gpgparticipants/fillinsha256sum.py

   1 #!/usr/bin/env python2
   2
   3 __author__ = "Stefan Huber <shuber@sthu.org>"
   4
   5 import sys
   6 import hashlib
   7 import getopt
   8
   9
  10 def insertspaces(s):
  11     """Inserts a space after every 4-th character, and three spaces after every
  12     8-th character of string s."""
  13
  14     def inpacks(s, n):
  15         while len(s) > 0:
  16             yield s[0:n]
  17             s = s[n:]
  18
  19     out = "   ".join([ " ".join(inpacks(octp, 4)) for octp in inpacks(s, 8)])
  20     return out
  21
  22
  23 def range_hex(length):
  24     """Give all hex-strings from 00...0 until ff...f of given length."""
  25
  26     if length == 0:
  27         yield ""
  28
  29     elif length == 1:
  30         for c in "0123456789abcdef":
  31             yield c
  32     elif length > 1:
  33         for prefix in range_hex(length-1):
  34             for postfix in range_hex(1):
  35                 yield prefix + postfix
  36
  37
  38 def usage():
  39     """Print --help text"""
  40
  41     print("""Usage:
  42   {0} <emptylist> <filledlist>
  43   {0} --help
  44   {0} -h
  45
  46 Takes a file produced by gpgparticipants as <emptylist> and trys to fill in
  47 some digits into the SHA256 field such that the resulting list actually has
  48 a SHA256 checksum that starts with those digits. Whenever a match is found a
  49 file with the digits filled in is written to `<filledlist>.DIGITS`.
  50
  51 OPTIONS:
  52
  53   --fastforward        If a match is found of given length and --fastforward
  54                        is given then the programm immediately jumps to the next
  55                        length.
  56   --min-length NUM     Start looking for hex strings of given length
  57
  58 """.format(sys.argv[0]))
  59
  60 if __name__ == "__main__":
  61
  62     fastforward = False
  63     minlength = 1
  64
  65     optlist, args = getopt.getopt(sys.argv[1:], 'h', ['fastforward', 'min-length='])
  66     for o, a in optlist:
  67
  68         if o in ("-h", "--help"):
  69             usage()
  70             exit(0)
  71
  72         if o in ("--fastforward"):
  73             fastforward = True
  74
  75         if o in ("--min-length"):
  76             minlength = int(a)
  77
  78     if len(args) < 2:
  79         print >>sys.stderr, "You need to give two filenames."""
  80         exit(1)
  81
  82     emptyfile = open(args[0]).read()
  83
  84     idx = emptyfile.find("SHA256 Checksum:")
  85     idx = emptyfile.find("_", idx)
  86
  87     for l in range(minlength, 32):
  88         print "Looking at length", l
  89
  90         for h in range_hex(l):
  91
  92             H = insertspaces(h.upper())
  93             filledfile = emptyfile[:idx] + H + emptyfile[idx+len(H):]
  94             actual = hashlib.sha256(filledfile).hexdigest()
  95
  96             if actual[:len(h)] == h:
  97                 print "Found: ", H
  98                 open(args[1] + "." + h, "w").write(filledfile)
  99
 100                 if fastforward:
 101                     break