Oauth Implementation Skill for Claude

OAuth 2.0 and OpenID Connect authentication with secure flows. Use for third-party integrations, SSO systems, token-based API access, or encountering authorization code flow, PKCE, token refresh, scope management errors.

2k tokens

context cost

the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

202

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/secondsky/claude-skills --skill oauth-implementation

The instruction itself

7 sections, as written by the author

OAuth Implementation

Implement OAuth 2.0 and OpenID Connect for secure authentication.

OAuth 2.0 Flows

| Flow | Use Case |

|------|----------|

| Authorization Code | Web apps (most secure) |

| Authorization Code + PKCE | SPAs, mobile apps |

| Client Credentials | Service-to-service |

| Refresh Token | Session renewal |

Authorization Code Flow (Express)

const express = require('express');
const jwt = require('jsonwebtoken');

// Step 1: Redirect to authorization
app.get('/auth/login', (req, res) => {
  const state = crypto.randomBytes(16).toString('hex');
  req.session.oauthState = state;

  const params = new URLSearchParams({
    client_id: process.env.CLIENT_ID,
    redirect_uri: process.env.REDIRECT_URI,
    response_type: 'code',
    scope: 'openid profile email',
    state
  });

  res.redirect(`${PROVIDER_URL}/authorize?${params}`);
});

// Step 2: Handle callback
app.get('/auth/callback', async (req, res) => {
  if (req.query.state !== req.session.oauthState) {
    return res.status(400).json({ error: 'Invalid state' });
  }

  const tokenResponse = await fetch(`${PROVIDER_URL}/token`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    body: new URLSearchParams({
      grant_type: 'authorization_code',
      code: req.query.code,
      redirect_uri: process.env.REDIRECT_URI,
      client_id: process.env.CLIENT_ID,
      client_secret: process.env.CLIENT_SECRET
    })
  });

  const tokens = await tokenResponse.json();
  // Store tokens securely and create session
});

PKCE for Public Clients

function generatePKCE() {
  const verifier = crypto.randomBytes(32).toString('base64url');
  const challenge = crypto
    .createHash('sha256')
    .update(verifier)
    .digest('base64url');
  return { verifier, challenge };
}

Security Requirements

Always use HTTPS
Validate redirect URIs strictly
Use PKCE for public clients
Store tokens in HttpOnly cookies
Implement token rotation
Use short-lived access tokens (15 min)

Additional Implementations

See references/python-java.md for:

Python Flask with Authlib OIDC provider
OpenID Connect discovery and JWKS endpoints
Java Spring Security OAuth2 server
Token introspection and revocation

Never Do

Store tokens in localStorage
Use implicit flow
Skip state parameter validation
Expose client secrets in frontend
Use long-lived access tokens

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How to use it

Copy the folder

Take secondsky/oauth-implementation from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.