You can let your users authenticate with Firebase using OAuth providers like
Yahoo by integrating web-based generic OAuth Login into your app using the
Firebase SDK to carry out the end to end sign-in flow. Since this flow requires
the use of the phone-based Firebase SDKs, it is only supported on Android and
Apple platforms.
Before you begin
- Add Firebase to your C++ project
.
- In the
Firebase console
, open the
Auth
section.
- On the
Sign in method
tab, enable the
Yahoo
provider.
- Add the
Client ID
and
Client Secret
from that provider's developer console to the
provider configuration:
-
To register a Yahoo OAuth client, follow the Yahoo developer
documentation on
registering a web application with Yahoo
.
Be sure to select the two OpenID Connect API permissions:
profile
and
email
.
- When registering apps with these providers, be sure to register the
*.firebaseapp.com
domain for your project as the redirect domain for your
app.
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 your
firebase::App
.
There is a one-to-one mapping between
App
and
Auth
.
firebase::auth::Auth* auth = firebase::auth::Auth::GetAuth(app);
Handle the sign-in flow with the Firebase SDK
To handle the sign-in flow with the Firebase SDK, follow these steps:
Construct an instance of a
FederatedOAuthProviderData
configured with
the provider ID appropriate for Yahoo.
firebase::auth::FederatedOAuthProviderData
provider_data(firebase::auth::YahooAuthProvider::kProviderId);
Optional
: Specify additional custom OAuth parameters that you want to
send with the OAuth request.
// Prompt user to re-authenticate to Yahoo.
provider_data.custom_parameters["prompt"] = "login";
// Localize to French.
provider_data.custom_parameters["language"] = "fr";
For the parameters Yahoo supports, see the
Yahoo OAuth documentation
.
Note that you can't pass Firebase-required parameters with
custom_parameters()
. These parameters are
client_id
,
redirect_uri
,
response_type
,
scope
and
state
.
Optional
: Specify additional OAuth 2.0 scopes beyond
profile
and
email
that you want to request from the authentication provider. If your
application requires access to private user data from Yahoo APIs, you'll
need to request permissions to Yahoo APIs under
API Permissions
in the
Yahoo developer console. Requested OAuth scopes must be exact matches to the
preconfigured ones in the app's API permissions. For example if, read/write
access is requested to user contacts and preconfigured in the app's API
permissions,
sdct-w
has to be passed instead of the readonly OAuth scope
sdct-r
. Otherwise,the flow will fail and an error would be shown to the
end user.
// Request access to Yahoo Mail API.
provider_data.scopes.push_back("mail-r");
// This must be preconfigured in the app's API permissions.
provider_data.scopes.push_back("sdct-w");
To learn more, refer to the
Yahoo scopes documentation
.
Once your provider data has been configured, use it to create a
FederatedOAuthProvider.
// Construct a FederatedOAuthProvider for use in Auth methods.
firebase::auth::FederatedOAuthProvider provider(provider_data);
Authenticate with Firebase using the Auth provider object. Note that unlike
other FirebaseAuth operations, this will take control of your UI by popping
up a web view in which the user can enter their credentials.
To start the sign in flow, call
SignInWithProvider
:
firebase::Future<firebase::auth::AuthResult> result =
auth->SignInWithProvider(provider_data);
Your application may then wait or
register a callback on the Future
.
While the above examples focus on sign-in flows, you also have the
ability to link a Yahoo provider to an existing user using
LinkWithProvider
. For example, you can link multiple
providers to the same user allowing them to sign in with either.
firebase::Future<firebase::auth::AuthResult> result = user.LinkWithProvider(provider_data);
The same pattern can be used with
ReauthenticateWithProvider
which can be
used to retrieve fresh credentials for sensitive operations that require
recent login.
firebase::Future<firebase::auth::AuthResult> result =
user.ReauthenticateWithProvider(provider_data);
Your application may then wait or
register a callback on
the Future
.
Advanced: Handle the sign-in flow manually
Unlike other OAuth providers supported by Firebase such as Google, Facebook,
and Twitter, where sign-in can directly be achieved with OAuth access token
based credentials, Firebase Auth does not support the same capability for
providers such as Yahoo due to the inability of the Firebase
Auth server to verify the audience of Yahoo OAuth access tokens.
This is a critical security requirement and could expose applications and
websites to replay attacks where a Yahoo OAuth access token obtained for
one project (attacker) can be used to sign in to another project (victim).
Instead, Firebase Auth offers the ability to handle the entire OAuth flow and
the authorization code exchange using the OAuth client ID and secret
configured in the Firebase Console. As the authorization code can only be used
in conjunction with a specific client ID/secret, an authorization code
obtained for one project cannot be used with another.
If these providers are required to be used in unsupported environments, a
third party OAuth library and
Firebase custom authentication
would need to be used. The former is needed to authenticate with the provider
and the latter to exchange the provider's credential for a custom token.
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();