Need

Secure generation and handling of cookies

Context

• Usage of C# for developing robust and efficient software applications
• Usage of Microsoft.AspNetCore.Builder for configuring and building ASP.NET Core applications
• Usage of Microsoft.AspNetCore.Hosting for hosting ASP.NET Core applications
• Usage of Microsoft.AspNetCore.CookiePolicy for managing and enforcing cookie policies in ASP.NET Core applications
• Usage of Microsoft.AspNetCore.Authentication for implementing authentication in ASP.NET Core applications

Description

Non compliant code

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseCookiePolicy(new CookiePolicyOptions
    {
        MinimumSameSitePolicy = SameSiteMode.None,
    });

    app.UseAuthentication();

    // Rest of your code
}
        
        

The above code is configuring the cookie policy for an ASP.NET Core application. The UseCookiePolicy method sets the cookie policy options for the application.

Here, the MinimumSameSitePolicy is set to SameSiteMode.None. This means that the application will send cookies with all requests, regardless of the site. This is a security vulnerability as it could potentially expose sensitive information contained in the cookies to third parties.

Furthermore, the code does not set any security attributes for the cookies, such as the Secure and HttpOnly attributes. The Secure attribute ensures that the cookie is only sent over HTTPS, protecting it from being intercepted in plain text. The HttpOnly attribute prevents the cookie from being accessed through client-side scripts, protecting it from cross-site scripting (XSS) attacks.

In summary, the insecure configuration of cookies in this code could lead to the exposure of sensitive information, making the application vulnerable to attacks such as session hijacking and cross-site scripting.

Steps

• Set the Secure attribute for sensitive cookies to ensure they are only sent over secure connections (HTTPS).
• Set the HttpOnly attribute for sensitive cookies to prevent client-side scripts from accessing them.
• Set the SameSite attribute for sensitive cookies to control when they are sent in cross-site requests.
• Use a strong and unique encryption algorithm to protect the contents of the cookies.
• Implement proper session management to minimize the use of cookies for sensitive data.
• Regularly review and update the cookie settings to ensure they align with the latest security best practices.

Compliant code

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseCookiePolicy(new CookiePolicyOptions
    {
        MinimumSameSitePolicy = SameSiteMode.Strict,
        HttpOnly = Microsoft.AspNetCore.CookiePolicy.HttpOnlyPolicy.Always,
        Secure = CookieSecurePolicy.Always
    });

    app.UseAuthentication();

    // Rest of your code
}
        
        

The updated code now sets the Secure, HttpOnly, and SameSite attributes for all cookies in the application.

- Secure attribute: This attribute ensures that cookies are only sent over secure connections, i.e., HTTPS. This prevents the cookie from being transmitted over unencrypted connections where it could be easily intercepted and read by an attacker.

- HttpOnly attribute: This attribute prevents client-side scripts from accessing the cookie. This is particularly useful to help prevent cross-site scripting (XSS) attacks, where an attacker might try to access the cookie value through JavaScript.

- SameSite attribute: This attribute controls when cookies are sent in cross-site requests. Setting it to SameSiteMode.Strict means that the cookie will only be sent in a first-party context, i.e., only to the site that it originated from. This can help to protect against cross-site request forgery (CSRF) attacks.

By setting these attributes, the application is taking steps to protect sensitive data stored in cookies from being intercepted or manipulated by attackers. It's also important to note that these settings should be reviewed and updated regularly to align with the latest security best practices.

References

• 042. Insecurely generated cookies