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Applies to SUSE Enterprise Storage 5.5 (SES 5 & SES 5.5)

6 Authentication with cephx Edit source

To identify clients and protect against man-in-the-middle attacks, Ceph provides its cephx authentication system. Clients in this context are either human users—such as the admin user—or Ceph-related services/daemons, for example OSDs, monitors, or Object Gateways.

Note
Note

The cephx protocol does not address data encryption in transport, such as TLS/SSL.

6.1 Authentication Architecture Edit source

cephx uses shared secret keys for authentication, meaning both the client and Ceph Monitors have a copy of the client’s secret key. The authentication protocol enables both parties to prove to each other that they have a copy of the key without actually revealing it. This provides mutual authentication, which means the cluster is sure the user possesses the secret key, and the user is sure that the cluster has a copy of the secret key as well.

A key scalability feature of Ceph is to avoid a centralized interface to the Ceph object store. This means that Ceph clients can interact with OSDs directly. To protect data, Ceph provides its cephx authentication system, which authenticates Ceph clients.

Each monitor can authenticate clients and distribute keys, so there is no single point of failure or bottleneck when using cephx. The monitor returns an authentication data structure that contains a session key for use in obtaining Ceph services. This session key is itself encrypted with the client’s permanent secret key, so that only the client can request services from the Ceph monitors. The client then uses the session key to request its desired services from the monitor, and the monitor provides the client with a ticket that will authenticate the client to the OSDs that actually handle data. Ceph monitors and OSDs share a secret, so the client can use the ticket provided by the monitor with any OSD or metadata server in the cluster. cephx tickets expire, so an attacker cannot use an expired ticket or session key obtained wrongfully.

To use cephx, an administrator must setup clients/users first. In the following diagram, the client.admin user invokes ceph auth get-or-create-key from the command line to generate a user name and secret key. Ceph’s auth subsystem generates the user name and key, stores a copy with the monitor(s) and transmits the user’s secret back to the client.admin user. This means that the client and the monitor share a secret key.

Basic cephx Authentication
Figure 6.1: Basic cephx Authentication

To authenticate with the monitor, the client passes the user name to the monitor. The monitor generates a session key and encrypts it with the secret key associated with the user name and transmits the encrypted ticket back to the client. The client then decrypts the data with the shared secret key to retrieve the session key. The session key identifies the user for the current session. The client then requests a ticket related to the user, which is signed by the session key. The monitor generates a ticket, encrypts it with the user’s secret key and transmits it back to the client. The client decrypts the ticket and uses it to sign requests to OSDs and metadata servers throughout the cluster.

cephx Authentication
Figure 6.2: cephx Authentication

The cephx protocol authenticates ongoing communications between the client machine and the Ceph servers. Each message sent between a client and a server after the initial authentication is signed using a ticket that the monitors, OSDs, and metadata servers can verify with their shared secret.

cephx Authentication - MDS and OSD
Figure 6.3: cephx Authentication - MDS and OSD
Important
Important

The protection offered by this authentication is between the Ceph client and the Ceph cluster hosts. The authentication is not extended beyond the Ceph client. If the user accesses the Ceph client from a remote host, Ceph authentication is not applied to the connection between the user’s host and the client host.

6.2 Key Management Edit source

This section describes Ceph client users and their authentication and authorization with the Ceph storage cluster. Users are either individuals or system actors such as applications, which use Ceph clients to interact with the Ceph storage cluster daemons.

When Ceph runs with authentication and authorization enabled (enabled by default), you must specify a user name and a keyring containing the secret key of the specified user (usually via the command line). If you do not specify a user name, Ceph will use client.admin as the default user name. If you do not specify a keyring, Ceph will look for a keyring via the keyring setting in the Ceph configuration file. For example, if you execute the ceph health command without specifying a user name or keyring, Ceph interprets the command like this:

cephadm > ceph -n client.admin --keyring=/etc/ceph/ceph.client.admin.keyring health

Alternatively, you may use the CEPH_ARGS environment variable to avoid re-entering the user name and secret.

6.2.1 Background Information Edit source

Regardless of the type of Ceph client (for example, block device, object storage, file system, native API), Ceph stores all data as objects within pools. Ceph users need to have access to pools in order to read and write data. Additionally, Ceph users must have execute permissions to use Ceph's administrative commands. The following concepts will help you understand Ceph user management.

6.2.1.1 User Edit source

A user is either an individual or a system actor such as an application. Creating users allows you to control who (or what) can access your Ceph storage cluster, its pools, and the data within pools.

Ceph uses types of users. For the purposes of user management, the type will always be client. Ceph identifies users in period (.) delimited form, consisting of the user type and the user ID. For example, TYPE.ID, client.admin, or client.user1. The reason for user typing is that Ceph monitors, OSDs, and metadata servers also use the cephx protocol, but they are not clients. Distinguishing the user type helps to distinguish between client users and other users, streamlining access control, user monitoring, and traceability.

Note
Note

A Ceph storage cluster user is not the same as a Ceph object storage user or a Ceph file system user. The Ceph Object Gateway uses a Ceph storage cluster user to communicate between the gateway daemon and the storage cluster, but the gateway has its own user management functionality for end users. The Ceph file system uses POSIX semantics. The user space associated with it is not the same as a Ceph storage cluster user.

6.2.1.2 Authorization and Capabilities Edit source

Ceph uses the term 'capabilities' (caps) to describe authorizing an authenticated user to exercise the functionality of the monitors, OSDs, and metadata servers. Capabilities can also restrict access to data within a pool or pool namespace. A Ceph administrative user sets a user's capabilities when creating or updating a user.

Capability syntax follows the form:

daemon-type 'allow capability' [...]

Following is a list of capabilities for each service type:

Monitor capabilities

include r, w, x and allow profile cap.

mon 'allow rwx'
mon 'allow profile osd'
OSD capabilities

include r, w, x, class-read, class-write and profile osd. Additionally, OSD capabilities also allow for pool and namespace settings.

osd 'allow capability' [pool=poolname] [namespace=namespace-name]
MDS capability

simply requires allow, or blank.

mds 'allow'

The following entries describe each capability:

allow

Precedes access settings for a daemon. Implies rw for MDS only.

r

Gives the user read access. Required with monitors to retrieve the CRUSH map.

w

Gives the user write access to objects.

x

Gives the user the capability to call class methods (both read and write) and to conduct auth operations on monitors.

class-read

Gives the user the capability to call class read methods. Subset of x.

class-write

Gives the user the capability to call class write methods. Subset of x.

*

Gives the user read, write, and execute permissions for a particular daemon/pool, and the ability to execute admin commands.

profile osd

Gives a user permissions to connect as an OSD to other OSDs or monitors. Conferred on OSDs to enable OSDs to handle replication heartbeat traffic and status reporting.

profile mds

Gives a user permissions to connect as an MDS to other MDSs or monitors.

profile bootstrap-osd

Gives a user permissions to bootstrap an OSD. Delegated to deployment tools so that they have permissions to add keys when bootstrapping an OSD.

profile bootstrap-mds

Gives a user permissions to bootstrap a metadata server. Delegated to deployment tools so they have permissions to add keys when bootstrapping a metadata server.

6.2.2 Managing Users Edit source

User management functionality provides Ceph cluster administrators with the ability to create, update, and delete users directly in the Ceph cluster.

When you create or delete users in the Ceph cluster, you may need to distribute keys to clients so that they can be added to keyrings. See Section 6.2.3, “Keyring Management” for details.

6.2.2.1 Listing Users Edit source

To list the users in your cluster, execute the following:

cephadm > ceph auth list

Ceph will list all users in your cluster. For example, in a cluster with two nodes, ceph auth list output looks similar to this:

installed auth entries:

osd.0
        key: AQCvCbtToC6MDhAATtuT70Sl+DymPCfDSsyV4w==
        caps: [mon] allow profile osd
        caps: [osd] allow *
osd.1
        key: AQC4CbtTCFJBChAAVq5spj0ff4eHZICxIOVZeA==
        caps: [mon] allow profile osd
        caps: [osd] allow *
client.admin
        key: AQBHCbtT6APDHhAA5W00cBchwkQjh3dkKsyPjw==
        caps: [mds] allow
        caps: [mon] allow *
        caps: [osd] allow *
client.bootstrap-mds
        key: AQBICbtTOK9uGBAAdbe5zcIGHZL3T/u2g6EBww==
        caps: [mon] allow profile bootstrap-mds
client.bootstrap-osd
        key: AQBHCbtT4GxqORAADE5u7RkpCN/oo4e5W0uBtw==
        caps: [mon] allow profile bootstrap-osd
Note
Note: TYPE.ID Notation

Note that the TYPE.ID notation for users applies such that osd.0 specifies a user of type osd and its ID is 0. client.admin is a user of type client and its ID is admin. Note also that each entry has a key: value entry, and one or more caps: entries.

You may use the -o filename option with ceph auth list to save the output to a file.

6.2.2.2 Getting Information about Users Edit source

To retrieve a specific user, key, and capabilities, execute the following:

cephadm > ceph auth get TYPE.ID

For example:

cephadm > ceph auth get client.admin
exported keyring for client.admin
[client.admin]
	key = AQA19uZUqIwkHxAAFuUwvq0eJD4S173oFRxe0g==
	caps mds = "allow"
	caps mon = "allow *"
 caps osd = "allow *"

Developers may also execute the following:

cephadm > ceph auth export TYPE.ID

The auth export command is identical to auth get, but also prints the internal authentication ID.

