refactor: remove SendTransfer, require IBC transfers to be initiated with MsgTransfer (#2446)

## Description



closes: #1918 

---

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- [x] Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
- [x] Code follows the [module structure standards](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules/structure.md).
- [x] Wrote unit and integration [tests](https://github.com/cosmos/ibc-go/blob/master/CONTRIBUTING.md#testing)
- [x] Updated relevant documentation (`docs/`) or specification (`x/<module>/spec/`)
- [x] Added relevant `godoc` [comments](https://blog.golang.org/godoc-documenting-go-code).
- [x] Added a relevant changelog entry to the `Unreleased` section in `CHANGELOG.md`
- [x] Re-reviewed `Files changed` in the Github PR explorer
- [x] Review `Codecov Report` in the comment section below once CI passes

Author: colin-axner

CHANGELOG.md

@@ -42,6 +42,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### API Breaking
 
+* (apps/transfer) [\#2446](https://github.com/cosmos/ibc-go/pull/2446) Remove `SendTransfer` function in favor of a private `sendTransfer` function. All IBC transfers must be initiated with `MsgTransfer`.
 * (apps/29-fee) [\#2395](https://github.com/cosmos/ibc-go/pull/2395) Remove param space from ics29 NewKeeper function. The field was unused.
 * (apps/27-interchain-accounts) [\#2133](https://github.com/cosmos/ibc-go/pull/2133) Generates genesis protos in a separate directory to avoid circular import errors. The protobuf package name has changed for the genesis types.
 * (light-clients/tendermint)[\#1768](https://github.com/cosmos/ibc-go/pull/1768) Removed `AllowUpdateAfterExpiry`, `AllowUpdateAfterMisbehaviour` booleans as they are deprecated (see ADR026)

modules/apps/transfer/keeper/mbt_relay_test.go

@@ -339,16 +339,18 @@ func (suite *KeeperTestSuite) TestModelBasedRelay() {
 						if !ok {
 							panic("MBT failed to parse amount from string")
 						}
-						err = suite.chainB.GetSimApp().TransferKeeper.SendTransfer(
-							suite.chainB.GetContext(),
+						msg := types.NewMsgTransfer(
 							tc.packet.SourcePort,
 							tc.packet.SourceChannel,
 							sdk.NewCoin(denom, amount),
-							sender,
+							sender.String(),
 							tc.packet.Data.Receiver,
-							clienttypes.NewHeight(1, 110),
-							0,
-							nil)
+							suite.chainA.GetTimeoutHeight(), 0, // only use timeout height
+							nil,
+						)
+
+						_, err = suite.chainB.GetSimApp().TransferKeeper.Transfer(sdk.WrapSDKContext(suite.chainB.GetContext()), msg)
+
 					}
 				case "OnRecvPacket":
 					err = suite.chainB.GetSimApp().TransferKeeper.OnRecvPacket(suite.chainB.GetContext(), packet, tc.packet.Data)

modules/apps/transfer/keeper/msg_server.go

@@ -4,6 +4,7 @@ import (
 	"context"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
+	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 
 	"github.com/cosmos/ibc-go/v6/modules/apps/transfer/types"
 )
@@ -14,11 +15,19 @@ var _ types.MsgServer = Keeper{}
 func (k Keeper) Transfer(goCtx context.Context, msg *types.MsgTransfer) (*types.MsgTransferResponse, error) {
 	ctx := sdk.UnwrapSDKContext(goCtx)
 
+	if !k.GetSendEnabled(ctx) {
+		return nil, types.ErrSendDisabled
+	}
+
 	sender, err := sdk.AccAddressFromBech32(msg.Sender)
 	if err != nil {
 		return nil, err
 	}
 
+	if k.bankKeeper.BlockedAddr(sender) {
+		return nil, sdkerrors.Wrapf(sdkerrors.ErrUnauthorized, "%s is not allowed to send funds", sender)
+	}
+
 	sequence, err := k.sendTransfer(
 		ctx, msg.SourcePort, msg.SourceChannel, msg.Token, sender, msg.Receiver, msg.TimeoutHeight, msg.TimeoutTimestamp,
 		msg.Metadata)

modules/apps/transfer/keeper/msg_server_test.go

@@ -19,6 +19,17 @@ func (suite *KeeperTestSuite) TestMsgTransfer() {
 			func() {},
 			true,
 		},
+		{
+			"send transfers disabled",
+			func() {
+				suite.chainA.GetSimApp().TransferKeeper.SetParams(suite.chainA.GetContext(),
+					types.Params{
+						SendEnabled: false,
+					},
+				)
+			},
+			false,
+		},
 		{
 			"invalid sender",
 			func() {
@@ -43,31 +54,33 @@ func (suite *KeeperTestSuite) TestMsgTransfer() {
 	}
 
 	for _, tc := range testCases {
-		suite.SetupTest()
+		suite.Run(tc.name, func() {
+			suite.SetupTest()
 
