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     krb5.conf — configuration file for Kerberos 5


     #include <krb5.h>


     The krb5.conf file specifies several configuration parameters for the Kerberos 5 library, as
     well as for some programs.

     The file consists of one or more sections, containing a number of bindings.  The value of
     each binding can be either a string or a list of other bindings.  The grammar looks like:

                   /* empty */

                   section sections

                   '[' section_name ']' bindings


                   binding bindings

                   name '=' STRING
                   name '=' '{' bindings '}'


     STRINGs consists of one or more non-whitespace characters.

     STRINGs that are specified later in this man-page uses the following notation.

                values can be either yes/true or no/false.

                values can be a list of year, month, day, hour, min, second.  Example: 1 month 2
                days 30 min.  If no unit is given, seconds is assumed.

                valid encryption types are: des-cbc-crc, des-cbc-md4, des-cbc-md5, des3-cbc-sha1,
                arcfour-hmac-md5, aes128-cts-hmac-sha1-96, and aes256-cts-hmac-sha1-96 .

                an address can be either a IPv4 or a IPv6 address.

     Currently recognised sections and bindings are:

                Specifies the default values to be used for Kerberos applications.  You can
                specify defaults per application, realm, or a combination of these.  The
                preference order is:
                1.   application realm option
                2.   application option
                3.   realm option
                4.   option

                The supported options are:

                      forwardable = boolean
                           When obtaining initial credentials, make the credentials forwardable.

                      proxiable = boolean
                           When obtaining initial credentials, make the credentials proxiable.

                      no-addresses = boolean
                           When obtaining initial credentials, request them for an empty set of
                           addresses, making the tickets valid from any address.

                      ticket_lifetime = time
                           Default ticket lifetime.

                      renew_lifetime = time
                           Default renewable ticket lifetime.

                      encrypt = boolean
                           Use encryption, when available.

                      forward = boolean
                           Forward credentials to remote host (for rsh(1), telnet(1), etc).


                      default_realm = REALM
                           Default realm to use, this is also known as your “local realm”.  The
                           default is the result of krb5_get_host_realm(local hostname).

                      allow_weak_crypto = boolean
                           is weaks crypto algorithms allowed to be used, among others, DES is
                           considered weak.

                      clockskew = time
                           Maximum time differential (in seconds) allowed when comparing times.
                           Default is 300 seconds (five minutes).

                      kdc_timeout = time
                           Maximum time to wait for a reply from the kdc, default is 3 seconds.


                           These are described in the krb5_425_conv_principal(3) manual page.

                      capath = {

                                 destination-realm = next-hop-realm


                           This is deprecated, see the capaths section below.

                      default_cc_type = cctype
                           sets the default credentials type.

                      default_cc_name = ccname
                           the default credentials cache name.  If you want to change the type
                           only use default_cc_type.  The string can contain variables that are
                           expanded on runtime.  Only support variable now is %{uid} that expands
                           to the current user id.

                      default_etypes = etypes ...
                           A list of default encryption types to use. (Default: all enctypes if
                           allow_weak_crypto = TRUE, else all enctypes except single DES

                      default_as_etypes = etypes ...
                           A list of default encryption types to use in AS requests.  (Default:
                           the value of default_etypes.)

                      default_tgs_etypes = etypes ...
                           A list of default encryption types to use in TGS requests.  (Default:
                           the value of default_etypes.)

                      default_etypes_des = etypes ...
                           A list of default encryption types to use when requesting a DES

                      default_keytab_name = keytab
                           The keytab to use if no other is specified, default is

                      dns_lookup_kdc = boolean
                           Use DNS SRV records to lookup KDC services location.

                      dns_lookup_realm = boolean
                           Use DNS TXT records to lookup domain to realm mappings.

                      kdc_timesync = boolean
                           Try to keep track of the time differential between the local machine
                           and the KDC, and then compensate for that when issuing requests.

