GNU bug report logs - #22930
X11 forwarding fails without /tmp/.X11-unix directory

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#22930: closed (X11 forwarding fails without /tmp/.X11-unix
 directory)
Date: Tue, 06 Oct 2020 04:05:02 +0000

[Message part 1 (text/plain, inline)]

Your message dated Tue, 06 Oct 2020 00:04:26 -0400
with message-id <87h7r8huet.fsf <at> gmail.com>
and subject line Re: bug#24049: GuixSD - problem with X11 forwarding
has caused the debbugs.gnu.org bug report #22930,
regarding X11 forwarding fails without /tmp/.X11-unix directory
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
22930: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=22930
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: myglc2 <myglc2 <at> gmail.com>
To: bug-guix <at> gnu.org
Subject: X11 forwarding fails without /tmp/.X11-unix directory
Date: Sun, 06 Mar 2016 20:10:33 -0500

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Example: using guix commit 59a4dd5 with openssh xauth & emacs in the
user profile (c02glc.scm) and a minimal system profile (c02system.scm),
after a reboot we see ...

nemo:~ $ ssh g1
glc <at> g1's password:
X11 forwarding request failed on channel 0

... and in /var/log/messages ...

Mar  6 19:23:35 localhost lshd[372]: lshd: Failed to cd to `/tmp/.X11-unix' (errno = 2): No such file or directory 
Mar  6 19:23:35 localhost lshd[372]: lshd: Updating utmp for login failed (errno = 2): No such file or directory 

If we do ...

mkdir /tmp/.X11-unix

... logout and login, forwarding works, emacs runs in X, and
/var/log/messages is clean. If we reboot, X11 forwarding again fails.

[c02glc.scm (application/octet-stream, attachment)]

[c02system.scm (application/octet-stream, attachment)]

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From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: ludo <at> gnu.org (Ludovic Courtès)
Cc: myglc2 <myglc2 <at> gmail.com>, 24049-done <at> debbugs.gnu.org,
 22930-done <at> debbugs.gnu.org
Subject: Re: bug#24049: GuixSD - problem with X11 forwarding
Date: Tue, 06 Oct 2020 00:04:26 -0400

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Hello,

ludo <at> gnu.org (Ludovic Courtès) writes:

[...]

> I believe this is a bug in lshd fixed by something along the lines of
> the attached patch.
>
> Niels, what do you think?
>
> (Strangely I can’t find equivalent code in OpenSSH.)
>
> Thanks,
> Ludo’.
>
> --- /tmp/lsh-2.1/src/server_x11.c	2016-08-01 11:58:54.714647794 +0200
> +++ /tmp/lsh-2.1/src/server_x11.c.new	2016-08-01 11:58:46.606563478 +0200
> @@ -151,7 +151,7 @@ DEFINE_COMMAND(open_forwarded_x11)
>  #define X11_MIN_DISPLAY 10
>  #define X11_MAX_DISPLAY 1000
>  
> -/* FIXME: Create the /tmp/.X11-unix directory, if needed. Figure out
> +/* FIXME: Figure out
>   * if and how we should use /tmp/.X17-lock. Consider using display
>   * "unix:17" instead of just ":17".
>   */
> @@ -253,6 +253,7 @@ open_x11_socket(struct ssh_channel *chan
>  
>    old_umask = umask(0077);
>    
> +  mkdir(X11_SOCKET_DIR, S_IRWXU | S_IRWXG | S_IRWXO | S_ISVTX);
>    old_cd = lsh_pushd(X11_SOCKET_DIR, &dir, 0, 0);
>    if (old_cd < 0)
>      {

I tried the above fix and ran a VM with the attached config (the custom
kernel stuff was to try something else at the same time).  It fixes the
error about the directory, but it would still fail at X11 forwarding
(there was an error message: "Can't find any xauth information for X11
display").

I ended up figuring out it needed libxau to work; combined with your
patch, this fixes X11 forwarding.

Fixed in commit 0ec195ff02.

For the record, I've done the tests in a VM using the attached system
config.  The custom kernel stuff is unrelated.

Thanks,

Closing,

Maxim

[config-custom-kernel.scm (text/plain, attachment)]

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