180 lines
4.5 KiB
Python
180 lines
4.5 KiB
Python
"""
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PRNG management routines, thin wrappers.
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See the file RATIONALE for a short explanation of why this module was written.
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"""
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from functools import partial
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from six import integer_types as _integer_types
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from OpenSSL._util import (
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ffi as _ffi,
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lib as _lib,
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exception_from_error_queue as _exception_from_error_queue)
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class Error(Exception):
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"""
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An error occurred in an `OpenSSL.rand` API.
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"""
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_raise_current_error = partial(_exception_from_error_queue, Error)
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_unspecified = object()
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_builtin_bytes = bytes
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def bytes(num_bytes):
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"""
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Get some random bytes as a string.
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:param num_bytes: The number of bytes to fetch
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:return: A string of random bytes
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"""
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if not isinstance(num_bytes, _integer_types):
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raise TypeError("num_bytes must be an integer")
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if num_bytes < 0:
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raise ValueError("num_bytes must not be negative")
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result_buffer = _ffi.new("char[]", num_bytes)
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result_code = _lib.RAND_bytes(result_buffer, num_bytes)
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if result_code == -1:
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# TODO: No tests for this code path. Triggering a RAND_bytes failure
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# might involve supplying a custom ENGINE? That's hard.
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_raise_current_error()
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return _ffi.buffer(result_buffer)[:]
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def add(buffer, entropy):
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"""
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Add data with a given entropy to the PRNG
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:param buffer: Buffer with random data
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:param entropy: The entropy (in bytes) measurement of the buffer
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:return: None
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"""
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if not isinstance(buffer, _builtin_bytes):
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raise TypeError("buffer must be a byte string")
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if not isinstance(entropy, int):
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raise TypeError("entropy must be an integer")
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# TODO Nothing tests this call actually being made, or made properly.
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_lib.RAND_add(buffer, len(buffer), entropy)
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def seed(buffer):
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"""
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Alias for rand_add, with entropy equal to length
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:param buffer: Buffer with random data
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:return: None
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"""
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if not isinstance(buffer, _builtin_bytes):
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raise TypeError("buffer must be a byte string")
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# TODO Nothing tests this call actually being made, or made properly.
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_lib.RAND_seed(buffer, len(buffer))
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def status():
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"""
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Retrieve the status of the PRNG
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:return: True if the PRNG is seeded enough, false otherwise
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"""
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return _lib.RAND_status()
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def egd(path, bytes=_unspecified):
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"""
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Query an entropy gathering daemon (EGD) for random data and add it to the
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PRNG. I haven't found any problems when the socket is missing, the function
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just returns 0.
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:param path: The path to the EGD socket
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:param bytes: (optional) The number of bytes to read, default is 255
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:returns: The number of bytes read (NB: a value of 0 isn't necessarily an
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error, check rand.status())
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"""
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if not isinstance(path, _builtin_bytes):
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raise TypeError("path must be a byte string")
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if bytes is _unspecified:
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bytes = 255
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elif not isinstance(bytes, int):
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raise TypeError("bytes must be an integer")
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return _lib.RAND_egd_bytes(path, bytes)
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def cleanup():
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"""
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Erase the memory used by the PRNG.
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:return: None
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"""
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# TODO Nothing tests this call actually being made, or made properly.
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_lib.RAND_cleanup()
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def load_file(filename, maxbytes=_unspecified):
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"""
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Seed the PRNG with data from a file
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:param filename: The file to read data from
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:param maxbytes: (optional) The number of bytes to read, default is
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to read the entire file
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:return: The number of bytes read
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"""
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if not isinstance(filename, _builtin_bytes):
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raise TypeError("filename must be a string")
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if maxbytes is _unspecified:
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maxbytes = -1
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elif not isinstance(maxbytes, int):
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raise TypeError("maxbytes must be an integer")
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return _lib.RAND_load_file(filename, maxbytes)
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def write_file(filename):
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"""
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Save PRNG state to a file
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:param filename: The file to write data to
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:return: The number of bytes written
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"""
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if not isinstance(filename, _builtin_bytes):
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raise TypeError("filename must be a string")
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return _lib.RAND_write_file(filename)
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# TODO There are no tests for screen at all
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def screen():
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"""
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Add the current contents of the screen to the PRNG state. Availability:
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Windows.
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:return: None
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"""
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_lib.RAND_screen()
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if getattr(_lib, 'RAND_screen', None) is None:
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del screen
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# TODO There are no tests for the RAND strings being loaded, whatever that
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# means.
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_lib.ERR_load_RAND_strings()
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