Introduction
Content Security Policy (CSP) is an added layer of security that helps to detect and mitigate certain types of attacks, including Cross-Site Scripting (XSS) and data injection attacks. It allows web developers to specify which resources (e.g., scripts, stylesheets, images) are allowed to be loaded on a web page, thereby reducing the risk of malicious code execution.
Configuring CSP in ASP.NET MVC
In ASP.NET MVC, you can configure CSP by adding the necessary headers to the HTTP response. One way to achieve this is by modifying the web.config file of your application.
To enable CSP protection, you need to add the following code to your web.config file:
The above code snippet adds the Content-Security-Policy header to the HTTP response with a set of directives. Let's break down the directives:
- default-src: Specifies the default source for all resource types if no other directive is specified.
- script-src: Specifies the allowed sources for JavaScript code.
- style-src: Specifies the allowed sources for CSS stylesheets.
- img-src: Specifies the allowed sources for images.
In the example above, we have set the default-src directive to ‘self', which means that all resources should be loaded from the same origin as the web page itself. This helps to prevent loading resources from external domains, reducing the risk of XSS attacks.
Additional Directives
In addition to the basic directives shown above, CSP provides several other directives that can be used to further enhance security. Some of these directives include:
- connect-src: Specifies the allowed sources for making network requests.
- font-src: Specifies the allowed sources for fonts.
- media-src: Specifies the allowed sources for media files (e.g., audio, video).
- frame-src: Specifies the allowed sources for embedding frames.
You can customize these directives based on your application's specific requirements.
Example
Let's consider an example where we want to allow loading scripts from a specific domain and inline scripts from the same origin. We also want to allow images from any source.
In the above example, we have added ‘example.com' to the script-src directive to allow loading scripts from that domain. The ‘unsafe-inline' keyword allows inline scripts from the same origin. The img-src directive is set to ‘*' to allow loading images from any source.
Conclusion
Configuring Content Security Policy (CSP) in ASP.NET MVC provides an additional layer of security to protect against various types of attacks. By specifying the allowed sources for different types of resources, you can reduce the risk of malicious code execution and enhance the overall security of your application.
