image: add support for Netgear encrypted image

[openwrt/openwrt.git] / scripts / netgear-encrypted-factory.py

diff --git a/scripts/netgear-encrypted-factory.py b/scripts/netgear-encrypted-factory.py
new file mode 100755 (executable)
index 0000000..b6bb72f
--- /dev/null
+++ b/scripts/netgear-encrypted-factory.py
@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+
+import argparse
+import re
+import struct
+import subprocess
+import zlib
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--input-file', type=str, required=True)
+    parser.add_argument('--output-file', type=str, required=True)
+    parser.add_argument('--model', type=str, required=True)
+    parser.add_argument('--region', type=str, required=True)
+    parser.add_argument('--version', type=str, required=True)
+    parser.add_argument('--encryption-block-size', type=str, required=True)
+    parser.add_argument('--openssl-bin', type=str, required=True)
+    parser.add_argument('--key', type=str, required=True)
+    parser.add_argument('--iv', type=str, required=True)
+    args = parser.parse_args()
+
+    assert re.match(r'V[0-9]\.[0-9]\.[0-9]\.[0-9]',
+                    args.version), 'Version must start with Vx.x.x.x'
+    encryption_block_size = int(args.encryption_block_size, 0)
+    assert (encryption_block_size > 0 and encryption_block_size % 16 ==
+            0), 'Encryption block size must be a multiple of the AES block size (16)'
+
+    image = open(args.input_file, 'rb').read()
+    image_enc = []
+    for i in range(0, len(image), encryption_block_size):
+        chunk = image[i:i + encryption_block_size]
+        chunk += b'\x00' * ((-len(chunk)) % 16)  # pad to AES block size (16)
+        res = subprocess.run([
+            args.openssl_bin,
+            'enc',
+            '-aes-256-cbc',
+            '-nosalt',
+            '-nopad',
+            '-K', args.key,
+            '-iv', args.iv
+        ],
+            check=True, input=chunk, stdout=subprocess.PIPE)
+        image_enc.append(res.stdout)
+    image_enc = b''.join(image_enc)
+
+    image_with_header = struct.pack(
+        '>32s32s64s64s64s256s12sII',
+        args.model.encode('ascii'),
+        args.region.encode('ascii'),
+        args.version.encode('ascii'),
+        b'Thu Jan 1 00:00:00 1970',  # static date for reproducibility
+        b'',  # reserved
+        b'',  # RSA signature - omitted for now
+        b'encrpted_img',
+        len(image_enc),
+        encryption_block_size,
+    ) + image_enc
+
+    checksum = zlib.crc32(image_with_header, 0xffffffff) ^ 0xffffffff
+
+    with open(args.output_file, 'wb') as outfile:
+        outfile.write(image_with_header)
+        outfile.write(struct.pack('>I', checksum))
+
+
+if __name__ == "__main__":
+    main()