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NAME

       krb5.conf - Kerberos configuration file

DESCRIPTION

       krb5.conf  contains configuration information needed by the Kerberos V5
       library.  This includes information  describing  the  default  Kerberos
       realm,  and  the  location of the Kerberos key distribution centers for
       known realms.

       The krb5.conf file uses an INI-style format.  Sections are delimited by
       square  braces; within each section, there are relations where tags can
       be  assigned  to  have  specific  values.   Tags  can  also  contain  a
       subsection, which contains further relations or subsections.  A tag can
       be assigned to multiple values.  Here is an example  of  the  INI-style
       format used by krb5.conf:

                 [section1]
                      tag1 = value_a
                      tag1 = value_b
                      tag2 = value_c

                 [section 2]
                      tag3 = {
                           subtag1 = subtag_value_a
                           subtag1 = subtag_value_b
                           subtag2 = subtag_value_c
                      }
                      tag4 = {
                           subtag1 = subtag_value_d
                           subtag2 = subtag_value_e
                      }

       The following sections are currently used in the krb5.conf file:

       [libdefaults]
              Contains various default values used by the Kerberos V5 library.

       [login]
              Contains default values used by the Kerberos V5  login  program,
              login.krb5(8).

       [appdefaults]
              Contains  default  values  that  can  be  used  by  Kerberos  V5
              applications.

       [realms]
              Contains  subsections  keyed  by  Kerberos  realm  names   which
              describe  where  to  find  the Kerberos servers for a particular
              realm, and other realm-specific information.

       [domain_realm]
              Contains relations which map  subdomains  and  domain  names  to
              Kerberos  realm  names.   This  is used by programs to determine
              what realm a host should be in, given its fully qualified domain
              name.

       [logging]
              Contains  relations which determine how Kerberos entities are to
              perform their logging.

       [capaths]
              Contains the authentication  paths  used  with  non-hierarchical
              cross-realm.  Entries  in  the section are used by the client to
              determine the intermediate realms which may be  used  in  cross-
              realm  authentication.  It  is also used by the end-service when
              checking the transited field for trusted intermediate realms.

       [dbdefaults]
              Contains default values for database specific parameters.

       [dbmodules]
              Contains database  specific  parameters  used  by  the  database
              library.

       Each of these sections will be covered in more details in the following
       sections.

LIBDEFAULTS SECTION

       The following relations are defined in the [libdefaults] section:

       default_keytab_name
              This relation specifies the default keytab name to  be  used  by
              application  severs such as telnetd and rlogind.  The default is
              "/etc/krb5.keytab".  This formerly defaulted to "/etc/v5srvtab",
              but was changed to the current value.

       default_realm
              This  relation  identifies  the  default  realm  to be used in a
              client host’s Kerberos activity.

       default_tgs_enctypes
              This relation identifies  the  supported  list  of  session  key
              encryption  types  that  should be returned by the KDC. The list
              may be delimited with commas or whitespace.

       default_tkt_enctypes
              This relation identifies  the  supported  list  of  session  key
              encryption  types that should be requested by the client, in the
              same format.

       permitted_enctypes
              This relation identifies  the  permitted  list  of  session  key
              encryption types.

       allow_weak_crypto
              If this is set to 0 (for false), then weak encryption types will
              be filtered out of the previous three lists.  The default  value
              for  this  tag is false, which may cause authentication failures
              in existing Kerberos infrastructures that do not support  strong
              crypto.   Users  in affected environments should set this tag to
              true until their infrastructure adopts stronger ciphers.

       clockskew
              This relation sets the maximum allowable amount of clockskew  in
              seconds  that  the  library will tolerate before assuming that a
              Kerberos message is invalid.  The default value is 300  seconds,
              or five minutes.

       kdc_timesync
              If  the  value  of  this relation is non-zero (the default), the
              library will compute the difference between the system clock and
              the  time  returned  by  the  KDC and in order to correct for an
              inaccurate system clock.  This corrective factor is only used by
              the Kerberos library.

       kdc_req_checksum_type
              For compatibility with DCE security servers which do not support
              the default CKSUMTYPE_RSA_MD5 used by this version of  Kerberos.
              Use  a  value  of  2  to use the CKSUMTYPE_RSA_MD4 instead. This
              applies to DCE 1.1 and earlier.  This value is only used for DES
              keys; other keys use the preferred checksum type for those keys.

