Manpages - kdc.conf.5

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.)

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:

#+begin_quote

      [realms]
          ATHENA.MIT.EDU = {
              max_renewable_life = 7d 0h 0m 0s
          }

#+end_quote

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. To operate without an ACL file, set this relation to the empty string with acl_file = “”. The default value is /var/lib/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 /var/lib/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:

#+begin_quote

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.

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(8) 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(8) 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(8) 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(8) 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 var/lib/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(8) 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(8) 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(8) 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(8) 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(8) 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(8) 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

(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.

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.

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(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. For lists of possible values, see Keysalt lists.

#+end_quote

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

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:

#+begin_quote

      [dbmodules]
          ATHENA.MIT.EDU = {
              disable_last_success = true
          }

#+end_quote

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 /var/lib/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(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.

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.

The [logging] section indicates how krb5kdc(8) and kadmind(8) perform logging. It may contain the following relations:

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.

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 **/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.

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.

#+begin_quote

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

#+end_quote

If no logging specification is given, the default is to use syslog. To disable logging entirely, specify default = DEVICE=/dev/null.

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 /var/lib/krb5kdc/<name>.socket.

secret

This tag indicates a filename (which may be relative to /var/lib/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:

#+begin_quote

      [otp]
          MyRemoteTokenType = {
              server = radius.mydomain.com:1812
              secret = SEmfiajf42$
              timeout = 15
              retries = 5
              strip_realm = true
          }

#+end_quote

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:

#+begin_quote

      [otp]
          DEFAULT = {
              strip_realm = false
          }

#+end_quote