#!/usr/bin/python
#
# Tool to decode the internal Nintendo mails.
#
# Some of the emails are encoded using XOR. Use the -k option to give the tool an XOR key.
#
# Keys for all the emails in the leak:
#     /usr01/eng/Mail/inbox/1 - nishi\0
#     /usr01/eng/Mail/inbox/2 - is\0
#     /usr01/eng/Mail/inbox/3 - isw\0
#     /usr01/eng/Mail/inbox/4 - is\0
#     /usr01/eng/Mail/inbox/5 - newscad\0
#
#     /usr01/noa/Mail/inbox/1 - angry\0
#     /usr01/noa/Mail/inbox/#2 - antepaenultima\0
#
#     /usr01/rd1/Mail/inbox/1 - izushi\0
#
#     /usr01/uji/Mail/inbox/#1 - pmdawn\0
#     /usr01/uji/Mail/inbox/1 - sickboy\0
#     /usr01/uji/Mail/inbox/2 - starwing\0
#     /usr01/uji/Mail/inbox/3 - toomanygames\0
#
# How it works:
#     The emails created using a Unix tool called "tarmail".
#     It accepts a number of files, archives them in a .tar file and compresses it using the Unix tool "compress".
#     The resulting .tar.Z file is then Ascii85 encoded after being optionally XOR encoded.
#     Finally, the Ascii85 encoded blob is added to the email between "xbtoa Begin" and "xbtoa End" guards.
#
# Sidenote:
#     The "N 1069052 104ffc E bf S 5a188d9 R 40799495" junk after "xbtoa End" is just some checksums.
#     You can find a btoa implementation which generates the checksum here:
#     https://github.com/geoffmcl/compressW/blob/master/src/btoa.c
#
# Example usage:
#     python decode.py -i 'other/NEWS/テープリストア/NEWS_02/usr01/uji/Mail/inbox/1' -k 'sickboy\0'
#
#
import sys, os, getopt, base64

def printHelp():
    print('decode.py -i <inputfile> -o <outputfile> -k <keyword>')

def main(argv):
    inputfilename = ''
    outputfilename = ''
    keyword = ''
    infile = ''

    try:
        opts, args = getopt.getopt(argv,'hi:o:k:')
    except getopt.GetoptError:
        printHelp()
        sys.exit(2)
    for opt, arg in opts:
        if opt == '-h':
            printHelp()
            sys.exit()
        elif opt == '-i':
            inputfilename = arg
        elif opt == '-o':
            outputfilename = arg
        elif opt == '-k':
            keyword = arg
    if inputfilename == '':
        printHelp()
        sys.exit(2)

    # Read
    infile = open(inputfilename, 'r')
    data = infile.read()
    infile.close()

    # Extract encoded section of the email
    xbtoaBeginStr = 'xbtoa Begin\n'
    xbtoaEndStr = 'xbtoa End'
    xbtoaBegin = data.find(xbtoaBeginStr)
    xbtoaEnd = data.find(xbtoaEndStr)
    if xbtoaBegin == -1 or xbtoaEnd == -1:
        print('Not a valid tarmail')
        sys.exit(1)

    # Ascii85 decode
    xbtoa = data[(xbtoaBegin+len(xbtoaBeginStr)):xbtoaEnd]
    binary = bytearray(base64.a85decode(xbtoa))

    # XOR decode the file, if key was given
    if keyword != '':
        keyword = keyword.replace('\\0', '\x00') # Replace \0 in the key with 0x00
        keyword = keyword.encode()
        klen = len(keyword)
        for i in range(len(binary)):
            binary[i] ^= keyword[i % klen]

    # Make output filename if non was given
    if outputfilename == '':
        inbasename = os.path.basename(inputfilename)
        outputfilename = inbasename+'.tar.Z'

    # Output
    outfile = open(outputfilename, 'wb')
    outfile.write(bytes(binary))
    outfile.close()

if __name__ == "__main__":
    main(sys.argv[1:])