adding ssz for get block endpoint (#15390)

* adding get ssz

* adding some tests

* gaz

* adding ssz to e2e

* wip ssz

* adding in additional check on header type

* remove unused

* renaming json rest handler, and adding in usage of use ssz debug flag

* fixing unit tests

* fixing tests

* gaz

* radek feedback

* Update config/features/config.go

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

* Update config/features/flags.go

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

* Update config/features/flags.go

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

* Update validator/client/beacon-api/get_beacon_block.go

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

* Update validator/client/beacon-api/get_beacon_block.go

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

* Update validator/client/beacon-api/get_beacon_block.go

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

* addressing feedback

* missing import

* another missing import

* fixing tests

* gaz

* removing unused

* gaz

* more radek feedback

* fixing context

* adding in check for non accepted conent type

* reverting to not create more edgecases

---------

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

changelog/james-prysm_ssz-validator-block.md

@@ -0,0 +1,7 @@
+### Added
+
+- New ssz-only flag for validator client to enable calling rest apis in SSZ, starting with get block endpoint.
+
+### Changed
+
+- when REST api is enabled the get Block api defaults to requesting and receiving SSZ instead of JSON, JSON is the fallback.

config/features/config.go

@@ -52,6 +52,7 @@ type Flags struct {
 	EnableExperimentalAttestationPool   bool // EnableExperimentalAttestationPool enables an experimental attestation pool design.
 	EnableDutiesV2                      bool // EnableDutiesV2 sets validator client to use the get Duties V2 endpoint
 	EnableWeb                           bool // EnableWeb enables the webui on the validator client
+	SSZOnly                             bool // SSZOnly forces the validator client to use SSZ for communication with the beacon node when REST mode is enabled (useful for debugging)
 	// Logging related toggles.
 	DisableGRPCConnectionLogs bool // Disables logging when a new grpc client has connected.
 	EnableFullSSZDataLogging  bool // Enables logging for full ssz data on rejected gossip messages
@@ -344,6 +345,11 @@ func ConfigureValidator(ctx *cli.Context) error {
 		logEnabled(EnableWebFlag)
 		cfg.EnableWeb = true
 	}
+	if ctx.Bool(SSZOnly.Name) {
+		logEnabled(SSZOnly)
+		cfg.SSZOnly = true
+	}
+
 	cfg.KeystoreImportDebounceInterval = ctx.Duration(dynamicKeyReloadDebounceInterval.Name)
 	Init(cfg)
 	return nil

config/features/flags.go

@@ -201,6 +201,12 @@ var (
 		Usage: "(Work in progress): Enables the web portal for the validator client.",
 		Value: false,
 	}
+
+	// SSZOnly forces the validator client to use SSZ for communication with the beacon node when REST mode is enabled
+	SSZOnly = &cli.BoolFlag{
+		Name:  "ssz-only",
+		Usage: "(debug): Forces the validator client to use SSZ for communication with the beacon node when REST mode is enabled",
+	}
 )
 
 // devModeFlags holds list of flags that are set when development mode is on.
@@ -223,6 +229,7 @@ var ValidatorFlags = append(deprecatedFlags, []cli.Flag{
 	EnableBeaconRESTApi,
 	EnableDutiesV2,
 	EnableWebFlag,
+	SSZOnly,
 }...)
 
 // E2EValidatorFlags contains a list of the validator feature flags to be tested in E2E.

proto/prysm/v1alpha1/beacon_block.go

@@ -5,6 +5,12 @@ import (
 	enginev1 "github.com/OffchainLabs/prysm/v6/proto/engine/v1"
 )
 
+// GenericConverter defines any struct that can be converted to a generic beacon block.
+// We assume all your versioned block structs implement this method.
+type GenericConverter interface {
+	ToGeneric() (*GenericBeaconBlock, error)
+}
+
 // ----------------------------------------------------------------------------
 // Phase 0
 // ----------------------------------------------------------------------------

testing/endtoend/components/validator.go

@@ -248,6 +248,9 @@ func (v *ValidatorNode) Start(ctx context.Context) error {
 		args = append(args,
 			fmt.Sprintf("--%s=http://localhost:%d", flags.BeaconRESTApiProviderFlag.Name, beaconRestApiPort),
 			fmt.Sprintf("--%s", features.EnableBeaconRESTApi.Name))
+		if v.config.UseSSZOnly {
+			args = append(args, fmt.Sprintf("--%s", features.SSZOnly.Name))
+		}
 	}
 
 	// Only apply e2e flags to the current branch. New flags may not exist in previous release.

testing/endtoend/minimal_scenario_e2e_test.go

@@ -29,6 +29,10 @@ func TestEndToEnd_MinimalConfig_ValidatorRESTApi(t *testing.T) {
 	e2eMinimal(t, types.InitForkCfg(version.Bellatrix, version.Electra, params.E2ETestConfig()), types.WithCheckpointSync(), types.WithValidatorRESTApi()).run()
 }
 
