OctoPrint Auth LDAP Plugin

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Prerequisites

Before installing this plugin, consult the python-ldap documentation for its build prerequisites on your system or instructions for installing pre-built binaries on your system. For example, on Debian-based systems (such as Raspbian), it is necessary to preinstall a collection of supporting libraries in order for python-ldap to install properly:

apt-get install build-essential python3-dev python2.7-dev libldap2-dev \
    libsasl2-dev slapd ldap-utils python-tox lcov valgrind

Minimally, on Raspbian:

apt-get install libsasl2-dev python-dev libldap2-dev libssl-dev

Installation

You can install this via the OctoPrint plugin manager GUI using this URL:

https://github.com/gillg/OctoPrint-LDAP/archive/master.zip

The plugin may also be installed within the oprint venv using the command

pip install https://github.com/gillg/OctoPrint-LDAP/archive/master.zip

General Configuration

You could configure LDAP server in plugin config, or manually in config.yaml

plugins:
  auth_ldap:
    uri: ldaps://example.com
    auth_user: example\authuser
    auth_password: s00p3rS3KRE7
    search_base: dc=example,dc=com
    ou: Lab Users, Lab Staff

Details

The plugin extends the FilebasedUserManager to becomae an LDAPUserManager such that when a user logs in:

1. The local users.yaml user list is consulted first -- and, if the user is present, treated as the authoritative credential record
2. If the user is not found locally, the LDAP directory is searched for their username and, optionally, their membership ins specific groups is verified.
3. If the user is found in the LDAP directory, they are optionally cached locally in users.yaml as an LDAPUser (extending User) with configurable default roles in OctoPrint.
4. An attempt is made to bind the user to the LDAP directory using the provided password, double-checking that the user is still a member of any required groups, if configured. If successful, the user is logged in.

Optional Authenticated Search

Most LDAP servers require some level of authentication to perform a search of the directory. Credentials with which to search the directory can be provided:

plugins:
  auth_ldap:
    auth_user: example\authuser
    auth_password: s00p3rS3KRE7

If no authentication username is provided, an anonymous search will be performed (which may not generate useful results on most servers). The auth_user can be provided as a distinguished name (uid=authuser,dc=example,dc=com), principal name ([email protected]) or UID (example\authuser), depending on the needs of the system.

Default Roles/Activity

By default, all LDAP users are treated as active OctoPrint users. They may be configured to default to being admins as well. If LDAP users are cached locally, individual users may be marked inactive within OctoPrint and denied access.

Local Caching

By default, LDAP users are not cached locally, to prevent the potentially complex outcomes described below.

If the LDAP users are cached locally, admin users can manage user permissions and account state within Octoprint. This would allow the default role for LDAP users to be generic OctoPrint users, but for some trusted individuals to have their OctoPrint permissions upgraded to admin locally. Additionally, LDAP users can procure API keys for the system.

As the plugin's group filter (or the group memberships within the LDAP directory) may change over time, LDAP users' group membership is verified against the configured groups, along with their password, on each login.

In users.yaml, the LDAP users are stored thus:

example_user:
  active: true
  apikey: null
  dn: cn=Example user,dc=example,dc=com
  groups:
  - ldap_lab_users
  - users
  password: null
  settings: {}
  type: LDAP

Note that the password hash is stored as null intentionally, to prevent accidental password matching. The assumption being that, if this plugin is disabled, the LDAP users in users.yaml are still parseable by the FilebasedUserManager (since doing otherwise causes the system to choke), so lingering cached LDAP users could then be treated as standard local users. Fortunately, as password checking is done by hashing the proffered password and comparing with the stored hash... and nothing hashes to null, it is impossible to provide a password for a cached LDAP user that will provide access.

Search Base Gotcha

Observationally, I have noticed that the Microsoft LDAP server appears to require the search base to include an organizational unit, as well as the domain controller. (e.g. OU=All Users,DC=example,DC=com), while OpenLDAP appears to be less demanding and will simply accept a domain controller as the search base (e.g. DC=example,DC=com).

If your users are partitioned into more than one top-level organizational unit within the Microsoft LDAP server, there is no way to configure a wild-card search base -- the only way forward would likely be to update the plugin source to accept multiple search bases and then search against each base in turn. Or create one super-OU to contain your disparate OUs.

Groups

In addition to authenticating against the LDAP directory, users may also be filtered for current membership in specific LDAP groups (a.k.a. OUs or Organizational Units). If not specified, no group membership check is performed. Groups are listed as a comma-separated (white space agnostic) list. For example:

plugins:
  auth_ldap:
    ou: Lab Users, Lab Staff

If local caching is enabled, LDAP OU groups will by synced as OctoPrint groups, to allow for per-group permissions configuration. All synced groups are subgroups of a parent OctoPrint group. By default the parent group is LDAP-Authorized Users with key ldap and the synced OU-as-groups are named based on the settings configuration (e.g. Lab Users OU would become a group named Lab Users with key ldap_lab_users).

The naming scheme on these groups can be configured directly through config.yaml with the following keys (and default values):

plugins:
  auth_ldap:
    ldap_group_key_prefix: ldap_
    ldap_parent_group_description: Generated by Auth LDAP plugin, with membership synced automatically based on LDAP configuration
    ldap_parent_group_key: ldap
    ldap_parent_group_name: LDAP-Authenticated Users

Configurable Search Filters

As LDAP directory configuration varies, it may be necessary to configure how users are searched for within the directory.

User Search Filter

By default, the provided userid is searched for using the provided search base and the search filter template uid=%s. This may be configured differently on some systems. For example, one alternate search filter template configuration might be:

plugins:
  auth_ldap:
    search_filter: userPrincipalName=%[email protected]

This would match the provided username as an email address against the userPrincipalName field. The %s placeholder would be replaced with the provided user id.

Group Membership

Membership in LDAP groups is verified by searching for a group with a particular name that has a member with the LDAP distinguished name (DN) that matches the provided user. Two configuration fields affect this matching:

plugins:
  auth_ldap:
    ou_filter: cn=%s
    ou_member_filter: uniqueMember=%s

This configuration would generate a search filter that would test against each provided OU name in turn, using the user's LDAP-provided DN: "(&(cn=%s)(uniqueMember=%s))" % (ou_name, dn), which would end up looking like (&(cn=Lab Users)(uniqueMember=uid=example_user,dc=example.dc=com))

Search Term Transform

OctoPrint searches for users in a case-sensitve manner by default. However, it becomes a management issue (if local caching is turned on) to have cached each case-sensitive search for the same user (e.g. testuser, TESTUSER, TestUser, tEsTuSeR, etc.). In order to manage this issue, the search_term_transform setting allows you to specify a string transformation (e.g. upper or lower) to be applied to search terms if they are not found already cached.

plugins:
  auth_ldap:
    search_term_transform: lower

The result of this will be that the user ID entered in the login dialog will be transformed using this call:

userid = getattr(str, "lower")(str(userid))

Note that this does not provide a capability for more nuanced transformations at this pouint.