authelia/docs/content/en/reference/guides/ldap.md

title	description	lead	date	draft	images	menu	weight	toc
LDAP	A reference guide on the LDAP implementation specifics	This section contains reference documentation for Authelia's LDAP implementation specifics.	2022-06-17T21:03:47+10:00	false		reference parent guides	220	true

Binding

When it comes to LDAP there are several considerations for deciding how to bind to the LDAP server.

Unauthenticated Binding

The most insecure method is unauthenticated binds. They are generally considered insecure due to the fact allowing them at all ensures anyone with any level of network access can easily obtain objects and their attributes.

Authelia does support unauthenticated binds but it is not by default, you must configure the permit_unauthenticated_bind configuration option.

End-User Binding

One method to bind to the server that is favored by a lot of people is binding to the LDAP server as the end user. While this is more secure than methods such as Unauthenticated Binding the drawback is that it can only be used securely at the time the user enters their credentials. Storing a password in memory in general is not very secure and prone to breakage due to outside influences (i.e. the user changes their password).

In addition, this method is not compatible with the password reset / forgot password flow at all (not to be confused with a change password flow).

Authelia doesn't currently support such a binding method excluding for checking user passwords.

Service-User Binding

This is the most common method of binding to LDAP. This involves setting up a special service user with a complex password which has the minimum permissions required to do the tasks required.

Authelia primarily supports this method.

Implementation Guide

There are currently two implementations, custom and activedirectory. The activedirectory implementation must be used if you wish to allow users to change or reset their password as Active Directory uses a custom attribute for this, and an input format other implementations do not use. The long term intention of this is to have logical defaults for various RFC implementations of LDAP.

Filter replacements

Various replacements occur in the user and groups filter. The replacements either occur at startup or upon an LDAP search.

Users filter replacements

Placeholder	Phase	Replacement
{username_attribute}	startup	The configured username attribute
{mail_attribute}	startup	The configured mail attribute
{display_name_attribute}	startup	The configured display name attribute
{input}	search	The input into the username field

Groups filter replacements

Placeholder	Phase	Replacement
{input}	search	The input into the username field
{username}	search	The username from the profile lookup obtained from the username attribute
{dn}	search	The distinguished name from the profile lookup

Defaults

The below tables describes the current attribute defaults for each implementation.

Attribute defaults

This table describes the attribute defaults for each implementation. i.e. the username_attribute is described by the Username column.

Implementation	Username	Display Name	Mail	Group Name
custom	N/A	displayName	mail	cn
activedirectory	sAMAccountName	displayName	mail	cn

Filter defaults

The filters are probably the most important part to get correct when setting up LDAP. You want to exclude disabled accounts. The active directory example has two attribute filters that accomplish this as an example (more examples would be appreciated). The userAccountControl filter checks that the account is not disabled and the pwdLastSet makes sure that value is not 0 which means the password requires changing at the next login.

Implementation	Users Filter	Groups Filter
custom	N/A	N/A
activedirectory	(&(|({username_attribute}={input})({mail_attribute}={input}))(sAMAccountType=805306368)(!(userAccountControl:1.2.840.113556.1.4.803:=2))(!(pwdLastSet=0)))	(&(member={dn})(sAMAccountType=268435456))

Microsoft Active Directory sAMAccountType

Account Type Value	Description	Equivalent Filter
268435456	Normal Group Objects	N/A
805306368	Normal User Accounts	(&(objectCategory=person)(objectClass=user))

References:

• Account Type Values: Microsoft Learn.
• LDAP Syntax Filters: Microsoft TechNet Wiki