# # Random/OSRNG/posix.py : OS entropy source for POSIX systems # # 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__ = "$Id$" __all__ = ['DevURandomRNG'] import errno import os import stat from rng_base import BaseRNG from Crypto.Util.py3compat import b class DevURandomRNG(BaseRNG): def __init__(self, devname=None): if devname is None: self.name = "/dev/urandom" else: self.name = devname # Test that /dev/urandom is a character special device f = open(self.name, "rb", 0) fmode = os.fstat(f.fileno())[stat.ST_MODE] if not stat.S_ISCHR(fmode): f.close() raise TypeError("%r is not a character special device" % (self.name,)) self.__file = f BaseRNG.__init__(self) def _close(self): self.__file.close() def _read(self, N): # Starting with Python 3 open with buffering=0 returns a FileIO object. # FileIO.read behaves like read(2) and not like fread(3) and thus we # have to handle the case that read returns less data as requested here # more carefully. data = b("") while len(data) < N: try: d = self.__file.read(N - len(data)) except IOError, e: # read(2) has been interrupted by a signal; redo the read if e.errno == errno.EINTR: continue raise if d is None: # __file is in non-blocking mode and no data is available return data if len(d) == 0: # __file is in blocking mode and arrived at EOF return data data += d return data def new(*args, **kwargs): return DevURandomRNG(*args, **kwargs) # vim:set ts=4 sw=4 sts=4 expandtab: