feat(lib/parachain): introduced parachain candidate validation (#3249)

This commit adds all the functions required for parachain candidate validations.

With this commit, we are able to take candidate receipts and
- get validation data for it,
- perform basic checks on it,
- run respective parachain's validate_block on parachain's runtime,
- get validate results from parachain's runtime and verify those validation results again relaychain runtime,
- and declare candidate as valid or invalid in the end.

This commit also includes tests for candidate validation.

lib/parachain/available_data_fetching.go

@@ -1,3 +1,6 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
 package parachain
 
 import (

lib/parachain/available_data_fetching_test.go

@@ -1,3 +1,6 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
 package parachain
 
 import (

lib/parachain/candidate_validation.go

@@ -0,0 +1,139 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
+package parachain
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+
+	"github.com/ChainSafe/gossamer/lib/common"
+	parachainruntime "github.com/ChainSafe/gossamer/lib/parachain/runtime"
+	parachaintypes "github.com/ChainSafe/gossamer/lib/parachain/types"
+
+	"github.com/ChainSafe/gossamer/pkg/scale"
+)
+
+var (
+	ErrValidationCodeMismatch   = errors.New("validation code hash does not match")
+	ErrValidationInputOverLimit = errors.New("validation input is over the limit")
+)
+
+// PoVRequestor gets proof of validity by issuing network requests to validators of the current backing group.
+// TODO: Implement PoV requestor
+type PoVRequestor interface {
+	RequestPoV(povHash common.Hash) PoV
+}
+
+func getValidationData(runtimeInstance parachainruntime.RuntimeInstance, paraID uint32,
+) (*parachaintypes.PersistedValidationData, *parachaintypes.ValidationCode, error) {
+
+	var mergedError error
+
+	for _, assumptionValue := range []scale.VaryingDataTypeValue{
+		parachaintypes.IncludedOccupiedCoreAssumption{},
+		parachaintypes.TimedOutOccupiedCoreAssumption{},
+		parachaintypes.Free{},
+	} {
+		assumption := parachaintypes.NewOccupiedCoreAssumption()
+		err := assumption.Set(assumptionValue)
+		if err != nil {
+			return nil, nil, fmt.Errorf("getting assumption: %w", err)
+		}
+		persistedValidationData, err := runtimeInstance.ParachainHostPersistedValidationData(paraID, assumption)
+		if err != nil {
+			mergedError = errors.Join(mergedError, err)
+			continue
+		}
+
+		validationCode, err := runtimeInstance.ParachainHostValidationCode(paraID, assumption)
+		if err != nil {
+			return nil, nil, fmt.Errorf("getting validation code: %w", err)
+		}
+
+		return persistedValidationData, validationCode, nil
+	}
+
+	return nil, nil, fmt.Errorf("getting persisted validation data: %w", mergedError)
+}
+
+// ValidateFromChainState validates a candidate parachain block with provided parameters using relay-chain
+// state and using the parachain runtime.
+func ValidateFromChainState(runtimeInstance parachainruntime.RuntimeInstance, povRequestor PoVRequestor,
+	candidateReceipt parachaintypes.CandidateReceipt) (
+	*parachaintypes.CandidateCommitments, *parachaintypes.PersistedValidationData, bool, error) {
+
+	persistedValidationData, validationCode, err := getValidationData(runtimeInstance, candidateReceipt.Descriptor.ParaID)
+	if err != nil {
+		return nil, nil, false, fmt.Errorf("getting validation data: %w", err)
+	}
+
+	// check that the candidate does not exceed any parameters in the persisted validation data
+	pov := povRequestor.RequestPoV(candidateReceipt.Descriptor.PovHash)
+
+	// basic checks
+
+	// check if encoded size of pov is less than max pov size
+	buffer := bytes.NewBuffer(nil)
+	encoder := scale.NewEncoder(buffer)
+	err = encoder.Encode(pov)
+	if err != nil {
+		return nil, nil, false, fmt.Errorf("encoding pov: %w", err)
+	}
+	encodedPoVSize := buffer.Len()
+	if encodedPoVSize > int(persistedValidationData.MaxPovSize) {
+		return nil, nil, false, fmt.Errorf("%w, limit: %d, got: %d", ErrValidationInputOverLimit,
+			persistedValidationData.MaxPovSize, encodedPoVSize)
+	}
+
+	validationCodeHash, err := common.Blake2bHash([]byte(*validationCode))
+	if err != nil {
+		return nil, nil, false, fmt.Errorf("hashing validation code: %w", err)
+	}
+
+	if validationCodeHash != common.Hash(candidateReceipt.Descriptor.ValidationCodeHash) {
+		return nil, nil, false, fmt.Errorf("%w, expected: %s, got %s", ErrValidationCodeMismatch,
+			candidateReceipt.Descriptor.ValidationCodeHash, validationCodeHash)
+	}
+
+	// check candidate signature
+	err = candidateReceipt.Descriptor.CheckCollatorSignature()
+	if err != nil {
+		return nil, nil, false, fmt.Errorf("verifying collator signature: %w", err)
+	}
+
+	validationParams := parachainruntime.ValidationParameters{
+		ParentHeadData:         persistedValidationData.ParentHead,
+		BlockData:              pov.BlockData,
+		RelayParentNumber:      persistedValidationData.RelayParentNumber,
+		RelayParentStorageRoot: persistedValidationData.RelayParentStorageRoot,
+	}
+
+	parachainRuntimeInstance, err := parachainruntime.SetupVM(*validationCode)
+	if err != nil {
+		return nil, nil, false, fmt.Errorf("setting up VM: %w", err)
+	}
+
+	validationResults, err := parachainRuntimeInstance.ValidateBlock(validationParams)
+	if err != nil {
+		return nil, nil, false, fmt.Errorf("executing validate_block: %w", err)
+	}
+
+	candidateCommitments := parachaintypes.CandidateCommitments{
+		UpwardMessages:            validationResults.UpwardMessages,
+		HorizontalMessages:        validationResults.HorizontalMessages,
+		NewValidationCode:         validationResults.NewValidationCode,
+		HeadData:                  validationResults.HeadData,
+		ProcessedDownwardMessages: validationResults.ProcessedDownwardMessages,
+		HrmpWatermark:             validationResults.HrmpWatermark,
+	}
+
+	isValid, err := runtimeInstance.ParachainHostCheckValidationOutputs(
+		candidateReceipt.Descriptor.ParaID, candidateCommitments)
+	if err != nil {
+		return nil, nil, false, fmt.Errorf("executing validate_block: %w", err)
+	}
+
+	return &candidateCommitments, persistedValidationData, isValid, nil
+}

