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Yeah, i think it is a feature, and a very beneficial one for the people this system was designed for - those who want a lot of privacy-desiring users to settle on using an encryption solution which isn’t too difficult to circumvent.

This you need to prove somehow. Has there be any attack that happened like this? Has there been any content leaked this way, or provided to law enforcement? In other words, did they use this "feature" in any way? Because if this is just a design limitation, then it's not a feature, it's a risk exactly like using someone else's code exposes you to supply chain risk. Would you say that anybody who uses any external library is actually a snake-oil seller about the property of their product because if a supplier (library, dependency, etc.) get compromised their product could be compromised? I wouldn't say so. I think that intentions matter here.

Note that, throughout this discussion, I’m not really just talking about Proton but rather them and Tuta and Hushmail and anything else that shares this architecture.

Yes, I understand.

Well, they could be honest and inform their users: “to have the convenience of using webmail you must sacrifice the benefit of end-to-end encryption (not needing to trust the server and its operators to refrain from reading your messages).”

But that's not true. End-to-end encryption simply means that the encrypt/decrypt operation happen on the client side. It doesn't mean that it's an unbreakable design. Following this logic, every software that does PGP encryption should say "to have the convenience of not having to rewrite all the code ourselves we use suppliers which might allow third parties to read your messages". Proton content is still end-to-end encrypted, with the code hosted publicly. The fact that vectors exist to invalidate that is not a reason to invalidate the whole thing, exactly like the existence of supply chain attacks are not a reason to dismiss the validity of e2ee for CLI tools and the like.

Also, I mentioned the potential to use the bridge. That is a fully client-side tool which does not run in the browser, does that satisfy your risk appetite?

Yep. But no matter how tight their processes are, there are still single points of failure that can be coerced to gain access to anyone’s email.

They are a point of failure, not a single point of failure necessary (as in a single person).

but I don’t have the energy to explain to you why selling something as e2ee while it reduces to (among other things) specifically the security of TLS is dishonest.

But this was not your claim, your claim was that compromising them and serving backdoored JS was not the only way, and that an attacker in an appropriate network position could achieve the same. I am saying that particular vector does not apply, because your browser will actually refuse to serve Proton without a valid certificate due to HSTS. So an attacker can tamper with the code only at either of the "ends" (either compromising them or compromising your endpoint).

I just checked their site and they still say it’s “for journalists”, and “we can never access your messages”, etc etc.

Just for reference, what I meant is that people referred by the statement "and the incorrect perception that ProtonMail’s end-to-end encryption provides meaningful security is undoubtedly preventing some of their customers from using better tools instead." are not those who have that risk model. Journalist and other at-risk people have technical consultants and are (hopefully?) aware of the risks, and can apply additional controls (for example, using Proton to send encrypted content). They are not those who won't use other - more secure - channels than email because they read Proton pages.

If what you want is not privacy from adversaries who can compromise your mailserver, but rather just protection from GMail reading your mail, then you don’t need e2ee: you need a provider with a privacy policy you believe they will honor.

e2ee is just a very nice and clear-cut way to enforce the privacy policy. Law enforcement can still get the data from a provider. If the data is not collected, the data cannot be given. Sure, it's possible that a 3-letter agency will coerce Proton to compromise a user but a) this did not happen yet (as far as we know?) and 2) again, if that's part of your risks, don't use emails or just use email to send encrypted content...

Why would you assume they are when they’re lying about their ability to read your emails?

You seem to be really fixated with this statement, but it's not true. They don't have the "ability" to read emails. They have a setup that - provided the violation of controls that we both don't know about - can possibly grant them that ability. I really don't understand why you think it's different from any other software. If the NSA goes to https://www.gnupg.org and says "you know what, the next time you serve your software to IP x.x.x.x", you serve this package, you will never know and your encryption is toast. Would you say that the folks behind GnuPG "have the ability to read your emails"? I wouldn't, because they are not backdooring the software, although the possibility for them, contributors and national actors to do that exists.

rather you are just saying that you think it is very unlikely that they would ever abuse that capability and that you assume their procedures make it so that one rogue employee couldn’t do it alone. You do seem to understand that, contrary to what they’ve written in the screenshot above, ProtonMail as a company technically could decide to.

Yeah, you are correct. This is exactly the same as me saying that technically a lot of people in my organization could tamper with payments and violate the integrity of most of UK bank transfers. In practice, there are a bazillions controls in place to ensure that this does not happen, and before touching production there are tons of safeguards, but theoretically my company could decide to break compliance, remove procedure and allow a free-for-all on banking transactions before being fined/shut down/to the abyss.

