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From: Arvind Sankar <nivedita@alum.mit.edu>
To: Roberto Sassu <roberto.sassu@huawei.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	Andy Lutomirski <luto@kernel.org>, Rob Landley <rob@landley.net>,
	Arvind Sankar <niveditas98@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	linux-integrity <linux-integrity@vger.kernel.org>,
	initramfs@vger.kernel.org
Subject: Re: [PATCH v2 0/3] initramfs: add support for xattrs in the initial ram disk
Date: Tue, 14 May 2019 20:25:57 -0400
Message-ID: <20190515002556.GA88615@rani.riverdale.lan> (raw)
In-Reply-To: <f01ad775-54de-033f-d8cb-f27f36e92f0c@huawei.com>

On Tue, May 14, 2019 at 07:20:15PM +0200, Roberto Sassu wrote:
> On 5/14/2019 6:58 PM, Greg KH wrote:
> > On Tue, May 14, 2019 at 06:33:29PM +0200, Roberto Sassu wrote:
> >> Right, the measurement/signature verification of the kernel image is
> >> sufficient.
> >>
> >> Now, assuming that we defer the IMA initialization until /init in the
> >> embedded initramfs has been executed, the problem is how to handle
> >> processes launched with the user mode helper or files directly read by
> >> the kernel (if it can happen before /init is executed). If IMA is not
> >> yet enabled, these operations will be performed without measurement and
> >> signature verification.
> > 
> > If you really care about this, don't launch any user mode helper
> > programs (hint, you have the kernel option to control this and funnel
> > everything into one, or no, binaries).  And don't allow the kernel to
> > read any files either, again, you have control over this.
> > 
> > Or start IMA earlier if you need/want/care about this.
> 
> Yes, this is how it works now. It couldn't start earlier than
> late_initcall, as it has to wait until the TPM driver is initialized.
> 
> Anyway, it is enabled at the time /init is executed. And this would be
> an issue because launching /init and reading xattrs from /.xattr-list
> would be denied (the signature is missing).
> 
> And /.xattr-list won't have a signature, if initramfs is generated
> locally.
> 
> Roberto
> 
> -- 
> HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
> Managing Director: Bo PENG, Jian LI, Yanli SHI

The uevent and firmware loader user mode helpers are both obsolete I
believe, so those shouldn't be an issue.

There is still the internal firmware loader (CONFIG_FW_LOADER). If this
is built-in, there's probably no way to 100% stop it racing with /init if we
depend on an embedded /init and a malicious external initramfs image
contains /lib/firmware, but it can be built as an external module, in
which case there should be no danger until the boot process actually loads it.

  reply index

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-09 11:24 Roberto Sassu
2019-05-09 11:24 ` [PATCH v2 1/3] fs: add ksys_lsetxattr() wrapper Roberto Sassu
2019-05-10 21:28   ` Jann Horn
2019-05-09 11:24 ` [PATCH v2 2/3] initramfs: set extended attributes Roberto Sassu
2019-05-09 11:24 ` [PATCH v2 3/3] initramfs: introduce do_readxattrs() Roberto Sassu
2019-05-10 21:33   ` Jann Horn
2019-05-13 13:03     ` Roberto Sassu
2019-05-09 18:34 ` [PATCH v2 0/3] initramfs: add support for xattrs in the initial ram disk Rob Landley
2019-05-10  6:56   ` Roberto Sassu
2019-05-10 11:49     ` Mimi Zohar
2019-05-10 20:46       ` Rob Landley
2019-05-10 22:38         ` Mimi Zohar
2019-05-11 22:44 ` Andy Lutomirski
2019-05-12  4:04   ` Rob Landley
2019-05-12  4:12     ` Rob Landley
2019-05-12  9:17 ` Dominik Brodowski
2019-05-12 10:18   ` hpa
2019-05-12 15:31     ` Dominik Brodowski
2019-05-13  0:02       ` Mimi Zohar
2019-05-13  0:21         ` hpa
2019-05-13  0:23       ` hpa
2019-05-12 12:52   ` Mimi Zohar
2019-05-12 17:05     ` Rob Landley
2019-05-12 19:43       ` Arvind Sankar
2019-05-13  7:49         ` Roberto Sassu
2019-05-13  9:07           ` Rob Landley
2019-05-13 12:08             ` Mimi Zohar
2019-05-13 12:47             ` Roberto Sassu
2019-05-13 17:20               ` Arvind Sankar
2019-05-13 17:51                 ` Arvind Sankar
2019-05-13 17:52                 ` Arvind Sankar
2019-05-13 18:36                   ` Mimi Zohar
2019-05-13 18:47                     ` Arvind Sankar
2019-05-13 22:09                       ` Mimi Zohar
2019-05-14  6:06                         ` Rob Landley
2019-05-14 14:44                           ` Arvind Sankar
2019-05-14  6:06               ` Rob Landley
2019-05-14 11:52                 ` Roberto Sassu
2019-05-14 15:12                   ` Rob Landley
2019-05-14 15:27                   ` Arvind Sankar
2019-05-14 15:57                     ` Arvind Sankar
2019-05-14 17:44                       ` Roberto Sassu
2019-05-15  1:00                         ` Arvind Sankar
2019-05-14 15:19               ` Andy Lutomirski
2019-05-14 16:33                 ` Roberto Sassu
2019-05-14 16:58                   ` Greg KH
2019-05-14 17:20                     ` Roberto Sassu
2019-05-15  0:25                       ` Arvind Sankar [this message]
2019-05-14 19:18                 ` James Bottomley
2019-05-14 23:39                   ` Rob Landley
2019-05-14 23:54                     ` James Bottomley
2019-05-15  0:52                       ` Arvind Sankar
2019-05-15 11:19                         ` Roberto Sassu
2019-05-15 16:08                           ` Arvind Sankar
2019-05-15 17:06                             ` Roberto Sassu
2019-05-16  5:29                               ` Arvind Sankar
2019-05-16 11:42                                 ` Roberto Sassu
2019-05-16 13:31                                 ` Mimi Zohar

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