DRMLab Project

tools/decrypt.py

@@ -0,0 +1,56 @@
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad
+import sys
+import os
+
+
+def decrypt_file(input_file, key_hex):
+    try:
+        key = bytes.fromhex(key_hex)
+    except ValueError:
+        print("[-] Invalid AES key")
+        return
+
+    with open(input_file, "rb") as f:
+        encrypted_data = f.read()
+
+    cipher = AES.new(key, AES.MODE_ECB)
+    dec_data = cipher.decrypt(pad(encrypted_data, 16))
+
+    if b"INNER_MSTAR" not in dec_data:
+        print("[-] AES key not working")
+        return
+
+    payload = None
+    for offset in (64, 96):
+        candidate = dec_data[offset:]
+        if b"CHAI" in candidate or b"kbox" in candidate:
+            payload = candidate
+            break
+
+    if payload is None:
+        payload = dec_data[64:]
+
+    if b"CHAI" in payload:
+        out_data = payload
+    elif b"kbox" in payload:
+        out_data = payload[:128]
+    else:
+        out_data = payload[:32]
+
+    base, _ = os.path.splitext(input_file)
+    out_file = f"{base}_encrypted.dat"
+
+    with open(out_file, "wb") as f:
+        f.write(out_data)
+
+    print(f"[+] Saved {out_file}")
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 2:
+        print(f"Usage: python3 {sys.argv[0]} <file.dat>")
+        sys.exit(1)
+
+    aes_key = input("AES key (hex): ").strip()
+    decrypt_file(sys.argv[1], aes_key)