core: vm: remove opRand and use oracle contract to get random number

7 files changed, 85 insertions, 34 deletions

diff --git a/core/vm/evm.go b/core/vm/evm.go
index 84b98d7c2..ea370f11f 100644
--- a/core/vm/evm.go
+++ b/core/vm/evm.go
@@ -103,7 +103,7 @@ type Context struct {
 	Difficulty  *big.Int       // Provides information for DIFFICULTY
 	Round       *big.Int       // Current round number.
 
-	RandCallIndex uint64 // Number of times opRand is called
+	RandCallIndex uint64 // Number of times RandomContract is called
 }
 
 // EVM is the Ethereum Virtual Machine base object and provides
diff --git a/core/vm/instructions.go b/core/vm/instructions.go
index b096bfdd4..587acf002 100644
--- a/core/vm/instructions.go
+++ b/core/vm/instructions.go
@@ -17,7 +17,6 @@
 package vm
 
 import (
-	"encoding/binary"
 	"errors"
 	"fmt"
 	"math/big"
@@ -25,7 +24,6 @@ import (
 	"github.com/tangerine-network/go-tangerine/common"
 	"github.com/tangerine-network/go-tangerine/common/math"
 	"github.com/tangerine-network/go-tangerine/core/types"
-	"github.com/tangerine-network/go-tangerine/crypto"
 	"github.com/tangerine-network/go-tangerine/params"
 	"golang.org/x/crypto/sha3"
 )
@@ -410,28 +408,6 @@ func opSha3(pc *uint64, interpreter *EVMInterpreter, contract *Contract, memory
 	return nil, nil
 }
 
-func opRand(pc *uint64, interpreter *EVMInterpreter, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
-	evm := interpreter.evm
-
-	nonce := evm.StateDB.GetNonce(evm.Origin)
-	binaryOriginNonce := make([]byte, binary.MaxVarintLen64)
-	binary.PutUvarint(binaryOriginNonce, nonce)
-
-	binaryUsedIndex := make([]byte, binary.MaxVarintLen64)
-	binary.PutUvarint(binaryUsedIndex, evm.RandCallIndex)
-
-	evm.RandCallIndex += 1
-
-	hash := crypto.Keccak256(
-		evm.Randomness,
-		evm.Origin.Bytes(),
-		binaryOriginNonce,
-		binaryUsedIndex)
-
-	stack.push(interpreter.intPool.get().SetBytes(hash))
-	return nil, nil
-}
-
 func opAddress(pc *uint64, interpreter *EVMInterpreter, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
 	stack.push(contract.Address().Big())
 	return nil, nil
diff --git a/core/vm/jump_table.go b/core/vm/jump_table.go
index c1b57ea89..ba11b57f3 100644
--- a/core/vm/jump_table.go
+++ b/core/vm/jump_table.go
@@ -301,12 +301,6 @@ func newFrontierInstructionSet() [256]operation {
 			memorySize:    memorySha3,
 			valid:         true,
 		},
-		RAND: {
-			execute:       opRand,
-			gasCost:       constGasFunc(params.RandGas),
-			validateStack: makeStackFunc(0, 1),
-			valid:         true,
-		},
 		ADDRESS: {
 			execute:       opAddress,
 			gasCost:       constGasFunc(GasQuickStep),
diff --git a/core/vm/opcodes.go b/core/vm/opcodes.go
index 8762d4b43..4349ffd29 100644
--- a/core/vm/opcodes.go
+++ b/core/vm/opcodes.go
@@ -71,7 +71,6 @@ const (
 	SAR
 
 	SHA3 = 0x20
-	RAND = 0x2f
 )
 
 // 0x30 range - closure state.
@@ -252,7 +251,6 @@ var opCodeToString = map[OpCode]string{
 
 	// 0x20 range - crypto.
 	SHA3: "SHA3",
-	RAND: "RAND",
 
 	// 0x30 range - closure state.
 	ADDRESS:        "ADDRESS",
@@ -422,7 +420,6 @@ var stringToOp = map[string]OpCode{
 	"ADDMOD":         ADDMOD,
 	"MULMOD":         MULMOD,
 	"SHA3":           SHA3,
-	"RAND":           RAND,
 	"ADDRESS":        ADDRESS,
 	"BALANCE":        BALANCE,
 	"ORIGIN":         ORIGIN,
diff --git a/core/vm/oracle.go b/core/vm/oracle.go
index b2dac4521..2e27983b5 100644
--- a/core/vm/oracle.go
+++ b/core/vm/oracle.go
@@ -25,6 +25,7 @@ import (
 )
 
 var GovernanceContractAddress = common.HexToAddress("63751838d6485578b23e8b051d40861ecc416794")
+var RandomContractAddress = common.HexToAddress("03C90084388Be8E088425DA9835F7f43F8a319c7")
 
 var GovernanceABI *OracleContractABI
 
@@ -44,6 +45,9 @@ var OracleContracts = map[common.Address]func() OracleContract{
 			coreDKGUtils: &defaultCoreDKGUtils{},
 		}
 	},
+	RandomContractAddress: func() OracleContract {
+		return &RandomContract{}
+	},
 }
 
 // Run oracle contract.
diff --git a/core/vm/oracle_contracts.go b/core/vm/oracle_contracts.go
index 484ed82b8..7e245e6bd 100644
--- a/core/vm/oracle_contracts.go
+++ b/core/vm/oracle_contracts.go
@@ -19,6 +19,7 @@ package vm
 
 import (
 	"bytes"
+	"encoding/binary"
 	"errors"
 	"fmt"
 	"math"
@@ -2952,3 +2953,34 @@ func PackResetDKG(newSignedCRS []byte) ([]byte, error) {
 	data := append(method.Id(), res...)
 	return data, nil
 }
+
+// RandomContract provides access to on chain randomness.
+type RandomContract struct {
+	evm      *EVM
+	contract *Contract
+}
+
+func (*RandomContract) Run(evm *EVM, input []byte,
+	contract *Contract) (ret []byte, err error) {
+	nonce := evm.StateDB.GetNonce(evm.Origin)
+
+	cost := params.RandGas
+	if !contract.UseGas(cost) {
+		return nil, ErrOutOfGas
+	}
+
+	binaryOriginNonce := make([]byte, binary.MaxVarintLen64)
+	binary.PutUvarint(binaryOriginNonce, nonce)
+
+	binaryUsedIndex := make([]byte, binary.MaxVarintLen64)
+	binary.PutUvarint(binaryUsedIndex, evm.RandCallIndex)
+
+	evm.RandCallIndex += 1
+
+	ret = crypto.Keccak256(
+		evm.Randomness,
+		evm.Origin.Bytes(),
+		binaryOriginNonce,
+		binaryUsedIndex)
+	return
+}
diff --git a/core/vm/oracle_contracts_test.go b/core/vm/oracle_contracts_test.go
index 33fdba886..ddd75810e 100644
--- a/core/vm/oracle_contracts_test.go
+++ b/core/vm/oracle_contracts_test.go
@@ -1247,3 +1247,51 @@ func (g *OracleContractsTestSuite) TestResetDKG() {
 func TestOracleContracts(t *testing.T) {
 	suite.Run(t, new(OracleContractsTestSuite))
 }
+
+type RandomContractTestSuite struct {
+	suite.Suite
+
+	context Context
+	stateDB *state.StateDB
+	config  *params.DexconConfig
+}
+
+func (r *RandomContractTestSuite) SetupTest() {
+	memDB := ethdb.NewMemDatabase()
+	stateDB, err := state.New(common.Hash{}, state.NewDatabase(memDB))
+	if err != nil {
+		panic(err)
+	}
+	r.stateDB = stateDB
+	r.context = Context{
+		CanTransfer: func(db StateDB, addr common.Address, amount *big.Int) bool {
+			return db.GetBalance(addr).Cmp(amount) >= 0
+		},
+		Transfer: func(db StateDB, sender common.Address, recipient common.Address, amount *big.Int) {
+			db.SubBalance(sender, amount)
+			db.AddBalance(recipient, amount)
+		},
+	}
+	r.config = params.TestnetChainConfig.Dexcon
+}
+
+func (r *RandomContractTestSuite) TestRun() {
+	evm := NewEVM(r.context, r.stateDB, params.TestChainConfig,
+		Config{IsBlockProposer: true})
+	contractAddr := RandomContractAddress
+	caller := r.config.Owner
+	randCallIndex := evm.RandCallIndex
+
+	ret, _, err := evm.Call(AccountRef(caller), contractAddr, nil, 64, big.NewInt(0))
+	r.Require().Nil(err)
+	r.Require().Equal(randCallIndex+1, evm.RandCallIndex)
+	r.Require().NotNil(ret)
+
+	_, _, err = evm.Call(AccountRef(caller), contractAddr, nil, 63, big.NewInt(0))
+	r.Require().Equal(err, ErrOutOfGas)
+	r.Require().Equal(randCallIndex+1, evm.RandCallIndex)
+}
+
+func TestRandomContract(t *testing.T) {
+	suite.Run(t, new(RandomContractTestSuite))
+}