Merge pull request #130 from m-Peter/eth-get-code-rpc-endpoint

Implement the `eth_getCode` JSON-RPC endpoint

api/api.go

@@ -544,6 +544,28 @@ func (b *BlockChainAPI) EstimateGas(
 	return hexutil.Uint64(estimatedGas), nil
 }
 
+// GetCode returns the code stored at the given address in
+// the state for the given block number.
+func (b *BlockChainAPI) GetCode(
+	ctx context.Context,
+	address common.Address,
+	blockNumberOrHash *rpc.BlockNumberOrHash,
+) (hexutil.Bytes, error) {
+	// todo support previous block heights
+	if blockNumberOrHash != nil && *blockNumberOrHash.BlockNumber != rpc.LatestBlockNumber {
+		// but still return latest for now
+		b.logger.Warn().Msg("get code for special blocks not supported")
+	}
+
+	code, err := b.evm.GetCode(ctx, address, 0)
+	if err != nil {
+		b.logger.Error().Err(err).Msg("failed to retrieve account code")
+		return nil, err
+	}
+
+	return hexutil.Bytes(code), nil
+}
+
 // handleError takes in an error and in case the error is of type ErrNotFound
 // it returns nil instead of an error since that is according to the API spec,
 // if the error is not of type ErrNotFound it will return the error and the generic
@@ -696,15 +718,6 @@ func (b *BlockChainAPI) SendTransaction(
 	return common.Hash{}, errs.ErrNotSupported
 }
 
-// GetCode returns the code stored at the given address in the state for the given block number.
-func (b *BlockChainAPI) GetCode(
-	ctx context.Context,
-	address common.Address,
-	blockNumberOrHash *rpc.BlockNumberOrHash,
-) (hexutil.Bytes, error) {
-	return nil, errs.ErrNotSupported
-}
-
 // GetProof returns the Merkle-proof for a given account and optionally some storage keys.
 func (b *BlockChainAPI) GetProof(
 	ctx context.Context,

integration/e2e_test.go

@@ -524,6 +524,13 @@ func TestE2E_API_DeployEvents(t *testing.T) {
 
 	contractAddress := rcp.ContractAddress
 
+	// Check code retrieval
+	code, err := rpcTester.getCode(contractAddress)
+	require.NoError(t, err)
+	// The deployed byte code is a subset of the byte code provided in
+	// contract deployment tx.
+	assert.Contains(t, hex.EncodeToString(deployData), hex.EncodeToString(code))
+
 	callRetrieve, err := storeContract.call("retrieve")
 	require.NoError(t, err)
 

integration/helpers.go

@@ -584,6 +584,27 @@ func (r *rpcTest) call(
 	return result, nil
 }
 
+func (r *rpcTest) getCode(from common.Address) ([]byte, error) {
+	rpcRes, err := r.request(
+		"eth_getCode",
+		fmt.Sprintf(
+			`["%s","latest"]`,
+			from.Hex(),
+		),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	var code hexutil.Bytes
+	err = json.Unmarshal(rpcRes, &code)
+	if err != nil {
+		return nil, err
+	}
+
+	return code, nil
+}
+
 func uintHex(x uint64) string {
 	return fmt.Sprintf("0x%x", x)
 }

services/requester/cadence/get_code.cdc

@@ -0,0 +1,9 @@
+import EVM
+
+access(all)
+fun main(hexEncodedAddress: String): String {
+    let addressBytes = hexEncodedAddress.decodeHex().toConstantSized<[UInt8; 20]>()!
+    let address = EVM.EVMAddress(bytes: addressBytes)
+
+    return String.encodeHex(address.code())
+}

services/requester/requester.go

@@ -43,6 +43,9 @@ var (
 
 	//go:embed cadence/get_nonce.cdc
 	getNonceScript []byte
+
+	//go:embed cadence/get_code.cdc
+	getCodeScript []byte
 )
 
 const minFlowBalance = 2
@@ -70,6 +73,10 @@ type Requester interface {
 
 	// GetNonce gets nonce from the network.
 	GetNonce(ctx context.Context, address common.Address) (uint64, error)
+
+	// GetCode returns the code stored at the given address in
+	// the state for the given block number.
+	GetCode(ctx context.Context, address common.Address, height uint64) ([]byte, error)
 }
 
 var _ Requester = &EVM{}
@@ -242,9 +249,7 @@ func (e *EVM) signAndSend(ctx context.Context, script []byte, args ...cadence.Va
 
