packer

from Crypto.Cipher import AES
from Crypto.Util import Counter
import struct

import hashlib
from binascii import hexlify, unhexlify

"""
typedef struct boot_dat_hdr
{
    unsigned char ident[0x10];
    unsigned char sha2_s2[0x20];
    unsigned int s2_dst;
    unsigned int s2_size;
    unsigned int s2_enc;
    unsigned char pad[0x10];
    unsigned int s3_size;
    unsigned char pad2[0x90];
    unsigned char sha2_hdr[0x20];
} boot_dat_hdr_t;
"""

def aes_ctr_dec(buf, key, iv):
    ctr = Counter.new(128, initial_value=int(hexlify(iv), 16))
    return AES.new(key, AES.MODE_CTR, counter=ctr).encrypt(buf)

def aes_ctr_enc(buf, key, iv):
    ctr = Counter.new(128, initial_value=int(hexlify(iv), 16))
    return AES.new(key, AES.MODE_CTR, counter=ctr).decrypt(buf)

boot = open('boot_recompiled.dat', 'wb')
e0sHashBytes = b""

# Get rights keys
f = open("boot.dat", "rb")
b = f.read()
f.close()

boot_ver = struct.unpack("I", b[0x0C:0x10])[0]
print(hex(boot_ver))
s2_base, s2_size = struct.unpack("II", b[0x30:0x38])

stage2 = open("stage2_{0:08X}.bin".format(s2_base), 'rb').read()

if boot_ver == 0x302E3156:
    s2_key = unhexlify("47E6BFB05965ABCD00E2EE4DDF540261")
    s2_ctr = unhexlify("8E4C7889CBAE4A3D64797DDA84BDB086")

    arm64_key = unhexlify("35D8FFC4AA1BAB9514825EB0658FB493")
    arm64_ctr = unhexlify("C38EA26FF3CCE98FD8D5ED431D9D5B94")
    arm64_off = 0x53BAB0
    arm64_size = 0x36370
    arm64_base = 0x80FFFE00

    fb_key = unhexlify("E2AC05206A701C9AA514D2B2B7C9F395")
    fb_ctr = unhexlify("46FAB59AF0E469EF116614DEC366D15F")
    fb_off = 0x17BAB0
    fb_size = 0x3C0000
    fb_base = 0xF0000000

    data_key = unhexlify("030D865B7E458B10AD5706F6E227F4EB")
    data_ctr = unhexlify("AFFC93692EBD2E3D252339F01E03416B")
    data_off = 0x5F40
    data_size = 0x175B70
    data_base = 0x80000000
elif boot_ver == 0x312E3156:
    s2_key = unhexlify("47E6BFB05965ABCD00E2EE4DDF540261")
    s2_ctr = unhexlify("8E4C7889CBAE4A3D64797DDA84BDB086")

    arm64_key = unhexlify("51A39F0B46BAE4691AD39A698146E865")
    arm64_ctr = unhexlify("7A307ED7F1ECC792F0E821ECD6999853")
    arm64_off = 0x53BAE0
    arm64_size = 0x36370
    arm64_base = 0x80FFFE00

    fb_key = unhexlify("27BABEE3DCFEF100C744A2388B57E957")
    fb_ctr = unhexlify("0B88AC25AFAF9B92D81372331AD66E24")
    fb_off = 0x17BAE0
    fb_size = 0x3C0000
    fb_base = 0xF0000000

    data_key = unhexlify("8D6FEABE0F3936145A474D3F05D33679")
    data_ctr = unhexlify("2846EFA9DACB065C51C71C154F0E9EA2")
    data_off = 0x5F50
    data_size = 0x175B90
    data_base = 0x80000000
else:
    exit()

#ident
e0sHashBytes += b'\x54\x58\x20\x42\x4F\x4F\x54\x00\x00\x00\x00\x00'
e0sHashBytes += b[0x0C:0x10]
#sha-256 of stage2_40020000.bin
sha256 = hashlib.new('sha256')
sha256.update(stage2)
e0sHashBytes += sha256.digest()
# todo: write s2_dst, hardcoded :\
e0sHashBytes += b'\x00\x00\x02\x40'
# write s2_size
e0sHashBytes += struct.pack('I', len(stage2))
# write s2_enc
e0sHashBytes += struct.pack('I', 1)
# 0x10 size padding
e0sHashBytes += b'\x00' * 0x10
# s3_size?
if boot_ver == 0x302E3156:
    e0sHashBytes += b'\x50\x2B\xED\x00'
elif boot_ver == 0x312E3156:
    e0sHashBytes += b'\x20\x2F\xED\x00'
# 0x90 size padding
e0sHashBytes += b'\x00' * 0x90
# write all that data
boot.write(e0sHashBytes)
# calculate e0ssha256
sha256 = hashlib.new('sha256')
sha256.update(e0sHashBytes)
boot.write(sha256.digest())
# stage2
boot.write(aes_ctr_enc(stage2, s2_key, s2_ctr))
# data
print("Data offset : " + hex(boot.tell()))
boot.write(aes_ctr_enc(open("data_{0:08X}.bin".format(data_base), 'rb').read(), data_key, data_ctr))
# fb
print("fb offset : " + hex(boot.tell()))
boot.write(aes_ctr_enc(open("fb_{0:08X}.bin".format(fb_base), 'rb').read(), fb_key, fb_ctr))
# arm64
print("arm64 offset : " + hex(boot.tell()))
boot.write(aes_ctr_enc(open("arm64_{0:08X}.bin".format(arm64_base), 'rb').read(), arm64_key, arm64_ctr))

# write rest of boot.dat
with open('boot.dat', 'rb') as fh:
    fh.seek(boot.tell(), 0)
    boot.write(fh.read())

boot.close()