Game Webview

Game Webview

Security posture

The game <webview> (views/kan-game-wrapper.tsx) runs with contextIsolation: true and disablewebsecurity. The preload (assets/js/webview-preload.js) runs in the isolated world — keeping Node and @electron/remote — and pushes page-facing hacks into the page's main world via contextBridge.executeInMainWorld, communicating through the exposed poiPreloadBridge.

Why disablewebsecurity stays: enabling standard web security in the page's main world breaks (a) the cross-origin game-iframe traversal used by the canvas screenshot (window.capture in capture-page.js) and (b) historically file:// asset loads. The canvas capture is deliberately kept (better raw/resize-correct screenshots), so disablewebsecurity must remain. contextIsolation still isolates the preload's Node from the untrusted page — that is the security win.

The main poi window and plugin windows remain contextIsolation: false (plugins run Node in-page) — out of scope for this skill.

Asset hack — everything serves through poi-cache://

lib/kcs-resource.ts registers a privileged poi-cache:// scheme plus a handler that net.fetches the local file, sets ACAO: *, and sets an explicit Content-Type by extension. Two trigger paths:

Scripts — two-tier policy

• .hack.* script overrides are served proactively by the main-process webRequest (override-only, so a mod always applies).
• Plain cached scripts are served only on load failure: a page-side capture-phase error listener in resource-hack.js re-injects a /kcs* script from cache when its network load fails.
• Proactive plain-cache serving is forbidden: stale version-pinned scripts (main.js?version=...) plus gadget RPC under /gadget_html5/ break login with Unexpected identifier 'error'. This was tried both ways — do not re-attempt.
• The separate login onError path (runtime kcsLogin failure) still re-injects and re-runs the gadget handlers, which webRequest cannot do — so the page-side fallback stays regardless.

Images and login scripts — page-side

resource-hack.js: an isolated-world resolver maps to poi-cache://resource<pathname>, applied by the main-world new Image() hook and login-script reinjection.

Ship art is drawn onto the game's WebGL canvas, and a cross-origin image taints the texture (texImage2D SecurityError). The fix is a CORS-clean load: the new Image() hook sets crossOrigin = 'anonymous' on hacked images, paired with the handler's ACAO: *. Only hacked images get crossOrigin, so same-origin network images are untouched. Images are deliberately not in the webRequest path (page-side crossOrigin avoids both the WebGL taint and a 400).

stylesheet / media / font / script — main-process webRequest.onBeforeRequest

HACKABLE_RESOURCE_TYPES = { stylesheet, media, font, script }. stylesheet/media/font resolve .hack.* first, then the plain cached origin. script is in OVERRIDE_ONLY_RESOURCE_TYPES, so findHackFilePathAsync(..., overrideOnly = true) serves only .hack.*. xhr and documents are excluded because login evaluates XHR bodies.

Implementation notes

• Content-Type comes from the mime package (v4, ESM-only) via a cached native dynamic import('mime') plus import type { Mime }. Babel keeps import() for poi files; a static import would transpile to a broken require of an ESM-only package.
• The webview uses session.defaultSession (no partition) — confirmed by resource-notifier.ts also hooking defaultSession.
• Shared path logic is plain JS in assets/js/kcs-resource-path.js, required from both the main process and the renderer preload, because main only babel-registers .es / .ts / .tsx.
• Broadcaster events (network.on.response etc.) are consumed in views/env-parts/data-resolver.ts, filtered to /kcsapi plus the /kcs2/js/main.js game-start marker — so the bridge's input validation allows the /kcs prefix.

The window.open popup crash (diagnosed 2026-08-07)

Opening the DMM point-charge page (point.dmm.com/choice/pay -> /choice/point) from the game killed the renderer: reason: "crashed", exit code -2147483645 (0x80000003 STATUS_BREAKPOINT), twice per attempt, with no CHECK/FATAL line in either the Chromium log or stderr.

Root cause: disablewebsecurity. A window.open popup keeps an opener relationship with the game page and therefore shares its renderer process; loading an ordinary secure page into that web-security-disabled process crashes it, taking the game down too.

Fix: wc.setWindowOpenHandler on the guest webContents in lib/webcontent-utils.ts — deny http(s) popups and re-open them in a detached BrowserWindow (webSecurity: true, sandbox: true, no node), which drops the opener link. about:blank popups still take the normal allow path, since the opener scripts them.

Ruled out — do not re-test: --disable-site-isolation-trials (app.ts), devtools extensions (poi.devtool.enable), the proxy, Sentry, plugins, @electron/remote, and inherited webPreferences (Electron's makeWebPreferences does not inherit preload or disablewebsecurity into child windows). A top-level window loading the same URL never crashes — the opener relationship is required to reproduce. The original symptom was a misleading @electron/remote / Sentry error about a disposed WebFrameMain, which is downstream of the crash, not its cause.

Deferred: WebContentsView migration

Replacing <webview> with WebContentsView has been scoped but deferred — it is blocked on an Electron per-view click-through API. Do not start it without checking with the user.