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Question: how can one re-create Apple’s defunct ‘Back To My Mac’ service with specific open-source tools or, if necessary, with limited custom (non-commercial) software?

(Ideally, this would be done in a way that would preserve integration with Apple applications such as Finder or Terminal; that might, however, happen automatically as soon as a VPN allowing network discovery is enabled on a particular computer.)

Background: Apple discontinued the 'Back to My Mac' service in 2019 after twelve years of operation.

As I understand it, this used a combination of Wide-Area Bonjour, a VPN, and probably some sort of iCloud database/directory to automatically keep all of the Macs signed in under a particular AppleID on a VPN so that they could communicate and use built-in services such as file sharing (AFP/SMB), screen sharing, and SSH through NATs and with dynamic IP addresses. No network configuration was required, once one had signed into a computer with their AppleID and enabling the checkbox for 'Back to My Mac' in Settings.

The other computers appeared in the Finder (and in other applications, such as Terminal) just as they currently do if they were on the same network.

I believe the AppleTV (and possibly other devices) were also used to provide Wake-on-LAN functionality.

Conjecture: It is possible that Apple discontinued this for any number of these (or other) reasons:

  1. to minimize their engineering / maintenance costs
  2. to drive iCloud Drive storage revenue
  3. they had been licensing some of the underlying technology since the beginning, and wanted to avoid those costs
  4. a key component was found to be covered by someone else's patent, patent(s) they were unwilling or unable to license

It is of note, however, that they disabled the feature for all existing installations of older operating systems, instead of just making it an unsupported / depreciated feature.

Possible starting points:

  • if either of the last two reasons are true, does anyone know the patent numbers (or patent holders) and technologies that were licensed?

  • are there any open-source replacements for this functionality (beyond what Apple mentions in the above link)?

  • what technical references are available documenting Apple's implementation and what is still missing to create an open-source replacement?

  • do you know of any other online discussions of this topic that can be linked to this question?

Technologies used by some iteration of BTMM:

  • DNS-based Service Discovery (DNS-SD; RFC 6763, RFC 8553, RFC 8552) to announce host reachability information

  • Dynamic DNS update (RFC 2136) to refresh the DNS resource records (RRs) when a host detects network changes

  • DNS Long-lived Queries (LLQ / DNS-LLQ) to notify hosts immediately when the answers to their earlier DNS queries have changed (Wikipedia and IETF)

  • IPv6 Unique Local Address (ULA; RFC 4193) as the host identifier

  • NAT Port Mapping Protocol (PMP / NAT-PMP; RFC 6886) to assist NAT traversal

  • Kerberos (RFC 4120) for end-to-end authentication

  • IPsec (RFC 4301) to secure data communications between two end hosts

References:

Thank you!! (and thanks to jksoegaard for comments to the previous question)

Note to moderator(s): this is a edited restatement of a previous question, “What technical and/or patent information exists for Apple's discontinued 'Back to My Mac' (BTMM) service, and/or what are possible replacements”, that was recently auto-deleted; if you close this current question in the future, please consider doing so in a way that allows it to remain as a searchable reference for future users.

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  • 1
    I'd love to see an answer to this which involves a) zero outlay & b) a one-button setup. I lost the ability to support my folks' Mac when this was removed from macOS. 2,000 miles away, on a different continent… makes it a bit tough to support them remotely, nor can I get in to configure anything new; it would have to be done next time I'm there, which in 2020 doesn't feel like it's going to be anytime soon :\
    – Tetsujin
    Dec 9 '20 at 17:59
  • @tetsujin If I figure something out I’ll be sure to post it here. I don’t think basic operation would have to be that complicated: one could link each computer to the same VPN (or each to a separate VPN terminating on a common network/router). That/those VPN(s) would have to pass mDNS discovery packets, and you’d probably only want to certain network traffic (i.e. NOT normal internet traffic) to travel over that VPN. That would allow any computers you wish to connect to appear to be on the same physical network.
    – Jim Grisham
    Dec 9 '20 at 18:21
  • @tetsujin: as for configuring or supporting them now, a free tool such as Zoom, Chrome Remote Destkop, or TeamViewer (and maybe still FaceTime??) should allow you to share and control their screen remotely as long as the computer is attended. Zoom is probably the lowest-barrier-to-entry these days - they can share their screen (and allow you control) while on a video call with you, and you can share yours with them first to demonstrate to them how to do so. Once you have access through Zoom, you can set up Chrome Remote Desktop, allowing you unattended access going forward.
    – Jim Grisham
    Dec 9 '20 at 18:25
  • The question you refer to was put on hold for clarification and then deleted by the system automatically because no further edits have been made so there was no vote on a potential reopening. As mentioned by another moderator already it might have been easier to flag the deleted question for mod attention.
    – nohillside ♦
    Dec 9 '20 at 19:46
  • @nohillside Thank you for that - it wasn’t clear at the time that there was any way to have a person review the autodeletion... TIL about AskMeta. :)
    – Jim Grisham
    Dec 9 '20 at 19:59
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Your question is broad and contains numerous elements, therefore I'll need to enumerate my answer accordingly:

