Using LDAP for Apache Authentication

This method authenticates using Apache 2.0/2.2 and the LDAP authentication modules on Linux (supplied by default with most Linux distros) and an LDAP server. LDAP can be used to authenticate user accounts on Linux and other computer systems as well as web site logins.

Try this out with your Apache server authenticating to our open LDAP server using our Three Stooges example.

 

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Apache LDAP modules:

Note that the following configurations work if the LDAP modules are enabled:

• Apache 2.0 (Red Hat Enterprise 4/CentOS4): mod_ldap , mod_auth_ldap
• Apache 2.2 (Red Hat Enterprise 5/CentOS 5): mod_ldap , mod_authnz_ldap

These are turned on by default. See /etc/httpd/conf/httpd.conf

• Apache 2.0:

  LoadModule ldap_module modules/mod_ldap.so
  LoadModule auth_ldap_module modules/mod_auth_ldap.so
                  

• Apache 2.2:

  LoadModule ldap_module modules/mod_ldap.so
  LoadModule authnz_ldap_module modules/mod_authnz_ldap.so
                  

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Apache Authentication Configuration:

Apache 2.0:

Authenticate to an Open LDAP server. (No bind name/password required to access LDAP server)

File: httpd.conf (portion)

..
...

<Directory /var/www/html


>
   AuthType Basic
   AuthName "Stooges Web Site: Login with email address"
   AuthLDAPURL ldap://ldap.yo-linux.com:389/o=stooges?mail
   require valid-user
</Directory>
...
..
                

or create the file /var/www/html/.htaccess

AuthName "Stooges Web Site: Login with email address"
AuthType Basic
AuthLDAPURL ldap://ldap.your-domain


.com:389/o=stooges?mail
require valid-user
                

Point your browser to http://localhost/
Login with the user id "[e-mail]" and password "larrysecret".
You will be asked to use a user id (email address) and password to enter the site.

Bind with a bind DN: (password protected LDAP repository)

File: httpd.conf (portion)

..
...

<Directory /var/www/html


>
   AuthType Basic
   AuthName "Stooges Web Site: Login with email address"
   AuthLDAPEnabled on
   AuthLDAPURL ldap://ldap.your-domain


.com:389/o=stooges?mail
   AuthLDAPBindDN "cn=StoogeAdmin,o=stooges"
   AuthLDAPBindPassword secret1



   require valid-user
</Directory>
...
..
                

Examples:

• require valid-user : Allow all users if authentication (password) is correct.
• require user greg phil bob : Allow only greg phil bob to login.
• require group accounting : Allow only users in group "accounting" to authenticate.

This example specified the use of the email address as a login id. If using user id's specify:

AuthLDAPURL ldap://ldap.your-domain .com:389/o=stooges?uid

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Apache 2.2:

Authenticate using Apache httpd 2.2 AuthzLDAP:

User Authentication:

File: httpd.conf (portion)

..
...

<Directory /var/www/html


>
   AuthType Basic
   AuthName "Stooges Web Site: Login with user id"
   AuthBasicProvider ldap
   AuthzLDAPAuthoritative on
   AuthLDAPURL ldap://ldap.your-domain


.com:389/o=stooges?uid?sub
   AuthLDAPBindDN "cn=StoogeAdmin,o=stooges"
   AuthLDAPBindPassword secret1



   require ldap-user lary curley moe joe bob mary 
</Directory>
...
..
                

There are two configurations for the directive AuthzLDAPAuthoritative :

AuthzLDAPAuthoritative on (default)

AuthzLDAPAuthoritative on

...

require ldap-user lary curley moe joe bob mary 
                

 

AuthzLDAPAuthoritative off

AuthzLDAPAuthoritative off

...

require valid-user
                

This configuration allows a waterfall of other authentication methods to be employed along side LDAP.

Group Authentication:

LDAP LDIF file:

dn: cn=users,ou=group,o=stooges
cn: users
objectClass: top
objectClass: posixGroup
gidNumber: 100
memberUid: larry
memberUid: moe

Apache Configuration:

...

<Directory /var/www/html


>
   Order deny,allow
   Deny from All
   AuthType Basic
   AuthName "Stooges Web Site: Login with user id"
   AuthBasicProvider ldap
   AuthzLDAPAuthoritative on
   AuthLDAPURL ldap://ldap.your-domain


.com:389/o=stooges?uid?sub
   AuthLDAPBindDN "cn=StoogeAdmin,o=stooges"
   AuthLDAPBindPassword secret1



   AuthLDAPGroupAttribute memberUid
   AuthLDAPGroupAttributeIsDN off
   Require ldap-group cn=users,ou=group,o=stooges
   Require ldap-attribute gidNumber=100
   Satisfy any
</Directory>
...

Note:

• Allow users (LDAP attribute: memberUid ) in group gidNumber: 100 of objectClass: posixGroup which match to the login uid , authentication approval.
  The directive AuthLDAPGroupAttribute identifies the attribute to match with the login uid .
• AuthLDAPGroupAttributeIsDN:
  • on (default): Use DN (Distinguished name) cn=Moe Howard,ou=MemberGroupA,o=stooges
  • off: Use username moe
• Multiple Require ldap-group ... statements may be included to allow multiple groups.
• Multiple Require ldap-attribute ... statements may be included to allow multiple groups.
• The directive Satisfy any is required if testing multiple conditions. Only one positive in any of the conditions is required to authenticate. Thus you can combine the following authorization schemes as well:
  • Require ldap-user
  • Require ldap-dn
  • Require ldap-attribute
  • Require ldap-filter

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Concurrent File and LDAP authentication:

Apache can use both File and LDAP authentication concurently. This is sometimes required to run cron jobs with a login where you do not want to use a system login or login managed by a directory server in another department.

<Directory /ABC>
   Order deny,allow
   Deny from All
   AuthType Basic
   AuthBasicProvider file ldap
   AuthName "Directory services login"
   AuthBasicAuthoritative  off
   AuthUserFile /srv/htpasswd
   AuthGroupFile /dev/null
   AuthzLDAPAuthoritative off
   AuthLDAPURL "ldap://ldap.megacorp.com:389/ou=person,o=megacorp.com,c=us?uid?sub"
#  This user created for local cron jobs. It is not a system user and allows
#  the cron job to perform its task.
#  This user is not in the LDAP directory but in the password file /srv/htpasswd
   Require user cronuserjobx



   Require ldap-user usera userb



</Directory>

Note:

• AuthBasicProvider file ldap - Check password "file" authentication then LDAP
• AuthBasicAuthoritative off - Allows fall back to another auth scheme, in this case LDAP
• AuthzLDAPAuthoritative off - Allows fall back to other auth scheme besides LDAP, in this case file

 

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Debugging Apache Authentication:

Set LogLevel debug when debugging authentication. This will log all the LDAP connection events and the LDAP attributes requested.

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Authenticating with Microsoft Active directory using Microsoft's "Unix services for Windows":

AuthLDAPURL ldap://ldap.your-domain .com:389/ou=Employees,ou=Accounts,dc=sos,dc=com?sAMAccountName?sub

Also note that encrypted connections will use the URL prefix "ldaps:// " and the added directives:

• LDAPTrustedCA directory-path/filename
• LDAPTrustedCAType type
  Where the "type" is one of:
  • DER_FILE: file in binary DER format
  • BASE64_FILE: file in Base64 format
  • CERT7_DB_PATH: Netscape certificate database file

Restart Apache after editing the configuration file: service httpd restart for configuration changes to take effect.
See /var/log/httpd/error_log for configuration errors.

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