Re: [Suit] suit-firmware-encryption-00

[Brendan Moran <[e-mail]>]

> On 1 Jun 2021, at 14:19, Dick Brooks <[e-mail]> wrote:
>
> Hannes,
>
> Will the SUIT manifest contain an attestation of a clean malware scan that
> can be verifiably validated for the encrypted software in hand? That would
> help, if a malware scan is not an option.

Please bear in mind what a manifest is. It’s not a declaration of anything at all. It’s a set of instructions to a device to perform certain operations that will result in an installed firmware image. That’s not quite compatible with an attestation of a malware scan. However, what you could do is require multiple signatures: the manifest could be rejected if it is not signed by both the firmware author (and/or any other relevant authorities) and the malware scanning provider. This requires no changes to the manifest specification as it stands.

> The other issue that needs to be addressed is the ability for a software
> consumer to verify that the signing party of a software object has been
> given authorization to sign code on behalf of a software source supplier
> (VENDOR ID) in the manifest, using a standard method - something similar to
> DNS CAA records, but for digital signatures, e.g. maybe DNS DSA records.

This concept (without DNS) already incorporated into SUIT. The SUIT Delegation chains allow a trust anchor to delegate authority. The delegation of authority for any given component identifier is left out-of-scope int he SUIT manifest, but can be achieved using a fairly simple ACL.

Key-lookup systems (like DNS CAA) are explicitly avoided because they require interactive operations, which are expensive on constrained networks.

> Ref: "Vendor ID is not intended to be a human-readable element.  It is
> intended for binary match/mismatch comparison only."
>
> Thanks,
>
> Dick Brooks

