Merge branch 'fix/third-review-h1-h2-m1-m6'

Third security review (docs/third-review.md) plus its remediation.

Fixed and verified:
- H1  moderator could grant admin / hard-revoke  → handler split by field
- H2  unauthenticated 2-report global blocklist  → auth + distinct reporters
      + rate limit + refused when public groups are off
- M1  registration reCAPTCHA was inert           → gate unconditional; the
      desktop client's CSP allows the widget
- M2  QUIC chat/stream handlers lagged WebRTC    → brought to parity; the QUIC
      listener is now off by default ([node] quic_enabled)
- M3  link-preview SSRF gaps                      → rate limit + port allowlist
      + connect-address re-check + decompression-bomb guard
- M4  federated peer over-trust                   → source bound to the signer,
      push capped, revocation prunes the peer's own entries, replay rejected
- M5  no CSP / security headers on the SPA        → middleware; verified against
      the live app with no violations

Withdrawn:
- M6  add_group_member accepting node tokens is deliberate (commit 0443cf8,
      the CLI invite flow). The "fix" broke that flow on the deployed hub and
      was reverted.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011pG75yGK3NthNfyjH74omG

1 files changed, 65 insertions, 0 deletions

diff --git a/packages/meshbay-hub/tests/test_security_headers.py b/packages/meshbay-hub/tests/test_security_headers.py
new file mode 100644
index 0000000..b4d7e6d
--- /dev/null
+++ b/packages/meshbay-hub/tests/test_security_headers.py
@@ -0,0 +1,65 @@
+"""
+The hub sends a Content-Security-Policy and the other protective headers on
+every response — the SPA shell, its assets, and the API alike.
+
+Second-review L5 / third-review M5: previously there were none, so an injection
+that landed in the SPA (rendered third-party OG data, a federated group name,
+chat content) had nothing stopping it from loading more code or exfiltrating.
+"""
+
+import pytest
+from meshbay_hub.api.webapp import CSP
+
+
+def _directive(csp: str, name: str) -> str:
+    for part in csp.split(";"):
+        part = part.strip()
+        if part == name or part.startswith(name + " "):
+            return part
+    return ""
+
+
+@pytest.mark.asyncio
+async def test_the_spa_shell_carries_the_policy(client):
+    r = await client.get("/")
+    assert r.headers["content-security-policy"] == CSP
+    assert r.headers["x-content-type-options"] == "nosniff"
+    assert r.headers["x-frame-options"] == "DENY"
+    assert "referrer-policy" in r.headers
+
+
+@pytest.mark.asyncio
+async def test_the_api_carries_the_headers_too(client):
+    r = await client.get("/v1/health")
+    assert r.status_code == 200
+    assert "content-security-policy" in r.headers
+    assert r.headers["x-content-type-options"] == "nosniff"
+
+
+@pytest.mark.asyncio
+async def test_even_a_404_carries_the_headers(client):
+    # The middleware runs on every response, so a probe for a missing path
+    # cannot be framed or content-sniffed either.
+    r = await client.get("/no/such/path")
+    assert r.status_code == 404
+    assert r.headers["x-frame-options"] == "DENY"
+
+
+def test_the_policy_is_locked_down_where_it_matters():
+    assert "default-src 'none'" in CSP          # covers object-src, etc.
+    assert _directive(CSP, "frame-ancestors") == "frame-ancestors 'none'"
+    assert _directive(CSP, "base-uri") == "base-uri 'none'"
+
+    script = _directive(CSP, "script-src")
+    # The hub's own origin must not be able to serve executable script (T3):
+    # 'self' and the wasm token are fine, a bare `https:` scheme is not.
+    assert "'self'" in script and "'wasm-unsafe-eval'" in script
+    assert "https:" not in script.split()
+
+
+def test_recaptcha_is_the_only_external_origin():
+    hosts = {"https://www.google.com", "https://www.gstatic.com"}
+    for part in CSP.split(";"):
+        for tok in part.strip().split()[1:]:
+            if tok.startswith(("http://", "https://")):
+                assert tok in hosts, f"unexpected external origin in CSP: {tok}"