Elementary PKINIT questions (MIT Kerberos/Linux configuration)
Jason White
jason at jasonjgw.net
Tue Mar 28 08:18:45 EDT 2023
Dear kerberos community,
I've set up a very small MIT Kerberos installation for my own use, with
MIT Kerberos under Linux. In experimenting with the PKINIT
configuration, I have essentially followed the MIT Kerberos
documentation (using openssl to generate keys and certificates), and
reached the point at which I can authenticate as principal "jason"
without a password. (I also have ssd configured on my Linux client with
sssd-kcm for caching and the PAM module for login.)
First problem: I have a second principal, jason/admin, for use with
kadmin. I've generated a certificate that can authenticate. However, now
that I have two certificates (one for jason and another for
jason/admin), it isn't clear how to configure the client to offer the
correct certificate to the kdc. If I specify both certificates on
pkinit_identities lines in the client's krb5.conf file, "jason" can log
in, but kadmin returns a "Client name mismatch while initializing kadmin
interface" error. My assumptions is that the wrong certificate was
offered to the KDC (i.e., not the jason/admin certificate). Specifying
the directory containing the certificates in pkinit_identities results
in finding two certificates where one is expected, with an error message
to that effect.
Do I need to specify a PKINIT certificate matching rule, or is there
some other configuration that is required?
Second problem: securing the client's private key. The Linux client has
a TPM 2.0 module, but I haven't found any documentation on how to
configure it for use with Kerberos, if indeed this is supported.
References would be welcome.
The machine has a smartcard reader, so my other options would be to
purchase some compatible smartcards (after finding out what those are),
or a security key. In the latter case, I would probably choose a FIDO 2
key with smartcard support.
As mentioned, this is simply for my own use/experimentation, so there's
no urgency at all.
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