linux-kernel - Re: [PATCH v6] pidns: introduce syscall translate

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Date:   Mon, 23 Jul 2018 20:55:41 +0000
From:   Michael Tirado <mtirado418@...il.com>
To:     Nagarathnam Muthusamy <nagarathnam.muthusamy@...cle.com>
Cc:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        linux-api@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Jann Horn <jannh@...gle.com>,
        Serge Hallyn <serge.hallyn@...ntu.com>,
        Prakash Sangappa <prakash.sangappa@...cle.com>,
        Oleg Nesterov <oleg@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Subject: Re: [PATCH v6] pidns: introduce syscall translate_pid

Hey, I'm not seeing much activity on this so here's my $0.02

> Unix socket automatically translates pid attached to SCM_CREDENTIALS.
> This requires CAP_SYS_ADMIN for sending arbitrary pids and entering
> into pid namespace, this expose process and could be insecure.

Perhaps it would be a good idea to add a sysctl switch that prevents
credential spoofing over AF_UNIX \by default\ if that is the main
concern, or is there another concern and I have read this wrong?  I'm
having trouble thinking of a legitimate use of SCM_CREDENTIALS
spoofing that isn't in a debugging or troubleshooting context and
would be more comfortable if it were not possible at all... Anyone
know of a program that relies on this spoofing functionality?

If you look at socket(7) under SO_PEERCRED there is a way to get
credentials at time of connect() for an AF_UNIX SOCK_STREAM, or at
time of socketpair() for a SOCK_DGRAM. I would like to think these
credentials are reliable, but will probably require some extra daemon
to proxy a dgram syslog socket.