fix(#828): bound persisted broker token state

Prune consumed and revoked tokens, cap pending token state, reject oversized serialization before replacement, and roll back in-memory mutations when persistence fails.\n\ncloses #828

docs/architecture/lease-broker-protocol.md

@@ -13,6 +13,6 @@ Each connection carries exactly one UTF-8 JSON object followed by one newline, c
 - `mint_token`: authenticated identity plus `binding` containing exactly `compaction_epoch`, `request_epoch`, `h_source`, `h_payload`, and `schema_version`.
 - `consume_token`: authenticated identity plus `token`.
 
-A higher generation for the same anchor atomically replaces the stored incarnation and consumes all prior tokens for that session. A lower generation is stale. Tokens are 256-bit values from the operating-system cryptographic RNG and are single use. Their persisted binding is the WI-1 substrate for later receipt work; WI-1 does not implement receipts, promotion, hooks, payload builders, mutator gates, or recovery.
+A higher generation for the same anchor atomically replaces the stored incarnation and deletes all prior tokens for that session. A lower generation is stale. Tokens are 256-bit values from the operating-system cryptographic RNG and are single use. At most 256 pending tokens may be persisted; another mint fails with `TOKEN_CAPACITY` before mutation. Successful consumption deletes the token, while a replay still fails with `TOKEN_REPLAY`. Live v1 token records retain the existing `consumed: false` schema. Their persisted binding is the WI-1 substrate for later receipt work; WI-1 does not implement receipts, promotion, hooks, payload builders, mutator gates, or recovery.
 
-State replacement uses a mode-`0600` temporary file, `fsync`, atomic rename, and parent-directory `fsync`. Existing state is opened without following symlinks, must be a bounded regular file at mode `0600`, and is fully schema- and invariant-validated before use. Session identity is uniquely keyed by `(anchor_pid,anchor_starttime)`; duplicate logical sessions for one anchor refuse startup. State integrity or mode failures refuse startup. The daemon does not log session IDs or tokens.
+State replacement serializes and enforces the 4 MiB maximum before opening a temporary file, then uses a mode-`0600` temporary file, `fsync`, atomic rename, and parent-directory `fsync`. Every broker mutation snapshots the prior v1 state and restores that in-memory snapshot if commit fails, leaving durable state unchanged. Existing state is opened without following symlinks, must be a bounded regular file at mode `0600`, and is fully schema- and invariant-validated before use. Session identity is uniquely keyed by `(anchor_pid,anchor_starttime)`; duplicate logical sessions for one anchor refuse startup. State integrity or mode failures refuse startup. The daemon does not log session IDs or tokens.

docs/architecture/lease-broker-security.md

@@ -5,7 +5,7 @@
 - Runtime generations are monotonic per anchor; a bump revokes prior-incarnation tokens before persistence commits.
 - Session IDs and cycle tokens use the OS cryptographic RNG. `Math.random` and model output are not token sources.
 - Framing and persistence failures fail closed. Sensitive tokens are not logged.
-- Same-principal filesystem modes are minimum hardening, not socket authenticity against the same UID. Distinct-principal service isolation is required for that stronger claim.
+- Built-in `0700`/`0600` filesystem modes provide same-principal hardening only, not socket authenticity against the same UID. WI-1 provides no distinct-principal isolation. That stronger deployment requires an external protected proxy, ACL, or service boundary, and the boundary must preserve authenticated client identity for the broker's `SO_PEERCRED` and ancestry authorization rather than substituting a shared proxy identity.
 - WI-2+ security surfaces—receipts, promotion transactions, mutator gates, hooks, payload construction, and recovery—are explicitly out of scope.
 
 Coordinator security review must rerun the real socket/peercred acceptance suite on an unrestricted Linux runner and obtain the mandated independent Opus-SECREV review before integration.

docs/guides/lease-broker-operations.md

@@ -16,4 +16,4 @@ There is no automated recovery workflow in WI-1. After a crash, preserve the pro
 
 ## Security posture
 
-Directory `0700` plus socket/state `0600` is minimum same-principal hardening: it excludes other UIDs but does **not** stop the same UID from unlinking and counterfeiting the socket. It therefore does not close T-C same-UID replacement. The stronger deployment runs the broker as a distinct principal behind a protected service boundary whose clients cannot unlink or rebind the socket; that is the T-C-closing option. Server-side branch protection remains the irreducible backstop.
+Directory `0700` plus socket/state `0600` is built-in same-principal hardening only: it excludes other UIDs but does **not** stop the same UID from unlinking and counterfeiting the socket. It therefore does not close T-C same-UID replacement. WI-1 does not provide a distinct-principal boundary. A stronger distinct-principal deployment requires an external protected proxy, ACL, or service boundary that clients cannot unlink or rebind and that preserves the authenticated client identity required by the broker's `SO_PEERCRED` and ancestry checks. Server-side branch protection remains the irreducible backstop.

