Add vrf as a precompile in evm

consensus/consensus_v2.go

@@ -724,7 +724,7 @@ func (consensus *Consensus) GenerateVrfAndProof(newHeader *block.Header) error {
 	consensus.getLogger().Info().
 		Uint64("BlockNum", newHeader.Number().Uint64()).
 		Uint64("Epoch", newHeader.Epoch().Uint64()).
-		Bytes("VRF+Proof", newHeader.Vrf()).
+		Hex("VRF+Proof", newHeader.Vrf()).
 		Msg("[GenerateVrfAndProof] Leader generated a VRF")
 
 	return nil

core/evm.go

@@ -55,6 +55,11 @@ func NewEVMContext(msg Message, header *block.Header, chain ChainContext, author
 	} else {
 		beneficiary = *author
 	}
+	vrf := common.Hash{}
+	if len(header.Vrf()) >= 32 {
+		vrfAndProof := header.Vrf()
+		copy(vrf[:], vrfAndProof[:32])
+	}
 	return vm.Context{
 		CanTransfer: CanTransfer,
 		Transfer:    Transfer,
@@ -64,6 +69,7 @@ func NewEVMContext(msg Message, header *block.Header, chain ChainContext, author
 		Coinbase:    beneficiary,
 		BlockNumber: header.Number(),
 		EpochNumber: header.Epoch(),
+		VRF:         vrf,
 		Time:        header.Time(),
 		GasLimit:    header.GasLimit(),
 		GasPrice:    new(big.Int).Set(msg.GasPrice()),

core/vm/contracts.go

@@ -76,6 +76,21 @@ var PrecompiledContractsIstanbul = map[common.Address]PrecompiledContract{
 	common.BytesToAddress([]byte{9}): &blake2F{},
 }
 
+// PrecompiledContractsIstanbul contains the default set of pre-compiled Ethereum
+// contracts used in the Istanbul release.
+var PrecompiledContractsVRF = map[common.Address]PrecompiledContract{
+	common.BytesToAddress([]byte{1}):   &ecrecover{},
+	common.BytesToAddress([]byte{2}):   &sha256hash{},
+	common.BytesToAddress([]byte{3}):   &ripemd160hash{},
+	common.BytesToAddress([]byte{4}):   &dataCopy{},
+	common.BytesToAddress([]byte{5}):   &bigModExp{},
+	common.BytesToAddress([]byte{6}):   &bn256AddIstanbul{},
+	common.BytesToAddress([]byte{7}):   &bn256ScalarMulIstanbul{},
+	common.BytesToAddress([]byte{8}):   &bn256PairingIstanbul{},
+	common.BytesToAddress([]byte{9}):   &blake2F{},
+	common.BytesToAddress([]byte{255}): &vrf{},
+}
+
 // RunPrecompiledContract runs and evaluates the output of a precompiled contract.
 func RunPrecompiledContract(p PrecompiledContract, input []byte, contract *Contract) (ret []byte, err error) {
 	gas := p.RequiredGas(input)
@@ -501,3 +516,20 @@ func (c *blake2F) Run(input []byte) ([]byte, error) {
 	}
 	return output, nil
 }
+
+// VRF implemented as a native contract.
+type vrf struct{}
+
+// RequiredGas returns the gas required to execute the pre-compiled contract.
+//
+// This method does not require any overflow checking as the input size gas costs
+// required for anything significant is so high it's impossible to pay for.
+func (c *vrf) RequiredGas(input []byte) uint64 {
+	return GasQuickStep
+}
+
+func (c *vrf) Run(input []byte) ([]byte, error) {
+	// Note the input was overwritten with the vrf of the block.
+	// So here we simply return it
+	return append([]byte{}, input...), nil
+}

core/vm/evm.go

@@ -54,7 +54,14 @@ func run(evm *EVM, contract *Contract, input []byte, readOnly bool) ([]byte, err
 		if evm.chainRules.IsIstanbul {
 			precompiles = PrecompiledContractsIstanbul
 		}
+		if evm.chainRules.IsVRF {
+			precompiles = PrecompiledContractsVRF
+		}
 		if p := precompiles[*contract.CodeAddr]; p != nil {
+			if _, ok := p.(*vrf); ok {
+				// Override the input with vrf data of the current block so it can be returned to the contract program.
+				input = evm.Context.VRF.Bytes()
+			}
 			return RunPrecompiledContract(p, input, contract)
 		}
 	}
@@ -69,6 +76,7 @@ func run(evm *EVM, contract *Contract, input []byte, readOnly bool) ([]byte, err
 				evm.interpreter = interpreter
 			}
 			return interpreter.Run(contract, input, readOnly)
+
 		}
 	}
 	return nil, ErrNoCompatibleInterpreter
@@ -99,6 +107,7 @@ type Context struct {
 	BlockNumber *big.Int       // Provides information for NUMBER
 	EpochNumber *big.Int       // Provides information for EPOCH
 	Time        *big.Int       // Provides information for TIME
+	VRF         common.Hash    // Provides information for VRF
 
 	TxType types.TransactionType
 }
@@ -225,6 +234,10 @@ func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas
 		if evm.chainRules.IsIstanbul {
 			precompiles = PrecompiledContractsIstanbul
 		}
+		if evm.chainRules.IsVRF {
+			precompiles = PrecompiledContractsVRF
+		}
+
 		if precompiles[addr] == nil && evm.ChainConfig().IsS3(evm.EpochNumber) && value.Sign() == 0 {
 			// Calling a non existing account, don't do anything, but ping the tracer
 			if evm.vmConfig.Debug && evm.depth == 0 {

core/vm/interpreter.go

@@ -271,6 +271,7 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 
 		// execute the operation
 		res, err = operation.execute(&pc, in, contract, mem, stack)
+
 		// verifyPool is a build flag. Pool verification makes sure the integrity
 		// of the integer pool by comparing values to a default value.
 		if verifyPool {

core/vm/runtime/env.go

@@ -34,6 +34,7 @@ func NewEnv(cfg *Config) *vm.EVM {
 		Coinbase:    cfg.Coinbase,
 		BlockNumber: cfg.BlockNumber,
 		EpochNumber: cfg.EpochNumber,
+		VRF:         cfg.VRF,
 		Time:        cfg.Time,
 		GasLimit:    cfg.GasLimit,
 		GasPrice:    cfg.GasPrice,

core/vm/runtime/runtime.go

@@ -38,6 +38,7 @@ type Config struct {
 	Coinbase    common.Address
 	BlockNumber *big.Int
 	EpochNumber *big.Int
+	VRF         common.Hash
 	Time        *big.Int
 	GasLimit    uint64
 	GasPrice    *big.Int

internal/params/config.go

@@ -468,9 +468,9 @@ func isForked(s, epoch *big.Int) bool {
 // Rules is a one time interface meaning that it shouldn't be used in between transition
 // phases.
 type Rules struct {
-	ChainID                                               *big.Int
-	EthChainID                                            *big.Int
-	IsCrossLink, IsEIP155, IsS3, IsReceiptLog, IsIstanbul bool
+	ChainID                                                      *big.Int
+	EthChainID                                                   *big.Int
+	IsCrossLink, IsEIP155, IsS3, IsReceiptLog, IsIstanbul, IsVRF bool
 }
 
 // Rules ensures c's ChainID is not nil.
@@ -491,5 +491,6 @@ func (c *ChainConfig) Rules(epoch *big.Int) Rules {
 		IsS3:         c.IsS3(epoch),
 		IsReceiptLog: c.IsReceiptLog(epoch),
 		IsIstanbul:   c.IsIstanbul(epoch),
+		IsVRF:        c.IsVRF(epoch),
 	}
 }