HP-UX System Administrator's Guide: Security Management HP-UX 11i v3 (B3921-90020, September 2010)

7.4.1 Privilege Model
Each process has three privilege sets associated with it:
• Permitted Privilege Set
The maximum set of privileges a process can raise. The process can drop any
privilege from this set, but cannot add any privileges to this set. Privileges from
this set can be added to the effective privilege set of the process.
• Effective Privilege Set
The set of currently active privileges for a process. A privilege-aware process can
modify effective privilege set to keep only the necessary privileges in this set at
any given time. The process can remove any privilege from the effective privilege
set, but can only add privileges from the permitted privilege set.
The effective privilege set is always a subset of the permitted privilege set.
• Retained Privilege Set
The set of privileges retained when a process calls the execve system call. The
process can remove any privilege from this set, but cannot add privileges to this
set.
The retained privilege set is always a subset of the permitted privileges set.
The first process, init, starts with a small set of privileges. It then creates other
processes that execute other binaries using exec family calls (execv, execve, and so
on). During this exec call, the extended attributes of the binary, the attributes set with
setfilexsec command, may cause these processes to gain privileges that their parent
process do not have, or lose the privileges that the parent process had. For instance, if
a binary has a permitted minimum of DACREAD (setfilexsec –p DACREAD has
been performed on the binary), the new process will have the DACREAD privilege
whether or not the parent process had that privilege. On the other hand, if process
already has the DACREAD privilege, but if the binary it executes does not have this
privilege in permitted max (for example, setfilexsec -P none …. has been
performed on the file already), it would lose the privilege as a side-effect of executing
the binary.
7.4.2 Compound Privileges
Compound privileges are a shorthand way of specifying a predefined set of simple
privileges.
132 Fine-Grained Privileges