China now blocking ESNI-enabled TLS 1.3 connections, say Great-Firewall-watchers

And needs a very blunt instrument to do the job, because the protocol works as planned

China is now blocking encrypted HTTPS traffic that uses TLS 1.3 with ESNI enabled, according to observers at the Great Firewall Report (GFR).

TLS is the foundation of secure online communication and hides content users wish to access or have generated so it can pass over the internet without being observed by unrelated parties.

While TLS hides the content of a user's communication, it cannot always hide the server they are communicating with because its handshake optionally contains a Server Name Indication (SNI) field designed to explain where traffic is going. China and other nations have used this info to block their users from accessing particular websites.

To address that privacy gap, TLS introduced Encrypted SNI (ESNI). ENSI encrypts the SNI so that intermediaries cannot view it and thus, in theory at least, prevent overzealous censors from sniffing and blocking traffic headed to and from places they don't like.

But according to the GFR, China has found one way around this: outright block all TLS 1.3 connections with ESNI enabled.

Alibaba Cloud

Alibaba takes VMware where AWS and Microsoft don't – behind the Great Firewall


The banhammer is implemented by simply dropping offending packets, which is blunter than China's previous content-control strategies. These relied on sending forged TCP reset commands to both server and client to close a connection.

The GFR team also found that any time an ESNI connection was black-holed, any connection with the same tuple triple of source IP, destination, and destination port would continue to be blocked for up to 180 seconds. The block also happens on all ports, not just port 443 as is usually the case.

The GFR found that it could circumvent the new blocks using Geneva, a genetic algorithm developed by the University of Maryland in America that manipulates packet streams without impacting the original connection. Using Geneva, the GFR team discovering six strategies that work from the client side and four that work from the server side with 100 per cent reliability. ®

Other stories you might like

  • Cheers ransomware hits VMware ESXi systems
    Now we can say extortionware has jumped the shark

    Another ransomware strain is targeting VMware ESXi servers, which have been the focus of extortionists and other miscreants in recent months.

    ESXi, a bare-metal hypervisor used by a broad range of organizations throughout the world, has become the target of such ransomware families as LockBit, Hive, and RansomEXX. The ubiquitous use of the technology, and the size of some companies that use it has made it an efficient way for crooks to infect large numbers of virtualized systems and connected devices and equipment, according to researchers with Trend Micro.

    "ESXi is widely used in enterprise settings for server virtualization," Trend Micro noted in a write-up this week. "It is therefore a popular target for ransomware attacks … Compromising ESXi servers has been a scheme used by some notorious cybercriminal groups because it is a means to swiftly spread the ransomware to many devices."

    Continue reading
  • Twitter founder Dorsey beats hasty retweet from the board
    We'll see you around the Block

    Twitter has officially entered the post-Dorsey age: its founder and two-time CEO's board term expired Wednesday, marking the first time the social media company hasn't had him around in some capacity.

    Jack Dorsey announced his resignation as Twitter chief exec in November 2021, and passed the baton to Parag Agrawal while remaining on the board. Now that board term has ended, and Dorsey has stepped down as expected. Agrawal has taken Dorsey's board seat; Salesforce co-CEO Bret Taylor has assumed the role of Twitter's board chair. 

    In his resignation announcement, Dorsey – who co-founded and is CEO of Block (formerly Square) – said having founders leading the companies they created can be severely limiting for an organization and can serve as a single point of failure. "I believe it's critical a company can stand on its own, free of its founder's influence or direction," Dorsey said. He didn't respond to a request for further comment today. 

    Continue reading
  • Snowflake stock drops as some top customers cut usage
    You might say its valuation is melting away

    IPO darling Snowflake's share price took a beating in an already bearish market for tech stocks after filing weaker than expected financial guidance amid a slowdown in orders from some of its largest customers.

    For its first quarter of fiscal 2023, ended April 30, Snowflake's revenue grew 85 percent year-on-year to $422.4 million. The company made an operating loss of $188.8 million, albeit down from $205.6 million a year ago.

    Although surpassing revenue expectations, the cloud-based data warehousing business saw its valuation tumble 16 percent in extended trading on Wednesday. Its stock price dived from $133 apiece to $117 in after-hours trading, and today is cruising back at $127. That stumble arrived amid a general tech stock sell-off some observers said was overdue.

    Continue reading

Biting the hand that feeds IT © 1998–2022