package beacon import ( "context" "fmt" "github.com/Secured-Finance/dione/lib" "github.com/sirupsen/logrus" "github.com/Secured-Finance/dione/types" ) type Response struct { Entry types.BeaconEntry Err error } type Schedule []BeaconPoint func (bs Schedule) BeaconForEpoch(e types.TaskEpoch) RandomBeacon { for i := len(bs) - 1; i >= 0; i-- { bp := bs[i] if e >= bp.Start { return bp.Beacon } } return bs[0].Beacon } type BeaconPoint struct { Start types.TaskEpoch Beacon RandomBeacon } // RandomBeacon represents a system that provides randomness. // Other components interrogate the RandomBeacon to acquire randomness that's // valid for a specific chain epoch. Also to verify beacon entries that have // been posted on chain. type RandomBeacon interface { Entry(context.Context, uint64) <-chan Response VerifyEntry(types.BeaconEntry, types.BeaconEntry) error MaxBeaconRoundForEpoch(types.TaskEpoch) uint64 } func ValidateTaskValues(bSchedule Schedule, t *types.DioneTask, parentEpoch types.TaskEpoch, prevEntry types.BeaconEntry) error { { parentBeacon := bSchedule.BeaconForEpoch(parentEpoch) currBeacon := bSchedule.BeaconForEpoch(t.Epoch) if parentBeacon != currBeacon { if len(t.BeaconEntries) != 2 { return fmt.Errorf("expected two beacon entries at beacon fork, got %d", len(t.BeaconEntries)) } err := currBeacon.VerifyEntry(t.BeaconEntries[1], t.BeaconEntries[0]) if err != nil { return fmt.Errorf("beacon at fork point invalid: (%v, %v): %w", t.BeaconEntries[1], t.BeaconEntries[0], err) } return nil } } // TODO: fork logic b := bSchedule.BeaconForEpoch(t.Epoch) maxRound := b.MaxBeaconRoundForEpoch(t.Epoch) if maxRound == prevEntry.Round { if len(t.BeaconEntries) != 0 { return fmt.Errorf("expected not to have any beacon entries in this task, got %d", len(t.BeaconEntries)) } return nil } if len(t.BeaconEntries) == 0 { return fmt.Errorf("expected to have beacon entries in this task, but didn't find any") } last := t.BeaconEntries[len(t.BeaconEntries)-1] if last.Round != maxRound { return fmt.Errorf("expected final beacon entry in task to be at round %d, got %d", maxRound, last.Round) } for i, e := range t.BeaconEntries { if err := b.VerifyEntry(e, prevEntry); err != nil { return fmt.Errorf("beacon entry %d (%d - %x (%d)) was invalid: %w", i, e.Round, e.Data, len(e.Data), err) } prevEntry = e } return nil } func BeaconEntriesForTask(ctx context.Context, bSchedule Schedule, epoch types.TaskEpoch, parentEpoch types.TaskEpoch, prev types.BeaconEntry) ([]types.BeaconEntry, error) { { parentBeacon := bSchedule.BeaconForEpoch(parentEpoch) currBeacon := bSchedule.BeaconForEpoch(epoch) if parentBeacon != currBeacon { // Fork logic round := currBeacon.MaxBeaconRoundForEpoch(epoch) out := make([]types.BeaconEntry, 2) rch := currBeacon.Entry(ctx, round-1) res := <-rch if res.Err != nil { return nil, fmt.Errorf("getting entry %d returned error: %w", round-1, res.Err) } out[0] = res.Entry rch = currBeacon.Entry(ctx, round) res = <-rch if res.Err != nil { return nil, fmt.Errorf("getting entry %d returned error: %w", round, res.Err) } out[1] = res.Entry return out, nil } } beacon := bSchedule.BeaconForEpoch(epoch) start := lib.Clock.Now() maxRound := beacon.MaxBeaconRoundForEpoch(epoch) if maxRound == prev.Round { return nil, nil } // TODO: this is a sketchy way to handle the genesis block not having a beacon entry if prev.Round == 0 { prev.Round = maxRound - 1 } cur := maxRound var out []types.BeaconEntry for cur > prev.Round { rch := beacon.Entry(ctx, cur) select { case resp := <-rch: if resp.Err != nil { return nil, fmt.Errorf("beacon entry request returned error: %w", resp.Err) } out = append(out, resp.Entry) cur = resp.Entry.Round - 1 case <-ctx.Done(): return nil, fmt.Errorf("context timed out waiting on beacon entry to come back for epoch %d: %w", epoch, ctx.Err()) } } logrus.Debug("fetching beacon entries", "took", lib.Clock.Since(start), "numEntries", len(out)) reverse(out) return out, nil } func reverse(arr []types.BeaconEntry) { for i := 0; i < len(arr)/2; i++ { arr[i], arr[len(arr)-(1+i)] = arr[len(arr)-(1+i)], arr[i] } }