HTTP parameter pollution

HTTP Parameter Pollution (HPP) is an often overlooked web security vulnerability, primarily affecting web applications by manipulating the data sent via HTTP requests. This article delves into the history, operation, and key features of HPP, as well as its various types, potential uses, and related problems and solutions. The article also explores the connection between HPP and proxy servers, along with future perspectives related to this web-based phenomenon.

The Evolution of HTTP Parameter Pollution

HTTP Parameter Pollution was first identified as a distinct web application vulnerability around the early 2000s, with the rapid development of web technologies and the expansion of the World Wide Web. As websites began to rely more heavily on HTTP GET and POST requests to transfer data, hackers discovered the potential for exploiting the way these requests processed parameters.

The first documented mention of HPP can be traced back to the 2000s, but the term itself was officially recognized by the web security community following the release of a paper by OWASP (Open Web Application Security Project) in 2010, bringing this vulnerability into the limelight.

Unpacking HTTP Parameter Pollution

HTTP Parameter Pollution is a type of web vulnerability that involves the injection of manipulated parameters into HTTP requests. This could potentially allow attackers to alter the way a web application functions, bypass input validation checks, access sensitive data, and carry out other forms of web-based attacks.

HPP occurs when a web application combines HTTP parameters with the same name from different parts of an HTTP request into one. By manipulating these parameters, an attacker can control the application’s behavior in unexpected ways, leading to a wide range of potential security risks.

The Mechanics of HTTP Parameter Pollution

The inner workings of HPP are rooted in the way web applications handle HTTP requests. In an HTTP request, parameters are sent as part of the URL in a GET request or within the body of a POST request. These parameters can be used to specify the data that the web application should return or operate upon.

When an HTTP request is made to a web application, the application’s server processes the parameters included in the request. However, if the application does not correctly handle instances where the same parameter is included multiple times, this creates an opportunity for an HPP attack.

In an HPP attack, the attacker includes the same parameter multiple times within an HTTP request, each time with different values. The application server then combines these values in a way that was not intended by the developers, leading to potential security vulnerabilities.

Key Features of HTTP Parameter Pollution

Several defining features distinguish HTTP Parameter Pollution from other web vulnerabilities:

1. Targeting HTTP Requests: HPP specifically targets the parameters within HTTP GET and POST requests.
2. Manipulation of Parameters: The core of an HPP attack involves manipulating the values of these parameters.
3. Dependent on Application Behaviour: The impact of an HPP attack is highly dependent on how the targeted web application handles repeated parameters within an HTTP request.
4. Potential for Widespread Impact: As HPP can potentially affect any web application that does not properly handle repeated HTTP parameters, its potential for impact is widespread.
5. Stealthy Approach: HPP attacks can be difficult to detect as they can masquerade as legitimate user input.

Types of HTTP Parameter Pollution

There are two primary types of HTTP Parameter Pollution based on the HTTP method used:

1. GET-Based HPP: This type of HPP attack manipulates the parameters within the URL of an HTTP GET request.
2. POST-Based HPP: This type of HPP attack manipulates the parameters within the body of an HTTP POST request.

Implementing HTTP Parameter Pollution: Problems and Solutions

Despite its stealthy nature, there are ways to detect and mitigate the risks posed by HPP attacks. Most involve properly handling and sanitizing input, particularly with respect to HTTP parameters:

1. Validate Input: Web applications should validate all input to ensure it meets expected formats.
2. Sanitize Input: All input should be sanitized to remove potential harmful data.
3. Implement a Web Application Firewall (WAF): WAFs can detect and block many HPP attempts.
4. Regular Security Audits: Regularly reviewing code and conducting penetration testing can help identify and address potential vulnerabilities.

Comparisons with Similar Vulnerabilities

Here are a few web vulnerabilities that bear some resemblance to HPP:

Future Perspectives of HTTP Parameter Pollution

As web applications continue to evolve, so too will the techniques used to exploit them. While HTTP Parameter Pollution has been known for a while, it is still not widely understood or checked for, meaning it may become a more prominent threat in the future. Additionally, as more devices become web-enabled with the Internet of Things, the potential attack surface for HPP expands.

However, this also means that the tools and techniques used to defend against HPP are likely to improve. There’s an increasing focus on secure coding practices and automated tools to detect and prevent such vulnerabilities. In the future, we may see more sophisticated WAFs and similar technologies specifically designed to defend against parameter pollution attacks.

Proxy Servers and HTTP Parameter Pollution

Proxy servers act as an intermediary for requests from clients seeking resources from other servers, which could potentially be used to guard against HPP attacks. They can inspect incoming HTTP requests for signs of HPP (like repeated parameters) and block or alter these requests to mitigate the threat.

Furthermore, proxy servers can be used as a form of isolation, protecting internal networks from direct exposure to the internet and potential HPP attacks. They can also be configured to log all incoming HTTP requests, providing valuable data for identifying and analyzing attempted HPP attacks.

Related Links

For more information about HTTP Parameter Pollution, please visit the following resources:

1. OWASP: HTTP Parameter Pollution
2. Acunetix: What is HTTP Parameter Pollution
3. HTTP Parameter Pollution Vulnerabilities
4. HTTP Parameter Pollution (HPP) for Fun and Profit
5. Defending Against HTTP Parameter Pollution Attacks