87 lines
2.9 KiB
Python
87 lines
2.9 KiB
Python
#
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# Random/OSRNG/posix.py : OS entropy source for POSIX systems
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#
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# Written in 2008 by Dwayne C. Litzenberger <dlitz@dlitz.net>
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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__revision__ = "$Id$"
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__all__ = ['DevURandomRNG']
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import errno
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import os
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import stat
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from .rng_base import BaseRNG
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from Crypto.Util.py3compat import b
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class DevURandomRNG(BaseRNG):
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def __init__(self, devname=None):
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if devname is None:
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self.name = "/dev/urandom"
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else:
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self.name = devname
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# Test that /dev/urandom is a character special device
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f = open(self.name, "rb", 0)
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fmode = os.fstat(f.fileno())[stat.ST_MODE]
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if not stat.S_ISCHR(fmode):
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f.close()
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raise TypeError("%r is not a character special device" % (self.name,))
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self.__file = f
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BaseRNG.__init__(self)
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def _close(self):
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self.__file.close()
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def _read(self, N):
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# Starting with Python 3 open with buffering=0 returns a FileIO object.
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# FileIO.read behaves like read(2) and not like fread(3) and thus we
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# have to handle the case that read returns less data as requested here
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# more carefully.
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data = b("")
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while len(data) < N:
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try:
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d = self.__file.read(N - len(data))
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except IOError as e:
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# read(2) has been interrupted by a signal; redo the read
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if e.errno == errno.EINTR:
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continue
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raise
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if d is None:
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# __file is in non-blocking mode and no data is available
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return data
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if len(d) == 0:
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# __file is in blocking mode and arrived at EOF
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return data
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data += d
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return data
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def new(*args, **kwargs):
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return DevURandomRNG(*args, **kwargs)
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# vim:set ts=4 sw=4 sts=4 expandtab:
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