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.