cultmesh-py: port CultMesh authority route verification

ECDSA P-256 route certificate and session proof verification ported from
CultMeshAuthorityProof.cs, with typed refusals, judged against the shared
contracts/cultmesh authority route vectors (C# written and TS signed).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
This commit is contained in:
Libby 2026-11-07 01:34:22 +00:00
commit a36a60b106
4 changed files with 558 additions and 1 deletions

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@ -228,6 +228,17 @@ prediction = session.predict(note_doc, "input:python:move", {"body": "predicted
unsubscribe()
```
## Authority route verification
`cultmesh_py.authority` ports the C# reference
(`src/GameCult.Mesh/CultMeshAuthorityProof.cs`): `AuthorityTrustPolicy.validate`
judges an Odin-signed ECDSA P-256 route (channel protection, trusted root,
validity window, IEEE P1363 signature over the canonical bytes) and
`verify_session_proof` checks the provider nonce proof. Refusals raise
`AuthorityRouteRefusal` with the C# message text. It needs `cryptography`.
`tests/test_authority_route_vectors.py` judges
`contracts/cultmesh/authority-route-vectors*.json`.
## Verify
`cultmesh_py.verify` checks the public exports and `py.typed` markers of all

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@ -16,7 +16,7 @@ classifiers = [
"Programming Language :: Python :: 3.11",
"Programming Language :: Python :: 3.12",
]
dependencies = ["cultcache-py>=0.2.0", "cultnet-py>=0.1.0"]
dependencies = ["cultcache-py>=0.2.0", "cultnet-py>=0.1.0", "cryptography>=41"]
[project.scripts]
cultmesh-py-daemon = "cultmesh_py.daemon:main"
cultmesh-py-verify = "cultmesh_py.verify:main"

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@ -0,0 +1,338 @@
"""CultMesh authority route verification.
Port of `src/GameCult.Mesh/CultMeshAuthorityProof.cs` (the reference) and of the
route constructors in `CultMeshVerse.cs`. Rule for rule, in the same order, the
same input yields the same refusal text as `CultMeshAuthorityTrustPolicy.Verify`:
unsigned, channel protection, root lookup, validity window, signature.
Shared vectors: `contracts/cultmesh/authority-route-vectors.json` (C# written).
"""
from __future__ import annotations
import base64
import binascii
import re
import struct
from dataclasses import dataclass
from typing import Iterable, Mapping, Sequence
from cryptography.exceptions import InvalidSignature
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.hazmat.primitives.asymmetric.utils import encode_dss_signature
ROUTE_DOMAIN = "gamecult.cultmesh.route-certificate.v1"
SESSION_DOMAIN = "gamecult.cultmesh.session-proof.v1"
AUTHENTICATED_REMOTE = "authenticated-remote"
LOCAL_DEVELOPMENT = "local-development"
# .NET `char.IsWhiteSpace`: Unicode Zs, Zl, Zp, U+0009-U+000D and U+0085.
# `str.strip()` is a different set (it also strips U+001C-U+001F).
_CSHARP_WHITESPACE = (
"\u0009\u000a\u000b\u000c\u000d \u0085  "
"           "
"

   "
)
def trim_csharp(value: str) -> str:
return value.strip(_CSHARP_WHITESPACE)
def is_blank_csharp(value: str | None) -> bool:
return value is None or trim_csharp(value) == ""
def _require(value: str | None, name: str) -> str:
if is_blank_csharp(value):
raise ValueError(f"Value must be non-empty. (Parameter '{name}')")
return trim_csharp(value) # type: ignore[arg-type]
class AuthorityRouteRefusal(Exception):
"""A route or proof the consumer's trust policy refuses.
Mirrors `CultMeshSessionException` carrying a `CultMeshSessionFailure` with
reason `Authentication`: `reason` is always "authentication".
