361 lines
12 KiB
Go
361 lines
12 KiB
Go
package daemon
|
||
|
||
import (
|
||
"archive/tar"
|
||
"bytes"
|
||
"encoding/json"
|
||
"io"
|
||
"io/ioutil"
|
||
"os"
|
||
"path"
|
||
|
||
"github.com/containers/image/manifest"
|
||
"github.com/containers/image/types"
|
||
"github.com/docker/docker/client"
|
||
"github.com/opencontainers/go-digest"
|
||
"github.com/pkg/errors"
|
||
"golang.org/x/net/context"
|
||
)
|
||
|
||
const temporaryDirectoryForBigFiles = "/var/tmp" // Do not use the system default of os.TempDir(), usually /tmp, because with systemd it could be a tmpfs.
|
||
|
||
type daemonImageSource struct {
|
||
ref daemonReference
|
||
tarCopyPath string
|
||
// The following data is only available after ensureCachedDataIsPresent() succeeds
|
||
tarManifest *manifestItem // nil if not available yet.
|
||
configBytes []byte
|
||
configDigest digest.Digest
|
||
orderedDiffIDList []diffID
|
||
knownLayers map[diffID]*layerInfo
|
||
// Other state
|
||
generatedManifest []byte // Private cache for GetManifest(), nil if not set yet.
|
||
}
|
||
|
||
type layerInfo struct {
|
||
path string
|
||
size int64
|
||
}
|
||
|
||
// newImageSource returns a types.ImageSource for the specified image reference.
|
||
// The caller must call .Close() on the returned ImageSource.
|
||
//
|
||
// It would be great if we were able to stream the input tar as it is being
|
||
// sent; but Docker sends the top-level manifest, which determines which paths
|
||
// to look for, at the end, so in we will need to seek back and re-read, several times.
|
||
// (We could, perhaps, expect an exact sequence, assume that the first plaintext file
|
||
// is the config, and that the following len(RootFS) files are the layers, but that feels
|
||
// way too brittle.)
|
||
func newImageSource(ctx *types.SystemContext, ref daemonReference) (types.ImageSource, error) {
|
||
c, err := client.NewClient(client.DefaultDockerHost, "1.22", nil, nil) // FIXME: overridable host
|
||
if err != nil {
|
||
return nil, errors.Wrap(err, "Error initializing docker engine client")
|
||
}
|
||
// Per NewReference(), ref.StringWithinTransport() is either an image ID (config digest), or a !reference.NameOnly() reference.
|
||
// Either way ImageSave should create a tarball with exactly one image.
|
||
inputStream, err := c.ImageSave(context.TODO(), []string{ref.StringWithinTransport()})
|
||
if err != nil {
|
||
return nil, errors.Wrap(err, "Error loading image from docker engine")
|
||
}
|
||
defer inputStream.Close()
|
||
|
||
// FIXME: use SystemContext here.
|
||
tarCopyFile, err := ioutil.TempFile(temporaryDirectoryForBigFiles, "docker-daemon-tar")
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
defer tarCopyFile.Close()
|
||
|
||
succeeded := false
|
||
defer func() {
|
||
if !succeeded {
|
||
os.Remove(tarCopyFile.Name())
|
||
}
|
||
}()
|
||
|
||
if _, err := io.Copy(tarCopyFile, inputStream); err != nil {
|
||
return nil, err
|
||
}
|
||
|
||
succeeded = true
|
||
return &daemonImageSource{
|
||
ref: ref,
|
||
tarCopyPath: tarCopyFile.Name(),
|
||
}, nil
|
||
}
|
||
|
||
// Reference returns the reference used to set up this source, _as specified by the user_
|
||
// (not as the image itself, or its underlying storage, claims). This can be used e.g. to determine which public keys are trusted for this image.
|
||
func (s *daemonImageSource) Reference() types.ImageReference {
|
||
return s.ref
|
||
}
|
||
|
||
// Close removes resources associated with an initialized ImageSource, if any.
