I'm trying to fully grasp the concept of setuid and setgid, and I'm not quite sure in what way permissions are actually elevated. Let me provide an example:
userA (groups: userA groupA)
userB (groups: userB groupB GroupC)
Permission owner group filename
-rws-----x userA groupD file
-rwsrws--x userA groupD file2
If userB executes
file2, what group permission will the executables have? What I'm not completely sure about, is whether the executable gains user/group permissions of both the caller and the file owner, or if permissions are "replaced".
I know this is a silly example, as setuid and setgid will normally be used to envoke "all-powerful" applications, but I hope this example will be better at actually conceptualizing how setuid and setgid works.