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Server-side Attacks

A backend that handles user-supplied input insecurely can lead to devastating security vulnerabilities such as sensitive information disclosure and remote code execution. This module covers how to identify and exploit server-side bugs, including Server-Side Request Forgery (SSRF), Server-Side Template Injection (SSTI), and Server-Side Includes (SSI) injection attacks.

4.33

Created by vautia

Medium Offensive

Summary

This module covers common server-side security vulnerabilities that lead to devastating security issues and potentially even full web server takeover. Specifically, in this module, we will cover:

  • Identifying and Exploiting SSRF vulnerabilities
  • Identifying and Exploiting SSTI vulnerabilities
  • Identifying and Exploiting SSI Injection vulnerabilities
  • Identifying and Exploiting XSLT Injection vulnerabilities

This module is broken into sections with accompanying hands-on exercises to practice each of the tactics and techniques we cover. The module ends with a practical hands-on skills assessment to gauge your understanding of the various topic areas.

You can start and stop the module at any time and pick up where you left off. There is no time limit or "grading," but you must complete all of the exercises and the skills assessment to receive the maximum number of cubes and have this module marked as complete in any paths you have chosen.

As you work through the module, you will see example commands and command output for the various topics introduced. It is worth reproducing as many of these examples as possible to reinforce further the concepts presented in each section. You can do this in the PwnBox provided in the interactive sections or your virtual machine.

A firm grasp of the following modules can be considered a prerequisite for the successful completion of this module:

  • Linux Fundamentals
  • Web Requests
  • Introduction to Web Applications

Introduction to Server-side Attacks

Server-side attacks target the application or service provided by a server, whereas a client-side attack takes place at the client's machine, not the server itself. Understanding and identifying the differences is essential for penetration testing and bug bounty hunting.

For instance, vulnerabilities like Cross-Site Scripting (XSS) target the web browser, i.e., the client. On the other hand, server-side attacks target the web server. In this module, we will discuss four classes of server-side vulnerabilities:

  • Server-Side Request Forgery (SSRF)
  • Server-Side Template Injection (SSTI)
  • Server-Side Includes (SSI) Injection
  • eXtensible Stylesheet Language Transformations (XSLT) Server-Side Injection

Server-Side Request Forgery (SSRF)

Server-Side Request Forgery (SSRF) is a vulnerability where an attacker can manipulate a web application into sending unauthorized requests from the server. This vulnerability often occurs when an application makes HTTP requests to other servers based on user input. Successful exploitation of SSRF can enable an attacker to access internal systems, bypass firewalls, and retrieve sensitive information.

Server-Side Template Injection (SSTI)

Web applications can utilize templating engines and server-side templates to generate responses such as HTML content dynamically. This generation is often based on user input, enabling the web application to respond to user input dynamically. When an attacker can inject template code, a Server-Side Template Injection vulnerability can occur. SSTI can lead to various security risks, including data leakage and even full server compromise via remote code execution.

Server-Side Includes (SSI) Injection

Similar to server-side templates, server-side includes (SSI) can be used to generate HTML responses dynamically. SSI directives instruct the webserver to include additional content dynamically. These directives are embedded into HTML files. For instance, SSI can be used to include content that is present in all HTML pages, such as headers or footers. When an attacker can inject commands into the SSI directives, Server-Side Includes (SSI) Injection can occur. SSI injection can lead to data leakage or even remote code execution.

XSLT Server-Side Injection

XSLT (Extensible Stylesheet Language Transformations) server-side injection is a vulnerability that arises when an attacker can manipulate XSLT transformations performed on the server. XSLT is a language used to transform XML documents into other formats, such as HTML, and is commonly employed in web applications to generate content dynamically. In the context of XSLT server-side injection, attackers exploit weaknesses in how XSLT transformations are handled, allowing them to inject and execute arbitrary code on the server.

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Sections

Relevant Paths

This module progresses you towards the following Paths

Bug Bounty Hunter

Bug Bounty Hunter

The Bug Bounty Hunter Job Role Path is for individuals who want to enter the world of Bug Bounty Hunting with little to no prior experience. This path covers core web application security assessment and bug bounty hunting concepts and provides a deep understanding of the attack tactics used during bug bounty hunting. Armed with the necessary theoretical background, multiple practical exercises, and a proven bug bounty hunting methodology, students will go through all bug bounty hunting stages, from reconnaissance and bug identification to exploitation, documentation, and communication to vendors/programs. Upon completing this job role path, you will have become proficient in the most common bug bounty hunting and attack techniques against web applications and be in the position of professionally reporting bugs to a vendor.

