Add a utility for encrypting/decrypting NVRAM files.

bemani/utils/nvram.py

@@ -0,0 +1,62 @@
+import argparse
+import os
+
+from bemani.protocol import EAmuseProtocol
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description="A utility to encrypt or decrypt NVRAM files.")
+    parser.add_argument(
+        "file",
+        help="File to encrypt or decrypt.",
+        type=str,
+    )
+    parser.add_argument(
+        "-o",
+        "--output",
+        default=None,
+        type=str,
+        help="Output to a different file instead of overwriting original.",
+    )
+    parser.add_argument(
+        "--strip-padding",
+        action="store_true",
+        default=False,
+        help="Strip null padding on decryption.",
+    )
+    parser.add_argument(
+        "--add-padding",
+        action="store_true",
+        default=False,
+        help="Add null padding on encryption.",
+    )
+    args = parser.parse_args()
+
+    with open(args.file, "rb") as bfp:
+        data = bfp.read()
+
+    if args.add_padding:
+        off_by = len(data) % 768
+        if off_by != 0:
+            data = data + b"\x00" * (768 - off_by)
+
+        assert (len(data) % 768) == 0
+
+    chunks = [data[x:x + 768] for x in range(0, len(data), 768)]
+    outputs = []
+    proto = EAmuseProtocol()
+
+    for chunk in chunks:
+        outputs.append(proto.rc4_crypt(chunk, b""))
+
+    output = b"".join(outputs)
+    if args.strip_padding:
+        while output[-1] == 0:
+            output = output[:-1]
+
+    with open(args.output or args.file, "wb") as bfp:
+        bfp.write(output)
+
+
+if __name__ == "__main__":
+    main()