Express OAuth 2 handlers

This library provides pre-built boilerplate code for obtaining and storing OAuth 2.0 tokens on Google Cloud Platform.

Installation

npm install @google-cloud/express-oauth2-handlers

Configuration

In order to use the library, several variables must be set. These values can be stored as Linux environment variables.

If a web application client secret file named client_secret.json is present in the root directory of your function/app, the required values below will be automatically imported.

Required values

The following values can be obtained by generating a new OAuth 2.0 client ID or reusing an existing one:

• GOOGLE_CLIENT_ID
• GOOGLE_CLIENT_SECRET
• GOOGLE_CALLBACK_URL

Note These values (and in particular the GOOGLE_CLIENT_SECRET value) should not be stored/committed alongside your codebase except when deployed to GCP hosting platforms. As such, this library does not support specifying these values programmatically.

Reserved values

FUNCTION_TRIGGER_TYPE

This value is set by some (but not all) Google Cloud hosting platforms. Do not set it yourself or change its value.

GCP_PROJECT_ID

This value should be set to your GCP project ID automatically. If it isn't, make sure you do this manually.

Optional settings values

The following values can be specified during either the configuration or initialization processes. Where values are different between the two, those specified during initialization take precedence.

TOKEN_STORAGE_METHOD

Specify how OAuth 2.0 tokens will be stored. Must be one of the following values:

• cookie Stores tokens on a per-user basis using browser cookies.
• datastore Stores tokens globally using Cloud Datastore.

We recommend using cookie unless you have code running in a non-HTTP environment, as this delegates authentication to the user's browser.

The datastore option is best when part or all of your code isn't triggered by HTTP. However, you must manually verify the authenticity of all datastore requests yourself.

DEFAULT_SCOPES

A comma-separated list (such as scope1,scope2,scope3) of OAuth 2.0 scopes to use. See this page for a list of OAuth 2.0 scopes supported by Google APIs.

USER_ID_FORMAT

The format to use for unique User IDs. Two formats are supported:

• email email addresses
• gaiaId Google accounts ID numbers

We recommend using gaiaId when possible. However, some external platforms require the use of email addresses as unique User IDs.

TOKEN_ENCRYPTION_KEY

Specifies the encryption method and/or key to use when encrypting OAuth 2.0 tokens as follows, from least secure to most secure:

• undefined or not specified: use the GOOGLE_CLIENT_SECRET value of your OAuth 2.0 configuration as a tweetnacl symmetric encryption key
• any other string: use this value as a tweetnacl symmetric encryption key. This string should be generated using cryptography-safe randomness tools and kept secret.
• KMS (case insensitive): use Cloud KMS

When using tweetnacl, the TOKEN_ENCRYPTION_KEY value is hashed using sha256 and truncated to generate the key used in the application.

KMS_KEY_RING and KMS_KEY_NAME

These values are used to encrypt stored OAuth 2.0 tokens when using Cloud KMS (i.e. when TOKEN_ENCRYPTION_KEY is set to KMS), and can be obtained by creating a Cloud KMS encryption key.

Initialization

When importing and initializing the library, several different parameters are used.

storageMethod

Optional. Specify how OAuth 2.0 tokens will be stored. Identical to (and takes precedence over) TOKEN_STORAGE_METHOD above.

scopes

Optional. An array of OAuth 2.0 scopes to request. See this page for a list of OAuth 2.0 scopes supported by Google APIs. Takes precedence over the DEFAULT_SCOPES environment variable.

userIdFormat

Optional. The format to use for unique User IDs. Identical to (and takes precedence over) USER_ID_FORMAT above.

showInternals

Optional. If set to true, certain internal methods will be exposed.

Example

const Auth = require('@google-cloud/express-oauth2-handlers');

// Cookie
const auth = Auth('cookie', ['profile', 'email']);

// Datastore
const auth = Auth('datastore', ['profile', 'email'], 'email');

Storage Methods

Use the following chart to decide which storage method is right for your use case.

	cookie	datastore
Requires user IDs?	No	Yes
Requires end-user interaction? ^	Yes	No
Works with free tier? +	Yes	No
Platform restricted?	No	Google Cloud only

^ When fetching existing tokens

+ Cloud KMS can be used for token encryption, and does not have a free tier.

Methods

auth.tryAuth

Attempts to authenticate the specified user while failing gracefully.

Arguments

req An Express-like request object for HTTP invocations; null otherwise.

res An Express-like response object for HTTP invocations; null otherwise.

userId Datastore token-storage only. A unique User ID specifying which user to associate the token with.

Returns

true if the authentication succeeded, false otherwise.

auth.requireAuth

Attempts to authenticate the specified user, but does not fail gracefully.

Arguments

req An Express-like request object for HTTP invocations; null otherwise.

res An Express-like response object for HTTP invocations; null otherwise.

userId Datastore token-storage only. A unique User ID specifying which user to associate the token with.

Returns

A Promise containing a scoped token if the authentication succeeds; a rejected Promise containing an Error otherwise.

auth.authedUser.hasScope

Check if the authenticated user's token contains a specified OAuth 2.0 scope.

