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)

boot = open('boot_recompiled.dat', 'wb')

with open('data_80000000.bin', 'rb') as fh:
	data = fh.read()

with open('stage2_40020000.bin', 'rb') as fh:
	# patch 0x5DA0 -> 32 bytes (sha2-256 of data.bin)
	stage2 = bytearray(fh.read())
	sha256 = hashlib.new('sha256')
	sha256.update(data)

	stage2[0x5DA0 : 0x5DA0 + 0x20] = sha256.digest()
	stage2 = bytes(stage2)

header = b''

# ident
header += b'\x54\x58\x20\x42\x4F\x4F\x54\x00\x00\x00\x00\x00\x56\x31\x2E\x30'

# sha2-256 of stage2_40020000.bin
sha256 = hashlib.new('sha256')
sha256.update(stage2)

header += sha256.digest()

# todo: s2_dst, hardcoded :\
header += b'\x00\x00\x02\x40'

# s2_size
header += struct.pack('I', len(stage2))

# s2_enc
header += struct.pack('I', 1)

# add 0x10 padding
header += b'\x00' * 0x10

# s3_size, hardcoded :\
header += b'\x50\x2B\xED\x00'

# 0x90 padding
header += b'\x00' * 0x90

# write sha2_hdr
sha256 = hashlib.new('sha256')
sha256.update(header)
header += sha256.digest()

# write header
boot.write(header)

# write stage2 encrypted
s2_key = unhexlify("47E6BFB05965ABCD00E2EE4DDF540261")
s2_ctr = unhexlify("8E4C7889CBAE4A3D64797DDA84BDB086")

boot.write(aes_ctr_dec(stage2, s2_key, s2_ctr))

# write data
data_key = unhexlify("030D865B7E458B10AD5706F6E227F4EB")
data_ctr = unhexlify("AFFC93692EBD2E3D252339F01E03416B")
data_off = 0x5F40
data_size = 0x175B70
data_base = 0x80000000

with open('data_80000000.bin', 'rb') as fh:
	boot.write(aes_ctr_dec(fh.read(), data_key, data_ctr))

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

with open('fb_F0000000.bin', 'rb') as fh:
	boot.write(aes_ctr_dec(fh.read(), fb_key, fb_ctr))

# write arm64
arm64_key = unhexlify("35D8FFC4AA1BAB9514825EB0658FB493")
arm64_ctr = unhexlify("C38EA26FF3CCE98FD8D5ED431D9D5B94")
arm64_off = 0x53BAB0
arm64_size = 0x36370
arm64_base = 0x80FFFE00


with open('arm64_80FFFE00.bin', 'rb') as fh:
	boot.write(aes_ctr_dec(fh.read(), arm64_key, arm64_ctr))

# write the unecripted part from original boot.dat 0x571e20
with open('boot.dat', 'rb') as fh:
	fh.seek(0x571E20, 0)
	boot.write(fh.read())

boot.close()