kdc.conf — MIT Kerberos Documentation

kdc.conf — MIT Kerberos Documentation
MIT Kerberos Documentation
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kdc.conf
The kdc.conf file supplements
krb5.conf
for programs which
are typically only used on a KDC, such as the
krb5kdc
and
kadmind
daemons and the
kdb5_util
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,
LOCALSTATEDIR
/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
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]
Some 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_listen
kdc_ports
kdc_tcp_listen
kdc_tcp_ports
no_host_referral
restrict_anonymous_to_tgt
The following [kdcdefaults] variables have no per-realm equivalent:
kdc_max_dgram_reply_size
Specifies the maximum packet size that can be sent over UDP. The
default value is 4096 bytes.
kdc_tcp_listen_backlog
(Integer.) Set the size of the listen queue length for the KDC
daemon. The value may be limited by OS settings. The default
value is 5.
spake_preauth_kdc_challenge
(String.) Specifies the group for a SPAKE optimistic challenge.
See the
spake_preauth_groups
variable in
[libdefaults]
for possible values. The default is not to issue an optimistic
challenge. (New in release 1.17.)
[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
The following tags may be specified in a [realms] subsection:
acl_file
(String.) Location of the access control list file that
kadmind
uses to determine which principals are allowed
which permissions on the Kerberos database. To operate without an
ACL file, set this relation to the empty string with
acl_file
""
. The default value is
LOCALSTATEDIR
/krb5kdc
/kadm5.acl
. For more
information on Kerberos ACL file see
kadm5.acl
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
LOCALSTATEDIR
/krb5kdc
/principal
default_principal_expiration
Absolute time
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 KDC to issue user-to-user
service tickets 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. In release 1.17 and later, user-to-user
service tickets are still allowed if the
dup-skey
flag is
set.
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.
disable_pac
(Boolean value.) If true, the KDC will not issue PACs for this
realm, and S4U2Self and S4U2Proxy operations will be disabled.
The default is false, which will permit the KDC to issue PACs.
New in release 1.20.
encrypted_challenge_indicator
(String.) Specifies the authentication indicator value that the KDC
asserts into tickets obtained using FAST encrypted challenge
pre-authentication. New in 1.16.
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_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. New in release
1.19.
iprop_master_ulogsize
The name for
iprop_ulogsize
prior to release 1.19. Its value is
used as a fallback if
iprop_ulogsize
is not specified.
iprop_replica_poll
(Delta time string.) Specifies how often the replica KDC polls
for new updates from the primary. The default value is
2m
(that is, two minutes). New in release 1.17.
iprop_slave_poll
(Delta time string.) The name for
iprop_replica_poll
prior to
release 1.17. Its value is used as a fallback if
iprop_replica_poll
is not specified.
iprop_listen
(Whitespace- or comma-separated list.) Specifies the iprop RPC
listening addresses and/or ports for the
kadmind
daemon.
Each entry may be an interface address, a port number, or an
address and port number separated by a colon. If the address
contains colons, enclose it in square brackets. If no address is
specified, the wildcard address is used. If kadmind fails to bind
to any of the specified addresses, it will fail to start. The
default (when
iprop_enable
is true) is to bind to the wildcard
address at the port specified in
iprop_port
. New in release
1.15.
iprop_port
(Port number.) Specifies the port number to be used for
incremental propagation. When
iprop_enable
is true, this
relation is required in the replica KDC configuration file, and
this relation or
iprop_listen
is required in the primary
configuration file, as there is no default port number. Port
numbers specified in
iprop_listen
entries will override this
port number for the
kadmind
daemon.
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 replica 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_listen
(Whitespace- or comma-separated list.) Specifies the kadmin RPC
listening addresses and/or ports for the
kadmind
daemon.
