Re: Random MIME boundary needed? (was: Security findings)

On Tue, Apr 21, 2026 at 06:13:44PM +0800, Kevin J. McCarthy wrote:
> On Tue, Apr 21, 2026 at 09:40:37AM +0200, Werner Koch wrote:
> > I see no attack here.  However, mutt_random_bytes is also used to
> > construct message ids.  I would suggest to make them less predictable.
> > But do not use new crypto algorithms for that.  All systems come with
> > proper random number generators these days.  Something like
> > 
> >  /* Create an unpredicable nonce of LENGTH bytes in BUFFER. */
> >  void gcry_create_nonce (void *buffer, size_t length);
> > 
> > if you anyway link to Libgcrypt, or use the respective functions from
> > the other crypto libs.
> 
> Thank you Werner and Greg KH! (I'll just reply to you both here)
> 
> Something like gcry_create_nonce() sounds perfect.  Unfortunately we
> don't link to Libgcrypt.
> 
> Perhaps, as Greg KH suggested we could try checking for getrandom(), and
> then arc4random_buf(), and if both are missing I guess fall back to what
> we have now?

I would recommend that.  I would hope that most modern systems have
getrandom() by now.

thanks,

greg k-h