man `5 sssd-ad`

SSSD-AD(5) File Formats and Conventions SSSD-AD(5)

NAME
sssd-ad - SSSD Active Directory provider

DESCRIPTION
This manual page describes the configuration of the AD provider for
sssd(8). For a detailed syntax reference, refer to the "FILE FORMAT"
section of the sssd.conf(5) manual page.

The AD provider is a back end used to connect to an Active Directory
server. This provider requires that the machine be joined to the AD
domain and a keytab is available. Back end communication occurs over a
GSSAPI-encrypted channel, SSL/TLS options should not be used with the
AD provider and will be superseded by Kerberos usage.

The AD provider supports connecting to Active Directory 2008 R2 or
later. Earlier versions may work, but are unsupported.

The AD provider can be used to get user information and authenticate
users from trusted domains. Currently only trusted domains in the same
forest are recognized. In addition servers from trusted domains are
always auto-discovered.

The AD provider enables SSSD to use the sssd-ldap(5) identity provider
and the sssd-krb5(5) authentication provider with optimizations for
Active Directory environments. The AD provider accepts the same options
used by the sssd-ldap and sssd-krb5 providers with some exceptions.
However, it is neither necessary nor recommended to set these options.

The AD provider primarily copies the traditional ldap and krb5 provider
default options with some exceptions, the differences are listed in the
"MODIFIED DEFAULT OPTIONS" section.

The AD provider can also be used as an access, chpass, sudo and autofs
provider. No configuration of the access provider is required on the
client side.

If "auth_provider=ad" or "access_provider=ad" is configured in
sssd.conf then the id_provider must also be set to "ad".

By default, the AD provider will map UID and GID values from the
objectSID parameter in Active Directory. For details on this, see the
"ID MAPPING" section below. If you want to disable ID mapping and
instead rely on POSIX attributes defined in Active Directory, you
should set

ldap_id_mapping = False

If POSIX attributes should be used, it is recommended for performance
reasons that the attributes are also replicated to the Global Catalog.
If POSIX attributes are replicated, SSSD will attempt to locate the
domain of a requested numerical ID with the help of the Global Catalog
and only search that domain. In contrast, if POSIX attributes are not
replicated to the Global Catalog, SSSD must search all the domains in
the forest sequentially. Please note that the "cache_first" option
might be also helpful in speeding up domainless searches. Note that if
only a subset of POSIX attributes is present in the Global Catalog, the
non-replicated attributes are currently not read from the LDAP port.

Users, groups and other entities served by SSSD are always treated as
case-insensitive in the AD provider for compatibility with Active
Directory's LDAP implementation.

SSSD only resolves Active Directory Security Groups. For more
information about AD group types see: Active Directory security
groups[1]

SSSD filters out Domain Local groups from remote domains in the AD
forest. By default they are filtered out e.g. when following a nested
group hierarchy in remote domains because they are not valid in the
local domain. This is done to be in agreement with Active Directory's
group-membership assignment which can be seen in the PAC of the
Kerberos ticket of a user issued by Active Directory.

CONFIGURATION OPTIONS
Refer to the section "DOMAIN SECTIONS" of the sssd.conf(5) manual page
for details on the configuration of an SSSD domain.

ad_domain (string)
Specifies the name of the Active Directory domain. This is
optional. If not provided, the configuration domain name is used.

For proper operation, this option should be specified as the
lower-case version of the long version of the Active Directory
domain.

The short domain name (also known as the NetBIOS or the flat name)
is autodetected by the SSSD.

ad_enabled_domains (string)
A comma-separated list of enabled Active Directory domains. If
provided, SSSD will ignore any domains not listed in this option.
If left unset, all discovered domains from the AD forest will be
available.

During the discovery of the domains SSSD will filter out some
domains where flags or attributes indicate that they do not belong
to the local forest or are not trusted. If ad_enabled_domains is
set, SSSD will try to enable all listed domains.

For proper operation, this option must be specified in all
lower-case and as the fully qualified domain name of the Active
Directory domain. For example:

ad_enabled_domains = sales.example.com, eng.example.com

The short domain name (also known as the NetBIOS or the flat name)
will be autodetected by SSSD.

Default: Not set

ad_server, ad_backup_server (string)
The comma-separated list of hostnames of the AD servers to which
SSSD should connect in order of preference. For more information on
failover and server redundancy, see the "FAILOVER" section.

This is optional if autodiscovery is enabled. For more information
on service discovery, refer to the "SERVICE DISCOVERY" section.

Note: Trusted domains will always auto-discover servers even if the
primary server is explicitly defined in the ad_server option.

ad_hostname (string)
Optional. On machines where the hostname(5) does not reflect the
fully qualified name, sssd will try to expand the short name. If it
is not possible or the short name should be really used instead,
set this parameter explicitly.

This field is used to determine the host principal in use in the
keytab and to perform dynamic DNS updates. It must match the
hostname for which the keytab was issued.

ad_enable_dns_sites (boolean)
Enables DNS sites - location based service discovery.