       ap_req_checksum_type
              If set  this variable  controls what  ap-req  checksum  will  be
              used  in   authenticators.  This variable should be unset so the
              appropriate checksum for the encryption key in use will be used.
              This  can  be  set if backward compatibility requires a specific
              checksum type.

       safe_checksum_type
              This allows you to set the preferred keyed-checksum type for use
              in  KRB_SAFE  messages.   The  default  value  for  this type is
              CKSUMTYPE_RSA_MD5_DES.   For  compatibility  with   applications
              linked  against  DCE  version 1.1 or earlier Kerberos libraries,
              use a value of 3 to use the CKSUMTYPE_RSA_MD4_DES instead.  This
              field is ignored when its value is incompatible with the session
              key type.

       preferred_preauth_types
              This allows you to set  the  preferred  preauthentication  types
              which  the  client  will  attempt  before  others  which  may be
              advertised by a KDC.  The default value for this setting is "17,
              16, 15, 14", which forces libkrb5 to attempt to use PKINIT if it
              is supported.

       ccache_type
              User this parameter on systems which are DCE clients, to specify
              the  type  of  cache  to  be created by kinit, or when forwarded
              tickets are received. DCE and Kerberos can share the cache,  but
              some versions of DCE do not support the default cache as created
              by this version of Kerberos. Use a value  of  1  on  DCE  1.0.3a
              systems, and a value of 2 on DCE 1.1 systems.

       dns_lookup_kdc
              Indicate  whether  DNS  SRV  records shoud be used to locate the
              KDCs and other servers for a realm, if they are  not  listed  in
              the  information  for  the  realm.   The default is to use these
              records.

       dns_lookup_realm
              Indicate whether DNS TXT records should be used to determine the
              Kerberos  realm  of  a  host.   The  default is not to use these
              records.

       dns_fallback
              General  flag  controlling  the  use   of   DNS   for   Kerberos
              information.   If  both  of the preceding options are specified,
              this option has no effect.

       realm_try_domains
              Indicate whether a host’s domain components should  be  used  to
              determine  the  Kerberos  realm  of the host.  The value of this
              variable is an integer: -1 means not to search, 0 means  to  try
              the  host’s  domain  itself,  1  means  to also try the domain’s
              immediate parent, and so forth.  The library’s  usual  mechanism
              for  locating  Kerberos  realms  is  used to determine whether a
              domain is a valid realm--which may  involve  consulting  DNS  if
              dns_lookup_kdc  is  set.   The  default  is not to search domain
              components.

       extra_addresses
              This allows a computer to use multiple local addresses, in order
              to  allow  Kerberos  to  work  in a network that uses NATs.  The
              addresses should be in a comma-separated list.

       udp_preference_limit
              When sending a message to the KDC, the library  will  try  using
              TCP   before   UDP   if   the  size  of  the  message  is  above
              "udp_preference_limit".   If  the  message   is   smaller   than
              "udp_preference_limit",  then  UDP  will  be  tried  before TCP.
              Regardless of the size, both protocols  will  be  tried  if  the
              first attempt fails.

       verify_ap_req_nofail
              If  this flag is set, then an attempt to get initial credentials
              will fail if the client machine does not  have  a  keytab.   The
              default for the flag is false.

       ticket_lifetime
              The  value  of  this  tag  is  the  default lifetime for initial
              tickets.  The default value for the tag is 1 day (1d).

       renew_lifetime
              The value of this tag is  the  default  renewable  lifetime  for
              initial tickets.  The default value for the tag is 0.

       noaddresses
              Setting  this  flag  causes  the  initial  Kerberos ticket to be
              addressless.  The default for the flag is true.

       forwardable
              If this  flag  is  set,  initial  tickets  by  default  will  be
              forwardable.  The default value for this flag is false.

       proxiable
              If  this  flag  is  set,  initial  tickets  by  default  will be
              proxiable.  The default value for this flag is false.

