Forgot to convert the jstring to char* in certificate request.

android_security_CertTool_generateCertificateRequest(JNIEnv* env,

                                                     jobject thiz,

                                                     jint bits,

                                                     jstring subject)

                                                     jstring jChallenge)

{

    int ret = -1;

    jboolean bIsCopy;

    char csr[REPLY_MAX];

    if (gen_csr(bits, subject, csr) == 0) {

        return (*env)->NewStringUTF(env, csr);

    }

    const char* challenge = (*env)->GetStringUTFChars(env, jChallenge, &bIsCopy);

    ret = gen_csr(bits, challenge , csr);

    (*env)->ReleaseStringUTFChars(env, jChallenge, challenge);

    if (ret == 0) return (*env)->NewStringUTF(env, csr);

    return NULL;

}