go-authcrunch: Skill for Codex

.codex/skills/oauth-identity-provider/SKILL.md

oauth-identity-provider is a skill for Codex from greenpau/go-authcrunch. It costs 54 tokens per session (2,042 once invoked), scanned A, original, Apache-2.0.

A guide for connecting the portal to an upstream OAuth or OpenID Connect identity provider. It covers provider discovery, redirects, code exchange, signed-token verification, public-key retrieval, and key refresh.

In plain words
What is it for?
Use it when adding or changing upstream OAuth/OIDC providers, redirect and code exchange handling, token validation, Ed25519 verification, remote JWKS keys, static key pins, or provider tests.
Why use it?
It keeps trust in outside identity providers separate from the portal's own token signing, reducing the risk of mixing their keys, algorithms, issuers, or token settings.

Skill for Codex

Written for Codex: agents/openai.yaml present.

This is greenpau/go-authcrunch's own configuration. It tells Codex how to work on go-authcrunch itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything go-authcrunch configures →

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is make test TEST_DIR='./internal/jwtutil ./pkg/idp/... ./pkg/kms' COVERAGE_DIR='.coverage/oauth-core'.

Reuse

Borrowing it

Nothing to install: this file belongs to greenpau/go-authcrunch. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/greenpau/go-authcrunch/main/.codex/skills/oauth-identity-provider/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/greenpau/go-authcrunch

Made for: 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-identity-provider

README.md
[![agentmods](https://agentmods.dev/badge/skills/greenpau/go-authcrunch/oauth-identity-provider/github.svg)](https://agentmods.dev/skills/greenpau/go-authcrunch/oauth-identity-provider)
Your own site
<a href="https://agentmods.dev/skills/greenpau/go-authcrunch/oauth-identity-provider"><img src="https://agentmods.dev/badge/skills/greenpau/go-authcrunch/oauth-identity-provider/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 oauth-identity-provider

Your own site · 80×15
<a href="https://agentmods.dev/skills/greenpau/go-authcrunch/oauth-identity-provider"><img src="https://agentmods.dev/badge/skills/greenpau/go-authcrunch/oauth-identity-provider.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 54 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,042 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 $0.00054 $0.02042
Opus 5 $0.00027 $0.01021
Sonnet 5 $0.00011 $0.00408
Haiku 4.5 $0.00005 $0.00204

Measured yesterday against content hash 2be2adef80af, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-14, from the pricing page.

Security

Grade A, and why

oauth-identity-provider 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 yesterday.

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.

.codex/skills/oauth-identity-provider/SKILL.md · 171 lines

How it starts

The opening of the file, as written. The whole thing — 171 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OAuth Identity Provider

Ownership and Entry Points

pkg/idp/config.go validates the shared provider parameter allowlist; pkg/idp/provider.go constructs the concrete provider. OAuth behavior lives under pkg/idp/oauth. Exercise this dispatcher as well as concrete helpers: an OAuth Config field is not usable through the shared API until dispatch accepts it and checks its type.

authenticate.go owns redirects and code exchange; validator.go owns token roles and trust claims; jwt.go owns signature verification and bounded retry; jwks.go owns key conversion; jwks_store.go owns remote ingestion, static pins, candidate selection, and refresh. provider.go owns setup/discovery.

The provider verifies upstream credentials. The portal subsequently signs a separate credential using its existing KMS configuration. Keep upstream keys, algorithms, issuer metadata, and key refresh independent of portal signing selection, token settings, and portal JWKS publication. ES512 is the existing autogeneration fallback, not a mandatory portal signing algorithm.

Ed25519 Verification Contract

internal/jwtutil registers the exact Ed25519 JOSE name and recognizes the two concrete supported methods. The pinned JWT library provides EdDSA. Both use pure Ed25519 over the original JWS bytes. Preserve exact method names and never rewrite a signed header, prehash the message, or duplicate registry initialization. KMS also consumes this helper. The key representation follows RFC 8037; the fully specified JOSE name follows RFC 9864.

New OKP keys require crv: Ed25519 and canonical unpadded base64url x with exactly 32 bytes. Return a typed ed25519.PublicKey, never an HMAC byte secret. Reject encryption use, incompatible public parameters, private d, and other curves. Ed448 and X25519 are unsupported. Unknown unrelated extensions can be ignored. For key_ops, omission allows verification; an explicit list must contain verify, may also contain sign, and cannot contain duplicates or other operations. Empty, null, and malformed lists are rejected for OKP. Present empty or null alg/use values are invalid in remote OKP entries; Go struct zero values still represent omitted optional fields.

Read the full file on GitHub · 171 lines

Files

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.

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. yesterday First seen · 171 lines · 54 tokens per session scan A 2be2adef80af

Subscribe to this mod's changes

oauth-identity-provider is a skill published in the GitHub repository greenpau/go-authcrunch (59 stars, last pushed yesterday), licensed Apache-2.0. It adds 54 tokens to every session and 2,042 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 2026-09-13.

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