APPDEFAULTS SECTION

       Each tag in the [appdefaults] section names a Kerberos  V5  application
       or an option that is used by some Kerberos V5 application[s].  The four
       ways that you can set values for options are as follows, in  decreasing
       order of precedence:

                 #1)
                      application = {
                           realm1 = {
                                option = value
                           }
                           realm2 = {
                                option = value
                           }
                      }
                 #2)
                      application = {
                           option1 = value
                           option2 = value
                      }
                 #3)
                      realm = {
                           option = value
                      }
                 #4)
                      option = value

LOGIN SECTION

       The  [login]  section is used to configure the behavior of the Kerberos
       V5 login  program,  login.krb5(8).   Refer  to  the  manual  entry  for
       login.krb5  for a description of the relations allowed in this section.

REALMS SECTION

       Each tag in the [realms] section of the file names  a  Kerberos  realm.
       The  value  of  the  tag  is  a  subsection where the relations in that
       subsection  define  the  properties  of  that  particular  realm.   For
       example:

                 [realms]
                      ATHENA.MIT.EDU = {
                           admin_server = KERBEROS.MIT.EDU
                           default_domain = MIT.EDU
                           database_module = ldapconf
                           v4_instance_convert = {
                                mit = mit.edu
                                lithium = lithium.lcs.mit.edu
                           }
                           v4_realm = LCS.MIT.EDU
                      }

       For  each  realm,  the  following  tags may be specified in the realm’s
       subsection:

       kdc    The value of this relation is the name of a host running  a  KDC
              for  that  realm.  An optional port number (preceded by a colon)
              may be appended to the hostname.  This tag should  generally  be
              used   only   if  the  realm  administrator  has  not  made  the
              information available through DNS.

       admin_server
              This relation  identifies  the  host  where  the  administration
              server  is  running.   Typically  this  is  the  Master Kerberos
              server.

       database_module
              This relation indicates the name of  the  configuration  section
              under  dbmodules  for  database  specific parameters used by the
              loadable database library.

       default_domain
              This relation identifies the default domain for which  hosts  in
              this realm are assumed to be in.  This is needed for translating
              V4 principal names (which do not contain a domain  name)  to  V5
              principal names (which do).

       v4_instance_convert
              This subsection allows the administrator to configure exceptions
              to the default_domain mapping rule.  It  contains  V4  instances
              (the  tag  name)  which  should  be  translated to some specific
              hostname (the tag value) as the second component in  a  Kerberos
              V5 principal name.

       v4_realm
              This  relation  is  used  by  the  krb524  library routines when
              converting a V5 principal name to a V4  principal  name.  It  is
              used  when  V4 realm name and the V5 realm are not the same, but
              still share the same principal  names  and  passwords.  The  tag
              value is the Kerberos V4 realm name.

       auth_to_local_names
              This  subsection  allows  you  to  set  explicit  mappings  from
              principal names to local user names.  The  tag  is  the  mapping
              name, and the value is the corresponding local user name.

       auth_to_local
              This  tag allows you to set a general rule for mapping principal
              names to local user names.  It will be used if there is  not  an
              explicit   mapping   for   the  principal  name  that  is  being
              translated.  The possible values are:

                   DB:<filename>
                        The principal  will  be  looked  up  in  the  database
                        <filename>.    Support   for  this  is  not  currently
                        compiled in by default.
                   RULE:<exp>
                        The local name will be formulated from <exp>.
                   DEFAULT
                        The principal name will be used as the local name.  If
                        the principal has more than one component or is not in
                        the default realm, this rule is not applicable and the
                        conversion will fail.

DOMAIN_REALM SECTION

       The  [domain_realm]  section  provides a translation from a hostname to
       the Kerberos realm name for the services provided by that host.

       The tag name can be a hostname, or a domain name,  where  domain  names
       are  indicated  by  a prefix of a period (’.’) character.  The value of
       the relation is the Kerberos realm name for  that  particular  host  or
       domain.  Host names and domain names should be in lower case.

       If  no  translation entry applies, the host’s realm is considered to be
       the hostname’s domain portion converted to upper  case.   For  example,
       the following [domain_realm] section:

                 [domain_realm]
                      .mit.edu = ATHENA.MIT.EDU
                      mit.edu = ATHENA.MIT.EDU
                      dodo.mit.edu = SMS_TEST.MIT.EDU
                      .ucsc.edu = CATS.UCSC.EDU

       maps  dodo.mit.edu  into the SMS_TEST.MIT.EDU realm, all other hosts in
       the MIT.EDU domain to the ATHENA.MIT.EDU realm, and all  hosts  in  the
       UCSC.EDU  domain  into  the  CATS.UCSC.EDU  realm.  ucbvax.berkeley.edu
       would be mapped by the default rules to the BERKELEY.EDU  realm,  while
       sage.lcs.mit.edu would be mapped to the LCS.MIT.EDU realm.

