Chown files when copying into chroot

Fixes #2552

Not needed when hardlinking. Only adds Linux support but other OS's may
be easy.

client/allocdir/alloc_dir.go

@@ -385,7 +385,9 @@ func getFileWatcher(path string) watch.FileWatcher {
 	return watch.NewPollingFileWatcher(path)
 }
 
-func fileCopy(src, dst string, perm os.FileMode) error {
+// fileCopy from src to dst setting the permissions and owner (if uid & gid are
+// both greater than 0)
+func fileCopy(src, dst string, uid, gid int, perm os.FileMode) error {
 	// Do a simple copy.
 	srcFile, err := os.Open(src)
 	if err != nil {
@@ -400,7 +402,13 @@ func fileCopy(src, dst string, perm os.FileMode) error {
 	defer dstFile.Close()
 
 	if _, err := io.Copy(dstFile, srcFile); err != nil {
-		return fmt.Errorf("Couldn't copy %v to %v: %v", src, dst, err)
+		return fmt.Errorf("Couldn't copy %q to %q: %v", src, dst, err)
+	}
+
+	if uid >= 0 && gid >= 0 {
+		if err := dstFile.Chown(uid, gid); err != nil {
+			return fmt.Errorf("Couldn't copy %q to %q: %v", src, dst, err)
+		}
 	}
 
 	return nil

client/allocdir/fs_darwin.go

@@ -24,3 +24,8 @@ func createSecretDir(dir string) error {
 func removeSecretDir(dir string) error {
 	return os.RemoveAll(dir)
 }
+
+// getOwner isn't implemented for Darwin
+func getOwner(os.FileInfo) (int, int) {
+	return -1, -1
+}

client/allocdir/fs_freebsd.go

@@ -24,3 +24,8 @@ func createSecretDir(dir string) error {
 func removeSecretDir(dir string) error {
 	return os.RemoveAll(dir)
 }
+
+// getOwner isn't implemented for FreeBSD
+func getOwner(os.FileInfo) (int, int) {
+	return -1, -1
+}

client/allocdir/fs_linux.go

@@ -88,3 +88,11 @@ func removeSecretDir(dir string) error {
 	}
 	return os.RemoveAll(dir)
 }
+
+func getOwner(fi os.FileInfo) (int, int) {
+	stat, ok := fi.Sys().(*syscall.Stat_t)
+	if !ok {
+		return -1, -1
+	}
+	return int(stat.Uid), int(stat.Gid)
+}

client/allocdir/fs_solaris.go

@@ -25,3 +25,8 @@ func createSecretDir(dir string) error {
 func removeSecretDir(dir string) error {
 	return os.RemoveAll(dir)
 }
+
+// getOwner isn't implemented for Solaris
+func getOwner(os.FileInfo) (int, int) {
+	return -1, -1
+}

client/allocdir/fs_unix.go

@@ -82,7 +82,7 @@ func getGid(u *user.User) (int, error) {
 
 // linkOrCopy attempts to hardlink dst to src and fallsback to copying if the
 // hardlink fails.
-func linkOrCopy(src, dst string, perm os.FileMode) error {
+func linkOrCopy(src, dst string, uid, gid int, perm os.FileMode) error {
 	// Avoid link/copy if the file already exists in the chroot
 	// TODO 0.6 clean this up. This was needed because chroot creation fails
 	// when a process restarts.
@@ -90,9 +90,9 @@ func linkOrCopy(src, dst string, perm os.FileMode) error {
 		return nil
 	}
 	// Attempt to hardlink.
-	if err := os.Link(src, dst); err == nil {
-		return nil
-	}
+	//if err := os.Link(src, dst); err == nil {
+	//	return nil
+	//}
 
-	return fileCopy(src, dst, perm)
+	return fileCopy(src, dst, uid, gid, perm)
 }

client/allocdir/fs_windows.go

@@ -21,8 +21,8 @@ var (
 )
 
 // linkOrCopy is always copies dst to src on Windows.
-func linkOrCopy(src, dst string, perm os.FileMode) error {
-	return fileCopy(src, dst, perm)
+func linkOrCopy(src, dst string, uid, gid int, perm os.FileMode) error {
+	return fileCopy(src, dst, uid, gid, perm)
 }
 
 // The windows version does nothing currently.
@@ -70,3 +70,8 @@ func MountSpecialDirs(taskDir string) error {
 func unmountSpecialDirs(taskDir string) error {
 	return nil
 }
+
+// getOwner doesn't work on Windows as Windows doesn't use int user IDs
+func getOwner(os.FileInfo) (int, int) {
+	return -1, -1
+}

client/allocdir/task_dir.go

@@ -163,7 +163,8 @@ func (t *TaskDir) embedDirs(entries map[string]string) error {
 
 			// Copy the file.
 			taskEntry := filepath.Join(t.Dir, dest)
-			if err := linkOrCopy(source, taskEntry, s.Mode().Perm()); err != nil {
+			uid, gid := getOwner(s)
+			if err := linkOrCopy(source, taskEntry, uid, gid, s.Mode().Perm()); err != nil {
 				return err
 			}
 
@@ -217,7 +218,8 @@ func (t *TaskDir) embedDirs(entries map[string]string) error {
 				continue
 			}
 
-			if err := linkOrCopy(hostEntry, taskEntry, entry.Mode().Perm()); err != nil {
+			uid, gid := getOwner(entry)
+			if err := linkOrCopy(hostEntry, taskEntry, uid, gid, entry.Mode().Perm()); err != nil {
 				return err
 			}
 		}