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

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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
/r/ldap

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

The following implementations exist:

  • custom:
    • Not specific to any particular LDAP provider
  • activedirectory:
    • Specific configuration defaults for Active Directory
    • Special implementation details:
      • Includes a special encoding format required for changing passwords with Active Directory
  • freeipa:
    • Specific configuration defaults for FreeIPA
    • No special implementation details
  • lldap:
    • Specific configuration defaults for lldap
    • No special implementation details
  • glauth:
    • Specific configuration defaults for GLAuth
    • No special implementation details

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
{date-time:generalized} search The current UTC time formatted as a LDAP generalized time in the format of 20060102150405.0Z
{date-time:unix-epoch} search The current time formatted as a Unix epoch
{date-time:msft-nt-epoch} search The current time formatted as a Microsoft NT epoch which is used by some Microsoft Active Directory attributes

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.

Search Base defaults

The following set defaults for the additional_users_dn and additional_groups_dn values.

Implementation Users Groups
lldap OU=people OU=groups

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
freeipa uid displayName mail cn
lldap uid cn mail cn
glauth cn description mail cn

Filter defaults

The filters are probably the most important part to get correct when setting up LDAP. You want to exclude accounts under the following conditions:

  • The account is disabled or locked:
    • The Active Directory implementation achieves this via the (!(userAccountControl:1.2.840.113556.1.4.803:=2)) filter.
    • The FreeIPA implementation achieves this via the (!(nsAccountLock=TRUE)) filter.
    • The GLAuth implementation achieves this via the (!(accountStatus=inactive)) filter.
  • Their password is expired:
    • The Active Directory implementation achieves this via the (!(pwdLastSet=0)) filter.
    • The FreeIPA implementation achieves this via the (krbPasswordExpiration>={date-time:generalized}) filter.
  • Their account is expired:
    • The Active Directory implementation achieves this via the (|(!(accountExpires=*))(accountExpires=0)(accountExpires>={date-time:msft-nt-epoch})) filter.
    • The FreeIPA implementation achieves this via the (|(!(krbPrincipalExpiration=*))(krbPrincipalExpiration>={date-time:generalized})) filter.
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))(|(!(accountExpires=*))(accountExpires=0)(accountExpires>={date-time:msft-nt-epoch}))) (&(member={dn})(sAMAccountType=268435456))
freeipa (&(|({username_attribute}={input})({mail_attribute}={input}))(objectClass=person)(!(nsAccountLock=TRUE))(krbPasswordExpiration>={date-time:generalized})(|(!(krbPrincipalExpiration=*))(krbPrincipalExpiration>={date-time:generalized}))) (&(member={dn})(objectClass=groupOfNames))
lldap (&(|({username_attribute}={input})({mail_attribute}={input}))(objectClass=person)) (&(member={dn})(objectClass=groupOfNames))
glauth (&(|({username_attribute}={input})({mail_attribute}={input}))(objectClass=posixAccount)(!(accountStatus=inactive))) (&(uniqueMember={dn})(objectClass=posixGroup))
Microsoft Active Directory sAMAccountType
Account Type Value Description Equivalent Filter
268435456 Global/Universal Security Group Objects N/A
536870912 Domain Local Security Group Objects N/A
805306368 Normal User Accounts (&(objectCategory=person)(objectClass=user))

References: