scedecrypt.py

#!/usr/bin/python3

import argparse
import os
import pathlib
import sys
import zlib
import sceutils
from scetypes import SceHeader
from Cryptodome.Cipher import AES
from Cryptodome.Util import Counter

import keys


def scedecrypt(inf, outdir, decompress=True, silent=False):
    sce = SceHeader.unpack(inf)
    if not silent:
        print(sce)
    (sysver, selftype), use_spkg2 = sceutils.get_key_type(inf, sce, silent)
    scesegs = sceutils.get_segments(inf, sce, sysver, selftype, silent=silent, use_spkg2=use_spkg2)
    for i, sceseg in scesegs.items():
        if not silent:
            print(f'Decrypting segment {i}...')
        outf = open(os.path.join(outdir, f"{os.path.basename(inf.name)}.seg{i:02}"), "wb")
        inf.seek(sceseg.offset)
        dat = inf.read(sceseg.size)
        ctr = Counter.new(128, initial_value=int.from_bytes(sceseg.iv, "big"))
        section_aes = AES.new(sceseg.key, AES.MODE_CTR, counter=ctr)
        dat = section_aes.decrypt(dat)
        if decompress and sceseg.compressed:
            if not silent:
                print(f'Decompressing segment {i}...')
            z = zlib.decompressobj()
            dat = z.decompress(dat)
        outf.write(dat)


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("filename", type=pathlib.Path)
    parser.add_argument("outdir", type=pathlib.Path)
    parser.add_argument("-keys", type=pathlib.Path, default="keys_external.py", required=False)
    args = parser.parse_args()

    keys.use_keys(args.keys)

    with open(args.filename, "rb") as inf:
        scedecrypt(inf, args.outdir)