nslcd.conf(5) - Man pages

nslcd.conf(5) System Manager's Manual nslcd.conf(5)

NAME
nslcd.conf - configuration file for LDAP nameservice daemon

DESCRIPTION
The nss-pam-ldapd package allows 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 histori-
cally stored in flat files or NIS.)

The file nslcd.conf contains the configuration information for running
nslcd (see nslcd(8)). The file contains options, one on each line,
defining the way NSS lookups and PAM actions are mapped to LDAP lookups.

OPTIONS
RUNTIME OPTIONS
threads NUM
Specifies the number of threads to start that can handle requests
and perform LDAP queries. Each thread opens a separate connec-
tion to the LDAP server. The default is to start 5 threads.

uid UID
This specifies the user id with which the daemon should be run.
This can be a numerical id or a symbolic value. If no uid is
specified no attempt to change the user will be made. Note that
you should use values that don't need LDAP to resolve.

gid GID
This specifies the group id with which the daemon should be run.
This can be a numerical id or a symbolic value. If no gid is
specified no attempt to change the group will be made. Note that
you should use values that don't need LDAP to resolve.

log SCHEME [LEVEL]
This option controls the way logging is done. The SCHEME argu-
ment may either be none, syslog or an absolute file name. The
LEVEL argument is optional and specifies the log level. The log
level may be one of: crit, error, warning, notice, info or debug.
The default log level is info. All messages with the specified
loglevel or higher are logged. This option can be supplied mul-
tiple times. If this option is omitted syslog info is assumed.

GENERAL CONNECTION OPTIONS
uri URI ...
Specifies the LDAP URI of the server to connect to. The URI
scheme may be ldap, ldapi or ldaps, specifying LDAP over TCP, ICP
or SSL respectively (if supported by the LDAP library).

Alternatively, the value DNS may be used to try to lookup the
server using DNS SRV records. By default the current domain is
used but another domain can be queried by using the DNS:DOMAIN
syntax. To convert SRV records for port 389 into an ldaps://
URI, DNSLDAPS can be used.

When using the ldapi scheme, %2f should be used to escape slashes
(e.g. ldapi://%2fvar%2frun%2fslapd%2fldapi/), although most of
the time this should not be needed.

This option may be specified multiple times and/or with more URIs
on the line, separated by spaces. Normally, only the first server
will be used with the following servers as fall-back (see
bind_timelimit below).

If LDAP lookups are used for host name resolution, any host names
should be specified as an IP address or name that can be resolved
without using LDAP.

ldap_version VERSION
Specifies the version of the LDAP protocol to use. The default
is to use the maximum version supported by the LDAP library.

binddn DN
Specifies the distinguished name with which to bind to the direc-
tory server for lookups. The default is to bind anonymously.

bindpw PASSWORD
Specifies the credentials with which to bind. This option is
only applicable when used with binddn above. If you set this op-
tion you should consider changing the permissions of the
nslcd.conf file to only grant access to the root user.

rootpwmoddn DN
Specifies the distinguished name to use when the root user tries
to modify a user's password using the PAM module.

Note that currently this DN needs to exist as a real entry in the
LDAP directory.

rootpwmodpw PASSWORD
Specifies the credentials with which to bind if the root user
tries to change a user's password. This option is only applica-
ble when used with rootpwmoddn above. If this option is not
specified the PAM module prompts the user for this password. If
you set this option you should consider changing the permissions
of the nslcd.conf file to only grant access to the root user.

SASL AUTHENTICATION OPTIONS
sasl_mech MECHANISM
Specifies the SASL mechanism to be used when performing SASL au-
thentication.

sasl_realm REALM
Specifies the SASL realm to be used when performing SASL authen-
tication.

sasl_authcid AUTHCID
Specifies the authentication identity to be used when performing
SASL authentication.

sasl_authzid AUTHZID
Specifies the authorization identity to be used when performing
SASL authentication. Must be specified in one of the formats:
dn:<distinguished name> or u:<username>.

sasl_secprops PROPERTIES
Specifies Cyrus SASL security properties. Allowed values are de-
scribed in the ldap.conf(5) manual page.

sasl_canonicalize yes|no
Determines whether the LDAP server host name should be canoni-
calised. If this is set to yes the LDAP library will do a reverse
host name lookup. By default, it is left up to the LDAP library
whether this check is performed or not.

