Provided by: krb5-kdc_1.13.2+dfsg-5ubuntu2.2_amd64 
NAME
kdc.conf - Kerberos V5 KDC configuration file
The kdc.conf file supplements krb5.conf(5) for programs which are typically only used on a KDC, such as
the krb5kdc(8) and kadmind(8) daemons and the kdb5_util(8) program. Relations documented here may also
be specified in krb5.conf; for the KDC programs mentioned, krb5.conf and kdc.conf will be merged into a
single configuration profile.
Normally, the kdc.conf file is found in the KDC state directory, /etc/krb5kdc. You can override the
default location by setting the environment variable KRB5_KDC_PROFILE.
Please note that you need to restart the KDC daemon for any configuration changes to take effect.
STRUCTURE
The kdc.conf file is set up in the same format as the krb5.conf(5) file.
SECTIONS
The kdc.conf file may contain the following sections:
┌───────────────┬───────────────────────────────────────┐
│ [kdcdefaults] │ Default values for KDC behavior │
├───────────────┼───────────────────────────────────────┤
│ [realms] │ Realm-specific database configuration │
│ │ and settings │
├───────────────┼───────────────────────────────────────┤
│ [dbdefaults] │ Default database settings │
├───────────────┼───────────────────────────────────────┤
│ [dbmodules] │ Per-database settings │
├───────────────┼───────────────────────────────────────┤
│ [logging] │ Controls how Kerberos daemons perform │
│ │ logging │
└───────────────┴───────────────────────────────────────┘
[kdcdefaults]
With one exception, relations in the [kdcdefaults] section specify default values for realm variables, to
be used if the [realms] subsection does not contain a relation for the tag. See the [realms] section for
the definitions of these relations.
• host_based_services
• kdc_ports
• kdc_tcp_ports
• no_host_referral
• restrict_anonymous_to_tgt
kdc_max_dgram_reply_size
Specifies the maximum packet size that can be sent over UDP. The default value is 4096 bytes.
[realms]
Each tag in the [realms] section is the name of a Kerberos realm. The value of the tag is a subsection
where the relations define KDC parameters for that particular realm. The following example shows how to
define one parameter for the ATHENA.MIT.EDU realm:
[realms]
ATHENA.MIT.EDU = {
max_renewable_life = 7d 0h 0m 0s
}
The following tags may be specified in a [realms] subsection:
acl_file
(String.) Location of the access control list file that kadmind(8) uses to determine which
principals are allowed which permissions on the Kerberos database. The default value is
/etc/krb5kdc/kadm5.acl. For more information on Kerberos ACL file see kadm5.acl(5).
database_module
(String.) This relation indicates the name of the configuration section under [dbmodules] for
database-specific parameters used by the loadable database library. The default value is the
realm name. If this configuration section does not exist, default values will be used for all
database parameters.
database_name
(String, deprecated.) This relation specifies the location of the Kerberos database for this
realm, if the DB2 module is being used and the [dbmodules] configuration section does not specify
a database name. The default value is /etc/krb5kdc/principal.
default_principal_expiration
(abstime string.) Specifies the default expiration date of principals created in this realm. The
default value is 0, which means no expiration date.
default_principal_flags
(Flag string.) Specifies the default attributes of principals created in this realm. The format
for this string is a comma-separated list of flags, with '+' before each flag that should be
enabled and '-' before each flag that should be disabled. The postdateable, forwardable,
tgt-based, renewable, proxiable, dup-skey, allow-tickets, and service flags default to enabled.
