[Bug 882878] Re: With IPv6 disable openssh will on forward X connections

[Robie Basak]

Thanks for reporting this.

I'm a bit confused as to what sshd is trying to do, since on my system I
have an IPv4-only localhost and an IPv6-only localhost6 defined in
/etc/hosts.

I'm setting the priority to Low as this is an unusual configuration and
a workaround is available.

** Changed in: openssh (Ubuntu)
   Importance: Undecided => Low

** Summary changed:

- With IPv6 disable openssh will on forward X connections
+ With IPv6 disabled, openssh will not forward X connections

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https://bugs.launchpad.net/bugs/882878

Title:
  With IPv6 disabled, openssh will not forward X connections

Status in “openssh” package in Ubuntu:
  New

Bug description:
  If you disable IPv6 in /etc/sysctl.conf sshd will not forward X11.

  It logs the failue in /var/log/auth.log

  Oct 27 18:49:26 uscps002 sshd[14722]: Accepted password for root from 172.20.10.50 port 60322 ssh2
  Oct 27 18:49:26 uscps002 sshd[14722]: pam_unix(sshd:session): session opened for user root by (uid=0)
  Oct 27 18:49:27 uscps002 sshd[14722]: error: Failed to allocate internet-domain X11 display socket.

  Aparently the compiled sshd version will not try an ipv4 localhost if
  an ipv6 localhost does not exist.

  Placing the following line in /etc/ssh/sshd_config fixes the issue

  X11UseLocalHost no


  
  root at uscps002:/var/log# lsb_release -rd
  Description:	Ubuntu 11.10
  Release:	11.10
  root at uscps002:/var/log# 

  
  root at uscps002:/var/log# uname -a
  Linux uscps002 3.0.0-12-server #20-Ubuntu SMP Fri Oct 7 16:36:30 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

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