fix: AppImage required --no-sandbox

Not tested enough but works on my machine

electron/CONTEXT.md

@@ -21,6 +21,7 @@ Owns the desktop runtime: the Electron main process, the preload bridge that exp
 | **Local API server** | An in-process HTTP server (`electron/api/local-api-server.ts`) that serves the prebuilt Docusaurus docs and OpenAPI views to the renderer over `http://localhost:<port>/`. | "internal API" |
 | **Plugin library** | The plugin loader (`electron/plugin-library.ts`) — resolves manifests, validates entry points, and prepares the sandbox the renderer mounts plugins into. | "plugin manager" |
 | **Data archive** | The export/import format implemented in `electron/data-archive.ts` for moving a user's local database between installs. | "backup" |
+| **Linux launcher** | The shell script installed as the packaged Linux executable by `tools/after-pack.js`; built by `electron/app/linux-launcher.rules.ts`, it picks the sandbox switches and hands over to the renamed real binary `<executableName>-bin`. | "wrapper", "AppRun" |
 
 ## Relationships
 
@@ -49,6 +50,7 @@ Owns the desktop runtime: the Electron main process, the preload bridge that exp
 - Every schema change is accompanied by a **TypeORM migration**; the database is never mutated outside the migration system.
 - IPC handler errors are translated to typed error envelopes before crossing back into the renderer — the renderer never sees a raw `Error` from main.
 - The **Preload bridge** exposes a frozen, allow-listed set of methods; adding a method requires touching both `preload.ts` and the matching handler.
+- Chromium sandbox and Ozone switches are only ever set on the real command line — the **Linux launcher** for packaged builds, the launch scripts in development. `app.commandLine.appendSwitch` runs too late for them and must not be used to fake it.
 
 ## Flagged ambiguities
 

electron/app/flags.ts

@@ -4,7 +4,6 @@ import { readDesktopSettings } from '../desktop-settings';
 
 export function configureAppFlags(): void {
   configureDesktopBranding();
-  linuxSpecificFlags();
   networkFlags();
   setupGpuEncodingFlags();
   chromiumFlags();
@@ -21,6 +20,10 @@ function chromiumFlags(): void {
   const enabledFeatures: string[] = [];
 
   if (process.platform === 'linux') {
+    // Sandbox and Ozone platform selection happen before this file runs. The
+    // packaged launcher script and the dev launch scripts pass those switches
+    // on the real command line instead.
+
     // PipeWire-based audio pipeline for screen share audio capture
     enabledFeatures.push('AudioServiceOutOfProcess');
     // PipeWire-based screen capture so the xdg-desktop-portal system picker works
@@ -38,20 +41,6 @@ function chromiumFlags(): void {
   }
 }
 
-function linuxSpecificFlags(): void {
-  if (process.platform !== 'linux') {
-    return;
-  }
-
-  // Disable sandbox on Linux to avoid SUID / /tmp shared-memory issues
-  app.commandLine.appendSwitch('no-sandbox');
-  app.commandLine.appendSwitch('disable-dev-shm-usage');
-
-  // Chromium chooses the Linux Ozone platform before Electron runs this file.
-  // The launch scripts pass `--ozone-platform=wayland` up front for Wayland
-  // sessions so the browser process selects the correct backend early enough.
-}
-
 function networkFlags(): void {
   // Accept self-signed certificates in development (for --ssl dev server)
   if (process.env['SSL'] === 'true') {