LOGGING SECTION

       The  [logging]  section indicates how a particular entity is to perform
       its logging.  The relations specified in this  section  assign  one  or
       more values to the entity name.

       Currently, the following entities are used:

       kdc    These entries specify how the KDC is to perform its logging.

       admin_server
              These  entries  specify  how  the  administrative  server  is to
              perform its logging.

       default
              These entries specify how to perform logging in the  absence  of
              explicit specifications otherwise.

       Values are of the following forms:

       FILE=<filename>

       FILE:<filename>
              This  value  causes  the  entity’s logging messages to go to the
              specified file.  If the  =  form  is  used,  then  the  file  is
              overwritten.  Otherwise, the file is appended to.

       STDERR This  value  causes  the  entity’s logging messages to go to its
              standard error stream.

       CONSOLE
              This value causes the entity’s logging messages  to  go  to  the
              console, if the system supports it.

       DEVICE=<devicename>
              This causes the entity’s logging messages to go to the specified
              device.

       SYSLOG[:<severity>[:<facility>]]
              This causes the entity’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:
              LOG_EMERG,   LOG_ALERT,    LOG_CRIT,    LOG_ERR,    LOG_WARNING,
              LOG_NOTICE,  LOG_INFO,  and  LOG_DEBUG.  For example, to specify
              LOG_CRIT severity, one would use CRIT for severity.

              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:  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, and 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/log/kadmin.log
       and sent to the device /dev/tty04.

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

CAPATHS SECTION

       Cross-realm authentication is typically organized hierarchically.  This
       hierarchy  is  based  on  the  name  of  the  realm, which thus imposes
       restrictions on the choice of realm names, and on who  may  participate
       in  a  cross-realm authentication. A non hierarchical orgization may be
       used, but requires a database to  construct  the  authentication  paths
       between the realms. This section defines that database.

       A  client will use this section to find the authentication path between
       its realm and the realm of the server. The server will use this section
       to  verify  the authentication path used be the client, by checking the
       transited field of the received ticket.

       There is a tag name for each participating  realm,  and  each  tag  has
       subtags  for  each  of  the  realms.  The  value  of  the subtags is an
       intermediate  realm  which   may   participate   in   the   cross-realm
       authentication.  The  subtags may be repeated if there is more then one
       intermediate realm. A value of "." means that the two realms share keys
       directly,  and no intermediate realms should be allowed to participate.

       There are n**2 possible entries in this table, but only  those  entries
       which  will  be  needed on the client or the server need to be present.
       The client needs a tag for its local realm, with subtags  for  all  the
       realms  of servers it will need to authenticate with.  A server needs a
       tag for each realm of the clients it will serve.

       For example, ANL.GOV, PNL.GOV, and NERSC.GOV all wish to use the ES.NET
       realm  as  an  intermediate  realm. ANL has a sub realm of TEST.ANL.GOV
       which will authenticate with NERSC.GOV but not PNL.GOV.   The  [capath]
       section for ANL.GOV systems would look like this:

                 [capaths]
                      ANL.GOV = {
                           TEST.ANL.GOV = .
                           PNL.GOV = ES.NET
                           NERSC.GOV = ES.NET
                           ES.NET = .
                      }
                      TEST.ANL.GOV = {
                           ANL.GOV = .
                      }
                      PNL.GOV = {
                           ANL.GOV = ES.NET
                      }
                      NERSC.GOV = {
                           ANL.GOV = ES.NET
                      }
                      ES.NET = {
                           ANL.GOV = .
                      }

       The  [capath]  section  of  the  configuration  file  used on NERSC.GOV
       systems would look like this:

                 [capaths]
                      NERSC.GOV = {
                           ANL.GOV = ES.NET
                           TEST.ANL.GOV = ES.NET
                           TEST.ANL.GOV = ANL.GOV
                           PNL.GOV = ES.NET
                           ES.NET = .
                      }
                      ANL.GOV = {
                           NERSC.GOV = ES.NET
                      }
                      PNL.GOV = {
                           NERSC.GOV = ES.NET
                      }
                      ES.NET = {
                           NERSC.GOV = .
                      }
                      TEST.ANL.GOV = {
                           NERSC.GOV = ANL.GOV
                           NERSC.GOV = ES.NET
                      }

       In the above examples, the ordering is not important, except  when  the
       same  subtag  name  is used more then once. The client will use this to
       determing the path. (It is not  important  to  the  server,  since  the
       transited field is not sorted.)

