Harden auth storage and sign-in guards (#23)

Keep GitHub sign-in data in session storage instead of persisting it
to local extension storage, and clear legacy auth data on access.

Add a stricter device-flow URL check before opening GitHub tabs,
restore avatar URL sanitization in the optimized renderer, and tighten
the extension CSP to match the allowed image sources.

Update tests and user-facing security copy to reflect the new session-
only auth behavior.

Co-authored-by: jonmartin721 <jonmartin721@users.noreply.github.com>

Author: jonmartin721

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to GitHub Devwatch will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Security
+- GitHub sign-in sessions now stay in Chrome session storage only instead of persisting to local extension storage
+- Added validation for the GitHub device-flow verification URL before opening a browser tab
+- Tightened remote image handling for activity avatars and extension page CSP rules
+
 ## [1.0.2] - 2025-11-19
 
 ### Fixed

PRIVACY.md

@@ -14,8 +14,8 @@ GitHub Devwatch collects and stores the following data **locally on your device
 
 1. **GitHub OAuth Session**
    - Created when you connect GitHub through the built-in device-flow sign-in
-   - Stored by the extension in Chrome storage
-   - Current builds encrypt the auth session before writing it to local storage and keep a decrypted session copy while the extension is running
+   - Stored by the extension in Chrome session storage for the current browser session only
+   - Cleared when the browser session ends or when you disconnect GitHub in DevWatch
    - Used only to authenticate with GitHub's API
    - Not sent to third-party services operated by this project
    - Never shared with anyone
@@ -56,7 +56,7 @@ All data collected is used exclusively to provide the extension's functionality:
 
 - The extension uses Chrome storage APIs for settings, cached activity, and GitHub sign-in handling
 - Settings and repository lists can optionally sync across your Chrome browsers if you use Chrome Sync
-- GitHub sign-in data uses local and session storage rather than Chrome sync
+- GitHub sign-in data uses session storage rather than Chrome sync and is not persisted across browser restarts
 - You can clear all data at any time by uninstalling the extension or using Chrome's "Clear extension data" feature
 
 ## Third-Party Services
@@ -112,7 +112,7 @@ You have complete control over your data:
 Current builds include several concrete safeguards:
 
 - All API requests use HTTPS
-- The GitHub auth session is encrypted before it is persisted locally
+- The GitHub auth session is kept in session storage for the current browser session only
 - The codebase includes input sanitization and GitHub URL validation checks
 - Extension pages use a Content Security Policy
 

SECURITY.md

@@ -33,8 +33,8 @@ These are better suited for regular issues:
 The extension includes several concrete protections, but this project has not been through a formal external security audit.
 
 ### GitHub Sign-In Storage
-- GitHub auth sessions are encrypted before they are written to local extension storage
-- A decrypted copy may be cached in session storage while the extension is running
+- GitHub auth sessions are kept in `chrome.storage.session` for the current browser session only
+- Legacy on-disk auth storage is cleared by current builds during sign-in handling
 - Never transmitted to third-party servers
 
 ### Content Security Policy

manifest.json

@@ -34,6 +34,6 @@
     "128": "icons/icon128.png"
   },
   "content_security_policy": {
-    "extension_pages": "script-src 'self'; object-src 'self'; connect-src 'self' https://api.github.com https://github.com https://registry.npmjs.org; img-src 'self' https: data:; default-src 'self'; style-src 'self'"
+    "extension_pages": "script-src 'self'; object-src 'self'; connect-src 'self' https://api.github.com https://github.com https://registry.npmjs.org; img-src 'self' data: https://github.com https://*.github.com https://githubusercontent.com https://*.githubusercontent.com; default-src 'self'; style-src 'self'"
   }
 }

options/options.html

@@ -94,7 +94,7 @@ <h3>Connect GitHub</h3>
                   <svg class="info-icon" fill="none" stroke="currentColor" viewBox="0 0 24 24" aria-hidden="true">
 	                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 15v2m-6 4h12a2 2 0 002-2v-6a2 2 0 00-2-2H6a2 2 0 00-2 2v6a2 2 0 002 2zm10-10V7a4 4 0 00-8 0v4h8z"/>
 	                  </svg>
-	                  <span><strong>Security:</strong> Your GitHub sign-in session is encrypted with AES-GCM and stored locally on your device.</span>
+	                  <span><strong>Security:</strong> Your GitHub sign-in stays in Chrome session storage and is cleared when the browser session ends.</span>
 	                </p>
 	              </div>
 	              <div class="info-box info-box-compact">

