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https://github.com/davidje13/auth-backend

minimal API for integration with external authentication providers
https://github.com/davidje13/auth-backend

github-login gitlab-login google-login google-sso oauth

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minimal API for integration with external authentication providers

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# Authentication Backend



Provides minimal backend functionality for integrating with external

authentication providers.



Currently supports Google, GitHub and GitLab.



## Install dependency



```bash

npm install --save authentication-backend

```



## Usage



```javascript

import express from 'express';

import { buildAuthenticationBackend } from 'authentication-backend';



const config = {

  google: {

    clientId: 'my-google-client-id',

    authUrl: 'https://accounts.google.com/o/oauth2/auth',

    tokenInfoUrl: 'https://oauth2.googleapis.com/tokeninfo',

  },

  github: {

    clientId: 'my-github-client-id',

    clientSecret: 'my-github-client-secret',

    authUrl: 'https://github.com/login/oauth/authorize',

    accessTokenUrl: 'https://github.com/login/oauth/access_token',

    userUrl: 'https://api.github.com/user',

  },

  gitlab: {

    clientId: 'my-gitlab-client-id',

    authUrl: 'https://gitlab.com/oauth/authorize',

    tokenInfoUrl: 'https://gitlab.com/oauth/token/info',

  },

};



function tokenGranter(userId, service, externalId) {

  // database-based example:

  const myUserSessionToken = uuidv4();

  myDatabase.recordUserSession(myUserSessionToken, userId);

  return myUserSessionToken;

}



const auth = buildAuthenticationBackend(config, tokenGranter);

express()

  .use('/my-prefix', auth.router)

  .listen(8080);

```



You will need to do some work for each service on the client-side too.

See the source in `/example/static` for a reference implementation.



### Mock SSO server






This package also contains a mock SSO server, which can be run alongside your app

(this is useful for local development and testing):






```javascript

import express from 'express';

import { buildAuthenticationBackend, buildMockSsoApp } from 'authentication-backend';



buildMockSsoApp().listen(9000);



const config =

  google: {

    clientId: 'my-google-client-id',

    authUrl: 'http://localhost:9000/auth',

    tokenInfoUrl: 'http://localhost:9000/tokeninfo',

  },

};



// ...



const auth = buildAuthenticationBackend(config, tokenGranter);

express()

  .use('/my-prefix', auth.router)

  .listen(8080);

```



## Authentication Providers



### Google sign in



You will need a Google client ID:



1. Go to 

2. Create a new project (if necessary)

3. In the "Credentials" screen, find the auto-generated OAuth client

   entry (if it was not created automatically, create one manually with

   "Create credentials" → "OAuth client ID")

4. Record the client ID (you will not need the client secret)

5. Update the authorised JavaScript origins to match your deployment.

   e.g. for local testing, this could be `http://localhost:8080`

6. Update the authorised redirect URIs to the same value, with

   `//google` appended to the end.

7. You may want to change the "Support email" listed under

   "OAuth consent screen", as this will be visible to users of your

   deployed app.



You can now configure the client ID in your app:



```javascript

const config =

  google: {

    clientId: 'something.apps.googleusercontent.com', // <-- replace

    authUrl: 'https://accounts.google.com/o/oauth2/auth',

    tokenInfoUrl: 'https://oauth2.googleapis.com/tokeninfo',

  },

};

```



### GitHub sign in



You will need a GitHub client ID:



1. Go to 

2. Set the "Homepage URL" to match your deployment. e.g. for local

   testing, this could be `http://localhost:8080`

3. Set the "Authorization callback URL" to the same value, with

   `//github` appended to the end.

4. Record the client ID and client secret.



You can now configure the client ID and secret in your app:



```javascript

const config =

  github: {

    clientId: 'my-github-client-id',         // <-- replace

    clientSecret: 'my-github-client-secret', // <-- replace

    authUrl: 'https://github.com/login/oauth/authorize',

    accessTokenUrl: 'https://github.com/login/oauth/access_token',

    userUrl: 'https://api.github.com/user',

  },

};

```



### GitLab sign in



You will need a GitLab client ID:



1. Go to 

2. Set the "Redirect URI" to match your deployment with

   `//gitlab` appended to the end. e.g. for local

   testing, this could be `http://localhost:8080//gitlab`

3. Untick the "confidential" option. You do not need to enable

   any scopes.

4. Record the application ID (you will not need the secret).



You can now configure the application ID in your app:



```javascript

const config =

  gitlab: {

    clientId: 'my-gitlab-application-id', // <-- replace

    authUrl: 'https://gitlab.com/oauth/authorize',

    tokenInfoUrl: 'https://gitlab.com/oauth/token/info',

  },

};

```



## API



This expects you to create a frontend which handles the user interaction and propagates returned data to the API.



### GET `/`



This will return the public parts of your config (i.e. `clientId` and `authUrl` for each service).



Example:



```json

{

  "google": {

    "clientId": "my-google-client-id",

    "authUrl": "https://accounts.google.com/o/oauth2/auth"

  },

  "github": {

    "clientId": "my-github-client-id",

    "authUrl": "https://github.com/login/oauth/authorize"

  },

  "gitlab": {

    "clientId": "my-gitlab-client-id",

    "authUrl": "https://gitlab.com/oauth/authorize"

  }

}

```



Any services which have not been configured will be omitted from the response.



### POST `/`



Where `` is `google`, `github` or `gitlab`.



This expects to receive JSON-encoded data:



```json

{

  "externalToken": "token-returned-by-service"

}

```



It will check the token with the service, and if successful, will invoke the configured

`tokenGranter` function with a user ID, service name, and service user ID. The string

returned by `tokenGranter` will be sent to the user in a JSON response:



```json

{

  "userToken": "returned-token-granter-value"

}

```



If the check fails, an error will be returned instead, with a status code of 4xx or 5xx:



```json

{

  "error": "an error message"

}

```