checks to verify that the username is not empty and that the email follows a valid pattern. These checks improve the security and reliability of the application by preventing invalid or harmful data from being processed. Additionally, the ActionErrors object is initialized at the start of the validate() method, and any errors from the superclass are added to this object, ensuring comprehensive validation.