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245 lines
6.7 KiB
245 lines
6.7 KiB
3 years ago
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"""
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passlib.crypto._md4 -- fallback implementation of MD4
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Helper implementing insecure and obsolete md4 algorithm.
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used for NTHASH format, which is also insecure and broken,
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since it's just md4(password).
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Implementated based on rfc at http://www.faqs.org/rfcs/rfc1320.html
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.. note::
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This shouldn't be imported directly, it's merely used conditionally
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by ``passlib.crypto.lookup_hash()`` when a native implementation can't be found.
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"""
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#=============================================================================
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# imports
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#=============================================================================
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# core
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from binascii import hexlify
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import struct
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# site
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from passlib.utils.compat import bascii_to_str, irange, PY3
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# local
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__all__ = ["md4"]
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#=============================================================================
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# utils
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#=============================================================================
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def F(x,y,z):
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return (x&y) | ((~x) & z)
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def G(x,y,z):
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return (x&y) | (x&z) | (y&z)
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##def H(x,y,z):
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## return x ^ y ^ z
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MASK_32 = 2**32-1
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#=============================================================================
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# main class
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#=============================================================================
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class md4(object):
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"""pep-247 compatible implementation of MD4 hash algorithm
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.. attribute:: digest_size
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size of md4 digest in bytes (16 bytes)
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.. method:: update
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update digest by appending additional content
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.. method:: copy
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create clone of digest object, including current state
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.. method:: digest
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return bytes representing md4 digest of current content
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.. method:: hexdigest
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return hexadecimal version of digest
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"""
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# FIXME: make this follow hash object PEP better.
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# FIXME: this isn't threadsafe
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name = "md4"
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digest_size = digestsize = 16
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block_size = 64
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_count = 0 # number of 64-byte blocks processed so far (not including _buf)
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_state = None # list of [a,b,c,d] 32 bit ints used as internal register
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_buf = None # data processed in 64 byte blocks, this holds leftover from last update
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def __init__(self, content=None):
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self._count = 0
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self._state = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476]
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self._buf = b''
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if content:
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self.update(content)
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# round 1 table - [abcd k s]
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_round1 = [
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[0,1,2,3, 0,3],
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[3,0,1,2, 1,7],
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[2,3,0,1, 2,11],
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[1,2,3,0, 3,19],
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[0,1,2,3, 4,3],
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[3,0,1,2, 5,7],
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[2,3,0,1, 6,11],
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[1,2,3,0, 7,19],
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[0,1,2,3, 8,3],
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[3,0,1,2, 9,7],
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[2,3,0,1, 10,11],
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[1,2,3,0, 11,19],
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[0,1,2,3, 12,3],
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[3,0,1,2, 13,7],
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[2,3,0,1, 14,11],
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[1,2,3,0, 15,19],
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]
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# round 2 table - [abcd k s]
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_round2 = [
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[0,1,2,3, 0,3],
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[3,0,1,2, 4,5],
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[2,3,0,1, 8,9],
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[1,2,3,0, 12,13],
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[0,1,2,3, 1,3],
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[3,0,1,2, 5,5],
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[2,3,0,1, 9,9],
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[1,2,3,0, 13,13],
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[0,1,2,3, 2,3],
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[3,0,1,2, 6,5],
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[2,3,0,1, 10,9],
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[1,2,3,0, 14,13],
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[0,1,2,3, 3,3],
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[3,0,1,2, 7,5],
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[2,3,0,1, 11,9],
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[1,2,3,0, 15,13],
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]
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# round 3 table - [abcd k s]
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_round3 = [
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[0,1,2,3, 0,3],
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[3,0,1,2, 8,9],
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[2,3,0,1, 4,11],
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[1,2,3,0, 12,15],
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[0,1,2,3, 2,3],
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[3,0,1,2, 10,9],
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[2,3,0,1, 6,11],
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[1,2,3,0, 14,15],
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[0,1,2,3, 1,3],
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[3,0,1,2, 9,9],
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[2,3,0,1, 5,11],
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[1,2,3,0, 13,15],
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[0,1,2,3, 3,3],
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[3,0,1,2, 11,9],
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[2,3,0,1, 7,11],
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[1,2,3,0, 15,15],
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]
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def _process(self, block):
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"""process 64 byte block"""
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# unpack block into 16 32-bit ints
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X = struct.unpack("<16I", block)
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# clone state
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orig = self._state
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state = list(orig)
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# round 1 - F function - (x&y)|(~x & z)
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for a,b,c,d,k,s in self._round1:
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t = (state[a] + F(state[b],state[c],state[d]) + X[k]) & MASK_32
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state[a] = ((t<<s) & MASK_32) + (t>>(32-s))
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# round 2 - G function
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for a,b,c,d,k,s in self._round2:
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t = (state[a] + G(state[b],state[c],state[d]) + X[k] + 0x5a827999) & MASK_32
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state[a] = ((t<<s) & MASK_32) + (t>>(32-s))
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# round 3 - H function - x ^ y ^ z
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for a,b,c,d,k,s in self._round3:
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t = (state[a] + (state[b] ^ state[c] ^ state[d]) + X[k] + 0x6ed9eba1) & MASK_32
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state[a] = ((t<<s) & MASK_32) + (t>>(32-s))
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# add back into original state
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for i in irange(4):
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orig[i] = (orig[i]+state[i]) & MASK_32
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def update(self, content):
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if not isinstance(content, bytes):
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if PY3:
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raise TypeError("expected bytes")
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else:
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# replicate behavior of hashlib under py2
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content = content.encode("ascii")
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buf = self._buf
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if buf:
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content = buf + content
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idx = 0
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end = len(content)
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while True:
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next = idx + 64
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if next <= end:
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self._process(content[idx:next])
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self._count += 1
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idx = next
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else:
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self._buf = content[idx:]
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return
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def copy(self):
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other = md4()
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other._count = self._count
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other._state = list(self._state)
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other._buf = self._buf
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return other
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def digest(self):
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# NOTE: backing up state so we can restore it after _process is called,
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# in case object is updated again (this is only attr altered by this method)
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orig = list(self._state)
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# final block: buf + 0x80,
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# then 0x00 padding until congruent w/ 56 mod 64 bytes
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# then last 8 bytes = msg length in bits
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buf = self._buf
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msglen = self._count*512 + len(buf)*8
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block = buf + b'\x80' + b'\x00' * ((119-len(buf)) % 64) + \
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struct.pack("<2I", msglen & MASK_32, (msglen>>32) & MASK_32)
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if len(block) == 128:
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self._process(block[:64])
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self._process(block[64:])
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else:
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assert len(block) == 64
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self._process(block)
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# render digest & restore un-finalized state
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out = struct.pack("<4I", *self._state)
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self._state = orig
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return out
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def hexdigest(self):
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return bascii_to_str(hexlify(self.digest()))
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#===================================================================
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# eoc
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#===================================================================
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#=============================================================================
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# eof
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#=============================================================================
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