/*
 * 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) 2015-2017, The Linux Foundation.
 */

/*
 * Contributed by: Giesecke & Devrient GmbH.
 */

package com.android.se.security.arf.pkcs15;

import android.util.Log;

import com.android.se.security.arf.ASN1;
import com.android.se.security.arf.DERParser;
import com.android.se.security.arf.SecureElement;
import com.android.se.security.arf.SecureElementException;

import java.io.IOException;
import java.util.Arrays;

/** Base class for ARF Data Objects */
public class EF {

    public static final String TAG = "SecureElementService ACE ARF";

    public static final int APDU_SUCCESS = 0x9000;
    private static final int BUFFER_LEN = 253;

    private static final short EF = 0x04;
    private static final short TRANSPARENT = 0x00;
    private static final short LINEAR_FIXED = 0x01;
    private static final short UNKNOWN = 0xFF;
    // Handle to "Secure Element" object
    protected SecureElement mSEHandle = null;
    // Selected file parameters
    private short mFileType = UNKNOWN, mFileStructure = UNKNOWN, mFileNbRecords;
    private int mFileID, mFileSize, mFileRecordSize;

    public EF(SecureElement handle) {
        mSEHandle = handle;
    }

    public int getFileId() {
        return mFileID;
    }

    private void decodeFileProperties(byte[] data) throws SecureElementException {
        if (data != null) {
            // check if first byte is the FCP tag
            // then do USIM decoding
            if (data[0] == 0x62) {
                decodeUSIMFileProps(data);
            } else {
                // otherwise sim decoding
                decodeSIMFileProps(data);
            }
        }
    }

    /**
     * Decodes file properties (SIM cards)
     *
     * @param data TS 51.011 encoded characteristics
     */
    private void decodeSIMFileProps(byte[] data) throws SecureElementException {
        if ((data == null) || (data.length < 15)) {
            throw new SecureElementException("Invalid Response data");
        }

        // 2012-04-13
        // check type of file
        if ((short) (data[6] & 0xFF) == (short) 0x04) {
            mFileType = EF;
        } else {
            mFileType = UNKNOWN; // may also be DF or MF, but we are not interested in them.
        }
        if ((short) (data[13] & 0xFF) == (short) 0x00) {
            mFileStructure = TRANSPARENT;
        } else if ((short) (data[13] & 0xFF) == (short) 0x01) {
            mFileStructure = LINEAR_FIXED;
        } else {
            mFileStructure = UNKNOWN; // may also be cyclic
        }
        mFileSize = ((data[2] & 0xFF) << 8) | (data[3] & 0xFF);

        // check if file is cyclic or linear fixed
        if (mFileType == EF
                && // is EF ?
                mFileStructure != TRANSPARENT) {
            mFileRecordSize = data[14] & 0xFF;
            mFileNbRecords = (short) (mFileSize / mFileRecordSize);
        }
    }

    /**
     * Decodes file properties (USIM cards)
     *
     * @param data TLV encoded characteristics
     */
    private void decodeUSIMFileProps(byte[] data) throws SecureElementException {
        try {
            byte[] buffer = null;
            DERParser der = new DERParser(data);

            der.parseTLV(ASN1.TAG_FCP);
            while (!der.isEndofBuffer()) {
                switch (der.parseTLV()) {
                    case (byte) 0x80: // File size
                        buffer = der.getTLVData();
                        if ((buffer != null) && (buffer.length >= 2)) {
                            mFileSize = ((buffer[0] & 0xFF) << 8) | (buffer[1] & 0xFF);
                        }
                        break;
                    case (byte) 0x82: // File descriptor
                        buffer = der.getTLVData();
                        if ((buffer != null) && (buffer.length >= 2)) {
                            if ((short) (buffer[0] & 0x07) == (short) 0x01) {
                                mFileStructure = TRANSPARENT;
                            } else if ((short) (buffer[0] & 0x07) == (short) 0x02) {
                                mFileStructure = LINEAR_FIXED;
                            } else {
                                mFileStructure = UNKNOWN; // may also be cyclic
                            }

                            // check if bit 4,5,6 are set
                            // then this is a DF or ADF, but we mark it with UNKNOWN,
                            // since we are only interested in EFs.
                            if ((short) (buffer[0] & 0x38) == (short) 0x38) {
                                mFileType = UNKNOWN;
                            } else {
                                mFileType = EF;
                            }
                            if (buffer.length == 5) {
                                mFileRecordSize = buffer[3] & 0xFF;
                                mFileNbRecords = (short) (buffer[4] & 0xFF);
                            }
                        }
                        break;
                    default:
                        der.skipTLVData();
                        break;
                }
            }
        } catch (Exception e) {
            throw new SecureElementException("Invalid GetResponse");
        }
    }

    /**
     * Selects a file (INS 0xA4)
     *
     * @param path Path of the file
     * @return Command status code [sw1 sw2]
     */
    public int selectFile(byte[] path) throws IOException, SecureElementException {
        if ((path == null) || (path.length == 0) || ((path.length % 2) != 0)) {
            throw new SecureElementException("Incorrect path");
        }
        int length = path.length;

        byte[] data = null;
        byte[] cmd = new byte[]{0x00, (byte) 0xA4, 0x00, 0x04, 0x02, 0x00, 0x00};

        mFileType = UNKNOWN;
        mFileStructure = UNKNOWN;
        mFileSize = 0;
        mFileRecordSize = 0;
        mFileNbRecords = 0;

        // iterate through path
        for (int index = 0; index < length; index += 2) {
            mFileID = ((path[index] & 0xFF) << 8) | (path[index + 1] & 0xFF);
            cmd[5] = (byte) (mFileID >> 8);
            cmd[6] = (byte) mFileID;

            data = mSEHandle.exchangeAPDU(this, cmd);

            // Check ADPU status
            int sw1 = data[data.length - 2] & 0xFF;
            if ((sw1 != 0x62) && (sw1 != 0x63) && (sw1 != 0x90) && (sw1 != 0x91)) {
                return (sw1 << 8) | (data[data.length - 1] & 0xFF);
            }
        }

        // Analyse file properties
        decodeFileProperties(data);

        return APDU_SUCCESS;
    }

    /**
     * Reads data from the current selected file (INS 0xB0)
     *
     * @param offset  Offset at which to start reading
     * @param nbBytes Number of bytes to read
     * @return Data retreived from the file
     */
    public byte[] readBinary(int offset, int nbBytes) throws IOException, SecureElementException {
        if (mFileSize == 0) return null;
        if (nbBytes == -1) nbBytes = mFileSize;
        if (mFileType != EF) throw new SecureElementException("Incorrect file type");
        if (mFileStructure != TRANSPARENT) {
            throw new SecureElementException(
                    "Incorrect file structure");
        }

        int length, pos = 0;
        byte[] result = new byte[nbBytes];
        byte[] cmd = {0x00, (byte) 0xB0, 0x00, 0x00, 0x00};

        while (nbBytes != 0) {
            if (nbBytes < BUFFER_LEN) {
                length = nbBytes;
            } else {
                length = BUFFER_LEN; // Set to max buffer size
            }

            cmd[2] = (byte) (offset >> 8);
            cmd[3] = (byte) offset;
            cmd[4] = (byte) length;
            System.arraycopy(mSEHandle.exchangeAPDU(this, cmd), 0, result, pos, length);
            nbBytes -= length;
            offset += length;
            pos += length;
        }
        return result;
    }

    /**
     * Reads a record from the current selected file (INS 0xB2)
     *
     * @param record Record ID [0..n]
     * @return Data from requested record
     */
    public byte[] readRecord(short record) throws IOException, SecureElementException {
        // Check the type of current selected file
        if (mFileType != EF) throw new SecureElementException("Incorrect file type");
        if (mFileStructure != LINEAR_FIXED) {
            throw new SecureElementException("Incorrect file structure");
        }

        // Check if requested record is valid
        if ((record < 0) || (record > mFileNbRecords)) {
            throw new SecureElementException("Incorrect record number");
        }

        Log.i(TAG, "ReadRecord [" + record + "/" + mFileRecordSize + "b]");
        byte[] cmd = {0x00, (byte) 0xB2, (byte) record, 0x04, (byte) mFileRecordSize};

        return Arrays.copyOf(mSEHandle.exchangeAPDU(this, cmd), mFileRecordSize);
    }

    /**
     * Returns the number of records in the current selected file
     *
     * @return Number of records [0..n]
     */
    public short getFileNbRecords() throws SecureElementException {
        // Check the type of current selected file
        if (mFileNbRecords < 0) throw new SecureElementException("Incorrect file type");
        return mFileNbRecords;
    }
}