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:
- application
realm option
- application
option
- realm
option
- 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
- 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.
-
-
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.
-
-
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)