Add support for bucket encryption feature (#8890)

- pkg/bucket/encryption provides support for handling bucket 
  encryption configuration
- changes under cmd/ provide support for AES256 algorithm only

Co-Authored-By: Poorna  <poornas@users.noreply.github.com>
Co-authored-by: Harshavardhana <harsha@minio.io>

cmd/bucket-encryption.go

@@ -0,0 +1,169 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
+ *
+ * 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 cmd
+
+import (
+	"bytes"
+	"context"
+	"encoding/xml"
+	"errors"
+	"io"
+	"path"
+	"sync"
+
+	bucketsse "github.com/minio/minio/pkg/bucket/encryption"
+)
+
+// BucketSSEConfigSys - in-memory cache of bucket encryption config
+type BucketSSEConfigSys struct {
+	sync.RWMutex
+	bucketSSEConfigMap map[string]bucketsse.BucketSSEConfig
+}
+
+// NewBucketSSEConfigSys - Creates an empty in-memory bucket encryption configuration cache
+func NewBucketSSEConfigSys() *BucketSSEConfigSys {
+	return &BucketSSEConfigSys{
+		bucketSSEConfigMap: make(map[string]bucketsse.BucketSSEConfig),
+	}
+}
+
+// load - Loads the bucket encryption configuration for the given list of buckets
+func (sys *BucketSSEConfigSys) load(buckets []BucketInfo, objAPI ObjectLayer) error {
+	for _, bucket := range buckets {
+		config, err := objAPI.GetBucketSSEConfig(context.Background(), bucket.Name)
+		if err != nil {
+			if _, ok := err.(BucketSSEConfigNotFound); ok {
+				sys.Remove(bucket.Name)
+			}
+			continue
+		}
+		sys.Set(bucket.Name, *config)
+	}
+
+	return nil
+}
+
+// Init - Initializes in-memory bucket encryption config cache for the given list of buckets
+func (sys *BucketSSEConfigSys) Init(buckets []BucketInfo, objAPI ObjectLayer) error {
+	if objAPI == nil {
+		return errServerNotInitialized
+	}
+
+	// We don't cache bucket encryption config in gateway mode, nothing to do.
+	if globalIsGateway {
+		return nil
+	}
+
+	// Load bucket encryption config cache once during boot.
+	return sys.load(buckets, objAPI)
+}
+
+// Get - gets bucket encryption config for the given bucket.
+func (sys *BucketSSEConfigSys) Get(bucket string) (config bucketsse.BucketSSEConfig, ok bool) {
+	// We don't cache bucket encryption config in gateway mode.
+	if globalIsGateway {
+		objAPI := newObjectLayerWithoutSafeModeFn()
+		if objAPI == nil {
+			return
+		}
+
+		cfg, err := objAPI.GetBucketSSEConfig(context.Background(), bucket)
+		if err != nil {
+			return
+		}
+		return *cfg, true
+	}
+
+	sys.Lock()
+	defer sys.Unlock()
+	config, ok = sys.bucketSSEConfigMap[bucket]
+	return
+}
+
+// Set - sets bucket encryption config to given bucket name.
+func (sys *BucketSSEConfigSys) Set(bucket string, config bucketsse.BucketSSEConfig) {
+	// We don't cache bucket encryption config in gateway mode.
+	if globalIsGateway {
+		return
+	}
+
+	sys.Lock()
+	defer sys.Unlock()
+	sys.bucketSSEConfigMap[bucket] = config
+}
+
+// Remove - removes bucket encryption config for given bucket.
+func (sys *BucketSSEConfigSys) Remove(bucket string) {
+	sys.Lock()
+	defer sys.Unlock()
+
+	delete(sys.bucketSSEConfigMap, bucket)
+}
+
+// saveBucketSSEConfig - save bucket encryption config for given bucket.
+func saveBucketSSEConfig(ctx context.Context, objAPI ObjectLayer, bucket string, config *bucketsse.BucketSSEConfig) error {
+	data, err := xml.Marshal(config)
+	if err != nil {
+		return err
+	}
+
+	// Path to store bucket encryption config for the given bucket.
+	configFile := path.Join(bucketConfigPrefix, bucket, bucketSSEConfig)
+	return saveConfig(ctx, objAPI, configFile, data)
+}
+
+// getBucketSSEConfig - get bucket encryption config for given bucket.
+func getBucketSSEConfig(objAPI ObjectLayer, bucket string) (*bucketsse.BucketSSEConfig, error) {
+	// Path to bucket-encryption.xml for the given bucket.
+	configFile := path.Join(bucketConfigPrefix, bucket, bucketSSEConfig)
+	configData, err := readConfig(context.Background(), objAPI, configFile)
+	if err != nil {
+		if err == errConfigNotFound {
+			err = BucketSSEConfigNotFound{Bucket: bucket}
+		}
+		return nil, err
+	}
+
+	return bucketsse.ParseBucketSSEConfig(bytes.NewReader(configData))
+}
+
+// removeBucketSSEConfig - removes bucket encryption config for given bucket.
+func removeBucketSSEConfig(ctx context.Context, objAPI ObjectLayer, bucket string) error {
+	// Path to bucket-encryption.xml for the given bucket.
+	configFile := path.Join(bucketConfigPrefix, bucket, bucketSSEConfig)
+
+	if err := objAPI.DeleteObject(ctx, minioMetaBucket, configFile); err != nil {
+		if _, ok := err.(ObjectNotFound); ok {
+			return BucketSSEConfigNotFound{Bucket: bucket}
+		}
+		return err
+	}
+	return nil
+}
+
+// validateBucketSSEConfig parses bucket encryption configuration and validates if it is supported by MinIO.
+func validateBucketSSEConfig(r io.Reader) (*bucketsse.BucketSSEConfig, error) {
+	encConfig, err := bucketsse.ParseBucketSSEConfig(r)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(encConfig.Rules) == 1 && encConfig.Rules[0].DefaultEncryptionAction.Algorithm == bucketsse.AES256 {
+		return encConfig, nil
+	}
+	return nil, errors.New("Unsupported bucket encryption configuration")
+}