Ensure that when a cached torrent is used, the info hash is correct

diff --git a/client.go b/client.go
index be352eac7012bec4ab3f18222a8e27812c48f35f..24af34da4f8c636e92ac1a654fae409e525c9dc4 100644 (file)
--- a/client.go
+++ b/client.go
@@ -1378,6 +1378,10 @@ func (cl *Client) saveTorrentFile(t *torrent) error {
        if err != nil {
                return fmt.Errorf("error marshalling metainfo: %s", err)
        }
+       mi, _ := cl.torrentCacheMetaInfo(t.InfoHash)
+       if !bytes.Equal(mi.Info.Hash, t.InfoHash[:]) {
+               log.Fatalf("%x != %x", mi.Info.Hash, t.InfoHash[:])
+       }
        return nil
 }
 
@@ -1526,12 +1530,38 @@ func (me Torrent) ReadAt(p []byte, off int64) (n int, err error) {
        return me.cl.TorrentReadAt(me.InfoHash, off, p)
 }
 
+func (cl *Client) torrentCacheMetaInfo(ih InfoHash) (mi *metainfo.MetaInfo, err error) {
+       f, err := os.Open(cl.torrentFileCachePath(ih))
+       if err != nil {
+               if os.IsNotExist(err) {
+                       err = nil
+               }
+               return
+       }
+       defer f.Close()
+       dec := bencode.NewDecoder(f)
+       err = dec.Decode(&mi)
+       if err != nil {
+               return
+       }
+       if !bytes.Equal(mi.Info.Hash, ih[:]) {
+               err = fmt.Errorf("cached torrent has wrong infohash: %x != %x", mi.Info.Hash, ih[:])
+               return
+       }
+       return
+}
+
 func (cl *Client) AddMagnet(uri string) (T Torrent, err error) {
        m, err := ParseMagnetURI(uri)
        if err != nil {
                return
        }
-       cl.AddTorrentFromFile(cl.torrentFileCachePath(m.InfoHash))
+       mi, err := cl.torrentCacheMetaInfo(m.InfoHash)
+       if err != nil {
+               log.Printf("error getting cached metainfo for %x: %s", m.InfoHash[:], err)
+       } else if mi != nil {
+               cl.AddTorrent(mi)
+       }
        cl.mu.Lock()
        defer cl.mu.Unlock()
        T, err = cl.addOrMergeTorrent(m.InfoHash, [][]string{m.Trackers})