Re: [STDS-802-11-TGM] 11-26/0789r0: SAE group downgrade detection in mesh networks
--- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
Jouni
Would a MITM be able to inject an the SAE Commit message with a modified list of groups in this case and potentially eliminate some groups from the list of possible groups?
This would also lead to a downgrade scenario no?
Thanks
Sidharth
> On May 13, 2026, at 05:18, Jouni Malinen <jkmalinen@xxxxxxxxx> wrote:
>
> --- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
>
> Unfortunately, I might have to miss the upcoming TGmf discussion on
> this due to a conflict with TGbi. It looks like the updated 789r1 is
> proposing mitigation #1 to be standardized. If that is the selected
> direction, I would consider a different approach for downgrade
> protection instead of continuing to use the somewhat complex use of
> listing the rejected groups. The new option would be to include the
> list of all supported groups in the SAE commit when both peers
> indicate support for the new mechanism (which is done in option #1).
> The lists of the supported groups from each peer would then be
> concatenated into the salt (this can use an explicit length/delimiter
> as well, but that is not as important for this case since each peer
> know their own list of supported groups and it is obvious that
> anything else is from the peer). This type of use of supported groups
> instead of rejected groups is likely much more convenient to use and
> less likely to result in strange corner cases since it is a static
> list and does not depend in the order in which the various groups are
> attempted in any particular instance of SAE authentication. In
> addition, listing the supported groups in the first message would
> allow optimization for group negotiation cases by removing need to
> probe groups one by one multiple times.
>
> PS.
>
> Indicating the supported groups is also the way that P802.11bi ended
> up getting extended to cover downgrade protection for SAE group
> negotiation for cases where SAE is wrapped in PASN/EPPKE
> Authentication frames.
>
> - Jouni
>
>
> On Sun, May 3, 2026 at 3:07 PM Mathy Vanhoef <mathy.vanhoef@xxxxxxxxxxx> wrote:
>>
>> --- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
>> Dear all,
>>
>> At the May Interim, I will present 11-26/0789r0, which discusses an issue with SAE group downgrade detection in mesh networks. This topic was previously presented during the teleconf on 20 April, where the recommendation was to also share it on the mailing list so that people can review it in advance.
>>
>> Arguably, the main question is which mitigation would be most appropriate. The document expresses a slight preference for mitigation #2 or #3, but it may also be worth considering mitigation #1 as the defence to standardize, since it appears to be the most proper solution and requires support from both STAs. Individual vendors could then still choose to implement mitigation #2 if they wish, as it can be adopted independently by a single STA.
>>
>> Best regards,
>> Mathy
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