fix(security): close MEDIUM ASVS findings — JWT pinning, SSE tickets, SSRF, mTLS pin, rate limits + correctness bugs

Auth (V2.1.1/V3.1.2, V2.1.3, V3.1.1):
- Pin JWT iss/aud/typ at mint and require+verify them at decode; revocation
  (jti denylist + tokens_valid_from) still enforced.
- Change-password now requires min_length=12.
- SSE auth moves off JWT-in-URL to a single-use 60s opaque ticket
  (POST /auth/sse-ticket); raw JWT in query no longer authenticates a stream.
  Removed dead fail-open get_stream_user helper.

Egress (V5.1.1, V9.1.1/V14.1.3):
- Webhook delivery + CRUD reject SSRF destinations (private/loopback/link-local/
  metadata, IPv4-mapped, multi-A-record) via resolved-IP validation, pin to the
  vetted IP, and never auto-follow redirects. Opt-out via DECNET_WEBHOOK_ALLOW_PRIVATE.
- UpdaterClient pins the worker leaf cert SHA-256 against the stored per-host
  fingerprint (fail closed on missing/mismatch); DECNET_VERIFY_HOSTNAME now
  defaults True.

Hardening (V13.1.3, V4.1.4, V13.1.2):
- Rate-limit change-password (5/min), enroll-bundle (10/min), webhook-create
  (20/min), host-delete (20/min) via the existing slowapi limiter.
- Correct false 'global auth middleware' comment; document enroll-bundle proxy
  trust.

Correctness (BUG-7..11):
- BUG-7 unbound bus in finally; BUG-8 apply_ceiling clamps to min(base,ceiling);
  BUG-9 commit before emit; BUG-10 multi-actor rearm for sub-threshold identities;
  BUG-11 normalize naive timestamps to UTC.

Already-closed (no change): V14.1.1, V2.1.2/V3.1.3, V5.1.2. Tests added for
every fix; unanimous adversarial review.

decnet/swarm/client.py

@@ -112,11 +112,11 @@ class AgentClient:
         """Either pass a SwarmHost dict, or explicit address/port.
 
         ``verify_hostname`` defers to ``DECNET_VERIFY_HOSTNAME`` when the
-        caller doesn't pass an explicit value — production deploys flip
-        the env var on so the worker's cert SAN must match the address
-        the master connects to, on top of the existing CA + fingerprint
-        pin. Defaults to False so dev/test enrollments with mismatched
-        SANs keep working unchanged.
+        caller doesn't pass an explicit value — the worker's cert SAN must
+        match the address the master connects to, on top of the existing CA
+        + fingerprint pin. Defaults to True; operators opt out explicitly
+        via ``DECNET_VERIFY_HOSTNAME=false`` for dev/test enrollments with
+        mismatched SANs.
         """
         if verify_hostname is None:
             from decnet.env import DECNET_VERIFY_HOSTNAME
@@ -155,9 +155,10 @@ class AgentClient:
         )
         ctx.load_verify_locations(cafile=str(self._identity.ca_cert_path))
         ctx.verify_mode = ssl.CERT_REQUIRED
-        # Pin by CA + cert chain, not by DNS — workers enroll with arbitrary
-        # SANs (IPs, hostnames) and we don't want to force operators to keep
-        # those in sync with whatever URL the master happens to use.
+        # Pin by CA + cert chain; hostname verification is on by default
+        # (DECNET_VERIFY_HOSTNAME=true) so the cert SAN must match the
+        # master's connect address.  Operators set the env var to false only
+        # for dev/test enrollments with mismatched SANs.
         ctx.check_hostname = self._verify_hostname
         return httpx.AsyncClient(
             base_url=f"https://{self._address}:{self._port}",

decnet/swarm/updater_client.py

@@ -13,14 +13,20 @@ the connection on purpose (the updater re-execs itself mid-response).
 """
 from __future__ import annotations
 
