properly handle whiteout opaque dirs when unpacking

#267 If a file in the layer tarball is labeled foo/.wh..wh..opq, that indicates that the existing contents of the directory foo/ should be emptied. We were previously treating this the same as normal whiteout files (e.g. foo/.wh.myfile means delete foo/myfile), which doesn't work properly. With this commit, we're now able to delete a directory and recreate it in the same layer, and have it be unpacked properly. Signed-off-by: Esteban Foronda <[email protected]> Co-authored-by: Aidan Oldershaw <[email protected]>
concourse · Jun 22, 2021 · 753290b · 753290b
1 parent 17186cf
commit 753290b
Show file tree

Hide file tree

Showing 4 changed files with 32 additions and 3 deletions.
diff --git a/commands/unpack.go b/commands/unpack.go
@@ -11,13 +11,14 @@ import (
 
 	"github.com/concourse/go-archive/tarfs"
 	"github.com/fatih/color"
-	"github.com/google/go-containerregistry/pkg/v1"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/sirupsen/logrus"
 	"github.com/vbauerster/mpb"
 	"github.com/vbauerster/mpb/decor"
 )
 
 const whiteoutPrefix = ".wh."
+const whiteoutOpaqueDir = whiteoutPrefix + whiteoutPrefix + ".opq"
 
 func unpackImage(dest string, img v1.Image, debug bool, out io.Writer) error {
 	layers, err := img.Layers()
@@ -102,7 +103,24 @@ func extractLayer(dest string, layer v1.Layer, bar *mpb.Bar, chown bool) error {
 
 		log.Debug("unpacking")
 
-		if strings.HasPrefix(base, whiteoutPrefix) {
+		if base == whiteoutOpaqueDir {
+			fi, err := os.Lstat(dir)
+			if err != nil && !os.IsNotExist(err) {
+				return err
+			}
+
+			log.Debugf("removing contents of %s", dir)
+
+			if err := os.RemoveAll(dir); err != nil {
+				return err
+
+			}
+			if err := os.Mkdir(dir, fi.Mode()&os.ModePerm); err != nil {
+				return err
+			}
+
+			continue
+		} else if strings.HasPrefix(base, whiteoutPrefix) {
 			// layer has marked a file as deleted
 			name := strings.TrimPrefix(base, whiteoutPrefix)
 			removedPath := filepath.Join(dir, name)

diff --git a/in_test.go b/in_test.go
@@ -221,6 +221,14 @@ var _ = Describe("In", func() {
 
 			stat, err = os.Stat(rootfsPath("top-dir-2"))
 			Expect(err).To(HaveOccurred())
+
+			infos, err = ioutil.ReadDir(rootfsPath("top-dir-3"))
+			Expect(err).ToNot(HaveOccurred())
+			Expect(infos).To(HaveLen(1))
+
+			stat, err = os.Stat(rootfsPath("top-dir-3", "nested-dir"))
+			Expect(err).ToNot(HaveOccurred())
+			Expect(stat.IsDir()).To(BeTrue())
 		})
 	})
 

diff --git a/suite_test.go b/suite_test.go
@@ -40,7 +40,7 @@ const OLDER_LIBRARY_DIGEST = "sha256:2131f09e4044327fd101ca1fd4043e6f3ad921ae7ee
 
 // see testdata/static/Dockerfile
 const OLDER_STATIC_DIGEST = "sha256:7dabedca9d367a71d1cd646bd8d79f14de7b07327e4417ab691f5f13be5647a9"
-const LATEST_STATIC_DIGEST = "sha256:fc484c7e21a5616c600778d7ee720b3adfe1373c896be4f068c3da4a205d4a2e"
+const LATEST_STATIC_DIGEST = "sha256:29eddd288c312215a0af1070d26478b1f530a3137d4589314df1bc79e586860a"
 
 // see testdata/static.tagged/Dockerfile
 const LATEST_TAGGED_STATIC_DIGEST = "sha256:ecfdc2527b0a5d7d134be55234590336209e7feafc2ec364a930adf4a9c722e2"

diff --git a/testdata/whiteout/Dockerfile b/testdata/whiteout/Dockerfile
@@ -15,9 +15,12 @@ RUN touch top-dir-2/file-gone
 RUN mkdir top-dir-2/nested-dir-gone
 RUN touch top-dir-2/nested-dir-gone/nested-file-gone
 RUN rm -rf top-dir-2
+RUN mkdir -p top-dir-3/nested-dir-gone
+RUN rm -r top-dir-3 && mkdir -p top-dir-3/nested-dir
 
 # resulting file tree should be:
 # /top-dir-1/nested-file
 # /top-dir-1/nested-dir/file-here
 # /top-dir-1/nested-dir/file-recreated
 # /top-dir-1/nested-dir/file-then-dir
+# /top-dir-3/nested-dir