offensive-toctou SKILL.md skillA
offensive-toctou from miosa-osa/osa is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add miosa-osa/osa/offensive-toctou@git:20260913.e13b6b8Pins git:20260913.e13b6b8 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- miosa-osa/osa
- Path
priv/skills/offensive-toctou/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260913.e13b6b8, committed Sep 13, 2026
- Size
- 13,974 bytes
- Repository stars
- 78
- License
- Apache-2.0
Time-of-Check / Time-of-Use (TOCTOU) race condition exploitation methodology across binary, kernel, filesystem, web, and container layers. Covers symbolic-link races (open/access/stat split), file-descriptor races, fopen/realpath traversal races, /proc and procfs races, FUSE-backed slow-fs races to widen the window, ptrace and signal races, kernel double-fetch / userspace pointer races, container/runc/symlink escape primitives, kubernetes admission/authz TOCTOU, web auth-vs-authz TOCTOU…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# TOCTOU — Time-of-Check / Time-of-Use Exploitation
A TOCTOU bug exists wherever code checks a property (file owner, path target, token validity, balance) and then acts on it as if the property still holds. Between check and use is a window — your job is to widen it and swap the underlying object.
## Quick Workflow
1. Identify the **check** (syscall, function, validation step) and the **use** (the privileged action)
2. Confirm the check and use don't operate on the same kernel object (FD, inode, atomic snapshot)
3. Build a primitive that swaps the object between check and use (symlink, mount, mv, parallel request)
4. **Widen the window** with FUSE, slow filesystems, scheduler tricks, or single-packet HTTP/2
5. Run a tight loop and confirm the post-use state corresponds to the swapped target
---
## The Core Pattern
```c
// Vulnerable
if (access(path, W_OK) == 0) { // check — resolves "path" now
fd = open(path, O_WRONLY); // use — re-resolves "path" later
write(fd, attacker_data, n);
}
```
Between `access` and `open`, an attacker replaces `path` with a symlink to `/etc/shadow`. The check sees an attacker-owned file; the use opens shadow as root.
…Read the whole file at its exact version.
How to install
mdr add miosa-osa/osa/offensive-toctou@sha256:e5fc9d0096211126The line at the top of this page pins the label git:20260913.e13b6b8, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_dknhq473n7hfzsqr)
6 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on Sep 13, 2026.
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (13974 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
miosa-osa/osa · 78 stars · license Apache-2.0 · pushed 2026-10-29 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_dknhq473n7hfzsqr GET https://markdownregistry.com/api/v1/resolve?ref=miosa-osa/osa/offensive-toctou GET https://markdownregistry.com/api/v1/blob/e5fc9d0096211126d01641497334b283c447696f7d32993c023e42fba2847507
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.