packages/mosaic/framework/tools/lease-broker/daemon.py

@@ -4,6 +4,7 @@
 from __future__ import annotations
 
 import argparse
+import copy
 import errno
 import json
 import os
@@ -19,6 +20,7 @@ from typing import Final
 
 MAX_FRAME: Final = 64 * 1024
 MAX_STATE: Final = 4 * 1024 * 1024
+MAX_PENDING_TOKENS: Final = 256
 STATE_VERSION: Final = 1
 CONNECTION_DEADLINE_SECONDS: Final = 1.0
 HEX_256_LENGTH: Final = 64
@@ -209,14 +211,16 @@ class StateStore:
         return tokens
 
     def commit(self) -> None:
+        payload = (
+            json.dumps(self.value, sort_keys=True, separators=(",", ":")) + "\n"
+        ).encode()
+        if len(payload) > MAX_STATE:
+            raise BrokerFailure("STATE_TOO_LARGE")
         temporary = self.path.with_name(f".{self.path.name}.{os.getpid()}.tmp")
         descriptor = os.open(temporary, os.O_WRONLY | os.O_CREAT | os.O_EXCL, 0o600)
         replaced = False
         try:
             try:
-                payload = (
-                    json.dumps(self.value, sort_keys=True, separators=(",", ":")) + "\n"
-                ).encode()
                 remaining = memoryview(payload)
                 while remaining:
                     written = os.write(descriptor, remaining)
@@ -269,7 +273,6 @@ class Broker:
         if generation > current_generation:
             session["runtime_generation"] = generation
             self.revoke_session_tokens(session_id)
-            self.store.commit()
         return session_id, session
 
     def session_for_anchor(
@@ -284,11 +287,24 @@ class Broker:
         return None
 
     def revoke_session_tokens(self, session_id: str) -> None:
-        for token in self.store.tokens().values():
-            if token["session_id"] == session_id:
-                token["consumed"] = True
+        tokens = self.store.tokens()
+        for token_value in [
+            value for value, token in tokens.items() if token["session_id"] == session_id
+        ]:
+            del tokens[token_value]
 
     def handle(self, peer: tuple[int, int, int], request: dict[str, object]) -> dict[str, object]:
+        previous = copy.deepcopy(self.store.value)
+        try:
+            response = self._handle(peer, request)
+            if self.store.value != previous:
+                self.store.commit()
+            return response
+        except Exception:
+            self.store.value = previous
+            raise
+
+    def _handle(self, peer: tuple[int, int, int], request: dict[str, object]) -> dict[str, object]:
         peer_pid, peer_uid, peer_gid = peer
         action = request.get("action")
         if action == "register_anchor":
@@ -307,7 +323,6 @@ class Broker:
                     "anchor_starttime": anchor_starttime,
                     "runtime_generation": generation,
                 }
-                self.store.commit()
             else:
                 session_id, session = existing
                 current_generation = session["runtime_generation"]
@@ -316,7 +331,6 @@ class Broker:
                 if generation > current_generation:
                     session["runtime_generation"] = generation
                     self.revoke_session_tokens(session_id)
-                    self.store.commit()
             return {"ok": True, "session_id": session_id, "peer": {"pid": peer_pid, "uid": peer_uid, "gid": peer_gid, "starttime": anchor["starttime"]}}
         if action == "authenticate":
             self.authenticate(peer_pid, request)
@@ -326,6 +340,8 @@ class Broker:
             binding = request.get("binding")
             if not valid_binding(binding):
                 raise BrokerFailure("INVALID_BINDING")
+            if len(self.store.tokens()) >= MAX_PENDING_TOKENS:
+                raise BrokerFailure("TOKEN_CAPACITY")
             token = secrets.token_hex(32)
             self.store.tokens()[token] = {
                 "session_id": session_id,
@@ -333,7 +349,6 @@ class Broker:
                 "binding": binding,
                 "consumed": False,
             }
-            self.store.commit()
             return {"ok": True, "token": token}
         if action == "consume_token":
             session_id, _ = self.authenticate(peer_pid, request)
@@ -341,8 +356,7 @@ class Broker:
             token = self.store.tokens().get(token_value) if isinstance(token_value, str) else None
             if not isinstance(token, dict) or token.get("session_id") != session_id or token.get("runtime_generation") != request.get("runtime_generation") or token.get("consumed") is not False:
                 raise BrokerFailure("TOKEN_REPLAY")
-            token["consumed"] = True
-            self.store.commit()
+            del self.store.tokens()[token_value]
             return {"ok": True}
         raise BrokerFailure("UNKNOWN_ACTION")