                      max_retries = number
                           The max number of times to try to contact each KDC.

                      large_msg_size = number
                           The threshold where protocols with tiny maximum message sizes are not
                           considered usable to send messages to the KDC.

                      ticket_lifetime = time
                           Default ticket lifetime.

                      renew_lifetime = time
                           Default renewable ticket lifetime.

                      forwardable = boolean
                           When obtaining initial credentials, make the credentials forwardable.
                           This option is also valid in the [realms] section.

                      proxiable = boolean
                           When obtaining initial credentials, make the credentials proxiable.
                           This option is also valid in the [realms] section.

                      verify_ap_req_nofail = boolean
                           If enabled, failure to verify credentials against a local key is a
                           fatal error.  The application has to be able to read the corresponding
                           service key for this to work.  Some applications, like su(1), enable
                           this option unconditionally.

                      warn_pwexpire = time
                           How soon to warn for expiring password.  Default is seven days.

                      http_proxy = proxy-spec
                           A HTTP-proxy to use when talking to the KDC via HTTP.

                      dns_proxy = proxy-spec
                           Enable using DNS via HTTP.

                      extra_addresses = address ...
                           A list of addresses to get tickets for along with all local addresses.

                      time_format = string
                           How to print time strings in logs, this string is passed to

                      date_format = string
                           How to print date strings in logs, this string is passed to

                      log_utc = boolean
                           Write log-entries using UTC instead of your local time zone.

                      scan_interfaces = boolean
                           Scan all network interfaces for addresses, as opposed to simply using
                           the address associated with the system's host name.

                      fcache_version = int
                           Use file credential cache format version specified.

                      krb4_get_tickets = boolean
                           Also get Kerberos 4 tickets in kinit, login, and other programs.  This
                           option is also valid in the [realms] section.

                      fcc-mit-ticketflags = boolean
                           Use MIT compatible format for file credential cache.  It's the field
                           ticketflags that is stored in reverse bit order for older than Heimdal
                           0.7.  Setting this flag to TRUE make it store the MIT way, this is
                           default for Heimdal 0.7.

                           If set to "ignore", the framework will ignore any the server input to
                           krb5_rd_req(3,) this is very useful when the GSS-API server input the
                           wrong server name into the gss_accept_sec_context call.

                      k5login_directory = directory
                           Alternative location for user .k5login files. Tokens in the form of
                           %{luser} are expanded to the name of the user whose .k5login file is
                           needed. This option is provided for compatibility with MIT krb5
                           configuration files.

                      k5login_authoritative = boolean
                           If true then if a principal is not found in k5login files then
                           krb5_userok(3) will not fallback on principal to username mapping.
                           This option is provided for compatibility with MIT krb5 configuration

                      kuserok = rule ...
                           Specifies krb5_userok(3) behavior.  If multiple values are given, then
                           krb5_userok(3) will evaluate them in order until one succeeds or all
                           fail.  Rules are implemented by plugins, with three built-in plugins
                           described below. Default: USER-K5LOGIN SIMPLE DENY.

                      kuserok = DENY
                           If set and evaluated then krb5_userok(3) will deny access to the given
                           username no matter what the principal name might be.

                      kuserok = SIMPLE
                           If set and evaluated then krb5_userok(3) will use principal to
                           username mapping (see auth_to_local below).  If the principal maps to
                           the requested username then access is allowed.

                      kuserok = SYSTEM-K5LOGIN[:directory]
                           If set and evaluated then krb5_userok(3) will use k5login files named
                           after the luser argument to krb5_userok(3) in the given directory or
                           in /etc/k5login.d/.  If a directory is given then tokens will be
                           expanded; the %{luser} token will be replaced with the luser argument
                           to krb5_userok(3).  K5login files are text files, with each line
                           containing just a principal name; principals apearing in a user's
                           k5login file are permitted access to the user's account. Note: this
                           rule performs no ownership nor permissions checks on k5login files;
                           proper ownership and permissions/ACLs are expected due to the system
                           k5login location being a system location.

                      kuserok = USER-K5LOGIN
                           If set and evaluated then krb5_userok(3) will use ~luser/.k5login and
                           ~luser/.k5login.d/*.  User k5login files and directories must be owned
                           by the user and must not have world nor group write permissions.

                      aname2lname-text-db = filename
                           The named file must be a sorted (in increasing order) text file where
                           every line consists of an unparsed principal name optionally followed
                           by whitespace and a username.  The aname2lname function will do a
                           binary search on this file, if configured, looking for lines that
                           match the given principal name, and if found the given username will
                           be used, or, if the username is missing, an error will be returned.
                           If the file doesn't exist, or if no matching line is found then other
                           plugins will be allowed to run.

                      name_canon_rules = rules
                           One or more name canonicalization rules.  Each rule consists of one or
                           more tokens separated by colon (':').  The first token must be a rule
                           type, one of: as-is, qualify, use-resolver-searchlist, or nss.  The
                           remaining tokens must be options tokens: secure, ccache_only,
                           use_referrals, no_referrals, mindots= number , domain= domain , and
                           realm= realm. These rules are applied to host-based service principal
                           names in order until one rule succeeds or all fail.  The as-is rules
                           match on number of dots in the hostname or domain suffix of the
                           hostname and attempt the hostname as-is on match.  The qualify rules
                           qualify the hostname with the given domain (and realm, if given) if
                           necessary and attempt the resulting hostname.  The resolver searchlist
                           rule expands to qualify rules using the corresponding domainnames from
                           the DNS resolver's searchlist.  The "nss" rule performs a hostname
                           lookup.  The secure option indicates that an insecure service
                           principal unknown error will result in immediate failure.  Name
                           canonicalization is deferred unless only the default rule is given.
                           Default: nss.

                This is a list of mappings from DNS domain to Kerberos realm.  Each binding in
                this section looks like:

                      domain = realm

                The domain can be either a full name of a host or a trailing component, in the
                latter case the domain-string should start with a period.  The trailing component
                only matches hosts that are in the same domain, ie “” matches
                “”, but not “”.

                The realm may be the token `dns_locate', in which case the actual realm will be
                determined using DNS (independently of the setting of the `dns_lookup_realm'


                      REALM = {

                                 kdc = [service/]host[:port]
                                      Specifies a list of kdcs for this realm.  If the optional
                                      port is absent, the default value for the “kerberos/udp”
                                      “kerberos/tcp”, and “http/tcp” port (depending on service)
                                      will be used.  The kdcs will be used in the order that they
                                      are specified.

                                      The optional service specifies over what medium the kdc
                                      should be contacted.  Possible services are “udp”, “tcp”,
                                      and “http”.  Http can also be written as “http://”.
                                      Default service is “udp” and “tcp”.

                                 admin_server = host[:port]
                                      Specifies the admin server for this realm, where all the
                                      modifications to the database are performed.

                                 kpasswd_server = host[:port]
                                      Points to the server where all the password changes are
                                      performed.  If there is no such entry, the kpasswd port on
                                      the admin_server host will be tried.

                                 krb524_server = host[:port]
                                      Points to the server that does 524 conversions.  If it is
                                      not mentioned, the krb524 port on the kdcs will be tried.



                                      See krb5_425_conv_principal(3).

                                      a boolan variable that defaults to false.  Old DCE secd
                                      (pre 1.1) might need this to be true.

                                 auth_to_local_names = {

                                            principal_name = username
                                                 The given principal_name will be mapped to the
                                                 given username if the REALM is a default realm.


                                 auth_to_local = HEIMDAL_DEFAULT
                                      Use the Heimdal default principal to username mapping.
                                      Applies to principals from the REALM if and only if REALM
                                      is a default realm.

                                 auth_to_local = DEFAULT
                                      Use the MIT default principal to username mapping.  Applies
                                      to principals from the REALM if and only if REALM is a
                                      default realm.

