[CoinThrow]

Summary

A native, build-gated reconstruction of Ascension's own logon protocol — the client side of the
handshake the genuine DLL installs by hot-patching three exe thunks. It lets the client speak that
protocol against a server that implements it (the feature/ascension-native-login branch of an
AzerothCore CoA fork), with no runtime byte-patching — everything ships inside the DLL, behind a
build option that defaults to OFF.

What's in the branch

• src/Ascension/AscNativeLogon.cpp / .hpp — the protocol module (crypto self-test, three thunk
  replacements, four length gates).
• tools/ascension-auth-keygen.ps1 — X25519 key-pair generator (RFC 7748 self-test included).
• CMakeLists.txt + PatchConfig.hpp.in — -DASCENSION_NATIVE_LOGON=ON (default OFF) and
  -DASCENSION_NATIVE_LOGON_SERVER_KEY=<64 hex> (the server's public key / KC1 slot value).
• src/Ascension/AscMain.cpp — DllMain install call, option-gated.
• README + DLL_REFERENCE — build section, live-validation record, and the server requirement found
  during validation.

What it installs (only with the option ON)

site	stock behaviour	reconstruction
0x8CCE00	hello serializer	appends the custom hello record verified live: [size][FC F4 F4 E6][tag16][masked payload][trailer]; payload carries login, X25519 public key, nonce, password tag, ChaCha20-encrypted password
0x9A83E0	SRP6 K from challenge	copies the 40-byte key_session into the auth object (lands at auth-context+0xC8)
0x9A88C0	SRP6 M2 compare	verifies the 32-byte HMAC-SHA256(key_derived, "OK")
0x8CC7FA, 0x8CC856, 0xDFC024, 0xDFC034	0x14-byte proof field	length gates to 0x20 so the reply handler reads the 32-byte proof

Crypto (byte-exact copies of the live-verified values): X25519(secret, server public) → HMAC-SHA256
KDF → key_derived (32B) / key_session (40B); ChaCha20 record + password encryption; HMAC proof.
The module runs a crypto self-test first and refuses to install on failure.

Verification (2026-10-10, live end-to-end)

Against a server with the custom auth toggle on and the matching key pair:

• client: native-logon: proof check PASSED (HMAC-SHA256(key_derived, "OK"))
• server: Ascension custom auth: proof replied, session authorised
• client: COP_AUTHENTICATE ... AUTH_OK → COP_GET_CHARACTERS ... result=TRUE → character list rendered
• world handoff completed after the server-side fix below; no client-side patches involved

Server requirement found during validation

After the custom proof, the authserver must persist the handshake's 40-byte key_session as
account.session_key — the worldserver's CMSG_AUTH_SESSION digest and header cipher depend on it,
and without it the client drops right after auth. That fix lives on the server branch
(AuthSession.cpp, Ascension client branch), not in this PR.

Build / try it

cmake -G Ninja -DCMAKE_BUILD_TYPE=RelWithDebInfo -DASCENSION_NATIVE_LOGON=ON ^
      -DASCENSION_NATIVE_LOGON_SERVER_KEY=<64 hex chars> -S . -B build\nl
cmake --build build\nl

Run the client with -extlog 1 and watch Logs\Extensions.log for the native-logon: lines.

Deliberate limits (test/translation build, not a match for the obfuscated original)

• No device fingerprinting. The original's hello derivation mixes unique machine identifiers into
  the handshake — the NVMe disk serial (Win32_DiskDrive.SerialNumber) and a CPUID.1 snapshot — via
  its token pipeline. This reconstruction deliberately does not reproduce them: the module
  collects no device data (no disk, CPUID or SMBIOS queries anywhere in it), and every
  per-connection field — the 16-byte record tag, the 12-byte nonce, the 16-byte password tag —
  carries fresh rand_s randomness, matching the original's measured per-connection RNG behaviour
  for the tag and password tag. The server treats these fields as opaque, as the live validation
  shows.
• Record-constant fields (platform, locale, timezone bias, IP) are the verified reference values; the
  server does not read them.
• The stock SRP6 fallbacks on the patched sites are not kept when the option is ON — it is installed
  only for servers that speak the custom handshake.
• Option OFF (the default): nothing is compiled in; behaviour is exactly as before (SRP6 restore,
  hooks not installed).

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Stacking note: this branch currently sits on the callback-order line (#12). Once #12 lands, the diff
here narrows to the single logon commit; I can rebase on request.