[Libguestfs] [PATCH nbdkit] server: Add -D nbdkit.environ=1 to dump the environment

[Richard W.M. Jones]

On Mon, May 08, 2023 at 08:35:53AM -0500, Eric Blake wrote:
> On Sun, May 07, 2023 at 11:43:17AM +0100, Richard W.M. Jones wrote:
> > This is not secure so should not be used routinely.  Also we do not
> > attempt to filter environment variables, so even ones containing
> > multiple lines or special characters are all sent to nbdkit_debug.
> > 
> > The reason for adding this is to allow for debugging the new
> > nbd_set_socket_activation_name(3) API added in libnbd 1.16.
> > ---
> 
> > +static void
> > +dump_environment (void)
> > +{
> > +  size_t i;
> > +
> > +  for (i = 0; environ[i]; ++i)
> > +    nbdkit_debug ("%s", environ[i]);
> 
> We have shell_quote in common/utils/quote.c; shouldn't we use it here
> to avoid ambiguities when an env-var contains newline?

I was wondering more generally about this.  I actually think that
nbdkit_debug ought to be more tolerant of unusual inputs -- not least
because there are potential security concerns.  All kinds of random
user-controlled strings are sent to nbdkit_debug and it just dumps it
to stderr entirely unfiltered.  So rather than fixing this one
instance, we should fix nbdkit_debug.  I'll look at a follow-up patch.

> > +}
> > +
> > +#endif /* !WIN32 */
> > +
> >  int
> >  main (int argc, char *argv[])
> >  {
> > @@ -662,6 +682,14 @@ main (int argc, char *argv[])
> >    /* Check all debug flags were used, and free them. */
> >    free_debug_flags ();
> >  
> > +#ifndef WIN32
> > +  /* Dump the environment if asked.  This is the earliest we can do it
> > +   * because it uses a debug flag.
> > +   */
> > +  if (nbdkit_debug_environ && verbose)
> > +    dump_environment ();
> 
> Why does this not work on WIN32?

I just assumed it wouldn't, but you're right that it would work.

I'll respin this patch once I've tested what it would do on Windows.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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