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This directory contains a slapd overlay, nssov, that handles
NSS lookup requests through a local Unix Domain socket. It uses the
same IPC protocol as Arthur de Jong's nss-ldapd, and a complete
copy of the nss-ldapd source is included here. It also handles
PAM requests.
To use this code, you will need the client-side stuf library from
nss-pam-ldapd. You can get it from:
http://arthurdejong.org/nss-pam-ldapd
You will not need the nslcd daemon; this overlay replaces that part.
To disable building of the nslcd daemon in nss-pam-ldapd, add the
--disable-nslcd option to the nss-pam-ldapd configure script. You
should already be familiar with the RFC2307 and RFC2307bis schema
to use this overlay. See the nss-pam-ldapd README for more information
on the schema and which features are supported.
To use the overlay, add:
include <path to>nis.schema
moduleload <path to>nssov.so
...
database mdb
...
overlay nssov
to your slapd configuration file. (The nis.schema file contains
the original RFC2307 schema. Some modifications will be needed to
use RFC2307bis.)
The overlay may be configured with Service Search Descriptors (SSDs)
for each NSS service that will be used. SSDs are configured using
nssov-ssd <service> <url>
where the <service> may be one of
aliases
ethers
group
hosts
netgroup
networks
passwd
protocols
rpc
services
shadow
and the <url> must be of the form
ldap:///[<basedn>][??[<scope>][?<filter>]]
The <basedn> will default to the first suffix of the current database.
The <scope> defaults to "subtree". The default <filter> depends on which
service is being used.
If the local database is actually a proxy to a foreign LDAP server, some
mapping of schema may be needed. Some simple attribute substitutions may
be performed using
nssov-map <service> <orig> <new>
See the nss-ldapd/README for the original attribute names used in this code.
The overlay also supports dynamic configuration in cn=config. The layout
of the config entry is
dn: olcOverlay={0}nssov,olcDatabase={1}mdb,cn=config
objectClass: olcOverlayConfig
objectClass: olcNssOvConfig
olcOverlay: {0}nssov
olcNssSsd: passwd ldap:///ou=users,dc=example,dc=com??one
olcNssMap: passwd uid accountName
which enables the passwd service, and uses the accountName attribute to
fetch what is usually retrieved from the uid attribute.
PAM authentication, account management, session management, and password
management are supported.
Authentication is performed using Simple Binds. Since all operations occur
inside the slapd overlay, "fake" connections are used and they are
inherently secure. Two methods of mapping the PAM username to an LDAP DN
are provided:
the mapping can be accomplished using slapd's authz-regexp facility. In
this case, a DN of the form
cn=<service>+uid=<user>,cn=<hostname>,cn=pam,cn=auth
is fed into the regexp matcher. If a match is produced, the resulting DN
is used.
otherwise, the NSS passwd map is invoked (which means it must already
be configured).
If no DN is found, the overlay returns PAM_USER_UNKNOWN. If the DN is
found, and Password Policy is supported, then the Bind will use the
Password Policy control and return expiration information to PAM.
Account management also uses two methods. These methods depend on the
ldapns.schema included with the nssov source.
The first is identical to the method used in PADL's pam_ldap module:
host and authorizedService attributes may be looked up in the user's entry,
and checked to determine access. Also a check may be performed to see if
the user is a member of a particular group. This method is pretty
inflexible and doesn't scale well to large networks of users, hosts,
and services.
The second uses slapd's ACL engine to check if the user has "compare"
privilege on an ipHost object whose name matches the current hostname, and
whose authorizedService attribute matches the current service name. This
method is preferred, since it allows authorization to be centralized in
the ipHost entries instead of scattered across the entire user population.
The ipHost entries must have an authorizedService attribute (e.g. by way
of the authorizedServiceObject auxiliary class) to use this method.
Session management: the overlay may optionally add a "logged in" attribute
to a user's entry for successful logins, and delete the corresponding
value upon logout. The attribute value is of the form
<generalizedTime> <host> <service> <tty> (<ruser@rhost>)
Password management: the overlay will perform a PasswordModify exop
in the server for the given user.
---
This work is part of OpenLDAP Software <http://www.openldap.org/>.
Copyright 1998-2022 The OpenLDAP Foundation.
Portions Copyright 2008-2009 Howard Chu, Symas Corp. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted only as authorized by the OpenLDAP
Public License.
A copy of this license is available in the file LICENSE in the
top-level directory of the distribution or, alternatively, at
<http://www.OpenLDAP.org/license.html>.
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