KCLIENT(8) Maintenance Commands and Procedures KCLIENT(8)

kclient - set up a machine as a Kerberos client

/usr/sbin/kclient [-n] [-R realm] [-k kdc] [-a adminuser]


     [-c filepath] [-d dnsarg] [-f fqdn_list] [-h logical_host_name]


     [-k kdc_list] [-m master_kdc] [-p profile] [-s pam_service]


     [-T kdc_vendor]

By specifying the various command options, you can use the kclient utility to:

Configure a machine as a Kerberos client for a specified realm and for KDC by setting up krb5.conf(5).
Add the Kerberos host principal to the local host's keytab file (/etc/krb5/krb5.keytab).
Set up the machine to do kerberized NFS.
Bring over a master krb5.conf copy from a specified pathname.
Setup a machine to do server and/or host/domain name-to-realm mapping lookups by means of DNS.
Configure a Kerberos client to use an MS Active Directory server. This generates a keytab file with the Kerberos client's service keys populated.
Setup a Kerberos client that has no service keys. This is useful when the client does not require service keys, because the client does not wish to host a service that uses Kerberos for security.
Configure a Kerberos client that is part of a cluster. This option requires the logical host name of the cluster so that the proper service keys are created and populated in the client's keytab file.
Setup a Kerberos client to join an environment that consists of Kerberos servers that are non-Solaris and non-MS Active Directory servers.
Configure pam.conf(5) to use Kerberos authentication for specified services.
Configure the client as a simple NTP broadcast/multicast client.
Specify custom domain/host name-to-realm name mappings.
Setup the Kerberos client to use multiple KDC servers.

The kclient utility needs to be run on the client machine with root permission and can be run either interactively or non-interactively. In the non-interactive mode, the user feeds in the required inputs by means of a profile, command-line options, or a combination of profile and command-line options. The user is prompted for "required" parameter values (realm and adminuser), if found missing in the non-interactive run. The interactive mode is invoked when the utility is run without any command-line arguments.

Both the interactive and non-interactive forms of kclient can add the host/fqdn entry to the local host's keytab file. They also can require the user to enter the password for the administrative user requested, to obtain the Kerberos Ticket Granting Ticket (TGT) for adminuser. The host/fqdn, nfs/fqdn, and root/fqdn principals can be added to the KDC database (if not already present) before their possible addition to the local host's keytab.

The kclient utility assumes that the local host has been setup for DNS and requires the presence of a valid resolv.conf(5). Also, kclient can fail if the localhost time is not synchronized with that of the KDC. For Kerberos to function the localhost time must be within five minutes of that of the KDC. It is advised that both systems run some form of time synchronization protocol, such as the Network Time Protocol (NTP). See the ntpd man page, delivered in the SUNWntpu package (not a SunOS man page).

The non-interactive mode supports the following options:

-n

Set up the machine for kerberized NFS. This involves making changes to krb5* security flavors in nfssec.conf(5). This option will also add nfs/fqdn and root/fqdn entries to the local host's keytab file if the -K option has not been specified.

-R [ realm ]

Specifies the Kerberos realm.

-k kdc_list

The -k option specifies the KDC host names for the Kerberos client. kdc_list is a comma-separated list of KDCs. If the -m option is not used, it is assumed that the first (or only) host in kdc_list is the master KDC host name. Note that the list specified is used verbatim. This is helpful when specifying non-fully qualified KDC host names that can be canonicalized by DNS.

-a [ adminuser ]

Specifies the Kerberos administrative user.

-T kdc_vendor

Configure the Kerberos client to associate with a third party server. Valid kdc_vendor currently supported are:

ms_ad

Microsoft Active Directory

mit

MIT KDC server

heimdal

Heimdal KDC server

shishi

Shishi KDC server

Knowing the administrative password will be required to associate the client with the server if the ms_ad option is specified.

-c [ filepath ]

Specifies the pathname to the krb5.conf(5) master file, to be copied over to the local host. The path specified normally points to a master copy on a remote host and brought over to the local host by means of NFS.

-d [ dnsarg ]

Specifies the DNS lookup option to be used and specified in the krb5.conf(5) file. Valid dnsarg entries are: none, dns_lookup_kdc, dns_lookup_realm and dns_fallback. Any other entry is considered invalid. The latter three dnsarg values assume the same meaning as those described in krb5.conf. dns_lookup_kdc implies DNS lookups for the KDC and the other servers. dns_lookup_realm is for host/domain name-to-realm mapping by means of DNS. dns_fallback is a superset and does DNS lookups for both the servers and the host/domain name-to-realm mapping. A lookup option of none specifies that DNS is not be used for any kind of mapping lookup.

-D domain_list

Specifies the host and/or domain names to be mapped to the Kerberos client's default realm name. domain_list is a comma-separated list, for example "example.com,host1.example.com". If the -D option is not used, then only the client's domain is used for this mapping. For example, if the client is host1.eng.example.com, then the domain that is mapped to the EXAMPLE.COM realm is example.com.

-K

Configure the Kerberos client without service keys, which are usually stored in /etc/krb5/krb5.keytab. This is useful in the following scenarios:
The client IP address is dynamically assigned and therefore does not host Kerberized services.
Client has a static IP address, but does not want to host any Kerberized services.
Client has a static IP address, but the local administrator does not currently have service keys available for the machine. It is expected that, at a later time, these keys will be installed on the machine.

