SSSD-AD(5)

📦
version 2.13.1 · 22 versions
, in centos-stream 10

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

okay bestie, this is SSSD-AD(5), filed under File Formats and Conventions — the manual page for the SSSD Active Directory provider. It’s giving directory-services main character energy, and we’re getting into all of it. 🦋

✨ 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occurs over a GSSAPI-encrypted channel, SSL/TLS options should not be used with the AD provider and will be superseded by Kerberos usage.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 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 SSSD can do the access control thing, it first security-filters the GPOs — like, an actual vibe check on every single one. Every time a user logs in, SSSD goes through all the GPOs linked to the host and asks "does this one even apply to you, bestie?" For a GPO to apply to a user, the user — or literally at least one of the groups they're in — needs these two permissions on that GPO:

  • Read — the user, or one of their groups, has to have read access to the GPO's properties (RIGHT_DS_READ_PROPERTY).
  • Apply Group Policy — the user, or at least one of their groups, has to be allowed to apply the GPO (RIGHT_DS_CONTROL_ACCESS).

By default the Authenticated Users group is sitting right there on a GPO, and it's got both Read and Apply Group Policy access rights. And since a user has to be authenticated successfully before GPO security filtering and access control even kick off, those Authenticated Users permissions on the GPO always apply to the user too. It's giving "you're in by default, congrats 🎀".

NOTE: if you set the operation mode to enforcing, it's totally possible that users who used to be allowed logon access will now get denied (because that's what the GPO policy settings be saying). So that admins don't get whiplash, there's a permissive mode that doesn't enforce the access control rules — it evaluates them and drops a syslog message if access would have been denied. Read those logs, make your changes, and only then flip to enforcing. For logging GPO-based access control you need the debug level 'trace functions' (peep the sssctl(8) manual page for that one 👀).

There are exactly three supported values for this option:

  • disabled — GPO-based access control rules are neither evaluated nor enforced. We're literally not doing this today ✨
  • enforcing — GPO-based access control rules are evaluated and enforced. No notes, the rules are the rules.
  • permissive — GPO-based access control rules are evaluated but not enforced. Instead a syslog message gets emitted telling you the user would have been denied if this option's value were set to enforcing.

Default: enforcing

ad_gpo_implicit_deny (boolean)

So normally, when no applicable GPOs get found, users are just allowed access — like, whatever, no rules means you're free 🦋. But when this option is set to True, users are allowed access only when a GPO rule explicitly allows them. Otherwise? Denied.

This is highkey a security-hardening move, but be careful bestie, because it can deny access even to users in the built-in Administrators group if no GPO rules apply to them. Iconic but scary 😭

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_implicit_deny = False (default)

  • allow-rules: missing, deny-rules: missing → all users are allowed
  • allow-rules: missing, deny-rules: present → only users not in deny-rules are allowed
  • allow-rules: present, deny-rules: missing → only users in allow-rules are allowed
  • allow-rules: present, deny-rules: present → only users in allow-rules and not in deny-rules are allowed

ad_gpo_implicit_deny = True

  • allow-rules: missing, deny-rules: missing → no users are allowed
  • allow-rules: missing, deny-rules: present → no users are allowed
  • allow-rules: present, deny-rules: missing → only users in allow-rules are allowed
  • allow-rules: present, deny-rules: present → only users in allow-rules and not in deny-rules are allowed

ad_gpo_ignore_unreadable (boolean)

Okay so normally, if some group policy containers (that's an AD object, bestie) of the applicable group policy objects just aren't readable by SSSD, then users get denied access. Kind of harsh tbh. This option lets you ignore those group policy containers — and the policies associated with them — when their attributes in the group policy containers aren't readable for SSSD. Problem? Ignored. 🫶

Default: False

ad_gpo_cache_timeout (integer)

The amount of time between lookups of GPO policy files against the AD server. Why do we care? Because if there are a lot of access-control requests flying in over a short period, this cuts down the latency and the load on the AD server. Server gets to breathe, we get answers faster. Win-win 🌸

Default: 5 (seconds)

ad_gpo_map_interactive (string)

A comma-separated list of PAM service names for which GPO-based access control gets evaluated based on the InteractiveLogonRight and DenyInteractiveLogonRight policy settings. Only those GPOs where the user has Read and Apply Group Policy permission get evaluated (see the option “ad_gpo_access_control”, above 👆).

Here's the tea on how the decision goes down:

  • If an evaluated GPO contains the deny interactive logon setting for the user or one of their 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".

You can absolutely add another PAM service name to the default set by using “+service_name”, or explicitly remove a PAM service name from the default set by using “-service_name”. For example, to swap out a default PAM service name for this logon right (say, “login”) with a custom PAM service name (say, “my_pam_service”), you'd write:

ad_gpo_map_interactive = +my_pam_service, -login

Default: the default set of PAM service names includes:

  • login
  • su
  • su-l
  • gdm-fingerprint
  • gdm-password
  • gdm-smartcard
  • kdm
  • lightdm
  • lxdm
  • plasmalogin
  • sddm
  • unity
  • xdm

ad_gpo_map_remote_interactive (string)

A comma-separated list of PAM service names for which GPO-based access control gets evaluated based on the RemoteInteractiveLogonRight and DenyRemoteInteractiveLogonRight policy settings. Again, only those GPOs get evaluated where the user has Read and Apply Group Policy permission (see the option “ad_gpo_access_control”).

