Subject: [alpine-devel] main/xorg-server: Enable xcsecurity to allow ssh X11 forwarding

From: Jean-Louis Fuchs <[email-masked]>
Date: Sat, 4 Mar 2017 14:51:50 +0100

Hi

Could somebody take a look at this issue:

http://bugs.alpinelinux.org/issues/6696

I know I should have sent a patch to the aports list, but I missed the
wiki-page about patches. I don't want to duplicate things, so I hope
we can solve this on the bug-tracker.

Best,
    Jean-Louis

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From: Igor Falcomatà <[email-masked]>
Date: Sat, 4 Mar 2017 15:57:21 +0100

> we can solve this on the bug-tracker.

AFAIK, XCSECURITY are disabled on most (linux) Xorg packages, and on 
freebsd and cygwin too (just search xcsecurity/xsecurity on google).

I just tried some weeks ago to use ssh -X on a OpenBSD X11 server, and 
many applications just crashes with "bad access" or similar, as noted in 
this mail:
https://cygwin.com/ml/cygwin-xfree/2008-11/msg00154.html

Of course it is still possible to use ssh -Y to connect to Xorg 
remotely, using the "trusted forwarding".

ciao,
I.

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From: "[email-masked]" <[email-masked]>
Date: Sat, 4 Mar 2017 16:00:28 +0100

ciao,
I.

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From: Jean-Louis Fuchs <[email-masked]>
Date: Sat, 4 Mar 2017 16:54:00 +0100

Hi I

On Sat, Mar 04, 2017 at 04:00:28PM +0100, [email-masked] wrote:
> AFAIK, XCSECURITY are disabled on most (linux) Xorg packages, and on freebsd
> and cygwin too (just search xcsecurity/xsecurity on google).

ssh -X works on Debian, Arch, Ubuntu, Fedora, CentOS, SuSE.
The only distro that I know that has no xcsecurity is alpine.

> I just tried some weeks ago to use ssh -X on a OpenBSD X11 server, and many
> applications just crashes with "bad access" or similar, as noted in this
> mail:

All my applications work without problems. We are using it since more
than 10 years, never had a single problem.
 
> Of course it is still possible to use ssh -Y to connect to Xorg remotely,
> using the "trusted forwarding".

Well, I don't want to do trusted forwarding, because you have to trust
the machine you forward to 100%.

ssh -X is definitely nothing special, instable or esoteric. But I
don't understand the security implications completely, so I can accept
a well-founded no.

Best,
    Jean-Louis

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From: "[email-masked]" <[email-masked]>
Date: Sat, 4 Mar 2017 18:53:05 +0100

>>> http://bugs.alpinelinux.org/issues/6696

NB: i'm not the/a mantainer of the xorg package (on any other package)

> The only distro that I know that has no xcsecurity is alpine.

Ok, my fault, when I was researching on this subject some time ago, I 
found that these extension where disabled by default by the upstream 
(generic reasons like "obsolete" a/o "insecure") in favor of the new 
XACE extensions (which seems to be at least not used/incomplete, maybe 
someone has more updated infos?)

After that various distro (debian, red-hat, ..) have re-enabled it, eg:
https://www.redhat.com/archives/rhsa-announce/2013-November/msg00028.html
http://metadata.ftp-master.debian.org/changelogs/main/x/xorg-server/stable_changelog

but i'm on Slackware (and Alpine) so I didn't noticed it :)

 > ssh -X is definitely nothing special, instable or esoteric. But I

That's interesting, good to know; I was also using ssh -X a lot, but 
since it was disabled upstream I got this kind of troubles all the times 
I tried; probabily I have to test again, using the same distro/settings 
on both clients and server.

> don't understand the security implications completely, so I can accept

Did you already tried to recompile xorg on alpine with -xcsecurity enabled?

ciao,
I.

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