Enable Fee Delegation

client/flags/flags.go

@@ -54,6 +54,7 @@ const (
 	FlagRPCWriteTimeout    = "write-timeout"
 	FlagOutputDocument     = "output-document" // inspired by wget -O
 	FlagSkipConfirmation   = "yes"
+	FlagFeeAccount         = "fee-account"
 )
 
 // LineBreak can be included in a command list to provide a blank line
@@ -99,6 +100,7 @@ func PostCommands(cmds ...*cobra.Command) []*cobra.Command {
 		c.Flags().Bool(FlagDryRun, false, "ignore the --gas flag and perform a simulation of a transaction, but don't broadcast it")
 		c.Flags().Bool(FlagGenerateOnly, false, "Build an unsigned transaction and write it to STDOUT (when enabled, the local Keybase is not accessible and the node operates offline)")
 		c.Flags().BoolP(FlagSkipConfirmation, "y", false, "Skip tx broadcasting prompt confirmation")
+		c.Flags().String(FlagFeeAccount, "", "Set a fee account to pay fess with if they have been delegated by this account")
 
 		// --gas can accept integers and "simulate"
 		c.Flags().Var(&GasFlagVar, "gas", fmt.Sprintf(

simapp/app.go

@@ -21,6 +21,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/x/crisis"
 	distr "github.com/cosmos/cosmos-sdk/x/distribution"
 	"github.com/cosmos/cosmos-sdk/x/evidence"
+	"github.com/cosmos/cosmos-sdk/x/feegrant"
 	"github.com/cosmos/cosmos-sdk/x/genutil"
 	"github.com/cosmos/cosmos-sdk/x/gov"
 	"github.com/cosmos/cosmos-sdk/x/mint"
@@ -55,6 +56,7 @@ var (
 		params.AppModuleBasic{},
 		crisis.AppModuleBasic{},
 		slashing.AppModuleBasic{},
+		feegrant.AppModuleBasic{},
 		evidence.AppModuleBasic{},
 	)
 
@@ -105,6 +107,7 @@ type SimApp struct {
 	DistrKeeper    distr.Keeper
 	GovKeeper      gov.Keeper
 	CrisisKeeper   crisis.Keeper
+	FeeGrantKeeper feegrant.Keeper
 	ParamsKeeper   params.Keeper
 	EvidenceKeeper evidence.Keeper
 
@@ -130,6 +133,7 @@ func NewSimApp(
 	keys := sdk.NewKVStoreKeys(
 		bam.MainStoreKey, auth.StoreKey, staking.StoreKey, supply.StoreKey, mint.StoreKey,
 		distr.StoreKey, slashing.StoreKey, gov.StoreKey, params.StoreKey, evidence.StoreKey,
+		feegrant.StoreKey,
 	)
 	tkeys := sdk.NewTransientStoreKeys(params.TStoreKey)
 
@@ -182,6 +186,9 @@ func NewSimApp(
 	app.CrisisKeeper = crisis.NewKeeper(
 		app.subspaces[crisis.ModuleName], invCheckPeriod, app.SupplyKeeper, auth.FeeCollectorName,
 	)
+	app.FeeGrantKeeper = feegrant.NewKeeper(
+		app.cdc, keys[feegrant.StoreKey],
+	)
 
 	// create evidence keeper with router
 	evidenceKeeper := evidence.NewKeeper(
@@ -221,6 +228,7 @@ func NewSimApp(
 		distr.NewAppModule(app.DistrKeeper, app.SupplyKeeper),
 		slashing.NewAppModule(app.SlashingKeeper, app.StakingKeeper),
 		staking.NewAppModule(app.StakingKeeper, app.AccountKeeper, app.SupplyKeeper),
+		feegrant.NewAppModule(app.FeeGrantKeeper),
 		evidence.NewAppModule(app.EvidenceKeeper),
 	)
 
