CWE 862 - Missing Authorization

Disclaimer

The code provided is for **educational purposes** only and should not be used in a **production environment** without proper review and testing.

The provided code should be regarded as **best practice**. There are also several ways to remediate the Vulnerabilities.

The code provided **may contain vulnerabilities** that could be exploited by attackers, and is intended to be used as a learning tool to help improve security awareness and best practices.

The mitigations provided are intended to address **specific vulnerabilities** in the code, but may not be effective against all potential attack vectors or scenarios.

The code provided is not **guaranteed to be secure or free** from all vulnerabilities, and should be reviewed and tested thoroughly before being used in a production environment.

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About CWE 862

Missing Authorization

This Vulnerability occurs when an application or system fails to enforce proper authorization controls, allowing unauthorized users or entities to access restricted resources or perform actions they should not be able to.

Impact

Unauthorized access
Data exposure
Privilege escalation
Unauthorized actions
System compromise

Example with Code Explanation

Let us consider an example case and understand the CWE-862 with context of Vulnerable code and Mitigated code.

`JAVA`

Vulnerable Code

public class FileProcessor {
    private String filePath;

    public FileProcessor(String filePath) {
        this.filePath = filePath;
    }

    public void processFile() {
        File file = new File(filePath);
        if (file.exists()) {
            System.out.println("Processing file: " + filePath);
            // Perform file processing operations
        } else {
            System.out.println("File does not exist.");
        }
    }
}

public class Main {
    public static void main(String[] args) {
        FileProcessor processor = new FileProcessor("C:/SensitiveData.txt");
        processor.processFile();
    }
}

In the above code, the FileProcessor class processes a file specified by the filePath parameter. However, there is no authorization mechanism in place to check if the caller has permission to access the file. The vulnerability arises when an unauthorized user, running the code with insufficient privileges, is able to access sensitive files.

Some of the ways the Vulnerable code can be mitigated is:
- Implement Authentication and Authorization: Implement a robust authentication mechanism to verify the identity of users. Once authenticated, perform authorization checks to ensure that only authorized users have access to sensitive resources or functionalities.
- Role-Based Access Control (RBAC): Implement RBAC to define different roles within the system and assign permissions to those roles. Users can be assigned specific roles, and their access rights are determined based on those roles.
- Access Control Lists (ACLs): Utilize ACLs to specify granular access permissions for individual resources. This allows for fine-grained control over which users or roles can access specific files.
- Secure Configuration Management: Ensure that the application's configuration files, such as access control lists or user roles, are securely managed. Protect them from unauthorized modifications and regularly review and update configurations as needed.
- Principle of Least Privilege (PoLP): Apply the principle of least privilege by granting users the minimum privileges required to perform their tasks. Avoid granting excessive permissions that are not needed for their specific roles or functionalities.
- Secure File System Permissions: Set appropriate file system permissions on sensitive files to restrict access to authorized users only. Ensure that only the necessary user accounts or roles have read or write permissions on those files.
- Input Validation and Sanitization: Validate and sanitize user input related to authorization, such as usernames or roles, to prevent injection attacks or unauthorized access attempts.

Mitigated Code

import java.io.File;
import java.util.HashSet;
import java.util.Set;

public class FileProcessor {
    private String filePath;
    private Set<String> authorizedUsers;

    public FileProcessor(String filePath) {
        this.filePath = filePath;
        this.authorizedUsers = new HashSet<>();
        this.authorizedUsers.add("admin"); // Authorized user list
    }

    public void processFile(String user) {
        if (isUserAuthorized(user)) {
            File file = new File(filePath);
            if (file.exists()) {
                System.out.println("Processing file: " + filePath);
                // Perform file processing operations
            } else {
                System.out.println("File does not exist.");
            }
        } else {
            System.out.println("Unauthorized access.");
        }
    }

    private boolean isUserAuthorized(String user) {
        // Perform authentication and authorization checks
        if (user != null && authorizedUsers.contains(user)) {
            return true;
        }
        return false;
    }
}

public class Main {
    public static void main(String[] args) {
        FileProcessor processor = new FileProcessor("C:/SensitiveData.txt");
        processor.processFile("admin");
    }
}

The Mitigated code does the following:
- The authorizedUsers set is introduced to store the usernames of authorized users who have permission to access sensitive files. In this example, only the user "admin" is authorized.
- The processFile method now requires the user parameter to be passed. The method checks if the user is authorized by calling the isUserAuthorized private method, which performs authentication and authorization checks.
- The isUserAuthorized method verifies if the user is non-null and exists in the authorizedUsers set. This ensures that only authenticated and authorized users can access sensitive files.
- If an unauthorized user attempts to access the file, the code will display Unauthorized access.

