Apache HTTP Server Version 2.0
Description: | Allows an LDAP directory to be used to store the database for HTTP Basic authentication. |
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Status: | Experimental |
Module Identifier: | auth_ldap_module |
Source File: | mod_auth_ldap.c |
Compatibility: | Available in version 2.0.41 and later |
mod_auth_ldap
supports the following features:
There are two phases in granting access to a user. The first
phase is authentication, in which mod_auth_ldap
verifies that the user's credentials are valid. This also called
the search/bind phase. The second phase is
authorization, in which mod_auth_ldap
determines
if the authenticated user is allowed access to the resource in
question. This is also known as the compare
phase.
During the authentication phase, mod_auth_ldap
searches for an entry in the directory that matches the username
that the HTTP client passes. If a single unique match is found,
then mod_auth_ldap
attempts to bind to the
directory server using the DN of the entry plus the password
provided by the HTTP client. Because it does a search, then a
bind, it is often referred to as the search/bind phase. Here are
the steps taken during the search/bind phase.
AuthLDAPURL
directive with
the username passed by the HTTP client.The following directives are used during the search/bind phase
AuthLDAPURL |
Specifies the LDAP server, the base DN, the attribute to use in the search, as well as the extra search filter to use. |
AuthLDAPBindDN |
An optional DN to bind with during the search phase. |
AuthLDAPBindPassword |
An optional password to bind with during the search phase. |
During the authorization phase, mod_auth_ldap
attempts to determine if the user is authorized to access the
resource. Many of these checks require
mod_auth_ldap
to do a compare operation on the
LDAP server. This is why this phase is often referred to as the
compare phase. mod_auth_ldap
accepts the
following Require
directives to determine if the credentials are acceptable:
require
valid-user
directive.require user
directive, and the
username in the directive matches the username passed by the
client.require
dn
directive, and the DN in the directive matches
the DN fetched from the LDAP directory.require group
directive, and
the DN fetched from the LDAP directory (or the username
passed by the client) occurs in the LDAP group.mod_auth_ldap
uses the following directives during the
compare phase:
AuthLDAPURL |
The attribute specified in the
URL is used in compare operations for the require
user operation. |
AuthLDAPCompareDNOnServer |
Determines the behavior of the
require dn directive. |
AuthLDAPGroupAttribute |
Determines the attribute to
use for comparisons in the require group
directive. |
AuthLDAPGroupAttributeIsDN |
Specifies whether to use the
user DN or the username when doing comparisons for the
require group directive. |
Apache's Require
directives are used during the authorization phase to ensure that
a user is allowed to access a resource.
If this directive exists, mod_auth_ldap
grants
access to any user that has successfully authenticated during the
search/bind phase.
The require user
directive specifies what
usernames can access the resource. Once
mod_auth_ldap
has retrieved a unique DN from the
directory, it does an LDAP compare operation using the username
specified in the require user
to see if that username
is part of the just-fetched LDAP entry. Multiple users can be
granted access by putting multiple usernames on the line,
separated with spaces. If a username has a space in it, then it
must be the only user on the line. In this case, multiple users
can be granted access by using multiple require user
directives, with one user per line. For example, with a AuthLDAPURL
of
ldap://ldap/o=Airius?cn
(i.e., cn
is
used for searches), the following require directives could be used
to restrict access:
require user Barbara Jenson
require user Fred User
require user Joe Manager
Because of the way that mod_auth_ldap
handles this
directive, Barbara Jenson could sign on as Barbara
Jenson, Babs Jenson or any other cn
that
she has in her LDAP entry. Only the single require
user
line is needed to support all values of the attribute
in the user's entry.
