Add google-endpoints to third_party/.

third_party/google-endpoints/Crypto/Random/OSRNG/nt.py

+#
+#  Random/OSRNG/nt.py : OS entropy source for MS Windows
+#
+# Written in 2008 by Dwayne C. Litzenberger <dlitz@dlitz.net>
+#
+# ===================================================================
+# The contents of this file are dedicated to the public domain.  To
+# the extent that dedication to the public domain is not available,
+# everyone is granted a worldwide, perpetual, royalty-free,
+# non-exclusive license to exercise all rights associated with the
+# contents of this file for any purpose whatsoever.
+# No rights are reserved.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# ===================================================================
+
+
+__revision__ = "$Id$"
+__all__ = ['WindowsRNG']
+
+import winrandom
+from rng_base import BaseRNG
+
+class WindowsRNG(BaseRNG):
+
+    name = "<CryptGenRandom>"
+
+    def __init__(self):
+        self.__winrand = winrandom.new()
+        BaseRNG.__init__(self)
+
+    def flush(self):
+        """Work around weakness in Windows RNG.
+
+        The CryptGenRandom mechanism in some versions of Windows allows an
+        attacker to learn 128 KiB of past and future output.  As a workaround,
+        this function reads 128 KiB of 'random' data from Windows and discards
+        it.
+
+        For more information about the weaknesses in CryptGenRandom, see
+        _Cryptanalysis of the Random Number Generator of the Windows Operating
+        System_, by Leo Dorrendorf and Zvi Gutterman and Benny Pinkas
+        http://eprint.iacr.org/2007/419
+        """
+        if self.closed:
+            raise ValueError("I/O operation on closed file")
+        data = self.__winrand.get_bytes(128*1024)
+        assert (len(data) == 128*1024)
+        BaseRNG.flush(self)
+
+    def _close(self):
+        self.__winrand = None
+
+    def _read(self, N):
+        # Unfortunately, research shows that CryptGenRandom doesn't provide
+        # forward secrecy and fails the next-bit test unless we apply a
+        # workaround, which we do here.  See http://eprint.iacr.org/2007/419
+        # for information on the vulnerability.
+        self.flush()
+        data = self.__winrand.get_bytes(N)
+        self.flush()
+        return data
+
+def new(*args, **kwargs):
+    return WindowsRNG(*args, **kwargs)
+
+# vim:set ts=4 sw=4 sts=4 expandtab: