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

phelix001 · 2026-02-16T21:45:13Z

Summary

Adds Edge/Chromium (Chrome 111+, Edge 111+) support to the browser extension, unified with the existing Firefox extension into a single codebase.

Unified webext/add-on/ with shared JS and browser-specific manifests
Both browsers use the same MAIN + ISOLATED world content script architecture

Architecture

Both Firefox and Chromium now share the same content script architecture:

Script	World	Role
`content-main.js`	MAIN	Overrides `navigator.credentials.create/get`, serializes ArrayBuffers via native `Uint8Array.toBase64()/fromBase64()`
`content-bridge.js`	ISOLATED	Bridges `window.postMessage` to `runtime.connect()` for native messaging
`background.js`	Background	Forwards messages between content scripts and native messaging host

Browser differences handled via:

manifest.firefox.json — background scripts, gecko.strict_min_version: 140.0
manifest.chromium.json — service worker, Chrome 111+
globalThis.browser || globalThis.chrome for API detection

The Python native messaging host (credential_manager_shim.py) is reused unchanged.

Commits

feat: add Edge/Chromium web extension port — initial port with separate add-on-edge/ directory
refactor: merge Firefox and Chromium add-ons into unified folder — addresses review feedback, eliminates code duplication, removes cloneInto()/exportFunction() in favor of shared MAIN+ISOLATED architecture
docs: update READMEs for unified browser extension — updates README for Chromium support, fixes stale add-on-edge/ references in webext/README

Test plan

Load extension in Edge via edge://extensions → "Load unpacked" (copy manifest.chromium.json to manifest.json first)
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 (copy manifest.firefox.json to manifest.json)

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.

phelix001 · 2026-02-24T22:40:16Z

Pushed two new commits on top of the refactor:

docs: update READMEs for unified browser extension (58d581e)

Updated main README to document Edge/Chromium support alongside Firefox
Fixed webext/README.md — references to the deleted add-on-edge/ directory are gone, and both Firefox and Chromium dev workflows now include the manifest.json copy step (since browsers won't read manifest.firefox.json or manifest.chromium.json directly)
Added webext/add-on/manifest.json to .gitignore (generated file from the copy step)

ci: pin Rust toolchain, update actions, add audit and JS checks (612f201)

Added rust-toolchain.toml pinning to Rust 1.85 (MSRV for edition 2024 used by credentialsd-common and credentialsd-ui)
Updated actions/checkout from v2 to v4
Removed manual rustup component add rustfmt clippy — now declared in rust-toolchain.toml
Added cargo audit step for dependency vulnerability scanning
Added node --check step to validate web extension JS syntax

Happy to split the CI/toolchain changes into a separate PR if you'd prefer to keep this one focused on the web extension work.

- Update README to document Edge/Chromium support alongside Firefox - Fix webext/README references to deleted add-on-edge/ directory - Add manifest.json copy step for both Firefox and Chromium dev workflows - Add webext/add-on/manifest.json to .gitignore (generated for local dev) Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

iinuwa · 2026-02-27T21:40:23Z

Thanks for the update! I'm hoping to get to this sometime this weekend.

In the meantime can you remove the CLAUDE.md? We're not ready to declare a policy on AI usage yet.

The unrelated CI changes should also move to a separate PR to make this one easier to review.

phelix001 · 2026-02-27T21:50:54Z

Done! Two changes:

CLAUDE.md removed — it was never in the committed files, but I've cleaned up the PR description that referenced it. It won't appear anywhere in this PR.
CI changes split out — the toolchain/actions commit is now in a separate PR: ci: pin Rust toolchain, update actions, add audit and JS checks #143

This PR is now 3 commits, all focused on the web extension work.

@iinuwa ready when you are this weekend.

iinuwa requested changes Feb 20, 2026

View reviewed changes

phelix001 changed the title ~~feat: add Edge/Chromium web extension port~~ feat: add Edge/Chromium browser extension support Feb 24, 2026

phelix001 force-pushed the feat/edge-chromium-webext branch from 1f2f730 to 612f201 Compare February 24, 2026 22:42

phelix001 force-pushed the feat/edge-chromium-webext branch from 612f201 to 58d581e Compare February 27, 2026 21:50

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feat: add Edge/Chromium browser extension support#138

feat: add Edge/Chromium browser extension support#138
phelix001 wants to merge 3 commits intolinux-credentials:mainfrom
phelix001:feat/edge-chromium-webext

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