func validateSnapshot(role string, oldSnap *data.SignedSnapshot, snapUpdate storage.MetaUpdate, roles map[string]storage.MetaUpdate, kdb *keys.KeyDB) error {
s := &data.Signed{}
err := json.Unmarshal(snapUpdate.Data, s)
if err != nil {
return errors.New("could not parse snapshot")
}
// version specifically gets validated when writing to store to
// better handle race conditions there.
if err := signed.Verify(s, role, 0, kdb); err != nil {
return err
}
snap, err := data.SnapshotFromSigned(s)
if err != nil {
return errors.New("could not parse snapshot")
}
if !data.ValidTUFType(snap.Signed.Type, data.CanonicalSnapshotRole) {
return errors.New("snapshot has wrong type")
}
err = checkSnapshotEntries(role, oldSnap, snap, roles)
if err != nil {
return err
}
return nil
}
// SetSnapshot parses the Signed object into a SignedSnapshots object
// and sets the TufRepo.Snapshot field.
func (tr *TufRepo) SetSnapshot(s *data.Signed) error {
snap, err := data.SnapshotFromSigned(s)
if err != nil {
return err
}
tr.Snapshot = snap
return nil
}
func TestValidateTargetsModifiedHash(t *testing.T) {
_, repo, _ := testutils.EmptyRepo()
store := storage.NewMemStorage()
r, tg, sn, ts, err := testutils.Sign(repo)
assert.NoError(t, err)
snap, err := data.SnapshotFromSigned(sn)
assert.NoError(t, err)
snap.Signed.Meta["targets"].Hashes["sha256"][0] = snap.Signed.Meta["targets"].Hashes["sha256"][0] ^ 0xff
sn, err = snap.ToSigned()
assert.NoError(t, err)
root, targets, snapshot, timestamp, err := testutils.Serialize(r, tg, sn, ts)
assert.NoError(t, err)
updates := []storage.MetaUpdate{
{
Role: "root",
Version: 1,
Data: root,
},
{
Role: "targets",
Version: 1,
Data: targets,
},
{
Role: "snapshot",
Version: 1,
Data: snapshot,
},
{
Role: "timestamp",
Version: 1,
Data: timestamp,
},
}
err = validateUpdate("testGUN", updates, store)
assert.Error(t, err)
assert.IsType(t, ErrBadSnapshot{}, err)
}
// downloadSnapshot is responsible for downloading the snapshot.json
func (c *Client) downloadSnapshot() error {
logrus.Debug("downloadSnapshot")
role := data.RoleName("snapshot")
if c.local.Timestamp == nil {
return ErrMissingMeta{role: "snapshot"}
}
size := c.local.Timestamp.Signed.Meta[role].Length
expectedSha256, ok := c.local.Timestamp.Signed.Meta[role].Hashes["sha256"]
if !ok {
return ErrMissingMeta{role: "snapshot"}
}
var download bool
old := &data.Signed{}
version := 0
raw, err := c.cache.GetMeta(role, size)
if raw == nil || err != nil {
logrus.Debug("no snapshot in cache, must download")
download = true
} else {
// file may have been tampered with on disk. Always check the hash!
genHash := sha256.Sum256(raw)
if !bytes.Equal(genHash[:], expectedSha256) {
logrus.Debug("hash of snapshot in cache did not match expected hash, must download")
download = true
}
err := json.Unmarshal(raw, old)
if err == nil {
snap, err := data.TimestampFromSigned(old)
if err == nil {
version = snap.Signed.Version
} else {
logrus.Debug("Could not parse Signed part of snapshot, must download")
download = true
}
} else {
logrus.Debug("Could not parse snapshot, must download")
download = true
}
}
var s *data.Signed
if download {
raw, s, err = c.downloadSigned(role, size, expectedSha256)
if err != nil {
return err
}
} else {
logrus.Debug("using cached snapshot")
s = old
}
err = signed.Verify(s, role, version, c.keysDB)
if err != nil {
return err
}
logrus.Debug("successfully verified snapshot")
snap, err := data.SnapshotFromSigned(s)
if err != nil {
return err
}
c.local.SetSnapshot(snap)
if download {
err = c.cache.SetMeta(role, raw)
if err != nil {
logrus.Errorf("Failed to write snapshot to local cache: %s", err.Error())
}
}
return nil
}
