Linux-Security-Module Archive on lore.kernel.org
 help / color / Atom feed
From: Andy Lutomirski <luto@kernel.org>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	Stephen Smalley <sds@tycho.nsa.gov>,
	Cedric Xing <cedric.xing@intel.com>,
	LSM List <linux-security-module@vger.kernel.org>,
	selinux@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	linux-sgx@vger.kernel.org,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	James Morris <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Paul Moore <paul@paul-moore.com>,
	Eric Paris <eparis@parisplace.org>,
	Jethro Beekman <jethro@fortanix.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	nhorman@redhat.com, pmccallum@redhat.com, "Ayoun,
	Serge" <serge.ayoun@intel.com>,
	"Katz-zamir, Shay" <shay.katz-zamir@intel.com>,
	"Huang, Haitao" <haitao.huang@intel.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	"Svahn, Kai" <kai.svahn@intel.com>,
	Borislav Petkov <bp@alien8.de>,
	Josh Triplett <josh@joshtriplett.org>,
	"Huang, Kai" <kai.huang@intel.com>,
	David Rientjes <rientjes@google.com>,
	"Roberts, William C" <william.c.roberts@intel.com>,
	Philip Tricca <philip.b.tricca@intel.com>
Subject: Re: [RFC PATCH v1 2/3] LSM/x86/sgx: Implement SGX specific hooks in SELinux
Date: Mon, 17 Jun 2019 10:08:26 -0700
Message-ID: <CALCETrW9Mt70UY3NWGQq3rpxCxSpR4GfsBgt0jTib3bNDMTXkw@mail.gmail.com> (raw)
In-Reply-To: <20190617164915.GA25085@linux.intel.com>

On Mon, Jun 17, 2019 at 9:49 AM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> On Sun, Jun 16, 2019 at 03:14:51PM -0700, Andy Lutomirski wrote:
> > On Fri, Jun 14, 2019 at 8:38 AM Sean Christopherson
> > <sean.j.christopherson@intel.com> wrote:
> > > > Andy and/or Cedric, can you please weigh in with a concrete (and practical)
> > > > use case that will break if we go with #1?  The auditing issues for #2/#3
> > > > are complex to say the least...
> >
> > The most significant issue I see is the following.  Consider two
> > cases. First, an SGX2 enclave that dynamically allocates memory but
> > doesn't execute code from dynamic memory.  Second, an SGX2 enclave
> > that *does* execute code from dynamic memory.  In #1, the untrusted
> > stack needs to decide whether to ALLOW_EXEC when the memory is
> > allocated, which means that it either needs to assume the worst or it
> > needs to know at allocation time whether the enclave ever intends to
> > change the permission to X.
>
> I'm just not convinced that folks running enclaves that can't communicate
> their basic functionality will care one whit about SELinux restrictions,
> i.e. will happily give EXECMOD even if it's not strictly necessary.

At least when permissions are learned, if there's no ALLOW_EXEC for
EAUG, then EXECMOD won't get learned if there's no eventual attempt to
execute the memory.

>
> > I suppose there's a middle ground.  The driver could use model #1 for
> > driver-filled pages and model #2 for dynamic pages.  I haven't tried
> > to fully work it out, but I think there would be the ALLOW_READ /
> > ALLOW_WRITE / ALLOW_EXEC flag for EADD-ed pages but, for EAUG-ed
> > pages, there would be a different policy.  This might be as simple as
> > internally having four flags instead of three:
> >
> > ALLOW_READ, ALLOW_WRITE, ALLOW_EXEC: as before
> >
> > ALLOW_EXEC_COND: set implicitly by the driver for EAUG.
> >
> > As in #1, if you try to mmap or protect a page with neither ALLOW_EXEC
> > variant, it fails (-EACCES, perhaps).  But, if you try to mmap or
> > mprotect an ALLOW_EXEC_COND page with PROT_EXEC, you ask LSM for
> > permission.  There is no fancy DIRTY tracking here, since it's
> > reasonable to just act as though *every* ALLOW_EXEC_COND page is
> > dirty.  There is no real auditing issue here, since LSM can just log
> > what permission is missing.
> >
> > Does this seem sensible?  It might give us the best of #1 and #2.
>
> It would work and is easy to implement *if* SELinux ties permissions to
> the process, as the SIGSTRUCT vma/file won't be available at
> EAUG+mprotect().  I already have a set of patches to that effect, I'll
> send 'em out in a bit.

I'm okay with that.

>
> FWIW, we still need to differentiate W->X from WX on SGX1, i.e. declaring
> ALLOW_WRITE + ALLOW_EXEC shouldn't imply WX.  This is also addressed in
> the forthcoming updated RFC.

Sounds good.

