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package sun.security.util;

import java.io.IOException;
import java.util.ArrayList;


A package private utility class to convert indefinite length DER
encoded byte arrays to definite length DER encoded byte arrays.
This assumes that the basic data structure is "tag, length, value"
triplet. In the case where the length is "indefinite", terminating
end-of-contents bytes are expected.

Author:Hemma Prafullchandra
/**
 * A package private utility class to convert indefinite length DER
 * encoded byte arrays to definite length DER encoded byte arrays.
 *
 * This assumes that the basic data structure is "tag, length, value"
 * triplet. In the case where the length is "indefinite", terminating
 * end-of-contents bytes are expected.
 *
 * @author Hemma Prafullchandra
 */
class DerIndefLenConverter {

    private static final int TAG_MASK            = 0x1f; // bits 5-1
    private static final int FORM_MASK           = 0x20; // bits 6
    private static final int CLASS_MASK          = 0xC0; // bits 8 and 7

    private static final int LEN_LONG            = 0x80; // bit 8 set
    private static final int LEN_MASK            = 0x7f; // bits 7 - 1
    private static final int SKIP_EOC_BYTES      = 2;

    private byte[] data, newData;
    private int newDataPos, dataPos, dataSize, index;
    private int unresolved = 0;

    private ArrayList<Object> ndefsList = new ArrayList<Object>();

    private int numOfTotalLenBytes = 0;

    private boolean isEOC(int tag) {
        return (((tag & TAG_MASK) == 0x00) &&  // EOC
                ((tag & FORM_MASK) == 0x00) && // primitive
                ((tag & CLASS_MASK) == 0x00)); // universal
    }

    // if bit 8 is set then it implies either indefinite length or long form
    static boolean isLongForm(int lengthByte) {
        return ((lengthByte & LEN_LONG) == LEN_LONG);
    }

    /*
     * Default package private constructor
     */
    DerIndefLenConverter() { }

    
Checks whether the given length byte is of the form
Indefinite.

Params:
  • lengthByte – the length byte from a DER encoded
       object.
Returns:true if the byte is of Indefinite form otherwise
        returns false.
/**
     * Checks whether the given length byte is of the form
     * <em>Indefinite</em>.
     *
     * @param lengthByte the length byte from a DER encoded
     *        object.
     * @return true if the byte is of Indefinite form otherwise
     *         returns false.
     */
    static boolean isIndefinite(int lengthByte) {
        return (isLongForm(lengthByte) && ((lengthByte & LEN_MASK) == 0));
    }

    
Parse the tag and if it is an end-of-contents tag then
add the current position to the eocList vector.

/**
     * Parse the tag and if it is an end-of-contents tag then
     * add the current position to the <code>eocList</code> vector.
     */
    private void parseTag() throws IOException {
        if (dataPos == dataSize)
            return;
        try {
            if (isEOC(data[dataPos]) && (data[dataPos + 1] == 0)) {
                int numOfEncapsulatedLenBytes = 0;
                Object elem = null;
                int index;
                for (index = ndefsList.size()-1; index >= 0; index--) {
                    // Determine the first element in the vector that does not
                    // have a matching EOC
                    elem = ndefsList.get(index);
                    if (elem instanceof Integer) {
                        break;
                    } else {
                        numOfEncapsulatedLenBytes += ((byte[])elem).length - 3;
                    }
                }
                if (index < 0) {
                    throw new IOException("EOC does not have matching " +
                                          "indefinite-length tag");
                }
                int sectionLen = dataPos - ((Integer)elem).intValue() +
                                 numOfEncapsulatedLenBytes;
                byte[] sectionLenBytes = getLengthBytes(sectionLen);
                ndefsList.set(index, sectionLenBytes);
                unresolved--;

                // Add the number of bytes required to represent this section
                // to the total number of length bytes,
                // and subtract the indefinite-length tag (1 byte) and
                // EOC bytes (2 bytes) for this section
                numOfTotalLenBytes += (sectionLenBytes.length - 3);
            }
            dataPos++;
        } catch (IndexOutOfBoundsException iobe) {
            throw new IOException(iobe);
        }
    }

    
Write the tag and if it is an end-of-contents tag
then skip the tag and its 1 byte length of zero.