If true and service discovery (see Service Discovery paragraph at
the bottom of the man page) is enabled, the SSSD will first attempt
to discover the Active Directory server to connect to using the
Active Directory Site Discovery and fall back to the DNS SRV
records if no AD site is found. The DNS SRV configuration,
including the discovery domain, is used during site discovery as
well.

Default: true

ad_access_filter (string)
Specifies an LDAP access control filter that a user must match to
gain access. The "access_provider" option must be explicitly set to
"ad" for this option to take effect. If you want to use the
"ad_access_filter" as the only access control scheme, you must
disable GPO based access control (see option
"ad_gpo_access_control" for details).

The option also supports specifying different filters per domain or
forest. This extended filter would consist of:
"KEYWORD:NAME:FILTER". The keyword can be either "DOM", "FOREST" or
missing.

If the keyword equals to "DOM" or is missing, then "NAME" specifies
the domain or subdomain the filter applies to. If the keyword
equals to "FOREST", then the filter equals to all domains from the
forest specified by "NAME".

Multiple filters can be separated with the "?" character,
similarly to how search bases work.

Nested group membership must be searched for using a special OID
":1.2.840.113556.1.4.1941:" in addition to the full
DOM:domain.example.org: syntax to ensure the parser does not
attempt to interpret the colon characters associated with the OID.
If you do not use this OID then nested group membership will not be
resolved. See usage example below and refer here for further
information about the OID: [MS-ADTS] section LDAP extensions[2]

The most specific match is always used. For example, if the option
specified filter for a domain the user is a member of and a global
filter, the per-domain filter would be applied. If there are more
matches with the same specification, the first one is used.

Examples:

# apply filter on domain called dom1 only:
dom1:(memberOf=cn=admins,ou=groups,dc=dom1,dc=com)

# apply filter on domain called dom2 only:
DOM:dom2:(memberOf=cn=admins,ou=groups,dc=dom2,dc=com)

# apply filter on forest called EXAMPLE.COM only:
FOREST:EXAMPLE.COM:(memberOf=cn=admins,ou=groups,dc=example,dc=com)

# apply filter for a member of a nested group in dom1:
DOM:dom1:(memberOf:1.2.840.113556.1.4.1941:=cn=nestedgroup,ou=groups,dc=example,dc=com)

Default: Not set

ad_site (string)
Specify AD site to which client should try to connect. If this
option is not provided, the AD site will be auto-discovered.

Default: Not set

ad_enable_gc (boolean)
By default, the SSSD connects to the Global Catalog first to
retrieve users from trusted domains and uses the LDAP port to
retrieve group memberships or as a fallback. Disabling this option
makes the SSSD only connect to the LDAP port of the current AD
server.

Please note that disabling Global Catalog support does not disable
retrieving users from trusted domains. The SSSD would connect to
the LDAP port of trusted domains instead. However, Global Catalog
must be used in order to resolve cross-domain group memberships.

Default: true

ad_gpo_access_control (string)
This option specifies the operation mode for GPO-based access
control functionality: whether it operates in disabled mode,
enforcing mode, or permissive mode. Please note that the
"access_provider" option must be explicitly set to "ad" in order
for this option to have an effect.

GPO-based access control functionality uses GPO policy settings to
determine whether or not a particular user is allowed to logon to
the host. For more information on the supported policy settings
please refer to the "ad_gpo_map" options.

Please note that current version of SSSD does not support Active
Directory's built-in groups. Built-in groups (such as
Administrators with SID S-1-5-32-544) in GPO access control rules
will be ignored by SSSD. See upstream issue tracker
https://github.com/SSSD/sssd/issues/5063 .

Before performing access control SSSD applies group policy security
filtering on the GPOs. For every single user login, the
applicability of the GPOs that are linked to the host is checked.
In order for a GPO to apply to a user, the user or at least one of
the groups to which it belongs must have following permissions on
the GPO:

o Read: The user or one of its groups must have read access to
the properties of the GPO (RIGHT_DS_READ_PROPERTY)

o Apply Group Policy: The user or at least one of its groups must
be allowed to apply the GPO (RIGHT_DS_CONTROL_ACCESS).

By default, the Authenticated Users group is present on a GPO and
this group has both Read and Apply Group Policy access rights.
Since authentication of a user must have been completed
successfully before GPO security filtering and access control are
started, the Authenticated Users group permissions on the GPO
always apply also to the user.

NOTE: If the operation mode is set to enforcing, it is possible
that users that were previously allowed logon access will now be
denied logon access (as dictated by the GPO policy settings). In
order to facilitate a smooth transition for administrators, a
permissive mode is available that will not enforce the access
control rules, but will evaluate them and will output a syslog
message if access would have been denied. By examining the logs,
administrators can then make the necessary changes before setting
the mode to enforcing. For logging GPO-based access control debug
level 'trace functions' is required (see sssctl(8) manual page).

There are three supported values for this option:

o disabled: GPO-based access control rules are neither evaluated
nor enforced.

o enforcing: GPO-based access control rules are evaluated and
enforced.

o permissive: GPO-based access control rules are evaluated, but
not enforced. Instead, a syslog message will be emitted
indicating that the user would have been denied access if this
option's value were set to enforcing.

