Hi,

Diego Nicola Barbato <dnbarbato@posteo.de> skribis:

> XLockMore (as invoked by the command `xlock') displays the wrong time on
> the lock screen.  Instead of honouring the timezone set in `config.scm'
> (as do other programs e.g. the `date' command) it displays UTC.

The problem is that setuid programs ignore $TZDIR; quoth ‘tzfile.c’ in
libc:

      /* We must not allow to read an arbitrary file in a setuid
	 program.  So we fail for any file which is not in the
	 directory hierachy starting at TZDIR
	 and which is not the system wide default TZDEFAULT.  */
      if (__libc_enable_secure
	  && ((*file == '/'
	       && memcmp (file, TZDEFAULT, sizeof TZDEFAULT)
	       && memcmp (file, default_tzdir, sizeof (default_tzdir) - 1))
	      || strstr (file, "../") != NULL))
	/* This test is certainly a bit too restrictive but it should
	   catch all critical cases.  */
	goto ret_free_transitions;

Thus, if I set TZ=Europe/Paris, I see that setuid binaries look for
timezone data only under
/gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/share/zoneinfo/Europe/Paris,
which doesn’t exist.

Since GuixSD provides /etc/localtime already, we can actually unset TZ.
And when we do so, setuid binaries simply honor /etc/localtime and don’t
go searching for timezone data elsewhere, and they see the right time.

Can you confirm that:

  (unset TZ; xlock)

works for you?

I’ll commit the patch below if it does.

Thanks,
Ludo’.