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2be70baa0d
This implements an extended form of primality verification using certificates based on Pocklington's theorem. You make a Pockle object, and then try to convince it that one number after another is prime, by means of providing it with a list of prime factors of p-1 and a primitive root. (Or just by saying 'this prime is small enough for you to check yourself'.) Pocklington's theorem requires you to have factors of p-1 whose product is at least the square root of p. I've extended that to support factorisations only as big as the cube root, via an extension of the theorem given in Maurer's paper on generating provable primes. The Pockle object is more or less write-only: it has no methods for reading out its contents. Its only output channel is the return value when you try to insert a prime into it: if it isn't sufficiently convinced that your prime is prime, it will return an error code. So anything for which it returns POCKLE_OK you can be confident of. I'm going to use this for provable prime generation. But exposing this part of the system as an object in its own right means I can write a set of unit tests for this specifically. My negative tests exercise all the different ways a certification can be erroneous or inadequate; the positive tests include proofs of primality of various primes used in elliptic-curve crypto. The Poly1305 proof in particular is taken from a proof in DJB's paper, which has exactly the form of a Pocklington certificate only written in English.
324 lines
12 KiB
Python
324 lines
12 KiB
Python
import sys
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import os
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import numbers
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import subprocess
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import re
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import struct
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from binascii import hexlify
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# Expect to be run from the 'test' subdirectory, one level down from
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# the main source
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putty_srcdir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
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def unicode_to_bytes(arg):
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# Slightly fiddly way to do this which should work in Python 2 and 3
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if isinstance(arg, type(u'a')) and not isinstance(arg, type(b'a')):
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arg = arg.encode("UTF-8")
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return arg
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def bytevals(b):
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return struct.unpack("{:d}B".format(len(b)), b)
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def valbytes(b):
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b = list(b)
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return struct.pack("{:d}B".format(len(b)), *b)
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class ChildProcessFailure(Exception):
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pass
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class ChildProcess(object):
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def __init__(self):
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self.sp = None
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self.debug = None
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self.exitstatus = None
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self.exception = None
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dbg = os.environ.get("PUTTY_TESTCRYPT_DEBUG")
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if dbg is not None:
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if dbg == "stderr":
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self.debug = sys.stderr
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else:
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sys.stderr.write("Unknown value '{}' for PUTTY_TESTCRYPT_DEBUG"
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" (try 'stderr'\n")
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def start(self):
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assert self.sp is None
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override_command = os.environ.get("PUTTY_TESTCRYPT")
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if override_command is None:
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cmd = [os.path.join(putty_srcdir, "testcrypt")]
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shell = False
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else:
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cmd = override_command
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shell = True
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self.sp = subprocess.Popen(
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cmd, shell=shell, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
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def write_line(self, line):
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if self.exception is not None:
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# Re-raise our fatal-error exception, if it previously
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# occurred in a context where it couldn't be propagated (a
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# __del__ method).
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raise self.exception
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if self.debug is not None:
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self.debug.write("send: {}\n".format(line))
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self.sp.stdin.write(line + b"\n")
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self.sp.stdin.flush()
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def read_line(self):
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line = self.sp.stdout.readline()
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if len(line) == 0:
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self.exception = ChildProcessFailure("received EOF from testcrypt")
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raise self.exception
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line = line.rstrip(b"\r\n")
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if self.debug is not None:
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self.debug.write("recv: {}\n".format(line))
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return line
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def already_terminated(self):
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return self.sp is None and self.exitstatus is not None
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def funcall(self, cmd, args):
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if self.sp is None:
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assert self.exitstatus is None
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self.start()
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self.write_line(unicode_to_bytes(cmd) + b" " + b" ".join(
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unicode_to_bytes(arg) for arg in args))
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argcount = int(self.read_line())
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return [self.read_line() for arg in range(argcount)]
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def wait_for_exit(self):
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if self.sp is not None:
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self.sp.stdin.close()
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self.exitstatus = self.sp.wait()
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self.sp = None
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def check_return_status(self):
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self.wait_for_exit()
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if self.exitstatus is not None and self.exitstatus != 0:
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raise ChildProcessFailure("testcrypt returned exit status {}"
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.format(self.exitstatus))
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childprocess = ChildProcess()
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method_prefixes = {
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'val_wpoint': 'ecc_weierstrass_',
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'val_mpoint': 'ecc_montgomery_',
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'val_epoint': 'ecc_edwards_',
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'val_hash': 'ssh_hash_',