                                 auth_to_local = DB:/path/to/db.txt
                                      Use a binary search of the given DB.  The DB must be a
                                      flat-text file sortedf in the "C" locale, with each record
                                      being a line (separated by either LF or CRLF) consisting of
                                      a principal name followed by whitespace followed by a
                                      username.  Applies to principals from the REALM if and only
                                      if REALM is a default realm.

                                 auth_to_local = DB:/path/to/db
                                      Use the given DB, if there's a plugin for it.  Applies to
                                      principals from the REALM if and only if REALM is a default

                                 auth_to_local = RULE:...
                                      Use the given rule, if there's a plugin for it.  Applies to
                                      principals from the REALM if and only if REALM is a default

                                 auth_to_local = NONE
                                      No additional principal to username mapping is done. Note
                                      that auth_to_local_names and any preceding auth_to_local
                                      rules have precedence.



                      client-realm = {

                                 server-realm = hop-realm ...
                                      This serves two purposes. First the first listed hop-realm
                                      tells a client which realm it should contact in order to
                                      ultimately obtain credentials for a service in the
                                      server-realm.  Secondly, it tells the KDC (and other
                                      servers) which realms are allowed in a multi-hop traversal
                                      from client-realm to server-realm.  Except for the client
                                      case, the order of the realms are not important.



                      entity = destination
                           Specifies that entity should use the specified destination for
                           logging.  See the krb5_openlog(3) manual page for a list of defined


                      database = {

                                 dbname = DATABASENAME
                                      Use this database for this realm.  See the info
                                      documetation how to configure different database backends.

                                 realm = REALM
                                      Specifies the realm that will be stored in this database.
                                      It realm isn't set, it will used as the default database,
                                      there can only be one entry that doesn't have a realm

                                 mkey_file = FILENAME
                                      Use this keytab file for the master key of this database.
                                      If not specified DATABASENAME.mkey will be used.

                                 acl_file = PA FILENAME
                                      Use this file for the ACL list of this database.

                                 log_file = FILENAME
                                      Use this file as the log of changes performed to the
                                      database.  This file is used by ipropd-master for
                                      propagating changes to slaves.


                      max-request = SIZE
                           Maximum size of a kdc request.

                      require-preauth = BOOL
                           If set pre-authentication is required.  Since krb4 requests are not
                           pre-authenticated they will be rejected.

                      ports = list of ports
                           List of ports the kdc should listen to.

                      addresses = list of interfaces
                           List of addresses the kdc should bind to.

                      enable-kerberos4 = BOOL
                           Turn on Kerberos 4 support.

                      v4-realm = REALM
                           To what realm v4 requests should be mapped.

                      enable-524 = BOOL
                           Should the Kerberos 524 converting facility be turned on.  Default is
                           the same as enable-kerberos4.

                      enable-http = BOOL
                           Should the kdc answer kdc-requests over http.

                      tgt-use-strongest-session-key = BOOL
                           If this is TRUE then the KDC will prefer the strongest key from the
                           client's AS-REQ or TGS-REQ enctype list for the ticket session key
                           that is supported by the KDC and the target principal when the target
                           principal is a krbtgt principal.  Else it will prefer the first key
                           from the client's AS-REQ enctype list that is also supported by the
                           KDC and the target principal. Defaults to TRUE.

                      svc-use-strongest-session-key = BOOL
                           Like tgt-use-strongest-session-key, but applies to the session key
                           enctype of tickets for services other than krbtgt principals. Defaults
                           to TRUE.

                      preauth-use-strongest-session-key = BOOL
                           If TRUE then select the strongest possible enctype from the client's
                           AS-REQ for PA-ETYPE-INFO2 (i.e., for password-based pre-
                           authentication).  Else pick the first supported enctype from the
                           client's AS-REQ. Defaults to TRUE.

