Remove third_party/twisted_8_1

third_party/twisted_8_1/twisted/python/randbytes.py

-# -*- test-case-name: twisted.test.test_randbytes -*-
-# Copyright (c) 2007 Twisted Matrix Laboratories.
-# See LICENSE for details.
-
-"""
-Cryptographically secure random implementation, with fallback on normal random.
-"""
-
-# System imports
-import warnings, os, random
-
-getrandbits = getattr(random, 'getrandbits', None)
-
-try:
-    from Crypto.Util import randpool
-except ImportError:
-    randpool = None
-
-
-
-class SecureRandomNotAvailable(RuntimeError):
-    """
-    Exception raised when no secure random algorithm is found.
-    """
-
-
-
-class SourceNotAvailable(RuntimeError):
-    """
-    Internal exception used when a specific random source is not available.
-    """
-
-
-
-class RandomFactory(object):
-    """
-    Factory providing L{secureRandom} and L{insecureRandom} methods.
-
-    You shouldn't have to instantiate this class, use the module level
-    functions instead: it is an implementation detail and could be removed or
-    changed arbitrarily.
-
-    @ivar randomPool: pool of random data.
-    @type randomPool: C{randpool.RandomPool}
-
-    @cvar randomSources: list of file sources used when os.urandom is not
-        available.
-    @type randomSources: C{tuple}
-    """
-    randpool = randpool
-    randomPool = None
-    randomSources = ('/dev/urandom',)
-    getrandbits = getrandbits
-
-
-    def _osUrandom(self, nbytes):
-        """
-        Wrapper around C{os.urandom} that cleanly manage its absence.
-        """
-        try:
-            return os.urandom(nbytes)
-        except (AttributeError, NotImplementedError), e:
-            raise SourceNotAvailable(e)
-
-
-    def _fileUrandom(self, nbytes):
-        """
-        Wrapper around random file sources.
-
-        This method isn't meant to be call out of the class and could be
-        removed arbitrarily.
-        """
-        for src in self.randomSources:
-            try:
-                f = file(src, 'rb')
-            except (IOError, OSError):
-                pass
-            else:
-                bytes = f.read(nbytes)
-                f.close()
-                return bytes
-        raise SourceNotAvailable("File sources not available: %s" %
-                                 (self.randomSources,))
-
-
-    def _cryptoRandom(self, nbytes):
-        """
-        Wrapper around Crypo random pool.
-        """
-        if self.randpool is not None:
-            if self.randomPool is None:
-                self.randomPool = self.randpool.RandomPool()
-                self.randomPool.stir()
-            return self.randomPool.get_bytes(nbytes)
-        raise SourceNotAvailable("PyCrypto isn't installed")
-
-
-    def secureRandom(self, nbytes, fallback=False):
-        """
-        Return a number of secure random bytes.
-
-        @param nbytes: number of bytes to generate.
-        @type nbytes: C{int}.
-        @param fallback: whether the function should fallback on non secure
-            random or not. Default to C{false}.
-        @type fallback: C{bool}
-
-        @return: a string of random bytes.
-        @rtype: C{str}.
-        """
-        for src in ("_osUrandom", "_fileUrandom", "_cryptoRandom"):
-            try:
-                return getattr(self, src)(nbytes)
-            except SourceNotAvailable:
-                pass
-        if fallback:
-            warnings.warn(
-                "Neither PyCrypto nor urandom available - "
-                "proceeding with non-cryptographically secure random source",
-                category=RuntimeWarning,
-                stacklevel=2
-            )
-            return self.insecureRandom(nbytes)
-        else:
-            raise SecureRandomNotAvailable("No secure random source available")
-
-
-    def _randBits(self, nbytes):
-        """
-        Wrapper around C{os.getrandbits}.
-        """
-        if self.getrandbits is not None:
-            n = self.getrandbits(nbytes * 8)
-            hexBytes = ("%%0%dx" % (nbytes * 2)) % n
-            return hexBytes.decode('hex')
-        raise SourceNotAvailable("random.getrandbits is not available")
-
-
-    def _randRange(self, nbytes):
-        """
-        Wrapper around C{random.randrange}.
-        """
-        bytes = ""
-        for i in xrange(nbytes):
-            bytes += chr(random.randrange(0, 255))
-        return bytes
-
-
-    def insecureRandom(self, nbytes):
-        """
-        Return a number of non secure random bytes.
-
-        @param nbytes: number of bytes to generate.
-        @type nbytes: C{int}.
-
-        @return: a string of random bytes.
-        @rtype: C{str}.
-        """
-        for src in ("_randBits", "_randRange"):
-            try:
-                return getattr(self, src)(nbytes)
-            except SourceNotAvailable:
-                pass
-
-
-
-factory = RandomFactory()
-
-secureRandom = factory.secureRandom
-
-insecureRandom = factory.insecureRandom
-
-del factory
-
-
-__all__ = ["secureRandom", "insecureRandom", "SecureRandomNotAvailable"]
-