SMB access of UNIX-created files

No UID-to-SID or GID-to-SID mappings are performed when creating an ACL for a file; all UIDs and GIDs are converted to SIDs or principals when the ACL is returned.

OneFS initiates a two-step process for returning a security descriptor, which contains SIDs for the owner and primary group of an object:

  1. The current security descriptor is retrieved from the file. If the file does not have a discretionary access control list (DACL), a synthetic ACL is constructed from the file’s lower 9 mode bits, which are separated into three sets of permission triples—one each for owner, group, and everyone. For details about mode bits, see the UNIX permissions topic.
  2. Two access control entries (ACEs) are created for each triple: the allow ACE contains the corresponding rights that are granted according to the permissions; the deny ACE contains the corresponding rights that are denied. In both cases, the trustee of the ACE corresponds to the file owner, group, or everyone. After all of the ACEs are generated, any that are not needed are removed before the synthetic ACL is returned.