lib/parachain/candidate_validation_test.go

@@ -0,0 +1,134 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
+package parachain
+
+import (
+	"os"
+	"testing"
+
+	"github.com/ChainSafe/gossamer/lib/common"
+	"github.com/ChainSafe/gossamer/lib/crypto/sr25519"
+	parachaintypes "github.com/ChainSafe/gossamer/lib/parachain/types"
+	"github.com/ChainSafe/gossamer/pkg/scale"
+	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/require"
+)
+
+func createTestCandidateReceiptAndValidationCode(t *testing.T) (
+	parachaintypes.CandidateReceipt, parachaintypes.ValidationCode) {
+	// this wasm was achieved by building polkadot's adder test parachain
+	runtimeFilePath := "./testdata/test_parachain_adder.wasm"
+	validationCodeBytes, err := os.ReadFile(runtimeFilePath)
+	require.NoError(t, err)
+
+	validationCode := parachaintypes.ValidationCode(validationCodeBytes)
+
+	validationCodeHashV := common.MustBlake2bHash(validationCodeBytes)
+
+	collatorKeypair, err := sr25519.GenerateKeypair()
+	require.NoError(t, err)
+	collatorID, err := sr25519.NewPublicKey(collatorKeypair.Public().Encode())
+	require.NoError(t, err)
+
+	candidateReceipt := parachaintypes.CandidateReceipt{
+		Descriptor: parachaintypes.CandidateDescriptor{
+			ParaID:                      uint32(1000),
+			RelayParent:                 common.MustHexToHash("0xded542bacb3ca6c033a57676f94ae7c8f36834511deb44e3164256fd3b1c0de0"), //nolint:lll
+			Collator:                    collatorID.AsBytes(),
+			PersistedValidationDataHash: common.MustHexToHash("0x690d8f252ef66ab0f969c3f518f90012b849aa5ac94e1752c5e5ae5a8996de37"), //nolint:lll
+			PovHash:                     common.MustHexToHash("0xe7df1126ac4b4f0fb1bc00367a12ec26ca7c51256735a5e11beecdc1e3eca274"), //nolint:lll
+			ErasureRoot:                 common.MustHexToHash("0xc07f658163e93c45a6f0288d229698f09c1252e41076f4caa71c8cbc12f118a1"), //nolint:lll
+			ParaHead:                    common.MustHexToHash("0x9a8a7107426ef873ab89fc8af390ec36bdb2f744a9ff71ad7f18a12d55a7f4f5"), //nolint:lll
+			ValidationCodeHash:          parachaintypes.ValidationCodeHash(validationCodeHashV),
+		},
+
+		CommitmentsHash: common.MustHexToHash("0xa54a8dce5fd2a27e3715f99e4241f674a48f4529f77949a4474f5b283b823535"),
+	}
+
+	payload, err := candidateReceipt.Descriptor.CreateSignaturePayload()
+	require.NoError(t, err)
+
+	signatureBytes, err := collatorKeypair.Sign(payload)
+	require.NoError(t, err)
+
+	signature := [sr25519.SignatureLength]byte{}
+	copy(signature[:], signatureBytes)
+
+	candidateReceipt.Descriptor.Signature = parachaintypes.CollatorSignature(signature)
+
+	return candidateReceipt, validationCode
+}
+
+func TestValidateFromChainState(t *testing.T) {
+
+	candidateReceipt, validationCode := createTestCandidateReceiptAndValidationCode(t)
+
+	bd, err := scale.Marshal(BlockDataInAdderParachain{
+		State: uint64(1),
+		Add:   uint64(1),
+	})
+	require.NoError(t, err)
+
+	pov := PoV{
+		BlockData: bd,
+	}
+
+	// NOTE: adder parachain internally compares postState with bd.State in it's validate_block,
+	// so following is necessary.
+	encodedState, err := scale.Marshal(uint64(1))
+	require.NoError(t, err)
+	postState, err := common.Keccak256(encodedState)
+	require.NoError(t, err)
+
+	hd, err := scale.Marshal(HeadDataInAdderParachain{
+		Number:     uint64(1),
+		ParentHash: common.MustHexToHash("0x0102030405060708090001020304050607080900010203040506070809000102"),
+		PostState:  postState,
+	})
+	require.NoError(t, err)
+
+	expectedPersistedValidationData := parachaintypes.PersistedValidationData{
+		ParentHead:             parachaintypes.HeadData{Data: hd},
+		RelayParentNumber:      uint32(1),
+		RelayParentStorageRoot: common.MustHexToHash("0x50c969706800c0e9c3c4565dc2babb25e4a73d1db0dee1bcf7745535a32e7ca1"),
+		MaxPovSize:             uint32(2048),
+	}
+
+	ctrl := gomock.NewController(t)
+
+	mockInstance := NewMockRuntimeInstance(ctrl)
+	mockInstance.EXPECT().
+		ParachainHostPersistedValidationData(
+			uint32(1000),
+			gomock.AssignableToTypeOf(parachaintypes.OccupiedCoreAssumption{})).
+		Return(&expectedPersistedValidationData, nil)
+	mockInstance.EXPECT().
+		ParachainHostValidationCode(uint32(1000), gomock.AssignableToTypeOf(parachaintypes.OccupiedCoreAssumption{})).
+		Return(&validationCode, nil)
+	mockInstance.EXPECT().
+		ParachainHostCheckValidationOutputs(uint32(1000), gomock.AssignableToTypeOf(parachaintypes.CandidateCommitments{})).
+		Return(true, nil)
+
+	mockPoVRequestor := NewMockPoVRequestor(ctrl)
+	mockPoVRequestor.EXPECT().
+		RequestPoV(common.MustHexToHash("0xe7df1126ac4b4f0fb1bc00367a12ec26ca7c51256735a5e11beecdc1e3eca274")).Return(pov)
+
+	candidateCommitments, persistedValidationData, isValid, err := ValidateFromChainState(
+		mockInstance, mockPoVRequestor, candidateReceipt)
+	require.NoError(t, err)
+	require.True(t, isValid)
+	require.NotNil(t, candidateCommitments)
+	require.Equal(t, expectedPersistedValidationData, *persistedValidationData)
+}
+
+type HeadDataInAdderParachain struct {
+	Number     uint64
+	ParentHash [32]byte
+	PostState  [32]byte
+}
+
+type BlockDataInAdderParachain struct {
+	State uint64
+	Add   uint64
+}

