Unix sysdeps: Only copy /etc/machine-id to ${sysconfdir} in "ensure" mode

System integration scripts use dbus-uuidgen --ensure, so they are
unaffected by this, and in particular the solution to Bug #77941
is still valid.

The shared library is typically loaded by unprivileged users, so
trying to write out the machine-id file is not going to work anyway.
However, if we *can* write to our ${sysconfdir} - notably during
`make distcheck` - then it is unexpected that merely reading the
machine ID has the side-effect of writing to ${sysconfdir},
and in particular it will make the check for a complete uninstall
fail. We definitely must not delete the machine ID during
`make uninstall`.

Signed-off-by: Simon McVittie <smcv@collabora.com>
Reviewed-by: Philip Withnall <withnall@endlessm.com>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=101257

1 files changed, 7 insertions, 4 deletions

diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
index 8b6ac306..7bfb66fe 100644
--- a/dbus/dbus-sysdeps-unix.c
+++ b/dbus/dbus-sysdeps-unix.c
@@ -3922,10 +3922,13 @@ _dbus_read_local_machine_uuid (DBusGUID   *machine_id,
 
   if (b)
     {
-      /* try to copy it to the DBUS_MACHINE_UUID_FILE, but do not
-       * complain if that isn't possible for whatever reason */
-      _dbus_string_init_const (&filename, DBUS_MACHINE_UUID_FILE);
-      _dbus_write_uuid_file (&filename, machine_id, NULL);
+      if (create_if_not_found)
+        {
+          /* try to copy it to the DBUS_MACHINE_UUID_FILE, but do not
+           * complain if that isn't possible for whatever reason */
+          _dbus_string_init_const (&filename, DBUS_MACHINE_UUID_FILE);
+          _dbus_write_uuid_file (&filename, machine_id, NULL);
+        }
 
       return TRUE;
     }