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Authenticate Using SASL and LDAP with OpenLDAP

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MongoDB Enterprise provides support for proxy authentication of users. This allows administrators to configure a MongoDB cluster to authenticate users by proxying authentication requests to a specified Lightweight Directory Access Protocol (LDAP) service.

Note

For MongoDB 4.2 (and 4.0.9) Enterprise binaries linked against libldap (such as when running on RHEL), access to the libldap is synchronized, incurring some performance/latency costs.

For MongoDB 4.2 (and 4.0.9) Enterprise binaries linked against libldap_r, there is no change in behavior from earlier MongoDB versions.

Considerations

Warning

MongoDB Enterprise for Windows does not support binding via saslauthd.

  • Linux MongoDB servers support binding to an LDAP server via the saslauthd daemon.
  • Use secure encrypted or trusted connections between clients and the server, as well as between saslauthd and the LDAP server. The LDAP server uses the SASL PLAIN mechanism, sending and receiving data in plain text. You should use only a trusted channel such as a VPN, a connection encrypted with TLS/SSL, or a trusted wired network.

Configure saslauthd

LDAP support for user authentication requires proper configuration of the saslauthd daemon process as well as the MongoDB server.

1

Specify the mechanism.

On systems that configure saslauthd with the /etc/sysconfig/saslauthd file, such as Red Hat Enterprise Linux, Fedora, CentOS, and Amazon Linux AMI, set the mechanism MECH to ldap:

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MECH=ldap

On systems that configure saslauthd with the /etc/default/saslauthd file, such as Ubuntu, set the MECHANISMS option to ldap:

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MECHANISMS="ldap"
2

Adjust caching behavior.

On certain Linux distributions, saslauthd starts with the caching of authentication credentials enabled. Until restarted or until the cache expires, saslauthd will not contact the LDAP server to re-authenticate users in its authentication cache. This allows saslauthd to successfully authenticate users in its cache, even in the LDAP server is down or if the cached users’ credentials are revoked.

To set the expiration time (in seconds) for the authentication cache, see the -t option of saslauthd.

3

Configure LDAP Options with OpenLDAP.

If the saslauthd.conf file does not exist, create it. The saslauthd.conf file usually resides in the /etc folder. If specifying a different file path, see the -O option of saslauthd.

To connect to an OpenLDAP server, update the saslauthd.conf file with the following configuration options:

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ldap_servers: <ldap uri>
ldap_search_base: <search base>
ldap_filter: <filter>

The ldap_servers specifies the uri of the LDAP server used for authentication. In general, for OpenLDAP installed on the local machine, you can specify the value ldap://localhost:389 or if using LDAP over TLS/SSL, you can specify the value ldaps://localhost:636.

The ldap_search_base specifies distinguished name to which the search is relative. The search includes the base or objects below.

The ldap_filter specifies the search filter.

The values for these configuration options should correspond to the values specific for your test. For example, to filter on email, specify ldap_filter: (mail=%n) instead.

OpenLDAP Example

A sample saslauthd.conf file for OpenLDAP includes the following content:

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ldap_servers: ldaps://ad.example.net
ldap_search_base: ou=Users,dc=example,dc=com
ldap_filter: (uid=%u)

To use this sample OpenLDAP configuration, create users with a uid attribute (login name) and place under the Users organizational unit (ou) under the domain components (dc) example and com.

For more information on saslauthd configuration, see http://www.openldap.org/doc/admin24/guide.html#Configuringsaslauthd.

4

Test the saslauthd configuration.

Use testsaslauthd utility to test the saslauthd configuration. For example:

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testsaslauthd -u testuser -p testpassword -f /var/run/saslauthd/mux
  • 0: OK "Success" indicates successful authentication.
  • 0: NO "authentication failed" indicates a username, password, or configuration error.

Modify the file path with respect to the location of the saslauthd directory on the host operating system.

Important

The parent directory of the saslauthd Unix domain socket file specified to security.sasl.saslauthdSocketPath or --setParameter saslauthdPath must grant read and execute (r-x) permissions for either:

  • The user starting the mongod or mongos, or
  • A group to which that user belongs.

The mongod or mongos cannot successfully authenticate via saslauthd without the specified permission on the saslauthd directory and its contents.

Configure MongoDB

1

Add user to MongoDB for authentication.

Add the user to the $external database in MongoDB. To specify the user’s privileges, assign roles to the user.

Changed in version 3.6.3: To use sessions with $external authentication users (i.e. Kerberos, LDAP, x.509 users), the usernames cannot be greater than 10k bytes.

For example, the following adds a user with read-only access to the records database.

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db.getSiblingDB("$external").createUser(
    {
      user : <username>,
      roles: [ { role: "read", db: "records" } ]
    }
)

Add additional principals as needed. For more information about creating and managing users, see User Management Commands.

2

Configure MongoDB server.

To configure the MongoDB server to use the saslauthd instance for proxy authentication, include the following options when starting mongod:

If you use the authorization option to enforce authentication, you will need privileges to create a user.

Use specific saslauthd socket path.

For socket path of /<some>/<path>/saslauthd, set the saslauthdPath to /<some>/<path>/saslauthd/mux, as in the following command line example:

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mongod --auth --setParameter saslauthdPath=/<some>/<path>/saslauthd/mux --setParameter authenticationMechanisms=PLAIN

Include additional options as required for your configuration. For instance, if you wish remote clients to connect to your deployment or your deployment members are run on different hosts, specify the --bind_ip. For more information, see Localhost Binding Compatibility Changes.

Or if using a YAML format configuration file, specify the following settings in the file:

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security:
   authorization: enabled

setParameter:
   saslauthdPath: /<some>/<path>/saslauthd/mux
   authenticationMechanisms: PLAIN

Or, if using the older configuration file format:

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auth=true
setParameter=saslauthdPath=/<some>/<path>/saslauthd/mux
setParameter=authenticationMechanisms=PLAIN

Use default Unix-domain socket path.

To use the default Unix-domain socket path, set the saslauthdPath to the empty string "", as in the following command line example:

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mongod --auth --setParameter saslauthdPath="" --setParameter authenticationMechanisms=PLAIN

Include additional options as required for your configuration. For instance, if you wish remote clients to connect to your deployment or your deployment members are run on different hosts, specify the --bind_ip. For more information, see Localhost Binding Compatibility Changes.

Or if using a YAML format configuration file, specify the following settings in the file:

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security:
   authorization: enabled

setParameter:
   saslauthdPath: ""
   authenticationMechanisms: PLAIN

Or, if using the older configuration file format:

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auth=true
setParameter=saslauthdPath=""
setParameter=authenticationMechanisms=PLAIN

Include additional options as required for your configuration. For instance, if you wish remote clients to connect to your deployment or your deployment members are run on different hosts, specify the net.bindIp setting. For more information, see Localhost Binding Compatibility Changes.

3

Authenticate the user in the mongo shell.

You can authenticate from the command line during connection, or connect first and then authenticate using db.auth() method.

To authenticate when connecting with the mongo shell, run mongo with the following command-line options, substituting <host> and <user>, and enter your password when prompted:

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mongo --host <host> --authenticationMechanism PLAIN --authenticationDatabase '$external' -u <user> -p

Alternatively, connect without supplying credentials and then call the db.auth() method on the $external database. Specify the value "PLAIN" in the mechanism field, the user and password in the user and pwd fields respectively. Use the default digestPassword value (false) since the server must receive an undigested password to forward on to saslauthd, as in the following example:

Tip

Starting in version 4.2 of the mongo shell, you can use the passwordPrompt() method in conjunction with various user authentication/management methods/commands to prompt for the password instead of specifying the password directly in the method/command call. However, you can still specify the password directly as you would with earlier versions of the mongo shell.

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db.getSiblingDB("$external").auth(
   {
     mechanism: "PLAIN",
     user: <username>,
     pwd:  passwordPrompt() // or cleartext password
   }
)

Enter the password when prompted.

The server forwards the password in plain text. In general, use only on a trusted channel (VPN, TLS/SSL, trusted wired network). See Considerations.

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