A handful of tiny fixes

5 files changed, 77 insertions, 59 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 0394ebd9..cf6d2252 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -19,9 +19,9 @@ Changelog
 * Added support for encoding and decoding :rfc:`6979` signatures in
   :doc:`/hazmat/primitives/asymmetric/utils`.
 * Added
-  :func:`~cryptography.hazmat.primitives.serialization.load_ssh_public_key`
-  to support the loading of OpenSSH public keys (:rfc:`4253`). Currently, only RSA
-  is supported.
+  :func:`~cryptography.hazmat.primitives.serialization.load_ssh_public_key` to
+  support the loading of OpenSSH public keys (:rfc:`4253`). Currently, only RSA
+  keys are supported.
 
 0.6.1 - 2014-10-15
 ~~~~~~~~~~~~~~~~~~
diff --git a/docs/hazmat/primitives/asymmetric/serialization.rst b/docs/hazmat/primitives/asymmetric/serialization.rst
index 45c7a5bc..a9392c7b 100644
--- a/docs/hazmat/primitives/asymmetric/serialization.rst
+++ b/docs/hazmat/primitives/asymmetric/serialization.rst
@@ -199,7 +199,7 @@ KEY-----`` or ``-----BEGIN DSA PRIVATE KEY-----``.
 OpenSSH Public Key
 ~~~~~~~~~~~~~~~~~~
 
-The format used by OpenSSH to store public keys as specified in :rfc:`4253`.
+The format used by OpenSSH to store public keys, as specified in :rfc:`4253`.
 
 Currently, only RSA public keys are supported. Any other type of key will
 result in an exception being thrown.
@@ -224,7 +224,8 @@ purposes)::
 
     :param bytes data: The OpenSSH encoded key data.
 
-    :param backend: A backend provider.
+    :param backend: An
+        :class:`~cryptography.hazmat.backends.interfaces.RSABackend` provider.
 
     :returns: A new instance of a public key type.
 
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))
diff --git a/tests/hazmat/primitives/test_serialization.py b/tests/hazmat/primitives/test_serialization.py
index 9180b9aa..2b9d05a7 100644
--- a/tests/hazmat/primitives/test_serialization.py
+++ b/tests/hazmat/primitives/test_serialization.py
@@ -704,53 +704,58 @@ class TestSSHSerialization(object):
             load_ssh_public_key(ssh_key, backend)
 
     def test_load_ssh_public_key_rsa_key_types_dont_match(self, backend):
-        ssh_key = textwrap.dedent("""\
-            ssh-bad AAAAB3NzaC1yc2EAAAADAQABAAABAQDDu/XRP1kyK6Cgt36gts9XAk
-            FiiuJLW6RU0j3KKVZSs1I7Z3UmU9/9aVh/rZV43WQG8jaR6kkcP4stOR0DEtll
-            PDA7ZRBnrfiHpSQYQ874AZaAoIjgkv7DBfsE6gcDQLub0PFjWyrYQUJhtOLQEK
-            vY/G0vt2iRL3juawWmCFdTK3W3XvwAdgGk71i6lHt+deOPNEPN2H58E4odrZ2f
-            sxn/adpDqfb2sM0kPwQs0aWvrrKGvUaustkivQE4XWiSFnB0oJB/lKK/CKVKuy
-            ///ImSCGHQRvhwariN2tvZ6CBNSLh3iQgeB0AkyJlng7MXB2qYq/Ci2FUOryCX
-            2MzHvnbv testkey@localhost extra""").encode()  # ssh-bad
+        ssh_key = (
+            b"ssh-bad AAAAB3NzaC1yc2EAAAADAQABAAABAQDDu/XRP1kyK6Cgt36gts9XAk"
+            b"FiiuJLW6RU0j3KKVZSs1I7Z3UmU9/9aVh/rZV43WQG8jaR6kkcP4stOR0DEtll"
+            b"PDA7ZRBnrfiHpSQYQ874AZaAoIjgkv7DBfsE6gcDQLub0PFjWyrYQUJhtOLQEK"
+            b"vY/G0vt2iRL3juawWmCFdTK3W3XvwAdgGk71i6lHt+deOPNEPN2H58E4odrZ2f"
+            b"sxn/adpDqfb2sM0kPwQs0aWvrrKGvUaustkivQE4XWiSFnB0oJB/lKK/CKVKuy"
+            b"///ImSCGHQRvhwariN2tvZ6CBNSLh3iQgeB0AkyJlng7MXB2qYq/Ci2FUOryCX"
+            b"2MzHvnbv testkey@localhost extra"
+        )
 
         with pytest.raises(ValueError):
             load_ssh_public_key(ssh_key, backend)
 
