geedge.lantern.io
detection confidence: high public

TSG's SSL decoder could not parse TLCP (China's national TLS variant) SNI as of v24.02, classifying such flows as generic BASE traffic and defeating server-name blocking; TLCP parsing was added in v24.08/24.09 per a tracked MESA_Platform/ssl commit.

工程部同事在测试 中信银行 APP的时候发现...TLCP协议的数据流,其中包含SNI,尝试用server name进行阻断发现无效果...SSL Decoder不支持解析TLCP,预计v24.08版本支持。

Defense implications

censorscn
techniquessni-blocking
productstsg
capabilitydpi-signature

extracted_by: claude-sonnet-5 · added 2026-08-26 · id: 2026-tlcp-sni-blindspot

Related findings

detection

TSG automatically generates recurring weekly "SNI Report of Overseas APP" and companion "Server IP and Location of Overseas APP" reports at what is almost certainly a China-national (not export-customer) scale — single weekly runs process from ~5.7 trillion to over 135 billion rows and up to ~775TB/week — breaking down QUIC.SNI/SSL.SNI/HTTP.Host traffic per named blocked-in-China platform (YouTube, Facebook, Google, Twitter, Instagram, Telegram, WhatsApp, Netflix, BBC, Viber, Line, Snapchat, Gmail, HBO, and more), down to individual CDN edge hostnames (e.g. specific scontent-*.fbcdn.net and rr*---sn-*.googlevideo.com nodes ranked by bytes). The report series recurs weekly from at least Feb 2023 through Mar 2024.

deployment

A dedicated internal "运营商前端分析团队" (Carrier Front-end Analysis Team) produces weekly, carrier-specific traffic-analysis reports explicitly titled "新疆移动流量分析报告" (Xinjiang Mobile Traffic Analysis Report) and "新疆联通流量分析报告" (Xinjiang Unicom Traffic Analysis Report), with instances dated from at least July 2022 through March 2024. One instance (Xinjiang Mobile, 2023-05-15) reports total carrier bandwidth of 4.4Tbps (1Tbps access bandwidth), 27.34PB of weekly throughput, 123 distinct identified application-layer protocols, and a section (4.1, pages 17+) explicitly tracking server IP/location for 28 named overseas apps (BBC, Discord, ESPN, Facebook, Gmail, Google, Hulu, Instagram, Netflix, Reddit, Skype, Telegram, Twitter, Uber, WhatsApp, Wikipedia, YouTube, Zoom, etc.).

detection

TSG maintains a traffic-volume-ranked "Top SNI" / "Top Server IP" allowlist (Galaxy component, learned from live traffic, capped at top ~2000 SNIs / ~40000 server IPs per Nacos config) that is checked before a VPN/circumvention-tool deny policy (including a Psiphon3-specific policy) is enforced. Confirmed empirically: Psiphon3 client traffic whose destination SNI was in the Top SNI list passed through undenied, while traffic to the same client IPs with an SNI not yet in the list was blocked. A 2022-06 incident over-blocked TikTok/BBC/CNN/NYTimes because their SNIs were not yet in the learned allowlist at the time.

detection

As of TSG v23.07, FQDN matching supports left-anchored prefix/wildcard matching (e.g. 'voice-group-80x-api.*'), added specifically so a Fujian domestic deployment could detect domains with a fixed subdomain prefix but rotating remainder. Earlier versions only supported exact FQDN match.

detection

Extensive engineering effort to extend TSG's built-in 'APP Sketch DB' fingerprint database with signatures for major domestic Chinese apps (Douyin, Kuaishou, Mango TV, JD, Tencent Cloud, etc.), primarily via SSL SNI matching, with iterative per-feature test/fail/patch cycles against specific in-app actions (e.g. certain Douyin menu items stayed unblocked after the main signature succeeded).

detection

For a domestic Fujian deployment, Geedge validated SNI-wildcard blocking (*.sohucs.com, *.sns.sohu.com) as technically effective against a specific Chinese social app ('Huyou'), but rejected it for production because the domain is shared with a third-party SDK platform and would cause false-positive blocking of unrelated services -- falling back to destination server-IP blocking, deployed inline via TCP RST injection.