Default: enforcing

ad_gpo_implicit_deny (boolean)
Normally when no applicable GPOs are found the users are allowed
access. When this option is set to True users will be allowed
access only when explicitly allowed by a GPO rule. Otherwise users
will be denied access. This can be used to harden security but be
careful when using this option because it can deny access even to
users in the built-in Administrators group if no GPO rules apply to
them.

Default: False

The following 2 tables should illustrate when a user is allowed or
rejected based on the allow and deny login rights defined on the
server-side and the setting of ad_gpo_implicit_deny.

ad_gpo_ignore_unreadable (boolean)
Normally when some group policy containers (AD object) of
applicable group policy objects are not readable by SSSD then users
are denied access. This option allows to ignore group policy
containers and with them associated policies if their attributes in
group policy containers are not readable for SSSD.

Default: False

ad_gpo_cache_timeout (integer)
The amount of time between lookups of GPO policy files against the
AD server. This will reduce the latency and load on the AD server
if there are many access-control requests made in a short period.

Default: 5 (seconds)

ad_gpo_map_interactive (string)
A comma-separated list of PAM service names for which GPO-based
access control is evaluated based on the InteractiveLogonRight and
DenyInteractiveLogonRight policy settings. Only those GPOs are
evaluated for which the user has Read and Apply Group Policy
permission (see option "ad_gpo_access_control"). If an evaluated
GPO contains the deny interactive logon setting for the user or one
of its groups, the user is denied local access. If none of the
evaluated GPOs has an interactive logon right defined, the user is
granted local access. If at least one evaluated GPO contains
interactive logon right settings, the user is granted local access
only, if it or at least one of its groups is part of the policy
settings.

Note: Using the Group Policy Management Editor this value is called
"Allow log on locally" and "Deny log on locally".

It is possible to add another PAM service name to the default set
by using "+service_name" or to explicitly remove a PAM service name
from the default set by using "-service_name". For example, in
order to replace a default PAM service name for this logon right
(e.g. "login") with a custom pam service name (e.g.
"my_pam_service"), you would use the following configuration:

ad_gpo_map_interactive = +my_pam_service, -login

Default: the default set of PAM service names includes:

o login

o su

o su-l

o gdm-fingerprint

o gdm-password

o gdm-smartcard

o kdm

o lightdm

o lxdm

o sddm

o unity

o xdm

ad_gpo_map_remote_interactive (string)
A comma-separated list of PAM service names for which GPO-based
access control is evaluated based on the
RemoteInteractiveLogonRight and DenyRemoteInteractiveLogonRight
policy settings. Only those GPOs are evaluated for which the user
has Read and Apply Group Policy permission (see option
"ad_gpo_access_control"). If an evaluated GPO contains the deny
remote logon setting for the user or one of its groups, the user is
denied remote interactive access. If none of the evaluated GPOs has
a remote interactive logon right defined, the user is granted
remote access. If at least one evaluated GPO contains remote
interactive logon right settings, the user is granted remote access
only, if it or at least one of its groups is part of the policy
settings.

Note: Using the Group Policy Management Editor this value is called
"Allow log on through Remote Desktop Services" and "Deny log on
through Remote Desktop Services".

It is possible to add another PAM service name to the default set
by using "+service_name" or to explicitly remove a PAM service name
from the default set by using "-service_name". For example, in
order to replace a default PAM service name for this logon right
(e.g. "sshd") with a custom pam service name (e.g.
"my_pam_service"), you would use the following configuration:

ad_gpo_map_remote_interactive = +my_pam_service, -sshd

Default: the default set of PAM service names includes:

o sshd

o cockpit

ad_gpo_map_network (string)
A comma-separated list of PAM service names for which GPO-based
access control is evaluated based on the NetworkLogonRight and
DenyNetworkLogonRight policy settings. Only those GPOs are
evaluated for which the user has Read and Apply Group Policy
permission (see option "ad_gpo_access_control"). If an evaluated
GPO contains the deny network logon setting for the user or one of
its groups, the user is denied network logon access. If none of the
evaluated GPOs has a network logon right defined, the user is
granted logon access. If at least one evaluated GPO contains
network logon right settings, the user is granted logon access
only, if it or at least one of its groups is part of the policy
settings.

Note: Using the Group Policy Management Editor this value is called
"Access this computer from the network" and "Deny access to this
computer from the network".

It is possible to add another PAM service name to the default set
by using "+service_name" or to explicitly remove a PAM service name
from the default set by using "-service_name". For example, in
order to replace a default PAM service name for this logon right
(e.g. "ftp") with a custom pam service name (e.g.
"my_pam_service"), you would use the following configuration:

ad_gpo_map_network = +my_pam_service, -ftp

Default: the default set of PAM service names includes:

o ftp

o samba

ad_gpo_map_batch (string)
A comma-separated list of PAM service names for which GPO-based
access control is evaluated based on the BatchLogonRight and
DenyBatchLogonRight policy settings. Only those GPOs are evaluated
for which the user has Read and Apply Group Policy permission (see
option "ad_gpo_access_control"). If an evaluated GPO contains the
deny batch logon setting for the user or one of its groups, the
user is denied batch logon access. If none of the evaluated GPOs
has a batch logon right defined, the user is granted logon access.
If at least one evaluated GPO contains batch logon right settings,
the user is granted logon access only, if it or at least one of its
groups is part of the policy settings.

