solve-challenge

name	solve-challenge
description	Solves CTF challenges by analyzing files, connecting to services, and applying exploitation techniques. Orchestrates category-specific CTF skills for pwn, crypto, web, reverse engineering, forensics, OSINT, malware analysis, remote, and miscellaneous challenges. Use when given a CTF challenge to solve, a challenge file to analyze, or a service endpoint to exploit.
license	MIT
compatibility	Requires filesystem-based agent (Claude Code or similar) with bash, Python 3, and internet access. Orchestrates other ctf-* skills.
allowed-tools	Bash Read Write Edit Glob Grep Task WebFetch WebSearch Skill
metadata	{"user-invocable":"true","argument-hint":"[category] [challenge-file-or-url]"}

CTF Challenge Solver

You're a skilled CTF player. Your goal is to solve the challenge and find the flag.

Environment Setup

Two setup strategies depending on your workflow:

Pre-install (recommended before competitions)

Python packages (all platforms):

pip install pwntools pycryptodome z3-solver sympy gmpy2 hashpumpy fpylll py_ecc \
  angr frida-tools qiling requests flask-unsign sqlmap \
  ropper ROPgadget volatility3 yara-python pefile capstone \
  oletools unicorn scapy Pillow numpy matplotlib shodan \
  uncompyle6 lief dnspython dnslib dissect.cobaltstrike

Linux (apt):

apt install gdb radare2 binutils binwalk foremost libimage-exiftool-perl \
  tshark sleuthkit ffmpeg steghide testdisk john pcapfix \
  nmap whois dnsutils hashcat strace ltrace imagemagick curl jq \
  apktool upx qemu-system-x86 sagemath qrencode

macOS (Homebrew):

brew install gdb radare2 binutils binwalk exiftool wireshark sleuthkit \
  ffmpeg testdisk john-jumbo nmap whois bind hashcat ghidra \
  imagemagick curl jq apktool upx qemu qrencode

Ruby gems (all platforms):

gem install one_gadget seccomp-tools zsteg

Go tools (all platforms, requires Go):

go install github.com/ffuf/ffuf/v2@latest

Manual install:

• pwndbg — Linux: github.com/pwndbg/pwndbg, macOS: brew install pwndbg/tap/pwndbg-gdb
• RsaCtfTool — git clone https://github.com/RsaCtfTool/RsaCtfTool
• SageMath — Linux: apt install sagemath, macOS: brew install --cask sage
• steghide — Linux: apt install steghide (not available via Homebrew)
• dnSpy — github.com/dnSpy/dnSpy (.NET decompiler, Windows)

On-demand (during challenges)

Each category skill's SKILL.md has a Prerequisites section listing only the tools needed for that category. Install as you go.

Workflow

Step 0: Create Challenge Folder

Always create a dedicated folder for each challenge before doing anything else.

Name the folder: c:\CTFRun\<CTFName>\<Category>-<ChallengeName>\

Example structure:

c:\CTFRun\
  picoCTF2026\
    web-ORDER_ORDER\          ← this challenge
      solve.py                ← exploit script
      notes.md                ← findings / observations
      flag.txt                ← confirmed flag
      <downloaded files>      ← any challenge files

Create the folder immediately:

mkdir "c:\CTFRun\<CTFName>\<Category>-<ChallengeName>"
Set-Location "c:\CTFRun\<CTFName>\<Category>-<ChallengeName>"

• All scripts and downloaded files go inside this folder
• Save the final flag in flag.txt once found
• Write key findings in notes.md as you go (endpoints, vuln type, payloads tried)

Step 1: Recon

1. Explore files -- List the challenge directory, run file * on everything
2. Triage binaries -- strings, xxd | head, binwalk, checksec on binaries
3. Fetch links -- If the challenge mentions URLs, fetch them FIRST for context
4. Connect -- Try remote services (nc) to understand what they expect
5. Read hints -- Challenge descriptions, filenames, and comments often contain clues

Step 2: Categorize

Determine the primary category, then invoke the matching skill.

By file type:

• .pcap, .pcapng, .evtx, .raw, .dd, .E01 -> forensics
• .elf, .exe, .so, .dll, binary with no extension -> reverse or pwn (check if remote service provided -- if yes, likely pwn)
• .py, .sage, .txt with numbers -> crypto
• .apk, .wasm, .pyc -> reverse
• Web URL or source code with HTML/JS/PHP/templates -> web
• Images, audio, PDFs with no obvious content -> forensics (steganography)

By challenge description keywords:

• "buffer overflow", "ROP", "shellcode", "libc", "heap" -> pwn
• "RSA", "AES", "cipher", "encrypt", "prime", "modulus", "lattice", "LWE", "GCM" -> crypto
• "XSS", "SQL", "injection", "cookie", "JWT", "SSRF" -> web
• "disk image", "memory dump", "packet capture", "registry", "power trace", "side-channel", "spectrogram", "audio tracks", "MKV" -> forensics
• "find", "locate", "identify", "who", "where" -> osint
• "obfuscated", "packed", "C2", "malware", "beacon" -> malware
• "jail", "sandbox", "escape", "encoding", "signal", "game", "Nim", "commitment", "Gray code" -> misc

