Fix encoding bug in donut during encoding phase

Stream reading needs to check for length parameter being non zero,
after Reading() a predefined set of buffer length an EOF might be returned
with length == 0.

Erasure taking this zeroed data in might wrongly encode it as part of existing
data blocks which leads to errors while decoding even when the other contents
are intact.

pkg/donut/bucket.go

@@ -444,7 +444,8 @@ func (b bucket) writeObjectData(k, m uint8, writers []io.WriteCloser, objectData
 		var length int
 		inputData := make([]byte, chunkSize)
 		length, e = objectData.Read(inputData)
-		encodedBlocks, err := encoder.Encode(inputData)
+		if length != 0 {
+			encodedBlocks, err := encoder.Encode(inputData[0:length])
 			if err != nil {
 				return 0, 0, err.Trace()
 			}
@@ -466,6 +467,7 @@ func (b bucket) writeObjectData(k, m uint8, writers []io.WriteCloser, objectData
 			totalLength += length
 			chunkCount = chunkCount + 1
 		}
+	}
 	if e != io.EOF {
 		return 0, 0, probe.NewError(e)
 	}

server-api-signature.go

@@ -17,7 +17,6 @@
 package main
 
 import (
-	"bytes"
 	"encoding/base64"
 	"io"
 	"io/ioutil"
@@ -131,7 +130,7 @@ func initSignatureV4(req *http.Request) (*signv4.Signature, *probe.Error) {
 func extractHTTPFormValues(reader *multipart.Reader) (io.Reader, map[string]string, *probe.Error) {
 	/// HTML Form values
 	formValues := make(map[string]string)
-	filePart := new(bytes.Buffer)
+	var filePart io.Reader
 	var err error
 	for err == nil {
 		var part *multipart.Part
@@ -144,11 +143,7 @@ func extractHTTPFormValues(reader *multipart.Reader) (io.Reader, map[string]stri
 				}
 				formValues[part.FormName()] = string(buffer)
 			} else {
-				// FIXME: this will hog memory
-				_, err := io.Copy(filePart, part)
-				if err != nil {
-					return nil, nil, probe.NewError(err)
-				}
+				filePart = part
 			}
 		}
 	}