[pve-devel] [PATCH pve-docs 3/3] pveum: better LDAP/AD explanation + restructuring

Dylan Whyte d.whyte at proxmox.com
Fri Oct 1 17:30:51 CEST 2021 

Begin "Authentication Realms" section with brief introduction to each
realm (this was there already, but inconsistent in the level of detail
given for each part).

Give each realm type its own subsection

Adds some more information on LDAP and Active Directory configuration.

Restructure the document to bring the "Syncing LDAP-Based Realms" section
closer to the LDAP and AD sections.

Explain LDAP parameters/options individually in list format

Remove some non-relevant information such as how to add system users

Some more minor langauge and formatting fixup
---
 pveum.adoc | 324 +++++++++++++++++++++++++++++++++++------------------
 1 file changed, 216 insertions(+), 108 deletions(-)

diff --git a/pveum.adoc b/pveum.adoc
index 97e0005..492aa8f 100644
--- a/pveum.adoc
+++ b/pveum.adoc
@@ -127,39 +127,78 @@ As {pve} users are just counterparts for users existing on some external
 realm, the realms have to be configured in `/etc/pve/domains.cfg`.
 The following realms (authentication methods) are available:
 
-Linux PAM standard authentication::
-In this case, a system user must exist (for example, created via the `adduser`
-command) on each node which the user is allowed to log in, and the user
-authenticates with their usual system password.
-+
-[source,bash]
-----
-useradd heinz
-passwd heinz
-groupadd watchman
-usermod -a -G watchman heinz
-----
+Linux PAM Standard Authentication::
 
-Proxmox VE authentication server::
-This is a Unix-like password store (`/etc/pve/priv/shadow.cfg`).
-Passwords are encrypted using the SHA-256 hashing algorithm.
-This is the most convenient method for small-scale (or even mid-scale)
-installations, where users do not need access to anything outside of
-{pve}. In this case, users are fully managed by {pve} and are able to
-change their own passwords via the GUI.
+Linux PAM is a framework for system-wide user authentication. These users are
+created on the host system with commands such as `adduser`. If PAM users exist
+on the {pve} host system, corresponding entries can be added to {pve}, to allow
+these users to log in via their system username and password.
+
+{pve} Authentication Server::
+
+This is a Unix-like password store, which stores hashed passwords in
+`/etc/pve/priv/shadow.cfg`. Passwords are hashed using the SHA-256 hashing
+algorithm. This is the most convenient realm for small-scale (or even
+mid-scale) installations, where users do not need access to anything outside of
+{pve}. In this case, users are fully managed by {pve} and are able to change
+their own passwords via the GUI.
 