 func (e *EVM) GetBalance(ctx context.Context, address common.Address, height uint64) (*big.Int, error) {
 	// todo make sure provided height is used
-	hexEncodedAddress, err := cadence.NewString(
-		strings.TrimPrefix(address.Hex(), "0x"),
-	)
+	hexEncodedAddress, err := addressToCadenceString(address)
 	if err != nil {
 		return nil, err
 	}
@@ -269,9 +274,7 @@ func (e *EVM) GetBalance(ctx context.Context, address common.Address, height uin
 }
 
 func (e *EVM) GetNonce(ctx context.Context, address common.Address) (uint64, error) {
-	hexEncodedAddress, err := cadence.NewString(
-		strings.TrimPrefix(address.Hex(), "0x"),
-	)
+	hexEncodedAddress, err := addressToCadenceString(address)
 	if err != nil {
 		return 0, err
 	}
@@ -302,9 +305,7 @@ func (e *EVM) Call(ctx context.Context, address common.Address, data []byte) ([]
 	}
 
 	// todo make "to" address optional, this can be used for contract deployment simulations
-	hexEncodedAddress, err := cadence.NewString(
-		strings.TrimPrefix(address.Hex(), "0x"),
-	)
+	hexEncodedAddress, err := addressToCadenceString(address)
 	if err != nil {
 		return nil, err
 	}
@@ -323,24 +324,18 @@ func (e *EVM) Call(ctx context.Context, address common.Address, data []byte) ([]
 		return nil, fmt.Errorf("failed to execute script: %w", err)
 	}
 
-	// sanity check, should never occur
-	if _, ok := scriptResult.(cadence.String); !ok {
-		e.logger.Panic().Msg(fmt.Sprintf("failed to convert script result %v to String", scriptResult))
-	}
-
-	output := scriptResult.(cadence.String).ToGoValue().(string)
-	byteOutput, err := hex.DecodeString(output)
+	output, err := cadenceStringToBytes(scriptResult)
 	if err != nil {
-		return nil, fmt.Errorf("failed to convert call output: %w", err)
+		return nil, err
 	}
 
 	e.logger.Info().
 		Str("address", address.Hex()).
 		Str("data", fmt.Sprintf("%x", data)).
-		Str("result", output).
+		Str("result", hex.EncodeToString(output)).
 		Msg("call executed")
 
-	return byteOutput, nil
+	return output, nil
 }
 
 func (e *EVM) EstimateGas(ctx context.Context, data []byte) (uint64, error) {
@@ -380,6 +375,43 @@ func (e *EVM) EstimateGas(ctx context.Context, data []byte) (uint64, error) {
 	return gasUsed, nil
 }
 
+func (e *EVM) GetCode(
+	ctx context.Context,
+	address common.Address,
+	height uint64,
+) ([]byte, error) {
+	e.logger.Debug().
+		Str("addess", address.Hex()).
+		Str("height", fmt.Sprintf("%d", height)).
+		Msg("get code")
+
+	hexEncodedAddress, err := addressToCadenceString(address)
+	if err != nil {
+		return nil, err
+	}
+
+	value, err := e.client.ExecuteScriptAtLatestBlock(
+		ctx,
+		e.replaceAddresses(getCodeScript),
+		[]cadence.Value{hexEncodedAddress},
+	)
+	if err != nil {
+		return nil, fmt.Errorf("failed to execute script for get code: %w", err)
+	}
+
+	code, err := cadenceStringToBytes(value)
+	if err != nil {
+		return nil, err
+	}
+
+	e.logger.Info().
+		Str("address", address.Hex()).
+		Str("code size", fmt.Sprintf("%d", len(code))).
+		Msg("get code executed")
+
+	return code, nil
+}
+
 // getSignerNetworkInfo loads the signer account from network and returns key index and sequence number
 func (e *EVM) getSignerNetworkInfo(ctx context.Context) (int, uint64, error) {
 	account, err := e.client.GetAccount(ctx, e.address)
@@ -418,6 +450,27 @@ func (e *EVM) replaceAddresses(script []byte) []byte {
 	return []byte(s)
 }
 
+func addressToCadenceString(address common.Address) (cadence.String, error) {
+	return cadence.NewString(
+		strings.TrimPrefix(address.Hex(), "0x"),
+	)
+}
+
+func cadenceStringToBytes(value cadence.Value) ([]byte, error) {
+	cdcString, ok := value.(cadence.String)
+	if !ok {
+		return nil, fmt.Errorf("failed to convert cadence value to string: %v", value)
+	}
+
+	hexEncodedCode := cdcString.ToGoValue().(string)
+	code, err := hex.DecodeString(hexEncodedCode)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode string to byte array: %w", err)
+	}
+
+	return code, nil
+}
+
 // TODO(m-Peter): Consider moving this to flow-go repository
 func getErrorForCode(errorCode uint64) error {
 	switch evmTypes.ErrorCode(errorCode) {