+func TestEndToEnd_MinimalConfig_ValidatorRESTApi_SSZ(t *testing.T) {
+	e2eMinimal(t, types.InitForkCfg(version.Bellatrix, version.Electra, params.E2ETestConfig()), types.WithCheckpointSync(), types.WithValidatorRESTApi(), types.WithSSZOnly()).run()
+}
+
 func TestEndToEnd_ScenarioRun_EEOffline(t *testing.T) {
 	t.Skip("TODO(#10242) Prysm is current unable to handle an offline e2e")
 	cfg := types.InitForkCfg(version.Bellatrix, version.Deneb, params.E2ETestConfig())

testing/endtoend/types/types.go

@@ -51,6 +51,12 @@ func WithValidatorRESTApi() E2EConfigOpt {
 	}
 }
 
+func WithSSZOnly() E2EConfigOpt {
+	return func(cfg *E2EConfig) {
+		cfg.UseSSZOnly = true
+	}
+}
+
 func WithBuilder() E2EConfigOpt {
 	return func(cfg *E2EConfig) {
 		cfg.UseBuilder = true
@@ -70,6 +76,7 @@ type E2EConfig struct {
 	UseFixedPeerIDs         bool
 	UseValidatorCrossClient bool
 	UseBeaconRestApi        bool
+	UseSSZOnly              bool
 	UseBuilder              bool
 	EpochsToRun             uint64
 	Seed                    int64

validator/accounts/cli_manager.go

@@ -87,7 +87,7 @@ func (acm *CLIManager) prepareBeaconClients(ctx context.Context) (*iface.Validat
 		acm.beaconApiTimeout,
 	)
 
-	restHandler := beaconApi.NewBeaconApiJsonRestHandler(
+	restHandler := beaconApi.NewBeaconApiRestHandler(
 		http.Client{Timeout: acm.beaconApiTimeout},
 		acm.beaconApiEndpoint,
 	)

validator/client/beacon-api/BUILD.bazel

@@ -18,7 +18,6 @@ go_library(
         "genesis.go",
         "get_beacon_block.go",
         "index.go",
-        "json_rest_handler.go",
         "log.go",
         "metrics.go",
         "prepare_beacon_proposer.go",
@@ -27,6 +26,7 @@ go_library(
         "propose_exit.go",
         "prysm_beacon_chain_client.go",
         "registration.go",
+        "rest_handler_client.go",
         "state_validators.go",
         "status.go",
         "stream_blocks.go",
@@ -47,6 +47,7 @@ go_library(
         "//api/server/structs:go_default_library",
         "//beacon-chain/core/helpers:go_default_library",
         "//beacon-chain/core/signing:go_default_library",
+        "//config/features:go_default_library",
         "//config/fieldparams:go_default_library",
         "//config/params:go_default_library",
         "//consensus-types/primitives:go_default_library",
@@ -91,7 +92,6 @@ go_test(
         "genesis_test.go",
         "get_beacon_block_test.go",
         "index_test.go",
-        "json_rest_handler_test.go",
         "prepare_beacon_proposer_test.go",
         "propose_attestation_test.go",
         "propose_beacon_block_altair_test.go",
@@ -110,6 +110,7 @@ go_test(
         "propose_exit_test.go",
         "prysm_beacon_chain_client_test.go",
         "registration_test.go",
+        "rest_handler_client_test.go",
         "state_validators_test.go",
         "status_test.go",
         "stream_blocks_test.go",
@@ -128,6 +129,7 @@ go_test(
         "//api/server/structs:go_default_library",
         "//beacon-chain/core/helpers:go_default_library",
         "//beacon-chain/rpc/eth/shared/testing:go_default_library",
+        "//config/features:go_default_library",
         "//config/params:go_default_library",
         "//consensus-types/primitives:go_default_library",
         "//consensus-types/validator:go_default_library",
@@ -145,6 +147,8 @@ go_test(
         "@com_github_ethereum_go_ethereum//common/hexutil:go_default_library",
         "@com_github_golang_protobuf//ptypes/empty",
         "@com_github_pkg_errors//:go_default_library",
+        "@com_github_sirupsen_logrus//:go_default_library",
+        "@com_github_sirupsen_logrus//hooks/test:go_default_library",
         "@org_golang_google_protobuf//types/known/emptypb:go_default_library",
         "@org_golang_google_protobuf//types/known/timestamppb:go_default_library",
         "@org_uber_go_mock//gomock:go_default_library",

validator/client/beacon-api/beacon_api_beacon_chain_client.go

@@ -17,7 +17,7 @@ import (
 
 type beaconApiChainClient struct {
 	fallbackClient          iface.ChainClient
-	jsonRestHandler         JsonRestHandler
+	jsonRestHandler         RestHandler
 	stateValidatorsProvider StateValidatorsProvider
 }
 
@@ -333,7 +333,7 @@ func (c beaconApiChainClient) ValidatorParticipation(ctx context.Context, in *et
 	return nil, errors.New("beaconApiChainClient.ValidatorParticipation is not implemented. To use a fallback client, pass a fallback client as the last argument of NewBeaconApiChainClientWithFallback.")
 }
 
-func NewBeaconApiChainClientWithFallback(jsonRestHandler JsonRestHandler, fallbackClient iface.ChainClient) iface.ChainClient {
+func NewBeaconApiChainClientWithFallback(jsonRestHandler RestHandler, fallbackClient iface.ChainClient) iface.ChainClient {
 	return &beaconApiChainClient{
 		jsonRestHandler:         jsonRestHandler,
 		fallbackClient:          fallbackClient,

validator/client/beacon-api/beacon_api_node_client.go

@@ -20,7 +20,7 @@ var (
 
 type beaconApiNodeClient struct {
 	fallbackClient  iface.NodeClient
-	jsonRestHandler JsonRestHandler
+	jsonRestHandler RestHandler
 	genesisProvider GenesisProvider
 	healthTracker   health.Tracker
 }
@@ -111,7 +111,7 @@ func (c *beaconApiNodeClient) HealthTracker() health.Tracker {
 	return c.healthTracker
 }
 