"""
reason = "authentication"
def __init__(self, message: str, endpoint: str = "") -> None:
super().__init__(message)
self.message = message
self.endpoint = endpoint
def _b64_strict(value: str) -> bytes:
# `Convert.FromBase64String`: standard alphabet, padded, whitespace ignored.
stripped = re.sub(r"[ \t\r\n]", "", value)
return base64.b64decode(stripped, validate=True)
@dataclass(frozen=True)
class P256PublicKey:
key_id: str
x: str
y: str
def __post_init__(self) -> None:
object.__setattr__(self, "key_id", _require(self.key_id, "keyId"))
for name in ("x", "y"):
value = _require(getattr(self, name), name)
try:
_b64_strict(value)
except (binascii.Error, ValueError) as error:
raise ValueError(f"Coordinate must be base64. (Parameter '{name}')") from error
object.__setattr__(self, name, value)
def verify(self, payload: bytes, signature_base64: str) -> bool:
"""IEEE P1363 (r || s) ECDSA-SHA256 verification; False on any malformation."""
try:
x, y = _b64_strict(self.x), _b64_strict(self.y)
signature = _b64_strict(signature_base64)
if len(x) != 32 or len(y) != 32 or len(signature) != 64:
return False
key = ec.EllipticCurvePublicNumbers(
int.from_bytes(x, "big"), int.from_bytes(y, "big"), ec.SECP256R1()
).public_key()
der = encode_dss_signature(
int.from_bytes(signature[:32], "big"), int.from_bytes(signature[32:], "big")
)
key.verify(der, payload, ec.ECDSA(hashes.SHA256()))
return True
except (InvalidSignature, ValueError, binascii.Error):
return False
@dataclass(frozen=True)
class RouteCertificate:
provider_key: P256PublicKey
odin_key_id: str
issued_at_unix_milliseconds: int
expires_at_unix_milliseconds: int
signature: str = ""
def __post_init__(self) -> None:
if is_blank_csharp(self.odin_key_id):
raise ValueError("Odin key identity is required. (Parameter 'odinKeyId')")
object.__setattr__(self, "odin_key_id", trim_csharp(self.odin_key_id))
if self.issued_at_unix_milliseconds < 0:
raise ValueError("issuedAtUnixMilliseconds must not be negative.")
if self.expires_at_unix_milliseconds <= self.issued_at_unix_milliseconds:
raise ValueError("expiresAtUnixMilliseconds must be after issuedAtUnixMilliseconds.")
object.__setattr__(self, "signature", trim_csharp(self.signature or ""))
@dataclass(frozen=True)
class AuthorityRoute:
"""`CultMeshAuthorityRoute`: construction cleans every field as the C# does."""
authority_runtime_id: str
endpoint: str
protocol_ids: Sequence[str] = ()
priority: int = 0
generation: str | None = None
certificate: RouteCertificate | None = None
def __post_init__(self) -> None:
runtime_id = _require(self.authority_runtime_id, "authorityRuntimeId")
endpoint = _require(self.endpoint, "endpoint")
if self.priority < 0:
raise ValueError("priority must not be negative.")
object.__setattr__(self, "authority_runtime_id", runtime_id)
object.__setattr__(self, "endpoint", endpoint)
object.__setattr__(
self,
"protocol_ids",
tuple(
sorted(
{trim_csharp(v) for v in self.protocol_ids if not is_blank_csharp(v)},
key=lambda v: v.encode("utf-16-be"), # StringComparer.Ordinal is UTF-16 code-unit order
)
),
)
object.__setattr__(
self,
"generation",
f"{runtime_id}@{endpoint}" if is_blank_csharp(self.generation) else trim_csharp(self.generation), # type: ignore[arg-type]
)
@dataclass(frozen=True)
class SessionOpen:
"""The fields of `CultMeshSessionOpenMessage` the session proof covers."""
