Moves load_key_file to Cryptographer and updates pisad to use it

common/cryptographer.py

@@ -146,6 +146,35 @@ class Cryptographer:
 
         return blob
 
+    @staticmethod
+    def load_key_file(file_path):
+        """
+        Loads a key from a key file.
+
+        Args:
+            file_path (:obj:`str`): the path to the key file to be loaded.
+
+        Returns:
+            :obj:`bytes` or :obj:`None`: the key file data if the file can be found and read. ``None`` otherwise.
+        """
+
+        if not isinstance(file_path, str):
+            logger.error("Key file path was expected, {} received".format(type(file_path)))
+            return None
+
+        try:
+            with open(file_path, "rb") as key_file:
+                key = key_file.read()
+            return key
+
+        except FileNotFoundError:
+            logger.error("Key file not found. Please check your settings")
+            return None
+
+        except IOError as e:
+            logger.error("I/O error({}): {}".format(e.errno, e.strerror))
+            return None
+
     @staticmethod
     def load_public_key_der(pk_der):
         """
@@ -199,7 +228,7 @@ class Cryptographer:
             return sk
 
         except UnsupportedAlgorithm:
-            raise ValueError("Could not deserialize the private key (unsupported algorithm).")
+            logger.error("Could not deserialize the private key (unsupported algorithm)")
 
         except ValueError:
             logger.error("The provided data cannot be deserialized (wrong size or format)")
@@ -207,6 +236,8 @@ class Cryptographer:
         except TypeError:
             logger.error("The provided data cannot be deserialized (wrong type)")
 
+        return None
+
     @staticmethod
     def sign(data, sk, rtype="str"):
         """

pisa/pisad.py

@@ -3,6 +3,7 @@ from sys import argv, exit
 from signal import signal, SIGINT, SIGQUIT, SIGTERM
 
 from common.logger import Logger
+from common.cryptographer import Cryptographer
 
 from pisa import config, LOG_PREFIX
 from pisa.api import API
@@ -44,8 +45,9 @@ def main():
 
     else:
         try:
-            with open(config.get("PISA_SECRET_KEY"), "rb") as key_file:
-                secret_key_der = key_file.read()
+            secret_key_der = Cryptographer.load_key_file(config.get("PISA_SECRET_KEY"))
+            if not secret_key_der:
+                raise IOError("PISA private key can't be loaded")
 
             watcher = Watcher(db_manager, Responder(db_manager), secret_key_der, config)
 

test/common/unit/test_cryptographer.py

@@ -1,3 +1,5 @@
+import os
+import pytest
 import binascii
 from cryptography.hazmat.backends import default_backend
 from cryptography.hazmat.primitives.asymmetric import ec
@@ -181,6 +183,30 @@ def test_decrypt_wrong_return():
         assert True
 
 
+def test_load_key_file():
+    dummy_sk = ec.generate_private_key(ec.SECP256K1, default_backend())
+    dummy_sk_der = dummy_sk.private_bytes(
+        encoding=serialization.Encoding.DER,
+        format=serialization.PrivateFormat.TraditionalOpenSSL,
+        encryption_algorithm=serialization.NoEncryption(),
+    )
+
+    # If file exists and has data in it, function should work.
+    with open("key_test_file", "wb") as f:
+        f.write(dummy_sk_der)
+
+    appt_data = Cryptographer.load_key_file("key_test_file")
+    assert appt_data
+
+    os.remove("key_test_file")
+
+    # If file doesn't exist, function should return None
+    assert Cryptographer.load_key_file("nonexistent_file") is None
+
+    # If something that's not a file_path is passed as parameter the method should also return None
+    assert Cryptographer.load_key_file(0) is None and Cryptographer.load_key_file(None) is None
+
+
 def test_load_public_key_der():
     # load_public_key_der expects a byte encoded data. Any other should fail and return None
     for wtype in WRONG_TYPES: