https://openjdk.java.net/ 
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * accompanied this code).
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package sun.security.util;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.util.Date;
import sun.util.calendar.CalendarDate;
import sun.util.calendar.CalendarSystem;


DER input buffer ... this is the main abstraction in the DER library
which actively works with the "untyped byte stream" abstraction.  It
does so with impunity, since it's not intended to be exposed to
anyone who could violate the "typed value stream" DER model and hence
corrupt the input stream of DER values.

Author:David Brownell
/**
 * DER input buffer ... this is the main abstraction in the DER library
 * which actively works with the "untyped byte stream" abstraction.  It
 * does so with impunity, since it's not intended to be exposed to
 * anyone who could violate the "typed value stream" DER model and hence
 * corrupt the input stream of DER values.
 *
 * @author David Brownell
 */
class DerInputBuffer extends ByteArrayInputStream implements Cloneable {

    boolean allowBER = true;

    // used by sun/security/util/DerInputBuffer/DerInputBufferEqualsHashCode.java
    DerInputBuffer(byte[] buf) {
        this(buf, true);
    }

    DerInputBuffer(byte[] buf, boolean allowBER) {
        super(buf);
        this.allowBER = allowBER;
    }

    DerInputBuffer(byte[] buf, int offset, int len, boolean allowBER) {
        super(buf, offset, len);
        this.allowBER = allowBER;
    }

    DerInputBuffer dup() {
        try {
            DerInputBuffer retval = (DerInputBuffer)clone();
            retval.mark(Integer.MAX_VALUE);
            return retval;
        } catch (CloneNotSupportedException e) {
            throw new IllegalArgumentException(e.toString());
        }
    }

    byte[] toByteArray() {
        int     len = available();
        if (len <= 0)
            return null;
        byte[]  retval = new byte[len];

        System.arraycopy(buf, pos, retval, 0, len);
        return retval;
    }

    int peek() throws IOException {
        if (pos >= count)
            throw new IOException("out of data");
        else
            return buf[pos];
    }

    
Compares this DerInputBuffer for equality with the specified
object.

/**
     * Compares this DerInputBuffer for equality with the specified
     * object.
     */
    public boolean equals(Object other) {
        if (other instanceof DerInputBuffer)
            return equals((DerInputBuffer)other);
        else
            return false;
    }

    boolean equals(DerInputBuffer other) {
        if (this == other)
            return true;

        int max = this.available();
        if (other.available() != max)
            return false;
        for (int i = 0; i < max; i++) {
            if (this.buf[this.pos + i] != other.buf[other.pos + i]) {
                return false;
            }
        }
        return true;
    }

    
Returns a hashcode for this DerInputBuffer.

Returns:a hashcode for this DerInputBuffer.
/**
     * Returns a hashcode for this DerInputBuffer.
     *
     * @return a hashcode for this DerInputBuffer.
     */
    public int hashCode() {
        int retval = 0;

        int len = available();
        int p = pos;

        for (int i = 0; i < len; i++)
            retval += buf[p + i] * i;
        return retval;
    }

    void truncate(int len) throws IOException {
        if (len > available())
            throw new IOException("insufficient data");
        count = pos + len;
    }

    
Returns the integer which takes up the specified number
of bytes in this buffer as a BigInteger.

Params:
  • len – the number of bytes to use.
  • makePositive – whether to always return a positive value,
  irrespective of actual encoding
Returns:the integer as a BigInteger.
/**
     * Returns the integer which takes up the specified number
     * of bytes in this buffer as a BigInteger.
     * @param len the number of bytes to use.
     * @param makePositive whether to always return a positive value,
     *   irrespective of actual encoding
     * @return the integer as a BigInteger.
     */
    BigInteger getBigInteger(int len, boolean makePositive) throws IOException {
        if (len > available())
            throw new IOException("short read of integer");

        if (len == 0) {
            throw new IOException("Invalid encoding: zero length Int value");
        }

        byte[] bytes = new byte[len];

        System.arraycopy(buf, pos, bytes, 0, len);
        skip(len);

        // BER allows leading 0s but DER does not
        if (!allowBER && (len >= 2 && (bytes[0] == 0) && (bytes[1] >= 0))) {
            throw new IOException("Invalid encoding: redundant leading 0s");
        }

        if (makePositive) {
            return new BigInteger(1, bytes);
        } else {
            return new BigInteger(bytes);
        }
    }

    
Returns the integer which takes up the specified number
of bytes in this buffer.

