Complain if contract address changes (#1724)

* complain if wrong contract address

* add comment

beacon-chain/db/BUILD.bazel

@@ -13,6 +13,7 @@ go_library(
         "setup_db.go",
         "state.go",
         "validator.go",
+        "verify_contract.go",
     ],
     importpath = "github.com/prysmaticlabs/prysm/beacon-chain/db",
     visibility = ["//beacon-chain:__subpackages__"],
@@ -23,6 +24,7 @@ go_library(
         "//shared/bytesutil:go_default_library",
         "//shared/hashutil:go_default_library",
         "@com_github_boltdb_bolt//:go_default_library",
+        "@com_github_ethereum_go_ethereum//common:go_default_library",
         "@com_github_gogo_protobuf//proto:go_default_library",
         "@com_github_opentracing_opentracing_go//:go_default_library",
         "@com_github_prometheus_client_golang//prometheus:go_default_library",
@@ -42,6 +44,7 @@ go_test(
         "pending_deposits_test.go",
         "state_test.go",
         "validator_test.go",
+        "verify_contract_test.go",
     ],
     embed = [":go_default_library"],
     deps = [
@@ -51,6 +54,7 @@ go_test(
         "//shared/hashutil:go_default_library",
         "//shared/params:go_default_library",
         "//shared/testutil:go_default_library",
+        "@com_github_ethereum_go_ethereum//common:go_default_library",
         "@com_github_gogo_protobuf//proto:go_default_library",
     ],
 )

beacon-chain/db/verify_contract.go

@@ -0,0 +1,37 @@
+package db
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+
+	"github.com/boltdb/bolt"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/opentracing/opentracing-go"
+)
+
+var depositContractAddressKey = []byte("deposit-contract")
+
+// VerifyContractAddress that represents the data in this database. The
+// contract address is the address of the deposit contract on the proof of work
+// Ethereum chain. This value will never change or all of the data in the
+// database would be made invalid.
+func (db *BeaconDB) VerifyContractAddress(ctx context.Context, addr common.Address) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "BeaconDB.VerifyContractAddress")
+	defer span.Finish()
+
+	return db.update(func(tx *bolt.Tx) error {
+		chainInfo := tx.Bucket(chainInfoBucket)
+
+		expectedAddress := chainInfo.Get(depositContractAddressKey)
+		if expectedAddress == nil {
+			return chainInfo.Put(depositContractAddressKey, addr.Bytes())
+		}
+
+		if !bytes.Equal(expectedAddress, addr.Bytes()) {
+			return fmt.Errorf("invalid deposit contract address, expected %#x", expectedAddress)
+		}
+
+		return nil
+	})
+}

beacon-chain/db/verify_contract_test.go

@@ -0,0 +1,31 @@
+package db
+
+import (
+	"context"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+func TestVerifyContractAddress(t *testing.T) {
+	db := setupDB(t)
+	defer teardownDB(t, db)
+
+	ctx := context.Background()
+
+	address := common.HexToAddress("0x0cd549b4abcbc0cb63012ea7de6fd34ebdccfd45")
+	// There should be no error the first time.
+	if err := db.VerifyContractAddress(ctx, address); err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	// There should be no error the second time.
+	if err := db.VerifyContractAddress(ctx, address); err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	// But there should be an error with a different address.
+	otherAddr := common.HexToAddress("0x247b06d9890ab9b032ec318ca436aef262d0f08a")
+	if err := db.VerifyContractAddress(ctx, otherAddr); err == nil {
+		t.Fatal("Expected error, but didn't receive one")
+	}
+
+}

beacon-chain/node/node.go

@@ -202,8 +202,8 @@ func (b *BeaconNode) registerOperationService() error {
 	return b.services.RegisterService(operationService)
 }
 
-func (b *BeaconNode) registerPOWChainService(ctx *cli.Context) error {
-	if !ctx.GlobalBool(utils.EnablePOWChain.Name) {
+func (b *BeaconNode) registerPOWChainService(cliCtx *cli.Context) error {
+	if !cliCtx.GlobalBool(utils.EnablePOWChain.Name) {
 		return nil
 	}
 
@@ -213,9 +213,10 @@ func (b *BeaconNode) registerPOWChainService(ctx *cli.Context) error {
 	}
 	powClient := ethclient.NewClient(rpcClient)
 
-	delay := ctx.GlobalUint64(utils.ChainStartDelay.Name)
+	delay := cliCtx.GlobalUint64(utils.ChainStartDelay.Name)
 
-	web3Service, err := powchain.NewWeb3Service(context.TODO(), &powchain.Web3ServiceConfig{
+	ctx := context.Background()
+	cfg := &powchain.Web3ServiceConfig{
 		Endpoint:        b.ctx.GlobalString(utils.Web3ProviderFlag.Name),
 		DepositContract: common.HexToAddress(b.ctx.GlobalString(utils.DepositContractFlag.Name)),
 		Client:          powClient,
@@ -225,10 +226,16 @@ func (b *BeaconNode) registerPOWChainService(ctx *cli.Context) error {
 		ContractBackend: powClient,
 		BeaconDB:        b.db,
 		ChainStartDelay: delay,
-	})
+	}
+	web3Service, err := powchain.NewWeb3Service(ctx, cfg)
 	if err != nil {
 		return fmt.Errorf("could not register proof-of-work chain web3Service: %v", err)
 	}
+
+	if err := b.db.VerifyContractAddress(ctx, cfg.DepositContract); err != nil {
+		return err
+	}
+
 	return b.services.RegisterService(web3Service)
 }