electron/app/linux-launcher.rules.spec.ts

@@ -0,0 +1,147 @@
+import { execFileSync } from 'node:child_process';
+import {
+  mkdtempSync,
+  rmSync,
+  writeFileSync
+} from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+
+import {
+  afterEach,
+  beforeEach,
+  describe,
+  expect,
+  it
+} from 'vitest';
+
+import { buildLinuxLauncherScript, resolveLinuxLauncherNames } from './linux-launcher.rules';
+
+interface KernelFlags {
+  apparmorRestriction: string;
+  unprivilegedUsernsClone: string;
+  maxUserNamespaces: string;
+}
+
+const PERMISSIVE_KERNEL: KernelFlags = {
+  apparmorRestriction: '0',
+  unprivilegedUsernsClone: '1',
+  maxUserNamespaces: '15000'
+};
+
+let workspace = '';
+
+function writeKernelFlags(flags: KernelFlags): Record<keyof KernelFlags, string> {
+  const paths = {
+    apparmorRestriction: join(workspace, 'apparmor_restrict_unprivileged_userns'),
+    unprivilegedUsernsClone: join(workspace, 'unprivileged_userns_clone'),
+    maxUserNamespaces: join(workspace, 'max_user_namespaces')
+  };
+
+  for (const key of Object.keys(paths) as (keyof KernelFlags)[]) {
+    writeFileSync(paths[key], `${flags[key]}\n`, 'utf8');
+  }
+
+  return paths;
+}
+
+function runLauncher(flags: KernelFlags, args: string[] = []): string {
+  const paths = writeKernelFlags(flags);
+  const { launcherFileName, binaryFileName } = resolveLinuxLauncherNames('toju');
+  const launcherPath = join(workspace, launcherFileName);
+  const binaryPath = join(workspace, binaryFileName);
+
+  writeFileSync(binaryPath, '#!/bin/sh\nprintf \'%s\\n\' "$@"\n', { encoding: 'utf8', mode: 0o755 });
+  writeFileSync(
+    launcherPath,
+    buildLinuxLauncherScript({
+      binaryFileName,
+      apparmorRestrictionPath: paths.apparmorRestriction,
+      unprivilegedUsernsClonePath: paths.unprivilegedUsernsClone,
+      maxUserNamespacesPath: paths.maxUserNamespaces
+    }),
+    { encoding: 'utf8', mode: 0o755 }
+  );
+
+  return execFileSync(launcherPath, args, { encoding: 'utf8' }).trim();
+}
+
+describe('buildLinuxLauncherScript', () => {
+  beforeEach(() => {
+    workspace = mkdtempSync(join(tmpdir(), 'toju-launcher-'));
+  });
+
+  afterEach(() => {
+    rmSync(workspace, { force: true, recursive: true });
+  });
+
+  it('keeps the sandbox on when the kernel allows unprivileged user namespaces', () => {
+    expect(runLauncher(PERMISSIVE_KERNEL)).toBe('');
+  });
+
+  it('disables the sandbox when AppArmor confines unprivileged user namespaces', () => {
+    const output = runLauncher({ ...PERMISSIVE_KERNEL, apparmorRestriction: '1' });
+
+    expect(output).toBe('--no-sandbox');
+  });
+
+  it('disables the sandbox when the kernel forbids unprivileged namespace cloning', () => {
+    const output = runLauncher({ ...PERMISSIVE_KERNEL, unprivilegedUsernsClone: '0' });
+
+    expect(output).toBe('--no-sandbox');
+  });
+
+  it('disables the sandbox when no user namespaces are available at all', () => {
+    const output = runLauncher({ ...PERMISSIVE_KERNEL, maxUserNamespaces: '0' });
+
+    expect(output).toBe('--no-sandbox');
+  });
+
+  it('forwards launch arguments to the real binary', () => {
+    const output = runLauncher(PERMISSIVE_KERNEL, ['toju://invite/abc', '--ozone-platform=wayland']);
+
+    expect(output.split('\n')).toEqual(['toju://invite/abc', '--ozone-platform=wayland']);
+  });
+
+  it('never repeats a sandbox switch the caller already supplied', () => {
+    const output = runLauncher(
+      { ...PERMISSIVE_KERNEL, apparmorRestriction: '1' },
+      ['--no-sandbox', '%U']
+    );
+
+    expect(output.split('\n')).toEqual(['--no-sandbox', '%U']);
+  });
+
+  it('assumes a blocked sandbox is fine when the kernel switches are unreadable', () => {
+    const { launcherFileName, binaryFileName } = resolveLinuxLauncherNames('toju');
+    const launcherPath = join(workspace, launcherFileName);
+
+    writeFileSync(
+      join(workspace, binaryFileName),
+      '#!/bin/sh\nprintf \'%s\\n\' "$@"\n',
+      { encoding: 'utf8', mode: 0o755 }
+    );
+
+    writeFileSync(
+      launcherPath,
+      buildLinuxLauncherScript({
+        binaryFileName,
+        apparmorRestrictionPath: join(workspace, 'missing-apparmor'),
+        unprivilegedUsernsClonePath: join(workspace, 'missing-clone'),
+        maxUserNamespacesPath: join(workspace, 'missing-max')
+      }),
+      { encoding: 'utf8', mode: 0o755 }
+    );
+
+    expect(execFileSync(launcherPath, { encoding: 'utf8' }).trim()).toBe('');
+  });
+});
+
+describe('resolveLinuxLauncherNames', () => {
+  it('keeps the published executable name for the launcher and renames the binary', () => {
+    expect(resolveLinuxLauncherNames('toju')).toEqual({
+      launcherFileName: 'toju',
+      binaryFileName: 'toju-bin'
+    });
+  });
+});

