evm: implement vm.GetHashFn (#620)

* evm: implement vm.GetHashFn

* check nil case

* test

* handle 3 cases

* use switch statement

* stateDB tests

* abci changes

* fix LGTM issue

* final tests

* changelog

* remove epoch

* update test

* clean test

* rm epoch

CHANGELOG.md

@@ -40,6 +40,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### Bug Fixes
 
 * (evm) [\#621](https://github.com/cosmos/ethermint/issues/621) EVM `GenesisAccount` fields now share the same format as the auth module `Account`.
+* (evm) [\#618](https://github.com/cosmos/ethermint/issues/618) Add missing EVM `Context` `GetHash` field that retrieves a the header hash from a given block height.
 * (app) [\#617](https://github.com/cosmos/ethermint/issues/617) Fix genesis export functionality.
 
 ## [v0.3.1] - 2020-11-24

app/export.go

@@ -28,7 +28,6 @@ func NewDefaultGenesisState() simapp.GenesisState {
 func (app *EthermintApp) ExportAppStateAndValidators(
 	forZeroHeight bool, jailWhiteList []string,
 ) (appState json.RawMessage, validators []tmtypes.GenesisValidator, err error) {
-
 	// Creates context with current height and checks txs for ctx to be usable by start of next block
 	ctx := app.NewContext(true, abci.Header{Height: app.LastBlockHeight()})
 

x/evm/keeper/abci.go

@@ -8,6 +8,8 @@ import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 
 	ethtypes "github.com/ethereum/go-ethereum/core/types"
+
+	"github.com/cosmos/ethermint/x/evm/types"
 )
 
 // BeginBlock sets the block hash -> block height map for the previous block height
@@ -29,18 +31,25 @@ func (k *Keeper) BeginBlock(ctx sdk.Context, req abci.RequestBeginBlock) {
 
 // EndBlock updates the accounts and commits state objects to the KV Store, while
 // deleting the empty ones. It also sets the bloom filers for the request block to
-// the store. The EVM end block loginc doesn't update the validator set, thus it returns
+// the store. The EVM end block logic doesn't update the validator set, thus it returns
 // an empty slice.
 func (k Keeper) EndBlock(ctx sdk.Context, req abci.RequestEndBlock) []abci.ValidatorUpdate {
 	// Gas costs are handled within msg handler so costs should be ignored
 	ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
 
+	// Set the hash for the current height.
+	// NOTE: we set the hash here instead of on BeginBlock in order to set the final block prior to
+	// an upgrade. If we set it on BeginBlock the last block from prior to the upgrade wouldn't be
+	// included on the store.
+	hash := types.HashFromContext(ctx)
+	k.SetHeightHash(ctx, uint64(ctx.BlockHeight()), hash)
+
 	// Update account balances before committing other parts of state
 	k.UpdateAccounts(ctx)
 
 	// Commit state objects to KV store
-	_, err := k.Commit(ctx, true)
-	if err != nil {
+	if _, err := k.Commit(ctx, true); err != nil {
+		k.Logger(ctx).Error("failed to commit state objects", "error", err, "height", ctx.BlockHeight())
 		panic(err)
 	}
 

x/evm/keeper/keeper.go

@@ -88,6 +88,21 @@ func (k Keeper) SetBlockHash(ctx sdk.Context, hash []byte, height int64) {
 	store.Set(hash, bz)
 }
 
+// ----------------------------------------------------------------------------
+// Epoch Height -> hash mapping functions
+// Required by EVM context's GetHashFunc
+// ----------------------------------------------------------------------------
+
+// GetHeightHash returns the block header hash associated with a given block height and chain epoch number.
+func (k Keeper) GetHeightHash(ctx sdk.Context, height uint64) common.Hash {
+	return k.CommitStateDB.WithContext(ctx).GetHeightHash(height)
+}
+
+// SetHeightHash sets the block header hash associated with a given height.
+func (k Keeper) SetHeightHash(ctx sdk.Context, height uint64, hash common.Hash) {
+	k.CommitStateDB.WithContext(ctx).SetHeightHash(height, hash)
+}
+
 // ----------------------------------------------------------------------------
 // Block bloom bits mapping functions
 // Required by Web3 API.

