KRB5.CONF(4)KRB5.CONF(4)NAMEkrb5.conf - Kerberos configuration file
SYNOPSIS
/etc/krb5/krb5.conf
DESCRIPTION
The krb5.conf file contains Kerberos configuration information, includ‐
ing the locations of KDCs and administration daemons for the Kerberos
realms of interest, defaults for the current realm and for Kerberos
applications, and mappings of host names onto Kerberos realms. This
file must reside on all Kerberos clients.
The format of the krb5.conf consists of sections headings in square
brackets. Each section can contain zero or more configuration variables
(called relations), of the form:
relation= relation-value
or
relation-subsection = {
relation= relation-value
relation= relation-value
}
The krb5.conf file can contain any or all of the following sections:
libdefaults
Contains default values used by the Kerberos V5 library.
appdefaults
Contains subsections for Kerberos V5 applications, where relation-
subsection is the name of an application. Each subsection describes
application-specific defaults.
realms
Contains subsections for Kerberos realms, where relation-subsection
is the name of a realm. Each subsection contains relations that
define the properties for that particular realm.
domain_realm
Contains relations which map domain names and subdomains onto Ker‐
beros realm names. This is used by programs to determine what realm
a host should be in, given its fully qualified domain name.
logging
Contains relations which determine how Kerberos programs are to
perform logging.
capaths
Contains the authentication paths used with direct (nonhierarchi‐
cal) cross-realm authentication. Entries in this section are used
by the client to determine the intermediate realms which can be
used in cross-realm authentication. It is also used by the end-ser‐
vice when checking the transited field for trusted intermediate
realms.
dbmodules
Contains relations for Kerberos database plug-in-specific configu‐
ration information.
kdc
For a Key Distribution Center (KDC), can contain the location of
the kdc.conf file.
The [libdefaults] Section
The [libdefaults] section can contain any of the following relations:
database_module
Selects the dbmodule section entry to use to access the Kerberos
database. If this parameter is not present the code uses the stan‐
dard db2-based Kerberos database.
default_keytab_name
Specifies the default keytab name to be used by application servers
such as telnetd and rlogind. The default is /etc/krb5/krb5.keytab.
default_realm
Identifies the default Kerberos realm for the client. Set its value
to your Kerberos realm.
default_tgs_enctypes
Identifies the supported list of session key encryption types that
should be returned by the KDC. The list can be delimited with com‐
mas or whitespace. The supported encryption types are des3-cbc-
sha1-kd, des-cbc-crc, des-cbc-md5, arcfour-hmac-md5, arcfour-hmac-
md5-exp, aes128-cts-hmac-sha1-96, and aes256-cts-hmac-sha1-96.
default_tkt_enctypes
Identifies the supported list of session key encryption types that
should be requested by the client. The format is the same as for
default_tgs_enctypes. The supported encryption types are des3-cbc-
sha1-kd, des-cbc-crc, des-cbc-md5, arcfour-hmac-md5, arcfour-hmac-
md5-exp, aes128-cts-hmac-sha1-96, and aes256-cts-hmac-sha1-96.
clockskew
Sets the maximum allowable amount of clock skew in seconds that the
library tolerates before assuming that a Kerberos message is
invalid. The default value is 300 seconds, or five minutes.
forwardable = [true | false]
Sets the "forwardable" flag in all tickets. This allows users to
transfer their credentials from one host to another without reau‐
thenticating. This option can also be set in the [appdefaults] or
[realms] section (see below) to limit its use in particular appli‐
cations or just to a specific realm.
permitted_enctypes
This relation controls the encryption types for session keys per‐
mitted by server applications that use Kerberos for authentication.
In addition, it controls the encryption types of keys added to a
keytab by means of the kadmin(1M) ktadd command. The default is:
aes256-cts-hmac-sha1-96, aes128-cts-hmac-sha1-96, des3-hmac-
sha1-kd, arcfour-hmac-md5, arcfour-hmac-md5-exp, des-cbc-md5, des-
cbc-crc.
proxiable = [true | false]
Sets the proxiable flag in all tickets. This allows users to create
a proxy ticket that can be transferred to a kerberized service to
allow that service to perform some function on behalf of the origi‐
nal user. This option can also be set in the [appdefaults] or
[realms] section (see below) to limit its use in particular appli‐
cations or just to a specific realm.
