Add an experimental googleclientauth extension (#703)

* add gcp client auth extension

extension/googleclientauthextension/README.md

@@ -0,0 +1,53 @@
+# Authenticator - Google Client Credentials
+
+| Status        |           |
+| ------------- |-----------|
+| Stability     | [alpha]  |
+
+[alpha]: https://github.com/open-telemetry/opentelemetry-collector#alpha
+
+This extension provides Google OAuth2 Client Credentials and Metadata for gRPC and http based exporters.
+
+The authenticator type has to be set to `googleclientauth`.
+
+## Configuration
+
+```yaml
+extensions:
+  googleclientauth:
+
+receivers:
+  otlp:
+    protocols:
+      grpc:
+
+exporters:
+  otlp/withauth:
+    endpoint: 0.0.0.0:5000
+    ca_file: /tmp/certs/ca.pem
+    auth:
+      authenticator: googleclientauth
+
+service:
+  extensions: [googleclientauth]
+  pipelines:
+    metrics:
+      receivers: [otlp]
+      processors: []
+      exporters: [otlp/withauth]
+```
+
+Following are the configuration fields:
+- **project** - The Google Cloud Project telemetry is sent to if the gcp.project.id resource attribute is not set. If unspecified, this is determined using application default credentials.
+- [**scopes**](https://datatracker.ietf.org/doc/html/rfc6749#section-3.3) - The oauth 2.0 scopes requested by the extension.
+- [**quota_project**](https://cloud.google.com/apis/docs/system-parameters) - The project for quota and billing purposes. The caller must have serviceusage.services.use permission on the project.
+
+## Building into a Collector
+
+This extension is not included in any collector distributions today. To build a collector with this component, add the following to your collector builder configuration:
+
+```yaml
+extensions:
+  - import: github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension
+    gomod: github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension v0.43.0
+```

extension/googleclientauthextension/config.go

@@ -0,0 +1,61 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package googleclientauthextension // import "github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension"
+
+import (
+	"go.opentelemetry.io/collector/component"
+)
+
+// Config stores the configuration for GCP Client Credentials.
+type Config struct {
+	// Project is the project telemetry is sent to if the gcp.project.id
+	// resource attribute is not set. If unspecified, this is determined using
+	// application default credentials.
+	Project string `mapstructure:"project"`
+
+	// QuotaProject specifies a project for quota and billing purposes. The
+	// caller must have serviceusage.services.use permission on the project.
+	//
+	// For more information please read:
+	// https://cloud.google.com/apis/docs/system-parameters
+	QuotaProject string `mapstructure:"quota_project"`
+
+	// Scope specifies optional requested permissions.
+	// See https://datatracker.ietf.org/doc/html/rfc6749#section-3.3
+	Scopes []string `mapstructure:"scopes,omitempty"`
+
+	// TODO: Support impersonation, similar to what exists in the googlecloud collector exporter.
+}
+
+var _ component.Config = (*Config)(nil)
+
+// Validate checks if the extension configuration is valid.
+func (cfg *Config) Validate() error {
+	return nil
+}
+
+// defaultScopes are the scopes required for writing logs, metrics, and traces.
+var defaultScopes = []string{
+	"https://www.googleapis.com/auth/cloud-platform",
+	"https://www.googleapis.com/auth/logging.write",
+	"https://www.googleapis.com/auth/monitoring.write",
+	"https://www.googleapis.com/auth/trace.append",
+}
+
+func createDefaultConfig() component.Config {
+	return &Config{
+		Scopes: defaultScopes,
+	}
+}

extension/googleclientauthextension/config_test.go

@@ -0,0 +1,57 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package googleclientauthextension // import "github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension"
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/confmap/confmaptest"
+
+	"github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension/internal/metadata"
+)
+
+func TestLoadConfig(t *testing.T) {
+	cm, err := confmaptest.LoadConf(filepath.Join("testdata", "config.yaml"))
+	require.NoError(t, err)
+	factory := NewFactory()
+	cfg := factory.CreateDefaultConfig()
+
+	sub, err := cm.Sub(component.NewIDWithName(metadata.Type, "").String())
+	require.NoError(t, err)
+	require.NoError(t, component.UnmarshalConfig(sub, cfg))
+
+	assert.Equal(t, cfg.(*Config), factory.CreateDefaultConfig().(*Config))
+
+	sub, err = cm.Sub(component.NewIDWithName(metadata.Type, "customname").String())
+	require.NoError(t, err)
+	require.NoError(t, component.UnmarshalConfig(sub, cfg))
+
+	assert.Equal(t,
+		&Config{
+			Project:      "my-project",
+			Scopes:       []string{"https://www.something.com/hello", "https://www.something.com/world"},
+			QuotaProject: "other-project",
+		},
+		cfg,
+	)
+}
+
+func TestValidate(t *testing.T) {
+	assert.NoError(t, NewFactory().CreateDefaultConfig().(*Config).Validate())
+}

extension/googleclientauthextension/doc.go

@@ -0,0 +1,17 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package googleclientauthextension provides gRPC and HTTP credentials and metadata
+// using Application Default Credentials: https://cloud.google.com/docs/authentication#adc
+package googleclientauthextension // import "github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension"

