[FAB-1698] Add block data hashing structure config

https://jira.hyperledger.org/browse/FAB-1698

This commit adds a proto message for BlockDataHashingStructure which
dictates the width of the Merkle tree to use when computing the
BlockData hash.

It also adds this value to the chainconfig Reader, although no one
currently consumes this.

Change-Id: I17c4b13a30df8da0c39310be9c0f2a32a76ce859
Signed-off-by: Jason Yellick <jyellick@us.ibm.com>

common/chainconfig/chainconfig.go

@@ -30,6 +30,9 @@ import (
 const (
 	// HashingAlgorithmKey is the cb.ConfigurationItem type key name for the HashingAlgorithm message
 	HashingAlgorithmKey = "HashingAlgorithm"
+
+	// BlockDataHashingStructureKey is the cb.ConfigurationItem type key name for the BlockDataHashingStructure message
+	BlockDataHashingStructureKey = "BlockDataHashingStructure"
 )
 
 // Hashing algorithm types
@@ -48,10 +51,15 @@ type Descriptor interface {
 	// HashingAlgorithm returns the default algorithm to be used when hashing
 	// such as computing block hashes, and CreationPolicy digests
 	HashingAlgorithm() func(input []byte) []byte
+
+	// BlockDataHashingStructureWidth returns the width to use when constructing the
+	// Merkle tree to compute the BlockData hash
+	BlockDatahashingStructureWidth() int
 }
 
 type chainConfig struct {
-	hashingAlgorithm func(input []byte) []byte
+	hashingAlgorithm               func(input []byte) []byte
+	blockDataHashingStructureWidth uint32
 }
 
 // DescriptorImpl is an implementation of Manager and configtx.ConfigHandler
@@ -73,6 +81,11 @@ func (pm *DescriptorImpl) HashingAlgorithm() func(input []byte) []byte {
 	return pm.config.hashingAlgorithm
 }
 
+// BlockDataHashingStructure returns the width to use when forming the block data hashing structure
+func (pm *DescriptorImpl) BlockDataHashingStructureWidth() uint32 {
+	return pm.config.blockDataHashingStructureWidth
+}
+
 // BeginConfig is used to start a new configuration proposal
 func (pm *DescriptorImpl) BeginConfig() {
 	if pm.pendingConfig != nil {
@@ -113,6 +126,17 @@ func (pm *DescriptorImpl) ProposeConfig(configItem *cb.ConfigurationItem) error
 		default:
 			return fmt.Errorf("Unknown hashing algorithm type: %s", hashingAlgorithm.Name)
 		}
+	case BlockDataHashingStructureKey:
+		blockDataHashingStructure := &cb.BlockDataHashingStructure{}
+		if err := proto.Unmarshal(configItem.Value, blockDataHashingStructure); err != nil {
+			return fmt.Errorf("Unmarshaling error for BlockDataHashingStructure: %s", err)
+		}
+
+		if blockDataHashingStructure.Width == 0 {
+			return fmt.Errorf("BlockDataHashStructure width must not be zero")
+		}
+
+		pm.pendingConfig.blockDataHashingStructureWidth = blockDataHashingStructure.Width
 	default:
 		logger.Warningf("Uknown Chain configuration item with key %s", configItem.Key)
 	}

common/chainconfig/chainconfig_test.go

@@ -102,3 +102,46 @@ func TestHashingAlgorithm(t *testing.T) {
 		t.Fatalf("Should have set default hashing algorithm")
 	}
 }
+
+func TestBlockDataHashingStructure(t *testing.T) {
+	expectedWidth := uint32(7)
+	invalidMessage :=
+		&cb.ConfigurationItem{
+			Type:  cb.ConfigurationItem_Chain,
+			Key:   BlockDataHashingStructureKey,
+			Value: []byte("Garbage Data"),
+		}
+	invalidWidth := &cb.ConfigurationItem{
+		Type:  cb.ConfigurationItem_Chain,
+		Key:   BlockDataHashingStructureKey,
+		Value: utils.MarshalOrPanic(&cb.BlockDataHashingStructure{Width: 0}),
+	}
+	validWidth := &cb.ConfigurationItem{
+		Type:  cb.ConfigurationItem_Chain,
+		Key:   BlockDataHashingStructureKey,
+		Value: utils.MarshalOrPanic(&cb.BlockDataHashingStructure{Width: expectedWidth}),
+	}
+	m := NewDescriptorImpl()
+	m.BeginConfig()
+
+	err := m.ProposeConfig(invalidMessage)
+	if err == nil {
+		t.Fatalf("Should have failed on invalid message")
+	}
+
+	err = m.ProposeConfig(invalidWidth)
+	if err == nil {
+		t.Fatalf("Should have failed on invalid width")
+	}
+
+	err = m.ProposeConfig(validWidth)
+	if err != nil {
+		t.Fatalf("Error applying valid config: %s", err)
+	}
+
+	m.CommitConfig()
+
+	if newWidth := m.BlockDataHashingStructureWidth(); newWidth != expectedWidth {
+		t.Fatalf("Unexpected width, got %d expected %d", newWidth, expectedWidth)
+	}
+}

protos/common/configuration.proto

@@ -118,9 +118,17 @@ message SignaturePolicy {
 }
 
 
-// HashingAlgorithm is encoded into the configuration transaction as  a configuration item of type CHAIN
-// with a Key of "HashingAlgorithm" as marshaled protobuf bytes
+// HashingAlgorithm is encoded into the configuration transaction as  a configuration item of type Chain
+// with a Key of "HashingAlgorithm" and a Value of  HashingAlgorithm as marshaled protobuf bytes
 message HashingAlgorithm {
     // Currently supported algorithms are: SHAKE256
     string name = 1;
 }
+
+// BlockDataHashingStructure is encoded into the configuration transaction as a configuration item of
+// type Chain with a Key of "BlockDataHashingStructure" and a Value of HashingAlgorithm as marshaled protobuf bytes
+message BlockDataHashingStructure {
+    // width specifies the width of the Merkle tree to use when computing the BlockDataHash
+    // in order to replicate flat hashing, set this width to MAX_UINT32
+    uint32 width  = 1;
+}