KERBEROS AUTHENTICATION OPTIONS
krb5_ccname NAME
Set the name for the GSS-API Kerberos credentials cache.

SEARCH/MAPPING OPTIONS
base [MAP] DN
Specifies the distinguished name (DN) to use as search base.
This option may be supplied multiple times and all specified
bases will be searched.

A global search base may be specified or a MAP-specific one. If
no MAP-specific search bases are defined the global ones are
used.

If, instead of a DN, the value DOMAIN is specified, the host's
DNS domain is used to construct a search base. A value of "" can
be used to indicate an empty search base (quotes are not other-
wise supported for base values and not all LDAP server configura-
tions support this).

If this value is not defined an attempt is made to look it up in
the configured LDAP server. If the LDAP server is unavailable
during start-up nslcd will not start.

scope [MAP] sub[tree]|one[level]|base|children
Specifies the search scope (subtree, onelevel, base or children).
The default scope is subtree; base scope is almost never useful
for name service lookups; children scope is not supported on all
servers.

deref never|searching|finding|always
Specifies the policy for dereferencing aliases. The default pol-
icy is to never dereference aliases.

referrals yes|no
Specifies whether automatic referral chasing should be enabled.
The default behaviour is to chase referrals.

filter MAP FILTER
The FILTER is an LDAP search filter to use for a specific map.
The default filter is a basic search on the objectClass for the
map (e.g. (objectClass=posixAccount)).

map MAP ATTRIBUTE NEWATTRIBUTE
This option allows for custom attributes to be looked up instead
of the default RFC 2307 attributes. The MAP may be one of the
supported maps below. The ATTRIBUTE is the one as used in RFC
2307 (e.g. userPassword, ipProtocolNumber, macAddress, etc.).

The NEWATTRIBUTE may be the name of any attribute as it is avail-
able in the directory.

If the NEWATTRIBUTE is quoted (") as "EXPRESSION" it is treated
as an expression which will be evaluated to build up the actual
value used. See the section on attribute mapping expressions be-
low for more details.

Only some attributes for group, passwd and shadow entries may be
mapped with an expression (because other attributes may be used
in search filters). For group entries only the userPassword at-
tribute may be mapped with an expression. For passwd entries the
following attributes may be mapped with an expression: userPass-
word, gidNumber, gecos, homeDirectory and loginShell. For shadow
entries the following attributes may be mapped with an expres-
sion: userPassword, shadowLastChange, shadowMin, shadowMax, shad-
owWarning, shadowInactive, shadowExpire and shadowFlag.

The uidNumber and gidNumber attributes in the passwd and group
maps may be mapped to the objectSid followed by the domain SID to
derive numeric user and group ids from the SID (e.g. object-
Sid:S-1-5-21-3623811015-3361044348-30300820).

By default all userPassword attributes are mapped to the unmatch-
able password ("*") to avoid accidentally leaking password infor-
mation.

TIMING/RECONNECT OPTIONS
bind_timelimit SECONDS
Specifies the time limit (in seconds) to use when connecting to
the directory server. This is distinct from the time limit spec-
ified in timelimit and affects the set-up of the connection only.
Note that not all LDAP client libraries have support for setting
the connection time out. The default bind_timelimit is 10 sec-
onds.

timelimit SECONDS
Specifies the time limit (in seconds) to wait for a response from
the LDAP server. A value of zero (0), which is the default, is
to wait indefinitely for searches to be completed.

idle_timelimit SECONDS
Specifies the period of inactivity (in seconds) after which the
connection to the LDAP server will be closed. The default is not
to time out connections.

reconnect_sleeptime SECONDS
Specifies the number of seconds to sleep when connecting to all
LDAP servers fails. By default 1 second is waited between the
first failure and the first retry.

reconnect_retrytime SECONDS
Specifies the time after which the LDAP server is considered to
be permanently unavailable. Once this time is reached retries
will be done only once per this time period. The default value
is 10 seconds.

