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#gRPC Authentication support |
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|
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gRPC is designed to plug-in a number of authentication mechanisms. This document |
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provides a quick overview of the various auth mechanisms supported, discusses |
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the API with some examples, and concludes with a discussion of extensibility. |
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More documentation and examples are coming soon! |
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|
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## Supported auth mechanisms |
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|
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###SSL/TLS |
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gRPC has SSL/TLS integration and promotes the use of SSL/TLS to authenticate the |
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server, and encrypt all the data exchanged between the client and the server. |
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Optional mechanisms are available for clients to provide certificates to |
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accomplish mutual authentication. |
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|
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###OAuth 2.0 |
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gRPC provides a generic mechanism (described below) to attach metadata to |
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requests and responses. This mechanism can be used to attach OAuth 2.0 Access |
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Tokens to RPCs being made at a client. Additional support for acquiring Access |
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Tokens while accessing Google APIs through gRPC is provided for certain auth |
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flows, demonstrated through code examples below. |
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|
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## API |
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To reduce complexity and minimize API clutter, gRPC works with a unified concept |
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of a Credentials object. Users construct gRPC credentials using corresponding |
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bootstrap credentials (e.g., SSL client certs or Service Account Keys), and use |
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the credentials while creating a gRPC channel to any server. Depending on the |
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type of credential supplied, the channel uses the credentials during the initial |
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SSL/TLS handshake with the server, or uses the credential to generate and |
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attach Access Tokens to each request being made on the channel. |
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|
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###SSL/TLS for server authentication and encryption |
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This is the simplest authentication scenario, where a client just wants to |
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authenticate the server and encrypt all data. |
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|
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```cpp |
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SslCredentialsOptions ssl_opts; // Options to override SSL params, empty by default |
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// Create the credentials object by providing service account key in constructor |
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std::shared_ptr<ChannelCredentials> creds = SslCredentials(ssl_opts); |
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// Create a channel using the credentials created in the previous step |
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std::shared_ptr<Channel> channel = CreateChannel(server_name, creds); |
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// Create a stub on the channel |
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std::unique_ptr<Greeter::Stub> stub(Greeter::NewStub(channel)); |
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// Make actual RPC calls on the stub. |
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grpc::Status s = stub->sayHello(&context, *request, response); |
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``` |
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For advanced use cases such as modifying the root CA or using client certs, |
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the corresponding options can be set in the SslCredentialsOptions parameter |
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passed to the factory method. |
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###Authenticating with Google |
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gRPC applications can use a simple API to create a credential that works in various deployment scenarios. |
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```cpp |
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std::shared_ptr<ChannelCredentials> creds = GoogleDefaultCredentials(); |
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// Create a channel, stub and make RPC calls (same as in the previous example) |
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std::shared_ptr<Channel> channel = CreateChannel(server_name, creds); |
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std::unique_ptr<Greeter::Stub> stub(Greeter::NewStub(channel)); |
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grpc::Status s = stub->sayHello(&context, *request, response); |
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``` |
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This credential works for applications using Service Accounts as well as for |
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applications running in [Google Compute Engine (GCE)](https://cloud.google.com/compute/). In the former case, the |
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service account’s private keys are loaded from the file named in the environment |
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variable `GOOGLE_APPLICATION_CREDENTIALS`. The |
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keys are used to generate bearer tokens that are attached to each outgoing RPC |
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on the corresponding channel. |
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|
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For applications running in GCE, a default service account and corresponding |
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OAuth scopes can be configured during VM setup. At run-time, this credential |
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handles communication with the authentication systems to obtain OAuth2 access |
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tokens and attaches them to each outgoing RPC on the corresponding channel. |
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Extending gRPC to support other authentication mechanisms |
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The gRPC protocol is designed with a general mechanism for sending metadata |
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associated with RPC. Clients can send metadata at the beginning of an RPC and |
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servers can send back metadata at the beginning and end of the RPC. This |
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provides a natural mechanism to support OAuth2 and other authentication |
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mechanisms that need attach bearer tokens to individual request. |
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|