/**
     * Write the tag and if it is an end-of-contents tag
     * then skip the tag and its 1 byte length of zero.
     */
    private void writeTag() {
        if (dataPos == dataSize)
            return;
        int tag = data[dataPos++];
        if (isEOC(tag) && (data[dataPos] == 0)) {
            dataPos++;  // skip length
            writeTag();
        } else
            newData[newDataPos++] = (byte)tag;
    }

    
Parse the length and if it is an indefinite length then add
the current position to the ndefsList vector.

/**
     * Parse the length and if it is an indefinite length then add
     * the current position to the <code>ndefsList</code> vector.
     */
    private int parseLength() throws IOException {
        int curLen = 0;
        if (dataPos == dataSize)
            return curLen;
        int lenByte = data[dataPos++] & 0xff;
        if (isIndefinite(lenByte)) {
            ndefsList.add(new Integer(dataPos));
            unresolved++;
            return curLen;
        }
        if (isLongForm(lenByte)) {
            lenByte &= LEN_MASK;
            if (lenByte > 4) {
                throw new IOException("Too much data");
            }
            if ((dataSize - dataPos) < (lenByte + 1)) {
                throw new IOException("Too little data");
            }
            for (int i = 0; i < lenByte; i++) {
                curLen = (curLen << 8) + (data[dataPos++] & 0xff);
            }
            if (curLen < 0) {
                throw new IOException("Invalid length bytes");
            }
        } else {
           curLen = (lenByte & LEN_MASK);
        }
        return curLen;
    }

    
Write the length and if it is an indefinite length
then calculate the definite length from the positions
of the indefinite length and its matching EOC terminator.
Then, write the value.

/**
     * Write the length and if it is an indefinite length
     * then calculate the definite length from the positions
     * of the indefinite length and its matching EOC terminator.
     * Then, write the value.
     */
    private void writeLengthAndValue() throws IOException {
        if (dataPos == dataSize)
           return;
        int curLen = 0;
        int lenByte = data[dataPos++] & 0xff;
        if (isIndefinite(lenByte)) {
            byte[] lenBytes = (byte[])ndefsList.get(index++);
            System.arraycopy(lenBytes, 0, newData, newDataPos,
                             lenBytes.length);
            newDataPos += lenBytes.length;
            return;
        }
        if (isLongForm(lenByte)) {
            lenByte &= LEN_MASK;
            for (int i = 0; i < lenByte; i++) {
                curLen = (curLen << 8) + (data[dataPos++] & 0xff);
            }
            if (curLen < 0) {
                throw new IOException("Invalid length bytes");
            }
        } else {
            curLen = (lenByte & LEN_MASK);
        }
        writeLength(curLen);
        writeValue(curLen);
    }

    private void writeLength(int curLen) {
        if (curLen < 128) {
            newData[newDataPos++] = (byte)curLen;

        } else if (curLen < (1 << 8)) {
            newData[newDataPos++] = (byte)0x81;
            newData[newDataPos++] = (byte)curLen;

        } else if (curLen < (1 << 16)) {
            newData[newDataPos++] = (byte)0x82;
            newData[newDataPos++] = (byte)(curLen >> 8);
            newData[newDataPos++] = (byte)curLen;

        } else if (curLen < (1 << 24)) {
            newData[newDataPos++] = (byte)0x83;
            newData[newDataPos++] = (byte)(curLen >> 16);
            newData[newDataPos++] = (byte)(curLen >> 8);
            newData[newDataPos++] = (byte)curLen;

