Ubuntu Manpage: slapo-nssov - NSS and PAM requests through a local Unix Domain socket

Provided by: slapd_2.4.49+dfsg-2ubuntu1.10_amd64

NAME

       slapo-nssov - NSS and PAM requests through a local Unix Domain socket

SYNOPSIS

       ETCDIR/slapd.conf

DESCRIPTION

The nssov overlay to slapd(8) services NSS and PAM requests through a local Unix Domain
socket. It uses the same IPC protocol as Arthur de Jong's nss-pam-ldapd. An extract of
the nss-ldapd source is included along with the nssov source code to allow the overlay to
communicate with the nss-pam-ldapd client stubs.

Using a separate IPC protocol for NSS and PAM requests eliminates the libldap
dependencies/clashes that the current pam_ldap/nss_ldap solutions all suffer from. Both
the original nss-ldapd and this nssov solution are free from these library issues.

Unlike nss-pam-ldapd, since this overlay executes inside slapd it allows for the
possibility of sophisticated caching, without any of the weaknesses of nscd and other
related caching solutions. E.g., a remote LDAP database can be accessed using back-ldap
with proxy caching (see slapd-ldap(5) and slapo-pcache(5) ) to leverage back-ldap's
connection pooling as well as pcache's persistent caching, to provide high performance and
a measure of support for disconnected operation. Alternatively, cache considerations can
be completely eliminated by running a regular database with syncrepl to maintain
synchronization with a remote LDAP database.

Another major benefit of nssov is that it allows all security policy to be administered
centrally via LDAP, instead of having fragile rules scattered across multiple flat files.
As such, there is no client-side configuration at all for the NSS/PAM stub libraries. (The
stubs talk to the server via a Unix domain socket whose path is hardcoded to NSLCDPATH).
As a side benefit, this can finally eliminate the perpetual confusion between OpenLDAP's
ldap.conf file in ETCDIR/ldap.conf and the similarly named files typically used by
pam_ldap and nss_ldap.

User authentication is performed by internal simple Binds. User authorization leverages
the slapd ACL engine, which offers much more power and flexibility than the simple
group/hostname checks in the old pam_ldap code.

To use this code, you will need the client-side stub 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.

You will also need to include the nis.schema in your slapd configuration for RFC2307
support. If you wish to use RFC2307bis you will need a slightly different schema. You will
also need the ldapns.schema for PAM authorization management.

You must select ldap in the appropriate services in /etc/nsswitch.conf in order for these
NSS features to take effect. Likewise, you must enable pam_ldap for the authenticate,
account, session, and password services in /etc/pam.conf or /etc/pam.d for these PAM
features to take effect.

overlay nssov
This directive adds the nssov overlay to the current backend.

nssov-ssd <service> <url>
This directive configures a Service Search Descriptor (SSD) for each NSS service
that will be used. 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.

nssov-map <service> <orig> <new>
If the local database is actually a proxy to a foreign LDAP server, some mapping of
schema may be needed. This directive allows some simple attribute substitutions to
be performed. See the nss-ldapd/README for the original attribute names used in
this code.

nssov-pam <option> [...]
This directive determines a number of PAM behaviors. Multiple options may be used
at once, and available levels are:
userhost
check host attribute in user entry for authorization
userservice
check authorizedService attribute in user entry for authorization
usergroup
check that user is a member of specific group for authorization
hostservice
check authorizedService attribute in host entry for authorization
authz2dn
use authz-regexp mapping to map uid to LDAP DN
uid2dn use NSS passwd SSD to map uid to LDAP DN

Setting the userhost, userservice, and usergroup options duplicates the original
pam_ldap authorization behavior.

The recommended approach is to use hostservice instead. In this case, ipHost
entries must be created for all hosts being managed, and they must also have the
authorizedServiceObject class to allow authorizedService attributes to be used.
Also the NSS host SSD must be configured so that ipHost entries can be found.
Authorization is checked by performing an LDAP Compare operation looking for the
PAM service name in the authorizedService attribute. slapd ACLs should be set to
grant or deny Compare privilege to the appropriate users or groups as desired.

