轉：Android開發：使用JNI讀取應用簽名

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    博文轉自http://www.tuicool.com/articles/UVjme2r,感謝博主的分享

    為了防止被反編譯，打算把關鍵代碼寫到so裡(比如加解密)，在so裡加上判斷APk包簽名是否一致的代碼，避免so被二次打包。其實用JNI讀簽名就是用了Java的反射機制。

    先看Java讀取簽名的方法:

1 try {2       PackageInfo info = context.getPackageManager().getPackageInfo(context.getPackageName(), 64);3       Signature sign = info.signatures[0];4       Log.i("test", "hashCode : " + sign.hashCode());5     } catch (NameNotFoundException e) {6       e.printStackTrace();7     }

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    然後我們用JNI c語言實現,同樣需要傳遞Context：

 1 int getSignHashCode(JNIEnv *env, jobject context) { 2   //Context的類 3   jclass context_clazz = (*env)->GetObjectClass(env, context); 4   // 得到 getPackageManager 方法的 ID 5   jmethodID methodID_getPackageManager = (*env)->GetMethodID(env, context_clazz, 6       "getPackageManager", "()Landroid/content/pm/PackageManager;"); 7   8   // 獲得PackageManager對象 9   jobject packageManager = (*env)->CallObjectMethod(env, context,10       methodID_getPackageManager);11 //    // 獲得 PackageManager 類12   jclass pm_clazz = (*env)->GetObjectClass(env, packageManager);13   // 得到 getPackageInfo 方法的 ID14   jmethodID methodID_pm = (*env)->GetMethodID(env, pm_clazz, "getPackageInfo",15       "(Ljava/lang/String;I)Landroid/content/pm/PackageInfo;");16 //17 //    // 得到 getPackageName 方法的 ID18   jmethodID methodID_pack = (*env)->GetMethodID(env, context_clazz,19       "getPackageName", "()Ljava/lang/String;");20  21   // 獲得當前應用的包名22   jstring application_package = (*env)->CallObjectMethod(env, context,23       methodID_pack);24   const char *str = (*env)->GetStringUTFChars(env, application_package, 0);25   __android_log_print(ANDROID_LOG_DEBUG, "JNI", "packageName: %s\n", str);26  27   // 獲得PackageInfo28   jobject packageInfo = (*env)->CallObjectMethod(env, packageManager,29       methodID_pm, application_package, 64);30  31   jclass packageinfo_clazz = (*env)->GetObjectClass(env, packageInfo);32   jfieldID fieldID_signatures = (*env)->GetFieldID(env, packageinfo_clazz,33       "signatures", "[Landroid/content/pm/Signature;");34   jobjectArray signature_arr = (jobjectArray)(*env)->GetObjectField(env,35       packageInfo, fieldID_signatures);36   //Signature數組中取出第一個元素37   jobject signature = (*env)->GetObjectArrayElement(env, signature_arr, 0);38   //讀signature的hashcode39   jclass signature_clazz = (*env)->GetObjectClass(env, signature);40   jmethodID methodID_hashcode = (*env)->GetMethodID(env, signature_clazz,41       "hashCode", "()I");42   jint hashCode = (*env)->CallIntMethod(env, signature, methodID_hashcode);43   __android_log_print(ANDROID_LOG_DEBUG, "JNI", "hashcode: %d\n", hashCode);44   return hashCode;45 }

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    第二個參數jobject不是JNI函數的預設參數，而是傳入的Context執行個體。

轉：Android開發：使用JNI讀取應用簽名