A handful of tiny fixes

2 files changed, 34 insertions, 22 deletions

diff --git a/src/cryptography/hazmat/primitives/serialization.py b/src/cryptography/hazmat/primitives/serialization.py
index 8a4c8bd8..858ec043 100644
--- a/src/cryptography/hazmat/primitives/serialization.py
+++ b/src/cryptography/hazmat/primitives/serialization.py
@@ -49,7 +49,7 @@ def load_pem_public_key(data, backend):
 def load_ssh_public_key(data, backend):
     key_parts = data.split(b' ')
 
-    if len(key_parts) < 2 or len(key_parts) > 3:
+    if len(key_parts) != 2 and len(key_parts) != 3:
         raise ValueError(
             'Key is not in the proper format or contains extra data.')
 
@@ -62,21 +62,21 @@ def load_ssh_public_key(data, backend):
     if not key_type.startswith(b'ssh-rsa'):
         raise UnsupportedAlgorithm('Only RSA keys are currently supported.')
 
-    return _load_ssh_rsa_public_key(key_type, key_body, backend)
+    return _load_ssh_rsa_public_key(key_body, backend)
 
 
-def _load_ssh_rsa_public_key(key_type, key_body, backend):
+def _load_ssh_rsa_public_key(key_body, backend):
     data = base64.b64decode(key_body)
 
-    key_body_type, rest = _read_next_string(data)
+    key_type, rest = _read_next_string(data)
     e, rest = _read_next_mpint(rest)
     n, rest = _read_next_mpint(rest)
 
-    if key_type != key_body_type:
+    if key_type != b'ssh-rsa':
         raise ValueError(
             'Key header and key body contain different key type values.')
 
-    if len(rest) != 0:
+    if rest:
         raise ValueError('Key body contains extra bytes.')
 
     return backend.load_rsa_public_numbers(RSAPublicNumbers(e, n))
@@ -84,26 +84,37 @@ def _load_ssh_rsa_public_key(key_type, key_body, backend):
 
 def _read_next_string(data):
     """Retrieves the next RFC 4251 string value from the data."""
-    str_len, = struct.unpack('>I', data[0:4])
+    str_len, = struct.unpack('>I', data[:4])
     return data[4:4 + str_len], data[4 + str_len:]
 
 
 def _read_next_mpint(data):
-    """Reads the next mpint from the data. Currently, all mpints are
-    interpreted as unsigned."""
+    """
+    Reads the next mpint from the data.
+
+    Currently, all mpints are interpreted as unsigned.
+    """
     mpint_data, rest = _read_next_string(data)
 
-    if sys.version_info >= (3, 2):
-        # If we're using >= 3.2, use int.from_bytes for identical results.
-        return int.from_bytes(mpint_data, byteorder='big', signed=False), rest
+    return _int_from_bytes(mpint_data, byteorder='big', signed=False), rest
+
+
+
+if hasattr(int, "from_bytes"):
+    _int_from_bytes = int.from_bytes
+else:
+    def _int_from_bytes(data, byteorder, signed=False):
+        assert byteorder == 'big'
+        assert not signed
 
-    if len(mpint_data) % 4 != 0:
-        mpint_data = (b'\x00' * (4 - (len(mpint_data) % 4))) + mpint_data
+        if len(data) % 4 != 0:
+            data = (b'\x00' * (4 - (len(data) % 4))) + data
 
-    result = 0
+        result = 0
 
-    while len(mpint_data) > 0:
-        result = (result << 32) + struct.unpack('>I', mpint_data[0:4])[0]
-        mpint_data = mpint_data[4:]
+        while len(data) > 0:
+            digit, = struct.unpack('>I', data[:4])
+            result = (result << 32) + digit
+            data = data[4:]
 
-    return result, rest
+        return result
diff --git a/src/cryptography/utils.py b/src/cryptography/utils.py
index 63464dfa..78f73464 100644
--- a/src/cryptography/utils.py
+++ b/src/cryptography/utils.py
@@ -48,8 +48,9 @@ def verify_interface(iface, klass):
             )
 
 
-def bit_length(x):
-    if sys.version_info >= (2, 7):
+if sys.version_info >= (2, 7):
+    def bit_length(x):
         return x.bit_length()
-    else:
+else:
+    def bit_length(x):
         return len(bin(x)) - (2 + (x <= 0))