Provides reverse engineering techniques for CTF challenges. Use when the main job is to understand how a compiled, obfuscated, packed, or virtualized target works before exploiting or solving it, including binaries, APKs, WASM, firmware, custom VMs, bytecode, game clients, malware-like loaders, and anti-debug or anti-analysis logic. Do not use it when the vulnerability is already understood and the remaining task is exploitation; use pwn instead. Do not use it for pure web workflows, log or disk forensics, or standalone crypto problems unless reversing the implementation is the real blocker.
Installation
Installer avec Codex ou Claude Copiez ce prompt, collez-le dans Codex, Claude ou un autre assistant, puis laissez-le vérifier la page du skill et l'installer pour vous.
Provides reverse engineering techniques for CTF challenges. Use when the main job is to understand how a compiled, obfuscated, packed, or virtualized target works before exploiting or solving it, including binaries, APKs, WASM, firmware, custom VMs, bytecode, game clients, malware-like loaders, and anti-debug or anti-analysis logic. Do not use it when the vulnerability is already understood and the remaining task is exploitation; use pwn instead. Do not use it for pure web workflows, log or disk forensics, or standalone crypto problems unless reversing the implementation is the real blocker.
license
MIT
compatibility
Requires filesystem-based agent (Claude Code or similar) with bash, Python 3, and internet access for tool installation.
If you already understand the binary and now need heap, ROP, or kernel exploitation, switch to /ctf-pwn.
If the challenge is really about recovering deleted files, PCAP data, or disk artifacts, switch to /ctf-forensics.
If the target is a web app and you are only reversing a small client-side helper script, switch to /ctf-web.
If the binary implements a machine learning model and the challenge is about model attacks or adversarial inputs, switch to /ctf-ai-ml.
If the reversed binary's core logic is a cryptographic algorithm or math problem, switch to /ctf-crypto.
If the binary is a real malware sample with C2, packing, or evasion behavior, switch to /ctf-malware.
If the challenge is a toy VM, encoding puzzle, or pyjail rather than a real binary, switch to /ctf-misc.
Problem-Solving Workflow
Start with strings extraction - many easy challenges have plaintext flags
Try ltrace/strace - dynamic analysis often reveals flags without reversing
Try Frida hooking - hook strcmp/memcmp to capture expected values without reversing
Try angr - symbolic execution solves many flag-checkers automatically
Try Qiling - emulate foreign-arch binaries or bypass heavy anti-debug without artifacts
Map control flow before modifying execution
Automate manual processes via scripting (r2pipe, Frida, angr, Python)
Validate assumptions by comparing decompiler outputs (dogbolt.org for side-by-side)
Quick Wins (Try First!)
# Plaintext flag extraction
strings binary | grep -E "flag\{|CTF\{|pico"
strings binary | grep -iE "flag|secret|password"
rabin2 -z binary | grep -i "flag"# Dynamic analysis - often captures flag directly
ltrace ./binary
strace -f -s 500 ./binary
# Hex dump search
xxd binary | grep -i flag
# Run with test inputs
./binary AAAA
echo"test" | ./binary
Initial Analysis
file binary # Type, architecture
checksec --file=binary # Security features (for pwn)chmod +x binary # Make executable
Memory Dumping Strategy
Key insight: Let the program compute the answer, then dump it. Break at final comparison (b *main+OFFSET), enter any input of correct length, then x/s $rsi to dump computed flag.
Decoy Flag Detection
Pattern: Multiple fake targets before real check. Look for multiple comparison targets in sequence with different success messages. Set breakpoint at FINAL comparison, not earlier ones.
GDB PIE Debugging
PIE binaries randomize base address. Use relative breakpoints:
gdb ./binary
start # Forces PIE base resolution
b *main+0xca # Relative to main
run
Comparison Direction (Critical!)
Two patterns: (1) transform(flag) == stored_target — reverse the transform. (2) transform(stored_target) == flag — flag IS the transformed data, just apply transform to stored target.
Common Encryption Patterns
XOR with single byte - try all 256 values
XOR with known plaintext (flag{, CTF{)
RC4 with hardcoded key
Custom permutation + XOR
XOR with position index (^ i or ^ (i & 0xff)) layered with a repeating key
Quick Tool Reference
# Radare2
r2 -d ./binary # Debug mode
aaa # Analyze
afl # List functions
pdf @ main # Disassemble main# Ghidra (headless)
analyzeHeadless project/ tmp -import binary -postScript script.py
# IDA
ida64 binary # Open in IDA64
Deep-Dive Notes
Use field-notes.md after the first round of triage when you know what kind of target you have.
