DESCRIPTION
The
nss_ldap
module is a set of C library extensions which allows X.500 and LDAP
directory servers to be used as a primary source of name service
information. (Name service information typically includes users,
hosts, groups, and other such data historically stored in flat files
or NIS.)
Features of the PADL nss_ldap module include support for both the
RFC 2307 and RFC 2307bis schema, a common implementation across multiple
platforms, Kerberos and SSL security, configurable schema mapping,
and configuration file compatibility with the
pam_ldap(5)
module.
Because LDAP is a hierarchical directory service, one can distribute the
information in a manner which reflects organizational structure.
This contrasts with the flat, single domain policy of NIS. LDAP has many
of the advantages of NIS+ (security and scalability) without the complexity.
nss_ldap
will work alongside existing NIS, NIS+, DNS and flat file
name services. More importantly, because it builds as a shared library,
it is not necessary to recompile any applications to take advantage
of LDAP.
The present version of
nss_ldap
supports AIX 4.3.3 and above, FreeBSD 5.1, HP-UX 11i, Linux and
Solaris 2.6 and above. Many vendors provide their own LDAP nameservice
providers, often also called nss_ldap. This manual page applies to the
PADL
nss_ldap
module only. If you are using a vendor provided module, consult the
relevant documentation instead.
The features supported by the version of
nss_ldap
depend on which flags
were enabled when the software was built. Most features are enabled
in the configuration file, described below. (The location of the
configuration file is
configurable at compile time; the default path is /etc/libnss-ldap.conf.)
Also, some features may be unavailable on certain
operating systems or with certain LDAP libraries. For more information,
consult your vendor.
CONFIGURATION
nss_ldap
stores its configuration in the
ldap.conf
file, the location of which is configurable at compile time.
(It should be noted that some LDAP client libraries, such as
OpenLDAP, also use a configuration file of the same name.
nss_ldap
supports many of the same configuration file options as OpenLDAP,
but it adds several that are specific to the functionality it provides.
Additionally, it is not guaranteed that
nss_ldap
will continue to match the configuration file semantics of OpenLDAP.
You may wish to use different files.)
Configuration file options consist of a keyword followed by a
space and any arguments. The following options are supported by
both
nss_ldap
and the PADL
pam_ldap
module:
- host <name:port ...>
Specifies the name(s) or IP address(es) of the
LDAP
server(s) to connect to. In the case that
nss_ldap
is used for host name resolution, each server should be specified as an
IP address or name that can be resolved without using
LDAP.
Multiple servers may be specified, each separated by a space.
The failover time depends on whether the
LDAP
client library supports configurable network or connect timeouts
(see
bind_timelimit
below).
base <base>
Specifies the default base distinguished name (DN) to use for searches.
uri <ldap[is]://[name[:port]] ...>
For
LDAP
client libraries that support it, specifies the URI(s) of the LDAP
server(s) to connect to. The URI scheme may be
ldap,
ldapi,
or
ldaps,
specifying LDAP over TCP, IPC and SSL respectively. If applicable,
a port number can be specified; the default port number for the
selected protocol is used if omitted. This option takes
precedence over the
host
option; it is not possible to combine the two.
ldap_version <version>
Specifies the version of the
LDAP
protocol to use. Presently
version
must be 2 or 3. The default is to use the maximum version supported
by the client library.
binddn <binddn>
Specifies the distinguished name with which to bind to the directory
server(s). This option is optional; the default is to bind
anonymously.
bindpw <bindpw>
Specifies the cleartext credentials with which to bind. This option
is only applicable when used with
binddn
above. The default is no credential (anonymous bind). When binding to
the directory using
SASL
or other authentication mechanisms apart from simple binds, this
option is not used.
rootbinddn <binddn>
This option has the same syntax and effect as the
binddn
option above, except it applies when the effective user ID is
zero. If not specified, then the identity specified in
binddn
is used instead. Because the configuration file may be readable by
many users, the root bind DN credentials are stored in the
ldap.secret
file instead. This file is usually in the same directory as the
configuration file.
port <port>
Specifies the port to connect to; this option is used with the
host
option, and is ignored with the
uri
option.
scope <sub|one|base>
Specifies the search scope (subtree, one level or base object). The
default scope is subtree; base scope is almost never useful for
nameservice lookups.
deref <never|searching|finding|always>
Specifies the policy for dereferencing aliases. The default policy is
to never dereference aliases.
timelimit <timelimit>
Specifies the time limit (in seconds) to use when performing searches. A value
of zero (0), which is the default, is to wait indefinitely for
searches to be completed.
bind_timelimit <timelimit>
Specifies the time limit (in seconds) to use when connecting to the directory
server. This is distinct from the time limit specified in
timelimit
and affects the initial server connection only. (Server connections
are otherwise cached.) Only some
LDAP
client libraries have the underlying functionality necessary to
support this option. The default bind timelimit is 30 seconds.
referrals <yes|no>
Specifies whether automatic referral chasing should be enabled. The
default behaviour is specified by the
LDAP
client library.
restart <yes|no>
Specifies whether the
LDAP
client library should restart the
select(2)
system call when interrupted. This feature is not supported by all
client libraries.
logdir <directory>
Specifies the directory used for logging by the
LDAP
client library. This feature is not supported by all client
libraries.
debug <level>
Specifies the debug level used for logging by the
LDAP
client library. This feature is not supported by all client
libraries, and does not apply to the
nss_ldap
and
pam_ldap
modules themselves (debugging, if any, is configured separately
and usually at compile time).
ssl <on|off|start_tls>
Specifies whether to use SSL/TLS or not (the default is not to). If
start_tls
is specified then StartTLS is used rather than raw LDAP over SSL.
