.. _sssd-support-5fb6c4b0320b: ============================================================ SSH User Authentication using Windows Active Directory (WAD) ============================================================ By default, |SSH| to |prod| hosts supports authentication using the 'sysadmin' Local Linux Account and |prod| Local |LDAP| Linux User Accounts. |SSH| can also be optionally configured to support authentication with 1 or more remote |LDAP| identity providers (such as Windows Active Directory (WAD)). Internally, |SSH| uses |SSSD| service to provide NSS and PAM interfaces and a backend system able to remotely connect to multiple different |LDAP| domains. |SSSD| provides a secure solution by using data encryption for |LDAP| user authentication. |SSSD| supports authentication only over an encrypted channel. In summary the |SSH|/|SSSD| solution for remote |LDAP| authentication includes: - Multi domain remote |LDAP| authentication - Extra security by using data encryption for |LDAP| user authentication - Offline authentication if a |LDAP| identity store is unavailable, by caching users and managing caching timeout and refresh - High authentication and authorization performance In |prod| a maximum of 3 |LDAP| |WAD| domains are supported besides the local Openldap domain. .. note:: SSH/SSSD authentication configuration described in this section also applies to local console logins. You can find more information about |SSSD| configuration at `https://linux.die.net/man/5/sssd.conf `__ and `https://linux.die.net/man/5/sssd-ldap `__. -------------------------- Install WAD CA Certificate -------------------------- To be able to successfully connect to a |WAD| domain through a secure |SSL| connection, |SSSD| requires the |SSL| Certificate of the |CA| that signed the remote |WAD| server's SSL Certificate to be installed on the |prod| system. The |WAD| |CA| |SSL| certificate needs to be installed before the corresponding AD domain is added. The command to add |WAD| |CA| certificate: .. code-block:: none system certificate-install --mode ssl_ca --------------------- Add Remote WAD Domain --------------------- A maximum of three remote |LDAP| AD domains are supported in |prod|: ``ldap-domain1``, ``ldap-domain2``, ``ldap-domain3``. Each domain needs to be configured using mandatory and optional service parameters. Each parameter will be validated according to industry standard validation rules for correct syntax that apply to domain names, ldap url, and directory names. An error message will be displayed if the parameter does not have the standard syntax. Mandatory parameters -------------------- To add a new remote ldap |WAD| domain the following mandatory |SSSD| parameters need to be added using system service parameter commands: - ``domain_name`` - ``ldap_uri`` - ``ldap_access_filter`` - ``ldap_search_base`` - ``ldap_default_bind_dn`` - ``ldap_default_authtok`` If a mandatory parameter is missing, an error will be displayed, naming the missing parameter for the domain and the domain will not be created. Commands to add mandatory parameters for a remote ldap domain: .. code-block:: none system service-parameter-add parameter_name= # is “identity” for all domains. # identifies a domain as either “ldap-domain1”, “ldap-domain2” or “ldap-domain3”. E.g.: system service-parameter-add identity ldap-domain1 domain_name=ad.wad-server.com system service-parameter-add identity ldap-domain1 ldap_uri=ldaps://ad.wad-server.com system service-parameter-add identity ldap-domain1 ldap_access_filter=memberOf=CN=WRCP_Admin,CN=Users,DC=wad-server,DC=com system service-parameter-add identity ldap-domain1 ldap_search_base=CN=Users,DC=wad-server,DC=com system service-parameter-add identity ldap-domain1 ldap_default_bind_dn=CN=Administrator,CN=Users,DC=wad-server,DC=com system service-parameter-add identity ldap-domain1 ldap_default_authtok =Passw0rd* Optional Parameters ------------------- There are two optional domain parameters that can be added using system service parameter commands: - ``ldap_user_search_base`` - ``ldap_group_search_base`` For example: .. code-block:: none system service-parameter-add identity ldap-domain1 ldap_user_search_base=CN=Users,DC=wad-server,DC=com system service-parameter-add identity ldap-domain1 ldap_group_search_base=CN=Groups,DC=wad-server,DC=com .. note:: When not set, the 2 optional service parameters, will have as default value, the value of ``ldap_search_base`` service parameter. Apply parameters ---------------- After all the domain mandatory parameters are added and if needed, the optional ones, the parameters will be applied using :command:`service-parameter-apply` command. Only after “apply” command the sssd domain configuration will be added to ``/etc/sssd/sssd.conf`` and becomes active, and the SSSD daemon will connect to the remote |WAD| server. The :command:`system service-parameter-apply` command has been enhanced for this feature to include a ``section`` parameter that did not exist in the previous release. The new ``section`` parameter is an optional parameter of the :command:`service-parameter-apply` command. In the context of the ``identity`` service ldap domains it is needed to specify the domain section name, as follows: .. code-block:: none system service-parameter-apply --section E.g.: system service-parameter-apply