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Deploy Sharded Cluster with Keyfile Authentication

Overview

Enforcing access control on a sharded cluster requires configuring:

• Security between components of the cluster using Internal Authentication.
• Security between connecting clients and the cluster using User Access Controls.

For this tutorial, each member of the sharded cluster must use the same internal authentication mechanism and settings. This means enforcing internal authentication on each mongos and mongod in the cluster.

The following tutorial uses a keyfile to enable internal authentication.

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 Access Control.

CloudManager and OpsManager

If you are using Cloud Manager or Ops Manager to manage your deployment, see the respective Cloud Manager manual or the Ops Manager manual to enforce authentication.

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 with MongoDB 3.6, MongoDB binaries, mongod and mongos, bind to localhost by default. From MongoDB versions 2.6 to 3.4, only the binaries from the official MongoDB RPM (Red Hat, CentOS, Fedora Linux, and derivatives) and DEB (Debian, Ubuntu, and derivatives) packages would bind to localhost by default. To learn more about this change, see Localhost Binding Compatibility Changes.

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.

Access Control

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.

Users

In general, to create users for a sharded clusters, connect to the mongos and add the sharded cluster users.

However, some maintenance operations require direct connections to specific shards in a sharded cluster. To perform these operations, you must connect directly to the shard and authenticate as a shard-local administrative user.

Shard-local users exist only in the specific shard and should only be used for shard-specific maintenance and configuration. You cannot connect to the mongos with shard-local users.

This tutorial requires creating sharded cluster users, but includes optional steps for adding shard-local users.

See the Users security documentation for more information.

Operating System

This tutorial uses the mongod and mongos programs. Windows users should use the mongod.exe and mongos.exe programs instead.

Deploy Sharded Cluster with Keyfile Access Control

The following procedures involve creating a new sharded cluster that consists of a mongos, the config servers, and two shards.

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.

Create the Keyfile

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

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 sharded cluster 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.

Distribute the Keyfile

Copy the keyfile to each server hosting the sharded cluster members. Ensure that the user running the mongod or mongos 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 or mongos instances, such as a USB drive or a network attached storage device.

Create the Config Server Replica Set

The following steps deploys a config server replica set.

For a production deployment, deploys a config server replica set with at least three members. For testing purposes, you can create a single-member replica set.

1

Start each mongod in the config server replica set. Include the keyFile setting. The keyFile setting enforces both Internal/Membership Authentication and Role-Based Access Control.

You can specify the mongod settings either via a configuration file or the command line.

Configuration File

If using a configuration file, set security.keyFile to the keyfile’s path, sharding.clusterRole to configsvr, and replication.replSetName to the desired name of the config server replica set.

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security:
  keyFile: <path-to-keyfile>
sharding:
  clusterRole: configsvr
replication:
  replSetName: <setname>

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.

Start the mongod specifying the --config option and the path to the configuration file.

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

Command Line

If using the command line parameters, start the mongod with the --keyFile, --configsvr, and --replSet parameters.

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mongod --keyFile <path-to-keyfile> --configsvr --replSet <setname> --dbpath <path>

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.

2

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.

3

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

• The _id. The _id must match the --replSet parameter passed to the mongod.
• The members field. The members field is an array and requires a document per each member of the replica set.
• The configsvr field. The configsvr field must be set to true for the config server replica set.

See Replica Set Configuration for more information on replica set configuration documents.

Initiate the replica set using the rs.initiate() method and a configuration document:

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rs.initiate(
  {
    _id: "<replSetName>",
    configsvr: true,
    members: [
      { _id : 0, host : "cfg1.example.net:27019" },
      { _id : 1, host : "cfg2.example.net:27019" },
      { _id : 2, host : "cfg3.example.net:27019" }
    ]
  }
)

Once the config server replica set (CSRS) is initiated and up, proceed to creating the shard replica sets.

Create the Shard Replica Sets

For a production deployment, use a replica set with at least three members. For testing purposes, you can create a single-member replica set.

These steps include optional procedures for adding shard-local users. Executing them now ensures that there are users available for each shard to perform shard-level maintenance.

1

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

Running a mongod with the keyFile parameter enforces both Internal/Membership Authentication and Role-Based Access Control.

Start each mongod in the replica set using either a configuration file or the command line.

Configuration File

If using a configuration file, set the security.keyFile option to the keyfile’s path, the replication.replSetName to the desired name of the replica set, and the sharding.clusterRole option to shardsvr.

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security:
  keyFile: <path-to-keyfile>
sharding:
  clusterRole: shardsvr
replication:
  replSetName: <replSetName>
storage:
   dbPath: <path>

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.

Start the mongod specifying the --config option and the path to the configuration file.

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

Command Line

If using the command line option, when starting the component, specify the --keyFile, replSet, and --shardsvr parameters, as in the following example:

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mongod --keyFile <path-to-keyfile> --shardsvr --replSet <replSetName>  --dbpath <path>

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.

