merge: Phase 11.5 security remediation, invite redesign, per-node identity

Brings in the security remediation branch. Three bodies of work, and what they
changed about what this project may claim.

Phase 11.5 closed the gap between the documents and the code: the unauthenticated
node HTTP API and the TCP transport deleted, one handshake shared by the
remaining two transports, mutual authentication, structured admin transcripts,
upload confinement, group isolation, revocation that reaches nodes. Six critical
and seven high findings closed, bounded, or deferred by decision.

The invite redesign closed H3 and M3 — the last open High. The hub was the key
directory: an inviter fetched the invitee's key from it and wrapped the group key
for whatever came back, so a hub answering with its own key was handed the group
key by an honest member following the protocol exactly. That lookup is gone. The
node holds the group key and wraps it itself, for a key its recipient proves
possession of, bound to an account by a one-time code the hub never sees. M3 fell
out of the same work: node authority comes from a local roster, never from the
hub.

Per-node identity cut what remains of C4 down to one operator. A single keypair
used to be copied to every node its owner joined; each node now gets its own, so
cracking the bundle on one machine yields a key that is a stranger everywhere
else — and on that machine, one that unlocks nothing its holder did not already
serve. The bundle KDF moved to Argon2id 128 MB, and the hub stopped storing or
publishing user keys at all.

What this project may now say: the hub cannot read your content unless it ships
you malicious client code. T3 remains, accepted (D1), and is what the native
client removes. C4 is reduced, not closed, until 13.3. Chat is still plaintext at
rest until Phase 15. Draft-v5 §2 states each claim against the adversary it holds
against, which is the convention this branch exists to keep.

Four defects were found by deploying it and using a browser, none by the test
suite: a node going deaf on its hub socket, a token that predated group
membership, a client reading values before they were assigned, and identity keys
a browser held but never re-read. The lessons are recorded in CLAUDE.md.

Tests: 343 across the three packages, plus QE/deploy/e2e.py — register, pair,
invite, join, download, stream, second browser, revoke — run against the live
deployment on a wiped hub and node.

1 files changed, 0 insertions, 148 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/transport/client.py b/packages/meshbay-node/src/meshbay_node/transport/client.py
deleted file mode 100644
index 63d50af..0000000
--- a/packages/meshbay-node/src/meshbay_node/transport/client.py
+++ /dev/null
@@ -1,148 +0,0 @@
-"""
-MeshBay — TCP+TLS chunk client (MNP v1).
-
-Used by the web client (or other nodes) to fetch files from a Mesh Node.
-Verifies Ed25519 chunk signatures using the node's public key from the hub.
-"""
-
-import asyncio
-import base64
-import logging
-import struct
-from pathlib import Path
-
-import blake3
-import msgpack
-from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PublicKey
-
-from meshbay_common import MNP_VERSION
-from meshbay_common.crypto import (
-    chunk_key as derive_chunk_key,
-    decrypt_chunk,
-    verify_chunk_signature,
-)
-from meshbay_common.protocol import MNP
-from meshbay_node.transport.tls_cert import client_ssl_context
-
-log = logging.getLogger(__name__)
-
-MAX_MSG = 64 * 1024 * 1024
-
-
-async def _send(writer, obj):
-    data = msgpack.packb(obj, use_bin_type=True)
-    writer.write(struct.pack(">I", len(data)) + data)
-    await writer.drain()
-
-async def _recv(reader):
-    header = await reader.readexactly(4)
-    length = struct.unpack(">I", header)[0]
-    if length > MAX_MSG:
-        raise ValueError(f"Message too large: {length}")
-    return msgpack.unpackb(await reader.readexactly(length), raw=False)
-
-
-class ChunkClient:
-    """
-    Async client for fetching encrypted chunks from a ChunkServer.
-
-    Usage:
-        async with ChunkClient(host, port, jwt_token, gek, pk_node_b64) as client:
-            data = await client.fetch_chunk(file_id, chunk_index=0)
-    """
-
-    def __init__(
-        self,
-        host: str,
-        port: int,
-        jwt_token: str,
-        gek: bytes,
-        pk_node_b64: str,     # node's Ed25519 PK from hub — used for sig verification
-        group_id: str = "",
-    ):
-        self._host       = host
-        self._port       = port
-        self._jwt_token  = jwt_token
-        self._gek        = gek
-        self._group_id   = group_id
-        self._pk_node    = Ed25519PublicKey.from_public_bytes(
-            base64.b64decode(pk_node_b64))
-        self._reader: asyncio.StreamReader | None = None
-        self._writer: asyncio.StreamWriter | None = None
-
-    async def __aenter__(self):
-        await self.connect()
-        return self
-
-    async def __aexit__(self, *_):
-        await self.close()
-
-    async def connect(self) -> None:
-        ssl_ctx = client_ssl_context()
-        self._reader, self._writer = await asyncio.open_connection(
-            self._host, self._port, ssl=ssl_ctx)
-
-        handshake_msg = {
-            "type":  MNP.HANDSHAKE,
-            "v":     MNP_VERSION,
-            "token": self._jwt_token,
-        }
-        if self._group_id:
-            handshake_msg["group_id"] = self._group_id
-        await _send(self._writer, handshake_msg)
-        ack = await _recv(self._reader)
-        if ack.get("type") != MNP.HANDSHAKE_ACK:
-            raise ConnectionError(f"Handshake rejected: {ack}")
-        log.debug("Connected to node %s:%d", self._host, self._port)
-
-    async def close(self) -> None:
-        if self._writer:
-            self._writer.close()
-            await self._writer.wait_closed()
-
-    async def fetch_index(self) -> bytes:
-        """Request the Mesh Group Index. Returns raw wire bytes (encrypted)."""
-        await _send(self._writer, {"type": MNP.INDEX_SYNC, "v": MNP_VERSION})
-        msg = await _recv(self._reader)
-        return base64.b64decode(msg["index_b64"])
-
-    async def fetch_chunk(self, file_id: str, chunk_index: int) -> bytes:
-        """
-        Fetch, verify, and decrypt one chunk.
-        Returns plaintext bytes.
-        """
-        await _send(self._writer, {
-            "type":        MNP.FILE_REQUEST,
-            "v":           MNP_VERSION,
-            "file_id":     file_id,
-            "chunk_index": chunk_index,
-        })
-        msg = await _recv(self._reader)
-
-        if msg.get("type") == "error":
-            raise LookupError(msg.get("detail", "Unknown error"))
-
-        ct        = base64.b64decode(msg["ct_b64"])
-        nonce     = base64.b64decode(msg["nonce_b64"])
-        ct_hash   = base64.b64decode(msg["ct_hash_b64"])
-        pt_hash   = base64.b64decode(msg["pt_hash_b64"])
-        sig       = base64.b64decode(msg["sig_b64"])
-        file_hash = base64.b64decode(msg["file_hash_b64"])
-        ci        = msg["chunk_index"]
-
-        # 1. Verify Ed25519 signature
-        verify_chunk_signature(self._pk_node, ci, nonce, ct_hash, sig)
-
-        # 2. Verify ciphertext hash
-        if blake3.blake3(ct).digest() != ct_hash:
-            raise ValueError("Ciphertext hash mismatch")
-
-        # 3. Decrypt
-        ckey = derive_chunk_key(self._gek, file_hash, ci)
-        plaintext = decrypt_chunk(ckey, nonce, ct)
-
-        # 4. Verify plaintext hash
-        if blake3.blake3(plaintext).digest() != pt_hash:
-            raise ValueError("Plaintext hash mismatch after decryption")
-
-        return plaintext