derinputstream.java

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/*
 *
 *
 * Copyright  1990-2007 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 only, as published by the Free Software Foundation.
 *
 * This program 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 version 2 for more details (a copy is
 * included at /legal/license.txt).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this work; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 or visit www.sun.com if you need additional
 * information or have any questions.
 */

package com.sun.midp.pki;

import java.io.InputStream;
import java.io.IOException;
import java.util.Date;
import java.util.Vector;
import java.io.DataInputStream;

/**
 * A DER input stream, used for parsing ASN.1 DER-encoded data such as
 * that found in X.509 certificates.  DER is a subset of BER/1, which has
 * the advantage that it allows only a single encoding of primitive data.
 * (High level data such as dates still support many encodings.)  That is,
 * it uses the "Definite" Encoding Rules (DER) not the "Basic" ones (BER).
 *
 * <P>Note that, like BER/1, DER streams are streams of explicitly
 * tagged data values.  Accordingly, this programming interface does
 * not expose any variant of the java.io.InputStream interface, since
 * that kind of input stream holds untagged data values and using that
 * I/O model could prevent correct parsing of the DER data.
 *
 * <P>At this time, this class supports only a subset of the types of DER
 * data encodings which are defined.  That subset is sufficient for parsing
 * most X.509 certificates.
 */

public class DerInputStream {

    /*
     * This version only supports fully buffered DER.  This is easy to
     * work with, though if large objects are manipulated DER becomes
     * awkward to deal with.  That's where BER is useful, since BER
     * handles streaming data relatively well.
     */
    DerInputBuffer      buffer;

    /** The DER tag of the value; one of the tag_ constants. */
    public byte         tag;

    /**
     * Create a DER input stream from a data buffer.  The buffer is not
     * copied, it is shared.  Accordingly, the buffer should be treated
     * as read-only.
     *
     * @param data the buffer from which to create the string (CONSUMED)
     */
    public DerInputStream(byte[] data) throws IOException {
        init(data, 0, data.length);
    }

    /**
     * Create a DER input stream from part of a data buffer.
     * The buffer is not copied, it is shared.  Accordingly, the
     * buffer should be treated as read-only.
     *
     * @param data the buffer from which to create the string (CONSUMED)
     * @param offset the first index of <em>data</em> which will
     *          be read as DER input in the new stream
     * @param len how long a chunk of the buffer to use,
     *          starting at "offset"
     */
    public DerInputStream(byte[] data, int offset, int len) throws IOException {
        init(data, offset, len);
    }

    /*
     * private helper routine
     */
    private void init(byte[] data, int offset, int len) throws IOException {
        if ((offset+2 > data.length) || (offset+len > data.length)) {
            throw new IOException("Encoding bytes too short");
        }
        // check for indefinite length encoding
        if (DerIndefLenConverter.isIndefinite(data[offset+1])) {
            byte[] inData = new byte[len];
            System.arraycopy(data, offset, inData, 0, len);

            DerIndefLenConverter derIn = new DerIndefLenConverter();
            buffer = new DerInputBuffer(derIn.convert(inData));
        } else {
            buffer = new DerInputBuffer(data, offset, len);
        }
        buffer.mark(Integer.MAX_VALUE);
    }

    DerInputStream(DerInputBuffer buf) {
        buffer = buf;
        buffer.mark(Integer.MAX_VALUE);
    }

    /**
     * Creates a new DER input stream from part of this input stream.
     *
     * @param len how long a chunk of the current input stream to use,
     *          starting at the current position.
     * @param do_skip true if the existing data in the input stream should
     *          be skipped.  If this value is false, the next data read
     *          on this stream and the newly created stream will be the
     *          same.
     */
    public DerInputStream subStream(int len, boolean do_skip)
            throws IOException {
        DerInputBuffer  newbuf = buffer.dup();

        newbuf.truncate(len);
        if (do_skip) {
            buffer.skip(len);
        }
        return new DerInputStream(newbuf);
    }

    /**
     * Return what has been written to this DerInputStream
     * as a byte array. Useful for debugging.
     */
    public byte[] toByteArray() {
        return buffer.toByteArray();
    }

    /*
     * PRIMITIVES -- these are "universal" ASN.1 simple types.
     *
     *  INTEGER, ENUMERATED, BIT STRING, OCTET STRING, NULL
     *  OBJECT IDENTIFIER, SEQUENCE (OF), SET (OF)
     *  UTF8String, PrintableString, T61String, IA5String, UTCTime,
     *  GeneralizedTime, BMPString.
     * Note: UniversalString not supported till encoder is available.
     */

