Yeah, iOS is definitely a weaker spot and we're aware of it. Monal is currently working on an overhaul of their UI (they have a grant allocated for it: https://nlnet.nl/project/Monal-IM-UI/ ).
There is also a new app in the works between Cheogram and Snikket. There is a beta available, but it's still young (and we won't apply any Snikket branding until E2EE is complete).
Be aware that this post has known issues that the author is not interested in fixing. In their own words (in response to clarifications by one of the OMEMO folk):
"I'll make an edit later about the protocol version thing, but I'm not interested in having questions answered. My entire horse in this race is for evangelists to f** off and leave me alone. That's it. That's all I want." [censorship of profanity mine]
You won't find this quote in the article with Ctrl+F, it's in the screenshot, where they omitted the original constructive comment by one of the OMEMO contributors that they chose to moderate, which you can find here: https://www.moparisthebest.com/tim-henkes-omemo-response.txt
So, by all means, read the blog post. But just be aware that its ultimate goal was not to be an unbiased accurate technical article.
The post is an opinion piece and not a technical article for sure, but I'm not sure the takeaway from that quote is that the article is inaccurate, but rather they aren't really looking to start a conversation but rather state their opinions. It seems they've made multiple edits where they believe there are inaccuracies.
FWIW, I personally think Henke is correct to state that creating "...a product based on XMPP+OMEMO that, exactly like Signal, can only communicate with other Signal users and always has encryption on." would largely address most of the critiques (or at least the ones that bother me most), but that Soatok is also correct in concluding that the XMPP ecosystem and the way OMEMO is used in clients today does not meet their definition of "Signal competitor"[0], which I think is still a useful way to frame things.
I'm the founder of both the Prosody and Snikket projects. Sorry about triggering alarms :) I can try to explain...
Prosody is a popular choice of XMPP server software. It's used for all kinds of stuff, from self-hosted chat servers to powering Jitsi Meet, to Internet-of-Things applications.
Prosody is extremely flexible, and has a bunch of configuration options that allow you to adapt it and extend it however you want. For some people, this is ideal. Those people should continue using Prosody.
Snikket has a different scope. It is specifically an answer to a question like "How can I easily make a self-hosted WhatsApp/Signal for my family/friends using open-source software?"
- Snikket contains Prosody, for the core chat part. But it's Prosody with a very specific configuration, and the configuration is part of the project, it's not intended to be modified by the person deploying Snikket. They only need to provide the domain name.
- Snikket also includes additional components that a modern chat service needs. For example, it includes a STUN/TURN server to ensure that audio/video calls work reliably (again, preconfigured).
- Snikket provides its own apps, which are tested and developed in sync with each other and with the server. This avoids the common problem of incompatibilities that occur when you have an open ecosystem such as XMPP, where different open-source project developers may develop features at different paces, leaving users to figure out which ones support which feature. It also solves the discoverability and decision fatigue for users (searching "Snikket" on an app store will get you an app that you know is compatible with your Snikket server, you don't have to go through a list of XMPP clients and figure out which one is suitable).
- Snikket servers are not designed to be open public servers (these are an administrative nightmare). Instead, your server is closed and private by default. As the admin, you choose who signs up to your server by sending invitation links. The invitations also serve to simplify the account setup process - no need to prompt users to "choose a server", etc. They just need to provide a username.
Projects such as Conversations differ by running a single public server (conversations.im) and guiding people to sign up on that server, or choose one of a long list of free public XMPP providers. In some cases that's all what you want. But onboarding a group of people that way is not fun (for example, they all have to share their addresses with the group add each other to their contact lists one-by-one - Snikket makes discovery of contacts within the same server automatic).
Beyond these things, Snikket is all open-source and XMPP. But there is a focus on making a good polished and secure "product", if you like, rather than supporting the entire diverse XMPP ecosystem which includes a range of software of varying quality (weekend projects and more recently, 100% vibe-coded clients). For example, Snikket servers require certain security and authentication features which some older codebases that have fallen far behind modern XMPP standards (think Pidgin, etc.) simply don't support today.
> it’s actually all based on prosody and conversations?
As mentioned, I develop Prosody. I also collaborate with the Conversations developer and other XMPP projects. There's nothing shady here. The goal is just to make a best-in-class XMPP project that solves one particular use case (and it was primarily my own use case to begin with of course - I wanted to move my family off WhatsApp).
Ohh, wow. First off, thanks for prosody, been using it for several years, ever since I switched from my early 2000s jabber.org account to selfhosted.
And yeah, I get what you are saying, I'm using it the same way you envision snikket, just for my wife and I. Considering how much time I spent on the initial setup, I can very much see wanting a preconfigured version.
I guess the site was just too "non technical" and went over my head when I tried to grok it (before, a while ago, and now before writing the comment), the lack of a download option for the client on the snikket site combined with repeatably talking about invites just rubbed me wrong.
