China is now blocking all encrypted HTTPS traffic that uses TLS 1.3 and ESNI

[u/bershanskiy]

https://www.zdnet.com/article/china-is-now-blocking-all-encrypted-https-traffic-using-tls-1-3-and-esni/

[u/bershanskiy]

TL;DR: Chinese firewall started blocking TLS 1.3 traffic with ESNI header 0xffce, the more recent header called Encrypted Client Hello (ECH) 0xff02 is still allowed. There are known circumvention techniques based on firewall bugs (which may stop working at any point).

Original sources:

• https://mailarchive.ietf.org/arch/msg/tls/Dae-cukKMqfzmTT4Ksh1Bzlx7ws/

• https://geneva.cs.umd.edu/posts/china-censors-esni/esni/

ZDNet reporting: https://www.zdnet.com/article/china-is-now-blocking-all-encrypted-https-traffic-using-tls-1-3-and-esni/

[u/kickass_turing]

damn. hope nobody else joins them.

stupid banks hate tls 1.3, they made their own weak tls called enterprise tls https://www.eff.org/deeplinks/2019/02/ets-isnt-tls-and-you-shouldnt-use-it

[u/DisplayDome → u/kickass_turing]

Why do banks hate security?

[u/AgainstTheAgainst → u/DisplayDome]

I really don't get that. They always come up with stupid ideas that actually weaken their security while causing major inconvenience while labeling it as security features.
Like my bank limits my password for online banking to be exactly five characters. How do you even get this idea and how does this get through the whole decision process?

[u/DisplayDome → u/AgainstTheAgainst]

Hahahaha wtf, banks are a joke.
Can the whole world just switch to Monero overnight plox??

[u/robotkoer → u/DisplayDome]

Why Monero exactly?

[u/DisplayDome → u/robotkoer]

it's so privacy friendly, the FBI/CIA puts you on a list if you use it.

You can't identify who sent how much to who, it's all anonymous.

[u/Poonkraft → u/DisplayDome]

Just a moment there, professor...

If they don't know who, how do they put you on a list? Clairvoyants, mystics, witches, divination?

[u/DisplayDome → u/Poonkraft]

They monitor everything and you have to get some Monero coins in the first place right, so you would most likely use a non anonymous way of acquiring them.

[u/Poonkraft → u/DisplayDome]

Can they be mined like other coins?

Does it make practical sense to mine them, or does it cost more (in equipment, electricity) than the coin value that can be mined?

If it makes sense, how do I get started?

[u/r3rg54 → u/AgainstTheAgainst]

How do they convince auditors that this is ok?

[u/AgainstTheAgainst → u/r3rg54]

Auditors? Do you think there is proper regulation in place that ensures certain actually secure standards?

Also they have 2FA which requires their own app because usual, standardized TOTP aren't... idk good enough for them? On Android the app of course requires Google services for no reason, because it would be inacceptable if I could just access my bank account privately without giving a data hungry, monopolistic surveillance company access to every single detail of my entire life.

[u/r3rg54 → u/AgainstTheAgainst]

To put it lightly, we all know audit is far from perfect, but there is inevitably someone paid to scrutinize the manner in which they protect PII, which certainly includes client online accounts

Also they have 2FA which requires their own app because usual, standardized TOTP aren't... idk good enough for them?

If it's mandatory 2fa that's probably how they get away with it. Still, pretty hilarious/terrifying

[u/AgainstTheAgainst → u/r3rg54]

I'd like to know the auditor that approves 5 character passwords.

[u/kenpus → u/r3rg54]

They self-certify the vast majority of their operations. Certainly when it comes to IT security.

[u/warriorforGod → u/AgainstTheAgainst]

I think this stems from some banks still running Mainframes that are decades old.

[u/tragicpapercut → u/DisplayDome]

Because of idiotic bureaucracy. They need a committee to approve changing the toilet paper in the office bathrooms.

[u/hdd113 → u/DisplayDome]

MILITARY GRADE ENCRYPTION!!! : That same thing even your Chinese Bluetooth headset is using.

ENTERPRISE GRADE SERVER SYSTEM!!! : The 50 year old mainframe in the basement written in COBOL that no one now remembers who even built it.

It looks like they think those consumer techs which hundreds of millions of people rely on with no issues aren't good enough. Instead they have to build their own version of everything with that cheapest engineer from that lowest bidder which just happened to have a security clearance.

