Content Security Policy (CSP)

Definition

Content Security Policy (CSP) is a security feature that helps prevent a variety of attacks, such as cross-site scripting (XSS) and data injection attacks, by specifying which content sources are trustworthy for web applications. CSP allows developers to define rules that control the sources from which scripts, styles, images, and other resources can be loaded, providing a robust mechanism to reduce the risk of malicious content being executed in the browser.

5 Must Know Facts For Your Next Test

1. CSP is implemented via HTTP headers or `<meta>` tags in HTML, allowing developers to specify security policies for their web applications.
2. A well-configured CSP can significantly reduce the risk of XSS attacks by blocking inline scripts and only allowing scripts from trusted sources.
3. CSP can provide a report-only mode, enabling developers to test their policies without enforcing them, which helps identify potential issues before going live.
4. CSP supports various directives like `default-src`, `script-src`, and `img-src`, each defining different types of content that can be loaded from specified sources.
5. Using CSP effectively requires regular updates and testing, as changing content sources or adding new features may necessitate adjustments to the policy.

Review Questions

• How does Content Security Policy (CSP) enhance the security of web applications against common vulnerabilities?
  • Content Security Policy enhances web application security by defining trusted sources for various content types, effectively reducing the likelihood of executing malicious scripts. By restricting where resources can be loaded from using directives such as `script-src`, CSP helps mitigate attacks like cross-site scripting (XSS). This proactive approach ensures that only vetted and expected content is allowed to run, creating a safer browsing experience for users.
• Evaluate the role of Content Security Policy in relation to the OWASP Top 10 vulnerabilities, particularly regarding data injection attacks.
  • Content Security Policy plays a significant role in addressing several OWASP Top 10 vulnerabilities, especially those related to data injection attacks like XSS. By enforcing strict content loading policies through its directives, CSP can prevent unauthorized scripts from being executed within a user's browser. This capability aligns with the broader goal of mitigating vulnerabilities such as A5:2017-Broken Access Control and A7:2017-Cross-Site Scripting in the OWASP Top 10 list, making it an essential tool for developers aiming to secure their applications against these risks.
• Critically analyze how implementing Content Security Policy affects both client-side and server-side security controls in modern web applications.
  • Implementing Content Security Policy has a profound impact on both client-side and server-side security controls in modern web applications. On the client side, CSP reduces the attack surface by limiting where scripts and resources can be loaded from, which directly addresses issues like XSS and data injection. On the server side, CSP mandates that developers actively manage their content sources, promoting better coding practices and increasing awareness of potential security risks. This dual effect not only enhances overall application security but also fosters a culture of vigilance among developers regarding secure coding practices.

Related terms

Cross-Site Scripting (XSS): A type of security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users, potentially compromising sensitive information.

Subresource Integrity (SRI): A security feature that enables browsers to verify that fetched resources are delivered without unexpected manipulation, ensuring the integrity of external scripts and styles.

HTTP Headers: Part of the HTTP response sent by the server that provides essential information about the web page, including security policies such as CSP directives.