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LDAP Proxy Authentication

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MongoDB Enterprise supports proxying authentication requests to a Lightweight Directory Access Protocol (LDAP) service.

MongoDB supports simple and SASL binding to LDAP servers:

ViaDescription
Operating system librariesStarting in version 3.4, MongoDB supports binding to an LDAP server via operating system libraries.
This allows MongoDB servers on Linux and Windows to use an LDAP server for authentication.
In earlier versions, MongoDB on Microsoft Windows cannot connect to LDAP servers.
saslauthdMongoDB servers on Linux supports binding to an LDAP server via the saslauthd daemon.
Not available for MongoDB on Windows.

Considerations

A full description of LDAP is beyond the scope of this documentation. This page assumes prior knowledge of LDAP.

This documentation only describes MongoDB LDAP authentication, and does not replace other resources on LDAP. We encourage you to thoroughly familiarize yourself with LDAP and its related subject matter before configuring LDAP authentication.

MongoDB can provide professional services for optimal configuration of LDAP authentication for your MongoDB deployment.

Connection Pool

Starting in version 4.2.0, when connecting to the LDAP server for authentication/authorization, MongoDB, by default:

  • Uses connection pooling if run:

    • on Windows or
    • on Linux where MongoDB Enterprise binaries are linked against libldap_r.
  • Does not use connection pooling if run:

    • on Linux where MongoDB Enterprise binaries are linked against libldap.

To change the connection pooling behavior, update the ldapUseConnectionPool parameter.

saslauthd and Directory Permissions

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.

libldap and libldap_r

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

Managing LDAP Users on the MongoDB server

User management requires managing users both on the LDAP server and the MongoDB server. For each user authenticating via LDAP, MongoDB requires a user on the $external database whose name exactly matches the authentication username. Changes to a user on the LDAP server may require changes to the corresponding MongoDB $external user.

To use Client Sessions and Causal Consistency Guarantees with $external authentication users (Kerberos, LDAP, or x.509 users), usernames cannot be greater than 10k bytes.

Example

A user authenticates as sam@dba.example.com. The MongoDB server binds to the LDAP server and authenticates the user, respecting any username transformations. On successful authentication, the MongoDB server then checks the $external database for a user sam@dba.example.com and grants the authenticated user the roles and privileges associated to that user.

To manage users on the MongoDB server, you must authenticate as an LDAP user whose corresponding MongoDB $external user has user administrative privileges on the $external database, such as those provided by userAdmin.

Important

If no $external users have user administrative privileges on $external database, you cannot perform user management for LDAP authentication. This scenario may occur if you configure users prior to enabling LDAP authentication, but do not create the appropriate user administrators.

Managing existing non-LDAP users

If there are existing users not on the $external database, you must meet the following requirements for each user to ensure continued access:

  • User has a corresponding user object on the LDAP server
  • User exists on the $external database with equivalent roles and privileges

If you want to continue allowing access by users not on the $external database, you must configure setParameter authenticationMechanisms to include SCRAM-SHA-1 and/or SCRAM-SHA-256 as appropriate. Users must then specify --authenticationMechanism SCRAM-SHA-1 or SCRAM-SHA-256 when authenticating.

Deploying LDAP authentication on a replica set

For replica sets, configure LDAP authentication on secondary and arbiter members first before configuring the primary. This also applies to shard replica sets, or config server replica sets. Configure one replica set member at a time to maintain a majority of members for write availability.

Deploying LDAP authentication on a sharded cluster

In sharded clusters, you must configure LDAP authentication on the config servers and each mongos for cluster-level users. You can optionally configure LDAP authorization on each shard for shard-local users.

LDAP Authentication via the Operating System LDAP libraries

The LDAP authentication via OS libraries process is summarized below:

  1. A client authenticates to MongoDB, providing a user's credentials.
  2. If the username requires mapping to an LDAP DN prior to binding against the LDAP server, MongoDB can apply transformations based on the configured security.ldap.userToDNMapping setting.
  3. MongoDB binds to an LDAP server specified in security.ldap.servers using the provided username or, if a transformation was applied, the transformed username.

    MongoDB uses simple binding by default, but can also use sasl binding if configured in security.ldap.bind.method and security.ldap.bind.saslMechanisms.

    If a transformation requires querying the LDAP server, or if the LDAP server disallows anonymous binds, MongoDB uses the username and password specified to security.ldap.bind.queryUser and security.ldap.bind.queryPassword to bind to the LDAP server before attempting to authenticate the provided user credentials.

  4. The LDAP server returns the result of the bind attempt to MongoDB. On success, MongoDB attempts to authorize the user.
  5. The MongoDB server attempts to map the username to a user on the $external database, assigning the user any roles or privileges associated to a matching user. If MongoDB cannot find a matching user, authentication fails.
  6. The client can perform those actions for which MongoDB granted the authenticated user roles or privileges.

To use LDAP for authentication via operating system libraries, specify the following settings as a part of your mongod or mongos configuration file:

OptionDescriptionRequired
security.ldap.serversQuote-enclosed comma-separated list of LDAP servers in host[:port] format.YES
security.ldap.bind.methodUsed to specify the method the mongod or mongos uses to authenticate, or bind, to the LDAP server. Specify sasl to use one of the SASL protocols defined in security.ldap.bind.saslMechanisms.
Defaults to simple. 		NO, unless using sasl for binding to the LDAP server.
security.ldap.bind.saslMechanismsUsed to specify the SASL mechanisms mongod or mongos can use when authenticating or binding to the LDAP server. MongoDB and the LDAP server must agree on at least one SASL mechanism.
Defaults to DIGEST-MD5. 		NO, unless setting method to sasl and you need different or additional SASL mechanisms.
security.ldap.bind.queryUserThe LDAP entity, identified by its distinguished name (DN) or SASL name, with which the MongoDB server authenticates, or binds, when connecting to an LDAP server.
Use with queryPassword.
The user specified must have the appropriate privileges to execute queries on the LDAP server. 		NO, unless specifying a query as part of a userToDNMapping transformation, or if the LDAP server's security settings disallow anonymous binds.
security.ldap.bind.queryPasswordThe password used to authenticate to an LDAP server when using queryUser.NO, unless specifying queryUser.
security.ldap.bind.useOSDefaultsWindows MongoDB deployments can use the operating system credentials in place of queryUser and queryPassword for authenticating or binding as when connecting to the LDAP server.NO, unless replacing queryUser and queryPassword.
security.ldap.userToDNMappingClients may authenticate using a username whose format is incompatible with the format expected by the configured bind method. For example, simple binding may require a full LDAP DN while the username used to authenticate to MongoDB might be an e-mail address.
userToDNMapping allows MongoDB to transform incoming usernames into a format compatible with your LDAP schema. MongoDB supports transformations using either a substitution template or an LDAP query template.
If you specify a userToDNMapping transformation that uses LDAP queries as part of the transformation, you must also specify a queryUser with the appropriate level of permissions for the LDAP server 		NO, unless client authenticate using usernames that require transformation.

LDAP Authentication via saslauthd

Warning

MongoDB Enterprise for Windows does not support binding via saslauthd.

Considerations

  • 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.

Configuration

To configure the MongoDB server to bind to the LDAP server using via saslauthd, start the mongod using either the following command line options or the following configuration file settings:

You need to create or update the saslauthd.conf file with the parameters appropriate for your LDAP server. Documenting saslauthd.conf is out of scope for this documentation.

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.

The following tutorials provide basic information on configuring saslauthd.conf to work with two popular LDAP services:

Please see the documentation for saslauthd as well as your specific LDAP service for guidance.

Connect to a MongoDB server via LDAP authentication

To authenticate to a MongoDB server via LDAP authentication, use db.auth() on the $external database with the following parameters:

OptionDescription
usernameThe username to authenticate as.
passwordThe password to authenticate with.
mechanismSet to PLAIN.