Dynamically fetch & cache Frida server downloads

Author: pimterry

src/dynamic-dep-store.ts

@@ -0,0 +1,41 @@
+import * as path from 'path';
+import * as fs from './util/fs';
+import * as stream from 'stream';
+
+import { HtkConfig } from './config';
+
+/**
+ * This retrieves a stream for a dependency file, either from disk if it's already available
+ * or by calling the fetch() function (and then saving the result to disk in parallel for
+ * future calls).
+ */
+export async function getDependencyStream<K extends readonly string[]>(options: {
+    config: HtkConfig,
+    key: K,
+    ext: string,
+    fetch: (key: K) => Promise<stream.Readable>
+}) {
+    const depPath = path.join(options.config.configPath, `${options.key.join('-')}.${options.ext}`);
+
+    if (await fs.canAccess(depPath)) {
+        return fs.createReadStream(depPath);
+    }
+
+    const tmpDownloadPath = depPath + `.tmp-${Math.random().toString(36).slice(2)}`;
+    const downloadStream = await options.fetch(options.key);
+    const diskStream = fs.createWriteStream(tmpDownloadPath);
+    downloadStream.pipe(diskStream);
+
+    downloadStream.on('error', (e) => {
+        console.warn(`Failed to download dependency to ${depPath}:`, e);
+        diskStream.destroy();
+        fs.deleteFile(tmpDownloadPath).catch(() => {});
+    });
+
+    diskStream.on('finish', () => {
+        fs.moveFile(tmpDownloadPath, depPath)
+            .catch(console.warn);
+    });
+
+    return downloadStream;
+}

src/interceptors/frida/frida-android-integration.ts

@@ -1,22 +1,22 @@
 import { Client as AdbClient, DeviceClient } from '@devicefarmer/adbkit';
 import * as FridaJs from 'frida-js';
 
+import { waitUntil } from '../../util/promise';
+import { HtkConfig } from '../../config';
 import {
     EMULATOR_HOST_IPS,
     createPersistentReverseTunnel,
     getConnectedDevices,
     getRootCommand,
     isProbablyRooted
 } from '../android/adb-commands';
-import { waitUntil } from '../../util/promise';
 import { buildAndroidFridaScript } from './frida-scripts';
 import {
     FRIDA_ALTERNATE_PORT,
     FRIDA_BINARY_NAME,
     FRIDA_DEFAULT_PORT,
-    FRIDA_SRIS,
-    FRIDA_VERSION,
     FridaHost,
+    getFridaServer,
     killProcess,
     launchScript,
     testAndSelectProxyAddress
@@ -96,7 +96,7 @@ const ANDROID_ABI_FRIDA_ARCH_MAP = {
     'x86_64': 'x86_64'
 } as const;
 
-export async function setupAndroidHost(adbClient: AdbClient, hostId: string) {
+export async function setupAndroidHost(config: HtkConfig, adbClient: AdbClient, hostId: string) {
     const deviceClient = adbClient.getDevice(hostId);
 
     const deviceProperties = await deviceClient.getProperties();
@@ -111,13 +111,7 @@ export async function setupAndroidHost(adbClient: AdbClient, hostId: string) {
     if (!firstKnownAbi) throw new Error(`Did not recognize any device ABIs from ${supportedAbis.join(',')}`);
 
     const deviceArch = ANDROID_ABI_FRIDA_ARCH_MAP[firstKnownAbi];
-
-    const serverStream = await FridaJs.downloadFridaServer({
-        version: FRIDA_VERSION,
-        platform: 'android',
-        arch: deviceArch,
-        sri: FRIDA_SRIS.android[deviceArch]
-    });
+    const serverStream = await getFridaServer(config, 'android', deviceArch);
 
     await deviceClient.push(serverStream, ANDROID_FRIDA_BINARY_PATH, 0o555);
 }

src/interceptors/frida/frida-android-interceptor.ts

@@ -6,7 +6,7 @@ import { Interceptor } from "..";
 import { HtkConfig } from '../../config';
 
 import { createAdbClient } from '../android/adb-commands';
-import { FridaHost, FridaTarget, killProcess } from './frida-integration';
+import { FridaTarget, killProcess } from './frida-integration';
 import {
     getAndroidFridaHosts,
     getAndroidFridaTargets,
@@ -61,7 +61,7 @@ export class FridaAndroidInterceptor implements Interceptor {
             | { action: 'intercept', hostId: string, targetId: string }
     ): Promise<void> {
         if (options.action === 'setup') {
-            await setupAndroidHost(this.adbClient, options.hostId);
+            await setupAndroidHost(this.config, this.adbClient, options.hostId);
         } else if (options.action === 'launch') {
             const fridaServer = await launchAndroidHost(this.adbClient, options.hostId);
 

src/interceptors/frida/frida-integration.ts

@@ -1,9 +1,12 @@
 import * as FridaJs from 'frida-js';
 import { CustomError, delay } from '@httptoolkit/util';
 
+import { withTimeout } from '../../util/promise';
 import { getReachableInterfaces } from '../../util/network';
+import { HtkConfig } from '../../config';
+import * as dynamicDeps from '../../dynamic-dep-store';
+
 import { buildIpTestScript } from './frida-scripts';
-import { withTimeout } from '../../util/promise';
 
 /**
  * Terminology:
@@ -44,6 +47,26 @@ export const FRIDA_SRIS = {
     }
 } as const;
 
+export const getFridaServer = (
+    config: HtkConfig,
+    platform: 'android',
+    arch: 'arm' | 'arm64' | 'x86' | 'x86_64'
+) => {
+    return dynamicDeps.getDependencyStream({
+        config,
+        key: ['frida-server', platform, arch, FRIDA_VERSION] as const,
+        ext: '.bin',
+        fetch: ([, platform, arch, version]) => {
+            return FridaJs.downloadFridaServer({
+                version: version,
+                platform: platform,
+                arch: arch,
+                sri: FRIDA_SRIS.android[arch]
+            });
+        }
+    });
+}
+
 class FridaScriptError extends CustomError {
     constructor(
         message: FridaJs.ScriptAgentErrorMessage