From e42d2d1da81cd766478ee29d3fc07e80ef7cadac Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher <jakobunt@gmail.com>
Date: Sun, 9 Sep 2018 11:43:18 +0200
Subject: [PATCH] restore: suppress lchown errors when not running as root

Like "cp -a" and "rsync -a" do, only report lchown errors if we run
as root.

Like cp from GNU coreutils does, we check Geteuid() to determine if
we are running as root
( http://git.savannah.gnu.org/cgit/coreutils.git/tree/src/copy.c#n3012 ).

On Windows, lchown errors are always reported.

Fixes https://github.com/restic/restic/issues/1766
---
 changelog/unreleased/issue-1766 |  7 +++++++
 internal/restic/node.go         | 11 ++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 changelog/unreleased/issue-1766

diff --git a/changelog/unreleased/issue-1766 b/changelog/unreleased/issue-1766
new file mode 100644
index 000000000..6d8e312dd
--- /dev/null
+++ b/changelog/unreleased/issue-1766
@@ -0,0 +1,7 @@
+Enhancement: restore: suppress lchown errors when not running as root
+
+Like "cp" and "rsync" do, restic now only reports errors for changing
+the ownership of files during restore if it is run as root, on non-Windows
+operating systems. On Windows, the error is reported as usual.
+
+https://github.com/restic/restic/issues/1766
diff --git a/internal/restic/node.go b/internal/restic/node.go
index cec7938e5..c8b089791 100644
--- a/internal/restic/node.go
+++ b/internal/restic/node.go
@@ -186,7 +186,16 @@ func (node Node) restoreMetadata(path string) error {
 	var firsterr error
 
 	if err := lchown(path, int(node.UID), int(node.GID)); err != nil {
-		firsterr = errors.Wrap(err, "Lchown")
+		// Like "cp -a" and "rsync -a" do, we only report lchown permission errors
+		// if we run as root.
+		// On Windows, Geteuid always returns -1, and we always report lchown
+		// permission errors.
+		if os.Geteuid() > 0 && os.IsPermission(err) {
+			debug.Log("not running as root, ignoring lchown permission error for %v: %v",
+				path, err)
+		} else {
+			firsterr = errors.Wrap(err, "Lchown")
+		}
 	}
 
 	if node.Type != "symlink" {