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'val_mac': 'ssh_mac_',
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'val_key': 'ssh_key_',
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'val_cipher': 'ssh_cipher_',
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'val_dh': 'dh_',
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'val_ecdh': 'ssh_ecdhkex_',
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'val_rsakex': 'ssh_rsakex_',
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'val_prng': 'prng_',
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'val_pcs': 'pcs_',
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'val_pockle': 'pockle_',
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}
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method_lists = {t: [] for t in method_prefixes}
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class Value(object):
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def __init__(self, typename, ident):
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self._typename = typename
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self._ident = ident
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for methodname, function in method_lists.get(self._typename, []):
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setattr(self, methodname,
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(lambda f: lambda *args: f(self, *args))(function))
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def _consumed(self):
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self._ident = None
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def __repr__(self):
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return "Value({!r}, {!r})".format(self._typename, self._ident)
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def __del__(self):
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if self._ident is not None and not childprocess.already_terminated():
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try:
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childprocess.funcall("free", [self._ident])
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except ChildProcessFailure:
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# If we see this exception now, we can't do anything
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# about it, because exceptions don't propagate out of
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# __del__ methods. Squelch it to prevent the annoying
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# runtime warning from Python, and the
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# 'self.exception' mechanism in the ChildProcess class
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# will raise it again at the next opportunity.
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#
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# (This covers both the case where testcrypt crashes
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# _during_ one of these free operations, and the
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# silencing of cascade failures when we try to send a
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# "free" command to testcrypt after it had already
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# crashed for some other reason.)
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pass
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def __long__(self):
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if self._typename != "val_mpint":
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raise TypeError("testcrypt values of types other than mpint"
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" cannot be converted to integer")
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hexval = childprocess.funcall("mp_dump", [self._ident])[0]
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return 0 if len(hexval) == 0 else int(hexval, 16)
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def __int__(self):
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return int(self.__long__())
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def make_argword(arg, argtype, fnname, argindex, to_preserve):
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typename, consumed = argtype
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if typename.startswith("opt_"):
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if arg is None:
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return "NULL"
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typename = typename[4:]
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if typename == "val_string":
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arg = unicode_to_bytes(arg)
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if isinstance(arg, bytes):
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retwords = childprocess.funcall(
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"newstring", ["".join("%{:02x}".format(b)
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for b in bytevals(arg))])
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arg = make_retvals([typename], retwords, unpack_strings=False)[0]
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to_preserve.append(arg)
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if typename == "val_mpint" and isinstance(arg, numbers.Integral):
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retwords = childprocess.funcall("mp_literal", ["0x{:x}".format(arg)])
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arg = make_retvals([typename], retwords)[0]
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to_preserve.append(arg)
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if isinstance(arg, Value):
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if arg._typename != typename:
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raise TypeError(
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"{}() argument {:d} should be {} ({} given)".format(
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fnname, argindex, typename, arg._typename))
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ident = arg._ident
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if consumed:
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arg._consumed()
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return ident
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if typename == "uint" and isinstance(arg, numbers.Integral):
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return "0x{:x}".format(arg)
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if typename in {
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"hashalg", "macalg", "keyalg", "cipheralg",
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"dh_group", "ecdh_alg", "rsaorder", "primegenpolicy"}:
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arg = unicode_to_bytes(arg)
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if isinstance(arg, bytes) and b" " not in arg:
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return arg
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if typename == "mpint_list":
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sublist = [make_argword(len(arg), ("uint", False),
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fnname, argindex, to_preserve)]
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for val in arg:
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sublist.append(make_argword(val, ("val_mpint", False),
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fnname, argindex, to_preserve))
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return b" ".join(unicode_to_bytes(sub) for sub in sublist)
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raise TypeError(
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"Can't convert {}() argument {:d} to {} (value was {!r})".format(
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fnname, argindex, typename, arg))
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def unpack_string(identifier):
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retwords = childprocess.funcall("getstring", [identifier])
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childprocess.funcall("free", [identifier])
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return re.sub(b"%[0-9A-F][0-9A-F]",
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lambda m: valbytes([int(m.group(0)[1:], 16)]),
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retwords[0])
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def unpack_mp(identifier):
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retwords = childprocess.funcall("mp_dump", [identifier])
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childprocess.funcall("free", [identifier])
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return int(retwords[0], 16)
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def make_retval(rettype, word, unpack_strings):
