// downloadTimestamp is responsible for downloading the timestamp.json
// Timestamps are special in that we ALWAYS attempt to download and only
// use cache if the download fails (and the cache is still valid).
func (c *Client) downloadTimestamp() error {
logrus.Debug("downloadTimestamp")
role := data.RoleName("timestamp")
// We may not have a cached timestamp if this is the first time
// we're interacting with the repo. This will result in the
// version being 0
var download bool
old := &data.Signed{}
version := 0
cachedTS, err := c.cache.GetMeta(role, maxSize)
if err == nil {
err := json.Unmarshal(cachedTS, old)
if err == nil {
ts, err := data.TimestampFromSigned(old)
if err == nil {
version = ts.Signed.Version
}
} else {
old = nil
}
}
// unlike root, targets and snapshot, always try and download timestamps
// from remote, only using the cache one if we couldn't reach remote.
raw, s, err := c.downloadSigned(role, maxSize, nil)
if err != nil || len(raw) == 0 {
if err, ok := err.(store.ErrMetaNotFound); ok {
return err
}
if old == nil {
if err == nil {
// couldn't retrieve data from server and don't have valid
// data in cache.
return store.ErrMetaNotFound{}
}
return err
}
logrus.Debug("using cached timestamp")
s = old
} else {
download = true
}
err = signed.Verify(s, role, version, c.keysDB)
if err != nil {
return err
}
logrus.Debug("successfully verified timestamp")
if download {
c.cache.SetMeta(role, raw)
}
ts, err := data.TimestampFromSigned(s)
if err != nil {
return err
}
c.local.SetTimestamp(ts)
return nil
}
// SetTimestamp parses the Signed object into a SignedTimestamp object
// and sets the TufRepo.Timestamp field.
func (tr *TufRepo) SetTimestamp(s *data.Signed) error {
ts, err := data.TimestampFromSigned(s)
if err != nil {
return err
}
tr.Timestamp = ts
return nil
}
// 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
}
// downloadSnapshot is responsible for downloading the snapshot.json
func (c *Client) downloadSnapshot() error {
logrus.Debug("downloadSnapshot")
role := data.RoleName("snapshot")
size := c.local.Timestamp.Signed.Meta[role].Length
expectedSha256, ok := c.local.Timestamp.Signed.Meta[role].Hashes["sha256"]
if !ok {
return fmt.Errorf("Sha256 is currently the only hash supported by this client. No Sha256 found for 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 {
logrus.Debug("downloading new snapshot")
raw, err = c.remote.GetMeta(role, size)
if err != nil {
return err
}
genHash := sha256.Sum256(raw)
if !bytes.Equal(genHash[:], expectedSha256) {
return fmt.Errorf("Retrieved snapshot did not verify against hash in timestamp.")
}
s = &data.Signed{}
err = json.Unmarshal(raw, s)
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")
c.local.SetSnapshot(s)
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
}
