From 936e0184982169ef28c07d6f93132cb4923e7b53 Mon Sep 17 00:00:00 2001
From: Bluzume <39113159+KuromeSan@users.noreply.github.com>
Date: Sun, 3 Oct 2021 17:58:31 +1300
Subject: [PATCH] fix decrypt on files larger than 0x8000 bytes..

---
 decrypt.py | 135 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 111 insertions(+), 24 deletions(-)

diff --git a/decrypt.py b/decrypt.py
index 1c4ad6f..30674e0 100644
--- a/decrypt.py
+++ b/decrypt.py
@@ -1,62 +1,149 @@
 import os
 import binascii
 import sys
+import struct
+import math
 from Crypto.Cipher import AES
 
 game_key = b""
+content_id = b""
+original_iv = b""
 
+def IvRoll(location):
+    iv_next = location
+    iv = bytearray(original_iv)
+    new_iv = bytearray(iv_next.to_bytes(0x10, "little"))
+    for i in range(0,0x10):
+        new_iv[i] ^= iv[i] 
+    
+    return bytes(new_iv)
+    
 def ReadGameKey(filename):
     global game_key
+    global content_id
+    
     riffd = open(filename, "rb")
-    riffd.seek(0x120)
+    riffd.seek(0x50, 0)
+    content_id = riffd.read(0x24)
+    riffd.seek(0x120, 0)
     game_key = riffd.read(0x10)
     riffd.close()
-def DecryptFile(filename):
-    fd = open(filename, "rb")
+
+
+
+def GetBlock(fd, blockNo):
+    global game_key
+    current_iv = IvRoll(blockNo)
+    blockId = blockNo
+    blockNo = blockNo * 0x8000
+    total_read = 0x8000
+    if blockId == 0: # Skip to filedata
+        blockNo = 0x680
+        total_read -= 0x680    
+    elif blockNo % 0x80000 == 0: # Skip signature block
+        blockNo += 0x400
+        total_read -= 0x400
+    fd.seek(blockNo, 0)
+
+    file_data = fd.read(total_read)
+    cipher = AES.new(game_key, AES.MODE_CBC, current_iv)
+    return cipher.decrypt(file_data)
+
+def DecryptFile(input_filename):
+    global game_key
+    global content_id
+    global original_iv
+    fd = open(input_filename, "rb")
+    
     header = fd.read(4)
     if header != b"PSSE" and header != b"PSME":
-        print(filename + " Not a PSSE File")
+        print("Not a valid PSSE File")
         exit()
-    fd.seek(0x50, 0)
-    enc1 = fd.read(0x20)
+        
+    fd.seek(0x4, 0)
+    version = struct.unpack('i', fd.read(4))[0]
+    if version != 0x01:
+        print("Unsupported version: "+str(version))
+        exit()
+    
+    fd.seek(0x8, 0)
+    size = struct.unpack('i', fd.read(4))[0]
+    totalBlocks = math.ceil(size/0x8000)+1
+    
+    fd.seek(0x14, 0)
+    read_content_id = fd.read(0x24)
+    if read_content_id == b"IP9100-NPXS10074_00-0000000000000000": #Runtime Files
+        game_key = b"\xA8\x69\x3C\x4D\xF0\xAE\xED\xBC\x9A\xBF\xD8\x21\x36\x92\x91\x2D"
+    elif content_id != read_content_id:
+        print("Content ID Mismatch! Expected: "+content_id.decode("UTF-8")+" but got"+read_content_id.decode("UTF-8"))
+        
+    #not sure what this part is for
+    #fd.seek(0x50, 0)
+    #enc1 = fd.read(0x20)
+    
+    #iv
     fd.seek(0x70, 0)
     enc2 = fd.read(0x10)
-    fd.seek(0x680, 0)
-    file_data = fd.read()
-    fd.close()
 
     iv = b"\x00\x01\x02\x03\04\x05\x06\x07\x08\x09\x0A\x0B\x0C\x0D\x0E\x0F"
     key = b"\x4E\x29\x8B\x40\xF5\x31\xF4\x69\xD2\x1F\x75\xB1\x33\xC3\x07\xBE"
+    #cipher = AES.new(key, AES.MODE_CBC, iv)
+    #dec1 = cipher.decrypt(enc1)
     cipher = AES.new(key, AES.MODE_CBC, iv)
-    dec1 = cipher.decrypt(enc1)
-    cipher = AES.new(key, AES.MODE_CBC, iv)
-    iv2 = cipher.decrypt(enc2)
-
-    cipher = AES.new(game_key, AES.MODE_CBC, iv2)
-    game_data_dec = cipher.decrypt(file_data)
-    return game_data_dec
+    original_iv = cipher.decrypt(enc2)
     
+    total_file_data = b""
+    for i in range(0,totalBlocks):
+        total_file_data += GetBlock(fd, i)
+        
+    fd.close()
+    
+
+    return total_file_data[:size] # trim to sz
+    
+
+if len(sys.argv) <= 1:
+    print("PSSE Decryptor by SilicaAndPina")
+    print("Usage: decrypt.py <PSM_GAME_FOLDER>")
+    print("Where the game folder contains \"RO/License/FAKE.RIF\" and \"RO/Application/psse.list\"")
+    exit()
     
 file = sys.argv[1]
 
-ReadGameKey(file+"\\RO\\License\\FAKE.RIF")
+if os.path.isfile(file):
+    print("Decrypting: "+file)
+    data = DecryptFile(file)
+    open(file, "wb").write(data)
+    exit()
+    
+licenseFile = os.path.normpath(file+"/RO/License/FAKE.RIF")
+if not os.path.exists(licenseFile):
+    print("Cannot find license "+licenseFile)
+    exit()
+    
+ReadGameKey(licenseFile)
 print("Reading Game key from FAKE.RIF: "+binascii.hexlify(game_key).decode("UTF-8"))
-FileData = DecryptFile(file+"\\RO\\Application\\psse.list")
+
+psseList = os.path.normpath(file+"/RO/Application/psse.list")
+if not os.path.exists(psseList):
+    print("Cannot find "+psseList)
+    exit()
+
+FileData = DecryptFile(psseList)
 FilesList = FileData.replace(b"\r", b"").split(b"\n")
 
 for File in FilesList:
     if File == b"":
         continue
-    File = File.replace(b"/", b"\\")
     path = file.encode("UTF-8")
-    FilePath = path+b"\\RO\\Application\\"+File
+    FilePath = os.path.normpath(path+b"/RO/Application/"+File)
     print((b"Decrypting: "+FilePath).decode("UTF-8"))
     if os.path.exists(FilePath):
-        FileData = DecryptFile(FilePath)
-        open(FilePath, "wb").write(FileData)
+        DecryptedData = DecryptFile(FilePath)
+        open(FilePath, "wb").write(DecryptedData)
     else:
         print("Error: File not Found")
     
 
-open(file+"\\RO\\Application\\psse.list", "wb").write(FileData)
-print("Done")
\ No newline at end of file
+open(psseList, "wb").write(FileData)
+print("Done")