Provided by: slapd_2.4.28-1.1ubuntu4_i386
slapo-ppolicy - Password Policy overlay to slapd
The ppolicy overlay is an implementation of the most recent IETF
Password Policy proposal for LDAP. When instantiated, it intercepts,
decodes and applies specific password policy controls to overall use of
a backend database, changes to user password fields, etc.
The overlay provides a variety of password control mechanisms. They
include password aging -- both minimum and maximum ages, password reuse
and duplication control, account time-outs, mandatory password resets,
acceptable password content, and even grace logins. Different groups
of users may be associated with different password policies, and there
is no limit to the number of password policies that may be created.
Note that some of the policies do not take effect when the operation is
performed with the rootdn identity; all the operations, when performed
with any other identity, may be subjected to constraints, like access
Note that the IETF Password Policy proposal for LDAP makes sense when
considering a single-valued password attribute, while the userPassword
attribute allows multiple values. This implementation enforces a
single value for the userPassword attribute, despite its specification.
These slapd.conf configuration options apply to the ppolicy overlay.
They should appear after the overlay directive.
Specify the DN of the pwdPolicy object to use when no specific
policy is set on a given user's entry. If there is no specific
policy for an entry and no default is given, then no policies
will be enforced.
Specify that policy state changes that result from Bind
operations (such as recording failures, lockout, etc.) on a
consumer should be forwarded to a master instead of being
written directly into the consumer's local database. This
setting is only useful on a replication consumer, and also
requires the updateref setting and chain overlay to be
Specify that cleartext passwords present in Add and Modify
requests should be hashed before being stored in the database.
This violates the X.500/LDAP information model, but may be
needed to compensate for LDAP clients that don't use the
Password Modify extended operation to manage passwords. It is
recommended that when this option is used that compare, search,
and read access be denied to all directory users.
A client will always receive an LDAP InvalidCredentials response
when Binding to a locked account. By default, when a Password
Policy control was provided on the Bind request, a Password
Policy response will be included with no special error code set.
This option changes the Password Policy response to include the
AccountLocked error code. Note that sending the AccountLocked
error code provides useful information to an attacker; sites
that are sensitive to security issues should not enable this
The ppolicy overlay depends on the pwdPolicy object class. The
definition of that class is as follows:
MUST ( pwdAttribute )
pwdMinAge $ pwdMaxAge $ pwdInHistory $
pwdCheckQuality $ pwdMinLength $
pwdExpireWarning $ pwdGraceAuthnLimit $
pwdLockout $ pwdLockoutDuration $
pwdMaxFailure $ pwdFailureCountInterval $
pwdMustChange $ pwdAllowUserChange $
pwdSafeModify ) )
This implementation also provides an additional pwdPolicyChecker
objectclass, used for password quality checking (see below).
MAY ( pwdCheckModule ) )
Every account that should be subject to password policy control should
have a pwdPolicySubentry attribute containing the DN of a valid
pwdPolicy entry, or they can simply use the configured default. In
this way different users may be managed according to different
OBJECT CLASS ATTRIBUTES
Each one of the sections below details the meaning and use of a
particular attribute of this pwdPolicy object class.
This attribute contains the name of the attribute to which the password
policy is applied. For example, the password policy may be applied to
the userPassword attribute.
Note: in this implementation, the only value accepted for pwdAttribute
is userPassword .
SYNTAX 18.104.22.168.4.1.1422.214.171.124.38 )
This attribute contains the number of seconds that must elapse between
modifications allowed to the password. If this attribute is not
present, zero seconds is assumed (i.e. the password may be modified
whenever and however often is desired).
This attribute contains the number of seconds after which a modified
password will expire. If this attribute is not present, or if its
value is zero (0), then passwords will not expire.
This attribute is used to specify the maximum number of used passwords
that will be stored in the pwdHistory attribute. If the pwdInHistory
attribute is not present, or if its value is zero (0), used passwords
will not be stored in pwdHistory and thus any previously-used password
may be reused. No history checking occurs if the password is being
modified by the rootdn, although the password is saved in the history.
This attribute indicates if and how password syntax will be checked
while a password is being modified or added. If this attribute is not
present, or its value is zero (0), no syntax checking will be done. If
its value is one (1), the server will check the syntax, and if the
server is unable to check the syntax, whether due to a client-side
hashed password or some other reason, it will be accepted. If its value
is two (2), the server will check the syntax, and if the server is
unable to check the syntax it will return an error refusing the
When syntax checking is enabled (see also the pwdCheckQuality
attribute), this attribute contains the minimum number of characters
that will be accepted in a password. If this attribute is not present,
minimum password length is not enforced. If the server is unable to
check the length of the password, whether due to a client-side hashed
password or some other reason, the server will, depending on the value
of pwdCheckQuality, either accept the password without checking it (if
pwdCheckQuality is zero (0) or one (1)) or refuse it (if
pwdCheckQuality is two (2)).
This attribute contains the maximum number of seconds before a password
is due to expire that expiration warning messages will be returned to a
user who is authenticating to the directory. If this attribute is not
present, or if the value is zero (0), no warnings will be sent.
This attribute contains the number of times that an expired password
may be used to authenticate a user to the directory. If this attribute
is not present or if its value is zero (0), users with expired
passwords will not be allowed to authenticate to the directory.
This attribute specifies the action that should be taken by the
directory when a user has made a number of failed attempts to
authenticate to the directory. If pwdLockout is set (its value is
"TRUE"), the user will not be allowed to attempt to authenticate to the
directory after there have been a specified number of consecutive
failed bind attempts. The maximum number of consecutive failed bind
attempts allowed is specified by the pwdMaxFailure attribute. If
pwdLockout is not present, or if its value is "FALSE", the password may
be used to authenticate no matter how many consecutive failed bind
attempts have been made.
This attribute contains the number of seconds during which the password
cannot be used to authenticate the user to the directory due to too
many consecutive failed bind attempts. (See also pwdLockout and
pwdMaxFailure.) If pwdLockoutDuration is not present, or if its value
is zero (0), the password cannot be used to authenticate the user to
the directory again until it is reset by an administrator.
This attribute contains the number of consecutive failed bind attempts
after which the password may not be used to authenticate a user to the
directory. If pwdMaxFailure is not present, or its value is zero (0),
then a user will be allowed to continue to attempt to authenticate to
the directory, no matter how many consecutive failed bind attempts have
occurred with that user's DN. (See also pwdLockout and
This attribute contains the number of seconds after which old
consecutive failed bind attempts are purged from the failure counter,
even though no successful authentication has occurred. If
pwdFailureCountInterval is not present, or its value is zero (0), the
failure counter will only be reset by a successful authentication.
This attribute specifies whether users must change their passwords when
they first bind to the directory after a password is set or reset by
the administrator, or not. If pwdMustChange has a value of "TRUE",
users must change their passwords when they first bind to the directory
after a password is set or reset by the administrator. If
pwdMustChange is not present, or its value is "FALSE", users are not
required to change their password upon binding after the administrator
sets or resets the password.
This attribute specifies whether users are allowed to change their own
passwords or not. If pwdAllowUserChange is set to "TRUE", or if the
attribute is not present, users will be allowed to change their own
passwords. If its value is "FALSE", users will not be allowed to
change their own passwords.
Note: this implies that when pwdAllowUserChange is set to "TRUE", users
will still be able to change the password of another user, subjected to
access control. This restriction only applies to modifications of
ones's own password. It should also be noted that pwdAllowUserChange
was defined in the specification to provide rough access control to the
password attribute in implementations that do not allow fine-grain
access control. Since OpenLDAP provides fine-grain access control, the
use of this attribute is discouraged; ACLs should be used instead (see
slapd.access(5) for details).
This attribute denotes whether the user's existing password must be
sent along with their new password when changing a password. If
pwdSafeModify is set to "TRUE", the existing password must be sent
along with the new password. If the attribute is not present, or its
value is "FALSE", the existing password need not be sent along with the
This attribute names a user-defined loadable module that must
instantiate the check_password() function. This function will be
called to further check a new password if pwdCheckQuality is set to one
(1) or two (2), after all of the built-in password compliance checks
have been passed. This function will be called according to this
int check_password (char *pPasswd, char **ppErrStr, Entry *pEntry);
The pPasswd parameter contains the clear-text user password, the
ppErrStr parameter contains a double pointer that allows the function
to return human-readable details about any error it encounters. The
optional pEntry parameter, if non-NULL, carries a pointer to the entry
whose password is being checked. If ppErrStr is NULL, then funcName
must NOT attempt to use it/them. A return value of LDAP_SUCCESS from
the called function indicates that the password is ok, any other value
indicates that the password is unacceptable. If the password is
unacceptable, the server will return an error to the client, and
ppErrStr may be used to return a human-readable textual explanation of
the error. The error string must be dynamically allocated as it will be
free()'d by slapd.
Note: The user-defined loadable module named by pwdCheckModule must be
in slapd's standard executable search PATH.
Note: pwdCheckModule is a non-standard extension to the LDAP password
The operational attributes used by the ppolicy module are stored in the
user's entry. Most of these attributes are not intended to be changed
directly by users; they are there to track user activity. They have
been detailed here so that administrators and users can both understand
the workings of the ppolicy module.