I do believe that they have no interest whatsoever to abuse this architectural feature, but I agree that they could be coerced to. However, as I said before, I believe the same to be true for any other software, which is why I don't agree on the risk model to be significantly different from many other tools. In fact, the fact that they are in Swiss jurisdiction might help, compared to a lot of (F)OSS entities which are in the US.

But, do you think most of their customers understand that?

No, I think most people don't.

which of these statements do you think is the most likely to be accurate:

I have no idea. I would say 1 or 3 are the most likely. It seems a very unnecessary way (if I were a certain 3 letter agency) to gain access to a small set of data, when I can compromise the whole device and maintain persistence much more conveniently (for example coercing the ISP to give me access to the router and go from there, or ask directly Apple and Microsoft, etc.).

If it were revealed that #4 were in fact the case, would you agree that it is snakeoil? If you agree with me that #3 is the most likely scenario, approximately how many times per hour/week/year would they need to be complying with these requests before you would agree that they are, in fact, snakeoil?

I would say that they should disclose that for sure, at least with a warrant canary, since they might actually not even be allowed to fully disclose it. I am fairly conflicted about the fact that government surveillance has -sometimes- reason to be exercised, provided a judge has vetted it and proper guarantees are in place (not the US way, to be clear), and the fact it is routinely abused. I also believe that perfect security does not exist, and it's enough for me to send an encrypted attachment via Proton and mitigate this whole risk.

To answer your question, I would say that if this is a forced action that happened a handful of times, for extremely high profile cases and severe reasons, then I might still consider their claim legitimate. If it's a routine procedure to satisfy pretty much any request, then I would agree that this becomes more of a feature than an attack.

That said, I also have a couple of final questions for you too:

• Proton bridge runs on the client and does not use the browser. The code is open source. Since they provide this too, would you consider this on-par with using your favorite CLI/plugin for PGP? Would this solve the problem you raise?
• Do you think that it's possible that any of the 3-letters agencies could coerce a software author (or some collaborator) and produce a malicious release for the code that is served only to you (for example, by IP, fingerprint or other identifier) or that it activates only for you (device ID etc.)? For example go to Kevin McCarthy and force him to produce a backdoored version of Mutt (http://www.mutt.org/download.html) which is backdoored to leak your keys.
• Do you think that alternatively Github/Bitbucket for example could be coerced by said agencies to backdoor the version (and signature) you get for a given code, say https://bitbucket.org/mutt/mutt/downloads/mutt-2.2.12.tar.gz (maybe after graciously "asking" Kevin for his key to sign the software).
• If you think the above is possible, do you think there is any distributor for software that could not be coerced? And how this vector is actually different from Proton being forced to break their own encryption?
• If you agree that the above is possible, would you say that any claim about Mutt using PGP to e2e encrypt/decrypt your emails are snakeoil?

What you describe it’s an attack, not a feature though

Yeah, i think it is a feature, and a very beneficial one for the people this system was designed for - those who want a lot of privacy-desiring users to settle on using an encryption solution which isn't too difficult to circumvent.

They have no way to prevent the attack you mention completely because that’s inherent to the fact that the same entity that serves the software handles the ciphertext.

Yep! That is what I've been saying: that is the problem with this architecture!

Note that, throughout this discussion, I'm not really just talking about Proton but rather them and Tuta and Hushmail and anything else that shares this architecture.

There is absolutely nothing they could do to improve their stance on this “promise”.

Well, they could be honest and inform their users: "to have the convenience of using webmail you must sacrifice the benefit of end-to-end encryption (not needing to trust the server and its operators to refrain from reading your messages)."

Do you think telling users that would surprise many/most of them, and cause them to stop using it? Could that be why they don't mention it?

They might have extremely tight processes [...] but I can’t know either way.

Yep. But no matter how tight their processes are, there are still single points of failure that can be coerced to gain access to anyone's email.

not everyone has the same risk appetite that Snowden has

It's funny you mention Snowden. Even he was naive enough to use a Proton/Tuta/Hushmail-like system back in 2013... it was called Lavabit. In the case of Lavabit, I think the operator was actually also naive and well-intentioned because when people investigating Snowden asked him to perform the exact attack i've been describing (which his architecture enabled him to) he instead opted to shut down the entire service and to notify Snowden and the world.

ProtonMail operating with the architecture they have in a post-Lavabit world (they were actually founded just after that happened, and rode the Snowden privacy-awareness wave to success) is pretty strong evidence that they would not shut down their system if the alternative was being forced to spy on some of their users.

