snapshotter/tests: verify snapdb post-state against trie (#20812)

* core/state/snapshot: basic trie-to-hash implementation

* tests: validate snapshot after test

* core/state/snapshot: fix review concerns

core/blockchain.go

@@ -520,6 +520,15 @@ func (bc *BlockChain) CurrentBlock() *types.Block {
 	return bc.currentBlock.Load().(*types.Block)
 }
 
+// Snapshot returns the blockchain snapshot tree. This method is mainly used for
+// testing, to make it possible to verify the snapshot after execution.
+//
+// Warning: There are no guarantees about the safety of using the returned 'snap' if the
+// blockchain is simultaneously importing blocks, so take care.
+func (bc *BlockChain) Snapshot() *snapshot.Tree {
+	return bc.snaps
+}
+
 // CurrentFastBlock retrieves the current fast-sync head block of the canonical
 // chain. The block is retrieved from the blockchain's internal cache.
 func (bc *BlockChain) CurrentFastBlock() *types.Block {

core/state/snapshot/conversion.go

@@ -0,0 +1,114 @@
+// Copyright 2020 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package snapshot
+
+import (
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb/memorydb"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+// conversionAccount is used for converting between full and slim format. When
+// doing this, we can consider 'balance' as a byte array, as it has already
+// been converted from big.Int into an rlp-byteslice.
+type conversionAccount struct {
+	Nonce    uint64
+	Balance  []byte
+	Root     []byte
+	CodeHash []byte
+}
+
+// SlimToFull converts data on the 'slim RLP' format into the full RLP-format
+func SlimToFull(data []byte) ([]byte, error) {
+	acc := &conversionAccount{}
+	if err := rlp.DecodeBytes(data, acc); err != nil {
+		return nil, err
+	}
+	if len(acc.Root) == 0 {
+		acc.Root = emptyRoot[:]
+	}
+	if len(acc.CodeHash) == 0 {
+		acc.CodeHash = emptyCode[:]
+	}
+	fullData, err := rlp.EncodeToBytes(acc)
+	if err != nil {
+		return nil, err
+	}
+	return fullData, nil
+}
+
+// trieKV represents a trie key-value pair
+type trieKV struct {
+	key   common.Hash
+	value []byte
+}
+
+type trieGeneratorFn func(in chan (trieKV), out chan (common.Hash))
+
+// GenerateTrieRoot takes an account iterator and reproduces the root hash.
+func GenerateTrieRoot(it AccountIterator) common.Hash {
+	return generateTrieRoot(it, stdGenerate)
+}
+
+func generateTrieRoot(it AccountIterator, generatorFn trieGeneratorFn) common.Hash {
+	var (
+		in  = make(chan trieKV)      // chan to pass leaves
+		out = make(chan common.Hash) // chan to collect result
+		wg  sync.WaitGroup
+	)
+	wg.Add(1)
+	go func() {
+		generatorFn(in, out)
+		wg.Done()
+	}()
+	// Feed leaves
+	start := time.Now()
+	logged := time.Now()
+	accounts := 0
+	for it.Next() {
+		slimData := it.Account()
+		fullData, _ := SlimToFull(slimData)
+		l := trieKV{it.Hash(), fullData}
+		in <- l
+		if time.Since(logged) > 8*time.Second {
+			log.Info("Generating trie hash from snapshot",
+				"at", l.key, "accounts", accounts, "elapsed", time.Since(start))
+			logged = time.Now()
+		}
+		accounts++
+	}
+	close(in)
+	result := <-out
+	log.Info("Generated trie hash from snapshot", "accounts", accounts, "elapsed", time.Since(start))
+	wg.Wait()
+	return result
+}
+
+// stdGenerate is a very basic hexary trie builder which uses the same Trie
+// as the rest of geth, with no enhancements or optimizations
+func stdGenerate(in chan (trieKV), out chan (common.Hash)) {
+	t, _ := trie.New(common.Hash{}, trie.NewDatabase(memorydb.New()))
+	for leaf := range in {
+		t.TryUpdate(leaf.key[:], leaf.value)
+	}
+	out <- t.Hash()
+}

tests/block_test_util.go

@@ -32,6 +32,7 @@ import (
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/state/snapshot"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/params"
@@ -144,6 +145,19 @@ func (t *BlockTest) Run(snapshotter bool) error {
 	if err = t.validatePostState(newDB); err != nil {
 		return fmt.Errorf("post state validation failed: %v", err)
 	}
+	// Cross-check the snapshot-to-hash against the trie hash
+	if snapshotter {
+		snapTree := chain.Snapshot()
+		root := chain.CurrentBlock().Root()
+		it, err := snapTree.AccountIterator(root, common.Hash{})
+		if err != nil {
+			return fmt.Errorf("Could not create iterator for root %x: %v", root, err)
+		}
+		generatedRoot := snapshot.GenerateTrieRoot(it)
+		if generatedRoot != root {
+			return fmt.Errorf("Snapshot corruption, got %d exp %d", generatedRoot, root)
+		}
+	}
 	return t.validateImportedHeaders(chain, validBlocks)
 }