Overview#

The kinit command obtains or renews a Kerberos ticket-granting ticket from the Key Distribution Center options specified in the /etc/krb5.conf file or DNS SRV records if you do not specify these options on the command-line.

To test the operation of Kerberos, request a Ticket-Granting Ticket (TGT) with the Kinit command, as shown below. Any valid Kerberos principal (AD User) can be substituted for "Administrator".

   kinit -p Administrator@LAB.EXAMPLE.COM
   Password for Administrator@LAB.EXAMPLE.COM: ****
or
   kinit -p Administrator@LAB.EXAMPLE.COM%password
If you get no errors You can verify that you have correctly obtained a ticket using the klist tool.

Troubleshooting#

Note: The realm name is CASE SENSITIVE and is usually UPPERCASE.

There are many possible reason why you can't get a ticket.

kinit: krb5_get_init_creds: unable to reach any KDC in realm EXAMPLE.COM

Such a error says that the server is not reachable. Check those points :

  • The realm name is CASE SENSITIVE and is usually UPPERCASE.
  • Is the KDC server started ?
  • Is the EXAMPLE.COM domain declared in your DNS (or /etc/hosts file) ?

Kinit - Linux man page#

kinit - obtain and cache Kerberos ticket-granting ticket

Synopsis#

kinit
[-V] [-l lifetime] [-s start_time] [-r renewable_life] [-p | -P] [-f | -F] [-a] [-A] [-C] [-E] [-v] [-R] [-k [-t keytab_file]] [-c cache_name] [-n] [-S service_name][-T armor_ccache] [-X attribute[=value]] [principal]

Description#

kinit obtains and caches an initial ticket-granting ticket for principal.

Options#

  • -V - display verbose output.
  • -l lifetime requests a ticket with the lifetime lifetime. The value for lifetime must be followed immediately by one of the following delimiters:
    • s seconds
    • m minutes
    • h hours
    • d days
    • as in "kinit -l 90m". You cannot mix units; a value of '3h30m' will result in an error.
      If the -l option is not specified, the default ticket lifetime (configured by each site) is used. Specifying a ticket lifetime longer than the maximum ticket lifetime (configured by each site) results in a ticket with the maximum lifetime.
  • -s start_time - requests a postdated ticket, valid starting at start_time. Postdated tickets are issued with the invalid flag set, and need to be fed back to the kdc before use.
  • -r renewable_life - requests renewable tickets, with a total lifetime of renewable_life. The duration is in the same format as the -l option, with the same delimiters.
  • -f - request forwardable tickets.
  • -F - do not request forwardable tickets.
  • -p - request proxiable tickets.
  • -P - do not request proxiable tickets.
  • -a - request tickets with the local address(es).
  • -A - request address-less tickets.
  • -C - requests canonicalization of the principal name.
  • -E - treats the principal name as an enterprise name.
  • -v - requests that the ticket granting ticket in the cache (with the invalid flag set) be passed to the kdc for validation. If the ticket is within its requested time range, the cache is replaced with the validated ticket.
  • -R - requests renewal of the ticket-granting ticket. Note that an expired ticket cannot be renewed, even if the ticket is still within its renewable life.
  • -k [-t keytab_file] - requests a ticket, obtained from a key in the local host's keytab file. The name and location of the keytab file may be specified with the -t keytab_file option; otherwise the default name and location will be used. By default a host ticket is requested but any principal may be specified. On a KDC, the special keytab location KDB: can be used to indicate that kinit should open the KDC database and look up the key directly. This permits an administrator to obtain tickets as any principal that supports password-based authentication.
  • -n - Requests anonymous processing. Two types of anonymous principals are supported. For fully anonymous Kerberos, configure pkinit on the KDC and configure pkinit_anchors in the client's krb5.conf. Then use the -n option with a principal of the form @REALM (an empty principal name followed by the at-sign and a realm name). If permitted by the KDC, an anonymous ticket will be returned. A second form of anonymous tickets is supported; these realm-exposed tickets hide the identity of the client but not the client's realm. For this mode, use kinit -n with a normal principal name. If supported by the KDC, the principal (but not realm) will be replaced by the anonymous principal. As of release 1.8, the MIT Kerberos KDC only supports fully anonymous operation.
  • -T armor_ccache - Specifies the name of a credential cache that already contains a ticket. If supported by the KDC, This ccache will be used to armor the request so that an attacker would have to know both the key of the armor ticket and the key of the principal used for authentication in order to attack the request. Armoring also makes sure that the response from the KDC is not modified in transit.
  • -c cache_name - use cache_name as the Kerberos 5 credentials (ticket) cache name and location; if this option is not used, the default cache name and location are used.
    The default credentials cache may vary between systems. If the KRB5CCNAME environment variable is set, its value is used to name the default ticket cache. If a principal name is specified and the type of the default credentials cache supports a collection (such as the DIR type), an existing cache containing credentials for the principal is selected or a new one is created and becomes the new primary cache. Otherwise, any existing contents of the default cache are destroyed by kinit.
  • -S service_name - specify an alternate service name to use when getting initial tickets.
  • -X attribute[=value] - specify a pre-authentication attribute and value to be passed to pre-authentication plugins. The acceptable attribute and value values vary from pre-authentication plugin to plugin. This option may be specified multiple times to specify multiple attributes. If no value is specified, it is assumed to be "yes".

OpenSSL pkinit#

The following attributes are recognized by the OpenSSL pkinit pre-authentication mechanism:
  • X509_user_identity=value - specify where to find user's X509 identity information
  • X509_anchors=value - specify where to find trusted X509 anchor information
  • flag_RSA_PROTOCOL[=yes] - specify use of RSA, rather than the default Diffie-Hellman protocol

Environment#

Kinit uses the following environment variables:
  • KRB5CCNAME - Location of the default Kerberos 5 credentials (ticket) cache, in the form type:residual. If no type prefix is present, the FILE type is assumed. The type of the default cache may determine the availability of a cache collection; for instance, a default cache of type DIR causes caches within the directory to be present in the collection.

Files#

/tmp/krb5cc_[uid]
default location of Kerberos 5 credentials cache (uidNumber is the decimal UID of the user).
/etc/krb5.keytab
default location for the local host's keytab file.

More Information#

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« This page (revision-6) was last changed on 11-May-2017 13:29 by jim