-func NewNodeClientWithFallback(jsonRestHandler JsonRestHandler, fallbackClient iface.NodeClient) iface.NodeClient {
+func NewNodeClientWithFallback(jsonRestHandler RestHandler, fallbackClient iface.NodeClient) iface.NodeClient {
 	b := &beaconApiNodeClient{
 		jsonRestHandler: jsonRestHandler,
 		fallbackClient:  fallbackClient,

validator/client/beacon-api/beacon_api_validator_client.go

@@ -22,13 +22,13 @@ type beaconApiValidatorClient struct {
 	genesisProvider         GenesisProvider
 	dutiesProvider          dutiesProvider
 	stateValidatorsProvider StateValidatorsProvider
-	jsonRestHandler         JsonRestHandler
+	jsonRestHandler         RestHandler
 	beaconBlockConverter    BeaconBlockConverter
 	prysmChainClient        iface.PrysmChainClient
 	isEventStreamRunning    bool
 }
 
-func NewBeaconApiValidatorClient(jsonRestHandler JsonRestHandler, opts ...ValidatorClientOpt) iface.ValidatorClient {
+func NewBeaconApiValidatorClient(jsonRestHandler RestHandler, opts ...ValidatorClientOpt) iface.ValidatorClient {
 	c := &beaconApiValidatorClient{
 		genesisProvider:         &beaconApiGenesisProvider{jsonRestHandler: jsonRestHandler},
 		dutiesProvider:          beaconApiDutiesProvider{jsonRestHandler: jsonRestHandler},

validator/client/beacon-api/duties.go

@@ -27,7 +27,7 @@ type dutiesProvider interface {
 }
 
 type beaconApiDutiesProvider struct {
-	jsonRestHandler JsonRestHandler
+	jsonRestHandler RestHandler
 }
 
 type attesterDuty struct {

validator/client/beacon-api/genesis.go

@@ -20,7 +20,7 @@ type GenesisProvider interface {
 }
 
 type beaconApiGenesisProvider struct {
-	jsonRestHandler JsonRestHandler
+	jsonRestHandler RestHandler
 	genesis         *structs.Genesis
 	once            sync.Once
 }

validator/client/beacon-api/get_beacon_block.go

@@ -6,7 +6,10 @@ import (
 	"encoding/json"
 	"fmt"
 	neturl "net/url"
+	"strconv"
+	"strings"
 
+	"github.com/OffchainLabs/prysm/v6/api"
 	"github.com/OffchainLabs/prysm/v6/api/apiutil"
 	"github.com/OffchainLabs/prysm/v6/api/server/structs"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/primitives"
@@ -22,160 +25,224 @@ func (c *beaconApiValidatorClient) beaconBlock(ctx context.Context, slot primiti
 	if len(graffiti) > 0 {
 		queryParams.Add("graffiti", hexutil.Encode(graffiti))
 	}
-
 	queryUrl := apiutil.BuildURL(fmt.Sprintf("/eth/v3/validator/blocks/%d", slot), queryParams)
-	produceBlockV3ResponseJson := structs.ProduceBlockV3Response{}
+	data, header, err := c.jsonRestHandler.GetSSZ(ctx, queryUrl)
-	err := c.jsonRestHandler.Get(ctx, queryUrl, &produceBlockV3ResponseJson)
 	if err != nil {
 		return nil, err
 	}
-
+	if strings.Contains(header.Get("Content-Type"), api.OctetStreamMediaType) {
-	return processBlockResponse(
+		ver, err := version.FromString(header.Get(api.VersionHeader))
-		produceBlockV3ResponseJson.Version,
+		if err != nil {
-		produceBlockV3ResponseJson.ExecutionPayloadBlinded,
+			return nil, errors.Wrap(err, fmt.Sprintf("unsupported header version %s", header.Get(api.VersionHeader)))
-		json.NewDecoder(bytes.NewReader(produceBlockV3ResponseJson.Data)),
+		}
-	)
+		isBlindedRaw := header.Get(api.ExecutionPayloadBlindedHeader)
+		isBlinded, err := strconv.ParseBool(isBlindedRaw)
+		if err != nil {
+			return nil, err
+		}
+		return processBlockSSZResponse(ver, data, isBlinded)
+	} else {
+		decoder := json.NewDecoder(bytes.NewBuffer(data))
+		produceBlockV3ResponseJson := structs.ProduceBlockV3Response{}
+		if err = decoder.Decode(&produceBlockV3ResponseJson); err != nil {
+			return nil, errors.Wrapf(err, "failed to decode response body into json for %s", queryUrl)
+		}
+		return processBlockJSONResponse(
+			produceBlockV3ResponseJson.Version,
+			produceBlockV3ResponseJson.ExecutionPayloadBlinded,
+			json.NewDecoder(bytes.NewReader(produceBlockV3ResponseJson.Data)),
+		)
+	}
 }
 
