From a66440c66816c919acfaa4cd079fe2fae7043294 Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Mon, 28 Nov 2016 22:46:04 +0100
Subject: fusefrontend: use Lchown when preserving owner

This prevents (unlikely) symlink race attacks
---
 internal/fusefrontend/fs.go     |  2 +-
 internal/fusefrontend/fs_dir.go | 13 ++++++-------
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/internal/fusefrontend/fs.go b/internal/fusefrontend/fs.go
index f41e9a7..261d690 100644
--- a/internal/fusefrontend/fs.go
+++ b/internal/fusefrontend/fs.go
@@ -157,7 +157,7 @@ func (fs *FS) Create(path string, flags uint32, mode uint32, context *fuse.Conte
 	if fs.args.PreserveOwner {
 		err = fd.Chown(int(context.Owner.Uid), int(context.Owner.Gid))
 		if err != nil {
-			tlog.Warn.Printf("Create: Chown failed: %v", err)
+			tlog.Warn.Printf("Create: fd.Chown failed: %v", err)
 		}
 	}
 	return NewFile(fd, writeOnly, fs)
diff --git a/internal/fusefrontend/fs_dir.go b/internal/fusefrontend/fs_dir.go
index 6b581b1..05cea75 100644
--- a/internal/fusefrontend/fs_dir.go
+++ b/internal/fusefrontend/fs_dir.go
@@ -54,9 +54,9 @@ func (fs *FS) Mkdir(newPath string, mode uint32, context *fuse.Context) (code fu
 		err = os.Mkdir(cPath, os.FileMode(mode))
 		// Set owner
 		if fs.args.PreserveOwner {
-			err = os.Chown(cPath, int(context.Owner.Uid), int(context.Owner.Gid))
+			err = os.Lchown(cPath, int(context.Owner.Uid), int(context.Owner.Gid))
 			if err != nil {
-				tlog.Warn.Printf("Mkdir: Chown failed: %v", err)
+				tlog.Warn.Printf("Mkdir: Lchown failed: %v", err)
 			}
 		}
 		return fuse.ToStatus(err)
@@ -94,7 +94,6 @@ func (fs *FS) Mkdir(newPath string, mode uint32, context *fuse.Context) (code fu
 			return fuse.ToStatus(err)
 		}
 	}
-
 	// Set permissions back to what the user wanted
 	if origMode != mode {
 		err = os.Chmod(cPath, os.FileMode(origMode))
@@ -104,13 +103,13 @@ func (fs *FS) Mkdir(newPath string, mode uint32, context *fuse.Context) (code fu
 	}
 	// Set owner
 	if fs.args.PreserveOwner {
-		err = os.Chown(cPath, int(context.Owner.Uid), int(context.Owner.Gid))
+		err = os.Lchown(cPath, int(context.Owner.Uid), int(context.Owner.Gid))
 		if err != nil {
-			tlog.Warn.Printf("Mkdir: Chown failed: %v", err)
+			tlog.Warn.Printf("Mkdir: Lchown 1 failed: %v", err)
 		}
-		err = os.Chown(filepath.Join(cPath, nametransform.DirIVFilename), int(context.Owner.Uid), int(context.Owner.Gid))
+		err = os.Lchown(filepath.Join(cPath, nametransform.DirIVFilename), int(context.Owner.Uid), int(context.Owner.Gid))
 		if err != nil {
-			tlog.Warn.Printf("Mkdir: Chown failed: %v", err)
+			tlog.Warn.Printf("Mkdir: Lchown 2 failed: %v", err)
 		}
 	}
 	return fuse.OK
-- 
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