identity --section ldap-domain1 Default WAD Domain Configuration --------------------------------- The default WAD domain configuration parameters are pre-configured. Main |SSSD| default configuration settings include: - Offline Authentication is enabled, allowing users to still authenticate even if the ldap identity provider is unavailable. using their cached credentials. User credentials caching is enabled by parameter setting ``cache_credentials = true``. After a successful login user credentials are stored as part of the user account in the |SSSD| cache. - |WAD| Domain enumeration is disabled by using the default setting ``enumerate = false`` for performance reasons. - User home directory on the |prod| platform gets created after the first user login with the following path ``/home//``. - |CA| server certificate verification is always required by using the default setting for ``ldap_tls_reqcert`` parameter as ``demand``. ----------------------------- SSH using the WAD domain user ----------------------------- Verify SSSD is Connected to the Domain -------------------------------------- If the |SSSD| is connected to a |WAD| domain, then the domain users have been discovered and cached on the host. The same applies to the domain groups. Run ``getent passwd @``, to see if the user has been cached on the host. .. code-block:: none getent passwd pvtest1@ad.wad-server.com Run ``getent group @`` to see the group and its members. .. code-block:: none getent passwd eng@ad.wad-server.com Remote SSH ---------- Once the |SSSD| is connected to the domain, a domain user can be used to |SSH| to the |prod| host. If a user has the same user login name in multiple domains, the domain name can be used to distinguish between the common name users. .. code-block:: none ssh -l @ The automatically created home directory for the user is ``/home//``. ----------------------------------- Modify/Delete WAD Domain parameters ----------------------------------- Modify an |SSSD| parameter for an ldap domain using system service parameter command. The ``service-parameter-apply`` needs to follow the ``service-parameter-modify`` so the parameter value change can take effect. For example: .. code-block:: none system service-parameter-modify identity ldap-domain1 ldap_group_search_base=CN=Users,DC=wad-server,DC=com system service-parameter-apply identity --section ldap-domain1 Regarding deleting |WAD| domain parameters, only optional |SSSD| service parameters can be individually deleted: .. code-block:: none system service-parameter-delete system service-parameter-apply identity --section --------------------------------- Delete a WAD Domain configuration --------------------------------- Optional domain parameters can be deleted individually. Mandatory parameters cannot be deleted individually, is all or none. To fully delete a domain, delete all the mandatory parameters and the configured optional parameters. After that, execute the :command:`service-parameter-apply`` command. .. code-block:: none system service-parameter-delete ------------ delete all parameters of the domain----------- system service-parameter-apply identity --section Deleting a domain will cause the users to not show up with ``getent passwd`` command anymore even if they may have not been removed from cache just yet. The users will be removed from cache according to cache expiration configuration. The cache expiry configuration for this release, uses default values. The |WAD| users home directories created on the platform will not be removed after the |WAD| domain configuration is removed. It is administrator's responsibility to clean up users' home directories that are no longer used. ------------------------------------------ SUDO Capability and Local Group Membership ------------------------------------------ Support of sudo users and local linux group membership (e.g. ``sys_protected``) in |prod| platform is done locally after |WAD| users have been discovered by |SSSD|. For example: .. code-block:: none # To add the WAD-discovered user "pvtest1" to the group 'sudo' sudo usermod -a -G sudo pvtest1@ad.wad-server.com # To add the WAD-discovered user "pvtest1" to the group 'sys_protected' sudo usermod -a -G sys_protected pvtest1@ad.wad-server.com ------------------------------------------- Default Local OpenLDAP Domain Configuration ------------------------------------------- The configuration for the local OpenLDAP domain is part of the default |SSSD| configuration. All the local OpenLDAP domain parameters are pre-configured. Main |SSSD| default configuration settings include: - Domain enumeration is enabled as the local domain number of users is not as large to pose performance issues. The use of command :command:`getent passwd` will list all the remote domain discovered users. - The user home directory on the |prod| platform gets created after the first user login and has the following path ``/home/``. - |CA| server certificate verification is always required by using the default setting for ``ldap_tls_reqcert`` parameter as ``demand``. The OpenLDAP |SSL| certificate is created and managed internally by |prod| platform. --------- SSSD logs --------- |SSSD| logs can be viewed on the host, in directory ``/var/log/sssd/sssd.log``. Each domain also has its own log file: ``/var/log/sssd/sssd_.log``.