src/com/android/se/security/gpac/BerTlv.java

/*
 * 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;
import java.util.Arrays;

/** Base Class for all Access Control Data Objects */
public class BerTlv {

    private byte[] mRawData = new byte[0];

    private int mTag = 0;

    private int mValueIndex = 0;
    private int mValueLength = 0;

    public BerTlv(byte[] rawData, int tag, int valueIndex, int valueLength) {
        if (rawData != null) mRawData = rawData;
        mTag = tag;
        mValueIndex = valueIndex;
        mValueLength = valueLength;
    }

    /** Converts the byte into Hex */
    public static String toHex(byte[] digest) {
        String digits = "0123456789abcdef";
        StringBuilder sb = new StringBuilder(digest.length * 2);
        for (byte b : digest) {
            int bi = b & 0xff;
            sb.append(digits.charAt(bi >> 4));
            sb.append(digits.charAt(bi & 0xf));
        }
        return sb.toString();
    }

    /** Decodes the byte array into BerTlv Object. Performs checks for length and tag */
    public static BerTlv decode(byte[] data, int startIndex) throws ParserException {
        return BerTlv.decode(data, startIndex, true);
    }

    /** Decodes the byte array into BerTlv Object. Performs checks for length and tag */
    public static BerTlv decode(byte[] data, int startIndex, boolean containsAllData)
            throws ParserException {

        if (data == null || data.length == 0) {
            throw new ParserException("No data given!");
        }

        int curIndex = startIndex;
        int tag = 0;

    /* tag */
        if (curIndex < data.length) {
            int temp = data[curIndex++] & 0xff;
            switch (temp) {
                case 0xff: // tag is in two byte format
                case 0xdf:
                    if (curIndex < data.length) {
                        tag = ((temp & 0xff) << 8) | (data[curIndex++] & 0xff);
                    } else {
                        throw new ParserException(
                                "Index " + curIndex + " out of range! [0..[" + data.length);
                    }
                    break;

                default: // tag is in single-byte format
                    tag = temp;
                    break;
            }
        } else {
            throw new ParserException("Index " + curIndex + " out of range! [0..[" + data.length);
        }

    /* length */
        int length;
        if (curIndex < data.length) {
            int temp = data[curIndex++] & 0xff;
            if (temp < 0x80) {
                length = temp;
            } else if (temp == 0x81) {
                if (curIndex < data.length) {
                    length = data[curIndex++] & 0xff;
                    if (length < 0x80) {
                        throw new ParserException("Invalid TLV length encoding!");
                    }
                    if (containsAllData && data.length < length + curIndex) {
                        throw new ParserException("Not enough data provided!");
                    }
                } else {
                    throw new ParserException(
                            "Index " + curIndex + " out of range! [0..[" + data.length);
                }
            } else if (temp == 0x82) {
                if ((curIndex + 1) < data.length) {
                    length = ((data[curIndex] & 0xff) << 8) | (data[curIndex + 1] & 0xff);
                } else {
                    throw new ParserException("Index out of range! [0..[" + data.length);
                }
                curIndex += 2;
                if (length < 0x100) {
                    throw new ParserException("Invalid TLV length encoding!");
                }
                if (containsAllData && data.length < length + curIndex) {
                    throw new ParserException("Not enough data provided!");
                }
            } else if (temp == 0x83) {
                if ((curIndex + 2) < data.length) {
                    length =
                            ((data[curIndex] & 0xff) << 16)
                                    | ((data[curIndex + 1] & 0xff) << 8)
                                    | (data[curIndex + 2] & 0xff);
                } else {
                    throw new ParserException("Index out of range! [0..[" + data.length);
                }
                curIndex += 3;
                if (length < 0x10000) {
                    throw new ParserException("Invalid TLV length encoding!");
                }
                if (containsAllData && data.length < length + curIndex) {
                    throw new ParserException("Not enough data provided!");
                }
            } else {
                throw new ParserException("Unsupported TLV length encoding!");
            }
        } else {
            throw new ParserException("Index " + curIndex + " out of range! [0..[" + data.length);
        }
        // create object
        return new BerTlv(data, tag, curIndex, length);
    }

    /**
     * Encodes length according to ASN1. Supported are length values up to 3 bytes -> 83 xx yy zz.
     */
    public static void encodeLength(int length, ByteArrayOutputStream stream) {

        if (length > 0x0000FFFF) {
            stream.write(0x83);
            stream.write(((length & 0x00FF0000) >> 16));
            stream.write(((length & 0x0000FF00) >> 8));
            stream.write((length & 0x000000FF));
        } else if (length > 0x000000FF) {
            stream.write(0x82);
            stream.write(((length & 0x0000FF00) >> 8));
            stream.write((length & 0x000000FF));
        } else if (length > 0x0000007F) {
            stream.write(0x81);
            stream.write((length & 0x000000FF));
        } else {
            stream.write((length & 0x000000FF));
        }
    }

    /**
     * Interprets the byte stream and performs the required checks.
     * To to overridden in the derived class.
     */
    public void interpret() throws ParserException {
    }

    /**
     * Builds up the TLV into a byte stream.
     *
     * <p>Tags can be encoded as one or two bytes
     */
    public void build(ByteArrayOutputStream stream) throws DO_Exception {

        // put tag into stream
        if (mTag > 0xFF) {
            stream.write(((mTag & 0x0000FF00) >> 8));
            stream.write((mTag & 0x000000FF));
        } else {
            stream.write((mTag & 0x000000FF));
        }

        // write length
        encodeLength(mValueLength, stream);

        // write value
        if (mValueLength > 0) {
            stream.write(mRawData, mValueIndex, mValueLength);
        }
    }

    public int getTag() {
        return mTag;
    }

    public int getValueIndex() {
        return mValueIndex;
    }

    /** Returns the byte array of only the data values */
    public byte[] getValue() {
        // quick checks
        if (mRawData == null
                || mValueLength == 0
                || mValueIndex < 0
                || mValueIndex > mRawData.length
                || mValueIndex + mValueLength > mRawData.length) {
            return new byte[0];
        }

        byte[] data = new byte[mValueLength];

        System.arraycopy(mRawData, mValueIndex, data, 0, mValueLength);

        return data;
    }

    protected byte[] getRawData() {
        return mRawData;
    }

    public int getValueLength() {
        return mValueLength;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof BerTlv) {
            BerTlv berTlv = (BerTlv) obj;
            if (mTag == berTlv.mTag) {
                byte[] test1 = this.getValue();
                byte[] test2 = berTlv.getValue();
                return Arrays.equals(test1, test2);
            }
        }
        return false;
    }
}