+import asyncio
 import hashlib
+import socket
 import ssl
 from typing import Any, Optional
 
 import httpx
 
 from decnet.logging import get_logger
-from decnet.swarm.client import MasterIdentity, ensure_master_identity
+from decnet.swarm.client import (
+    FingerprintMismatchError,
+    MasterIdentity,
+    ensure_master_identity,
+)
 
 log = get_logger("swarm.updater_client")
 
@@ -47,11 +53,19 @@ class UpdaterClient:
         if host is not None:
             self._address = host["address"]
             self._host_name = host.get("name")
+            # SHA-256 of the worker's UPDATER leaf cert, recorded at enroll
+            # time (api_enroll_host.py writes ``updater_cert_fingerprint``).
+            # This is a distinct identity from the agent cert AgentClient
+            # pins — the updater channel pip-installs code as root, so it
+            # gets its own pin against its own cert.
+            fp = host.get("updater_cert_fingerprint")
+            self._expected_fingerprint = fp.lower() if isinstance(fp, str) else None
         else:
             if address is None:
                 raise ValueError("UpdaterClient requires host dict or address")
             self._address = address
             self._host_name = None
+            self._expected_fingerprint = None
         self._port = updater_port
         self._identity = identity or ensure_master_identity()
         self._client: Optional[httpx.AsyncClient] = None
@@ -70,8 +84,64 @@ class UpdaterClient:
             timeout=timeout,
         )
 
+    def _fetch_peer_fingerprint(self) -> str:
+        """Open a throwaway TLS connection to the updater port and return the
+        SHA-256 hex of the leaf cert it presents. Mirrors
+        ``AgentClient._fetch_peer_fingerprint`` exactly."""
+        ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        ctx.load_cert_chain(
+            str(self._identity.cert_path), str(self._identity.key_path),
+        )
+        ctx.load_verify_locations(cafile=str(self._identity.ca_cert_path))
+        ctx.verify_mode = ssl.CERT_REQUIRED
+        ctx.check_hostname = self._verify_hostname
+        sock = socket.create_connection((self._address, self._port), timeout=10.0)
+        try:
+            server_hostname = self._address if self._verify_hostname else None
+            with ctx.wrap_socket(sock, server_hostname=server_hostname) as ssock:
+                der = ssock.getpeercert(binary_form=True)
+        finally:
+            try:
+                sock.close()
+            except OSError:
+                pass
+        if not der:
+            raise FingerprintMismatchError(
+                f"{self._address}:{self._port}", self._expected_fingerprint or "", ""
+            )
+        return hashlib.sha256(der).hexdigest().lower()
+
+    async def _verify_pin(self) -> None:
+        """Fail closed unless the updater leaf cert SHA-256 matches the pin.
+
+        Unlike ``AgentClient`` (which falls through to CA-only when no pin is
+        recorded), the updater channel pip-installs code as root — so a host
+        with NO recorded ``updater_cert_fingerprint`` is rejected outright
+        rather than accepted on CA validity alone. A missing pin means the
+        host was never enrolled with an updater identity; we refuse to drive
+        code into it."""
+        if not self._expected_fingerprint:
+            raise FingerprintMismatchError(
+                f"{self._address}:{self._port}",
+                "<no updater_cert_fingerprint recorded for host>",
+                "",
+            )
+        actual = await asyncio.to_thread(self._fetch_peer_fingerprint)
+        if actual != self._expected_fingerprint:
+            raise FingerprintMismatchError(
+                f"{self._address}:{self._port}",
+                self._expected_fingerprint,
+                actual,
+            )
+
     async def __aenter__(self) -> "UpdaterClient":
         self._client = self._build_client(_TIMEOUT_CONTROL)
+        try:
+            await self._verify_pin()
+        except BaseException:
+            await self._client.aclose()
+            self._client = None
+            raise
         return self
 
     async def __aexit__(self, *exc: Any) -> None: