// --- BEGIN COPYRIGHT BLOCK ---
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; version 2 of the License.
//
// 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 for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// (C) 2007 Red Hat, Inc.
// All rights reserved.
// --- END COPYRIGHT BLOCK ---
package netscape.security.util;

import java.io.IOException;
import java.io.InputStream;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;
import java.util.Vector;

/**
 * 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.
 *
 * @version 1.35
 *
 * @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;

    /**
     * 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) {
        buffer = new DerInputBuffer(data);
        buffer.mark(Integer.MAX_VALUE);
    }

    /**
     * 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) {
        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.
     * @throws IOException
     */
    public byte[] toByteArray() throws IOException {
        return buffer.toByteArray();
    }

    /*
     * PRIMITIVES -- these are "universal" ASN.1 simple types.
     *
     * 	INTEGER, BIT STRING, OCTET STRING, NULL
     *	OBJECT IDENTIFIER, SEQUENCE (OF), SET (OF)
     *	PrintableString, T61String, IA5String, UTCTime
     */

    /**
     * Get an (unsigned) integer from the input stream.
     */
    public BigInt getInteger() throws IOException {
        if (buffer.read() != DerValue.tag_Integer)
            throw new IOException("DER input, Integer tag error");

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

    /**
     * Get a bit string from the input stream. Only octet-aligned
     * bitstrings (multiples of eight bits in length) are handled
     * by this method.
     */
    public byte[] getBitString() throws IOException {
        if (buffer.read() != DerValue.tag_BitString)
            throw new IOException("DER input not an bit string");
        int length = getLength(buffer);

        /*
         * This byte affects alignment and padding (for the last byte).
         * Use getUnalignedBitString() for none 8-bit aligned bit strings.
         */
        if (buffer.read() != 0)
            return null;
        length--;

        /*
         * Just read the data into an aligned, padded octet buffer.
         */
        byte[] retval = new byte[length];
        if (buffer.read(retval) != length)
            throw new IOException("short read of DER bit string");
        return retval;
    }

    /**
     * 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 (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 (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) {
            if (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 {
        int b = buffer.read();
        if (b != DerValue.tag_Sequence)
            throw new IOException("Sequence tag error " + b);
        return readVector(startLen);
    }

    public void skipSequence(int startLen) throws IOException {
        int b = buffer.read();
        if (b != DerValue.tag_Sequence)
            throw new IOException("Sequence tag error " + b);
        int len = getLength(buffer);
        buffer.skip(len);
    }

    /**
     * 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 {
        if (buffer.read() != 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 {
        int tag = 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 {
        int len = getLength(buffer);
        DerInputStream newstr;

        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);
    }

    public String getPrintableString() throws IOException {
        return (new DerValue(buffer)).getPrintableString();
    }

    public String getT61String() throws IOException {
        return (new DerValue(buffer)).getT61String();
    }

    public String getIA5String() throws IOException {
        return (new DerValue(buffer)).getIA5String();
    }

    public String getBMPString() throws IOException {
        return (new DerValue(buffer)).getBMPString();
    }

    public String getUniversalString() throws IOException {
        return (new DerValue(buffer)).getUniversalString();
    }

    public String getDirectoryString() throws IOException {
        return (new DerValue(buffer)).getDirectoryString();
    }

    /**
     * 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 ");
        if (buffer.available() < 11)
            throw new IOException("DER input, UTCtime short input");

        int len = getLength(buffer);

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

        /*
         * UTC time encoded as ASCII chars, YYMMDDhhmmss.
         * If YY <= 50, we assume 20YY;
         * if YY > 50, we assume 19YY, as per IETF-PKIX part I.
         */
        int year, month, day, hour, minute, second;

        year = 10 * Character.digit((char) buffer.read(), 10);
        year += Character.digit((char) buffer.read(), 10);
        if (year <= 50) // origin 2000
            year += 2000;
        else
            year += 1900; // origin 1900

        month = 10 * Character.digit((char) buffer.read(), 10);
        month += Character.digit((char) buffer.read(), 10);
        month -= 1; // months are 0-11

        day = 10 * Character.digit((char) buffer.read(), 10);
        day += Character.digit((char) buffer.read(), 10);

        hour = 10 * Character.digit((char) buffer.read(), 10);
        hour += Character.digit((char) buffer.read(), 10);

        minute = 10 * Character.digit((char) buffer.read(), 10);
        minute += Character.digit((char) buffer.read(), 10);

        len -= 10;

        /**
         * 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.
         */

        if (len == 3 || len == 7) {
            second = 10 * Character.digit((char) buffer.read(), 10);
            second += Character.digit((char) buffer.read(), 10);
            len -= 2;
        } else
            second = 0;

        if (month < 0 || day <= 0
                || month > 11 || day > 31 || hour >= 24
                || minute >= 60 || second >= 60)
            throw new IOException("Parse UTC time, invalid format");

        Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
        cal.set(year, month, day, hour, minute, second);
        cal.set(Calendar.MILLISECOND, 0); /* To clear millisecond field */
        cal.set(Calendar.ERA, GregorianCalendar.AD);
        Date readDate = cal.getTime();
        long utcTime = readDate.getTime();