    /**
     * Get an integer from the input stream as an integer.
     *
     * @return the integer held in this DER input stream.
     */
    public int getInteger() throws IOException {
        if (buffer.read() != DerValue.tag_Integer) {
            throw new IOException("DER input, Integer tag error");
        }
        return buffer.getInteger(getLength(buffer));
    }

    /**
     * Get a integer from the input stream as a BigInteger object.
     *
     * @return the integer held in this DER input stream.
     */
    public BigInteger getBigInteger() throws IOException {
        if (buffer.read() != DerValue.tag_Integer) {
            throw new IOException("DER input, Integer tag error");
        }
        return buffer.getBigInteger(getLength(buffer), false);
    }

    /**
     * Returns an ASN.1 INTEGER value as a positive BigInteger.
     * This is just to deal with implementations that incorrectly encode
     * some values as negative.
     *
     * @return the integer held in this DER value as a BigInteger.
     */
    public BigInteger getPositiveBigInteger() throws IOException {
        if (buffer.read() != DerValue.tag_Integer) {
            throw new IOException("DER input, Integer tag error");
        }
        return buffer.getBigInteger(getLength(buffer), true);
    }
    
    /**
     * Get an enumerated from the input stream.
     *
     * @return the integer held in this DER input stream.
     */
    public int getEnumerated() throws IOException {
        if (buffer.read() != DerValue.tag_Enumerated) {
            throw new IOException("DER input, Enumerated tag error");
        }
        return buffer.getInteger(getLength(buffer));
    }

    /**
     * Get a bit string from the input stream. Padded bits (if any)
     * will be stripped off before the bit string is returned.
     */
    public byte[] getBitString() throws IOException {
        if (buffer.read() != DerValue.tag_BitString) {
            throw new IOException("DER input not an bit string");
        }

        return buffer.getBitString(getLength(buffer));
    }

    /**
     * Returns an ASN.1 OCTET STRING from the input stream.
     */
    public byte[] getOctetString() throws IOException {
        if (buffer.read() != DerValue.tag_OctetString) {
            throw new IOException("DER input not an octet string");
        }

        int length = getLength(buffer);
        byte[] retval = new byte[length];
        if ((length != 0) && (buffer.read(retval) != length)) {
            throw new IOException("short read of DER octet string");
        }

        return retval;
    }

    /**
     * Returns the asked number of bytes from the input stream.
     */
    public void getBytes(byte[] val) throws IOException {
        if ((val.length != 0) && (buffer.read(val) != val.length)) {
            throw new IOException("short read of DER octet string");
        }
    }

    /**
     * Reads an encoded null value from the input stream.
     */
    public void getNull() throws IOException {
        if (buffer.read() != DerValue.tag_Null || buffer.read() != 0) {
            throw new IOException("getNull, bad data");
        }
    }

    /**
     * Reads an X.200 style Object Identifier from the stream.
     */
    public ObjectIdentifier getOID() throws IOException {
        return new ObjectIdentifier(this);
    }

    /**
     * Return a sequence of encoded entities.  ASN.1 sequences are
     * ordered, and they are often used, like a "struct" in C or C++,
     * to group data values.  They may have optional or context
     * specific values.
     *
     * @param startLen guess about how long the sequence will be
     *          (used to initialize an auto-growing data structure)
     * @return array of the values in the sequence
     */
    public DerValue[] getSequence(int startLen) throws IOException {
        tag = (byte)buffer.read();
        if (tag != DerValue.tag_Sequence) {
            throw new IOException("Sequence tag error");
        }
        return readVector(startLen);
    }

    /**
     * Return a set of encoded entities.  ASN.1 sets are unordered,
     * though DER may specify an order for some kinds of sets (such
     * as the attributes in an X.500 relative distinguished name)
     * to facilitate binary comparisons of encoded values.
     *
     * @param startLen guess about how large the set will be
     *          (used to initialize an auto-growing data structure)
     * @return array of the values in the sequence
     */
    public DerValue[] getSet(int startLen) throws IOException {
        tag = (byte)buffer.read();
        if (tag != DerValue.tag_Set) {
            throw new IOException("Set tag error");
        }