feat(evmutil): implement MsgConvertCosmosCoinFromERC20 (#1609)

* first pass at convert cosmos coin -> evm msg

* test ConvertCosmosCoinFromERC20 method

* test message server for MsgConvertCosmosCoinFromERC20

* update spec to include MsgConvertCosmosCoinFromERC20

* update changelog

* add CLI command for convert-cosmos-coin-from-erc20

* add test of removed/re-enable denom for convert

CHANGELOG.md

@@ -43,6 +43,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 - (evmutil) [#1603] Add MsgConvertCosmosCoinToERC20 for converting an sdk.Coin to an ERC20 in the EVM
 - (evmutil) [#1604] Emit events for MsgConvertCosmosCoinToERC20: `message` & `convert_cosmos_coin_to_erc20`
 - (evmutil) [#1605] Add query for deployed ERC20 contracts representing Cosmos coins in the EVM
+- (evmutil) [#1609] Add MsgConvertCosmosCoinFromERC20 for converting the ERC20 back to an sdk.Coin
 
 ### Client Breaking
 - (evmutil) [#1603] Renamed error `ErrConversionNotEnabled` to `ErrEVMConversionNotEnabled`
@@ -251,6 +252,7 @@ the [changelog](https://github.com/cosmos/cosmos-sdk/blob/v0.38.4/CHANGELOG.md).
 - [#257](https://github.com/Kava-Labs/kava/pulls/257) Include scripts to run
   large-scale simulations remotely using aws-batch
 
+[#1609]: https://github.com/Kava-Labs/kava/pull/1609
 [#1605]: https://github.com/Kava-Labs/kava/pull/1605
 [#1604]: https://github.com/Kava-Labs/kava/pull/1604
 [#1603]: https://github.com/Kava-Labs/kava/pull/1603

docs/core/proto-docs.md

@@ -3914,7 +3914,7 @@ MsgConvertCoinToERC20Response defines the response value from Msg/ConvertCoinToE
 <a name="kava.evmutil.v1beta1.MsgConvertCosmosCoinFromERC20"></a>
 
 ### MsgConvertCosmosCoinFromERC20
-ConvertCosmosCoinFromERC20 defines a conversion from ERC20 to cosmos coins for cosmos-native assets.
+MsgConvertCosmosCoinFromERC20 defines a conversion from ERC20 to cosmos coins for cosmos-native assets.
 
 
 | Field | Type | Label | Description |
@@ -3941,7 +3941,7 @@ MsgConvertCosmosCoinFromERC20Response defines the response value from Msg/MsgCon
 <a name="kava.evmutil.v1beta1.MsgConvertCosmosCoinToERC20"></a>
 
 ### MsgConvertCosmosCoinToERC20
-ConvertCosmosCoinToERC20 defines a conversion from cosmos sdk.Coin to ERC20 for cosmos-native assets.
+MsgConvertCosmosCoinToERC20 defines a conversion from cosmos sdk.Coin to ERC20 for cosmos-native assets.
 
 
 | Field | Type | Label | Description |

proto/kava/evmutil/v1beta1/tx.proto

@@ -57,7 +57,7 @@ message MsgConvertERC20ToCoin {
 // Msg/MsgConvertERC20ToCoin.
 message MsgConvertERC20ToCoinResponse {}
 
-// ConvertCosmosCoinToERC20 defines a conversion from cosmos sdk.Coin to ERC20 for cosmos-native assets.
+// MsgConvertCosmosCoinToERC20 defines a conversion from cosmos sdk.Coin to ERC20 for cosmos-native assets.
 message MsgConvertCosmosCoinToERC20 {
   // Kava bech32 address initiating the conversion.
   string initiator = 1;
@@ -70,7 +70,7 @@ message MsgConvertCosmosCoinToERC20 {
 // MsgConvertCosmosCoinToERC20Response defines the response value from Msg/MsgConvertCosmosCoinToERC20.
 message MsgConvertCosmosCoinToERC20Response {}
 