Medium Path Sections 268 Sections
Required: 1410
Reward: +330
Path Modules
Web Requests
Fundamental
Path Sections 8 Sections
Reward: +10
This module introduces the topic of HTTP web requests and how different web applications utilize them to communicate with their backends.
Introduction to Web Applications
Fundamental
Path Sections 17 Sections
Reward: +10
In the Introduction to Web Applications module, you will learn all of the basics of how web applications work and begin to look at them from an information security perspective.
Using Web Proxies
Easy
Path Sections 15 Sections
Reward: +20
Web application penetration testing frameworks are an essential part of any web penetration test. This module will teach you two of the best frameworks: Burp Suite and OWASP ZAP.
Information Gathering - Web Edition
Easy
Path Sections 19 Sections
Reward: +20
This module equips learners with essential web reconnaissance skills, crucial for ethical hacking and penetration testing. It explores both active and passive techniques, including DNS enumeration, web crawling, analysis of web archives and HTTP headers, and fingerprinting web technologies.
Attacking Web Applications with Ffuf
Easy
Path Sections 13 Sections
Reward: +10
This module covers the fundamental enumeration skills of web fuzzing and directory brute forcing using the Ffuf tool. The techniques learned in this module will help us in locating hidden pages, directories, and parameters when targeting web applications.
JavaScript Deobfuscation
Easy
Path Sections 11 Sections
Reward: +10
This module will take you step-by-step through the fundamentals of JavaScript Deobfuscation until you can deobfuscate basic JavaScript code and understand its purpose.
Cross-Site Scripting (XSS)
Easy
Path Sections 10 Sections
Reward: +20
Cross-Site Scripting (XSS) vulnerabilities are among the most common web application vulnerabilities. An XSS vulnerability may allow an attacker to execute arbitrary JavaScript code within the target's browser and result in complete web application compromise if chained together with other vulnerabilities. This module will teach you how to identify XSS vulnerabilities and exploit them.
SQL Injection Fundamentals
Medium
Path Sections 17 Sections
Reward: +10
Databases are an important part of web application infrastructure and SQL (Structured Query Language) to store, retrieve, and manipulate information stored in them. SQL injection is a code injection technique used to take advantage of coding vulnerabilities and inject SQL queries via an application to bypass authentication, retrieve data from the back-end database, or achieve code execution on the underlying server.
SQLMap Essentials
Easy
Path Sections 11 Sections
Reward: +20
The SQLMap Essentials module will teach you the basics of using SQLMap to discover various types of SQL Injection vulnerabilities, all the way to the advanced enumeration of databases to retrieve all data of interest.
Command Injections
Medium
Path Sections 12 Sections
Reward: +20
Command injection vulnerabilities can be leveraged to compromise a hosting server and its entire network. This module will teach you how to identify and exploit command injection vulnerabilities and how to use various filter bypassing techniques to avoid security mitigations.
File Upload Attacks
Medium
Path Sections 11 Sections
Reward: +20
Arbitrary file uploads are among the most critical web vulnerabilities. These flaws enable attackers to upload malicious files, execute arbitrary commands on the back-end server, and even take control over the entire server and all web applications hosted on it and potentially gain access to sensitive data or cause a service disruption.
Server-side Attacks
Medium
Path Sections 19 Sections
Reward: +20
A backend that handles user-supplied input insecurely can lead to devastating security vulnerabilities such as sensitive information disclosure and remote code execution. This module covers how to identify and exploit server-side bugs, including Server-Side Request Forgery (SSRF), Server-Side Template Injection (SSTI), and Server-Side Includes (SSI) injection attacks.
Login Brute Forcing
Easy
Path Sections 13 Sections
Reward: +20
The module contains an exploration of brute-forcing techniques, including the use of tools like Hydra and Medusa, and the importance of strong password practices. It covers various attack scenarios, such as targeting SSH, FTP, and web login forms.
Broken Authentication
Medium
Path Sections 14 Sections
Reward: +20
Authentication is probably the most straightforward and prevalent measure used to secure access to resources, and it's the first line of defense against unauthorized access. Broken authentication is listed as #7 on the 2021 OWASP Top 10 Web Application Security Risks, falling under the broader category of Identification and Authentication failures. A vulnerability or misconfiguration at the authentication stage can impact an application's overall security.
Web Attacks
Medium
Path Sections 18 Sections
Reward: +20
This module covers three common web vulnerabilities, HTTP Verb Tampering, IDOR, and XXE, each of which can have a significant impact on a company's systems. We will cover how to identify, exploit, and prevent each of them through various methods.
File Inclusion
Medium
Path Sections 11 Sections
Reward: +10
File Inclusion is a common web application vulnerability, which can be easily overlooked as part of a web application's functionality.
Session Security
Medium
Path Sections 14 Sections
Reward: +20
Maintaining and keeping track of a user's session is an integral part of web applications. It is an area that requires extensive testing to ensure it is set up robustly and securely. This module covers the most common attacks and vulnerabilities that can affect web application sessions, such as Session Hijacking, Session Fixation, Cross-Site Request Forgery, Cross-Site Scripting, and Open Redirects.
Web Service & API Attacks
Medium
Path Sections 13 Sections
Reward: +20
Web services and APIs are frequently exposed to provide certain functionalities in a programmatic way between heterogeneous devices and software components. Both web services and APIs can assist in integrating different applications or facilitate separation within a given application. This module covers how to identify the functionality a web service or API offers and exploit any security-related inefficiencies.
Hacking WordPress
Easy
Path Sections 16 Sections
Reward: +20
WordPress is an open-source Content Management System (CMS) that can be used for multiple purposes.
Bug Bounty Hunting Process
Easy
Path Sections 6 Sections
Reward: +10
Bug bounty programs encourage security researchers to identify bugs and submit vulnerability reports. Getting into the world of bug bounty hunting without any prior experience can be a daunting task, though. This module covers the bug bounty hunting process to help you start bug bounty hunting in an organized and well-structured way. It's all about effectiveness and professionally communicating your findings.