You can use Firebase Authentication to let your users authenticate with Firebase using their email addresses and passwords, and to manage your app's password-based accounts.
Before you begin
- Add Firebase to your C++ project.
- If you haven't yet connected your app to your Firebase project, do so from the Firebase console.
- Enable Email/Password sign-in:
- In the Firebase console, open the Auth section.
- On the Sign in method tab, enable the Email/password sign-in method and click Save.
Access the firebase::auth::Auth
class
The Auth
class is the gateway for all API calls.
- Add the Auth and App header files:
#include "firebase/app.h" #include "firebase/auth.h"
- In your initialization code, create a
firebase::App
class.#if defined(__ANDROID__) firebase::App* app = firebase::App::Create(firebase::AppOptions(), my_jni_env, my_activity); #else firebase::App* app = firebase::App::Create(firebase::AppOptions()); #endif // defined(__ANDROID__)
- Acquire the
firebase::auth::Auth
class for yourfirebase::App
. There is a one-to-one mapping betweenApp
andAuth
.firebase::auth::Auth* auth = firebase::auth::Auth::GetAuth(app);
Create a password-based account
To create a new user account with a password, complete the following steps in your app's sign-in code:
- When a new user signs up using your app's sign-up form, complete any new account validation steps that your app requires, such as verifying that the new account's password was correctly typed and meets your complexity requirements.
- Create a new account by passing the new user's email address and password
to
Auth::CreateUserWithEmailAndPassword
:firebase::Future<firebase::auth::AuthResult> result = auth->CreateUserWithEmailAndPassword(email, password);
- If your program has an update loop that runs regularly (say at 30 or 60
times per second), you can check the results once per update with
Auth::CreateUserWithEmailAndPasswordLastResult
: Or, if your program is event driven, you may prefer to register a callback on the Future.firebase::Future<firebase::auth::AuthResult> result = auth->CreateUserWithEmailAndPasswordLastResult(); if (result.status() == firebase::kFutureStatusComplete) { if (result.error() == firebase::auth::kAuthErrorNone) { const firebase::auth::AuthResult auth_result = *result.result(); printf("Create user succeeded for email %s\n", auth_result.user.email().c_str()); } else { printf("Created user failed with error '%s'\n", result.error_message()); } }
Sign in a user with an email address and password
The steps for signing in a user with a password are similar to the steps for creating a new account. In your app's sign-in function, do the following:
- When a user signs in to your app, pass the user's email address and
password to
firebase::auth::Auth::SignInWithEmailAndPassword
:firebase::Future<firebase::auth::AuthResult> result = auth->SignInWithEmailAndPassword(email, password);
- If your program has an update loop that runs regularly (say at 30 or 60
times per second), you can check the results once per update with
Auth::SignInWithEmailAndPasswordLastResult
: Or, if your program is event driven, you may prefer to register a callback on the Future.firebase::Future<firebase::auth::AuthResult> result = auth->SignInWithEmailAndPasswordLastResult(); if (result.status() == firebase::kFutureStatusComplete) { if (result.error() == firebase::auth::kAuthErrorNone) { const firebase::auth::AuthResult auth_result = *result.result(); printf("Sign in succeeded for email %s\n", auth_result.user.email().c_str()); } else { printf("Sign in failed with error '%s'\n", result.error_message()); } }
Register a callback on a Future
Some programs haveUpdate
functions that are called 30 or 60 times per second.
For example, many games follow this model. These programs can call the LastResult
functions to poll asynchronous calls.
However, if your program is event driven, you may prefer to register callback functions.
A callback function is called upon completion of the Future.
void OnCreateCallback(const firebase::Future<firebase::auth::User*>& result, void* user_data) { // The callback is called when the Future enters the `complete` state. assert(result.status() == firebase::kFutureStatusComplete); // Use `user_data` to pass-in program context, if you like. MyProgramContext* program_context = static_cast<MyProgramContext*>(user_data); // Important to handle both success and failure situations. if (result.error() == firebase::auth::kAuthErrorNone) { firebase::auth::User* user = *result.result(); printf("Create user succeeded for email %s\n", user->email().c_str()); // Perform other actions on User, if you like. firebase::auth::User::UserProfile profile; profile.display_name = program_context->display_name; user->UpdateUserProfile(profile); } else { printf("Created user failed with error '%s'\n", result.error_message()); } } void CreateUser(firebase::auth::Auth* auth) { // Callbacks work the same for any firebase::Future. firebase::Future<firebase::auth::AuthResult> result = auth->CreateUserWithEmailAndPasswordLastResult(); // `&my_program_context` is passed verbatim to OnCreateCallback(). result.OnCompletion(OnCreateCallback, &my_program_context); }
void CreateUserUsingLambda(firebase::auth::Auth* auth) { // Callbacks work the same for any firebase::Future. firebase::Future<firebase::auth::AuthResult> result = auth->CreateUserWithEmailAndPasswordLastResult(); // The lambda has the same signature as the callback function. result.OnCompletion( [](const firebase::Future<firebase::auth::User*>& result, void* user_data) { // `user_data` is the same as &my_program_context, below. // Note that we can't capture this value in the [] because std::function // is not supported by our minimum compiler spec (which is pre C++11). MyProgramContext* program_context = static_cast<MyProgramContext*>(user_data); // Process create user result... (void)program_context; }, &my_program_context); }
Recommended: Enable email enumeration protection
Some Firebase Authentication methods that take email addresses as parameters throw specific errors if the email address is unregistered when it must be registered (for example, when signing in with an email address and password), or registered when it must be unused (for example, when changing a user's email address). While this can be helpful for suggesting specific remedies to users, it can also be abused by malicious actors to discover the email addresses registered by your users.
To mitigate this risk, we recommend you enable email enumeration protection
for your project using the Google Cloud gcloud
tool. Note that enabling this
feature changes Firebase Authentication's error reporting behavior: be sure your app
doesn't rely on the more specific errors.
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
firebase::auth::User
object:firebase::auth::User user = auth->current_user(); if (user.is_valid()) { std::string name = user.display_name(); std::string email = user.email(); std::string photo_url = user.photo_url(); // The user's ID, unique to the Firebase project. // Do NOT use this value to authenticate with your backend server, // if you have one. Use firebase::auth::User::Token() instead. std::string uid = user.uid(); }
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.
To sign out a user, call
SignOut()
:
auth->SignOut();