MAC randomisation and DHCP pools

Rudy Zijlstra rudy at grumpydevil.homelinux.org
Sun Jul 26 09:22:33 UTC 2020


Hi Glenn,

Would need to check the RFC, but if that remains stable on the network 
it is sufficient.

This is also why i say i need to start playing/inveztigating with it. 
Android10 also has this feature. Of course, the likelyhood that goodle 
and Apple implement in the same way is not high :)

Cheers

Rudy

On 26-07-2020 10:50, glenn.satchell at uniq.com.au wrote:
> Hi Rudy,
>
> That's good to know, but bypasses all the security offered by random 
> MAC addresses, since a site can track using the DHCP ID :)
>
> regards,
> -glenn
>
> On 2020-07-26 18:26, Rudy Zijlstra wrote:
>> Hi Glenn,
>>
>> The DHCP Id should be stable, at least according to the dhcp RFC. I
>> need to start playing around a bit...
>>
>> I do understand the privacy concerns here, and why this is being 
>> implemented.
>>
>> Cheers
>>
>> Rudy
>>
>> On 26-07-2020 05:02, glenn.satchell at uniq.com.au wrote:
>>> Hi Mike,
>>>
>>> I think in the short term setting the lease time to 24 hours would 
>>> free up old leases after the MAC address changes, meaning the old 
>>> client effectively goes away. Public places like shopping malls, 
>>> should already have shorter leases due to the massive churn in 
>>> clients, so it's not going to bother them much.
>>>
>>> But that doesn't address any of the issues with identifying 
>>> individual devices, eg to put into different classes. For that I 
>>> think it will need an education scheme with your users to turn off 
>>> the feature on networks where identifying the client matters, eg 
>>> corporate or home networks.
>>>
>>> I think this will evolve to having some other persistent identifier 
>>> for systems to use.
>>>
>>> regards,
>>> -glenn
>>>
>>> On 2020-07-25 11:46, Joshua Stark wrote:
>>>> The user can decide to turn the feature off on the Apple device per
>>>> WiFi network:
>>>>
>>>> Rarely, a network might allow you to join with a private address, but
>>>> won't allow Internet access. If that happens, you can choose to stop
>>>> using private addresses [1] with that network
>>>> (https://support.apple.com/en-us/HT211227)
>>>>
>>>> I agree, this will make things different, harder initially. One
>>>> example that comes to mind is white/black lists on WiFi networks, that
>>>> will go out the window.
>>>> And the other of being able to set a static IPv4 will be next to
>>>> impossible.
>>>>
>>>> But was that not the point of IPv6 - totally random
>>>>
>>>> In my mind this means we need an evolution of how we do things, like
>>>> how AWS/GCP have taken the classic firewall of IP/Port to a Service
>>>> Layer Firewall.
>>>> There is going to need to be another way to identify a device to allow
>>>> automatic re-authentication, like public WiFi where you purchase
>>>> access for greater then 24hrs.
>>>>
>>>> How we do that, I don't know, but it's time to start thinking about
>>>> how to implement the next evolution in technology!
>>>>
>>>> Thanks
>>>> Josh
>>>>
>>>> On 24/7/20 20:59, Mike Richardson wrote:
>>>>
>>>>>> Hi Mike,
>>>>>>
>>>>>> This is not something new, it has been around since IOS 8 in 2014.
>>>>>> I think
>>>>>> this page summarises how it works and has links to Apple's site
>>>>>> with more
>>>>>> details.
>>>>>>
>>>>>>
>>>>>
>>>> https://9to5mac.com/2014/09/26/more-details-on-how-ios-8s-mac-address-randomization-feature-works-and-when-it-doesnt/ 
>>>>
>>>>>>
>>>>>> It appears that it randomises the MAC address when the device is
>>>>>> passively
>>>>>> scanning for networks and other particular settings are enabled or
>>>>>> disabled,
>>>>>> so systems can't use the MAC address to persistently track
>>>>>> wherever you go.
>>>>>> However, it seems that any associations/joining of networks is
>>>>>> based on the
>>>>>> actual MAC address.
>>>>>>
>>>>>> Or am I talking about something else entirely different?
>>>>>
>>>>> Something new I believe:
>>>>>
>>>>>
>>>> https://wifinowglobal.com/news-and-blog/new-private-wi-fi-address-iphone-feature-could-severely-impact-the-wi-fi-industry-expert-says/?mc_cid=9ff8988c11&mc_eid=000d85d9e3 
>>>>
>>>>> https://support.apple.com/en-us/HT211227
>>>>>
>>>>> Apple, in IOS14, are going to implement the changing of MACs every
>>>>> 24 hours
>>>>> as the default, and different ones for each SSID, I believe.
>>>>>
>>>>> I'm just trying to evaluate the impact on things like DHCP, but I'm
>>>>> not sure
>>>>> about exactly what happens when pools are, sort of, exhausted.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Mike
>>>>
>>>>
>>>>
>>>> Links:
>>>> ------
>>>> [1] https://support.apple.com/en-us/HT211227#onoff
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