1 files changed, 200 insertions, 0 deletions
diff --git a/internal/monitor/tail.go b/internal/monitor/tail.go
new file mode 100644
index 0000000..0e16476
--- /dev/null
+++ b/internal/monitor/tail.go
@@ -0,0 +1,200 @@
+package monitor
+
+import (
+	"context"
+	"crypto/sha256"
+	"fmt"
+	"sync"
+	"time"
+
+	ct "github.com/google/certificate-transparency-go"
+	"github.com/google/certificate-transparency-go/client"
+	"github.com/google/certificate-transparency-go/scanner"
+	"gitlab.torproject.org/rgdd/ct/pkg/merkle"
+)
+
+type tail struct {
+	cfg     Config
+	matcher Matcher
+	scanner scanner.LogClient
+	checker client.CheckLogClient
+}
+
+func (t *tail) run(ctx context.Context, mon MonitoredLog, eventCh chan Event, errorCh chan error) {
+	chunkCh := make(chan *chunk)
+	defer close(chunkCh)
+
+	mctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	var wg sync.WaitGroup
+	defer wg.Wait()
+
+	callback := func(eb scanner.EntryBatch) {
+		c := chunk{startIndex: uint64(eb.Start)}
+		for i := 0; i < len(eb.Entries); i++ {
+			c.leafHashes = append(c.leafHashes, merkle.HashLeafNode(eb.Entries[i].LeafInput))
+			match, err := t.matcher.Match(eb.Entries[i].LeafInput, eb.Entries[i].ExtraData)
+			if err != nil {
+				c.errors = append(c.errors, fmt.Errorf("while processing index %d for %s: %v", i, mon.Config.URL, err))
+				continue
+			}
+			if !match {
+				continue
+			}
+
+			c.matches = append(c.matches, LogEntry{
+				LeafIndex: c.startIndex + uint64(i),
+				LeafData:  eb.Entries[i].LeafInput,
+				ExtraData: eb.Entries[i].ExtraData,
+			})
+		}
+
+		chunkCh <- &c
+	}
+
+	fetcher := scanner.NewFetcher(t.scanner, &scanner.FetcherOptions{
+		BatchSize:     int(t.cfg.BatchSize),
+		StartIndex:    int64(mon.State.NextIndex),
+		ParallelFetch: int(t.cfg.NumWorkers),
+		Continuous:    true, // FIXME: don't set this for read-only log
+	})
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		defer cancel()
+		fetcher.Run(mctx, callback)
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		defer cancel()
+		t.sequence(mctx, mon, eventCh, errorCh, chunkCh)
+	}()
+}
+
+func (t *tail) sequence(ctx context.Context, mon MonitoredLog, eventCh chan Event, errorCh chan error, chunkCh chan *chunk) {
+	state := mon.State
+	heap := newChunks()
+	for {
+		select {
+		case <-ctx.Done():
+			return // FIXME: check if we can pop something before return
+		case c := <-chunkCh:
+			heap.push(c)
+			if heap.gap(state.NextIndex) {
+				continue
+			}
+			c = heap.pop()
+			if len(c.matches) == 0 && len(c.leafHashes) < int(t.cfg.ChunkSize) {
+				heap.push(c)
+				continue // FIXME: don't trigger if we havn't run nextState for too long
+			}
+			nextState, err := t.nextState(ctx, state, c)
+			if err != nil {
+				errorCh <- err
+				heap.push(c)
+				continue
+			}
+
+			state = nextState
+			eventCh <- Event{State: state, Matches: c.matches, Errors: c.errors}
+		}
+	}
+}
+
+func (t *tail) nextState(ctx context.Context, state State, c *chunk) (State, error) {
+	newState, err := t.nextConsistentState(ctx, state)
+	if err != nil {
+		return State{}, err
+	}
+	newState, err = t.nextIncludedState(ctx, newState, c)
+	if err != nil {
+		return State{}, err
+	}
+	return newState, nil
