How can you design a web application architecture that resists man-in-the-middle attacks?

1 Use HTTPS and HSTS

The first and most important step to resist MITM attacks is to use HTTPS (Hypertext Transfer Protocol Secure) for all web traffic. HTTPS encrypts the data exchanged between the client and the server, making it harder for attackers to eavesdrop or tamper with the messages. HTTPS also relies on certificates and public key cryptography to verify the identity of the server and the client, preventing attackers from impersonating them. To enforce HTTPS, you should also use HSTS (HTTP Strict Transport Security), a header that tells the browser to only connect to the server using HTTPS and reject any insecure connections.

2 Implement TLS Pinning

Another technique to resist MITM attacks is to implement TLS (Transport Layer Security) pinning, which is a way of hardcoding the expected certificate or public key of the server in the client application. This way, the client can check if the server's certificate or public key matches the expected one, and reject any connection that does not. TLS pinning can prevent attackers from using fraudulent certificates or proxy servers to intercept the communication between the client and the server. However, TLS pinning also has some drawbacks, such as the need to update the client application if the server's certificate or public key changes, and the risk of breaking compatibility with some browsers or platforms.

3 Use Secure Cookies and Tokens

Another layer of protection against MITM attacks is to use secure cookies and tokens for web application authentication and authorization. Cookies and tokens are pieces of data that store information about the user's identity and session, and are sent along with each request to the server. To make them more secure, you should set the secure flag on cookies, which instructs the browser to only send them over HTTPS connections. You should also set the HttpOnly flag on cookies, which prevents JavaScript code from accessing them and reduces the risk of cross-site scripting (XSS) attacks. Moreover, you should set the SameSite flag on cookies, which restricts the browser from sending them to other domains and reduces the risk of cross-site request forgery (CSRF) attacks. Additionally, you should use short-lived and random tokens, as well as encryption and digital signatures on tokens, which ensure their confidentiality and integrity.

4 Apply Content Security Policy and Subresource Integrity

Another way to resist MITM attacks is to apply Content Security Policy (CSP) and Subresource Integrity (SRI) on the web application. CSP is a header that tells the browser what sources of content are allowed to load on the web page, such as scripts, stylesheets, images, fonts, etc. CSP can prevent attackers from injecting malicious code or resources into the web page, which could compromise the web application or the user's data. SRI is an attribute that tells the browser what hash value the content should have, and verifies that the content has not been altered or corrupted. SRI can prevent attackers from replacing or modifying the content that the web application loads from external sources, such as third-party libraries or APIs.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?