@@ -235,7 +243,7 @@ func NewSimApp(
 	app.mm.SetOrderInitGenesis(
 		auth.ModuleName, distr.ModuleName, staking.ModuleName, bank.ModuleName,
 		slashing.ModuleName, gov.ModuleName, mint.ModuleName, supply.ModuleName,
-		crisis.ModuleName, genutil.ModuleName, evidence.ModuleName,
+		crisis.ModuleName, genutil.ModuleName, evidence.ModuleName, feegrant.ModuleName,
 	)
 
 	app.mm.RegisterInvariants(&app.CrisisKeeper)

types/errors.go

@@ -320,7 +320,6 @@ func ConvertError(err error) Error {
 	if sdkError, ok := err.(Error); ok {
 		return sdkError
 	}
-
 	space, code, log := sdkerrors.ABCIInfo(err, false)
 	return NewError(CodespaceType(space), CodeType(code), log)
 }

x/feegrant/alias.go

@@ -0,0 +1,73 @@
+// nolint
+package feegrant
+
+import (
+	"github.com/cosmos/cosmos-sdk/x/feegrant/internal/ante"
+	"github.com/cosmos/cosmos-sdk/x/feegrant/internal/keeper"
+	"github.com/cosmos/cosmos-sdk/x/feegrant/internal/types"
+)
+
+// autogenerated code using github.com/rigelrozanski/multitool
+// aliases generated for the following subdirectories:
+// ALIASGEN: github.com/cosmos/cosmos-sdk/x/feegrant/internal/ante
+// ALIASGEN: github.com/cosmos/cosmos-sdk/x/feegrant/internal/types
+// ALIASGEN: github.com/cosmos/cosmos-sdk/x/feegrant/internal/keeper
+
+const (
+	DefaultCodespace        = types.DefaultCodespace
+	EventTypeUseFeeGrant    = types.EventTypeUseFeeGrant
+	EventTypeRevokeFeeGrant = types.EventTypeRevokeFeeGrant
+	EventTypeSetFeeGrant    = types.EventTypeSetFeeGrant
+	AttributeKeyGranter     = types.AttributeKeyGranter
+	AttributeKeyGrantee     = types.AttributeKeyGrantee
+	ModuleName              = types.ModuleName
+	StoreKey                = types.StoreKey
+	RouterKey               = types.RouterKey
+	QuerierRoute            = types.QuerierRoute
+	QueryGetFeeAllowances   = keeper.QueryGetFeeAllowances
+)
+
+var (
+	// functions aliases
+	NewDeductGrantedFeeDecorator = ante.NewDeductGrantedFeeDecorator
+	DeductFees                   = ante.DeductFees
+	RegisterCodec                = types.RegisterCodec
+	ExpiresAtTime                = types.ExpiresAtTime
+	ExpiresAtHeight              = types.ExpiresAtHeight
+	ClockDuration                = types.ClockDuration
+	BlockDuration                = types.BlockDuration
+	FeeAllowanceKey              = types.FeeAllowanceKey
+	FeeAllowancePrefixByGrantee  = types.FeeAllowancePrefixByGrantee
+	NewMsgGrantFeeAllowance      = types.NewMsgGrantFeeAllowance
+	NewMsgRevokeFeeAllowance     = types.NewMsgRevokeFeeAllowance
+	NewFeeGrantTx                = types.NewFeeGrantTx
+	CountSubKeys                 = types.CountSubKeys
+	NewGrantedFee                = types.NewGrantedFee
+	StdSignBytes                 = types.StdSignBytes
+	NewKeeper                    = keeper.NewKeeper
+	NewQuerier                   = keeper.NewQuerier
+
+	// variable aliases
+	ModuleCdc             = types.ModuleCdc
+	ErrFeeLimitExceeded   = types.ErrFeeLimitExceeded
+	ErrFeeLimitExpired    = types.ErrFeeLimitExpired
+	ErrInvalidDuration    = types.ErrInvalidDuration
+	ErrNoAllowance        = types.ErrNoAllowance
+	FeeAllowanceKeyPrefix = types.FeeAllowanceKeyPrefix
+)
+
+type (
+	GrantedFeeTx              = ante.GrantedFeeTx
+	DeductGrantedFeeDecorator = ante.DeductGrantedFeeDecorator
+	BasicFeeAllowance         = types.BasicFeeAllowance
+	ExpiresAt                 = types.ExpiresAt
+	Duration                  = types.Duration
+	FeeAllowanceGrant         = types.FeeAllowanceGrant
+	MsgGrantFeeAllowance      = types.MsgGrantFeeAllowance
+	MsgRevokeFeeAllowance     = types.MsgRevokeFeeAllowance
+	PeriodicFeeAllowance      = types.PeriodicFeeAllowance
+	FeeGrantTx                = types.FeeGrantTx
+	GrantedFee                = types.GrantedFee
+	DelegatedSignDoc          = types.DelegatedSignDoc
+	Keeper                    = keeper.Keeper
+)