-// nolint: gocognit
+func processBlockSSZResponse(ver int, data []byte, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
-func processBlockResponse(ver string, isBlinded bool, decoder *json.Decoder) (*ethpb.GenericBeaconBlock, error) {
+	if ver >= version.Fulu {
-	var response *ethpb.GenericBeaconBlock
+		return processBlockSSZResponseFulu(data, isBlinded)
+	}
+	if ver >= version.Electra {
+		return processBlockSSZResponseElectra(data, isBlinded)
+	}
+	if ver >= version.Deneb {
+		return processBlockSSZResponseDeneb(data, isBlinded)
+	}
+	if ver >= version.Capella {
+		return processBlockSSZResponseCapella(data, isBlinded)
+	}
+	if ver >= version.Bellatrix {
+		return processBlockSSZResponseBellatrix(data, isBlinded)
+	}
+	if ver >= version.Altair {
+		block := &ethpb.BeaconBlockAltair{}
+		if err := block.UnmarshalSSZ(data); err != nil {
+			return nil, err
+		}
+		return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_Altair{Altair: block}}, nil
+	}
+	if ver >= version.Phase0 {
+		block := &ethpb.BeaconBlock{}
+		if err := block.UnmarshalSSZ(data); err != nil {
+			return nil, err
+		}
+		return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_Phase0{Phase0: block}}, nil
+	}
+	return nil, fmt.Errorf("unsupported block version %s", version.String(ver))
+}
+
+func processBlockSSZResponseFulu(data []byte, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		blindedBlock := &ethpb.BlindedBeaconBlockFulu{}
+		if err := blindedBlock.UnmarshalSSZ(data); err != nil {
+			return nil, err
+		}
+		return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_BlindedFulu{BlindedFulu: blindedBlock}, IsBlinded: true}, nil
+	}
+	block := &ethpb.BeaconBlockContentsFulu{}
+	if err := block.UnmarshalSSZ(data); err != nil {
+		return nil, err
+	}
+	return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_Fulu{Fulu: block}}, nil
+}
+
+func processBlockSSZResponseElectra(data []byte, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		blindedBlock := &ethpb.BlindedBeaconBlockElectra{}
+		if err := blindedBlock.UnmarshalSSZ(data); err != nil {
+			return nil, err
+		}
+		return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_BlindedElectra{BlindedElectra: blindedBlock}, IsBlinded: true}, nil
+	}
+	block := &ethpb.BeaconBlockContentsElectra{}
+	if err := block.UnmarshalSSZ(data); err != nil {
+		return nil, err
+	}
+	return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_Electra{Electra: block}}, nil
+}
+
+func processBlockSSZResponseDeneb(data []byte, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		blindedBlock := &ethpb.BlindedBeaconBlockDeneb{}
+		if err := blindedBlock.UnmarshalSSZ(data); err != nil {
+			return nil, err
+		}
+		return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_BlindedDeneb{BlindedDeneb: blindedBlock}, IsBlinded: true}, nil
+	}
+	block := &ethpb.BeaconBlockContentsDeneb{}
+	if err := block.UnmarshalSSZ(data); err != nil {
+		return nil, err
+	}
+	return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_Deneb{Deneb: block}}, nil
+}
+
+func processBlockSSZResponseCapella(data []byte, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		blindedBlock := &ethpb.BlindedBeaconBlockCapella{}
+		if err := blindedBlock.UnmarshalSSZ(data); err != nil {
+			return nil, err
+		}
+		return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_BlindedCapella{BlindedCapella: blindedBlock}, IsBlinded: true}, nil
+	}
+	block := &ethpb.BeaconBlockCapella{}
+	if err := block.UnmarshalSSZ(data); err != nil {
+		return nil, err
+	}
+	return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_Capella{Capella: block}}, nil
+}
+
+func processBlockSSZResponseBellatrix(data []byte, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		blindedBlock := &ethpb.BlindedBeaconBlockBellatrix{}
+		if err := blindedBlock.UnmarshalSSZ(data); err != nil {
+			return nil, err
+		}
+		return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_BlindedBellatrix{BlindedBellatrix: blindedBlock}, IsBlinded: true}, nil
+	}
+	block := &ethpb.BeaconBlockBellatrix{}
+	if err := block.UnmarshalSSZ(data); err != nil {
+		return nil, err
+	}
+	return &ethpb.GenericBeaconBlock{Block: &ethpb.GenericBeaconBlock_Bellatrix{Bellatrix: block}}, nil
+}
+
+func convertBlockToGeneric(decoder *json.Decoder, dest ethpb.GenericConverter, version string, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	typeName := version
+	if isBlinded {
+		typeName = "blinded " + typeName
+	}
+
+	if err := decoder.Decode(dest); err != nil {
+		return nil, errors.Wrapf(err, "failed to decode %s block response json", typeName)
+	}
+
+	genericBlock, err := dest.ToGeneric()
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to convert %s block", typeName)
+	}
+	return genericBlock, nil
+}
+
+func processBlockJSONResponse(ver string, isBlinded bool, decoder *json.Decoder) (*ethpb.GenericBeaconBlock, error) {
 	if decoder == nil {
 		return nil, errors.New("no produce block json decoder found")
 	}
+
 	switch ver {
 	case version.String(version.Phase0):
-		jsonPhase0Block := structs.BeaconBlock{}
+		return convertBlockToGeneric(decoder, &structs.BeaconBlock{}, version.String(version.Phase0), false)
-		if err := decoder.Decode(&jsonPhase0Block); err != nil {
+
-			return nil, errors.Wrap(err, "failed to decode phase0 block response json")
-		}
-		genericBlock, err := jsonPhase0Block.ToGeneric()
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to get phase0 block")
-		}
-		response = genericBlock
 	case version.String(version.Altair):
-		jsonAltairBlock := structs.BeaconBlockAltair{}
+		return convertBlockToGeneric(decoder, &structs.BeaconBlockAltair{}, "altair", false)
-		if err := decoder.Decode(&jsonAltairBlock); err != nil {
+
-			return nil, errors.Wrap(err, "failed to decode altair block response json")
-		}
-		genericBlock, err := jsonAltairBlock.ToGeneric()
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to get altair block")
-		}
-		response = genericBlock
