feat: add transfer authorization (#100)

* wip: add transfer auithorization

* feat: update transferAuthPayload

* switch to MAX_INT for value and use revoke flag
* tranfer handler: fix nonce rollback on EOA account

* feat: switch to session based session transfer auth

* Demurrage contracts require setting the approval value to 0 before updating the value after the initial limit is set
* This implementation auto-revokes every 15 min after arequest is created. Subsequent requests will fail untill the value is set back to 0

* feat: settable approve session timeout

internal/tasker/task/account_refill_gas.go

@@ -17,10 +17,6 @@ import (
 	"github.com/hibiken/asynq"
 )
 
-const (
-	gasGiveToLimit = 250000
-)
-
 func AccountRefillGasProcessor(cu *custodial.Custodial) func(context.Context, *asynq.Task) error {
 	return func(ctx context.Context, t *asynq.Task) error {
 		var (

internal/tasker/task/sign_transfer.go

@@ -60,13 +60,16 @@ func SignTransfer(cu *custodial.Custodial) func(context.Context, *asynq.Task) er
 		}
 		defer func() {
 			if err != nil {
-				if nErr := cu.Noncestore.Return(ctx, cu.SystemPublicKey); nErr != nil {
+				if nErr := cu.Noncestore.Return(ctx, payload.From); nErr != nil {
 					err = nErr
 				}
 			}
 		}()
 
-		input, err := cu.Abis[custodial.Transfer].EncodeArgs(celoutils.HexToAddress(payload.To), new(big.Int).SetUint64(payload.Amount))
+		input, err := cu.Abis[custodial.Transfer].EncodeArgs(
+			celoutils.HexToAddress(payload.To),
+			new(big.Int).SetUint64(payload.Amount),
+		)
 		if err != nil {
 			return err
 		}

