[receiver/azuremonitor] Add support for azure workload identity auth (o…

…pen-telemetry#24543)

Enhances azuremonitor receiver authentication by using [azure workload
identity](https://azure.github.io/azure-workload-identity/docs/). I have
added a new config parameter `auth` to specify the used authentication
method (default set to service-principal) in order to possibly add more
methods in the future.

Fixes open-telemetry#24451 

**Testing:** Tested on my AKS

.chloggen/azuremonitor-workload-identity.yaml

@@ -0,0 +1,20 @@
+# Use this changelog template to create an entry for release notes.
+# If your change doesn't affect end users, such as a test fix or a tooling change,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: receiver/azuremonitorreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add support for authenticating using AD workload identity
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [24451]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

receiver/azuremonitorreceiver/README.md

@@ -18,20 +18,29 @@ This receiver scrapes Azure Monitor API for resources metrics.
 
 The following settings are required:
 - `subscription_id`
-- `tenant_id`
-- `client_id`
-- `client_secret`
 
 The following settings are optional:
+- `auth` (default = service_principal): Specifies the used authentication method. Supported values are `service_principal`, `workload_identity`.
 - `resource_groups` (default = none): Filter metrics for specific resource groups, not setting a value will scrape metrics for all resources in the subscription.
 - `services` (default = none): Filter metrics for specific services, not setting a value will scrape metrics for all services integrated with Azure Monitor.
 - `cache_resources` (default = 86400): List of resources will be cached for the provided amount of time in seconds.
 - `cache_resources_definitions` (default = 86400): List of metrics definitions will be cached for the provided amount of time in seconds.
 - `maximum_number_of_metrics_in_a_call` (default = 20): Maximum number of metrics to fetch in per API call, current limit in Azure is 20 (as of 03/27/2023).
 - `initial_delay` (default = `1s`): defines how long this receiver waits before starting.
 
-### Example Configuration
+Authenticating using service principal requires following additional settings:
+- `tenant_id`
+- `client_id`
+- `client_secret`
+
+Authenticating using workload identities requires following additional settings:
+- `tenant_id`
+- `client_id`
+- `federate_token_file`
+
+### Example Configurations
 
+Using Service Principal for authentication:
 ```yaml
 receivers:
   azuremonitor:
@@ -49,6 +58,17 @@ receivers:
     initial_delay: 1s
 ```
 
+Using Azure Workload Identity for authentication:
+```yaml
+receivers:
+  azuremonitor:
+    subscription_id: "${subscription_id}"
+    auth: "workload_identity"
+    tenant_id: "${env:AZURE_TENANT_ID}"
+    client_id: "${env:AZURE_CLIENT_ID}"
+    federated_token_file: "${env:AZURE_FEDERATED_TOKEN_FILE}"
+```
+
 ## Metrics
 
 Details about the metrics scraped by this receiver can be found in [Supported metrics with Azure Monitor](https://learn.microsoft.com/en-us/azure/azure-monitor/essentials/metrics-supported). This receiver adds the prefix "azure_" to all scraped metrics.

receiver/azuremonitorreceiver/config.go

@@ -5,6 +5,7 @@ package azuremonitorreceiver // import "github.com/open-telemetry/opentelemetry-
 
 import (
 	"errors"
+	"fmt"
 
 	"go.opentelemetry.io/collector/receiver/scraperhelper"
 	"go.uber.org/multierr"
@@ -18,6 +19,7 @@ var (
 	errMissingSubscriptionID = errors.New(`SubscriptionID" is not specified in config`)
 	errMissingClientID       = errors.New(`ClientID" is not specified in config`)
 	errMissingClientSecret   = errors.New(`ClientSecret" is not specified in config`)
+	errMissingFedTokenFile   = errors.New(`FederatedTokenFile is not specified in config`)
 
