EXCELLENT piece of work. Thanks for sharing this.

Excellent work!

Out of interest are the SIP details returned from the call to https://linediscovery.hub.bt.com/ likely to be enough for a third-party ATA / VoIP client to connect to the BT SIP server?

In reply to a post by tdw42:

Excellent work!

Out of interest are the SIP details returned from the call to https://linediscovery.hub.bt.com/ likely to be enough for a third-party ATA / VoIP client to connect to the BT SIP server?

I imagine they probably would be enough for a 3rd party VOIP client. The problem is that the messages are encrypted and so I can't see the content of them.

If there's some way of getting hold of the SH2 firmware, it might be possible to search through it and work out the format of the call to https://linediscovery.hub.bt.com/ but I don't know where that can be downloaded from as it doesn't seem possible to download the firmware and update the SH2, and I can't see any way to extract the firmware from the SH2.

Also, one thing that did surprise me is that only the Host-Uniq and PPPoE session ID seem to be needed. I would have thought that the AC Name would also be needed to be completely sure that the combination was unique, otherwise there would be a very tiny possibility that 2 SH2s had the same Host-Uniq and PPPoE session ID if they were connected to different exchanges.

In reply to a post by chrisu:

The problem is that the messages are encrypted and so I can't see the content of them.

It depends on how good their HTTPS implementation is - if the SH2 does not present a client certificate to the server and also does not check the server certificate CA there are a number of HTTPS proxies, e.g. mitmproxy, which can be used to intercept and decode the traffic.

In order to test this, I set up a DNS server which resolved linediscovery.hub.bt.com to my web server, and set that DNS server to be the one passed to the SH2 on the PPP connection. I then turned on the SH2 and used wireshark to observe the traffic. The TLS key exchange failed with the SH2 generating the error : TLSv1.2 Record Layer: Alert (Level: Fatal, Description: Unknown CA). So the SH2 is checking that the server cert is signed by a valid CA and doesn't proceed any further.

Hi Chris

I signed up today just to commend you on your work with this
I'm not yet on BT's FTTP, but that's only because I was yet to find a solution to being able to use their Digital Voice service (via the SH2), but using my own router for 'normal' traffic (Linksys WRT1900ACS - running OpenWRT).

Your post gives me hope that it is possible, even if I haven't yet worked out what each bit is!

I'm sure there will be more guides / helpful posts when more users get online with FTTP.

We've recently had to change landline numbers (long, boring story) and my other half is insistent that it doesn't happen again any time soon (I'm still looking at a number port to a proper VOIP solution).

Thanks

MilesR

BT's solution is a proper VOIP one, just a secure one to meet all the Gov standards. It is likely to be the most secure one an ordinary punter can buy.

What you actually want is the service to run on a plug in ATA ( adaptor) so you can use it on any router. However that will let people break the security and make the voice service hackable / interceptable so is unlikely to happen.

( breaking the security may also be an offense but you would have to trawl the communication acts to check this)

Sorry, wrong word chosen.
I meant "alternative" rather than "proper"

I've already got an account & number with Sipgate and am looking at the various adapters (e.g. Grandstream HT802 etc.) but as I mentioned, getting my other half to agree to switching to that number is proving the hardest part!
I never use it, but she had a number of older friends who aren't heavy mobile users and still rely on landlines for their method of communication.

If I can manage a move to using another provider (i.e sip gate) then I can decouple the 'need' for a physical landline tied to the broadband provision.

Why not switch your existing telephone number to a separate VOIP provider when you moved to FTTP

Edit: Your post just before mine supersedes my post.

Edited by dect (Sun 24-Jan-21 13:13:31)

In reply to a post by dect:

Why not switch your existing telephone number to a separate VOIP provider when you moved to FTTP

This is the option I took, but no FTTP here, I used Virgin Media cable. My old openreach number is now VoIP with AAISP.