feat: add Edge/Chromium web extension port by phelix001 · Pull Request #138 · linux-credentials/credentialsd

phelix001 · 2026-02-16T21:45:13Z

Summary

Ports the Firefox web extension to Edge/Chromium (MV3, Chrome 111+/Edge 111+)
Adds webext/add-on-edge/ with a dual content-script architecture to work around Chromium's security model (no exportFunction/cloneInto)
Adds native messaging manifest template for Chromium-based browsers

Architecture

The Firefox extension uses exportFunction() to directly override navigator.credentials from a content script. Chromium doesn't support this API, so the Edge port uses two content scripts:

Script	World	Role
`content-main.js`	MAIN	Overrides `navigator.credentials.create/get`, communicates via `window.postMessage`
`content-bridge.js`	ISOLATED	Bridges `postMessage` to `chrome.runtime.connect()` for native messaging
`background.js`	Service Worker	Connects to the same native messaging host (`credential_manager_shim.py`)

Other differences from Firefox version:

Base64url encoding via btoa/atob helpers (Chromium lacks Uint8Array.toBase64/fromBase64)
chrome.* namespace instead of browser.*
Service worker background instead of persistent background page

The Python native messaging host (credential_manager_shim.py) is completely reused — no changes needed.

New files

webext/add-on-edge/manifest.json — MV3 manifest with dual content scripts
webext/add-on-edge/content-main.js — MAIN world credential override
webext/add-on-edge/content-bridge.js — ISOLATED world IPC bridge
webext/add-on-edge/background.js — Service worker for native messaging
webext/app/credential_manager_shim_edge.json.in — Native messaging manifest template
Updated webext/README.md with Edge/Chromium setup instructions

Test plan

Load extension in Edge via edge://extensions → "Load unpacked"
Configure native messaging manifest with extension ID
Start credentialsd + credentialsd-ui D-Bus services
Test credential registration on https://webauthn.io
Test credential assertion on https://webauthn.io
Test on Chrome (chrome://extensions) with equivalent setup
Verify Firefox extension still works unchanged

🤖 Generated with Claude Code

Port the Firefox web extension to Edge/Chromium (MV3, Chrome 111+). Key architectural differences from Firefox version: - Two content scripts: MAIN world (overrides navigator.credentials) and ISOLATED world (bridges to background via chrome.runtime) - window.postMessage bridge between MAIN and ISOLATED worlds (Firefox uses exportFunction/cloneInto which don't exist in Chromium) - Base64url encoding via btoa/atob helpers instead of Uint8Array.toBase64/fromBase64 (not available in Chromium) - Service worker background script instead of persistent background page - chrome.* namespace instead of browser.* New files: - webext/add-on-edge/ - Complete Edge/Chromium extension - webext/app/credential_manager_shim_edge.json.in - Native messaging manifest template for Chromium-based browsers Updated README with Edge/Chromium setup instructions. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

iinuwa

Hello! Thanks for looking into this!

I haven't gotten the chance to test this out yet, but I did an initial look through, and there's quite a bit of duplicated code. We hope not to have to keep this around long term, but I still think it'd be helpful not to duplicate the code.

I think this means that I'd like to see if we can keep all the JavaScript files in the one add-on folder, with different manifests and "utils" files that contain the differences between Firefox and Chromium, and a check at runtime to import the correct one. If that means creating the extra "bridge" port in Firefox and/or a shim of cloneInto() for Chromium even if it's technically unnecessary, then that's fine with me.

Then we'd use Meson to bundle the add-ons for each browser platform.

I can help with the Meson parts; would you be willing to look into merging these two folders together?

iinuwa · 2026-02-20T05:27:53Z

webext/add-on-edge/background.js

+function arrayBufferToBase64url(buffer) {
+  const bytes = new Uint8Array(buffer);
+  let binary = '';
+  for (let i = 0; i < bytes.length; i++) {
+    binary += String.fromCharCode(bytes[i]);
+  }
+  return btoa(binary).replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '');
+}
+
+function base64urlToBytes(str) {
+  if (!str) return null;
+  const padded = str.replace(/-/g, '+').replace(/_/g, '/');
+  const binary = atob(padded);
+  const bytes = new Uint8Array(binary.length);
+  for (let i = 0; i < binary.length; i++) {
+    bytes[i] = binary.charCodeAt(i);
+  }
+  return bytes;
+}


This is built into Chromium as Uint8Array.from/toBase64; can we use those?

