From: Theo Buehler <tb@theobuehler.org>
Subject: Re: xlock: convert to new imsg API
To: tech@openbsd.org
Date: Thu, 18 Jan 2024 15:20:53 +0100

On Thu, Jan 18, 2024 at 03:16:01PM +0100, Claudio Jeker wrote:
> On Thu, Jan 18, 2024 at 03:07:35PM +0100, Theo Buehler wrote:
> > On Thu, Jan 18, 2024 at 03:04:37PM +0100, Theo Buehler wrote:
> > > On Thu, Jan 18, 2024 at 02:33:25PM +0100, Claudio Jeker wrote:
> > > > This diff converts the privsep code in xlock to use the new imsg API.
> > > > Overall I think the resulting code is easier to understand which is
> > > > important.
> > > > 
> > > > Use a do { } while (n == 0); loop to read until a full message was
> > > > received. I'm not sure if this pathological case can be triggered but
> > > > better to fix this.
> > > 
> > > ok, but please see below
> > > 
> > > > -- 
> > > > :wq Claudio
> > > > 
> > > > Index: app/xlockmore/xlock/privsep.c
> > > > ===================================================================
> > > > RCS file: /cvs/xenocara/app/xlockmore/xlock/privsep.c,v
> > > > diff -u -p -r1.3 privsep.c
> > > > --- app/xlockmore/xlock/privsep.c	14 Dec 2023 09:44:15 -0000	1.3
> > > > +++ app/xlockmore/xlock/privsep.c	5 Jan 2024 16:56:28 -0000
> > > > @@ -118,7 +118,6 @@ send_cmd(struct imsgbuf *ibuf, char *use
> > > >  			warn("imsg_add");
> > > >  			return -1;
> > > >  		}
> > > > -	wbuf->fd = -1;
> > > >  	imsg_close(ibuf, wbuf);
> > > 
> > > Out of curiosity, do you know where this idiom of setting the fd to -1
> > > before imsg_close() from? Did people malloc ibufs before this was
> > > centralized in libutil?
> 
> No idea. At least I did not see this pattern often.

I saw it in got and mdnsd predominantly, so I figured it may have been
an old habit.

> > ... and of course the freezeros need to be done conditionally on user/pass
> > != NULL
> > 
> 
> Uhm. The man page tells me an other story:
>      The freezero() function is similar to the free() function except it
>      ensures memory is explicitly discarded.  If ptr is NULL, no action
>      occurs.  If ptr is not NULL, the size argument must be equal to or
>      smaller than the size of the earlier allocation that returned ptr.

Yes. But strlen(NULL) explodes. So please do the freezero()
conditionally

	if (user != NULL)
		freezero(user, strlen(user));
		
	if (pass != NULL)
		freezero(pass, strlen(pass));

Then it's ok tb