imp: check length tokens array against maximum allowed (#6349)

* check length of tokens array against maximum allowed

* chore: add note on arbitrary selection

---------

Co-authored-by: Colin Axnér <25233464+colin-axner@users.noreply.github.com>

Author: crodriguezvega

modules/apps/transfer/types/msgs.go

@@ -15,6 +15,7 @@ import (
 const (
 	MaximumReceiverLength = 2048  // maximum length of the receiver address in bytes (value chosen arbitrarily)
 	MaximumMemoLength     = 32768 // maximum length of the memo in bytes (value chosen arbitrarily)
+	MaximumTokensLength   = 100   // maximum number of tokens that can be transferred in a single message (value chosen arbitrarily)
 )
 
 var (
@@ -81,6 +82,10 @@ func (msg MsgTransfer) ValidateBasic() error {
 		return errorsmod.Wrap(ErrInvalidAmount, "cannot fill both token and token array")
 	}
 
+	if len(msg.Tokens) > MaximumTokensLength {
+		return errorsmod.Wrapf(ibcerrors.ErrInvalidCoins, "number of tokens must not exceed %d", MaximumTokensLength)
+	}
+
 	_, err := sdk.AccAddressFromBech32(msg.Sender)
 	if err != nil {
 		return errorsmod.Wrapf(ibcerrors.ErrInvalidAddress, "string could not be parsed as address: %v", err)

modules/apps/transfer/types/msgs_test.go

@@ -74,6 +74,7 @@ func TestMsgTransferValidation(t *testing.T) {
 		{"multidenom: invalid denom", types.NewMsgTransfer(validPort, validChannel, coins.Add(invalidDenomCoins...), sender, receiver, timeoutHeight, 0, ""), false},
 		{"multidenom: invalid ibc denom", types.NewMsgTransfer(validPort, validChannel, coins.Add(invalidIBCCoins...), sender, receiver, timeoutHeight, 0, ""), false},
 		{"multidenom: zero coins", types.NewMsgTransfer(validPort, validChannel, zeroCoins, sender, receiver, timeoutHeight, 0, ""), false},
+		{"multidenom: too many coins", types.NewMsgTransfer(validPort, validChannel, make([]sdk.Coin, types.MaximumTokensLength+1), sender, receiver, timeoutHeight, 0, ""), false},
 	}
 
 	for i, tc := range testCases {