        } else {
            newData[newDataPos++] = (byte)0x84;
            newData[newDataPos++] = (byte)(curLen >> 24);
            newData[newDataPos++] = (byte)(curLen >> 16);
            newData[newDataPos++] = (byte)(curLen >> 8);
            newData[newDataPos++] = (byte)curLen;
        }
    }

    private byte[] getLengthBytes(int curLen) {
        byte[] lenBytes;
        int index = 0;

        if (curLen < 128) {
            lenBytes = new byte[1];
            lenBytes[index++] = (byte)curLen;

        } else if (curLen < (1 << 8)) {
            lenBytes = new byte[2];
            lenBytes[index++] = (byte)0x81;
            lenBytes[index++] = (byte)curLen;

        } else if (curLen < (1 << 16)) {
            lenBytes = new byte[3];
            lenBytes[index++] = (byte)0x82;
            lenBytes[index++] = (byte)(curLen >> 8);
            lenBytes[index++] = (byte)curLen;

        } else if (curLen < (1 << 24)) {
            lenBytes = new byte[4];
            lenBytes[index++] = (byte)0x83;
            lenBytes[index++] = (byte)(curLen >> 16);
            lenBytes[index++] = (byte)(curLen >> 8);
            lenBytes[index++] = (byte)curLen;

        } else {
            lenBytes = new byte[5];
            lenBytes[index++] = (byte)0x84;
            lenBytes[index++] = (byte)(curLen >> 24);
            lenBytes[index++] = (byte)(curLen >> 16);
            lenBytes[index++] = (byte)(curLen >> 8);
            lenBytes[index++] = (byte)curLen;
        }

        return lenBytes;
    }

    // Returns the number of bytes needed to represent the given length
    // in ASN.1 notation
    private int getNumOfLenBytes(int len) {
        int numOfLenBytes = 0;

        if (len < 128) {
            numOfLenBytes = 1;
        } else if (len < (1 << 8)) {
            numOfLenBytes = 2;
        } else if (len < (1 << 16)) {
            numOfLenBytes = 3;
        } else if (len < (1 << 24)) {
            numOfLenBytes = 4;
        } else {
            numOfLenBytes = 5;
        }
        return numOfLenBytes;
    }

    
Parse the value;

/**
     * Parse the value;
     */
    private void parseValue(int curLen) {
        dataPos += curLen;
    }

    
Write the value;

/**
     * Write the value;
     */
    private void writeValue(int curLen) {
        for (int i=0; i < curLen; i++)
            newData[newDataPos++] = data[dataPos++];
    }

    
Converts a indefinite length DER encoded byte array to
a definte length DER encoding.

Params:
  • indefData – the byte array holding the indefinite
       length encoding.
Throws:
Returns:the byte array containing the definite length
        DER encoding.
/**
     * Converts a indefinite length DER encoded byte array to
     * a definte length DER encoding.
     *
     * @param indefData the byte array holding the indefinite
     *        length encoding.
     * @return the byte array containing the definite length
     *         DER encoding.
     * @exception IOException on parsing or re-writing errors.
     */
    byte[] convert(byte[] indefData) throws IOException {
        data = indefData;
        dataPos=0; index=0;
        dataSize = data.length;
        int len=0;
        int unused = 0;

        // parse and set up the vectors of all the indefinite-lengths
        while (dataPos < dataSize) {
            parseTag();
            len = parseLength();
            parseValue(len);
            if (unresolved == 0) {
                unused = dataSize - dataPos;
                dataSize = dataPos;
                break;
            }
        }

        if (unresolved != 0) {
            throw new IOException("not all indef len BER resolved");
        }

        newData = new byte[dataSize + numOfTotalLenBytes + unused];
        dataPos=0; newDataPos=0; index=0;

        // write out the new byte array replacing all the indefinite-lengths
        // and EOCs
        while (dataPos < dataSize) {
           writeTag();
           writeLengthAndValue();
        }
        System.arraycopy(indefData, dataSize,
                         newData, dataSize + numOfTotalLenBytes, unused);

        return newData;
    }
}