Each entry may be an interface address, a port number, or an
address and port number separated by a colon. If the address
contains colons, enclose it in square brackets. If no address is
specified, the wildcard address is used. If kadmind fails to bind
to any of the specified addresses, it will fail to start. The
default is to bind to the wildcard address at the port specified
in
kadmind_port
, or the standard kadmin port (749). New in
release 1.15.
kadmind_port
(Port number.) Specifies the port on which the
kadmind
daemon is to listen for this realm. Port numbers specified in
kadmind_listen
entries will override this port number. 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
LOCALSTATEDIR
/krb5kdc
/.k5.REALM
, where
REALM
is the Kerberos realm.
kdc_listen
(Whitespace- or comma-separated list.) Specifies the UDP
listening addresses and/or ports for the
krb5kdc
daemon.
Each entry may be an interface address, a port number, or an
address and port number separated by a colon. If the address
contains colons, enclose it in square brackets. If no address is
specified, the wildcard address is used. If no port is specified,
the standard port (88) is used. If the KDC daemon fails to bind
to any of the specified addresses, it will fail to start. The
default is to bind to the wildcard address on the standard port.
New in release 1.15.
kdc_ports
(Whitespace- or comma-separated list, deprecated.) Prior to
release 1.15, this relation lists the ports for the
krb5kdc
daemon to listen on for UDP requests. In
release 1.15 and later, it has the same meaning as
kdc_listen
if that relation is not defined.
kdc_tcp_listen
(Whitespace- or comma-separated list.) Specifies the TCP
listening addresses and/or ports for the
krb5kdc
daemon.
Each entry may be an interface address, a port number, or an
address and port number separated by a colon. If the address
contains colons, enclose it in square brackets. If no address is
specified, the wildcard address is used. If no port is specified,
the standard port (88) is used. To disable listening on TCP, set
this relation to the empty string with
kdc_tcp_listen
""
If the KDC daemon fails to bind to any of the specified addresses,
it will fail to start. The default is to bind to the wildcard
address on the standard port. New in release 1.15.
kdc_tcp_ports
(Whitespace- or comma-separated list, deprecated.) Prior to
release 1.15, this relation lists the ports for the
krb5kdc
daemon to listen on for UDP requests. In
release 1.15 and later, it has the same meaning as
kdc_tcp_listen
if that relation is not defined.
kpasswd_listen
(Comma-separated list.) Specifies the kpasswd listening addresses
and/or ports for the
kadmind
daemon. Each entry may be
an interface address, a port number, or an address and port number
separated by a colon. If the address contains colons, enclose it
in square brackets. If no address is specified, the wildcard
address is used. If kadmind fails to bind to any of the specified
addresses, it will fail to start. The default is to bind to the
wildcard address at the port specified in
kpasswd_port
, or the
standard kpasswd port (464). New in release 1.15.
kpasswd_port
(Port number.) Specifies the port on which the
kadmind
daemon is to listen for password change requests for this realm.
Port numbers specified in
kpasswd_listen
entries will override
this port number. The assigned port for password change requests
is 464, which is used by default.
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
Time 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
Time 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.
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
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.
spake_preauth_indicator
(String.) Specifies an authentication indicator value that the
KDC asserts into tickets obtained using SPAKE pre-authentication.
The default is not to add any indicators. This option may be
specified multiple times. New in release 1.17.
supported_enctypes
(List of
key
salt
strings.) Specifies the default key/salt
combinations of principals for this realm. Any principals created
through
kadmin
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
. 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_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
LOCALSTATEDIR
/krb5kdc
/principal
db_library
This tag indicates the name of the loadable database module. The
value should be
db2
for the DB2 module,
klmdb
for the LMDB
module, or
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
daemon uses
ldap_kdc_dn
, while the
kadmind
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.
mapsize
This LMDB-specific tag indicates the maximum size of the two
database environments in megabytes. The default value is 128.
Increase this value to address “Environment mapsize limit reached”
errors. New in release 1.17.
max_readers
This LMDB-specific tag indicates the maximum number of concurrent
reading processes for the databases. The default value is 128.
