android - 检查 C/ native 代码中的 .apk 签名

Question

我开发了一个 Android 应用程序，其中还包含一个用 C 编写的 native 部分(不依赖于应用程序)。

如果共享库不工作，应用程序本身就毫无用处。

我想让 native 部分(一个共享库)只做它的工作，如果存在一个未修改的应用程序版本(.apk)，它已经交付。

对我来说最好的方法是这样的:

1. 安装应用
2. 共享库检查应用程序/.apk 的签名/哈希
3. 仅当签名与已知签名匹配时才工作

通过这种方式，我想保护我的应用程序免受修改和盗版。

这样做有什么技巧吗？我刚刚找到了在 Java 中检查自己的签名的帖子，但如果可以反编译应用程序，那就不是开玩笑了。

Answer 1

由于我被要求发布一些代码，我现在如何从 C 中检查我的 Java 应用程序的 CRC 代码，这里有一些 fragment 。

由于性能原因，我无法发布完整的工作解决方案，因为它分布在多行中，但我希望这是最完整和最有效的:

在您的 MyApplication.java 中:

public class MyApplication extends Application {
    private static Context context;

    public static Context getAppContext() {
        return MyApplication.context;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        MyApplication.context = getApplicationContext();
    }
}

Android.mk:

LOCAL_CFLAGS += -O3 -DDEBUG_MODE=0 -DCLASSES_CRC=2331492378

在您的 C 代码中:

#define LOG_TAG "Your Log Tag"

#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)

#if DEBUG_MODE
#define LOGDH(...) LOGD(__VA_ARGS__)
#define LOGIH(...) LOGI(__VA_ARGS__)
#define LOGEH(...) LOGE(__VA_ARGS__)
#else
#define LOGDH(...) //
#define LOGIH(...) //
#define LOGEH(...) //
#endif

int isSecure = -1;

jclass MyApplication;
jclass Context;
jclass ApplicationInfo;


jclass ZipFile;
jclass ZipEntry;
jclass CheckedInputStream;
jclass Adler32;
jclass Checksum;

jmethodID MyApplication_getAppContextMethodId;
jmethodID Context_getApplicationInfoMethodId;

jmethodID ZipFile_ConstructorMethodId;
jmethodID CheckedInputStream_ConstructorMethodId;
jmethodID Adler32_ConstructorMethodId;

jmethodID ZipFile_getEntryMethodId;
jmethodID ZipFile_getInputStreamMethodId;
jmethodID CheckedInputStream_readMethodId;
jmethodID CheckedInputStream_getChecksumMethodId;
jmethodID Checksum_getValueMethodId;

jfieldID ApplicationInfo_flagsFieldId;
jfieldID ApplicationInfo_FLAG_DEBUGGABLEFieldId;
jfieldID ApplicationInfo_sourceDirFieldId;


static long getClassesCRC(JNIEnv *env) {
    jobject appContextInstance = (*env)->CallStaticObjectMethod(env,
            MyApplication, MyApplication_getAppContextMethodId);
    if (!appContextInstance) {
        LOGEH("Unable to get instance of AppContext");
        return false;
    }

    jobject applicationInfoInstance = (*env)->CallObjectMethod(env,
            appContextInstance, Context_getApplicationInfoMethodId);
    if (!appContextInstance) {
        LOGEH("Unable to get instance of ApplicationInfo");
        return false;
    }

    jobject zipFileInstance = (*env)->NewObject(env, ZipFile,
            ZipFile_ConstructorMethodId,
            (*env)->GetObjectField(env, applicationInfoInstance,
                    ApplicationInfo_sourceDirFieldId));
    if (!zipFileInstance) {
        LOGEH("Unable to get instance of ZipFile");
        return -1;
    }

    jstring classesDexString = (*env)->NewStringUTF(env, "classes.dex");
    jobject zipEntryInstance = (*env)->CallObjectMethod(env, zipFileInstance,
            ZipFile_getEntryMethodId, classesDexString);
    if (!zipFileInstance) {
        LOGEH("Unable to get instance of ZipEntry");
        return -1;
    }
    (*env)->DeleteLocalRef(env, classesDexString);

    jobject adler32Instance = (*env)->NewObject(env, Adler32,
            Adler32_ConstructorMethodId);
    if (!adler32Instance) {
        LOGEH("Unable to get instance of Adler32");
        return -1;
    }

    jobject inputStreamInstance = (*env)->CallObjectMethod(env, zipFileInstance,
            ZipFile_getInputStreamMethodId, zipEntryInstance);
    if (!inputStreamInstance) {
        LOGEH("Unable to get instance of InputStream");
        return -1;
    }

    jobject checkedInputStreamInstance = (*env)->NewObject(env,
            CheckedInputStream, CheckedInputStream_ConstructorMethodId,
            inputStreamInstance, adler32Instance);
    if (!checkedInputStreamInstance) {
        LOGEH("Unable to get instance of CheckedInputStream");
        return -1;
    }

    int bufferSize = 128;
    jbyteArray bufferBytes = (*env)->NewByteArray(env, bufferSize);