renew_lifetime =lifetime
Requests renewable tickets, with a total lifetime of lifetime. The
value for lifetime must be followed immediately by one of the fol‐
lowing delimiters:
s
seconds
m
minutes
h
hours
d
days
Example:
renew_lifetime = 90m
Do not mix units. A value of "3h30m" results in an error.
max_lifetime =lifetime
Sets the requested maximum lifetime of the ticket. The values for
lifetime follow the format described for the renew_lifetime option,
above.
dns_lookup_kdc
Indicates whether DNS SRV records need to be used to locate the
KDCs and the other servers for a realm, if they have not already
been listed in the [realms] section. This option makes the machine
vulnerable to a certain type of DoS attack if somone spoofs the DNS
records and does a redirect to another server. This is, however, no
worse than a DoS, since the bogus KDC is unable to decode anything
sent (excepting the initial ticket request, which has no encrypted
data). Also, anything the fake KDC sends out isl not trusted with‐
out verification (the local machine is unaware of the secret key to
be used). If dns_lookup_kdc is not specified but dns_fallback is,
then that value is used instead. In either case, values (if
present) in the [realms] section override DNS. dns_lookup_kdc is
enabled by default.
dns_lookup_realm
Indicates whether DNS TXT records need to be used to determine the
Kerberos realm information and/or the host/domain name-to-realm
mapping of a host, if this information is not already present in
the krb5.conf file. Enabling this option might make the host vul‐
nerable to a redirection attack, wherein spoofed DNS replies per‐
suade a client to authenticate to the wrong realm. In a realm with
no cross-realm trusts, this a DoS attack. If dns_lookup_realm is
not specified but dns_fallback is, then that value is used instead.
In either case, values (if present) in the [libdefaults] and
[domain_realm] sections override DNS.
dns_fallback
Generic flag controlling the use of DNS for retrieval of informa‐
tion about Kerberos servers and host/domain name-to-realm mapping.
If both dns_lookup_kdc and dns_lookup_realm have been specified,
this option has no effect.
verify_ap_req_nofail [true | false]
If true, the local keytab file (/etc/krb5/krb5.keytab) must contain
an entry for the local host principal, for example,
host/foo.bar.com@FOO.COM. This entry is needed to verify that the
TGT requested was issued by the same KDC that issued the key for
the host principal. If undefined, the behavior is as if this option
were set to true. Setting this value to false leaves the system
vulnerable to DNS spoofing attacks. This parameter can be in the
[realms] section to set it on a per-realm basis, or it can be in
the [libdefaults] section to make it a network-wide setting for all
realms.
The [appdefaults] Section
This section contains subsections for Kerberos V5 applications, where
relation-subsection is the name of an application. Each subsection con‐
tains relations that define the default behaviors for that application.
The following relations can be found in the [appdefaults] section,
though not all relations are recognized by all kerberized applications.
Some are specific to particular applications.
autologin = [true | false]
Forces the application to attempt automatic login by presenting
Kerberos credentials. This is valid for the following applications:
rlogin, rsh, rcp, rdist, and telnet.
encrypt = [true | false]
Forces applications to use encryption by default (after authentica‐
tion) to protect the privacy of the sessions. This is valid for the
following applications: rlogin, rsh, rcp, rdist, and telnet.
forward = [true | false]
Forces applications to forward the user'ss credentials (after
authentication) to the remote server. This is valid for the follow‐
ing applications: rlogin, rsh, rcp, rdist, and telnet.
forwardable = [true | false]
See the description in the [libdefaults] section above. This is
used by any application that creates a ticket granting ticket and
also by applications that can forward tickets to a remote server.
proxiable = [true | false]
See the description in the [libdefaults] section above. This is
used by any application that creates a ticket granting ticket.
renewable = [true | false]
Creates a TGT that can be renewed (prior to the ticket expiration
time). This is used by any application that creates a ticket grant‐
ing ticket.
no_addresses = [true | false]
Creates tickets with no address bindings. This is to allow tickets
to be used across a NAT boundary or when using multi-homed systems.