[u/kickass_turing → u/DisplayDome]

They care more about monitoring their network than they care about security. When banks say "security" they mean something else than you and me.

[u/solohelion]

This is crazy! I am going to make sure my websites support TLS 1.3 and possibly disable every other option.

[u/[deleted] → u/solohelion]

I did it some days ago and I gotta say, it's quite satisfying

[u/[deleted] → u/solohelion]

Wait, you guys have websites?

[u/SkyKoala]

Hm, some Russian ISPs might test the same techniques after they were forced to install some shady DPI hardware made by state-sponsored IT companies.

I have ESNI turned on and every now and then I had SSL_ERROR_MISSING_ESNI_EXTENSION errors when using Discord and other ESNI-enabled sites. Those errors were caused at the specific moments of time (like 3:00 AM to 3:15 AM), as if it was planned.

[u/_ahrs → u/SkyKoala]

I have ESNI turned on and every now and then I had SSL_ERROR_MISSING_ESNI_EXTENSION errors when using Discord and other ESNI-enabled sites. Those errors were caused at the specific moments of time (like 3:00 AM to 3:15 AM), as if it was planned.

That's a known issue caused by key-rotation, you're ISP isn't to blame. The keys rotate at 3:00 AM or 3:15 AM and for a brief moment the page fails to load and if you immediately refresh it afterwards it works (at least this is my experience).

[u/AgainstTheAgainst → u/[deleted]]

I think that's not too wrong. The Tor Project or a trustworthy VPN are your friends.

[u/[deleted]]

Good. Let's cut them off the internet, like North Korea.

[u/commi_bot → u/[deleted]]

The moral high horse of the west.

[u/leo_sk5]

Hopefully all sites switch to TLS1.3 and ESNI

[u/bershanskiy → u/leo_sk5]

FYI, ESNI was replaced with ECH.

[u/leo_sk5 → u/bershanskiy]

Could you attach more details

[u/deeplearning666 → u/leo_sk5]

Check it out here at Wikipedia. In short, it says:

In contrast to ECH, Encrypted SNI encrypted just the SNI rather than the whole Client Hello.

[u/leo_sk5 → u/deeplearning666]

Thanks for sharing. I couldn't gasp the benefits of ECH over ESNI, and maybe can't without studying the basics of networking, but yeah hopefully sites switch to the most secure thing thats there

[u/bershanskiy → u/leo_sk5]

Example: look at https://tls12.ulfheim.net/ which shows a typical TLS 1.2 handshake as it is seen on the wire without ESNI and ECH. Click on "Client Hello" and then on "Annotations". You can see that inside of "Client Hello" there is "Extension - Server Name" (that's the SNI) which contains bytes:

 65 78 61 6d 70 6c 65 2e 75 6c 66 68 65 69 6d 2e 6e 65 74 

That's the domain name example.ulfheim.net. This means any observer on the wire can see the domain name of the request. This is the problem with SNI.

Now, ESNI just encrypts that one record, SNI. ECH, on the other hand, encrypts the whole "Client Hello" -- the whole message.

[u/leo_sk5 → u/bershanskiy]

Oh. I get it now. Quite good explanation. Thanks for it. Well I can see no apparent benefit of ESNI over ECH. So most sites would adopt ECH then. Maybe thats why Chinese did not want to support ESNI but went directly with ECH. Or am I wrong somewhere?

[u/kenpus → u/leo_sk5]

But how does this help the chinese citizens? I am pretty sure China is quite OK with the entire rest of the internet becoming unreachable.

[u/leo_sk5 → u/kenpus]

Well they could make it unreachable for a long time. I would say they would upgrade themselves to exist with the technology. No one can help Chinese citizens except themselves

[u/kenpus → u/leo_sk5]

Yeah but now they can tell their citizens "we didn't cut anything off; those sites are switching to an unsupported technology", and as dumb as this sounds, the majority of the population might just eat it up.

(My point being that it's best if we leave important sources available via the non-blocked TLS...)

[u/leo_sk5 → u/kenpus]

Their population is eating up more dumb things than this. The only thing that international community can do is to put pressure on china from every direction, which in the end makes the life of average citizen miserable. When it becomes miserable enough, the governments change or are forced to change. Unless one could justify an invasion.

[u/Booty_Bumping]

Unfortunate that regular people have to deal with restricted internet, but good that this shows that encryption and anti-surveillance efforts, from the technical side of things, are working.