client_nonce: str | None = None
message_id: str | None = None
source_runtime_id: str | None = None
verse_id: str | None = None
authority_runtime_id: str | None = None
protocol_id: str | None = None
route_generation: str | None = None
@dataclass(frozen=True)
class SessionAccepted:
client_nonce: str | None
provider_key_id: str | None
provider_signature: str | None
@dataclass(frozen=True)
class VerifiedRoute:
route: AuthorityRoute
provider_key: P256PublicKey | None
is_local_development: bool
def canonical_fields(*values: str | None) -> bytes:
out = bytearray()
for value in values:
encoded = (value or "").encode("utf-8")
out += struct.pack(">I", len(encoded)) + encoded
return bytes(out)
def canonical_route(verse_id: str, route: AuthorityRoute) -> bytes:
certificate = route.certificate
if certificate is None:
raise ValueError("Route certificate is required.")
return canonical_fields(
ROUTE_DOMAIN,
verse_id,
route.authority_runtime_id,
route.endpoint,
"\u001f".join(route.protocol_ids), # already ordinally sorted; Python sorts by code point
str(route.priority),
route.generation,
certificate.provider_key.key_id,
certificate.provider_key.x,
certificate.provider_key.y,
certificate.odin_key_id,
str(certificate.issued_at_unix_milliseconds),
str(certificate.expires_at_unix_milliseconds),
)
def canonical_session(request: SessionOpen, endpoint: str) -> bytes:
return canonical_fields(
SESSION_DOMAIN,
request.client_nonce,
request.message_id,
request.source_runtime_id,
request.verse_id,
request.authority_runtime_id,
request.protocol_id,
endpoint,
request.route_generation,
)
# `System.Uri` refuses spellings WHATWG parsers repair; a lenient parse could call
# a refused endpoint loopback or protected. Same shape rule as the TypeScript port.
_AUTHORITY = re.compile(r"^[A-Za-z][A-Za-z0-9+\-.]*://([^/?#]+)")
def _split_endpoint(value: str) -> tuple[str, str] | None:
"""Return (scheme, lowercase host) or None where System.Uri would refuse."""
raw = re.sub(r"^[\x00-\x20]+|[\x00-\x20]+$", "", value)
if "\\" in raw:
return None
shape = _AUTHORITY.match(raw)
if not shape:
return None
authority = shape.group(1)
after_user = authority[authority.rfind("@") + 1 :]
if after_user.startswith("["):
host = after_user[: after_user.find("]") + 1]
else:
host = after_user.split(":")[0]
if not host or re.search(r"[^!-~]", host) or host.endswith("."):
return None
return raw.split("://", 1)[0].lower(), host.strip("[]").lower()
def is_loopback_endpoint(endpoint: str) -> bool:
parts = _split_endpoint(endpoint)
if parts is None:
return False
host = parts[1]
return host in ("localhost", "loopback", "::1", "::ffff:127.0.0.1") or bool(
re.fullmatch(r"127\.\d{1,3}\.\d{1,3}\.\d{1,3}", host)
)
def is_protected_endpoint(endpoint: str) -> bool:
parts = _split_endpoint(endpoint)
return parts is not None and (parts[0] in ("wss", "https") or "quic" in parts[0])
class AuthorityTrustPolicy:
"""Consumer-owned policy. Fails closed unless a route is valid under it."""
def __init__(self, mode: str, odin_roots: Iterable[P256PublicKey] = ()) -> None:
if mode not in (AUTHENTICATED_REMOTE, LOCAL_DEVELOPMENT):
raise ValueError(f"Unknown trust mode '{mode}'.")
self.mode = mode
self._roots: dict[str, P256PublicKey] = {}
for root in odin_roots:
if root.key_id in self._roots:
raise ValueError(f"Odin root key id '{root.key_id}' is listed more than once in the trust policy.")
self._roots[root.key_id] = root
def validate(self, verse_id: str, route: AuthorityRoute, now_unix_milliseconds: int) -> None:
self.verify(verse_id, route, now_unix_milliseconds)
def verify(self, verse_id: str, route: AuthorityRoute, now_unix_milliseconds: int) -> VerifiedRoute:
local = self.mode == LOCAL_DEVELOPMENT and is_loopback_endpoint(route.endpoint)
def refuse(message: str) -> AuthorityRouteRefusal:
return AuthorityRouteRefusal(message, route.endpoint)
certificate = route.certificate
if certificate is None or is_blank_csharp(certificate.signature):
if local:
return VerifiedRoute(route, None, True)
raise refuse("Remote CultMesh routes require an Odin-signed authority certificate.")
