In addition to the common parameters, the POSIX backend has the following configurable parameters:

  • username_attribute: Username (user ID) attribute name is the name of the attribute in the user object, which contains the user’s plain username.

  • membership_check: Enable POSIX group membership check enables POSIX primary and supplementary group membership checking. When enabled, it has the following configurable parameter:

    • member_uid_attribute: the optional POSIX group membership attribute name is the name of the attribute in a posixGroup group object, which lists the plain usernames that are members of the group. These groups are usually referred to as supplementary groups of the referred user.

User identification in POSIX

To determine the user entry for a given plain username, One Identity Safeguard for Privileged Sessions (SPS) performs a search under user_base_dn for objects having the username_attribute equal to the plain username of the user. The objectClass of the user object is not restricted.

The user object returned here is used for group membership checks.

Group membership resolution in POSIX

For all group membership checks, only the LDAP user object returned during user identification phase is used.

The plain group name is always compared to the cn attribute of the group object.

A user is treated as a member of a group given by its plain group name if the plain group name matches the cn attribute of the group object, and any of the following is true:

  • The group is the user’s primary group. That is, the group is a posixGroup, and the user’s gidNumber attribute is equal to the group’s gidNumber attribute.

    This check is performed only when the membership_check option is enabled for POSIX.

    NOTE:

    It is OK for the user to have no gidNumber attribute, in which case this check will be skipped.

  • The group lists the user’s short username. That is, the group is a posixGroup, and it’s member_uid_attribute contains the short username from the user object.

    This check is performed only when the membership_check option is enabled, and the member_uid_attribute is configured.

    NOTE:

    For the purpose of this check, the user’s short username is retrieved from the user object’s username_attribute. Currently, this attribute should only contain a single username. A warning will appear in the logs if this is not the case, and the first value of the attribute will be used as returned by the server. This is a known limitation.

  • The group lists the user’s dn in any of the additional group objects configured in user_dn_in_groups.

    For example, if a row is added with objectClass set to groupOfNames and attribute set to member, SPS will treat the user as a member of all groups where the group is a groupOfNames, and the group’s member attribute contains the user’s dn.

  • The user lists the group’s dn. That is, the user’s memberof_user_attribute contains the dn of the group, and the objectClass of the referred group is memberof_group_objectclass.

    This check is performed only when the memberof_check option is enabled for POSIX.

    NOTE:

    SPS compares the dn stored in the memberof_user_attribute to the dn of the group object itself in a strict stringwise manner. Therefore, the user attribute must contain the group DN exactly as it would be returned by the LDAP server. No case or accent differences are allowed.