Methods
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Last updated
#Source: https://gist.githubusercontent.com/dhondta/90a07d9d106775b0cd29bb51ffe15954/raw/e85a13e7fe1805daa314d776926df470d344aca6/paddinganograph.py
#!/usr/bin/python3
# -*- coding: UTF-8 -*-
import math
from tinyscript import *
__author__ = "Alexandre D'Hondt"
__version__ = "1.2"
__copyright__ = "A. D'Hondt"
__license__ = "agpl-3.0"
__reference__ = "https://inshallhack.org/paddinganography/"
__doc__ = """
This tool allows to unhide data hidden in base32/base64 strings. It can take a
PNG or JPG in input to retrieve an EXIF value as the input data.
"""
__examples__ = [
"-s . -f \"Comment\" < image.jpg > base32.enc",
"-e base32 < base32.enc"
]
DEF_BASE64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
DEF_BASE32 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
def exif(raw_data, key):
t = TempPath().tempfile().name
with open(str(t), 'wb') as f:
f.write(raw_data)
logger.debug("Getting EXIF data...")
exif = subprocess.check_output(["exiftool", str(t)])
exif = codecs.decode(exif, "utf-8")
exif = {l.split(':', 1)[0].strip(): l.split(':', 1)[1].strip() \
for l in exif.split('\n') if l.strip() != ""}
return exif if not key else exif[key]
def unhide(encoded, encoding="base64", charset=None, sep=".", pad="=", n_pad=8):
try:
charset = (charset or \
globals()["DEF_{}".format(encoding.upper())]).strip()
except NameError:
raise ValueError("Bad encoding")
logger.debug("Unhidding data...")
bits = ""
for token in encoded.split(b(sep)):
bits += unhide_bits(token.strip(), charset, pad, n_pad) or ""
return "".join(ts.bin2str(bits[i:i+8]) for i in range(0, len(bits), 8))
def unhide_bits(encoded, charset, pad="=", n_pad=8):
def __gcd(a,b):
while b > 0:
a, b = b, a % b
return a
padding = encoded.count(b(pad))
n_repr = int(math.ceil(math.log(len(charset), 2)))
w_len = n_repr * n_pad / __gcd(n_repr, n_pad)
n_char = int(math.ceil(float(w_len) / n_repr))
if encoded == "" or len(encoded) % n_char != 0 or padding == 0:
return
unused = {n: int(w_len - n * n_repr) % n_pad for n in range(n_char)}
b_val = bin(b(charset).index(encoded.rstrip(b(pad))[-1]))[2:].zfill(n_repr)
return b_val[-unused[padding]:]
if __name__ == '__main__':
parser.add_argument("-c", "--charset",
help="characters set")
parser.add_argument("-e", "--encoding", choices=["base32", "base64"],
default="base64", help="character encoding")
parser.add_argument("-f", "--exif-field", dest="exif", default="Comment",
help="EXIF metadata field to be selected")
parser.add_argument("-p", "--padding-char", default="=",
help="padding character")
parser.add_argument("-s", "--separator", default="\n",
help="base-encoded token separator")
initialize()
data = b("").join(l for l in ts.stdin_pipe())
if data.startswith(b("\x89PNG")) or data.startswith(b("\xff\xd8\xff\xe0")):
data = exif(data, args.exif)
print(unhide(data, args.encoding, args.charset, args.separator))#Base 64 paddinganogarphy
#Source: http://delimitry.blogspot.com/2014/02/olympic-ctf-2014-find-da-key-writeup.html
def get_base64_diff_value(s1, s2):
base64chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
res = 0
for i in xrange(len(s1)):
if s1[i] != s2[i]:
return abs(base64chars.index(s1[i]) - base64chars.index(s2[i]))
return res
def solve_stego():
with open('stego.txt', 'rb') as f:
file_lines = f.readlines()
bin_str = ''
for line in file_lines:
steg_line = line.replace('\n', '')
norm_line = line.replace('\n', '').decode('base64').encode('base64').replace('\n', '')
diff = get_base64_diff_value(steg_line, norm_line)
pads_num = steg_line.count('=')
if diff:
bin_str += bin(diff)[2:].zfill(pads_num * 2)
else:
bin_str += '0' * pads_num * 2
res_str = ''
for i in xrange(0, len(bin_str), 8):
res_str += chr(int(bin_str[i:i+8], 2))
print res_str
solve_stego()