/
prover.go
440 lines (386 loc) · 11.9 KB
/
prover.go
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package prover
import (
"context"
"errors"
"fmt"
"io"
"math"
"os"
"path/filepath"
"regexp"
"strconv"
"strings"
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/spacemeshos/merkle-tree"
"github.com/spacemeshos/merkle-tree/cache"
mshared "github.com/spacemeshos/merkle-tree/shared"
"go.uber.org/zap"
"go.uber.org/zap/zapcore"
"golang.org/x/exp/maps"
"github.com/spacemeshos/poet/logging"
"github.com/spacemeshos/poet/shared"
)
const (
// MerkleMinCacheLayer set the min layer in which all layers above will be cached, in addition to the base layer.
MerkleMinCacheLayer = 0
// LowestMerkleMinMemoryLayer set the lowest-allowed layer in which all layers above will be cached in-memory.
LowestMerkleMinMemoryLayer = 1
// The rate, in leaves, in which the proof generation state snapshot will be saved to disk
// to allow potential crash recovery.
hardShutdownCheckpointRate = 1 << 24
)
type TreeConfig struct {
MinMemoryLayer uint
Datadir string
FileWriterBufSize uint
}
type persistFunc func(ctx context.Context, treeCache *cache.Writer, nextLeafId uint64) error
// GenerateProof generates the Proof of Sequential Work. It stops when the given deadline is reached.
func GenerateProof(
ctx context.Context,
leavesCounter prometheus.Counter,
treeCfg TreeConfig,
labelHashFunc func(data []byte) []byte,
merkleHashFunc merkle.HashFunc,
deadline time.Time,
securityParam uint8,
persist persistFunc,
) (uint64, *shared.MerkleProof, error) {
tree, treeCache, err := makeProofTree(treeCfg, merkleHashFunc)
if err != nil {
return 0, nil, err
}
defer treeCache.Close()
return generateProof(ctx, leavesCounter, labelHashFunc, tree, treeCache, deadline, 0, securityParam, persist)
}
// GenerateProofRecovery recovers proof generation, from a given 'nextLeafID'.
func GenerateProofRecovery(
ctx context.Context,
leavesCounter prometheus.Counter,
treeCfg TreeConfig,
labelHashFunc func(data []byte) []byte,
merkleHashFunc merkle.HashFunc,
deadline time.Time,
securityParam uint8,
nextLeafID uint64,
persist persistFunc,
) (uint64, *shared.MerkleProof, error) {
treeCache, tree, err := makeRecoveryProofTree(ctx, treeCfg, merkleHashFunc, nextLeafID)
if err != nil {
return 0, nil, err
}
defer treeCache.Close()
return generateProof(
ctx,
leavesCounter,
labelHashFunc,
tree,
treeCache,
deadline,
nextLeafID,
securityParam,
persist,
)
}
// GenerateProofWithoutPersistency calls GenerateProof with disabled persistency functionality.
// Tree recovery will not be possible. Meant to be used for testing purposes only.
// It doesn't expose metrics too.
func GenerateProofWithoutPersistency(
ctx context.Context,
treeCfg TreeConfig,
labelHashFunc func(data []byte) []byte,
merkleHashFunc merkle.HashFunc,
deadline time.Time,
securityParam uint8,
) (uint64, *shared.MerkleProof, error) {
leavesCounter := prometheus.NewCounter(prometheus.CounterOpts{})
return GenerateProof(
ctx,
leavesCounter,
treeCfg,
labelHashFunc,
merkleHashFunc,
deadline,
securityParam,
func(context.Context, *cache.Writer, uint64) error { return nil },
)
}
// Create a new merkle tree for proof generation.
func makeProofTree(treeCfg TreeConfig, merkleHashFunc merkle.HashFunc) (*merkle.Tree, *cache.Writer, error) {
// Make sure there are no existing layer files.
layersFiles, err := getLayersFiles(treeCfg.Datadir)
if err != nil {
return nil, nil, err
}
if len(layersFiles) > 0 {
return nil, nil, fmt.Errorf("datadir is not empty. %v layer files exist", maps.Values(layersFiles))
}
minMemoryLayer := max(treeCfg.MinMemoryLayer, LowestMerkleMinMemoryLayer)
treeCache := cache.NewWriter(
cache.Combine(
cache.SpecificLayersPolicy(map[uint]bool{0: true}),
cache.MinHeightPolicy(MerkleMinCacheLayer)),
GetLayerFactory(minMemoryLayer, treeCfg.Datadir, treeCfg.FileWriterBufSize),
)
tree, err := merkle.NewTreeBuilder().WithHashFunc(merkleHashFunc).WithCacheWriter(treeCache).Build()
if err != nil {
return nil, nil, err
}
return tree, treeCache, nil
}
// Recover merkle tree from existing cache files.
