Tribblix: manual page: kdc.conf.5

KDC.CONF(5) File Formats and Configurations KDC.CONF(5)

NAME

kdc.conf - Key Distribution Center (KDC) configuration file

SYNOPSIS

/etc/krb5/kdc.conf

DESCRIPTION

The kdc.conf file contains KDC configuration information, including
defaults used when issuing Kerberos tickets. This file must reside on
all KDC servers. After you make any changes to the kdc.conf file,
stop and restart the krb5kdc daemon on the KDC for the changes to
take effect.

The format of the kdc.conf consists of section headings in square
brackets ([]). Each section contains zero or more configuration
variables (called relations), of the form of:

relation = relation-value

or

relation-subsection = {
relation = relation-value
relation = relation-value
}

The kdc.conf file contains one of more of the following three
sections:

kdcdefaults

Contains default values for overall behavior of the KDC.

realms

Contains subsections for Kerberos realms, where relation-
subsection is the name of a realm. Each subsection contains
relations that define KDC properties for that particular realm,
including where to find the Kerberos servers for that realm.

logging

Contains relations that determine how Kerberos programs perform
logging.

The kdcdefaults Section
The following relation can be defined in the [kdcdefaults] section:

kdc_ports

This relation lists the UDP ports on which the Kerberos server
should listen by default. This list is a comma-separated list of
integers. If the assigned value is 0, the Kerberos server does
not listen on any UDP port. If this relation is not specified,
the Kerberos server listens on port 750 and port 88.

kdc_tcp_ports

This relation lists the TCP ports on which the Kerberos server
should listen by default. This list is a comma-separated list of
integers. If the assigned value is 0, the Kerberos server does
not listen on any TCP port. If this relation is not specified,
the Kerberos server listens on the kdc TCP port specified in
/etc/services. If this port is not found in /etc/services the
Kerberos server defaults to listen on TCP port 88.

kdc_max_tcp_connections

This relation controls the maximum number of TCP connections the
KDC allows. The minimum value is 10. If this relation is not
specified, the Kerberos server allows a maximum of 30 TCP
connections.

The realms Section
This section contains subsections for Kerberos realms, where
relation-subsection is the name of a realm. Each subsection contains
relations that define KDC properties for that particular realm.

The following relations can be specified in each subsection:

acl_file

(string) Location of the Kerberos V5 access control list (ACL)
file that kadmin uses to determine the privileges allowed to each
principal on the database. The default location is
/etc/krb5/kadm5.acl.

admin_keytab

(string) Location of the keytab file that kadmin uses to
authenticate to the database. The default location is
/etc/krb5/kadm5.keytab.

database_name

(string) Location of the Kerberos database for this realm. The
default location is /var/krb5/principal.

default_principal_expiration

(absolute time string) The default expiration date of principals
created in this realm. See the Time Format section in kinit(1)
for the valid absolute time formats you can use for
default_principal_expiration.

default_principal_flags

(flag string) The default attributes of principals created in
this realm. Some of these flags are better to set on an
individual principal basis through the use of the attribute
modifiers when using the kadmin command to create and modify
principals. However, some of these options can be applied to all
principals in the realm by adding them to the list of flags
associated with this relation.

A "flag string" is a list of one or more of the flags listed
below preceded by a minus (-) or a plus (+) character, indicating
that the option that follows should be enabled or disabled.

Flags below marked with an asterisk (*) are flags that are best
applied on an individual principal basis through the kadmin
interface rather than as a blanket attribute to be applied to all
principals.

postdateable

Create postdatable tickets.

forwardable

Create forwardable tickets.

tgt-based

Allow TGT-based requests.

renewable

Create Renewable tickets.

proxiable

Create Proxiable tickets.

dup-skey

Allow DUP_SKEY requests, this enables user-to-user
authentication.

preauth

Require the use of pre-authentication data whenever
principals request TGTs.

hwauth

Require the use of hardware-based pre-authentication data
whenever principals request TGTs.

* allow-tickets

Allow tickets to be issued for all principals.

* pwdchange

Require principal's to change their password.

* service

Enable or disable a service.

* pwservice

Mark principals as password changing principals.

