Encrypted ClientHello / ESNI blocking

An internal TSG functional-requirements spec ('加密协议JG') defines device support for identifying and blocking ECH, ESNI and QUIC traffic via per-connection SNI/region-matching tables (e.g. DF_QUIC_REGION), plus a companion 'FD报文全流程感知' feature that both passively monitors and actively injects synthetic verification traffic end-to-end through the network path to compute a live per-rule 'CT率' (breakthrough/penetration rate) — the system self-measures how often its own QUIC/ESNI/ECH blocks fail to take effect, and separately throttles logging/blocking detail for rule IDs receiving unusually high hit counts (DF_ATTACK_PROTECTION, 'targeted attack detection').

In the same live TSG capture, rows show ssl_ech_flag=1 recorded for real observed TLS sessions (to connect-api.guardianapp.com) alongside a populated ssl_ja3_hash and an intact ssl_sni value, and the session was still denied by name-based rule Deny_Brave. This confirms the DPI engine parses and logs the TLS ClientHello ECH extension as a distinct per-session flag in production/test traffic, i.e. ECH usage is visible to the gateway even though SNI in this particular capture was not itself encrypted from the classifier's point of view.

The same 224-column TSG per-session log schema carries a full TLS- interception field set — proxy_pinning_status, proxy_intercept_status, proxy_passthrough_reason, proxy_cert_verify, proxy_intercept_error, sc_rsp_raw and sc_rsp_decrypted (raw vs. decrypted server response content) — plus ssl_esni_flag and ssl_ech_flag (explicit ECH/ESNI-usage flags), ssl_ja3_hash/ssl_ja3s_hash, and ssh_hassh (SSH client fingerprinting), confirming certstore-style MITM interception, ECH/ESNI detection, and TLS/SSH fingerprinting are all first-class fields logged on every session, not experimental add-ons.

A raw TSG session-log export shows the full production log schema: per-flow fields include subscriber_id, imei, imsi, phone_number and apn alongside ssl_ja3_hash/ja3s_hash, ssl_esni_flag, ssl_ech_flag, quic_sni, dtls_ja3_fingerprint, and proxy_pinning_status/proxy_intercept_status/ proxy_cert_verify fields for the MITM proxy path. This confirms TSG's session logging natively joins network-flow identity to subscriber identity and captures TLS fingerprint/ESNI-ECH state and MITM-interception outcome in the same record.

A MESA Lab Go tool (modikai/edns_svcb_https) measures EDNS, SVCB, and HTTPS DNS record support across a top-1M domain list and a set of DNS servers — record types that carry Encrypted ClientHello (ECH) configuration, suggesting reconnaissance ahead of possible ECH-aware blocking.

A production feature spec ("加密协议JG") requires detection-and-control capability for QUIC, ESNI, and ECH, with a per-connection log field c_encrypt_type explicitly distinguishing ClientHello encryption (0=unencrypted, 1=ESNI, 2=ECH) and a DF_QUIC_REGION rule table matching QUIC by SNI. The system computes a per-rule "CT" (穿透/penetration) rate from paired mirror-vs-functional RST-packet logs (TF-RST-LOG / TF-MIRROR-RST-LOG) to grade each block rule's effectiveness, and runs continuous active-verification probes against its own rules, deliberately varying the probe 4-tuple each run "to ensure it doesn't hit the blacklist" so the verification traffic itself reaches the target.

A MESA Lab thesis/report states that ESNI/ECH protocol-identification technology, based on TLS extension field type numbers, "has already been applied in actual projects," and lists the researcher's own project participation as "G1系统 - ESNI、ECH加密协议识别" (Feb-Aug 2023) and "G1系统 - QUIC协议旁路ZD" (Feb-Nov 2023, QUIC bypass/blocking), plus a separately implemented "DNS主动探测模块" (DNS active-probing module, marked 已实现/already implemented). "G1" also appears independently as a named legacy system in the Maat/Transformer DPI header (PROTO_VPN comment: "G1历史遗留"), corroborating it as a real internal system name, not a typo.

The same SSL plugin added explicit detection of the Encrypted Client Hello extension (type 0xFE0D) with test cases in June 2023, and separately implements JA3/JA3S (2020) and JA4/JA4S (2024) TLS client/server fingerprint calculation as first-class features -- so TSG-class DPI can flag 'ECH is in use' even without decrypting it, and independently fingerprints TLS stacks via JA3/JA4.

A leaked SQL migration renames/normalizes a session-attribute-dictionary entry to `ssl.analysis.sni_absent` (backed by virtual_table `ATTR_SSL_NO_SNI`), confirming the detection pipeline maintains an explicit, first-class boolean signal for "TLS ClientHello with no SNI present" — a classic tell for ECH, domain fronting, and custom TLS stacks that omit SNI to evade SNI-based blocking.