 LDAP::
-It is possible to authenticate users via an LDAP server (for example,
-openldap). A server and optional fallback server can be
-configured, and the connection can be encrypted via SSL.
-+
-Users are searched under a 'Base Domain Name' (`base_dn`), with the
-username found in the attribute specified in the 'User Attribute Name'
+
+LDAP (Lightweight Directory Access Protocol) is an open, cross-platform protocol
+for authentication using directory services. OpenLDAP is a popular open-source
+implementations of the LDAP protocol.
+
+Microsoft Active Directory (AD)::
+
+Microsoft Active Directory (AD) is a directory service for Windows domain
+networks and is supported as an authentication realm for {pve}. It supports LDAP
+as an authentication protocol.
+
+OpenID Connect::
+
+OpenID Connect is implemented as an identity layer on top of the OATH 2.0
+protocol. It allows clients to verify the identity of the user, based on
+authentication performed by an external authorization server.
+
+Linux PAM Standard Authentication
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+As Linux PAM corresponds to host system users, a system user must exist on each
+node which the user is allowed to log in on. The user authenticates with their
+usual system password. This realm is added by default and can't be removed. In
+terms of configurability, an administrator can choose to require two-factor
+authentication with logins from the realm and to set the realm as the default
+authentication realm.
+
+
+{pve} Authentication Server
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The {pve} authentication server realm is a simple Unix-like password store.
+The realm is created by default, and as with Linux PAM, the only configuration
+items available are the ability to require two-factor authentication for users
+of the realm, and to set it as the default realm for login.
+
+Unlike the other {pve} realm types, users are created and authenticated entirely
+through {pve}, rather than authenticating against another system. Hence, you are
+required to set a password for this type of user upon creation.
+
+
+LDAP
+~~~~
+
+You can also use an external LDAP server for user authentication (for examle,
+OpenLDAP). In this realm type, users are searched under a 'Base Domain Name'
+(`base_dn`), using the username attribute specified in the 'User Attribute Name'
 (`user_attr`) field.
-+
-For instance, if a user is represented via the
-following LDIF dataset:
-+
+
+A server and optional fallback server can be configured, and the connection can
+be encrypted via SSL. Furthermore, filters can be configured for directories and
+groups. Filters allow you to further limit the scope of the realm.
+
+For instance, if a user is represented via the following LDIF dataset:
+
 ----
 # user1 of People at ldap-test.com
 dn: uid=user1,ou=People,dc=ldap-test,dc=com
@@ -172,33 +211,160 @@ cn: Test User 1
 sn: Testers
 description: This is the first test user.
 ----
-+
+
 The 'Base Domain Name' would be `ou=People,dc=ldap-test,dc=com` and the user
 attribute would be `uid`.
-+
+
 If {pve} needs to authenticate (bind) to the LDAP server before being
 able to query and authenticate users, a bind domain name can be
 configured via the `bind_dn` property in `/etc/pve/domains.cfg`. Its
 password then has to be stored in `/etc/pve/priv/ldap/<realmname>.pw`
 (for example, `/etc/pve/priv/ldap/my-ldap.pw`). This file should contain a
 single line with the raw password.
-+
+
 To verify certificates, you need to set `capath`. You can set it either
 directly to the CA certificate of your LDAP server, or to the system path
 containing all trusted CA certificates (`/etc/ssl/certs`).
 Additionally, you need to set the `verify` option, which can also be done over
 the web interface.
 
+The main configuration options for an LDAP server realm are as follows:
+
+* `Realm` (`realm`): The realm identifier for {pve} users
+
+* `Base Domain Name` (`base_dn`): The directory which users are searched under
+
+* `User Attribute Name` (`user_attr`): The LDAP attribute containing the
+  username that users will log in with
+
+* `Server` (`server1`): The server hosting the LDAP directory
+
+* `Fallback Server` (`server2`): An optional fallback server address, in case
+  the primary server is unreachable
+
+* `Port` (`port`): The port that the LDAP server listens on
+
 NOTE: In order to allow a particular user to authenticate using the LDAP server,
-you must also add them as a user of that realm from the {pve} server.
+you must also add them as a user of that realm from the {pve} server. This can
+be carried out automatically with <<pveum_ldap_sync, syncing>>.
 
-A server and authentication domain need to be specified. Like with LDAP, an
-optional fallback server, port, and SSL encryption can be configured.
 
