feat(): add ManagedIdentity in Azure Blob Storage (#4858)

* feat(): add ManagedIdentity in Azure

* fix(): fix merge error

* fix(): fix a problem during conflict resolving

* fix(): fix the problems based on reviews

* feat(): add deps

* Update pkg/storage/chunk/azure/blob_storage_client.go

* chore(): adjust mi logics

Co-authored-by: Cyril Tovena <cyril.tovena@gmail.com>

docs/sources/configuration/_index.md

@@ -707,6 +707,10 @@ The `azure_storage_config` configures Azure as a general storage for different d
 # Maximum time to wait before retrying a request.
 # CLI flag: -<prefix>.azure.max-retry-delay
 [max_retry_delay: <duration> | default = 500ms]
+
+# Use Managed Identity or not.
+# CLI flag: -ruler.storage.azure.use-managed-identity
+[use_managed_identity: <boolean> | default = false]
 ```
 
 ## gcs_storage_config

docs/sources/storage/_index.md

@@ -307,6 +307,7 @@ storage_config:
     # See https://docs.microsoft.com/en-us/azure/storage/blobs/storage-blobs-introduction#containers
     container_name: <container-name>
     request_timeout: 0
+    use_managed_identity: <true|false>
   boltdb_shipper:
     active_index_directory: /data/loki/boltdb-shipper-active
     cache_location: /data/loki/boltdb-shipper-cache

go.mod

@@ -8,6 +8,7 @@ require (
 	cloud.google.com/go/storage v1.10.0
 	github.com/Azure/azure-pipeline-go v0.2.3
 	github.com/Azure/azure-storage-blob-go v0.13.0
+	github.com/Azure/go-autorest/autorest/adal v0.9.17
 	github.com/Masterminds/sprig/v3 v3.2.2
 	github.com/NYTimes/gziphandler v1.1.1
 	github.com/Shopify/sarama v1.30.0
@@ -114,7 +115,6 @@ require (
 	github.com/Azure/go-ansiterm v0.0.0-20210617225240-d185dfc1b5a1 // indirect
 	github.com/Azure/go-autorest v14.2.0+incompatible // indirect
 	github.com/Azure/go-autorest/autorest v0.11.22 // indirect
-	github.com/Azure/go-autorest/autorest/adal v0.9.17 // indirect
 	github.com/Azure/go-autorest/autorest/azure/auth v0.5.8 // indirect
 	github.com/Azure/go-autorest/autorest/azure/cli v0.4.2 // indirect
 	github.com/Azure/go-autorest/autorest/date v0.3.0 // indirect

pkg/storage/chunk/azure/blob_storage_client.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/Azure/azure-pipeline-go/pipeline"
 	"github.com/Azure/azure-storage-blob-go/azblob"
+	"github.com/Azure/go-autorest/autorest/adal"
 	"github.com/mattn/go-ieproxy"
 	"github.com/prometheus/client_golang/prometheus"
 
@@ -93,6 +94,7 @@ type BlobStorageConfig struct {
 	MaxRetries         int            `yaml:"max_retries"`
 	MinRetryDelay      time.Duration  `yaml:"min_retry_delay"`
 	MaxRetryDelay      time.Duration  `yaml:"max_retry_delay"`
+	UseManagedIdentity bool           `yaml:"use_managed_identity"`
 }
 
 // RegisterFlags adds the flags required to config this to the given FlagSet
@@ -113,6 +115,7 @@ func (c *BlobStorageConfig) RegisterFlagsWithPrefix(prefix string, f *flag.FlagS
 	f.IntVar(&c.MaxRetries, prefix+"azure.max-retries", 5, "Number of retries for a request which times out.")
 	f.DurationVar(&c.MinRetryDelay, prefix+"azure.min-retry-delay", 10*time.Millisecond, "Minimum time to wait before retrying a request.")
 	f.DurationVar(&c.MaxRetryDelay, prefix+"azure.max-retry-delay", 500*time.Millisecond, "Maximum time to wait before retrying a request.")
+	f.BoolVar(&c.UseManagedIdentity, prefix+"azure.use-managed-identity", false, "Use Managed Identity or not.")
 }
 
 func (c *BlobStorageConfig) ToCortexAzureConfig() cortex_azure.BlobStorageConfig {
@@ -241,11 +244,7 @@ func (b *BlobStorage) buildContainerURL() (azblob.ContainerURL, error) {
 }
 
 func (b *BlobStorage) newPipeline(hedgingCfg hedging.Config, hedging bool) (pipeline.Pipeline, error) {
-	credential, err := azblob.NewSharedKeyCredential(b.cfg.AccountName, b.cfg.AccountKey.Value)
-	if err != nil {
-		return nil, err
-	}
-
+	// defining the Azure Pipeline Options
 	opts := azblob.PipelineOptions{
 		Retry: azblob.RetryOptions{
 			Policy:        azblob.RetryPolicyExponential,
@@ -255,6 +254,12 @@ func (b *BlobStorage) newPipeline(hedgingCfg hedging.Config, hedging bool) (pipe
 			MaxRetryDelay: b.cfg.MaxRetryDelay,
 		},
 	}
+
+	credential, err := azblob.NewSharedKeyCredential(b.cfg.AccountName, b.cfg.AccountKey.Value)
+	if err != nil {
+		return nil, err
+	}
+
 	client := defaultClientFactory()
 
 	opts.HTTPSender = pipeline.FactoryFunc(func(next pipeline.Policy, po *pipeline.PolicyOptions) pipeline.PolicyFunc {
@@ -277,7 +282,61 @@ func (b *BlobStorage) newPipeline(hedgingCfg hedging.Config, hedging bool) (pipe
 		})
 	}
 
-	return azblob.NewPipeline(credential, opts), nil
+	if !b.cfg.UseManagedIdentity {
+		return azblob.NewPipeline(credential, opts), nil
+	}
+
+	tokenCredential, err := b.getOAuthToken()
+	if err != nil {
+		return nil, err
+	}
+
+	return azblob.NewPipeline(*tokenCredential, opts), nil
+
+}
+
+func (b *BlobStorage) getOAuthToken() (*azblob.TokenCredential, error) {
+	spt, err := b.fetchMSIToken()
+	if err != nil {
+		return nil, err
+	}
+
+	// Refresh obtains a fresh token
+	err = spt.Refresh()
+	if err != nil {
+		return nil, err
+	}
+
+	tc := azblob.NewTokenCredential(spt.Token().AccessToken, func(tc azblob.TokenCredential) time.Duration {
+		err := spt.Refresh()
+		if err != nil {
+			// something went wrong, prevent the refresher from being triggered again
+			return 0
+		}
+
+		// set the new token value
+		tc.SetToken(spt.Token().AccessToken)
+
+		// get the next token slightly before the current one expires
+		return time.Until(spt.Token().Expires()) - 10*time.Second
+	})
+
+	return &tc, nil
+}
+
+func (b *BlobStorage) fetchMSIToken() (*adal.ServicePrincipalToken, error) {
+	// msiEndpoint is the well known endpoint for getting MSI authentications tokens
+	// msiEndpoint := "http://169.254.169.254/metadata/identity/oauth2/token" for production Jobs
+	msiEndpoint, _ := adal.GetMSIVMEndpoint()
+
+	// both can be empty, systemAssignedMSI scenario
+	spt, err := adal.NewServicePrincipalTokenFromMSI(msiEndpoint, "https://storage.azure.com/")
+
+	if err != nil {
+		return nil, err
+	}
+
+	return spt, spt.Refresh()
 }
 
 // List implements chunk.ObjectClient.