x/evm/keeper/keeper_test.go

@@ -42,7 +42,7 @@ func (suite *KeeperTestSuite) SetupTest() {
 	checkTx := false
 
 	suite.app = app.Setup(checkTx)
-	suite.ctx = suite.app.BaseApp.NewContext(checkTx, abci.Header{Height: 1, ChainID: "3", Time: time.Now().UTC()})
+	suite.ctx = suite.app.BaseApp.NewContext(checkTx, abci.Header{Height: 1, ChainID: "ethermint-3", Time: time.Now().UTC()})
 	suite.querier = keeper.NewQuerier(suite.app.EvmKeeper)
 	suite.address = ethcmn.HexToAddress(addrHex)
 

x/evm/types/journal_test.go

@@ -124,7 +124,7 @@ func (suite *JournalTestSuite) setup() {
 	evmSubspace := paramsKeeper.Subspace(types.DefaultParamspace).WithKeyTable(ParamKeyTable())
 
 	ak := auth.NewAccountKeeper(cdc, authKey, authSubspace, ethermint.ProtoAccount)
-	suite.ctx = sdk.NewContext(cms, abci.Header{ChainID: "8"}, false, tmlog.NewNopLogger())
+	suite.ctx = sdk.NewContext(cms, abci.Header{ChainID: "ethermint-8"}, false, tmlog.NewNopLogger())
 	suite.stateDB = NewCommitStateDB(suite.ctx, storeKey, evmSubspace, ak).WithContext(suite.ctx)
 	suite.stateDB.SetParams(DefaultParams())
 }

x/evm/types/key.go

@@ -27,8 +27,18 @@ var (
 	KeyPrefixCode        = []byte{0x04}
 	KeyPrefixStorage     = []byte{0x05}
 	KeyPrefixChainConfig = []byte{0x06}
+	KeyPrefixHeightHash  = []byte{0x07}
 )
 
+// HeightHashKey returns the key for the given chain epoch and height.
+// The key will be composed in the following order:
+//   key = prefix + bytes(height)
+// This ordering facilitates the iteration by height for the EVM GetHashFn
+// queries.
+func HeightHashKey(height uint64) []byte {
+	return sdk.Uint64ToBigEndian(height)
+}
+
 // BloomKey defines the store key for a block Bloom
 func BloomKey(height int64) []byte {
 	return sdk.Uint64ToBigEndian(uint64(height))

x/evm/types/state_transition.go

@@ -47,11 +47,42 @@ type ExecutionResult struct {
 	GasInfo GasInfo
 }
 
-func (st StateTransition) newEVM(ctx sdk.Context, csdb *CommitStateDB, gasLimit uint64, gasPrice *big.Int, config ChainConfig) *vm.EVM {
+// GetHashFn implements vm.GetHashFunc for Ethermint. It handles 3 cases:
+//  1. The requested height matches the current height from context (and thus same epoch number)
+//  2. The requested height is from an previous height from the same chain epoch
+//  3. The requested height is from a height greater than the latest one
+func GetHashFn(ctx sdk.Context, csdb *CommitStateDB) vm.GetHashFunc {
+	return func(height uint64) common.Hash {
+		switch {
+		case ctx.BlockHeight() == int64(height):
+			// Case 1: The requested height matches the one from the context so we can retrieve the header
+			// hash directly from the context.
+			return HashFromContext(ctx)
+
+		case ctx.BlockHeight() > int64(height):
+			// Case 2: if the chain is not the current height we need to retrieve the hash from the store for the
+			// current chain epoch. This only applies if the current height is greater than the requested height.
+			return csdb.WithContext(ctx).GetHeightHash(height)
+
+		default:
+			// Case 3: heights greater than the current one returns an empty hash.
+			return common.Hash{}
+		}
+	}
+}
+
+func (st StateTransition) newEVM(
+	ctx sdk.Context,
+	csdb *CommitStateDB,
+	gasLimit uint64,
+	gasPrice *big.Int,
+	config ChainConfig,
+) *vm.EVM {
 	// Create context for evm
 	context := vm.Context{
 		CanTransfer: core.CanTransfer,
 		Transfer:    core.Transfer,
+		GetHash:     GetHashFn(ctx, csdb),
 		Origin:      st.Sender,
 		Coinbase:    common.Address{}, // there's no benefitiary since we're not mining
 		BlockNumber: big.NewInt(ctx.BlockHeight()),
@@ -134,7 +165,7 @@ func (st StateTransition) TransitionDb(ctx sdk.Context, config ChainConfig) (*Ex
 		recipientLog = fmt.Sprintf("contract address %s", contractAddress.String())
 	default:
 		if !params.EnableCall {
-			return nil, ErrCreateDisabled
+			return nil, ErrCallDisabled
 		}
 