 	case version.String(version.Bellatrix):
-		if isBlinded {
+		return processBellatrixBlock(decoder, isBlinded)
-			jsonBellatrixBlock := structs.BlindedBeaconBlockBellatrix{}
+
-			if err := decoder.Decode(&jsonBellatrixBlock); err != nil {
-				return nil, errors.Wrap(err, "failed to decode blinded bellatrix block response json")
-			}
-			genericBlock, err := jsonBellatrixBlock.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get blinded bellatrix block")
-			}
-			response = genericBlock
-		} else {
-			jsonBellatrixBlock := structs.BeaconBlockBellatrix{}
-			if err := decoder.Decode(&jsonBellatrixBlock); err != nil {
-				return nil, errors.Wrap(err, "failed to decode bellatrix block response json")
-			}
-			genericBlock, err := jsonBellatrixBlock.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get bellatrix block")
-			}
-			response = genericBlock
-		}
 	case version.String(version.Capella):
-		if isBlinded {
+		return processCapellaBlock(decoder, isBlinded)
-			jsonCapellaBlock := structs.BlindedBeaconBlockCapella{}
+
-			if err := decoder.Decode(&jsonCapellaBlock); err != nil {
-				return nil, errors.Wrap(err, "failed to decode blinded capella block response json")
-			}
-			genericBlock, err := jsonCapellaBlock.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get blinded capella block")
-			}
-			response = genericBlock
-		} else {
-			jsonCapellaBlock := structs.BeaconBlockCapella{}
-			if err := decoder.Decode(&jsonCapellaBlock); err != nil {
-				return nil, errors.Wrap(err, "failed to decode capella block response json")
-			}
-			genericBlock, err := jsonCapellaBlock.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get capella block")
-			}
-			response = genericBlock
-		}
 	case version.String(version.Deneb):
-		if isBlinded {
+		return processDenebBlock(decoder, isBlinded)
-			jsonDenebBlock := structs.BlindedBeaconBlockDeneb{}
+
-			if err := decoder.Decode(&jsonDenebBlock); err != nil {
-				return nil, errors.Wrap(err, "failed to decode blinded deneb block response json")
-			}
-			genericBlock, err := jsonDenebBlock.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get blinded deneb block")
-			}
-			response = genericBlock
-		} else {
-			jsonDenebBlockContents := structs.BeaconBlockContentsDeneb{}
-			if err := decoder.Decode(&jsonDenebBlockContents); err != nil {
-				return nil, errors.Wrap(err, "failed to decode deneb block response json")
-			}
-			genericBlock, err := jsonDenebBlockContents.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get deneb block")
-			}
-			response = genericBlock
-		}
 	case version.String(version.Electra):
-		if isBlinded {
+		return processElectraBlock(decoder, isBlinded)
-			jsonElectraBlock := structs.BlindedBeaconBlockElectra{}
+
-			if err := decoder.Decode(&jsonElectraBlock); err != nil {
-				return nil, errors.Wrap(err, "failed to decode blinded electra block response json")
-			}
-			genericBlock, err := jsonElectraBlock.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get blinded electra block")
-			}
-			response = genericBlock
-		} else {
-			jsonElectraBlockContents := structs.BeaconBlockContentsElectra{}
-			if err := decoder.Decode(&jsonElectraBlockContents); err != nil {
-				return nil, errors.Wrap(err, "failed to decode electra block response json")
-			}
-			genericBlock, err := jsonElectraBlockContents.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get electra block")
-			}
-			response = genericBlock
-		}
 	case version.String(version.Fulu):
-		if isBlinded {
+		return processFuluBlock(decoder, isBlinded)
-			jsonFuluBlock := structs.BlindedBeaconBlockFulu{}
+
-			if err := decoder.Decode(&jsonFuluBlock); err != nil {
-				return nil, errors.Wrap(err, "failed to decode blinded fulu block response json")
-			}
-			genericBlock, err := jsonFuluBlock.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get blinded fulu block")
-			}
-			response = genericBlock
-		} else {
-			jsonFuluBlockContents := structs.BeaconBlockContentsFulu{}
-			if err := decoder.Decode(&jsonFuluBlockContents); err != nil {
-				return nil, errors.Wrap(err, "failed to decode fulu block response json")
-			}
-			genericBlock, err := jsonFuluBlockContents.ToGeneric()
-			if err != nil {
-				return nil, errors.Wrap(err, "failed to get fulu block")
-			}
-			response = genericBlock
-		}
 	default:
 		return nil, errors.Errorf("unsupported consensus version `%s`", ver)
 	}
-	return response, nil
+}
+
+func processBellatrixBlock(decoder *json.Decoder, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		return convertBlockToGeneric(decoder, &structs.BlindedBeaconBlockBellatrix{}, "bellatrix", true)
+	}
+	return convertBlockToGeneric(decoder, &structs.BeaconBlockBellatrix{}, "bellatrix", false)
+}
+
+func processCapellaBlock(decoder *json.Decoder, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		return convertBlockToGeneric(decoder, &structs.BlindedBeaconBlockCapella{}, "capella", true)
+	}
+	return convertBlockToGeneric(decoder, &structs.BeaconBlockCapella{}, "capella", false)
+}
+
+func processDenebBlock(decoder *json.Decoder, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		return convertBlockToGeneric(decoder, &structs.BlindedBeaconBlockDeneb{}, "deneb", true)
+	}
+	return convertBlockToGeneric(decoder, &structs.BeaconBlockContentsDeneb{}, "deneb", false)
+}
+
+func processElectraBlock(decoder *json.Decoder, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		return convertBlockToGeneric(decoder, &structs.BlindedBeaconBlockElectra{}, "electra", true)
+	}
+	return convertBlockToGeneric(decoder, &structs.BeaconBlockContentsElectra{}, "electra", false)
+}
+
+func processFuluBlock(decoder *json.Decoder, isBlinded bool) (*ethpb.GenericBeaconBlock, error) {
+	if isBlinded {
+		return convertBlockToGeneric(decoder, &structs.BlindedBeaconBlockFulu{}, "fulu", true)
+	}
+	return convertBlockToGeneric(decoder, &structs.BeaconBlockContentsFulu{}, "fulu", false)
 }