An example of default_principal_flags is shown in EXAMPLES,
below.

dict_file

(string) Location of the dictionary file containing strings that
are not allowed as passwords. A principal with any password
policy is not allowed to select a password in the dictionary. The
default location is /var/krb5/kadm5.dict.

kadmind_port

(port number) The port that the kadmind daemon is to listen on
for this realm. The assigned port for kadmind is 749.

key_stash_file

(string) Location where the master key has been stored (by
kdb5_util stash). The default location is /var/krb5/.k5.realm,
where realm is the Kerberos realm.

kdc_ports

(string) The list of UDP ports that the KDC listens on for this
realm. By default, the value of kdc_ports as specified in the
[kdcdefaults] section is used.

kdc_tcp_ports

(string) The list of TCP ports that the KDC listens on (in
addition to the UDP ports specified by kdc_ports) for this realm.
By default, the value of kdc_tcp_ports as specified in the
[kdcdefaults] section is used.

master_key_name

(string) The name of the master key.

master_key_type

(key type string) The master key's key type. This is used to
determine the type of encryption that encrypts the entries in the
principal db. des-cbc-crc, des3-cbc-md5, des3-cbc-sha1-kd,
arcfour-hmac-md5, arcfour-hmac-md5-exp, aes128-cts-hmac-sha1-96,
and aes256-cts-hmac-sha1-96 are supported at this time (des-cbc-
crc is the default). If you set this to des3-cbc-sha1-kd all
systems that receive copies of the principal db, such as those
running slave KDC's, must support des3-cbc-sha1-kd.

max_life

(delta time string) The maximum time period for which a ticket is
valid in this realm. See the Time Format section in kinit(1) for
the valid time duration formats you can use for max_life.

max_renewable_life

(delta time string) The maximum time period during which a valid
ticket can be renewed in this realm. See the Time Format section
in kinit(1) for the valid time duration formats you can use for
max_renewable_life.

sunw_dbprop_enable = [true | false]

Enable or disable incremental database propagation. Default is
false.

sunw_dbprop_master_ulogsize = N

Specifies the maximum number of log entries available for
incremental propagation to the slave KDC servers. The maximum
value that this can be is 2500 entries. Default value is 1000
entries.

sunw_dbprop_slave_poll = N[s, m, h]

Specifies how often the slave KDC polls for new updates that the
master might have. Default is 2m (two minutes).

supported_enctypes

List of key/salt strings. The default key/salt combinations of
principals for this realm. The key is separated from the salt by
a colon (:) or period (.). Multiple key/salt strings can be used
by separating each string with a space. The salt is additional
information encoded within the key that tells what kind of key it
is. Only the normal salt is supported at this time, for example,
des-cbc-crc:normal. If this relation is not specified, the
default setting is:

aes256-cts-hmac-sha1-96:normal \ (see note below)
aes128-cts-hmac-sha1-96:normal \
des3-cbc-sha1-kd:normal \
arcfour-hmac-md5:normal \
des-cbc-md5:normal

Note -

The unbundled Strong Cryptographic packages must be installed
for the aes256-cts-hmac-sha1-96:normal enctype to be available
for Kerberos.

reject_bad_transit

This boolean specifies whether the list of transited realms for
cross-realm tickets should be checked against the transit path
computed from the realm names and the [capaths] section of its
krb5.conf(5) file.

The default for reject_bad_transit is true.

The logging Section
This section indicates how Kerberos programs perform logging. The
same relation can be repeated if you want to assign it multiple
logging methods. The following relations can be defined in the
[logging] section:

kdc

Specifies how the KDC is to perform its logging. The default is
FILE:/var/krb5/kdc.log.

admin_server

Specifies how the administration server is to perform its
logging. The default is FILE:/var/krb5/kadmin.log.

default

Specifies how to perform logging in the absence of explicit
specifications.

The [logging] relations can have the following values:

FILE:filename

or

FILE=filename

This value causes the entity's logging messages to go to the
specified file. If the `=' form is used, the file is overwritten.
If the `:' form is used, the file is appended to.

STDERR

This value sends the entity's logging messages to its standard
error stream.

CONSOLE

This value sends the entity's logging messages to the console, if
the system supports it.