Not all
LDAP
client libraries support both SSL and StartTLS, and all related
configuration options.
sslpath <cert7_path>
For the Netscape and Mozilla
LDAP
client libraries only, this specifies the path to the X.509
certificate database.
tls_checkpeer <yes|no>
Specifies whether to require and verify the server certificate
or not, when using SSL/TLS with the OpenLDAP client library.
The default is to use the default behaviour of the client
library; for OpenLDAP 2.0 and earlier it is "no", for OpenLDAP
2.1 and later it is "yes". At least one of
tls_cacertdir
and
tls_cacertfile
is required if peer verification is enabled.
tls_cacertdir <certificate_dir>
Specifies the directory containing X.509 certificates for peer
authentication.
tls_cacertfile <certificate_file>
Specifies the path to the X.509 certificate for peer authentication.
tls_randfile <entropy_file>
Specifies the path to an entropy source.
tls_ciphers <ciphers>
Specifies the ciphers to use for TLS. See your TLS implementation's
documentation for further information.
tls_cert <certificate_file>
Specifies the path to the file containing the local certificate for
client TLS authentication.
tls_key <key_file>
Specifies the path to the file containing the private key for client
TLS authentication.
The following configuration options apply to nss_ldap only:
bind_policy <hard_open|hard_init|soft>
Specifies the policy to use for reconnecting to an unavailable
LDAP
server. The default is
hard_open,
which reconnects if opening the connection to the directory server
failed. By contrast,
hard_init
reconnects if initializing the connection failed. Initializing may not
actually contact the directory server, and it is possible that a
malformed configuration file will trigger reconnection. If
soft
is specified, then
nss_ldap
will return immediately on server failure. All "hard" reconnect
policies block with exponential backoff before retrying.
nss_connect_policy <persist|oneshot>
Determines whether nss_ldap persists connections. The default
is for the connection to the LDAP server to remain open after
the first request.
idle_timelimit <timelimit>
Specifies the time (in seconds) after which
nss_ldap
will close connections to the directory server. The default is not to
time out connections.
sasl_authid <authid>
Specifies the authorization identity to be used when performing SASL
authentication.
rootsasl_auth_id <authid>
Specifies the authorization identity to be used when performing SASL
authentication as root (when the effective user ID is zero).
sasl_secprops <properties>
Specifies Cyrus SASL security properties. Allowed values are described
in the
ldap.conf(5)
manual page.
rootuse_sasl <yes|no>
Specifies whether SASL authentication should be used when the effective
user ID is zero.
krb5_ccname <PREFIX:args>
If
nss_ldap
is built with configurable GSS-API credentials cache name support,
specifies the Kerberos credentials cache to use.
nss_paged_results <yes|no>
Enables support for paged results.
pagesize <pagesize>
When paged results are enabled (see above), specifies the number of
entries to return in a single page. The default is 1000.
nss_base_<map> <basedn?scope?filter>
Specify the search base, scope and filter to be used for specific
maps. (Note that
map
forms part of the configuration file keyword and is one of
passwd, shadow, group, hosts, services, networks, protocols,
rpc, ethers, netmasks, bootparams, aliases and netgroup.)
The syntax of
basedn
and
scope
are the same as for the configuration file options of the same
name, with the addition of being able to omit the trailing suffix
of the base DN (in which case the global base DN will be appended
instead). The
filter
is a search filter to be added to the default search filter for a
specific map, such that the effective filter is the logical
intersection of the two. The base DN, scope and filter are separated
with literal question marks (?) as given above; this is for
compatibility with the DUA configuration profile schema and the
ldapprofile
tool. This option may be specified multiple times.
nss_map_attribute <from_attribute> <to_attribute>
This option may be specified multiple times, and directs
nss_ldap
to use the attribute
to_attribute
instead of the RFC 2307 attribute
from_attribute
in all lookups.
If
nss_ldap
was built without schema mapping support, then this option
is ignored.
nss_map_objectclass <from_objectclass> <to_objectclass>
This option may be specified multiple times, and directs
nss_ldap
to use the object class
to_objectclass
instead of the RFC 2307 object class
from_objectclass
in all lookups.
If
nss_ldap
was built without schema mapping support, then this option
is ignored.
nss_default_attribute_value <attribute> <value>
Specifies the default value to use for entries that lack the
specified attribute. This option may be specified multiple times,
for different attributes.
If
nss_ldap
was built without schema mapping support, then this option
is ignored.
nss_override_attribute_value <attribute> <value>
Specifies a value to use for the specified attribute in preference
to that contained in the actual entry. This option may be specified
multiple times, for different attributes.
If
nss_ldap
was built without schema mapping support, then this option
is ignored.
nss_schema <rfc2307bis|rfc2307>
If the value of this option is
rfc2307bis
then support for the RFC2307bis schema (distinguished names in
groups) will be enabled.
nss_initgroups <backlink>
This option directs the
nss_ldap
implementation of
initgroups(3)
to determine a user's group membership by reading the memberOf
attribute of their directory entry (and of any nested groups),
rather than querying on uniqueMember. This may provide increased
performance with certain directory servers that have peculiar
indexing configurations.
If RFC2307bis support is disabled, then this option is ignored.
nss_initgroups_ignoreusers <user1,user2,...,userN>
This option directs the
nss_ldap
implementation of
initgroups(3)
to return NSS_STATUS_NOTFOUND if called with a listed users as
its argument.
nss_getgrent_skipmembers <yes|no>
Specifies whether or not to populate the members list in
the group structure for group lookups. If very large groups
are present, enabling this option will greatly increase
performance, at the cost of some lost functionality. You should
verify no local applications rely on this information before
enabling this on a production system.
nss_srv_domain <domain>
This option determines the DNS domain used for performing SRV
lookups.
