Apache Module mod_authnz_ldap 236m16

Contents 2w746

• General caveats
• Operation
  • The Authentication Phase
  • The Authorization Phase
• The Require Directives
  • Require ldap-
  • Require ldap-group
  • Require ldap-dn
  • Require ldap-attribute
  • Require ldap-filter
• Examples
• Using TLS
• Using SSL
• Exposing Information
• Using Active Directory
• mod_authnz_ldap
  • How It Works
  • Caveats

General caveats 1v3n2c

This module caches authentication and authorization results based on the configuration of mod_ldap for details of the cache tunables.

Operation 354l6t

There are two phases in granting access to a . The first phase is authentication, in which the mod_authnz_ldap determines if the authenticated is allowed access to the resource in question. This is also known as the compare phase.

Require directive's authorization types by adding ldap-, ldap-dn and ldap-group values.

The Authentication Phase 4g244l

During the authentication phase, mod_authnz_ldap attempts to bind to the directory server using the DN of the entry plus the 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.

1. Generate a search filter by combining the attribute and filter provided in the AuthLDAPURL directive with the name ed by the HTTP client.
2. Search the directory using the generated filter. If the search does not return exactly one entry, deny or decline access.
3. Fetch the distinguished name of the entry retrieved from the search and attempt to bind to the LDAP server using that DN and the ed by the HTTP client. If the bind is unsuccessful, deny or decline access.

The following directives are used during the search/bind phase

The Authorization Phase n6h5o

During the authorization phase, Require directives to determine if the credentials are acceptable:

• Grant access if there is a Require ldap- directive, and the name in the directive matches the name ed by the client.
• Grant access if there is a Require ldap-dn directive, and the DN in the directive matches the DN fetched from the LDAP directory.
• Grant access if there is a Require ldap-group directive, and the DN fetched from the LDAP directory (or the name ed by the client) occurs in the LDAP group or, potentially, in one of its sub-groups.
• Grant access if there is a Require ldap-attribute directive, and the attribute fetched from the LDAP directory matches the given value.
• Grant access if there is a Require ldap-filter directive, and the search filter successfully finds a single object that matches the dn of the authenticated .
• otherwise, deny or decline access

Other Require values may also be used which may require loading additional authorization modules.

• Grant access to all successfully authenticated s if there is a mod_authz_)
• Grant access if there is a AuthGroupFile directive set.
• others...

mod_authnz_ldap uses the following directives during the compare phase:

The Require Directives 503h1o

Apache's Require directives are used during the authorization phase to ensure that a is allowed to access a resource. mod_authnz_ldap extends the authorization types with ldap-, 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.

Since v2.4.8, expressions are ed within the LDAP require directives.

Require ldap- 126b1u

The Require ldap- directive specifies what names can access the resource. Once AuthLDAPURL of ldap://ldap/o=Example?cn (i.e., cn is used for searches), the following Require directives could be used to restrict access:

Require ldap- "Barbara Jenson"
Require ldap- "Fred "
Require ldap- "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- line is needed to all values of the attribute in the '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- bjenson f jmanager

Require ldap-group 201y5h

This directive specifies an LDAP group whose 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=s, o=Example
objectClass: groupOfUniqueNames
uniqueMember: cn=Barbara Jenson, o=Example
uniqueMember: cn=Fred , o=Example

The following directive would grant access to both Fred and Barbara:

Require ldap-group cn=s, o=Example

can also be found within sub-groups of a specified LDAP group if AuthLDAPMaxSubGroupDepth is set to a value greater than 0. For example, assume the following entries exist in the LDAP directory:

dn: cn=Employees, o=Example
objectClass: groupOfUniqueNames
uniqueMember: cn=Managers, o=Example
uniqueMember: cn=s, o=Example
uniqueMember: cn=s, o=Example

dn: cn=Managers, o=Example
objectClass: groupOfUniqueNames
uniqueMember: cn=Bob Ellis, o=Example
uniqueMember: cn=Tom Jackson, o=Example

dn: cn=s, o=Example
objectClass: groupOfUniqueNames
uniqueMember: cn=Barbara Jenson, o=Example
uniqueMember: cn=Fred , o=Example

dn: cn=s, o=Example
objectClass: groupOfUniqueNames
uniqueMember: cn=Allan Jefferson, o=Example
uniqueMember: cn=Paul Tilley, o=Example
uniqueMember: cn=Temporary Employees, o=Example

dn: cn=Temporary Employees, o=Example
objectClass: groupOfUniqueNames
uniqueMember: cn=Jim Swenson, o=Example
uniqueMember: cn=Elliot Rhodes, o=Example

The following directives would allow access for Bob Ellis, Tom Jackson, Barbara Jenson, Fred , Allan Jefferson, and Paul Tilley but would not allow access for Jim Swenson, or Elliot Rhodes (since they are at a sub-group depth of 2):

Require ldap-group cn=Employees, o=Example
AuthLDAPMaxSubGroupDepth 1

Behavior of this directive is modified by the AuthLDAPSubGroupClass directives.

Require ldap-dn b1736

The Require ldap-dn directive allows the 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=Example

Behavior of this directive is modified by the AuthLDAPCompareDNOnServer directive.

Require ldap-attribute 573w5p

The Require ldap-attribute directive allows the to grant access based on attributes of the authenticated 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 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"

Require ldap-filter 2i45t

The Require ldap-filter directive allows the to grant access based on a complex LDAP search filter. If the dn returned by the filter search matches the authenticated 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.

Examples 412u42

• Grant access to anyone who exists in the LDAP directory, using their UID for searches.

  AuthLDAPURL "ldap://ldap1.example.com:389/ou=People, o=Example?uid?sub?(objectClass=*)"
  Require valid-

• The next example is the same as above; but with the fields that have useful defaults omitted. Also, note the use of a redundant LDAP server.

  AuthLDAPURL "ldap://ldap1.example.com ldap2.example.com/ou=People, o=Example"
  Require valid-

• The next example is similar to the previous one, but it uses the common name instead of the UID. Note that this could be problematical if multiple people in the directory share the same 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.example.com/ou=People, o=Example?cn"
  Require valid-

• Grant access to anybody in the s group. The s must authenticate using their UID.

  AuthLDAPURL ldap://ldap.example.com/o=Example?uid
  Require ldap-group cn=s, o=Example

• Grant access to anybody in the group whose name matches the hostname of the virtual host. In this example an expression is used to build the filter.

  AuthLDAPURL ldap://ldap.example.com/o=Example?uid
  Require ldap-group cn=%{SERVER_NAME}, o=Example

• The next example assumes that everyone at Example who carries an alphanumeric pager will have an LDAP attribute of qpagePagerID. The example will grant access only to people (authenticated via their UID) who have alphanumeric pagers:

  AuthLDAPURL ldap://ldap.example.com/o=Example?uid??(qpagePagerID=*)
  Require valid-

• The next example demonstrates the power of using filters to accomplish complicated istrative requirements. Without filters, it would have been necessary to create a new LDAP group and ensure that the group's remain synchronized with the pager s. 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.example.com/o=Example?uid??(|(qpagePagerID=*)(uid=jmanager))
  Require valid-

  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 connects as f, the filter would look like

  (&(|(qpagePagerID=*)(uid=jmanager))(uid=f))

  The above search will only succeed if f 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.

Using TLS h2w1h

To use TLS, see the LDAPTrustedMode.

An optional second parameter can be added to the LDAPTrustedMode. This will allow the connection established by an ldap:// Url to be upgraded to a secure connection on the same port.

Using SSL 512x5v

To use SSL, see the LDAPTrustedMode.

To specify a secure LDAP server, use ldaps:// in the AuthLDAPURL directive, instead of ldap://.

Exposing Information 494j60

when this module performs authentication, ldap attributes specified in the AuthLDAPURL directive are placed in environment variables with the prefix "AUTHENTICATE_".

when this module performs authorization, ldap attributes specified in the AuthLDAPURL directive are placed in environment variables with the prefix "AUTHORIZE_".

If the attribute field contains the name, common name and telephone number of a , 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.

Using Active Directory 101h2f

An Active Directory installation may multiple domains at the same time. To distinguish s between domains, an identifier called a Principle Name (UPN) can be added to a 's entry in the directory. This UPN usually takes the form of the 's name, followed by the domain components of the particular domain, for example [email protected].

You may wish to configure the mod_authnz_ldap module to authenticate s present in any of the domains making up the Active Directory forest. In this way both [email protected] and [email protected] can be authenticated using the same query at the same time.

To make this practical, Active Directory s the concept of a Global Catalog. This Global Catalog is a read only copy of selected attributes of all the Active Directory servers within the Active Directory forest. Querying the Global Catalog allows all the domains to be queried in a single query, without the query spanning servers over potentially slow links.

If enabled, the Global Catalog is an independent directory server that runs on port 3268 (3269 for SSL). To search for a , do a subtree search for the attribute PrincipalName, with an empty search root, like so:

AuthLDAPBindDN [email protected]
AuthLDAPBind 
AuthLDAPURL ldap://10.0.0.1:3268/?PrincipalName?sub

s will need to enter their Principal Name as a , in the form [email protected].

Using Microsoft FrontPage with mod_authnz_ldap 1u3xu

Normally, FrontPage uses FrontPage-web-specific /group files (i.e., the 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"

How It Works 703m5c

FrontPage restricts access to a web by adding the Require valid- directive to the .htaccess files. The Require valid- directive will succeed for any 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 , whereas FrontPage considers only those people in the local file to be valid. By substituting the ldap-group with group file authorization, Apache is allowed to consult the local file (which is managed by FrontPage) - instead of LDAP - when handling authorizing the .

Once directives have been added as specified above, FrontPage s will be able to perform all management operations from the FrontPage client.

Caveats 2x3r6m

• When choosing the LDAP URL, the attribute to use for authentication should be something that will also be valid for putting into a mod_authn_file file. The ID is ideal for this.
• When adding s via FrontPage, FrontPage s should choose names that already exist in the LDAP directory (for obvious reasons). Also, the that the enters into the form is ignored, since Apache will actually be authenticating against the in the LDAP database, and not against the in the local file. This could cause confusion for web s.
• Apache must be compiled with mod_authz_groupfile group file for determine the extent of a 's access to the FrontPage web.
• The directives must be put in the .htaccess files. Attempting to put them inside mod_authnz_ldap will never get a chance to process the .htaccess file, and won't be able to find the FrontPage-managed file.