Arguments

req An Express-like request object for HTTP invocations; null otherwise.

res An Express-like response object for HTTP invocations; null otherwise.

scope The OAuth 2.0 scope to check for

Returns

A Promise containing a boolean value if a user has been authenticated; a rejected Promise otherwise.

auth.authedUser.getClient

Retrieves the current user's (initialized and auto-authenticated) OAuth 2.0 client.

Arguments

req An Express-like request object for HTTP invocations; null otherwise.

res An Express-like response object for HTTP invocations; null otherwise.

userId Datastore token-storage only. A unique User ID specifying which user the auth client will associate with.

Returns

A Promise containing a reference to the current user's authenticated OAuth 2.0 client.

auth.authedUser.getToken

Retrieves the standard non-scoped OAuth 2.0 token associated with the specified (and auto-authenticated) user.

Arguments

req An Express-like request object for HTTP invocations; null otherwise.

res An Express-like response object for HTTP invocations; null otherwise.

userId Datastore token-storage only. A unique User ID specifying which user's non-scoped token should be fetched.

Returns

A Promise containing the currently-authenticated user's OAuth 2.0 token.

auth.getRawClient

Internal. Retrieves a reference to an unauthenticated OAuth 2.0 client object.

Arguments

req An Express-like request object for HTTP invocations; null otherwise.

res An Express-like response object for HTTP invocations; null otherwise.

Returns

A Promise that resolves to the unauthenticated OAuth 2.0 client object.

auth.authedUser.getUserId

Internal. Returns the unique User ID of the currently authenticated user.

Arguments

req An Express-like request object for HTTP invocations; null otherwise.

res An Express-like response object for HTTP invocations; null otherwise.

Returns

A Promise containing the current user's Google user ID (gaiaId) or email address, depending on the value of USER_ID_FORMAT.

auth.storeScopedToken

Internal. Stores a scoped token associated with the specified user.

Arguments

req An Express-like request object for HTTP invocations; null otherwise.

res An Express-like response object for HTTP invocations; null otherwise.

scopedToken The scoped token to associate with the specified user.

userId Datastore token-storage only. A unique User ID specifying which user to associate the token with.

Returns

A Promise that resolves once the token is stored.

auth.authedUser.getScopedToken

Internal. Retrieves the scoped token associated with the specified (and auto-authenticated) user.

Arguments

req An Express-like request object for HTTP invocations; null otherwise.

res An Express-like response object for HTTP invocations; null otherwise.

userId Datastore token-storage only. A unique User ID specifying which user's scoped token should be fetched.

Returns

A Promise containing the scoped token.

Routes

Routes are functions that emulate Connect-style middleware. They are compatible with Express, as well as Express-like platforms such as Google Cloud Functions.

routes.init

init is a route that redirects end-users to a consent prompt.

Arguments

scope_array Optional. An array of OAuth2 scopes to request

routes.cb

cb is a route that serves as an OAuth 2.0 callback URL. It consumes a one-time authorization code, converts it into a reusable access token, and stores the access token using the specified storage method.

Arguments

onSuccess Optional. A URL to redirect to or a callback function that accepts Express-like req and res parameters to be called once the cb route successfully obtains and stores an access token.

onFailure Optional. A URL to redirect to or a callback function that accepts Express-like req and res parameters to be called if the cb route fails to obtain and store an access token.

Note: if one of onSuccess and onFailure is provided, the other must be provided as well.

Invocation

App Engine

// Express middleware format - no arguments
app.get('/oauth2init', oauth2.routes.init);
app.get('/oauth2callback', oauth2.routes.cb);

// Express middleware format - all arguments
app.get('/oauth2init', oauth2.routes.init(['scope_1', 'scope_2'])); // Array of OAuth scopes to request
app.get('/oauth2callback', oauth2.routes.cb('/success', '/failure')); // "onSuccess" and "onFailure" as redirect URLs

// Express middleware format - "onSuccess" and "onFailure" as callbacks
// - Technically possible, but not documented because it's bad practice
// - Instead, use additional Express middleware functions

Cloud Functions

// HTTP Cloud Function format - no arguments
exports.oauth2init = oauth2.routes.init;
exports.oauth2callback = oauth2.routes.cb;

// HTTP Cloud Function format - all arguments
exports.oauth2init = oauth2.routes.init(['scope_1', 'scope_2']);
exports.oauth2callback = oauth2.routes.cb('/oauth2success', '/oauth2failure');

// HTTP Cloud Function format - "onSuccess" and "onFailure" as callbacks
// - Cloud Functions doesn't support Express-style middleware
// - Instead, you can use callbacks to handle post-route logic
const onSuccess = (req, res) => { ... }
const onFailure = (err, req, res) => { ... }

exports.oauth2init = ... // same as above
exports.oauth2callback = oauth2.routes.cb(onSuccess, onFailure);

Legal terms

License

This project is licensed under the Apache 2.0 license.

Product status

This is not a Google product, official or otherwise.

Support level

Support for this library is not guaranteed, and it may be abandoned, deprecated, and/or deleted at any time with or without notice.

Contributing

Pull requests and issues are very much appreciated. Please read through CONTRIBUTING.md before making any contributions.