-// ConvertCosmosCoinFromERC20 defines a conversion from ERC20 to cosmos coins for cosmos-native assets.
+// MsgConvertCosmosCoinFromERC20 defines a conversion from ERC20 to cosmos coins for cosmos-native assets.
 message MsgConvertCosmosCoinFromERC20 {
   // EVM hex address initiating the conversion.
   string initiator = 1;

x/evmutil/client/cli/tx.go

@@ -31,6 +31,7 @@ func GetTxCmd() *cobra.Command {
 		getCmdMsgConvertCoinToERC20(),
 		getCmdConvertERC20ToCoin(),
 		getCmdMsgConvertCosmosCoinToERC20(),
+		getCmdMsgConvertCosmosCoinFromERC20(),
 	}
 
 	for _, cmd := range cmds {
@@ -159,3 +160,42 @@ func getCmdMsgConvertCosmosCoinToERC20() *cobra.Command {
 		},
 	}
 }
+
+func getCmdMsgConvertCosmosCoinFromERC20() *cobra.Command {
+	return &cobra.Command{
+		Use:   "convert-cosmos-coin-from-erc20 [receiver_kava_address] [amount] [flags]",
+		Short: "converts asset native to Cosmos Co-chain back from an ERC20 on the EVM co-chain",
+		Example: fmt.Sprintf(
+			`Convert ERC20 representation of 500 ATOM back to a Cosmos coin, sending to kava1q0dkky0505r555etn6u2nz4h4kjcg5y8dg863a:
+  %s tx %s convert-cosmos-coin-from-erc20 kava1q0dkky0505r555etn6u2nz4h4kjcg5y8dg863a 500000000ibc/27394FB092D2ECCD56123C74F36E4C1F926001CEADA9CA97EA622B25F41E5EB2 --from <key> --gas 2000000`,
+			version.AppName, types.ModuleName,
+		),
+		Args: cobra.ExactArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			clientCtx, err := client.GetClientTxContext(cmd)
+			if err != nil {
+				return err
+			}
+
+			receiver, err := sdk.AccAddressFromBech32(args[0])
+			if err != nil {
+				return fmt.Errorf("receiver '%s' is an invalid kava address", args[0])
+			}
+
+			amount, err := sdk.ParseCoinNormalized(args[1])
+			if err != nil {
+				return err
+			}
+
+			signer := clientCtx.GetFromAddress()
+			initiator := common.BytesToAddress(signer.Bytes())
+
+			msg := types.NewMsgConvertCosmosCoinFromERC20(initiator.String(), receiver.String(), amount)
+			if err := msg.ValidateBasic(); err != nil {
+				return err
+			}
+
+			return tx.GenerateOrBroadcastTxCLI(clientCtx, cmd.Flags(), &msg)
+		},
+	}
+}

x/evmutil/keeper/conversion_cosmos_native.go

@@ -1,8 +1,11 @@
 package keeper
 
 import (
+	"fmt"
+
 	errorsmod "cosmossdk.io/errors"
 	sdk "github.com/cosmos/cosmos-sdk/types"
+	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 
 	"github.com/kava-labs/kava/x/evmutil/types"
 )
@@ -54,3 +57,51 @@ func (k *Keeper) ConvertCosmosCoinToERC20(
 
 	return nil
 }
+
+// ConvertCosmosCoinFromERC20 burns the ERC20 wrapper of the cosmos coin and
+// sends the underlying sdk coin form the module account to the receiver.
+func (k *Keeper) ConvertCosmosCoinFromERC20(
+	ctx sdk.Context,
+	initiator types.InternalEVMAddress,
+	receiver sdk.AccAddress,
+	coin sdk.Coin,
+) error {
+	amount := coin.Amount.BigInt()
+	// get deployed contract
+	contractAddress, found := k.GetDeployedCosmosCoinContract(ctx, coin.Denom)
+	if !found {
+		// no contract deployed
+		return errorsmod.Wrapf(types.ErrInvalidCosmosDenom, fmt.Sprintf("no erc20 contract found for %s", coin.Denom))
+	}
+
+	// verify sufficient balance
+	balance, err := k.QueryERC20BalanceOf(ctx, contractAddress, initiator)
+	if err != nil {
+		return errorsmod.Wrapf(types.ErrEVMCall, "failed to retrieve balance %s", err.Error())
+	}
+	if balance.Cmp(amount) == -1 {
+		return errorsmod.Wrapf(sdkerrors.ErrInsufficientFunds, "failed to convert to cosmos coins")
+	}
+
+	// burn initiator's ERC20 tokens
+	err = k.BurnERC20(ctx, contractAddress, initiator, amount)
+	if err != nil {
+		return err
+	}
+
+	// send sdk coins to receiver, unlocking them from the module account
+	err = k.bankKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, receiver, sdk.NewCoins(coin))
+	if err != nil {
+		return err
+	}
+
+	ctx.EventManager().EmitEvent(sdk.NewEvent(
+		types.EventTypeConvertCosmosCoinFromERC20,
+		sdk.NewAttribute(types.AttributeKeyInitiator, initiator.String()),
+		sdk.NewAttribute(types.AttributeKeyReceiver, receiver.String()),
+		sdk.NewAttribute(types.AttributeKeyERC20Address, contractAddress.Hex()),
+		sdk.NewAttribute(types.AttributeKeyAmount, coin.String()),
+	))
+
+	return nil
+}

x/evmutil/keeper/conversion_cosmos_native_test.go

@@ -15,29 +15,29 @@ import (
 	"github.com/kava-labs/kava/x/evmutil/types"
 )
 
