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Date: Thu, 1 Aug 2002 15:51:12 +0100
From: Niall O Broin <niall@linux.ie>
To: ilug@linux.ie
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Subject: [ILUG] Strange ssh problem
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I have a strange problem with one user in a small network using ssh.
Everyone in the network uses ssh and they run an ssh-agent on login. This
works fine for conveniently wandering around the network and to some of our
external boxes - or did, until today. Suddenly, when one user (alfred) tries
to ssh anywhere he's asked for a password. He says He changed nothing (don't
they all) but I do actually believe him. I used ssh-keygen to make new keys
but that didn't help. 

I created a new user alfio into whose home directory I copied alfred's .ssh
directory - alfio can wander around free as a bird without being asked for a
password ever (except of course for the passphrase to load the identiy into
the agent).

In case there was something else in Alfred' environment, I copied .??* from
alfred's home directory to alfio's, remembering to change ownership
afterwards. Still alfio is as free as a bird.

We use only SSH2 with DSA keys. An extract from a ssh -v for alfio is below

debug1: got SSH2_MSG_SERVICE_ACCEPT
debug1: authentications that can continue: publickey,password
debug1: next auth method to try is publickey
debug1: userauth_pubkey_agent: testing agent key /home/alfio/.ssh/id_dsa
debug1: input_userauth_pk_ok: pkalg ssh-dss blen 434 lastkey 0x80916f0 hint -1
debug1: ssh-userauth2 successful: method publickey

and before starting this ssh attempt, ssh-add -l for alfio said:

1024 07:4c:7c:90:0d:28:41:3a:95:c2:81:3d:ba:c4:3d:03 /home/alfio/.ssh/id_dsa (DSA)

whereas with alfred the same segment of the debug log went

debug1: got SSH2_MSG_SERVICE_ACCEPT
debug1: authentications that can continue: publickey,password
debug1: next auth method to try is publickey
debug1: userauth_pubkey_agent: testing agent key /nfshome/alfred/.ssh/id_dsa
debug1: authentications that can continue: publickey,password

and before starting this ssh attempt, ssh-add -l for alfred said:

1024 07:4c:7c:90:0d:28:41:3a:95:c2:81:3d:ba:c4:3d:03 /home/alfred/.ssh/id_dsa (DSA)


This problem is definitely related to alfred as a user - it happens when he
logs in on differing workstations (all NFS mounting the same home
directories) and the other users (including good old alfio) don't have any
problems.


Niall

-- 
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