-f [ fqdn_list ]

This option creates a service principal entry (host/nfs/root) associated with each of the listed fqdn's, if required, and subsequently adds the entries to the local host's keytab.

fqdn_list is a comma-separated list of one or more fully qualified DNS domain names.

This option is especially useful in Kerberos realms having systems offering kerberized services, but situated in multiple different DNS domains.

-h logical_host_name

Specifies that the Kerberos client is a node in a cluster. The logical_host_name is the logical host name given to the cluster. The resulting /etc/krb5/krb5.conf and /etc/krb5/krb5.keytab files must be manually copied over to the other members of the cluster.

-m master_kdc

This option specifies the master KDC to be used by the Kerberos client. master_kdc is the host name of the master KDC for the client. If the -m option is not used, then it is assumed that the first KDC host name listed with the -k option is the master KDC.

-p [ profile ]

Specifies the profile to be used to enable the reading in of the values of all the parameters required for setup of the machine as a Kerberos client.

The profile should have entries in the format:


PARAM <value>

Valid PARAM entries are: REALM, KDC, ADMIN, FILEPATH, NFS, DNSLOOKUP, FQDN, NOKEY, NOSOL, LHN, KDCVENDOR, RMAP, MAS, and PAM.

These profile entries correspond to the -R [realm], -k [kdc], -a [adminuser], -c [filepath], -n, -d [dnsarg], -f [fqdn_list], -K, -h [logical_host_name], -T [kdc_vendor], -D [domain_list], -m [master_kdc], and -s [pam_service] command-line options, respectively. Any other PARAM entry is considered invalid and is ignored.

The NFS profile entry can have a value of 0 (do nothing) or 1 (operation is requested). Any other value is considered invalid and is ignored.

Keep in mind that the command line options override the PARAM values listed in the profile.

-s pam_service

Specifies that the PAM service names, listed in pam_service, are authenticated through Kerberos before any other type of authentication. Using this option updates pam.conf(5) to include pam_krb5(7) to existing authentication stacks for the specified service(s) in pam_service. An example of a possible pam_service value is: dtlogin,sshd-kbdint.

Example 1 Setting Up a Kerberos Client Using Command-Line Options

To setup a Kerberos client using the clntconfig/admin administrative principal for realm 'EXAMPLE.COM', kdc `example1.example.com' and that also does kerberized NFS, enter:


# /usr/sbin/kclient -n -R EXAMPLE.COM -k example1.example.com -a clntconfig

Alternatively, to set up a Kerberos client using the clntconfig/admin administrative principal for the realm `EAST.EXAMPLE.COM', kdc `example2.east.example.com' and that also needs service principal(s) created and/or added to the local keytab for multiple DNS domains, enter:


# /usr/sbin/kclient -n -R EAST.EXAMPLE.COM -k example2.east.example.com \
-f west.example.com,central.example.com -a clntconfig

Note that the krb5 administrative principal used by the administrator needs to have only add, inquire, change-pwd and modify privileges (for the principals in the KDC database) in order for the kclient utility to run. A sample kadm5.acl(5) entry is:


clntconfig/admin@EXAMPLE.COM acmi

Example 2 Setting Up a Kerberos Client Using the Profile Option

To setup a Kerberos client using the clntconfig/admin administrative principal for realm `EXAMPLE.COM', kdc `example1.example.com' and that also copies over the master krb5.conf from a specified location, enter:


# /usr/sbin/kclient -p /net/example1.example.com/export/profile.krb5

The contents of profile.krb5:


REALM EXAMPLE.COM
KDC example1.example.com
ADMIN clntconfig
FILEPATH /net/example1.example.com/export/krb5.conf
NFS 0
DNSLOOKUP none

Example 3 Setting Up a Kerberos Client That Has a Dynamic IP Address

In this example a Kerberos client is a DHCP client that has a dynamic IP address. This client does not wish to host any Kerberized services and therefore does not require a keytab (/etc/krb5/krb5.keytab) file.

For this type of client the administrator would issue the following command to configure this machine to be a Kerberos client of the EXAMPLE.COM realm with the KDC server kdc1.example.com:


# /usr/sbin/kclient -K -R EXAMPLE.COM -k kdc1.example.com

/etc/krb5/kadm5.acl

Kerberos access control list (ACL) file.

/etc/krb5/krb5.conf

Default location for the local host's configuration file.

/etc/krb5/krb5.keytab

Default location for the local host's keytab file.

/etc/nfssec.conf

File listing NFS security modes.

/etc/resolv.conf

DNS resolver configuration file.

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Committed

encrypt(1), ksh93(1), ldapdelete(1), ldapmodify(1), ldapsearch(1), kadm5.acl(5), krb5.conf(5), nfssec.conf(5), pam.conf(5), resolv.conf(5), attributes(7), pam_krb5(7), dd(8), smbadm(8)

fqdn stands for the Fully Qualified Domain Name of the local host. The kclient utility saves copies of both the krb5.conf(5) and nfssec.conf(5) files to files with corresponding names and .sav extensions. The optional copy of the krb5.conf(5) master file is neither encrypted nor integrity-protected and it takes place over regular NFS.

November 22, 2021 OmniOS