This option is valid in the kinit [appdefault] section only.
max_life =lifetime
Sets the maximum lifetime of the ticket, with a total lifetime of
lifetime. The values for lifetime follow the format described in
the [libdefaults] section above. This option is obsolete and is
removed in a future release of the Solaris operating system.
max_renewable_life =lifetime
Requests renewable tickets, with a total lifetime of lifetime. The
values for lifetime follow the format described in the [libde‐
faults] section above. This option is obsolete and is removed in a
future release of the Solaris operating system.
rcmd_protocol = [ rcmdv1 | rcmdv2 ]
Specifies which Kerberized "rcmd" protocol to use when using the
Kerberized rlogin(1), rsh(1), rcp(1), or rdist(1) programs. The
default is to use rcmdv2 by default, as this is the more secure and
more recent update of the protocol. However, when talking to older
MIT or SEAM-based "rcmd" servers, it can be necessary to force the
new clients to use the older rcmdv1 protocol. This option is valid
only for the following applications: rlogin, rcp, rsh, and rdist.
gkadmin = {
help_url = \
http://docs.sun.com/app/docs/doc/816-4557/6maosrjmr?q=gkadmin&a=view
}
The preceding URL is subject to change. On the docs.sun.com web site,
view the chapter on the Solaris Kerberos implementation in the System
Administration Guide: Security Services.
The following application defaults can be set to true or false:
kinit
forwardable = true
proxiable = true
renewable = true
no_addresses = true
max_life = delta_time
max_renewable_life = delta_time
See kinit(1) for the valid time duration formats you can specify for
delta_time.
In the following example, kinit gets forwardable tickets by default and
telnet has three default behaviors specified:
[appdefaults]
kinit = {
forwardable = true
}
telnet = {
forward = true
encrypt = true
autologin = true
}
The application defaults specified here are overridden by those speci‐
fied in the [realms] section.
The [realms] Section
This section contains subsections for Kerberos realms, where relation-
subsection is the name of a realm. Each subsection contains relations
that define the properties for that particular realm. The following
relations can be specified in each [realms] subsection:
admin_server
Identifies the host where the Kerberos administration daemon (kad‐
mind) is running. Typically, this is the master KDC.
application defaults
Application defaults that are specific to a particular realm can be
specified within a [realms] subsection. Realm-specific application
defaults override the global defaults specified in the [appde‐
faults] section.
auth_to_local_realm
For use in the default realm, non-default realms can be equated
with the default realm for authenticated name-to-local name map‐
ping.
auth_to_local_names
This subsection allows you to set explicit mappings from principal
names to local user names. The tag is the mapping name and the
value is the corresponding local user name.
auth_to_local
This tag allows you to set a general rule for mapping principal
names to local user names. It is used if there is not an explicit
mapping for the principal name that is being translated. The possi‐
ble values are:
RULE:[<ncomps>:<format>](<regex>)s/<regex>/<text>/
Each rule has three parts:
First part—Formulate the string on which to perform operations:
If not present then the string defaults to the fully flattened
principal minus the realm name. Otherwise the syntax is as fol‐
lows:
"[" <ncomps> ":" <format> "]"
Where:
<ncomps> is the number of expected components for this rule. If
the particular principal does not have this number of compo‐
nents, then this rule does not apply.
<format> is a string of <component> or verbatim characters to
be inserted.
<component> is of the form "$"<number> to select the <number>th
component. <number> begins from 1.
Second part—select rule validity:
If not present, this rule can apply to all selections. Other‐
wise the syntax is as follows:
"(" <regex> ")"
Where:
<regex> is a selector regular expression. If this regular
expression matches the whole pattern generated from the first
part, then this rule still applies.
Third part—Transform rule:
If not present, then the selection string is passed verbatim
and is matched. Otherwise, the syntax is as follows:
<rule> ...
Where:
<rule> is of the form:
"s/" <regex> "/" <text> "/" ["g"]
Regular expressions are defined in regex(5).
For example:
auth_to_local = RULE:[1:$1@$0](.*@.*ACME.COM)s/@.*//
The preceding maps username@ACME.COM and all sub-realms of
ACME.COM to username.
DEFAULT
The principal name is used as the local name. If the principal
has more than one component or is not in the default realm,
this rule is not applicable and the conversion fails.
database_module
Selects the dbmodule section entry to use to access the Kerberos
database.
extra_addresses...
