Encode empty extra_data as "0x" and base_fee_per_gas as Uint256 i… (#10539)

* Encode empty `extra_data` as "0x" and `base_fee_per_gas` as Uint256 in the Beacon API

* Fixed parsing of Uint256 in the API

* Add missing tests for empty hex & Uint256 fields in `apimiddleware`

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

api/gateway/apimiddleware/process_field.go

@@ -3,6 +3,7 @@ package apimiddleware
 import (
 	"encoding/base64"
 	"fmt"
+	"math/big"
 	"reflect"
 	"strconv"
 	"strings"
@@ -73,6 +74,10 @@ func processField(s interface{}, processors []fieldProcessor) error {
 }
 
 func hexToBase64Processor(v reflect.Value) error {
+	if v.String() == "0x" {
+		v.SetString("")
+		return nil
+	}
 	b, err := bytesutil.FromHexString(v.String())
 	if err != nil {
 		return err
@@ -83,6 +88,8 @@ func hexToBase64Processor(v reflect.Value) error {
 
 func base64ToHexProcessor(v reflect.Value) error {
 	if v.String() == "" {
+		// Empty hex values are represented as "0x".
+		v.SetString("0x")
 		return nil
 	}
 	b, err := base64.StdEncoding.DecodeString(v.String())
@@ -93,6 +100,55 @@ func base64ToHexProcessor(v reflect.Value) error {
 	return nil
 }
 
+func base64ToUint256Processor(v reflect.Value) error {
+	if v.String() == "" {
+		return nil
+	}
+	littleEndian, err := base64.StdEncoding.DecodeString(v.String())
+	if err != nil {
+		return err
+	}
+	if len(littleEndian) != 32 {
+		return errors.New("invalid length for Uint256")
+	}
+
+	// Integers are stored as little-endian, but
+	// big.Int expects big-endian. So we need to reverse
+	// the byte order before decoding.
+	var bigEndian [32]byte
+	for i := 0; i < len(littleEndian); i++ {
+		bigEndian[i] = littleEndian[len(littleEndian)-1-i]
+	}
+	var uint256 big.Int
+	uint256.SetBytes(bigEndian[:])
+	v.SetString(uint256.String())
+	return nil
+}
+
+func uint256ToBase64Processor(v reflect.Value) error {
+	if v.String() == "" {
+		return nil
+	}
+	uint256, ok := new(big.Int).SetString(v.String(), 10)
+	if !ok {
+		return fmt.Errorf("could not parse Uint256")
+	}
+	bigEndian := uint256.Bytes()
+	if len(bigEndian) > 32 {
+		return fmt.Errorf("number too big for Uint256")
+	}
+
+	// Integers are stored as little-endian, but
+	// big.Int gives big-endian. So we need to reverse
+	// the byte order before encoding.
+	var littleEndian [32]byte
+	for i := 0; i < len(bigEndian); i++ {
+		littleEndian[i] = bigEndian[len(bigEndian)-1-i]
+	}
+	v.SetString(base64.StdEncoding.EncodeToString(littleEndian[:]))
+	return nil
+}
+
 func enumToLowercaseProcessor(v reflect.Value) error {
 	v.SetString(strings.ToLower(v.String()))
 	return nil

api/gateway/apimiddleware/process_request.go

@@ -37,6 +37,10 @@ func ProcessRequestContainerFields(requestContainer interface{}) ErrorJson {
 			tag: "hex",
 			f:   hexToBase64Processor,
 		},
+		{
+			tag: "uint256",
+			f:   uint256ToBase64Processor,
+		},
 	}); err != nil {
 		return InternalServerErrorWithMessage(err, "could not process request data")
 	}
@@ -153,6 +157,10 @@ func ProcessMiddlewareResponseFields(responseContainer interface{}) ErrorJson {
 			tag: "time",
 			f:   timeToUnixProcessor,
 		},
+		{
+			tag: "uint256",
+			f:   base64ToUint256Processor,
+		},
 	}); err != nil {
 		return InternalServerErrorWithMessage(err, "could not process response data")
 	}

api/gateway/apimiddleware/process_request_test.go

@@ -15,30 +15,40 @@ import (
 )
 
 type testRequestContainer struct {
-	TestString    string
-	TestHexString string `hex:"true"`
+	TestString         string
+	TestHexString      string `hex:"true"`
+	TestEmptyHexString string `hex:"true"`
+	TestUint256String  string `uint256:"true"`
 }
 
