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I have this strange issue where a kerberos/openldap environment has gotten bricked. I can't add new users, computers, or other things to it, as everything I try results in various variations on SERVER_NOT_FOUND PERMISSION_DENIED, INSUFFICIENT ACCESS, CLIENT_NOT_FOUND.

Does this usually happen if nothing is modified in a kerberos environment for, say, a year?

Its purpose was to secure an NFS share. Now that I want to add another NFS share to copy over data, I can't change the configuration in any way.

Even logged in as root, using kadmin.local I can't do any of these:

  • Create a new admin user
  • Change the password of the admin user.
  • Login as the admin user
  • Add a principal

I can do this:

  • Execute commands against openLDAP (like adding entries) with its password.

I can also do this:

  • Mount and use the existing share. (Which means that openLDAP and krb5 are both still running, I just can't change anything about the configuration).

I verified these things.

  • krb5kdc/openldap are running
  • The ACL is set in the .acl file
  • The realm name, domain name, etc. are correct
  • Hosts file points to the realm name to local host.
  • krb5kdc, slapd, kadmind are listening on their respective ports.
  • No firewall rules are present
  • Apparmor/SELinux are not present.

The errors are spat out by the various systems. For example: krb5kdc spits out this one, if trying to add a principal via kadmin.local:

10.0.26.21: SERVER_NOT_FOUND: kadmin/[email protected] for kadmin/[email protected], Server not found in Kerberos database

While kadmin says: Principal add failed: Insufficient access while creating "[email protected]@COMPANY.COM"

This creates a catch-22, somehow needing a principal to add a principal? I was under the impression that kadmin.local is a sort of 'bootstrap' mechanism when creating the setup. The error message makes no sense.

Try to login with kadmin/admin also doesn't work, with the same message from krb5kdc.

I'm also seeing this one, which I find interesting: preauth spake failed to initialize: No SPAKE preauth groups configured. Searching about this magic SPAKE (why the incomprehensible acronyms), turns up nothing useful.

Trying out slapcat to list all the contents of the ldap database, I find that kadmin/admin has krbLoginFailedCount: 0. So as far as LDAP is concerned, no logins have been made? Maybe? I have no clue what this means, because the documentation (how do these components interact with eachother?) is awful.

Trying to capture packets, on either lo or all interfaces, there is no LDAP traffic being sent at all. Even though both /etc/krb5.conf and /etc/krb5kdc/kdc.conf have this section:

[dbmodules]
    openldap_ldapconf = {
        ldap_servers = ldapi:///

        

Any other things to try before I nuke it from orbit and start from scratch?

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    To help try and figure out what is happening you should post in your question which actions you are taking, and which errors those actions provide. Currently, there are conflicts in your post that I am unable to interpret such as you saying you get SERVER_NOT_FOUND errors but then state you can execute commands against openLDAP (so the server can be found, but the useful information would be what action(s) caused the SERVER_NOT_FOUND and all the other errors). Since you say you have not touched this server in a while, have you checked available disk space? Sep 20, 2023 at 18:03
  • @GracefulRestart Things like disk space are monitored. The system hasn't even been updated since krb was installed (~1yr ago), so I have no idea what could have broken it so.
    – aphid
    Sep 21, 2023 at 7:40
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    I haven't ever used Kerberos, but couple of possibilities that comes to mind due to the 1 year time period are 1. TLS certificates that might have expired, 2. System time drifting away and you don't use NTP.
    – muru
    Sep 21, 2023 at 9:56

1 Answer 1

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No, it cannot.

10.0.26.21: SERVER_NOT_FOUND: kadmin/[email protected] for kadmin/[email protected], Server not found in Kerberos database

This does not look like you're using 'kadmin.local' at all. While it is normal for the kadmin/<fqdn> principal to be absent (instead kadmin/admin is the preferred one), only the RPC-based 'kadmin' gets such tickets in the first place while 'kadmin.local' directly accesses your LDAP database.

Also, from the error message, it seems that you're using -p kadmin/admin. Don't do that – this is a service principal, not a "user" or "administrator" principal. (kadmin.local doesn't need any principal at all, though, as it does not speak Kerberos as such.)

While kadmin says: Principal add failed: Insufficient access while creating "[email protected]@COMPANY.COM"

Access issues aside, that doesn't look like valid syntax for a Kerberos principal name. The format service@fqdn is used by GSSAPI generically, but it is translated to service/fqdn for Kerberos.

This creates a catch-22, somehow needing a principal to add a principal? I was under the impression that kadmin.local is a sort of 'bootstrap' mechanism when creating the setup. The error message makes no sense.

Indeed it doesn't, because none of what you're showing would be printed by kadmin.local at all. It sounds like you're trying to run the regular network-based kadmin instead. (Was there any filesystem corruption that would cause the contents of the former to be overwritten with the latter? Did someone accidentally cp one over the other?)

Trying out slapcat to list all the contents of the ldap database, I find that kadmin/admin has krbLoginFailedCount: 0. So as far as LDAP is concerned, no logins have been made?

This is a service principal, not a client (user) principal, so no logins are ever made "to" it. This attribute only tracks how many kinits have been done to a user account, not how many tickets have been issued for a particular service.

(Host principals are typically both client and service, but this isn't that.)

Even for client principals, the value may be zero if the KDC has been given only read-only access to the backend LDAP database, which is not an uncommon thing to do.

as far as LDAP is concerned, no logins have been made? Maybe? I have no clue what this means, because the documentation (how do these components interact with eachother?) is awful.

In this situation, LDAP is really nothing more than a dumb database. The krb5kdc service (or the kadmin.local tool) connects to it and reads or writes some data. There is no interaction with Kerberos authentication or kinit – at most, the service has a single LDAP password (in ldap.stash) that both krb5kdc and kadmin.local use to access the DB contents.

I'm also seeing this one, which I find interesting: preauth spake failed to initialize: No SPAKE preauth groups configured. Searching about this magic SPAKE (why the incomprehensible acronyms), turns up nothing useful.

As far as acronyms go, it's from the same series as "RSA" or "AES". It's a cryptographic algorithm that's optionally used to strengthen a password-based kinit against network monitoring (offline password cracking).

SPAKE is optional – the existing traditional (timestamp) preauth mechanism always functions.

Trying to capture packets, on either lo or all interfaces, there is no LDAP traffic being sent at all. Even though both /etc/krb5.conf and /etc/krb5kdc/kdc.conf have this section:

ldap_servers = ldapi:///

That's because you have this section. It tells the LDAP client code to use a Unix socket at /run/openldap/ldapi instead of a local TCP connection.

Switch your LDAP server's olcLogLevel to stats to get more information about what queries are being made.

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