There are a number of possible flags:
allow-tickets
Enabling this flag means that the KDC will issue tickets for this principal. Disabling
this flag essentially deactivates the principal within this realm.
dup-skey
Enabling this flag allows the principal to obtain a session key for another user,
permitting user-to-user authentication for this principal.
forwardable
Enabling this flag allows the principal to obtain forwardable tickets.
hwauth If this flag is enabled, then the principal is required to preauthenticate using a hardware
device before receiving any tickets.
no-auth-data-required
Enabling this flag prevents PAC or AD-SIGNEDPATH data from being added to service tickets
for the principal.
ok-as-delegate
If this flag is enabled, it hints the client that credentials can and should be delegated
when authenticating to the service.
ok-to-auth-as-delegate
Enabling this flag allows the principal to use S4USelf tickets.
postdateable
Enabling this flag allows the principal to obtain postdateable tickets.
preauth
If this flag is enabled on a client principal, then that principal is required to
preauthenticate to the KDC before receiving any tickets. On a service principal, enabling
this flag means that service tickets for this principal will only be issued to clients with
a TGT that has the preauthenticated bit set.
proxiable
Enabling this flag allows the principal to obtain proxy tickets.
pwchange
Enabling this flag forces a password change for this principal.
pwservice
If this flag is enabled, it marks this principal as a password change service. This should
only be used in special cases, for example, if a user's password has expired, then the user
has to get tickets for that principal without going through the normal password
authentication in order to be able to change the password.
renewable
Enabling this flag allows the principal to obtain renewable tickets.
service
Enabling this flag allows the the KDC to issue service tickets for this principal.
tgt-based
Enabling this flag allows a principal to obtain tickets based on a ticket-granting-ticket,
rather than repeating the authentication process that was used to obtain the TGT.
dict_file
(String.) Location of the dictionary file containing strings that are not allowed as passwords.
The file should contain one string per line, with no additional whitespace. If none is specified
or if there is no policy assigned to the principal, no dictionary checks of passwords will be
performed.
host_based_services
(Whitespace- or comma-separated list.) Lists services which will get host-based referral
processing even if the server principal is not marked as host-based by the client.
iprop_enable
(Boolean value.) Specifies whether incremental database propagation is enabled. The default
value is false.
iprop_master_ulogsize
(Integer.) Specifies the maximum number of log entries to be retained for incremental
propagation. The default value is 1000. Prior to release 1.11, the maximum value was 2500.
iprop_slave_poll
(Delta time string.) Specifies how often the slave KDC polls for new updates from the master.
The default value is 2m (that is, two minutes).
iprop_port
(Port number.) Specifies the port number to be used for incremental propagation. This is
required in both master and slave configuration files.
iprop_resync_timeout
(Delta time string.) Specifies the amount of time to wait for a full propagation to complete.
This is optional in configuration files, and is used by slave KDCs only. The default value is 5
minutes (5m). New in release 1.11.
iprop_logfile
(File name.) Specifies where the update log file for the realm database is to be stored. The
default is to use the database_name entry from the realms section of the krb5 config file, with
.ulog appended. (NOTE: If database_name isn't specified in the realms section, perhaps because
the LDAP database back end is being used, or the file name is specified in the [dbmodules]
section, then the hard-coded default for database_name is used. Determination of the
iprop_logfile default value will not use values from the [dbmodules] section.)
kadmind_port
(Port number.) Specifies the port on which the kadmind(8) daemon is to listen for this realm.
The assigned port for kadmind is 749, which is used by default.
key_stash_file
(String.) Specifies the location where the master key has been stored (via kdb5_util stash). The
default is /etc/krb5kdc/.k5.REALM, where REALM is the Kerberos realm.
kdc_ports
(Whitespace- or comma-separated list.) Lists the ports on which the Kerberos server should listen
for UDP requests, as a comma-separated list of integers. The default value is 88,750, which are
the assigned Kerberos port and the port historically used by Kerberos V4.
kdc_tcp_ports
(Whitespace- or comma-separated list.) Lists the ports on which the Kerberos server should listen
for TCP connections, as a comma-separated list of integers. To disable listening on TCP, set this
relation to the empty string with kdc_tcp_ports = "". If this relation is not specified, the
default is to listen on TCP port 88 (the standard port). Prior to release 1.13, the default was
not to listen for TCP connections at all.
