/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * Copyright (c) 2017, The Linux Foundation.
 */

/*
 * Copyright 2012 Giesecke & Devrient GmbH.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.android.se.security.gpac;

import java.io.ByteArrayOutputStream;

/**
 * NFC-AR-DO: In the NFC use case, mobile device application gather information from their
 * associated card application using the SE access API. However, when the card application needs to
 * trigger its associated mobile application, it sends an HCI EVT_TRANSACTION according to ETSI TS
 * 102 622 [102 622] over SWP to the device. This event is handled by the NFC chipset stack which
 * has to start the corresponding device application. Disclosure of this event to malicious
 * applications can lead to phishing and denial of service attacks. To prevent this, it shall be
 * possible to use the applications signature to authorize device applications to receive HCI events
 * issued by the secure element application. An NFC event data object defines an access rule for
 * generating NFC events for a specific terminal application. The NFC event access can be restricted
 * by a rule based on an event access is NEVER/ ALWAYS allowed policy.
 */
public class NFC_AR_DO extends BerTlv {

    public static final int TAG = 0xD1;

    private boolean mNfcAllowed = false;

    public NFC_AR_DO(byte[] rawData, int valueIndex, int valueLength) {
        super(rawData, TAG, valueIndex, valueLength);
    }

    public NFC_AR_DO(boolean allowed) {
        super(null, TAG, 0, 0);
        mNfcAllowed = allowed;
    }

    public boolean isNfcAllowed() {
        return mNfcAllowed;
    }

    @Override
    /**
     * Tag: D1 Length: 1 Value: Contains a NFC event access rule: NEVER (00): NFC event access is
     * not
     * allowed ALWAYS(01): NFC event access is allowed
     */
    public void interpret() throws ParserException {

        mNfcAllowed = false;

        byte[] data = getRawData();
        int index = getValueIndex();

        if (index + getValueLength() > data.length) {
            throw new ParserException("Not enough data for NFC_AR_DO!");
        }

        if (getValueLength() != 1) {
            throw new ParserException("Invalid length of NFC-AR-DO!");
        } else if ((data[index] != 0x01) && (data[index] != 0x00)) {
            throw new ParserException(
                    "Invalid value of NFC-AR-DO : " + String.format("%02x", data[index] & 0xff));
        }

        mNfcAllowed = (data[index] == 0x01);
    }

    @Override
    /**
     * Tag: D1 Length: 1 Value: Contains a NFC event access rule: NEVER (00): NFC event access is
     * not
     * allowed ALWAYS(01): NFC event access is allowed
     */
    public void build(ByteArrayOutputStream stream) throws DO_Exception {

        // write tag
        stream.write(getTag());
        stream.write(0x01);
        stream.write(mNfcAllowed ? 0x01 : 0x00);
    }
}