oauth-expert

oauth-expert is a skill for Claude Code, Codex from ginkida/rustyhand. It costs 24 tokens per session (722 once invoked), scanned A, a copy of oauth-expert, MIT.

An expert guide for OAuth 2.0 and OpenID Connect, standards used to let applications sign users in and access services securely. It covers authorization flows, PKCE, tokens, and identity federation.

In plain words
What is it for?
Use it to implement sign-in for web, mobile, and command-line apps, connect services, validate JWTs, design permission scopes, and manage access and refresh tokens.
Why use it?
It helps avoid insecure login flows, improperly checked tokens, overly broad permissions, and unsafe token storage.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

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.

agentmods
npx agentmods add skills/ginkida/rustyhand/oauth-expert
Any agent
npx skills add ginkida/rustyhand --skill oauth-expert
Clone the repo
git clone --depth 1 https://github.com/ginkida/rustyhand

Made for: Claude Code, Codex.

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 oauth-expert

README.md
[![agentmods](https://agentmods.dev/badge/skills/ginkida/rustyhand/oauth-expert.svg)](https://agentmods.dev/skills/ginkida/rustyhand/oauth-expert)
Your own site
<a href="https://agentmods.dev/skills/ginkida/rustyhand/oauth-expert"><img src="https://agentmods.dev/badge/skills/ginkida/rustyhand/oauth-expert.svg" alt="Measured on agentmods" height="20"></a>
Per session 24 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 722 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00024 $0.00722
Opus 5 $0.00012 $0.00361
Sonnet 5 $0.00005 $0.00144
Haiku 4.5 $0.00002 $0.00072

Measured 6d ago against content hash 05b766c565b2, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

oauth-expert 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 6d 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.

Origin

This is a copy

100% identical to oauth-expert — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

crates/rusty-hand-skills/bundled/oauth-expert/SKILL.md · 39 lines

How it starts

The opening of the file, as written. The whole thing — 39 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OAuth and OpenID Connect Expert

An identity and access management specialist with deep expertise in OAuth 2.0, OpenID Connect, and token-based authentication architectures. This skill provides guidance for implementing secure authorization flows, token lifecycle management, and identity federation patterns across web applications, mobile apps, SPAs, and machine-to-machine services.

Key Principles

  • Always use the Authorization Code flow with PKCE for public clients (SPAs, mobile apps, CLI tools); the implicit flow is deprecated and insecure
  • Validate every JWT thoroughly: check the signature algorithm, issuer (iss), audience (aud), expiration (exp), and not-before (nbf) claims before trusting its contents
  • Design scopes to represent specific permissions (read:documents, write:orders) rather than broad roles; fine-grained scopes enable least-privilege access
  • Store tokens securely: HTTP-only secure cookies for web apps, secure storage APIs for mobile, and encrypted credential stores for server-side services
  • Treat refresh tokens as highly sensitive credentials; bind them to the client, rotate on use, and set reasonable absolute expiration times

Techniques

  • Implement Authorization Code + PKCE: generate a random code_verifier, derive code_challenge via S256, send the challenge in the authorize request, and send the verifier in the token exchange
  • Use Client Credentials flow for server-to-server authentication where no user context is needed; scope the resulting token narrowly
  • Configure token refresh with sliding window expiration: issue short-lived access tokens (5-15 minutes) with longer refresh tokens (hours to days), rotating the refresh token on each use
  • Implement OIDC by requesting the openid scope; validate the id_token signature and claims, then use the userinfo endpoint for additional profile data
  • Set up the Backend-for-Frontend (BFF) pattern for SPAs: the BFF server handles the OAuth flow and stores tokens in HTTP-only cookies, keeping tokens out of JavaScript entirely
  • Implement token revocation by calling the revocation endpoint on logout and maintaining a server-side deny list for JWTs that must be invalidated before expiration

Read the full file on GitHub · 39 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. 6d ago First seen · 39 lines · 24 tokens per session scan A 05b766c565b2

Subscribe to this mod's changes

oauth-expert is a skill published in the GitHub repository ginkida/rustyhand (20 stars, last pushed 25d ago), licensed MIT. It adds 24 tokens to every session and 722 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to oauth-expert, differing in 0 lines, and is treated as a copy.

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