Note: Using the Group Policy Management Editor this value is called
"Allow log on as a batch job" and "Deny log on as a batch job".

It is possible to add another PAM service name to the default set
by using "+service_name" or to explicitly remove a PAM service name
from the default set by using "-service_name". For example, in
order to replace a default PAM service name for this logon right
(e.g. "crond") with a custom pam service name (e.g.
"my_pam_service"), you would use the following configuration:

ad_gpo_map_batch = +my_pam_service, -crond

Note: Cron service name may differ depending on Linux distribution
used.

Default: the default set of PAM service names includes:

o crond

ad_gpo_map_service (string)
A comma-separated list of PAM service names for which GPO-based
access control is evaluated based on the ServiceLogonRight and
DenyServiceLogonRight policy settings. Only those GPOs are
evaluated for which the user has Read and Apply Group Policy
permission (see option "ad_gpo_access_control"). If an evaluated
GPO contains the deny service logon setting for the user or one of
its groups, the user is denied service logon access. If none of the
evaluated GPOs has a service logon right defined, the user is
granted logon access. If at least one evaluated GPO contains
service logon right settings, the user is granted logon access
only, if it or at least one of its groups is part of the policy
settings.

Note: Using the Group Policy Management Editor this value is called
"Allow log on as a service" and "Deny log on as a service".

It is possible to add a PAM service name to the default set by
using "+service_name". Since the default set is empty, it is not
possible to remove a PAM service name from the default set. For
example, in order to add a custom pam service name (e.g.
"my_pam_service"), you would use the following configuration:

ad_gpo_map_service = +my_pam_service

Default: not set

ad_gpo_map_permit (string)
A comma-separated list of PAM service names for which GPO-based
access is always granted, regardless of any GPO Logon Rights.

It is possible to add another PAM service name to the default set
by using "+service_name" or to explicitly remove a PAM service name
from the default set by using "-service_name". For example, in
order to replace a default PAM service name for unconditionally
permitted access (e.g. "sudo") with a custom pam service name
(e.g. "my_pam_service"), you would use the following
configuration:

ad_gpo_map_permit = +my_pam_service, -sudo

Default: the default set of PAM service names includes:

o polkit-1

o sudo

o sudo-i

o systemd-user

ad_gpo_map_deny (string)
A comma-separated list of PAM service names for which GPO-based
access is always denied, regardless of any GPO Logon Rights.

ad_gpo_map_deny = +my_pam_service

Default: not set

ad_gpo_default_right (string)
This option defines how access control is evaluated for PAM service
names that are not explicitly listed in one of the ad_gpo_map_*
options. This option can be set in two different manners. First,
this option can be set to use a default logon right. For example,
if this option is set to 'interactive', it means that unmapped PAM
service names will be processed based on the InteractiveLogonRight
and DenyInteractiveLogonRight policy settings. Alternatively, this
option can be set to either always permit or always deny access for
unmapped PAM service names.

Supported values for this option include:

o interactive

o remote_interactive

o network

o batch

o service

o permit

o deny

Default: deny

ad_maximum_machine_account_password_age (integer)
SSSD will check once a day if the machine account password is older
than the given age in days and try to renew it. A value of 0 will
disable the renewal attempt.

Default: 30 days

ad_machine_account_password_renewal_opts (string)
This option should only be used to test the machine account renewal
task. The option expects 2 integers separated by a colon (':'). The
first integer defines the interval in seconds how often the task is
run. The second specifies the initial timeout in seconds before the
task is run for the first time after startup.

Default: 86400:750 (24h and 15m)

ad_update_samba_machine_account_password (boolean)
If enabled, when SSSD renews the machine account password, it will
also be updated in Samba's database. This prevents Samba's copy of
the machine account password from getting out of date when it is
set up to use AD for authentication.

Default: false

ad_use_ldaps (bool)
By default SSSD uses the plain LDAP port 389 and the Global Catalog
port 3628. If this option is set to True SSSD will use the LDAPS
port 636 and Global Catalog port 3629 with LDAPS protection. Since
AD does not allow to have multiple encryption layers on a single
connection and we still want to use SASL/GSSAPI or SASL/GSS-SPNEGO
for authentication the SASL security property maxssf is set to 0
(zero) for those connections.

Default: False

ad_allow_remote_domain_local_groups (boolean)
If this option is set to "true" SSSD will not filter out Domain
Local groups from remote domains in the AD forest. By default they
are filtered out e.g. when following a nested group hierarchy in
remote domains because they are not valid in the local domain. To
be compatible with other solutions which make AD users and groups
available on Linux client this option was added.

Please note that setting this option to "true" will be against the
intention of Domain Local group in Active Directory and SHOULD ONLY
BE USED TO FACILITATE MIGRATION FROM OTHER SOLUTIONS. Although the
group exists and user can be member of the group the intention is
that the group should be only used in the domain it is defined and
in no others. Since there is only one type of POSIX groups the only
way to achieve this on the Linux side is to ignore those groups.
This is also done by Active Directory as can be seen in the PAC of
the Kerberos ticket for a local service or in tokenGroups requests
where remote Domain Local groups are missing as well.

Given the comments above, if this option is set to "true" the
tokenGroups request must be disabled by setting
"ldap_use_tokengroups" to "false" to get consistent
group-memberships of a users. Additionally the Global Catalog
lookup should be skipped as well by setting "ad_enable_gc" to
"false". Finally it might be necessary to modify
"ldap_group_nesting_level" if the remote Domain Local groups can
only be found with a deeper nesting level.

Default: False

dyndns_update (boolean)
Optional. This option tells SSSD to automatically update the Active
Directory DNS server with the IP address of this client. The update
is secured using GSS-TSIG. As a consequence, the Active Directory
administrator only needs to allow secure updates for the DNS zone.
The IP address of the AD LDAP connection is used for the updates,
if it is not otherwise specified by using the "dyndns_iface"
option.

NOTE: On older systems (such as RHEL 5), for this behavior to work
reliably, the default Kerberos realm must be set properly in
/etc/krb5.conf

Default: true

dyndns_ttl (integer)
The TTL to apply to the client DNS record when updating it. If
dyndns_update is false this has no effect. This will override the
TTL serverside if set by an administrator.

Default: 3600 (seconds)

dyndns_iface (string)
Optional. Applicable only when dyndns_update is true. Choose the
interface or a list of interfaces whose IP addresses should be used
for dynamic DNS updates. Special value "*" implies that IPs from
all interfaces should be used.

Default: Use the IP addresses of the interface which is used for AD
LDAP connection

Example: dyndns_iface = em1, vnet1, vnet2

dyndns_refresh_interval (integer)
How often should the back end perform periodic DNS update in
addition to the automatic update performed when the back end goes
online. This option is optional and applicable only when
dyndns_update is true. Note that the lowest possible value is 60
seconds in-case if value is provided less than 60, parameter will
assume lowest value only.

Default: 86400 (24 hours)

dyndns_update_ptr (bool)
Whether the PTR record should also be explicitly updated when
updating the client's DNS records. Applicable only when
dyndns_update is true.

Note that dyndns_update_per_family parameter does not apply for PTR
record updates. Those updates are always sent separately.

Default: True

dyndns_force_tcp (bool)
Whether the nsupdate utility should default to using TCP for
communicating with the DNS server.

Default: False (let nsupdate choose the protocol)

dyndns_auth (string)
Whether the nsupdate utility should use GSS-TSIG authentication for
secure updates with the DNS server, insecure updates can be sent by
setting this option to 'none'.

Default: GSS-TSIG

dyndns_auth_ptr (string)
Whether the nsupdate utility should use GSS-TSIG authentication for
secure PTR updates with the DNS server, insecure updates can be
sent by setting this option to 'none'.

Default: Same as dyndns_auth

dyndns_server (string)
The DNS server to use when performing a DNS update. In most setups,
it's recommended to leave this option unset.

Setting this option makes sense for environments where the DNS
server is different from the identity server or when we use
encrypted DNS.

The parameter can be a simple string containing DNS name or IP
address. It can also be an URI. The URI can look like
dns://servername/ or dns+tls://1.2.3.4:853#servername/.

The second example enables DNS-over-TLS protocol for DNS updates.
The nsupdate utility must support DoT - check the man nsupdate
before enabling it in SSSD.

Please note that this option will be only used in fallback attempt
when previous attempt using autodetected settings failed or when
DNS-over-TLS is enabled.

Default: None (let nsupdate choose the server)

dyndns_update_per_family (boolean)
DNS update is by default performed in two steps - IPv4 update and
then IPv6 update. In some cases it might be desirable to perform
IPv4 and IPv6 update in single step.

Default: true

dyndns_dot_cacert (string)
This option specifies the file of the certificate authorities
certificates (in PEM format) in order to verify the remote server
TLS certificate when using DoT.

Default: None (use global certificate store)

dyndns_dot_cert (string)
This option sets the certificate(s) file for authentication for the
DoT transport to the remote server. The certificate chain file is
expected to be in PEM format.

The dyndns_dot_cert and dyndns_dot_key options must be both set to
achieve mutual TLS authentication.

Default: None (Do not use TLS authentication)

dyndns_dot_key (string)
This option sets the key file for authenticated encryption for the
DoT transport to the remote server. The private key file is
expected to be in PEM format.

Default: None (Do not use TLS authentication)

override_homedir (string)
Override the user's home directory. You can either provide an
absolute value or a template. In the template, the following
sequences are substituted:

%u
login name

%U
UID number

%d
domain name

%f
fully qualified user name (user@domain)

%l
The first letter of the login name.

