fix: avoid double body reads in SelectObject call (#9638)

Bonus fix handle encryption headers in response
properly for both notification and response to
the client.

cmd/object-handlers.go

@@ -173,11 +173,13 @@ func (api objectAPIHandlers) SelectObjectContentHandler(w http.ResponseWriter, r
 	if api.CacheAPI() != nil {
 		getObjectNInfo = api.CacheAPI().GetObjectNInfo
 	}
+
 	getObject := func(offset, length int64) (rc io.ReadCloser, err error) {
 		isSuffixLength := false
 		if offset < 0 {
 			isSuffixLength = true
 		}
+
 		rs := &HTTPRangeSpec{
 			IsSuffixLength: isSuffixLength,
 			Start:          offset,
@@ -193,6 +195,20 @@ func (api objectAPIHandlers) SelectObjectContentHandler(w http.ResponseWriter, r
 		return
 	}
 
+	// filter object lock metadata if permission does not permit
+	getRetPerms := checkRequestAuthType(ctx, r, policy.GetObjectRetentionAction, bucket, object)
+	legalHoldPerms := checkRequestAuthType(ctx, r, policy.GetObjectLegalHoldAction, bucket, object)
+
+	// filter object lock metadata if permission does not permit
+	objInfo.UserDefined = objectlock.FilterObjectLockMetadata(objInfo.UserDefined, getRetPerms != ErrNone, legalHoldPerms != ErrNone)
+
+	if objectAPI.IsEncryptionSupported() {
+		if _, err = DecryptObjectInfo(&objInfo, r.Header); err != nil {
+			writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL, guessIsBrowserReq(r))
+			return
+		}
+	}
+
 	s3Select, err := s3select.NewS3Select(r.Body)
 	if err != nil {
 		if serr, ok := err.(s3select.SelectError); ok {
@@ -212,12 +228,6 @@ func (api objectAPIHandlers) SelectObjectContentHandler(w http.ResponseWriter, r
 		return
 	}
 
-	getRetPerms := checkRequestAuthType(ctx, r, policy.GetObjectRetentionAction, bucket, object)
-	legalHoldPerms := checkRequestAuthType(ctx, r, policy.GetObjectLegalHoldAction, bucket, object)
-
-	// filter object lock metadata if permission does not permit
-	objInfo.UserDefined = objectlock.FilterObjectLockMetadata(objInfo.UserDefined, getRetPerms != ErrNone, legalHoldPerms != ErrNone)
-
 	if err = s3Select.Open(getObject); err != nil {
 		if serr, ok := err.(s3select.SelectError); ok {
 			encodedErrorResponse := encodeResponse(APIErrorResponse{
@@ -236,6 +246,24 @@ func (api objectAPIHandlers) SelectObjectContentHandler(w http.ResponseWriter, r
 		return
 	}
 
+	// Set encryption response headers
+	if objectAPI.IsEncryptionSupported() {
+		if crypto.IsEncrypted(objInfo.UserDefined) {
+			switch {
+			case crypto.S3.IsEncrypted(objInfo.UserDefined):
+				w.Header().Set(crypto.SSEHeader, crypto.SSEAlgorithmAES256)
+			case crypto.SSEC.IsEncrypted(objInfo.UserDefined):
+				// Validate the SSE-C Key set in the header.
+				if _, err = crypto.SSEC.UnsealObjectKey(r.Header, objInfo.UserDefined, bucket, object); err != nil {
+					writeErrorResponseHeadersOnly(w, toAPIError(ctx, err))
+					return
+				}
+				w.Header().Set(crypto.SSECAlgorithm, r.Header.Get(crypto.SSECAlgorithm))
+				w.Header().Set(crypto.SSECKeyMD5, r.Header.Get(crypto.SSECKeyMD5))
+			}
+		}
+	}
+
 	s3Select.Evaluate(w)
 	s3Select.Close()