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from __future__ import absolute_import
from __future__ import division
import argparse
import six
import string
import sys
import pwnlib.args
pwnlib.args.free_form = False
from pwn import *
from pwnlib.commandline import common
parser = common.parser_commands.add_parser(
'cyclic',
help = "Cyclic pattern creator/finder",
description = "Cyclic pattern creator/finder"
)
parser.add_argument(
'-a', '--alphabet',
metavar = 'alphabet',
default = string.ascii_lowercase.encode(),
type = packing._encode,
help = 'The alphabet to use in the cyclic pattern (defaults to all lower case letters)',
)
parser.add_argument(
'-n', '--length',
metavar = 'length',
default = 4,
type = int,
help = 'Size of the unique subsequences (defaults to 4).'
)
parser.add_argument(
'-c', '--context',
metavar = 'context',
action = 'append',
type = common.context_arg,
choices = common.choices,
help = 'The os/architecture/endianness/bits the shellcode will run in (default: linux/i386), choose from: %s' % common.choices,
)
group = parser.add_mutually_exclusive_group(required=False)
group.add_argument(
'-l', '-o', '--offset', '--lookup',
dest = 'lookup',
metavar = 'lookup_value',
help = 'Do a lookup instead printing the alphabet',
)
group.add_argument(
'count',
type=int,
nargs='?',
default=None,
help='Number of characters to print'
)
def main(args):
alphabet = args.alphabet
subsize = args.length
if args.lookup:
pat = args.lookup
if six.PY3:
pat = bytes(pat, encoding='utf-8')
try:
pat = int(pat, 0)
pat = pack(pat, 'all')
except ValueError:
pass
pat = flat(pat, bytes=args.length)
if len(pat) < subsize:
log.critical('Subpattern must be at least %d bytes' % subsize)
sys.exit(1)
else:
pat = pat[:subsize]
if not all(c in alphabet for c in pat):
log.critical('Pattern contains characters not present in the alphabet')
sys.exit(1)
offset = cyclic_find(pat, alphabet, subsize)
if offset == -1:
log.critical('Given pattern does not exist in cyclic pattern')
sys.exit(1)
else:
print(offset)
else:
want = args.count
result = cyclic(want, alphabet, subsize)
got = len(result)
if want is not None and got < want:
log.failure("Alphabet too small (max length = %i)" % got)
out = getattr(sys.stdout, 'buffer', sys.stdout)
out.write(result)
if out.isatty():
out.write(b'\n')
if __name__ == '__main__':
pwnlib.commandline.common.main(__file__, main)
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