Messages in this thread | | | Subject | Re: [PATCH 2/2] net: Implement SO_PEERCGROUP | From | Simo Sorce <> | Date | Wed, 12 Mar 2014 17:16:22 -0400 |
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On Wed, 2014-03-12 at 14:12 -0700, Andy Lutomirski wrote: > On Wed, Mar 12, 2014 at 2:00 PM, Andy Lutomirski <luto@amacapital.net> wrote: > > On 03/12/2014 01:46 PM, Vivek Goyal wrote: > >> Implement SO_PEERCGROUP along the lines of SO_PEERCRED. This returns the > >> cgroup of first mounted hierarchy of the task. For the case of client, > >> it represents the cgroup of client at the time of opening the connection. > >> After that client cgroup might change. > > > > Even if people decide that sending cgroups over a unix socket is a good > > idea, this API has my NAK in the strongest possible sense, for whatever > > my NAK is worth. > > > > IMO SO_PEERCRED is a disaster. Calling send(2) or write(2) should > > *never* imply the use of a credential. A program should always have to > > *explicitly* request use of a credential. What you want is SCM_CGROUP. > > > > (I've found privilege escalations before based on this observation, and > > I suspect I'll find them again.) > > > > > > Note that I think that you really want SCM_SOMETHING_ELSE and not > > SCM_CGROUP, but I don't know what the use case is yet. > > This might not be quite as awful as I thought. At least you're > looking up the cgroup at connection time instead of at send time. > > OTOH, this is still racy -- the socket could easily outlive the cgroup > that created it.
I think you do not understand how this whole problem space works.
The problem is exactly the same as with SO_PEERCRED, so we are taking the same proven solution.
Connection time is all we do and can care about.
Simo.
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