From b2c317209554d098fbe10452528f1450b719f7e6 Mon Sep 17 00:00:00 2001
From: "Frederick F. Kautz IV" <fkautz@alumni.cmu.edu>
Date: Sun, 22 Mar 2015 20:11:25 -0700
Subject: [PATCH] Adding sha512 support for pre-encoded data and verification
 on decode

---
 pkg/storage/donut/erasure.go | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/pkg/storage/donut/erasure.go b/pkg/storage/donut/erasure.go
index 731796f7c..060d17720 100644
--- a/pkg/storage/donut/erasure.go
+++ b/pkg/storage/donut/erasure.go
@@ -6,16 +6,22 @@ import (
 	"strconv"
 	"time"
 
+	"encoding/hex"
+	"errors"
 	"github.com/minio-io/minio/pkg/encoding/erasure"
+	"github.com/minio-io/minio/pkg/utils/crypto/sha512"
 	"github.com/minio-io/minio/pkg/utils/split"
 )
 
 func erasureReader(readers []io.ReadCloser, donutMetadata map[string]string, writer *io.PipeWriter) {
+	// TODO handle errors
 	totalChunks, _ := strconv.Atoi(donutMetadata["chunkCount"])
 	totalLeft, _ := strconv.Atoi(donutMetadata["totalLength"])
 	blockSize, _ := strconv.Atoi(donutMetadata["blockSize"])
 	k, _ := strconv.Atoi(donutMetadata["erasureK"])
 	m, _ := strconv.Atoi(donutMetadata["erasureM"])
+	expectedSha512, _ := hex.DecodeString(donutMetadata["sha512"])
+	summer := sha512.New()
 	// TODO select technique properly
 	params, _ := erasure.ParseEncoderParams(uint8(k), uint8(m), erasure.Cauchy)
 	encoder := erasure.NewEncoder(params)
@@ -32,6 +38,7 @@ func erasureReader(readers []io.ReadCloser, donutMetadata map[string]string, wri
 		encodedBytes := make([][]byte, 16)
 		for i, reader := range readers {
 			var bytesBuffer bytes.Buffer
+			// TODO watch for errors
 			io.CopyN(&bytesBuffer, reader, int64(curChunkSize))
 			encodedBytes[i] = bytesBuffer.Bytes()
 		}
@@ -40,9 +47,14 @@ func erasureReader(readers []io.ReadCloser, donutMetadata map[string]string, wri
 			writer.CloseWithError(err)
 			return
 		}
+		summer.Write(decodedData)
 		io.Copy(writer, bytes.NewBuffer(decodedData))
 		totalLeft = totalLeft - blockSize
 	}
+	actualSha512 := summer.Sum(nil)
+	if bytes.Compare(expectedSha512, actualSha512) != 0 {
+		writer.CloseWithError(errors.New("decoded sha512 did not match"))
+	}
 	writer.Close()
 }
 
@@ -75,16 +87,19 @@ func erasureGoroutine(r *io.PipeReader, eWriter erasureWriter, isClosed chan<- b
 	encoder := erasure.NewEncoder(params)
 	chunkCount := 0
 	totalLength := 0
+	summer := sha512.New()
 	for chunk := range chunks {
 		if chunk.Err == nil {
 			totalLength = totalLength + len(chunk.Data)
 			encodedBlocks, _ := encoder.Encode(chunk.Data)
+			summer.Write(chunk.Data)
 			for blockIndex, block := range encodedBlocks {
 				io.Copy(eWriter.writers[blockIndex], bytes.NewBuffer(block))
 			}
 		}
 		chunkCount = chunkCount + 1
 	}
+	dataSha512 := summer.Sum(nil)
 	metadata := make(map[string]string)
 	metadata["blockSize"] = strconv.Itoa(10 * 1024 * 1024)
 	metadata["chunkCount"] = strconv.Itoa(chunkCount)
@@ -93,6 +108,7 @@ func erasureGoroutine(r *io.PipeReader, eWriter erasureWriter, isClosed chan<- b
 	metadata["erasureM"] = "8"
 	metadata["erasureTechnique"] = "Cauchy"
 	metadata["totalLength"] = strconv.Itoa(totalLength)
+	metadata["sha512"] = hex.EncodeToString(dataSha512)
 	for _, nodeWriter := range eWriter.writers {
 		if nodeWriter != nil {
 			nodeWriter.SetMetadata(eWriter.metadata)