 		// Increment the nonce for the next transaction	(just for evm state transition)
@@ -223,3 +254,21 @@ func (st StateTransition) TransitionDb(ctx sdk.Context, config ChainConfig) (*Ex
 
 	return executionResult, nil
 }
+
+// HashFromContext returns the Ethereum Header hash from the context's Tendermint
+// block header.
+func HashFromContext(ctx sdk.Context) common.Hash {
+	// cast the ABCI header to tendermint Header type
+	tmHeader := AbciHeaderToTendermint(ctx.BlockHeader())
+
+	// get the Tendermint block hash from the current header
+	tmBlockHash := tmHeader.Hash()
+
+	// NOTE: if the validator set hash is missing the hash will be returned as nil,
+	// so we need to check for this case to prevent a panic when calling Bytes()
+	if tmBlockHash == nil {
+		return common.Hash{}
+	}
+
+	return common.BytesToHash(tmBlockHash.Bytes())
+}

x/evm/types/state_transition_test.go

@@ -3,16 +3,108 @@ package types_test
 import (
 	"math/big"
 
+	abci "github.com/tendermint/tendermint/abci/types"
+
 	sdk "github.com/cosmos/cosmos-sdk/types"
 
 	"github.com/cosmos/ethermint/crypto/ethsecp256k1"
 	ethermint "github.com/cosmos/ethermint/types"
 	"github.com/cosmos/ethermint/x/evm/types"
 
+	"github.com/ethereum/go-ethereum/common"
 	ethcmn "github.com/ethereum/go-ethereum/common"
 	ethcrypto "github.com/ethereum/go-ethereum/crypto"
 )
 
+func (suite *StateDBTestSuite) TestGetHashFn() {
+	testCase := []struct {
+		name         string
+		height       uint64
+		malleate     func()
+		expEmptyHash bool
+	}{
+		{
+			"valid hash, case 1",
+			1,
+			func() {
+				suite.ctx = suite.ctx.WithBlockHeader(
+					abci.Header{
+						ChainID:        "ethermint-1",
+						Height:         1,
+						ValidatorsHash: []byte("val_hash"),
+					},
+				)
+			},
+			false,
+		},
+		{
+			"case 1, nil tendermint hash",
+			1,
+			func() {},
+			true,
+		},
+		{
+			"valid hash, case 2",
+			1,
+			func() {
+				suite.ctx = suite.ctx.WithBlockHeader(
+					abci.Header{
+						ChainID:        "ethermint-1",
+						Height:         100,
+						ValidatorsHash: []byte("val_hash"),
+					},
+				)
+				hash := types.HashFromContext(suite.ctx)
+				suite.stateDB.WithContext(suite.ctx).SetHeightHash(1, hash)
+			},
+			false,
+		},
+		{
+			"height not found, case 2",
+			1,
+			func() {
+				suite.ctx = suite.ctx.WithBlockHeader(
+					abci.Header{
+						ChainID:        "ethermint-1",
+						Height:         100,
+						ValidatorsHash: []byte("val_hash"),
+					},
+				)
+			},
+			true,
+		},
+		{
+			"empty hash, case 3",
+			1000,
+			func() {
+				suite.ctx = suite.ctx.WithBlockHeader(
+					abci.Header{
+						ChainID:        "ethermint-1",
+						Height:         100,
+						ValidatorsHash: []byte("val_hash"),
+					},
+				)
+			},
+			true,
+		},
+	}
+
+	for _, tc := range testCase {
+		suite.Run(tc.name, func() {
+			suite.SetupTest() // reset
+
+			tc.malleate()
+
+			hash := types.GetHashFn(suite.ctx, suite.stateDB)(tc.height)
+			if tc.expEmptyHash {
+				suite.Require().Equal(common.Hash{}.String(), hash.String())
+			} else {
+				suite.Require().NotEqual(common.Hash{}.String(), hash.String())
+			}
+		})
+	}
+}
+
 func (suite *StateDBTestSuite) TestTransitionDb() {
 	suite.stateDB.SetNonce(suite.address, 123)
 
