You can integrate Firebase Authentication with a custom authentication system by
modifying your authentication server to produce custom signed tokens when a user
successfully signs in. Your app receives this token and uses it to authenticate
with Firebase.
Before you begin
- Add Firebase to your C++
project
.
- Get your project's server keys:
- Go to the
Service Accounts
page in your project's settings.
- Click
Generate New Private Key
at the bottom of the
Firebase Admin SDK
section of the
Service Accounts
page.
- The new service account's public/private key pair is automatically
saved on your computer. Copy this file to your authentication server.
Authenticate with Firebase
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 your
firebase::App
.
There is a one-to-one mapping between
App
and
Auth
.
firebase::auth::Auth* auth = firebase::auth::Auth::GetAuth(app);
Call
Auth::SignInWithCustomToken
with the token from your authentication server.
- When users sign in to your app, send their sign-in credentials (for
example, their username and password) to your authentication server. Your
server checks the credentials and returns a
custom token
if they are valid.
- After you receive the custom token from your authentication server, pass
it to
Auth::SignInWithCustomToken
to sign in the user:
firebase::Future<firebase::auth::AuthResult> result =
auth->SignInWithCustomToken(custom_token);
- 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::SignInWithCustomTokenLastResult
:
firebase::Future<firebase::auth::AuthResult> result =
auth->SignInWithCustomTokenLastResult();
if (result.status() == firebase::kFutureStatusComplete) {
if (result.error() == firebase::auth::kAuthErrorNone) {
firebase::auth::AuthResult auth_result = *result.result();
printf("Sign in succeeded for `%s`\n",
auth_result.user.display_name().c_str());
} else {
printf("Sign in failed with error '%s'\n", result.error_message());
}
}
Or, if your program is event driven, you may prefer to
register a callback on the
Future
.
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();