|
||
func (s *daemonImageSource) Close() {
|
||
_ = os.Remove(s.tarCopyPath)
|
||
}
|
||
|
||
// tarReadCloser is a way to close the backing file of a tar.Reader when the user no longer needs the tar component.
|
||
type tarReadCloser struct {
|
||
*tar.Reader
|
||
backingFile *os.File
|
||
}
|
||
|
||
func (t *tarReadCloser) Close() error {
|
||
return t.backingFile.Close()
|
||
}
|
||
|
||
// openTarComponent returns a ReadCloser for the specific file within the archive.
|
||
// This is linear scan; we assume that the tar file will have a fairly small amount of files (~layers),
|
||
// and that filesystem caching will make the repeated seeking over the (uncompressed) tarCopyPath cheap enough.
|
||
// The caller should call .Close() on the returned stream.
|
||
func (s *daemonImageSource) openTarComponent(componentPath string) (io.ReadCloser, error) {
|
||
f, err := os.Open(s.tarCopyPath)
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
succeeded := false
|
||
defer func() {
|
||
if !succeeded {
|
||
f.Close()
|
||
}
|
||
}()
|
||
|
||
tarReader, header, err := findTarComponent(f, componentPath)
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
if header == nil {
|
||
return nil, os.ErrNotExist
|
||
}
|
||
if header.FileInfo().Mode()&os.ModeType == os.ModeSymlink { // FIXME: untested
|
||
// We follow only one symlink; so no loops are possible.
|
||
if _, err := f.Seek(0, os.SEEK_SET); err != nil {
|
||
return nil, err
|
||
}
|
||
// The new path could easily point "outside" the archive, but we only compare it to existing tar headers without extracting the archive,
|
||
// so we don't care.
|
||
tarReader, header, err = findTarComponent(f, path.Join(path.Dir(componentPath), header.Linkname))
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
if header == nil {
|
||
return nil, os.ErrNotExist
|
||
}
|
||
}
|
||
|
||
if !header.FileInfo().Mode().IsRegular() {
|
||
return nil, errors.Errorf("Error reading tar archive component %s: not a regular file", header.Name)
|
||
}
|
||
succeeded = true
|
||
return &tarReadCloser{Reader: tarReader, backingFile: f}, nil
|
||
}
|
||
|
||
// findTarComponent returns a header and a reader matching path within inputFile,
|
||
// or (nil, nil, nil) if not found.
|
||
func findTarComponent(inputFile io.Reader, path string) (*tar.Reader, *tar.Header, error) {
|
||
t := tar.NewReader(inputFile)
|
||
for {
|
||
h, err := t.Next()
|
||
if err == io.EOF {
|
||
break
|
||
}
|
||
if err != nil {
|
||
return nil, nil, err
|
||
}
|
||
if h.Name == path {
|
||
return t, h, nil
|
||
}
|
||
}
|
||
return nil, nil, nil
|
||
}
|
||
|
||
// readTarComponent returns full contents of componentPath.
|
||
func (s *daemonImageSource) readTarComponent(path string) ([]byte, error) {
|
||
file, err := s.openTarComponent(path)
|
||
if err != nil {
|
||
return nil, errors.Wrapf(err, "Error loading tar component %s", path)
|
||
}
|
||
defer file.Close()
|
||
bytes, err := ioutil.ReadAll(file)
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
return bytes, nil
|
||
}
|
||
|
||
// ensureCachedDataIsPresent loads data necessary for any of the public accessors.
|
||
func (s *daemonImageSource) ensureCachedDataIsPresent() error {
|
||
if s.tarManifest != nil {
|
||
return nil
|
||
}
|
||
|
||
// Read and parse manifest.json
|
||
tarManifest, err := s.loadTarManifest()
|
||
if err != nil {
|
||
return err
|
||
}
|
||
|
||
// Read and parse config.