@@ -104,9 +196,52 @@ func (suite *StateDBTestSuite) TestTransitionDb() {
 			},
 			false,
 		},
+		{
+			"call disabled",
+			func() {
+				params := types.NewParams(ethermint.AttoPhoton, true, false)
+				suite.stateDB.SetParams(params)
+			},
+			types.StateTransition{
+				AccountNonce: 123,
+				Price:        big.NewInt(10),
+				GasLimit:     11,
+				Recipient:    &recipient,
+				Amount:       big.NewInt(50),
+				Payload:      []byte("data"),
+				ChainID:      big.NewInt(1),
+				Csdb:         suite.stateDB,
+				TxHash:       &ethcmn.Hash{},
+				Sender:       suite.address,
+				Simulate:     suite.ctx.IsCheckTx(),
+			},
+			false,
+		},
+		{
+			"create disabled",
+			func() {
+				params := types.NewParams(ethermint.AttoPhoton, false, true)
+				suite.stateDB.SetParams(params)
+			},
+			types.StateTransition{
+				AccountNonce: 123,
+				Price:        big.NewInt(10),
+				GasLimit:     11,
+				Recipient:    nil,
+				Amount:       big.NewInt(50),
+				Payload:      []byte("data"),
+				ChainID:      big.NewInt(1),
+				Csdb:         suite.stateDB,
+				TxHash:       &ethcmn.Hash{},
+				Sender:       suite.address,
+				Simulate:     suite.ctx.IsCheckTx(),
+			},
+			false,
+		},
 		{
 			"nil gas price",
 			func() {
+				suite.stateDB.SetParams(types.DefaultParams())
 				invalidGas := sdk.DecCoins{
 					{Denom: ethermint.AttoPhoton},
 				}

x/evm/types/statedb.go

@@ -10,7 +10,7 @@ import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/x/params"
 
-	emint "github.com/cosmos/ethermint/types"
+	ethermint "github.com/cosmos/ethermint/types"
 
 	ethcmn "github.com/ethereum/go-ethereum/common"
 	ethstate "github.com/ethereum/go-ethereum/core/state"
@@ -107,7 +107,7 @@ func NewCommitStateDB(
 	}
 }
 
-// WithContext returns a Database with an updated sdk context
+// WithContext returns a Database with an updated SDK context
 func (csdb *CommitStateDB) WithContext(ctx sdk.Context) *CommitStateDB {
 	csdb.ctx = ctx
 	return csdb
@@ -117,6 +117,13 @@ func (csdb *CommitStateDB) WithContext(ctx sdk.Context) *CommitStateDB {
 // Setters
 // ----------------------------------------------------------------------------
 
+// SetHeightHash sets the block header hash associated with a given height.
+func (csdb *CommitStateDB) SetHeightHash(height uint64, hash ethcmn.Hash) {
+	store := prefix.NewStore(csdb.ctx.KVStore(csdb.storeKey), KeyPrefixHeightHash)
+	key := HeightHashKey(height)
+	store.Set(key, hash.Bytes())
+}
+
 // SetParams sets the evm parameters to the param space.
 func (csdb *CommitStateDB) SetParams(params Params) {
 	csdb.paramSpace.SetParamSet(csdb.ctx, &params)
@@ -286,6 +293,18 @@ func (csdb *CommitStateDB) SlotInAccessList(addr ethcmn.Address, slot ethcmn.Has
 // Getters
 // ----------------------------------------------------------------------------
 
+// GetHeightHash returns the block header hash associated with a given block height and chain epoch number.
+func (csdb *CommitStateDB) GetHeightHash(height uint64) ethcmn.Hash {
+	store := prefix.NewStore(csdb.ctx.KVStore(csdb.storeKey), KeyPrefixHeightHash)
+	key := HeightHashKey(height)
+	bz := store.Get(key)
+	if len(bz) == 0 {
+		return ethcmn.Hash{}
+	}
+
+	return ethcmn.BytesToHash(bz)
+}
+
 // GetParams returns the total set of evm parameters.
 func (csdb *CommitStateDB) GetParams() (params Params) {
 	csdb.paramSpace.GetParamSet(csdb.ctx, &params)
@@ -680,7 +699,7 @@ func (csdb *CommitStateDB) Reset(_ ethcmn.Hash) error {
 func (csdb *CommitStateDB) UpdateAccounts() {
 	for _, stateEntry := range csdb.stateObjects {
 		currAcc := csdb.accountKeeper.GetAccount(csdb.ctx, sdk.AccAddress(stateEntry.address.Bytes()))
-		emintAcc, ok := currAcc.(*emint.EthAccount)
+		ethermintAcc, ok := currAcc.(*ethermint.EthAccount)
 		if !ok {
 			continue
 		}
@@ -688,12 +707,12 @@ func (csdb *CommitStateDB) UpdateAccounts() {
 		evmDenom := csdb.GetParams().EvmDenom
 		balance := sdk.Coin{
 			Denom:  evmDenom,
-			Amount: emintAcc.GetCoins().AmountOf(evmDenom),
+			Amount: ethermintAcc.GetCoins().AmountOf(evmDenom),
 		}
 
