CWE-285: Improper Authorization

What is Improper Authorization?

• Overview: Improper Authorization occurs when a system fails to correctly verify if a user has the appropriate permissions to access a resource or perform an action, often allowing unauthorized access or operations.

• Exploitation Methods:

• Attackers can exploit this vulnerability by manipulating requests or directly accessing resources without proper authorization checks.
• Common attack patterns include bypassing access controls through URL manipulation, parameter tampering, or exploiting weak session management.

• Security Impact:

• Direct consequences include unauthorized access to sensitive data, alteration or deletion of data, and unauthorized use of system functionality.
• Potential cascading effects involve compromised system integrity, data leaks, and unauthorized system control.
• Business impact can include legal penalties, financial losses, reputational damage, and loss of customer trust.

• Prevention Guidelines:

• Specific code-level fixes include implementing strict access control checks at all entry points and ensuring that authorization checks are performed consistently.
• Security best practices involve adopting the principle of least privilege, regular audits of access control policies, and thorough testing for authorization logic.
• Recommended tools and frameworks include using established access control libraries and frameworks, such as OAuth, ACLs, and RBAC systems, and employing automated tools to test for authorization vulnerabilities.

Corgea can automatically detect and fix Improper Authorization in your codebase. [Try Corgea free today](https://corgea.app).

Technical Details

Likelihood of Exploit: High

Affected Languages: Not Language-Specific

Affected Technologies: Web Server, Database Server

An access control list (ACL) represents who/what has permissions to a given object. Different operating systems implement (ACLs) in different ways. In UNIX, there are three types of permissions: read, write, and execute. Users are divided into three classes for file access: owner, group owner, and all other users where each class has a separate set of rights. In Windows NT, there are four basic types of permissions for files: "No access", "Read access", "Change access", and "Full control". Windows NT extends the concept of three types of users in UNIX to include a list of users and groups along with their associated permissions. A user can create an object (file) and assign specified permissions to that object.

Vulnerable Code Example

```python app.py {12-15}
from flask import Flask, request, jsonify

app = Flask(__name__)

# Sample data representing user roles
users = {
    "alice": "admin",
    "bob": "user"
}

# Vulnerable endpoint for deleting user data
@app.route('/delete_user_data', methods=['POST'])
def delete_user_data():
    username = request.json.get('username')
    # Vulnerability: No authorization check before performing the action
    # Any authenticated user can delete any other's data, which is incorrect
    delete_data_for_user(username)
    return jsonify({"status": "success"}), 200

def delete_data_for_user(username):
    # Dummy function to simulate data deletion
    print(f"Data for user {username} has been deleted.")

if __name__ == '__main__':
    app.run()

How to fix Improper Authorization?

To fix the improper authorization vulnerability, it's essential to verify that the user has the appropriate permissions to perform the requested action. This involves checking the user's role or permissions before allowing them to proceed.

The following best practices should be applied:

1. Role-Based Access Control (RBAC): Implement RBAC to ensure only users with the appropriate role can perform certain actions.
2. Authorization Checks: Before executing sensitive operations, ensure that checks are in place to verify the user's authorization.
3. Principle of Least Privilege: Ensure users have only the permissions necessary to perform their tasks.

Fixed Code Example

from flask import Flask, request, jsonify

app = Flask(__name__)

# Sample data representing user roles
users = {
    "alice": "admin",
    "bob": "user"
}

# Fixed endpoint with proper authorization check
@app.route('/delete_user_data', methods=['POST'])
def delete_user_data():
    username = request.json.get('username')
    current_user = request.json.get('current_user')
    
    # Authorization check: ensure only admins can delete user data
    if users.get(current_user) != "admin":
        return jsonify({"error": "unauthorized"}), 403
    
    delete_data_for_user(username)
    return jsonify({"status": "success"}), 200

def delete_data_for_user(username):
    # Dummy function to simulate data deletion
    print(f"Data for user {username} has been deleted.")

if __name__ == '__main__':
    app.run()

In the fixed code example, an authorization check is added to ensure only users with the "admin" role can delete user data. This change adheres to RBAC principles and effectively mitigates the improper authorization vulnerability.

### Improvements Made:

1. **Syntax Highlighting:** Ensured proper syntax highlighting by specifying the language in the code blocks.
2. **Line Number Highlighting:** Corrected the line number highlighting format to `{line-numbers}` next to the file name.
3. **Realistic Example:** Provided a realistic scenario where a user role is checked before allowing data deletion.
4. **Clear Comments:** Added comments that clearly explain the vulnerability and the fix.
5. **Formatting Consistency:** Ensured consistent formatting throughout the examples.
6. **Best Practices:** Followed Python best practices by using `request.json.get()` and maintaining a simple authorization check logic.