-type ConversionCosmosNativeSuite struct {
+type convertCosmosCoinToERC20Suite struct {
 	testutil.Suite
 }
 
-func TestConversionCosmosNativeSuite(t *testing.T) {
+func TestConversionCosmosNativeToEvmSuite(t *testing.T) {
-	suite.Run(t, new(ConversionCosmosNativeSuite))
+	suite.Run(t, new(convertCosmosCoinToERC20Suite))
 }
 
 // fail test if contract for denom not registered
-func (suite *ConversionCosmosNativeSuite) denomContractRegistered(denom string) types.InternalEVMAddress {
+func (suite *convertCosmosCoinToERC20Suite) denomContractRegistered(denom string) types.InternalEVMAddress {
 	contractAddress, found := suite.Keeper.GetDeployedCosmosCoinContract(suite.Ctx, denom)
 	suite.True(found)
 	return contractAddress
 }
 
 // fail test if contract for denom IS registered
-func (suite *ConversionCosmosNativeSuite) denomContractNotRegistered(denom string) {
+func (suite *convertCosmosCoinToERC20Suite) denomContractNotRegistered(denom string) {
 	_, found := suite.Keeper.GetDeployedCosmosCoinContract(suite.Ctx, denom)
 	suite.False(found)
 }
 
 // more tests of tests of this method are made to the msg handler, see ./msg_server_test.go
-func (suite *ConversionCosmosNativeSuite) TestConvertCosmosCoinToERC20() {
+func (suite *convertCosmosCoinToERC20Suite) TestConvertCosmosCoinToERC20() {
 	allowedDenom := "ibc/27394FB092D2ECCD56123C74F36E4C1F926001CEADA9CA97EA622B25F41E5EB2"
 	initialFunding := sdk.NewInt64Coin(allowedDenom, int64(1e10))
 	initiator := app.RandomAddress()
@@ -171,3 +171,129 @@ func (suite *ConversionCosmosNativeSuite) TestConvertCosmosCoinToERC20() {
 		)
 	})
 }
+
+type convertCosmosCoinFromERC20Suite struct {
+	testutil.Suite
+
+	denom     string
+	initiator types.InternalEVMAddress
+	receiver  sdk.AccAddress
+
+	contractAddress types.InternalEVMAddress
+	initialPosition sdk.Coin
+
+	query func(method string, args ...interface{}) ([]interface{}, error)
+}
+
+func (suite *convertCosmosCoinFromERC20Suite) SetupTest() {
+	var err error
+	suite.Suite.SetupTest()
+
+	suite.denom = "magic"
+	suite.initiator = testutil.RandomInternalEVMAddress()
+	suite.receiver = app.RandomAddress()
+
+	// manually create an initial position - sdk coin locked in module
+	suite.initialPosition = sdk.NewInt64Coin(suite.denom, 1e12)
+	err = suite.App.FundModuleAccount(suite.Ctx, types.ModuleName, sdk.NewCoins(suite.initialPosition))
+	suite.NoError(err)
+
+	// deploy erc20 contract for the denom
+	tokenInfo := types.AllowedCosmosCoinERC20Token{
+		CosmosDenom: suite.denom,
+		Name:        "Test Token",
+		Symbol:      "MAGIC",
+		Decimals:    6,
+	}
+	suite.contractAddress, err = suite.Keeper.GetOrDeployCosmosCoinERC20Contract(suite.Ctx, tokenInfo)
+	suite.NoError(err)
+
+	// manually create an initial position - minted tokens
+	err = suite.Keeper.MintERC20(suite.Ctx, suite.contractAddress, suite.initiator, suite.initialPosition.Amount.BigInt())
+	suite.NoError(err)
+
+	caller, key := testutil.RandomEvmAccount()
+	suite.query = func(method string, args ...interface{}) ([]interface{}, error) {
+		return suite.QueryContract(
+			types.ERC20KavaWrappedCosmosCoinContract.ABI,
+			caller,
+			key,
+			suite.contractAddress,
+			method,
+			args...,
+		)
+	}
+}
+
+func (suite *convertCosmosCoinFromERC20Suite) checkTotalSupply(expectedSupply sdkmath.Int) {
+	res, err := suite.query("totalSupply")
+	suite.NoError(err)
+	suite.Len(res, 1)
+	suite.BigIntsEqual(expectedSupply.BigInt(), res[0].(*big.Int), "unexpected total supply")
+}
+
+func (suite *convertCosmosCoinFromERC20Suite) checkBalanceOf(address types.InternalEVMAddress, expectedBalance sdkmath.Int) {
+	res, err := suite.query("balanceOf", address.Address)
+	suite.NoError(err)
+	suite.Len(res, 1)
+	suite.BigIntsEqual(expectedBalance.BigInt(), res[0].(*big.Int), fmt.Sprintf("unexpected balanceOf for %s", address))
+}
+
+func TestConversionCosmosNativeFromEVMSuite(t *testing.T) {
+	suite.Run(t, new(convertCosmosCoinFromERC20Suite))
+}
+
+func (suite *convertCosmosCoinFromERC20Suite) TestConvertCosmosCoinFromERC20_NoContractDeployed() {
+	err := suite.Keeper.ConvertCosmosCoinFromERC20(
+		suite.Ctx,
+		suite.initiator,
+		suite.receiver,
+		sdk.NewInt64Coin("unsupported-denom", 1e6),
+	)
+	suite.ErrorContains(err, "no erc20 contract found for unsupported-denom")
+}
+
+func (suite *convertCosmosCoinFromERC20Suite) TestConvertCosmosCoinFromERC20() {
+	// half the initial position
+	amount := suite.initialPosition.SubAmount(suite.initialPosition.Amount.QuoRaw(2))
+
+	suite.Run("partial withdraw", func() {
+		err := suite.Keeper.ConvertCosmosCoinFromERC20(
+			suite.Ctx,
+			suite.initiator,
+			suite.receiver,
+			amount,
+		)
+		suite.NoError(err)
+
+		suite.checkTotalSupply(amount.Amount)
+		suite.checkBalanceOf(suite.initiator, amount.Amount)
+		suite.App.CheckBalance(suite.T(), suite.Ctx, suite.receiver, sdk.NewCoins(amount))
+	})
+
+	suite.Run("full withdraw", func() {
+		err := suite.Keeper.ConvertCosmosCoinFromERC20(
+			suite.Ctx,
+			suite.initiator,
+			suite.receiver,
+			amount,
+		)
+		suite.NoError(err)
+
+		// expect no remaining erc20 balance
+		suite.checkTotalSupply(sdkmath.ZeroInt())
+		suite.checkBalanceOf(suite.initiator, sdkmath.ZeroInt())
+		// expect full amount withdrawn to receiver
+		suite.App.CheckBalance(suite.T(), suite.Ctx, suite.receiver, sdk.NewCoins(suite.initialPosition))
+	})
+
+	suite.Run("insufficient balance", func() {
+		err := suite.Keeper.ConvertCosmosCoinFromERC20(
+			suite.Ctx,
+			suite.initiator,
+			suite.receiver,
+			amount,
+		)
+		suite.ErrorContains(err, "failed to convert to cosmos coins: insufficient funds")
+	})
+}

x/evmutil/keeper/erc20.go

@@ -158,6 +158,27 @@ func (k Keeper) MintERC20(
 	return err
 }
 
+// BurnERC20 burns the token amount from the initiator's balance.
+func (k Keeper) BurnERC20(
+	ctx sdk.Context,
+	contractAddr types.InternalEVMAddress,
+	initiator types.InternalEVMAddress,
+	amount *big.Int,
+) error {
+	_, err := k.CallEVM(
+		ctx,
+		types.ERC20KavaWrappedCosmosCoinContract.ABI,
+		types.ModuleEVMAddress,
+		contractAddr,
+		"burn",
+		// Burn ERC20 args
+		initiator.Address,
+		amount,
+	)
+
+	return err
+}
+
 func (k Keeper) QueryERC20BalanceOf(
 	ctx sdk.Context,
 	contractAddr types.InternalEVMAddress,

