From 64aa2255c6aa3395a48630cd999de97fc27aad28 Mon Sep 17 00:00:00 2001
From: Assaf Morami <assaf.morami@gmail.com>
Date: Thu, 11 May 2023 11:46:31 +0300
Subject: [PATCH 1/2] Infinite feegrant bug test

This test is designed to reproduce an infinite Feegrant bug that occurs when using AllowedMsgAllowance with an internal BasicAllowance.

I suspect that this line (https://github.com/scrtlabs/cosmos-sdk/blob/61091b357e/x/feegrant/basic_fee.go#L31) does not update the internal BasicAllowance after using part of the grant. This may be related to this line (https://github.com/scrtlabs/cosmos-sdk/blob/61091b357e/x/feegrant/filtered_fee.go#L47) as well.
---
 x/feegrant/filtered_fee_test.go | 82 +++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 x/feegrant/filtered_fee_test.go

diff --git a/x/feegrant/filtered_fee_test.go b/x/feegrant/filtered_fee_test.go
new file mode 100644
index 00000000000..a1be11fa65a
--- /dev/null
+++ b/x/feegrant/filtered_fee_test.go
@@ -0,0 +1,82 @@
+package feegrant_test
+
+import (
+	"testing"
+	"time"
+
+	bank "github.com/cosmos/cosmos-sdk/x/bank/types"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
+
+	codectypes "github.com/cosmos/cosmos-sdk/codec/types"
+	"github.com/cosmos/cosmos-sdk/simapp"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/x/feegrant"
+)
+
+func TestFilteredFeeValidAllow(t *testing.T) {
+	app := simapp.Setup(false)
+
+	smallAtom := sdk.NewCoins(sdk.NewInt64Coin("atom", 488))
+	bigAtom := sdk.NewCoins(sdk.NewInt64Coin("atom", 1000))
+	leftAtom := sdk.NewCoins(sdk.NewInt64Coin("atom", 512))
+
+	basicAllowance, _ := codectypes.NewAnyWithValue(&feegrant.BasicAllowance{
+		SpendLimit: bigAtom,
+	})
+
+	cases := map[string]struct {
+		allowance *feegrant.AllowedMsgAllowance
+		// all other checks are ignored if valid=false
+		fee       sdk.Coins
+		blockTime time.Time
+		valid     bool
+		accept    bool
+		remove    bool
+		remains   sdk.Coins
+	}{
+		"internal fee is updated": {
+			allowance: &feegrant.AllowedMsgAllowance{
+				Allowance:       basicAllowance,
+				AllowedMessages: []string{"/cosmos.bank.v1beta1.MsgSend"},
+			},
+			fee:     smallAtom,
+			accept:  true,
+			remove:  false,
+			remains: leftAtom,
+		},
+	}
+
+	for name, stc := range cases {
+		tc := stc // to make scopelint happy
+		t.Run(name, func(t *testing.T) {
+			err := tc.allowance.ValidateBasic()
+			require.NoError(t, err)
+
+			ctx := app.BaseApp.NewContext(false, tmproto.Header{}).WithBlockTime(tc.blockTime)
+
+			// now try to deduct
+			removed, err := tc.allowance.Accept(ctx, tc.fee, []sdk.Msg{
+				&bank.MsgSend{
+					FromAddress: "gm",
+					ToAddress:   "gn",
+					Amount:      tc.fee,
+				},
+			})
+			if !tc.accept {
+				require.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+
+			require.Equal(t, tc.remove, removed)
+			if !removed {
+				var basicAllowanceLeft feegrant.BasicAllowance
+				app.AppCodec().Unmarshal(tc.allowance.Allowance.Value, &basicAllowanceLeft)
+
+				assert.Equal(t, tc.remains, basicAllowanceLeft.SpendLimit)
+			}
+		})
+	}
+}

From 034306f904245dc72060dc38e4fa4bf6275d1537 Mon Sep 17 00:00:00 2001
From: Assaf Morami <assaf.morami@gmail.com>
Date: Thu, 11 May 2023 12:08:37 +0300
Subject: [PATCH 2/2] Fix infinite feegrant bug

The internal allowance update in AllowedMsgAllowance was never propagated to the parent AllowedMsgAllowance.
---
 x/feegrant/filtered_fee.go | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/x/feegrant/filtered_fee.go b/x/feegrant/filtered_fee.go
index f83f3c5f627..b9eaff18cbd 100644
--- a/x/feegrant/filtered_fee.go
+++ b/x/feegrant/filtered_fee.go
@@ -63,7 +63,17 @@ func (a *AllowedMsgAllowance) Accept(ctx sdk.Context, fee sdk.Coins, msgs []sdk.
 		return false, err
 	}
 
-	return allowance.Accept(ctx, fee, msgs)
+	remove, err := allowance.Accept(ctx, fee, msgs)
+	if err != nil {
+		return false, err
+	}
+
+	a.Allowance, err = types.NewAnyWithValue(allowance.(proto.Message))
+	if err != nil {
+		return false, err
+	}
+
+	return remove, nil
 }
 
 func (a *AllowedMsgAllowance) allowedMsgsToMap(ctx sdk.Context) map[string]bool {