x/feegrant/doc.go

@@ -0,0 +1,28 @@
+/*
+Package feegrant provides functionality for delegating the payment of transaction fees
+from one account (key) to another account (key).
+
+Effectively, this allows for a user to pay fees using the balance of an account
+different from their own. Example use cases would be allowing a key on a device to
+pay for fees using a master wallet, or a third party service allowing users to
+pay for transactions without ever really holding their own tokens. This package
+provides ways for specifying fee allowances such that delegating fees
+to another account can be done with clear and safe restrictions.
+
+A user would delegate fees to a user using MsgDelegateFeeAllowance and revoke
+that delegation using MsgRevokeFeeAllowance. In both cases Granter is the one
+who is delegating fees and Grantee is the one who is receiving the delegation.
+So grantee would correspond to the one who is signing a transaction and the
+granter would be the address they place in DelegatedFee.FeeAccount.
+
+The fee allowance that a grantee receives is specified by an implementation of
+the FeeAllowance interface. Two FeeAllowance implementations are provided in
+this package: BasicFeeAllowance and PeriodicFeeAllowance.
+
+In order to integrate this into an application, we must use the DeductDelegatedFeeDecorator
+ante handler from this package instead of the default DeductFeeDecorator from auth.
+To allow handling txs from empty accounts (with fees paid from an existing account),
+we have to re-order the decorators as well. You can see an example in
+`x/delegate_fees/internal/ante/fee_test.go:newAnteHandler()`
+*/
+package feegrant

x/feegrant/exported/external.go

@@ -0,0 +1,21 @@
+package exported
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	auth "github.com/cosmos/cosmos-sdk/x/auth/exported"
+	supply "github.com/cosmos/cosmos-sdk/x/supply/exported"
+)
+
+// SupplyKeeper defines the expected supply Keeper (noalias)
+type SupplyKeeper interface {
+	SendCoinsFromAccountToModule(ctx sdk.Context, senderAddr sdk.AccAddress, recipientModule string, amt sdk.Coins) sdk.Error
+	GetModuleAccount(ctx sdk.Context, moduleName string) supply.ModuleAccountI
+	GetModuleAddress(moduleName string) sdk.AccAddress
+}
+
+// SupplyKeeper defines the expected auth Account Keeper (noalias)
+type AccountKeeper interface {
+	NewAccountWithAddress(ctx sdk.Context, addr sdk.AccAddress) auth.Account
+	GetAccount(ctx sdk.Context, addr sdk.AccAddress) auth.Account
+	SetAccount(ctx sdk.Context, acc auth.Account)
+}