x/evmutil/keeper/msg_server.go

@@ -154,7 +154,36 @@ func (s msgServer) ConvertCosmosCoinToERC20(
 // back into an sdk.Coin.
 func (s msgServer) ConvertCosmosCoinFromERC20(
 	goCtx context.Context,
-	req *types.MsgConvertCosmosCoinFromERC20,
+	msg *types.MsgConvertCosmosCoinFromERC20,
 ) (*types.MsgConvertCosmosCoinFromERC20Response, error) {
-	panic("unimplemented - coming soon!")
+	ctx := sdk.UnwrapSDKContext(goCtx)
+
+	initiator, err := types.NewInternalEVMAddressFromString(msg.Initiator)
+	if err != nil {
+		return nil, fmt.Errorf("invalid initiator address: %w", err)
+	}
+
+	receiver, err := sdk.AccAddressFromBech32(msg.Receiver)
+	if err != nil {
+		return nil, fmt.Errorf("invalid receiver address: %w", err)
+	}
+
+	if err := s.keeper.ConvertCosmosCoinFromERC20(
+		ctx,
+		initiator,
+		receiver,
+		*msg.Amount,
+	); err != nil {
+		return nil, err
+	}
+
+	ctx.EventManager().EmitEvent(
+		sdk.NewEvent(
+			sdk.EventTypeMessage,
+			sdk.NewAttribute(sdk.AttributeKeyModule, types.AttributeValueCategory),
+			sdk.NewAttribute(sdk.AttributeKeySender, msg.Initiator),
+		),
+	)
+
+	return &types.MsgConvertCosmosCoinFromERC20Response{}, nil
 }

