Fix ETag handling with auto-encryption with CopyObject conditions (#7000)

minio-java tests were failing under multiple places when
auto encryption was turned on, handle all the cases properly

This PR fixes

 - CopyObject should decrypt ETag before it does if-match
 - CopyObject should not try to preserve metadata of source
   when rotating keys, unless explicitly asked by the user.
 - We should not try to decrypt Compressed object etag, the
   potential case was if user sets encryption headers along
   with compression enabled.

cmd/object-api-utils.go

@@ -503,6 +503,9 @@ func NewGetObjectReader(rs *HTTPRangeSpec, oi ObjectInfo, cleanUpFns ...func())
 				return nil, err
 			}
 
+			// Decrypt the ETag before top layer consumes this value.
+			oi.ETag = getDecryptedETag(h, oi, copySource)
+
 			// Apply the skipLen and limit on the
 			// decrypted stream
 			decReader = io.LimitReader(ioutil.NewSkipReader(decReader, skipLen), decRangeLength)

cmd/object-handlers.go

@@ -935,9 +935,12 @@ func (api objectAPIHandlers) CopyObjectHandler(w http.ResponseWriter, r *http.Re
 					return
 				}
 			}
+
 			for k, v := range srcInfo.UserDefined {
+				if hasPrefix(k, ReservedMetadataPrefix) {
 					encMetadata[k] = v
 				}
+			}
 
 			// In case of SSE-S3 oldKey and newKey aren't used - the KMS manages the keys.
 			if err = rotateKey(oldKey, newKey, srcBucket, srcObject, encMetadata); err != nil {
@@ -1317,15 +1320,15 @@ func (api objectAPIHandlers) PutObjectHandler(w http.ResponseWriter, r *http.Req
 		return
 	}
 
+	etag := objInfo.ETag
 	if objInfo.IsCompressed() {
 		// Ignore compressed ETag.
-		objInfo.ETag = objInfo.ETag + "-1"
-	}
-	if hasServerSideEncryptionHeader(r.Header) {
-		w.Header().Set("ETag", "\""+getDecryptedETag(r.Header, objInfo, false)+"\"")
-	} else {
-		w.Header().Set("ETag", "\""+objInfo.ETag+"\"")
+		etag = objInfo.ETag + "-1"
+	} else if hasServerSideEncryptionHeader(r.Header) {
+		etag = getDecryptedETag(r.Header, objInfo, false)
 	}
+	w.Header().Set("ETag", "\""+etag+"\"")
+
 	if objectAPI.IsEncryptionSupported() {
 		if crypto.IsEncrypted(objInfo.UserDefined) {
 			switch {
@@ -1970,19 +1973,16 @@ func (api objectAPIHandlers) PutObjectPartHandler(w http.ResponseWriter, r *http
 		writeErrorResponse(w, toAPIErrorCode(ctx, err), r.URL, guessIsBrowserReq(r))
 		return
 	}
+
+	etag := partInfo.ETag
 	if isCompressed {
 		pipeWriter.Close()
 		// Suppress compressed ETag.
-		partInfo.ETag = partInfo.ETag + "-1"
-	}
-
-	if partInfo.ETag != "" {
-		if isEncrypted {
-			w.Header().Set("ETag", "\""+tryDecryptETag(objectEncryptionKey, partInfo.ETag, crypto.SSEC.IsRequested(r.Header))+"\"")
-		} else {
-			w.Header().Set("ETag", "\""+partInfo.ETag+"\"")
-		}
+		etag = partInfo.ETag + "-1"
+	} else if isEncrypted {
+		etag = tryDecryptETag(objectEncryptionKey, partInfo.ETag, crypto.SSEC.IsRequested(r.Header))
 	}
+	w.Header().Set("ETag", "\""+etag+"\"")
 
 	writeSuccessResponseHeadersOnly(w)
 }