    while ((*env)->CallIntMethod(env, checkedInputStreamInstance,
            CheckedInputStream_readMethodId, bufferBytes) > 0) {
    }
    (*env)->DeleteLocalRef(env, bufferBytes);

    jobject checksumInstance = (*env)->CallObjectMethod(env,
            checkedInputStreamInstance, CheckedInputStream_getChecksumMethodId);
    if (!checksumInstance) {
        LOGEH("Unable to get instance of CheckSum");
        return -1;
    }

    return (*env)->CallLongMethod(env, checksumInstance,
            Checksum_getValueMethodId);
}

static bool isDebuggable(JNIEnv *env) {
    jobject appContextInstance = (*env)->CallStaticObjectMethod(env,
            MyApplication, Application_getAppContextMethodId);
    if (!appContextInstance) {
        LOGEH("Unable to get instance of AppContext");
        return false;
    }

    jobject applicationInfoInstance = (*env)->CallObjectMethod(env,
            appContextInstance, Context_getApplicationInfoMethodId);
    if (!appContextInstance) {
        LOGEH("Unable to get instance of ApplicationInfo");
        return false;
    }

    int FLAG_DEBUGGABLE = (*env)->GetStaticIntField(env, ApplicationInfo,
            ApplicationInfo_FLAG_DEBUGGABLEFieldId);
    int flags = (*env)->GetIntField(env, applicationInfoInstance,
            ApplicationInfo_flagsFieldId);

    return (0 != (flags &= FLAG_DEBUGGABLE));
}

static bool isSecureEnvironment(JNIEnv *env) {

    //isSecure = true; // TODO remove this

    if (isSecure == -1) {
        isSecure = true;

        if (isDebuggable(env)) {
            // someone used the app in debug-mode
#if DEBUG_MODE != 1
            // TODO report

#endif
            LOGEH("App IS DEBUGGABLE!");
            isSecure = false;
        } else {

            // check CRC
            long classesCRC = getClassesCRC(env);
            if (classesCRC != (long) CLASSES_CRC) {
#if DEBUG_MODE != 1
                // TODO report
#endif
                LOGEH("CRC-CHECK FAILED: %lu", classesCRC);

                isSecure = false;
            }
        }
    }
    return isSecure;
}


static bool initJavaClasses(JNIEnv * env) {
    jclass local = (*env)->FindClass(env, "eu/my/MyApplication");
    MyApplication = (*env)->NewGlobalRef(env, local);
    if (!MyApplication) {
    LOGEH("Unable to find the MyApplication class");
    return false;
    }
    local = (*env)->FindClass(env, "android/content/Context");
    Context = (*env)->NewGlobalRef(env, local);
    (*env)->DeleteLocalRef(env, local);
    if (!Context) {
    LOGEH("Unable to find the Context class");
    return false;
    }
    local = (*env)->FindClass(env, "android/content/pm/ApplicationInfo");
    ApplicationInfo = (*env)->NewGlobalRef(env, local);
    (*env)->DeleteLocalRef(env, local);
    if (!ApplicationInfo) {
    LOGEH("Unable to find the ApplicationInfo class");
    return false;
    }

    local = (*env)->FindClass(env, "java/util/zip/ZipFile");
    ZipFile = (*env)->NewGlobalRef(env, local);
    (*env)->DeleteLocalRef(env, local);
    if (!ZipFile) {
    LOGEH("Unable to find the ZipFile class");
    return false;
    }

    local = (*env)->FindClass(env, "java/util/zip/ZipEntry");
    ZipEntry = (*env)->NewGlobalRef(env, local);
    (*env)->DeleteLocalRef(env, local);
    if (!ZipEntry) {
    LOGEH("Unable to find the ZipEntry class");
    return false;
    }

    local = (*env)->FindClass(env, "java/util/zip/CheckedInputStream");
    CheckedInputStream = (*env)->NewGlobalRef(env, local);
    (*env)->DeleteLocalRef(env, local);
    if (!CheckedInputStream) {
    LOGEH("Unable to find the CheckedInputStream class");
    return false;
    }

    local = (*env)->FindClass(env, "java/util/zip/Adler32");
    Adler32 = (*env)->NewGlobalRef(env, local);
    (*env)->DeleteLocalRef(env, local);
    if (!Adler32) {
    LOGEH("Unable to find the Adler32 class");
    return false;
    }

    local = (*env)->FindClass(env, "java/util/zip/Checksum");
    Checksum = (*env)->NewGlobalRef(env, local);
    (*env)->DeleteLocalRef(env, local);
    if (!Checksum) {
    LOGEH("Unable to find the Checksum class");
    return false;
    }

    return true;
}

static bool initJavaMethods(JNIEnv * env) {
    MyApplication_getAppContextMethodId = (*env)->GetStaticMethodID(env,
    MyApplication, "getAppContext", "()Landroid/content/Context;");
    if (!MyApplication_getAppContextMethodId) {
    LOGEH("Unable to find the getAppContext method");
    return false;
    }
    Context_getApplicationInfoMethodId = (*env)->GetMethodID(env, Context,
    "getApplicationInfo", "()Landroid/content/pm/ApplicationInfo;");
    if (!Context_getApplicationInfoMethodId) {
    LOGEH("Unable to find the getApplicationInfo method");
    return false;
    }