|
||
configBytes, err := s.readTarComponent(tarManifest.Config)
|
||
if err != nil {
|
||
return err
|
||
}
|
||
var parsedConfig dockerImage // Most fields ommitted, we only care about layer DiffIDs.
|
||
if err := json.Unmarshal(configBytes, &parsedConfig); err != nil {
|
||
return errors.Wrapf(err, "Error decoding tar config %s", tarManifest.Config)
|
||
}
|
||
|
||
knownLayers, err := s.prepareLayerData(tarManifest, &parsedConfig)
|
||
if err != nil {
|
||
return err
|
||
}
|
||
|
||
// Success; commit.
|
||
s.tarManifest = tarManifest
|
||
s.configBytes = configBytes
|
||
s.configDigest = digest.FromBytes(configBytes)
|
||
s.orderedDiffIDList = parsedConfig.RootFS.DiffIDs
|
||
s.knownLayers = knownLayers
|
||
return nil
|
||
}
|
||
|
||
// loadTarManifest loads and decodes the manifest.json.
|
||
func (s *daemonImageSource) loadTarManifest() (*manifestItem, error) {
|
||
// FIXME? Do we need to deal with the legacy format?
|
||
bytes, err := s.readTarComponent(manifestFileName)
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
var items []manifestItem
|
||
if err := json.Unmarshal(bytes, &items); err != nil {
|
||
return nil, errors.Wrap(err, "Error decoding tar manifest.json")
|
||
}
|
||
if len(items) != 1 {
|
||
return nil, errors.Errorf("Unexpected tar manifest.json: expected 1 item, got %d", len(items))
|
||
}
|
||
return &items[0], nil
|
||
}
|
||
|
||
func (s *daemonImageSource) prepareLayerData(tarManifest *manifestItem, parsedConfig *dockerImage) (map[diffID]*layerInfo, error) {
|
||
// Collect layer data available in manifest and config.
|
||
if len(tarManifest.Layers) != len(parsedConfig.RootFS.DiffIDs) {
|
||
return nil, errors.Errorf("Inconsistent layer count: %d in manifest, %d in config", len(tarManifest.Layers), len(parsedConfig.RootFS.DiffIDs))
|
||
}
|
||
knownLayers := map[diffID]*layerInfo{}
|
||
unknownLayerSizes := map[string]*layerInfo{} // Points into knownLayers, a "to do list" of items with unknown sizes.
|
||
for i, diffID := range parsedConfig.RootFS.DiffIDs {
|
||
if _, ok := knownLayers[diffID]; ok {
|
||
// Apparently it really can happen that a single image contains the same layer diff more than once.
|
||
// In that case, the diffID validation ensures that both layers truly are the same, and it should not matter
|
||
// which of the tarManifest.Layers paths is used; (docker save) actually makes the duplicates symlinks to the original.
|
||
continue
|
||
}
|
||
layerPath := tarManifest.Layers[i]
|
||
if _, ok := unknownLayerSizes[layerPath]; ok {
|
||
return nil, errors.Errorf("Layer tarfile %s used for two different DiffID values", layerPath)
|
||
}
|
||
li := &layerInfo{ // A new element in each iteration
|
||
path: layerPath,
|
||
size: -1,
|
||
}
|
||
knownLayers[diffID] = li
|
||
unknownLayerSizes[layerPath] = li
|
||
}
|
||
|
||
// Scan the tar file to collect layer sizes.
|
||
file, err := os.Open(s.tarCopyPath)
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
defer file.Close()
|
||
t := tar.NewReader(file)
|
||
for {
|
||
h, err := t.Next()
|
||
if err == io.EOF {
|
||
break
|
||
}
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
if li, ok := unknownLayerSizes[h.Name]; ok {
|
||
li.size = h.Size
|
||
delete(unknownLayerSizes, h.Name)
|
||
}
|
||
}
|
||
if len(unknownLayerSizes) != 0 {
|
||
return nil, errors.Errorf("Some layer tarfiles are missing in the tarball") // This could do with a better error reporting, if this ever happened in practice.