if not is_protected_endpoint(route.endpoint) and not local:
raise refuse("Authenticated remote CultMesh routes require TLS or QUIC channel protection.")
root = self._roots.get(certificate.odin_key_id)
if root is None:
raise refuse(f"Odin key '{certificate.odin_key_id}' is not trusted by this consumer.")
if not (certificate.issued_at_unix_milliseconds <= now_unix_milliseconds < certificate.expires_at_unix_milliseconds):
raise refuse("The Odin route certificate is not currently valid.")
try:
signature = _b64_strict(certificate.signature)
except (binascii.Error, ValueError):
raise refuse("The Odin route signature is not base64.") from None
if len(signature) != 64:
raise refuse("The Odin route signature is not IEEE P1363 P-256.")
if not root.verify(canonical_route(verse_id, route), certificate.signature):
raise refuse("The Odin route certificate signature is invalid.")
return VerifiedRoute(route, certificate.provider_key, False)
def verify_session_proof(
request: SessionOpen,
response: SessionAccepted,
verse_id: str,
route: AuthorityRoute,
trust: AuthorityTrustPolicy,
now_unix_milliseconds: int,
) -> bool:
"""Verifies the Odin route certificate (raising) and the provider nonce proof."""
verified = trust.verify(verse_id, route, now_unix_milliseconds)
if verified.is_local_development:
return True
key = verified.provider_key
if (
key is None
or response.provider_key_id != key.key_id
or response.client_nonce != request.client_nonce
or is_blank_csharp(response.provider_signature)
):
return False
return key.verify(canonical_session(request, route.endpoint), response.provider_signature) # type: ignore[arg-type]

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@ -0,0 +1,208 @@
"""Judges `contracts/cultmesh/authority-route-vectors*.json` in Python.
`authority-route-vectors.json` is written by the C# reference (signatures are
captured C# bytes); the `.ts-signed.json` file is signed by TypeScript over awkward
inputs. Each negative case fails when the matching check is removed from
`cultmesh_py.authority`.
"""
from __future__ import annotations
import base64
import json
import unittest
from dataclasses import replace
from pathlib import Path
from cryptography.hazmat.primitives.asymmetric import ec
from cultmesh_py.authority import (
AUTHENTICATED_REMOTE,
LOCAL_DEVELOPMENT,
AuthorityRoute,
AuthorityRouteRefusal,
AuthorityTrustPolicy,
P256PublicKey,
RouteCertificate,
SessionAccepted,
SessionOpen,
canonical_route,
verify_session_proof,
)
CONTRACTS = Path(__file__).resolve().parents[3] / "contracts" / "cultmesh"
def _key(element: dict) -> P256PublicKey:
return P256PublicKey(element["keyId"], element["x"], element["y"])
class Vector:
def __init__(self, name: str) -> None:
doc = json.loads((CONTRACTS / name).read_text(encoding="utf-8"))
self.now = doc["nowUnixMilliseconds"]
self.root = _key(doc["odinRoot"])
r = doc["route"]
self.verse_id = r["verseId"]
c = r["certificate"]
self.certificate = RouteCertificate(
_key(c["providerKey"]), c["odinKeyId"], c["issuedAtUnixMilliseconds"],
c["expiresAtUnixMilliseconds"], c["signature"],
)
self.route = AuthorityRoute(
r["authorityRuntimeId"], r["endpoint"], r["protocolIds"], r["priority"],
r["generation"], self.certificate,
)
p = doc["sessionProof"]
q = p["request"]
self.request = SessionOpen(
q["clientNonce"], q["messageId"], q["sourceRuntimeId"], q["verseId"],
q["authorityRuntimeId"], q["protocolId"], q["routeGeneration"],
)
self.accepted = SessionAccepted(q["clientNonce"], p["providerKeyId"], p["providerSignature"])
self.trust = AuthorityTrustPolicy(AUTHENTICATED_REMOTE, [self.root])
def with_certificate(self, **changes) -> AuthorityRoute:
return replace(self.route, certificate=replace(self.certificate, **changes))
def refusal(test: unittest.TestCase, fn) -> str:
with test.assertRaises(AuthorityRouteRefusal) as raised:
fn()
test.assertEqual("authentication", raised.exception.reason)
return raised.exception.message
class AuthorityRouteVectorTests(unittest.TestCase):
def test_cs_written_vector_verifies_route_and_session_proof(self) -> None:
v = Vector("authority-route-vectors.json")
v.trust.validate(v.verse_id, v.route, v.now)
self.assertTrue(verify_session_proof(v.request, v.accepted, v.verse_id, v.route, v.trust, v.now))
def test_ts_signed_vector_verifies_and_tamper_is_refused(self) -> None:
v = Vector("authority-route-vectors.ts-signed.json")
v.trust.validate(v.verse_id, v.route, v.now)
self.assertTrue(verify_session_proof(v.request, v.accepted, v.verse_id, v.route, v.trust, v.now))
tampered = replace(v.route, priority=v.route.priority + 1)
self.assertEqual(
"The Odin route certificate signature is invalid.",
refusal(self, lambda: v.trust.validate(v.verse_id, tampered, v.now)),
)
def test_canonical_route_is_length_prefixed_and_sorted(self) -> None:
v = Vector("authority-route-vectors.json")
data = canonical_route(v.verse_id, v.route)
self.assertTrue(data.startswith(b"\x00\x00\x00\x26gamecult.cultmesh.route-certificate.v1\x00\x00\x00\x08aetheria"))
self.assertIn(b"cultmesh.content.v1\x1fcultmesh.documents.v1", data)
def test_tampered_payload_fields_are_refused(self) -> None:
v = Vector("authority-route-vectors.json")
invalid = "The Odin route certificate signature is invalid."
for tampered, verse in (
(replace(v.route, priority=8), v.verse_id),
(replace(v.route, endpoint="wss://evil.example/mesh"), v.verse_id),
(replace(v.route, protocol_ids=("cultmesh.documents.v1",)), v.verse_id),
(replace(v.route, generation="other"), v.verse_id),
(v.with_certificate(expires_at_unix_milliseconds=v.certificate.expires_at_unix_milliseconds + 1), v.verse_id),
(v.route, "other-verse"),
):
self.assertEqual(invalid, refusal(self, lambda: v.trust.validate(verse, tampered, v.now)))
def test_wrong_root_key_is_refused(self) -> None:
v = Vector("authority-route-vectors.json")
numbers = ec.generate_private_key(ec.SECP256R1()).public_key().public_numbers()
impostor = P256PublicKey(
v.root.key_id,
base64.b64encode(numbers.x.to_bytes(32, "big")).decode(),
base64.b64encode(numbers.y.to_bytes(32, "big")).decode(),
)
trust = AuthorityTrustPolicy(AUTHENTICATED_REMOTE, [impostor])
self.assertEqual(
"The Odin route certificate signature is invalid.",
refusal(self, lambda: trust.validate(v.verse_id, v.route, v.now)),
)
def test_untrusted_odin_key_id_is_refused(self) -> None:
v = Vector("authority-route-vectors.json")
trust = AuthorityTrustPolicy(AUTHENTICATED_REMOTE, [replace(v.root, key_id="someone-else")])
self.assertEqual(
"Odin key 'odin-vector' is not trusted by this consumer.",
refusal(self, lambda: trust.validate(v.verse_id, v.route, v.now)),
)
def test_expired_and_not_yet_valid_are_refused(self) -> None:
v = Vector("authority-route-vectors.json")
window = "The Odin route certificate is not currently valid."
