fix: add leveldb recover ability (#352)

While fixing #349, the leveldb supports a Recover() method in case the
manifest is broken. I validated that the Recover would have recovered
the manifest file using the db file (that still existed). Add a test
that validates if the manifest is truncated, it can be recovered.

Signed-off-by: Mike Marchetti <[email protected]>

client/leveldbstore/leveldbstore.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 
 	"github.com/syndtr/goleveldb/leveldb"
+	"github.com/syndtr/goleveldb/leveldb/errors"
 	"github.com/syndtr/goleveldb/leveldb/storage"
 
 	tuf_client "github.com/theupdateframework/go-tuf/client"
@@ -16,6 +17,10 @@ func FileLocalStore(path string) (tuf_client.LocalStore, error) {
 	}
 
 	db, err := leveldb.Open(fd, nil)
+	if err != nil && errors.IsCorrupted(err) {
+		db, err = leveldb.Recover(fd, nil)
+	}
+
 	return &fileLocalStore{fd: fd, db: db}, err
 }
 

client/leveldbstore/leveldbstore_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	. "gopkg.in/check.v1"
+	"os"
 )
 
 type LocalStoreSuite struct{}
@@ -81,3 +82,42 @@ func (LocalStoreSuite) TestDeleteMeta(c *C) {
 		c.Fatalf("Metadata is not deleted!")
 	}
 }
+
+func (LocalStoreSuite) TestCorruptManifest(c *C) {
+	tmp := c.MkDir()
+	path := filepath.Join(tmp, "tuf.db")
+
+	store, err := FileLocalStore(path)
+	c.Assert(err, IsNil)
+
+	// now break the manifest file
+	err = os.Truncate(filepath.Join(path, "MANIFEST-000000"), 1)
+	c.Assert(err, IsNil)
+	err = store.Close()
+	c.Assert(err, IsNil)
+
+	store, err = FileLocalStore(path)
+	c.Assert(err, IsNil)
+
+	type meta map[string]json.RawMessage
+
+	assertGet := func(expected meta) {
+		actual, err := store.GetMeta()
+		c.Assert(err, IsNil)
+		c.Assert(meta(actual), DeepEquals, expected)
+	}
+
+	// initial GetMeta should return empty meta
+	assertGet(meta{})
+
+	// SetMeta should persist
+	rootJSON := []byte(`{"_type":"Root"}`)
+	c.Assert(store.SetMeta("root.json", rootJSON), IsNil)
+	assertGet(meta{"root.json": rootJSON})
+
+	store.DeleteMeta("root.json")
+	m, _ := store.GetMeta()
+	if _, ok := m["root.json"]; ok {
+		c.Fatalf("Metadata is not deleted!")
+	}
+}