core, dex/downloader: polish headers verification and blocks insertion logic (#168)

Refactor GenerateDexonChain function, move governance tx logic to
the user of GenerateDexonChain (testchain_test.go) and move fake node set
code to FakeDexcon.

3 files changed, 217 insertions, 32 deletions

diff --git a/dex/downloader/downloader.go b/dex/downloader/downloader.go
index 6ff8c122e..e15844668 100644
--- a/dex/downloader/downloader.go
+++ b/dex/downloader/downloader.go
@@ -27,6 +27,7 @@ import (
 
 	ethereum "github.com/dexon-foundation/dexon"
 	"github.com/dexon-foundation/dexon/common"
+	"github.com/dexon-foundation/dexon/consensus/dexcon"
 	"github.com/dexon-foundation/dexon/core/rawdb"
 	"github.com/dexon-foundation/dexon/core/state"
 	"github.com/dexon-foundation/dexon/core/types"
@@ -177,7 +178,8 @@ type LightChain interface {
 	GetGovStateByNumber(number uint64) (*types.GovState, error)
 
 	// InsertDexonHeaderChain inserts a batch of headers into the local chain.
-	InsertDexonHeaderChain([]*types.HeaderWithGovState, *dexCore.TSigVerifierCache) (int, error)
+	InsertDexonHeaderChain([]*types.HeaderWithGovState,
+		dexcon.GovernanceStateFetcher, *dexCore.TSigVerifierCache) (int, error)
 
 	// Rollback removes a few recently added elements from the local chain.
 	Rollback([]common.Hash)
@@ -1428,7 +1430,7 @@ func (d *Downloader) processHeaders(origin uint64, pivot uint64, number uint64)
 						}
 					}
 
-					if n, err := d.lightchain.InsertDexonHeaderChain(chunk, d.verifierCache); err != nil {
+					if n, err := d.lightchain.InsertDexonHeaderChain(chunk, d.gov, d.verifierCache); err != nil {
 						// If some headers were inserted, add them too to the rollback list
 						if n > 0 {
 							for _, h := range chunk[:n] {
diff --git a/dex/downloader/downloader_test.go b/dex/downloader/downloader_test.go
index 0d92ad97f..80993bd75 100644
--- a/dex/downloader/downloader_test.go
+++ b/dex/downloader/downloader_test.go
@@ -26,12 +26,16 @@ import (
 
 	ethereum "github.com/dexon-foundation/dexon"
 	dexCore "github.com/dexon-foundation/dexon-consensus/core"
+	coreTypes "github.com/dexon-foundation/dexon-consensus/core/types"
+
 	"github.com/dexon-foundation/dexon/common"
+	"github.com/dexon-foundation/dexon/consensus/dexcon"
 	"github.com/dexon-foundation/dexon/core/state"
 	"github.com/dexon-foundation/dexon/core/types"
 	"github.com/dexon-foundation/dexon/core/vm"
 	"github.com/dexon-foundation/dexon/ethdb"
 	"github.com/dexon-foundation/dexon/event"
+	"github.com/dexon-foundation/dexon/rlp"
 	"github.com/dexon-foundation/dexon/trie"
 )
 
@@ -200,7 +204,8 @@ func (dl *downloadTester) FastSyncCommitHead(hash common.Hash) error {
 }
 
 // InsertDexonHeaderChain injects a new batch of headers into the simulated chain.
-func (dl *downloadTester) InsertDexonHeaderChain(headers []*types.HeaderWithGovState, verifierCache *dexCore.TSigVerifierCache) (i int, err error) {
+func (dl *downloadTester) InsertDexonHeaderChain(headers []*types.HeaderWithGovState,
+	gov dexcon.GovernanceStateFetcher, verifierCache *dexCore.TSigVerifierCache) (i int, err error) {
 	dl.lock.Lock()
 	defer dl.lock.Unlock()
 