6.2.2.3 Adding Users Edit source

Adding a user creates a user name (TYPE.ID), a secret key, and any capabilities included in the command you use to create the user.

A user's key enables the user to authenticate with the Ceph storage cluster. The user's capabilities authorize the user to read, write, or execute on Ceph monitors (mon), Ceph OSDs (osd), or Ceph metadata servers (mds).

There are a few commands available to add a user:

ceph auth add

This command is the canonical way to add a user. It will create the user, generate a key, and add any specified capabilities.

ceph auth get-or-create

This command is often the most convenient way to create a user, because it returns a keyfile format with the user name (in brackets) and the key. If the user already exists, this command simply returns the user name and key in the keyfile format. You may use the -o filename option to save the output to a file.

ceph auth get-or-create-key

This command is a convenient way to create a user and return the user's key (only). This is useful for clients that need the key only (for example libvirt). If the user already exists, this command simply returns the key. You may use the -o filename option to save the output to a file.

When creating client users, you may create a user with no capabilities. A user with no capabilities can authenticate but nothing more. Such client cannot retrieve the cluster map from the monitor. However, you can create a user with no capabilities if you want to defer adding capabilities later using the ceph auth caps command.

A typical user has at least read capabilities on the Ceph monitor and read and write capabilities on Ceph OSDs. Additionally, a user's OSD permissions are often restricted to accessing a particular pool.

cephadm > ceph auth add client.john mon 'allow r' osd \
 'allow rw pool=liverpool'
cephadm > ceph auth get-or-create client.paul mon 'allow r' osd \
 'allow rw pool=liverpool'
cephadm > ceph auth get-or-create client.george mon 'allow r' osd \
 'allow rw pool=liverpool' -o george.keyring
cephadm > ceph auth get-or-create-key client.ringo mon 'allow r' osd \
 'allow rw pool=liverpool' -o ringo.key
Important
Important

If you provide a user with capabilities to OSDs, but you do not restrict access to particular pools, the user will have access to all pools in the cluster.

6.2.2.4 Modifying User Capabilities Edit source

The ceph auth caps command allows you to specify a user and change the user's capabilities. Setting new capabilities will overwrite current ones. To view current capabilities run ceph auth get USERTYPE.USERID. To add capabilities, you also need to specify the existing capabilities when using the following form:

cephadm > ceph auth caps USERTYPE.USERID daemon 'allow [r|w|x|*|...] \
     [pool=pool-name] [namespace=namespace-name]' [daemon 'allow [r|w|x|*|...] \
     [pool=pool-name] [namespace=namespace-name]']

For example:

cephadm > ceph auth get client.john
cephadm > ceph auth caps client.john mon 'allow r' osd 'allow rw pool=prague'
cephadm > ceph auth caps client.paul mon 'allow rw' osd 'allow r pool=prague'
cephadm > ceph auth caps client.brian-manager mon 'allow *' osd 'allow *'

To remove a capability, you may reset the capability. If you want the user to have no access to a particular daemon that was previously set, specify an empty string:

cephadm > ceph auth caps client.ringo mon ' ' osd ' '

6.2.2.5 Deleting Users Edit source

To delete a user, use ceph auth del:

cephadm > ceph auth del TYPE.ID

where TYPE is one of client, osd, mon, or mds, and ID is the user name or ID of the daemon.

If you created users with permissions strictly for a pool that no longer exists, you should consider deleting those users too.

6.2.2.6 Printing a User's Key Edit source

To print a user’s authentication key to standard output, execute the following:

cephadm > ceph auth print-key TYPE.ID

where TYPE is one of client, osd, mon, or mds, and ID is the user name or ID of the daemon.

Printing a user's key is useful when you need to populate client software with a user's key (such as libvirt), as in the following example:

root # mount -t ceph host:/ mount_point \
-o name=client.user,secret=`ceph auth print-key client.user`

6.2.2.7 Importing Users Edit source

To import one or more users, use ceph auth import and specify a keyring:

cephadm > ceph auth import -i /etc/ceph/ceph.keyring
Note
Note

The Ceph storage cluster will add new users, their keys and their capabilities and will update existing users, their keys and their capabilities.

6.2.3 Keyring Management Edit source

When you access Ceph via a Ceph client, the client will look for a local keyring. Ceph presets the keyring setting with the following four keyring names by default so you do not need to set them in your Ceph configuration file unless you want to override the defaults:

/etc/ceph/cluster.name.keyring
/etc/ceph/cluster.keyring
/etc/ceph/keyring
/etc/ceph/keyring.bin

The cluster metavariable is your Ceph cluster name as defined by the name of the Ceph configuration file. ceph.conf means that the cluster name is ceph, thus ceph.keyring. The name metavariable is the user type and user ID, for example client.admin, thus ceph.client.admin.keyring.

