KDC.CONF(4)KDC.CONF(4)NAMEkdc.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 vari‐
ables (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 Ker‐
beros 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 Ker‐
beros server listens on the kdc TCP port specified in /etc/ser‐
vices. 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 spec‐
ified, 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 prin‐
cipal on the database. The default location is /etc/krb5/kadm5.acl.
admin_keytab
(string) Location of the keytab file that kadmin uses to authenti‐
cate 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_princi‐
pal_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 prin‐
cipal 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 or
gkadmin 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 authentica‐
tion.
preauth
Require the use of pre-authentication data whenever principals
request TGTs.
hwauth
Require the use of hardware-based pre-authentication data when‐
ever 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 [kdcde‐
faults] 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 deter‐
mine the type of encryption that encrypts the entries in the prin‐
cipal 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 incremen‐
tal 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 infor‐
mation 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 set‐
ting 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 com‐
puted from the realm names and the [capaths] section of its
krb5.conf(4) 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] sec‐
tion:
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 speci‐
fications.
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 speci‐
fied 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 sup‐
ported 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 mes‐
sages are logged. This can be any of the following facilities sup‐
ported 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 speci‐
fied 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 cer‐
tificates which can be used by the KDC to com‐
plete the trust chain between a client's cer‐
tificate 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 Revoca‐
tion List (CRL) information to be used by the
KDC when verifying the validity of client cer‐
tificates. This option can be specified multi‐
ple times. The default certificate verifica‐
tion process always checks the available revo‐
cation information to see if a certificate has
been revoked. If a match is found for the cer‐
tificate in a CRL, verification fails. If the
certificate being verified is not listed in a
CRL, or there is no CRL present for its issu‐
ing 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 issu‐
ing 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 User‐
PrincipalName (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 cer‐
tificates with the id-pkinit-san as defined in
RFC4556. There is currently no option to dis‐
able 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 certifi‐
cates 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. Oth‐
erwise, 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 match‐
ing 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 infra‐
structure is encouraged, but all files in the
directory is examined and if they contain cer‐
tificates (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][:certla‐
bel=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 kad‐
min/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(5) 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.
SEE ALSOkpasswd(1), gkadmin(1M), kadmind(1M), kadmin.local(1M), kdb5_util(1M),
kpropd(1M), libpkcs11(3LIB), syslog(3C), kadm5.acl(4), krb5.conf(4),
attributes(5), kerberos(5)
Nov 12, 2008 KDC.CONF(4)