master_key_name
(String.) Specifies the name of the principal associated with the master key. The default is
K/M.
master_key_type
(Key type string.) Specifies the master key's key type. The default value for this is
aes256-cts-hmac-sha1-96. For a list of all possible values, see Encryption types.
max_life
(duration string.) Specifies the maximum time period for which a ticket may be valid in this
realm. The default value is 24 hours.
max_renewable_life
(duration string.) Specifies the maximum time period during which a valid ticket may be renewed
in this realm. The default value is 0.
no_host_referral
(Whitespace- or comma-separated list.) Lists services to block from getting host-based referral
processing, even if the client marks the server principal as host-based or the service is also
listed in host_based_services. no_host_referral = * will disable referral processing altogether.
des_crc_session_supported
(Boolean value). If set to true, the KDC will assume that service principals support des-cbc-crc
for session key enctype negotiation purposes. If allow_weak_crypto in libdefaults is false, or if
des-cbc-crc is not a permitted enctype, then this variable has no effect. Defaults to true. New
in release 1.11.
reject_bad_transit
(Boolean value.) If set to true, the KDC will check the list of transited realms for cross-realm
tickets against the transit path computed from the realm names and the capaths section of its
krb5.conf(5) file; if the path in the ticket to be issued contains any realms not in the computed
path, the ticket will not be issued, and an error will be returned to the client instead. If this
value is set to false, such tickets will be issued anyways, and it will be left up to the
application server to validate the realm transit path.
If the disable-transited-check flag is set in the incoming request, this check is not performed at
all. Having the reject_bad_transit option will cause such ticket requests to be rejected always.
This transit path checking and config file option currently apply only to TGS requests.
The default value is true.
restrict_anonymous_to_tgt
(Boolean value.) If set to true, the KDC will reject ticket requests from anonymous principals to
service principals other than the realm's ticket-granting service. This option allows anonymous
PKINIT to be enabled for use as FAST armor tickets without allowing anonymous authentication to
services. The default value is false. New in release 1.9.
supported_enctypes
(List of key:salt strings.) Specifies the default key/salt combinations of principals for this
realm. Any principals created through kadmin(1) will have keys of these types. The default value
for this tag is aes256-cts-hmac-sha1-96:normal aes128-cts-hmac-sha1-96:normal des3-cbc-sha1:normal
arcfour-hmac-md5:normal. For lists of possible values, see Keysalt lists.
[dbdefaults]
The [dbdefaults] section specifies default values for some database parameters, to be used if the
[dbmodules] subsection does not contain a relation for the tag. See the [dbmodules] section for the
definitions of these relations.
• ldap_kerberos_container_dn
• ldap_kdc_dn
• ldap_kdc_sasl_authcid
• ldap_kdc_sasl_authzid
• ldap_kdc_sasl_mech
• ldap_kdc_sasl_realm
• ldap_kadmind_dn
• ldap_kadmind_sasl_authcid
• ldap_kadmind_sasl_authzid
• ldap_kadmind_sasl_mech
• ldap_kadmind_sasl_realm
• ldap_service_password_file
• ldap_servers
• ldap_conns_per_server
[dbmodules]
The [dbmodules] section contains parameters used by the KDC database library and database modules. Each
tag in the [dbmodules] section is the name of a Kerberos realm or a section name specified by a realm's
database_module parameter. The following example shows how to define one database parameter for the
ATHENA.MIT.EDU realm:
[dbmodules]
ATHENA.MIT.EDU = {
disable_last_success = true
}
The following tags may be specified in a [dbmodules] subsection:
database_name
This DB2-specific tag indicates the location of the database in the filesystem. The default is
/etc/krb5kdc/principal.
db_library
This tag indicates the name of the loadable database module. The value should be db2 for the DB2
module and kldap for the LDAP module.