Params:
  • len – the number of bytes to use.
Throws:
  • IOException – if the result is not within the valid
range for integer, i.e. between Integer.MIN_VALUE and
Integer.MAX_VALUE.
Returns:the integer.
/**
     * Returns the integer which takes up the specified number
     * of bytes in this buffer.
     * @throws IOException if the result is not within the valid
     * range for integer, i.e. between Integer.MIN_VALUE and
     * Integer.MAX_VALUE.
     * @param len the number of bytes to use.
     * @return the integer.
     */
    public int getInteger(int len) throws IOException {

        BigInteger result = getBigInteger(len, false);
        if (result.compareTo(BigInteger.valueOf(Integer.MIN_VALUE)) < 0) {
            throw new IOException("Integer below minimum valid value");
        }
        if (result.compareTo(BigInteger.valueOf(Integer.MAX_VALUE)) > 0) {
            throw new IOException("Integer exceeds maximum valid value");
        }
        return result.intValue();
    }

    
Returns the bit string which takes up the specified
number of bytes in this buffer.

/**
     * Returns the bit string which takes up the specified
     * number of bytes in this buffer.
     */
    public byte[] getBitString(int len) throws IOException {
        if (len > available())
            throw new IOException("short read of bit string");

        if (len == 0) {
            throw new IOException("Invalid encoding: zero length bit string");
        }

        int numOfPadBits = buf[pos];
        if ((numOfPadBits < 0) || (numOfPadBits > 7)) {
            throw new IOException("Invalid number of padding bits");
        }
        // minus the first byte which indicates the number of padding bits
        byte[] retval = new byte[len - 1];
        System.arraycopy(buf, pos + 1, retval, 0, len - 1);
        if (numOfPadBits != 0) {
            // get rid of the padding bits
            retval[len - 2] &= (0xff << numOfPadBits);
        }
        skip(len);
        return retval;
    }

    
Returns the bit string which takes up the rest of this buffer.

/**
     * Returns the bit string which takes up the rest of this buffer.
     */
    byte[] getBitString() throws IOException {
        return getBitString(available());
    }

    
Returns the bit string which takes up the rest of this buffer.
The bit string need not be byte-aligned.

/**
     * Returns the bit string which takes up the rest of this buffer.
     * The bit string need not be byte-aligned.
     */
    BitArray getUnalignedBitString() throws IOException {
        if (pos >= count)
            return null;
        /*
         * Just copy the data into an aligned, padded octet buffer,
         * and consume the rest of the buffer.
         */
        int len = available();
        int unusedBits = buf[pos] & 0xff;
        if (unusedBits > 7 ) {
            throw new IOException("Invalid value for unused bits: " + unusedBits);
        }
        byte[] bits = new byte[len - 1];
        // number of valid bits
        int length = (bits.length == 0) ? 0 : bits.length * 8 - unusedBits;

        System.arraycopy(buf, pos + 1, bits, 0, len - 1);

        BitArray bitArray = new BitArray(length, bits);
        pos = count;
        return bitArray;
    }

    
Returns the UTC Time value that takes up the specified number
of bytes in this buffer.

Params:
  • len – the number of bytes to use
/**
     * Returns the UTC Time value that takes up the specified number
     * of bytes in this buffer.
     * @param len the number of bytes to use
     */
    public Date getUTCTime(int len) throws IOException {
        if (len > available())
            throw new IOException("short read of DER UTC Time");

        if (len < 11 || len > 17)
            throw new IOException("DER UTC Time length error");

        return getTime(len, false);
    }

    
Returns the Generalized Time value that takes up the specified
number of bytes in this buffer.

Params:
  • len – the number of bytes to use
/**
     * Returns the Generalized Time value that takes up the specified
     * number of bytes in this buffer.
     * @param len the number of bytes to use
     */
    public Date getGeneralizedTime(int len) throws IOException {
        if (len > available())
            throw new IOException("short read of DER Generalized Time");

        if (len < 13)
            throw new IOException("DER Generalized Time length error");

        return getTime(len, true);

    }

    
Private helper routine to extract time from the der value.

Params:
  • len – the number of bytes to use
  • generalized – true if Generalized Time is to be read, false
if UTC Time is to be read.
/**
     * Private helper routine to extract time from the der value.
     * @param len the number of bytes to use
     * @param generalized true if Generalized Time is to be read, false
     * if UTC Time is to be read.
     */
    private Date getTime(int len, boolean generalized) throws IOException {

        /*
         * UTC time encoded as ASCII chars:
         *       YYMMDDhhmmZ
         *       YYMMDDhhmmssZ
         *       YYMMDDhhmm+hhmm
         *       YYMMDDhhmm-hhmm
         *       YYMMDDhhmmss+hhmm
         *       YYMMDDhhmmss-hhmm
         * UTC Time is broken in storing only two digits of year.
         * If YY < 50, we assume 20YY;
         * if YY >= 50, we assume 19YY, as per RFC 5280.
         *
         * Generalized time has a four-digit year and allows any
         * precision specified in ISO 8601. However, for our purposes,
         * we will only allow the same format as UTC time, except that
         * fractional seconds (millisecond precision) are supported.
         */

        int year, month, day, hour, minute, second, millis;
        String type = null;

