// Create a default SSL ChannelCredentials object.
auto channel_creds = grpc::SslCredentials(grpc::SslCredentialsOptions());
// Create a channel using the credentials created in the previous step.
auto channel = grpc::CreateChannel(server_name, channel_creds);
// Create a stub on the channel.
std::unique_ptr<Greeter::Stub> stub(Greeter::NewStub(channel));
// Make actual RPC calls on the stub.
grpc::Status s = stub->sayHello(&context, *request, response);

auto creds = grpc::GoogleDefaultCredentials();
// Create a channel, stub and make RPC calls (same as in the previous example)
auto channel = grpc::CreateChannel(server_name, creds);
std::unique_ptr<Greeter::Stub> stub(Greeter::NewStub(channel));
grpc::Status s = stub->sayHello(&context, *request, response);

class MyCustomAuthenticator : public grpc::MetadataCredentialsPlugin {
 public:
  MyCustomAuthenticator(const grpc::string& ticket) : ticket_(ticket) {}

  grpc::Status GetMetadata(
      grpc::string_ref service_url, grpc::string_ref method_name,
      const grpc::AuthContext& channel_auth_context,
      std::multimap<grpc::string, grpc::string>* metadata) override {
    metadata->insert(std::make_pair("x-custom-auth-ticket", ticket_));
    return grpc::Status::OK;
  }

 private:
  grpc::string ticket_;
};

auto call_creds = grpc::MetadataCredentialsFromPlugin(
    std::unique_ptr<grpc::MetadataCredentialsPlugin>(
        new MyCustomAuthenticator("super-secret-ticket")));

stub = Helloworld::Greeter::Stub.new('localhost:50051', :this_channel_is_insecure)
...

creds = GRPC::Core::ChannelCredentials.new(load_certs)  # load_certs typically loads a CA roots file
stub = Helloworld::Greeter::Stub.new('myservice.example.com', creds)

require 'googleauth'  # from http://www.rubydoc.info/gems/googleauth/0.1.0
...
ssl_creds = GRPC::Core::ChannelCredentials.new(load_certs)  # load_certs typically loads a CA roots file
authentication = Google::Auth.get_application_default()
call_creds = GRPC::Core::CallCredentials.new(authentication.updater_proc)
combined_creds = ssl_creds.compose(call_creds)
stub = Helloworld::Greeter::Stub.new('greeter.googleapis.com', combined_creds)

var stub = new helloworld.Greeter('localhost:50051', grpc.credentials.createInsecure());

const root_cert = fs.readFileSync('path/to/root-cert');
const ssl_creds = grpc.credentials.createSsl(root_cert);
const stub = new helloworld.Greeter('myservice.example.com', ssl_creds);

// Authenticating with Google
var GoogleAuth = require('google-auth-library'); // from https://www.npmjs.com/package/google-auth-library
...
var ssl_creds = grpc.credentials.createSsl(root_certs);
(new GoogleAuth()).getApplicationDefault(function(err, auth) {
  var call_creds = grpc.credentials.createFromGoogleCredential(auth);
  var combined_creds = grpc.credentials.combineChannelCredentials(ssl_creds, call_creds);
  var stub = new helloworld.Greeter('greeter.googleapis.com', combined_credentials);
});

var GoogleAuth = require('google-auth-library'); // from https://www.npmjs.com/package/google-auth-library
...
var ssl_creds = grpc.Credentials.createSsl(root_certs); // load_certs typically loads a CA roots file
var scope = 'https://www.googleapis.com/auth/grpc-testing';
(new GoogleAuth()).getApplicationDefault(function(err, auth) {
  if (auth.createScopeRequired()) {
    auth = auth.createScoped(scope);
  }
  var call_creds = grpc.credentials.createFromGoogleCredential(auth);
  var combined_creds = grpc.credentials.combineChannelCredentials(ssl_creds, call_creds);
  var stub = new helloworld.Greeter('greeter.googleapis.com', combined_credentials);
});

const rootCert = fs.readFileSync('path/to/root-cert');
const channelCreds = grpc.credentials.createSsl(rootCert);
const metaCallback = (_params, callback) => {
    const meta = new grpc.Metadata();
    meta.add('custom-auth-header', 'token');
    callback(null, meta);
}
const callCreds = grpc.credentials.createFromMetadataGenerator(metaCallback);
const combCreds = grpc.credentials.combineChannelCredentials(channelCreds, callCreds);
const stub = new helloworld.Greeter('myservice.example.com', combCreds);

$client = new helloworld\GreeterClient('localhost:50051', [
    'credentials' => Grpc\ChannelCredentials::createInsecure(),
]);

$client = new helloworld\GreeterClient('myservice.example.com', [
    'credentials' => Grpc\ChannelCredentials::createSsl(file_get_contents('roots.pem')),
]);

function updateAuthMetadataCallback($context)
{
    $auth_credentials = ApplicationDefaultCredentials::getCredentials();
    return $auth_credentials->updateMetadata($metadata = [], $context->service_url);
}
$channel_credentials = Grpc\ChannelCredentials::createComposite(
    Grpc\ChannelCredentials::createSsl(file_get_contents('roots.pem')),
    Grpc\CallCredentials::createFromPlugin('updateAuthMetadataCallback')
);
$opts = [
  'credentials' => $channel_credentials
];
$client = new helloworld\GreeterClient('greeter.googleapis.com', $opts);

// the environment variable "GOOGLE_APPLICATION_CREDENTIALS" needs to be set
$scope = "https://www.googleapis.com/auth/grpc-testing";
$auth = Google\Auth\ApplicationDefaultCredentials::getCredentials($scope);
$opts = [
  'credentials' => Grpc\Credentials::createSsl(file_get_contents('roots.pem'));
  'update_metadata' => $auth->getUpdateMetadataFunc(),
];
$client = new helloworld\GreeterClient('greeter.googleapis.com', $opts);

final channel = new ClientChannel('localhost',
      port: 50051,
      options: const ChannelOptions(
          credentials: const ChannelCredentials.insecure()));
final stub = new GreeterClient(channel);

// Load a custom roots file.
final trustedRoot = new File('roots.pem').readAsBytesSync();
final channelCredentials =
    new ChannelCredentials.secure(certificates: trustedRoot);
final channelOptions = new ChannelOptions(credentials: channelCredentials);
final channel = new ClientChannel('myservice.example.com',
    options: channelOptions);
final client = new GreeterClient(channel);

// Uses publicly trusted roots by default.
final channel = new ClientChannel('greeter.googleapis.com');
final serviceAccountJson =
     new File('service-account.json').readAsStringSync();
final credentials = new JwtServiceAccountAuthenticator(serviceAccountJson);
final client =
    new GreeterClient(channel, options: credentials.toCallOptions);

// Uses publicly trusted roots by default.
final channel = new ClientChannel('greeter.googleapis.com');
final client = new GreeterClient(channel);
...
final serviceAccountJson =
     new File('service-account.json').readAsStringSync();
final credentials = new JwtServiceAccountAuthenticator(serviceAccountJson);
final response =
    await client.sayHello(request, options: credentials.toCallOptions);