Understanding HTTP Headers

HTTP headers let the client and the server pass additional information with an HTTP request or response. They define the operating parameters of an HTTP transaction. Headers can be grouped according to their contexts: Request headers, Response headers, and Entity headers.

Exploiting HTTP Headers

HTTP headers can be exploited in various ways by attackers. For instance, they can manipulate headers to bypass security controls, perform cross-site scripting (XSS) attacks, HTTP response splitting, and cache poisoning. Understanding these headers and how they work is crucial for both launching attacks and defending against them.

HTTP Headers Example

Here is a simple example of HTTP headers in a request:

             GET / HTTP/1.1
             Host: www.example.com
             User-Agent: Mozilla/5.0
             Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
             Accept-Language: en-US,en;q=0.5
             Accept-Encoding: gzip, deflate
             Connection: keep-alive
             

Example of Hypothetical Manipulated HTTP header

               GET / HTTP/1.1
               Host: malicious.com
               User-Agent: EvilBot/1.0
               Accept: */*
               Accept-Language: es-ES,es;q=0.9
               Accept-Encoding: gzip, deflate
               Connection: close
               X-Attack: <malicious_payload>
               X-Malicious-Header: exploit
             

Prevention

Preventing HTTP header attacks involves proper input validation, sanitization, and setting security-related headers. This includes:

• Input validation: Validate user input by only accepting expected values.
• Use allow lists: Only allow known good input to pass through.
• Sanitize input: Remove or replace special characters from user input.
• Set security-related headers: Headers like Content-Security-Policy, X-Content-Type-Options, and Strict-Transport-Security can help prevent attacks.