KRB5.CONF(5)

NAME
krb5.conf - configuration file for Kerberos 5

SYNOPSIS
#include <krb5.h>

DESCRIPTION
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:

    file:
    	/* empty */
    	sections
    sections:
    	section sections
    	section
    section:
    	'[' section_name ']' bindings
    section_name:
    	STRING
    bindings:
    	binding bindings
    	binding
    binding:
    	name '=' STRING
    	name '=' '{' bindings '}'
    name:
    	STRING

STRINGs consists of one or more non-whitespace characters.

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

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

time
    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.

etypes
    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 .

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

Currently recognised sections and bindings are:

[appdefaults]
    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).

[libdefaults]

    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.

    v4_name_convert

    v4_instance_resolve
        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 enctypes.)

    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 credential.

    default_keytab_name = keytab
        The keytab to use if no other is specified, default is “FILE:/etc/krb5.keytab”.

    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.

    max_msg_size = number
        The threshold where Kerberos protocol packets are consider too large and are dropped.

    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 strftime(3).

    date_format = string
        How to print date strings in logs, this string is passed to strftime(3).

    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.

    check-rd-req-server
        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.

[domain_realm]
    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 “.example.com” matches “foo.example.com”, but not “foo.test.example.com”.

    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' option).

[realms]

    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.

        v4_instance_convert

        v4_name_convert

        default_domain
            See krb5_425_conv_principal(3).

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

    }

[capaths]

    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.

    }

[logging]

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

[kdc]

    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 stanza.

        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.

    enable-kaserver = BOOL
        If this kdc should emulate the AFS kaserver.

    as-use-strongest-session-key = BOOL
        If this is TRUE then the KDC will prefer the strongest key from the client's AS-REQ enctype list, that is also supported by the KDC and the target principal, for the ticket session key. 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.

    preauth-use-strongest-session-key = BOOL
        Like as-use-strongest-session-key, but applies to the session key enctype selection for PA-ETYPE-INFO2 (i.e., for password-based pre-authentication). Defaults to TRUE.

    tgs-use-strongest-session-key = BOOL
        Like as-use-strongest-session-key, but applies to the session key enctype of tickets issued by the TGS. 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 did.

    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.

[kadmin]

    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:

        [(des|des3|etype):](pw-salt|afs3-salt)[:string]

        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.

[password_quality]
    Check the Password quality assurance in the info documentation for more information.

    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.

ENVIRONMENT
KRB5CCNAME the Kerberos credential cache to use. KRB5CCPRINCIPAL the Kerberos credential cache use, specified by principal, if the strings starts with an @, only the realm is used for matching. Example @REALM will only match the (exact match) of cache that have the realm REALM. The first cache found is picked. KRB5_CONFIG points to the configuration file to read.

FILES

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

EXAMPLES

    [libdefaults]
    	default_realm = FOO.SE
    [domain_realm]
    	.foo.se = FOO.SE
    	.bar.se = FOO.SE
    [realms]
    	FOO.SE = {
    		kdc = kerberos.foo.se
    		v4_name_convert = {
    			rcmd = host
    		}
    		v4_instance_convert = {
    			xyz = xyz.bar.se
    		}
    		default_domain = foo.se
    	}
    [logging]
    	kdc = FILE:/var/heimdal/kdc.log
    	kdc = SYSLOG:INFO
    	default = SYSLOG:INFO:USER

DIAGNOSTICS
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.

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