From Fedora Project Wiki


Demonstrate that MIT Kerberos 1.11 reverts to default behavior (rather than categorically rejecting the authentication) in the scenario where:

  • The client does not present a domain name to authenticate against.
  • Reverse DNS is enabled in /etc/krb5.conf
  • The server does not have a PTR record on the DNS server.


  1. Verify that your ActiveDirectory domain access works. If you don't have an Active Directory domain, you can set one up.
  2. You need a domain user or administrator account.
  3. Make sure you have krb5-workstation-1.11 or later installed.
  4. Make note of the the DNS name for a domain controller on your domain
    $ host -t SRV
  5. Make note of the IP address of the domain controller you chose above
    $ host
  6. Now verify that the reverse DNS record for that IP address does not exist or does not match that of your domain controller.
    If it does match, then either find a way to break the mapping (if you set it up yourself) or skip this test.
  7. Verify that /etc/krb5.conf exists, and contains this line, in the [libdefaults] section:
    rdns = false
    If the file does not exist, reinstall krb5-libs:
    $ sudo yum reinstall krb5-libs

How to test

  1. Use your Active Directory domain user account to authenticate to the Active Directory server using kinit without a realm name.
    $ kinit user@AD.EXAMPLE.COM
    • Type your domain account password
    • Make sure that you capitalize the domain name.
    • If the above fails with 'Preauthentication failed' then you probably typed the wrong password.
  2. Now do an LDAP search against your domain controller
    $ ldapwhoami -H ldap:// -Y GSSAPI
    You must use the exact domain controller name (as discovered in the above stages, in order for this to work).

Expected Results

  1. The ldapwhoami command should output your user name on the last line, and should not fail.
    $ klist
    • You should see a line that contains the domain controller host name


If you want to file a bug related to this issue, run the command with the the KRB5_TRACE=/dev/stderr environment variable, like this:

$ KRB5_TRACE=/dev/stderr kinit user@AD.EXAMPLE.COM