 	monitorServices = []string{
 		"Microsoft.EventGrid/eventSubscriptions",
@@ -224,9 +226,11 @@ type Config struct {
 	scraperhelper.ScraperControllerSettings `mapstructure:",squash"`
 	MetricsBuilderConfig                    metadata.MetricsBuilderConfig `mapstructure:",squash"`
 	SubscriptionID                          string                        `mapstructure:"subscription_id"`
+	Authentication                          string                        `mapstructure:"auth"`
 	TenantID                                string                        `mapstructure:"tenant_id"`
 	ClientID                                string                        `mapstructure:"client_id"`
 	ClientSecret                            string                        `mapstructure:"client_secret"`
+	FederatedTokenFile                      string                        `mapstructure:"federated_token_file"`
 	ResourceGroups                          []string                      `mapstructure:"resource_groups"`
 	Services                                []string                      `mapstructure:"services"`
 	CacheResources                          float64                       `mapstructure:"cache_resources"`
@@ -235,22 +239,44 @@ type Config struct {
 	AppendTagsAsAttributes                  bool                          `mapstructure:"append_tags_as_attributes"`
 }
 
+const (
+	servicePrincipal = "service_principal"
+	workloadIdentity = "workload_identity"
+)
+
 // Validate validates the configuration by checking for missing or invalid fields
 func (c Config) Validate() (err error) {
-	if c.TenantID == "" {
-		err = multierr.Append(err, errMissingTenantID)
-	}
-
 	if c.SubscriptionID == "" {
 		err = multierr.Append(err, errMissingSubscriptionID)
 	}
 
-	if c.ClientID == "" {
-		err = multierr.Append(err, errMissingClientID)
-	}
+	switch c.Authentication {
+	case servicePrincipal:
+		if c.TenantID == "" {
+			err = multierr.Append(err, errMissingTenantID)
+		}
+
+		if c.ClientID == "" {
+			err = multierr.Append(err, errMissingClientID)
+		}
+
+		if c.ClientSecret == "" {
+			err = multierr.Append(err, errMissingClientSecret)
+		}
+	case workloadIdentity:
+		if c.TenantID == "" {
+			err = multierr.Append(err, errMissingTenantID)
+		}
+
+		if c.ClientID == "" {
+			err = multierr.Append(err, errMissingClientID)
+		}
 
-	if c.ClientSecret == "" {
-		err = multierr.Append(err, errMissingClientSecret)
+		if c.FederatedTokenFile == "" {
+			err = multierr.Append(err, errMissingFedTokenFile)
+		}
+	default:
+		return fmt.Errorf("authentication %v is not supported. supported authentications include [%v,%v]", c.Authentication, servicePrincipal, workloadIdentity)
 	}
 
 	return

receiver/azuremonitorreceiver/factory.go

@@ -41,6 +41,7 @@ func createDefaultConfig() component.Config {
 		CacheResourcesDefinitions:     24 * 60 * 60,
 		MaximumNumberOfMetricsInACall: 20,
 		Services:                      monitorServices,
+		Authentication:                servicePrincipal,
 	}
 }
 

receiver/azuremonitorreceiver/factory_test.go

@@ -44,6 +44,7 @@ func TestNewFactory(t *testing.T) {
 					CacheResources:                24 * 60 * 60,
 					CacheResourcesDefinitions:     24 * 60 * 60,
 					MaximumNumberOfMetricsInACall: 20,
+					Authentication:                servicePrincipal,
 				}
 
 				require.Equal(t, expectedCfg, factory.CreateDefaultConfig())

receiver/azuremonitorreceiver/go.mod

@@ -3,8 +3,8 @@ module github.com/open-telemetry/opentelemetry-collector-contrib/receiver/azurem
 go 1.20
 
 require (
-	github.com/Azure/azure-sdk-for-go/sdk/azcore v1.3.1
-	github.com/Azure/azure-sdk-for-go/sdk/azidentity v1.2.1
+	github.com/Azure/azure-sdk-for-go/sdk/azcore v1.6.0
+	github.com/Azure/azure-sdk-for-go/sdk/azidentity v1.3.0
 	github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/monitor/armmonitor v0.8.0
 	github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/resources/armresources v1.0.0
 	github.com/google/go-cmp v0.5.9
@@ -21,14 +21,14 @@ require (
 )
 
