Implement AES-GCM in tlslite.

third_party/tlslite/tlslite/handshakesettings.py

 # Authors: 
 #   Trevor Perrin
 #   Dave Baggett (Arcode Corporation) - cleanup handling of constants
 #   Yngve Pettersen (ported by Paul Sokolovsky) - TLS 1.2
 #
 # See the LICENSE file for legal information regarding use of this file.
 
 """Class for setting handshake parameters."""
 
 from .constants import CertificateType
 from .utils import cryptomath
 from .utils import cipherfactory
 
-# RC4 is preferred as faster in Python, works in SSL3, and immune to CBC
-# issues such as timing attacks

[davidben, 2015/01/25 02:43:41]

This and similar comments removed because I'm pretty sure they're false. The
order of the parameters in HandshakeSettings doesn't actually do anything, as
far as I can tell.

-CIPHER_NAMES = ["rc4", "aes256", "aes128", "3des"]
-MAC_NAMES = ["sha", "sha256"] # Don't allow "md5" by default.
-ALL_MAC_NAMES = ["sha", "sha256", "md5"]
+CIPHER_NAMES = ["aes128gcm", "rc4", "aes256", "aes128", "3des"]
+MAC_NAMES = ["sha", "sha256", "aead"] # Don't allow "md5" by default.
+ALL_MAC_NAMES = MAC_NAMES + ["md5"]
 KEY_EXCHANGE_NAMES = ["rsa", "dhe_rsa", "srp_sha", "srp_sha_rsa", "dh_anon"]
 CIPHER_IMPLEMENTATIONS = ["openssl", "pycrypto", "python"]
 CERTIFICATE_TYPES = ["x509"]
 TLS_INTOLERANCE_TYPES = ["alert", "close", "reset"]
 
 class HandshakeSettings(object):
     """This class encapsulates various parameters that can be used with
     a TLS handshake.
     @sort: minKeySize, maxKeySize, cipherNames, macNames, certificateTypes,
     minVersion, maxVersion
 
     @type minKeySize: int
     @ivar minKeySize: The minimum bit length for asymmetric keys.
 
     If the other party tries to use SRP, RSA, or Diffie-Hellman
     parameters smaller than this length, an alert will be
     signalled.  The default is 1023.
 
     @type maxKeySize: int
     @ivar maxKeySize: The maximum bit length for asymmetric keys.
 
     If the other party tries to use SRP, RSA, or Diffie-Hellman
     parameters larger than this length, an alert will be signalled.
     The default is 8193.
 
     @type cipherNames: list
-    @ivar cipherNames: The allowed ciphers, in order of preference.
+    @ivar cipherNames: The allowed ciphers.
 
     The allowed values in this list are 'aes256', 'aes128', '3des', and
     'rc4'.  If these settings are used with a client handshake, they
     determine the order of the ciphersuites offered in the ClientHello
     message.
 
     If these settings are used with a server handshake, the server will
     choose whichever ciphersuite matches the earliest entry in this
     list.
 
     NOTE:  If '3des' is used in this list, but TLS Lite can't find an
     add-on library that supports 3DES, then '3des' will be silently
     removed.
 
     The default value is ['rc4', 'aes256', 'aes128', '3des'].
 
     @type macNames: list
     @ivar macNames: The allowed MAC algorithms.
     
     The allowed values in this list are 'sha' and 'md5'.
     
     The default value is ['sha'].
 
 
     @type certificateTypes: list
-    @ivar certificateTypes: The allowed certificate types, in order of
-    preference.
+    @ivar certificateTypes: The allowed certificate types.
 
     The only allowed certificate type is 'x509'.  This list is only used with a
     client handshake.  The client will advertise to the server which certificate
     types are supported, and will check that the server uses one of the
     appropriate types.
 
 
     @type minVersion: tuple
     @ivar minVersion: The minimum allowed SSL/TLS version.
 
@@ skipping 107 matching lines @@
 
         if other.minVersion > other.maxVersion:
             raise ValueError("Versions set incorrectly")
 
         if not other.minVersion in ((3,0), (3,1), (3,2), (3,3)):
             raise ValueError("minVersion set incorrectly")
 
         if not other.maxVersion in ((3,0), (3,1), (3,2), (3,3)):
             raise ValueError("maxVersion set incorrectly")
 
-        if other.maxVersion < (3,3):
-            # No sha256 pre TLS 1.2
-            other.macNames = [e for e in self.macNames if e != "sha256"]

[davidben, 2015/01/25 02:43:41]

Moved to constants.py to handle the server end too.

-
         return other
 
     def _getCertificateTypes(self):
         l = []
         for ct in self.certificateTypes:
             if ct == "x509":
                 l.append(CertificateType.x509)
             else:
                 raise AssertionError()
         return l