    ZipFile_ConstructorMethodId = (*env)->GetMethodID(env, ZipFile, "<init>",
    "(Ljava/lang/String;)V");
    if (!ZipFile_ConstructorMethodId) {
    LOGEH("Unable to find the constructor method");
    return false;
    }

    CheckedInputStream_ConstructorMethodId = (*env)->GetMethodID(env,
    CheckedInputStream, "<init>",
    "(Ljava/io/InputStream;Ljava/util/zip/Checksum;)V");
    if (!CheckedInputStream_ConstructorMethodId) {
    LOGEH("Unable to find the constructor method");
    return false;
    }

    Adler32_ConstructorMethodId = (*env)->GetMethodID(env, Adler32, "<init>",
    "()V");
    if (!Adler32_ConstructorMethodId) {
    LOGEH("Unable to find the constructor method");
    return false;
    }

    ZipFile_getEntryMethodId = (*env)->GetMethodID(env, ZipFile, "getEntry",
    "(Ljava/lang/String;)Ljava/util/zip/ZipEntry;");
    if (!ZipFile_getEntryMethodId) {
    LOGEH("Unable to find the getEntry method");
    return false;
    }

    ZipFile_getInputStreamMethodId = (*env)->GetMethodID(env, ZipFile,
    "getInputStream", "(Ljava/util/zip/ZipEntry;)Ljava/io/InputStream;");
    if (!ZipFile_getInputStreamMethodId) {
    LOGEH("Unable to find the getInputStream method");
    return false;
    }

    CheckedInputStream_readMethodId = (*env)->GetMethodID(env, CheckedInputStream,
    "read", "([B)I");
    if (!CheckedInputStream_readMethodId) {
    LOGEH("Unable to find the read method");
    return false;
    }

    CheckedInputStream_getChecksumMethodId = (*env)->GetMethodID(env,
    CheckedInputStream, "getChecksum", "()Ljava/util/zip/Checksum;");
    if (!CheckedInputStream_getChecksumMethodId) {
    LOGEH("Unable to find the getChecksum method");
    return false;
    }

    Checksum_getValueMethodId = (*env)->GetMethodID(env, Checksum, "getValue",
    "()J");
    if (!Checksum_getValueMethodId) {
    LOGEH("Unable to find the getValue method");
    return false;
    }

    return true;
}

static bool initJavaFields(JNIEnv * env) {
    ApplicationInfo_flagsFieldId = (*env)->GetFieldID(env, ApplicationInfo, "flags",
    "I");

    if (!ApplicationInfo_flagsFieldId) {
    LOGEH("Unable to find the flags field");
    return false;
    }

    ApplicationInfo_FLAG_DEBUGGABLEFieldId = (*env)->GetStaticFieldID(env,
    ApplicationInfo, "FLAG_DEBUGGABLE", "I");
    if (!ApplicationInfo_FLAG_DEBUGGABLEFieldId) {
    LOGEH("Unable to get static field FLAG_DEBUGGABLE");
    return false;
    }

    ApplicationInfo_sourceDirFieldId = (*env)->GetFieldID(env, ApplicationInfo,
    "sourceDir", "Ljava/lang/String;");
    if (!ApplicationInfo_sourceDirFieldId) {
    LOGEH("Unable to get static field sourceDir");
    return false;
    }

    return true;
}


jint JNI_OnLoad(JavaVM* vm, void* reserved) {
    (void) reserved; // Suppress the warning.
    JNIEnv * env;

    if ((*vm)->GetEnv(vm, (void **) &env, JNI_VERSION_1_6) != JNI_OK) {
    return -1;
    }

    if (!initJavaClasses(env)) {
    return -1;
    }

    if (!initJavaMethods(env)) {
    return -1;
    }

    if (!initJavaFields(env)) {
    return -1;
    }

    return JNI_VERSION_1_6;
}

不要忘记将 MyApplication 的方法添加到 Proguard 设置中以防止它们被删除!

用法:

1. 使用 -DDEBUG_MODE=1 创建您的 APK
2. 在您的 Android 上启动 APK
3. 读取“CRC-check failed:xxx”中的值
4. 获取该值并将其插入 CLASSES_CRC=xxxx
5. 切换到-DDEBUG_MODE=0
6. 重建您的 APK
7. 检查您的应用是否运行良好
8. 发布

此方法稍微复杂一些，因为它需要 2 次构建才能获得有效的 APK。但由于 CRC 是在 C 内部检查的，而不仅仅是 APK 文件的虚拟签名被采用，所以这种检查几乎是防弹的。

在我的情况下，例如，我什至不设置许可机制以防签名无效。

此外，由于此方法仅使用数字而不使用字符，因此已完全编译。

希望这对某人有帮助!