Apache HTTP Server Version 2.2
Description: | Allows an LDAP directory to be used to store the database for HTTP Basic authentication. |
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Status: | Extension |
Module Identifier: | authnz_ldap_module |
Source File: | mod_authnz_ldap.c |
Compatibility: | Available in version 2.1 and later |
This module provides authentication front-ends such as
mod_auth_basic
to authenticate users through
an ldap directory.
mod_authnz_ldap
supports the following features:
When using mod_auth_basic
, this module is invoked
via the AuthBasicProvider
directive with the ldap
value.
There are two phases in granting access to a user. The first
phase is authentication, in which the mod_authnz_ldap
authentication provider verifies that the user's credentials are valid.
This is also called the search/bind phase. The second phase is
authorization, in which mod_authnz_ldap
determines
if the authenticated user is allowed access to the resource in
question. This is also known as the compare
phase.
mod_authnz_ldap
registers both an authn_ldap authentication
provider and an authz_ldap authorization handler. The authn_ldap
authentication provider can be enabled through the
AuthBasicProvider
directive
using the ldap
value. The authz_ldap handler extends the
Require
directive's authorization types
by adding ldap-user
, ldap-dn
and ldap-group
values.
During the authentication phase, mod_authnz_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_authnz_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_authnz_ldap
attempts to determine if the user is authorized to access the
resource. Many of these checks require
mod_authnz_ldap
to do a compare operation on the
LDAP server. This is why this phase is often referred to as the
compare phase. mod_authnz_ldap
accepts the
following Require
directives to determine if the credentials are acceptable:
Require ldap-user
directive, and the
username in the directive matches the username passed by the
client.Require
ldap-dn
directive, and the DN in the directive matches
the DN fetched from the LDAP directory.Require ldap-group
directive, and
the DN fetched from the LDAP directory (or the username
passed by the client) occurs in the LDAP group.Require ldap-attribute
directive, and the attribute fetched from the LDAP directory
matches the given value.Require ldap-filter
directive, and the search filter successfully finds a single user
object that matches the dn of the authenticated user.Other Require
values may also
be used which may require loading additional authorization modules.
Note that if you use a Require
value from another authorization module, you will need to ensure that
AuthzLDAPAuthoritative
is set to off
to allow the authorization phase to fall
back to the module providing the alternate
Require
value. When no
LDAP-specific Require
directives
are used, authorization is allowed to fall back to other modules
as if AuthzLDAPAuthoritative
was set to off
.
Require valid-user
directive. (requires mod_authz_user
)Require group
directive, and
mod_authz_groupfile
has been loaded with the
AuthGroupFile
directive set.mod_authnz_ldap
uses the following directives during the
compare phase:
AuthLDAPURL |
The attribute specified in the
URL is used in compare operations for the Require
ldap-user operation. |
AuthLDAPCompareDNOnServer |
Determines the behavior of the
Require ldap-dn directive. |
AuthLDAPGroupAttribute |
Determines the attribute to
use for comparisons in the Require ldap-group
directive. |
AuthLDAPGroupAttributeIsDN |
Specifies whether to use the
user DN or the username when doing comparisons for the
Require ldap-group directive. |
Apache's Require
directives are used during the authorization phase to ensure that
a user is allowed to access a resource. mod_authnz_ldap extends the
authorization types with ldap-user
, ldap-dn
,
ldap-group
, ldap-attribute
and
ldap-filter
. Other authorization types may also be
used but may require that additional authorization modules be loaded.
The Require ldap-user
directive specifies what
usernames can access the resource. Once
mod_authnz_ldap
has retrieved a unique DN from the
directory, it does an LDAP compare operation using the username
specified in the Require ldap-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 surrounded with double quotes. Multiple users can also be
granted access by using multiple Require ldap-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 ldap-user "Barbara Jenson"
Require ldap-user "Fred User"
Require ldap-user "Joe Manager"
Because of the way that mod_authnz_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
ldap-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 ldap-user bjenson fuser jmanager
This directive specifies an LDAP group whose members are allowed access. It takes the distinguished name of the LDAP group. Note: Do not surround the group name with quotes. 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 ldap-group cn=Administrators, o=Airius
Behavior of this directive is modified by the AuthLDAPGroupAttribute
and
AuthLDAPGroupAttributeIsDN
directives.
The Require ldap-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 ldap-dn
, then
authorization is granted. Note: do not surround the distinguished
name with quotes.
The following directive would grant access to a specific DN:
Require ldap-dn cn=Barbara Jenson, o=Airius
Behavior of this directive is modified by the AuthLDAPCompareDNOnServer
directive.
The Require ldap-attribute
directive allows the
administrator to grant access based on attributes of the authenticated
user in the LDAP directory. If the attribute in the directory
matches the value given in the configuration, access is granted.
The following directive would grant access to anyone with the attribute employeeType = active
Require ldap-attribute employeeType=active
Multiple attribute/value pairs can be specified on the same line
separated by spaces or they can be specified in multiple
Require ldap-attribute
directives. The effect of listing
multiple attribute/values pairs is an OR operation. Access will be
granted if any of the listed attribute values match the value of the
corresponding attribute in the user object. If the value of the
attribute contains a space, only the value must be within double quotes.
The following directive would grant access to anyone with the city attribute equal to "San Jose" or status equal to "Active"
Require ldap-attribute city="San Jose" status=active
The Require ldap-filter
directive allows the
administrator to grant access based on a complex LDAP search filter.
If the dn returned by the filter search matches the authenticated user
dn, access is granted.
The following directive would grant access to anyone having a cell phone and is in the marketing department
Require ldap-filter &(cell=*)(department=marketing)
The difference between the Require ldap-filter
directive and the
Require ldap-attribute
directive is that ldap-filter
performs a search operation on the LDAP directory using the specified search
filter rather than a simple attribute comparison. If a simple attribute
comparison is all that is required, the comparison operation performed by
ldap-attribute
will be faster than the search operation
used by ldap-filter
especially within a large directory.
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 ldap-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 pager, 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. 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, see the mod_ldap
directives LDAPTrustedClientCert
, LDAPTrustedGlobalCert
and LDAPTrustedMode
.
An optional second parameter can be added to the
AuthLDAPURL
to override
the default connection type set by LDAPTrustedMode
.
This will allow the connection established by an ldap:// Url
to be upgraded to a secure connection on the same port.
To use SSL, see the mod_ldap
directives LDAPTrustedClientCert
, LDAPTrustedGlobalCert
and LDAPTrustedMode
.
To specify a secure LDAP server, use ldaps:// in the
AuthLDAPURL
directive, instead of ldap://.
When this module performs authentication, LDAP attributes specified
in the AuthLDAPUrl
directive are placed in environment variables with the prefix "AUTHENTICATE_".
If the attribute field contains the username, common name and telephone number of a user, a CGI program will have access to this information without the need to make a second independent LDAP query to gather this additional information.
This has the potential to dramatically simplify the coding and configuration required in some web applications.
Normally, FrontPage uses FrontPage-web-specific user/group
files (i.e., the mod_authn_file
and
mod_authz_groupfile
modules) 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" AuthGroupFile mygroupfile Require group mygroupfile
FrontPage restricts access to a web by adding the Require
valid-user
directive to the .htaccess
files. 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. By substituting the ldap-group with group file authorization,
Apache is allowed to consult the local user file (which is managed by
FrontPage) - instead of LDAP - when handling authorizing the user.
Once directives have been added as specified above, FrontPage users will be able to perform all management operations from the FrontPage client.
mod_authn_file
user file.
The user ID is ideal for this.mod_auth_basic
,
mod_authn_file
and
mod_authz_groupfile
in order to
use FrontPage support. This is because Apache will still use
the mod_authz_groupfile
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_authnz_ldap
has to be able to grab
the AuthGroupFile
directive that is found in FrontPage .htaccess
files so that it knows where to look for the valid user list. If
the mod_authnz_ldap
directives aren't in the same
.htaccess
file as the FrontPage directives, then
the hack won't work, because mod_authnz_ldap
will
never get a chance to process the .htaccess
file,
and won't be able to find the FrontPage-managed user file.Description: | Determines if other authentication providers are used when a user can be mapped to a DN but the server cannot successfully bind with the user's credentials. |
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Syntax: | AuthLDAPBindAuthoritativeoff|on |
Default: | AuthLDAPBindAuthoritative on |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_authnz_ldap |
Compatibility: | Available in versions later than 2.2.14 |
By default, subsequent authentication providers are only queried if a
user cannot be mapped to a DN, but not if the user can be mapped to a DN and their
password cannot be verified with an LDAP bind.
If AuthLDAPBindAuthoritative
is set to off, other configured authentication modules will have
a chance to validate the user if the LDAP bind (with the current user's credentials)
fails for any reason.
This allows users present in both LDAP and
AuthUserFile
to authenticate
when the LDAP server is available but the user's account is locked or password
is otherwise unusable.
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: | Extension |
Module: | mod_authnz_ldap |
An optional DN used to bind to the server when searching for
entries. If not provided, mod_authnz_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: | Extension |
Module: | mod_authnz_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: | Language to charset conversion configuration file |
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Syntax: | AuthLDAPCharsetConfig file-path |
Context: | server config |
Status: | Extension |
Module: | mod_authnz_ldap |
The AuthLDAPCharsetConfig
directive sets the location
of the language to charset conversion configuration file. File-path is relative
to the ServerRoot
. This file specifies
the list of language extensions to character sets.
Most administrators use the provided charset.conv
file, which associates common language extensions to character sets.
The file contains lines in the following format:
Language-Extension charset [Language-String] ...
The case of the extension does not matter. Blank lines, and lines
beginning with a hash character (#
) are ignored.
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: | Extension |
Module: | mod_authnz_ldap |
When set, mod_authnz_ldap
will use the LDAP
server to compare the DNs. This is the only foolproof way to
compare DNs. mod_authnz_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_authnz_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: | Extension |
Module: | mod_authnz_ldap |
This directive specifies when mod_authnz_ldap
will
de-reference aliases during LDAP operations. The default is
always
.
Description: | LDAP attributes used to check for group membership |
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Syntax: | AuthLDAPGroupAttribute attribute |
Default: | AuthLDAPGroupAttribute member uniquemember |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_authnz_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_authnz_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: | Extension |
Module: | mod_authnz_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_authnz_ldap
will check if the group has
cn=Babs Jenson, o=Airius
as a member. If this
directive is not set, then mod_authnz_ldap
will
check if the group has bjenson
as a member.
Description: | Use the value of the attribute returned during the user query to set the REMOTE_USER environment variable |
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Syntax: | AuthLDAPRemoteUserAttribute uid |
Default: | none |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_authnz_ldap |
If this directive is set, the value of the
REMOTE_USER
environment variable will be set to the
value of the attribute specified. Make sure that this attribute is
included in the list of attributes in the AuthLDAPUrl definition,
otherwise this directive will have no effect. This directive, if
present, takes precedence over AuthLDAPRemoteUserIsDN. This
directive is useful should you want people to log into a website
using an email address, but a backend application expects the
username as a userid.
Description: | Use the DN of the client username to set the REMOTE_USER environment variable |
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Syntax: | AuthLDAPRemoteUserIsDN on|off |
Default: | AuthLDAPRemoteUserIsDN off |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_authnz_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: | URL specifying the LDAP search parameters |
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Syntax: | AuthLDAPUrl url [NONE|SSL|TLS|STARTTLS] |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_authnz_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_authnz_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_authnz_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 more 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))
.
An optional parameter can be added to allow the LDAP Url to override the connection type. This parameter can be one of the following:
ldap://
on port 389.ldaps://
See above for examples of AuthLDAPURL
URLs.
When AuthLDAPURL
is enabled in a particular context, but some other module has performed
authentication for the request, the server will try to map the username to a DN
during authorization regardless of whether or not LDAP-specific requirements
are present. To ignore the failures to map a username to a DN during
authorization, set
AuthzLDAPAutoritative
to "off".
Description: | Prevent other authentication modules from authenticating the user if this one fails |
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Syntax: | AuthzLDAPAuthoritative on|off |
Default: | AuthzLDAPAuthoritative on |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_authnz_ldap |
Set to off
if this module should let other
authorization modules attempt to authorize the user, should
authorization 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).
When no LDAP-specific Require
directives
are used, authorization is allowed to fall back to other modules
as if AuthzLDAPAuthoritative
was set to off
.