@@ -221,6 +226,29 @@ func (dl *downloadTester) InsertDexonHeaderChain(headers []*types.HeaderWithGovS
 		if _, ok := dl.ownHeaders[header.ParentHash]; !ok {
 			return i, errors.New("unknown parent")
 		}
+
+		// Verify witness
+		var coreBlock coreTypes.Block
+		if err := rlp.DecodeBytes(header.DexconMeta, &coreBlock); err != nil {
+			return i, err
+		}
+
+		var witnessBlockHash common.Hash
+		if err := rlp.DecodeBytes(coreBlock.Witness.Data, &witnessBlockHash); err != nil {
+			return i, err
+		}
+
+		if uint64(len(dl.ownHashes)) < coreBlock.Witness.Height+1 {
+			return i, errors.New("unknown witness")
+		}
+		h := dl.ownHeaders[dl.ownHashes[coreBlock.Witness.Height]]
+		if h == nil {
+			return i, errors.New("unknown witness")
+		}
+
+		if h.Hash() != witnessBlockHash {
+			return i, errors.New("witness root mismatch")
+		}
 		dl.ownHashes = append(dl.ownHashes, header.Hash())
 		dl.ownHeaders[header.Hash()] = header.Header
 	}
@@ -807,6 +835,7 @@ func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
 	missing := fsHeaderSafetyNet + MaxHeaderFetch + 1
 	fastAttackChain := chain.shorten(chain.len())
 	delete(fastAttackChain.headerm, fastAttackChain.chain[missing])
+
 	tester.newPeer("fast-attack", protocol, fastAttackChain)
 
 	if err := tester.sync("fast-attack", 0, mode); err == nil {
@@ -860,6 +889,43 @@ func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
 		}
 	}
 
+	// witness mismatch
+	realChain := chain.shorten(chain.len())
+	fakeChain := chain.shorten(chain.len())
+
+	for i := chain.len() - 100; i < chain.len(); i++ {
+		realHash := realChain.chain[i]
+		realHeader := realChain.headerm[realHash]
+		realBlock := realChain.blockm[realHash]
+		realReceipt := realChain.receiptm[realHash]
+		fakeHeader := types.CopyHeader(realHeader)
+		if i == chain.len()-100 {
+			fakeHeader.Root = common.Hash{}
+		} else {
+			fakeHeader.ParentHash = fakeChain.chain[i-1]
+		}
+
+		fakeBlock := types.NewBlock(fakeHeader, realBlock.Transactions(), realBlock.Uncles(), realReceipt)
+
+		fakeChain.chain[i] = fakeBlock.Hash()
+		fakeChain.blockm[fakeBlock.Hash()] = fakeBlock
+		fakeChain.headerm[fakeBlock.Hash()] = fakeBlock.Header()
+		fakeChain.receiptm[fakeBlock.Hash()] = realReceipt
+	}
+
+	tester.newPeer("mismatch-attack", protocol, fakeChain)
+	if err := tester.sync("mismatch-attack", 0, mode); err == nil {
+		t.Fatalf("succeeded block attacker synchronisation")
+	}
+	if head := tester.CurrentHeader().Number.Int64(); int(head) > 2*fsHeaderSafetyNet+MaxHeaderFetch {
+		t.Errorf("rollback head mismatch: have %v, want at most %v", head, 2*fsHeaderSafetyNet+MaxHeaderFetch)
+	}
+	if mode == FastSync {
+		if head := tester.CurrentBlock().NumberU64(); head != 0 {
+			t.Errorf("fast sync pivot block #%d not rolled back", head)
+		}
+	}
+
 	// synchronise with the valid peer and make sure sync succeeds. Since the last rollback
 	// should also disable fast syncing for this process, verify that we did a fresh full
 	// sync. Note, we can't assert anything about the receipts since we won't purge the
diff --git a/dex/downloader/testchain_test.go b/dex/downloader/testchain_test.go
index 810fb41b3..d96ebcfbf 100644
--- a/dex/downloader/testchain_test.go
+++ b/dex/downloader/testchain_test.go
@@ -17,11 +17,12 @@
 package downloader
 
 import (
+	"crypto/ecdsa"
 	"fmt"
 	"math/big"
 
 	"github.com/dexon-foundation/dexon/common"
-	"github.com/dexon-foundation/dexon/consensus/ethash"
+	"github.com/dexon-foundation/dexon/consensus/dexcon"
 	"github.com/dexon-foundation/dexon/core"
 	"github.com/dexon-foundation/dexon/core/state"
 	"github.com/dexon-foundation/dexon/core/types"
@@ -33,17 +34,17 @@ import (
 
 // Test chain parameters.
 var (
-	testKey, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
-	testAddress = crypto.PubkeyToAddress(testKey.PublicKey)
-	testDB      = ethdb.NewMemDatabase()
-	testGenesis = genesisBlockForTesting(testDB, testAddress, big.NewInt(1000000000))
+	testKey, _             = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+	testAddress            = crypto.PubkeyToAddress(testKey.PublicKey)
+	testDB                 = ethdb.NewMemDatabase()
+	testGenesis, testNodes = genesisBlockForTesting(testDB, testAddress, big.NewInt(1000000000))
 )
 