(To be clear, Lavabit should've known better too, existing in a post-Hushmail world...)

if an attacker has the ability to install the certificate on the device

🤦 that is (obviously, i thought) not what i'm talking about. i know how the PKI and HSMs and HSTS and CT and CAA (protonmail's CAA records authorize 3 different CAs to sign for them) etc etc work, and their many failures over the years that have lead to the current set of mitigations, and how HPKP worked/works (which, btw, i just checked, and protonmail is sending a public-key-pins-report-only: header, very nice 🤣) but I don't have the energy to explain to you why selling something as e2ee while it reduces to (among other things) specifically the security of TLS is dishonest.

Yeah, perhaps. But then again, those people are probably not those who have this kind of attack in their risk model.

I just checked their site and they still say it's "for journalists", and "we can never access your messages", etc etc.

Someone hiding from a violent criminal organization might well realize that they have a life-or-death "risk model" and yet not realize that ProtonMail's (lauded by knowledgeable people like yourself) security actually has numerous human single points of failure which their adversary can coerce to read their email.

The people who need security most are often people who lack the expertise to adequately evaluate the veracity of claims like ProtonMail's. They look to knowledgeable people (like you and i) to help them decide what is reasonable. Also, even very knowledgeable people who badly need security will sometimes sacrifice security for convenience (eg, Snowden; he also used other things, but, he used Lavabit too, presumably assuming that this type of attack, while possible, would not actually happen).

If what you want is not privacy from adversaries who can compromise your mailserver, but rather just protection from GMail reading your mail, then you don't need e2ee: you need a provider with a privacy policy you believe they will honor. By saying things like this:

... ProtonMail is demonstrating that they are not trustworthy. When they aren't circumventing their encryption, are they honoring their privacy policy with regard to the things the encryption doesn't protect (metadata like social graph, location, etc)? Why would you assume they are when they're lying about their ability to read your emails?

From your replies here, it's becoming clear to me that you do see this: if i understand you correctly, you are not saying that ProtonMail "cannot read or give anyone else access to your emails" as they are saying; rather you are just saying that you think it is very unlikely that they would ever abuse that capability and that you assume their procedures make it so that one rogue employee couldn't do it alone. You do seem to understand that, contrary to what they've written in the screenshot above, ProtonMail as a company technically could decide to. But, do you think most of their customers understand that?

Proton has 100million users

I'm growing rather tired of this discussion, but I have a few more questions for you.

Given that they have 100 million users, which of these statements do you think is the most likely to be accurate:

1. ProtonMail has never been asked to circumvent their encryption
2. They get asked to frequently, and they always steadfastly refuse to do so
3. They get asked to frequently, and they almost always say no, but, depending on who is asking (and what kind of legal or other threats the request is sent with) they do it sometimes
4. They get asked to frequently, and they do it for anyone who represents law enforcement (or appears to?) in any country from some list of countries

Personally, I think #3 is a bit more likely than #4, while #1 and #2 are extremely unlikely.

So, my last questions are:

• If it were revealed that #4 were in fact the case, would you agree that it is snakeoil?
• If you agree with me that #3 is the most likely scenario, approximately how many times per hour/week/year would they need to be complying with these requests before you would agree that they are, in fact, snakeoil?

In any case, as you said, we "can’t know either way".

I see your point, and I generally agree.

However:

Ability for users to know when the software is being updated

This is relatively useless, unless you (the user) can actually verify the legitimacy of the code, which you can't. You may verify provenance, but that doesn't tell you anything.

Ability for users to verify that they’re running the same software as other people

Nobody checks this really. I cannot think of a single example where I have done this or where I would be able to do this.

Ability for users to download the software without identifying themselves

This is technically feasible, but obviously not in the context of actual usage, so I agree.

---

That said, you are forgetting that:

When you use credible end-to-end encryption software, that is exactly what you are doing: you are getting the encryption software from someone other (literally anyone would be better) than the entity who’s job it is to store your ciphertext.

I think you underestimate the whole supply chain of the software that uses your PGP key. The CLI tool, the libraries. All it takes is one malicious commit in any of that, and you are toast (provided you install that version). The only protection you have is the chance that someone will notice the malicious commit(s). There are examples of similar attacks where nobody noticed.

Think about what an attacker needs to circumvent the encryption between two proton users: they need one protonmail employee. Done.

This might be an overstatement. We don't know what internal security measures they have. Even basic compliance require separation of duty, which means a single person cannot carry out such a process end-to-end (replacing code). They might also have internal monitoring etc., it's not so trivial.