-		path := NewTransferPath(suite.chainA, suite.chainB)
-		suite.coordinator.Setup(path)
+			path := NewTransferPath(suite.chainA, suite.chainB)
+			suite.coordinator.Setup(path)
 
-		coin := sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewInt(100))
-		msg = types.NewMsgTransfer(
-			path.EndpointA.ChannelConfig.PortID,
-			path.EndpointA.ChannelID,
-			coin, suite.chainA.SenderAccount.GetAddress().String(), suite.chainB.SenderAccount.GetAddress().String(),
-			suite.chainB.GetTimeoutHeight(), 0, // only use timeout height
-			[]byte("custom metadata"),
-		)
+			coin := sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewInt(100))
+			msg = types.NewMsgTransfer(
+				path.EndpointA.ChannelConfig.PortID,
+				path.EndpointA.ChannelID,
+				coin, suite.chainA.SenderAccount.GetAddress().String(), suite.chainB.SenderAccount.GetAddress().String(),
+				suite.chainB.GetTimeoutHeight(), 0, // only use timeout height
+				[]byte("custom metadata"),
+			)
 
-		tc.malleate()
+			tc.malleate()
 
-		res, err := suite.chainA.GetSimApp().TransferKeeper.Transfer(sdk.WrapSDKContext(suite.chainA.GetContext()), msg)
+			res, err := suite.chainA.GetSimApp().TransferKeeper.Transfer(sdk.WrapSDKContext(suite.chainA.GetContext()), msg)
 
-		if tc.expPass {
-			suite.Require().NotEqual(res.Sequence, uint64(0))
-			suite.Require().NoError(err)
-			suite.Require().NotNil(res)
-		} else {
-			suite.Require().Error(err)
-			suite.Require().Nil(res)
-		}
+			if tc.expPass {
+				suite.Require().NoError(err)
+				suite.Require().NotNil(res)
+				suite.Require().NotEqual(res.Sequence, uint64(0))
+			} else {
+				suite.Require().Error(err)
+				suite.Require().Nil(res)
+			}
+		})
 	}
 }

modules/apps/transfer/keeper/relay.go

@@ -16,7 +16,7 @@ import (
 	coretypes "github.com/cosmos/ibc-go/v6/modules/core/types"
 )
 
-// SendTransfer handles transfer sending logic. There are 2 possible cases:
+// sendTransfer handles transfer sending logic. There are 2 possible cases:
 //
 // 1. Sender chain is acting as the source zone. The coins are transferred
 // to an escrow address (i.e locked) on the sender chain and then transferred
@@ -48,34 +48,6 @@ import (
 // 4. A -> C : sender chain is sink zone. Denom upon receiving: 'C/B/denom'
 // 5. C -> B : sender chain is sink zone. Denom upon receiving: 'B/denom'
 // 6. B -> A : sender chain is sink zone. Denom upon receiving: 'denom'
-//
-// Note: An IBC Transfer must be initiated using a MsgTransfer via the Transfer rpc handler
-func (k Keeper) SendTransfer(
-	ctx sdk.Context,
-	sourcePort,
-	sourceChannel string,
-	token sdk.Coin,
-	sender sdk.AccAddress,
-	receiver string,
-	timeoutHeight clienttypes.Height,
-	timeoutTimestamp uint64,
-	metadata []byte,
-) error {
-	_, err := k.sendTransfer(
-		ctx,
-		sourcePort,
-		sourceChannel,
-		token,
-		sender,
-		receiver,
-		timeoutHeight,
-		timeoutTimestamp,
-		metadata,
-	)
-	return err
-}
-
-// sendTransfer handles transfer sending logic.
 func (k Keeper) sendTransfer(
 	ctx sdk.Context,
 	sourcePort,
@@ -87,14 +59,6 @@ func (k Keeper) sendTransfer(
 	timeoutTimestamp uint64,
 	metadata []byte,
 ) (uint64, error) {
-	if !k.GetSendEnabled(ctx) {
-		return 0, types.ErrSendDisabled
-	}
-
-	if k.bankKeeper.BlockedAddr(sender) {
-		return 0, sdkerrors.Wrapf(sdkerrors.ErrUnauthorized, "%s is not allowed to send funds", sender)
-	}
-
 	channel, found := k.channelKeeper.GetChannel(ctx, sourcePort, sourceChannel)
 	if !found {
 		return 0, sdkerrors.Wrapf(channeltypes.ErrChannelNotFound, "port ID (%s) channel ID (%s)", sourcePort, sourceChannel)