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# Passport Google OAuth
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Passport Google OAuth provides Google authentication strategies for Passport.js applications. This is a meta-module that combines OAuth 1.0a and OAuth 2.0 authentication strategies, offering a unified interface for Google authentication while maintaining backwards compatibility with existing applications.
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## Package Information
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- **Package Name**: passport-google-oauth
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- **Package Type**: npm
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- **Language**: JavaScript
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- **Installation**: `npm install passport-google-oauth`
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## Core Imports
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```javascript
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var GoogleStrategy = require('passport-google-oauth').Strategy;  // OAuth 1.0a
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var GoogleOAuth2Strategy = require('passport-google-oauth').OAuth2Strategy;  // OAuth 2.0
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```
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Individual strategy imports:
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```javascript
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var { Strategy, OAuthStrategy, OAuth2Strategy } = require('passport-google-oauth');
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```
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Full module import:
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```javascript
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var strategies = require('passport-google-oauth');
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```
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## Basic Usage
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```javascript
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var passport = require('passport');
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var GoogleOAuth2Strategy = require('passport-google-oauth').OAuth2Strategy;
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// OAuth 2.0 strategy (recommended)
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passport.use(new GoogleOAuth2Strategy({
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    clientID: GOOGLE_CLIENT_ID,
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    clientSecret: GOOGLE_CLIENT_SECRET,
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    callbackURL: "http://www.example.com/auth/google/callback"
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  },
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  function(accessToken, refreshToken, profile, done) {
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    User.findOrCreate({ googleId: profile.id }, function (err, user) {
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      return done(err, user);
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    });
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  }
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));
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// OAuth 1.0a strategy (legacy)
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var GoogleStrategy = require('passport-google-oauth').Strategy;
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passport.use(new GoogleStrategy({
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    consumerKey: GOOGLE_CONSUMER_KEY,
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    consumerSecret: GOOGLE_CONSUMER_SECRET,
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    callbackURL: "http://www.example.com/auth/google/callback"
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  },
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  function(token, tokenSecret, profile, done) {
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    User.findOrCreate({ googleId: profile.id }, function (err, user) {
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      return done(err, user);
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    });
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  }
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));
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```
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## Architecture
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This package is a meta-module that re-exports authentication strategies from two underlying packages:
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- **passport-google-oauth1**: Provides OAuth 1.0a strategy implementation
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- **passport-google-oauth20**: Provides OAuth 2.0 strategy implementation
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The package serves as a backwards-compatibility layer, allowing applications to import both OAuth versions from a single package while maintaining support for legacy applications that used the combined package before version 1.0.0.
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## Capabilities
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### Strategy (OAuth 1.0a)
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Default export providing backwards compatibility. This is an alias for OAuthStrategy.
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```javascript { .api }
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/**
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 * Backwards compatibility alias for OAuthStrategy
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 * @constructor
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 * @param {Object} options - Configuration options for OAuth 1.0a authentication
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 * @param {Function} verify - Verification callback function
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 */
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Strategy = OAuthStrategy;
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```
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### OAuthStrategy (OAuth 1.0a)
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Google OAuth 1.0a authentication strategy for legacy applications.
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```javascript { .api }
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/**
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 * Google OAuth 1.0a authentication strategy
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 * @constructor
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 * @param {Object} options - Configuration options
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 * @param {string} options.consumerKey - Google consumer key
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 * @param {string} options.consumerSecret - Google consumer secret
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 * @param {string} options.callbackURL - Callback URL for authentication
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 * @param {Function} verify - Verification callback function
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 * @param {string} verify.token - OAuth token
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 * @param {string} verify.tokenSecret - OAuth token secret
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 * @param {Object} verify.profile - User profile information
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 * @param {Function} verify.done - Completion callback
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 */
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function OAuthStrategy(options, verify);
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```
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### OAuth2Strategy
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Google OAuth 2.0 authentication strategy for modern applications.
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```javascript { .api }
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/**
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 * Google OAuth 2.0 authentication strategy
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 * @constructor
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 * @param {Object} options - Configuration options
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 * @param {string} options.clientID - Google client ID
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 * @param {string} options.clientSecret - Google client secret
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 * @param {string} options.callbackURL - Callback URL for authentication
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 * @param {string[]} [options.scope] - Access scopes to request
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 * @param {Function} verify - Verification callback function
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 * @param {string} verify.accessToken - OAuth 2.0 access token
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 * @param {string} verify.refreshToken - OAuth 2.0 refresh token
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 * @param {Object} verify.profile - User profile information
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 * @param {Function} verify.done - Completion callback
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 */
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function OAuth2Strategy(options, verify);
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```
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## Usage Examples
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### OAuth 2.0 Authentication (Recommended)
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```javascript
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var passport = require('passport');
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var GoogleOAuth2Strategy = require('passport-google-oauth').OAuth2Strategy;
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passport.use(new GoogleOAuth2Strategy({
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    clientID: process.env.GOOGLE_CLIENT_ID,
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    clientSecret: process.env.GOOGLE_CLIENT_SECRET,
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    callbackURL: "/auth/google/callback",
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    scope: ['profile', 'email']
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  },
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  function(accessToken, refreshToken, profile, done) {
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    // Find or create user based on Google profile
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    return done(null, profile);
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  }
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));
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// Routes
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app.get('/auth/google',
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  passport.authenticate('google', { scope: ['profile', 'email'] })
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);
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app.get('/auth/google/callback', 
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  passport.authenticate('google', { failureRedirect: '/login' }),
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  function(req, res) {
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    res.redirect('/');
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  }
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);
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```
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### OAuth 1.0a Authentication (Legacy)
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```javascript
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var passport = require('passport');
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var GoogleStrategy = require('passport-google-oauth').Strategy;
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passport.use(new GoogleStrategy({
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    consumerKey: process.env.GOOGLE_CONSUMER_KEY,
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    consumerSecret: process.env.GOOGLE_CONSUMER_SECRET,
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    callbackURL: "/auth/google/callback"
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  },
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  function(token, tokenSecret, profile, done) {
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    // Find or create user based on Google profile
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    return done(null, profile);
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  }
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));
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// Routes
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app.get('/auth/google',
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  passport.authenticate('google')
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);
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app.get('/auth/google/callback', 
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  passport.authenticate('google', { failureRedirect: '/login' }),
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  function(req, res) {
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    res.redirect('/');
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  }
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);
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```
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## Migration Notes
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As of version 1.0.0, it is recommended to declare dependencies on the specific OAuth version modules:
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- For OAuth 2.0: Use `passport-google-oauth20` directly
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- For OAuth 1.0a: Use `passport-google-oauth1` directly
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This meta-module exists primarily for backwards compatibility with existing applications.