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Date: Wed, 13 Feb 2019 11:32:00 +0100
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: sshd: computer name's case must match?
Message-ID: <20190213103200.GK3718@calimero.vinschen.de>
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On Feb 12 16:07, Bill Stewart wrote:
> Good day,
>=20
> I am testing sshd using the cygwin1.dll 3.x version (run as SYSTEM -
> S4U logon - works great!).
>=20
> One thing I've noticed is that if I use ssh log onto a remote
> domain-joined machine (e.g., connect with COMPUTER+localname), the
> 'COMPUTER' prefix must be uppercase - if I specify
> 'computer+LocalName', the user is unknown.
>=20
> This doesn't seem to be the case if I change the username's case -
> 'COMPUTER+localname' also works.
>=20
> Is this by design or by accident?

sshd checks usernames case-sensitive against their name stored in the
user DB.  The problem that you can use differently cased usernames
here is that the Windows function for checking the name is case-
insensitive, so it takes the username any way it comes in and
sshd eventually checks against the wrongly cased name.

I fixed that partially in Cygwin by making sure that the account name
stored in the internal passwd/group info is stored case-correct:
https://cygwin.com/git/?p=3Dnewlib-cygwin.git;a=3Dcommitdiff;h=3D9a3cc77b2a=
fc

So if you have a domain DOMAIN and a user xyz

$ getent passwd DoMaIn+XyZ

Prior to the above patch  it returned

  DOMAIN+XyZ:...

Now it will return

  DOMAIN+xyz:...

The problem is this:  If the account is from another domain than the
local machine or the machine domain, the call to LookupAccountSid to fix
the account name won't fix the account name.

Apparently the account name is cached on the local machine in exactly
the same spelling as has been used when asking for the account the first
time.  I still have to find a way to workaround that.


Thanks,
Corinna

--=20
Corinna Vinschen
Cygwin Maintainer

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