disable_last_success
If set to true, suppresses KDC updates to the "Last successful authentication" field of principal
entries requiring preauthentication. Setting this flag may improve performance. (Principal
entries which do not require preauthentication never update the "Last successful authentication"
field.). First introduced in release 1.9.
disable_lockout
If set to true, suppresses KDC updates to the "Last failed authentication" and "Failed password
attempts" fields of principal entries requiring preauthentication. Setting this flag may improve
performance, but also disables account lockout. First introduced in release 1.9.
ldap_conns_per_server
This LDAP-specific tag indicates the number of connections to be maintained per LDAP server.
ldap_kdc_dn and ldap_kadmind_dn
These LDAP-specific tags indicate the default DN for binding to the LDAP server. The krb5kdc(8)
daemon uses ldap_kdc_dn, while the kadmind(8) daemon and other administrative programs use
ldap_kadmind_dn. The kadmind DN must have the rights to read and write the Kerberos data in the
LDAP database. The KDC DN must have the same rights, unless disable_lockout and
disable_last_success are true, in which case it only needs to have rights to read the Kerberos
data. These tags are ignored if a SASL mechanism is set with ldap_kdc_sasl_mech or
ldap_kadmind_sasl_mech.
ldap_kdc_sasl_mech and ldap_kadmind_sasl_mech
These LDAP-specific tags specify the SASL mechanism (such as EXTERNAL) to use when binding to the
LDAP server. New in release 1.13.
ldap_kdc_sasl_authcid and ldap_kadmind_sasl_authcid
These LDAP-specific tags specify the SASL authentication identity to use when binding to the LDAP
server. Not all SASL mechanisms require an authentication identity. If the SASL mechanism
requires a secret (such as the password for DIGEST-MD5), these tags also determine the name within
the ldap_service_password_file where the secret is stashed. New in release 1.13.
ldap_kdc_sasl_authzid and ldap_kadmind_sasl_authzid
These LDAP-specific tags specify the SASL authorization identity to use when binding to the LDAP
server. In most circumstances they do not need to be specified. New in release 1.13.
ldap_kdc_sasl_realm and ldap_kadmind_sasl_realm
These LDAP-specific tags specify the SASL realm to use when binding to the LDAP server. In most
circumstances they do not need to be set. New in release 1.13.
ldap_kerberos_container_dn
This LDAP-specific tag indicates the DN of the container object where the realm objects will be
located.
ldap_servers
This LDAP-specific tag indicates the list of LDAP servers that the Kerberos servers can connect
to. The list of LDAP servers is whitespace-separated. The LDAP server is specified by a LDAP
URI. It is recommended to use ldapi: or ldaps: URLs to connect to the LDAP server.
ldap_service_password_file
This LDAP-specific tag indicates the file containing the stashed passwords (created by
kdb5_ldap_util stashsrvpw) for the ldap_kdc_dn and ldap_kadmind_dn objects, or for the
ldap_kdc_sasl_authcid or ldap_kadmind_sasl_authcid names for SASL authentication. This file must
be kept secure.
unlockiter
If set to true, this DB2-specific tag causes iteration operations to release the database lock
while processing each principal. Setting this flag to true can prevent extended blocking of KDC
or kadmin operations when dumps of large databases are in progress. First introduced in release
1.13.
The following tag may be specified directly in the [dbmodules] section to control where database modules
are loaded from:
db_module_dir
This tag controls where the plugin system looks for database modules. The value should be an
absolute path.
[logging]
The [logging] section indicates how krb5kdc(8) and kadmind(8) perform logging. The keys in this section
are daemon names, which may be one of:
admin_server
Specifies how kadmind(8) performs logging.
kdc Specifies how krb5kdc(8) performs logging.
default
Specifies how either daemon performs logging in the absence of relations specific to the daemon.
Values are of the following forms:
FILE=filename or FILE:filename
This value causes the daemon's logging messages to go to the filename. If the = form is used, the
file is overwritten. If the : form is used, the file is appended to.
