[FAB-4464] Fix configtx manager nil dereference

When sending a specially crafted malformed configtx, it is possible to
trick the configtx manager into dereferencing a nil pointer for the
channel group.

This CR adds a check to guard against this, and adds a test case to
cover it.

Change-Id: I3b6bdb464f931214819cd582ba72df938d3eeee3
Signed-off-by: Jason Yellick <[email protected]>

Author: Jason Yellick

common/configtx/manager.go

@@ -98,6 +98,10 @@ func NewManagerImpl(envConfig *cb.Envelope, initializer api.Initializer, callOnU
 		return nil, fmt.Errorf("Nil config envelope Config")
 	}
 
+	if configEnv.Config.ChannelGroup == nil {
+		return nil, fmt.Errorf("nil channel group")
+	}
+
 	if err := validateChainID(header.ChannelId); err != nil {
 		return nil, fmt.Errorf("Bad channel id: %s", err)
 	}

common/configtx/manager_test.go

@@ -133,6 +133,23 @@ func TestCallback(t *testing.T) {
 	}
 }
 
+func TestEmptyChannel(t *testing.T) {
+	_, err := NewManagerImpl(&cb.Envelope{
+		Payload: utils.MarshalOrPanic(&cb.Payload{
+			Header: &cb.Header{
+				ChannelHeader: utils.MarshalOrPanic(&cb.ChannelHeader{
+					Type:      int32(cb.HeaderType_CONFIG),
+					ChannelId: "foo",
+				}),
+			},
+			Data: utils.MarshalOrPanic(&cb.ConfigEnvelope{
+				Config: &cb.Config{},
+			}),
+		}),
+	}, defaultInitializer(), nil)
+	assert.Error(t, err)
+}
+
 // TestDifferentChainID tests that a config update for a different chain ID fails
 func TestDifferentChainID(t *testing.T) {
 	cm, err := NewManagerImpl(