Kerberos Authentication
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Overview
MongoDB Enterprise provides support for Kerberos authentication of
MongoDB clients to mongod and mongos
instances. Kerberos is an industry standard authentication protocol for
large client/server systems. Kerberos allows MongoDB and applications to
take advantage of existing authentication infrastructure and processes.
MongoDB Enterprise only supports the MIT implementation of Kerberos.
Kerberos Components and MongoDB
Principals
In a Kerberos-based system, every participant in the authenticated communication is known as a "principal", and every principal must have a unique name.
Principals belong to administrative units called realms. For each realm, the Kerberos Key Distribution Center (KDC) maintains a database of the realm's principal and the principals' associated "secret keys".
For a client-server authentication, the client requests from the KDC a "ticket" for access to a specific asset. KDC uses the client's secret and the server's secret to construct the ticket which allows the client and server to mutually authenticate each other, while keeping the secrets hidden.
For the configuration of MongoDB for Kerberos support, two kinds of principal names are of interest: user principals and service principals.
User Principal
To authenticate using Kerberos, you must add the Kerberos user
principals to MongoDB to the $external database. User principal
names have the form:
<username>@<KERBEROS REALM>
For every user you want to authenticate using Kerberos, you must create
a corresponding user in MongoDB in the $external database.
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.
For examples of adding a user to MongoDB as well as authenticating as that user, see Configure MongoDB with Kerberos Authentication on Linux and Configure MongoDB with Kerberos Authentication on Windows.
Tip
See also:
Manage Users and Roles for general information regarding creating and managing users in MongoDB.
Service Principal
Every MongoDB mongod and mongos instance (or
exe or exe on Windows) must have an
associated service principal. Service principal names have the form:
<service>/<fully qualified domain name>@<KERBEROS REALM>
For MongoDB, the <service> defaults to mongodb. For example, if
m1.example.com is a MongoDB server, and example.com maintains
the EXAMPLE.COM Kerberos realm, then m1 should have the service
principal name mongodb/m1.example.com@EXAMPLE.COM.
To specify a different value for <service>, use
serviceName during the start up of mongod or
mongos (or exe or exe).
mongosh or other clients may also specify a different
service principal name using serviceName.
Service principal names must be reachable over the network using the fully qualified domain name (FQDN) part of its service principal name.
By default, Kerberos attempts to identify hosts using the
/etc/krb5.conf file before using DNS to resolve hosts.
On Windows, if running MongoDB as a service, see Assign Service Principal Name to MongoDB Windows Service.
Linux Keytab Files
Linux systems can store Kerberos authentication keys for a
service principal in keytab
files. Each Kerberized mongod and mongos instance
running on Linux must have access to a keytab file containing keys for
its service principal.
To keep keytab files secure, use file permissions that restrict access
to only the user that runs the mongod or mongos
process.
Tickets
On Linux, MongoDB clients can use Kerberos's kinit program to
initialize a credential cache for authenticating the user principal to
servers.
Windows Active Directory
Unlike on Linux systems, mongod and mongos
instances running on Windows do not require access to keytab files.
Instead, the mongod and mongos instances read
their server credentials from a credential store specific to the
operating system.
However, from the Windows Active Directory, you can export a keytab file for use on Linux systems. See Ktpass for more information.
Authenticate With Kerberos
To configure MongoDB for Kerberos support and authenticate, see Configure MongoDB with Kerberos Authentication on Linux and Configure MongoDB with Kerberos Authentication on Windows.
Operational Considerations
DNS
Each host that runs a mongod or mongos instance
must have both A and PTR DNS records to provide forward and
reverse lookup.
Without A and PTR DNS records, the host cannot resolve the
components of the Kerberos domain or the Key Distribution Center (KDC).
System Time Synchronization
To successfully authenticate, the system time for each
mongod and mongos instance must be within
5 minutes of the system time of the other hosts in the Kerberos
infrastructure.
Kerberized MongoDB Environments
Driver Support
The following MongoDB drivers support Kerberos authentication:
Use with Additional MongoDB Authentication Mechanism
Although MongoDB supports the use of Kerberos authentication with other
authentication mechanisms, only add the other mechanisms as necessary.
See the Incorporate Additional Authentication Mechanisms section in
Configure MongoDB with Kerberos Authentication on Linux
and
Configure MongoDB with Kerberos Authentication on Windows
for details.
Testing and Verification
Introduced alongside MongoDB 4.4, the mongokerberos
program provides a convenient method to verify your platform's Kerberos
configuration for use with MongoDB, and to test that Kerberos
authentication from a MongoDB client works as expected. See the
mongokerberos documentation for more information.
mongokerberos is available in MongoDB Enterprise only.