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KRB5.CONF(5) File Formats Manual KRB5.CONF(5)
NAME
krb5.conf - configuration file for Kerberos 5
SYNOPSIS
#include <krb5/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).
historical_anon_pkinit = boolean
Enable legacy anonymous pkinit command-line syntax.
With this option set to true, the kinit(1)
--anonymous command with no principal argument
specified will request an anonymous pkinit ticket
from the default realm. If a principal argument is
specified, it is used as an explicit realm name for
anonymous pkinit even without an @ prefix.
[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
are weak 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.
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. The Only supported variable currently is
%{uid} which 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.
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.
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 makes 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
of 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. 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 files.
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/. 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 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.
fcache_strict_checking
strict checking in FILE credential caches that
owner, no symlink and permissions is correct.
name_canon_rules = rules
One or more service principal name canonicalization
rules. Each rule consists of one or more tokens
separated by colon (':'). Currently these rules
are used only for hostname canonicalization
(usually when getting a service ticket, from a
ccache or a TGS, but also when acquiring GSS
initiator credentials from a keytab). These rules
can be used to implement DNS resolver-like search
lists without having to use DNS.
NOTE: Name canonicalization rules are an
experimental feature.
The first token is a rule type, one of: as-is,
qualify, or nss.
Any remaining tokens must be options tokens:
use_fast (use FAST to protect TGS exchanges;
currently not supported), use_dnssec (use DNSSEC to
protect hostname lookups; currently not supported),
ccache_only , use_referrals, no_referrals,
lookup_realm, mindots=N, maxdots=N, order=N,
domain= domain, realm= realm, match_domain= domain,
and match_realm= realm.
When trying to obtain a service ticket for a host-
based service principal name, name canonicalization
rules are applied to that name in the order given,
one by one, until one succeds (a service ticket is
obtained), or all fail. Similarly when acquiring
GSS initiator credentials from a keytab, and when
comparing a non-canonical GSS name to a canonical
one.
For each rule the system checks that the hostname
has at least mindots periods (if given) in it, at
most maxdots periods (if given), that the hostname
ends in the given match_domain (if given), and that
the realm of the principal matches the match_realm
(if given).
As-is rules leave the hostname unmodified but may
set a realm. Qualify rules qualify the hostname
with the given domain and also may set the realm.
The nss rule uses the system resolver to lookup the
host's canonical name and is usually not secure.
Note that using the nss rule type implies having to
have principal aliases in the HDB (though not
necessarily in keytabs).
The empty realm denotes "ask the client's realm's
TGS". The empty realm may be set as well as
matched.
The order in which rules are applied is as follows:
first all the rules with explicit order then all
other rules in the order in which they appear. If
any two rules have the same explicit order, their
order of appearance in krb5.conf breaks the tie.
Explicitly specifying order can be useful where
tools read and write the configuration file without
preserving parameter order.
Malformed rules are ignored.
allow_hierarchical_capaths = boolean
When validating cross-realm transit paths, absent
any explicit capath from the client realm to the
server realm, allow a hierarchical transit path via
the common ancestor domain of the two realms.
Defaults to true. Note, absent an explicit
setting, hierarchical capaths are always used by
the KDC when generating a referral to a destination
with which is no direct trust.
[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.
tgs_require_subkey
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
realm.
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
realm.
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.
}
[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 = [DATBASETYPE:]DATABASENAME
Use this database for this realm. The
DATABASETYPE should be one of 'lmdb',
'db3', 'db1', 'db', 'sqlite', or 'ldap'.
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. It is also used by
kadmind and kadmin (when used with the
-l option), and by all applications
using libkadm5 with the local backend,
for two-phase commit functionality.
Slaves also use this. Setting this to
/dev/null disables two-phase commit and
incremental propagation. Use iprop-log
to show the contents of this log file.
log-max-size = number
When the log reaches this size (in
bytes), the log will be truncated,
saving some entries, and keeping the
latest version number so as to not
disrupt incremental propagation. If set
to a negative value then automatic log
truncation will be disabled. Defaults
to 52428800 (50MB).
}
max-request = SIZE
Maximum size of a kdc request.
require-preauth = BOOL
If set pre-authentication is required.
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-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 FALSE.
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 FALSE.
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 FALSE.
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.
historical_anon_realm = boolean
Enables pre-7.0 non-RFC-comformant KDC behavior.
With this option set to true the client realm in
anonymous pkinit AS replies will be the requested
realm, rather than the RFC-conformant
WELLKNOWN:ANONYMOUS realm. This can have a
security impact on servers that expect to grant
access to anonymous-but-authenticated to the KDC
users of the realm in question: they would also
grant access to unauthenticated anonymous users.
As such, it is not recommend to set this option to
true.
encode_as_rep_as_tgs_rep = BOOL
Encode as-rep as tgs-rep to be 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.
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.
kx509_ca = file
Specifies the PEM credentials for the kx509
certification authority.
require_initial_kca_tickets = boolean
Specified whether to require that tickets for the
kca_service service principal be INITIAL. This may
be set on a per-realm basis as well as globally.
Defaults to true for the global setting.
kx509_include_pkinit_san = boolean
If true then the kx509 client principal's name and
realm will be included in an id-pkinit-san
certificate extension. This can be set on a per-
realm basis as well as globally. Defaults to true
for the global setting.
kx509_template = file
Specifies the PEM file with a template for the
certificates to be issued. The following variables
can be interpolated in the subject name using
${variable} syntax:
principal-name
The full name of the kx509 client
principal.
principal-name-without-realm
The full name of the kx509 client
principal, excluding the realm name.
principal-name-realm
The name of the client principal's
realm.
The kx509, kx509_template, kx509_include_pkinit_san, and
require_initial_kca_tickets parameters may be set on a per-
realm basis as well.
[kadmin]
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
default_key_rules = {
globing-rule = keytypes...
a globbing rule to matching a principal,
and when true, use the keytypes as
specified the same format as
[kadmin]default_keys .
}
prune-key-history = BOOL
When adding keys to the key history, drop keys that
are too old to match unexpired tickets (based on
the principal's maximum ticket lifetime). If the
KDC keystore is later compromised traffic protected
with the discarded older keys may remain protected.
This also keeps the HDB records for principals with
key history from growing without bound. The
default (backwards compatible) value is "false".
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
KRB5_CONFIG points to the configuration file to read.
FILES
/etc/krb5.conf configuration file for Kerberos 5.
EXAMPLES
[libdefaults]
default_realm = FOO.SE
name_canon_rules = as-is:realm=FOO.SE
name_canon_rules = qualify:domain=foo.se:realm=FOO.SE
name_canon_rules = qualify:domain=bar.se:realm=FOO.SE
name_canon_rules = nss
[domain_realm]
.foo.se = FOO.SE
.bar.se = FOO.SE
[realms]
FOO.SE = {
kdc = kerberos.foo.se
default_domain = foo.se
}
[logging]
kdc = FILE:/var/heimdal/kdc.log
kdc = SYSLOG:INFO
default = SYSLOG:INFO:USER
[kadmin]
default_key_rules = {
*/ppp@* = arcfour-hmac-md5:pw-salt
}
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_openlog(3), strftime(3), verify_krb5_conf(8)
NetBSD 10.99 May 4, 2005 NetBSD 10.99