x/evmutil/keeper/msg_server_test.go

@@ -509,3 +509,222 @@ func (suite *MsgServerSuite) TestConvertCosmosCoinToERC20_AlreadyDeployedContrac
 	suite.Len(totalSupply, 1)
 	suite.Equal(amount.MulRaw(2).BigInt(), totalSupply[0].(*big.Int))
 }
+
+func (suite *MsgServerSuite) TestConvertCosmosCoinFromERC20() {
+	denom := "magic"
+	tokenInfo := types.NewAllowedCosmosCoinERC20Token(denom, "Cosmos Coin", "MAGIC", 6)
+	initialPosition := sdk.NewInt64Coin(denom, 1e10)
+	initiator := testutil.RandomInternalEVMAddress()
+
+	var contractAddress types.InternalEVMAddress
+	setup := func() {
+		suite.SetupTest()
+
+		// allow conversion to the denom
+		params := suite.Keeper.GetParams(suite.Ctx)
+		params.AllowedCosmosDenoms = append(params.AllowedCosmosDenoms, tokenInfo)
+		suite.Keeper.SetParams(suite.Ctx, params)
+
+		// setup initial position
+		addr := app.RandomAddress()
+		err := suite.App.FundAccount(suite.Ctx, addr, sdk.NewCoins(initialPosition))
+		suite.NoError(err)
+		err = suite.Keeper.ConvertCosmosCoinToERC20(suite.Ctx, addr, initiator, initialPosition)
+		suite.NoError(err)
+
+		contractAddress, _ = suite.Keeper.GetDeployedCosmosCoinContract(suite.Ctx, denom)
+	}
+
+	testCases := []struct {
+		name            string
+		msg             types.MsgConvertCosmosCoinFromERC20
+		amountConverted sdkmath.Int
+		expectedErr     string
+	}{
+		{
+			name: "valid - full convert",
+			msg: types.NewMsgConvertCosmosCoinFromERC20(
+				initiator.Hex(),
+				app.RandomAddress().String(),
+				initialPosition,
+			),
+			amountConverted: initialPosition.Amount,
+			expectedErr:     "",
+		},
+		{
+			name: "valid - partial convert",
+			msg: types.NewMsgConvertCosmosCoinFromERC20(
+				initiator.Hex(),
+				app.RandomAddress().String(),
+				sdk.NewInt64Coin(denom, 123456),
+			),
+			amountConverted: sdkmath.NewInt(123456),
+			expectedErr:     "",
+		},
+		{
+			name: "invalid - bad initiator",
+			msg: types.NewMsgConvertCosmosCoinFromERC20(
+				"invalid-address",
+				app.RandomAddress().String(),
+				sdk.NewInt64Coin(denom, 123456),
+			),
+			amountConverted: sdkmath.ZeroInt(),
+			expectedErr:     "invalid initiator address",
+		},
+		{
+			name: "invalid - bad receiver",
+			msg: types.NewMsgConvertCosmosCoinFromERC20(
+				testutil.RandomEvmAddress().Hex(),
+				"invalid-address",
+				sdk.NewInt64Coin(denom, 123456),
+			),
+			amountConverted: sdkmath.ZeroInt(),
+			expectedErr:     "invalid receiver address",
+		},
+		{
+			name: "invalid - unsupported asset",
+			msg: types.NewMsgConvertCosmosCoinFromERC20(
+				initiator.Hex(),
+				app.RandomAddress().String(),
+				sdk.NewInt64Coin("not-supported", 123456),
+			),
+			amountConverted: sdkmath.ZeroInt(),
+			expectedErr:     "no erc20 contract found",
+		},
+		{
+			name: "invalid - insufficient funds",
+			msg: types.NewMsgConvertCosmosCoinFromERC20(
+				initiator.Hex(),
+				app.RandomAddress().String(),
+				initialPosition.AddAmount(sdkmath.OneInt()),
+			),
+			amountConverted: sdkmath.ZeroInt(),
+			expectedErr:     "failed to convert to cosmos coins: insufficient funds",
+		},
+	}
+
+	for _, tc := range testCases {
+		suite.Run(tc.name, func() {
+			setup()
+
+			_, err := suite.msgServer.ConvertCosmosCoinFromERC20(suite.Ctx, &tc.msg)
+
+			if tc.expectedErr != "" {
+				suite.ErrorContains(err, tc.expectedErr)
+				// expect no change in erc20 balance
+				balance, err := suite.Keeper.QueryERC20BalanceOf(suite.Ctx, contractAddress, initiator)
+				suite.NoError(err)
+				suite.BigIntsEqual(initialPosition.Amount.BigInt(), balance, "expected no change in initiator's erc20 balance")
+				// expect no change in module balance
+				suite.Equal(initialPosition.Amount, suite.ModuleBalance(denom), "expected no change in module balance")
+				return
+			}
+
+			suite.NoError(err)
+
+			receiver := sdk.MustAccAddressFromBech32(tc.msg.Receiver)
+			// expect receiver to have the sdk coins
+			sdkBalance := suite.BankKeeper.GetBalance(suite.Ctx, receiver, denom)
+			suite.Equal(tc.amountConverted, sdkBalance.Amount)
+
+			newEvmBalance := initialPosition.SubAmount(tc.amountConverted)
+			// expect initiator to have the balance deducted
+			evmBalance, err := suite.Keeper.QueryERC20BalanceOf(suite.Ctx, contractAddress, initiator)
