1 files changed, 272 insertions, 0 deletions
diff --git a/plugin/evm/import_tx.go b/plugin/evm/import_tx.go
new file mode 100644
index 0000000..35ba8cc
--- /dev/null
+++ b/plugin/evm/import_tx.go
@@ -0,0 +1,272 @@
+// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package evm
+
+import (
+	"fmt"
+	"math/big"
+
+	"github.com/ava-labs/coreth/core/state"
+
+	"github.com/ava-labs/gecko/database"
+	"github.com/ava-labs/gecko/ids"
+	"github.com/ava-labs/gecko/snow"
+	"github.com/ava-labs/gecko/utils/crypto"
+	"github.com/ava-labs/gecko/utils/math"
+	"github.com/ava-labs/gecko/vms/components/avax"
+	"github.com/ava-labs/gecko/vms/secp256k1fx"
+	"github.com/ava-labs/go-ethereum/common"
+)
+
+// UnsignedImportTx is an unsigned ImportTx
+type UnsignedImportTx struct {
+	avax.Metadata
+	// true iff this transaction has already passed syntactic verification
+	syntacticallyVerified bool
+	// ID of the network on which this tx was issued
+	NetworkID uint32 `serialize:"true" json:"networkID"`
+	// ID of this blockchain.
+	BlockchainID ids.ID `serialize:"true" json:"blockchainID"`
+	// Which chain to consume the funds from
+	SourceChain ids.ID `serialize:"true" json:"sourceChain"`
+	// Inputs that consume UTXOs produced on the chain
+	ImportedInputs []*avax.TransferableInput `serialize:"true" json:"importedInputs"`
+	// Outputs
+	Outs []EVMOutput `serialize:"true" json:"outputs"`
+}
+
+// InputUTXOs returns the UTXOIDs of the imported funds
+func (tx *UnsignedImportTx) InputUTXOs() ids.Set {
+	set := ids.Set{}
+	for _, in := range tx.ImportedInputs {
+		set.Add(in.InputID())
+	}
+	return set
+}
+
+// Verify this transaction is well-formed
+func (tx *UnsignedImportTx) Verify(
+	avmID ids.ID,
+	ctx *snow.Context,
+	feeAmount uint64,
+	feeAssetID ids.ID,
+) error {
+	switch {
+	case tx == nil:
+		return errNilTx
+	case tx.syntacticallyVerified: // already passed syntactic verification
+		return nil
+	case tx.SourceChain.IsZero():
+		return errWrongChainID
+	case !tx.SourceChain.Equals(avmID):
+		return errWrongChainID
+	case len(tx.ImportedInputs) == 0:
+		return errNoImportInputs
+	case tx.NetworkID != ctx.NetworkID:
+		return errWrongNetworkID
+	case !ctx.ChainID.Equals(tx.BlockchainID):
+		return errWrongBlockchainID
+	}
+
+	for _, out := range tx.Outs {
+		if err := out.Verify(); err != nil {
+			return err
+		}
+	}
+
+	for _, in := range tx.ImportedInputs {
+		if err := in.Verify(); err != nil {
+			return err
+		}
+	}
+	if !avax.IsSortedAndUniqueTransferableInputs(tx.ImportedInputs) {
+		return errInputsNotSortedUnique
+	}
+
+	tx.syntacticallyVerified = true
+	return nil
+}
+
+// SemanticVerify this transaction is valid.
+func (tx *UnsignedImportTx) SemanticVerify(
+	vm *VM,
+	stx *Tx,
+) TxError {
+	if err := tx.Verify(vm.ctx.XChainID, vm.ctx, vm.txFee, vm.ctx.AVAXAssetID); err != nil {
+		return permError{err}
+	}
+
+	// do flow-checking
+	fc := avax.NewFlowChecker()
+	fc.Produce(vm.ctx.AVAXAssetID, vm.txFee)
+
+	for _, out := range tx.Outs {
+		fc.Produce(vm.ctx.AVAXAssetID, out.Amount)
+	}
+
+	for _, in := range tx.ImportedInputs {
+		fc.Consume(in.AssetID(), in.Input().Amount())
+	}
+	if err := fc.Verify(); err != nil {
+		return permError{err}
+	}
+
+	if !vm.ctx.IsBootstrapped() {
+		// Allow for force committing during bootstrapping
+		return nil
+	}
+
+	utxoIDs := make([][]byte, len(tx.ImportedInputs))
+	for i, in := range tx.ImportedInputs {
+		utxoIDs[i] = in.UTXOID.InputID().Bytes()
+	}
+	allUTXOBytes, err := vm.ctx.SharedMemory.Get(tx.SourceChain, utxoIDs)
+	if err != nil {
+		return tempError{err}
+	}
+
+	utxos := make([]*avax.UTXO, len(tx.ImportedInputs))
+	for i, utxoBytes := range allUTXOBytes {
+		utxo := &avax.UTXO{}
+		if err := vm.codec.Unmarshal(utxoBytes, utxo); err != nil {
+			return tempError{err}
+		}
+		utxos[i] = utxo
+	}
+
+	for i, in := range tx.ImportedInputs {
+		utxoBytes := allUTXOBytes[i]
+
+		utxo := &avax.UTXO{}
+		if err := vm.codec.Unmarshal(utxoBytes, utxo); err != nil {
+			return tempError{err}
+		}
+
+		cred := stx.Creds[i]
+
+		utxoAssetID := utxo.AssetID()
+		inAssetID := in.AssetID()
+		if !utxoAssetID.Equals(inAssetID) {
+			return permError{errAssetIDMismatch}
+		}
+
+		if err := vm.fx.VerifyTransfer(tx, in.In, cred, utxo.Out); err != nil {
+			return tempError{err}
+		}
+	}
+	return nil
+}
+
+// Accept this transaction and spend imported inputs
+// We spend imported UTXOs here rather than in semanticVerify because
+// we don't want to remove an imported UTXO in semanticVerify
+// only to have the transaction not be Accepted. This would be inconsistent.