func makeRecoveryProofTree(
ctx context.Context,
treeCfg TreeConfig,
merkleHashFunc merkle.HashFunc,
nextLeafID uint64,
) (*cache.Writer, *merkle.Tree, error) {
// Don't use memory cache. Just utilize the existing files cache.
layerFactory := GetLayerFactory(math.MaxUint, treeCfg.Datadir, treeCfg.FileWriterBufSize)
layersFiles, err := getLayersFiles(treeCfg.Datadir)
if err != nil {
return nil, nil, err
}
// Validate that layer 0 exists.
if _, ok := layersFiles[0]; !ok {
return nil, nil, errors.New("layer 0 cache file is missing")
}
var topLayer uint
parkedNodesMap := make(map[uint][]byte)
// Validate structure.
for layer, file := range layersFiles {
topLayer = max(topLayer, layer)
readWriter, err := layerFactory(layer)
if err != nil {
return nil, nil, err
}
defer readWriter.Close()
width, err := readWriter.Width()
if err != nil {
return nil, nil, err
}
// Each incremental layer divides the base layer by 2.
expectedWidth := nextLeafID >> layer
// If file is longer than expected, truncate the file.
if expectedWidth < width {
filename := filepath.Join(treeCfg.Datadir, file)
logging.FromContext(ctx).
Warn("Recovery: cache file width is ahead of the last known merkle tree state. Truncating file",
zap.String("file", filename),
zap.Uint("layer", layer),
zap.Uint64("expected", expectedWidth),
zap.Uint64("actual", width))
if err := os.Truncate(filename, int64(expectedWidth*merkle.NodeSize)); err != nil {
return nil, nil, fmt.Errorf("failed to truncate file: %v", err)
}
}
// If file is shorter than expected, proof cannot be recovered.
if expectedWidth > width {
return nil, nil, fmt.Errorf(
"layer %d cache file invalid width. expected: %d, found: %d",
layer,
expectedWidth,
width,
)
}
// recover parked node
if expectedWidth%2 != 0 {
if err := readWriter.Seek(expectedWidth - 1); err != nil {
return nil, nil, fmt.Errorf("seeking to parked node in layer %d: %w", layer, err)
}
parkedNode, err := readWriter.ReadNext()
if err != nil {
return nil, nil, fmt.Errorf("reading parked node in layer %d: %w", layer, err)
}
parkedNodesMap[layer] = parkedNode
}
}
// turn parkedNodesMap into a slice ordered by key
var parkedNodes [][]byte
for layer := 0; layer < len(layersFiles); layer++ {
if node, ok := parkedNodesMap[uint(layer)]; ok {
parkedNodes = append(parkedNodes, node)
} else {
parkedNodes = append(parkedNodes, []byte{})
}
}
layerReader, err := layerFactory(topLayer)
if err != nil {
return nil, nil, err
}
defer layerReader.Close()
memCachedParkedNodes, readCache, err := recoverMemCachedParkedNodes(layerReader, merkleHashFunc)
if err != nil {
return nil, nil, fmt.Errorf("recoveing parked nodes from top layer of disk-cache: %w", err)
}
parkedNodes = append(parkedNodes, memCachedParkedNodes...)
logging.FromContext(ctx).Debug("recovered parked nodes",
zap.Array("nodes", zapcore.ArrayMarshalerFunc(func(enc zapcore.ArrayEncoder) error {
for _, node := range parkedNodes {
enc.AppendString(fmt.Sprintf("%X", node))
}
return nil
})))
layers := make(map[uint]bool)
for layer := range layersFiles {
layers[layer] = true
}
treeCache := cache.NewWriter(
cache.SpecificLayersPolicy(layers),
layerFactory)
// populate layers from topLayer up with layers from the rebuilt tree
rebuildLayers := readCache.Layers()
for layer, reader := range rebuildLayers {
if layer == 0 {
continue
}
treeCache.SetLayer(topLayer+uint(layer), reader)
}
tree, err := merkle.NewTreeBuilder().
WithHashFunc(merkleHashFunc).
WithCacheWriter(treeCache).