As I have already setup my server, and have gajim/conversations (which afaik are the best modern Windows/Android clients, for Windows probably even the only one storing modern xmpp) for desktop/mobile, I have no need for snikket, but my view now went from negative to very positive ;)
I'm still experimenting with the messaging on the Snikket website. However my general approach with the site was to pitch Snikket to people who don't know what XMPP is, which is, frankly, the majority of people. Instead, I wanted to focus on explaining features it enables rather than protocol details. But I'm aware it has caused a lot of head-scratching among people who already know Snikket uses XMPP :)
I see Snikket as kind of a gateway into the XMPP ecosystem for people who are unfamiliar with it. After all, if you're already familiar with XMPP then the chances are you'll probably be happier with Prosody or ejabberd, and you'll already have opinions about which clients you want to use (e.g. the upstreams of Snikket).
I am the current lead developer of Pidgin, and would like to reinforce the level of collaboration in the XMPP world. Even with Pidgin being very far behind in XMPP (and everything else) everyone has been very helpful as we're trying to catch back up and answering questions about the prosody instance we run ourselves.
This is a great explanation; Prosody/ejabberd seem to kind of be "everything to everybody" but because they are so general it's hard to know if they're a good fit for any one particular purpose.
Snikket seems to just be a focus or lens on Prosody that answers that question for the mission statement you gave.
As the founder of both projects, explaining the difference between the two projects is roughly 20% of my working day (okay, not quite 20% but sometimes it feels that way).
They weren't "HTTPS certificates" originally, just certificates. They may be "HTTPS certificates" today if you listen to some people. However there was never a line drawn where one day they weren't "HTTPS certificates" and the next day they were. The ecosystem was just gradually pushed in that direction because of the dominance of the browser vendors and the popularity of the web.
I put "HTTPS certificates" in quotes in this comment because it is not a technical term defined anywhere, just a concept that "these certificates should only be used for HTTPS". The core specifications talk about "TLS servers" and "TLS clients".
This is technically true, and nobody contested the CABF's focus on HTTPS TLS.
However, eventually, the CABF started imposing restrictions on the public CA operators regarding the issuance of non-HTTPS certificates. Nominally, the CAs are still offering "TLS certificates", but due to the pressure from the CABF, the allowed certificates are getting more and more limited, with the removal of SRVname a few years ago, and the removal of clientAuth that this thread is about.
I can understand the CABF position of "just make your own PKI" to a degree, but in practice that would require a LetsEncrypt level of effort for something that is already perfectly provided by LetsEncrypt, if it wouldn't be for the CABF lobbying.
> CABF started imposing restrictions on the public CA operators regarding the issuance of non-HTTPS certificates.
The restriction is on signing non web certificates with the same root/intermediate as is part of the WebPKI.
There's no rule (that I'm aware of?) that says the CAs can't have different signing roots for whatever use-case that are then trusted by people who need that use case.
> The CA/Browser Forum is a voluntary organization of Certification Authorities and suppliers of Internet browser and other relying‐party software applications.
IMHO "other relying-party software applications" can include XMPP servers (also perhaps SMTP, IMAP, FTPS, NNTP, etc).
It is a single member of the CAB that is insisting on changing the MAY to a MUST NOT for clientAuth. Why does that single member, Google-Chrome, get to dictate this?
Has Mozilla insisted on changing the meaning of §1.3 to basically remove "other relying‐party software applications"? Apple-Safari? Or any other of the "Certificate Consumers":
The membership of CAB collectively agree to the requirements/restrictions they places on themselves, and those requirements (a) state both browser and non-browser use cases, and (b) explicitly allow clientAuth usage as a MAY; see §7.1.2.10.6, §7.1.2.7.10:
Of these, (1) and (2) are already implemented in XMPP.
(1) just isn't that widely deployed due to low DNSSEC adoption and setup complexity, but there is a push to get server operators to use it if they can.
(2) is defined in RFC 7711: https://www.rfc-editor.org/rfc/rfc7711 however it has more latency and complexity compared to just using a valid certificate directly in the XMPP connection's TLS handshake. Its main use is for XMPP hosting providers that don't have access to a domain's HTTPS.
Yes, definitely. Prosody supports DANE, but DNSSEC deployment continues to be an issue when talking about the public XMPP network at large. Ironically the .im TLD our own site is on still doesn't support it at all.
> Is there a reason why dialback isn't the answer?
There are some advantages to using TLS for authentication as well as encryption, which is already a standard across the internet.
For example, unlike an XMPP server, CAs typically perform checks from multiple vantage points ( https://letsencrypt.org/2020/02/19/multi-perspective-validat... ). There is also a lot of tooling around TLS, ACME, CT logs, and such, which we stand to gain from.
In comparison, dialback is a 20-year-old homegrown auth mechanism, which is more vulnerable to MITM.
