/*

 * Copyright 1996-2006 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code 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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * 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 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.security.util;

import java.io.InputStream;

import java.io.IOException;

import java.io.EOFException;

import java.util.Date;

import java.util.Vector;

import java.math.BigInteger;

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.

 *

 *

 * @author David Brownell

 * @author Amit Kapoor

 * @author Hemma Prafullchandra

 */

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));

    }

    /**

     * Get a bit string from the input stream.  The bit string need

     * not be byte-aligned.

     */

    public BitArray getUnalignedBitString() throws IOException {

        if (buffer.read() != DerValue.tag_BitString)

            throw new IOException("DER input not a bit string");

        int length = getLength(buffer) - 1;

        /*

         * First byte = number of excess bits in the last octet of the

         * representation.

         */

        int validBits = length*8 - buffer.read();

        byte[] repn = new byte[length];

        if ((length != 0) && (buffer.read(repn) != length))

            throw new IOException("short read of DER bit string");

        return new BitArray(validBits, repn);

    }

    /**

     * 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");

        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)

     * @param implicit if true tag is assumed implicit.

     * @return array of the values in the sequence

     */

    public DerValue[] getSet(int startLen, boolean implicit)

        throws IOException {

        tag = (byte)buffer.read();

        if (!implicit) {

            if (tag != DerValue.tag_Set) {

                throw new IOException("Set tag error");

            }

        }

        return (readVector(startLen));

    }

    /*

     * Read a "vector" of values ... set or sequence have the

     * same encoding, except for the initial tag, so both use

     * this same helper routine.

     */

    protected DerValue[] readVector(int startLen) throws IOException {

        DerInputStream  newstr;

        byte lenByte = (byte)buffer.read();

        int len = getLength((lenByte & 0xff), buffer);

        if (len == -1) {

           // indefinite length encoding found

           int readLen = buffer.available();

           int offset = 2;     // for tag and length bytes

           byte[] indefData = new byte[readLen + offset];

           indefData[0] = tag;

           indefData[1] = lenByte;

           DataInputStream dis = new DataInputStream(buffer);

           dis.readFully(indefData, offset, readLen);

           dis.close();

           DerIndefLenConverter derIn = new DerIndefLenConverter();

           buffer = new DerInputBuffer(derIn.convert(indefData));

           if (tag != buffer.read())

                throw new IOException("Indefinite length encoding" +

                        " not supported");

           len = DerInputStream.getLength(buffer);

        }

        if (len == 0)

            // return empty array instead of null, which should be

            // used only for missing optionals

            return new DerValue[0];

        /*

         * Create a temporary stream from which to read the data,

         * unless it's not really needed.

         */

        if (buffer.available() == len)

            newstr = this;

        else

            newstr = subStream(len, true);

        /*

         * Pull values out of the stream.

         */

        Vector<DerValue> vec = new Vector<DerValue>(startLen);

        DerValue value;

        do {

            value = new DerValue(newstr.buffer);

            vec.addElement(value);

        } while (newstr.available() > 0);

        if (newstr.available() != 0)

            throw new IOException("extra data at end of vector");

        /*

         * Now stick them into the array we're returning.

         */

        int             i, max = vec.size();

        DerValue[]      retval = new DerValue[max];

        for (i = 0; i < max; i++)

            retval[i] = vec.elementAt(i);

        return retval;

    }

    /**

     * Get a single DER-encoded value from the input stream.

     * It can often be useful to pull a value from the stream

     * and defer parsing it.  For example, you can pull a nested

     * sequence out with one call, and only examine its elements

     * later when you really need to.

     */

    public DerValue getDerValue() throws IOException {

        return new DerValue(buffer);

    }

    /**

     * Read a string that was encoded as a UTF8String DER value.

     */

    public String getUTF8String() throws IOException {

        return readString(DerValue.tag_UTF8String, "UTF-8", "UTF8");

    }

    /**

     * Read a string that was encoded as a PrintableString DER value.

     */

    public String getPrintableString() throws IOException {

        return readString(DerValue.tag_PrintableString, "Printable",

                          "ASCII");

    }

    /**

     * Read a string that was encoded as a T61String DER value.

     */

    public String getT61String() throws IOException {

        /*

         * Works for common characters between T61 and ASCII.

         */

        return readString(DerValue.tag_T61String, "T61", "ISO-8859-1");

    }

    /**

     * Read a string that was encoded as a IA5tring DER value.

     */

    public String getIA5String() throws IOException {

        return readString(DerValue.tag_IA5String, "IA5", "ASCII");

    }

    /**

     * Read a string that was encoded as a BMPString DER value.

     */

    public String getBMPString() throws IOException {

        return readString(DerValue.tag_BMPString, "BMP",

                          "UnicodeBigUnmarked");

    }

    /**

     * Read a string that was encoded as a GeneralString DER value.

     */

    public String getGeneralString() throws IOException {

        return readString(DerValue.tag_GeneralString, "General",

                          "ASCII");

    }

    /**

     * Private helper routine to read an encoded string from the input

     * stream.

     * @param stringTag the tag for the type of string to read

     * @param stringName a name to display in error messages

     * @param enc the encoder to use to interpret the data. Should

     * correspond to the stringTag above.

     */

    private String readString(byte stringTag, String stringName,

                              String enc) throws IOException {

        if (buffer.read() != stringTag)

            throw new IOException("DER input not a " +

                                  stringName + " string");

        int length = getLength(buffer);

        byte[] retval = new byte[length];

        if ((length != 0) && (buffer.read(retval) != length))

            throw new IOException("short read of DER " +

                                  stringName + " string");

        return new String(retval, enc);

    }

    /**

     * Get a UTC encoded time value from the input stream.

     */

    public Date getUTCTime() throws IOException {

        if (buffer.read() != DerValue.tag_UtcTime)

            throw new IOException("DER input, UTCtime tag invalid ");

        return buffer.getUTCTime(getLength(buffer));

    }

    /**

     * Get a Generalized encoded time value from the input stream.

     */

    public Date getGeneralizedTime() throws IOException {

        if (buffer.read() != DerValue.tag_GeneralizedTime)

            throw new IOException("DER input, GeneralizedTime tag invalid ");

        return buffer.getGeneralizedTime(getLength(buffer));

    }

    /*

     * Get a byte from the input stream.

     */

    // package private

    int getByte() throws IOException {

        return (0x00ff & buffer.read());

    }

    public int peekByte() throws IOException {

        return buffer.peek();

    }

    // package private

    int getLength() throws IOException {

        return getLength(buffer);

    }

    /*

     * Get a length from the input stream, allowing for at most 32 bits of