+			suite.NoError(err)
+			suite.BigIntsEqual(newEvmBalance.Amount.BigInt(), evmBalance, "unexpected initiator final erc20 balance")
+
+			// expect tokens to be deducted from module account
+			suite.True(newEvmBalance.Amount.Equal(suite.ModuleBalance(denom)), "unexpected module balance")
+
+			// expect erc20 total supply to reflect new value
+			caller, key := testutil.RandomEvmAccount()
+			totalSupply, err := suite.QueryContract(
+				types.ERC20KavaWrappedCosmosCoinContract.ABI,
+				caller,
+				key,
+				contractAddress,
+				"totalSupply",
+			)
+			suite.NoError(err)
+			suite.BigIntsEqual(newEvmBalance.Amount.BigInt(), totalSupply[0].(*big.Int), "unexpected total supply")
+		})
+	}
+}
+
+// the test verifies the behavior for when a denom is removed from the params list
+// after conversions have been made:
+// - it should prevent more conversions from sdk -> evm for that denom
+// - existing erc20s should be allowed to get converted back to a sdk.Coins
+// - allowing the denom again should use existing contract
+func (suite *MsgServerSuite) TestConvertCosmosCoinForRemovedDenom() {
+	denom := "magic"
+	tokenInfo := types.NewAllowedCosmosCoinERC20Token(denom, "MAGIC COIN", "MAGIC", 6)
+	account := app.RandomAddress()
+	evmAddr := types.BytesToInternalEVMAddress(account.Bytes())
+	coin := func(amt int64) sdk.Coin { return sdk.NewInt64Coin(denom, amt) }
+
+	// fund account
+	suite.NoError(suite.App.FundAccount(suite.Ctx, account, sdk.NewCoins(coin(1e10))))
+
+	// setup the token as allowed
+	params := suite.Keeper.GetParams(suite.Ctx)
+	params.AllowedCosmosDenoms = append(params.AllowedCosmosDenoms, tokenInfo)
+	suite.Keeper.SetParams(suite.Ctx, params)
+
+	// convert some coins while its allowed
+	msg := types.NewMsgConvertCosmosCoinToERC20(account.String(), evmAddr.Hex(), coin(5e9))
+	_, err := suite.msgServer.ConvertCosmosCoinToERC20(suite.Ctx, &msg)
+	suite.NoError(err)
+
+	// expect contract registered
+	contractAddress, isRegistered := suite.Keeper.GetDeployedCosmosCoinContract(suite.Ctx, denom)
+	suite.True(isRegistered)
+	suite.False(contractAddress.IsNil())
+
+	// unregister contract
+	params.AllowedCosmosDenoms = []types.AllowedCosmosCoinERC20Token{}
+	suite.Keeper.SetParams(suite.Ctx, params)
+
+	suite.Run("disallows sdk -> evm when removed", func() {
+		msg := types.NewMsgConvertCosmosCoinToERC20(account.String(), evmAddr.Hex(), coin(5e9))
+		_, err := suite.msgServer.ConvertCosmosCoinToERC20(suite.Ctx, &msg)
+		suite.ErrorContains(err, "sdk.Coin not enabled to convert to ERC20 token")
+	})
+
+	suite.Run("allows conversion of existing ERC20s", func() {
+		msg := types.NewMsgConvertCosmosCoinFromERC20(evmAddr.Hex(), account.String(), coin(5e9))
+		_, err := suite.msgServer.ConvertCosmosCoinFromERC20(suite.Ctx, &msg)
+		suite.NoError(err)
+
+		// should be fully withdrawn
+		erc20Bal, err := suite.Keeper.QueryERC20BalanceOf(suite.Ctx, contractAddress, evmAddr)
+		suite.NoError(err)
+		suite.BigIntsEqual(big.NewInt(0), erc20Bal, "cosmos coins were not converted back")
+		sdkBal := suite.BankKeeper.GetBalance(suite.Ctx, account, denom)
+		suite.Equal(coin(1e10), sdkBal)
+	})
+
+	suite.Run("contract stays registered", func() {
+		postDisableContractAddress, found := suite.Keeper.GetDeployedCosmosCoinContract(suite.Ctx, denom)
+		suite.True(found)
+		suite.Equal(contractAddress, postDisableContractAddress)
+	})
+
+	suite.Run("re-enable uses original contract", func() {
+		// re-enable contract
+		params.AllowedCosmosDenoms = append(params.AllowedCosmosDenoms, tokenInfo)
+		suite.Keeper.SetParams(suite.Ctx, params)
+
+		// attempt conversion
+		msg := types.NewMsgConvertCosmosCoinToERC20(account.String(), evmAddr.Hex(), coin(1e10))
+		_, err := suite.msgServer.ConvertCosmosCoinToERC20(suite.Ctx, &msg)
+		suite.NoError(err)
+
+		// should have balance on original ERC20 contract
+		erc20Bal, err := suite.Keeper.QueryERC20BalanceOf(suite.Ctx, contractAddress, evmAddr)
+		suite.NoError(err)
+		suite.BigIntsEqual(big.NewInt(1e10), erc20Bal, "cosmos coins were not converted")
+		sdkBal := suite.BankKeeper.GetBalance(suite.Ctx, account, denom)
+		suite.True(sdkBal.IsZero())
+	})
+}

