From: Kees Cook <keescook@chromium.org>
To: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Matthew Garrett <mjg@redhat.com>,
Khalid Aziz <khalid@gonehiking.org>,
kexec@lists.infradead.org, horms@verge.net.au,
Dave Young <dyoung@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
linux kernel mailing list <linux-kernel@vger.kernel.org>,
"Kasatkin, Dmitry" <dmitry.kasatkin@intel.com>
Subject: Re: [RFC] Kdump with signed images
Date: Wed, 24 Oct 2012 23:44:32 -0700 [thread overview]
Message-ID: <CAGXu5j+3CNmm6L2+18OKCairhS90N4SJ0zoZKVy+d5ncE67pbA@mail.gmail.com> (raw)
In-Reply-To: <1351143839.18115.57.camel@falcor>
On Wed, Oct 24, 2012 at 10:43 PM, Mimi Zohar <zohar@linux.vnet.ibm.com> wrote:
> On Wed, 2012-10-24 at 13:19 -0400, Vivek Goyal wrote:
>> On Tue, Oct 23, 2012 at 09:44:59AM -0700, Eric W. Biederman wrote:
>> > Matthew Garrett <mjg@redhat.com> writes:
>> >
>> > > On Tue, Oct 23, 2012 at 10:59:20AM -0400, Vivek Goyal wrote:
>> > >
>> > >> But what about creation of a new program which can call kexec_load()
>> > >> and execute an unsigned kernel. Doesn't look like that will be
>> > >> prevented using IMA.
>
> Like the existing kernel modules, kexec_load() is not file descriptor
> based. There isn't an LSM or IMA-appraisal hook here.
>
>> > > Right. Trusting userspace would require a new system call that passes in
>> > > a signature of the userspace binary, and the kernel would then have to
>> > > verify the ELF object in memory in order to ensure that it
>> > > matches the signature. Verifying that the copy on the filesystem is
>> > > unmodified isn't adequate - an attacker could simply have paused the
>> > > process and injected code.
>
> I haven't looked at kexec_load() in detail, but like kernel modules, I
> think the better solution would be to pass a file descriptor, especially
> if you're discussing a new system call. (cc'ing Kees.)
Yeah, it looks like kexec_load could use a nearly identical new
syscall that uses an fd, just like init_module is getting.
Another area, kind of related, is firmware loading. The interface for
that is a bit weird, if the documentation is up to date:
echo 1 > /sys/$DEVPATH/loading
cat $HOTPLUG_FW_DIR/$FIRMWARE > /sysfs/$DEVPATH/data
echo 0 > /sys/$DEVPATH/loading
It looks like there's a filp on the reader:
static ssize_t firmware_data_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr,
char *buffer, loff_t offset, size_t count)
But it's not clear to me yet if we'll actually get the firmware file,
or if we'll get a random pipe we can't evaluate. Has anyone looked at
handling "signed" firmware loading yet?
-Kees
--
Kees Cook
Chrome OS Security
next prev parent reply other threads:[~2012-10-25 6:44 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1350588121.30243.7.camel@rhapsody>
[not found] ` <20121018193831.GD18147@redhat.com>
[not found] ` <874nlrv2ni.fsf@xmission.com>
[not found] ` <20121019020630.GA27052@redhat.com>
[not found] ` <877gqnnnf0.fsf@xmission.com>
[not found] ` <20121019143112.GB27052@redhat.com>
[not found] ` <871ugqb4gj.fsf@xmission.com>
[not found] ` <20121023131854.GA16496@redhat.com>
[not found] ` <20121023145920.GD16496@redhat.com>
[not found] ` <87fw552mb4.fsf_-_@xmission.com>
2012-10-24 17:36 ` Kdump with signed images Vivek Goyal
2012-10-25 6:10 ` Mimi Zohar
2012-10-25 14:10 ` Vivek Goyal
2012-10-25 18:40 ` Mimi Zohar
2012-10-25 18:55 ` Vivek Goyal
2012-10-26 1:15 ` Mimi Zohar
2012-10-26 2:39 ` Matthew Garrett
2012-10-26 3:30 ` Eric W. Biederman
2012-10-26 17:06 ` Vivek Goyal
2012-10-26 18:37 ` Mimi Zohar
2012-11-01 13:10 ` Vivek Goyal
2012-11-01 13:53 ` Vivek Goyal
2012-11-01 14:29 ` Mimi Zohar
2012-11-01 14:43 ` Vivek Goyal
2012-11-01 14:52 ` Matthew Garrett
2012-11-02 13:23 ` Vivek Goyal
2012-11-02 14:29 ` Balbir Singh
2012-11-02 14:36 ` Vivek Goyal
2012-11-03 3:02 ` Balbir Singh
2012-11-02 21:34 ` H. Peter Anvin
2012-11-02 21:32 ` Eric W. Biederman
2012-11-05 18:03 ` Vivek Goyal
2012-11-05 19:44 ` Eric W. Biederman
2012-11-05 20:42 ` Vivek Goyal
2012-11-05 23:01 ` H. Peter Anvin
2012-11-06 19:34 ` Vivek Goyal
2012-11-06 23:51 ` Eric W. Biederman
2012-11-08 19:40 ` Vivek Goyal
2012-11-08 19:45 ` Vivek Goyal
2012-11-08 21:03 ` Eric W. Biederman
2012-11-09 14:39 ` Vivek Goyal
2012-11-15 5:09 ` Eric W. Biederman
2012-11-15 12:56 ` Mimi Zohar
2012-11-08 20:46 ` Mimi Zohar
2012-11-01 14:51 ` Vivek Goyal
2012-11-01 14:57 ` Matthew Garrett
2012-11-01 15:10 ` Khalid Aziz
2012-11-01 16:23 ` Matthew Garrett
2012-11-02 16:57 ` Khalid Aziz
2012-10-26 17:59 ` Mimi Zohar
2012-10-26 18:19 ` Matthew Garrett
2012-10-26 18:25 ` Mimi Zohar
[not found] ` <20121023154123.GA30730@srcf.ucam.org>
[not found] ` <87d309xhmc.fsf_-_@xmission.com>
2012-10-24 17:19 ` [RFC] " Vivek Goyal
2012-10-25 5:43 ` Mimi Zohar
2012-10-25 6:44 ` Kees Cook [this message]
2012-10-25 7:01 ` Mimi Zohar
2012-10-25 13:54 ` Vivek Goyal
2012-10-25 19:06 ` Mimi Zohar
2012-10-25 15:39 ` [RFC] Kdump with UEFI secure boot (Re: [PATCH v2] kdump: pass acpi_rsdp= to 2nd kernel for efi booting) Vivek Goyal
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