Fix docker cp Behavior With Symlinks

[pkg/archive] Update archive/copy path handling

  - Remove unused TarOptions.Name field.
  - Add new TarOptions.RebaseNames field.
  - Update some of the logic around path dir/base splitting.
  - Update some of the logic behind archive entry name rebasing.

[api/types] Add LinkTarget field to PathStat

[daemon] Fix stat, archive, extract of symlinks

  These operations *should* resolve symlinks that are in the path but if the
  resource itself is a symlink then it *should not* be resolved. This patch
  puts this logic into a common function `resolvePath` which resolves symlinks
  of the path's dir in scope of the container rootfs but does not resolve the
  final element of the path. Now archive, extract, and stat operations will
  return symlinks if the path is indeed a symlink.

[api/client] Update cp path hanling

[docs/reference/api] Update description of stat

  Add the linkTarget field to the header of the archive endpoint.
  Remove path field.

[integration-cli] Fix/Add cp symlink test cases

  Copying a symlink should do just that: copy the symlink NOT
  copy the target of the symlink. Also, the resulting file from
  the copy should have the name of the symlink NOT the name of
  the target file.

  Copying to a symlink should copy to the symlink target and not
  modify the symlink itself.

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

api/client/cp.go

@@ -232,6 +232,20 @@ func (cli *DockerCli) copyToContainer(srcPath, dstContainer, dstPath string) (er
 	// Prepare destination copy info by stat-ing the container path.
 	dstInfo := archive.CopyInfo{Path: dstPath}
 	dstStat, err := cli.statContainerPath(dstContainer, dstPath)
+
+	// If the destination is a symbolic link, we should evaluate it.
+	if err == nil && dstStat.Mode&os.ModeSymlink != 0 {
+		linkTarget := dstStat.LinkTarget
+		if !filepath.IsAbs(linkTarget) {
+			// Join with the parent directory.
+			dstParent, _ := archive.SplitPathDirEntry(dstPath)
+			linkTarget = filepath.Join(dstParent, linkTarget)
+		}
+
+		dstInfo.Path = linkTarget
+		dstStat, err = cli.statContainerPath(dstContainer, linkTarget)
+	}
+
 	// Ignore any error and assume that the parent directory of the destination
 	// path exists, in which case the copy may still succeed. If there is any
 	// type of conflict (e.g., non-directory overwriting an existing directory
@@ -242,15 +256,26 @@ func (cli *DockerCli) copyToContainer(srcPath, dstContainer, dstPath string) (er
 		dstInfo.Exists, dstInfo.IsDir = true, dstStat.Mode.IsDir()
 	}
 
-	var content io.Reader
+	var (
+		content         io.Reader
+		resolvedDstPath string
+	)
+
 	if srcPath == "-" {
 		// Use STDIN.
 		content = os.Stdin
+		resolvedDstPath = dstInfo.Path
 		if !dstInfo.IsDir {
 			return fmt.Errorf("destination %q must be a directory", fmt.Sprintf("%s:%s", dstContainer, dstPath))
 		}
 	} else {
-		srcArchive, err := archive.TarResource(srcPath)
+		// Prepare source copy info.
+		srcInfo, err := archive.CopyInfoSourcePath(srcPath)
+		if err != nil {
+			return err
+		}
+
+		srcArchive, err := archive.TarResource(srcInfo)
 		if err != nil {
 			return err
 		}
@@ -262,12 +287,6 @@ func (cli *DockerCli) copyToContainer(srcPath, dstContainer, dstPath string) (er
 		// it to the specified directory in the container we get the disired
 		// copy behavior.
 
-		// Prepare source copy info.
-		srcInfo, err := archive.CopyInfoStatPath(srcPath, true)
-		if err != nil {
-			return err
-		}
-
 		// See comments in the implementation of `archive.PrepareArchiveCopy`
 		// for exactly what goes into deciding how and whether the source
 		// archive needs to be altered for the correct copy behavior when it is
@@ -280,12 +299,12 @@ func (cli *DockerCli) copyToContainer(srcPath, dstContainer, dstPath string) (er
 		}
 		defer preparedArchive.Close()
 
-		dstPath = dstDir
+		resolvedDstPath = dstDir
 		content = preparedArchive
 	}
 
 	query := make(url.Values, 2)
-	query.Set("path", filepath.ToSlash(dstPath)) // Normalize the paths used in the API.
+	query.Set("path", filepath.ToSlash(resolvedDstPath)) // Normalize the paths used in the API.
 	// Do not allow for an existing directory to be overwritten by a non-directory and vice versa.
 	query.Set("noOverwriteDirNonDir", "true")
 

api/types/types.go

@@ -130,14 +130,13 @@ type CopyConfig struct {
 
 // ContainerPathStat is used to encode the header from
 // 	GET /containers/{name:.*}/archive
-// "name" is the file or directory name.
-// "path" is the absolute path to the resource in the container.
+// "name" is basename of the resource.
 type ContainerPathStat struct {
-	Name  string      `json:"name"`
-	Path  string      `json:"path"`
-	Size  int64       `json:"size"`
-	Mode  os.FileMode `json:"mode"`
-	Mtime time.Time   `json:"mtime"`
+	Name       string      `json:"name"`
+	Size       int64       `json:"size"`
+	Mode       os.FileMode `json:"mode"`
+	Mtime      time.Time   `json:"mtime"`
+	LinkTarget string      `json:"linkTarget"`
 }
 
 // GET "/containers/{name:.*}/top"