protocol and snapshot changes for public chunked media (#468)

Main changes:
- `deriveKeyAndIV` function that will return the same `key` and `iv` for
the same `spaceId`.
- space snaphot that will return the latest chunked media with the
`DerivedAESGCM` encryption.

core/node/events/events.go

@@ -281,6 +281,23 @@ func Make_SpacePayload_Membership(op MembershipOp, userId string, initiatorId st
 	return Make_MemberPayload_Membership(op, userAddress, initiatorAddress, nil)
 }
 
+func Make_SpacePayload_SpaceImage(
+	ciphertext string,
+	algorithm string,
+) *StreamEvent_SpacePayload {
+	encryptedData := &EncryptedData{
+		Ciphertext: ciphertext,
+		Algorithm:  algorithm,
+	}
+	return &StreamEvent_SpacePayload{
+		SpacePayload: &SpacePayload{
+			Content: &SpacePayload_SpaceImage{
+				SpaceImage: encryptedData,
+			},
+		},
+	}
+}
+
 func Make_SpacePayload_ChannelUpdate(
 	op ChannelOp,
 	channelId StreamId,

core/node/events/snapshot.go

@@ -158,7 +158,7 @@ func Update_Snapshot(iSnapshot *Snapshot, event *ParsedEvent, miniblockNum int64
 	iSnapshot = migrations.MigrateSnapshot(iSnapshot)
 	switch payload := event.Event.Payload.(type) {
 	case *StreamEvent_SpacePayload:
-		return update_Snapshot_Space(iSnapshot, payload.SpacePayload, eventNum)
+		return update_Snapshot_Space(iSnapshot, payload.SpacePayload, event.Event.CreatorAddress, eventNum)
 	case *StreamEvent_ChannelPayload:
 		return update_Snapshot_Channel(iSnapshot, payload.ChannelPayload)
 	case *StreamEvent_DmChannelPayload:
@@ -182,7 +182,12 @@ func Update_Snapshot(iSnapshot *Snapshot, event *ParsedEvent, miniblockNum int64
 	}
 }
 
-func update_Snapshot_Space(iSnapshot *Snapshot, spacePayload *SpacePayload, eventNum int64) error {
+func update_Snapshot_Space(
+	iSnapshot *Snapshot,
+	spacePayload *SpacePayload,
+	creatorAddress []byte,
+	eventNum int64,
+) error {
 	snapshot := iSnapshot.Content.(*Snapshot_SpaceContent)
 	if snapshot == nil {
 		return RiverError(Err_INVALID_ARGUMENT, "blockheader snapshot is not a space snapshot")
@@ -199,6 +204,12 @@ func update_Snapshot_Space(iSnapshot *Snapshot, spacePayload *SpacePayload, even
 		}
 		snapshot.SpaceContent.Channels = insertChannel(snapshot.SpaceContent.Channels, channel)
 		return nil
+	case *SpacePayload_SpaceImage:
+		snapshot.SpaceContent.SpaceImage = &SpacePayload_SnappedSpaceImage{
+			Data:           content.SpaceImage,
+			CreatorAddress: creatorAddress,
+		}
+		return nil
 	default:
 		return RiverError(Err_INVALID_ARGUMENT, "unknown space payload type %T", spacePayload.Content)
 	}
@@ -487,7 +498,6 @@ func update_Snapshot_Member(
 		}
 		snapshot.Pins = snapPins
 		return nil
-
 	default:
 		return RiverError(Err_INVALID_ARGUMENT, "unknown membership payload type %T", memberPayload.Content)
 	}

core/node/events/snapshot_test.go

@@ -13,6 +13,10 @@ import (
 	"google.golang.org/protobuf/proto"
 )
 
+const (
+	AES_GCM_DERIVED_ALGORITHM = "r.aes-256-gcm.derived"
+)
+
 func make_User_Inception(wallet *crypto.Wallet, streamId StreamId, t *testing.T) *ParsedEvent {
 	envelope, err := MakeEnvelopeWithPayload(
 		wallet,
@@ -84,6 +88,26 @@ func make_Space_Membership(
 	return parsed
 }
 
+func make_Space_Image(
+	wallet *crypto.Wallet,
+	ciphertext string,
+	prevMiniblockHash []byte,
+	t *testing.T,
+) *ParsedEvent {
+	envelope, err := MakeEnvelopeWithPayload(
+		wallet,
+		Make_SpacePayload_SpaceImage(
+			ciphertext,
+			AES_GCM_DERIVED_ALGORITHM,
+		),
+		prevMiniblockHash,
+	)
+	assert.NoError(t, err)
+	parsed, err := ParseEvent(envelope)
+	assert.NoError(t, err)
+	return parsed
+}
+
 func make_Space_Username(wallet *crypto.Wallet, username string, prevHash []byte, t *testing.T) *ParsedEvent {
 	envelope, err := MakeEnvelopeWithPayload(
 		wallet,
@@ -197,7 +221,9 @@ func TestCloneAndUpdateSpaceSnapshot(t *testing.T) {
 	membership := make_Space_Membership(wallet, MembershipOp_SO_JOIN, userId, nil, t)
 	username := make_Space_Username(wallet, "bob", nil, t)
 	displayName := make_Space_DisplayName(wallet, "bobIsTheGreatest", nil, t)
-	events := []*ParsedEvent{membership, username, displayName}
+	imageCipertext := "space_image_ciphertext"
+	image := make_Space_Image(wallet, imageCipertext, nil, t)
+	events := []*ParsedEvent{membership, username, displayName, image}
 	for i, event := range events[:] {
 		err = Update_Snapshot(snapshot, event, 1, int64(3+i))
 		assert.NoError(t, err)
@@ -231,6 +257,17 @@ func TestCloneAndUpdateSpaceSnapshot(t *testing.T) {
 		int64(5),
 		member.DisplayName.EventNum,
 	)
+
+	assert.Equal(
+		t,
+		imageCipertext,
+		snapshot.Content.(*Snapshot_SpaceContent).SpaceContent.SpaceImage.Data.Ciphertext,
+	)
+	assert.Equal(
+		t,
+		AES_GCM_DERIVED_ALGORITHM,
+		snapshot.Content.(*Snapshot_SpaceContent).SpaceContent.SpaceImage.Data.Algorithm,
+	)
 }
 
 func TestUpdateSnapshotFailsIfInception(t *testing.T) {