x/evmutil/spec/01_concepts.md

@@ -54,6 +54,8 @@ Only Cosmos co-chain denominations that are in the `AllowedCosmosDenoms` param (
 
 The ERC20 contracts are deployed and managed by x/evmutil. The contract is deployed on first convert of the coin. Once deployed, the addresses of the contracts can be queried via the `DeployedCosmosCoinContracts` query (`deployed_cosmos_coin_contracts` endpoint).
 
+If a denom is removed from the `AllowedCosmosDenoms` param, existing ERC20 tokens can be converted back to the underlying sdk.Coin via `MsgConvertCosmosCoinFromERC20`, but no conversions from sdk.Coin -> ERC via `MsgConvertCosmosCoinToERC20` are allowed.
+
 ### EVM-Native Assets
 
 ERC-20 tokens native to the EVM can be converted into an `sdk.Coin` in the Cosmos ecosystem. This works by transferring the tokens to `x/evmutil`'s module account and then minting an `sdk.Coin` to the receiver. Converting back is the inverse: the `sdk.Coin` of the initiator is burned and the original ERC-20 tokens that were locked into the module account are transferred back to the receiver.

x/evmutil/spec/03_messages.md

@@ -18,7 +18,7 @@ service Msg {
   rpc ConvertCosmosCoinToERC20(MsgConvertCosmosCoinToERC20) returns (MsgConvertCosmosCoinToERC20Response);
 }
 
-// ConvertCosmosCoinToERC20 defines a conversion from cosmos sdk.Coin to ERC20.
+// MsgConvertCosmosCoinToERC20 defines a conversion from cosmos sdk.Coin to ERC20.
 message MsgConvertCosmosCoinToERC20 {
   // Kava bech32 address initiating the conversion.
   string initiator = 1;
@@ -36,6 +36,33 @@ message MsgConvertCosmosCoinToERC20 {
 - The `amount` is deducted from the `initiator`'s balance and transferred to the module account.
 - An equivalent amount of ERC20 tokens are minted by `x/evmutil` to the `receiver`.
 
