linux-kernel - Re: SGX vs LSM (Re: [PATCH v20 00/28] Intel SGX1 support)

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Message-ID: <CALCETrVp+r_wz=sOwLC8oW2P54r=sudBtV+J-Ycq_JE2QxwxEQ@mail.gmail.com>
Date:   Fri, 24 May 2019 12:30:44 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     "Xing, Cedric" <cedric.xing@...el.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Andy Lutomirski <luto@...nel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...isplace.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        Jethro Beekman <jethro@...tanix.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Dr. Greg" <greg@...ellic.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "npmccallum@...hat.com" <npmccallum@...hat.com>,
        "Ayoun, Serge" <serge.ayoun@...el.com>,
        "Katz-zamir, Shay" <shay.katz-zamir@...el.com>,
        "Huang, Haitao" <haitao.huang@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Svahn, Kai" <kai.svahn@...el.com>, Borislav Petkov <bp@...en8.de>,
        Josh Triplett <josh@...htriplett.org>,
        "Huang, Kai" <kai.huang@...el.com>,
        David Rientjes <rientjes@...gle.com>
Subject: Re: SGX vs LSM (Re: [PATCH v20 00/28] Intel SGX1 support)

On Fri, May 24, 2019 at 12:13 PM Sean Christopherson
<sean.j.christopherson@...el.com> wrote:
>
> On Fri, May 24, 2019 at 11:34:32AM -0700, Xing, Cedric wrote:
> > > From: linux-sgx-owner@...r.kernel.org [mailto:linux-sgx-
> > > owner@...r.kernel.org] On Behalf Of Sean Christopherson
> > > Sent: Friday, May 24, 2019 10:55 AM

> I don't see a fundamental difference between having RWX in an enclave and
> RWX in normal memory, either way the process can execute arbitrary code,
> i.e. PROCESS__EXECMEM is appropriate.  Yes, an enclave will #UD on certain
> instructions, but that's easily sidestepped by having a trampoline in the
> host (marked RX) and piping arbitrary code into the enclave.  Or using
> EEXIT to do a bit of ROP.

There's a difference, albeit a somewhat weak one, if sigstructs are
whitelisted.  FILE__EXECMOD on
either /dev/sgx/enclave or on the sigstruct is not an entirely crazy
way to express this.