Add a new token and only allow fees in alnt (#68)

Part of https://www.notion.so/Multiple-tokens-support-and-disable-transfers-for-LSTAKE-1f2a6b22d47280269f87df3fe03e8d64
- Add base token with denoms `alps` and `lps` (`1 lps = 10^18 alps`)
- Keep `alnt` as the staking token and for laconic module ops
- Accept tx fees only in `alnt`

Reviewed-on: cerc-io/laconicd#68
Co-authored-by: Prathamesh Musale <prathamesh.musale0@gmail.com>
Co-committed-by: Prathamesh Musale <prathamesh.musale0@gmail.com>

app/ante.go

@@ -0,0 +1,79 @@
+package app
+
+import (
+	_ "embed"
+	"math"
+
+	errorsmod "cosmossdk.io/errors"
+	sdkmath "cosmossdk.io/math"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
+
+	"git.vdb.to/cerc-io/laconicd/app/params"
+)
+
+// Reference: https://github.com/cosmos/cosmos-sdk/blob/v0.50.10/x/auth/ante/validator_tx_fee.go#L15
+
+// checkTxFeeWithValidatorMinGasPrices implements the default fee logic, where the minimum price per
+// unit of gas is fixed and set by each validator, can the tx priority is computed from the gas price.
+func checkTxFeeWithValidatorMinGasPrices(ctx sdk.Context, tx sdk.Tx) (sdk.Coins, int64, error) {
+	feeTx, ok := tx.(sdk.FeeTx)
+	if !ok {
+		return nil, 0, errorsmod.Wrap(sdkerrors.ErrTxDecode, "Tx must be a FeeTx")
+	}
+
+	feeCoins := feeTx.GetFee()
+	gas := feeTx.GetGas()
+
+	// Only allow alnt as a fee token
+	for _, coin := range feeCoins {
+		if coin.Denom != params.CoinUnit {
+			return nil, 0, errorsmod.Wrapf(sdkerrors.ErrInvalidCoins, "invalid fee denom %s, only %s is accepted", coin.Denom, params.CoinUnit)
+		}
+	}
+
+	// Ensure that the provided fees meet a minimum threshold for the validator,
+	// if this is a CheckTx. This is only for local mempool purposes, and thus
+	// is only ran on check tx.
+	if ctx.IsCheckTx() {
+		minGasPrices := ctx.MinGasPrices()
+		if !minGasPrices.IsZero() {
+			requiredFees := make(sdk.Coins, len(minGasPrices))
+
+			// Determine the required fees by multiplying each required minimum gas
+			// price by the gas limit, where fee = ceil(minGasPrice * gasLimit).
+			glDec := sdkmath.LegacyNewDec(int64(gas))
+			for i, gp := range minGasPrices {
+				fee := gp.Amount.Mul(glDec)
+				requiredFees[i] = sdk.NewCoin(gp.Denom, fee.Ceil().RoundInt())
+			}
+
+			if !feeCoins.IsAnyGTE(requiredFees) {
+				return nil, 0, errorsmod.Wrapf(sdkerrors.ErrInsufficientFee, "insufficient fees; got: %s required: %s", feeCoins, requiredFees)
+			}
+		}
+	}
+
+	priority := getTxPriority(feeCoins, int64(gas))
+	return feeCoins, priority, nil
+}
+
+// getTxPriority returns a naive tx priority based on the amount of the smallest denomination of the gas price
+// provided in a transaction.
+// NOTE: This implementation should be used with a great consideration as it opens potential attack vectors
+// where txs with multiple coins could not be prioritize as expected.
+func getTxPriority(fee sdk.Coins, gas int64) int64 {
+	var priority int64
+	for _, c := range fee {
+		p := int64(math.MaxInt64)
+		gasPrice := c.Amount.QuoRaw(gas)
+		if gasPrice.IsInt64() {
+			p = gasPrice.Int64()
+		}
+		if priority == 0 || p < priority {
+			priority = p
+		}
+	}
+
+	return priority
+}

app/app.go

@@ -27,6 +27,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/server/config"
 	servertypes "github.com/cosmos/cosmos-sdk/server/types"
 	"github.com/cosmos/cosmos-sdk/types/module"
+	"github.com/cosmos/cosmos-sdk/x/auth/ante"
 	authkeeper "github.com/cosmos/cosmos-sdk/x/auth/keeper"
 	bankkeeper "github.com/cosmos/cosmos-sdk/x/bank/keeper"
 	consensuskeeper "github.com/cosmos/cosmos-sdk/x/consensus/keeper"
@@ -185,6 +186,9 @@ func NewLaconicApp(
 	app.sm = module.NewSimulationManagerFromAppModules(app.ModuleManager.Modules, make(map[string]module.AppModuleSimulation, 0))
 	app.sm.RegisterStoreDecoders()
 
+	// set custom ante handlers
+	app.setCustomAnteHandler()
+
 	if err := app.Load(loadLatest); err != nil {
 		return nil, err
 	}
@@ -232,3 +236,23 @@ func (app *LaconicApp) RegisterAPIRoutes(apiSvr *api.Server, apiConfig config.AP
 		panic(err)
 	}
 }
+
+// setCustomAnteHandler overwrites default ante handlers with custom ante handlers
+// Reference: https://github.com/cosmos/cosmos-sdk/blob/v0.50.10/x/auth/tx/config/config.go#L149
+func (app *LaconicApp) setCustomAnteHandler() {
+	anteHandler, err := ante.NewAnteHandler(
+		ante.HandlerOptions{
+			AccountKeeper:   app.AccountKeeper,
+			BankKeeper:      app.BankKeeper,
+			SignModeHandler: app.txConfig.SignModeHandler(),
+			SigGasConsumer:  ante.DefaultSigVerificationGasConsumer,
+			TxFeeChecker:    checkTxFeeWithValidatorMinGasPrices,
+		},
+	)
+	if err != nil {
+		panic(err)
+	}
+
+	// Set the AnteHandler for the app
+	app.SetAnteHandler(anteHandler)
+}

app/params/config.go

@@ -10,11 +10,14 @@ import (
 )
 
 const (
-	CoinUnit     = "lnt"
-	BaseCoinUnit = "alnt"
-	LntExponent  = 18
+	// Registered token
+	LpsCoinUnit     = "lps"
+	LpsBaseCoinUnit = "alps"
+	LpsExponent     = 18
 
-	DefaultBondDenom = BaseCoinUnit
+	// Native token, only denominated in alnt
+	// Used for staking, fees and laconic module ops
+	CoinUnit = "alnt"
 
 	// Bech32PrefixAccAddr defines the Bech32 prefix of an account's address.
 	Bech32PrefixAccAddr = "laconic"
@@ -39,12 +42,11 @@ func init() {
 }
 
 func RegisterDenoms() {
-	err := sdk.RegisterDenom(CoinUnit, math.LegacyOneDec())
+	err := sdk.RegisterDenom(LpsCoinUnit, math.LegacyOneDec())
 	if err != nil {
 		panic(err)
 	}
-
-	err = sdk.RegisterDenom(BaseCoinUnit, math.LegacyNewDecWithPrec(1, LntExponent))
+	err = sdk.RegisterDenom(LpsBaseCoinUnit, math.LegacyNewDecWithPrec(1, LpsExponent))
 	if err != nil {
 		panic(err)
 	}