 // The common prefix of all test chains:
-var testChainBase = newTestChain(blockCacheItems+200, testGenesis)
+var testChainBase = newTestChain(blockCacheItems+200, testGenesis, testNodes)
 
 func genesisBlockForTesting(db ethdb.Database,
-	addr common.Address, balance *big.Int) *types.Block {
+	addr common.Address, balance *big.Int) (*types.Block, *dexcon.NodeSet) {
 	var (
 		// genesis node set
 		nodekey1, _ = crypto.HexToECDSA("3cf5bdee098cc34536a7b0e80d85e07a380efca76fc12136299b9e5ba24193c8")
@@ -87,11 +88,17 @@ func genesisBlockForTesting(db ethdb.Database,
 		},
 	}
 	genesis := gspec.MustCommit(db)
-	return genesis
+
+	signedCRS := []byte(gspec.Config.Dexcon.GenesisCRSText)
+	signer := types.NewEIP155Signer(gspec.Config.ChainID)
+	nodeSet := dexcon.NewNodeSet(uint64(0), signedCRS, signer,
+		[]*ecdsa.PrivateKey{nodekey1, nodekey2, nodekey3, nodekey4})
+	return genesis, nodeSet
 }
 
 type testChain struct {
 	genesis  *types.Block
+	nodes    *dexcon.NodeSet
 	chain    []common.Hash
 	headerm  map[common.Hash]*types.Header
 	blockm   map[common.Hash]*types.Block
@@ -99,23 +106,16 @@ type testChain struct {
 }
 
 // newTestChain creates a blockchain of the given length.
-func newTestChain(length int, genesis *types.Block) *testChain {
+func newTestChain(length int, genesis *types.Block, nodes *dexcon.NodeSet) *testChain {
 	tc := new(testChain).copy(length)
 	tc.genesis = genesis
 	tc.chain = append(tc.chain, genesis.Hash())
 	tc.headerm[tc.genesis.Hash()] = tc.genesis.Header()
 	tc.blockm[tc.genesis.Hash()] = tc.genesis
-	tc.generate(length-1, 0, genesis, false)
+	tc.generate(length-1, 0, genesis, nodes, false)
 	return tc
 }
 
-// makeFork creates a fork on top of the test chain.
-func (tc *testChain) makeFork(length int, heavy bool, seed byte) *testChain {
-	fork := tc.copy(tc.len() + length)
-	fork.generate(length, seed, tc.headBlock(), heavy)
-	return fork
-}
-
 // shorten creates a copy of the chain with the given length. It panics if the
 // length is longer than the number of available blocks.
 func (tc *testChain) shorten(length int) *testChain {
@@ -146,16 +146,113 @@ func (tc *testChain) copy(newlen int) *testChain {
 // the returned hash chain is ordered head->parent. In addition, every 22th block
 // contains a transaction and every 5th an uncle to allow testing correct block
 // reassembly.
-func (tc *testChain) generate(n int, seed byte, parent *types.Block, heavy bool) {
+func (tc *testChain) generate(n int, seed byte, parent *types.Block, nodes *dexcon.NodeSet, heavy bool) {
 	// start := time.Now()
 	// defer func() { fmt.Printf("test chain generated in %v\n", time.Since(start)) }()
 
