Ubuntu Manpage: nslcd.conf - configuration file for LDAP nameservice daemon

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
       historically 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 connection 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 argument 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 multiple
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 directory 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 option 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 applicable 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 authentication.

sasl_realm REALM
Specifies the SASL realm to be used when performing SASL authentication.

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 described in the ldap.conf(5) manual
page.

sasl_canonicalize yes|no
Determines whether the LDAP server host name should be canonicalised. 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 otherwise
supported for base values and not all LDAP server configurations 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 policy 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 any
attribute as it is available in the directory.

If the NEWATTRIBUTE is presented in quotes (") it is treated as an expression which will be
evaluated to build up the actual value used. See the section on attribute mapping expressions
below 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
attribute may be mapped with an expression. For passwd entries the following attributes may be
mapped with an expression: userPassword, gidNumber, gecos, homeDirectory and loginShell. For
shadow entries the following attributes may be mapped with an expression: userPassword,
shadowLastChange, shadowMin, shadowMax, shadowWarning, 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.
objectSid:S-1-5-21-3623811015-3361044348-30300820).

By default all userPassword attributes are mapped to the unmatchable password ("*") to avoid
accidentally leaking password information.

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 specified 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 seconds.

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 certificate. 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 authentication.

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

tls_ciphers CIPHERS
Specifies the ciphers to use for TLS. See your TLS implementation'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 Revocation 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 returned 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 local 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 local 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
finding 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 option is not recommended for most configurations.

nss_disable_enumeration yes|no
If this option is set, functions which cause all user/group entries 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 typically 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, netgroup, 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 requested and handled from the LDAP
server when performing user authentication. 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 credentials after BIND (authentication)
to ensure that the BIND operation 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 operation
(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, $domain, $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 authorizedService 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
alternative means of changing their password.

reconnect_invalidate DB,DB,...
If this option is set, nslcd will try to flush the specified external 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 incorrect 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 remember that a particular entry was not found. If the second parameter
is absent, it is assumed to be the same as the first.

Time values are specified as a number followed by an s for seconds, 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 remember DN to username lookups that
are used when the member attribute 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 options above.

       alias[es]
              Mail  aliases.   Note  that  most  mail  servers  do not use the NSS interface 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.  Instead of  variable  substitution,
       attribute  lookups  are  done on the current entry and the attribute value is substituted.  The following
       expressions 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, otherwise substitute the empty string

       ${attr:offset:length}
              will substitute length characters (actually bytes) starting from position offset (which is counted
              starting at zero); the substituted 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 attributes from LDAP.  Some examples
       to demonstrate how these expressions may be used in attribute mapping:

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

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

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

       "${userPassword#{crypt\}}"
              strip the {crypt} prefix from the userPassword attribute, returning the raw hash value

FILES

       /etc/nslcd.conf
              the main configuration file

       /etc/nsswitch.conf
              Name Service Switch configuration file

AUTHOR

       This manual was written by Arthur de Jong <arthur@arthurdejong.org>  and  is  based  on  the  nss_ldap(5)
       manual developed by PADL Software Pty Ltd.

Version 0.9.12                                      Nov 2021                                       nslcd.conf(5)