CWE-315: Cleartext Storage of Sensitive Information in a Cookie

What is Cleartext Storage of Sensitive Information in a Cookie?

• Overview: CWE-315 refers to the storage of sensitive information in cleartext in a cookie, making it easily readable by attackers who can intercept or access the cookie data.

• Exploitation Methods:

• Attackers can use network sniffing tools to intercept cookies transmitted over the network.
• Tools like browser developer consoles or cookie editors can be used to view or modify cookies directly.
• Encoding or obfuscation techniques can be reverse-engineered to reveal the stored sensitive data.

• Security Impact:

• Direct consequences include unauthorized access to user accounts or sensitive data exposure.
• Potential cascading effects involve further attacks such as session hijacking or impersonation.
• Business impact can include loss of user trust, legal penalties, and financial losses due to data breaches.

• Prevention Guidelines:

• Use encryption to store sensitive data in cookies, ensuring it is not stored in cleartext.
• Implement secure cookie attributes like HttpOnly and Secure to protect cookies in transit.
• Regularly review and audit cookie usage to ensure compliance with security policies.
• Consider using secure frameworks and libraries that handle cookie management safely.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

from flask import Flask, request, make_response

app = Flask(__name__)

@app.route('/login', methods=['POST'])
def login():
    username = request.form['username']
    password = request.form['password']
    
    # Insecure: Storing password in cleartext in a cookie
    resp = make_response("Logged in successfully")
    resp.set_cookie('username', username)
    resp.set_cookie('password', password)  # Vulnerable line
    return resp

Explanation:

• Vulnerability: This code stores the user's password in cleartext within a cookie. Cookies can be intercepted by attackers or accessed by cross-site scripting (XSS) attacks, leading to potential exposure of sensitive information. Storing passwords or sensitive data in cookies is a significant security risk.

How to fix Cleartext Storage of Sensitive Information in a Cookie?

1. Avoid Storing Sensitive Data in Cookies: Do not store sensitive data like passwords in cookies. Use secure session identifiers instead.
2. Use Secure Cookies: If cookies must be used, ensure they are encrypted and marked as Secure and HttpOnly to reduce interception and script access risks.
3. Implement Strong Session Management: Store user identification and sensitive data server-side, utilizing secure session management.

Fixed Code Example

from flask import Flask, request, make_response, session
from werkzeug.security import generate_password_hash, check_password_hash

app = Flask(__name__)
app.secret_key = 'supersecretkey'  # Required for session management

@app.route('/login', methods=['POST'])
def login():
    username = request.form['username']
    password = request.form['password']
    
    # Secure: Use hashed passwords and sessions for authentication
    hashed_password = generate_password_hash(password)  # Hash the password
    # Validate user credentials (pseudo code)
    if check_password_hash(hashed_password, password):  # Replace with actual user validation
        session['username'] = username  # Store user identification in session
        return "Logged in successfully"
    return "Invalid credentials", 401

Explanation:

• Fixed Approach: The password is hashed using a secure hashing algorithm (generate_password_hash) before being stored or processed. User authentication is handled server-side, and only a session identifier is stored in the client's cookie.
• Session Management: The application uses Flask's session management, which keeps sensitive data on the server and uses a secure session identifier on the client-side.
• Security Practices: A secret key is set for session management, ensuring that session data is securely signed and validated.

By implementing these changes, the application avoids storing sensitive information like passwords in cleartext within cookies, significantly reducing the risk of data exposure. These practices align with security best practices for handling user authentication securely.