-	blocks, receipts := core.GenerateChain(params.TestnetChainConfig, parent, ethash.NewFaker(), testDB, n, func(i int, block *core.BlockGen) {
+	engine := dexcon.NewFaker(testNodes)
+	govFetcher := newGovStateFetcher(state.NewDatabase(testDB))
+	govFetcher.SnapshotRound(0, tc.genesis.Root())
+	engine.SetGovStateFetcher(govFetcher)
+
+	round := uint64(0)
+	roundInterval := int(100)
+
+	addTx := func(block *core.DexonBlockGen, node *dexcon.Node, data []byte) {
+		nonce := block.TxNonce(node.Address())
+		tx := node.CreateGovTx(nonce, data)
+		block.AddTx(tx)
+	}
+
+	blocks, receipts := core.GenerateDexonChain(params.TestnetChainConfig, parent, engine, testDB, n, func(i int, block *core.DexonBlockGen) {
 		block.SetCoinbase(common.Address{seed})
-		// If a heavy chain is requested, delay blocks to raise difficulty
-		if heavy {
-			block.OffsetTime(-1)
+		if round == 0 {
+			switch i {
+			case 1:
+				testNodes.RunDKG(round, 2)
+				// Add DKG MasterPublicKeys
+				for _, node := range testNodes.Nodes(round) {
+					data, err := vm.PackAddDKGMasterPublicKey(round, node.MasterPublicKey(round))
+					if err != nil {
+						panic(err)
+					}
+					addTx(block, node, data)
+				}
+			case 2:
+				// Add DKG MPKReady
+				for _, node := range testNodes.Nodes(round) {
+					data, err := vm.PackAddDKGMPKReady(round, node.DKGMPKReady(round))
+					if err != nil {
+						panic(err)
+					}
+					addTx(block, node, data)
+				}
+			case 3:
+				// Add DKG Finalize
+				for _, node := range testNodes.Nodes(round) {
+					data, err := vm.PackAddDKGFinalize(round, node.DKGFinalize(round))
+					if err != nil {
+						panic(err)
+					}
+					addTx(block, node, data)
+				}
+			}
 		}
+
+		half := roundInterval / 2
+		switch i % roundInterval {
+		case 0:
+			if round > 0 {
+				node := testNodes.Nodes(round)[0]
+				data, err := vm.PackNotifyRoundHeight(round, uint64(i))
+				if err != nil {
+					panic(err)
+				}
+				addTx(block, node, data)
+			}
+		case half:
+			// Sign current CRS to geneate the next round CRS and propose it.
+			testNodes.SignCRS(round)
+			node := testNodes.Nodes(round)[0]
+			data, err := vm.PackProposeCRS(round, testNodes.SignedCRS(round+1))
+			if err != nil {
+				panic(err)
+			}
+			addTx(block, node, data)
+		case half + 1:
+			// Run the DKG for next round.
+			testNodes.RunDKG(round+1, 2)
+
+			// Add DKG MasterPublicKeys
+			for _, node := range testNodes.Nodes(round + 1) {
+				data, err := vm.PackAddDKGMasterPublicKey(round+1, node.MasterPublicKey(round+1))
+				if err != nil {
+					panic(err)
+				}
+				addTx(block, node, data)
+			}
+		case half + 2:
+			// Add DKG MPKReady
+			for _, node := range testNodes.Nodes(round + 1) {
+				data, err := vm.PackAddDKGMPKReady(round+1, node.DKGMPKReady(round+1))
+				if err != nil {
+					panic(err)
+				}
+				addTx(block, node, data)
+			}
+		case half + 3:
+			// Add DKG Finalize
+			for _, node := range testNodes.Nodes(round + 1) {
+				data, err := vm.PackAddDKGFinalize(round+1, node.DKGFinalize(round+1))
+				if err != nil {
+					panic(err)
+				}
+				addTx(block, node, data)
+			}
+		case roundInterval - 1:
+			round++
+		}
+
 		// Include transactions to the miner to make blocks more interesting.
 		if parent == tc.genesis && i%22 == 0 {
 			signer := types.MakeSigner(params.TestnetChainConfig, block.Number())
@@ -165,13 +262,6 @@ func (tc *testChain) generate(n int, seed byte, parent *types.Block, heavy bool)
 			}
 			block.AddTx(tx)
 		}
-		// if the block number is a multiple of 5, add a bonus uncle to the block
-		if i > 0 && i%5 == 0 {
-			block.AddUncle(&types.Header{
-				ParentHash: block.PrevBlock(i - 1).Hash(),
-				Number:     big.NewInt(block.Number().Int64() - 1),
-			})
-		}
 	})
 
 	// Convert the block-chain into a hash-chain and header/block maps
@@ -258,3 +348,30 @@ func (tc *testChain) hashToNumber(target common.Hash) (uint64, bool) {
 	}
 	return 0, false
 }
+
+type govStateFetcher struct {
+	db          state.Database
+	rootByRound map[uint64]common.Hash
+}
+
+func newGovStateFetcher(db state.Database) *govStateFetcher {
+	return &govStateFetcher{
+		db:          db,
+		rootByRound: make(map[uint64]common.Hash),
+	}
+}
+
+func (g *govStateFetcher) SnapshotRound(round uint64, root common.Hash) {
+	g.rootByRound[round] = root
+}
+
+func (g *govStateFetcher) GetGovStateHelperAtRound(round uint64) *vm.GovernanceStateHelper {
+	if root, ok := g.rootByRound[round]; ok {
+		s, err := state.New(root, g.db)
+		if err != nil {
+			panic(err)
+		}
+		return &vm.GovernanceStateHelper{s}
+	}
+	return nil
+}