  reply index

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-06  2:11 [RFC PATCH v2 0/5] security: x86/sgx: SGX vs. LSM Sean Christopherson
2019-06-06  2:11 ` [RFC PATCH v2 1/5] mm: Introduce vm_ops->may_mprotect() Sean Christopherson
2019-06-10 15:06   ` Jarkko Sakkinen
2019-06-10 15:55     ` Sean Christopherson
2019-06-10 17:47       ` Xing, Cedric
2019-06-10 19:49         ` Sean Christopherson
2019-06-10 22:06           ` Xing, Cedric
2019-06-06  2:11 ` [RFC PATCH v2 2/5] x86/sgx: Require userspace to define enclave pages' protection bits Sean Christopherson
2019-06-10 15:27   ` Jarkko Sakkinen
2019-06-10 16:15     ` Sean Christopherson
2019-06-10 17:45       ` Jarkko Sakkinen
2019-06-10 18:17         ` Sean Christopherson
2019-06-12 19:26           ` Jarkko Sakkinen
2019-06-10 18:29   ` Xing, Cedric
2019-06-10 19:15     ` Andy Lutomirski
2019-06-10 22:28       ` Xing, Cedric
2019-06-12  0:09         ` Andy Lutomirski
2019-06-12 14:34           ` Sean Christopherson
2019-06-12 18:20             ` Xing, Cedric
2019-06-06  2:11 ` [RFC PATCH v2 3/5] x86/sgx: Enforce noexec filesystem restriction for enclaves Sean Christopherson
2019-06-10 16:00   ` Jarkko Sakkinen
2019-06-10 16:44     ` Andy Lutomirski
2019-06-11 17:21       ` Stephen Smalley
2019-06-06  2:11 ` [RFC PATCH v2 4/5] LSM: x86/sgx: Introduce ->enclave_load() hook for Intel SGX Sean Christopherson
2019-06-07 19:58   ` Stephen Smalley
2019-06-10 16:21     ` Sean Christopherson
2019-06-10 16:05   ` Jarkko Sakkinen
2019-06-06  2:11 ` [RFC PATCH v2 5/5] security/selinux: Add enclave_load() implementation Sean Christopherson
2019-06-07 21:16   ` Stephen Smalley
2019-06-10 16:46     ` Sean Christopherson
2019-06-17 16:38   ` Jarkko Sakkinen
2019-06-10  7:03 ` [RFC PATCH v1 0/3] security/x86/sgx: SGX specific LSM hooks Cedric Xing
2019-06-10  7:03   ` [RFC PATCH v1 1/3] LSM/x86/sgx: Add " Cedric Xing
2019-06-10  7:03   ` [RFC PATCH v1 2/3] LSM/x86/sgx: Implement SGX specific hooks in SELinux Cedric Xing
2019-06-11 13:40     ` Stephen Smalley
2019-06-11 22:02       ` Sean Christopherson
2019-06-12  9:32         ` Dr. Greg
2019-06-12 14:25           ` Sean Christopherson
2019-06-13  7:25             ` Dr. Greg
2019-06-12 19:30         ` Andy Lutomirski
2019-06-12 22:02           ` Sean Christopherson
2019-06-13  0:10             ` Xing, Cedric
2019-06-13  1:02             ` Xing, Cedric
2019-06-13 17:02         ` Stephen Smalley
2019-06-13 23:03           ` Xing, Cedric
2019-06-13 23:17             ` Sean Christopherson
2019-06-14  0:31               ` Xing, Cedric
2019-06-14  0:46           ` Sean Christopherson
2019-06-14 15:38             ` Sean Christopherson
2019-06-16 22:14               ` Andy Lutomirski
2019-06-17 16:49                 ` Sean Christopherson
2019-06-17 17:08                   ` Andy Lutomirski [this message]
2019-06-18 15:40                   ` Dr. Greg
2019-06-14 17:16             ` Xing, Cedric
2019-06-14 17:45               ` Sean Christopherson
2019-06-14 17:53                 ` Sean Christopherson
2019-06-14 20:01                   ` Sean Christopherson
2019-06-16 22:16               ` Andy Lutomirski
2019-06-14 23:19             ` Dr. Greg
2019-06-11 22:55       ` Xing, Cedric
2019-06-13 18:00         ` Stephen Smalley
2019-06-13 19:48           ` Sean Christopherson
2019-06-13 21:09             ` Xing, Cedric
2019-06-13 21:02           ` Xing, Cedric
2019-06-14  0:37           ` Sean Christopherson
2019-06-10  7:03   ` [RFC PATCH v1 3/3] LSM/x86/sgx: Call new LSM hooks from SGX subsystem Cedric Xing
2019-06-10 17:36   ` [RFC PATCH v1 0/3] security/x86/sgx: SGX specific LSM hooks Jarkko Sakkinen

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CALCETrW9Mt70UY3NWGQq3rpxCxSpR4GfsBgt0jTib3bNDMTXkw@mail.gmail.com \
    --to=luto@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=andriy.shevchenko@linux.intel.com \
    --cc=bp@alien8.de \
    --cc=cedric.xing@intel.com \
    --cc=dave.hansen@intel.com \
    --cc=eparis@parisplace.org \
    --cc=haitao.huang@intel.com \
    --cc=jarkko.sakkinen@linux.intel.com \
    --cc=jethro@fortanix.com \
    --cc=jmorris@namei.org \
    --cc=josh@joshtriplett.org \
    --cc=kai.huang@intel.com \
    --cc=kai.svahn@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=linux-sgx@vger.kernel.org \
    --cc=nhorman@redhat.com \
    --cc=paul@paul-moore.com \
    --cc=philip.b.tricca@intel.com \
    --cc=pmccallum@redhat.com \
    --cc=rientjes@google.com \
    --cc=sds@tycho.nsa.gov \
    --cc=sean.j.christopherson@intel.com \
    --cc=selinux@vger.kernel.org \
    --cc=serge.ayoun@intel.com \
    --cc=serge@hallyn.com \
    --cc=shay.katz-zamir@intel.com \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=william.c.roberts@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Security-Module Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-security-module/0 linux-security-module/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-security-module linux-security-module/ https://lore.kernel.org/linux-security-module \
		linux-security-module@vger.kernel.org linux-security-module@archiver.kernel.org
	public-inbox-index linux-security-module


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-security-module


AGPL code for this site: git clone https://public-inbox.org/ public-inbox