Re: One process with multiple user ids.

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Giuliano Gagliardi wrote:

I have a server that has to switch to different user ids, but because it does other complex things, I would rather not have it run as root. I only need the server to be able to switch to certain pre-defined user ids.

I have seen that two possible solutions have already been suggested here on the LKML, but it was some years ago, and nothing like it has been implemented.

(1) Having supplementary user ids like there are supplementary group ids and system calls getuids() and setuids() that work like getgroups() and setgroups()

(2) Allowing processes to pass user and group ids via sockets.

Both (1) and (2) would solve my problem. Now my question is whether there are any fundamental flaws with (1) or (2), or whether the right way to solve my problem is another one.

Changing to a limited set of IDs is interesting, I have never looked at what happens when a thread does setuid, and neither the man page or a very quick look at the code tells me. But the portable way is to do the things needed for init, then fork into three processes and give each a UID as needed. I would really evaluate the design which made this necessary, to see if some IPC could be used. Certainly that's more likely to be portable.

Bill Davidsen <[email protected]>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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