LDAP authentication

LDAP is an open standard for querying and modifying directory services that is commonly used for authentication, authorization and accounting (AAA). OMERO.server supports the use of an LDAP server to query (but not modify) AAA information for the purposes of automatic user creation.

This allows OMERO users to be automatically created and placed in groups according to your existing institution policies. This can significantly simplify your user administration burden.

The OMERO.server LDAP implementation can handle a number of use cases. For example:

• Allow every “inetOrgPerson” under omero.ldap.base to login
• but restrict access based upon an arbitrary LDAP filter, e.g.

omero.ldap.user_filter=(memberOf=cn=someGoup,ou=Lab,o=College)

• and add that user to some number of groups, e.g.

omero.ldap.new_user_group=:query:(member=@{dn})

How it works

On login, the username provided is searched for in OMERO. If the name does not exist, then the LDAP plugin is queried for a username matching the system-wide user filter. If such an LDAP entry exists and the password matches, a new user with the given username is created, and the user is added to any groups which match the new_user_group setting.

On subsequent logins, the user filter and the password are again checked against the LDAP server, and if there is no longer a match, login is refused. If you would prefer to only have the user_filter applied during user creation and not on every login, see Legacy password providers.

LDAP properties

The LDAP plugin is configured via several configuration properties, all starting with omero.ldap.. The default values for these properties are set in the file etc/omero.properties. An overview of all the properties is outlined in LDAP configuration overview.

Minimum configuration

The following properties are the minimum requirements for logging in to OMERO using LDAP.

omero.ldap.config=true
omero.ldap.urls=ldap://localhost:389
omero.ldap.username=
omero.ldap.password=
omero.ldap.base=ou=example,o=com

After having configured your connection, you can turn LDAP on and off between restarts by setting omero.ldap.config to false. The base property determines where in the LDAP tree searches will begin. No users or groups will be found if they are not under the base provided.

User lookup

Two user properties are used to look up users by login name and, if necessary, create new users based on the information in LDAP.

omero.ldap.user_filter=(objectClass=person)
omero.ldap.user_mapping=omeName=cn,firstName=givenName,lastName=sn,email=mail

omero.ldap.user_filter will be AND’ed to the username query, and can contain any valid LDAP filter string. The username query is taken from the LDAP attribute which gets mapped to “omeName” by omero.ldap.user_mapping. Here, the “cn” is mapped to “omeName”, so the username query is (cn=[login name]). The final query is (&(objectClass=person)(cn=[login name])), which must return a single result to be considered valid.

Group lookup

Three group properties are all concerned with what groups a user will be placed in on creation.

omero.ldap.group_filter=(objectClass=groupOfNames)
omero.ldap.group_mapping=name=cn
omero.ldap.new_user_group=default

The group filter and group mapping work just as the user filter and mapping do, in that the group name query will be AND’d with the group_filter. In this case, the final query would be (&(objectClass=groupOfNames)(cn=[group name])). However, these properties may not be used depending on the value of new_user_group, which can have several different values:

• If not prefixed at all, then the value is simply the name of a group which all users from LDAP should be added to.
• If prefixed with :ou:, then a user’s last organizational unit (OU) will be used as his or her group. For example, the user with the DN “cn=frank,ou=TheLab,ou=LifeSciences,o=TheCollege” will be placed in the group “TheLab”.
• If prefixed with :attribute:, then the rest of the string is taken to be an attribute all of whose values will be taken as group names. For example, omero.ldap.new_user_group=:attribute:memberOf would add a user to all the groups named by memberOf. You can prefix this value with filtered_ to have the group_filter applied to the attribute values, i.e. :filtered_attribute:memberOf will mean that only the values of memberOf which match group_filter will be considered.
• If prefixed with :dn_attribute:, then the rest of the string is taken to be an attribute all of whose values will be taken as group distinguished names. For example, omero.ldap.new_user_group=:dn_attribute:memberOf would add a user to all the groups named by memberOf, where the name of the group is mapped via group_mapping. You can prefix this value with filtered_ to have the group_filter applied to the attribute values, i.e. :filtered_dn_attribute:memberOf will mean that only the values of memberOf which match group_filter will be considered.
• If prefixed with :query:, then the rest of the value is taken as a query to be AND’ed to the group filter. In the query, values from the user such as “@{cn}”, “@{email}”, or “@{dn}” can be used as place holders.
• If prefixed with :bean:, then the rest of the string is the name of a Spring bean which implements the NewUserGroupBean interface. See the developer documentation LDAP plugin design for more info.

