Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/batteryshark/rekitnpx agentmods add skills/batteryshark/rekit/shellcode-stubWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/batteryshark/rekit/shellcode-stub)<a href="https://agentmods.dev/skills/batteryshark/rekit/shellcode-stub"><img src="https://agentmods.dev/badge/skills/batteryshark/rekit/shellcode-stub/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/batteryshark/rekit/shellcode-stub"><img src="https://agentmods.dev/badge/skills/batteryshark/rekit/shellcode-stub.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What 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 5.1 | $0.00133 | $0.01104 |
| Opus 5.5 | $0.00053 | $0.00442 |
| Sonnet 5.5 | $0.00027 | $0.00221 |
| Haiku 4.5 | $0.00013 | $0.00110 |
Grade A, and why
shellcode-stub 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Shellcode Stub Wrapper
🔨 Construct tier — builds a runnable PoC around shellcode; does not run it.
Workflow
Closes the write-side chain. asm-assemble makes bytes; shellcode-stub turns those
bytes into a native executable you can actually detonate or emulate:
asm-assemble ──→ sc.bin ──→ shellcode-stub ──→ poc ──→ exec-observe (native, ⚡ consent)
└──→ qiling-emulate (cross-arch/OS, contained)
What it does
Drops the shellcode into a tiny C loader and compiles it with clang. The loader's exit
code is the shellcode's return value, so a mov w0, #42; ret PoC exits 42 — trivial
to assert.
Two loader templates, picked by --os:
--os |
loader | OS | default target |
|---|---|---|---|
posix (default) |
mmap RW → memcpy → mprotect RX → call as int(void) |
Linux / macOS | host |
windows |
VirtualAlloc RWX → memcpy → call as int(void) → ExitProcess(r) |
Windows PE | x86_64-w64-mingw32 |
--emit exe(default) — the compiled PoC (needs clang).--emit c— just the loader source, to inspect/tweak or hand tocc-build. Needs no compiler at all — works even when the toolchain for the target OS isn't installed.--arch/--target— build a stub for another arch, to run underqiling-emulate. Native host-arch is the guaranteed path; a cross-OS--targetneeds a cross sysroot/toolchain — pass it via--cflags "--sysroot=… -fuse-ld=lld", else the link fails honestly.- Input from a
.binfile or--hex "48c7c0…".
Safety
executes_input: no — it BUILDS the exe, never runs it. Running the result is the
dynamic tier's job (exec-observe, consent-gated) or a contained emulator
(qiling-emulate).
Usage — the full loop (POSIX)
rekit run asm-assemble --arch arm64 --code "mov w0, #42; ret" --out sc.bin
rekit run shellcode-stub sc.bin --out poc
./poc; echo $? # → 42 (or: rekit run --allow-dynamic exec-observe ./poc)
rekit run shellcode-stub --hex "48c7c0370100... " --emit c --out loader.c # inspect first
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 1mo ago First seen · 82 lines · 133 tokens per session scan A 2d3952ce6a18
shellcode-stub is a skill published in the GitHub repository batteryshark/rekit (20 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 133 tokens to every session and 1,104 once invoked, about $0.0005 per session on Opus 5.5. 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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