[Flow EVM] populate PREVRANDAO with a random value from the FVM random generator

fvm/evm/emulator/config.go

@@ -200,3 +200,11 @@ func WithExtraPrecompiles(precompiles []types.Precompile) Option {
 		return c
 	}
 }
+
+// WithRandom sets the block context random field
+func WithRandom(rand *gethCommon.Hash) Option {
+	return func(c *Config) *Config {
+		c.BlockContext.Random = rand
+		return c
+	}
+}

fvm/evm/emulator/emulator.go

@@ -40,6 +40,7 @@ func newConfig(ctx types.BlockContext) *Config {
 		WithCoinbase(ctx.GasFeeCollector.ToCommon()),
 		WithDirectCallBaseGasUsage(ctx.DirectCallBaseGasUsage),
 		WithExtraPrecompiles(ctx.ExtraPrecompiles),
+		WithRandom(&ctx.Random),
 	)
 }
 

fvm/evm/emulator/emulator_test.go

@@ -131,7 +131,6 @@ func TestContractInteraction(t *testing.T) {
 
 			t.Run("call contract", func(t *testing.T) {
 				num := big.NewInt(10)
-
 				RunWithNewEmulator(t, backend, rootAddr, func(env *emulator.Emulator) {
 					RunWithNewBlockView(t, env, func(blk types.BlockView) {
 						res, err := blk.DirectCall(
@@ -184,7 +183,6 @@ func TestContractInteraction(t *testing.T) {
 						require.Equal(t, blockNumber, ret)
 					})
 				})
-
 			})
 
 			t.Run("test sending transactions (happy case)", func(t *testing.T) {

fvm/evm/evm_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/onflow/cadence/encoding/json"
 	"github.com/stretchr/testify/require"
 
+	"github.com/onflow/flow-go/engine/execution/testutil"
 	"github.com/onflow/flow-go/fvm"
 	"github.com/onflow/flow-go/fvm/evm/stdlib"
 	"github.com/onflow/flow-go/fvm/evm/testutils"
@@ -85,10 +86,12 @@ func TestEVMRun(t *testing.T) {
 }
 
 func RunWithNewTestVM(t *testing.T, chain flow.Chain, f func(fvm.Context, fvm.VM, snapshot.SnapshotTree)) {
+
 	opts := []fvm.Option{
 		fvm.WithChain(chain),
 		fvm.WithAuthorizationChecksEnabled(false),
 		fvm.WithSequenceNumberCheckAndIncrementEnabled(false),
+		fvm.WithEntropyProvider(testutil.EntropyProviderFixture(nil)),
 	}
 	ctx := fvm.NewContext(opts...)
 

fvm/evm/handler/handler.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"math/big"
 
+	gethCommon "github.com/ethereum/go-ethereum/common"
 	gethTypes "github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/onflow/cadence/runtime/common"
@@ -153,10 +154,14 @@ func (h *ContractHandler) emitEvent(event *types.Event) {
 func (h *ContractHandler) getBlockContext() types.BlockContext {
 	bp, err := h.blockstore.BlockProposal()
 	handleError(err)
+	rand := gethCommon.Hash{}
+	err = h.backend.ReadRandom(rand[:])
+	handleError(err)
 	return types.BlockContext{
 		BlockNumber:            bp.Height,
 		DirectCallBaseGasUsage: types.DefaultDirectCallBaseGasUsage,
 		ExtraPrecompiles:       h.precompiles,
+		Random:                 rand,
 	}
 }
 

fvm/evm/handler/handler_test.go

@@ -533,6 +533,39 @@
 		})
 	})
 
+	t.Run("test block.random call (with integrated emulator)", func(t *testing.T) {
+		t.Parallel()
+
+		testutils.RunWithTestBackend(t, func(backend *testutils.TestBackend) {
+			random := testutils.RandomCommonHash(t)
+			backend.ReadRandomFunc = func(buffer []byte) error {
+				copy(buffer, random.Bytes())
+				return nil
+			}
+			testutils.RunWithTestFlowEVMRootAddress(t, backend, func(rootAddr flow.Address) {
+				handler := SetupHandler(t, backend, rootAddr)
+
+				foa := handler.AccountByAddress(handler.AllocateAddress(), true)
+				require.NotNil(t, foa)
+
+				vault := types.NewFlowTokenVault(testutils.MakeABalanceInFlow(100))
+				foa.Deposit(vault)
+
+				testContract := testutils.GetStorageTestContract(t)
+				addr := foa.Deploy(testContract.ByteCode, math.MaxUint64, types.Balance(0))
+				require.NotNil(t, addr)
+
+				ret := foa.Call(
+					addr,
+					testContract.MakeCallData(t, "random"),
+					math.MaxUint64,
+					types.Balance(0))
+
+				require.Equal(t, random.Bytes(), []byte(ret))
+			})
+		})
+	})
+
 	// TODO add test with test emulator for unhappy cases (emulator)
 }
 