This allows a computer to use multiple local addresses, to allow
Kerberos to work in a network that uses NATs. The addresses should
be in a comma-separated list.
kdc
The name of a host running a KDC for that realm. An optional port
number (separated from the hostname by a colon) can be included.
kpasswd_server
Identifies the host where the Kerberos password-changing server is
running. Typically, this is the same as host indicated in the
admin_server. If this parameter is omitted, the host in
admin_server is used. You can also specify a port number if the
server indicated by kpasswd_server runs on a port other than 464
(the default). The format of this parameter is: hostname[:port].
kpasswd_protocol
Identifies the protocol to be used when communicating with the
server indicated by kpasswd_server. By default, this parameter is
defined to be RPCSEC_GSS, which is the protocol used by Solaris-
based administration servers. To be able to change a principal's
password stored on non-Solaris Kerberos server, such as Microsoft
Active Directory or MIT Kerberos, this value should be SET_CHANGE.
This indicates that a non-RPC- based protocol is used to communi‐
cate the password change request to the server in the
kpasswd_server entry.
udp_preference_limit
When sending a message to the KDC, the library tries using TCP
before UDP if the size of the message is above udp_prefer‐
ence_limit. If the message is smaller than udp_preference_limit,
then UDP is tried before TCP. Regardless of the size, both proto‐
cols are tried if the first attempt fails.
verify_ap_req_nofail [true | false]
If true, the local keytab file (/etc/krb5/krb5.keytab) must contain
an entry for the local host principal, for example,
host/foo.bar.com@FOO.COM. This entry is needed to verify that the
TGT requested was issued by the same KDC that issued the key for
the host principal. If undefined, the behavior is as if this option
were set to true. Setting this value to false leaves the system
vulnerable to DNS spoofing attacks. This parameter might be in the
[realms] section to set it on a per-realm basis, or it might be in
the [libdefaults] section to make it a network-wide setting for all
realms.
The parameters "forwardable", "proxiable", and "renew_lifetime" as
described in the [libdefaults] section (see above) are also valid in
the [realms] section.
Notice that kpasswd_server and kpasswd_protocol are realm-specific
parameters. Most often, you need to specify them only when using a non-
Solaris-based Kerberos server. Otherwise, the change request is sent
over RPCSEC_GSS to the Solaris Kerberos administration server.
The [domain_realm] Section
This section provides a translation from a domain name or hostname to a
Kerberos realm name. The relation can be a host name, or a domain name,
where domain names are indicated by a period (`.') prefix. relation-
value is the Kerberos realm name for that particular host or domain.
Host names and domain names should be in lower case.
If no translation entry applies, the host's realm is considered to be
the hostname's domain portion converted to upper case. For example, the
following [domain_realm] section maps crash.mit.edu into the
TEST.ATHENA.MIT.EDU realm:
[domain_realm]
.mit.edu = ATHENA.MIT.EDU
mit.edu = ATHENA.MIT.EDU
crash.mit.edu = TEST.ATHENA.MIT.EDU
.fubar.org = FUBAR.ORG
fubar.org = FUBAR.ORG
All other hosts in the mit.edu domain maps by default to the
ATHENA.MIT.EDU realm, and all hosts in the fubar.org domain maps by
default into the FUBAR.ORG realm. The entries for the hosts mit.edu and
fubar.org. Without these entries, these hosts would be mapped into the
Kerberos realms EDU and ORG, respectively.
The [logging] Section
This section indicates how Kerberos programs are to perform logging.
There are two types of relations for this section: relations to specify
how to log and a relation to specify how to rotate kdc log files.
The following relations can be defined to specify how to log. The same
relation can be repeated if you want to assign it multiple logging
methods.
admin_server
Specifies how to log the Kerberos administration daemon (kadmind).
The default is FILE:/var/krb5/kadmin.log.
default
Specifies how to perform logging in the absence of explicit speci‐
fications otherwise.
kdc
Specifies how the KDC is to perform its logging. The default is
FILE:/var/krb5/kdc.log.
The admin_server, default, and kdc relations can have the following
values:
FILE:filename
FILE=filename
This value causes the entity's logging messages to go to the speci‐
fied file. If the `=' form is used, the file is overwritten. If the
`:' form is used, the file is appended to.
STDERR
This value causes the entity's logging messages to go to its stan‐
dard error stream.
CONSOLE
This value causes the entity's logging messages to go to the con‐
sole, if the system supports it.
DEVICE=devicename
This causes the entity's logging messages to go to the specified
device.
SYSLOG[:severity[:facility]]
This causes the entity's logging messages to go to the system log.