-OpenID Connect::
+Microsoft Active Directory (AD)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-OpenID Connect allows clients to verify the identity of the user, based on
-authentication performed by an external authorization server.
+To set up Microsoft AD as a realm, a server address and authentication domain
+need to be specified. Active Directory supports most of the same properties as
+LDAP, such as an optional fallback server, port, and SSL encryption.
+Furthermore, users can be added to {pve} automatically via
+<<pveum_ldap_sync, sync>> operations, after configuration.
+
+As with LDAP, if {pve} needs to authenticate before it binds to the AD server,
+you must configure the 'Bind User' (`bind_dn`) property. This property is
+typically required by default for Microsoft AD.
+
+The main configuration settings for Microsoft Active Directory are:
+
+* `Realm` (`realm`): The realm identifier for {pve} users
+
+* `Domain` (`domain`): The AD domain of the server
+
+* `Server` (`server1`): The FQDN or IP address of the server
+
+* `Fallback Server` (`server2`): An optional fallback server address, in case
+  the primary server is unreachable
+
+* `Port` (`port`): The port that the Microsoft AD server listens on
+
+[[pveum_ldap_sync]]
+Syncing LDAP-Based Realms
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+[thumbnail="screenshot/gui-datacenter-realm-add-ldap.png"]
+
+It's possible to automatically sync users and groups for LDAP-based realms (LDAP
+& Microsoft Active Directory), rather than having to add them to {pve} manually.
+You can access the sync options from the Add/Edit window of the web interface's
+`Authentication` panel or via the `pveum realm add/modify` commands. You can
+then carry out the sync operation from the `Authentication` panel of the GUI or
+using the following command:
+
+----
+pveum realm sync <realm>
+----
+
+Users and groups are synced to the cluster-wide configuration file,
+`/etc/pve/user.cfg`.
+
+
+Sync Configuration
+^^^^^^^^^^^^^^^^^^
+
+The configuration options for syncing LDAP-based realms can be found in the
+`Sync Options` tab of the Add/Edit window.
+
+The configuration options are as follows:
+
+* `Bind User` (`bind_dn`): Refers to the LDAP account used to query users
+  and groups. This account needs access to all desired entries. If it's set, the
+  search will be carried out via binding; otherwise, the search will be carried
+  out anonymously. The user must be a complete LDAP formatted distinguished name
+  (DN), for example, `cn=admin,dc=example,dc=com`.
+
+* Groupname attr. (group_name_attr): Represents the
+  users' groups. Only entries which adhere to the usual character limitations of
+  the `user.cfg` are synced. Groups are synced with `-$realm` attached to the
+  name, in order to avoid naming conflicts. Please ensure that a sync does not
+  overwrite manually created groups.
+
+* `User classes` (`user_classes`): Objects classes associated with users.
+
+* `Group classes` (`group_classes`): Objects classes associated with groups.
+
+* `E-Mail attribute`: If the LDAP-based server specifies user email addresses,
+  these can also be included in the sync by setting the associated attribute
+  here. From the command line, this is achievable through the
+  `--sync_attributes` parameter.
+
+* `User Filter` (`filter`): For further filter options to target specific users.
+
+* `Group Filter` (`group_filter`): For further filter options to target specific
+  groups.
+
+NOTE: Filters allow you to create a set of additional match criteria, to narrow
+down the scope of a sync. Information on available LDAP filter types and their
+usage can be found at https://ldap.com/ldap-filters/[ldap.com].
+
+
+[[pveum_ldap_sync_options]]
+Sync Options
+^^^^^^^^^^^^
+
+[thumbnail="screenshot/gui-datacenter-realm-add-ldap-sync-options.png"]
+
+In addition to the options specified in the previous section, you can also
+configure further options that describe the behavior of the sync operation.
+
+These options are either set as parameters before the sync, or as defaults via
+the realm option `sync-defaults-options`.
+
+The main options for syncing are:
+
+* `Scope` (`scope`): The scope of what to sync. It can be either `users`,
+  `groups` or `both`.
+
+* `Enable new` (`enable-new`): If set, the newly synced users are enabled and
+  can log in. The default is `true`.
+
+* `Full` (`full`): If set, the sync uses the LDAP directory as a source of
+  truth, overwriting information set manually in the `user.cfg` and deleting
+  users and groups which are not present in the LDAP directory. If not set, only
+  new data is written to the configuration, and no stale users are deleted.
+
+* `Purge ACLs` (`purge`): If set, sync removes all corresponding ACLs when
+  removing users and groups. This is only useful with the option `full`.
+
+* `Preview` (`dry-run`): No data is written to the config. This is useful if you
+  want to see which users and groups would get synced to the `user.cfg`.
 