fvm/evm/testutils/backend.go

@@ -1,6 +1,7 @@
 package testutils
 
 import (
+	"crypto/rand"
 	"encoding/binary"
 	"fmt"
 	"math"
@@ -32,10 +33,11 @@ func RunWithTestFlowEVMRootAddress(t testing.TB, backend atree.Ledger, f func(fl
 
 func RunWithTestBackend(t testing.TB, f func(*TestBackend)) {
 	tb := &TestBackend{
-		TestValueStore:   GetSimpleValueStore(),
-		testEventEmitter: getSimpleEventEmitter(),
-		testMeter:        getSimpleMeter(),
-		TestBlockInfo:    &TestBlockInfo{},
+		TestValueStore:      GetSimpleValueStore(),
+		testEventEmitter:    getSimpleEventEmitter(),
+		testMeter:           getSimpleMeter(),
+		TestBlockInfo:       &TestBlockInfo{},
+		TestRandomGenerator: getSimpleRandomGenerator(),
 	}
 	f(tb)
 }
@@ -157,6 +159,7 @@ type TestBackend struct {
 	*testMeter
 	*testEventEmitter
 	*TestBlockInfo
+	*TestRandomGenerator
 }
 
 var _ types.Backend = &TestBackend{}
@@ -405,3 +408,25 @@ func (tb *TestBlockInfo) GetBlockAtHeight(height uint64) (runtime.Block, bool, e
 	}
 	return tb.GetBlockAtHeightFunc(height)
 }
+
+type TestRandomGenerator struct {
+	ReadRandomFunc func([]byte) error
+}
+
+var _ environment.RandomGenerator = &TestRandomGenerator{}
+
+func (t *TestRandomGenerator) ReadRandom(buffer []byte) error {
+	if t.ReadRandomFunc == nil {
+		panic("ReadRandomFunc method is not set")
+	}
+	return t.ReadRandomFunc(buffer)
+}
+
+func getSimpleRandomGenerator() *TestRandomGenerator {
+	return &TestRandomGenerator{
+		ReadRandomFunc: func(buffer []byte) error {
+			_, err := rand.Read(buffer)
+			return err
+		},
+	}
+}

fvm/evm/testutils/contract.go

@@ -38,10 +38,12 @@ func (tc *TestContract) SetDeployedAt(deployedAt types.Address) {
 }
 
 func GetStorageTestContract(tb testing.TB) *TestContract {
-	byteCodes, err := hex.DecodeString("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")
+	byteCodes, err := hex.DecodeString("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")
 	require.NoError(tb, err)
 	return &TestContract{
 		Code: `
+		pragma solidity >=0.7.0 <0.9.0;
+
 			contract Storage {
 				uint256 number;
 				constructor() payable {
@@ -56,11 +58,15 @@ func GetStorageTestContract(tb testing.TB) *TestContract {
 					return block.number;
 				}
 				function blockTime() public view returns (uint) {
-					return  block.timestamp;
+					return block.timestamp;
 				}
 				function blockHash(uint num)  public view returns (bytes32) {
 					return blockhash(num);
 				}
+
+				function random() public view returns (uint256) {
+					return block.prevrandao;
+				}
 			}
 		`,
 
@@ -116,6 +122,19 @@ func GetStorageTestContract(tb testing.TB) *TestContract {
 				"stateMutability": "view",
 				"type": "function"
 			},
+			{
+				"inputs": [],
+				"name": "random",
+				"outputs": [
+					{
+						"internalType": "uint256",
+						"name": "",
+						"type": "uint256"
+					}
+				],
+				"stateMutability": "view",
+				"type": "function"
+			},
 			{
 				"inputs": [],
 				"name": "retrieve",

fvm/evm/types/emulator.go

@@ -3,6 +3,7 @@ package types
 import (
 	"math/big"
 
+	gethCommon "github.com/ethereum/go-ethereum/common"
 	gethTypes "github.com/ethereum/go-ethereum/core/types"
 	gethVM "github.com/ethereum/go-ethereum/core/vm"
 )
@@ -26,6 +27,7 @@ type BlockContext struct {
 	DirectCallBaseGasUsage uint64
 	DirectCallGasPrice     uint64
 	GasFeeCollector        Address
+	Random                 gethCommon.Hash
 
 	// a set of extra precompiles to be injected
 	ExtraPrecompiles []Precompile

fvm/evm/types/handler.go

@@ -48,6 +48,7 @@ type Backend interface {
 	environment.Meter
 	environment.EventEmitter
 	environment.BlockInfo
+	environment.RandomGenerator
 }
 
 // AddressAllocator allocates addresses, used by the handler

fvm/fvm_test.go

@@ -78,6 +78,7 @@ func (vmt vmTest) run(
 		baseOpts := []fvm.Option{
 			// default chain is Testnet
 			fvm.WithChain(flow.Testnet.Chain()),
+			fvm.WithEntropyProvider(testutil.EntropyProviderFixture(nil)),
 		}
 
 		opts := append(baseOpts, vmt.contextOptions...)