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