sshd failing in jail

From: Peter Jeremy <peterjeremy_at_optushome.com.au>
Date: Tue, 25 Aug 2009 05:33:44 +1000
I am attempting to build an i386 jail on an amd64 box to build
packages for my netbook.  The host is running -current from just over
two weeks ago and the jail is -current from early June.  The jail was
built by doing a dump|restore of my netbook and then tweaking various
config files to give it a new identity.  The jail's devfs is using
"devfsrules_jail" from /etc/default/devfs.rules.

The jail starts OK but when I attempt to ssh into it, I just get
"Connection closed by <jail IP address>".  Adding debugging on the
child, I see that it occurs immediately following:
"debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY".

Looking at a ktrace of the jailed sshd, the problem is inside the
privilege separation child.  When I turned off privilege separation, I
can log into the jail.  When I added a syslog socket inside the jailed
chroot and left privilege separation enabled, I got:
Aug 24 19:04:40 server sshd[70809]: error: buffer_put_bignum2_ret: BN too small
Aug 24 19:04:40 server sshd[70809]: fatal: buffer_put_bignum2: buffer error
Unfortunately, buffer_put_bignum2() is called from a number of locations
so the actual problem is not clear.

Looking at google doesn't turn up anything useful.

Does anyone have any suggestions?

-- 
Peter Jeremy

Received on Mon Aug 24 2009 - 17:33:48 UTC

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