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

Alejandro Colomar via Mutt-dev <[email protected]> Tue, 21 Apr 2026 16:08:41 +0200

Newsgroups	gmane.mail.mutt.devel
Message-ID	<aeeEwViufDhMWTsS@devuan>

Hi Greg,

On 2026-04-21T15:48:28+0200, Greg KH wrote:
> On Tue, Apr 21, 2026 at 03:42:40PM +0200, Alejandro Colomar via Mutt-dev wrote:
> > Hi Kevin,
> > 
> > On 2026-04-21T21:20:17+0800, Kevin J. McCarthy wrote:
> > > On Tue, Apr 21, 2026 at 02:32:54PM +0200, Alejandro Colomar via Mutt-dev wrote:
> > > > On 2026-04-21T12:49:43+0200, Greg KH wrote:
> > > > > On Tue, Apr 21, 2026 at 06:13:44PM +0800, Kevin J. McCarthy wrote:
> > > > > > 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.
> > > >
> > > > BTW, getentropy(3) --which itself calls getrandom(2)-- was added to both
> > > > glibc and musl in the same versions as getrandom(2).  Should we prefer
> > > > getentropy(3) or getrandom(2)?  getentropy(3) seems to have been
> > > > standardized by POSIX.1-2024 --which I'll document in the manual page
> > > > right now--.
> > > 
> > > One tiny advantage for getrandom(2) is the GRND_NONBLOCK flag.  But
> > > perhaps there isn't a "real" issue there for the request sizes mutt will
> > > be passing.
> > 
> > AFAIK, these days getrandom(2) doesn't block except in weird cases at
> > boot.
> 
> And even then, that should not happen anymore on a sane system.

Thanks for confirming!

> 
> > The manual page random(7) needs to be updated, but I need someone expert
> > in the matter to send and discuss patches.  (CC += Mingye)
> > 
> > BTW, Greg, would you be able to help with that?
> 
> Nope! :)
> 
> I would recommend Jason, the random kernel maintainer, for help with
> that.

Thanks!  I've asked Ted and Jason.

> 
> > > I've already been playing with the code some tonight.  This is just a
> > > WIP below, compiled but not tested.  Of course, it would be easy to swap
> > > to using getentropy() if you and Greg think that's a better idea.
> > 
> > It makes sense to start with getrandom(2), since as you say, it's easy
> > to swap to it.
> 
> Agreed, the path seems sane.
> 
> thanks,
> 
> greg k-h


Cheers,
Alex

-- 
<https://www.alejandro-colomar.es>

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