A raw production SSL/TLS session log from sapp's monitoring pipeline (timestamps dated 2021-08-23, client IPs in domestic Chinese carrier ranges) shows the per-connection logging schema includes dedicated fields for a captured certificate chain (INDIVIDUAL_CERT_FILE, MIDDLE_CERT_FILE, ROOT_CERT_FILE, CHAIN_CERT_FILE) and for any injected packet (INJECTED_PKT_FILE), alongside SNI and TLS version -- confirming sapp's live SNI-logging and MITM-cert-capture instrumentation was operating against real user traffic to services including huobi.com, steamcommunity.com, and dropbox.com.
{"FOUND_TIME_PARTITION":"452684","CFG_ID":"10863320","FOUND_TIME":"1665383673","RECV_TIME":"1665383673","OVER_ID":"0","PROTOCOL":"IPV4_SSL","SERVER_IP":"104.18.25.210","CLIENT_IP":"140.206.157.21","SERVER_PORT":"443","CLIENT_PORT":"38902","SERVICE_TYPE":"12","ENTRANCE_ID":"10","CLJ_IP":"10.185.129.158","SCENE_FILE":"","INJECTED_PKT_FILE":"","ACTION":"1","VERSION":"TLS1.0","SNI":"www.huobi.com","INDIVIDUAL_CERT_FILE":"","MIDDLE_CERT_FILE":"","ROOT_CERT_FILE":"","CHAIN_CERT_FILE":"","DD":"2021-08-23","HH":"05"}
Defense implications
- Live confirmation that sapp logs SNI per-connection with slots ready to store a captured certificate chain and any injected packet even when unused (empty strings here) -- treat SNI as visible to this pipeline by default and design around ECH/domain-fronting rather than assuming SNI logging is only used for the blocking cases already documented elsewhere.
Related findings
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.
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.).
A 2020 MESA Lab monthly report describes building a sapp plugin that extracts packet-sequence features specifically "for DoH (DNS-over-HTTPS) service discovery," alongside a broader CSTNET DoH measurement-report effort and configuring a DNS-to-DoH gateway -- confirming sapp is used to fingerprint DoH traffic via statistical sequence features rather than plaintext DNS content.
MESA Lab researcher notes on an encrypted-video-identification project describe adding SSL-layer information output to more precisely trace a flow's true source/identity, and considering reinforcement learning so the identification model adapts as network conditions change, working within/around sapp's plugin limitations.
MESA_Platform's "quic" module (built and packaged as stellar-on-sapp/sapp RPMs) implements SNI/User-Agent extraction from both cleartext GQUIC (versions 23-59) and encrypted IETF QUIC RFC9000 ClientHello payloads, and supports a QUIC SNI whitelist -- i.e. the DPI pipeline decrypts/parses encrypted QUIC handshakes to recover the destination domain rather than being blocked by QUIC's encryption.
TSG's application-fingerprinting engine matches 'FlyVPN' via a combination of IP-address and FQDN/port feature objects (each independently versioned/timestamped); a false-positive bug investigation confirms the live traffic-classification component is called 'sapp' and that restarting it is a standard troubleshooting step for signature drift.