expires = v.certificate.expires_at_unix_milliseconds
issued = v.certificate.issued_at_unix_milliseconds
v.trust.validate(v.verse_id, v.route, expires - 1)
v.trust.validate(v.verse_id, v.route, issued)
self.assertEqual(window, refusal(self, lambda: v.trust.validate(v.verse_id, v.route, expires)))
self.assertEqual(window, refusal(self, lambda: v.trust.validate(v.verse_id, v.route, issued - 1)))
def test_unsigned_and_unprotected_routes_are_refused(self) -> None:
v = Vector("authority-route-vectors.json")
unsigned = replace(v.route, certificate=None)
self.assertEqual(
"Remote CultMesh routes require an Odin-signed authority certificate.",
refusal(self, lambda: v.trust.validate(v.verse_id, unsigned, v.now)),
)
blank = v.with_certificate(signature=" ")
self.assertEqual(
"Remote CultMesh routes require an Odin-signed authority certificate.",
refusal(self, lambda: v.trust.validate(v.verse_id, blank, v.now)),
)
plain = replace(v.route, endpoint="ws://provider.example/mesh")
self.assertEqual(
"Authenticated remote CultMesh routes require TLS or QUIC channel protection.",
refusal(self, lambda: v.trust.validate(v.verse_id, plain, v.now)),
)
def test_local_development_admits_only_unsigned_loopback(self) -> None:
v = Vector("authority-route-vectors.json")
dev = AuthorityTrustPolicy(LOCAL_DEVELOPMENT, [])
loop = AuthorityRoute("a", "ws://127.0.0.1:9/mesh")
dev.validate(v.verse_id, loop, v.now)
self.assertTrue(verify_session_proof(v.request, v.accepted, v.verse_id, loop, dev, v.now))
for endpoint in ("ws://provider.example/mesh", "ws://127.0.0.1./mesh", "ws:127.0.0.1"):
refusal(self, lambda e=endpoint: dev.validate(v.verse_id, AuthorityRoute("a", e), v.now))
authenticated = AuthorityTrustPolicy(AUTHENTICATED_REMOTE, [])
refusal(self, lambda: authenticated.validate(v.verse_id, loop, v.now))
def test_malformed_signatures_get_their_own_refusals(self) -> None:
v = Vector("authority-route-vectors.json")
not_base64 = v.with_certificate(signature="!!not base64!!")
self.assertEqual(
"The Odin route signature is not base64.",
refusal(self, lambda: v.trust.validate(v.verse_id, not_base64, v.now)),
)
short = v.with_certificate(signature=base64.b64encode(b"x" * 63).decode())
self.assertEqual(
"The Odin route signature is not IEEE P1363 P-256.",
refusal(self, lambda: v.trust.validate(v.verse_id, short, v.now)),
)
def test_session_proof_rejects_replay_wrong_key_and_forgery(self) -> None:
v = Vector("authority-route-vectors.json")
replayed = replace(v.request, client_nonce="replayed")
accepted = replace(v.accepted, client_nonce="replayed")
self.assertFalse(verify_session_proof(replayed, accepted, v.verse_id, v.route, v.trust, v.now))
self.assertFalse(verify_session_proof(
v.request, replace(v.accepted, provider_key_id="other"), v.verse_id, v.route, v.trust, v.now))
self.assertFalse(verify_session_proof(
v.request, replace(v.accepted, client_nonce="other"), v.verse_id, v.route, v.trust, v.now))
self.assertFalse(verify_session_proof(
v.request, replace(v.accepted, provider_signature=""), v.verse_id, v.route, v.trust, v.now))
raw = bytearray(base64.b64decode(v.accepted.provider_signature))
raw[0] ^= 1
forged = replace(v.accepted, provider_signature=base64.b64encode(bytes(raw)).decode())
self.assertFalse(verify_session_proof(v.request, forged, v.verse_id, v.route, v.trust, v.now))
moved = replace(v.request, protocol_id="cultmesh.content.v1")
self.assertFalse(verify_session_proof(moved, v.accepted, v.verse_id, v.route, v.trust, v.now))
# An expired route fails closed even with a good proof.
refusal(self, lambda: verify_session_proof(
v.request, v.accepted, v.verse_id, v.route, v.trust, v.certificate.expires_at_unix_milliseconds))
if __name__ == "__main__":
unittest.main()