By service behavior:

• Port with interactive prompt, crash on long input -> pwn
• HTTP service -> web
• netcat with math/crypto puzzles -> crypto
• netcat with restricted shell or eval -> misc (jail)

Step 3: Invoke the Category Skill

Once you identify the category, invoke the matching skill to get specialized techniques:

Category	Invoke	When to Use
Web	/ctf-web	XSS, SQLi, SSTI, SSRF, JWT, file uploads, prototype pollution
Pwn	/ctf-pwn	Buffer overflow, format string, heap, ROP, sandbox escape
Crypto	/ctf-crypto	RSA, AES, ECC, PRNG, ZKP, classical ciphers
Reverse	/ctf-reverse	Binary analysis, game clients, VMs, obfuscated code
Forensics	/ctf-forensics	Disk images, memory dumps, event logs, stego, network captures
OSINT	/ctf-osint	Social media, geolocation, DNS, public records
Malware	/ctf-malware	Obfuscated scripts, C2 traffic, PE/.NET analysis
Misc	/ctf-misc	Jails, encodings, RF/SDR, esoteric languages, constraint solving
Remote	/ctf-remote	SSH, remote access, Kali Linux, file transfer

You can also invoke /ctf-<category> to load the full skill instructions with detailed techniques.

Step 4: Pivot When Stuck

If your first approach doesn't work:

1. Re-examine assumptions -- Is this really the category you think? A "web" challenge might need crypto for JWT forgery. A "forensics" PCAP might contain a pwn exploit to replay.
2. Try a different category skill -- Many challenges span multiple categories. Invoke a second skill for the cross-cutting technique.
3. Look for what you missed -- Hidden files, alternate ports, response headers, comments in source, metadata in images.
4. Simplify -- If an exploit is too complex, check if there's a simpler path (default creds, known CVE, logic bug).
5. Check edge cases -- Off-by-one, race conditions, integer overflow, encoding mismatches.

Common multi-category patterns:

• Forensics + Crypto: encrypted data in PCAP/disk image, need crypto to decrypt
• Web + Reverse: WASM or obfuscated JS in web challenge
• Web + Crypto: JWT forgery, custom MAC/signature schemes
• Reverse + Pwn: reverse the binary first, then exploit the vulnerability
• Forensics + OSINT: recover data from dump, then trace it via public sources
• Misc + Crypto: jail escape requires building crypto primitives under constraints
• OSINT + Stego: social media posts with unicode homoglyph steganography (Cyrillic lookalikes encode bits)
• Web + Forensics: paywall bypass (curl reveals content hidden by CSS overlays)
• Misc + Crypto + Game Theory: multi-phase interactive challenges with AES decryption → HMAC commitment → combinatorial game solving (GF(256) Nim)
• Crypto + Geometry + Lattice: multi-layer challenges progressing from spatial reconstruction → subspace recovery → LWE solving → AES-GCM decryption
• Forensics + Signal Processing: power traces / side-channel analysis requiring statistical analysis of measurement data
• Forensics + Network + Encoding: timing-based encoding in PCAP (inter-packet intervals encode binary data)

Flag Formats

The user specifies the flag format in their request. Always check the challenge description or CTF rules for the exact format before searching.

Common formats:

CTF	Format	Example
picoCTF	picoCTF{...}	picoCTF{s3cr3t}
HackTheBox	HTB{...}	HTB{b4sh_1s_fun}
ENOCTF	ENO{...}	ENO{abc123}
NCSA / custom	NCSA{...}	NCSA{MD5_of_something}
Generic	flag{...} / CTF{...}	flag{h3ll0}
No wrapper	Plaintext / hash	d41d8cd98f00b204e9800998ecf8427e

If the user specifies a custom format (e.g., NCSA{MD5....}):

• Search for that prefix specifically: grep -rniE 'NCSA\{' .
• It might be composed (e.g., flag = NCSA{ + MD5 of some extracted value + })
• Always try to reconstruct if the raw value looks like an intermediate result

Search commands:

# Any flag-like pattern
grep -rniE '(flag|ctf|eno|htb|pico|ncsa)\{' .
# Binary / memory output
strings output.bin | grep -iE '\{.*\}'
# Custom prefix
grep -rniE 'NCSA\{' .

Validation rule:

• If multiple candidates found, prefer the one tied to the intended exploit path
• Save confirmed flag to flag.txt in the challenge folder

Quick Reference

# Recon
file *                                    # Identify file types
strings binary | grep -i flag             # Quick string search
xxd binary | head -20                     # Hex dump header
binwalk -e firmware.bin                   # Extract embedded files
checksec --file=binary                    # Check binary protections

# Connect
nc host port                              # Connect to challenge
echo -e "answer1\nanswer2" | nc host port # Scripted input
curl -v http://host:port/                 # HTTP recon

# Python exploit template
python3 -c "
from pwn import *
r = remote('host', port)
r.interactive()
"

Challenge

$ARGUMENTS