linux-kernel - Re: [PATCH v20 00/28] Intel SGX1 support

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Date:   Thu, 16 May 2019 10:02:36 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Jethro Beekman <jethro@...tanix.com>,
        "Xing, Cedric" <cedric.xing@...el.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: [PATCH v20 00/28] Intel SGX1 support

On Thu, May 16, 2019 at 09:51:03AM +0300, Jarkko Sakkinen wrote:
> On Thu, May 16, 2019 at 08:07:05AM +0300, Jarkko Sakkinen wrote:
> > On Wed, May 15, 2019 at 07:27:02AM -0700, Andy Lutomirski wrote:
> > > 
> > > > On May 15, 2019, at 4:00 AM, Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> wrote:
> > > > 
> > > >> On Wed, May 15, 2019 at 01:35:31PM +0300, Jarkko Sakkinen wrote:
> > > >> This brings me to an open question in Andy's model: lets say that we
> > > >> change the source for SIGSTRUCT from memory address to fd. How can the
> > > >> policy prevent the use not creating a file containing a SIGSTRUCT and
> > > >> passing fd of that to the EINIT ioctl?
> > > > 
> > > 
> > > The policy will presumably check the label on the file that the fd points to.
> > 
> > Right (checked SELinux documentation).
> > 
> > Got one idea from this. Right now creation and initialization does not
> > require any VMAs to be created (since v20). Requiring to map a VMA for
> > copying the data would bring in my opinion a glitch to this model that
> > we have done effort to build up.
> > 
> > What if we similarly change EADD ioctl in a way that it'd take an fd
> > and an offset? This way we can enforce policy to the source where the
> > enclave data is loaded from. On the other hand, loading SIGSTRUCT from
> > fd enforces a legit structure for the enclave.
> > 
> > This would still allow to construct enclaves in VMA independent way.
> 
> The API would turn into this:
> 
> /**
>  * struct sgx_enclave_add_page - parameter structure for the
>  *                               %SGX_IOC_ENCLAVE_ADD_PAGE ioctl
>  * @fd:		file containing the page data
>  * @offset:	offset in the file containing the page data
>  * @secinfo:	address for the SECINFO data
>  * @mrmask:	bitmask for the measured 256 byte chunks
>  */
> struct sgx_enclave_add_page {
> 	__u64	fd;
> 	__u64	offset;
> 	__u64	secinfo;
> 	__u16	mrmask;
> } __attribute__((__packed__));
> 
> 
> /**
>  * struct sgx_enclave_init - parameter structure for the
>  *                           %SGX_IOC_ENCLAVE_INIT ioctl
>  * @fd:		file containing the sigstruct
>  * @offset:	offset in the file containing the sigstruct
>  */
> struct sgx_enclave_init {
> 	__u64	fd;
> 	__u64	offset;
> };

The change to EADD/EINIT ioctl's would be simply fget/kernel_read/fput
sequence replacing copy_from_user().

/Jarkko