[FAB-11129] Ensure v1.3 digests are parsed by v1.2

This change set adds unit tests that ensure:

1) A v1.3 digest that represents digests as [][]byte
   and was marshaled by proto v1.1.0,
   can be successfully unmarshaled by pre v1.3 protobuf
   infrastructure.
2) Pre v1.3 protobuf treats bytes and string fields
   in the same manner and they are interchangable.

Change-Id: Ia7a6a63f6186348aa2b62386bc9386f75466c3c4
Signed-off-by: yacovm <yacovm@il.ibm.com>

protos/gossip/compatibility_test.go

@@ -0,0 +1,114 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package gossip
+
+import (
+	"io/ioutil"
+	"testing"
+
+	"encoding/hex"
+
+	"github.com/golang/protobuf/proto"
+	"github.com/hyperledger/fabric/protos/testutils"
+	"github.com/stretchr/testify/assert"
+)
+
+var digestMsg = &GossipMessage{
+	Channel: []byte("mychannel"),
+	Content: &GossipMessage_DataDig{
+		DataDig: &DataDigest{
+			Digests: []string{
+				string([]byte{255}),
+				string([]byte{255, 255}),
+				string([]byte{255, 255, 255}),
+				string([]byte{255, 255, 255, 255}),
+				"100",
+			},
+		},
+	},
+}
+
+var requestMsg = &GossipMessage{
+	Channel: []byte("mychannel"),
+	Content: &GossipMessage_DataReq{
+		DataReq: &DataRequest{
+			Digests: []string{
+				string([]byte{255}),
+				string([]byte{255, 255}),
+				string([]byte{255, 255, 255}),
+				string([]byte{255, 255, 255, 255}),
+				"100",
+			},
+		},
+	},
+}
+
+const (
+	v13DataDigestBytes  = "12096d796368616e6e656c52171201ff1202ffff1203ffffff1204ffffffff1203313030"
+	v13DataRequestBytes = "12096d796368616e6e656c5a171201ff1202ffff1203ffffff1204ffffffff1203313030"
+)
+
+func TestUnmarshalV13Digests(t *testing.T) {
+	// This test ensures that digests of data digest messages and data requests
+	// that originated from fabric v1.3 can be successfully parsed by v1.2
+	for msgBytes, expectedMsg := range map[string]*GossipMessage{
+		v13DataDigestBytes:  digestMsg,
+		v13DataRequestBytes: requestMsg,
+	} {
+		var err error
+		v13Envelope := &Envelope{}
+		v13Envelope.Payload, err = hex.DecodeString(msgBytes)
+		assert.NoError(t, err)
+		sMsg := &SignedGossipMessage{
+			Envelope: v13Envelope,
+		}
+		v13Digest, err := sMsg.ToGossipMessage()
+		assert.NoError(t, err)
+		assert.True(t, proto.Equal(expectedMsg, v13Digest.GossipMessage))
+	}
+}
+
+func TestCreateV12Digests(t *testing.T) {
+	t.Skip()
+	for fileName, msg := range map[string]*GossipMessage{
+		"dataReq.v12.pb": requestMsg,
+		"dataDig.v12.pb": digestMsg,
+	} {
+		sMsg, err := msg.NoopSign()
+		assert.NoError(t, err)
+		err = ioutil.WriteFile(fileName, sMsg.Envelope.Payload, 0600)
+		assert.NoError(t, err)
+	}
+}
+
+func TestStringsEncodedAsBytes(t *testing.T) {
+	// This test ensures that strings and bytes are
+	// interchangeable
+	t.Run("String interpreted as Bytes", func(t *testing.T) {
+		str := &testutils.String{
+			Str: "some string",
+		}
+		b, err := proto.Marshal(str)
+		assert.NoError(t, err)
+		bytes := &testutils.Bytes{}
+		err = proto.Unmarshal(b, bytes)
+		assert.NoError(t, err)
+		assert.Equal(t, "some string", string(bytes.B))
+	})
+
+	t.Run("Bytes interpreted as String", func(t *testing.T) {
+		bytes := &testutils.Bytes{
+			B: []byte("some string"),
+		}
+		b, err := proto.Marshal(bytes)
+		assert.NoError(t, err)
+		str := &testutils.String{}
+		err = proto.Unmarshal(b, str)
+		assert.NoError(t, err)
+		assert.Equal(t, "some string", str.Str)
+	})
+}

protos/testutils/compatibility.proto

@@ -0,0 +1,18 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+syntax = "proto3";
+
+option go_package = "github.com/hyperledger/fabric/protos/testutils";
+option java_package = "org.hyperledger.fabric.protos.testutils";
+
+message String {
+    string str = 1;
+}
+
+message Bytes {
+    bytes b = 1;
+}