X11 forwarding rejected:due to bug in particular ssh patch on solaris 9

Applicable to :
Operating system details : Solaris 9 9/05 s9s_u   Generic_118558-11

sshd version Sun_SSH_1.0.1

Problem:

I was getting the following error while trying to open X window using xterm.

Even after enabling X11Forwarding  in /etc/ssh/sshd_config , and restarting sshd daemon the problem was still there.

Solution:

Later i came to know it was due to a bug with a particular ssh patch.

I got the following messages in /var/adm/messages

Jun  4 20:38:17 PSBLD060 sshd[7646]: [ID 800047 auth.error] error: Failed to allocate internet-domain X11 display socket.

Jun  4 20:38:40 PSBLD060 sshd[7647]: [ID 800047 auth.error] error: Failed to allocate internet-domain X11 display socket.

Jun  4 20:38:48 PSBLD060 sshd[7648]: [ID 800047 auth.error] error: Failed to allocate internet-domain X11 display socket.

Jun  4 20:39:13 PSBLD060 sshd[7870]: [ID 800047 auth.error] error: Failed to allocate internet-domain X11 display socket.

Jun  4 20:40:38 PSBLD060 sshd[7873]: [ID 800047 auth.error] error: Failed to allocate internet-domain X11 display socket.

Jun  4 20:44:58 PSBLD060 sshd[7941]: [ID 800047 auth.error] error: Failed to allocate internet-domain X11 display socket.

sshd syslogs the message error: Failed to allocate internet-domain X11 display socket. What it really means is that it failed to allocate any IPv6 listening sockets because you don't have IPv6 enabled, and it refuses to fall back to IPv4.

There is a work around for this issue.

Just add ipv6 loopback interface as follows

# ifconfig   lo0   inet6   plumb  up

# ifconfig -a

lo0: flags=1000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4> mtu 8232 index 1

        inet 127.0.0.1 netmask ff000000

ce0: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2

        inet 10.1.18.169 netmask ffffff00 broadcast 10.1.18.255

        ether 0:14:4f:24:d5:a4

lo0: flags=2000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv6> mtu 8252 index 1

        inet6 ::1/128

# /etc/ssh/sshd stop

From ssh session itself we can do this you won't loose the session.

Then run

# /usr/lib/ssh/sshd   -4

Now try to connect using xterm it will work.

great you have done.

Now we will  summarise.

# vi /etc/ssh/sshd_config

X11Forwarding  yes

# ifconfig  lo0  inet6  plumb  up

# /etc/init.d/sshd  stop

# /usr/lib/ssh/sshd  -4

That is it.