validator/client/beacon-api/mock/json_rest_handler_mock.go

@@ -56,6 +56,23 @@ func (mr *MockJsonRestHandlerMockRecorder) Get(ctx, endpoint, resp any) *gomock.
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Get", reflect.TypeOf((*MockJsonRestHandler)(nil).Get), ctx, endpoint, resp)
 }
 
+
+// GetSSZ mocks base method.
+func (m *MockJsonRestHandler) GetSSZ(ctx context.Context, endpoint string) ([]byte, http.Header, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "GetSSZ", ctx, endpoint)
+	ret0, _ := ret[0].([]byte)
+	ret1, _ := ret[1].(http.Header)
+	ret2, _ := ret[2].(error)
+	return ret0, ret1, ret2
+}
+
+// GetSSZ indicates an expected call of GetSSZ.
+func (mr *MockJsonRestHandlerMockRecorder) GetSSZ(ctx, endpoint any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetSSZ", reflect.TypeOf((*MockJsonRestHandler)(nil).GetSSZ), ctx, endpoint)
+}
+
 // Host mocks base method.
 func (m *MockJsonRestHandler) Host() string {
 	m.ctrl.T.Helper()

validator/client/beacon-api/prysm_beacon_chain_client.go

@@ -18,7 +18,7 @@ import (
 )
 
 // NewPrysmChainClient returns implementation of iface.PrysmChainClient.
-func NewPrysmChainClient(jsonRestHandler JsonRestHandler, nodeClient iface.NodeClient) iface.PrysmChainClient {
+func NewPrysmChainClient(jsonRestHandler RestHandler, nodeClient iface.NodeClient) iface.PrysmChainClient {
 	return prysmChainClient{
 		jsonRestHandler: jsonRestHandler,
 		nodeClient:      nodeClient,
@@ -26,7 +26,7 @@ func NewPrysmChainClient(jsonRestHandler JsonRestHandler, nodeClient iface.NodeC
 }
 
 type prysmChainClient struct {
-	jsonRestHandler JsonRestHandler
+	jsonRestHandler RestHandler
 	nodeClient      iface.NodeClient
 }
 

validator/client/beacon-api/rest_handler_client.go

@@ -4,49 +4,53 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"fmt"
 	"io"
 	"net/http"
 	"strings"
 
 	"github.com/OffchainLabs/prysm/v6/api"
+	"github.com/OffchainLabs/prysm/v6/config/features"
 	"github.com/OffchainLabs/prysm/v6/network/httputil"
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 )
 
-type JsonRestHandler interface {
+type RestHandler interface {
 	Get(ctx context.Context, endpoint string, resp interface{}) error
+	GetSSZ(ctx context.Context, endpoint string) ([]byte, http.Header, error)
 	Post(ctx context.Context, endpoint string, headers map[string]string, data *bytes.Buffer, resp interface{}) error
 	HttpClient() *http.Client
 	Host() string
 	SetHost(host string)
 }
 
-type BeaconApiJsonRestHandler struct {
+type BeaconApiRestHandler struct {
 	client http.Client
 	host   string
 }
 
-// NewBeaconApiJsonRestHandler returns a JsonRestHandler
+// NewBeaconApiRestHandler returns a RestHandler
-func NewBeaconApiJsonRestHandler(client http.Client, host string) JsonRestHandler {
+func NewBeaconApiRestHandler(client http.Client, host string) RestHandler {
-	return &BeaconApiJsonRestHandler{
+	return &BeaconApiRestHandler{
 		client: client,
 		host:   host,
 	}
 }
 
 // HttpClient returns the underlying HTTP client of the handler
-func (c *BeaconApiJsonRestHandler) HttpClient() *http.Client {
+func (c *BeaconApiRestHandler) HttpClient() *http.Client {
 	return &c.client
 }
 
 // Host returns the underlying HTTP host
-func (c *BeaconApiJsonRestHandler) Host() string {
+func (c *BeaconApiRestHandler) Host() string {
 	return c.host
 }
 
 // Get sends a GET request and decodes the response body as a JSON object into the passed in object.
 // If an HTTP error is returned, the body is decoded as a DefaultJsonError JSON object and returned as the first return value.
-func (c *BeaconApiJsonRestHandler) Get(ctx context.Context, endpoint string, resp interface{}) error {
+func (c *BeaconApiRestHandler) Get(ctx context.Context, endpoint string, resp interface{}) error {
 	url := c.host + endpoint
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
 	if err != nil {
@@ -66,9 +70,61 @@ func (c *BeaconApiJsonRestHandler) Get(ctx context.Context, endpoint string, res
 	return decodeResp(httpResp, resp)
 }
 