options/options.js

@@ -1,5 +1,5 @@
 import { applyTheme, formatDateVerbose } from '../shared/utils.js';
-import { getAuthSession, getAccessToken, getLocalItems, getWatchedRepos, setLocalItem, setWatchedRepos } from '../shared/storage-helpers.js';
+import { clearAuthSession, getAuthSession, getAccessToken, getLocalItems, getWatchedRepos, setLocalItem, setWatchedRepos } from '../shared/storage-helpers.js';
 import { createHeaders } from '../shared/github-api.js';
 import { STORAGE_CONFIG, VALIDATION_PATTERNS } from '../shared/config.js';
 import { validateRepository } from '../shared/repository-validator.js';
@@ -1052,6 +1052,7 @@ async function resetSettings() {
 
   try {
     // Clear all storage (both sync and local)
+    await clearAuthSession();
     await chrome.storage.sync.clear();
     await chrome.storage.local.clear();
 

popup/views/onboarding-view.js

@@ -379,7 +379,7 @@ async function renderTokenStep() {
       <svg class="info-icon" fill="none" stroke="currentColor" viewBox="0 0 24 24" aria-hidden="true">
         <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 15v2m-6 4h12a2 2 0 002-2v-6a2 2 0 00-2-2H6a2 2 0 00-2 2v6a2 2 0 002 2zm10-10V7a4 4 0 00-8 0v4h8z"/>
       </svg>
-      Your GitHub sign-in session is encrypted with AES-GCM encryption and stored securely on your device. It's only used for GitHub API access and never shared.
+      Your GitHub sign-in stays in Chrome session storage for the current browser session only. It's used only for GitHub API access and is cleared when the browser session ends.
     </p>
   `;
 }

shared/auth.js

@@ -1,4 +1,5 @@
 import { API_CONFIG, OAUTH_CONFIG } from './config.js';
+import { isValidGitHubAuthUrl } from './security.js';
 
 function getStorageValue(area, key) {
   return new Promise((resolve) => {
@@ -181,9 +182,18 @@ export async function requestGitHubDeviceCode() {
 export function openGitHubDevicePage(deviceCodeData) {
   const targetUrl = deviceCodeData.verificationUriComplete || deviceCodeData.verificationUri || OAUTH_CONFIG.DEVICE_VERIFY_URL;
 
+  if (!isValidGitHubAuthUrl(targetUrl)) {
+    throw createOAuthError(
+      'GitHub sign-in returned an unexpected verification URL.',
+      'invalid_verification_url'
+    );
+  }
+
   if (chrome?.tabs?.create) {
     chrome.tabs.create({ url: targetUrl });
   }
+
+  return targetUrl;
 }
 
 export async function pollForGitHubAccessToken(deviceCodeData, options = {}) {

shared/crypto-utils.js

@@ -5,6 +5,7 @@
 
 import { UI_CONFIG } from './config.js';
 import { SNOOZE_ICON, CHECK_ICON } from './icons.js';
+import { sanitizeImageUrl } from './sanitize.js';
 
 /**
  * Basic DOM renderer with simple caching to avoid unnecessary re-renders
@@ -440,7 +441,8 @@ class ActivityListRenderer {
     const sanitizedType = escapeHtml(activity.type);
     const sanitizedTypeLabel = escapeHtml(this.getActivityTypeLabel(activity.type));
     const sanitizedDescription = activity.description ? escapeHtml(activity.description) : '';
-    const sanitizedAvatar = activity.authorAvatar || 'data:image/svg+xml,%3Csvg xmlns="http://www.w3.org/2000/svg"%3E%3C/svg%3E';
+    const sanitizedAvatar = sanitizeImageUrl(activity.authorAvatar)
+      || 'data:image/svg+xml,%3Csvg xmlns="http://www.w3.org/2000/svg"%3E%3C/svg%3E';
     const sanitizedUrl = escapeHtml(activity.url);
     const sanitizedId = escapeHtml(activity.id);
 
@@ -576,4 +578,4 @@ function escapeHtml(text) {
 }
 
 // Export classes and utilities
-export { DOMOptimizer, ActivityListRenderer, escapeHtml };
+export { DOMOptimizer, ActivityListRenderer, escapeHtml };