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XMPP: The secure communication protocol that respects privacy

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Re: XMPP: The secure communication protocol that respects privacy

#31

Post by southerntofu »

gefhfffh wrote: post #8
a3w wrote: post #4

Encryption is "activily bein worked on", sound about right - I never got encryption to work across two of my own devices with a third party. Yet I do not understand why a rewrite of messaging as [matrix] was necessary, when XMPP was already there and matrix did not even have an edit-message feature on release, perhaps not even now.

Well, matrix does a lot of things different. A rewrite seems pretty unavoidable with hat many and significant changes

What's so different about it? Historically XMPP was more geared towards message-passing without server-side archival, but that ship has long since sailed to support multi-client. As it is, i don't see any significant change except for the consensus algorithm for decentralized rooms which could very well be an extension to the XMPP s2s protocol.

Re: XMPP: The secure communication protocol that respects privacy

#33

Post by infosechandbook »

f1refly wrote: post #23
KaiserPro wrote: post #18

XMPP is many thing, but I doubt it could be described as secure. Yes it has SASL auth, TLS and you can run it on an intranet, but thats not the same as secure.

XMPP is as secure as Signal nowadays, it implements the same encryption scheme and is still completely federated: https://conversations.im/omemo/ Omemo is a relatively recent effort though and many people still remember the days when gpg and otr where the sad state of the art in the xmpp world.

> XMPP is as secure as Signal nowadays, it implements the same encryption scheme

Signal enforces E2EE, you can't disable it. If XMPP supports E2EE depends on the XMPP clients and servers, so it isn't enforced and can be disabled. Server admins can even inject XMPP messages that look like coming from the legitimate sender. This is far from "secure as Signal."

Re: XMPP: The secure communication protocol that respects privacy

#34

Post by southerntofu »

f1refly wrote: post #16
gefhfffh wrote: post #12

Earlier quoted context omitted.

How resistant to MITM is it though? Currently, verification seems to work on a session basis and not just per user, which makes it very tedious to have everything verified e.g. a group chat. If it is not almost impossible given peoples sessions change with time. Add a new session in the browser -> meet every contact to verify their sessions with your new browser session? Doesn't seem very practical, and reminds me of…

Security is always a tradeoff with convenience. How should a "per user" verification work in your opinion? A single master key that signs subkeys? Would the master key be secured with yet another password? What happens with already signed keys if a user loses access to the master key? Will I have to explain to my auntie over the phone that her master key password is somehow different to her account password and that…

> How should a "per user" verification work in your opinion?

The server could keep an append-only log of published keys, and then you could require m-of-n signatures of other published devices/keys to register a new one, in which case no further verification would be verifiable if you already trusted your peer's other keys. In addition, you could introduce peer keys in private rooms automatically and/or employ some form zero-knowledge proofs in public venues.

XEP-0450 Automated Trust Management is a first exploration in this direction. There a lot to explore and I only wished skilled cryptographers spent more time researching these issues on federated networks instead of advancing yet-another-centralized-messenger-of-the-month.

> Also you don't have to meet with everyone to verify new keys, you can just use a known good key for that.

Also known as a keyserver. But you could also employ cryptographic challenges like OTR does, like a shared password to establish the session.

Re: XMPP: The secure communication protocol that respects privacy

#35

Post by southerntofu »

folex wrote: post #25

How about XMPP performance on low-performance networks like mobile ones? I believe poor networking performance was one of the reasons XMPP had to be customised in WhatsApp and overall didn't become as widely used as I'd like it to be :) Is it still the case? Or was that problem addressed at standard level somehow?

Some extensions like XEP-0352 Client State Indication have been developed to fit the mobile world. XMPP on mobile is nowadays very reliable, except for iOS preventing 3rd party notifications.

Re: XMPP: The secure communication protocol that respects privacy

#36

Post by southerntofu »

f1refly wrote: post #26
rakoo wrote: post #24

Earlier quoted context omitted.

XMPP leaves a lot of metadata and user information around, so it does have a privacy issue that's probably not solvable. Whether it's a security issue is a completely different discussion though.

That's got nothing to do with the security problems OP complained about though. Are there even working solutions to those metadata problems apart from sending dummy decoy messages and purposeful delays on the server side to make correlating message relaying hard?

The metadata leaks are more about correlating pseudonymous identities to the same accounts than network leaks (for which we employ VPN/SSH tunnels or Tor). If you'd like to know more about the threat model of XMPP: https://joinjabber.org/faqs/security/ (critique welcome)

Re: XMPP: The secure communication protocol that respects privacy

#37

Post by southerntofu »

tacticaldev wrote: post #32

Isn't that Jabber? Haven't heard of XMPP in a while.

It's the same thing! XMPP usually refers to the protocol and Jabber the open federation, but since Cisco acquired the Jabber trademark some people have been reluctant to use that name.

And some people think a protocol name is irrelevant and would rather build a consistent product based on open standards: https://snikket.org/blog/products-vs-protocols/

Re: XMPP: The secure communication protocol that respects privacy

#38

Post by southerntofu »

Semaphor wrote: post #29
f1refly wrote: post #20

Earlier quoted context omitted.

Depending on when you last tried xmpp you might have experienced the OTR hell, which was never really codified 100% and spawned subtle incompatibilities between clients leading to weird and nondescript errors that never got addressed. Nowadays the popular clients support omemo ( https://conversations.im/omemo/ ), which makes encryption just work™ out of the box and without hassle. The only exception to this is xabber…

> just work™ YMMV™ We have yet to manage not getting any OMEMO issues in a 2 users, 5 clients situation (2 Conversations on android, 1 Gajim on win, 2 Pidgin on linux)

If you care to elaborate, i'm sure that'll be of interest to maintainers. Although to be fair Pidgin doesn't exactly have the reputation to be maintained (despite recent efforts to start again) so i would strongly recommend to try again without that specific client in the equation.

Re: XMPP: The secure communication protocol that respects privacy

#39

Post by tialaramex »

infosechandbook wrote: post #28

The article describes XMPP as "secure" by highlighting TLS (protecting data in transit only) and experimental OMEMO (protecting a small part of an XMPP message only if enabled and working). What about other crucial security features, see https://www.eff.org/deeplinks/2018/03/building-secure-messen... ? Then, XMPP is described as "privacy respecting" mostly because you can use a nickname instead of a phone number for…

I await future articles "Saudi Arabia: The resource poor country with a thriving democracy", "Bears: These vegetarians are too shy to defecate outdoors" and perhaps soon, "Popes: The married women who are rarely seen in church".

But maybe they've just never seen a protocol more secure than telnet or more privacy respecting than the News Of The World ? Nobody show them Signal or their head might explode.

Re: XMPP: The secure communication protocol that respects privacy

#40

Post by southerntofu »

infosechandbook wrote: post #28

The article describes XMPP as "secure" by highlighting TLS (protecting data in transit only) and experimental OMEMO (protecting a small part of an XMPP message only if enabled and working). What about other crucial security features, see https://www.eff.org/deeplinks/2018/03/building-secure-messen... ? Then, XMPP is described as "privacy respecting" mostly because you can use a nickname instead of a phone number for…

What would be your alternative? I agree there's a lot to research and improve in the XMPP ecosystem ( see also https://joinjabber.org/faqs/security/ ) but "admin in the middle" is not exactly a bug but a property of federated systems.

If your alternative is to use a centralized platform (which potentially requires a phone number to sign on) that's a trade-off i'm not willing to make. I'm personally very happy with my not-so-insecure pseudonymous communications (but always interested in constructive criticism).

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