x/feegrant/exported/fees.go

@@ -0,0 +1,32 @@
+package exported
+
+import (
+	"time"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+// FeeAllowance implementations are tied to a given fee delegator and delegatee,
+// and are used to enforce fee grant limits.
+type FeeAllowance interface {
+	// Accept can use fee payment requested as well as timestamp/height of the current block
+	// to determine whether or not to process this. This is checked in
+	// Keeper.UseGrantedFees and the return values should match how it is handled there.
+	//
+	// If it returns an error, the fee payment is rejected, otherwise it is accepted.
+	// The FeeAllowance implementation is expected to update it's internal state
+	// and will be saved again after an acceptance.
+	//
+	// If remove is true (regardless of the error), the FeeAllowance will be deleted from storage
+	// (eg. when it is used up). (See call to RevokeFeeAllowance in Keeper.UseGrantedFees)
+	Accept(fee sdk.Coins, blockTime time.Time, blockHeight int64) (remove bool, err error)
+
+	// If we export fee allowances the timing info will be quite off (eg. go from height 100000 to 0)
+	// This callback allows the fee-allowance to change it's state and return a copy that is adjusted
+	// given the time and height of the actual dump (may safely return self if no changes needed)
+	PrepareForExport(dumpTime time.Time, dumpHeight int64) FeeAllowance
+
+	// ValidateBasic should evaluate this FeeAllowance for internal consistency.
+	// Don't allow negative amounts, or negative periods for example.
+	ValidateBasic() error
+}

x/feegrant/genesis.go

@@ -0,0 +1,41 @@
+package feegrant
+
+import sdk "github.com/cosmos/cosmos-sdk/types"
+
+// GenesisState contains a set of fee allowances, persisted from the store
+type GenesisState []FeeAllowanceGrant
+
+// ValidateBasic ensures all grants in the genesis state are valid
+func (g GenesisState) ValidateBasic() error {
+	for _, f := range g {
+		err := f.ValidateBasic()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// InitGenesis will initialize the keeper from a *previously validated* GenesisState
+func InitGenesis(ctx sdk.Context, k Keeper, gen GenesisState) {
+	for _, f := range gen {
+		k.GrantFeeAllowance(ctx, f)
+	}
+}
+
+// ExportGenesis will dump the contents of the keeper into a serializable GenesisState
+//
+// All expiration heights will be thrown off if we dump state and start at a new
+// chain at height 0. Thus, we allow the Allowances to "prepare themselves"
+// for export, like if they have expiry at 5000 and current is 4000, they export with
+// expiry of 1000. Every FeeAllowance has a method `PrepareForExport` that allows
+// them to perform any changes needed prior to export.
+func ExportGenesis(ctx sdk.Context, k Keeper) (GenesisState, error) {
+	time, height := ctx.BlockTime(), ctx.BlockHeight()
+	var grants []FeeAllowanceGrant
+	err := k.IterateAllFeeAllowances(ctx, func(grant FeeAllowanceGrant) bool {
+		grants = append(grants, grant.PrepareForExport(time, height))
+		return false
+	})
+	return grants, err
+}

x/feegrant/handler.go

@@ -0,0 +1,36 @@
+package feegrant
+
+import (
+	"fmt"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+func NewHandler(k Keeper) sdk.Handler {
+	return func(ctx sdk.Context, msg sdk.Msg) sdk.Result {
+		ctx = ctx.WithEventManager(sdk.NewEventManager())
+
+		switch msg := msg.(type) {
+		case MsgGrantFeeAllowance:
+			return handleGrantFee(ctx, k, msg)
+
+		case MsgRevokeFeeAllowance:
+			return handleRevokeFee(ctx, k, msg)
+
+		default:
+			errMsg := fmt.Sprintf("Unrecognized data Msg type: %s", ModuleName)
+			return sdk.ErrUnknownRequest(errMsg).Result()
+		}
+	}
+}
+
+func handleGrantFee(ctx sdk.Context, k Keeper, msg MsgGrantFeeAllowance) sdk.Result {
+	grant := FeeAllowanceGrant(msg)
+	k.GrantFeeAllowance(ctx, grant)
+	return sdk.Result{Events: ctx.EventManager().Events()}
+}
+
+func handleRevokeFee(ctx sdk.Context, k Keeper, msg MsgRevokeFeeAllowance) sdk.Result {
+	k.RevokeFeeAllowance(ctx, msg.Granter, msg.Grantee)
+	return sdk.Result{Events: ctx.EventManager().Events()}
+}