netdev - Re: Security issue with vmxnet3 and e100 for AMD SEV(-SNP) / Intel TDX

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Date:   Mon, 11 Jan 2021 14:56:28 +0100
From:   Robert Buhren <robert.buhren@...t.tu-berlin.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Radev, Martin" <martin.radev@...ec.fraunhofer.de>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "doshir@...are.com" <doshir@...are.com>,
        "jesse.brandeburg@...el.com" <jesse.brandeburg@...el.com>,
        "anthony.l.nguyen@...el.com" <anthony.l.nguyen@...el.com>,
        "Morbitzer, Mathias" <mathias.morbitzer@...ec.fraunhofer.de>,
        "file@...t.tu-berlin.de" <file@...t.tu-berlin.de>,
        "Banse, Christian" <christian.banse@...ec.fraunhofer.de>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "Thomas.Lendacky@....com" <Thomas.Lendacky@....com>,
        "pv-drivers@...are.com" <pv-drivers@...are.com>,
        "martin.b.radev@...il.com" <martin.b.radev@...il.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Kleen, Andi" <andi.kleen@...el.com>
Subject: Re: Security issue with vmxnet3 and e100 for AMD SEV(-SNP) / Intel
 TDX


On 1/11/21 2:26 PM, Kirill A. Shutemov wrote:
> On Fri, Jan 08, 2021 at 03:31:56PM +0000, Radev, Martin wrote:
>> Just noticed that Intel TDX already does the device filtering. Check: https://github.com/intel/tdx/commit/6789eee52aab8985e49b362379fab73aa3eecde2
>>
>> CC-ing Kirill and Kuppuswamy from Intel in case they want to be part of the discussion.
>> ________________________________
>> From: Radev, Martin
>> Sent: Friday, January 8, 2021 12:57 PM
>> To: netdev@...r.kernel.org <netdev@...r.kernel.org>; intel-wired-lan@...ts.osuosl.org <intel-wired-lan@...ts.osuosl.org>
>> Cc: doshir@...are.com <doshir@...are.com>; jesse.brandeburg@...el.com <jesse.brandeburg@...el.com>; anthony.l.nguyen@...el.com <anthony.l.nguyen@...el.com>; Morbitzer, Mathias <mathias.morbitzer@...ec.fraunhofer.de>; Robert Buhren <robert.buhren@...t.tu-berlin.de>; file@...t.tu-berlin.de <file@...t.tu-berlin.de>; Banse, Christian <christian.banse@...ec.fraunhofer.de>; brijesh.singh@....com <brijesh.singh@....com>; Thomas.Lendacky@....com <Thomas.Lendacky@....com>; pv-drivers@...are.com <pv-drivers@...are.com>; martin.b.radev@...il.com <martin.b.radev@...il.com>
>> Subject: Security issue with vmxnet3 and e100 for AMD SEV(-SNP) / Intel TDX
>>
>> Hello everybody,
>>
>> tldr: Both drivers expose skb GVAs to untrusted devices which gives RIP
>>          control to a malicious e100 / vmxnet3 device implementation. This is
>>          an issue for AMD SEV (-SNP) [1] and likely Intel TDX [2].
>>
>> Felicitas and Robert have started a project on fuzzing device drivers which
>> may have negative security impact on solutions like AMD SEV Secure
>> Nested Paging and Intel Trusted Domain Extensions. These solutions protect
>> a VM from a malicious Hypervisor in various way.
>>
>> There are a couple of devices which carry security issues under the attacker
>> models of SEV-SNP / Intel TDX, but here we're only discussing VMXNET3 and
>> e100, because we have detailed PoCs for both.
>>
>> Maintainers of both vmxnet3 and e100 were added in this email because the
>> discussion will likely be the same. The issues were already sent to AMD PSIRT,
>> and Tom Lendacky and Brijesh Singh have volunteered to be part of the email
>> communication with the maintainers. Both have been working on AMD SEV.
>>
>> Please check the two attached files: vmxnet3_report.txt and e100_report.txt.
>> Both contain detailed information about what the issue is and how it can be
>> exploited by a malicious HV or attacker who has access to the QEMU process.
>>
>> Fix:
>> In an earlier discussion with AMD, there was the idea of making a list of
>> allowed devices with SEV and forbidding everything else. This would avoid
>> issues with other drivers whose implementation has not been yet scrutinized
>> under the threat model of SEV-SNP and Intel Trusted Domain Extensions.
> +Andi.
>
> Right. Our TDX guest enabling has white list of devices that allowed to be
> used. For now it's only VirtIO, but I believe it also requires hardening.
> We need to validate any VMM input.
>
> It might be beneficial to have coordination between Intel and AMD on what
> devices (and device drivers) considered to be safe for trusted computing.
> I think we can share burden of code audit and fuzzing.
Let us know if you are interested in our fuzzing/static analysis setup.
We're planning to submit a paper soon and we will publish the source
code along with the paper.

-- 
Robert Buhren <robert.buhren@...t.tu-berlin.de>
Security in Telecommunications <https://sect.tu-berlin.de>
TU Berlin / Telekom Innovation Laboratories
Ernst-Reuter-Platz 7, Sekr TEL 16 / D - 10587 Berlin, Germany
phone: +49 30 835358325