Mobile number authentication firebase

 

firebase mobile authentication android

You can use Firebase Authentication to sign in a user by sending an SMS message to the user's phone. The user signs in using a one-time code contained in the SMS message.

firebase mobile authentication android example

The easiest way to add phone number sign-in to your app is to use FirebaseUI, which includes a drop-in sign-in widget that implements sign-in flows for phone number sign-in, as well as password-based and federated sign-in. This document describes how to implement a phone number sign-in flow using the Firebase SDK.

Security concerns

Authentication using only a phone number, while convenient, is less secure than the other available methods, because possession of a phone number can be easily transferred between users. Also, on devices with multiple user profiles, any user that can receive SMS messages can sign in to an account using the device's phone number.

If you use phone number based sign-in in your app, you should offer it alongside more secure sign-in methods, and inform users of the security tradeoffs of using phone number sign-in.

Enable Phone Number sign-in for your Firebase project

To sign in users by SMS, you must first enable the Phone Number sign-in method for your Firebase project:

1. In the Firebase console, open the Authentication section.
2. On the Sign-in Method page, enable the Phone Number sign-in method.

Firebase's phone number sign-in request quota is high enough that most apps won't be affected. However, if you need to sign in a very high volume of users with phone authentication, you might need to upgrade your pricing plan. See the pricing page.

Send a verification code to the user's phone

To initiate phone number sign-in, present the user an interface that prompts them to type their phone number. Legal requirements vary, but as a best practice and to set expectations for your users, you should inform them that if they use phone sign-in, they might receive an SMS message for verification and standard rates apply.

Then, pass their phone number to the PhoneAuthProvider.verifyPhoneNumber method to request that Firebase verify the user's phone number.

onVerificationCompleted(PhoneAuthCredential)

This method is called in two situations:

• Instant verification: in some cases the phone number can be instantly verified without needing to send or enter a verification code.
• Auto-retrieval: on some devices, Google Play services can automatically detect the incoming verification SMS and perform verification without user action. (This capability might be unavailable with some carriers.)

In either case, the user's phone number has been verified successfully, and you can use the PhoneAuthCredential object that's passed to the callback to sign in the user.

onVerificationFailed(FirebaseException)

This method is called in response to an invalid verification request, such as a request that specifies an invalid phone number or verification code.

onCodeSent(String verificationId, PhoneAuthProvider.ForceResendingToken)

Optional. This method is called after the verification code has been sent by SMS to the provided phone number.

When this method is called, most apps display a UI that prompts the user to type the verification code from the SMS message. (At the same time, auto-verification might be proceeding in the background.) Then, after the user types the verification code, you can use the verification code and the verification ID that was passed to the method to create a PhoneAuthCredential object, which you can in turn use to sign in the user. However, some apps might wait until onCodeAutoRetrievalTimeOut is called before displaying the verification code UI (not recommended).

onCodeAutoRetrievalTimeOut(String verificationId)

Optional. This method is called after the timeout duration specified to verifyPhoneNumber has passed without onVerificationCompleted triggering first. On devices without SIM cards, this method is called immediately because SMS auto-retrieval isn't possible.

Some apps block user input until the auto-verification period has timed out, and only then display a UI that prompts the user to type the verification code from the SMS message (not recommended).

Create a PhoneAuthCredential object

After the user enters the verification code that Firebase sent to the user's phone, create a PhoneAuthCredential object, using the verification code and the verification ID that was passed to the onCodeSent or onCodeAutoRetrievalTimeOut callback. (When onVerificationCompleted is called, you get a PhoneAuthCredential object directly, so you can skip this step.)

Test with whitelisted phone numbers

You can whitelist phone numbers for development via the Firebase console. Whitelisting phone numbers provides these benefits:

• Test phone number authentication without consuming your usage quota.
• Test phone number authentication without sending an actual SMS message.
• Run consecutive tests with the same phone number without getting throttled. This minimizes the risk of rejection during App store review process if the reviewer happens to use the same phone number for testing.
• Test readily in development environments without any additional effort, such as the ability to develop in an iOS simulator or an Android emulator without Google Play Services.
• Write integration tests without being blocked by security checks normally applied on real phone numbers in a production environment.

Phone numbers to whitelist must meet these requirements:

1. Make sure you use fictional numbers that do not already exist. Firebase Authentication does not allow you to whitelist existing phone numbers used by real users. One option is to use 555 prefixed numbers as US test phone numbers, for example: +1 650-555-3434
2. Phone numbers have to be correctly formatted for length and other constraints. They will still go through the same validation as a real user's phone number.
3. You can add up to 10 phone numbers for development.
4. Use test phone numbers/codes that are hard to guess and change those frequently.

Whitelist phone numbers and verification codes

1. In the Firebase console, open the Authentication section.
2. In the Sign in method tab, enable the Phone provider if you haven't already.
3. Open the Phone numbers for testing accordion menu.
4. Provide the phone number you want to test, for example: +1 650-555-3434.
5. Provide the 6-digit verification code for that specific number, for example: 654321.
6. Add the number. If there's a need, you can delete the phone number and its code by hovering over the corresponding row and clicking the trash icon.

Manual testing

You can directly start using a whitelisted phone number in your application. This allows you to perform manual testing during development stages without running into quota issues or throttling. You can also test directly from an iOS simulator or Android emulator without Google Play Services installed.

When you provide the whitelisted phone number and send the verification code, no actual SMS is sent. Instead, you need to provide the previously configured verification code to complete the sign in.

On sign-in completion, a Firebase user is created with that phone number. The user has the same behavior and properties as a real phone number user, and can access Realtime Database/Cloud Firestore and other services the same way. The ID token minted during this process has the same signature as a real phone number user.

Next steps

After a user signs in for the first time, a new user account is created and linked to the credentials—that is, the user name and password, phone number, or auth provider information—the user signed in with. This new account is stored as part of your Firebase project, and can be used to identify a user across every app in your project, regardless of how the user signs in.

• In your apps, you can get the user's basic profile information from the FirebaseUser object. See Manage Users.

• In your Firebase Realtime Database and Cloud Storage Security Rules, you can get the signed-in user's unique user ID from the auth variable, and use it to control what data a user can access.

You can allow users to sign in to your app using multiple authentication providers by linking auth provider credentials to an existing user account.

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