encryption: Fix copy from encrypted multipart to single part (#6604)

CopyObject handler forgot to remove multipart encryption flag in metadata
when source is an encrypted multipart object and the target is also encrypted
but single part object.

This PR also simplifies the code to facilitate review.

cmd/encryption-v1.go

@@ -80,6 +80,28 @@ func hasServerSideEncryptionHeader(header http.Header) bool {
 	return crypto.S3.IsRequested(header) || crypto.SSEC.IsRequested(header)
 }
 
+// isEncryptedMultipart returns true if the current object is
+// uploaded by the user using multipart mechanism:
+// initiate new multipart, upload part, complete upload
+func isEncryptedMultipart(objInfo ObjectInfo) bool {
+	if len(objInfo.Parts) == 0 {
+		return false
+	}
+	if !crypto.IsMultiPart(objInfo.UserDefined) {
+		return false
+	}
+	for _, part := range objInfo.Parts {
+		_, err := sio.DecryptedSize(uint64(part.Size))
+		if err != nil {
+			return false
+		}
+	}
+	// Further check if this object is uploaded using multipart mechanism
+	// by the user and it is not about XL internally splitting the
+	// object into parts in PutObject()
+	return !(objInfo.backendType == BackendErasure && len(objInfo.ETag) == 32)
+}
+
 // ParseSSECopyCustomerRequest parses the SSE-C header fields of the provided request.
 // It returns the client provided key on success.
 func ParseSSECopyCustomerRequest(h http.Header, metadata map[string]string) (key []byte, err error) {
@@ -361,7 +383,7 @@ func newDecryptReaderWithObjectKey(client io.Reader, objectEncryptionKey []byte,
 // GetEncryptedOffsetLength - returns encrypted offset and length
 // along with sequence number
 func GetEncryptedOffsetLength(startOffset, length int64, objInfo ObjectInfo) (seqNumber uint32, encStartOffset, encLength int64) {
-	if len(objInfo.Parts) == 0 || !crypto.IsMultiPart(objInfo.UserDefined) {
+	if !isEncryptedMultipart(objInfo) {
 		seqNumber, encStartOffset, encLength = getEncryptedSinglePartOffsetLength(startOffset, length, objInfo)
 		return
 	}
@@ -378,7 +400,7 @@ func DecryptBlocksRequestR(inputReader io.Reader, h http.Header, offset,
 	bucket, object := oi.Bucket, oi.Name
 
 	// Single part case
-	if len(oi.Parts) == 0 || !crypto.IsMultiPart(oi.UserDefined) {
+	if !isEncryptedMultipart(oi) {
 		var reader io.Reader
 		var err error
 		if copySource {
@@ -708,7 +730,7 @@ func DecryptBlocksRequest(client io.Writer, r *http.Request, bucket, object stri
 	var seqNumber uint32
 	var encStartOffset, encLength int64
 
-	if len(objInfo.Parts) == 0 || !crypto.IsMultiPart(objInfo.UserDefined) {
+	if !isEncryptedMultipart(objInfo) {
 		seqNumber, encStartOffset, encLength = getEncryptedSinglePartOffsetLength(startOffset, length, objInfo)
 
 		var writer io.WriteCloser
@@ -870,7 +892,7 @@ func (o *ObjectInfo) DecryptedSize() (int64, error) {
 	if !crypto.IsEncrypted(o.UserDefined) {
 		return 0, errors.New("Cannot compute decrypted size of an unencrypted object")
 	}
-	if len(o.Parts) == 0 || !crypto.IsMultiPart(o.UserDefined) {
+	if !isEncryptedMultipart(*o) {
 		size, err := sio.DecryptedSize(uint64(o.Size))
 		if err != nil {
 			err = errObjectTampered // assign correct error type
@@ -918,7 +940,7 @@ func (o *ObjectInfo) GetDecryptedRange(rs *HTTPRangeSpec) (encOff, encLength, sk
 	}
 	sizes := []int64{int64(partSize)}
 	decObjSize = sizes[0]
-	if crypto.IsMultiPart(o.UserDefined) {
+	if isEncryptedMultipart(*o) {
 		sizes = make([]int64, len(o.Parts))
 		decObjSize = 0
 		for i, part := range o.Parts {

cmd/object-api-datatypes.go

@@ -109,8 +109,12 @@ type ObjectInfo struct {
 	Writer       io.WriteCloser `json:"-"`
 	Reader       *hash.Reader   `json:"-"`
 	metadataOnly bool
+
 	// Date and time when the object was last accessed.
 	AccTime time.Time
+
+	// backendType indicates which backend filled this structure
+	backendType BackendType
 }
 