If the authz2dn option is set then authz-regexp mappings will be used to map the
PAM username to an LDAP DN. The authentication DN will be of the form
cn=<service>+uid=<user>,cn=<hostname>,cn=pam,cn=auth

If no mapping is found for this authentication DN, then this mapping will be
ignored.

If the uid2dn option is set then the NSS passwd SSD will be used to map the PAM
username to an LDAP DN. The passwd SSD must have already been configured for this
mapping to succeed.

If neither the authz2dn nor the uid2dn mapping succeeds, the module will return a
PAM_USER_UNKNOWN failure code. If both options are set, the authz mapping is
attempted first; if it succeeds the uid2dn mapping will be skipped.

By default only the uid2dn option is set.

nssov-pam-defhost <hostname>
Specify a default hostname to check if an ipHost entry for the current hostname
cannot be found. This setting is only relevant if the hostservice option has been
set.

nssov-pam-group-dn <DN>
Specify the DN of an LDAP group to check for authorization. The LDAP user must be a
member of this group for the login to be allowed. There is no default value. This
setting is only relevant if the usergroup option has been set.

nssov-pam-group-ad <attribute>
Specify the attribute to use for group membership checks. There is no default
value. This setting is only relevant if the usergroup option has been set.

nssov-pam-min-uid <integer>
Specify a minimum uid that is allowed to login. Users with a uidNumber lower than
this value will be denied access. The default is zero, which disables this setting.

nssov-pam-max-uid <integer>
Specify a maximum uid that is allowed to login. Users with a uidNumber higher than
this value will be denied access. The default is zero, which disables this setting.

nssov-pam-template-ad <attribute>
Specify an attribute to check in a user's entry for a template login name. The
template login feature is used by FreeBSD's PAM framework. It can be viewed as a
form of proxying, where a user can authenticate with one username/password pair,
but is assigned the identity and credentials of the template user. This setting is
disabled by default.

nssov-pam-template <name>
Specify a default username to be used if no template attribute is found in the
user's entry. The nssov-pam-template-ad directive must be configured for this
setting to have any effect.

nssov-pam-session <service>
Specify a PAM service name whose sessions will be recorded. For the configured
services, logins will be recorded in the

nssov-pam-password-prohibit-message <message>
Diable password change service and return the specified message to users.

nssov-pam-pwdmgr-dn <dn>
Specify the dn of the password manager.

nssov-pam-pwdmgr-pwd <pwd>
Specify the pwd of the password manager.

loginStatus
operational attribute of the user's entry. The attribute's values are of the form
<generalizedTime> <host> <service> <tty> (<ruser@rhost>)
Upon logout the corresponding value will be deleted. This feature allows a single LDAP
Search to be used to check which users are logged in across all the hosts of a network.
The rootdn of the database is used to perform the updates of the loginStatus attribute, so
a rootdn must already be configured for this feature to work. By default no services are
configured.

The PAM functions support LDAP Password Policy as well. If the password policy overlay is
in use (see slapo-ppolicy(5)), policy information (e.g. password expiration, password
quality, etc.) may be returned to the PAM client as a result of authentication, account
management, and password modification requests.

The overlay also supports dynamic configuration in cn=config. An example of the config
entry is

dn: olcOverlay={0}nssov,ocDatabase={1}hdb,cn=config
objectClass: olcOverlayConfig
objectClass: olcNssOvConfig
olcOverlay: {0}nssov
olcNssSsd: passwd ldap:///ou=users,dc=example,dc=com??one
olcNssMap: passwd uid accountName
olcNssPam: hostservice uid2dn
olcNssPamDefHost: defaulthost
olcNssPamMinUid: 500
olcNssPamMaxUid: 32000
olcNssPamSession: login
olcNssPamSession: sshd

which enables the passwd service, and uses the accountName attribute to fetch what is
usually retrieved from the uid attribute. It also enables some PAM authorization controls,
and specifies that the PAM login and sshd services should have their logins recorded.

FILES

       ETCDIR/slapd.conf
              default slapd configuration file

AUTHOR

       Howard  Chu,  inspired  by  nss-ldapd  by  Arthur  de  Jong  and  pam_ldap  by Luke Howard
       Enhancements by Ted C. Cheng, Symas Corp.

NAME

SYNOPSIS

DESCRIPTION

FILES

SEE ALSO

AUTHOR