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During interpreter shutdown, depending on the order in which things happen, a module can be unloaded before all instances of classes defined in that module are garbage collected. In particular, this means that any global variables (including imported modules) become `None` by the time the instances `__del__` is called, resulting in ``` AttributeError: 'NoneType' object has no attribute 'wc_FreeRng' ``` being displayed while the process exits. This can be avoided simply by catching and ignoring the `AttributeError` in this case, since the process is shutting down anyways.
73 lines
2.2 KiB
Python
73 lines
2.2 KiB
Python
# random.py
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#
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# Copyright (C) 2006-2016 wolfSSL Inc.
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#
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# This file is part of wolfSSL. (formerly known as CyaSSL)
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#
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# wolfSSL is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# wolfSSL is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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from wolfcrypt._ffi import ffi as _ffi
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from wolfcrypt._ffi import lib as _lib
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from wolfcrypt.utils import t2b
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from wolfcrypt.exceptions import *
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class Random(object):
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"""
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A Cryptographically Secure Pseudo Random Number Generator - CSPRNG
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"""
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def __init__(self):
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self.native_object = _ffi.new("WC_RNG *")
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ret = _lib.wc_InitRng(self.native_object)
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if ret < 0:
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self.native_object = None
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raise WolfCryptError("RNG init error (%d)" % ret)
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def __del__(self):
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if self.native_object:
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try:
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_lib.wc_FreeRng(self.native_object)
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except AttributeError:
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# Can occur during interpreter shutdown
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pass
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def byte(self):
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"""
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Generate and return a random byte.
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"""
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result = _ffi.new('byte[1]')
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ret = _lib.wc_RNG_GenerateByte(self.native_object, result)
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if ret < 0:
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raise WolfCryptError("RNG generate byte error (%d)" % ret)
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return _ffi.buffer(result, 1)[:]
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def bytes(self, length):
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"""
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Generate and return a random sequence of length bytes.
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"""
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result = _ffi.new('byte[%d]' % length)
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ret = _lib.wc_RNG_GenerateBlock(self.native_object, result, length)
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if ret < 0:
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raise WolfCryptError("RNG generate block error (%d)" % ret)
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return _ffi.buffer(result, length)[:]
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