Note that the current IETF Password Policy proposal does not define how
these operational attributes are expected to behave in a replication
environment. In general, authentication attempts on a slave server only
affect the copy of the operational attributes on that slave and will
not affect any attributes for a user's entry on the master server.
Operational attribute changes resulting from authentication attempts on
a master server will usually replicate to the slaves (and also
overwrite any changes that originated on the slave). These behaviors
are not guaranteed and are subject to change when a formal
The userPassword attribute is not strictly part of the ppolicy module.
It is, however, the attribute that is tracked and controlled by the
module. Please refer to the standard OpenLDAP schema for its
This attribute refers directly to the pwdPolicy subentry that is to be
used for this particular directory user. If pwdPolicySubentry exists,
it must contain the DN of a valid pwdPolicy object. If it does not
exist, the ppolicy module will enforce the default password policy
rules on the user associated with this authenticating DN. If there is
no default, or the referenced subentry does not exist, then no policy
rules will be enforced.
DESC 'The pwdPolicy subentry in effect for
This attribute denotes the last time that the entry's password was
changed. This value is used by the password expiration policy to
determine whether the password is too old to be allowed to be used for
user authentication. If pwdChangedTime does not exist, the user's
password will not expire.
DESC 'The time the password was last changed'
This attribute contains the time that the user's account was locked.
If the account has been locked, the password may no longer be used to
authenticate the user to the directory. If pwdAccountLockedTime is set
to 000001010000Z, the user's account has been permanently locked and
may only be unlocked by an administrator. Note that account locking
only takes effect when the pwdLockout password policy attribute is set
DESC 'The time an user account was locked'
This attribute contains the timestamps of each of the consecutive
authentication failures made upon attempted authentication to this DN
(i.e. account). If too many timestamps accumulate here (refer to the
pwdMaxFailure password policy attribute for details), and the
pwdLockout password policy attribute is set to "TRUE", the account may
be locked. (Please also refer to the pwdLockout password policy
attribute.) Excess timestamps beyond those allowed by pwdMaxFailure
may also be purged. If a successful authentication is made to this DN
(i.e. to this user account), then pwdFailureTime will be cleansed of
DESC 'The timestamps of the last consecutive
USAGE directoryOperation )
This attribute contains the history of previously used passwords for
this DN (i.e. for this user account). The values of this attribute are
stored in string format as follows:
time "#" syntaxOID "#" length "#" data
GeneralizedTime as specified in section 3.3.13 of [RFC4517]
syntaxOID = numericoid
This is the string representation of the dotted-decimal OID
that defines the syntax used to store the password. numericoid
is described in section 1.4 of [RFC4512].
length = NumericString
The number of octets in the data. NumericString is described
in section 3.3.23 of [RFC4517].
Octets representing the password in the format specified by
This format allows the server to store and transmit a history of
passwords that have been used. In order for equality matching on the
values in this attribute to function properly, the time field is in GMT
DESC 'The history of user passwords'
pwdGraceUseTime This attribute contains the list of timestamps of
logins made after the user password in the DN has expired. These post-
expiration logins are known as "grace logins". If too many grace
logins have been used (please refer to the pwdGraceLoginLimit password
policy attribute), then the DN will no longer be allowed to be used to
authenticate the user to the directory until the administrator changes
the DN's userPassword attribute.
DESC 'The timestamps of the grace login once the password has
This attribute indicates whether the user's password has been reset by
the administrator and thus must be changed upon first use of this DN
for authentication to the directory. If pwdReset is set to "TRUE",
then the password was reset and the user must change it upon first
authentication. If the attribute does not exist, or is set to "FALSE",
the user need not change their password due to administrative reset.
DESC 'The indication that the password has
ldap(3), slapd.conf(5), slapd-config(5), slapo-chain(5).
"OpenLDAP Administrator's Guide" (http://www.OpenLDAP.org/doc/admin/)
IETF LDAP password policy proposal by P. Behera, L. Poitou and J.
Sermersheim: documented in IETF document "draft-behera-ldap-password-
The LDAP Password Policy specification is not yet an approved standard,
and it is still evolving. This code will continue to be in flux until
the specification is finalized.
This module was written in 2004 by Howard Chu of Symas Corporation with
significant input from Neil Dunbar and Kartik Subbarao of Hewlett-
This manual page borrows heavily and shamelessly from the specification
upon which the password policy module it describes is based. This
source is the IETF LDAP password policy proposal by P. Behera, L.
Poitou and J. Sermersheim. The proposal is fully documented in the
IETF document named draft-behera-ldap-password-policy-09.txt, written
in July of 2005.
OpenLDAP Software is developed and maintained by The OpenLDAP Project
<http://www.openldap.org/>. OpenLDAP Software is derived from
University of Michigan LDAP 3.3 Release.