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59 lines
1.8 KiB
Python
59 lines
1.8 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2014 IBM Corporation
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# Various utility functions that do not neatly fit into one category or another
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import base64
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import os
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import struct
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def randomstring(length=20):
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"""Generate a random string of requested length
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:param length: The number of characters to produce, defaults to 20
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"""
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chunksize = length / 4
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if length % 4 > 0:
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chunksize += 1
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strval = base64.urlsafe_b64encode(os.urandom(chunksize * 3))
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return strval[0:length-1]
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def securerandomnumber(low=0, high=4294967295):
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"""Return a random number within requested range
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Note that this function will not return smaller than 0 nor larger
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than 2^32-1 no matter what is requested.
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The python random number facility does not provide characteristics
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appropriate for secure rng, go to os.urandom
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:param low: Smallest number to return (defaults to 0)
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:param high: largest number to return (defaults to 2^32-1)
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"""
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number = -1
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while number < low or number > high:
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number = struct.unpack("I", os.urandom(4))[0]
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return number
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def monotonic_time():
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"""Return a monotoc time value
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In scenarios like timeouts and such, monotonic timing is preferred.
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"""
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# for now, just support POSIX systems
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return os.times()[4]
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