+func (c *BeaconApiRestHandler) GetSSZ(ctx context.Context, endpoint string) ([]byte, http.Header, error) {
+	url := c.host + endpoint
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, nil, errors.Wrapf(err, "failed to create request for endpoint %s", url)
+	}
+	primaryAcceptType := fmt.Sprintf("%s;q=%s", api.OctetStreamMediaType, "0.95")
+	secondaryAcceptType := fmt.Sprintf("%s;q=%s", api.JsonMediaType, "0.9")
+	acceptHeaderString := fmt.Sprintf("%s,%s", primaryAcceptType, secondaryAcceptType)
+	if features.Get().SSZOnly {
+		acceptHeaderString = api.OctetStreamMediaType
+	}
+	req.Header.Set("Accept", acceptHeaderString)
+	httpResp, err := c.client.Do(req)
+	if err != nil {
+		return nil, nil, errors.Wrapf(err, "failed to perform request for endpoint %s", url)
+	}
+	defer func() {
+		if err := httpResp.Body.Close(); err != nil {
+			return
+		}
+	}()
+	contentType := httpResp.Header.Get("Content-Type")
+	body, err := io.ReadAll(httpResp.Body)
+	if err != nil {
+		return nil, nil, errors.Wrapf(err, "failed to read response body for %s", httpResp.Request.URL)
+	}
+	if !strings.Contains(primaryAcceptType, contentType) {
+		log.WithFields(logrus.Fields{
+			"primaryAcceptType":   primaryAcceptType,
+			"secondaryAcceptType": secondaryAcceptType,
+			"receivedAcceptType":  contentType,
+		}).Debug("Server responded with non primary accept type")
+	}
+
+	// non-2XX codes are a failure
+	if !strings.HasPrefix(httpResp.Status, "2") {
+		decoder := json.NewDecoder(bytes.NewBuffer(body))
+		errorJson := &httputil.DefaultJsonError{}
+		if err = decoder.Decode(errorJson); err != nil {
+			return nil, nil, errors.Wrapf(err, "failed to decode response body into error json for %s", httpResp.Request.URL)
+		}
+		return nil, nil, errorJson
+	}
+
+	if features.Get().SSZOnly && contentType != api.OctetStreamMediaType {
+		return nil, nil, errors.Errorf("server responded with non primary accept type %s", contentType)
+	}
+
+	return body, httpResp.Header, nil
+}
+
 // Post sends a POST request and decodes the response body as a JSON object into the passed in object.
 // If an HTTP error is returned, the body is decoded as a DefaultJsonError JSON object and returned as the first return value.
-func (c *BeaconApiJsonRestHandler) Post(
+func (c *BeaconApiRestHandler) Post(
 	ctx context.Context,
 	apiEndpoint string,
 	headers map[string]string,
@@ -136,6 +192,6 @@ func decodeResp(httpResp *http.Response, resp interface{}) error {
 	return nil
 }
 
-func (c *BeaconApiJsonRestHandler) SetHost(host string) {
+func (c *BeaconApiRestHandler) SetHost(host string) {
 	c.host = host
 }

validator/client/beacon-api/rest_handler_client_test.go

@@ -2,6 +2,7 @@ package beacon_api
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"io"
 	"net/http"
@@ -15,6 +16,8 @@ import (
 	"github.com/OffchainLabs/prysm/v6/testing/assert"
 	"github.com/OffchainLabs/prysm/v6/testing/require"
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"github.com/sirupsen/logrus/hooks/test"
 )
 
 func TestGet(t *testing.T) {
@@ -39,7 +42,7 @@ func TestGet(t *testing.T) {
 	server := httptest.NewServer(mux)
 	defer server.Close()
 
-	jsonRestHandler := BeaconApiJsonRestHandler{
+	jsonRestHandler := BeaconApiRestHandler{
 		client: http.Client{Timeout: time.Second * 5},
 		host:   server.URL,
 	}
@@ -48,6 +51,98 @@ func TestGet(t *testing.T) {
 	assert.DeepEqual(t, genesisJson, resp)
 }
 
+func TestGetSSZ(t *testing.T) {
+	ctx := context.Background()
+	const endpoint = "/example/rest/api/ssz"
+	genesisJson := &structs.GetGenesisResponse{
+		Data: &structs.Genesis{
+			GenesisTime:           "123",
+			GenesisValidatorsRoot: "0x456",
+			GenesisForkVersion:    "0x789",
+		},
+	}
+
+	t.Run("Successful SSZ response", func(t *testing.T) {
+		expectedBody := []byte{10, 20, 30, 40}
+
+		mux := http.NewServeMux()
+		mux.HandleFunc(endpoint, func(w http.ResponseWriter, r *http.Request) {
+			assert.StringContains(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+			w.Header().Set("Content-Type", api.OctetStreamMediaType)
+			_, err := w.Write(expectedBody)
+			require.NoError(t, err)
+		})
+		server := httptest.NewServer(mux)
+		defer server.Close()
+
+		jsonRestHandler := BeaconApiRestHandler{
+			client: http.Client{Timeout: time.Second * 5},
+			host:   server.URL,
+		}
+
+		body, header, err := jsonRestHandler.GetSSZ(ctx, endpoint)
+		require.NoError(t, err)
+		assert.DeepEqual(t, expectedBody, body)
+		require.StringContains(t, api.OctetStreamMediaType, header.Get("Content-Type"))
+	})
+
+	t.Run("Json Content-Type response", func(t *testing.T) {
+		logrus.SetLevel(logrus.DebugLevel)
+		defer logrus.SetLevel(logrus.InfoLevel) // reset it afterwards
+		logHook := test.NewGlobal()
+		mux := http.NewServeMux()
+		mux.HandleFunc(endpoint, func(w http.ResponseWriter, r *http.Request) {
+			assert.StringContains(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+			w.Header().Set("Content-Type", api.JsonMediaType)
+
+			marshalledJson, err := json.Marshal(genesisJson)
+			require.NoError(t, err)
+
+			_, err = w.Write(marshalledJson)
+			require.NoError(t, err)
+		})
+		server := httptest.NewServer(mux)
+		defer server.Close()
+
+		jsonRestHandler := BeaconApiRestHandler{
+			client: http.Client{Timeout: time.Second * 5},
+			host:   server.URL,
+		}
+
+		body, header, err := jsonRestHandler.GetSSZ(ctx, endpoint)
+		require.NoError(t, err)
+		assert.LogsContain(t, logHook, "Server responded with non primary accept type")
+		require.Equal(t, api.JsonMediaType, header.Get("Content-Type"))
+		resp := &structs.GetGenesisResponse{}
+		require.NoError(t, json.Unmarshal(body, resp))
+		require.Equal(t, "123", resp.Data.GenesisTime)
+	})
+
+	t.Run("Wrong Content-Type response, doesn't error out and instead handled downstream", func(t *testing.T) {
+		logrus.SetLevel(logrus.DebugLevel)
+		defer logrus.SetLevel(logrus.InfoLevel) // reset it afterwards
+		logHook := test.NewGlobal()
+		mux := http.NewServeMux()
+		mux.HandleFunc(endpoint, func(w http.ResponseWriter, r *http.Request) {
+			assert.StringContains(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+			w.Header().Set("Content-Type", "text/plain") // Invalid content type
+			_, err := w.Write([]byte("some text"))
+			require.NoError(t, err)
+		})
+		server := httptest.NewServer(mux)
+		defer server.Close()
+
+		jsonRestHandler := BeaconApiRestHandler{
+			client: http.Client{Timeout: time.Second * 5},
+			host:   server.URL,
+		}
+
+		_, _, err := jsonRestHandler.GetSSZ(ctx, endpoint)
+		require.NoError(t, err)
+		assert.LogsContain(t, logHook, "Server responded with non primary accept type")
+	})
+}
+
 func TestPost(t *testing.T) {
 	ctx := t.Context()
 	const endpoint = "/example/rest/api/endpoint"
@@ -85,7 +180,7 @@ func TestPost(t *testing.T) {
 	server := httptest.NewServer(mux)
 	defer server.Close()
 