The severity argument specifies the default severity of system log mes‐
sages. This can be any of the following severities supported by the
syslog(3C) call, minus the LOG_ prefix: LOG_EMERG, LOG_ALERT, LOG_CRIT,
LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO, and LOG_DEBUG. For example,
a value of CRIT would specify LOG_CRIT severity.
The facility argument specifies the facility under which the messages
are logged. This can be any of the following facilities supported by
the syslog(3C) call minus the LOG_ prefix: LOG_KERN, LOG_USER,
LOG_MAIL, LOG_DAEMON, LOG_AUTH, LOG_LPR, LOG_NEWS, LOG_UUCP, LOG_CRON,
and LOG_LOCAL0 through LOG_LOCAL7.
If no severity is specified, the default is ERR. If no facility is
specified, the default is AUTH.
The following relation can be defined to specify how to rotate kdc log
files if the FILE: value is being used to log:
kdc_rotate
A relation subsection that enables kdc logging to be rotated to
multiple files based on a time interval. This can be used to avoid
logging to one file, which might grow too large and bring the KDC
to a halt.
The time interval for the rotation is specified by the period relation.
The number of log files to be rotated is specified by the versions
relation. Both the period and versions (described below) should be
included in this subsection. And, this subsection applies only if the
kdc relation has a FILE: value.
The following relations can be specified for the kdc_rotate relation
subsection:
period=delta_time
Specifies the time interval before a new log file is created. See
the TimeFormats section in kinit(1) for the valid time duration
formats you can specify for delta_time. If period is not specified
or set to never, no rotation occurs.
Specifying a time interval does not mean that the log files are rotated
at the time interval based on real time. This is because the time
interval is checked at each attempt to write a record to the log, or
when logging is actually occurring. Therefore, rotation occurs only
when logging has actually occurred for the specified time interval.
versions=number
Specifies how many previous versions are saved before the rotation
begins. A number is appended to the log file, starting with 0 and
ending with (number - 1). For example, if versions is set to 2, up
to three logging files are created (filename, filename.0, and file‐
name.1) before the first one is overwritten to begin the rotation.
Notice that if versions is not specified or set to 0, only one log file
is created, but it is overwritten whenever the time interval is met.
In the following example, the logging messages from the Kerberos admin‐
istration daemon goes to the console. The logging messages from the KDC
is appended to the /var/krb5/kdc.log, which is rotated between twenty-
one log files with a specified time interval of a day.
[logging]
admin_server = CONSOLE
kdc = FILE:/export/logging/kadmin.log
kdc_rotate = {
period = 1d
versions = 20
}
The [capaths] Section
In order to perform direct (non-hierarchical) cross-realm authentica‐
tion, a database is needed to construct the authentication paths
between the realms. This section defines that database.
A client uses this section to find the authentication path between its
realm and the realm of the server. The server uses this section to ver‐
ify the authentication path used by the client, by checking the tran‐
sited field of the received ticket.
There is a subsection for each participating realm, and each subsection
has relations named for each of the realms. The relation-value is an
intermediate realm which can participate in the cross-realm authentica‐
tion. The relations can be repeated if there is more than one interme‐
diate realm. A value of '.' means that the two realms share keys
directly, and no intermediate realms should be allowed to participate.
There are n**2 possible entries in this table, but only those entries
which is needed on the client or the server need to be present. The
client needs a subsection named for its local realm, with relations
named for all the realms of servers it needs to authenticate with. A
server needs a subsection named for each realm of the clients it
serves.
For example, ANL.GOV, PNL.GOV, and NERSC.GOV all wish to use the ES.NET
realm as an intermediate realm. ANL has a sub realm of TEST.ANL.GOV,
which authenticates with NERSC.GOV but not PNL.GOV. The [capath] sec‐
tion for ANL.GOV systems would look like this:
[capaths]
ANL.GOV = {
TEST.ANL.GOV = .
PNL.GOV = ES.NET
NERSC.GOV = ES.NET
ES.NET = .
}
TEST.ANL.GOV = {
ANL.GOV = .
}
PNL.GOV = {
ANL.GOV = ES.NET
}
NERSC.GOV = {
ANL.GOV = ES.NET
}
ES.NET = {
ANL.GOV = .
