[FAB-1700] Determinsitic BlockData hashing

https://jira.hyperledger.org/browse/FAB-1700

This is a companion item to

https://jira.hyperledger.org/browse/FAB-1699

It removes the protobuf serialization of the BlockData in favor a simple
concatenation of the byte contents.  Eventually, this should be encoded
as a Merkle tree at the configured width, but, like with our hashing
algorithm, for v1, we will make it configurable at a later date, see:

https://jira.hyperledger.org/browse/FAB-1983

Change-Id: I8a09e84f1c35d8fe1269339a443c44ba01b841a8
Signed-off-by: Jason Yellick <[email protected]>

Author: Jason Yellick

common/chainconfig/chainconfig.go

@@ -18,6 +18,7 @@ package chainconfig
 
 import (
 	"fmt"
+	"math"
 
 	"github.com/hyperledger/fabric/common/util"
 	cb "github.com/hyperledger/fabric/protos/common"
@@ -144,8 +145,8 @@ func (pm *DescriptorImpl) ProposeConfig(configItem *cb.ConfigurationItem) error
 			return fmt.Errorf("Unmarshaling error for BlockDataHashingStructure: %s", err)
 		}
 
-		if blockDataHashingStructure.Width == 0 {
-			return fmt.Errorf("BlockDataHashStructure width must not be zero")
+		if blockDataHashingStructure.Width != math.MaxUint32 {
+			return fmt.Errorf("BlockDataHashStructure width only supported at MaxUint32 in this version")
 		}
 
 		pm.pendingConfig.blockDataHashingStructureWidth = blockDataHashingStructure.Width

protos/common/block.go

@@ -21,7 +21,6 @@ import (
 	"fmt"
 	"math"
 
-	"github.com/golang/protobuf/proto"
 	"github.com/hyperledger/fabric/common/util"
 )
 
@@ -75,12 +74,15 @@ func (b *BlockHeader) Hash() []byte {
 	return util.ComputeCryptoHash(b.Bytes())
 }
 
+// Bytes returns a deterministically serialized version of the BlockData
+// eventually, this should be replaced with a true Merkle tree construction,
+// but for the moment, we assume a Merkle tree of infinite width (uint32_max)
+// which degrades to a flat hash
+func (b *BlockData) Bytes() []byte {
+	return util.ConcatenateBytes(b.Data...)
+}
+
 // Hash returns the hash of the marshaled representation of the block data.
 func (b *BlockData) Hash() []byte {
-	data, err := proto.Marshal(b) // XXX this is wrong, protobuf is not the right mechanism to serialize for a hash, AND, it is not a MerkleTree hash
-	if err != nil {
-		panic("This should never fail and is generally irrecoverable")
-	}
-
-	return util.ComputeCryptoHash(data)
+	return util.ComputeCryptoHash(b.Bytes())
 }