New in release 1.17.
nosync
This LMDB-specific tag can be set to improve the throughput of
kadmind and other administrative agents, at the expense of
durability (recent database changes may not survive a power outage
or other sudden reboot). It does not affect the throughput of the
KDC. The default value is false. New in release 1.17.
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
and
kadmind
perform logging. It may contain the following
relations:
admin_server
Specifies how
kadmind
performs logging.
kdc
Specifies how
krb5kdc
performs logging.
default
Specifies how either daemon performs logging in the absence of
relations specific to the daemon.
debug
(Boolean value.) Specifies whether debugging messages are
included in log outputs other than SYSLOG. Debugging messages are
always included in the system log output because syslog performs
its own priority filtering. The default value is false. New in
release 1.15.
Logging specifications may have 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=

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.
For backward compatibility, a severity argument may be specified,
and must be specified in order to specify a facility. This
argument will be ignored.
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
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, 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
If no logging specification is given, the default is to use syslog.
To disable logging entirely, specify
default
DEVICE=/dev/null
[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
LOCALSTATEDIR
/krb5kdc
/.socket
secret
This tag indicates a filename (which may be relative to
LOCALSTATEDIR
/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
indicator
This tag specifies an authentication indicator to be included in
the ticket if this token type is used to authenticate. This
option may be specified multiple times. (New in release 1.14.)
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:
realm-specific subsection of [realms]:
realms
EXAMPLE
COM
pkinit_anchors
FILE
usr
local
example
com
crt
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
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_indicator
Specifies an authentication indicator to include in the ticket if
pkinit is used to authenticate. This option may be specified
multiple times. (New in release 1.14.)
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.
pkinit_require_freshness
Specifies whether to require clients to include a freshness token
in PKINIT requests. The default value is false. (New in release
1.17.)
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” and “deprecated” are available for
compatibility but not recommended for use.
des3-cbc-raw
Triple DES cbc mode raw (weak)
des3-cbc-sha1 des3-hmac-sha1 des3-cbc-sha1-kd
Triple DES cbc mode with HMAC/sha1 (deprecated)
aes256-cts-hmac-sha1-96 aes256-cts aes256-sha1
AES-256 CTS mode with 96-bit SHA-1 HMAC
aes128-cts-hmac-sha1-96 aes128-cts aes128-sha1
AES-128 CTS mode with 96-bit SHA-1 HMAC
aes256-cts-hmac-sha384-192 aes256-sha2
AES-256 CTS mode with 192-bit SHA-384 HMAC
aes128-cts-hmac-sha256-128 aes128-sha2
AES-128 CTS mode with 128-bit SHA-256 HMAC
arcfour-hmac rc4-hmac arcfour-hmac-md5
RC4 with HMAC/MD5 (deprecated)
arcfour-hmac-exp rc4-hmac-exp arcfour-hmac-md5-exp
Exportable RC4 with HMAC/MD5 (weak)
camellia256-cts-cmac camellia256-cts
Camellia-256 CTS mode with CMAC
camellia128-cts-cmac camellia128-cts
Camellia-128 CTS mode with CMAC
des3
The triple DES family: des3-cbc-sha1
aes
The AES family: aes256-cts-hmac-sha1-96, aes128-cts-hmac-sha1-96, aes256-cts-hmac-sha384-192, and aes128-cts-hmac-sha256-128
rc4
The RC4 family: arcfour-hmac
camellia
The Camellia family: camellia256-cts-cmac and camellia128-cts-cmac
The string
DEFAULT
can be used to refer to the default set of
types for the variable in question. Types or families can be removed
from the current list by prefixing them with a minus sign (“-“).
Types or families can be prefixed with a plus sign (“+”) for symmetry;
it has the same meaning as just listing the type or family. For
example, “
DEFAULT
-rc4
” would be the default set of encryption
types with RC4 types removed, and “
des3
DEFAULT
” would be the
default set of encryption types with triple DES types moved to the
front.
