1. docker
  2. Commit 059e589c3427b1afa1b112acc931f59b5b063e16
Browse code

Compute TarSum on storage of image layer content

Now, newly created/imported layers will have the checksum of
the layer diff computed and stored in the image json file.

For now, it is not an error if the computed checksum does not
match an existing checksum, only a warning message is logged. The
eventual goal is to use the checksums in the image JSON to verify
the integrity of the layer contents when doing `docker load` or
`docker pull`, and error out if it does not match.

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)

Josh Hawn authored on 2014/11/05 08:23:21
Showing 2 changed files
graph/service.go
History View file @ 059e589
... ... 
@@ -150,6 +150,7 @@ func (s *TagStore) CmdLookup(job *engine.Job) engine.Status {
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 		out.Set("Os", image.OS)
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 		out.SetInt64("Size", image.Size)
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 		out.SetInt64("VirtualSize", image.GetParentsSize(0)+image.Size)
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+		out.Set("Checksum", image.Checksum)
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 		if _, err = out.WriteTo(job.Stdout); err != nil {
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 			return job.Error(err)
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 		}
image/image.go
History View file @ 059e589
... ... 
@@ -11,6 +11,7 @@ import (
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 	log "github.com/Sirupsen/logrus"
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 	"github.com/docker/docker/pkg/archive"
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+	"github.com/docker/docker/pkg/tarsum"
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 	"github.com/docker/docker/runconfig"
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 	"github.com/docker/docker/utils"
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 )
... ... 
@@ -32,6 +33,7 @@ type Image struct {
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 	Config          *runconfig.Config `json:"config,omitempty"`
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 	Architecture    string            `json:"architecture,omitempty"`
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 	OS              string            `json:"os,omitempty"`
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+	Checksum        string            `json:"checksum"`
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 	Size            int64
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 	graph Graph
... ... 
@@ -74,19 +76,43 @@ func LoadImage(root string) (*Image, error) {
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 	return img, nil
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 }
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+// StoreImage stores file system layer data for the given image to the
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+// image's registered storage driver. Image metadata is stored in a file
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+// at the specified root directory. This function also computes the TarSum
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+// of `layerData` (currently using tarsum.dev).
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 func StoreImage(img *Image, layerData archive.ArchiveReader, root string) error {
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 	// Store the layer
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 	var (
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-		size   int64
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-		err    error
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-		driver = img.graph.Driver()
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+		size        int64
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+		err         error
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+		driver      = img.graph.Driver()
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+		layerTarSum tarsum.TarSum
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 	)
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 	// If layerData is not nil, unpack it into the new layer
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 	if layerData != nil {
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-		if size, err = driver.ApplyDiff(img.ID, img.Parent, layerData); err != nil {
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+		layerDataDecompressed, err := archive.DecompressStream(layerData)
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+		if err != nil {
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 			return err
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 		}
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+
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+		defer layerDataDecompressed.Close()
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+
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+		if layerTarSum, err = tarsum.NewTarSum(layerDataDecompressed, true, tarsum.VersionDev); err != nil {
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+			return err
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+		}
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+
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+		if size, err = driver.ApplyDiff(img.ID, img.Parent, layerTarSum); err != nil {
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+			return err
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+		}
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+
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+		checksum := layerTarSum.Sum(nil)
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+
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+		if img.Checksum != "" && img.Checksum != checksum {
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+			log.Warn("image layer checksum mismatch: computed %q, expected %q", checksum, img.Checksum)
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+		}
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+
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+		img.Checksum = checksum
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 	}
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 	img.Size = size