 func defaultRequestContainer() *testRequestContainer {
 	return &testRequestContainer{
-		TestString:    "test string",
-		TestHexString: "0x666F6F", // hex encoding of "foo"
+		TestString:         "test string",
+		TestHexString:      "0x666F6F", // hex encoding of "foo"
+		TestEmptyHexString: "0x",
+		TestUint256String:  "4196",
 	}
 }
 
 type testResponseContainer struct {
-	TestString string
-	TestHex    string `hex:"true"`
-	TestEnum   string `enum:"true"`
-	TestTime   string `time:"true"`
+	TestString   string
+	TestHex      string `hex:"true"`
+	TestEmptyHex string `hex:"true"`
+	TestUint256  string `uint256:"true"`
+	TestEnum     string `enum:"true"`
+	TestTime     string `time:"true"`
 }
 
 func defaultResponseContainer() *testResponseContainer {
 	return &testResponseContainer{
-		TestString: "test string",
-		TestHex:    "Zm9v", // base64 encoding of "foo"
-		TestEnum:   "Test Enum",
-		TestTime:   "2006-01-02T15:04:05Z",
+		TestString:   "test string",
+		TestHex:      "Zm9v", // base64 encoding of "foo"
+		TestEmptyHex: "",
+		TestEnum:     "Test Enum",
+		TestTime:     "2006-01-02T15:04:05Z",
+
+		// base64 encoding of 4196 in little-endian
+		TestUint256: "ZBAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
 	}
 }
 
@@ -106,6 +116,8 @@ func TestProcessRequestContainerFields(t *testing.T) {
 		errJson := ProcessRequestContainerFields(container)
 		require.Equal(t, true, errJson == nil)
 		assert.Equal(t, "Zm9v", container.TestHexString)
+		assert.Equal(t, "", container.TestEmptyHexString)
+		assert.Equal(t, "ZBAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=", container.TestUint256String)
 	})
 
 	t.Run("error", func(t *testing.T) {
@@ -128,8 +140,8 @@ func TestSetRequestBodyToRequestContainer(t *testing.T) {
 	contentLengthHeader, ok := request.Header["Content-Length"]
 	require.Equal(t, true, ok)
 	require.Equal(t, 1, len(contentLengthHeader), "wrong number of header values")
-	assert.Equal(t, "55", contentLengthHeader[0])
-	assert.Equal(t, int64(55), request.ContentLength)
+	assert.Equal(t, "108", contentLengthHeader[0])
+	assert.Equal(t, int64(108), request.ContentLength)
 }
 
 func TestPrepareRequestForProxying(t *testing.T) {
@@ -234,6 +246,8 @@ func TestProcessMiddlewareResponseFields(t *testing.T) {
 		errJson := ProcessMiddlewareResponseFields(container)
 		require.Equal(t, true, errJson == nil)
 		assert.Equal(t, "0x666f6f", container.TestHex)
+		assert.Equal(t, "0x", container.TestEmptyHex)
+		assert.Equal(t, "4196", container.TestUint256)
 		assert.Equal(t, "test enum", container.TestEnum)
 		assert.Equal(t, "1136214245", container.TestTime)
 	})
@@ -278,7 +292,7 @@ func TestWriteMiddlewareResponseHeadersAndBody(t *testing.T) {
 		v, ok = writer.Header()["Content-Length"]
 		require.Equal(t, true, ok, "header not found")
 		require.Equal(t, 1, len(v), "wrong number of header values")
-		assert.Equal(t, "102", v[0])
+		assert.Equal(t, "181", v[0])
 		assert.Equal(t, 204, writer.Code)
 		assert.DeepEqual(t, responseJson, writer.Body.Bytes())
 	})

beacon-chain/rpc/apimiddleware/structs.go

@@ -434,7 +434,7 @@ type executionPayloadJson struct {
 	GasUsed       string   `json:"gas_used"`
 	TimeStamp     string   `json:"timestamp"`
 	ExtraData     string   `json:"extra_data" hex:"true"`
-	BaseFeePerGas string   `json:"base_fee_per_gas" hex:"true"`
+	BaseFeePerGas string   `json:"base_fee_per_gas" uint256:"true"`
 	BlockHash     string   `json:"block_hash" hex:"true"`
 	Transactions  []string `json:"transactions" hex:"true"`
 }