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

        switch (buffer.read()) {
        case '+': {
            int Htmp = 10 * Character.digit((char) buffer.read(), 10);
            Htmp += Character.digit((char) buffer.read(), 10);
            int Mtmp = 10 * Character.digit((char) buffer.read(), 10);
            Mtmp += Character.digit((char) buffer.read(), 10);

            if (Htmp >= 24 || Mtmp >= 60)
                throw new IOException("Parse UTCtime, +hhmm");

            utcTime += ((Htmp * 60) + Mtmp) * 60 * 1000L;
        }
            break;

        case '-': {
            int Htmp = 10 * Character.digit((char) buffer.read(), 10);
            Htmp += Character.digit((char) buffer.read(), 10);
            int Mtmp = 10 * Character.digit((char) buffer.read(), 10);
            Mtmp += Character.digit((char) buffer.read(), 10);

            if (Htmp >= 24 || Mtmp >= 60)
                throw new IOException("Parse UTCtime, -hhmm");

            utcTime -= ((Htmp * 60) + Mtmp) * 60 * 1000L;
        }
            break;

        case 'Z':
            break;

        default:
            throw new IOException("Parse UTCtime, garbage offset");
        }
        readDate.setTime(utcTime);
        return readDate;
    }

    /**
     * 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 ");

        if (buffer.available() < 13)
            throw new IOException("DER input, GeneralizedTime short input");

        int len = getLength(buffer);

        /*
         * Generalized time encoded as ASCII chars, YYYYMMDDhhmm[ss]
         */
        int year, month, day, hour, minute, second;

        year = 1000 * Character.digit((char) buffer.read(), 10);
        year += 100 * Character.digit((char) buffer.read(), 10);
        year += 10 * Character.digit((char) buffer.read(), 10);
        year += Character.digit((char) buffer.read(), 10);

        month = 10 * Character.digit((char) buffer.read(), 10);
        month += Character.digit((char) buffer.read(), 10);
        month -= 1; // Calendar months are 0-11

        day = 10 * Character.digit((char) buffer.read(), 10);
        day += Character.digit((char) buffer.read(), 10);

        hour = 10 * Character.digit((char) buffer.read(), 10);
        hour += Character.digit((char) buffer.read(), 10);

        minute = 10 * Character.digit((char) buffer.read(), 10);
        minute += Character.digit((char) buffer.read(), 10);

        len -= 12;

        /**
         * 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.
         */

        if (len == 3 || len == 7) {
            second = 10 * Character.digit((char) buffer.read(), 10);
            second += Character.digit((char) buffer.read(), 10);
            len -= 2;
        } else
            second = 0;

        if (month < 0 || day <= 0
                || month > 11 || day > 31 || hour >= 24
                || minute >= 60 || second >= 60)
            throw new IOException("Parse Generalized time, invalid format");

        /* Shouldn't this construct a Gregorian calendar directly???
         * We don't really want locale dependant processing here */
        Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
        cal.set(year, month, day, hour, minute, second);
        cal.set(Calendar.MILLISECOND, 0); /* To clear millisecond field */
        cal.set(Calendar.ERA, GregorianCalendar.AD);
        Date readDate = cal.getTime();
        long utcTime = readDate.getTime();

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

        switch (buffer.read()) {
        case '+': {
            int Htmp = 10 * Character.digit((char) buffer.read(), 10);
            Htmp += Character.digit((char) buffer.read(), 10);
            int Mtmp = 10 * Character.digit((char) buffer.read(), 10);
            Mtmp += Character.digit((char) buffer.read(), 10);

            if (Htmp >= 24 || Mtmp >= 60)
                throw new IOException("Parse GeneralizedTime, +hhmm");

            utcTime += ((Htmp * 60) + Mtmp) * 60 * 1000L;
        }
            break;

        case '-': {
            int Htmp = 10 * Character.digit((char) buffer.read(), 10);
            Htmp += Character.digit((char) buffer.read(), 10);
            int Mtmp = 10 * Character.digit((char) buffer.read(), 10);
            Mtmp += Character.digit((char) buffer.read(), 10);

            if (Htmp >= 24 || Mtmp >= 60)
                throw new IOException("Parse GeneralizedTime, -hhmm");

            utcTime -= ((Htmp * 60) + Mtmp) * 60 * 1000L;
        }
            break;

        case 'Z':
            break;

        default:
            throw new IOException("Parse GeneralizedTime, garbage offset");
        }
        readDate.setTime(utcTime);
        return readDate;
    }

    /*
     * 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
     * encoding to be used.  (Not the same as getting a tagged integer!)
     */
    static int getLength(InputStream in) throws IOException {
        int value, tmp;

        tmp = in.read();
        if ((tmp & 0x080) == 0x00) { // 1 byte datum?
            value = tmp;
        } else { // no, more ...
            tmp &= 0x07f;

            /*
             * NOTE:  tmp == 0 indicates BER encoded data.
             * tmp > 4 indicates more than 4Gb of data.
             */
            if (tmp <= 0 || tmp > 4)
                throw new IOException("DerInput.getLength(): lengthTag="
                        + tmp + ", "
                        + ((tmp == 0) ? "Indefinite length encoding not supported"
                                    + " or incorrect DER encoding."
                                  : "too big."));

            for (value = 0; tmp > 0; tmp--) {
                value <<= 8;
                value += 0x0ff & in.read();
            }
        }
        return value;
    }

    /**
     * Mark the current position in the buffer, so that
     * a later call to <code>reset</code> will return here.
     */
    public void mark(int value) {
        buffer.mark(value);
    }

    /**
     * Return to the position of the last <code>mark</code> call. A mark is implicitly set at the beginning of
     * the stream when it is created.
     */
    public void reset() {
        buffer.reset();
    }

    /**
     * Returns the number of bytes available for reading.
     * This is most useful for testing whether the stream is
     * empty.
     */
    public int available() {
        return buffer.available();
    }
}
