feat(sandbox): implement secret visibility lockdown for env files (#23712)

Co-authored-by: Tommaso Sciortino <sciortino@gmail.com>

packages/core/src/sandbox/linux/LinuxSandboxManager.test.ts

@@ -8,6 +8,7 @@ import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import { LinuxSandboxManager } from './LinuxSandboxManager.js';
 import type { SandboxRequest } from '../../services/sandboxManager.js';
 import fs from 'node:fs';
+import * as shellUtils from '../../utils/shell-utils.js';
 
 vi.mock('node:fs', async () => {
   const actual = await vi.importActual<typeof import('node:fs')>('node:fs');
@@ -20,17 +21,40 @@ vi.mock('node:fs', async () => {
       realpathSync: vi.fn((p) => p.toString()),
       statSync: vi.fn(() => ({ isDirectory: () => true }) as fs.Stats),
       mkdirSync: vi.fn(),
+      mkdtempSync: vi.fn((prefix: string) => prefix + 'mocked'),
       openSync: vi.fn(),
       closeSync: vi.fn(),
       writeFileSync: vi.fn(),
+      readdirSync: vi.fn(() => []),
+      chmodSync: vi.fn(),
+      unlinkSync: vi.fn(),
+      rmSync: vi.fn(),
     },
     existsSync: vi.fn(() => true),
     realpathSync: vi.fn((p) => p.toString()),
     statSync: vi.fn(() => ({ isDirectory: () => true }) as fs.Stats),
     mkdirSync: vi.fn(),
+    mkdtempSync: vi.fn((prefix: string) => prefix + 'mocked'),
     openSync: vi.fn(),
     closeSync: vi.fn(),
     writeFileSync: vi.fn(),
+    readdirSync: vi.fn(() => []),
+    chmodSync: vi.fn(),
+    unlinkSync: vi.fn(),
+    rmSync: vi.fn(),
+  };
+});
+
+vi.mock('../../utils/shell-utils.js', async (importOriginal) => {
+  const actual =
+    await importOriginal<typeof import('../../utils/shell-utils.js')>();
+  return {
+    ...actual,
+    spawnAsync: vi.fn(() =>
+      Promise.resolve({ status: 0, stdout: Buffer.from('') }),
+    ),
+    initializeShellParsers: vi.fn(),
+    isStrictlyApproved: vi.fn().mockResolvedValue(true),
   };
 });
 
@@ -452,4 +476,44 @@ describe('LinuxSandboxManager', () => {
       });
     });
   });
+
+  it('blocks .env and .env.* files in the workspace root', async () => {
+    vi.mocked(shellUtils.spawnAsync).mockImplementation((cmd, args) => {
+      if (cmd === 'find' && args?.[0] === workspace) {
+        // Assert that find is NOT excluding dotfiles
+        expect(args).not.toContain('-not');
+        expect(args).toContain('-prune');
+
+        return Promise.resolve({
+          status: 0,
+          stdout: Buffer.from(
+            `${workspace}/.env\0${workspace}/.env.local\0${workspace}/.env.test\0`,
+          ),
+        } as unknown as ReturnType<typeof shellUtils.spawnAsync>);
+      }
+      return Promise.resolve({
+        status: 0,
+        stdout: Buffer.from(''),
+      } as unknown as ReturnType<typeof shellUtils.spawnAsync>);
+    });
+
+    const bwrapArgs = await getBwrapArgs({
+      command: 'ls',
+      args: [],
+      cwd: workspace,
+      env: {},
+    });
+
+    const bindsIndex = bwrapArgs.indexOf('--seccomp');
+    const binds = bwrapArgs.slice(0, bindsIndex);
+
+    expect(binds).toContain(`${workspace}/.env`);
+    expect(binds).toContain(`${workspace}/.env.local`);
+    expect(binds).toContain(`${workspace}/.env.test`);
+
+    // Verify they are bound to a mask file
+    const envIndex = binds.indexOf(`${workspace}/.env`);
+    expect(binds[envIndex - 2]).toBe('--bind');
+    expect(binds[envIndex - 1]).toMatch(/gemini-cli-mask-file-.*mocked\/mask/);
+  });
 });

packages/core/src/sandbox/linux/LinuxSandboxManager.ts

@@ -5,7 +5,6 @@
  */
 
 import fs from 'node:fs';
-import { debugLogger } from '../../utils/debugLogger.js';
 import { join, dirname, normalize } from 'node:path';
 import os from 'node:os';
 import {
@@ -15,12 +14,15 @@ import {
   type SandboxedCommand,
   type SandboxPermissions,
   GOVERNANCE_FILES,
+  getSecretFileFindArgs,
   sanitizePaths,
 } from '../../services/sandboxManager.js';
 import {
   sanitizeEnvironment,
   getSecureSanitizationConfig,
 } from '../../services/environmentSanitization.js';
+import { debugLogger } from '../../utils/debugLogger.js';
+import { spawnAsync } from '../../utils/shell-utils.js';
 import { type SandboxPolicyManager } from '../../policy/sandboxPolicyManager.js';
 import {
   isStrictlyApproved,
@@ -32,6 +34,10 @@ import {
   resolveGitWorktreePaths,
   isErrnoException,
 } from '../utils/fsUtils.js';
+import {
+  isKnownSafeCommand,
+  isDangerousCommand,
+} from '../utils/commandSafety.js';
 
 let cachedBpfPath: string | undefined;
 