If the uid
attribute was used instead of the
cn
attribute in the URL above, the above three lines
could be condensed to
require user bjenson fuser jmanager
This directive specifies an LDAP group whose members are allowed access. It takes the distinguished name of the LDAP group. For example, assume that the following entry existed in the LDAP directory:
dn: cn=Administrators, o=Airius
objectClass: groupOfUniqueNames
uniqueMember: cn=Barbara Jenson, o=Airius
uniqueMember: cn=Fred User, o=Airius
The following directive would grant access to both Fred and Barbara:
require group cn=Administrators, o=Airius
Behavior of this directive is modified by the AuthLDAPGroupAttribute
and
AuthLDAPGroupAttributeIsDN
directives.
The require dn
directive allows the administrator
to grant access based on distinguished names. It specifies a DN
that must match for access to be granted. If the distinguished
name that was retrieved from the directory server matches the
distinguished name in the require dn
, then
authorization is granted.
The following directive would grant access to a specific DN:
require dn cn=Barbara Jenson, o=Airius
Behavior of this directive is modified by the AuthLDAPCompareDNOnServer
directive.
AuthLDAPURL ldap://ldap1.airius.com:389/ou=People, o=Airius?uid?sub?(objectClass=*)
require valid-user
AuthLDAPURL ldap://ldap1.airius.com ldap2.airius.com/ou=People, o=Airius
require valid-user
cn
, because a search on cn
must return exactly one entry. That's why
this approach is not recommended: it's a better idea to
choose an attribute that is guaranteed unique in your
directory, such as uid
.
AuthLDAPURL ldap://ldap.airius.com/ou=People, o=Airius?cn
require valid-user
AuthLDAPURL ldap://ldap.airius.com/o=Airius?uid
require group cn=Administrators, o=Airius
qpagePagerID
. The example will grant access
only to people (authenticated via their UID) who have
alphanumeric pagers:
AuthLDAPURL ldap://ldap.airius.com/o=Airius?uid??(qpagePagerID=*)
require valid-user
The next example demonstrates the power of using filters to accomplish complicated administrative requirements. Without filters, it would have been necessary to create a new LDAP group and ensure that the group's members remain synchronized with the pager users. This becomes trivial with filters. The goal is to grant access to anyone who has a filter, plus grant access to Joe Manager, who doesn't have a pager, but does need to access the same resource:
AuthLDAPURL ldap://ldap.airius.com/o=Airius?uid??(|(qpagePagerID=*)(uid=jmanager))
require valid-user
This last may look confusing at first, so it helps to
evaluate what the search filter will look like based on who
connects, as shown below. The text in blue is the part that
is filled in using the attribute specified in the URL. The
text in red is the part that is filled in using the filter
specified in the URL. The text in green is filled in using
the information that is retrieved from the HTTP client. If
Fred User connects as fuser
, the filter would look
like
(&(|(qpagePagerID=*)(uid=jmanager))(uid=fuser))
The above search will only succeed if fuser has a pager. When Joe Manager connects as jmanager, the filter looks like
(&(|(qpagePagerID=*)(uid=jmanager))(uid=jmanager))
The above search will succeed whether jmanager has a pager or not.
To use TLS, simply set the AuthLDAPStartTLS
to on.
Nothing else needs to be done (other than ensure that your LDAP
server is configured for TLS).
If mod_auth_ldap
is linked against the
Netscape/iPlanet LDAP SDK, it will not talk to any SSL server
unless that server has a certificate signed by a known Certificate
Authority. As part of the configuration
mod_auth_ldap
needs to be told where it can find
a database containing the known CAs. This database is in the same
format as Netscape Communicator's cert7.db
database. The easiest way to get this file is to start up a fresh
copy of Netscape, and grab the resulting
$HOME/.netscape/cert7.db
file.
To specify a secure LDAP server, use ldaps:// in the
AuthLDAPURL
directive, instead of ldap://.
Normally, FrontPage uses FrontPage-web-specific user/group
files (i.e., the mod_auth
module) to handle all
authentication. Unfortunately, it is not possible to just
change to LDAP authentication by adding the proper directives,
because it will break the Permissions forms in
the FrontPage client, which attempt to modify the standard
text-based authorization files.