+// Recall that imported UTXOs are not kept in a versionDB.
+func (tx *UnsignedImportTx) Accept(ctx *snow.Context, _ database.Batch) error {
+	// TODO: Is any batch passed in here?
+	utxoIDs := make([][]byte, len(tx.ImportedInputs))
+	for i, in := range tx.ImportedInputs {
+		utxoIDs[i] = in.InputID().Bytes()
+	}
+	return ctx.SharedMemory.Remove(tx.SourceChain, utxoIDs)
+}
+
+// Create a new transaction
+func (vm *VM) newImportTx(
+	chainID ids.ID, // chain to import from
+	to common.Address, // Address of recipient
+	keys []*crypto.PrivateKeySECP256K1R, // Keys to import the funds
+) (*Tx, error) {
+	if !vm.ctx.XChainID.Equals(chainID) {
+		return nil, errWrongChainID
+	}
+
+	kc := secp256k1fx.NewKeychain()
+	for _, key := range keys {
+		kc.Add(key)
+	}
+
+	atomicUTXOs, _, _, err := vm.GetAtomicUTXOs(chainID, kc.Addresses(), ids.ShortEmpty, ids.Empty, -1)
+	if err != nil {
+		return nil, fmt.Errorf("problem retrieving atomic UTXOs: %w", err)
+	}
+
+	importedInputs := []*avax.TransferableInput{}
+	signers := [][]*crypto.PrivateKeySECP256K1R{}
+
+	importedAmount := uint64(0)
+	now := vm.clock.Unix()
+	for _, utxo := range atomicUTXOs {
+		if !utxo.AssetID().Equals(vm.ctx.AVAXAssetID) {
+			continue
+		}
+		inputIntf, utxoSigners, err := kc.Spend(utxo.Out, now)
+		if err != nil {
+			continue
+		}
+		input, ok := inputIntf.(avax.TransferableIn)
+		if !ok {
+			continue
+		}
+		importedAmount, err = math.Add64(importedAmount, input.Amount())
+		if err != nil {
+			return nil, err
+		}
+		importedInputs = append(importedInputs, &avax.TransferableInput{
+			UTXOID: utxo.UTXOID,
+			Asset:  utxo.Asset,
+			In:     input,
+		})
+		signers = append(signers, utxoSigners)
+	}
+	avax.SortTransferableInputsWithSigners(importedInputs, signers)
+
+	if importedAmount == 0 {
+		return nil, errNoFunds // No imported UTXOs were spendable
+	}
+
+	nonce, err := vm.GetAcceptedNonce(to)
+	if err != nil {
+		return nil, err
+	}
+
+	outs := []EVMOutput{}
+	if importedAmount < vm.txFee { // imported amount goes toward paying tx fee
+		// TODO: spend EVM balance to compensate vm.txFee-importedAmount
+		return nil, errNoFunds
+	} else if importedAmount > vm.txFee {
+		outs = append(outs, EVMOutput{
+			Address: to,
+			Amount:  importedAmount - vm.txFee,
+			Nonce:   nonce,
+		})
+	}
+
+	// Create the transaction
+	utx := &UnsignedImportTx{
+		NetworkID:      vm.ctx.NetworkID,
+		BlockchainID:   vm.ctx.ChainID,
+		Outs:           outs,
+		ImportedInputs: importedInputs,
+		SourceChain:    chainID,
+	}
+	tx := &Tx{UnsignedTx: utx}
+	if err := tx.Sign(vm.codec, signers); err != nil {
+		return nil, err
+	}
+	return tx, utx.Verify(vm.ctx.XChainID, vm.ctx, vm.txFee, vm.ctx.AVAXAssetID)
+}
+
+func (tx *UnsignedImportTx) EVMStateTransfer(state *state.StateDB) error {
+	for _, to := range tx.Outs {
+		state.AddBalance(to.Address,
+			new(big.Int).Mul(
+				new(big.Int).SetUint64(to.Amount), x2cRate))
+		if state.GetNonce(to.Address) != to.Nonce {
+			return errInvalidNonce
+		}
+		state.SetNonce(to.Address, to.Nonce+1)
+	}
+	return nil
+}