extension/googleclientauthextension/factory.go

@@ -0,0 +1,88 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package googleclientauthextension // import "github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension"
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/extension"
+	"go.opentelemetry.io/collector/extension/auth"
+	"golang.org/x/oauth2/google"
+	"google.golang.org/grpc/credentials/oauth"
+
+	"github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension/internal/metadata"
+)
+
+// NewFactory creates a factory for the GCP Auth extension.
+func NewFactory() extension.Factory {
+	return extension.NewFactory(
+		metadata.Type,
+		createDefaultConfig,
+		createExtension,
+		metadata.ExtensionStability,
+	)
+}
+
+func createExtension(ctx context.Context, set extension.CreateSettings, cfg component.Config) (extension.Extension, error) {
+	config := cfg.(*Config)
+	creds, err := google.FindDefaultCredentials(ctx, config.Scopes...)
+	if err != nil {
+		return nil, err
+	}
+	if config.Project == "" {
+		config.Project = creds.ProjectID
+	}
+	if config.Project == "" {
+		return nil, errors.New("no project set in config or found with application default credentials")
+	}
+	if config.QuotaProject == "" {
+		config.QuotaProject = quotaProjectFromCreds(creds)
+	}
+
+	ca := clientAuthenticator{
+		TokenSource: oauth.TokenSource{TokenSource: creds.TokenSource},
+		config:      config,
+	}
+
+	return auth.NewClient(
+		auth.WithClientRoundTripper(ca.roundTripper),
+		auth.WithClientPerRPCCredentials(ca.perRPCCredentials),
+	), nil
+}
+
+// clientAuthenticator supplies credentials from an oauth.TokenSource.
+type clientAuthenticator struct {
+	oauth.TokenSource
+	config *Config
+}
+
+// quotaProjectFromCreds retrieves quota project from the credentials file.
+// Based on how the google go client gets quota project:
+// https://github.com/googleapis/google-api-go-client/blob/113082d14d54f188d1b6c34c652e416592fc51b5/internal/creds.go#L159
+func quotaProjectFromCreds(creds *google.Credentials) string {
+	if creds == nil {
+		return ""
+	}
+	var v struct {
+		QuotaProject string `json:"quota_project_id"`
+	}
+	if err := json.Unmarshal(creds.JSON, &v); err != nil {
+		return ""
+	}
+	return v.QuotaProject
+}

extension/googleclientauthextension/factory_test.go

@@ -0,0 +1,43 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package googleclientauthextension // import "github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension"
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/extension"
+)
+
+func TestCreateDefaultConfig(t *testing.T) {
+	factory := NewFactory()
+	cfg := factory.CreateDefaultConfig()
+	assert.NotNil(t, cfg, "failed to create default config")
+	assert.NoError(t, componenttest.CheckConfigStruct(cfg))
+}
+
+func TestNewFactory(t *testing.T) {
+	f := NewFactory()
+	assert.NotNil(t, f)
+}
+
+func TestCreateExtension(t *testing.T) {
+	t.Setenv("GOOGLE_APPLICATION_CREDENTIALS", "testdata/fake_creds.json")
+	ext, err := NewFactory().CreateExtension(context.Background(), extension.CreateSettings{}, createDefaultConfig())
+	assert.NotNil(t, ext)
+	assert.NoError(t, err)
+}

extension/googleclientauthextension/go.mod

@@ -0,0 +1,48 @@
+module github.com/GoogleCloudPlatform/opentelemetry-operations-go/extension/googleclientauthextension
+
+go 1.19
+
+require (
+	github.com/stretchr/testify v1.8.4
+	go.opentelemetry.io/collector/component v0.82.0
+	go.opentelemetry.io/collector/confmap v0.82.0
+	go.opentelemetry.io/collector/extension v0.82.0
+	go.opentelemetry.io/collector/extension/auth v0.82.0
+	golang.org/x/oauth2 v0.10.0
+	google.golang.org/grpc v1.57.0
+)
+
+require (
+	cloud.google.com/go/compute v1.20.1 // indirect
+	cloud.google.com/go/compute/metadata v0.2.3 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang/protobuf v1.5.3 // indirect
+	github.com/knadh/koanf v1.5.0 // indirect
+	github.com/knadh/koanf/v2 v2.0.1 // indirect
+	github.com/mitchellh/copystructure v1.2.0 // indirect
+	github.com/mitchellh/mapstructure v1.5.1-0.20220423185008-bf980b35cac4 // indirect
+	github.com/mitchellh/reflectwalk v1.0.2 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/collector/config/configtelemetry v0.82.0 // indirect
+	go.opentelemetry.io/collector/featuregate v1.0.0-rcv0014 // indirect
+	go.opentelemetry.io/collector/pdata v1.0.0-rcv0014 // indirect
+	go.opentelemetry.io/otel v1.16.0 // indirect
+	go.opentelemetry.io/otel/metric v1.16.0 // indirect
+	go.opentelemetry.io/otel/trace v1.16.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
+	go.uber.org/zap v1.25.0 // indirect
+	golang.org/x/net v0.12.0 // indirect
+	golang.org/x/sys v0.10.0 // indirect
+	golang.org/x/text v0.11.0 // indirect
+	google.golang.org/appengine v1.6.7 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20230530153820-e85fd2cbaebc // indirect
+	google.golang.org/protobuf v1.31.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
+
+retract (
+	v0.76.2
+	v0.76.1
+	v0.65.0
+)