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if rettype.startswith("opt_"):
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if word == b"NULL":
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return None
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rettype = rettype[4:]
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if rettype == "val_string" and unpack_strings:
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return unpack_string(word)
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if rettype == "val_keycomponents":
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kc = {}
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retwords = childprocess.funcall("key_components_count", [word])
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for i in range(int(retwords[0], 0)):
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args = [word, "{:d}".format(i)]
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retwords = childprocess.funcall("key_components_nth_name", args)
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kc_key = unpack_string(retwords[0])
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retwords = childprocess.funcall("key_components_nth_str", args)
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if retwords[0] != b"NULL":
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kc_value = unpack_string(retwords[0]).decode("ASCII")
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else:
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retwords = childprocess.funcall("key_components_nth_mp", args)
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kc_value = unpack_mp(retwords[0])
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kc[kc_key.decode("ASCII")] = kc_value
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childprocess.funcall("free", [word])
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return kc
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if rettype.startswith("val_"):
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return Value(rettype, word)
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elif rettype == "int" or rettype == "uint":
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return int(word, 0)
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elif rettype == "boolean":
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assert word == b"true" or word == b"false"
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return word == b"true"
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elif rettype == "pocklestatus":
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return word.decode("ASCII")
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raise TypeError("Can't deal with return value {!r} of type {!r}"
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.format(word, rettype))
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def make_retvals(rettypes, retwords, unpack_strings=True):
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assert len(rettypes) == len(retwords) # FIXME: better exception
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return [make_retval(rettype, word, unpack_strings)
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for rettype, word in zip(rettypes, retwords)]
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class Function(object):
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def __init__(self, fnname, rettypes, argtypes):
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self.fnname = fnname
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self.rettypes = rettypes
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self.argtypes = argtypes
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def __repr__(self):
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return "<Function {}>".format(self.fnname)
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def __call__(self, *args):
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if len(args) != len(self.argtypes):
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raise TypeError(
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"{}() takes exactly {} arguments ({} given)".format(
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self.fnname, len(self.argtypes), len(args)))
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to_preserve = []
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retwords = childprocess.funcall(
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self.fnname, [make_argword(args[i], self.argtypes[i],
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self.fnname, i, to_preserve)
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for i in range(len(args))])
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retvals = make_retvals(self.rettypes, retwords)
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if len(retvals) == 0:
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return None
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if len(retvals) == 1:
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return retvals[0]
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return tuple(retvals)
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def _setup(scope):
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header_file = os.path.join(putty_srcdir, "testcrypt.h")
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linere = re.compile(r'^FUNC\d+\((.*)\)$')
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valprefix = "val_"
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outprefix = "out_"
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optprefix = "opt_"
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consprefix = "consumed_"
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def trim_argtype(arg):
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if arg.startswith(optprefix):
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return optprefix + trim_argtype(arg[len(optprefix):])
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if (arg.startswith(valprefix) and
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"_" in arg[len(valprefix):]):
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# Strip suffixes like val_string_asciz
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arg = arg[:arg.index("_", len(valprefix))]
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return arg
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with open(header_file) as f:
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for line in iter(f.readline, ""):
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line = line.rstrip("\r\n").replace(" ", "")
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m = linere.match(line)
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if m is not None:
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words = m.group(1).split(",")
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function = words[1]
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rettypes = []
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argtypes = []
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argsconsumed = []
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if words[0] != "void":
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rettypes.append(trim_argtype(words[0]))
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for arg in words[2:]:
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if arg.startswith(outprefix):
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rettypes.append(trim_argtype(arg[len(outprefix):]))
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else:
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consumed = False
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if arg.startswith(consprefix):
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arg = arg[len(consprefix):]
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consumed = True
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arg = trim_argtype(arg)
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argtypes.append((arg, consumed))
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func = Function(function, rettypes, argtypes)
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scope[function] = func
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if len(argtypes) > 0:
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t = argtypes[0][0]
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if (t in method_prefixes and
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function.startswith(method_prefixes[t])):
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methodname = function[len(method_prefixes[t]):]
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method_lists[t].append((methodname, func))
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_setup(globals())
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del _setup
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