S27: HPKE-Base content wrap + public-key directory; reject xor on send

Routing/error fields stay clear. Content is X25519-HKDF-SHA256-ChaCha20.

tests/test_sm.py

@@ -93,23 +93,65 @@ class HistoryTests(unittest.TestCase):
                 h.append_change(actor="", prev_text="", new_text="x")
 
 
+class HpkeDirTests(unittest.TestCase):
+    def test_roundtrip_and_router_cannot_see_body(self):
+        from secure_messaging.content import routing_view, unwrap_content, wrap_content
+        from secure_messaging.pubkey_dir import PubKeyDir
+
+        with tempfile.TemporaryDirectory() as td:
+            d = PubKeyDir(Path(td))
+            d.create_endpoint("alice")
+            d.create_endpoint("pfc-repl")
+            avail = d.available()
+            self.assertIn("pfc-repl", avail["handles"])
+            self.assertTrue(all("sk" not in json.dumps(k) for k in avail["keys"]))
+            env = wrap_content(
+                to_handle="pfc-repl",
+                sender="alice",
+                body={"bytes_hex": "ab", "note": "secret-phi"},
+                directory=d,
+            )
+            self.assertEqual(env["alg"], "npe")
+            rv = routing_view(env)
+            self.assertNotIn("ct", rv)
+            blob = json.dumps(env)
+            self.assertNotIn("secret-phi", blob)
+            self.assertNotIn("bytes_hex", routing_view(env))
+            pt = unwrap_content(env, handle="pfc-repl", directory=d)
+            self.assertEqual(pt["note"], "secret-phi")
+            with self.assertRaises(Exception):
+                unwrap_content(env, handle="alice", directory=d)
+
+
 class RouterTests(unittest.TestCase):
     def test_good_passthrough(self):
-        from secure_messaging.envelope import seal
         from secure_messaging.router import handle_send
 
-        env = seal(to="npe.inbox.abc", sender="alice", body={"note": "hello"}, mode="lab-xor", lab_key=b"lab")
-        r = handle_send(json.dumps(env.wire()).encode())
+        env = {
+            "to": "npe.inbox.abc",
+            "to_handle": "pfc-repl",
+            "alg": "npe",
+            "ct": "abcd",
+            "enc": "00",
+            "from_lookup_id": "lid-npe",
+        }
+        r = handle_send(json.dumps(env).encode())
         self.assertTrue(r.accepted)
-        self.assertEqual(r.ack()["lookup_id"], env.from_lookup_id)
+        self.assertEqual(r.ack()["lookup_id"], "lid-npe")
         self.assertNotIn("ct", r.ack())
         self.assertEqual(r.events, [])
 
+    def test_xor_rejected_for_content(self):
+        from secure_messaging.router import handle_send
+
+        r = handle_send(b'{"to":"npe.inbox.x","alg":"lab-xor","ct":"ab"}')
+        self.assertEqual(r.error_code, "SM-BAD-ALG")
+
     def test_missing_to_failure_path(self):
         from secure_messaging.router import handle_send
         from secure_messaging.error_bundle import open_sender, open_system
 
-        r = handle_send(b'{"alg":"lab-xor","ct":"ab","from_lookup_id":"lid-x"}')
+        r = handle_send(b'{"alg":"npe","ct":"ab","from_lookup_id":"lid-x"}')
         self.assertFalse(r.accepted)
         self.assertEqual(r.error_code, "SM-MISSING-TO")
         subjects = [e["subject"] for e in r.events]
@@ -125,9 +167,9 @@ class RouterTests(unittest.TestCase):
     def test_empty_ct_and_plaintext_body(self):
         from secure_messaging.router import handle_send
 
-        r = handle_send(b'{"to":"npe.inbox.x","alg":"lab-xor","ct":""}')
+        r = handle_send(b'{"to":"npe.inbox.x","alg":"npe","ct":""}')
         self.assertEqual(r.error_code, "SM-EMPTY-CT")
-        r2 = handle_send(b'{"to":"npe.inbox.x","alg":"lab-xor","ct":"ab","body":{"secret":1}}')
+        r2 = handle_send(b'{"to":"npe.inbox.x","alg":"npe","ct":"ab","body":{"secret":1}}')
         self.assertEqual(r2.error_code, "SM-PLAINTEXT-BODY")