defog_strings.py

#!/usr/bin/env python

import base64
import sys
import re
import os

# defog dji fw 4.1.4 strings by adding the defogged version as comment to smali files
# - by nopcode, miek and bin4ry

key_414 = 'I Love Android'
key_415 = 'Y9*PI8B#gD^6Yhd1'
 
def defog(s,l):
	s = base64.decodestring(s)
	decr = ''.join([chr(ord(c) ^ ord(key[i%l*2])) for i,c in enumerate(s)])
	decr = decr.replace('\r', '').replace('\n', '').replace('"', '').replace('\\','')
	return decr

if len(sys.argv) != 3:
	print "Defogs base64 + silly fogging in DJI Go4 4.1.4 smali files. Adds defogged string as comment. Original smali file is replaced!"
	print "Syntax: {0} <key1 for 414 (1) or key2 for >=415 (2)> <folder>".format(sys.argv[0])
	sys.exit(1)

if sys.argv[1] == '1':
    key=key_414
    klen=7
if sys.argv[1] == '2':
    key=key_415
    klen=8
path = sys.argv[2]
for directory, subdirectories, files in os.walk(path):
    for file in files:
		fname = os.path.join(directory, file)
		if fname.endswith('.smali'):
			print(fname)
			base64_str_rex = re.compile('\s*const-string.*\s*v[0-9]+\s*,\s*\"([^\"]*)\"\s*')
			skip = 1
			i = 0
			
			with open(fname, "r") as fd:
				lines = list(fd)

			with open(fname, "w") as fd:	
				for l in lines:
					i += 1
					if (skip == 1):
						l = l.rstrip()
						match = base64_str_rex.match(l)
						if match:
							#print(l)
							enc = match.group(1)
							if enc:
								#print(l)
								next = lines[i+1]
								if (("com/dji/k/a/a/b" in next) or ("com/dji/k/a/a/a" in next) or ("com/dji/f/a/a/b" in next)):
									dec = defog(enc,klen)
									l = l.replace(enc,dec)
									print(l)
									fd.write(l + "\n")
									skip += 1
								else:
									fd.write(l + "\n")
									skip = 1
							#else:
								#print("Empty string!")
						else:
							fd.write(l + "\n")
					
					else:
						l=""
						if (skip == 5):
							skip = 1
						else:
							skip += 1
				else:
					foo=""