Note that the reconnect logic as described above is the mechanism that
is used between nslcd and the LDAP server. The mechanism between the NSS
and PAM client libraries on one end and nslcd on the other is simpler
with a fixed compiled-in time out of a 10 seconds for writing to nslcd
and a time out of 60 seconds for reading answers. nslcd itself has a
read time out of 0.5 seconds and a write time out of 60 seconds.

SSL/TLS OPTIONS
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,
StartTLS and all related configuration options.

tls_reqcert never|allow|try|demand|hard
Specifies what checks to perform on a server-supplied certifi-
cate. The meaning of the values is described in the ldap.conf(5)
manual page. At least one of tls_cacertdir and tls_cacertfile is
required if peer verification is enabled.

tls_cacertdir PATH
Specifies the directory containing X.509 certificates for peer
authentication. This parameter is ignored when using GnuTLS. On
Debian OpenLDAP is linked against GnuTLS.

tls_cacertfile PATH
Specifies the path to the X.509 certificate for peer authentica-
tion.

tls_randfile PATH
Specifies the path to an entropy source. This parameter is ig-
nored when using GnuTLS. On Debian OpenLDAP is linked against
GnuTLS.

tls_ciphers CIPHERS
Specifies the ciphers to use for TLS. See your TLS implementa-
tion's documentation for further information.

tls_cert PATH
Specifies the path to the file containing the local certificate
for client TLS authentication.

tls_key PATH
Specifies the path to the file containing the private key for
client TLS authentication.

tls_reqsan never|allow|try|demand|hard
Specifies the way server Subject Alternative Name (SAN) is
checked in the server-supplied certificate. The meaning of the
values is described in the ldap.conf(5) manual page.

tls_crlcheck none|peer|all
Specifies if the Certificate Revocation List (CRL) of the CA
should be used to verify if the server certificates have not been
revoked. The meaning of the values is described in the
ldap.conf(5) manual page.

tls_crlfile PATH
Specifies the path to the file containing a Certificate Revoca-
tion List to be used to verify if the server certificates. The
meaning of the values is described in the ldap.conf(5) manual
page.

OTHER OPTIONS
pagesize NUMBER
Set this to a number greater than 0 to request paged results from
the LDAP server in accordance with RFC2696. The default (0) is
to not request paged results.

This is useful for LDAP servers that contain a lot of entries
(e.g. more than 500) and limit the number of entries that are re-
turned with one request. For OpenLDAP servers you may need to
set sizelimit size.prtotal=unlimited for allowing more entries to
be returned over multiple pages.

nss_initgroups_ignoreusers user1,user2,...
This option prevents group membership lookups through LDAP for
the specified users. This can be useful in case of unavailability
of the LDAP server. This option may be specified multiple times.

Alternatively, the value ALLLOCAL may be used. With that value
nslcd builds a full list of non-LDAP users on startup.

nss_min_uid UID
This option ensures that LDAP users with a numeric user id lower
than the specified value are ignored. Also requests for users
with a lower user id are ignored.

nss_uid_offset NUMBER
This option specifies an offset that is added to all LDAP numeric
user ids. This can be used to avoid user id collisions with lo-
cal users or, when using objectSid attributes, for compatibility
reasons.

The value from the nss_min_uid option is evaluated after applying
the offset.

nss_gid_offset NUMBER
This option specifies an offset that is added to all LDAP numeric
group ids. This can be used to avoid user id collisions with lo-
cal groups or, when using objectSid attributes, for compatibility
reasons.

nss_nested_groups yes|no
If this option is set, the member attribute of a group may point
to another group. Members of nested groups are also returned in
the higher level group and parent groups are returned when find-
ing groups for a specific user. The default is not to perform
extra searches for nested groups.

nss_getgrent_skipmembers yes|no
If this option is set, the group member list is not retrieved
when looking up groups. Lookups for finding which groups a user
belongs to will remain functional so the user will likely still
get the correct groups assigned on login.

This can offer a speed-up on systems that have very large groups.
It has the downside of returning inconsistent information about
group membership which may confuse some applications. This op-
tion is not recommended for most configurations.

nss_disable_enumeration yes|no
If this option is set, functions which cause all user/group en-
tries to be loaded (getpwent(), getgrent(), setspent()) from the
directory will not succeed in doing so. Applications that depend
on being able to sequentially read all users and/or groups may
fail to operate correctly.

This can dramatically reduce LDAP server load in situations where
there are a great number of users and/or groups. This is typi-
cally used in situations where user/program access to enumerate
the entire directory is undesirable, and changing the behavior of
the user/program is not possible. This option is not recommended
for most configurations.

validnames REGEX
This option can be used to specify how user and group names are
verified within the system. This pattern is used to check all
user and group names that are requested and returned from LDAP.

The regular expression should be specified as a POSIX extended
regular expression. The expression itself needs to be separated
by slash (/) characters and the 'i' flag may be appended at the
end to indicate that the match should be case-insensitive. The
default value is /^[a-z0-9._@$()]([a-z0-9._@$()
\\~-]*[a-z0-9._@$()~-])?$/i

ignorecase yes|no
This specifies whether or not to perform searches for group, net-
group, passwd, protocols, rpc, services and shadow maps using
case-insensitive matching. Setting this to yes could open up the
system to authorisation bypass vulnerabilities and introduce nscd
cache poisoning vulnerabilities which allow denial of service.
The default is to perform case-sensitive filtering of LDAP search
results for the above maps.

pam_authc_ppolicy yes|no
This option specifies whether password policy controls are re-
quested and handled from the LDAP server when performing user au-
thentication. By default the controls are requested and handled
if available.

pam_authc_search FILTER
By default nslcd performs an LDAP search with the user's creden-
tials after BIND (authentication) to ensure that the BIND opera-
tion was successful. The default search is a simple check to see
if the user's DN exists.

A search filter can be specified that will be used instead. The
same substitutions as with the pam_authz_search option will be
performed and the search should at least return one entry.

The value BASE may be used to force the default search for the
user DN.

The value NONE may be used to indicate that no search should be
performed after BIND. Note that some LDAP servers do not always
return a correct error code as a result of a failed BIND opera-
tion (e.g. when an empty password is supplied).

pam_authz_search FILTER
This option allows flexible fine tuning of the authorisation
check that should be performed. The search filter specified is
executed and if any entries match, access is granted, otherwise
access is denied.

The search filter can contain the following variable references:
$username, $service, $ruser, $rhost, $tty, $hostname, $fqdn, $do-
main, $dn, and $uid. These references are substituted in the
search filter using the same syntax as described in the section
on attribute mapping expressions below.

For example, to check that the user has a proper authorizedSer-
vice value if the attribute is present (this almost emulates the
pam_check_service_attr option in PADL's pam_ldap):

(&(objectClass=posixAccount)(uid=$username)(|(authorizedService=$service)(!(authorizedService=*))))

The pam_check_host_attr option can be emulated with:

(&(objectClass=posixAccount)(uid=$username)(|(host=$hostname)(host=$fqdn)(host=\\*)))

This option may be specified multiple times and all specified
searches should at least return one entry for access to be
granted.

pam_password_prohibit_message "MESSAGE"
If this option is set password modification using pam_ldap will
be denied and the specified message will be presented to the user
instead. The message can be used to direct the user to an alter-
native means of changing their password.

reconnect_invalidate DB,DB,...
If this option is set, nslcd will try to flush the specified ex-
ternal caches on start-up and whenever a connection to the LDAP
server is re-established after an error.

DB can refer to one of the nsswitch maps, in which case nscd is
contacted to flush its cache for the specified database. If DB
is nfsidmap, nfsidmap is contacted to clear its cache.

Using this option ensures that external caches are cleared of in-
correct information (typically the absence of users) that may be
present due to unavailability of the LDAP server.

cache CACHE TIME [TIME]
Configure the time entries are kept in the specified internal
cache.

The first TIME value specifies the time to keep found entries in
the cache. The second TIME value specifies to the time to remem-
ber that a particular entry was not found. If the second parame-
ter is absent, it is assumed to be the same as the first.

Time values are specified as a number followed by an s for sec-
onds, m for minutes, h for hours or d for days. Use 0 or off to
disable the cache.

Currently, only the dn2uid cache is supported that is used to re-
member DN to username lookups that are used when the member at-
tribute is used. The default time value for this cache is 15m.

SUPPORTED MAPS
The following maps are supported. They are referenced as MAP in the op-
tions above.

alias[es]
Mail aliases. Note that most mail servers do not use the NSS in-
terface for requesting mail aliases and parse /etc/aliases on
their own.

ether[s]
Ethernet numbers (mac addresses).

group Posix groups.

host[s]
Host names.

netgroup
Host and user groups used for access control.

network[s]
Network numbers.

passwd Posix users.

protocol[s]
Protocol definitions (like in /etc/protocols).

rpc Remote procedure call names and numbers.

service[s]
Network service names and numbers.

shadow Shadow user password information.

ATTRIBUTE MAPPING EXPRESSIONS
For some attributes a mapping expression may be used to construct the
resulting value. This is currently only possible for attributes that do
not need to be used in search filters. The expressions are a subset of
the double quoted string expressions in the Bourne (POSIX) shell. In-
stead of variable substitution, attribute lookups are done on the cur-
rent entry and the attribute value is substituted. The following ex-
pressions are supported:

"${attr}" (or "$attr" for short)
will substitute the value of the attribute

"${attr:-word}"
(use default) will substitute the value of the attribute or, if
the attribute is not set or empty substitute the word

"${attr:+word}"
(use alternative) will substitute word if attribute is set, oth-
erwise substitute the empty string

"${attr:offset:length}"
will substitute length characters (actually bytes) starting from
position offset (which is counted starting at zero); the substi-
tuted string is truncated if it is too long; in particular, it
can be of length zero (if length is zero or offset falls out of
the original string)

"${attr#word}"
remove the shortest possible match of word from the left of the
attribute value

"${attr##word}"
remove the longest possible match of word from the left of the
attribute value (pynslcd only)

"${attr%word}"
remove the shortest possible match of word from the right of the
attribute value (pynslcd only)

"${attr%%word}"
remove the longest possible match of word from the right of the
attribute value (pynslcd only)

Only the # matching expression is supported in nslcd and only with the ?
wildcard symbol. The pynslcd implementation supports full matching.

Quote ("), dollar ($) and backslash (\) characters should be escaped
with a backslash (\).

The expressions are inspected to automatically fetch the appropriate at-
tributes from LDAP. Some examples to demonstrate how these expressions
may be used in attribute mapping:

map shadow shadowFlag "${shadowFlag:-0}"
use the shadowFlag attribute, using the value 0 as default

map passd homeDirectory "${homeDirectory:-/home/$uid}"
use the uid attribute to build a homeDirectory value if that at-
tribute is missing

map shadow shadowExpire "${isDisabled:+100}"
if the isDisabled attribute is set, return 100, otherwise leave
value empty

map shadow userPassword "${userPassword#{crypt\}}"
strip the {crypt} prefix from the userPassword attribute, return-
ing the raw hash value

FILES
/etc/nslcd.conf
the main configuration file

/etc/nsswitch.conf
Name Service Switch configuration file