Section: Maintenance Commands (8)
Updated: 14 January 2005
basic_ldap_auth - LDAP authentication helper for Squid
LDAP server name
" -f "
LDAP search filter
LDAP server name
allows Squid to connect to a LDAP directory to
validate the user name and password of Basic HTTP authentication.
LDAP options are specified as parameters on the command line,
while the username(s) and password(s) to be checked against the
LDAP directory are specified on subsequent lines of input to the
helper, one username/password pair per line separated by a space.
As expected by the basic authentication construct of Squid, after
specifying a username and password followed by a new line, this
helper will produce either
on the following line to show if the specified credentials are correct
according to the LDAP directory.
The program has two major modes of operation. In the default mode
of operation the users DN is constructed using the base DN and
user attribute. In the other mode of operation a search
filter is used to locate valid user DN's below the base DN.
- -b basedn
Specifies the base DN under which the users are located.
- -f filter
to locate the user DN. Required if the users
are in a hierarchy below the base DN, or if the login name is
not what builds the user specific part of the users DN.
The search filter can contain up to 15 occurrences of
which will be replaced by the username, as in
for RFC2037 directories. For a detailed description of LDAP search
filter syntax see RFC2254.
Will crash if other
are used, or if more than 15
- -u userattr
Specifies the name of the DN attribute that contains the username/login.
Combined with the base DN to construct the users DN when no search filter
is specified (
option). Defaults to
This can only be done if all your users are located directly under
the same position in the LDAP tree and the login name is used for naming
each user object. If your LDAP tree does not match these criteria or if
you want to filter who are valid users then you need to use a search filter
to search for your users DN (
- -U passwordattr
to verify the users password.
is the LDAP attribute storing the users password.
- -s base|one|sub
Search scope when performing user DN searches specified
option. Defaults to
level below the base object or
below the base object
- -D binddn -w password
The DN and password to bind as while performing searches. Required by the
flag if the directory does not allow anonymous searches.
As the password needs to be printed in plain text in your Squid configuration
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.
- -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.
Use a persistent LDAP connection. Normally the LDAP connection
is only open while validating a username 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.
Only bind once per LDAP connection. Some LDAP servers do not
allow re-binding as another user after a successful
The use of this option always opens a new connection for each
login attempt. If combined with the
option for persistent
LDAP connection then the connection used for searching for the
user DN is kept persistent but a new connection is opened
to verify each users password once the DN is found.
Do not follow referrals
- -a never|always|search|find
when to dereference aliases. Defaults to
dereference aliases (default),
dereference aliases, only during a
or only to
the base object.
- -H ldap_uri
Specify the LDAP server to connect to by LDAP URI (requires OpenLDAP libraries).
Servers can also be specified last on the command line.
- -h ldap_server
Specify the LDAP server to connect to. Servers can also be specified last
on the command line.
- -p ldap_port
Specify an alternate TCP port where the LDAP server is listening if
other than the default LDAP port 389. Can also be specified within the
server specification by using servername:port syntax.
- -v 2|3
LDAP protocol version. Defaults to
if not specified.
Use TLS encryption
- -S certpath
Enable LDAP over SSL (requires Netscape LDAP API libraries)
- -c connect_timeout
used when connecting to LDAP servers (requires
Netscape LDAP API libraries)
- -t search_timeout
Specify time limit on LDAP search operations
Debug mode where each step taken will get reported in detail.
Useful for understanding what goes wrong if the results is
not what is expected.
For directories using the RFC2307 layout with a single domain, all
you need to specify is usually the base DN under where your users
are located and the server name:
basic_ldap_auth -b ou=people,dc=your,dc=domain ldapserver
If you have sub-domains then you need to use a search filter approach
to locate your user DNs as these can no longer be constructed directly
from the base DN and login name alone:
basic_ldap_auth -b dc=your,dc=domain -f uid=%s ldapserver
And similarly if you only want to allow access to users having a
basic_ldap_auth -b dc=your,dc=domain -f (&(uid=%s)(specialattribute=value)) ldapserver
Or if the user attribute of the user DN is
and you do not want to have to search for the users then you could use something
like the following example for Active Directory:
basic_ldap_auth -u cn -b cn=Users,dc=your,dc=domain ldapserver
If you want to search for the user DN and your directory does not allow
anonymous searches then you must also use the
flags to specify a user DN and password to log in as to perform the searches, as in the
following complex Active Directory example
basic_ldap_auth -P -R -b dc=your,dc=domain -D cn=squid,cn=users,dc=your,dc=domain -w secretsquidpassword -f (&(userPrincipalName=%s)(objectClass=Person)) activedirectoryserver
When constructing search filters it is strongly recommended to test the filter
before you attempt to use
This to verify that the filter matches what you expect.
This program is written by
Glenn Newton <email@example.com>
Henrik Nordstrom <firstname.lastname@example.org>
This manual is written by
Henrik Nordstrom <email@example.com>
* Copyright (C) 1996-2019 The Squid Software Foundation and contributors
* Squid software is distributed under GPLv2+ license and includes
* contributions from numerous individuals and organizations.
* Please see the COPYING and CONTRIBUTORS files for details.
This program and documentation is copyright to the authors named above.
Distributed under the GNU General Public License (GNU GPL) version 2 or later (GPLv2+).
Questions on the usage of this program can be sent to the
Squid Users mailing list
Or to your favorite LDAP list/friend if the question is more related to
LDAP than Squid.
Bug reports need to be made in English.
for details of what you need to include with your bug report.
Report bugs or bug fixes using http://bugs.squid-cache.org/
Report serious security bugs to
Squid Bugs <firstname.lastname@example.org>
Report ideas for new improvements to the
Squid Developers mailing list
Your favorite LDAP documentation.
- The String Representation of LDAP Search Filters,
The Squid FAQ wiki
The Squid Configuration Manual