internal/tasker/task/sign_transfer_auth.go

@@ -0,0 +1,196 @@
+package task
+
+import (
+	"context"
+	"encoding/json"
+	"math/big"
+
+	"github.com/bsm/redislock"
+	"github.com/celo-org/celo-blockchain/common/hexutil"
+	"github.com/grassrootseconomics/celoutils"
+	"github.com/grassrootseconomics/cic-custodial/internal/custodial"
+	"github.com/grassrootseconomics/cic-custodial/internal/store"
+	"github.com/grassrootseconomics/cic-custodial/internal/tasker"
+	"github.com/grassrootseconomics/cic-custodial/pkg/enum"
+	"github.com/grassrootseconomics/w3-celo-patch/module/eth"
+	"github.com/hibiken/asynq"
+)
+
+type TransferAuthPayload struct {
+	Amount            uint64 `json:"amount"`
+	Authorizer        string `json:"authorizer"`
+	AuthorizedAddress string `json:"authorizedAddress"`
+	TrackingId        string `json:"trackingId"`
+	VoucherAddress    string `json:"voucherAddress"`
+}
+
+func SignTransferAuthorizationProcessor(cu *custodial.Custodial) func(context.Context, *asynq.Task) error {
+	return func(ctx context.Context, t *asynq.Task) error {
+		var (
+			err            error
+			networkBalance big.Int
+			payload        TransferAuthPayload
+		)
+
+		if err := json.Unmarshal(t.Payload(), &payload); err != nil {
+			return err
+		}
+
+		lock, err := cu.LockProvider.Obtain(
+			ctx,
+			lockPrefix+payload.Authorizer,
+			lockTimeout,
+			&redislock.Options{
+				RetryStrategy: lockRetry(),
+			},
+		)
+		if err != nil {
+			return err
+		}
+		defer lock.Release(ctx)
+
+		key, err := cu.Store.LoadPrivateKey(ctx, payload.Authorizer)
+		if err != nil {
+			return err
+		}
+
+		nonce, err := cu.Noncestore.Acquire(ctx, payload.Authorizer)
+		if err != nil {
+			return err
+		}
+		defer func() {
+			if err != nil {
+				if nErr := cu.Noncestore.Return(ctx, payload.Authorizer); nErr != nil {
+					err = nErr
+				}
+			}
+		}()
+
+		input, err := cu.Abis[custodial.Approve].EncodeArgs(
+			celoutils.HexToAddress(payload.AuthorizedAddress),
+			new(big.Int).SetUint64(payload.Amount),
+		)
+		if err != nil {
+			return err
+		}
+
+		builtTx, err := cu.CeloProvider.SignContractExecutionTx(
+			key,
+			celoutils.ContractExecutionTxOpts{
+				ContractAddress: celoutils.HexToAddress(payload.VoucherAddress),
+				InputData:       input,
+				GasFeeCap:       celoutils.SafeGasFeeCap,
+				GasTipCap:       celoutils.SafeGasTipCap,
+				GasLimit:        uint64(celoutils.SafeGasLimit),
+				Nonce:           nonce,
+			},
+		)
+		if err != nil {
+			return err
+		}
+
+		rawTx, err := builtTx.MarshalBinary()
+		if err != nil {
+			return err
+		}
+
+		id, err := cu.Store.CreateOtx(ctx, store.Otx{
+			TrackingId:    payload.TrackingId,
+			Type:          enum.TRANSFER_AUTH,
+			RawTx:         hexutil.Encode(rawTx),
+			TxHash:        builtTx.Hash().Hex(),
+			From:          cu.SystemPublicKey,
+			Data:          hexutil.Encode(builtTx.Data()),
+			GasPrice:      builtTx.GasPrice(),
+			GasLimit:      builtTx.Gas(),
+			TransferValue: 0,
+			Nonce:         builtTx.Nonce(),
+		})
+		if err != nil {
+			return err
+		}
+
+		if err := cu.CeloProvider.Client.CallCtx(
+			ctx,
+			eth.Balance(celoutils.HexToAddress(payload.Authorizer), nil).Returns(&networkBalance),
+		); err != nil {
+			return err
+		}
+
+		disptachJobPayload, err := json.Marshal(TxPayload{
+			OtxId: id,
+			Tx:    builtTx,
+		})
+		if err != nil {
+			return err
+		}
+
+		_, err = cu.TaskerClient.CreateTask(
+			ctx,
+			tasker.DispatchTxTask,
+			tasker.HighPriority,
+			&tasker.Task{
+				Payload: disptachJobPayload,
+			},
+		)
+		if err != nil {
+			return err
+		}
+
+		// Auto-revoke every session (15 min)
+		// Check if already a revoke request
+		if payload.Amount > 0 {
+			taskPayload, err := json.Marshal(TransferAuthPayload{
+				TrackingId:        payload.TrackingId,
+				Amount:            0,
+				Authorizer:        payload.Authorizer,
+				AuthorizedAddress: payload.AuthorizedAddress,
+				VoucherAddress:    payload.VoucherAddress,
+			})
+			if err != nil {
+				return err
+			}
+
+			_, err = cu.TaskerClient.CreateTask(
+				ctx,
+				tasker.SignTransferTaskAuth,
+				tasker.DefaultPriority,
+				&tasker.Task{
+					Payload: taskPayload,
+				},
+				asynq.ProcessIn(cu.ApprovalTimeout),
+			)
+			if err != nil {
+				return err
+			}
+		}
+
+		gasRefillPayload, err := json.Marshal(AccountPayload{
+			PublicKey:  payload.Authorizer,
+			TrackingId: payload.TrackingId,
+		})
+		if err != nil {
+			return err
+		}
+
+		if !balanceCheck(networkBalance) {
+			if err := cu.Store.GasLock(ctx, payload.Authorizer); err != nil {
+				return err
+			}
+
+			_, err = cu.TaskerClient.CreateTask(
+				ctx,
+				tasker.AccountRefillGasTask,
+				tasker.DefaultPriority,
+				&tasker.Task{
+					Payload: gasRefillPayload,
+				},
+			)
+			if err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}
+}