HOME DISCLOSURE NEWS SECURELAYER7 SERVICES COMPANY WEBSITE SECURELAYER7 LAB Introduction to Thick Client Penetration Testing – Part 1 on Posted on July 29, 2017. by Samrat Das Why thick client penetration testing? Thick client applications are not new having been in existence for a long time, however if given to perform a pentest on thick clients, it is not as simple as a Web Application Pentest. Thick clients are majorly used across organizations for their internal operations. In this series of articles, we will learn various tools and techniques used to perform thick client application penetration testing. A step by step breakdown being deployed, we will discuss about starting with the very basics to the advanced test cases. Introduction Referenced under multiple names, such as: Fat client/Heavy client/Rich client/Thick client, such applications follow a client–server architecture. For an easy to understand approach, thick clients are applications which are deployed locally on our systems. Such as skype/ outlook. Thick clients can be developed using multiple languages such as: .NET, C /C++, Java Architectural view of Thick Client applications: 2-tier applications A typical setup where a client and a database interacts with each other. Here the bulk of processing and operations are performed on the client side, while the database operations and queries once executed makes the data processed and stored on the database. 2 Tier Architecture Why is this insecure? Deploying such a setup opens up multiple vulnerabilities which may lead to compromise of database credentials along with plethora of multiple exploits within the application. 3-tier applications: This is the alternate and well-structured 3-tier architecture. Here the client server has three components de ned: The bulk of processing is done at the server side while the queries are performed at client side with requests. This makes security stringent at than a 2-tier application, however not fully safe. 3 Tier Architecture What are the security testing methods feasible for Thick Client? We can break down the di erent types of pen testing a thick client into: Dynamic Testing ( fuzzing, tra c interception, injections) System Testing ( checking for logs, data les, registry keys, process threads) Static Testing ( reverse engineering, binary analysis ) Dynamic testing generally follows data ow from the client side to server side. This gives rise to the following test cases: 1. Dynamic test cases: Input Validation (Fuzzing user input elds) Here our main goal is to test all the input parameters for di erent types of attacks which includes: SQL injection Command injection Malicious input acceptance. SQL injection is one of the prime attacks you can carry onto a thick client’s database. Do note performing thick client sql injection needs patience and is a time consuming task. You need to iterate multiple queries with a mix and match by observing response to each of them. Some good links for a collection of sqli payloads: 1. https://github.com/fuzzdb-project/fuzzdb/tree/master/attack/sqlinjection/payloads-sql-blind 2. http://pentestmonkey.net/cheat-sheet/sql-injection/mysql-sql-injection-cheatsheet You can crawl the net for multiple payloads to nd the one which is appropriate for the application you are testing. File Upload Here our goal is to attempt to upload malicious les which can be injected into the application input request which can lead us to shell upload/ malicious code execution. Here you can simply check for all the browse buttons and check the le upload logic. Bu er Over ow Here our goal is to examine C / C++ programmed thick clients majorly to test the memory functions deployed which will allow us to check how the bu er over ow vulnerabilities and memory violations. Secure tra c analysis (protocols) The testing for this case involves checking whether encryption is applied for sensitive data on the wire or not (example: clear text data transmission is a vulnerability) Business logic validations This has multiple sub test cases which can involve privilege escalation, price tampering, authorization bypass etc. Error handling/ Info Leakage Tester tries in this case to extract verbose error messages which may give information about underlying framework, application code and log details. Session management Test cases on session validity/ expiration/ xation comes under this method. Forced URL access via browser Many a times, con guration URLs can be directly connected via the web browser Log tampering Most of the applications we test does not validate the timestamp directly accepting the local system time from user, performing malicious transactions via changing the system time leads to inconsistency of the application logs. 2. System Test cases: Ex ltration of Sensitive data from memory Many times applications store username passwords. Such information is lethal for compromising the application. There are multiple tools which help us to check the same (A free tool for the same is Winhex) DLL High-jacking Test case for this involves: if the application validates the DLLs used by the application. If by replacing the actual DLLs with malicious le with the same name, this can lead to critical ndings in the application. 3. Static Testing: Analysing Con g les Many a times con guration les of the application reveals URL, Server credentials/ Cryptographic keys/ Hardcoded passwords. Even checking of certain parameters can be easily disabled with a value =yes with = no! Reverse Engineering Using reversing tools, executable le/ jar les can be decompiled which can be modi ed and repackaged. Here is a list of tools which are commonly used for performing thick client pentesting: Interception proxies: Burp Suite Fiddler Echo Mirage Charles Mallory JavaSnoop Tra c Analysis: TCPDump Wireshark Static Analysis: System Internals ( Process Monitor, Regedit, Regshot, AccessEnum) CFF Explorer Decompilers: Java Byte Code Editor JD GUI Ollydbg Packed executable checking tools: PE Explorer PEid UPX Decompression .Net Re ector IL Spy Memory Analysis: Winhex Volatility Tsearch ( nd and replace strings in memory) Userdump Exploitation: Metasploit ( used for side loading/ DLL and Exe injection) Key points: That’s all readers for now. This article gave you a brief idea of how to go about testing an application. In upcoming articles we will cover the following yet not limited to topics: 1. Intercepting thick client applications and tampering request/ response 2. Reverse engineering jar/ exe les 3. DLL Hijacking 4. Memory forensics 5. Deserialization of tra c analysis of java thick clients Posted in SecureLayer7 LabTagged BurpSuite, Introduction to Thick Client Penetration Testing, OWASP Thick Client Penetration Testing, Thick Client Penetration Testing, Why thick client penetration testing Read the Previous Post: Read the Next Post: How are work, life and things at SecureLayer7 2 Comments Recommend Detailed Tra c Analysis for Thick Client Penetration Testing – Part 2 1 Information Security - SecureLayer7 Login Sort by Best ⤤ Share Join the discussion… LOG IN WITH OR SIGN UP WITH DISQUS ? Name test • 9 months ago Hi Samrat, Can you list the tools you use for thick client testing △ ▽ • Reply • Share › Samrat Das > test • 9 months ago Hi Its updated ! △ ▽ • Reply • Share › ALSO ON INFORMATION SECURITY - SECURELAYER7 OWASP Top 10 Details About WebSocket Vulnerabilities and … Web Services and API Penetration Testing Part #1 1 comment • a year ago 1 comment • 4 months ago piero — Great POST. ;) Thank you. Siva Krishna — 1. Please explain how test webservices with WS security enabled. 2. How to test webservices … OWASP TOP 10: Security Misconfiguration #5 – CORS … Everything about the CSV Excel Macro Injection 2 comments • a year ago 16 comments • 2 years ago SaurabhB — @Peter, You are correct. I have Taha — Nice explanation brother! Keep it up. updated it. Thanks for letting us know that :) ✉ Blog Links Subscribe d Add Disqus to your site 🔒 People Talking on Privacy Home Disclosure News SecureLayer7 Services Company Website SecureLayer7 Lab Web Services and API Penetration Testing Part #2 Tabnabbing – An art of phishing Web Services and API Penetration Testing Part #1 Intercepting thick clients sans domain: Thick Client Penetration Testing – Part 5 Dark Web: Accessing the hidden content Part #2 Copyright © 2016 SecureLayer7, LLC. All rights reserved.
