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Old 10-26-2011, 09:56 AM
Rainer Traut
 
Default C6: ssh X-forwarding does not work

Hi all,

I have C6 i386 with cr repo enabled;

problem is, I can't get x-forwarding to work, xorg-x11-auth rpm is
installed, have checked sshd config for

#X11Forwarding no
X11Forwarding yes
#X11DisplayOffset 10

Here is a verbose ssh logon, I can't see any difference to a working server:

debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug1: Entering interactive session.
debug2: callback start
debug2: x11_get_proto: /usr/bin/xauth list unix:10.0 2>/dev/null
debug1: Requesting X11 forwarding with authentication spoofing.
debug2: channel 0: request x11-req confirm 0
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 0

and netstat does not show the open ports in the 60xx range:

# netstat -antp|grep 60
tcp 0 0 192.168.200.31:22 192.168.200.30:58604
VERBUNDEN 2537/sshd: xxx [

Display var is not set...:

[root@tr-centos ~]# env|grep -i DISPLAY
[root@tr-centos ~]#

Any obvious mistake?

Thx
Rainer
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Old 10-26-2011, 01:18 PM
John Hodrien
 
Default C6: ssh X-forwarding does not work

On Wed, 26 Oct 2011, Lorenzo Martínez Rodríguez wrote:


Hi,

I have a working configuration with CentOS 6. Can you try to set next
lines in /etc/ssh/sshd_config and restart SSH server please?

#X11Forwarding no
X11Forwarding yes
#X11DisplayOffset 10
X11UseLocalhost yes


In fact I do not have xorg-x11-auth rpm installed:

[root@Carmen ~]# rpm -qa|grep -i xorg-x11-auth
[root@Carmen ~]#

and it works...


He meant xorg-x11-xauth and I'm 99% certain you *need* that installed on the
target machine for ssh forwarding to work.

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Old 10-26-2011, 02:46 PM
Rainer Traut
 
Default C6: ssh X-forwarding does not work

Am 26.10.2011 15:18, schrieb John Hodrien:
> On Wed, 26 Oct 2011, Lorenzo Martínez Rodríguez wrote:
>
>> Hi,
>>
>> I have a working configuration with CentOS 6. Can you try to set next
>> lines in /etc/ssh/sshd_config and restart SSH server please?
>>
>> #X11Forwarding no
>> X11Forwarding yes
>> #X11DisplayOffset 10
>> X11UseLocalhost yes
>>
>>
>> In fact I do not have xorg-x11-auth rpm installed:
>>
>> [root@Carmen ~]# rpm -qa|grep -i xorg-x11-auth
>> [root@Carmen ~]#
>>
>> and it works...
>
> He meant xorg-x11-xauth and I'm 99% certain you *need* that installed on
> the
> target machine for ssh forwarding to work.

Yes, you need this rpm on the target machine.

Ok, solved.
I set debugging of sshd up and see this message:
error: Failed to allocate internet-domain X11 display socket.

Google shows this:
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/136947

And I have this in systl.conf:

# Disable ipv6
net.ipv6.conf.all.disable_ipv6 = 1

I added
AddressFamily inet
to sshd_config and now it works.

Thx guys,
Rainer
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Old 10-28-2011, 08:10 AM
Steve Brooks
 
Default C6: ssh X-forwarding does not work

On Wed, 26 Oct 2011, John Hodrien wrote:


On Wed, 26 Oct 2011, Lorenzo Martínez Rodríguez wrote:


Hi,

I have a working configuration with CentOS 6. Can you try to set next
lines in /etc/ssh/sshd_config and restart SSH server please?

#X11Forwarding no
X11Forwarding yes
#X11DisplayOffset 10
X11UseLocalhost yes


In fact I do not have xorg-x11-auth rpm installed:

[root@Carmen ~]# rpm -qa|grep -i xorg-x11-auth
[root@Carmen ~]#

and it works...


He meant xorg-x11-xauth and I'm 99% certain you *need* that installed on the
target machine for ssh forwarding to work.


I have a few "sl6.1" worstations that do not have "xorg-x11-xauth"
installed and it does *not* seem to appear in the repos. Yet
X11-Forwarding works fine.


Steve_____________________________________________ __
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Old 10-28-2011, 08:30 AM
John Hodrien
 
Default C6: ssh X-forwarding does not work

On Fri, 28 Oct 2011, Steve Brooks wrote:

> I have a few "sl6.1" worstations that do not have "xorg-x11-xauth"
> installed and it does *not* seem to appear in the repos. Yet
> X11-Forwarding works fine.