`PHP`

Vulnerable Code

<?php
// Insecure Password Reset Example

$userEmail = $_POST['email'];
$newPassword = $_POST['new_password'];

// Insecure authorization check
if (isValidEmail($userEmail)) {
    // Reset password for the user
    resetPassword($userEmail, $newPassword);
    echo "Password reset successfully!";
} else {
    echo "Invalid email address.";
}

function isValidEmail($email) {
    // Insecure email validation
    return filter_var($email, FILTER_VALIDATE_EMAIL);
}

function resetPassword($email, $newPassword) {
    // Insecure password reset logic
    // ...
    // Code to reset the password goes here
    // ...
}
?>

The vulnerability lies in the insecure authorization check implemented in the isValidEmail() function. The code uses filter_var() with the FILTER_VALIDATE_EMAIL filter to validate the email address provided by the user. However, this simple check is insufficient to ensure proper authorization. It assumes that any email address that passes the filter is valid and authorized to initiate a password reset.

Some of the Ways the Vulnerable code can be mitigated is:

Insecure User Privilege

Implement proper authentication and authorization: Implement a secure user authentication system that verifies the user's identity and assigns appropriate privileges based on their role or authorization level.
Use session management:Store user privileges in a session variable or token after successful authentication. Check the session or token for authorization before granting access to privileged actions.
Protect sensitive functionality with additional checks:If there are specific privileged actions or sensitive data, perform additional checks to ensure the user has the necessary privileges before granting access.

Insecure Password Reset

Implement secure email validation: Utilize a more robust email validation technique that not only checks the basic email format but also verifies if the email exists in the user database and is authorized for a password reset.
Use secure channels for password reset requests: Ensure that password reset requests are initiated through secure and authenticated channels, such as a password reset link sent to the user's registered email address or requiring the user to answer additional security questions.
Implement time-limited reset tokens: Generate and associate a unique, time-limited reset token with each password reset request. Verify the token's validity and authorization before allowing the password reset.

Insecure File Download

Implement strict validation of user input: Validate and sanitize the file parameter to ensure it contains only permitted characters and does not allow directory traversal sequences like ../.
Maintain a whitelist: Maintain a list of authorized files or directories and compare the user-provided file parameter against the whitelist to ensure it is within the allowed scope.
Use file permissions: Set appropriate file permissions on the server to restrict direct access to sensitive files, even if the authorization check fails.

Mitigated Code

<?php
// Secure Password Reset Example

$userEmail = $_POST['email'];
$newPassword = $_POST['new_password'];
$verificationCode = $_POST['verification_code'];

// Secure authorization check
if (isValidEmail($userEmail) && isAuthorizedForReset($userEmail)) {
    // Check if the verification code matches the one sent to the email address
    if (verifyCode($userEmail, $verificationCode)) {
        // Check if the new password meets some minimum security requirements
        if (isValidPassword($newPassword)) {
            // Reset password for the user
            resetPassword($userEmail, $newPassword);
            echo "Password reset successfully!";
        } else {
            echo "Invalid password. Please choose a stronger password.";
        }
    } else {
        echo "Invalid verification code. Please check your email and try again.";
    }
} else {
    echo "Invalid email address or unauthorized access.";
}

function isValidEmail($email) {
    // More secure email validation
    return filter_var($email, FILTER_VALIDATE_EMAIL) !== false;
}

function isAuthorizedForReset($email) {
    // Perform additional checks to verify if the email is authorized for password reset
    // ...
    // Code to check if the email is authorized goes here
    // ...
    return true; // Return true or false based on authorization status
}

function verifyCode($email, $code) {
    // Perform some checks to verify if the verification code matches the one sent to the email address
    // ...
    // Code to verify the code goes here
    // ...
    return true; // Return true or false based on verification status
}

function isValidPassword($password) {
    // Perform some checks to verify if the password meets some minimum security requirements
    // ...
    // Code to check if the password is valid goes here
    // ...
    return true; // Return true or false based on password strength
}

function resetPassword($email, $newPassword) {
    // Secure password reset logic
    // ...
    // Code to reset the password goes here
    // ...
}
?>

The Mitigated code does the following:

Secure authorization check**: The code verifies the email address ($userEmail**) using the isValidEmail() function, which employs the FILTER_VALIDATE_EMAIL filter for more secure email validation. It also checks if the email is authorized for password reset using the isAuthorizedForReset() function.
Verification code matching**: The code compares the verification code ($verificationCode**) submitted by the user with the one sent to the email address. It uses the verifyCode() function to perform the necessary checks and ensure that the provided code matches the one associated with the email address.
Password strength check: Before resetting the password, the code verifies the strength of the new password ($newPassword) using the isValidPassword() function. This function can include checks such as minimum length, complexity requirements, or the absence of commonly used passwords.
Secure password reset logic: The resetPassword() function represents the actual password reset logic, which should be implemented securely. The provided code acts as a placeholder, and you should replace it with your own implementation that ensures password security, such as hashing and salting the password.

`C++`

Vulnerable Code

#include <iostream>
#include <string>

void deleteFile(const std::string& filename, const std::string& username)
{
    if (username == "admin")
    {
        // Perform the file deletion
        std::cout << "File '" << filename << "' deleted successfully.\n";
    }
    else
    {
        std::cout << "Error: You are not authorized to delete files.\n";
    }
}

int main()
{
    std::string filename;
    std::cout << "Enter the file name: ";
    std::cin >> filename;

    std::string username;
    std::cout << "Enter your username: ";
    std::cin >> username;

    deleteFile(filename, username);

    return 0;
}

In this above vulnerable code, the deleteFile function is intended to delete a file, but it lacks proper authorization checks. It only checks if the username provided is equal to "admin" to determine whether the user is authorized to perform the file deletion.