Nevertheless, there are some experiments to combine dialback with TLS. For example, checking that you get the same cert (or at least public key) when connecting back. But this is not really standardized, and can pose problems for multi-server deployments.
> It has never been secure to accept the clientAuth EKU when using the Mozilla root store.
Good job we haven't been doing this for a very long time by now :)
Sorry, it's late here and I guess I didn't word it well. Dialback (these days) always runs over a TLS-encrypted connection, as all servers enforce TLS.
The next question is how to authenticate the peer, and that can be done a few ways, usually either via the certificate PKI, via dialback, or something else (e.g. DNSSEC/DANE).
My comment about "combining dialback with TLS" was to say that we can use information from the TLS channel to help make the dialback authentication more secure (by adding extra constraints to the basic "present this magic string" that raw dialback authentication is based on).
How would dialback-over-TLS be "more vulnerable to MITM" though? I think that claim was what led to the confusion, I don't see how TLS-with-client-EKU is more secure then TLS-with-dialback
Firstly, nobody is actually calling for authentication using client certificates. We use "normal" server certificates and validate the usual way, the only difference is that such a certificate may be presented on the "client" side of a connection when the connection is between two servers.
The statement that dialback is generally more susceptible to MITM is based on the premise that it is easier to MITM a single victim XMPP server (e.g. hijack its DNS queries or install an intercepting proxy somewhere on the path between the two servers) than it is to do the same attack to Let's Encrypt, which has various additional protections such as performing verification from multiple vantage points, always using DNSSEC, etc.
If an attacker gets a misissued cert not through BGP or DNS hijacks, but by exploiting a domain validation flaw in a CA (e.g. https://bugzilla.mozilla.org/show_bug.cgi?id=2011713) then it's trivial for them to use it as a client certificate, even if you're requiring the serverAuth EKU. On the other hand, dialback over TLS would require the attacker to also MitM the connection between XMPP servers, which is a higher bar.
The good news is that since Prosody requires the serverAuth EKU, the misissued cert would be in-scope of Mozilla's root program, so if it's discovered, Mozilla would require an incident report and potentially distrust the CA. But that's reactive, not proactive.
You're not wrong. PKI has better protections against MITM, dialback has better protections against certificate leaks/misissuance.
I think the ideal approach would be combining both (as mentioned, there have been some experiments with that), except when e.g. DANE can be used ( https://prosody.im/doc/modules/mod_s2s_auth_dane_in ). But if DANE can be used, the whole CA thing is irrelevant anyway :)
Firstly, nobody is actually calling for authentication using client certificates. We use "normal" server certificates and validate the usual way
I'm not sure I understand this point. You authenticate the data you receive using the client's certificate. How is that "nobody is calling for authentication using client certificates"? Maybe there's some nuance I'm missing here but if you're authenticating the data you're receiving based on the client's certificate, then how is that "validating the usual way"?
There is a lot of confusion caused by overlapping terminology in this issue.
By "client certificates" I mean (and generally take most others in this thread to mean) certificates which have been issues with the clientAuth key purpose defined in RFC 5280. This is the key purpose that Let's Encrypt will no longer be including in their certificates, and what this whole change is about.
However when one server connects to another server, all of TCP, TLS and the application code see the initiating party as a "client", which is distinct from say, an "XMPP client" which is an end-user application running on e.g. some laptop or phone.
The comment I was responding to clearly specified " I don't see how TLS-with-client-EKU [...]" which was more specific, however I used the more vague term "client certificates" to refer to the same thing in my response for brevity (thinking it would be clear from the context). Hope that clarifies things!
There might be some confusion here, as there is no refusal at all.
As stated in the blog post, we (Prosody) have been accepting (only) serverAuth certificates for a long time. However this is technically in violation of the relevant RFCs, and not the default behaviour of TLS libraries, so it's far from natural for software to be implementing this.
There was only one implementation discovered so far which was not accepting certificates unless they included the clientAuth purpose, and that was already updated 6+ months ago.
This blog post is intended to alert our users, and the broader XMPP community, about the issue that many were unaware of, and particularly to nudge server operators to upgrade their software if necessary, to avoid any federation issues on the network.
Sorry, I probably misunderstood, I thought there were resistance to update the corresponding specs. I understand that non XMPP specs might refuse to be updated, but at least this behavior could be standardized for XMPP specifically.
Yeah, the resistance is outside the XMPP community. However we have a long history of working with internet standards, and it's disappointing to now be in an era where "the internet" has become just a synonym for "the web", and so many interesting protocols and ideas get pushed aside because of the focus on browsers, the web and HTTPS.
Thanks! I didn't intentionally write this for a broader audience (I didn't expect to see it while casually opening HN!). Our user base is quite diverse, so I try to find the balance between being too technical and over-explanatory. Glad it was helpful!
There is also a new app in the works between Cheogram and Snikket. There is a beta available, but it's still young (and we won't apply any Snikket branding until E2EE is complete).
Thanks for sharing your experience!
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