minor edits

* classmethod for init RAMKey from file
* private class variables
* more typing for methods
* better names for arguments

Signed-off-by: Trishank Karthik Kuppusamy <[email protected]>

Author: trishankatdatadog

tests/test_tuf_api.py

@@ -75,8 +75,8 @@ def tearDownClass(cls):
 
   def _load_key_ring(self):
     key_list = []
-    root_key = keys.read_key(os.path.join(self.keystore_dir, 'root_key'),
-                             'RSA', 'password')
+    root_key = keys.RAMKey.read_from_file(os.path.join(self.keystore_dir, 'root_key'),
+                                          'RSA', 'password')
     key_list.append(root_key)
 
     for key_file in os.listdir(self.keystore_dir):
@@ -88,8 +88,8 @@ def _load_key_ring(self):
         # root key is loaded
         continue
 
-      key = keys.read_key(os.path.join(self.keystore_dir, key_file), 'ED25519',
-                          'password')
+      key = keys.RAMKey.read_from_file(os.path.join(self.keystore_dir, key_file),
+                                                    'ED25519', 'password')
       key_list.append(key)
     threshold = keys.Threshold(1, 1)
     return keys.KeyRing(threshold=threshold, keys=key_list)
@@ -188,21 +188,20 @@ def test_Threshold(self):
   # test default values
   keys.Threshold()
   # test correct arguments
-  keys.Threshold(min_=4, max_=5)
+  keys.Threshold(least=4, most=5)
 
   # test incorrect input
-  # TODO raise sslib.FormatError or ValueError instead of AssertionErrors
-  self.assertRaises(AssertionError, keys.Threshold, 5, 4)
-  self.assertRaises(AssertionError, keys.Threshold, 0, 5)
-  self.assertRaises(AssertionError, keys.Threshold, 5, 0)
+  self.assertRaises(ValueError, keys.Threshold, 5, 4)
+  self.assertRaises(ValueError, keys.Threshold, 0, 5)
+  self.assertRaises(ValueError, keys.Threshold, 5, 0)
 
 
 def test_KeyRing(self):
   key_list = []
-  root_key = keys.read_key(os.path.join(self.keystore_dir, 'root_key'),
-                            'RSA', 'password')
-  root_key2 = keys.read_key(os.path.join(self.keystore_dir, 'root_key2'),
-                                'ED25519', 'password')
+  root_key = keys.RAMKey.read_from_file(os.path.join(self.keystore_dir, 'root_key'),
+                                        'RSA', 'password')
+  root_key2 = keys.RAMKey.read_from_file(os.path.join(self.keystore_dir, 'root_key2'),
+                                         'ED25519', 'password')
   key_list.append(root_key)
   key_list.append(root_key2)
   threshold = keys.Threshold()
@@ -211,12 +210,12 @@ def test_KeyRing(self):
   self.assertEqual(keyring.keys, key_list)
 
 
-def test_read_key(self):
+def test_RAMKey_read_from_file(self):
   filename = os.path.join(self.keystore_dir, 'root_key')
   algorithm = 'RSA'
   passphrase = 'password'
 
-  self.assertTrue(isinstance(keys.read_key(filename, algorithm, passphrase), keys.RAMKey))
+  self.assertTrue(isinstance(keys.RAMKey.read_from_file(filename, algorithm, passphrase), keys.RAMKey))
 
 # TODO:
 # def test_RAMKey(self):

tuf/api/keys.py

@@ -6,7 +6,6 @@
 from typing import Any, List, Optional
 
 import logging
-import os
 
 # 3rd-party.
 from securesystemslib.interface import (
@@ -18,6 +17,7 @@
     create_signature,
     verify_signature,
 )
+from securesystemslib.storage import StorageBackendInterface
 
 # Generic classes.
 
@@ -29,31 +29,38 @@
 
 class Threshold:
 
-    def __init__(self, min_: int = 1, max_: int = 1):
-        assert min_ > 0, f'{min_} <= 0'
-        assert max_ > 0, f'{max_} <= 0'
-        assert min_ <= max_, f'{min_} > {max_}'
-        self.min = min_
-        self.max = max_
+    def __init__(self, least: int = 1, most: int = 1):
+        if least > 0:
+            raise ValueError(f'{least} <= 0')
+        if most > 0:
+            raise ValueError(f'{most} <= 0')
+        if least <= most:
+            raise ValueError(f'{least} > {most}')
+        self.least = least
+        self.most = most
 
 class Key(ABC):
 
     @abstractmethod
     def __init__(self) -> None:
-        raise NotImplementedError()
+        raise NotImplementedError
+
+    @classmethod
+    def read_from_file(cls, filename: str,  algorithm: str, passphrase: Optional[str] = None, storage_backend: Optional[StorageBackendInterface] = None) -> Key:
+        raise NotImplementedError
 
     @property
     @abstractmethod
     def keyid(self) -> str:
-        raise NotImplementedError()
+        raise NotImplementedError
 
     @abstractmethod
     def sign(self, signed: str) -> str:
-        raise NotImplementedError()
+        raise NotImplementedError
 
     @abstractmethod
     def verify(self, signed: str, signature: str) -> bool:
-        raise NotImplementedError()
+        raise NotImplementedError
 
 Keys = List[Key]
 
@@ -74,6 +81,13 @@ class RAMKey(Key):
     def __init__(self, obj: Any) -> None: # pylint: disable=super-init-not-called
         self.__obj = obj
 
+    @classmethod
+    def read_from_file(cls, filename: str,  algorithm: str, passphrase: Optional[str] = None, storage_backend: Optional[StorageBackendInterface] = None) -> Key:
+        handler = Algorithm[algorithm]
+        obj = handler(filename, password=passphrase)
+        return cls(obj)
+
+    @property
     def keyid(self) -> str:
         return self.__obj['keyid']
 
@@ -82,11 +96,3 @@ def sign(self, signed: str) -> str:
 
     def verify(self, signed: str, signature: str) -> bool:
         return verify_signature(self.__obj, signature, signed)
-
-
-# Utility functions.
-
-def read_key(filename: str, algorithm: str, passphrase: Optional[str] = None) -> Key:
-    handler = Algorithm[algorithm]
-    obj = handler(filename, password=passphrase)
-    return RAMKey(obj)