libnative-lib.cpp

bool checkCert(JNIEnv *env, jobject contextObject) {
    jclass contextTemp = env->FindClass("android/content/Context");
    jclass contextClass = (jclass) env->NewGlobalRef(contextTemp);
    jmethodID getPackageManager = env->GetMethodID(contextClass,
                                                   "getPackageManager",
                                                   "()Landroid/content/pm/PackageManager;");
    jobject share = (jobject) env->CallObjectMethod(contextObject, getPackageManager);

    jmethodID getPackageName = env->GetMethodID(contextClass, "getPackageName",
                                                "()Ljava/lang/String;");
    jstring packageName = (jstring) env->CallObjectMethod(contextObject, getPackageName);
    jclass clazz = env->FindClass("android/content/pm/PackageManager");

    jfieldID GET_SIGNATURESfid = env->GetStaticFieldID(clazz, "GET_SIGNATURES", "I");
    jint GET_SIGNATURES = env->GetStaticIntField(clazz, GET_SIGNATURESfid);

    jclass PackageManagerObj = (jclass) env->NewGlobalRef(clazz);
    jmethodID getPackageInfoId = env->GetMethodID(PackageManagerObj, "getPackageInfo",
                                                  "(Ljava/lang/String;I)Landroid/content/pm/PackageInfo;");
    jobject getPackageInfoObject = (jobject) env->CallObjectMethod(share, getPackageInfoId,
                                                                   packageName, GET_SIGNATURES);
    jclass packageInfoClass = env->FindClass("android/content/pm/PackageInfo");
    jfieldID signatures = env->GetFieldID(packageInfoClass, "signatures",
                                          "[Landroid/content/pm/Signature;");
    jobjectArray rows = reinterpret_cast<jobjectArray>(
            env->GetObjectField(getPackageInfoObject, signatures));
    int size = env->GetArrayLength(rows);
    jclass signaturesClass = env->FindClass("android/content/pm/Signature");
    jclass mEssage = env->FindClass("java/security/MessageDigest");
    jclass MessageDigestClass = (jclass) env->NewGlobalRef(mEssage);
    jmethodID mGetInstance = env->GetStaticMethodID(MessageDigestClass, "getInstance",
                                                    "(Ljava/lang/String;)Ljava/security/MessageDigest;");
    jmethodID updateMethod = env->GetMethodID(MessageDigestClass, "update", "([B)V");
    jmethodID toByteArrayMethod = env->GetMethodID(signaturesClass, "toByteArray", "()[B");

    jclass tempBase64 = env->FindClass("android/util/Base64");
    jclass Base64Class = (jclass) env->NewGlobalRef(tempBase64);

    jmethodID encodeToStringID = env->GetStaticMethodID(Base64Class, "encodeToString",
                                                        "([BI)Ljava/lang/String;");
    jmethodID digest = env->GetMethodID(MessageDigestClass, "digest", "()[B");
    for (int i = 0; i < size; i++) {
        jobject messageDigest = env->CallStaticObjectMethod(MessageDigestClass, mGetInstance,
                                                            env->NewStringUTF("SHA"));
        jobject signature = env->GetObjectArrayElement(rows, i);
        env->CallVoidMethod(messageDigest, updateMethod,
                            (jbyteArray) env->CallObjectMethod(signature, toByteArrayMethod));
        jstring signedCert = (jstring) env->CallStaticObjectMethod(Base64Class, encodeToStringID,
                                                                   env->CallObjectMethod(messageDigest, digest),
                                                                   (jint) 0);
        std::string signedCertStr = jstring2string(env, signedCert);
        std::string referenceCert = "yourReleaseSigningCertificate";
        return signedCertStr == referenceCert;
    }
    return false;
}