 
 [[pveum_openid]]
@@ -207,25 +373,26 @@ OpenID Connect
 
 The main OpenID Connect configuration options are:
 
-* `issuer-url`: This is the URL to the authorization server. Proxmox
-uses the OpenID Connect Discovery protocol to automatically configure
+* `Issuer URL` (`issuer-url`): This is the URL of the authorization server.
+Proxmox uses the OpenID Connect Discovery protocol to automatically configure
 further details.
 +
 While it is possible to use unencrypted `http://` URLs, we strongly recommend to
 use encrypted `https://` connections.
 
-* `client-id`:  OpenID Client ID.
+* `Realm` (`realm`): The realm identifier for {pve} users
 
-* `client-key`: Optional OpenID Client Key.
+* `Client ID` (`client-id`):  OpenID Client ID.
 
-* `autocreate`: Automatically create users if they do not exist. While
-authentication is done at the OpenID server, all users still need an
-entry in the {pve} user configuration. You can either add them
-manually, or use the `autocreate` option to automatically add new
-users.
+* `Client Key` (`client-key`): Optional OpenID Client Key.
 
-* `username-claim`: OpenID claim used to generate the unique username
-  (`subject`, `username` or `email`).
+* `Autocreate Users` (`autocreate`): Automatically create users if they do not
+exist. While authentication is done at the OpenID server, all users still need
+an entry in the {pve} user configuration. You can either add them manually, or
+use the `autocreate` option to automatically add new users.
+
+* `Username Claim` (`username-claim`): OpenID claim used to generate the unique
+username (`subject`, `username` or `email`).
 
 Username mapping
 ^^^^^^^^^^^^^^^^
@@ -280,65 +447,6 @@ WARNING: You need to ensure that the user is not allowed to edit
 the username setting themselves (on the Keycloak server).
 
 
-[[pveum_ldap_sync]]
-Syncing LDAP-based realms
-~~~~~~~~~~~~~~~~~~~~~~~~~
-
-[thumbnail="screenshot/gui-datacenter-realm-add-ldap.png"]
-
-It is possible to sync users and groups for LDAP-based realms. You can use the
-following CLI command:
-
-----
-pveum realm sync <realm>
-----
-
-or the `Authentication` panel of the GUI. Users and groups are synced to the
-cluster-wide user configuration file `/etc/pve/user.cfg`.
-
-Requirements and limitations
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-The `bind_dn` is used to query users and groups. This account needs access
-to all desired entries.
-
-The fields which represent the names of the users and groups can be configured
-via the `user_attr` and `group_name_attr` respectively. Only entries which
-adhere to the usual character limitations of the `user.cfg` are synced.
-
-Groups are synced with `-$realm` attached to the name, in order to avoid naming
-conflicts. Please ensure that a sync does not overwrite manually created
-groups.
-
-[[pveum_ldap_sync_options]]
-Options
-^^^^^^^
-
-[thumbnail="screenshot/gui-datacenter-realm-add-ldap-sync-options.png"]
-
-The main options for syncing are:
-
-* `dry-run`: No data is written to the config. This is useful if you want to
-  see which users and groups would get synced to the `user.cfg`. This is set
-  when you click `Preview` in the GUI.
-
-* `enable-new`: If set, the newly synced users are enabled and can log in.
-  The default is `true`.
-
-* `full`: If set, the sync uses the LDAP directory as a source of truth,
-  overwriting information set manually in the `user.cfg` and deleting users
-  and groups which are not present in the LDAP directory. If not set,
-  only new data is written to the config, and no stale users are deleted.
-
-* `purge`: If set, sync removes all corresponding ACLs when removing users
-  and groups. This is only useful with the option `full`.
-
-* `scope`: The scope of what to sync. It can be either `users`, `groups` or
-  `both`.
-
-These options are either set as parameters or as defaults via the
-realm option `sync-defaults-options`.
-
 [[pveum_tfa_auth]]
 Two-Factor Authentication
 -------------------------
-- 
2.30.2

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