}
The [capath] section of the configuration file used on NERSC.GOV sys‐
tems would look like this:
[capaths]
NERSC.GOV = {
ANL.GOV = ES.NET
TEST.ANL.GOV = ES.NET
TEST.ANL.GOV = ANL.GOV
PNL.GOV = ES.NET
ES.NET = .
}
ANL.GOV = {
NERSC.GOV = ES.NET
}
PNL.GOV = {
NERSC.GOV = ES.NET
}
ES.NET = {
NERSC.GOV = .
}
TEST.ANL.GOV = {
NERSC.GOV = ANL.GOV
NERSC.GOV = ES.NET
}
In the above examples, the ordering is not important, except when the
same relation is used more than once. The client uses this to determine
the path. (It is not important to the server, since the transited
field is not sorted.)
PKINIT-specific Options
The following are pkinit-specific options. These values can be speci‐
fied in [libdefaults] as global defaults, or within a realm-specific
subsection of [libdefaults], or can be specified as realm-specific val‐
ues in the [realms] section. A realm-specific value overrides, does not
add to, a generic [libdefaults] specification.
The search order is:
1. realm-specific subsection of [libdefaults]
[libdefaults]
EXAMPLE.COM = {
pkinit_anchors = FILE:/usr/local/example.com.crt
2. realm-specific value in the [realms] section
[realms]
OTHERREALM.ORG = {
pkinit_anchors = FILE:/usr/local/otherrealm.org.crt
3. generic value in the [libdefaults] section
[libdefaults]
pkinit_anchors = DIR:/usr/local/generic_trusted_cas/
The syntax for specifying Public Key identity, trust, and revocation
information for pkinit is as follows:
pkinit_identities = URI
Specifies the location(s) to be used to find the user's X.509 iden‐
tity information. This option can be specified multiple times.
Each value is attempted in order until identity information is
found and authentication is attempted. These values are not used if
the user specifies X509_user_identity on the command line.
Valid URI types are FILE, DIR, PKCS11, PKCS12, and ENV. See the
PKINIT URI Types section for more details.
pkinit_anchors = URI
Specifies the location of trusted anchor (root) certificates which
the client trusts to sign KDC certificates. This option can be
specified multiple times. These values from the config file are
not used if the user specifies X509_anchors on the command line.
Valid URI types are FILE and DIR. See the PKINIT URI Types section
for more details.
pkinit_pool = URI
Specifies the location of intermediate certificates which can be
used by the client to complete the trust chain between a KDC cer‐
tificate and a trusted anchor. This option can be specified multi‐
ple times.
Valid URI types are FILE and DIR. See the PKINIT URI Types
section for more details.
pkinit_revoke = URI
Specifies the location of Certificate Revocation List (CRL) infor‐
mation to be used by the client when verifying the validity of the
KDC certificate presented. This option can be specified multiple
times.
The only valid URI type is DIR. See the PKINIT URI Types section
for more details.
pkinit_require_crl_checking = value
The default certificate verification process always checks the
available revocation information to see if a certificate has been
revoked. If a match is found for the certificate in a CRL, verifi‐
cation fails. If the certificate being verified is not listed in a
CRL, or there is no CRL present for its issuing CA, and
pkinit_require_crl_checking is false, then verification succeeds.
However, if pkinit_require_crl_checking is true and there is no CRL
information available for the issuing CA, then verification fails.
pkinit_require_crl_checking should be set to true if the policy is
such that up-to-date CRLs must be present for every CA.
pkinit_dh_min_bits = value
Specifies the size of the Diffie-Hellman key the client attempts to
use. The acceptable values are currently 1024, 2048, and 4096. The
default is 2048.
pkinit_win2k = value
This flag specifies whether the target realm is assumed to support
only the old, pre-RFC version of the protocol. The default is
false.
pkinit_win2k_require_binding = value
If this flag is set to true, it expects that the target KDC is
patched to return a reply with a checksum rather than a nonce. The
default is false.
pkinit_eku_checking = value
This option specifies what Extended Key Usage value the KDC cer‐
tificate presented to the client must contain. If the KDC certifi‐
cate has the pkinit SubjectAlternativeName encoded as the Kerberos
TGS name, EKU checking is not necessary since the issuing CA has
certified this as a KDC certificate. The values recognized in the
krb5.conf file are:
kpKDC
This is the default value and specifies that the
KDC must have the id-pkinit-KPKdc EKU as defined in
RFC4556.