Done — switched to native Uint8Array.toBase64() / fromBase64() with {alphabet: "base64url", omitPadding: true} throughout. The manual btoa/atob helpers are removed entirely.

iinuwa · 2026-02-20T05:28:24Z

webext/add-on-edge/content-main.js

+// Base64url helpers (Chromium doesn't have Uint8Array.toBase64/fromBase64)
+function arrayBufferToBase64url(buffer) {
+  const bytes = new Uint8Array(buffer);
+  let binary = '';
+  for (let i = 0; i < bytes.length; i++) {
+    binary += String.fromCharCode(bytes[i]);
+  }
+  return btoa(binary).replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '');
+}
+
+function base64urlToArrayBuffer(str) {
+  if (!str) return null;
+  const padded = str.replace(/-/g, '+').replace(/_/g, '/');
+  const binary = atob(padded);
+  const bytes = new Uint8Array(binary.length);
+  for (let i = 0; i < binary.length; i++) {
+    bytes[i] = binary.charCodeAt(i);
+  }
+  return bytes.buffer;
+}


Same here; the comment is out of date: Chrome has had these for about 6 months.

Fixed — removed the outdated comment and the manual helpers. Using native Uint8Array.toBase64() / fromBase64() here as well.

Address PR review feedback to eliminate code duplication between webext/add-on/ (Firefox) and webext/add-on-edge/ (Chromium). Key changes: - Unified architecture: both browsers now use MAIN + ISOLATED world content scripts with window.postMessage bridge, eliminating the need for Firefox-specific cloneInto()/exportFunction() APIs - Use native Uint8Array.toBase64()/fromBase64() for base64url encoding/decoding (supported in both Firefox 140+ and Chrome 111+) - Simplified background.js: ArrayBuffer serialization now happens in content-main.js, so background just forwards messages - Browser-specific manifests: manifest.firefox.json (background scripts) and manifest.chromium.json (service worker) - Browser API detection via globalThis.browser || globalThis.chrome in content-bridge.js and background.js Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

phelix001 · 2026-02-20T10:51:31Z

Thanks for the review! I've pushed a commit that addresses all the feedback:

Merged into a single add-on/ folder — deleted add-on-edge/ entirely. Both browsers now share the same JS files:

content-main.js (MAIN world) — overrides navigator.credentials, handles all ArrayBuffer serialization
content-bridge.js (ISOLATED world) — relays messages between MAIN world and background via window.postMessage ↔ runtime.connect
background.js — simplified to just forward messages (no more serializeRequest needed since content-main.js handles serialization)

Browser-specific manifests: manifest.firefox.json (background scripts) and manifest.chromium.json (service worker)

Native Uint8Array.toBase64()/fromBase64() used everywhere — all manual btoa/atob helpers removed.

Browser API detection via globalThis.browser || globalThis.chrome in background.js and content-bridge.js.

Firefox now uses the same MAIN + ISOLATED world architecture as Chromium (with the bridge port as you suggested), which eliminates the need for cloneInto()/exportFunction() entirely.

I left a TODO in meson.build for the Chromium build target — happy to take your help on that part.

iinuwa requested changes Feb 20, 2026

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Comments

feat: add Edge/Chromium web extension port#138

feat: add Edge/Chromium web extension port#138
phelix001 wants to merge 2 commits intolinux-credentials:mainfrom
phelix001:feat/edge-chromium-webext

phelix001 commented Feb 16, 2026

Uh oh!

iinuwa left a comment

Uh oh!

iinuwa Feb 20, 2026

Uh oh!

phelix001 Feb 20, 2026

Uh oh!

iinuwa Feb 20, 2026

Uh oh!

phelix001 Feb 20, 2026

Uh oh!

phelix001 commented Feb 20, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Comments

Conversation

phelix001 commented Feb 16, 2026

Summary

Architecture

New files

Test plan

Uh oh!

iinuwa left a comment

Choose a reason for hiding this comment

Uh oh!

iinuwa Feb 20, 2026

Choose a reason for hiding this comment

Uh oh!

phelix001 Feb 20, 2026

Choose a reason for hiding this comment

Uh oh!

iinuwa Feb 20, 2026

Choose a reason for hiding this comment

Uh oh!

phelix001 Feb 20, 2026

Choose a reason for hiding this comment

Uh oh!

phelix001 commented Feb 20, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants