Deploy Replica Set With Keyfile Authentication¶

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Overview
Considerations
Deploy New Replica Set with Keyfile Access Control
x.509 Internal Authentication

Overview¶

Enforcing access control on a replica set requires configuring:

Security between members of the replica set using Internal Authentication, and
Security between connecting clients and the replica set using Role-Based Access Control.

For this tutorial, each member of the replica set uses the same internal authentication mechanism and settings.

Enforcing internal authentication also enforces user access control. To connect to the replica set, clients like the mongo shell need to use a user account. See Users and Authentication Mechanisms.

Cloud Manager and Ops Manager¶

If you are currently using or are planning to use Cloud Manager or Ops Manager, see the Cloud Manager manual or the Ops Manager manual for enforcing access control.

Considerations¶

Tip

When possible, use a logical DNS hostname instead of an ip address, particularly when configuring replica set members or sharded cluster members. The use of logical DNS hostnames avoids configuration changes due to ip address changes.

IP Binding¶

Changed in version 3.6.

Starting in MongoDB 3.6, mongod and mongos bind to localhost by default. If the members of your deployment are run on different hosts or if you wish remote clients to connect to your deployment, you must specify --bind_ip or net.bindIp. For more information, see Localhost Binding Compatibility Changes.

Operating System¶

This tutorial primarily refers to the mongod process. Windows users should use the mongod.exe program instead.

Keyfile Security¶

Keyfiles are bare-minimum forms of security and are best suited for testing or development environments. For production environments we recommend using x.509 certificates.

Users and Authentication Mechanisms¶

This tutorial covers creating the minimum number of administrative users on the admin database only. For the user authentication, the tutorial uses the default SCRAM authentication mechanism. Challenge-response security mechanisms are best suited for testing or development environments. For production environments, we recommend using x.509 certificates or LDAP Proxy Authentication (available for MongoDB Enterprise only) or Kerberos Authentication (available for MongoDB Enterprise only).

For details on creating users for specific authentication mechanism, refer to the specific authentication mechanism pages.

See ➤ Configure Role-Based Access Control for best practices for user creation and management.

Deploy New Replica Set with Keyfile Access Control¶

Tip

When possible, use a logical DNS hostname instead of an ip address, particularly when configuring replica set members or sharded cluster members. The use of logical DNS hostnames avoids configuration changes due to ip address changes.

1

Create a keyfile.¶

With keyfile authentication, each mongod instances in the replica set uses the contents of the keyfile as the shared password for authenticating other members in the deployment. Only mongod instances with the correct keyfile can join the replica set.

Note

Starting in MongoDB 4.2, keyfiles for internal membership authentication use YAML format to allow for multiple keys in a keyfile. The YAML format accepts content of:

a single key string (same as in earlier versions),
multiple key strings (each string must be enclosed in quotes), or
sequence of key strings.

The YAML format is compatible with the existing single-key keyfiles that use the text file format.

A key’s length must be between 6 and 1024 characters and may only contain characters in the base64 set. All members of the replica set must share at least one common key.

Note

On UNIX systems, the keyfile must not have group or world permissions. On Windows systems, keyfile permissions are not checked.

You can generate a keyfile using any method you choose. For example, the following operation uses openssl to generate a complex pseudo-random 1024 character string to use as a shared password. It then uses chmod to change file permissions to provide read permissions for the file owner only:

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openssl rand -base64 756 > <path-to-keyfile>
chmod 400 <path-to-keyfile>

See Keyfiles for additional details and requirements for using keyfiles.

2

Copy the keyfile to each replica set member.¶

Copy the keyfile to each server hosting the replica set members. Ensure that the user running the mongod instances is the owner of the file and can access the keyfile.

Avoid storing the keyfile on storage mediums that can be easily disconnected from the hardware hosting the mongod instances, such as a USB drive or a network attached storage device.

3

Start each member of the replica set with access control enabled.¶

For each member in the replica set, start the mongod with either the security.keyFile configuration file setting or the --keyFile command-line option. Running mongod with the --keyFile command-line option or the security.keyFile configuration file setting enforces both Internal/Membership Authentication and Role-Based Access Control.

Configuration File¶

If using a configuration file, set

security.keyFile to the keyfile’s path, and
replication.replSetName to the replica set name.

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.

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security:
  keyFile: <path-to-keyfile>
replication:
  replSetName: <replicaSetName>
net:
   bindIp: localhost,<hostname(s)|ip address(es)>

Start the mongod using the configuration file:

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mongod --config <path-to-config-file>

For more information on the configuration file, see configuration options.

Command Line¶

If using the command line options, start the mongod with the following options:

--keyFile set to the keyfile’s path, and
--replSet set to the replica set name.

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.

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mongod --keyFile <path-to-keyfile> --replSet <replicaSetName> --bind_ip localhost,<hostname(s)|ip address(es)>

Tip

When possible, use a logical DNS hostname instead of an ip address, particularly when configuring replica set members or sharded cluster members. The use of logical DNS hostnames avoids configuration changes due to ip address changes.

For more information on command-line options, see the mongod reference page.

4

Connect to a member of the replica set over the localhost interface.¶

Connect a mongo shell to one of the mongod instances over the localhost interface. You must run the mongo shell on the same physical machine as the mongod instance.

The localhost interface is only available since no users have been created for the deployment. The localhost interface closes after the creation of the first user.

5

Initiate the replica set.¶

From the mongo shell, run the rs.initiate() method.

rs.initiate() can take an optional replica set configuration document. In the replica set configuration document, include:

The _id field set to the replica set name specified in either the replication.replSetName or the --replSet option.
The members array with a document per each member of the replica set.

The following example initates a three member replica set.

Important

Run rs.initiate() on just one and only one mongod instance for the replica set.

Tip

When possible, use a logical DNS hostname instead of an ip address, particularly when configuring replica set members or sharded cluster members. The use of logical DNS hostnames avoids configuration changes due to ip address changes.

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rs.initiate(
  {
    _id : <replicaSetName>,
    members: [
      { _id : 0, host : "mongo1.example.net:27017" },
      { _id : 1, host : "mongo2.example.net:27017" },
      { _id : 2, host : "mongo3.example.net:27017" }
    ]
  }
)

rs.initiate() triggers an election and elects one of the members to be the primary.

Connect to the primary before continuing. Use rs.status() to locate the primary member.

6

Create the user administrator.¶

Important

After you create the first user, the localhost exception is no longer available.

The first user must have privileges to create other users, such as a user with the userAdminAnyDatabase. This ensures that you can create additional users after the Localhost Exception closes.

If at least one user does not have privileges to create users, once the localhost exception closes you may be unable to create or modify users with new privileges, and therefore unable to access necessary operations.

Add a user using the db.createUser() method. The user should have at minimum the userAdminAnyDatabase role on the admin database.

You must be connected to the primary to create users.

The following example creates the user fred with the userAdminAnyDatabase role on the admin database.

Important

Passwords should be random, long, and complex to ensure system security and to prevent or delay malicious access.

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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admin = db.getSiblingDB("admin")
admin.createUser(
  {
    user: "fred",
    pwd: passwordPrompt(), // or cleartext password
    roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]
  }
)

Enter the password when prompted. See Database User Roles for a full list of built-in roles and related to database administration operations.

7

Authenticate as the user administrator.¶

Authenticate to the admin database.

In the mongo shell, use db.auth() to authenticate. For example, the following authenticate as the user administrator fred:

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("admin").auth("fred", passwordPrompt()) // or cleartext password

Alternatively, connect a new mongo shell to the primary replica set member using the -u <username>, -p <password>, and the --authenticationDatabase parameters.

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mongo -u "fred" -p  --authenticationDatabase "admin"

If you do not specify the password to the -p command-line option, the mongo shell prompts for the password.

8

Create the cluster administrator.¶

The clusterAdmin role grants access to replication operations, such as configuring the replica set.

Create a cluster administrator user and assign the clusterAdmin role in the admin database:

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("admin").createUser(
  {
    "user" : "ravi",
    "pwd" : passwordPrompt(),     // or cleartext password
    roles: [ { "role" : "clusterAdmin", "db" : "admin" } ]
  }
)

Enter the password when prompted.

See Cluster Administration Roles for a full list of built-in roles related to replica set and sharded cluster operations.

9

Create additional users (Optional).¶

Create users to allow clients to connect and interact with the replica set. See Database User Roles for basic built-in roles to use in creating read-only and read-write users.

You may also want additional administrative users. For more information on users, see Users.

x.509 Internal Authentication¶

For details on using x.509 for internal authentication, see Use x.509 Certificate for Membership Authentication.

To upgrade from keyfile internal authentication to x.509 internal authentication, see Upgrade from Keyfile Authentication to x.509 Authentication.

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