 // ListPartsInfo - represents list of all parts.

cmd/object-handlers.go

@@ -795,10 +795,6 @@ func (api objectAPIHandlers) CopyObjectHandler(w http.ResponseWriter, r *http.Re
 		return
 	}
 
-	// Save the original size for later use when we want to copy
-	// encrypted file into an unencrypted one.
-	size := srcInfo.Size
-
 	var encMetadata = make(map[string]string)
 	if objectAPI.IsEncryptionSupported() && !srcInfo.IsCompressed() {
 		var oldKey, newKey []byte
@@ -806,10 +802,12 @@ func (api objectAPIHandlers) CopyObjectHandler(w http.ResponseWriter, r *http.Re
 		sseCopyC := crypto.SSECopy.IsRequested(r.Header)
 		sseC := crypto.SSEC.IsRequested(r.Header)
 		sseS3 := crypto.S3.IsRequested(r.Header)
-		if sseC || sseS3 {
+
+		isSourceEncrypted := sseCopyC || sseCopyS3
+		isTargetEncrypted := sseC || sseS3
+
 		if sseC {
 			newKey, err = ParseSSECustomerRequest(r)
-			}
 			if err != nil {
 				writeErrorResponse(w, toAPIErrorCode(err), r.URL)
 				return
@@ -836,31 +834,39 @@ func (api objectAPIHandlers) CopyObjectHandler(w http.ResponseWriter, r *http.Re
 			// Since we are rotating the keys, make sure to update the metadata.
 			srcInfo.metadataOnly = true
 		} else {
-			if sseCopyC || sseCopyS3 {
+			if isSourceEncrypted || isTargetEncrypted {
 				// We are not only copying just metadata instead
 				// we are creating a new object at this point, even
 				// if source and destination are same objects.
 				srcInfo.metadataOnly = false
-				if sseC || sseS3 {
-					size = srcInfo.Size
 			}
-			}
-			if sseC || sseS3 {
+
+			// Calculate the size of the target object
+			var targetSize int64
+
+			switch {
+			case !isSourceEncrypted && !isTargetEncrypted:
+				fallthrough
+			case isSourceEncrypted && isTargetEncrypted:
+				targetSize = srcInfo.Size
+			// Source not encrypted and target encrypted
+			case !isSourceEncrypted && isTargetEncrypted:
+				targetSize = srcInfo.EncryptedSize()
+			case isSourceEncrypted && !isTargetEncrypted:
+				targetSize, _ = srcInfo.DecryptedSize()
+			}
+
+			if isTargetEncrypted {
 				reader, err = newEncryptReader(reader, newKey, dstBucket, dstObject, encMetadata, sseS3)
 				if err != nil {
 					writeErrorResponse(w, toAPIErrorCode(err), r.URL)
 					return
 				}
-				// We are not only copying just metadata instead
-				// we are creating a new object at this point, even
-				// if source and destination are same objects.
-				srcInfo.metadataOnly = false
-				if !sseCopyC && !sseCopyS3 {
-					size = srcInfo.EncryptedSize()
 			}
-			} else {
-				if sseCopyC || sseCopyS3 {
-					size, _ = srcInfo.DecryptedSize()
+
+			if isSourceEncrypted {
+				// Remove all source encrypted related metadata to
+				// avoid copying them in target object.
 				delete(srcInfo.UserDefined, crypto.SSEIV)
 				delete(srcInfo.UserDefined, crypto.SSESealAlgorithm)
 				delete(srcInfo.UserDefined, crypto.SSECSealedKey)
@@ -869,9 +875,8 @@ func (api objectAPIHandlers) CopyObjectHandler(w http.ResponseWriter, r *http.Re
 				delete(srcInfo.UserDefined, crypto.S3KMSSealedKey)
 				delete(srcInfo.UserDefined, crypto.S3KMSKeyID)
 			}
-			}
 
-			srcInfo.Reader, err = hash.NewReader(reader, size, "", "", size) // do not try to verify encrypted content
+			srcInfo.Reader, err = hash.NewReader(reader, targetSize, "", "", targetSize) // do not try to verify encrypted content
 			if err != nil {
 				writeErrorResponse(w, toAPIErrorCode(err), r.URL)
 				return

cmd/xl-v1-metadata.go

@@ -218,6 +218,8 @@ func (m xlMetaV1) ToObjectInfo(bucket, object string) ObjectInfo {
 		ContentEncoding: m.Meta["content-encoding"],
 	}
 
+	objInfo.backendType = BackendErasure
+
 	// Extract etag from metadata.
 	objInfo.ETag = extractETag(m.Meta)