Starting point 1:

I cannot see how any of the involved technology could be patented, nor that any technology as such is licensed here. Apple could ofcourse be licensing an implementation, but they would be able to reimplement themselves. The BTTM system can be re-implemented in a variety of ways using various protocols and technologies and still end up with similar functionality - so patents is not a problem in recreating similar functionality.

Note also that modern versions of similar systems exist in the market place now. For example you could just install Tailscale and have similar access to all of your devices. As long as you're a single user and have less than 100 devices, it is free of charge.

Starting point 2:

There are open-source versions of almost everything included in Apple's BTTM system. You would however need to integrate those yourself and make it scalable. This would involve things like automatizing a CA, having a specialized DNS-server, etc. It is not rocket science, but it's not something you do in a Sunday afternoon either.

Note that there's a big difference between making a service like Apple's BTTM that is supposed to support thousands (if not millions) of users and even more devices - and making something that will just work for your own purposes. If you're just looking for some way to create a BTTM-like experience for yourself, it can be done much simpler than trying to replicate Apple's BTTM system.

Starting point 3:

For a technical reference you can just look up RFC6281. It holds information enough for a professional (or motivated hobbyist) to create a similar system. However if the goal is to make it interoperable with Apple's BTTM service (i.e. used with the clients included in older versions of macOS) - that is much harder (bordering on impossible) and not worth doing. Some of the issues here is that you wouldn't have access to Apple's secret keys, their me.com domain and the custom protocols for AppleID authentication.

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  • All fair points. While I’m something suitable for a single user could be cobbled together, my goal was not to re-invent the wheel ... perhaps someone out there has already done this (e.g. written a shell script to set up the applicable tools) and I was just not aware of the correct search terms, or perhaps someone has a theory (such as extant patents) that would prevent this from being practical at this time. If there is currently no wheel, though, then perhaps I or someone else will try to design one some long winter. Thank you for your comments and the time spent on your answer, sincerely!
    – Jim Grisham
    Dec 10 '20 at 15:59
  • Oh, and regarding patents.., I know that in the past, companies such as Skype had patented things like specific NAT-traversal methods; surely someone like Microsoft has considered a need for Remote Desktop access solution without a RD gateway, but for either business or technical reasons they have chosen not to offer a BTMM-like feature. (I have known several folks whose macOS/Windows 10 decision was tilted in the macOS direction specifically because of BTMM, usually to mount file shares and not for screen sharing).
    – Jim Grisham
    Dec 10 '20 at 16:03
  • I'm not sure if I'm getting my point across clearly here. 1) For a single user, elegant and finished solutions exist aplenty - there's nothing "cobbled together" about it. 2) Lots of people have implemented these things. It is not a matter of having to invent a wheel over a long winter. It is commonly available tools that have stood the test of time.
    – jksoegaard
    Dec 11 '20 at 8:21
  • Regarding patents for NAT-traversal: This is not a problem today. Everyone and their mother uses STUN, TURN and ICE. It is a completely standardized way of doing NAT traversal. It is used by Skype and other voice software (like for example Microsoft Teams), used by browsers (such as Google Chrome) and lots of other software. Implementations are freely available from several sources.
    – jksoegaard
    Dec 11 '20 at 8:23

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