Patch New 3DS exclusives to work with Old 3DS

n2o3ds.py

'''
n2o3ds by Glitch
convert new3ds exclusives to old3ds titles (perhaps)

run this on an extracted and decrypted main cxi
then rebuild the cia with:
makerom -f cia -o game.cia -target t -i 0.cxi:0:0
you might need to use an older makerom as the newer ones tend to throw a -10 error
don't take this too seriously, most likely the games that work on old3ds are simplistic and sucky XD
'''
import hashlib, os, sys
buff=""
replace=""
smdh=0
exefs=0
SMDH=-1
MB=1024*1024
MAX_READ=32*MB


f=open(sys.argv[1],"rb+")
#print(hashlib.sha256(test).digest())

def bytes2int(data):
	u32=(ord(data[0])*1)+(ord(data[1])*0x100)+(ord(data[2])*0x10000)+(ord(data[3])*0x1000000)
	return u32

def patchByte(f, offset, data):
	f.seek(offset)
	f.write(data)
	
def updateSHA256(f, hash_offset, data_offset, length):
	data=""
	hash=""
	f.seek(data_offset)
	data=f.read(length)
	hash=hashlib.sha256(data).digest()
	f.seek(hash_offset)
	f.write(hash)
	
def findSMDH(f):
	global exefs
	global smdh
	
	f.seek(0x1A0)
	bytes=f.read(4)
	exefs=bytes2int(bytes) * 0x200
	
	f.seek(exefs+0x28)
	bytes=f.read(4)
	smdh=bytes2int(bytes) + 0x200
	
	f.seek(exefs + smdh)
	bytes=f.read(4)
	if bytes != "SMDH":
		return -1
		
	return exefs + smdh
	
SMDH=findSMDH(f)
print(hex(smdh))

f.seek(SMDH+0x2029)
buff=f.read(1)
buff=chr(ord(buff) & 0xEF)
f.seek(SMDH+0x2029)
f.write(buff)

updateSHA256(f, exefs+0x1A0, SMDH, 0x36c0)
updateSHA256(f, 0x1C0, exefs, 0x200)

f.seek(0x40E)
buff=f.read(1)
buff=chr(ord(buff) | 0x30)
patchByte(f,0x40E,buff)

updateSHA256(f, 0x160, 0x200, 0x400)

f.seek(0x80E)
buff=f.read(1)
buff=chr(ord(buff) | 0x30)
patchByte(f,0x80E,buff)

patchByte(f, 0x150, "C")
#patchByte(f, 0x10B, "\x00")
#patchByte(f, 0x11B, "\x00")

print(hex(SMDH))
f.close()