Provided by: sssd-ad_2.2.0-4ubuntu1_amd64 bug

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       with the AD provider and will be superseded by Kerberos usage.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.

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 domains from the AD
           forest will be available.

           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. May be set on machines where the hostname(5) does not reflect the fully
           qualified name used in the Active Directory domain to identify this host.

           This field is used to determine the host principal in use in the keytab. 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)
           This option specifies LDAP access control filter that the user must match in order to
           be allowed access. Please note that the “access_provider” option must be explicitly
           set to “ad” in order for this option to have an effect.

           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[1]

           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 a particular host.

           NOTE: The current version of SSSD does not support host (computer) entries in the GPO
           'Security Filtering' list. Only user and group entries are supported. Host entries in
           the list have no effect.

           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.

           There are three supported values for this option:

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

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

           ·   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

       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.

           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:

           ·   login

           ·   su

           ·   su-l

           ·   gdm-fingerprint

           ·   gdm-password

           ·   gdm-smartcard

           ·   kdm

           ·   lightdm

           ·   lxdm

           ·   sddm

           ·   unity

           ·   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.

           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:

           ·   sshd

           ·   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.

           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:

           ·   ftp

           ·   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.

           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:

           ·   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.

           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:

           ·   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.

           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_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:

           ·   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)
           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)

       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.

           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_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.

           Please note that this option will be only used in fallback attempt when previous
           attempt using autodetected settings failed.

           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

       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 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)

       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 = gssapi

       ·   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".

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_op_timeout
           How long would SSSD talk to a single DNS server.

       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.

       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”.

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:

       ·   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.

   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 bound of the range of POSIX IDs to use for mapping Active
               Directory user and group SIDs.

               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 bound of the range of POSIX IDs to use for mapping Active
               Directory user and group SIDs.

               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 SID minus minimal SID 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 monatomically 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

       ·   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”, “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-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://pagure.io/SSSD/sssd/

NOTES

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