STDERR This value causes the daemon's logging messages to go to its standard error stream.
CONSOLE
This value causes the daemon's logging messages to go to the console, if the system supports it.
DEVICE=<devicename>
This causes the daemon's logging messages to go to the specified device.
SYSLOG[:severity[:facility]]
This causes the daemon's logging messages to go to the system log.
The severity argument specifies the default severity of system log messages. This may be any of
the following severities supported by the syslog(3) call, minus the LOG_ prefix: EMERG, ALERT,
CRIT, ERR, WARNING, NOTICE, INFO, and DEBUG.
The facility argument specifies the facility under which the messages are logged. This may be any
of the following facilities supported by the syslog(3) call minus the LOG_ prefix: KERN, USER,
MAIL, DAEMON, AUTH, LPR, NEWS, UUCP, CRON, and LOCAL0 through 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 will go to the console and to the system log
under the facility LOG_DAEMON with default severity of LOG_INFO; and the logging messages from the
administrative server will be appended to the file /var/adm/kadmin.log and sent to the device /dev/tty04.
[logging]
kdc = CONSOLE
kdc = SYSLOG:INFO:DAEMON
admin_server = FILE:/var/adm/kadmin.log
admin_server = DEVICE=/dev/tty04
[otp]
Each subsection of [otp] is the name of an OTP token type. The tags within the subsection define the
configuration required to forward a One Time Password request to a RADIUS server.
For each token type, the following tags may be specified:
server This is the server to send the RADIUS request to. It can be a hostname with optional port, an ip
address with optional port, or a Unix domain socket address. The default is
/etc/krb5kdc/<name>.socket.
secret This tag indicates a filename (which may be relative to /etc/krb5kdc) containing the secret used
to encrypt the RADIUS packets. The secret should appear in the first line of the file by itself;
leading and trailing whitespace on the line will be removed. If the value of server is a Unix
domain socket address, this tag is optional, and an empty secret will be used if it is not
specified. Otherwise, this tag is required.
timeout
An integer which specifies the time in seconds during which the KDC should attempt to contact the
RADIUS server. This tag is the total time across all retries and should be less than the time
which an OTP value remains valid for. The default is 5 seconds.
retries
This tag specifies the number of retries to make to the RADIUS server. The default is 3 retries
(4 tries).
strip_realm
If this tag is true, the principal without the realm will be passed to the RADIUS server.
Otherwise, the realm will be included. The default value is true.
In the following example, requests are sent to a remote server via UDP:
[otp]
MyRemoteTokenType = {
server = radius.mydomain.com:1812
secret = SEmfiajf42$
timeout = 15
retries = 5
strip_realm = true
}
An implicit default token type named DEFAULT is defined for when the per-principal configuration does not
specify a token type. Its configuration is shown below. You may override this token type to something
applicable for your situation:
[otp]
DEFAULT = {
strip_realm = false
}
PKINIT OPTIONS
NOTE:
The following are pkinit-specific options. These values may be specified in [kdcdefaults] as global
defaults, or within a realm-specific subsection of [realms]. Also note that a realm-specific value
over-rides, does not add to, a generic [kdcdefaults] specification. The search order is:
1. realm-specific subsection of [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/
For information about the syntax of some of these options, see Specifying PKINIT identity information in
krb5.conf(5).
pkinit_anchors
Specifies the location of trusted anchor (root) certificates which the KDC trusts to sign client
certificates. This option is required if pkinit is to be supported by the KDC. This option may
be specified multiple times.
pkinit_dh_min_bits
Specifies the minimum number of bits the KDC is willing to accept for a client's Diffie-Hellman
key. The default is 2048.
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 value is false.
