docs: add API tokens to documentation

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

docs/user-management.rst

@@ -70,7 +70,7 @@ The resulting user list looks like this:
   │ root@pam │      1 │        │           │          │                  │ Superuser        │
   └──────────┴────────┴────────┴───────────┴──────────┴──────────────────┴──────────────────┘
 
-Newly created users do not have any permissions. Please read the next
+Newly created users do not have any permissions. Please read the Access Control
 section to learn how to set access permissions.
 
 If you want to disable a user account, you can do that by setting ``--enable`` to ``0``
@@ -85,15 +85,69 @@ Or completely remove the user with:
 
   # proxmox-backup-manager user remove john@pbs
 
+.. _user_tokens:
+
+API Tokens
+----------
+
+Any authenticated user can generate API tokens which can in turn be used to
+configure various clients, instead of directly providing the username and
+password.
+
+API tokens serve two purposes:
+
+#. Easy revocation in case client gets compromised
+#. Limit permissions for each client/token within the users' permission
+
+An API token consists of two parts: an identifier consisting of the user name,
+the realm and a tokenname (``user@realm!tokenname``), and a secret value. Both
+need to be provided to the client in place of the user ID (``user@realm``) and
+the user password.
+
+The API token is passed from the client to the server by setting the
+``Authorization`` HTTP header with method ``PBSAPIToken`` to the value
+``TOKENID:TOKENSECRET``.
+
+Generating new tokens can done using ``proxmox-backup-manager`` or the GUI:
+
+.. code-block:: console
+
+  # proxmox-backup-manager user generate-token john@pbs client1
+  Result: {
+    "tokenid": "john@pbs!client1",
+    "value": "d63e505a-e3ec-449a-9bc7-1da610d4ccde"
+  }
+
+.. note:: The displayed secret value needs to be saved, since it cannot be
+  displayed again after generating the API token.
+
+The ``user list-tokens`` sub-command can be used to display tokens and their
+metadata:
+
+.. code-block:: console
+
+  # proxmox-backup-manager user list-tokens john@pbs
+  ┌──────────────────┬────────┬────────┬─────────┐
+  │ tokenid          │ enable │ expire │ comment │
+  ╞══════════════════╪════════╪════════╪═════════╡
+  │ john@pbs!client1 │      1 │        │         │
+  └──────────────────┴────────┴────────┴─────────┘
+
+Similarly, the ``user delete-token`` subcommand can be used to delete a token
+again.
+
+Newly generated API tokens don't have any permissions. Please read the next
+section to learn how to set access permissions.
+
 
 .. _user_acl:
 
 Access Control
 --------------
 
-By default new users do not have any permission. Instead you need to
+By default new users and API tokens do not have any permission. Instead you
-specify what is allowed and what is not. You can do this by assigning
+need to specify what is allowed and what is not. You can do this by assigning
-roles to users on specific objects like datastores or remotes. The
+roles to users/tokens on specific objects like datastores or remotes. The
 following roles exist:
 
 **NoAccess**
@@ -148,20 +202,21 @@ The data represented in each field is as follows:
 #. The object on which the permission is set. This can be a specific object
    (single datastore, remote, etc.) or a top level object, which with
    propagation enabled, represents all children of the object also.
-#. The user for which the permission is set
+#. The user(s)/token(s) for which the permission is set
 #. The role being set
 
-You can manage datastore permissions from **Configuration -> Permissions** in the
+You can manage permissions via **Configuration -> Access Control ->
-web interface. Likewise, you can use the ``acl`` subcommand to manage and
+Permissions** in the web interface. Likewise, you can use the ``acl``
-monitor user permissions from the command line. For example, the command below
+subcommand to manage and monitor user permissions from the command line. For
-will add the user ``john@pbs`` as a **DatastoreAdmin** for the datastore
+example, the command below will add the user ``john@pbs`` as a
-``store1``, located at ``/backup/disk1/store1``:
+**DatastoreAdmin** for the datastore ``store1``, located at
+``/backup/disk1/store1``:
 
 .. code-block:: console
 
-  # proxmox-backup-manager acl update /datastore/store1 DatastoreAdmin --userid john@pbs
+  # proxmox-backup-manager acl update /datastore/store1 DatastoreAdmin --auth-id john@pbs
 
-You can monitor the roles of each user using the following command:
+You can list the ACLs of each user/token using the following command:
 
 .. code-block:: console
 
@@ -172,7 +227,7 @@ You can monitor the roles of each user using the following command:
    │ john@pbs │ /datastore/disk1 │         1 │ DatastoreAdmin │
    └──────────┴──────────────────┴───────────┴────────────────┘
 
-A single user can be assigned multiple permission sets for different datastores.
+A single user/token can be assigned multiple permission sets for different datastores.
 
 .. Note::
   Naming convention is important here. For datastores on the host,
@@ -183,4 +238,39 @@ A single user can be assigned multiple permission sets for different datastores.
   remote (see `Remote` below) and ``{storename}`` is the name of the datastore on
   the remote.
 
+API Token permissions
+~~~~~~~~~~~~~~~~~~~~~
 
+API token permissions are calculated based on ACLs containing their ID
+independent of those of their corresponding user. The resulting permission set
+on a given path is then intersected with that of the corresponding user.
+
+In practice this means:
+
+#. API tokens require their own ACL entries
+#. API tokens can never do more than their corresponding user
+
+Effective permissions
+~~~~~~~~~~~~~~~~~~~~~
+
+To calculate and display the effective permission set of a user or API token
+you can use the ``proxmox-backup-manager user permission`` command:
+
+.. code-block:: console
+
+  # proxmox-backup-manager user permissions john@pbs -- path /datastore/store1
+  Privileges with (*) have the propagate flag set
+  
+  Path: /datastore/store1
+  - Datastore.Audit (*)
+  - Datastore.Backup (*)
+  - Datastore.Modify (*)
+  - Datastore.Prune (*)
+  - Datastore.Read (*)
+  
+  # proxmox-backup-manager acl update /datastore/store1 DatastoreBackup --auth-id 'john@pbs!client1'
+  # proxmox-backup-manager user permissions 'john@pbs!test' -- path /datastore/store1
+  Privileges with (*) have the propagate flag set
+  
+  Path: /datastore/store1
+  - Datastore.Backup (*)