98 lines
2.2 KiB
Go
98 lines
2.2 KiB
Go
//+build !windows
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package chrootarchive
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import (
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"bytes"
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"encoding/json"
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"flag"
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"fmt"
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"io/ioutil"
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"os"
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"path/filepath"
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"runtime"
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"github.com/docker/docker/pkg/archive"
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"github.com/docker/docker/pkg/reexec"
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"github.com/docker/docker/pkg/system"
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)
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type applyLayerResponse struct {
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LayerSize int64 `json:"layerSize"`
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}
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// applyLayer is the entry-point for docker-applylayer on re-exec. This is not
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// used on Windows as it does not support chroot, hence no point sandboxing
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// through chroot and rexec.
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func applyLayer() {
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var (
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tmpDir = ""
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err error
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)
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runtime.LockOSThread()
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flag.Parse()
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if err := chroot(flag.Arg(0)); err != nil {
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fatal(err)
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}
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// We need to be able to set any perms
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oldmask, err := system.Umask(0)
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defer system.Umask(oldmask)
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if err != nil {
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fatal(err)
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}
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if tmpDir, err = ioutil.TempDir("/", "temp-docker-extract"); err != nil {
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fatal(err)
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}
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os.Setenv("TMPDIR", tmpDir)
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size, err := archive.UnpackLayer("/", os.Stdin)
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os.RemoveAll(tmpDir)
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if err != nil {
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fatal(err)
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}
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encoder := json.NewEncoder(os.Stdout)
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if err := encoder.Encode(applyLayerResponse{size}); err != nil {
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fatal(fmt.Errorf("unable to encode layerSize JSON: %s", err))
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}
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flush(os.Stdout)
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flush(os.Stdin)
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os.Exit(0)
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}
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// ApplyLayer parses a diff in the standard layer format from `layer`, and
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// applies it to the directory `dest`. Returns the size in bytes of the
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// contents of the layer.
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func ApplyLayer(dest string, layer archive.ArchiveReader) (size int64, err error) {
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dest = filepath.Clean(dest)
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decompressed, err := archive.DecompressStream(layer)
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if err != nil {
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return 0, err
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}
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defer decompressed.Close()
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cmd := reexec.Command("docker-applyLayer", dest)
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cmd.Stdin = decompressed
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outBuf, errBuf := new(bytes.Buffer), new(bytes.Buffer)
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cmd.Stdout, cmd.Stderr = outBuf, errBuf
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if err = cmd.Run(); err != nil {
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return 0, fmt.Errorf("ApplyLayer %s stdout: %s stderr: %s", err, outBuf, errBuf)
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}
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// Stdout should be a valid JSON struct representing an applyLayerResponse.
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response := applyLayerResponse{}
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decoder := json.NewDecoder(outBuf)
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if err = decoder.Decode(&response); err != nil {
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return 0, fmt.Errorf("unable to decode ApplyLayer JSON response: %s", err)
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}
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return response.LayerSize, nil
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}
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