Without this option, the KDC will only accept certificates with the id-pkinit-san as defined in
RFC 4556. 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 RFC 4556.
scLogin
If scLogin is specified, client certificates with the Microsoft Smart Card Login EKU
(id-ms-kp-sc-logon) will be accepted.
none If none is specified, then client certificates will not be checked to verify they have an
acceptable EKU. The use of this option is not recommended.
pkinit_identity
Specifies the location of the KDC's X.509 identity information. This option is required if pkinit
is to be supported by the KDC.
pkinit_kdc_ocsp
Specifies the location of the KDC's OCSP.
pkinit_pool
Specifies the location of intermediate certificates which may be used by the KDC to complete the
trust chain between a client's certificate and a trusted anchor. This option may be specified
multiple times.
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 may be specified multiple times.
pkinit_require_crl_checking
The default certificate verification process will always check 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.
However, if pkinit_require_crl_checking is true and there is no CRL information available for the
issuing CA, then 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.
ENCRYPTION TYPES
Any tag in the configuration files which requires a list of encryption types can be set to some
combination of the following strings. Encryption types marked as "weak" are available for compatibility
but not recommended for use.
─────────────────────────────────────────────────────────────────────────────────
des-cbc-crc DES cbc mode with CRC-32 (weak)
─────────────────────────────────────────────────────────────────────────────────
des-cbc-md4 DES cbc mode with RSA-MD4 (weak)
─────────────────────────────────────────────────────────────────────────────────
des-cbc-md5 DES cbc mode with RSA-MD5 (weak)
─────────────────────────────────────────────────────────────────────────────────
des-cbc-raw DES cbc mode raw (weak)
─────────────────────────────────────────────────────────────────────────────────
des3-cbc-raw Triple DES cbc mode raw (weak)
─────────────────────────────────────────────────────────────────────────────────
des3-cbc-sha1 des3-hmac-sha1 Triple DES cbc mode with HMAC/sha1
des3-cbc-sha1-kd
─────────────────────────────────────────────────────────────────────────────────
des-hmac-sha1 DES with HMAC/sha1 (weak)
─────────────────────────────────────────────────────────────────────────────────
aes256-cts-hmac-sha1-96 aes256-cts CTS mode with 96-bit SHA-1 HMAC
AES-256
─────────────────────────────────────────────────────────────────────────────────
aes128-cts-hmac-sha1-96 aes128-cts CTS mode with 96-bit SHA-1 HMAC
AES-128
─────────────────────────────────────────────────────────────────────────────────
arcfour-hmac rc4-hmac RC4 with HMAC/MD5
arcfour-hmac-md5
─────────────────────────────────────────────────────────────────────────────────
arcfour-hmac-exp rc4-hmac-exp Exportable RC4 with HMAC/MD5 (weak)
arcfour-hmac-md5-exp
─────────────────────────────────────────────────────────────────────────────────
camellia256-cts-cmac camellia256-cts Camellia-256 CTS mode with CMAC
─────────────────────────────────────────────────────────────────────────────────
camellia128-cts-cmac camellia128-cts Camellia-128 CTS mode with CMAC
─────────────────────────────────────────────────────────────────────────────────
des The DES family: des-cbc-crc,
des-cbc-md5, and des-cbc-md4 (weak)
─────────────────────────────────────────────────────────────────────────────────
des3 The triple DES family: des3-cbc-sha1
─────────────────────────────────────────────────────────────────────────────────
aes The AES family:
aes256-cts-hmac-sha1-96 and
aes128-cts-hmac-sha1-96
─────────────────────────────────────────────────────────────────────────────────
rc4 The RC4 family: arcfour-hmac
─────────────────────────────────────────────────────────────────────────────────
camellia The Camellia family:
camellia256-cts-cmac and
camellia128-cts-cmac
┌───────────────────────────────────────┬───────────────────────────────────────┐
│ │ │
--
KEYSALT LISTS │ │ │
--
--
FILES
/etc/krb5kdc/kdc.conf
SEE ALSO
krb5.conf(5), krb5kdc(8), kadm5.acl(5)
AUTHOR
MIT
COPYRIGHT
1985-2015, MIT
1.13.2 KDC.CONF(5)