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In the simplest case, there is a single line of code required on the client |
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to add a specific token as metadata to an RPC and a corresponding access on |
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the server to retrieve this piece of metadata. The generation of the token |
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on the client side and its verification at the server can be done separately. |
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A deeper integration can be achieved by plugging in a gRPC credentials implementation for any custom authentication mechanism that needs to attach per-request tokens. gRPC internals also allow switching out SSL/TLS with other encryption mechanisms. |
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## Examples |
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These authentication mechanisms will be available in all gRPC's supported languages. |
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The following sections demonstrate how authentication and authorization features described above appear in each language: more languages are coming soon. |
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###SSL/TLS for server authentication and encryption (Ruby) |
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```ruby |
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# Base case - No encryption |
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stub = Helloworld::Greeter::Stub.new('localhost:50051') |
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... |
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# With server authentication SSL/TLS |
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creds = GRPC::Core::Credentials.new(load_certs) # load_certs typically loads a CA roots file |
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stub = Helloworld::Greeter::Stub.new('localhost:50051', creds: creds) |
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``` |
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|
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###SSL/TLS for server authentication and encryption (C#) |
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```csharp |
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// Base case - No encryption |
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var channel = new Channel("localhost:50051"); |
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var client = new Greeter.GreeterClient(channel); |
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... |
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// With server authentication SSL/TLS |
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var credentials = new SslCredentials(File.ReadAllText("ca.pem")); // Load a CA file |
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var channel = new Channel("localhost:50051", credentials); |
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var client = new Greeter.GreeterClient(channel); |
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``` |
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###SSL/TLS for server authentication and encryption (Objective-C) |
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The default for Objective-C is to use SSL/TLS, as that's the most common use case when accessing |
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remote APIs. |
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```objective-c |
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// Base case - With server authentication SSL/TLS |
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HLWGreeter *client = [[HLWGreeter alloc] initWithHost:@"localhost:50051"]; |
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// Same as using @"https://localhost:50051". |
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... |
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|
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// No encryption |
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HLWGreeter *client = [[HLWGreeter alloc] initWithHost:@"http://localhost:50051"]; |
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// Specifying the HTTP scheme explicitly forces no encryption. |
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``` |
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|
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###SSL/TLS for server authentication and encryption (Python) |
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```python |
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# Base case - No encryption |
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stub = early_adopter_create_GreeterService_stub('localhost', 50051) |
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... |
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# With server authentication SSL/TLS |
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stub = early_adopter_create_GreeterService_stub( |
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'localhost', 50051, secure=True, root_certificates=open('ca.pem').read()) |
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... |
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``` |
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n.b.: the beta API will look different |
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###Authenticating with Google (Ruby) |
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```ruby |
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# Base case - No encryption/authorization |
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stub = Helloworld::Greeter::Stub.new('localhost:50051') |
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... |
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# Authenticating with Google |
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require 'googleauth' # from http://www.rubydoc.info/gems/googleauth/0.1.0 |
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... |
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creds = GRPC::Core::Credentials.new(load_certs) # load_certs typically loads a CA roots file |
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scope = 'https://www.googleapis.com/auth/grpc-testing' |
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authorization = Google::Auth.get_application_default(scope) |
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stub = Helloworld::Greeter::Stub.new('localhost:50051', |
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creds: creds, |
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update_metadata: authorization.updater_proc) |
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``` |
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###Authenticating with Google (Node.js) |
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```node |
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// Base case - No encryption/authorization |
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var stub = new helloworld.Greeter('localhost:50051'); |
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... |
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// Authenticating with Google |
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var GoogleAuth = require('google-auth-library'); // from https://www.npmjs.com/package/google-auth-library |
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... |
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var creds = grpc.Credentials.createSsl(load_certs); // load_certs typically loads a CA roots file |
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var scope = 'https://www.googleapis.com/auth/grpc-testing'; |
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(new GoogleAuth()).getApplicationDefault(function(err, auth) { |
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if (auth.createScopeRequired()) { |
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auth = auth.createScoped(scope); |
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} |