kpServerAuth
If kpServerAuth is specified, a KDC certificate
with the id-kp-serverAuth EKU as used by Microsoft
is accepted.
none
If none is specified, then the KDC certificate is
not checked to verify it has an acceptable EKU. The
use of this option is not recommended.
pkinit_kdc_hostname = value
The presense of this option indicates that the client is willing to
accept a KDC certificate with a dNSName SAN (Subject Alternative
Name) rather than requiring the id-pkinit-san as defined in
RFC4556. This option can be specified multiple times. Its value
should contain the acceptable hostname for the KDC (as contained in
its certificate).
pkinit_cert_match = rule
Specifies matching rules that the client certificate must match
before it is used to attempt pkinit authentication. If a user has
multiple certificates available (on a smart card, or by way of
another media), there must be exactly one certificate chosen before
attempting pkinit authentication. This option can be specified
multiple times. All the available certificates are checked against
each rule in order until there is a match of exactly one certifi‐
cate.
The Subject and Issuer comparison strings are the RFC2253 string
representations from the certificate Subject DN and Issuer DN val‐
ues.
The syntax of the matching rules is:
[relation-operator]component-rule `...'
where
relation-operator
Specify relation-operator as &&, meaning all
component rules must match, or ||, meaning
only one component rule must match. If rela‐
tion-operator is not specified, the default is
&&.
component-rule
There is no punctuation or white space between
component rules.Specify component-rule as one
of the following:
`<SUBJECT>'regular-expression
`<ISSUER>'regular-expression
`<SAN>'regular-expression
`<EKU>'extended-key-usage-list
where extended-key-usage-list is a comma-separated list
of required Extended Key Usage values. All values in
the list must be present in the certificate.
`pkinit'
`msScLogin'
`clientAuth'
`emailProtection'
`<KU>'key-usage-list
where key-usage-list is a comma-separated list of
required Key Usage values. All values in the list must
be present in the certificate.
`digitalSignature'
Examples:
pkinit_cert_match = ||<SUBJECT>.*DoE.*<SAN>.*@EXAMPLE.COM
pkinit_cert_match = &&<EKU>msScLogin,clientAuth<ISSUER>.*DoE.*
pkinit_cert_match = <EKU>msScLogin,clientAuth<KU>digitalSignature
PKINIT URI Types
FILE:file-name[,key-file-name]
This option has context-specific behavior.
pkinit_identities
file-name specifies the name of a PEM-format
file containing the user's certificate. If
key-file-name is not specified, the user's
private key is expected to be in file-name as
well. Otherwise, key-file-name is the name of
the file containing the private key.
pkinit_anchors
pkinit_pool
file-name is assumed to be the name of an
OpenSSL-style ca-bundle file. The ca-bundle
file should be base-64 encoded.
DIR:directory-name
This option has context-specific behavior.
pkinit_identities
directory-name specifies a directory with
files named *.crt and *.key, where the first
part of the file name is the same for matching
pairs of certificate and private key files.
When a file with a name ending with .crt is
found, a matching file ending with .key is
assumed to contain the private key. If no such
file is found, then the certificate in the
.crt is not used.
pkintit_anchors
pkinit_pool
directory-name is assumed to be an OpenSSL-
style hashed CA directory where each CA cert
is stored in a file named hash-of-ca-cert.#.
This infrastructure is encouraged, but all
files in the directory is examined and if they
contain certificates (in PEM format), they are
used.
PKCS12:pkcs12-file-name
pkcs12-file-name is the name of a PKCS #12 format file, containing
the user's certificate and private key.
PKCS11:[slotid=slot-id][:token=token-label][:cert id=cert-id][:certla‐
bel=cert-label]
All keyword/values are optional. PKCS11 modules (for example,
opensc-pkcs11.so) must be installed as a crypto provider under
libpkcs11(3LIB). slotid= and/or token= can be specified to force
the use of a particular smart card reader or token if there is more
than one available. certid= and/or certlabel= can be specified to
force the selection of a particular certificate on the device. See
the pkinit_cert_match configuration option for more ways to select
a particular certificate to use for pkinit.
ENV:environment-variable-name
environment-variable-name specifies the name of an environment
variable which has been set to a value conforming to one of the
previous values. For example, ENV:X509_PROXY, where environment
variable X509_PROXY has been set to FILE:/tmp/my_proxy.pem.
