OpenWrt firmware image utilities https://git.openwrt.org/project/firmware-utils/atom?h=master 2026-10-20T22:56:17Z 2026-10-20T22:56:17Z Simon Wunderlich 2026-09-17T13:17:27Z urn:sha1:b2a93c6f77bac3a6525e93b383c987b073b4633b The bootmonitor of Bintec elmeg RS-series routers (RS123, RS230, RS353) expects a 52-byte BOSS header in front of a gzip-compressed image: a 23-byte magic string identifying the board family, followed by fw_version, image_type, image_version, image_length, a CRC32 over the payload and two vendor fields, all big-endian. No existing tool produces this. mkbrnimg, from which this is derived, writes a 12-byte trailing footer plus a signature string instead. The input is expected to carry a 52-byte placeholder header so the payload stays aligned to the flash sector size; it is skipped, and length and CRC are computed over the remainder. The CRC is the plain zlib CRC32. Output was verified byte-for-byte against the original implementation from armSeb/openwrt-RS353, and the header layout was cross-checked against a genuine vendor firmware image. Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de> Link: https://github.com/openwrt/firmware-utils/pull/78 Signed-off-by: Jonas Jelonek <jonas@jonasjelonek.de>