@@ -85,9 +91,20 @@ function getSeccompBpfPath(): string {
     buf.writeUInt32LE(inst.k, offset + 4);
   }
 
-  const bpfPath = join(os.tmpdir(), `gemini-cli-seccomp-${process.pid}.bpf`);
+  const tempDir = fs.mkdtempSync(join(os.tmpdir(), 'gemini-cli-seccomp-'));
+  const bpfPath = join(tempDir, 'seccomp.bpf');
   fs.writeFileSync(bpfPath, buf);
   cachedBpfPath = bpfPath;
+
+  // Cleanup on exit
+  process.on('exit', () => {
+    try {
+      fs.rmSync(tempDir, { recursive: true, force: true });
+    } catch {
+      // Ignore errors
+    }
+  });
+
   return bpfPath;
 }
 
@@ -110,11 +127,6 @@ function touch(filePath: string, isDirectory: boolean) {
   }
 }
 
-import {
-  isKnownSafeCommand,
-  isDangerousCommand,
-} from '../utils/commandSafety.js';
-
 /**
  * A SandboxManager implementation for Linux that uses Bubblewrap (bwrap).
  */
@@ -130,6 +142,8 @@ export interface LinuxSandboxOptions extends GlobalSandboxOptions {
 }
 
 export class LinuxSandboxManager implements SandboxManager {
+  private static maskFilePath: string | undefined;
+
   constructor(private readonly options: LinuxSandboxOptions) {}
 
   isKnownSafeCommand(args: string[]): boolean {
@@ -140,6 +154,31 @@ export class LinuxSandboxManager implements SandboxManager {
     return isDangerousCommand(args);
   }
 
+  private getMaskFilePath(): string {
+    if (
+      LinuxSandboxManager.maskFilePath &&
+      fs.existsSync(LinuxSandboxManager.maskFilePath)
+    ) {
+      return LinuxSandboxManager.maskFilePath;
+    }
+    const tempDir = fs.mkdtempSync(join(os.tmpdir(), 'gemini-cli-mask-file-'));
+    const maskPath = join(tempDir, 'mask');
+    fs.writeFileSync(maskPath, '');
+    fs.chmodSync(maskPath, 0);
+    LinuxSandboxManager.maskFilePath = maskPath;
+
+    // Cleanup on exit
+    process.on('exit', () => {
+      try {
+        fs.rmSync(tempDir, { recursive: true, force: true });
+      } catch {
+        // Ignore errors
+      }
+    });
+
+    return maskPath;
+  }
+
   async prepareCommand(req: SandboxRequest): Promise<SandboxedCommand> {
     const isReadonlyMode = this.options.modeConfig?.readonly ?? true;
     const allowOverrides = this.options.modeConfig?.allowOverrides ?? true;
@@ -319,6 +358,11 @@ export class LinuxSandboxManager implements SandboxManager {
       }
     }
 
+    // Mask secret files (.env, .env.*)
+    bwrapArgs.push(
+      ...(await this.getSecretFilesArgs(req.policy?.allowedPaths)),
+    );
+
     const bpfPath = getSeccompBpfPath();
 
     bwrapArgs.push('--seccomp', '9');
@@ -339,4 +383,68 @@ export class LinuxSandboxManager implements SandboxManager {
       cwd: req.cwd,
     };
   }
+
+  /**
+   * Generates bubblewrap arguments to mask secret files.
+   */
+  private async getSecretFilesArgs(allowedPaths?: string[]): Promise<string[]> {
+    const args: string[] = [];
+    const maskPath = this.getMaskFilePath();
+    const paths = sanitizePaths(allowedPaths) || [];
+    const searchDirs = new Set([this.options.workspace, ...paths]);
+    const findPatterns = getSecretFileFindArgs();
+
+    for (const dir of searchDirs) {
+      try {
+        // Use the native 'find' command for performance and to catch nested secrets.
+        // We limit depth to 3 to keep it fast while covering common nested structures.
+        // We use -prune to skip heavy directories efficiently while matching dotfiles.
+        const findResult = await spawnAsync('find', [
+          dir,
+          '-maxdepth',
+          '3',
+          '-type',
+          'd',
+          '(',
+          '-name',
+          '.git',
+          '-o',
+          '-name',
+          'node_modules',
+          '-o',
+          '-name',
+          '.venv',
+          '-o',
+          '-name',
+          '__pycache__',
+          '-o',
+          '-name',
+          'dist',
+          '-o',
+          '-name',
+          'build',
+          ')',
+          '-prune',
+          '-o',
+          '-type',
+          'f',
+          ...findPatterns,
+          '-print0',
+        ]);
+
+        const files = findResult.stdout.toString().split('\0');
+        for (const file of files) {
+          if (file.trim()) {
+            args.push('--bind', maskPath, file.trim());
+          }
+        }
+      } catch (e) {
+        debugLogger.log(
+          `LinuxSandboxManager: Failed to find or mask secret files in ${dir}`,
+          e,
+        );
+      }
+    }
+    return args;
+  }
 }