       If  this section is not present, or if the client or server cannot find
       a client/server path, then normal hierarchical orginization is assumed.

       This  feature  is  not currently supported by DCE. DCE security servers
       can be used with Kerberized clients and servers, but versions prior  to
       DCE  1.1  did  not fill in the transited field, and should be used with
       caution.

DATABASE DEFAULT SECTION

       The [dbdefaults] section indicates  default  values  for  the  database
       specific  parameters.   It  can  also specify the configuration section
       under dbmodules for database specific parameters used by  the  loadable
       database library.

       The following tags are used in this section:

       database_module
              This  relation  indicates  the name of the configuration section
              under dbmodules for database specific  parameters  used  by  the
              loadable database library.

       ldap_kerberos_container_dn
              This  LDAP specific tag indicates the DN of the container object
              where the realm objects will be located. This value is  used  if
              no  object  DN  is  mentioned in the configuration section under
              dbmodules.

       ldap_kdc_dn
              This LDAP specific tag indicates the default bind DN for the KDC
              server.   The  KDC  server does a login to the directory as this
              object. This value is used if no object DN is mentioned  in  the
              configuration section under dbmodules.

       ldap_kadmind_dn
              This  LDAP  specific  tag  indicates the default bind DN for the
              Administration server. The Administration server does a login to
              the directory as this object. This value is used if no object DN
              is mentioned in the configuration section under dbmodules.

       ldap_service_password_file
              This LDAP specific tag indicates the file containing the stashed
              passwords  for  the  objects  used  for  starting  the  Kerberos
              servers. This value is used  if  no  service  password  file  is
              mentioned in the configuration section under dbmodules.

       ldap_servers
              This  LDAP  specific tag indicates the list of LDAP servers. The
              list of LDAP servers is whitespace-separated. The LDAP server is
              specified  by a LDAP URI.  This value is used if no LDAP servers
              are mentioned in the configuration section under dbmodules.

       ldap_conns_per_server
              This LDAP specific tag indicates the number of connections to be
              maintained  per LDAP server. This value is used if the number of
              connections  per  LDAP  server  are   not   mentioned   in   the
              configuration section under dbmodules. The default value is 5.

DATABASE MODULE SECTION

       Each  tag  in the [dbmodules] section of the file names a configuration
       section for database specific parameters that can be referred to  by  a
       realm.   The  value  of  the tag is a subsection where the relations in
       that subsection define the database specific parameters.

       For  each  section,  the  following  tags  may  be  specified  in   the
       subsection:

       db_library
              This  tag  indicates  the name of the loadable database library.
              The value should be db2 for db2  database  and  kldap  for  LDAP
              database.

       ldap_kerberos_container_dn
              This  LDAP specific tag indicates the DN of the container object
              where the realm objects will be located.

       ldap_kdc_dn
              This LDAP specific tag indicates the bind DN for the KDC server.
              The KDC does a login to the directory as this object.

       ldap_kadmind_dn
              This   LDAP   specific   tag  indicates  the  bind  DN  for  the
              Administration server.  The Administration server does  a  login
              to the directory as this object.

       ldap_service_password_file
              This LDAP specific tag indicates the file containing the stashed
              passwords  for  the  objects  used  for  starting  the  Kerberos
              servers.

       ldap_servers
              This  LDAP  specific tag indicates the list of LDAP servers. The
              list of LDAP servers is whitespace-separated. The LDAP server is
              specified by a LDAP URI.

       ldap_conns_per_server
              This LDAP specific tag indicates the number of connections to be
              maintained per LDAP server.

FILES

       /etc/krb5.conf

SEE ALSO

       syslog(3)

                                                                  KRB5.CONF(5)