docs(grpc-events): Path A disproven — v8 OpenConnection coupled to ExchangeKey
Records the full v8 openParameters byte map, the ECDH ExchangeKey finding, and
the Path A live result: the v8 OpenConnection on a ValidateClientCredential
session is rejected with native 132/34 "EstablishConnection Failed to get client
key". The v8 path requires the client key established by HistoryService.ExchangeKey
(ECDH), so the next route is Path B — implement ExchangeKey ("ECK1" + 64-byte
P-256 point) via .NET ECDiffieHellman, then reissue the v8 open.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B6mcaT2PjRFKcogzp9UkfC
This commit is contained in:
Joseph Doherty
@@ -139,3 +139,93 @@ as the captured-correct request format** for when the open is rebuilt.
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Capture artifacts (gitignored): `artifacts/reverse-engineering/grpc-event-capture/` —
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Capture artifacts (gitignored): `artifacts/reverse-engineering/grpc-event-capture/` —
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`event-capture.ndjson` (Event), `process-connect-2.ndjson` (Process).
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`event-capture.ndjson` (Event), `process-connect-2.ndjson` (Process).
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## v8 `openParameters` fully decoded (2026-06-23) + the ECDH ExchangeKey finding
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Full byte map of the native Event-connection `openParameters` (302 bytes; identity values
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redacted — they are session-specific and sit in the gitignored capture):
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```
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[0] byte 0x08 format version = 8
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[1] byte 0xf0 constant marker
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[2..20] 19 × 0x00
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[21] byte 0x01 constant marker
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[22..37] 16B GUID per-session client key
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[38..41] u32 username length (chars)
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[42..N] UTF-16 username (HistorianString)
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[..+1] u16 credential-token length (= 26 in the capture)
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[..] 26B token ECDH-derived credential token <-- see below
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[94] byte 0x04 ClientType (= our NativeClientType 4)
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[95] byte ConnectionType 01 = Event / 02 = Process <-- THE GATE
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[96] byte flag 01 (Event) / 00 (Process)
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[97..] control bytes (0x03 ... small region, not fully named)
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[~114..117]u32 FormatVersion=3
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[..] HistorianString machine/server node name
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[..] HistorianString client node name "(<ver>)"
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[..] u32 session-variable (process-ish)
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[..] u32 / zeros
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[..] u32 datasource len
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[..] UTF-16 datasource id e.g. "2023.1219.4004.5"
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[270..285] 16 × 0xff ShardId (all-FF = unset; our v6 sends Empty)
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[286..289] u32 client/hcal version int
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[290..297] i64 FILETIME ClientTimestamp
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[298..301] u32 0
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```
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The tail (`FormatVersion` → machine → clientNode → datasource → ShardId → version → timestamp)
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is the **same `ClientCommonInfo` our v6 already emits**. The new/different parts are: version byte,
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the `[1]`/`[21]` markers, the GUID position, the **26-byte credential token** (vs v6's fixed-size
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block), the **`ConnectionType` byte**, and ShardId=FF.
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**The auth is ECDH, not Negotiate.** The capture's `ExchangeKey` buffers begin `45 43 4b 31` =
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ASCII **`"ECK1"`** + a 64-byte EC public-key point — a Diffie-Hellman key exchange — and the 26-byte
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`openParameters` token is derived from it. `HistorianSecurityMode` offers only `Disabled` / `None` /
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`TransportCertificate`; the harness used `TransportCertificate`, which is what drives the ECDH
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`ExchangeKey`. There is **no TLS+Negotiate mode** on the native client (it couples TLS with the cert
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ECDH path), so a Negotiate-auth v8 capture cannot be produced from the native client.
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**Key de-risking insight:** our SDK's v6 `OpenConnection` sends a **fully zeroed** 1026-byte
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credential block (`credentialBlock: new byte[1026]`) and reads still work — because authentication is
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actually carried by the separate `StorageService.ValidateClientCredential` (Negotiate) handshake, not
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by the bytes inside `openParameters`. By analogy the v8 `[68..93]` token may likewise be **ignorable**
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once `ValidateClientCredential` has run. So the first build hypothesis (cheapest, read-only to test):
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> Reuse the SDK's existing `ValidateClientCredential` handshake, then send a **v8 `OpenConnection`
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> with `ConnectionType=Event` and a zeroed credential token**, and see whether the 2023 R2 server
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> returns event rows.
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If that works, the ECDH ExchangeKey RE is unnecessary. If it fails, the fallback is full reproduction
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of the ECDH `ExchangeKey` handshake (curve/KDF/cipher) — a much larger crypto-RE effort. Build path:
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add `SerializeNativeOpenConnectionVersion8(connectionType)` to `HistorianOpen2Protocol`, wire the gRPC
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event handshake to use it (events only; reads stay on v6), live-test (non-destructive). Full hex in
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the gitignored capture.
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### Path A built + live-tested 2026-06-23 — DISPROVEN (v8 is coupled to ExchangeKey)
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Built `HistorianOpen2Protocol.SerializeNativeOpenConnectionVersion8` (golden-tested,
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`Version8EventSerializerReproducesCapturedNativeStructure` — reproduces the captured 302-byte
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structure exactly) + `HistorianNativeHandshake.BuildEventOpenConnectionVersion8Request` (zeroed
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credential token) + an `eventConnection` switch on `HistorianGrpcHandshake.OpenSession`, and live-ran
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the event read against the server. Result: the v8 `OpenConnection` was **parsed by the server** (got
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past the byte format) but **rejected at the auth check** with native error
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```
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type=132 code=34 "aahHcapLib::HistoryService::EstablishConnection — Failed to get client key"
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```
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i.e. `EstablishConnection` could not find a server-side **client key** for our session. In the v6
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path that key is established by `StorageService.ValidateClientCredential` (which is why v6 reads
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work); the v8 path looks it up in the registry that **`HistoryService.ExchangeKey` (ECDH)** populates,
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and there is **no `ValidateClientCredential` on `HistoryService`** in the gRPC contract. So the server
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branches on the OpenConnection version: v6 accepts the Negotiate-established key, **v8 requires the
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ExchangeKey-established key**. The zeroed-token hypothesis is therefore disproven — not because of the
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token bytes, but because the whole v8 path is gated on `ExchangeKey` having run first.
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**Status:** the v8 serializer/builder are correct and retained (golden-tested), plus the
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`OpenConnection` failure now decodes the native error (type/code/ASCII). The event orchestrator is
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reverted to the v6 session (gated test still pins the no-row throw). The remaining route is **Path B:
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implement `HistoryService.ExchangeKey`** — `"ECK1"` + a 64-byte EC public-key point (P-256 X‖Y, by the
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size) — using .NET `ECDiffieHellman`, establish the client key, then reissue the v8 `OpenConnection`.
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Open question for Path B: whether merely *completing* the ECDH key agreement registers the client key
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(so the zeroed openParameters token still rides through), or whether the token must also be derived
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from the shared secret (full KDF/cipher RE).
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