# # Random/OSRNG/rng_base.py : Base class for OSRNG # # Written in 2008 by Dwayne C. Litzenberger # # =================================================================== # 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__ = "$Id$" import sys if sys.version_info[0] == 2 and sys.version_info[1] == 1: from Crypto.Util.py21compat import * class BaseRNG(object): def __init__(self): self.closed = False self._selftest() def __del__(self): self.close() def _selftest(self): # Test that urandom can return data data = self.read(16) if len(data) != 16: raise AssertionError("read truncated") # Test that we get different data every time (if we don't, the RNG is # probably malfunctioning) data2 = self.read(16) if data == data2: raise AssertionError("OS RNG returned duplicate data") # PEP 343: Support for the "with" statement def __enter__(self): pass def __exit__(self): """PEP 343 support""" self.close() def close(self): if not self.closed: self._close() self.closed = True def flush(self): pass def read(self, N=-1): """Return N bytes from the RNG.""" if self.closed: raise ValueError("I/O operation on closed file") if not isinstance(N, int): raise TypeError("an integer is required") if N < 0: raise ValueError("cannot read to end of infinite stream") elif N == 0: return "" data = self._read(N) if len(data) != N: raise AssertionError("%s produced truncated output (requested %d, got %d)" % (self.name, N, len(data))) return data def _close(self): raise NotImplementedError("child class must implement this") def _read(self, N): raise NotImplementedError("child class must implement this") # vim:set ts=4 sw=4 sts=4 expandtab: