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ext_ldap_group_acl - Man Page


ext_ldap_group_acl — Squid LDAP external acl group helper

Version 2.18


ext_ldap_group_acl -b base-DN -f filter [ options ] [ server [ ':' port ] | URI ] ...


ext_ldap_group_acl allows Squid to connect to a LDAP directory to authorize users via LDAP groups. LDAP options are specified as parameters on the command line, while the username(s) and group(s) to be checked against the LDAP directory are specified on subsequent lines of input to the helper, one username/group pair per line separated by a space.

As expected by the external_acl_type construct of Squid, after specifying a username and group followed by a new line, this helper will produce either OK or ERR on the following line to show if the user is a member of the specified group.

The program operates by searching with a search filter based on the users user name and requested group, and if a match is found it is determined that the user belongs to the group.


-a never|always|search|find

When to dereference aliases. Defaults to 'never'

never dereference aliases (default), always dereference aliases, only during a search or only to find the base object

-b basedn

REQUIRED. Specifies the base DN under which the groups are located.

-B basedn

Specifies the base DN under which the users are located (if different)

-c connect_timeout

Specify timeout used when connecting to LDAP servers (requires Netscape LDAP API libraries)


Debug mode where each step taken will get reported in detail. Useful for understanding what goes wrong if the result is not what was expected.

-D binddn -w password

The DN and password to bind as while performing searches. Required if the LDAP directory does not allow anonymous searches.

As the password needs to be printed in plain text in your Squid configuration and will be sent on the command line to the helper it is strongly recommended to use a account with minimal associated privileges.  This to limit the damage in case someone could get hold of a copy of your Squid configuration file or extracts the password used from a process listing.

-D binddn -W secretfile

The DN and the name of a file containing the password to bind as while performing searches.

Less insecure version of the former parameter pair with two advantages: The password does not occur in the process listing,  and the password is not being compromised if someone gets the squid  configuration file without getting the secretfile.

-E certpath

Enable LDAP over SSL (requires Netscape LDAP API libraries)

-f filter

LDAP search filter used to search the LDAP directory for any matching group memberships. In the filter %u will be replaced by the user name (or DN if the -F or -u options are used) and %g by the requested group name.

-F filter

LDAP search filter used to search the LDAP directory for any matching users. In the filter %s will be replaced by the user name. If % is to be included literally in the filter then use %%


Specifies that the first query argument sent to the helper by Squid is a extension to the basedn and will be temporarily added in front of the global basedn for this query.

-h ldapserver

Specify the LDAP server to connect to

-H ldapuri

Specify the LDAP server to connect to by a LDAP URI (requires OpenLDAP libraries)


Strip Kerberos Realm component from user names (@ separated)

-p ldapport

Specify an alternate TCP port where the LDAP server is listening if other than the default LDAP port 389.


Use a persistent LDAP connection. Normally the LDAP connection is only open while verifying a users group membership to preserve resources at the LDAP server. This option causes the LDAP connection to be kept open, allowing it to be reused for further user validations. Recommended for larger installations.


Do not follow referrals

-s base|one|sub

search scope. Defaults to sub

base object only,

one level below the base object or

subtree below the base object


Strip NT domain name component from user names (/ or \ separated)

-t search_timeout

Specify time limit on LDAP search operations

-u attr

LDAP attribute used to construct the user DN from the user name and base dn without needing to search for the user. A maximum of 16 occurrences of %s are supported.

-v 2|3

LDAP protocol version. Defaults to 3 if not specified.


Use TLS encryption


This helper is intended to be used as an external_acl_type helper in squid.conf .

external_acl_type ldap_group %LOGIN /path/to/ext_ldap_group_acl ...
acl group1 external ldap_group Group1
acl group2 external ldap_group Group2

NOTE: When constructing search filters it is recommended to first test the filter using ldapsearch to verify that the filter matches what you expect before you attempt to use ext_ldap_group_acl


This program was written by Flavio Pescuma <flavio@marasystems.com> Henrik Nordstrom <hno@squid-cache.org>

Based on prior work in squid_ldap_auth by Glen Newton <glen.newton@nrc.ca>

This manual was written by Henrik Nordstrom <hno@marasystems.com>


Questions on the usage of this program can be sent to the Squid Users mailing list <squid-users@lists.squid-cache.org>

Or contact your favorite LDAP list/friend if the question is more related to LDAP than Squid.

Reporting Bugs

Bug reports need to be made in English. See https://wiki.squid-cache.org/SquidFaq/BugReporting for details of what you need to include with your bug report.

Report bugs or bug fixes using https://bugs.squid-cache.org/

Report serious security bugs to Squid Bugs <squid-bugs@lists.squid-cache.org>

Report ideas for new improvements to the Squid Developers mailing list <squid-dev@lists.squid-cache.org>

See Also

squid(8), basic_ldap_auth(8), ldapsearch(1), GPL(7),
Your favorite LDAP documentation
RFC2254 - The String Representation of LDAP Search Filters,
The Squid FAQ wiki https://wiki.squid-cache.org/SquidFaq
The Squid Configuration Manual http://www.squid-cache.org/Doc/config/

Referenced By


30 January 2005