%P
UPN - User Principal Name (name@REALM)

%o
The original home directory retrieved from the identity
provider.

%h
The original home directory retrieved from the identity
provider, but in lower case.

%H
The value of configure option homedir_substring.

%%
a literal '%'

This option can also be set per-domain.

example:

override_homedir = /home/%u

Default: Not set (SSSD will use the value retrieved from LDAP)

Please note, the home directory from a specific override for the
user, either locally (see sss_override(8)) or centrally managed IPA
id-overrides, has a higher precedence and will be used instead of
the value given by override_homedir.

homedir_substring (string)
The value of this option will be used in the expansion of the
override_homedir option if the template contains the format string
%H. An LDAP directory entry can directly contain this template so
that this option can be used to expand the home directory path for
each client machine (or operating system). It can be set per-domain
or globally in the [nss] section. A value specified in a domain
section will override one set in the [nss] section.

Default: /home

krb5_confd_path (string)
Absolute path of a directory where SSSD should place Kerberos
configuration snippets.

To disable the creation of the configuration snippets set the
parameter to 'none'.

Default: not set (krb5.include.d subdirectory of SSSD's pubconf
directory)

MODIFIED DEFAULT OPTIONS
Certain option defaults do not match their respective backend provider
defaults, these option names and AD provider-specific defaults are
listed below:

KRB5 Provider
o krb5_validate = true

o krb5_use_enterprise_principal = true

LDAP Provider
o ldap_schema = ad

o ldap_force_upper_case_realm = true

o ldap_id_mapping = true

o ldap_sasl_mech = GSS-SPNEGO

o ldap_referrals = false

o ldap_account_expire_policy = ad

o ldap_use_tokengroups = true

o ldap_sasl_authid = sAMAccountName@REALM (typically
SHORTNAME$@REALM)

The AD provider looks for a different principal than the LDAP
provider by default, because in an Active Directory environment the
principals are divided into two groups - User Principals and
Service Principals. Only User Principal can be used to obtain a TGT
and by default, computer object's principal is constructed from its
sAMAccountName and the AD realm. The well-known host/hostname@REALM
principal is a Service Principal and thus cannot be used to get a
TGT with.

NSS configuration
o fallback_homedir = /home/%d/%u

The AD provider automatically sets "fallback_homedir = /home/%d/%u"
to provide personal home directories for users without the
homeDirectory attribute. If your AD Domain is properly populated
with Posix attributes, and you want to avoid this fallback
behavior, you can explicitly set "fallback_homedir = %o".

Note that the system typically expects a home directory in /home/%u
folder. If you decide to use a different directory structure, some
other parts of your system may need adjustments.

For example automated creation of home directories in combination
with selinux requires selinux adjustment, otherwise the home
directory will be created with wrong selinux context.

FAILOVER
The failover feature allows back ends to automatically switch to a
different server if the current server fails.

Failover Syntax
The list of servers is given as a comma-separated list; any number of
spaces is allowed around the comma. The servers are listed in order of
preference. The list can contain any number of servers.

For each failover-enabled config option, two variants exist: primary
and backup. The idea is that servers in the primary list are preferred
and backup servers are only searched if no primary servers can be
reached. If a backup server is selected, a timeout of 31 seconds is
set. After this timeout SSSD will periodically try to reconnect to one
of the primary servers. If it succeeds, it will replace the current
active (backup) server.

The Failover Mechanism
The failover mechanism distinguishes between a machine and a service.
The back end first tries to resolve the hostname of a given machine; if
this resolution attempt fails, the machine is considered offline. No
further attempts are made to connect to this machine for any other
service. If the resolution attempt succeeds, the back end tries to
connect to a service on this machine. If the service connection attempt
fails, then only this particular service is considered offline and the
back end automatically switches over to the next service. The machine
is still considered online and might still be tried for another
service.

Further connection attempts are made to machines or services marked as
offline after a specified period of time; this is currently hard coded
to 30 seconds.

If there are no more machines to try, the back end as a whole switches
to offline mode, and then attempts to reconnect every 30 seconds.

Failover time outs and tuning
Resolving a server to connect to can be as simple as running a single
DNS query or can involve several steps, such as finding the correct
site or trying out multiple host names in case some of the configured
servers are not reachable. The more complex scenarios can take some
time and SSSD needs to balance between providing enough time to finish
the resolution process but on the other hand, not trying for too long
before falling back to offline mode. If the SSSD debug logs show that
the server resolution is timing out before a live server is contacted,
you can consider changing the time outs.

This section lists the available tunables. Please refer to their
description in the sssd.conf(5), manual page.

dns_resolver_server_timeout
Time in milliseconds that sets how long would SSSD talk to a single
DNS server before trying next one.

Default: 1000

dns_resolver_op_timeout
Time in seconds to tell how long would SSSD try to resolve single
DNS query (e.g. resolution of a hostname or an SRV record) before
trying the next hostname or discovery domain.

Default: 3

dns_resolver_timeout
How long would SSSD try to resolve a failover service. This service
resolution internally might include several steps, such as
resolving DNS SRV queries or locating the site.

Default: 6

For LDAP-based providers, the resolve operation is performed as part of
an LDAP connection operation. Therefore, also the "ldap_opt_timeout"
timeout should be set to a larger value than "dns_resolver_timeout"
which in turn should be set to a larger value than
"dns_resolver_op_timeout" which should be larger than
"dns_resolver_server_timeout".

SERVICE DISCOVERY
The service discovery feature allows back ends to automatically find
the appropriate servers to connect to using a special DNS query. This
feature is not supported for backup servers.

Configuration
If no servers are specified, the back end automatically uses service
discovery to try to find a server. Optionally, the user may choose to
use both fixed server addresses and service discovery by inserting a
special keyword, "_srv_", in the list of servers. The order of
preference is maintained. This feature is useful if, for example, the
user prefers to use service discovery whenever possible, and fall back
to a specific server when no servers can be discovered using DNS.

The domain name
Please refer to the "dns_discovery_domain" parameter in the
sssd.conf(5) manual page for more details.

The protocol
The queries usually specify _tcp as the protocol. Exceptions are
documented in respective option description.

See Also
For more information on the service discovery mechanism, refer to RFC
2782.

ID MAPPING
The ID-mapping feature allows SSSD to act as a client of Active
Directory without requiring administrators to extend user attributes to
support POSIX attributes for user and group identifiers.

NOTE: When ID-mapping is enabled, the uidNumber and gidNumber
attributes are ignored. This is to avoid the possibility of conflicts
between automatically-assigned and manually-assigned values. If you
need to use manually-assigned values, ALL values must be
manually-assigned.

Please note that changing the ID mapping related configuration options
will cause user and group IDs to change. At the moment, SSSD does not
support changing IDs, so the SSSD database must be removed. Because
cached passwords are also stored in the database, removing the database
should only be performed while the authentication servers are
reachable, otherwise users might get locked out. In order to cache the
password, an authentication must be performed. It is not sufficient to
use sss_cache(8) to remove the database, rather the process consists
of:

o Making sure the remote servers are reachable

o Stopping the SSSD service

o Removing the database

o Starting the SSSD service

Moreover, as the change of IDs might necessitate the adjustment of
other system properties such as file and directory ownership, it's
advisable to plan ahead and test the ID mapping configuration
thoroughly.

Mapping Algorithm
Active Directory provides an objectSID for every user and group object
in the directory. This objectSID can be broken up into components that
represent the Active Directory domain identity and the relative
identifier (RID) of the user or group object.

The SSSD ID-mapping algorithm takes a range of available UIDs and
divides it into equally-sized component sections - called "slices".
Each slice represents the space available to an Active Directory
domain.

When a user or group entry for a particular domain is encountered for
the first time, the SSSD allocates one of the available slices for that
domain. In order to make this slice-assignment repeatable on different
client machines, we select the slice based on the following algorithm:

The SID string is passed through the murmurhash3 algorithm to convert
it to a 32-bit hashed value. We then take the modulus of this value
with the total number of available slices to pick the slice.

NOTE: It is possible to encounter collisions in the hash and subsequent
modulus. In these situations, we will select the next available slice,
but it may not be possible to reproduce the same exact set of slices on
other machines (since the order that they are encountered will
determine their slice). In this situation, it is recommended to either
switch to using explicit POSIX attributes in Active Directory
(disabling ID-mapping) or configure a default domain to guarantee that
at least one is always consistent. See "Configuration" for details.

Configuration
Minimum configuration (in the "[domain/DOMAINNAME]" section):

ldap_id_mapping = True
ldap_schema = ad

The default configuration results in configuring 10,000 slices, each
capable of holding up to 200,000 IDs, starting from 200,000 and going
up to 2,000,200,000. This should be sufficient for most deployments.

Advanced Configuration
ldap_idmap_range_min (integer)
Specifies the lower (inclusive) bound of the range of POSIX IDs
to use for mapping Active Directory user and group SIDs. It is
the first POSIX ID which can be used for the mapping.

NOTE: This option is different from "min_id" in that "min_id"
acts to filter the output of requests to this domain, whereas
this option controls the range of ID assignment. This is a
subtle distinction, but the good general advice would be to
have "min_id" be less-than or equal to "ldap_idmap_range_min"

Default: 200000

ldap_idmap_range_max (integer)
Specifies the upper (exclusive) bound of the range of POSIX IDs
to use for mapping Active Directory user and group SIDs. It is
the first POSIX ID which cannot be used for the mapping
anymore, i.e. one larger than the last one which can be used
for the mapping.

NOTE: This option is different from "max_id" in that "max_id"
acts to filter the output of requests to this domain, whereas
this option controls the range of ID assignment. This is a
subtle distinction, but the good general advice would be to
have "max_id" be greater-than or equal to
"ldap_idmap_range_max"

Default: 2000200000

ldap_idmap_range_size (integer)
Specifies the number of IDs available for each slice. If the
range size does not divide evenly into the min and max values,
it will create as many complete slices as it can.