     def test_load_ssh_public_key_rsa_extra_string_after_comment(self, backend):
-        ssh_key = textwrap.dedent("""\
-            ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDDu/XRP1kyK6Cgt36gts9XAk
-            FiiuJLW6RU0j3KKVZSs1I7Z3UmU9/9aVh/rZV43WQG8jaR6kkcP4stOR0DEtll
-            PDA7ZRBnrfiHpSQYQ874AZaAoIjgkv7DBfsE6gcDQLub0PFjWyrYQUJhtOLQEK
-            vY/G0vt2iRL3juawWmCFdTK3W3XvwAdgGk71i6lHt+deOPNEPN2H58E4odrZ2f
-            sxn/adpDqfb2sM0kPwQs0aWvrrKGvUaustkivQE4XWiSFnB0oJB/lKK/CKVKuy
-            ///ImSCGHQRvhwariN2tvZ6CBNSLh3iQgeB0AkyJlng7MXB2qYq/Ci2FUOryCX
-            2MzHvnbv testkey@localhost extra""").encode()  # Extra appended
+        ssh_key = (
+            b"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDDu/XRP1kyK6Cgt36gts9XAk"
+            b"FiiuJLW6RU0j3KKVZSs1I7Z3UmU9/9aVh/rZV43WQG8jaR6kkcP4stOR0DEtll"
+            b"PDA7ZRBnrfiHpSQYQ874AZaAoIjgkv7DBfsE6gcDQLub0PFjWyrYQUJhtOLQEK"
+            b"vY/G0vt2iRL3juawWmCFdTK3W3XvwAdgGk71i6lHt+deOPNEPN2H58E4odrZ2f"
+            b"sxn/adpDqfb2sM0kPwQs0aWvrrKGvUaustkivQE4XWiSFnB0oJB/lKK/CKVKuy"
+            b"///ImSCGHQRvhwariN2tvZ6CBNSLh3iQgeB0AkyJlng7MXB2qYq/Ci2FUOryCX"
+            # Extra section appended
+            b"2MzHvnbv testkey@localhost extra"
+        )
 
         with pytest.raises(ValueError):
             load_ssh_public_key(ssh_key, backend)
 
     def test_load_ssh_public_key_rsa_extra_data_after_modulo(self, backend):
-        ssh_key = textwrap.dedent("""\
-            ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDDu/XRP1kyK6Cgt36gts9XAk
-            FiiuJLW6RU0j3KKVZSs1I7Z3UmU9/9aVh/rZV43WQG8jaR6kkcP4stOR0DEtll
-            PDA7ZRBnrfiHpSQYQ874AZaAoIjgkv7DBfsE6gcDQLub0PFjWyrYQUJhtOLQEK
-            vY/G0vt2iRL3juawWmCFdTK3W3XvwAdgGk71i6lHt+deOPNEPN2H58E4odrZ2f
-            sxn/adpDqfb2sM0kPwQs0aWvrrKGvUaustkivQE4XWiSFnB0oJB/lKK/CKVKuy
-            ///ImSCGHQRvhwariN2tvZ6CBNSLh3iQgeB0AkyJlng7MXB2qYq/Ci2FUOryCX
-            2MzHvnbvAQ== testkey@localhost""").encode()  # Extra 0x01 appended
+        ssh_key = (
+            b"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDDu/XRP1kyK6Cgt36gts9XAk"
+            b"FiiuJLW6RU0j3KKVZSs1I7Z3UmU9/9aVh/rZV43WQG8jaR6kkcP4stOR0DEtll"
+            b"PDA7ZRBnrfiHpSQYQ874AZaAoIjgkv7DBfsE6gcDQLub0PFjWyrYQUJhtOLQEK"
+            b"vY/G0vt2iRL3juawWmCFdTK3W3XvwAdgGk71i6lHt+deOPNEPN2H58E4odrZ2f"
+            b"sxn/adpDqfb2sM0kPwQs0aWvrrKGvUaustkivQE4XWiSFnB0oJB/lKK/CKVKuy"
+            b"///ImSCGHQRvhwariN2tvZ6CBNSLh3iQgeB0AkyJlng7MXB2qYq/Ci2FUOryCX"
+            b"2MzHvnbvAQ== testkey@localhost"
+        )
 
         with pytest.raises(ValueError):
             load_ssh_public_key(ssh_key, backend)
 
     def test_load_ssh_public_key_rsa(self, backend):
-        ssh_key = textwrap.dedent("""\
-            ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDDu/XRP1kyK6Cgt36gts9XAk
-            FiiuJLW6RU0j3KKVZSs1I7Z3UmU9/9aVh/rZV43WQG8jaR6kkcP4stOR0DEtll
-            PDA7ZRBnrfiHpSQYQ874AZaAoIjgkv7DBfsE6gcDQLub0PFjWyrYQUJhtOLQEK
-            vY/G0vt2iRL3juawWmCFdTK3W3XvwAdgGk71i6lHt+deOPNEPN2H58E4odrZ2f
-            sxn/adpDqfb2sM0kPwQs0aWvrrKGvUaustkivQE4XWiSFnB0oJB/lKK/CKVKuy
-            ///ImSCGHQRvhwariN2tvZ6CBNSLh3iQgeB0AkyJlng7MXB2qYq/Ci2FUOryCX
-            2MzHvnbv testkey@localhost""").encode()
+        ssh_key = (
+            b"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDDu/XRP1kyK6Cgt36gts9XAk"
+            b"FiiuJLW6RU0j3KKVZSs1I7Z3UmU9/9aVh/rZV43WQG8jaR6kkcP4stOR0DEtll"
+            b"PDA7ZRBnrfiHpSQYQ874AZaAoIjgkv7DBfsE6gcDQLub0PFjWyrYQUJhtOLQEK"
+            b"vY/G0vt2iRL3juawWmCFdTK3W3XvwAdgGk71i6lHt+deOPNEPN2H58E4odrZ2f"
+            b"sxn/adpDqfb2sM0kPwQs0aWvrrKGvUaustkivQE4XWiSFnB0oJB/lKK/CKVKuy"
+            b"///ImSCGHQRvhwariN2tvZ6CBNSLh3iQgeB0AkyJlng7MXB2qYq/Ci2FUOryCX"
+            b"2MzHvnbv testkey@localhost"
+        )
 
         key = load_ssh_public_key(ssh_key, backend)