Fix

modules/apps/transfer/types/errors.go

@@ -14,4 +14,5 @@ var (
 	ErrSendDisabled            = sdkerrors.Register(ModuleName, 7, "fungible token transfers from this chain are disabled")
 	ErrReceiveDisabled         = sdkerrors.Register(ModuleName, 8, "fungible token transfers to this chain are disabled")
 	ErrMaxTransferChannels     = sdkerrors.Register(ModuleName, 9, "max transfer channels")
+	ErrInvalidMemo             = sdkerrors.Register(ModuleName, 10, "invalid memo")
 )

modules/apps/transfer/types/msgs.go

@@ -12,7 +12,8 @@ import (
 
 // msg types
 const (
-	TypeMsgTransfer = "transfer"
+	TypeMsgTransfer   = "transfer"
+	MaximumMemoLength = 32768 // maximum length of the memo in bytes (value chosen arbitrarily)
 )
 
 // NewMsgTransfer creates a new MsgTransfer instance
@@ -69,6 +70,9 @@ func (msg MsgTransfer) ValidateBasic() error {
 	if strings.TrimSpace(msg.Receiver) == "" {
 		return sdkerrors.Wrap(sdkerrors.ErrInvalidAddress, "missing recipient address")
 	}
+	if len(msg.Memo) > MaximumMemoLength {
+		return sdkerrors.Wrapf(ErrInvalidMemo, "memo must not exceed %d bytes", MaximumMemoLength)
+	}
 	return ValidateIBCDenom(msg.Token.Denom)
 }
 

modules/apps/transfer/types/msgs_test.go

@@ -2,6 +2,7 @@ package types
 
 import (
 	"fmt"
+	"math/rand"
 	"testing"
 
 	"github.com/cosmos/cosmos-sdk/crypto/keys/secp256k1"
@@ -62,8 +63,20 @@ func TestMsgTransferGetSignBytes(t *testing.T) {
 	})
 }
 
+// GenerateString generates a random string of the given length in bytes
+func GenerateString(length uint) string {
+	charset := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+	bytes := make([]byte, length)
+	for i := range bytes {
+		bytes[i] = charset[rand.Intn(len(charset))]
+	}
+	return string(bytes)
+}
+
 // TestMsgTransferValidation tests ValidateBasic for MsgTransfer
 func TestMsgTransferValidation(t *testing.T) {
+	largeMemoTransfer := NewMsgTransfer(validPort, validChannel, coin, addr1, addr2, timeoutHeight, 0)
+	largeMemoTransfer.Memo = GenerateString(MaximumMemoLength + 1)
 	testCases := []struct {
 		name    string
 		msg     *MsgTransfer
@@ -77,6 +90,7 @@ func TestMsgTransferValidation(t *testing.T) {
 		{"port id contains non-alpha", NewMsgTransfer(invalidPort, validChannel, coin, addr1, addr2, timeoutHeight, 0), false},
 		{"too short channel id", NewMsgTransfer(validPort, invalidShortChannel, coin, addr1, addr2, timeoutHeight, 0), false},
 		{"too long channel id", NewMsgTransfer(validPort, invalidLongChannel, coin, addr1, addr2, timeoutHeight, 0), false},
+		{"too long memo", largeMemoTransfer, false},
 		{"channel id contains non-alpha", NewMsgTransfer(validPort, invalidChannel, coin, addr1, addr2, timeoutHeight, 0), false},
 		{"invalid denom", NewMsgTransfer(validPort, validChannel, invalidDenomCoin, addr1, addr2, timeoutHeight, 0), false},
 		{"zero coin", NewMsgTransfer(validPort, validChannel, zeroCoin, addr1, addr2, timeoutHeight, 0), false},

testing/simapp/utils.go

@@ -3,15 +3,14 @@ package simapp
 import (
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
-
 	"github.com/cosmos/cosmos-sdk/codec"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/types/kv"
 	"github.com/cosmos/cosmos-sdk/types/module"
 	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
 	"github.com/tendermint/tendermint/libs/log"
 	dbm "github.com/tendermint/tm-db"
+	"io/ioutil"
 
 	"github.com/cosmos/ibc-go/v3/testing/simapp/helpers"
 )