                      use-strongest-server-key = BOOL
                           If TRUE then the KDC picks, for the ticket encrypted part's key, the
                           first supported enctype from the target service principal's hdb
                           entry's current keyset. Else the KDC picks the first supported enctype
                           from the target service principal's hdb entry's current keyset.
                           Defaults to TRUE.

                      check-ticket-addresses = BOOL
                           Verify the addresses in the tickets used in tgs requests.

                      allow-null-ticket-addresses = BOOL
                           Allow address-less tickets.

                      allow-anonymous = BOOL
                           If the kdc is allowed to hand out anonymous tickets.

                      encode_as_rep_as_tgs_rep = BOOL
                           Encode as-rep as tgs-rep tobe compatible with mistakes older DCE secd

                      kdc_warn_pwexpire = TIME
                           The time before expiration that the user should be warned that her
                           password is about to expire.

                      logging = Logging
                           What type of logging the kdc should use, see also [logging]/kdc.

                      use_2b = {

                                 principal = BOOL
                                      boolean value if the 524 daemon should return AFS 2b tokens
                                      for principal.



                      hdb-ldap-structural-object structural object
                           If the LDAP backend is used for storing principals, this is the
                           structural object that will be used when creating and when reading
                           objects.  The default value is account .

                      hdb-ldap-create-base creation dn
                           is the dn that will be appended to the principal when creating
                           entries.  Default value is the search dn.

                      enable-digest = BOOL
                           Should the kdc answer digest requests. The default is FALSE.

                      digests_allowed = list of digests
                           Specifies the digests the kdc will reply to. The default is ntlm-v2.


                      require-preauth = BOOL
                           If pre-authentication is required to talk to the kadmin server.

                      password_lifetime = time
                           If a principal already have its password set for expiration, this is
                           the time it will be valid for after a change.

                      default_keys = keytypes...
                           For each entry in default_keys try to parse it as a sequence of
                           etype:salttype:salt syntax of this if something like:


                           If etype is omitted it means everything, and if string is omitted it
                           means the default salt string (for that principal and encryption
                           type).  Additional special values of keytypes are:

                                 v5   The Kerberos 5 salt pw-salt

                                 v4   The Kerberos 4 salt des:pw-salt:

                      use_v4_salt = BOOL
                           When true, this is the same as

                           default_keys = des3:pw-salt v4

                           and is only left for backwards compatibility.

                Check the Password quality assurance in the info documentation for more

                      check_library = library-name
                           Library name that contains the password check_function

                      check_function = function-name
                           Function name for checking passwords in check_library

                      policy_libraries = library1 ... libraryN
                           List of libraries that can do password policy checks

                      policies = policy1 ... policyN
                           List of policy names to apply to the password. Builtin policies are
                           among other minimum-length, character-class, external-check.


     KRB5_CONFIG points to the configuration file to read.


     /etc/krb5.conf  configuration file for Kerberos 5.


                   default_realm = FOO.SE
                   name_canon_rules = as-is:realm=FOO.SE
                   name_canon_rules =
                   name_canon_rules =
                   name_canon_rules = nss
          = FOO.SE
          = FOO.SE
                   FOO.SE = {
                           kdc =
                           v4_name_convert = {
                                   rcmd = host
                           v4_instance_convert = {
                                   xyz =
                           default_domain =
                   kdc = FILE:/var/heimdal/kdc.log
                   kdc = SYSLOG:INFO
                   default = SYSLOG:INFO:USER


     Since krb5.conf is read and parsed by the krb5 library, there is not a lot of opportunities
     for programs to report parsing errors in any useful format.  To help overcome this problem,
     there is a program verify_krb5_conf that reads krb5.conf and tries to emit useful
     diagnostics from parsing errors.  Note that this program does not have any way of knowing
     what options are actually used and thus cannot warn about unknown or misspelled ones.


     kinit(1), krb5_425_conv_principal(3), krb5_openlog(3), strftime(3), verify_krb5_conf(8)