test: nl_mkimage für OTA-Trailer-Erzeugung mit Tests anlegen

feat: nl_mkimage.py implementieren (Gegenstück zu nl_fwup_trailer.c aus Task 2)

tools/mkimage/nl_mkimage.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+"""Appends the ninlight OTA trailer to a `_gz.img` produced by wm_tool.
+
+Layout (512 bytes): "NINL" | version(1) | device[16] | fw_version[16] | sha256[32] | 0xFF padding.
+The hash covers the complete `_gz.img` (T_BOOTER header + payload), which is exactly what the
+firmware hashes while writing the image to flash.
+"""
+import argparse
+import hashlib
+import sys
+from pathlib import Path
+
+TRAILER_SIZE = 512
+TRAILER_VERSION = 1
+FIELD = 16
+
+
+def field(value: str, name: str) -> bytes:
+    raw = value.encode()
+    if len(raw) >= FIELD:
+        sys.exit(f"error: {name} '{value}' is too long (max {FIELD - 1} bytes)")
+    return raw.ljust(FIELD, b"\x00")
+
+
+def main() -> None:
+    p = argparse.ArgumentParser(description="append the ninlight OTA trailer")
+    p.add_argument("--image", required=True, type=Path, help="input _gz.img")
+    p.add_argument("--device", required=True, help="device id, e.g. e27_rgb")
+    p.add_argument("--version", required=True, help="firmware version")
+    p.add_argument("--out", required=True, type=Path, help="output _ota.img")
+    a = p.parse_args()
+
+    data = a.image.read_bytes()
+    if len(data) > TRAILER_SIZE and data[-TRAILER_SIZE : -TRAILER_SIZE + 4] == b"NINL":
+        sys.exit("error: image already carries a trailer")
+
+    trailer = bytearray(b"\xff" * TRAILER_SIZE)
+    trailer[0:4] = b"NINL"
+    trailer[4] = TRAILER_VERSION
+    trailer[5:21] = field(a.device, "device")
+    trailer[21:37] = field(a.version, "version")
+    trailer[37:69] = hashlib.sha256(data).digest()
+    a.out.write_bytes(data + bytes(trailer))
+    print(f"{a.out} ({len(data) + TRAILER_SIZE} bytes, device={a.device}, version={a.version})")
+
+
+if __name__ == "__main__":
+    main()