The [dbmodules] Section
This section consists of relations that provide configuration informa‐
tion for plug-in modules. In particular, the relations describe the
configuration for LDAP KDB plug-in. Use of the db2 KDB plug-in is the
default behavior and that this section does not need to be filled out
in that case.
db_library
Name of the plug-in library. To use the LDAP KDB plug-in the name
must be kdb_ldap. The default value is db2.
db_module_dir
Path to the plug-in libraries. The default is /usr/lib/krb5.
ldap_cert_path
Path to the Network Security Services (NSS) trusted database for an
SSL connection. This is a required parameter when using the LDAP
KDB plug-in.
ldap_conns_per_server
Number of connections per LDAP instance. The default is 5.
ldap_kadmind_dn
Bind DN for kadmind. This specifies the DN that the kadmind service
uses when binding to the LDAP Directory Server. The password for
this bind DN should be in the ldap_service_password_file.
ldap_kdc_dn
Bind DN for a Key Distribution Center (KDC). This specifies the DN
that the krb5kdc service use when binding to the LDAP Directory
Server. The password for this bind DN should be in the ldap_ser‐
vice_password_file.
ldap_servers
List of LDAP directory servers in URI format. Use of either of the
following is acceptable.
ldap://<ds hostname>:<SSL port>
ldap://<ds hostname>
Each server URI should be separated by whitespace.
ldap_service_password_file
File containing stashed passwords used by the KDC when binding to
the LDAP Directory Server. The default is /var/krb5/service_passwd.
This file is created using kdb5_ldap_util(1M).
ldap_ssl_port
Port number for SSL connection with directory server. The default
is 389.
EXAMPLES
Example 1 Sample File
The following is an example of a generic krb5.conf file:
[libdefaults]
default_realm = ATHENA.MIT.EDU
default_tkt_enctypes = des-cbc-crc
default_tgs_enctypes = des-cbc-crc
[realms]
ATHENA.MIT.EDU = {
kdc = kerberos.mit.edu
kdc = kerberos-1.mit.edu
kdc = kerberos-2.mit.edu
admin_server = kerberos.mit.edu
auth_to_local_realm = KRBDEV.ATHENA.MIT.EDU
}
FUBAR.ORG = {
kdc = kerberos.fubar.org
kdc = kerberos-1.fubar.org
admin_server = kerberos.fubar.org
}
[domain_realm]
.mit.edu = ATHENA.MIT.EDU
mit.edu = ATHENA.MIT.EDU
Example 2 KDC Using the LDAP KDB plug-in, realms and dbmodules Sections
The following is an example of the realms and dbmodules sections of a
Kerberos configuration file when the KDC is using the LDAP KDB plug-in.
[realms]
SUN.COM = {
kdc = kc-umpk-01.athena.mit.edu
kdc = kc-umpk-02.athena.mit.edu
admin_server = kc-umpk-01.athena.mit.edu
database_module = LDAP
}
[dbmodules]
LDAP = {
db_library = kdb_ldap
ldap_kerberos_container_dn = "cn=krbcontainer,dc=mit,dc=edu"
ldap_kdc_dn = "cn=kdc service,ou=profile,dc=mit,dc=edu"
ldap_kadmind_dn = "cn=kadmin service,ou=profile,dc=mit,dc=edu"
ldap_cert_path = /var/ldap
ldap_servers = ldaps://ds.mit.edu
}
FILES
/var/krb5/kdc.log
KDC logging file
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│Interface Stability │ See below. │
└────────────────────┴─────────────────┘
All of the keywords are Committed, except for the PKINIT keywords,
which are Volatile.
SEE ALSOkinit(1), rcp(1), rdist(1), rlogin(1), rsh(1), telnet(1), syslog(3C),
attributes(5), kerberos(5), regex(5)NOTES
If the krb5.conf file is not formatted properly, the telnet command
fails. However, the dtlogin and login commands still succeed, even if
the krb5.conf file is specified as required for the commands. If this
occurs, the following error message is displayed:
Error initializing krb5: Improper format of item
To bypass any other problems that might occur, you should fix the file
as soon as possible.
The max_life and max_renewable_life options are obsolete and is removed
in a future release of the Solaris operating system.
Jan 5, 2009 KRB5.CONF(4)
