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Insecure object reference - Session management

Need​

Secure session management

Context​

  • Usage of C# for building robust and scalable applications
  • Usage of _userManager for managing user authentication and authorization
  • Usage of _signInManager for managing user sign-in functionality

Description​

Non compliant code​

[HttpPost]
public async Task<IActionResult> Logout(string email)
{
    var user = await _userManager.FindByEmailAsync(email);
    if (user != null)
    {
        await _signInManager.SignOutAsync();
        return Ok();
    }
    return BadRequest();
}

In the code above, the Logout method is designed to sign out a user based on their email. This is done by first finding the user with the provided email using the _userManager.FindByEmailAsync(email) method. If a user with the provided email is found, the _signInManager.SignOutAsync() method is called to sign out the user.

However, this code is vulnerable due to Insecure Direct Object Reference (IDOR). Specifically, it does not check whether the current session user is the same as the user whose email is provided. This means that if an attacker knows the email of another user, they can call this method with the other user's email and sign them out. This can lead to unauthorized access and manipulation of user sessions.

The vulnerability lies in the fact that the application uses the email, an object reference, directly without proper access control checks. This allows an attacker to manipulate these references to access unauthorized data. In this case, the unauthorized action is signing out a user. Therefore, the code is susceptible to an Insecure Direct Object References (IDOR) vulnerability.

Steps​

  • Implement a secure session management mechanism.
  • Do not rely on email as the sole identifier for session management.
  • Generate a unique session identifier for each user upon login.
  • Store the session identifier securely, such as in a secure cookie or in a server-side session store.
  • When a user logs out, invalidate the session identifier and remove it from the session store.
  • Ensure that only the user associated with a session can perform actions on that session.
  • Implement proper access controls to prevent unauthorized access to other users' sessions.

Compliant code​

[HttpPost]
public async Task<IActionResult> Logout()
{
    var user = await _userManager.GetUserAsync(User);
    if (user != null)
    {
        await _signInManager.SignOutAsync();
        return Ok();
    }
    return BadRequest();
}

The original code was vulnerable to insecure object reference as it allowed the logout of users by simply knowing their email. This could lead to potential unauthorized session termination.

The fixed code now retrieves the currently logged-in user from the User object provided by ASP.NET Core, which is based on the current HttpContext. This ensures that only the user who is currently logged in can log themselves out, preventing the possibility of unauthorized session termination.

This code assumes that the user is authenticated and the User object is populated with the user's details. If the user is not authenticated, GetUserAsync(User) will return null and the method will return a BadRequest.

This fix is part of a secure session management mechanism. It is important to generate a unique session identifier for each user upon login and store it securely. When a user logs out, the session identifier should be invalidated and removed from the session store. Proper access controls should be implemented to prevent unauthorized access to other users' sessions.

References​

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