On 12/10/2012 6:59 AM, Serge Hallyn wrote: > Quoting Andy Lutomirski (l...@amacapital.net): >> It's especially bad because granting CAP_DAC_READ_SEARCH to user "foo" >> doesn't mean anything. Is he authorized to back things up to >> encrypted storage? > We're talking about privileges at the kernel level here, and there is > no way this could be expressed at that level. > > Higher level tools could/should certainly be exposing things at this > level. > > BUT > > You *are* doing a good job of making me feel that we should have > per-user fI xattrs or acls. Sudo is popular because people like to say > "user joe can run foo with privilege". Most people will never want to > be bothered to say "user joe can run foo with CAP_XYZ" (versus "as > root"), but I do think we could get programs/packages to do that.
Put an ACL on the program file. If you want different users to run with different privilege make two copies of the program and give them different ACLs and cap sets. If your program is so big that making a copy is a disk space issue it is too big to have privilege. If you can't deal with having the have different paths for different users write a shell script that redirects to the correct version based on user id. This is not rocket science. The kernel shouldn't be crammed with mechanism and complexity just because disto/"OS"/site developers can't be bothered with learning how the existing facilities work. I frequently get requests to make changes to the way Smack controls access that can easily be achieved using users and groups. It's amazing how often people seem to forget that Linux has security mechanisms other than the one that they think is the cat's pajamas. > > Note that another difficulty here likes in the age-old, as yet > unanswered imo, question of "how do I easily figure out what caps I need > to run my program." A few years ago I pointed to this (perhaps in > mostly private emails, don't recall) as something to be solved, but > the solution escapes me. The audit trail is your friend. If it doesn't tell you what capabilities are required that you don't have, it should. Unfortunately, the Linux (formerly Unix) security policy into which the capabilities mechanism was retrofit is implementation derived. Without understanding how the Linux security system, with users and groups and LSMs and all works it's impossible to just guess and even if you do understand all that there is going to be lots of environmental context to deal with. Sorry, there's no magic wand. If I had it to do over there would be many fewer capabilities. Please reread that. I said fewer. You need something that would make SELinux policy look small to break out a consistent fine granularity, so I say go consistently coarse. > > -serge > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