Best Regards,

Brendan



> Never trust software, always verify and report! T
> http://www.reliableenergyanalytics.com
> Email: [e-mail]
> Tel: [phone]
>
> -----Original Message-----
> From: Hannes Tschofenig <[e-mail]>
> Sent: Tuesday, June 1, 2021 9:05 AM
> To: [e-mail]; 'Russ Housley' <[e-mail]>
> Cc: 'Michael Richardson' <[e-mail]>; [e-mail]
> Subject: RE: [Suit] suit-firmware-encryption-00
>
> It is a challenge.
>
> The SUIT manifest provides the capabilities to give authorized parties extra
> information (via the manifest meta-data and software description*) while
> providing less info to adversaries.
>
> (*): I am assuming that the info offered via MUD, COSWID, and the textual
> description is of any help to you. If it is not, then you need to let us
> know what other pieces of information will have to be included in the
> manifest to become valuable to make the risk assessment.
>
> Ciao
> Hannes
>
> -----Original Message-----
> From: Dick Brooks <[e-mail]>
> Sent: Tuesday, June 1, 2021 1:32 PM
> To: Hannes Tschofenig <[e-mail]>; 'Russ Housley'
> <[e-mail]>
> Cc: 'Michael Richardson' <[e-mail]>; [e-mail]
> Subject: RE: [Suit] suit-firmware-encryption-00
>
> Hannes,
>
> I definitely see your point, it seems the real problem to solve is:
> - How do we (1) prevent the bad guys from discovering SW details (source
> code) from binaries while simultaneously (2) providing end use customers the
> ability to conduct malware scans, and other risk management functions?
>
> If we encrypt a binary distribution we achieve 1 but not 2 If we do not
> encrypt we achieve 2, but not 1
>
> Are we really looking at a mutually exclusive choice?
>
> Both of these objectives are trying to achieve the same thing: Keep the bad
> guys from causing harm.
>
> Thanks,
>
> Dick Brooks
>
> Never trust software, always verify and report! T
> http://www.reliableenergyanalytics.com
> Email: [e-mail]
> Tel: [phone]
>
> -----Original Message-----
> From: Hannes Tschofenig <[e-mail]>
> Sent: Tuesday, June 1, 2021 6:40 AM
> To: [e-mail]; 'Russ Housley' <[e-mail]>
> Cc: 'Michael Richardson' <[e-mail]>; [e-mail]
> Subject: RE: [Suit] suit-firmware-encryption-00
>
> Dick, I understand your line of argument.
>
> At the same time I want to create awareness for the attacker point of view.
> They need to get access to plaintext firmware of an embedded device (unless
> the attacker already knows what the source was used). This is why there are
> advanced disassemblers available (such as IDA Pro, Binary Ninja, and Ghidra
> -- to name a few).
>
> As a way forward I am proposing to use the additional data carried in the
> manifest for doing the SCRM risk assessment step. I believe that this should
> work.
>
> Ciao
> Hannes
>
> -----Original Message-----
> From: Dick Brooks <[e-mail]>
> Sent: Monday, May 31, 2021 10:00 PM
> To: Hannes Tschofenig <[e-mail]>; 'Russ Housley'
> <[e-mail]>
> Cc: 'Michael Richardson' <[e-mail]>; [e-mail]
> Subject: RE: [Suit] suit-firmware-encryption-00
>
> Thanks, Hannes. I just submitted a concern regarding the problem encryption
> creates for malware scanning, which is one of the SCRM risk assessment
> steps, performed before installation
>
> Thanks,
>
> Dick Brooks
>
> Never trust software, always verify and report! T
> http://www.reliableenergyanalytics.com
> Email: [e-mail]
> Tel: [phone]
>
> -----Original Message-----
> From: Hannes Tschofenig <[e-mail]>
> Sent: Monday, May 31, 2021 3:57 PM
> To: [e-mail]; 'Russ Housley' <[e-mail]>
> Cc: 'Michael Richardson' <[e-mail]>; [e-mail]
> Subject: RE: [Suit] suit-firmware-encryption-00
>
> Hi Dick,
>
> with the SUIT manifest format I hope we can make information available to
> trusted third parties (MUD, COSWID and alike) and at the same time use
> encrypted binaries. Having access to the plaintext binary is essential for
> adversaries to mount attacks. (Happy to give a tutorial about how this
> works.)
>
> Like-wise differential updates may make it difficult for SCRM vendors to
> make their analysis but the information in the manifest can help them.
>
> Severable fields allows to remove information from the manifest before it is
> sent to the device. This reduces overhead and prevents untrusted parties
> from gathering information from the manifest.
>
> Ciao
> Hannes
>
> -----Original Message-----
> From: Dick Brooks <[e-mail]>
> Sent: Monday, May 31, 2021 7:07 PM
> To: 'Russ Housley' <[e-mail]>
> Cc: 'Michael Richardson' <[e-mail]>; Hannes Tschofenig
> <[e-mail]>; [e-mail]
> Subject: RE: [Suit] suit-firmware-encryption-00
>
> I agree, Russ.
>
> Parties subject to the 5/12 Executive Order
> (https://www.whitehouse.gov/briefing-room/presidential-actions/2021/05/12/ex
> ecutive-order-on-improving-the-nations-cybersecurity/) will likely want to
> perform a proactive SCRM risk assessment prior to installation, if my
> interpretation of the EO is accurate.
>
> Thanks,
>
> Dick Brooks
>
> Never trust software, always verify and report! T
> http://www.reliableenergyanalytics.com
> Email: [e-mail]
> Tel: [phone]
>
> -----Original Message-----
> From: Russ Housley <[e-mail]>
> Sent: Monday, May 31, 2021 12:56 PM
> To: Dick Brooks <[e-mail]>
> Cc: Michael Richardson <[e-mail]>; Hannes Tschofenig
> <[e-mail]>; [e-mail]
> Subject: Re: [Suit] suit-firmware-encryption-00
>
> Dick:
>
> Yes, and there are other use cases that require encryption.
>
> Russ
>
>
>> On May 31, 2021, at 12:53 PM, Dick Brooks
> <[e-mail]> wrote:
>>
>> " If a trustworthy party in the middle of the distribution path is
>> able to detect a problem with cleartext (but signed) firmware, they
>> can report a vulnerability and refuse to pass the update along."
>>
>> This is precisely the function SCRM vendors are performing today.
>> Encrypting a binary object would be an impediment to software supply
>> chain risk assessment functions in place today.
>>
>> Thanks,
>>
>> Dick Brooks
>>
>> Never trust software, always verify and report! T
>> http://www.reliableenergyanalytics.com
>> Email: [e-mail]
>> Tel: [phone]
>>
>> -----Original Message-----
>> From: Suit <[e-mail]> On Behalf Of Russ Housley
>> Sent: Monday, May 31, 2021 12:49 PM
>> To: Michael Richardson <[e-mail]>
>> Cc: Hannes Tschofenig <[e-mail]>; [e-mail]
>> Subject: Re: [Suit] suit-firmware-encryption-00
>>
>> Michael:
>>
>>>>> I agree that there are also challenges with certification schemes
>>>>> that prevent developers from seeing the source code (or from
>>>>> publishing the source code). That's yet another issue.
>>>
>>>> SUIT is using signature for the authentication and integrity of the
>>>> firmware.  If the signature remains in place, a party in the middle
>>>> of the distribution cannot insert any malware.
>>>
>>> The encryption of the firmware keeps third parties from auditing the
>>> software updates to determine if malware has been inserted at the
>> "factory"
>>> Both white and black hats are currently using binary diff systems to
>>> look at patches.  Black hats use this to develop exploits in the gap
>>> between 9am EST and 9am PST!
>>> I am suggesting that this is a "Security Consideration"
>>
>> Yes, this is a reasonable thing to add to the Security Considerations.
>>
>> If a trustworthy party in the middle of the distribution path is able
>> to detect a problem with cleartext (but signed) firmware, they can
>> report a vulnerability and refuse to pass the update along.
>>
>> Russ
>> _______________________________________________
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>> https://www.ietf.org/mailman/listinfo/suit
>>
>
>
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