-	jsonRestHandler := BeaconApiJsonRestHandler{
+	jsonRestHandler := BeaconApiRestHandler{
 		client: http.Client{Timeout: time.Second * 5},
 		host:   server.URL,
 	}

validator/client/beacon-api/state_validators.go

@@ -21,7 +21,7 @@ type StateValidatorsProvider interface {
 }
 
 type beaconApiStateValidatorsProvider struct {
-	jsonRestHandler JsonRestHandler
+	jsonRestHandler RestHandler
 }
 
 func (c beaconApiStateValidatorsProvider) StateValidators(

validator/client/beacon-chain-client-factory/beacon_chain_client_factory.go

@@ -9,7 +9,7 @@ import (
 	validatorHelpers "github.com/OffchainLabs/prysm/v6/validator/helpers"
 )
 
-func NewChainClient(validatorConn validatorHelpers.NodeConnection, jsonRestHandler beaconApi.JsonRestHandler) iface.ChainClient {
+func NewChainClient(validatorConn validatorHelpers.NodeConnection, jsonRestHandler beaconApi.RestHandler) iface.ChainClient {
 	grpcClient := grpcApi.NewGrpcChainClient(validatorConn.GetGrpcClientConn())
 	if features.Get().EnableBeaconRESTApi {
 		return beaconApi.NewBeaconApiChainClientWithFallback(jsonRestHandler, grpcClient)
@@ -18,7 +18,7 @@ func NewChainClient(validatorConn validatorHelpers.NodeConnection, jsonRestHandl
 	}
 }
 
-func NewPrysmChainClient(validatorConn validatorHelpers.NodeConnection, jsonRestHandler beaconApi.JsonRestHandler) iface.PrysmChainClient {
+func NewPrysmChainClient(validatorConn validatorHelpers.NodeConnection, jsonRestHandler beaconApi.RestHandler) iface.PrysmChainClient {
 	if features.Get().EnableBeaconRESTApi {
 		return beaconApi.NewPrysmChainClient(jsonRestHandler, nodeClientFactory.NewNodeClient(validatorConn, jsonRestHandler))
 	} else {

validator/client/node-client-factory/node_client_factory.go

@@ -8,7 +8,7 @@ import (
 	validatorHelpers "github.com/OffchainLabs/prysm/v6/validator/helpers"
 )
 
-func NewNodeClient(validatorConn validatorHelpers.NodeConnection, jsonRestHandler beaconApi.JsonRestHandler) iface.NodeClient {
+func NewNodeClient(validatorConn validatorHelpers.NodeConnection, jsonRestHandler beaconApi.RestHandler) iface.NodeClient {
 	grpcClient := grpcApi.NewNodeClient(validatorConn.GetGrpcClientConn())
 	if features.Get().EnableBeaconRESTApi {
 		return beaconApi.NewNodeClientWithFallback(jsonRestHandler, grpcClient)

validator/client/service.go

@@ -179,7 +179,7 @@ func (v *ValidatorService) Start() {
 		return
 	}
 
-	restHandler := beaconApi.NewBeaconApiJsonRestHandler(
+	restHandler := beaconApi.NewBeaconApiRestHandler(
 		http.Client{Timeout: v.conn.GetBeaconApiTimeout(), Transport: otelhttp.NewTransport(http.DefaultTransport)},
 		hosts[0],
 	)

validator/client/validator-client-factory/validator_client_factory.go

@@ -10,7 +10,7 @@ import (
 
 func NewValidatorClient(
 	validatorConn validatorHelpers.NodeConnection,
-	jsonRestHandler beaconApi.JsonRestHandler,
+	jsonRestHandler beaconApi.RestHandler,
 	opt ...beaconApi.ValidatorClientOpt,
 ) iface.ValidatorClient {
 	if features.Get().EnableBeaconRESTApi {

validator/rpc/beacon.go

@@ -55,7 +55,7 @@ func (s *Server) registerBeaconClient() error {
 		s.beaconApiTimeout,
 	)
 
-	restHandler := beaconApi.NewBeaconApiJsonRestHandler(
+	restHandler := beaconApi.NewBeaconApiRestHandler(
 		http.Client{Timeout: s.beaconApiTimeout, Transport: otelhttp.NewTransport(http.DefaultTransport)},
 		s.beaconApiEndpoint,
 	)