HTTP response splitting vulnerability and its fix in Java

Abstract: In Java web applications, HTTP response splitting vulnerability is a common security threat . This article will introduce the principle and impact of the HTTP response splitting vulnerability, as well as how to fix the vulnerability, and use code examples to help developers better understand and prevent such security threats.

1. Introduction
   HTTP protocol is one of the most commonly used protocols in web applications. It communicates through HTTP requests and HTTP responses to provide interaction with the web server. However, due to design flaws in the HTTP protocol, security vulnerabilities occur.
2. Principle of HTTP response splitting vulnerability
   HTTP response splitting vulnerability means that an attacker can insert malicious content into the HTTP response, thereby bypassing the security mechanism and executing arbitrary code. This vulnerability usually occurs during the processing of HTTP responses by web applications.

The attacker splits the HTTP response into two independent HTTP responses by inserting a newline character in the header or body part of the HTTP response. As a result, the security mechanism may parse the first HTTP response and ignore the second HTTP response, allowing the attacker to successfully execute malicious code.

3. Impact of HTTP response splitting vulnerability
   HTTP response splitting vulnerability may cause the following security issues:

3.1 HTTP hijacking: attackers can tamper with HTTP The content of the response, thereby achieving malicious redirection and stealing the user's cookies or other sensitive information.

3.2 Cache poisoning: An attacker can store malicious content in the cache server through split HTTP responses, causing other users to be attacked when accessing the same resources.

3.3 Cross-site scripting (XSS): By inserting malicious script into a split HTTP response, an attacker can steal the user's session cookie and execute malicious code in the user's browser.

4. Fixing HTTP Response Splitting Vulnerabilities
   Before repairing HTTP response splitting vulnerabilities, you must first understand common repair strategies and how to implement these strategies in Java.

4.1 Regular expression-based filtering: Detect and filter potential splitting characters in HTTP responses, such as line feeds, carriage returns, etc.

4.2 Strictly verify HTTP responses: Ensure that all HTTP responses are complete and have not been split or modified.

4.3 Use a secure HTTP library: Use an HTTP library that has patched HTTP response splitting vulnerabilities, such as Apache HttpClient, etc.

The following is a sample code that uses Apache HttpClient to fix the HTTP response splitting vulnerability:

import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.BasicHttpParams;

public class HttpUtil {

    public static String getResponse(String url) {
        String response = null;
        HttpClient httpClient = new DefaultHttpClient(new BasicHttpParams());
        HttpGet httpGet = new HttpGet(url);
        
        try {
            response = httpClient.execute(httpGet).toString();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            httpClient.getConnectionManager().shutdown();
        }
        
        return response;
    }
    
    public static void main(String[] args) {
        String url = "http://example.com/";
        String response = getResponse(url);
        System.out.println("HTTP Response: " + response);
    }
}

By using the Apache HttpClient library that fixes the HTTP response splitting vulnerability, HTTP response splitting can be effectively prevented. Exploitation of vulnerabilities.

5. Conclusion
   When developing and maintaining Java Web applications, we must be aware of the dangers of HTTP response splitting vulnerabilities and take appropriate security measures to repair and prevent the occurrence of such vulnerabilities. . This article describes the principles and impact of the HTTP response splitting vulnerability, and how to fix the vulnerability using Java code. We hope that through the introduction of this article, developers can strengthen their understanding of HTTP response splitting vulnerabilities and improve the security of web applications.

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