#!/bin/sh
# Serves the admin-uploaded wallpaper pattern with headers a browser will not execute: opened
# directly, the /www symlink this replaces was a same-origin document with an authenticated LuCI
# session reachable from it (OpenWrt forum thread 251930, confirmed on a stand — a marker SVG set
# document.title, read location.origin as the router's, and reached document.cookie, pre-login
# too, since /www needs no session). The theme's own rendering never hits this: 15-wallpaper.css
# paints the same file through mask-image or a tiled background-image, and neither ever runs
# script inside it — the exposure was only the direct URL, which is what CSP 'none' + sandbox and
# nosniff below close, without touching how the mask/background paints it.
#
# Deliberately unauthenticated, on purpose and not an oversight: the pattern paints before login
# too (head.ut's pre-paint, from window.__fsSD). That is safe here ONLY because this script takes
# NO input at all — FILE below is a shell constant, never $QUERY_STRING, $PATH_INFO or anything
# else request-supplied — so there is nothing to traverse and nothing else this handler can be
# made to read.
#
# The login background (/etc/footstrap/login-bg) stays a plain /www symlink and does NOT get this
# treatment: fs-assets.js re-encodes every upload to a JPEG on a canvas before it is sent, so the
# stored bytes are pixels only and there is no script grammar left in the file for a direct hit to
# run — see docs/package.md.

FILE=/etc/footstrap/pattern.svg

if [ ! -r "$FILE" ]; then
	printf 'Status: 404 Not Found\r\n'
	printf 'Content-Type: text/plain\r\n'
	printf '\r\n'
	exit 0
fi

printf 'Status: 200 OK\r\n'
printf 'Content-Type: image/svg+xml\r\n'
# Cacheable forever, because the URL is not stable: fs-axes.js appends `?v=<token>` and the token
# changes with every upload, so a new file is a new URL. Without this the /www symlink's ETag and
# Last-Modified were gone and the tile was re-fetched on EVERY page load - a background image on a
# router that serves it off flash with no gzip, which is the cost this handler must not add.
printf 'Cache-Control: public, max-age=31536000, immutable\r\n'
printf 'X-Content-Type-Options: nosniff\r\n'
printf "Content-Security-Policy: default-src 'none'; sandbox\r\n"
printf '\r\n'
cat "$FILE"

exit 0