It's in the base repos for SL, so it definitely should be appearing. Without
a functioning xauth, I've never seen functional X forwarding.

I would be interested to know what ssh -Yv that-host-without-xauth shows.
Without xauth I get:

debug1: Remote: No xauth program; cannot forward with spoofing.

jh
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Old 10-28-2011, 03:00 PM
Lamar Owen
 
Default C6: ssh X-forwarding does not work

On Friday, October 28, 2011 04:10:05 AM Steve Brooks wrote:

> I have a few "sl6.1" worstations that do not have "xorg-x11-xauth"
> installed and it does *not* seem to appear in the repos. Yet
> X11-Forwarding works fine.

That's mighty strange, as a basically scratch SL6.1 install here shows:
[root@pe1600sc-2 ~]# repoquery --qf "%-20{repoid} %{name}" xorg-x11-xauth
sl xorg-x11-xauth
[root@pe1600sc-2 ~]# cat /etc/issue
Scientific Linux release 6.1 (Carbon)
Kernel
on an m

[root@pe1600sc-2 ~]#

On a CentOS 6.0+CR VM here:

[root@z1-c6 ~]# repoquery --qf "%-20{repoid} %{name}" xorg-x11-xauth
base xorg-x11-xauth
[root@z1-c6 ~]# cat /etc/issue
CentOS Linux release 6.0 (Final)
Kernel
on an m

[root@z1-c6 ~]#

I did absolutely nothing special to either of these two boxes (just a basic installation that included GNOME and other server things (these boxes get used as remote desktop servers in addition to other duties, so GUI is required), and X forwarding works fine. I typically use X forwarding to run a few GUI programs that are mighty handy, such as palimpsest (GNOME Disk Utility) which puts all in one place lots and lots of useful information about your disk devices that would otherwise require many command line invocations to grab.

Both boxes have xorg-x11-xauth installed.
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Old 10-28-2011, 11:08 PM
Les Mikesell
 
Default C6: ssh X-forwarding does not work

On Fri, Oct 28, 2011 at 5:59 PM, Lorenzo Martínez Rodríguez
<lorenzo@lorenzomartinez.es> wrote:
>
> oooooopssss my fail! I have mistyped one character
>
> [root@Carmen tmp]# rpm -qa| grep -i xorg-x11-xauth
> xorg-x11-xauth-1.0.2-7.1.el6.x86_64
> [root@Carmen tmp]# rpm -qa|grep -i xorg-x11-auth
> [root@Carmen tmp]#
>
> So, yes,.. I have that packet installed! Sorry for the misunderstood.
> Just the lack of one "x" started the flame.

Do some of the checkbox installs omit it? I just ran into this on a
system where I chose the 'web server' install, then wanted to run
gparted remotely.

--
Les Mikesell
lesmikesell@gmail.com
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Old 10-29-2011, 07:58 AM
John Hodrien
 
Default C6: ssh X-forwarding does not work

On Sat, 29 Oct 2011, Les Mikesell wrote:

> Do some of the checkbox installs omit it? I just ran into this on a
> system where I chose the 'web server' install, then wanted to run
> gparted remotely.

Yes, it's definitely possible to install without it. I've done the same as
you when setting up servers and had to add xauth afterwards to get remote X
working. It's a real gotcha for people who don't know about it, as other than
DISPLAY not being set, nothing leaps out at you to say it's because xauth
isn't installed. It'd be quite nice if default ssh emitted a warning message
about this at a non-debug level.

jh
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Old 10-29-2011, 08:18 AM
John R Pierce
 
Default C6: ssh X-forwarding does not work

On 10/29/11 12:58 AM, John Hodrien wrote:
> Yes, it's definitely possible to install without it. I've done the same as
> you when setting up servers and had to add xauth afterwards to get remote X
> working. It's a real gotcha for people who don't know about it, as other than
> DISPLAY not being set, nothing leaps out at you to say it's because xauth
> isn't installed. It'd be quite nice if default ssh emitted a warning message
> about this at a non-debug level.

well, there's the subtle clue that the first time you log onto a
particular account with X forwarding, xauth prints a message about
saving the .Xauth file....




--
john r pierce N 37, W 122
santa cruz ca mid-left coast

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Old 10-29-2011, 11:28 AM
John Hodrien
 
Default C6: ssh X-forwarding does not work

On Sat, 29 Oct 2011, John R Pierce wrote:

> well, there's the subtle clue that the first time you log onto a
> particular account with X forwarding, xauth prints a message about
> saving the .Xauth file....

Sure, but that means you're looking for absence of an info message (that you
typically don't care all that much about) to let you know something's wrong.
That's very easy to miss.

jh
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