MESA Lab's "stellar" SSL/TLS decoder (ssl_decoder, packaged in test fixtures as "stellar-on-sapp") ships a dedicated regression test case captured against an Ethiopia (E21) target host, alongside TLS 1.3 ESNI, encrypted ClientHello (ECH), and TachyonVPN-client test pcaps, showing the decoder is validated both against E21-deployment-style traffic and emerging TLS privacy extensions.

A DPI session-plugin ("stellar" framework) SSL/TLS decoder fully parses live ClientHello/ServerHello handshakes, computing JA3/JA3S fingerprints (MD5 over version+cipher-suites+extensions with GREASE values stripped per the standard JA3 spec), extracting plaintext SNI, explicitly flagging whether a ClientHello carries ESNI (extension type 0xFFCE) or ECH (extension type 0xFE0D), and decoding full X.509 certificate chains (issuer/subject RDN sequences, SAN, validity window, serial, pubkey, signature algorithm) in real time. It also recognizes TLCP 1.0 (China's national "国密"/GmSSL TLS variant) as a distinct protocol version alongside SSLv2 through TLS1.3.

chongming/traffic_replay is a Flask/tcpreplay-based QA harness that replays curated pcaps against a TSG instance to exercise its decoders, including SSL fixtures specifically named ssl_ech_false.pcap, ssl_no_sni.pcap and ssl_tls13.pcap alongside esni.pcap, openvpn.pcap, and major-platform captures (facebook/google/twitter/ youtube). A companion update_tsg_ca.py/tsg_ca.txt installs a TSG-issued CA cert on the test client, confirming the QA environment exercises TLS interception as part of routine detection testing.

Two independently-leaked TSG session-log CSV exports share an identical 224-field schema whose proxy_* columns (proxy_action, proxy_pinning_status, proxy_intercept_status, proxy_cert_verify, proxy_intercept_error) log the outcome of TLS interception per session, alongside ssl_ja3_hash/ssl_ja3s_hash, ssl_esni_flag, ssl_ech_flag, and quic_sni fields — confirming MITM/cert-pinning-bypass instrumentation and TLS/QUIC fingerprinting are built into TSG's standard traffic-logging pipeline, not a bolt-on feature.

A leaked TSG session-log CSV schema (device XXG-TSG-BJ) includes built-in per-session fields for TLS interception status (proxy_intercept_status, proxy_cert_verify, proxy_pinning_status, proxy_passthrough_reason) alongside JA3/JA3S TLS fingerprints and explicit ssl_esni_flag/ssl_ech_flag columns, confirming TSG logs whether a session was MITM'd and whether it used ECH/ESNI.

The full TSG session-log CSV schema header discloses the complete set of per-session fields the platform records, including TLS JA3/JA3S fingerprint hashes, explicit ssl_esni_flag/ssl_ech_flag columns, QUIC/DTLS SNI and JA3 fields, and direct subscriber-identity fields (subscriber_id, imei, imsi, apn, phone_number) captured on every logged session alongside ordinary network 5-tuple data.

TSG's core traffic-processing daemon (tango/tsg_master) added explicit support for treating Encrypted ClientHello (ECH) as a security-policy match condition (TSG-15163/TSG-15711) and tags app_full_path output with ESNI and ECH markers (TSG-15779), meaning field TSG deployments can write and enforce policy rules that specifically key on ECH/ESNI usage rather than only on plaintext SNI.

The same TSG QA suite includes purpose-built "hijack" test fixtures for at least seven content types (APK, EXE, GIF, HTML, JPEG, PNG, SVG) alongside JS/CSS insertion scripts and Lua replace/insert manipulation scripts, and its UI/API test cases reference a "Manipulation" policy object with replace/hijack/deny(drop) actions triggered by "Keywords" objects inside "http_signature" matching and an explicit "no_sni" traffic-matching condition; separate pcap test fixtures (esni.pcap, ssl_ech_false.pcap, ssl_no_sni.pcap, ssl_tls13.pcap) show this is specifically regression-tested against ESNI/ECH and SNI-less TLS 1.3 traffic.

TSG's security-policy verification engine (tango/verify-policy) supports 'ssl.no_sni', 'ssl.ech' (Encrypted ClientHello), and 'ssl.esni' (Encrypted SNI) as first-class Boolean match conditions in its policy language (TSG-18943), meaning TSG can write and evaluate blocking/monitoring policies that specifically trigger on TLS connections carrying no SNI, ECH, or ESNI.