 		if stateEntry.stateObject.Balance() != balance.Amount.BigInt() && balance.IsValid() ||
-			stateEntry.stateObject.Nonce() != emintAcc.GetSequence() {
-			stateEntry.stateObject.account = emintAcc
+			stateEntry.stateObject.Nonce() != ethermintAcc.GetSequence() {
+			stateEntry.stateObject.account = ethermintAcc
 		}
 	}
 }

x/evm/types/statedb_test.go

@@ -40,7 +40,7 @@ func (suite *StateDBTestSuite) SetupTest() {
 	checkTx := false
 
 	suite.app = app.Setup(checkTx)
-	suite.ctx = suite.app.BaseApp.NewContext(checkTx, abci.Header{Height: 1})
+	suite.ctx = suite.app.BaseApp.NewContext(checkTx, abci.Header{Height: 1, ChainID: "ethermint-1"})
 	suite.stateDB = suite.app.EvmKeeper.CommitStateDB.WithContext(suite.ctx)
 
 	privkey, err := ethsecp256k1.GenerateKey()
@@ -67,6 +67,17 @@ func (suite *StateDBTestSuite) TestParams() {
 	suite.Require().Equal(newParams, params)
 }
 
+func (suite *StateDBTestSuite) TestGetHeightHash() {
+	hash := suite.stateDB.GetHeightHash(0)
+	suite.Require().Equal(ethcmn.Hash{}.String(), hash.String())
+
+	expHash := ethcmn.BytesToHash([]byte("hash"))
+	suite.stateDB.SetHeightHash(10, expHash)
+
+	hash = suite.stateDB.GetHeightHash(10)
+	suite.Require().Equal(expHash.String(), hash.String())
+}
+
 func (suite *StateDBTestSuite) TestBloomFilter() {
 	// Prepare db for logs
 	tHash := ethcmn.BytesToHash([]byte{0x1})

x/evm/types/utils.go

@@ -8,6 +8,10 @@ import (
 	"github.com/pkg/errors"
 	"golang.org/x/crypto/sha3"
 
+	abci "github.com/tendermint/tendermint/abci/types"
+	tmtypes "github.com/tendermint/tendermint/types"
+	"github.com/tendermint/tendermint/version"
+
 	"github.com/cosmos/cosmos-sdk/codec"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
@@ -152,3 +156,36 @@ func recoverEthSig(R, S, Vb *big.Int, sigHash ethcmn.Hash) (ethcmn.Address, erro
 
 	return addr, nil
 }
+
+// AbciHeaderToTendermint is a util function to parse a tendermint ABCI Header to
+// tendermint types Header.
+func AbciHeaderToTendermint(header abci.Header) tmtypes.Header {
+	return tmtypes.Header{
+		Version: version.Consensus{
+			Block: version.Protocol(header.Version.Block),
+			App:   version.Protocol(header.Version.App),
+		},
+		ChainID: header.ChainID,
+		Height:  header.Height,
+		Time:    header.Time,
+
+		LastBlockID: tmtypes.BlockID{
+			Hash: header.LastBlockId.Hash,
+			PartsHeader: tmtypes.PartSetHeader{
+				Total: int(header.LastBlockId.PartsHeader.Total),
+				Hash:  header.LastBlockId.PartsHeader.Hash,
+			},
+		},
+		LastCommitHash: header.LastCommitHash,
+		DataHash:       header.DataHash,
+
+		ValidatorsHash:     header.ValidatorsHash,
+		NextValidatorsHash: header.NextValidatorsHash,
+		ConsensusHash:      header.ConsensusHash,
+		AppHash:            header.AppHash,
+		LastResultsHash:    header.LastResultsHash,
+
+		EvidenceHash:    header.EvidenceHash,
+		ProposerAddress: header.ProposerAddress,
+	}
+}