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var stub = new helloworld.Greeter('localhost:50051', |
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{credentials: creds}, |
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grpc.getGoogleAuthDelegate(auth)); |
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}); |
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``` |
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###Authenticating with Google (C#) |
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```csharp |
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// Base case - No encryption/authorization |
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var channel = new Channel("localhost:50051"); |
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var client = new Greeter.GreeterClient(channel); |
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... |
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// Authenticating with Google |
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using Grpc.Auth; // from Grpc.Auth NuGet package |
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... |
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var credentials = new SslCredentials(File.ReadAllText("ca.pem")); // Load a CA file |
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var channel = new Channel("localhost:50051", credentials); |
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string scope = "https://www.googleapis.com/auth/grpc-testing"; |
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var authorization = GoogleCredential.GetApplicationDefault(); |
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if (authorization.IsCreateScopedRequired) |
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{ |
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authorization = credential.CreateScoped(new[] { scope }); |
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} |
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var client = new Greeter.GreeterClient(channel, |
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new StubConfiguration(OAuth2InterceptorFactory.Create(credential))); |
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``` |
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###Authenticating with Google (PHP) |
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```php |
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// Base case - No encryption/authorization |
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$client = new helloworld\GreeterClient( |
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new Grpc\BaseStub('localhost:50051', [])); |
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... |
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// Authenticating with Google |
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// the environment variable "GOOGLE_APPLICATION_CREDENTIALS" needs to be set |
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$scope = "https://www.googleapis.com/auth/grpc-testing"; |
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$auth = Google\Auth\ApplicationDefaultCredentials::getCredentials($scope); |
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$opts = [ |
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'credentials' => Grpc\Credentials::createSsl(file_get_contents('ca.pem')); |
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'update_metadata' => $auth->getUpdateMetadataFunc(), |
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]; |
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$client = new helloworld\GreeterClient( |
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new Grpc\BaseStub('localhost:50051', $opts)); |
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``` |
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###Authenticating with Google (Objective-C) |
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This example uses the [Google iOS Sign-In library](https://developers.google.com/identity/sign-in/ios/), |
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but it's easily extrapolated to any other OAuth2 library. |
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```objective-c |
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// Base case - No authentication |
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[client sayHelloWithRequest:request handler:^(HLWHelloReply *response, NSError *error) { |
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... |
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}]; |
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... |
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// Authenticating with Google |
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// When signing the user in, ask her for the relevant scopes. |
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GIDSignIn.sharedInstance.scopes = @[@"https://www.googleapis.com/auth/grpc-testing"]; |
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... |
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#import <ProtoRPC/ProtoRPC.h> |
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// Create a not-yet-started RPC. We want to set the request headers on this object before starting |
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// it. |
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ProtoRPC *call = |
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[client RPCToSayHelloWithRequest:request handler:^(HLWHelloReply *response, NSError *error) { |
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... |
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}]; |
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// Set the access token to be used. |
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NSString *accessToken = GIDSignIn.sharedInstance.currentUser.authentication.accessToken; |
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call.requestMetadata[@"Authorization"] = [@"Bearer " stringByAppendingString:accessToken]}]; |
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// Start the RPC. |
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[call start]; |
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``` |
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You can see a working example app, with a more detailed explanation, [here](examples/objective-c/auth_sample). |
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### Authenticating with Google (Python) |
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```python |
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# Base case - No encryption |
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stub = early_adopter_create_GreeterService_stub('localhost', 50051) |
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... |
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# With server authentication SSL/TLS |
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import oauth2client.client |
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credentials = oauth2client.GoogleCredentials.get_application_default() |
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scope = 'https://www.googleapis.com/auth/grpc-testing' |
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scoped_credentials = credentials.create_scoped([scope]) |
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access_token = scoped_credentials.get_access_token().access_token |
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metadata_transformer = ( |
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lambda x: [('Authorization', 'Bearer {}'.format(access_token))]) |
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stub = early_adopter_create_GreeterService_stub( |
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'localhost', 50051, secure=True, root_certificates=open('ca.pem').read(), |
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metadata_transformer=metadata_transformer) |
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... |
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``` |
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n.b.: the beta API will look different |
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