Build()
if err != nil {
return nil, nil, err
}
if err := tree.SetParkedNodes(parkedNodes); err != nil {
return nil, nil, err
}
return treeCache, tree, nil
}
func sequentialWork(
ctx context.Context,
leavesCounter prometheus.Counter,
labelHashFunc func(data []byte) []byte,
tree *merkle.Tree,
treeCache *cache.Writer,
end time.Time,
nextLeafID uint64,
persist persistFunc,
) (uint64, error) {
var parkedNodes [][]byte
makeLabel := shared.MakeLabelFunc()
finished := time.NewTimer(time.Until(end))
defer finished.Stop()
leavesCounter.Add(float64(nextLeafID))
for {
// Generate the next leaf.
parkedNodes = tree.GetParkedNodes(parkedNodes[:0])
err := tree.AddLeaf(makeLabel(labelHashFunc, nextLeafID, parkedNodes))
if err != nil {
return 0, err
}
nextLeafID++
leavesCounter.Inc()
select {
case <-ctx.Done():
if err := persist(ctx, treeCache, nextLeafID); err != nil {
return 0, fmt.Errorf("persisting execution state: %w", err)
}
return nextLeafID, ctx.Err()
case <-finished.C:
if err := persist(ctx, treeCache, nextLeafID); err != nil {
return 0, fmt.Errorf("persisting execution state: %w", err)
}
return nextLeafID, nil
default:
}
if nextLeafID%hardShutdownCheckpointRate == 0 {
if err := persist(ctx, treeCache, nextLeafID); err != nil {
return 0, err
}
}
}
}
func generateProof(
ctx context.Context,
leavesCounter prometheus.Counter,
labelHashFunc func(data []byte) []byte,
tree *merkle.Tree,
treeCache *cache.Writer,
end time.Time,
nextLeafID uint64,
securityParam uint8,
persist persistFunc,
) (uint64, *shared.MerkleProof, error) {
logger := logging.FromContext(ctx)
logger.Info("generating proof", zap.Time("end", end), zap.Uint64("nextLeafID", nextLeafID))
leaves, err := sequentialWork(ctx, leavesCounter, labelHashFunc, tree, treeCache, end, nextLeafID, persist)
if err != nil {
return leaves, nil, err
}
logger.Sugar().Infof("merkle tree construction finished with %d leaves, generating proof...", leaves)
started := time.Now()
root := tree.Root()
cacheReader, err := treeCache.GetReader()
if err != nil {
return 0, nil, err
}
provenLeafIndices := shared.FiatShamir(root, leaves, securityParam)
_, provenLeaves, proofNodes, err := merkle.GenerateProof(provenLeafIndices, cacheReader)
if err != nil {
return 0, nil, err
}
logger.Sugar().Infof("proof generated, it took: %v", time.Since(started))
return leaves, &shared.MerkleProof{
Root: root,
ProvenLeaves: provenLeaves,
ProofNodes: proofNodes,
}, nil
}
func getLayersFiles(datadir string) (map[uint]string, error) {
entries, err := os.ReadDir(datadir)
if err != nil {
return nil, err
}
files := make(map[uint]string, 0)
for _, entry := range entries {
prefix := "layercache_"
name := entry.Name()
if !entry.IsDir() && strings.HasPrefix(name, prefix) {
re := regexp.MustCompile("layercache_(.*).bin")
matches := re.FindStringSubmatch(name)
if len(matches) != 2 {
return nil, fmt.Errorf("invalid layer cache filename: %v", name)
}
layerNum, err := strconv.Atoi(matches[1])
if err != nil {
return nil, fmt.Errorf("invalid layer cache filename: %v", name)
}
files[uint(layerNum)] = name
}
}
return files, nil
}
// build a small tree with the nodes from the top layer of the cache as leafs.
// this tree will be used to get parked nodes for the merkle tree.
func recoverMemCachedParkedNodes(
layerReader mshared.LayerReader,
merkleHashFunc merkle.HashFunc,
) ([][]byte, mshared.CacheReader, error) {
recoveryTreeCache := cache.NewWriter(func(uint) bool { return true }, GetLayerFactory(0, "", 0))
tree, err := merkle.NewTreeBuilder().WithHashFunc(merkleHashFunc).WithCacheWriter(recoveryTreeCache).Build()
if err != nil {
return nil, nil, err
}
// append nodes as leafs
for {
node, err := layerReader.ReadNext()
if errors.Is(err, io.EOF) {
break
}
if err != nil {
return nil, nil, fmt.Errorf("reading node from top layer of disk-cache: %w", err)
}
if err := tree.AddLeaf(node); err != nil {
return nil, nil, fmt.Errorf("adding node to small tree: %w", err)
}
}
rdr, err := recoveryTreeCache.GetReader()
if err != nil {
return nil, nil, fmt.Errorf("getting reader for small tree: %w", err)
}
// the first parked node is for the leaves from the layerReader.
return tree.GetParkedNodes(nil)[1:], rdr, nil
}