Separated signing logic of the Watcher in sign_appointment function; added unit test

pisa/watcher.py

@@ -34,6 +34,10 @@ class Watcher:
                 secret_key_pem = key_file.read().encode("utf-8")
                 self.signing_key = load_pem_private_key(secret_key_pem, password=None, backend=default_backend())
 
+    def sign_appointment(self, appointment):
+        data = appointment.to_json().encode("utf-8")
+        return self.signing_key.sign(data, ec.ECDSA(hashes.SHA256()))
+
     def add_appointment(self, appointment):
         # Rationale:
         # The Watcher will analyze every received block looking for appointment matches. If there is no work
@@ -73,10 +77,7 @@ class Watcher:
 
             logger.info("New appointment accepted.", locator=appointment.locator)
 
-            signature = self.signing_key.sign(
-                appointment.to_json().encode("utf-8"),
-                ec.ECDSA(hashes.SHA256())
-            )
+            signature = self.sign_appointment(appointment)
         else:
             appointment_added = False
 

test/unit/test_watcher.py

@@ -82,6 +82,15 @@ def create_appointments(n):
     return appointments, locator_uuid_map, dispute_txs
 
 
+def verify_signature(appointment, signature, pk):
+    # verify the signature
+    try:
+        data = appointment.to_json().encode('utf-8')
+        pk.verify(signature, data, ec.ECDSA(hashes.SHA256()))
+    except InvalidSignature:
+        assert False, "The appointment's signature is not correct"
+
+
 def test_init(watcher):
     assert type(watcher.appointments) is dict and len(watcher.appointments) == 0
     assert type(watcher.locator_uuid_map) is dict and len(watcher.locator_uuid_map) == 0
@@ -92,6 +101,12 @@ def test_init(watcher):
     assert type(watcher.responder) is Responder
 
 
+def test_sign_appointment(watcher):
+    appointment, _ = generate_dummy_appointment()
+    signature = watcher.sign_appointment(appointment)
+    verify_signature(appointment, signature, public_key)
+
+
 def test_add_appointment(run_bitcoind, watcher):
     # The watcher automatically fires do_watch and do_subscribe on adding an appointment if it is asleep (initial state)
     # Avoid this by setting the state to awake.
@@ -104,12 +119,7 @@ def test_add_appointment(run_bitcoind, watcher):
 
         assert added_appointment is True
 
-        # verify the signature
-        try:
-            data = appointment.to_json().encode('utf-8')
-            public_key.verify(sig, data, ec.ECDSA(hashes.SHA256()))
-        except InvalidSignature:
-            assert False, "The appointment's signature is not correct"
+        verify_signature(appointment, sig, public_key)
 
 
 def test_add_too_many_appointments(watcher):
@@ -121,6 +131,7 @@ def test_add_too_many_appointments(watcher):
         added_appointment, sig = watcher.add_appointment(appointment)
 
         assert added_appointment is True
+        verify_signature(appointment, sig, public_key)
 
     appointment, dispute_tx = generate_dummy_appointment()
     added_appointment, sig = watcher.add_appointment(appointment)