lib/parachain/chunk_fetching.go

@@ -1,3 +1,6 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
 package parachain
 
 import (

lib/parachain/chunk_fetching_test.go

@@ -1,3 +1,6 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
 package parachain
 
 import (

lib/parachain/collation_fetching.go

@@ -1,3 +1,6 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
 package parachain
 
 import (

lib/parachain/collation_fetching_test.go

@@ -1,3 +1,6 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
 package parachain
 
 import (

lib/parachain/collation_protocol.go

@@ -1,3 +1,6 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
 package parachain
 
 import (

lib/parachain/collation_protocol_test.go

@@ -1,3 +1,6 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
 package parachain
 
 import (
@@ -55,9 +58,11 @@ func TestCollationProtocol(t *testing.T) {
 			ValidationCodeHash:          parachaintypes.ValidationCodeHash(hash5),
 		},
 		Commitments: parachaintypes.CandidateCommitments{
-			UpwardMessages:            []parachaintypes.UpwardMessage{{1, 2, 3}},
-			NewValidationCode:         &parachaintypes.ValidationCode{1, 2, 3},
-			HeadData:                  []byte{1, 2, 3},
+			UpwardMessages:    []parachaintypes.UpwardMessage{{1, 2, 3}},
+			NewValidationCode: &parachaintypes.ValidationCode{1, 2, 3},
+			HeadData: parachaintypes.HeadData{
+				Data: []byte{1, 2, 3},
+			},
 			ProcessedDownwardMessages: uint32(5),
 			HrmpWatermark:             uint32(0),
 		},

lib/parachain/mocks_generate_test.go

@@ -0,0 +1,6 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
+package parachain
+
+//go:generate mockgen -destination=mocks_test.go -package=$GOPACKAGE . RuntimeInstance,PoVRequestor