Now think about what an attacker needs to do the same to users of some PGP implementation and a normal email host that doesn’t sell snakeoil:

I agree, but there is a problem: you will never in a million years get the average person to use PGP. The whole tooling is messed up, even for technical people. This is a fact, and while I agree that the security it offers is better, the average person who is not trying to protect themselves from nation states is much better off with Proton than with Gmail, since that's the realistic alternative. Also, even in the legal cases where Proton did disclose the data they had (anti-"terrorism" cases), they did not disclose any email content and what they had was minimal. I think if you are a target of nation state adversaries and you are thinking to communicate via Email, you are probably doomed.

Of course, they might also try to compromise the victim’s endpoint in various other ways

To be fair, this is much, much, much, much easier that compromising Proton or getting to one of the employees. It's also a much more reasonable attack to compromise multiple communication channels compared to only email.

Ultimately I think that you calling these product snake-oil is a misrepresentation of the reality. For the risk model of the average person, Proton (and similar) does deliver what it promises. The fact that sophisticated attackers might be able to compromise the provider and compromise the encryption is not a reason to invalidate the product tout court, in my opinion. Especially because neither me nor you know exactly the security controls they have internally to protect the integrity of that code.

But what security does this offer? If a malicious update is pushed through other channels (say, a release in an APT repo), you can get compromised when you update the software. Where is the substantial difference with getting compromised when “the page loads”?

The difference is that targeted delivery of malicious versions is far less likely to ever be noticed than backdooring binaries for everyone would be.

There are various shortcomings in the numerous software distribution mechanisms in use today, but very few that make it easier to undetectably deliver malicious code to specific targeted users than javascript on a web page does.

You would need a third party that verifies the software

🔔🔔🔔

When you use credible end-to-end encryption software, that is exactly what you are doing: you are getting the encryption software from someone other (literally anyone would be better) than the entity who's job it is to store your ciphertext.

Of course, the quality of software distribution channels varies widely, but, a few properties which are pretty common outside the browser (even for proprietary software) include:

• Ability for users to know when the software is being updated
• Ability for users to verify that they're running the same software as other people
• Ability for users to download the software without identifying themselves

Even if most users aren't taking additional manual steps to verify their software authenticity, a system where it is possible for them to makes it more difficult for attackers to execute a targeted attack without risking detection.

When you use things like Proton, Tuta, or Hushmail (which, again, is the same deceptively-marketed architecture as Proton and Tuta and has been doing this for literally 25 years) you lack all three of those properties and you instead constantly refetch the encryption implementation from the only (in most cases) 3rd party which happens to have your ciphertext. This architecture is designed for them to exfiltrate keys from targeted users.

Their marketing says that they can't read your mail, and this is a lie. Some non-zero number (maybe dozens? who knows) of employees at each of these companies have the ability to read any user's mail by serving them slightly different javascript one day, and therefore so do any 3rd parties who can coerce or compel one of these employees through legal or extralegal means.

Think about what an attacker needs to circumvent the encryption between two proton users: they need one protonmail employee. Done.

Now think about what an attacker needs to do the same to users of some PGP implementation and a normal email host that doesn't sell snakeoil:

• they would need to get the ciphertext somehow (perhaps by compromising an email provider, or an insider there), and
• they need a signing key for the software update mechanism for the victim's PGP implementation, and
• either they need to risk getting caught compromising the software distribution for everyone, or
• they need to be located in the right place on the network to target the victim and intercept their connection while they are updating their software

Of course, they might also try to compromise the victim's endpoint in various other ways, but I'm not trying to address all of the problems of computer security in this example: I'm just contrasting the properties provided by the Proton/Tuta/Hushmail architecture with how other email encryption works.

HTH!

I genuinely don’t see any difference between Proton encryption in the browser and or a Thunderbird plugin, or a CLI tool. If an attacker can push a malicious update, I have no protection.

In the browser you're effectively doing an "update" with every page load (and after you've identified yourself to the server!) and there is no authenticity check besides HTTPS and no possibility to confirm that you received the same thing as everyone else (or that you received something that corresponds to source code in git, if the javascript happens to be open source).

It is easy to confirm that two users are running an identical version of a piece of local software; it is nearly impossible to confirm the same in the web context. Every pageload is another opportunity to deliver malicious code to a targeted user with very little chance of being detected.

As I wrote in another comment:

People should be skeptical of anyone selling a service involving cryptography software which has nearly no conceivable purpose except for to protect against the entity delivering the software. Especially if they re-deliver the software to you every time you use it, via a practically-impossible-to-audit channel, and require you to identify yourself before re-receiving it (as almost any browser-based e2ee software which doesn’t require installing any software does, due to the current web architecture).

If you think this kind of perfect-for-targeted-exploitation architecture isn’t regularly used for targeted exploitation… well, you’re mistaken. In the web context specifically, it has been happening since the 90s.

... and still is today.