While
aes128-cts
and
aes256-cts
are supported for all Kerberos
operations, they are not supported by very old versions of our GSSAPI
implementation (krb5-1.3.1 and earlier). Services running versions of
krb5 without AES support must not be given keys of these encryption
types in the KDC database.
The
aes128-sha2
and
aes256-sha2
encryption types are new in
release 1.15. Services running versions of krb5 without support for
these newer encryption types must not be given keys of these
encryption types in the KDC database.
Keysalt lists
Kerberos keys for users are usually derived from passwords. Kerberos
commands and configuration parameters that affect generation of keys
take lists of enctype-salttype (“keysalt”) pairs, known as
keysalt
lists
. Each keysalt pair is an enctype name followed by a salttype
name, in the format
enc
salt
. Individual keysalt list members are
separated by comma (“,”) characters or space characters. For example:
kadmin
aes256
cts
normal
aes128
cts
normal
would start up kadmin so that by default it would generate
password-derived keys for the
aes256-cts
and
aes128-cts
encryption types, using a
normal
salt.
To ensure that people who happen to pick the same password do not have
the same key, Kerberos 5 incorporates more information into the key
using something called a salt. The supported salt types are as
follows:
normal
default for Kerberos Version 5
norealm
same as the default, without using realm information
onlyrealm
uses only realm information as the salt
special
generate a random salt
Sample kdc.conf File
Here’s an example of a kdc.conf file:
kdcdefaults
kdc_listen
88
kdc_tcp_listen
88
realms
ATHENA
MIT
EDU
kadmind_port
749
max_life
12
max_renewable_life
master_key_type
aes256
cts
hmac
sha1
96
supported_enctypes
aes256
cts
hmac
sha1
96
normal
aes128
cts
hmac
sha1
96
normal
database_module
openldap_ldapconf
logging
kdc
FILE
usr
local
var
krb5kdc
kdc
log
admin_server
FILE
usr
local
var
krb5kdc
kadmin
log
dbdefaults
ldap_kerberos_container_dn
cn
krbcontainer
dc
mit
dc
edu
dbmodules
openldap_ldapconf
db_library
kldap
disable_last_success
true
ldap_kdc_dn
"cn=krbadmin,dc=mit,dc=edu"
# this object needs to have read rights on
# the realm container and principal subtrees
ldap_kadmind_dn
"cn=krbadmin,dc=mit,dc=edu"
# this object needs to have read and write rights on
# the realm container and principal subtrees
ldap_service_password_file
etc
kerberos
service
keyfile
ldap_servers
ldaps
//
kerberos
mit
edu
ldap_conns_per_server
FILES
LOCALSTATEDIR
/krb5kdc
/kdc.conf
SEE ALSO
krb5.conf
krb5kdc
kadm5.acl
On this page
kdc.conf
Structure
Sections
[kdcdefaults]
[realms]
[dbdefaults]
[dbmodules]
[logging]
[otp]
PKINIT options
Encryption types
Keysalt lists
Sample kdc.conf File
FILES
SEE ALSO
Table of contents
For users
For administrators
Installation guide
Configuration Files
krb5.conf
kdc.conf
kadm5.acl
Realm configuration decisions
Database administration
Database types
Account lockout
Configuring Kerberos with OpenLDAP back-end
Application servers
Host configuration
Backups of secure hosts
PKINIT configuration
OTP Preauthentication
SPAKE Preauthentication
Addressing dictionary attack risks
Principal names and DNS
Encryption types
HTTPS proxy configuration
Authentication indicators
Administration programs
MIT Kerberos defaults
Environment variables
Troubleshooting
Advanced topics
Various links
For application developers
For plugin module developers
Building Kerberos V5
Kerberos V5 concepts
Protocols and file formats
MIT Kerberos features
How to build this documentation from the source
Contributing to the MIT Kerberos Documentation
Resources
Full Table of Contents
Release: 1.21.3
1985-2024, MIT.
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