DEFENSES
protocol-versioning Versioned protocol upgrade
Backward-compatible protocol versioning so changes can roll out without orphaning users.
2 papers on file
- 2017-frolov-water-pluggable WATER: a programmable framework for pluggable transports
- 2020-bock-detecting Detecting and Evading Censorship-in-Depth: A Case Study of Iran's Protocol Filter
7 findings tagged here
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Reproducing Zohaib et al.'s 10-payload QUIC parser test suite against Russian TSPU devices reveals that the Russian QUIC parser differs meaningfully from the GFW: payload 8 (PING and PADDING frames inserted before the Crypto frame), which circumvents the GFW, does not bypass Russian censorship. Payload 10 (QUICv2) bypasses both censors. Payload 9 (ECH with outer SNI cloudflare-ech.com) is blocked by Russia; payload 3 (version bytes 0x00000002 with invalid MAC) is blocked by both.
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The Henan Firewall is stateless in two exploitable ways: (1) it requires the TCP header to be exactly 20 bytes—enabling any TCP option (e.g., TCP Timestamps, which Windows disables by default) to bypass it entirely; (2) it does not perform TCP reassembly, so splitting a TLS ClientHello across two TCP segments such that the SNI extension straddles the boundary bypasses the censor. Both bypasses require only client-side changes and have already been implemented in Xray, GoodbyeDPI, and Shadowrocket. TLS record fragmentation (splitting the ClientHello across multiple TLS records within one TCP segment) also defeats both the Henan Firewall and the GFW, since neither performs TLS reassembly.
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The GFW's QUIC censor does not reassemble QUIC client Initial packets that are split across multiple UDP datagrams, nor does it reassemble QUIC CRYPTO frames split within a single datagram. Three practical bypasses follow: (1) send any UDP datagram with a random payload before the QUIC Initial—the GFW uses 60-second UDP flow state and won't inspect a mid-flow packet; (2) fragment the TLS ClientHello SNI across multiple QUIC CRYPTO frames; (3) use an unknown QUIC version number in the first packet (Version Negotiation bypass, payload undecryptable). Chrome independently exploits (2) through its Chaos Protection feature (since 2021) and post-quantum Kyber key-agreement (since v124, Sep 2024), whose larger key sizes force fragmentation across UDP datagrams. As of January 2025, the GFW also does not block ECH-containing QUIC payloads unless the outer (cleartext) SNI is on the blocklist.
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WATER (WebAssembly Transport Executables at Runtime) defines a pluggable-transport architecture in which the transport logic is compiled to a WASM module that is loaded and executed at runtime by a thin Go host process. This separates the stable host ABI (dial, accept, read, write) from the rapidly-evolving transport logic, allowing new or updated transports to be delivered as small WASM binaries without recompiling or redeploying the host application.
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WATER (WebAssembly Transport Executables Runtime) separates transport logic from the host application by compiling it to a WASM module (WATM) that is distributed and loaded independently at runtime. Deploying a new or updated circumvention technique requires only distributing the new WATM binary and optional configuration — no change to the host application and no app-store update cycle is required.
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Traditional circumvention tool development and deployment is slow because new strategies must be developed, integrated into each tool separately, and then distributed via platform app-stores. WATER's WASM module architecture specifically addresses this asymmetry: censors evolve blocking techniques quickly, while circumventors are bottlenecked by binary release cycles. The paper argues that dynamic WATM delivery breaks this bottleneck by decoupling transport updates from application releases.
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Proteus supports simultaneous execution of multiple Protocol Specification Files (PSFs) on a single server, selecting the correct protocol version by running all candidates in parallel on a shared read buffer and eliminating candidates as they fail to parse client messages. This enables servers to support legacy clients while deploying new evasion protocols, and to serve clients in different censorship regimes with localized protocol variants, without requiring synchronous client/server upgrades.