+}
+
+func (t *tail) nextConsistentState(ctx context.Context, state State) (State, error) {
+	sth, err := getSignedTreeHead(ctx, t.checker)
+	if err != nil {
+		return State{}, fmt.Errorf("%s: get-sth: %v", t.checker.BaseURI(), err)
+	}
+	sth.LogID = state.SignedTreeHead.LogID
+	oldSize := state.TreeSize
+	oldRoot := state.SHA256RootHash
+	newSize := sth.TreeSize
+	newRoot := sth.SHA256RootHash
+
+	proof, err := getConsistencyProof(ctx, t.checker, oldSize, newSize)
+	if err != nil {
+		return State{}, fmt.Errorf("%s: get-consistency: %v", t.checker.BaseURI(), err)
+	}
+	if err := merkle.VerifyConsistency(oldSize, newSize, oldRoot, newRoot, unslice(proof)); err != nil {
+		return State{}, fmt.Errorf("%s: verify consistency: %v", t.checker.BaseURI(), err)
+	}
+
+	return State{SignedTreeHead: *sth, NextIndex: state.NextIndex}, nil
+}
+
+func (t *tail) nextIncludedState(ctx context.Context, state State, c *chunk) (State, error) {
+	leafHash := c.leafHashes[0]
+	oldSize := state.NextIndex + uint64(len(c.leafHashes))
+	iproof, err := getInclusionProof(ctx, t.checker, leafHash, oldSize) // FIXME: set leaf index in ctx to hack into tile API
+	if err != nil {
+		return State{}, fmt.Errorf("%s: get-inclusion: %v", t.checker.BaseURI(), err)
+	}
+	if got, want := uint64(iproof.LeafIndex), state.NextIndex; got != want {
+		return State{}, fmt.Errorf("%s: wrong index for get-inclusion proof query %x:%d", t.checker.BaseURI(), leafHash[:], oldSize)
+	}
+	oldRoot, err := merkle.TreeHeadFromRangeProof(c.leafHashes, state.NextIndex, unslice(iproof.AuditPath))
+	if err != nil {
+		return State{}, fmt.Errorf("%s: range proof: %v", t.checker.BaseURI(), err)
+	}
+
+	newSize := state.TreeSize
+	newRoot := state.SHA256RootHash
+	cproof, err := getConsistencyProof(ctx, t.checker, oldSize, newSize)
+	if err != nil {
+		return State{}, fmt.Errorf("%s: get-consistency: %v", t.checker.BaseURI(), err)
+	}
+	if err := merkle.VerifyConsistency(oldSize, newSize, oldRoot, newRoot, unslice(cproof)); err != nil {
+		return State{}, fmt.Errorf("%s: verify consistency: %v", t.checker.BaseURI(), err)
+	}
+
+	state.NextIndex += uint64(len(c.leafHashes))
+	return state, nil
+}
+
+func getInclusionProof(ctx context.Context, cli client.CheckLogClient, leafHash [sha256.Size]byte, size uint64) (*ct.GetProofByHashResponse, error) {
+	rctx, cancel := context.WithTimeout(ctx, 10*time.Second)
+	defer cancel()
+	return cli.GetProofByHash(rctx, leafHash[:], size)
+}
+
+func getConsistencyProof(ctx context.Context, cli client.CheckLogClient, oldSize, newSize uint64) ([][]byte, error) {
+	if oldSize == 0 || oldSize >= newSize {
+		return [][]byte{}, nil
+	}
+	rctx, cancel := context.WithTimeout(ctx, 10*time.Second)
+	defer cancel()
+	return cli.GetSTHConsistency(rctx, oldSize, newSize)
+}
+
+func getSignedTreeHead(ctx context.Context, cli client.CheckLogClient) (*ct.SignedTreeHead, error) {
+	rctx, cancel := context.WithTimeout(ctx, 10*time.Second)
+	defer cancel()
+	return cli.GetSTH(rctx)
+}
+
+func unslice(hashes [][]byte) [][sha256.Size]byte {
+	var ret [][sha256.Size]byte
+	for _, hash := range hashes {
+		var h [sha256.Size]byte
+		copy(h[:], hash)
+		ret = append(ret, h)
+	}
+	return ret
+}