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security-authn-authz

security-authn-authz is a skill for Claude Code from contactandrewchl-wq/turtle-mcp. It costs 62 tokens per session (1,145 once invoked), scanned A, original, MIT.

A guide to user authentication and authorization: checking who a user is and deciding what that user may do. It covers passwords, sessions, tokens, OAuth2/OIDC, multi-factor authentication, and permission models.

In plain words
What is it for?
Implementing registration, login, logout, password resets, multi-factor authentication, sessions, tokens, role-based access, and other permission checks.
Why use it?
It helps keep login and access-control systems separate and apply safer patterns for passwords, sessions, and permissions.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the turtle plugin — 26 skills shipped together

not rated 2repo 2mo ago A scan 62 tokens original MIT

Good fit Implementing registration, login, logout, password resets, multi-factor authentication, sessions, tokens, role-based access, and other permission checks.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/contactandrewchl-wq/turtle-mcp/security-authn-authz
View source ↗ contactandrewchl-wq/turtle-mcp
Install

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.

Any agent
npx skills add contactandrewchl-wq/turtle-mcp --skill security-authn-authz
Clone the repo
git clone --depth 1 https://github.com/contactandrewchl-wq/turtle-mcp

Made for: Claude Code.

Or install turtle, the plugin that ships this one along with the rest of its 26 skills.

Wrote 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.

agentmods badge for security-authn-authz

README.md
[![agentmods](https://agentmods.dev/badge/skills/contactandrewchl-wq/turtle-mcp/security-authn-authz/github.svg)](https://agentmods.dev/skills/contactandrewchl-wq/turtle-mcp/security-authn-authz)
Your own site
<a href="https://agentmods.dev/skills/contactandrewchl-wq/turtle-mcp/security-authn-authz"><img src="https://agentmods.dev/badge/skills/contactandrewchl-wq/turtle-mcp/security-authn-authz/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.

agentmods 80×15 button for security-authn-authz

Your own site · 80×15
<a href="https://agentmods.dev/skills/contactandrewchl-wq/turtle-mcp/security-authn-authz"><img src="https://agentmods.dev/badge/skills/contactandrewchl-wq/turtle-mcp/security-authn-authz.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 62 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,145 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00062 $0.01145
Opus 5 $0.00031 $0.00573
Sonnet 5 $0.00012 $0.00229
Haiku 4.5 $0.00006 $0.00114

Measured 12d ago against content hash 6bb7906587cd, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

security-authn-authz 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 12d 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.

skills/security-authn-authz/SKILL.md · 112 lines

How it starts

The opening of the file, as written. The whole thing — 112 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Autenticación y autorización

Cuándo usar

  • Implementar registro, login, logout, reset de contraseña, MFA.
  • Diseñar el modelo de permisos.
  • Resolver un bug que toca sesión o autorización.

Distinguir

  • Autenticación (authn): ¿quién sos? (login).
  • Autorización (authz): ¿qué podés hacer? (permisos).
  • Son independientes. Casi todo el daño viene de mezclarlas.

Contraseñas

  • Hash con argon2id (preferido, parámetros: 64 MB, 3 iter, 4 paralelismo como base) o bcrypt con cost ≥12.
  • Nunca MD5, SHA-1, SHA-256, ni "salt + sha" caseros.
  • Reglas: longitud mínima 12, sin requerir mezcla forzada de mayúsculas/símbolos (NIST 800-63B). Sí permitir hasta ≥64 chars, incluir emojis.
  • Verificá contra breached password lists (HaveIBeenPwned API con k-anonymity).
  • Reset por email: link de un solo uso, expira en ≤1 h, invalida sesiones activas.

Sesiones

Dos modelos, elegí uno y respetalo:

Server session (recomendado para apps web)

  • Cookie Set-Cookie: session=<opaque-id>; HttpOnly; Secure; SameSite=Lax; Path=/.
  • Sesión almacenada server-side (Redis, BD). Invalidable instantánea.
  • Rotación de ID al elevar privilegios (post-login, post-MFA).

JWT (para APIs stateless o SPAs)

  • Access token corto (5–15 min) + refresh token largo (días/semanas).
  • Firmá con RS256/EdDSA (asymétrico) si distribuís verificación a varios servicios; HS256 si todo es un solo servicio.
  • Nunca confíes en alg: none. Verificá alg en una whitelist.
  • Refresh token rotativo y revocable (almacenado server-side).
  • JWT en localStorage queda expuesto a XSS. Para web, preferí cookie HttpOnly.

MFA

  • TOTP (RFC 6238) por defecto: apps tipo Authy/Google Authenticator.
  • WebAuthn / passkeys para experiencia moderna y phishing-resistant.
  • SMS solo como fallback, no como factor principal (SIM swap).
  • Códigos de recuperación: 8 códigos one-time, mostrados una vez, hash en BD.

OAuth2 / OIDC

  • Authorization Code + PKCE para cualquier app pública (SPA, mobile, CLI).
  • Client Credentials para service-to-service.
  • state siempre presente (anti-CSRF en el flow).
  • nonce en OIDC para prevenir replay.
  • Tokens nunca en URL, salvo el code corto.

Read the full file on GitHub · 112 lines

Changes

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.

  1. 12d ago First seen · 112 lines · 62 tokens per session scan A 6bb7906587cd

Subscribe to this mod's changes

security-authn-authz is a skill published in the GitHub repository contactandrewchl-wq/turtle-mcp (2 stars, last pushed 2mo ago), licensed MIT. It adds 62 tokens to every session and 1,145 once invoked, about $0.0003 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 2026-08-31.

Backend and APIsClaude CodeLLMSecurityai-agentsclilocal-firstmcp
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