Same energy as the last one, remote flavour:

  • If an evaluated GPO contains the deny remote logon setting for the user or one of their 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".

Same deal for editing the set: add a PAM service name to the default set with “+service_name”, or explicitly remove one with “-service_name”. For example, to replace a default PAM service name for this logon right (say, “sshd”) with a custom PAM service name (say, “my_pam_service”), you'd write:

ad_gpo_map_remote_interactive = +my_pam_service, -sshd

Default: the default set of PAM service names includes:

  • sshd
  • cockpit
  • ad_gpo_map_network (string) — bestie this one's a comma-separated list of PAM service names where GPO-based access control gets evaluated off the NetworkLogonRight and DenyNetworkLogonRight policy settings. Only those GPOs are evaluated for which the user has Read and Apply Group Policy permission (see the ad_gpo_access_control option 👀). If an evaluated GPO contains the deny network logon setting for the user or for one of its groups, the user gets denied network logon access, periodt. If none of the evaluated GPOs has a network logon right defined, the user is granted logon access. And 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: in the Group Policy Management Editor this value is called "Access this computer from the network" and "Deny access to this computer from the network".

You can totally add another PAM service name to the default set with +service_name, or explicitly remove one from the default set with -service_name. So like, 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'd write:

ad_gpo_map_network = +my_pam_service, -ftp

Default: the default set of PAM service names includes:

  • ftp
  • samba
  • ad_gpo_map_batch (string) — same energy, different right: 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 (again, see 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. And 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: in the Group Policy Management Editor this value is called "Allow log on as a batch job" and "Deny log on as a batch job".

Add another PAM service name to the default set with +service_name, or explicitly remove one with -service_name. Example — replacing a default PAM service name for this logon right (e.g. crond) with a custom pam service name (e.g. my_pam_service):

ad_gpo_map_batch = +my_pam_service, -crond
Note: the cron service name may differ depending on the Linux distribution used. 🙈

Default: the default set of PAM service names includes:

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

You can add a PAM service name to the default set with +service_name. Since the default set is empty, it's not possible to remove a PAM service name from the default set — nothing to remove, bestie 😭. So to add a custom pam service name (e.g. my_pam_service):

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. No vibe check, straight through. 👑

Add another PAM service name to the default set with +service_name, or explicitly remove one with -service_name. Example — replacing a default PAM service name for unconditionally permitted access (e.g. sudo) with a custom pam service name (e.g. my_pam_service):

ad_gpo_map_permit = +my_pam_service, -sudo

Default: the default set of PAM service names includes:

  • polkit-1
  • sudo
  • sudo-i
  • 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. Not the vibe, not today. 💀

You can add a PAM service name to the default set with +service_name. Since the default set is empty, it is not possible to remove a PAM service name from the default set. To add a custom pam service name (e.g. my_pam_service):

ad_gpo_map_deny = +my_pam_service

Default: not set

  • ad_gpo_default_right (string) — this one's the main character 🎀: it defines how access control is evaluated for PAM service names that aren't explicitly listed in one of the ad_gpo_map_* options. You can set it two different ways. First way: set it to use a default logon right. So like, if this option is set to 'interactive', that means unmapped PAM service names will be processed based on the InteractiveLogonRight and DenyInteractiveLogonRight policy settings. Second way: set it to either always permit or always deny access for unmapped PAM service names.

Supported values for this option include:

  • interactive
  • remote_interactive
  • network
  • batch
  • service
  • permit
  • 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) — okay so this option should only be used to test the machine account renewal task, fr fr. It expects 3 integers and a string 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. The optional third value specifies a maximal random offset to the previous two values to avoid updates of many hosts at the same time (the "thundering herd problem" 🐄🐄🐄). If this value is missing or empty in the value string, '0' will be used.

The optional fourth string value identifies the helper binary which should be used for the renewal. Currently adcli and realm are supported. If this value is missing or empty in the value string, realm will be used. Since the helper is started as the user SSSD is running as, there might be the chance that the renewal will fail if this user does not has permissions to modify the keytab file where the machine account credentials are stored. This will typically be the case for adcli 🙈.

realm is not updating the keytab directly but is calling the realmd process, which runs as root user, for this task. realmd can allow access to non-privileged users with the help of PolicyKit and by default SSSD provides suitable rules for the user SSSD is running as ✨.

Default: 86400:750:300:realm (24h, 12m30s and 5m)

  • 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's 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

  • 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, which means the Active Directory administrator only needs to allow secure updates for the DNS zone — iconic, honestly. 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 🌸. The name of the interface can be a wildcard pattern prefixed with ! for interface excluding. First match stops the evaluation. For example, the list !eth1, * instructs SSSD to use all interfaces except eth1. See man 7 glob for details about patterns.
NOTE: while it is still possible to use the old ipa_dyndns_iface option, users should migrate to using dyndns_iface in their config file. Do the glow-up bestie 💅

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

Example:

dyndns_iface = em[12], !vnet1, vnet*
  • dyndns_address (string) — Optional, bestie. Applicable only when dyndns_update is true. A list of IP addresses or IP networks to be used for dynamic DNS updates. Network addresses must be in CIDR format. An entry can be prefixed with ! to indicate exclusion. The best match is used to determine whether an address is included or excluded (i.e., a longer prefix takes precedence). Default: No filtering of IP addresses.