Compound Filters

Both the user_filter and the group_filter can contain any valid LDAP filter string. These must be a valid filter in themselves. e.g.

omero.ldap.group_filter=(&(objectClass=groupOfNames)(mail=omero.flag))

This filter is valid and will cause the filter to only match groups that have the mail attribute set to the value omero.flag. When combined with the group_mapping, the final query would be (&(&(objectClass=groupOfNames)(mail=omero.flag))(cn=[group name]))

This is the same as the query (&(objectClass=groupOfNames)(mail=omero.flag)(cn=[group name])) but setting group_filter to (objectClass=groupOfNames)(mail=omero.flag) is not valid as that is not a valid filter on its own.

To restrict the list of groups to just the ones returned by the above query, the following setting is also required to remove unmatched groups:

omero.ldap.new_user_group=:filtered_dn_attribute:memberOf

LDAP configuration overview

Like many pieces of OMERO.server configuration, LDAP-specific configuration is done by specifying extra properties during installation. The default values for the LDAP properties are listed in the etc/omero.properties file inside your OMERO installation directory.

Note

Please remember that once a change has been made, a server restart will be needed.

Change any settings that are necessary via bin/omero config.

• Enable or disable LDAP (true/false)

  bin/omero config set omero.ldap.config true
  

• LDAP server URL string

  bin/omero config set omero.ldap.urls ldap://ldap.example.com:389
  

  Note

  A SSL URL above should look like this: ldaps://ldap.example.com:636

• LDAP server bind DN (if required; can be empty)

  bin/omero config set omero.ldap.username cn=Manager,dc=example,dc=com
  

• LDAP server bind password (if required; can be empty)

  bin/omero config set omero.ldap.password secret
  

• LDAP server base search DN

  bin/omero config set omero.ldap.base dc=example,dc=com
  

• The filter applied to all users; can be empty in which case any LDAP user is valid

  bin/omero config set omero.ldap.user_filter '(objectClass=inetOrgPerson)'
  

• LDAP referral options (defaults to “ignore”; available options are “ignore, “follow” or “throw” as per the JNDI referrals documentation)

  bin/omero config set omero.ldap.referral follow
  

LDAP over SSL

If you are connecting to your server over SSL, that is, if your URL is of the form ldaps://ldap.example.com:636 you will need to configure a key and trust store for Java. See the Server security and firewalls page for more information.

Synchronizing LDAP on user login

This feature allows for LDAP to be considered the authority on user/group membership. With the following settings enabled each time a user logs in to OMERO their LDAP groups will be read from the LDAP server and reflected in OMERO. Enabling this will result in any bespoke OMERO groups that have been created being removed from the user’s profile. The groups will still exist on the server but the association between user and group will not be reflected unless such a link is made in LDAP.

bin/omero config set omero.ldap.sync_on_login true

Legacy password providers

The primary component of the LDAP plugin is the LdapPasswordProvider, which is responsible for creating users, checking their passwords, and adding them to or removing them from groups. The default password provider is the chainedPasswordProvider which first checks LDAP if LDAP is enabled, and then checks JDBC. This can explicitly be enabled by executing the system admin command:

bin/omero config set omero.security.password_provider chainedPasswordProvider

When the LDAP password provider implementation changes, previous versions can be configured as necessary.

chainedPasswordProviderNoSalt

The chainedPasswordProviderNoSalt uses the version of the JDBC password provider without password salting support as available in the OMERO 4.4.x series. To enable it, use:

bin/omero config set omero.security.password_provider chainedPasswordProviderNoSalt

chainedPasswordProvider431

With the 431 password provider, the user filter is only checked on first login and not kept on subsequent logins. This allows for an OMERO admin to change the username of a user in omero to be different than the one kept in LDAP. To enable it, use:

bin/omero config set omero.security.password_provider chainedPasswordProvider431

See also

OMERO.server installation

Installation guide for OMERO.server under UNIX-based platforms

Server security and firewalls

Security pages for OMERO.server

LDAP plugin design

Developer documentation on extending the LDAP plugin yourself.

What are your LDAP requirements?

Forum discussion if you have LDAP requirements that are not covered by the above configuration