However, this code is vulnerable because any user can specify the username as "admin" and gain unauthorized access to delete files, regardless of their actual role or permissions.

Some of the ways the Vulnerable code can be mitigated is:
- Implement Robust Authentication: Strengthen the authentication mechanism to ensure that only legitimate users with valid credentials can access the system. This may include using strong passwords, enforcing multi-factor authentication, and protecting against common authentication vulnerabilities like brute-force attacks.
- Role-Based Access Control (RBAC): Implement RBAC to define different user roles with specific permissions. Assign the "admin" role only to privileged users who need access to perform administrative tasks like file deletion. Ensure that the authorization check in the deleteFile function verifies the user's role rather than just checking the username.
- Principle of Least Privilege (PoLP): Apply the principle of least privilege, which means granting users the minimum level of permissions required to perform their tasks. Limit the file deletion functionality to authorized roles or users with specific privileges, rather than assuming that any user with the username "admin" is authorized.
- Input Validation and Sanitization: Validate and sanitize user inputs to prevent malicious input.
- Secure File Deletion Mechanism: Implement a secure file deletion mechanism that ensures proper file handling and prevents unauthorized access or recovery of deleted files. Consider using secure file deletion libraries or techniques provided by the operating system.

Mitigated Code

#include <iostream>
#include <string>
#include <bcrypt/BCrypt.hpp>
#include <fstream>

// A function that hashes a password using bcrypt
std::string hashPassword(const std::string& password)
{
    return BCrypt::generateHash(password);
}

// A function that compares a password with a hashed password using bcrypt
bool checkPassword(const std::string& password, const std::string& hash)
{
    return BCrypt::validatePassword(password, hash);
}

// A function that checks if the user is an admin by querying from a user management system
// For demonstration purposes, this function reads from a text file that contains the username and the hashed password of the admin
// In practice, this should be done using a secure database or API
bool isAdmin(const std::string& username, const std::string& password)
{
    // Open the file that contains the admin credentials
    std::ifstream file("admin.txt");
    if (file.is_open())
    {
        // Read the username and the hashed password from the file
        std::string adminUsername;
        std::string adminHash;
        file >> adminUsername >> adminHash;

        // Close the file
        file.close();

        // Check if the username and the password match with the admin credentials
        return (username == adminUsername && checkPassword(password, adminHash));
    }
    else
    {
        // Return false if the file cannot be opened
        return false;
    }
}

// A function that deletes a file if the user is authenticated and authorized
void deleteFile(const std::string& filename, const std::string& username, const std::string& password)
{
    // Check if the user is authenticated and authorized by calling the isAdmin function
    if (isAdmin(username, password))
    {
        // Try to open the file for writing
        std::ofstream file(filename);
        if (file.is_open())
        {
            // Close and remove the file
            file.close();
            std::remove(filename.c_str());

            // Report success
            std::cout << "File '" << filename << "' deleted successfully.\n";
        }
        else
        {
            // Report failure
            std::cout << "Error: File '" << filename << "' cannot be opened or does not exist.\n";
        }
    }
    else
    {
        // Report unauthorized access
        std::cout << "Error: You are not authorized to delete files.\n";
    }
}

int main()
{
    std::string filename;
    std::cout << "Enter the file name: ";
    std::cin >> filename;

    std::string username;
    std::cout << "Enter your username: ";
    std::cin >> username;

    std::string password;
    std::cout << "Enter your password: ";
    std::cin >> password;

    deleteFile(filename, username, password);

    return 0;
}

The Mitigated code does the following:
- Role-Based Access Control: The code implements a isAdmin function that queries a user management system (demonstrated using a file for simplicity) to determine if the provided username and password correspond to an admin user. This helps ensure that only admin users are authorized to delete files.
- Password Hashing: The code uses the bcrypt library to hash and compare passwords securely. The checkPassword function compares the provided password with the hashed password stored in the user management system, making it harder for attackers to retrieve passwords even if the system is compromised.
- Separate Authentication and Authorization: The deleteFile function separates the authentication and authorization checks. First, it authenticates the user by calling isAdmin and validating the provided username and password. If the authentication is successful, it proceeds to the authorization check to determine if the user is authorized to delete files.
- Secure Storage of Admin Credentials: The code demonstrates the use of a file (admin.txt) to store admin credentials (username and hashed password). However, it emphasizes the need for a secure database or API in a real-world scenario to ensure the proper storage of sensitive information.
- Error Handling and Reporting: The code includes error handling and reporting. If the file deletion operation encounters errors (e.g., the file cannot be opened or does not exist), appropriate error messages are displayed to the user.

References

CWE - CWE-862: Missing Authorization (4.18)cwe.mitre.org

A07 Identification and Authentication Failures - OWASP Top 10:2021

Authorization - OWASP Cheat Sheet Series

Last updated 1 year ago

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