+## MsgConvertCosmosCoinFromERC20
+
+`MsgConvertCosmosCoinFromERC20` is the inverse of `MsgConvertCosmosCoinToERC20`. It converts an ERC20 representation of a cosmos-sdk coin back to its underlying sdk.Coin.
+
+
+```proto
+service Msg {
+  // ConvertCosmosCoinFromERC20 defines a method for converting a cosmos sdk.Coin to an ERC20.
+  rpc ConvertCosmosCoinFromERC20(MsgConvertCosmosCoinFromERC20) returns (MsgConvertCosmosCoinFromERC20Response);
+}
+
+// MsgConvertCosmosCoinFromERC20 defines a conversion from ERC20 to cosmos coins for cosmos-native assets.
+message MsgConvertCosmosCoinFromERC20 {
+  // EVM hex address initiating the conversion.
+  string initiator = 1;
+  // Kava bech32 address that will receive the cosmos coins.
+  string receiver = 2;
+  // Amount is the amount to convert, expressed as a Cosmos coin.
+  cosmos.base.v1beta1.Coin amount = 3;
+}
+```
+
+### State Changes
+
+- The `amount` is transferred from the `x/evmutil` module account to the `receiver`.
+- The same amount of the corresponding ERC20 is burned from the `initiator` account in the EVM.
+
 ## MsgConvertERC20ToCoin
 
 `MsgConvertCoinToERC20` converts a Kava ERC20 coin to sdk.Coin. This message is for moving EVM-native assets from the EVM to the Cosmos ecosystem.

x/evmutil/spec/04_events.md

@@ -40,3 +40,14 @@ The evmutil module emits the following events:
 | convert_cosmos_coin_to_erc20 | amount        | `{amount}`         |
 | message                      | module        | evmutil            |
 | message                      | sender        | {'sender address'} |
+
+### MsgConvertCosmosCoinFromERC20
+
+| Type                           | Attribute Key | Attribute Value    |
+| ------------------------------ | ------------- | ------------------ |
+| convert_cosmos_coin_from_erc20 | initiator     | `{initiator}`      |
+| convert_cosmos_coin_from_erc20 | receiver      | `{receiver}`       |
+| convert_cosmos_coin_from_erc20 | erc20_address | `{erc20_address}`  |
+| convert_cosmos_coin_from_erc20 | amount        | `{amount}`         |
+| message                        | module        | evmutil            |
+| message                        | sender        | {'sender address'} |

x/evmutil/types/events.go

@@ -8,7 +8,8 @@ const (
 	EventTypeConvertERC20ToCoin = "convert_evm_erc20_to_coin"
 	EventTypeConvertCoinToERC20 = "convert_evm_erc20_from_coin"
 
-	EventTypeConvertCosmosCoinToERC20 = "convert_cosmos_coin_to_erc20"
+	EventTypeConvertCosmosCoinToERC20   = "convert_cosmos_coin_to_erc20"
+	EventTypeConvertCosmosCoinFromERC20 = "convert_cosmos_coin_from_erc20"
 
 	// Event Attributes - Common
 	AttributeKeyReceiver = "receiver"

x/evmutil/types/tx.pb.go

@@ -236,7 +236,7 @@ func (m *MsgConvertERC20ToCoinResponse) XXX_DiscardUnknown() {
 
 var xxx_messageInfo_MsgConvertERC20ToCoinResponse proto.InternalMessageInfo
 
-// ConvertCosmosCoinToERC20 defines a conversion from cosmos sdk.Coin to ERC20 for cosmos-native assets.
+// MsgConvertCosmosCoinToERC20 defines a conversion from cosmos sdk.Coin to ERC20 for cosmos-native assets.
 type MsgConvertCosmosCoinToERC20 struct {
 	// Kava bech32 address initiating the conversion.
 	Initiator string `protobuf:"bytes,1,opt,name=initiator,proto3" json:"initiator,omitempty"`
@@ -337,7 +337,7 @@ func (m *MsgConvertCosmosCoinToERC20Response) XXX_DiscardUnknown() {
 
 var xxx_messageInfo_MsgConvertCosmosCoinToERC20Response proto.InternalMessageInfo
 
-// ConvertCosmosCoinFromERC20 defines a conversion from ERC20 to cosmos coins for cosmos-native assets.
+// MsgConvertCosmosCoinFromERC20 defines a conversion from ERC20 to cosmos coins for cosmos-native assets.
 type MsgConvertCosmosCoinFromERC20 struct {
 	// EVM hex address initiating the conversion.
 	Initiator string `protobuf:"bytes,1,opt,name=initiator,proto3" json:"initiator,omitempty"`