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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
includes
sections:
section sections
section
section:
'[' section_name ']' bindings
section_name:
STRING
bindings:
binding bindings
binding
binding:
name '=' STRING
name '=' '{' bindings '}'
name:
STRING
includes:
'include' path
'includedir' path
path: STRING
STRINGs consists of one or more non-whitespace characters.
Files and directories may be included by absolute path. Including a directory causes all
files in the directory to be included as if each file had been included separately, but only
files whose names consist of alphanumeric, hyphen, and underscore are included, though they
may also end in '.conf'.
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)