fix read/write mode for various key encoders

fastecdsa/encoding/__init__.py

@@ -6,7 +6,9 @@
 class KeyEncoder:
     """Base class that any encoding class for EC keys should derive from.
 
-    All overriding methods should be static.
+    All overriding methods should be static. If your key encoder writes binary
+    data you must have a field named :code:`binary_data` set to :code:`True` in
+    order for keys to correctly read from and write to disk.
     """
     __metaclass__ = ABCMeta
 

fastecdsa/encoding/pem.py

@@ -18,6 +18,7 @@
 
 class PEMEncoder(KeyEncoder):
     ASN1_PARSED_DATA = []
+    binary_data = False
 
     @staticmethod
     def _parse_ascii_armored_base64(data: str) -> bytes:

fastecdsa/encoding/sec1.py

@@ -10,6 +10,8 @@ class InvalidSEC1PublicKey(Exception):
 
 
 class SEC1Encoder(KeyEncoder):
+    binary_data = True
+
     @staticmethod
     def encode_public_key(point: Point, compressed: bool = True) -> bytes:
         """ Encode a public key as described in http://www.secg.org/SEC1-Ver-1.0.pdf

fastecdsa/keys.py

@@ -143,9 +143,10 @@ def export_key(key, curve: Curve = None, filepath: str = None, encoder=PEMEncode
     if filepath is None:
         return encoded
     else:
-        f = open(filepath, 'wb')
-        f.write(encoded)
-        f.close()
+        # some encoder output strings, others bytes, need to determine what mode to write in
+        write_mode = 'w' + ('b' if getattr(encoder, 'binary_data', False) else '')
+        with open(filepath, write_mode) as f:
+            f.write(encoded)
 
 
 def import_key(filepath: str, curve: Curve = None, public: bool = False, decoder=PEMEncoder
@@ -161,7 +162,9 @@ def import_key(filepath: str, curve: Curve = None, public: bool = False, decoder
         (long, fastecdsa.point.Point): A (private key, public key) tuple. If a public key was
         imported then the first value will be None.
     """
-    with open(filepath, 'r') as f:
+    # some decoders read strings, others bytes, need to determine what mode to write in
+    read_mode = 'r' + ('b' if getattr(decoder, 'binary_data', False) else '')
+    with open(filepath, read_mode) as f:
         data = f.read()
 
     if public:

fastecdsa/tests/test_export_import.py → fastecdsa/tests/test_key_export_import.py

@@ -26,8 +26,9 @@ def test_export_import_public_key(self):
             for encoder in (PEMEncoder, SEC1Encoder):
                 d, Q = gen_keypair(curve)
                 export_key(Q, curve=curve, filepath=TEST_FILE_PATH, encoder=encoder)
-                _, Q_ = import_key(filepath=TEST_FILE_PATH, curve=curve, public=True, decoder=encoder)
+                d_, Q_ = import_key(filepath=TEST_FILE_PATH, curve=curve, public=True, decoder=encoder)
 
+                self.assertIsNone(d_)
                 self.assertEqual(Q, Q_)
 
                 remove(TEST_FILE_PATH)