NOTE: The value of this option must be at least as large as the
highest user RID planned for use on the Active Directory
server. User lookups and login will fail for any user whose RID
is greater than this value.

For example, if your most recently-added Active Directory user
has objectSid=S-1-5-21-2153326666-2176343378-3404031434-1107,
"ldap_idmap_range_size" must be at least 1108 as range size is
equal to maximal RID minus minimal RID plus one (e.g. 1108 =
1107 - 0 + 1).

It is important to plan ahead for future expansion, as changing
this value will result in changing all of the ID mappings on
the system, leading to users with different local IDs than they
previously had.

Default: 200000

ldap_idmap_default_domain_sid (string)
Specify the domain SID of the default domain. This will
guarantee that this domain will always be assigned to slice
zero in the ID map, bypassing the murmurhash algorithm
described above.

Default: not set

ldap_idmap_default_domain (string)
Specify the name of the default domain.

Default: not set

ldap_idmap_autorid_compat (boolean)
Changes the behavior of the ID-mapping algorithm to behave more
similarly to winbind's "idmap_autorid" algorithm.

When this option is configured, domains will be allocated
starting with slice zero and increasing monotonically with each
additional domain.

NOTE: This algorithm is non-deterministic (it depends on the
order that users and groups are requested). If this mode is
required for compatibility with machines running winbind, it is
recommended to also use the "ldap_idmap_default_domain_sid"
option to guarantee that at least one domain is consistently
allocated to slice zero.

Default: False

ldap_idmap_helper_table_size (integer)
Maximal number of secondary slices that is tried when
performing mapping from UNIX id to SID.

Note: Additional secondary slices might be generated when SID
is being mapped to UNIX id and RID part of SID is out of range
for secondary slices generated so far. If value of
ldap_idmap_helper_table_size is equal to 0 then no additional
secondary slices are generated.

Default: 10

Well-Known SIDs
SSSD supports to look up the names of Well-Known SIDs, i.e. SIDs with a
special hardcoded meaning. Since the generic users and groups related
to those Well-Known SIDs have no equivalent in a Linux/UNIX environment
no POSIX IDs are available for those objects.

The SID name space is organized in authorities which can be seen as
different domains. The authorities for the Well-Known SIDs are

o Null Authority

o World Authority

o Local Authority

o Creator Authority

o Mandatory Label Authority

o Authentication Authority

o NT Authority

o Built-in

The capitalized version of these names are used as domain names when
returning the fully qualified name of a Well-Known SID.

Since some utilities allow to modify SID based access control
information with the help of a name instead of using the SID directly
SSSD supports to look up the SID by the name as well. To avoid
collisions only the fully qualified names can be used to look up
Well-Known SIDs. As a result the domain names "NULL AUTHORITY", "WORLD
AUTHORITY", "LOCAL AUTHORITY", "CREATOR AUTHORITY", "MANDATORY LABEL
AUTHORITY", "AUTHENTICATION AUTHORITY", "NT AUTHORITY" and "BUILTIN"
should not be used as domain names in sssd.conf.

EXAMPLE
The following example assumes that SSSD is correctly configured and
example.com is one of the domains in the [sssd] section. This example
shows only the AD provider-specific options.

[domain/EXAMPLE]
id_provider = ad
auth_provider = ad
access_provider = ad
chpass_provider = ad

ad_server = dc1.example.com
ad_hostname = client.example.com
ad_domain = example.com

NOTES
The AD access control provider checks if the account is expired. It has
the same effect as the following configuration of the LDAP provider:

access_provider = ldap
ldap_access_order = expire
ldap_account_expire_policy = ad

However, unless the "ad" access control provider is explicitly
configured, the default access provider is "permit". Please note that
if you configure an access provider other than "ad", you need to set
all the connection parameters (such as LDAP URIs and encryption
details) manually.

When the autofs provider is set to "ad", the RFC2307 schema attribute
mapping (nisMap, nisObject, ...) is used, because these attributes are
included in the default Active Directory schema.

SEE ALSO
sssd(8), sssd.conf(5), sssd-ldap(5), sssd-ldap-attributes(5), sssd-
krb5(5), sssd-simple(5), sssd-ipa(5), sssd-ad(5), sssd-files(5), sssd-
sudo(5), sssd-session-recording(5), sss_cache(8), sss_debuglevel(8),
sss_obfuscate(8), sss_seed(8), sssd_krb5_locator_plugin(8),
sss_ssh_authorizedkeys(8), sss_ssh_knownhostsproxy(8), sssd-ifp(5),
pam_sss(8). sss_rpcidmapd(5) sssd-systemtap(5)

AUTHORS
The SSSD upstream - https://github.com/SSSD/sssd/

NOTES
1. Active Directory security groups
https://docs.microsoft.com/en-us/windows-server/identity/ad-ds/manage/understand-security-groups

2. [MS-ADTS] section LDAP extensions
https://msdn.microsoft.com/en-us/library/cc223367.aspx

SSSD 04/07/2025 SSSD-AD(5)

man 5 sssd-ad

man `5 sssd-ad`