 require (
-	github.com/Azure/azure-sdk-for-go/sdk/internal v1.1.2 // indirect
-	github.com/AzureAD/microsoft-authentication-library-for-go v0.8.1 // indirect
+	github.com/Azure/azure-sdk-for-go/sdk/internal v1.3.0 // indirect
+	github.com/AzureAD/microsoft-authentication-library-for-go v1.0.0 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/go-logr/logr v1.2.4 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
-	github.com/golang-jwt/jwt/v4 v4.4.2 // indirect
+	github.com/golang-jwt/jwt/v4 v4.5.0 // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/google/uuid v1.3.1 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
@@ -41,7 +41,7 @@ require (
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.86.0 // indirect
-	github.com/pkg/browser v0.0.0-20210115035449-ce105d075bb4 // indirect
+	github.com/pkg/browser v0.0.0-20210911075715-681adbf594b8 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	go.opencensus.io v0.24.0 // indirect
 	go.opentelemetry.io/collector v0.86.0 // indirect

receiver/azuremonitorreceiver/scraper.go

@@ -83,6 +83,7 @@ func newScraper(conf *Config, settings receiver.CreateSettings) *azureScraper {
 		settings:                        settings.TelemetrySettings,
 		mb:                              metadata.NewMetricsBuilder(conf.MetricsBuilderConfig, settings),
 		azIDCredentialsFunc:             azidentity.NewClientSecretCredential,
+		azIDWorkloadFunc:                azidentity.NewWorkloadIdentityCredential,
 		armClientFunc:                   armresources.NewClient,
 		armMonitorDefinitionsClientFunc: armmonitor.NewMetricDefinitionsClient,
 		armMonitorMetricsClientFunc:     armmonitor.NewMetricsClient,
@@ -103,6 +104,7 @@ type azureScraper struct {
 	resourcesUpdated                time.Time
 	mb                              *metadata.MetricsBuilder
 	azIDCredentialsFunc             func(string, string, string, *azidentity.ClientSecretCredentialOptions) (*azidentity.ClientSecretCredential, error)
+	azIDWorkloadFunc                func(options *azidentity.WorkloadIdentityCredentialOptions) (*azidentity.WorkloadIdentityCredential, error)
 	armClientFunc                   func(string, azcore.TokenCredential, *arm.ClientOptions) (*armresources.Client, error)
 	armMonitorDefinitionsClientFunc func(azcore.TokenCredential, *arm.ClientOptions) (*armmonitor.MetricDefinitionsClient, error)
 	armMonitorMetricsClientFunc     func(azcore.TokenCredential, *arm.ClientOptions) (*armmonitor.MetricsClient, error)
@@ -139,8 +141,7 @@ func (s *azureScraper) GetMetricsValuesClient() MetricsValuesClient {
 }
 
 func (s *azureScraper) start(_ context.Context, _ component.Host) (err error) {
-	s.cred, err = s.azIDCredentialsFunc(s.cfg.TenantID, s.cfg.ClientID, s.cfg.ClientSecret, nil)
-	if err != nil {
+	if err = s.loadCredentials(); err != nil {
 		return err
 	}
 
@@ -153,6 +154,22 @@ func (s *azureScraper) start(_ context.Context, _ component.Host) (err error) {
 	return
 }
 
+func (s *azureScraper) loadCredentials() (err error) {
+	switch s.cfg.Authentication {
+	case servicePrincipal:
+		if s.cred, err = s.azIDCredentialsFunc(s.cfg.TenantID, s.cfg.ClientID, s.cfg.ClientSecret, nil); err != nil {
+			return err
+		}
+	case workloadIdentity:
+		if s.cred, err = s.azIDWorkloadFunc(nil); err != nil {
+			return err
+		}
+	default:
+		return fmt.Errorf("unknown authentication %v", s.cfg.Authentication)
+	}
+	return nil
+}
+
 func (s *azureScraper) scrape(ctx context.Context) (pmetric.Metrics, error) {
 
 	s.getResources(ctx)