electron/app/linux-launcher.rules.ts

@@ -0,0 +1,97 @@
+export const LINUX_LAUNCHER_BINARY_SUFFIX = '-bin';
+
+export const APPARMOR_USERNS_RESTRICTION_PATH = '/proc/sys/kernel/apparmor_restrict_unprivileged_userns';
+export const UNPRIVILEGED_USERNS_CLONE_PATH = '/proc/sys/kernel/unprivileged_userns_clone';
+export const MAX_USER_NAMESPACES_PATH = '/proc/sys/user/max_user_namespaces';
+
+export interface LinuxLauncherNames {
+  launcherFileName: string;
+  binaryFileName: string;
+}
+
+export interface LinuxLauncherScriptOptions {
+  binaryFileName: string;
+  apparmorRestrictionPath?: string;
+  unprivilegedUsernsClonePath?: string;
+  maxUserNamespacesPath?: string;
+}
+
+export function resolveLinuxLauncherNames(executableName: string): LinuxLauncherNames {
+  return {
+    launcherFileName: executableName,
+    binaryFileName: `${executableName}${LINUX_LAUNCHER_BINARY_SUFFIX}`
+  };
+}
+
+/**
+ * Chromium reads `--no-sandbox` while the browser process boots, long before
+ * the main script runs, so `app.commandLine.appendSwitch` cannot influence it.
+ * The packaged executable is therefore this script, which decides before
+ * handing over to the real binary.
+ *
+ * The sandbox stays on wherever the kernel can host it. It is dropped only
+ * where unprivileged user namespaces are denied - Ubuntu 24.04+ confines
+ * unconfined binaries through AppArmor, and hardened kernels disable the
+ * namespaces outright. An AppImage cannot fall back to the SUID helper because
+ * its payload is mounted `nosuid`, so without this the app aborts at startup.
+ */
+export function buildLinuxLauncherScript(options: LinuxLauncherScriptOptions): string {
+  const apparmorRestrictionPath = options.apparmorRestrictionPath ?? APPARMOR_USERNS_RESTRICTION_PATH;
+  const unprivilegedUsernsClonePath = options.unprivilegedUsernsClonePath ?? UNPRIVILEGED_USERNS_CLONE_PATH;
+  const maxUserNamespacesPath = options.maxUserNamespacesPath ?? MAX_USER_NAMESPACES_PATH;
+
+  return [
+    '#!/bin/sh',
+    '# Generated during packaging. Chromium only honours --no-sandbox when it is',
+    '# present on the real command line, so the decision happens here.',
+    'set -eu',
+    '',
+    'launcher_path="$0"',
+    '',
+    'case "$launcher_path" in',
+    '  */*) ;;',
+    '  *) launcher_path="$(command -v -- "$launcher_path" 2>/dev/null || printf \'%s\' "$launcher_path")" ;;',
+    'esac',
+    '',
+    'launcher_path="$(readlink -f -- "$launcher_path" 2>/dev/null || printf \'%s\' "$launcher_path")"',
+    `binary_path="$(dirname -- "$launcher_path")/${options.binaryFileName}"`,
+    '',
+    'read_kernel_flag() {',
+    '  if [ ! -r "$1" ]; then',
+    '    printf \'%s\' "$2"',
+    '    return 0',
+    '  fi',
+    '',
+    '  cat -- "$1" 2>/dev/null || printf \'%s\' "$2"',
+    '}',
+    '',
+    'sandbox_is_blocked() {',
+    `  if [ "$(read_kernel_flag ${apparmorRestrictionPath} 0)" = "1" ]; then`,
+    '    return 0',
+    '  fi',
+    '',
+    `  if [ "$(read_kernel_flag ${unprivilegedUsernsClonePath} 1)" = "0" ]; then`,
+    '    return 0',
+    '  fi',
+    '',
+    `  if [ "$(read_kernel_flag ${maxUserNamespacesPath} 1)" = "0" ]; then`,
+    '    return 0',
+    '  fi',
+    '',
+    '  return 1',
+    '}',
+    '',
+    'for launcher_arg in "$@"; do',
+    '  case "$launcher_arg" in',
+    '    --no-sandbox) exec "$binary_path" "$@" ;;',
+    '  esac',
+    'done',
+    '',
+    'if sandbox_is_blocked; then',
+    '  exec "$binary_path" --no-sandbox "$@"',
+    'fi',
+    '',
+    'exec "$binary_path" "$@"',
+    ''
+  ].join('\n');
+}