Browser autofill agent — desktop + extension

[YoannDev90]

Closes #1524

What

Adds a browser autofill agent that bridges the browser extension (Chrome/Firefox/Vivaldi/Edge) and the desktop vault. The user enables the agent in settings, the extension communicates with the desktop via Native Messaging (Chrome/Firefox/Edge) or WebSocket (Safari), and credentials are filled automatically.

How it works

Desktop side:

• BrowserAutofillAgentManager launches two servers concurrently:
  • NM server — IPC socket for Native Messaging (the browser launches the agent binary)
  • WS server — Rust agent process listening on 127.0.0.1:<port> with ECDH + HMAC challenge-response handshake
• A pairing code is generated automatically on first activation, copied into the extension to derive the shared secret
• Status service (BrowserAutofillAgentStatusService) exposes state (Starting/Ready/Failed/Unsupported/Stopped) to the UI

Extension side:

• Modular architecture: background.js (orchestrator) + 10 modules in lib/
• Two communication modes: Native Messaging (nm-client.js) and WebSocket (ws-client.js)
• Crypto: X25519 ECDH native (Web Crypto API) + AES-256-GCM + HMAC-SHA256
• MV3 with separate manifests for Chrome (service_worker) and Firefox (scripts)
• Dynamic context menu, keyboard shortcut Ctrl+Shift+Space, locked/unlocked icon state

Desktop changes

File	Change
BrowserAutofillAgentManager.kt	Non-suspend start(), IPC cleanup in finally, @Volatile on wsAgentProcess, dead code removed (onBeforeStart, extraCliArgs)
Main.kt	LaunchedEffect with awaitCancellation(), status service, port constant, rememberUpdatedState for port
SettingBrowserAgent.kt	Status display (Starting/Ready/Failed/Unsupported/Stopped), pairing code with copy button
strings.xml	4 new i18n strings for status + pairing code
SettingsRepository.kt	Port + pairing code preferences
FingerprintRepositoryModule.kt	BrowserAutofillAgentStatusService binding
GlobalModuleCommon.kt	Get/Put browser agent use case bindings
AgentManager.kt, AgentIpcServer.kt	Browser agent integration into existing IPC infrastructure
desktopApp/build.gradle.kts, settings.gradle	desktopBrowserAgent module (Rust)

Extension changes (new)

File	Purpose
manifest.chrome.json	MV3 Chrome/Vivaldi/Edge — service_worker
manifest.firefox.json	MV3 Firefox — scripts + gecko settings
background.js	Orchestrator: mode detection, NM/WS routing, icon, shortcuts
content.js	Credential injection into forms
lib/crypto.js	X25519 ECDH + AES-256-GCM (native Web Crypto)
lib/ws-client.js	WebSocket client with ECDH + HMAC handshake, request IDs, 10s timeout
lib/nm-client.js	Native Messaging client with double-connect guard
lib/messaging.js	Internal message listeners (query, secret, fill, status)
lib/context-menu.js	Dynamic per-site context menu
lib/logger.js	Cross-context log ring buffer
lib/base64.js, lib/hmac.js	Utilities
options.js	Pairing/unpairing page, PBKDF2 600K iterations
switch-browser.sh	Script to switch between Chrome/Firefox manifests

Rust native host (new)

desktopBrowserAgent/ — Rust binary that bridges the IPC socket (nm) and the WS server. Built via Cargo for desktop.

Security

• X25519 native via Web Crypto (Chrome 133+, Firefox 130+, Safari TP 211+)
• Shared secret derived from pairing code via HKDF
• __kgSetSecret restricted to extension pages (chrome-extension:// / moz-extension://)
• fill message uses only sender.tab.id (no message.tabId fallback)
• PBKDF2 600K iterations for at-rest secret encryption

Testing

Tested with the AppImage on CachyOS + Firefox. If anyone can test the full flow on other OS/browsers (macOS, Windows, Chrome, Vivaldi, Edge, Safari), it would help catch issues before shipping to production.

Note

An AI coding assistant was used as a development aid to accelerate implementation and research.

[YoannDev90]

And sorry for the long AI comment, I didn't know what to say.