Resolve symlink targets to abs path before copying

integration/dockerfiles/Dockerfile_test_add_dest_symlink_dir

@@ -0,0 +1,2 @@
+FROM phusion/baseimage:0.11
+ADD context/foo /etc/service/foo

pkg/commands/add.go

@@ -141,3 +141,7 @@ func (a *AddCommand) FilesUsedFromContext(config *v1.Config, buildArgs *dockerfi
 func (a *AddCommand) MetadataOnly() bool {
  return false
 }
+
+func (a *AddCommand) RequiresUnpackedFS() bool {
+ return true
+}

pkg/commands/copy.go

@@ -66,6 +66,14 @@ func (c *CopyCommand) ExecuteCommand(config *v1.Config, buildArgs *dockerfile.Bu
  if err != nil {
  return err
  }
+
+ // If the destination dir is a symlink we need to resolve the path and use
+ // that instead of the symlink path
+ destPath, err = resolveIfSymlink(destPath)
+ if err != nil {
+ return err
+ }
+
  if fi.IsDir() {
  if !filepath.IsAbs(dest) {
  // we need to add '/' to the end to indicate the destination is a directory
@@ -178,3 +186,21 @@ func (cr *CachingCopyCommand) FilesToSnapshot() []string {
 func (cr *CachingCopyCommand) String() string {
  return cr.cmd.String()
 }
+
+func resolveIfSymlink(destPath string) (string, error) {
+ baseDir := filepath.Dir(destPath)
+ if info, err := os.Lstat(baseDir); err == nil {
+ switch mode := info.Mode(); {
+ case mode&os.ModeSymlink != 0:
+ linkPath, err := os.Readlink(baseDir)
+ if err != nil {
+ return "", errors.Wrap(err, "error reading symlink")
+ }
+ absLinkPath := filepath.Join(filepath.Dir(baseDir), linkPath)
+ newPath := filepath.Join(absLinkPath, filepath.Base(destPath))
+ logrus.Tracef("Updating destination path from %v to %v due to symlink", destPath, newPath)
+ return newPath, nil
+ }
+ }
+ return destPath, nil
+}

pkg/commands/copy_test.go

@@ -16,6 +16,7 @@ limitations under the License.
 package commands
 
 import (
+ "fmt"
  "io"
  "io/ioutil"
  "os"
@@ -165,3 +166,52 @@ func copySetUpBuildArgs() *dockerfile.BuildArgs {
  buildArgs.AddArg("buildArg2", &d)
  return buildArgs
 }
+
+func Test_resolveIfSymlink(t *testing.T) {
+ type testCase struct {
+ destPath string
+ expectedPath string
+ err error
+ }
+
+ tmpDir, err := ioutil.TempDir("", "copy-test")
+ if err != nil {
+ t.Error(err)
+ }
+
+ baseDir, err := ioutil.TempDir(tmpDir, "not-linked")
+ if err != nil {
+ t.Error(err)
+ }
+
+ path, err := ioutil.TempFile(baseDir, "foo.txt")
+ if err != nil {
+ t.Error(err)
+ }
+
+ thepath, err := filepath.Abs(filepath.Dir(path.Name()))
+ if err != nil {
+ t.Error(err)
+ }
+ cases := []testCase{{destPath: thepath, expectedPath: thepath, err: nil}}
+
+ baseDir = tmpDir
+ symLink := filepath.Join(baseDir, "symlink")
+ if err := os.Symlink(filepath.Base(thepath), symLink); err != nil {
+ t.Error(err)
+ }
+ cases = append(cases, testCase{filepath.Join(symLink, "foo.txt"), filepath.Join(thepath, "foo.txt"), nil})
+
+ for i, c := range cases {
+ t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+ res, e := resolveIfSymlink(c.destPath)
+ if e != c.err {
+ t.Errorf("%s: expected %v but got %v", c.destPath, c.err, e)
+ }
+
+ if res != c.expectedPath {
+ t.Errorf("%s: expected %v but got %v", c.destPath, c.expectedPath, res)
+ }
+ })
+ }
+}

pkg/util/fs_util.go

@@ -424,11 +424,17 @@ func FilepathExists(path string) bool {
 func CreateFile(path string, reader io.Reader, perm os.FileMode, uid uint32, gid uint32) error {
  // Create directory path if it doesn't exist
  baseDir := filepath.Dir(path)
- if _, err := os.Lstat(baseDir); os.IsNotExist(err) {
+ if info, err := os.Lstat(baseDir); os.IsNotExist(err) {
  logrus.Tracef("baseDir %s for file %s does not exist. Creating.", baseDir, path)
  if err := os.MkdirAll(baseDir, 0755); err != nil {
  return err
  }
+ } else {
+ switch mode := info.Mode(); {
+ case mode&os.ModeSymlink != 0:
+ logrus.Infof("destination cannot be a symlink %v", baseDir)
+ return errors.New("destination cannot be a symlink")
+ }
  }
  dest, err := os.Create(path)
  if err != nil {