solve-challenge

# 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) > 本部署注：本仓库不随附 `scripts/` 安装脚本（下述命令与链接仅作参考清单）；工具缺装走三级兜底提示，绝不自动安装。 Use the central installer entrypoint: ```bash bash scripts/install_ctf_tools.sh all ``` Run a narrower mode when you only want one tool group: ```bash bash scripts/install_ctf_tools.sh python bash scripts/install_ctf_tools.sh apt bash scripts/install_ctf_tools.sh brew bash scripts/install_ctf_tools.sh gems bash scripts/install_ctf_tools.sh go bash scripts/install_ctf_tools.sh manual ``` The full package lists now live in [scripts/install_ctf_tools.sh](../scripts/install_ctf_tools.sh). ### 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: CTFd Platform Detection If the CTF platform URL is known, check if it runs CTFd and switch to API-driven navigation: ```bash # Detect CTFd (look for /api/v1/ and /themes/core/) curl -s "$CTF_URL/api/v1/" | head -5 curl -s "$CTF_URL" | grep -oE '/themes/core/' ``` If CTFd is detected, **ask the user for their API token** (generated from CTFd Settings > Access Tokens). The token is not provided by default — the user must create one in the CTFd web UI first. Once provided, set the environment variables and proceed via API: ```bash export CTF_URL="https://ctf.example.com" export CTF_TOKEN="ctfd_..." # Ask user for this ``` Invoke `/ctf-misc` and load its `ctfd-navigation.md` for the full API reference and Python client class. ### 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 | 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) ### Step 5: Generate Write-up After solving the challenge, invoke `/ctf-writeup` to generate a standardized submission-style writeup — concise, reproducible, and ready for competition organizers or teammates to validate. ## Flag Formats Flags vary by CTF. Common formats: - `flag{...}`, `FLAG{...}`, `CTF{...}`, `TEAM{...}` - Custom prefixes: check the challenge description or CTF rules for the format (e.g., `ENO{...}`, `HTB{...}`, `picoCTF{...}`) - Sometimes just a plaintext string with no wrapper **Validation rule (important):** - If you find multiple flag-like strings, treat them as candidates and validate before finalizing. - Prefer the token tied to the intended artifact/workflow (not random metadata noise or obvious decoys). - Do a corpus-wide uniqueness check and include the source file/path when reporting. ```bash # Search for common flag patterns in files grep -rniE '(flag|ctf|eno|htb|pico)\{' . # Search in binary/memory output strings output.bin | grep -iE '\{.*\}' ``` ## Quick Reference ```bash # 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