|
||
}
|
||
|
||
return knownLayers, nil
|
||
}
|
||
|
||
// GetManifest returns the image's manifest along with its MIME type (which may be empty when it can't be determined but the manifest is available).
|
||
// It may use a remote (= slow) service.
|
||
func (s *daemonImageSource) GetManifest() ([]byte, string, error) {
|
||
if s.generatedManifest == nil {
|
||
if err := s.ensureCachedDataIsPresent(); err != nil {
|
||
return nil, "", err
|
||
}
|
||
m := schema2Manifest{
|
||
SchemaVersion: 2,
|
||
MediaType: manifest.DockerV2Schema2MediaType,
|
||
Config: distributionDescriptor{
|
||
MediaType: manifest.DockerV2Schema2ConfigMediaType,
|
||
Size: int64(len(s.configBytes)),
|
||
Digest: s.configDigest,
|
||
},
|
||
Layers: []distributionDescriptor{},
|
||
}
|
||
for _, diffID := range s.orderedDiffIDList {
|
||
li, ok := s.knownLayers[diffID]
|
||
if !ok {
|
||
return nil, "", errors.Errorf("Internal inconsistency: Information about layer %s missing", diffID)
|
||
}
|
||
m.Layers = append(m.Layers, distributionDescriptor{
|
||
Digest: digest.Digest(diffID), // diffID is a digest of the uncompressed tarball
|
||
MediaType: manifest.DockerV2Schema2LayerMediaType,
|
||
Size: li.size,
|
||
})
|
||
}
|
||
manifestBytes, err := json.Marshal(&m)
|
||
if err != nil {
|
||
return nil, "", err
|
||
}
|
||
s.generatedManifest = manifestBytes
|
||
}
|
||
return s.generatedManifest, manifest.DockerV2Schema2MediaType, nil
|
||
}
|
||
|
||
// GetTargetManifest returns an image's manifest given a digest. This is mainly used to retrieve a single image's manifest
|
||
// out of a manifest list.
|
||
func (s *daemonImageSource) GetTargetManifest(digest digest.Digest) ([]byte, string, error) {
|
||
// How did we even get here? GetManifest() above has returned a manifest.DockerV2Schema2MediaType.
|
||
return nil, "", errors.Errorf(`Manifest lists are not supported by "docker-daemon:"`)
|
||
}
|
||
|
||
// GetBlob returns a stream for the specified blob, and the blob’s size (or -1 if unknown).
|
||
func (s *daemonImageSource) GetBlob(info types.BlobInfo) (io.ReadCloser, int64, error) {
|
||
if err := s.ensureCachedDataIsPresent(); err != nil {
|
||
return nil, 0, err
|
||
}
|
||
|
||
if info.Digest == s.configDigest { // FIXME? Implement a more general algorithm matching instead of assuming sha256.
|
||
return ioutil.NopCloser(bytes.NewReader(s.configBytes)), int64(len(s.configBytes)), nil
|
||
}
|
||
|
||
if li, ok := s.knownLayers[diffID(info.Digest)]; ok { // diffID is a digest of the uncompressed tarball,
|
||
stream, err := s.openTarComponent(li.path)
|
||
if err != nil {
|
||
return nil, 0, err
|
||
}
|
||
return stream, li.size, nil
|
||
}
|
||
|
||
return nil, 0, errors.Errorf("Unknown blob %s", info.Digest)
|
||
}
|
||
|
||
// GetSignatures returns the image's signatures. It may use a remote (= slow) service.
|
||
func (s *daemonImageSource) GetSignatures() ([][]byte, error) {
|
||
return [][]byte{}, nil
|
||
}
|