fix: add path traversal validation to install_app tool (CWE-22)

src/server.ts

@@ -14,10 +14,11 @@ import { PNG } from "./png";
 import { isScalingAvailable, Image } from "./image-utils";
 import { Mobilecli } from "./mobilecli";
 import { MobileDevice } from "./mobile-device";
-import { validateOutputPath, validateFileExtension } from "./utils";
+import { validateOutputPath, validateInputPath, validateFileExtension } from "./utils";
 
 const ALLOWED_SCREENSHOT_EXTENSIONS = [".png", ".jpg", ".jpeg"];
 const ALLOWED_RECORDING_EXTENSIONS = [".mp4"];
+const ALLOWED_APP_EXTENSIONS = [".apk", ".ipa", ".zip", ".app"];
 
 interface MobilecliDevice {
 	id: string;
@@ -368,6 +369,8 @@ export const createMcpServer = (): McpServer => {
 		},
 		{ destructiveHint: true },
 		async ({ device, path }) => {
+			validateFileExtension(path, ALLOWED_APP_EXTENSIONS, "install_app");
+			validateInputPath(path);
 			const robot = getRobotFromDevice(device);
 			await robot.installApp(path);
 			return `Installed app from ${path}`;

src/utils.ts

@@ -66,7 +66,7 @@ function resolveWithSymlinks(filePath: string): string {
 	}
 }
 
-export function validateOutputPath(filePath: string): void {
+function validatePathAgainstAllowedRoots(filePath: string, label: string): void {
 	const resolved = resolveWithSymlinks(filePath);
 	const allowedRoots = getAllowedRoots();
 	const isWindows = process.platform === "win32";
@@ -86,3 +86,11 @@ export function validateOutputPath(filePath: string): void {
 		);
 	}
 }
+
+export function validateOutputPath(filePath: string): void {
+	validatePathAgainstAllowedRoots(filePath, "output");
+}
+
+export function validateInputPath(filePath: string): void {
+	validatePathAgainstAllowedRoots(filePath, "input");
+}

test/utils.ts

@@ -0,0 +1,84 @@
+import assert from "node:assert";
+import path from "node:path";
+import fs from "node:fs";
+
+import { validateFileExtension } from "../src/utils";
+import { ActionableError } from "../src/robot";
+
+const ALLOWED_APP_EXTENSIONS = [".apk", ".ipa", ".zip", ".app"];
+
+describe("validateInputPath (new: prevents CWE-22 in install_app)", () => {
+	let validateInputPath: (filePath: string) => void;
+
+	before(() => {
+		const utils = require("../src/utils");
+		validateInputPath = utils.validateInputPath;
+		if (!validateInputPath) {
+			throw new Error("validateInputPath is not exported from src/utils.ts — the fix has not been applied yet");
+		}
+	});
+
+	it("should allow paths under cwd", () => {
+		const filePath = path.join(process.cwd(), "test-input-file.apk");
+		fs.writeFileSync(filePath, "fake-apk");
+		try {
+			assert.doesNotThrow(() => validateInputPath(filePath));
+		} finally {
+			fs.unlinkSync(filePath);
+		}
+	});
+
+	it("should reject paths outside allowed roots like /etc", () => {
+		assert.throws(() => validateInputPath("/etc/passwd"), ActionableError);
+	});
+
+	it("should reject path traversal attempts via ../ from cwd", () => {
+		const filePath = path.join(process.cwd(), "..", "..", "etc", "passwd");
+		assert.throws(() => validateInputPath(filePath), ActionableError);
+	});
+
+	it("should reject absolute paths to /usr", () => {
+		assert.throws(() => validateInputPath("/usr/local/bin/malicious.apk"), ActionableError);
+	});
+
+	it("should reject paths under /home or /Users outside cwd", () => {
+		const otherUser = path.join("/Users", "otheruser", "malware.apk");
+		assert.throws(() => validateInputPath(otherUser), ActionableError);
+	});
+
+	it("should reject paths to root filesystem", () => {
+		assert.throws(() => validateInputPath("/malicious.apk"), ActionableError);
+	});
+});
+
+describe("validateFileExtension for install_app", () => {
+	it("should accept .apk files", () => {
+		assert.doesNotThrow(() => validateFileExtension("myapp.apk", ALLOWED_APP_EXTENSIONS, "install_app"));
+	});
+
+	it("should accept .ipa files", () => {
+		assert.doesNotThrow(() => validateFileExtension("myapp.ipa", ALLOWED_APP_EXTENSIONS, "install_app"));
+	});
+
+	it("should accept .zip files", () => {
+		assert.doesNotThrow(() => validateFileExtension("myapp.zip", ALLOWED_APP_EXTENSIONS, "install_app"));
+	});
+
+	it("should accept .app paths", () => {
+		assert.doesNotThrow(() => validateFileExtension("MyApp.app", ALLOWED_APP_EXTENSIONS, "install_app"));
+	});
+
+	it("should reject other extensions", () => {
+		assert.throws(
+			() => validateFileExtension("script.sh", ALLOWED_APP_EXTENSIONS, "install_app"),
+			ActionableError,
+		);
+	});
+
+	it("should reject files with no extension", () => {
+		assert.throws(
+			() => validateFileExtension("noext", ALLOWED_APP_EXTENSIONS, "install_app"),
+			ActionableError,
+		);
+	});
+});