        if (generalized) {
            type = "Generalized";
            year = 1000 * toDigit(buf[pos++], type);
            year += 100 * toDigit(buf[pos++], type);
            year += 10 * toDigit(buf[pos++], type);
            year += toDigit(buf[pos++], type);
            len -= 2; // For the two extra YY
        } else {
            type = "UTC";
            year = 10 * toDigit(buf[pos++], type);
            year += toDigit(buf[pos++], type);

            if (year < 50)              // origin 2000
                year += 2000;
            else
                year += 1900;   // origin 1900
        }

        month = 10 * toDigit(buf[pos++], type);
        month += toDigit(buf[pos++], type);

        day = 10 * toDigit(buf[pos++], type);
        day += toDigit(buf[pos++], type);

        hour = 10 * toDigit(buf[pos++], type);
        hour += toDigit(buf[pos++], type);

        minute = 10 * toDigit(buf[pos++], type);
        minute += toDigit(buf[pos++], type);

        len -= 10; // YYMMDDhhmm

        /*
         * We allow for non-encoded seconds, even though the
         * IETF-PKIX specification says that the seconds should
         * always be encoded even if it is zero.
         */

        millis = 0;
        if (len > 2) {
            second = 10 * toDigit(buf[pos++], type);
            second += toDigit(buf[pos++], type);
            len -= 2;
            // handle fractional seconds (if present)
            if (generalized && (buf[pos] == '.' || buf[pos] == ',')) {
                len --;
                if (len == 0) {
                    throw new IOException("Parse " + type +
                            " time, empty fractional part");
                }
                pos++;
                int precision = 0;
                while (buf[pos] != 'Z' &&
                       buf[pos] != '+' &&
                       buf[pos] != '-') {
                    // Validate all digits in the fractional part but
                    // store millisecond precision only
                    int thisDigit = toDigit(buf[pos], type);
                    precision++;
                    len--;
                    if (len == 0) {
                        throw new IOException("Parse " + type +
                                " time, invalid fractional part");
                    }
                    pos++;
                    switch (precision) {
                        case 1:
                            millis += 100 * thisDigit;
                            break;
                        case 2:
                            millis += 10 * thisDigit;
                            break;
                        case 3:
                            millis += thisDigit;
                            break;
                    }
                }
                if (precision == 0) {
                    throw new IOException("Parse " + type +
                            " time, empty fractional part");
                }
            }
        } else
            second = 0;

        if (month == 0 || day == 0
            || month > 12 || day > 31
            || hour >= 24 || minute >= 60 || second >= 60)
            throw new IOException("Parse " + type + " time, invalid format");

        /*
         * Generalized time can theoretically allow any precision,
         * but we're not supporting that.
         */
        CalendarSystem gcal = CalendarSystem.getGregorianCalendar();
        CalendarDate date = gcal.newCalendarDate(null); // no time zone
        date.setDate(year, month, day);
        date.setTimeOfDay(hour, minute, second, millis);
        long time = gcal.getTime(date);

        /*
         * Finally, "Z" or "+hhmm" or "-hhmm" ... offsets change hhmm
         */
        if (! (len == 1 || len == 5))
            throw new IOException("Parse " + type + " time, invalid offset");

        int hr, min;

        switch (buf[pos++]) {
        case '+':
            if (len != 5) {
                throw new IOException("Parse " + type + " time, invalid offset");
            }
            hr = 10 * toDigit(buf[pos++], type);
            hr += toDigit(buf[pos++], type);
            min = 10 * toDigit(buf[pos++], type);
            min += toDigit(buf[pos++], type);

            if (hr >= 24 || min >= 60)
                throw new IOException("Parse " + type + " time, +hhmm");

            time -= ((hr * 60) + min) * 60 * 1000;
            break;

        case '-':
            if (len != 5) {
                throw new IOException("Parse " + type + " time, invalid offset");
            }
            hr = 10 * toDigit(buf[pos++], type);
            hr += toDigit(buf[pos++], type);
            min = 10 * toDigit(buf[pos++], type);
            min += toDigit(buf[pos++], type);

            if (hr >= 24 || min >= 60)
                throw new IOException("Parse " + type + " time, -hhmm");

            time += ((hr * 60) + min) * 60 * 1000;
            break;

        case 'Z':
            if (len != 1) {
                throw new IOException("Parse " + type + " time, invalid format");
            }
            break;

        default:
            throw new IOException("Parse " + type + " time, garbage offset");
        }
        return new Date(time);
    }

    
Converts byte (represented as a char) to int.

Throws:
  • IOException – if integer is not a valid digit in the specified
   radix (10)
/**
     * Converts byte (represented as a char) to int.
     * @throws IOException if integer is not a valid digit in the specified
     *    radix (10)
     */
    private static int toDigit(byte b, String type) throws IOException {
        if (b < '0' || b > '9') {
            throw new IOException("Parse " + type + " time, invalid format");
        }
        return b - '0';
    }
}