DEVICE=devicename

This sends the entity's logging messages to the specified device.

SYSLOG[:severity[:facility]]

This sends the entity's logging messages to the system log.

The severity argument specifies the default severity of system
log messages. This default can be any of the following severities
supported by the syslog(3C) call, minus the LOG_ prefix:
LOG_EMERG, LOG_ALERT, LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_NOTICE,
LOG_INFO, and LOG_DEBUG. For example, a value of CRIT would
specify LOG_CRIT severity.

The facility argument specifies the facility under which the
messages are logged. This can be any of the following facilities
supported by the syslog(3C) call minus the LOG_ prefix: LOG_KERN,
LOG_USER, LOG_MAIL, LOG_DAEMON, LOG_AUTH, LOG_LPR, LOG_NEWS,
LOG_UUCP, LOG_CRON, and LOG_LOCAL0 through LOG_LOCAL7.

If no severity is specified, the default is ERR. If no facility
is specified, the default is AUTH.

In the following example, the logging messages from the KDC go to
the console and to the system log under the facility LOG_DAEMON
with default severity of LOG_INFO; the logging messages from the
administration server are appended to the /var/krb5/kadmin.log
file and sent to the /dev/tty04 device.

[logging]
kdc = CONSOLE
kdc = SYSLOG:INFO:DAEMON
admin_server = FILE:/export/logging/kadmin.log
admin_server = DEVICE=/dev/tty04

PKINIT-specific Options
The following are pkinit-specific options. These values can be
specified in [kdcdefaults] as global defaults, or within a realm-
specific subsection of [realms]. A realm-specific value overrides,
does not add to, a generic [kdcdefaults] specification. The search
order is

1. realm-specific subsection of [realms]

[realms]

[realms]
EXAMPLE.COM = {
pkinit_anchors = FILE:/usr/local/example.com.crt
}

2. generic value in the [kdcdefaults] section

[kdcdefaults]
pkinit_anchors = DIR:/usr/local/generic_trusted_cas/

pkinit_identity = URI
Specifies the location of the KDC's X.509
identity information. This option is
required if pkinit is supported by the KDC.
Valid URI types are FILE, DIR, PKCS11,
PKCS12, and ENV. See the PKINIT URI Types
section for more details.

pkinit_anchors = URI
Specifies the location of trusted anchor
(root) certificates which the KDC trusts to
sign client certificates. This option is
required if pkinit is supported by the KDC.
This option can be specified multiple times.
Valid URI types are FILE and DIR. See the
PKINIT URI Types section for details.

pkinit_pool
Specifies the location of intermediate
certificates which can be used by the KDC to
complete the trust chain between a client's
certificate and a trusted anchor. This
option can be specified multiple times.
Valid URI types are FILE and DIR. See the
PKINIT URI Types section for more details.

pkinit_revoke
Specifies the location of Certificate
Revocation List (CRL) information to be used
by the KDC when verifying the validity of
client certificates. This option can be
specified multiple times. The default
certificate verification process always
checks the available revocation information
to see if a certificate has been revoked. If
a match is found for the certificate in a
CRL, verification fails. If the certificate
being verified is not listed in a CRL, or
there is no CRL present for its issuing CA,
and pkinit_require_crl_checking is false,
then verification succeeds. The only valid
URI types is DIR. See the PKINIT URI Types
section for more details. If
pkinit_require_crl_checking is true and
there is no CRL information available for
the issuing CA, verification fails.
pkinit_require_crl_checking should be set to
true if the policy is such that up-to-date
CRLs must be present for every CA.

pkinit_dh_min_bits
Specifies the minimum number of bits the KDC
is willing to accept for a client's Diffie-
Hellman key.

pkinit_allow_upn
Specifies that the KDC is willing to accept
client certificates with the Microsoft
UserPrincipalName (UPN) Subject Alternative
Name (SAN). This means the KDC accepts the
binding of the UPN in the certificate to the
Kerberos principal name.

The default is false.

Without this option, the KDC only accepts
certificates with the id-pkinit-san as
defined in RFC4556. There is currently no
option to disable SAN checking in the KDC.

pkinit_eku_checking
This option specifies what Extended Key
Usage (EKU) values the KDC is willing to
accept in client certificates. The values
recognized in the kdc.conf file are:

kpClientAuth
This is the default value
and specifies that client
certificates must have the
id-pkinit-KPClientAuth EKU
as defined in RFC4556.

scLogin
If scLogin is specified,
client certificates with the
Microsoft Smart Card Login
EKU (id-ms-kp-sc-logon) is
accepted.

PKINIT URI Types

FILE:file-name[,key-file-name]

This option has context-specific behavior.

pkinit_identity
file-name specifies the name of a PEM-format
file containing the user's certificate. If
key-file-name is not specified, the user's
private key is expected to be in file-name as
well. Otherwise, key-file-name is the name of
the file containing the private key.

pkinit_anchors
pkinit_pool
file-name is assumed to be the name of an
OpenSSL-style ca-bundle file. The ca-bundle
file should be base-64 encoded.

DIR:directory-name

This option has context-specific behavior.

pkinit_identity
directory-name specifies a directory with
files named *.crt and *.key, where the first
part of the file name is the same for matching
pairs of certificate and private key files.
When a file with a name ending with .crt is
found, a matching file ending with .key is
assumed to contain the private key. If no such
file is found, then the certificate in the
.crt is not used.

pkinit_anchors
pkinit_pool
directory-name is assumed to be an OpenSSL-
style hashed CA directory where each CA cert
is stored in a file named hash-of-ca-cert.#.
This infrastructure is encouraged, but all
files in the directory is examined and if they
contain certificates (in PEM format), they are
used.

pkinit_revoke
directory-name is assumed to be an OpenSSL-
style hashed CA directory where each
revocation list is stored in a file named
hash-of-ca-cert.r#. This infrastructure is
encouraged, but all files in the directory is
examined and if they contain a revocation list
(in PEM format), they are used.

PKCS12:pkcs12-file-name

pkcs12-file-name is the name of a PKCS #12 format file,
containing the user's certificate and private key.

PKCS11:[slotid=slot-id][:token=token-label][:certid=cert-
id][:certlabel=cert-label]

All keyword/values are optional. PKCS11 modules (for example,
opensc-pkcs11.so) must be installed as a crypto provider under
libpkcs11(3LIB). slotid= and/or token= can be specified to force
the use of a particular smard card reader or token if there is
more than one available. certid= and/or certlabel= can be
specified to force the selection of a particular certificate on
the device. See the pkinit_cert_match configuration option for
more ways to select a particular certificate to use for pkinit.

ENV:environment-variable-name

environment-variable-name specifies the name of an environment
variable which has been set to a value conforming to one of the
previous values. For example, ENV:X509_PROXY, where environment
variable X509_PROXY has been set to FILE:/tmp/my_proxy.pem.

EXAMPLES

Example 1: Sample kdc.conf File

The following is an example of a kdc.conf file:

[kdcdefaults]
kdc_ports = 88

[realms]
ATHENA.MIT.EDU = {
kadmind_port = 749
max_life = 10h 0m 0s
max_renewable_life = 7d 0h 0m 0s
default_principal_flags = +preauth,+forwardable,-postdateable
master_key_type = des-cbc-crc
supported_enctypes = des-cbc-crc:normal
}

[logging]
kdc = FILE:/export/logging/kdc.log
admin_server = FILE:/export/logging/kadmin.log

FILES

/etc/krb5/kadm5.acl

List of principals and their kadmin administrative privileges.

/etc/krb5/kadm5.keytab

Keytab for kadmind principals: kadmin/fqdn, changepw/fqdn, and
kadmin/changepw.

/var/krb5/principal

Kerberos principal database.

/var/krb5/principal.ulog

The update log file for incremental propagation.

/var/krb5/kadm5.dict

Dictionary of strings explicitly disallowed as passwords.

/var/krb5/kdc.log

KDC logging file.

/var/krb5/kadmin.log

Kerberos administration server logging file.

ATTRIBUTES

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

+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | See below. |
+--------------------+-----------------+

All of the keywords, except for the PKINIT keywords are Committed.
The PKINIT keywords are Volatile.