I'm trying to get to the bottom of an issue with key authentication on
AIX and I'm not sure I believe IBM's answer so I thought I'd post here
to see what answer I'd get from the SSH side.

We have three different methods of authentication - local, VAS (AD),
NIS. On our Linux and Solaris servers it's very simple to set the
authentication order with nsswitch.conf and SSH follows that order on
those systems without any issues - even with key-authentication. On AIX
however if we use key-authentication it always hits NIS before VAS. IBM
is telling us that it is because that's how SSH works and we keep trying
to tell them that it doesn't work like that anywhere else - only on AIX.
It's my understanding that SHH will authenticate in the order
established by the OS and not vice-versa - is this thinking correct?

We have workarounds for the issue, but we'd like to have IBM own up to
what we perceive as a flaw in their authentication model instead of
blaming it on how SSH works.

Here is the latest from their developers:

"Discussed about the SSH design.
As we are copying the public key in the /home/(user). So in this case
authentication is done by the SSH Server. But in case of password
authenticationNIS server or VAS server is doing the authentication.
Therefore in the password case it is able to differentiate between NIS
and VAS user.
But in case of Public Key Authentication it is first taking the NIS
user and then server is doing the authentication.
So it is not able to differentiate between the two users in case of

My belief is even with key-authentication SSH still has to have the user
account validated by the OS and that the order in which this validation
will occur is determined by the OS not the SSH server. At least this is
what happens on our other operating systems - we can switch the
authentication order and it will authenticate to which ever option is

Frank LaMon

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