imp: represent unlimited approvals with MaxUint256 value

CHANGELOG.md

@@ -43,8 +43,8 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### State Machine Breaking
 
 ### Improvements
-
 * (tests) [\#3138](https://github.com/cosmos/ibc-go/pull/3138) Support benchmarks and fuzz tests through `testing.TB`.
+* (ics20) [\#3454](https://github.com/cosmos/ibc-go/pull/3454) Represent authz unlimited spending limit as `math.MaxInt64` value.
 
 ### Features
 

modules/apps/transfer/types/transfer_authorization.go

@@ -1,17 +1,21 @@
 package types
 
 import (
+	"math/big"
+
 	errorsmod "cosmossdk.io/errors"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/x/authz"
-
 	ibcerrors "github.com/cosmos/ibc-go/v7/internal/errors"
 	channeltypes "github.com/cosmos/ibc-go/v7/modules/core/04-channel/types"
 	host "github.com/cosmos/ibc-go/v7/modules/core/24-host"
 )
 
 var _ authz.Authorization = (*TransferAuthorization)(nil)
 
+// MaxUint256 is the maximum value for a 256 bit unsigned integer.
+var MaxUint256 = new(big.Int).Sub(new(big.Int).Lsh(big.NewInt(1), 256), big.NewInt(1))
+
 // NewTransferAuthorization creates a new TransferAuthorization object.
 func NewTransferAuthorization(allocations ...Allocation) *TransferAuthorization {
 	return &TransferAuthorization{
@@ -36,6 +40,10 @@ func (a TransferAuthorization) Accept(ctx sdk.Context, msg sdk.Msg) (authz.Accep
 			continue
 		}
 
+		if allocation.SpendLimit.AmountOf(msgTransfer.Token.Denom).Equal(sdk.NewIntFromBigInt(MaxUint256)) {
+			return authz.AcceptResponse{Accept: true, Delete: false, Updated: &a}, nil
+		}
+
 		limitLeft, isNegative := allocation.SpendLimit.SafeSub(msgTransfer.Token)
 		if isNegative {
 			return authz.AcceptResponse{}, errorsmod.Wrapf(ibcerrors.ErrInsufficientFunds, "requested amount is more than spend limit")
@@ -65,6 +73,7 @@ func (a TransferAuthorization) Accept(ctx sdk.Context, msg sdk.Msg) (authz.Accep
 			Allocations: a.Allocations,
 		}}, nil
 	}
+
 	return authz.AcceptResponse{}, errorsmod.Wrapf(ibcerrors.ErrNotFound, "requested port and channel allocation does not exist")
 }
 

modules/apps/transfer/types/transfer_authorization_test.go

@@ -3,7 +3,6 @@ package types_test
 import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/x/authz"
-
 	"github.com/cosmos/ibc-go/v7/modules/apps/transfer/types"
 	ibctesting "github.com/cosmos/ibc-go/v7/testing"
 	"github.com/cosmos/ibc-go/v7/testing/mock"
@@ -86,6 +85,22 @@ func (suite *TypesTestSuite) TestTransferAuthorizationAccept() {
 				suite.Require().Len(updatedAuthz.Allocations, 1)
 			},
 		},
+		{
+			"success: with unlimted spend limit uint256 max",
+			func() {
+				transferAuthz.Allocations[0].SpendLimit = sdk.NewCoins(sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewIntFromBigInt(types.MaxUint256)))
+			},
+			func(res authz.AcceptResponse, err error) {
+				suite.Require().NoError(err)
+
+				updatedTransferAuthz, ok := res.Updated.(*types.TransferAuthorization)
+				suite.Require().True(ok)
+
+				remainder := updatedTransferAuthz.Allocations[0].SpendLimit.AmountOf(sdk.DefaultBondDenom)
+				suite.Require().True(sdk.NewIntFromBigInt(types.MaxUint256).Equal(remainder))
+
+			},
+		},
 		{
 			"no spend limit set for MsgTransfer port/channel",
 			func() {
@@ -114,6 +129,26 @@ func (suite *TypesTestSuite) TestTransferAuthorizationAccept() {
 				suite.Require().Error(err)
 			},
 		},
+		{
+			"test multiple coins does not overspend",
+			func() {
+				transferAuthz.Allocations[0].SpendLimit = sdk.NewCoins(
+					sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewInt(100)),
+					sdk.NewCoin("test-denom", sdk.NewInt(100)),
+					sdk.NewCoin("test-denom2", sdk.NewInt(100)),
+				)
+				msgTransfer.Token = sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewInt(50))
+			},
+			func(res authz.AcceptResponse, err error) {
+				suite.Require().NoError(err)
+
+				updatedTransferAuthz, ok := res.Updated.(*types.TransferAuthorization)
+				suite.Require().True(ok)
+
+				remainder := updatedTransferAuthz.Allocations[0].SpendLimit.AmountOf(sdk.DefaultBondDenom)
+				suite.Require().True(sdk.NewInt(50).Equal(remainder))
+			},
+		},
 	}
 
 	for _, tc := range testCases {
@@ -190,6 +225,13 @@ func (suite *TypesTestSuite) TestTransferAuthorizationValidateBasic() {
 			},
 			true,
 		},
+		{
+			"success: with unlimited spend limit uint256 max",
+			func() {
+				transferAuthz.Allocations[0].SpendLimit = sdk.NewCoins(sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewIntFromBigInt(types.MaxUint256)))
+			},
+			true,
+		},
 		{
 			"empty allocations",
 			func() {