Once a FrontPage web has been created, adding LDAP
authentication to it is a matter of adding the following
directives to every .htaccess
file
that gets created in the web
AuthLDAPURL the url AuthLDAPAuthoritative off AuthLDAPFrontPageHack on
AuthLDAPAuthoritative
must be
off to allow mod_auth_ldap
to decline group
authentication so that Apache will fall back to file
authentication for checking group membership. This allows the
FrontPage-managed group file to be used.
FrontPage restricts access to a web by adding the require
valid-user
directive to the .htaccess
files. If AuthLDAPFrontPageHack
is not
on, the require valid-user
directive will succeed for
any user who is valid as far as LDAP is
concerned. This means that anybody who has an entry in
the LDAP directory is considered a valid user, whereas FrontPage
considers only those people in the local user file to be
valid. The purpose of the hack is to force Apache to consult the
local user file (which is managed by FrontPage) - instead of LDAP
- when handling the require valid-user
directive.
Once directives have been added as specified above, FrontPage users will be able to perform all management operations from the FrontPage client.
mod_auth
user file.
The user ID is ideal for this.mod_auth
in order to
use FrontPage support. This is because Apache will still use
the mod_auth
group file for determine the extent of a
user's access to the FrontPage web..htaccess
files. Attempting to put them inside <Location>
or <Directory>
directives won't work. This
is because mod_auth_ldap
has to be able to grab
the AuthUserFile
directive that is found in FrontPage .htaccess
files so that it knows where to look for the valid user list. If
the mod_auth_ldap
directives aren't in the same
.htaccess
file as the FrontPage directives, then
the hack won't work, because mod_auth_ldap
will
never get a chance to process the .htaccess
file,
and won't be able to find the FrontPage-managed user file.Description: | Prevent other authentication modules from authenticating the user if this one fails |
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Syntax: | AuthLDAPAuthoritative on|off |
Default: | AuthLDAPAuthoritative on |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
Set to off
if this module should let other
authentication modules attempt to authenticate the user, should
authentication with this module fail. Control is only passed on
to lower modules if there is no DN or rule that matches the
supplied user name (as passed by the client).
Description: | Optional DN to use in binding to the LDAP server |
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Syntax: | AuthLDAPBindDN distinguished-name |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
An optional DN used to bind to the server when searching for
entries. If not provided, mod_auth_ldap
will use
an anonymous bind.
Description: | Password used in conjuction with the bind DN |
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Syntax: | AuthLDAPBindPassword password |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
A bind password to use in conjunction with the bind DN. Note
that the bind password is probably sensitive data, and should be
properly protected. You should only use the AuthLDAPBindDN
and AuthLDAPBindPassword
if you
absolutely need them to search the directory.
Description: | Use the LDAP server to compare the DNs |
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Syntax: | AuthLDAPCompareDNOnServer on|off |
Default: | AuthLDAPCompareDNOnServer on |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
When set, mod_auth_ldap
will use the LDAP
server to compare the DNs. This is the only foolproof way to
compare DNs. mod_auth_ldap
will search the
directory for the DN specified with the require dn
directive, then,
retrieve the DN and compare it with the DN retrieved from the user
entry. If this directive is not set,
mod_auth_ldap
simply does a string comparison. It
is possible to get false negatives with this approach, but it is
much faster. Note the mod_ldap
cache can speed up
DN comparison in most situations.
Description: | When will the module de-reference aliases |
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Syntax: | AuthLDAPDereferenceAliases never|searching|finding|always |
Default: | AuthLDAPDereferenceAliases Always |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
This directive specifies when mod_auth_ldap
will
de-reference aliases during LDAP operations. The default is
always
.
Description: | Turn on or off LDAP authentication |
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Syntax: | AuthLDAPEnabled on|off |
Default: | AuthLDAPEnabled on |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
Set to off
to disable
mod_auth_ldap
in certain directories. This is
useful if you have mod_auth_ldap
enabled at or
near the top of your tree, but want to disable it completely in
certain locations.
Description: | Allow LDAP authentication to work with MS FrontPage |
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Syntax: | AuthLDAPFrontPageHack on|off |
Default: | AuthLDAPFronPageHack off |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
See the section on using Microsoft
FrontPage with mod_auth_ldap
.
Description: | LDAP attributes used to check for group membership |
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Syntax: | AuthLDAPGroupAttribute attribute |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
This directive specifies which LDAP attributes are used to
check for group membership. Multiple attributes can be used by
specifying this directive multiple times. If not specified,
then mod_auth_ldap
uses the member
and
uniquemember
attributes.
Description: | Use the DN of the client username when checking for group membership |
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Syntax: | AuthLDAPGroupAttributeIsDN on|off |
Default: | AuthLDAPGroupAttributeIsDN on |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
When set on
, this directive says to use the
distinguished name of the client username when checking for group
membership. Otherwise, the username will be used. For example,
assume that the client sent the username bjenson
,
which corresponds to the LDAP DN cn=Babs Jenson,
o=Airius
. If this directive is set,
mod_auth_ldap
will check if the group has
cn=Babs Jenson, o=Airius
as a member. If this
directive is not set, then mod_auth_ldap
will
check if the group has bjenson
as a member.
Description: | Use the DN of the client username to set the REMOTE_USER environment variable |
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Syntax: | AuthLDAPRemoteUserIsDN on|off |
Default: | AuthLDAPUserIsDN off |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
If this directive is set to on, the value of the
REMOTE_USER
environment variable will be set to the full
distinguished name of the authenticated user, rather than just
the username that was passed by the client. It is turned off by
default.
Description: | Use a secure TLS connection to the LDAP server |
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Syntax: | AuthLDAPStartTLS on|off |
Default: | AuthLDAPStartTLS off |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
If this directive is set to on
,
mod_auth_ldap
will start a secure TLS session
after connecting to the LDAP server. This requires your LDAP
server to support TLS.
Description: | URL specifying the LDAP search parameters |
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Syntax: | AuthLDAPUrl url |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Experimental |
Module: | mod_auth_ldap |
An RFC 2255 URL which specifies the LDAP search parameters to use. The syntax of the URL is
ldap://host:port/basedn?attribute?scope?filter
ldap
. For secure LDAP, use ldaps
instead. Secure LDAP is only available if Apache was linked
to an LDAP library with SSL support.The name/port of the ldap server (defaults to
localhost:389
for ldap
, and
localhost:636
for ldaps
). To
specify multiple, redundant LDAP servers, just list all
servers, separated by spaces. mod_auth_ldap
will try connecting to each server in turn, until it makes a
successful connection.
Once a connection has been made to a server, that
connection remains active for the life of the
httpd
process, or until the LDAP server goes
down.
If the LDAP server goes down and breaks an existing
connection, mod_auth_ldap
will attempt to
re-connect, starting with the primary server, and trying
each redundant server in turn. Note that this is different
than a true round-robin search.
uid
. It's a good
idea to choose an attribute that will be unique across all
entries in the subtree you will be using.one
or
sub
. Note that a scope of base
is
also supported by RFC 2255, but is not supported by this
module. If the scope is not provided, or if base
scope
is specified, the default is to use a scope of
sub
.(objectClass=*)
, which
will search for all objects in the tree. Filters are
limited to approximately 8000 characters (the definition of
MAX_STRING_LEN
in the Apache source code). This
should be than sufficient for any application.When doing searches, the attribute, filter and username passed
by the HTTP client are combined to create a search filter that
looks like
(&(filter)(attribute=username))
.
For example, consider an URL of
ldap://ldap.airius.com/o=Airius?cn?sub?(posixid=*)
. When
a client attempts to connect using a username of Babs
Jenson
, the resulting search filter will be
(&(posixid=*)(cn=Babs Jenson))
.
See above for examples of AuthLDAPURL
URLs.