bytes input for SigningKey.from_der()

add support for all bytes-like objects as input for
SigningKey.from_der

Author: tomato42

src/ecdsa/der.py

@@ -147,7 +147,7 @@ def remove_sequence(string):
 
 
 def remove_octet_string(string):
-    if not string.startswith(b("\x04")):
+    if string[:1] != b"\x04":
         n = string[0] if isinstance(string[0], integer_types) else ord(string[0])
         raise UnexpectedDER("wanted type 'octetstring' (0x04), got 0x%02x" % n)
     length, llen = read_length(string[1:])

src/ecdsa/keys.py

@@ -830,6 +830,7 @@ def from_der(cls, string, hashfunc=sha1):
         :return: Initialised VerifyingKey object
         :rtype: VerifyingKey
         """
+        string = normalise_bytes(string)
         s, empty = der.remove_sequence(string)
         if empty != b(""):
             raise der.UnexpectedDER("trailing junk after DER privkey: %s" %

src/ecdsa/test_keys.py

@@ -229,7 +229,7 @@ def test_VerifyingKey_verify(
 prv_key_bytes = (b'^\xc8B\x0b\xd6\xef\x92R\xa9B\xe9\x89\x04<\xa2'
                  b'\x9fV\x1f\xa5%w\x0e\xb1\xc5')
 assert len(prv_key_bytes) == 24
-keys = []
+converters = []
 for modifier, convert in [
         ("bytes", lambda x: x),
         ("bytes memoryview", buffer),
@@ -242,13 +242,33 @@ def test_VerifyingKey_verify(
         ("array.array of ints memoryview",
          lambda x: buffer(array.array('I', x)))
         ]:
-    keys.append(pytest.param(
+    converters.append(pytest.param(
         convert,
         id=modifier))
 
-@pytest.mark.parametrize("convert", keys)
+@pytest.mark.parametrize("convert", converters)
 def test_SigningKey_from_string(convert):
     key = convert(prv_key_bytes)
     sk = SigningKey.from_string(key)
 
     assert sk.to_string() == prv_key_bytes
+
+
+# test SigningKey.from_der()
+prv_key_str = (
+    "-----BEGIN EC PRIVATE KEY-----\n"
+    "MF8CAQEEGF7IQgvW75JSqULpiQQ8op9WH6Uldw6xxaAKBggqhkjOPQMBAaE0AzIA\n"
+    "BLiBd9CE7xf15FY5QIAoNg+fWbSk1yZOYtoGUdzkejWkxbRc9RWTQjqLVXucIJnz\n"
+    "bA==\n"
+    "-----END EC PRIVATE KEY-----\n")
+key_bytes = unpem(prv_key_str)
+assert isinstance(key_bytes, bytes)
+
+# last two converters are for array.array of ints, those require input
+# that's multiple of 4, which no curve we support produces
+@pytest.mark.parametrize("convert", converters[:-2])
+def test_SigningKey_from_der(convert):
+    key = convert(key_bytes)
+    sk = SigningKey.from_der(key)
+
+    assert sk.to_string() == prv_key_bytes