How can I restrict google login to my company's email domain (@company.com) in React Native?

Question

Question

What is the best way to prevent users from using an email address that does not end in @mycompany.com from logging in to our internal app through Firebase/Google auth?

Goal

• Prevent users from using the wrong email to login to the app
• Fetch the user's company email address and use that for authentication elsewhere (i.e. for pulling data from an internal website)

Restraints

• I am using react-native init because I had to implement with our company's native SDK module
• Preferably would like a solution with Firebase since we are already using it with said native SDK module for FCM/push notifications.

Research results

• I saw that react-native-google-signin had a "hostedDomain" option, but it doesn't seem to do anything. I'm not sure how to use it, and there are no docs or good examples of its use. There was a feature request for it here but that's all I can find.
• I saw that there is a similar repo, react-native-google-sign-in, but it doesn't offer any more information on this subject.
• I read somewhere that I'm probably thinking about this all wrong and authentication can't restrict email addresses(?), but I can restrict who can access information with said email addresses. This doesn't help me because we're not using Firebase's database for anything right now. I need a way to guide users to log in using their company email.
• This person seemed to have a similar issue and found a solution for passport, but I don't know how to apply this to my use case.

Setup

• IntelliJ Ultimate 2017.2.2
• React Native 0.47.1 (using react-native init, not CRNA or expo since I needed to integrate with a native SDK module)
• google-services.json from Firebase exists in android/app folder

Android Setup

package.json dependencies

"dependencies": {
    "create-react-class": "^15.6.0", /* Ignore this */
    "firebase": "^4.2.0",
    "react": "16.0.0-alpha.12",
    "react-native": "0.47.1",
    "react-native-app-intro": "^1.1.5",
    "react-native-google-signin": "^0.11.0",
    "react-native-linear-gradient": "^2.2.0",
    "react-navigation": "^1.0.0-beta.12"
}

android/settings.gradle

rootProject.name = '[My Project Name]'
include ':react-native-google-signin'
project(':react-native-google-signin').projectDir = new File(rootProject.projectDir, '../node_modules/react-native-google-signin/android')
include ':react-native-linear-gradient'
project(':react-native-linear-gradient').projectDir = new File(rootProject.projectDir, '../node_modules/react-native-linear-gradient/android')

include ':app', ':[Internal Android SDK]'

android/build.gradle

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.3'
        classpath 'com.google.gms:google-services:3.0.0'
    }
}

allprojects {
    repositories {
        mavenLocal()
        jcenter()
        maven {
            // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm
            url "$rootDir/../node_modules/react-native/android"
        }
    }
}

ext {
    compileSdkVersion = 26
    buildToolsVersion = "26.0.1"
}

subprojects { subproject ->
    afterEvaluate{
        if((subproject.plugins.hasPlugin('android') || subproject.plugins.hasPlugin('android-library'))) {
            android {
                compileSdkVersion rootProject.ext.compileSdkVersion
                buildToolsVersion rootProject.ext.buildToolsVersion
            }
        }
    }
}

android/app/build.gradle

apply plugin: "com.android.application"

[...]

dependencies {
    compile(project(":react-native-google-signin")){
        exclude group: "com.google.android.gms" // very important
    }
    compile project(':react-native-linear-gradient')
    compile project(':[Internal Android SDK]')
    compile fileTree(include: ['*.jar'], dir: 'libs')
    compile 'com.android.support:appcompat-v7:26.0.0-alpha1'
    compile 'com.facebook.react:react-native:+'
    compile 'com.facebook.fresco:animated-gif:1.0.1'
    compile 'com.google.android.gms:play-services-auth:10.0.1'
    compile 'com.google.firebase:firebase-messaging:10.0.1'
}

[...]

apply plugin: 'com.google.gms.google-services'

React Native setup

Current folder structure:

> app
    > components [...]
    > config [...]
    > screens
        HomeScreen.js
        LoginScreen.js
        [...]
    > styles [...]
    router.js (just a simple StackNavigator setup from react-navigation)
> assets
    > fonts [...]
    > img [...]
> node_modules [...]
index.android.js
index.ios.js
package.json
[...]

LoginScreen.js (This is a work in progress)

import React, { Component } from 'react';
import { Alert, Button, Image, Text, View } from 'react-native';
import {GoogleSignin, GoogleSigninButton} from 'react-native-google-signin';

export default class LoginScreen extends Component{

    constructor(props){
        super(props);
        this.state = {
            user: null
        }
    }

    componentDidMount() {
        this._setupGoogleSignin().then(() => console.log('Mounted & Google setup complete.'));
    }

    async _setupGoogleSignin() {
        try {
            await GoogleSignin.hasPlayServices({ autoResolve: true });
            await GoogleSignin.configure({
                hostedDomain: 'mycompany.com' //doesn't do anything
            });

            const user = await GoogleSignin.currentUserAsync();
            console.log('User: ',user);
            this.setState({user});
        }
        catch(err) {
            console.log("Play services error", err.code, err.message);
        }
    }

    _signIn() {
        GoogleSignin.signIn()
            .then((user) => {
                console.log('User: ',user);
                this.setState({user: user});
            })
            .catch((err) => {
                console.log('WRONG SIGNIN', err);
            })
            .done();
    }

    _signOut() {
        GoogleSignin.revokeAccess().then(() => GoogleSignin.signOut()).then(() => {
                this.setState({user: null});
            })
            .done();
    }

    render(){

        if (!this.state.user){
            return (
                <View style={{flex: 1}}>
                    <View style={{flex: 1.5, alignItems: 'center', justifyContent: 'center', marginTop: 40}}>
                        <Image
                            style={{width: 156, height: 156, resizeMode: 'contain'}}
                            source={require('../../assets/img/google_logo1600.png')} />
                        <Text style={{fontSize: 32, fontWeight: 'bold'}}>
                            Google Identity
                        </Text>
                        <Text style={[{fontSize: 15, paddingTop: 5}]}>
                            To continue, please sign-in.
                        </Text>
                    </View>
                    <View style={{flex: 1, alignItems: 'center', justifyContent: 'center', marginBottom: 40}}>
                        <GoogleSigninButton
                            style={{width: 312, height: 48}}
                            size={GoogleSigninButton.Size.Wide}
                            color={GoogleSigninButton.Color.Light}
                            onPress={() => this._signIn()}/>
                    </View>
                </View>
            );
        } else {
            return (
                <View style={{flex: 1}}>
                    <View style={{flex: 1.5, alignItems: 'center', justifyContent: 'center', marginTop: 40}}>
                        <Image
                            style={{width: 156, height: 156, resizeMode: 'contain'}}
                            source={require('../../assets/img/google_logo1600.png')} />
                        <Text style={{fontSize: 32, fontWeight: 'bold'}}>
                            Google Identity
                        </Text>
                        <Text style={[{fontSize: 15, paddingTop: 5}]}>
                            To continue, please sign-in.
                        </Text>
                    </View>
                    <View style={{flex: 1, alignItems: 'center', justifyContent: 'center', marginBottom: 40}}>
                        <Button style={{width: 312, height: 48, backgroundColor: '#4385F2', color: 'white'}} title="Log Out" onPress={() => this._signOut()} />
                    </View>
                </View>
            )
        }

    }
}

If there's a better way to do this, I'm all ears. Thanks!

Answer 1

There is no way to limit who can authenticate with the default Firebase Authentication Google provider. But all the user does by signing in is authenticating themselves: "I am Frank van Puffelen and here's the proof".

You can restrict what resources users have access to. For example for the Firebase Database you can use its server-side security rules to determine what each user is authorized to access. Here you can limit access to users from a specific domain.

Also see:

• Limit Firebase Google OAuth Authentication to specific users
• How to disable Signup in Firebase 3.x