[pve-devel] [PATCH cluster v6] implement chown and chmod for user root group www-data and perm 0640

[Thomas Lamprecht]

From: Stefan Priebe <s.priebe at profihost.ag>

This allows us to use management software for files inside of /etc/pve.
e.g. saltstack which rely on being able to set uid,gid and chmod

Signed-off-by: Thomas Lamprecht <t.lamprecht at proxmox.com>
Signed-off-by: Stefan Priebe <s.priebe at profihost.ag>
---

changes v5 -> v6: adress Wolfgangs comments:
* explicitly allow only setting the mode we support, do not mask out sgid/suid
  bits
* use more fitting -EPERM not -EACCES, EACCES is for the case that there are
  access problems on the path traversal to the file, whereas EPERM is for
  access/permission problems for the file itself.

 data/src/pmxcfs.c | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/data/src/pmxcfs.c b/data/src/pmxcfs.c
index 1b6cbcc..0f09937 100644
--- a/data/src/pmxcfs.c
+++ b/data/src/pmxcfs.c
@@ -186,6 +186,40 @@ ret:
 	return ret;
 }
 
+static int cfs_fuse_chmod(const char *path, mode_t mode)
+{
+	int ret = -EPERM;
+
+	cfs_debug("enter cfs_fuse_chmod %s", path);
+
+	mode_t allowed_mode = (S_IRUSR | S_IWUSR);
+	if (!path_is_private(path))
+		allowed_mode |= (S_IRGRP);
+
+	// allow only setting our supported modes (0600 for priv, 0640 for rest)
+	if (mode == allowed_mode)
+		ret = 0;
+
+	cfs_debug("leave cfs_fuse_chmod %s (%d) mode: %o", path, ret, (int)mode);
+
+	return ret;
+}
+
+static int cfs_fuse_chown(const char *path, uid_t user, gid_t group)
+{
+	int ret = -EPERM;
+
+	cfs_debug("enter cfs_fuse_chown %s", path);
+
+	// we get -1 if no change should be made
+	if ((user == 0 || user == -1) && (group == cfs.gid || group == -1))
+		ret = 0;
+
+	cfs_debug("leave cfs_fuse_chown %s (%d) (uid: %d; gid: %d)", path, ret, user, group);
+
+	return ret;
+}
+
 static int cfs_fuse_mkdir(const char *path, mode_t mode)
 {
 	cfs_debug("enter cfs_fuse_mkdir %s", path);
@@ -488,7 +522,9 @@ static struct fuse_operations fuse_ops = {
 	.readlink = cfs_fuse_readlink,
 	.utimens = cfs_fuse_utimens,
 	.statfs = cfs_fuse_statfs,
-	.init = cfs_fuse_init
+	.init = cfs_fuse_init,
+	.chown = cfs_fuse_chown,
+	.chmod = cfs_fuse_chmod
 };
 
 static char *
-- 
2.11.0