package drand import ( "bytes" "context" "fmt" "sync" "time" "github.com/Secured-Finance/dione/beacon" "github.com/drand/drand/chain" "github.com/drand/drand/client" httpClient "github.com/drand/drand/client/http" libp2pClient "github.com/drand/drand/lp2p/client" "github.com/drand/kyber" "github.com/sirupsen/logrus" pubsub "github.com/libp2p/go-libp2p-pubsub" "github.com/Secured-Finance/dione/config" "github.com/Secured-Finance/dione/lib" types "github.com/Secured-Finance/dione/types" ) // DrandRes structure representing response from drand network type DrandRes struct { // PreviousSig is the previous signature generated PreviousSig []byte // Round is the round number this beacon is tied to Round uint64 // Signature is the BLS deterministic signature over Round || PreviousRand Signature []byte // Randomness for specific round generated by Drand Randomness []byte } type DrandBeacon struct { DrandClient client.Client PublicKey kyber.Point Interval time.Duration chainGenesisTime uint64 chainRoundTime uint64 drandGenesisTime uint64 cacheLock sync.Mutex localCache map[uint64]types.BeaconEntry } func NewDrandBeacon(genesisTs, interval uint64, ps *pubsub.PubSub) (*DrandBeacon, error) { cfg := config.NewDrandConfig() drandChain, err := chain.InfoFromJSON(bytes.NewReader([]byte(cfg.ChainInfo))) if err != nil { return nil, fmt.Errorf("unable to unmarshal drand chain info: %w", err) } var clients []client.Client for _, url := range cfg.Servers { client, err := httpClient.NewWithInfo(url, drandChain, nil) if err != nil { return nil, fmt.Errorf("could not create http drand client: %w", err) } clients = append(clients, client) } opts := []client.Option{ client.WithChainInfo(drandChain), client.WithCacheSize(1024), client.WithAutoWatch(), } if ps != nil { opts = append(opts, libp2pClient.WithPubsub(ps)) } else { logrus.Info("Initiated drand with PubSub") } drandClient, err := client.Wrap(clients, opts...) if err != nil { return nil, fmt.Errorf("Couldn't create Drand clients") } db := &DrandBeacon{ DrandClient: drandClient, localCache: make(map[uint64]types.BeaconEntry), } db.PublicKey = drandChain.PublicKey db.Interval = drandChain.Period db.drandGenesisTime = uint64(drandChain.GenesisTime) db.chainRoundTime = interval db.chainGenesisTime = genesisTs return db, nil } func (db *DrandBeacon) Entry(ctx context.Context, round uint64) <-chan beacon.BeaconResult { out := make(chan beacon.BeaconResult, 1) if round != 0 { be := db.getCachedValue(round) if be != nil { out <- beacon.BeaconResult{Entry: *be} close(out) return out } } go func() { start := lib.Clock.Now() logrus.Info("start fetching randomness", "round", round) resp, err := db.DrandClient.Get(ctx, round) var br beacon.BeaconResult if err != nil { br.Err = fmt.Errorf("drand failed Get request: %w", err) } else { br.Entry.Round = resp.Round() br.Entry.Data = resp.Signature() } logrus.Info("done fetching randomness", "round", round, "took", lib.Clock.Since(start)) out <- br close(out) }() return out } func (db *DrandBeacon) cacheValue(res types.BeaconEntry) { db.cacheLock.Lock() defer db.cacheLock.Unlock() db.localCache[res.Round] = res } func (db *DrandBeacon) getCachedValue(round uint64) *types.BeaconEntry { db.cacheLock.Lock() defer db.cacheLock.Unlock() v, ok := db.localCache[round] if !ok { return nil } return &v } func (db *DrandBeacon) VerifyEntry(curr, prev types.BeaconEntry) error { if prev.Round == 0 { return nil } if be := db.getCachedValue(curr.Round); be != nil { return nil } b := &chain.Beacon{ PreviousSig: prev.Data, Round: curr.Round, Signature: curr.Data, } err := chain.VerifyBeacon(db.PublicKey, b) if err == nil { db.cacheValue(curr) } return err } func (db *DrandBeacon) LatestBeaconRound() uint64 { latestDround, err := db.DrandClient.Get(context.TODO(), 0) if err != nil { logrus.Errorf("failed to get latest drand round: %w", err) } return latestDround.Round() } var _ beacon.BeaconAPI = (*DrandBeacon)(nil)