2

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.

3

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.

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rs.initiate(
  {
    _id : <replicaSetName>,
    members: [
      { _id : 0, host : "s1-mongo1.example.net:27018" },
      { _id : 1, host : "s1-mongo2.example.net:27018" },
      { _id : 2, host : "s1-mongo3.example.net:27018" }
    ]
  }
)

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.

4

Create the shard-local user administrator (optional).

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.

5

Authenticate as the shard-local user administrator (optional).

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.

6

Create the shard-local cluster administrator (optional).

The shard-local cluster administrator user has the clusterAdmin role, which provides privileges that allow access to replication operations.

For a full list of roles related to replica set operations see Cluster Administration Roles.

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.

copy

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.

Connect a mongos to the Sharded Cluster

1

Connect a mongos to the cluster

Start a mongos specifying the keyfile using either a configuration file or a command line parameter.

Configuration File

If using a configuration file, set the security.keyFile to the keyfile’s path and the sharding.configDB to the replica set name and at least one member of the replica set in <replSetName>/<host:port> format.

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security:
  keyFile: <path-to-keyfile>
sharding:
  configDB: <configReplSetName>/cfg1.example.net:27019,cfg2.example.net:27019,...

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.

Start the mongos specifying the --config option and the path to the configuration file.

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mongos --config <path-to-config>

Command Line

If using command line parameters start the mongos and specify the --keyFile and --configdb parameters.

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mongos --keyFile <path-to-keyfile> --configdb <configReplSetName>/cfg1.example.net:27019,cfg2.example.net:27019,...

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.

2

Connect to a mongos over the localhost interface.

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

3

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 cannot create or modify users, and therefore may be unable to perform necessary operations.

Add a user using the db.createUser() method. The user should have at minimum 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.

The following example creates the user fred on 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.

copy

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

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

4

Authenticate as the user administrator.

Use db.auth() to authenticate as the user administrator to create additional users:

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.

copy

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

Enter the password when prompted.

Alternatively, connect a new mongo shell to the target replica set member using the -u <username>, -p <password>, and the --authenticationDatabase "admin" parameters. You must use the Localhost Exception to connect to the mongos.

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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.

5

Create Administrative User for Cluster Management

The cluster administrator user has the clusterAdmin role, which grants access to replication and sharding operations.

Create a clusterAdmin user in the admin database.

The following example creates the user ravi 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.

copy

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

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

7

Create additional users (Optional).

Create users to allow clients to connect and access the sharded cluster. See Database User Roles for available built-in roles, such as read and readWrite. You may also want additional administrative users. For more information on users, see Users.

To create additional users, you must authenticate as a user with userAdminAnyDatabase or userAdmin roles.

Add Shards to the Cluster

To proceed, you must be connected to the mongos and authenticated as the cluster administrator user for the sharded cluster.

Note

This is the cluster administrator for the sharded cluster and not the shard-local cluster administrator.

To add each shard to the cluster, use the sh.addShard() method. If the shard is a replica set, specify the name of the replica set and specify a member of the set. In production deployments, all shards should be replica sets.

The following operation adds a single shard replica set to the cluster:

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sh.addShard( "<replSetName>/s1-mongo1.example.net:27017")

The following operation is an example of adding a standalone mongod shard to the cluster:

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sh.addShard( "s1-mongo1.example.net:27017")

Repeat these steps until the cluster includes all shards. At this point, the sharded cluster enforces access control for the cluster as well as for internal communications between each sharded cluster component.

Enable Sharding for a Database

To proceed, you must be connected to the mongos and authenticated as the cluster administrator user for the sharded cluster.

Note

This is the cluster administrator for the sharded cluster and not the shard-local cluster administrator.

Enabling sharding on a database makes it possible to shard collections within the database. Use the sh.enableSharding() method to enable sharding on the target database.

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sh.enableSharding("<database>")

Shard a Collection

To proceed, you must be connected to the mongos and authenticated as the cluster administrator user for the sharded cluster.

Note

This is the cluster administrator for the sharded cluster and not the shard-local cluster administrator.

To shard a collection, use the sh.shardCollection() method. You must specify the full namespace of the collection and a document containing the shard key.

Your selection of shard key affects the efficiency of sharding, as well as your ability to take advantage of certain sharding features such as zones. See the selection considerations listed in the Choosing a Shard Key.

If the collection already contains data, you must create an index on the shard key using the db.collection.createIndex() method before using shardCollection().

If the collection is empty, MongoDB creates the index as part of sh.shardCollection().

The following is an example of the sh.shardCollection() method:

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sh.shardCollection("<database>.<collection>", { <key> : <direction> } )

Next Steps

Create users to allow clients to connect to and interact with the sharded cluster.

See Database User Roles for basic built-in roles to use in creating read-only and read-write 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.

See also

Sharded Cluster Components

Operational Restrictions in Sharded Clusters

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