Example for dyndns_address:

dyndns_address = 10.0.0.0/16, !10.0.1.0/24
  • 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 homedir value that is defined in the directory of the identity provider.

This substitution is designed to be used in an IPA-AD trust scenario. If this substitution is used for the subdomain_homedir option, it propagates the home directory value from the AD domain to the IPA clients. In this scenario, the option must be set in the SSSD configuration on the IPA server where SSSD is running in server mode.

  • %h — The path defined for the homedir directory attribute of the identity provider, but in lower case. For details of use, see %o.
  • %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 🔑

  • krb5_validate = true
  • krb5_use_enterprise_principal = true

🦋 LDAP Provider 🦋

  • ldap_schema = ad
  • ldap_force_upper_case_realm = true
  • ldap_id_mapping = true
  • ldap_sasl_mech = GSS-SPNEGO
  • ldap_referrals = false
  • ldap_account_expire_policy = ad
  • ldap_use_tokengroups = true
  • 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 🎀

  • 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 💫

okay so the failover feature is literally the back end's safety net 🫶 — it lets back ends automatically switch over to a different server when the current server fails. no manual drama, it just handles it. main character energy tbh.

✨ Failover Syntax ✨

bestie the servers go in a comma-separated list, and you can put any number of spaces around the comma — she's flexible like that 💅. The servers are listed in order of preference, and the list can contain any number of servers.

So for every failover-enabled config option, there are two variants: a primary one and a backup one. The idea is that servers in the primary list are preferred, and backup servers are only searched if no primary servers can be reached. And if a backup server does get selected? A timeout of 31 seconds is set ⏳. After that timeout, SSSD will periodically try to reconnect to one of the primary servers — and if it succeeds, it replaces the current active (backup) server. slay.

💅 The Failover Mechanism 💅

The failover mechanism distinguishes between a machine and a service (important distinction, iykyk).

The back end first tries to resolve the hostname of a given machine. If that resolution attempt fails, the machine is considered offline, and no further attempts are made to connect to this machine for any other service. periodt, she's done with it.

But 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 — the back end automatically switches over to the next service. The machine is still considered online and might still be tried for another service. no cap 💖

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.

And 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 it can involve several steps — like finding the correct site, or trying out multiple host names in case some of the configured servers aren't 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. it's giving ✨balance✨.

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”. it's a whole little ladder of timeouts, iconic 🎀

🦋 SERVICE DISCOVERY 🦋

The service discovery feature lets back ends automatically find the appropriate servers to connect to using a special DNS query ✨. nb: this feature is not supported for backup servers — backup servers, you're on your own bestie 💀.

🌈 Configuration 🌈

If no servers are specified, the back end automatically uses service discovery to try to find a server. Optionally, you (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. so smart honestly.

⭐ 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 💅

Okay so the ID-mapping feature is genuinely iconic — it lets SSSD act as a client of Active Directory without making admins go extend user attributes just to support POSIX attributes for user and group identifiers. No schema surgery, no tears. 🎀

NOTE: the moment ID-mapping is enabled, the uidNumber and gidNumber attributes are ignored. Like, completely. This is to avoid the possibility of conflicts between automatically-assigned and manually-assigned values. So if you need to use manually-assigned values, ALL values must be manually-assigned. All or nothing, bestie. ✨

Also pls be aware that changing the ID mapping related configuration options will cause user and group IDs to change. And rn 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. Fr fr. In order to cache the password, an authentication must be performed. And it is not sufficient to use sss_cache(8) to remove the database — rather the process consists of:

  • Making sure the remote servers are reachable
  • Stopping the SSSD service
  • Removing the database
  • 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. Do the vibe check before the chaos, okay? 🫶

🌸 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, 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. Math girl summer. 🔥

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. Slay, honestly.

💜 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". iykyk 💅

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. Again, 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. Main character domain energy, honestly. ⭐ 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

  • Null Authority
  • World Authority
  • Local Authority
  • Creator Authority
  • Mandatory Label Authority
  • Authentication Authority
  • NT Authority
  • 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. Don't do it, bestie, I'm begging. 🫶

🌈 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. Like, all of them. 👑

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-idp(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(1), sss_ssh_knownhosts(1), sssd-ifp(5), pam_sss(8). sss_rpcidmapd(5) sssd-systemtap(5)

👑 AUTHORS 👑

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

⭐ NOTES (the footnote vibes) ⭐

  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

and that's the whole page, bestie!! 🎀 this little gem is from the SSSD fam, dated 09/08/2026, and lives at SSSD-AD(5). go forth and map those IDs responsibly 💅✨🦋

📦 where this page comes from