After you create a user (for example client.ringo), you must get the key and add it to a keyring on a Ceph client so that the user can access the Ceph storage cluster.

Section 6.2, “Key Management” details how to list, get, add, modify and delete users directly in the Ceph storage cluster. However, Ceph also provides the ceph-authtool utility to allow you to manage keyrings from a Ceph client.

6.2.3.1 Creating a Keyring Edit source

When you use the procedures in Section 6.2, “Key Management” to create users, you need to provide user keys to the Ceph client(s) so that the client can retrieve the key for the specified user and authenticate with the Ceph storage cluster. Ceph clients access keyrings to look up a user name and retrieve the user's key:

cephadm > ceph-authtool --create-keyring /path/to/keyring

When creating a keyring with multiple users, we recommend using the cluster name (for example cluster.keyring) for the keyring file name and saving it in the /etc/ceph directory so that the keyring configuration default setting will pick up the file name without requiring you to specify it in the local copy of your Ceph configuration file. For example, create ceph.keyring by executing the following:

cephadm > ceph-authtool -C /etc/ceph/ceph.keyring

When creating a keyring with a single user, we recommend using the cluster name, the user type and the user name and saving it in the /etc/ceph directory. For example, ceph.client.admin.keyring for the client.admin user.

6.2.3.2 Adding a User to a Keyring Edit source

When you add a user to the Ceph storage cluster (see Section 6.2.2.3, “Adding Users”), you can retrieve the user, key and capabilities, and save the user to a keyring.

If you only want to use one user per keyring, the ceph auth get command with the -o option will save the output in the keyring file format. For example, to create a keyring for the client.admin user, execute the following:

cephadm > ceph auth get client.admin -o /etc/ceph/ceph.client.admin.keyring

When you want to import users to a keyring, you can use ceph-authtool to specify the destination keyring and the source keyring:

cephadm > ceph-authtool /etc/ceph/ceph.keyring \
  --import-keyring /etc/ceph/ceph.client.admin.keyring
Important
Important

If your keyring is compromised, delete your key from the /etc/ceph directory and recreate a new key using the same instructions from Section 6.2.3.1, “Creating a Keyring”.

6.2.3.3 Creating a User Edit source

Ceph provides the ceph auth add command to create a user directly in the Ceph storage cluster. However, you can also create a user, keys and capabilities directly on a Ceph client keyring. Then, you can import the user to the Ceph storage cluster:

cephadm > ceph-authtool -n client.ringo --cap osd 'allow rwx' \
  --cap mon 'allow rwx' /etc/ceph/ceph.keyring

You can also create a keyring and add a new user to the keyring simultaneously:

cephadm > ceph-authtool -C /etc/ceph/ceph.keyring -n client.ringo \
  --cap osd 'allow rwx' --cap mon 'allow rwx' --gen-key

In the previous scenarios, the new user client.ringo is only in the keyring. To add the new user to the Ceph storage cluster, you must still add the new user to the cluster:

cephadm > ceph auth add client.ringo -i /etc/ceph/ceph.keyring

6.2.3.4 Modifying Users Edit source

To modify the capabilities of a user record in a keyring, specify the keyring and the user followed by the capabilities:

cephadm > ceph-authtool /etc/ceph/ceph.keyring -n client.ringo \
  --cap osd 'allow rwx' --cap mon 'allow rwx'

To update the modified user within the Ceph cluster environment, you must import the changes from the keyring to the user entry in the Ceph cluster:

cephadm > ceph auth import -i /etc/ceph/ceph.keyring

See Section 6.2.2.7, “Importing Users” for details on updating a Ceph storage cluster user from a keyring.

6.2.4 Command Line Usage Edit source

The ceph command supports the following options related to the user name and secret manipulation:

--id or --user

Ceph identifies users with a type and an ID (TYPE.ID, such as client.admin or client.user1). The id, name and -n options enable you to specify the ID portion of the user name (for example admin or user1). You can specify the user with the --id and omit the type. For example, to specify user client.foo enter the following:

cephadm > ceph --id foo --keyring /path/to/keyring health
cephadm > ceph --user foo --keyring /path/to/keyring health
--name or -n

Ceph identifies users with a type and an ID (TYPE.ID, such as client.admin or client.user1). The --name and -n options enable you to specify the fully qualified user name. You must specify the user type (typically client) with the user ID:

cephadm > ceph --name client.foo --keyring /path/to/keyring health
cephadm > ceph -n client.foo --keyring /path/to/keyring health
--keyring

The path to the keyring containing one or more user name and secret. The --secret option provides the same functionality, but it does not work with Object Gateway, which uses --secret for another purpose. You may retrieve a keyring with ceph auth get-or-create and store it locally. This is a preferred approach, because you can switch user names without switching the keyring path:

cephadm > rbd map --id foo --keyring /path/to/keyring mypool/myimage
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