edu.vt.middleware.crypt.util.DERHelper.java Source code

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Here is the source code for edu.vt.middleware.crypt.util.DERHelper.java

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/*
  $Id$
    
  Copyright (C) 2003-2013 Virginia Tech.
  All rights reserved.
    
  SEE LICENSE FOR MORE INFORMATION
    
  Author:  Middleware Services
  Email:   middleware@vt.edu
  Version: $Revision$
  Updated: $Date$
*/
package edu.vt.middleware.crypt.util;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import org.bouncycastle.asn1.ASN1EncodableVector;
import org.bouncycastle.asn1.ASN1InputStream;
import org.bouncycastle.asn1.ASN1OctetString;
import org.bouncycastle.asn1.DEREncodable;
import org.bouncycastle.asn1.DERInteger;
import org.bouncycastle.asn1.DERObject;
import org.bouncycastle.asn1.DEROctetString;
import org.bouncycastle.asn1.DERSequence;

/**
 * Utility class with methods to facilitate common operations on BouncyCastle
 * DEREncodable objects.
 *
 * @author  Middleware Services
 * @version  $Revision$
 */
public final class DERHelper {

    /** Hidden constructor of utility class. */
    private DERHelper() {
    }

    /**
     * Extracts the integer value from a {@link DERInteger}.
     *
     * @param  e  DERInteger instance.
     *
     * @return  Integer value.
     */
    public static int asInt(final DEREncodable e) {
        if (!(e instanceof DERInteger)) {
            throw new IllegalArgumentException("Argument must be DERInteger.");
        }
        return ((DERInteger) e).getValue().intValue();
    }

    /**
     * Extracts the octet string (byte array) from a {@link DEROctetString}.
     *
     * @param  e  DEROctetString instance.
     *
     * @return  Bytes of octet string value.
     */
    public static byte[] asOctets(final DEREncodable e) {
        if (!(e instanceof DEROctetString)) {
            throw new IllegalArgumentException("Argument must be DEROctetString.");
        }
        return ((DEROctetString) e).getOctets();
    }

    /**
     * Attempts to create a Bouncy Castle <code>DERObject</code> from a byte array
     * representing ASN.1 encoded data.
     *
     * @param  data  ASN.1 encoded data as byte array.
     * @param  discardWrapper  Set to true to decode the octets of a DER octet
     * string as DER encoded data, thereby discarding the wrapping DER octet
     * string, false otherwise. Has no effect on other types of DER-encoded data.
     *
     * @return  DER object.
     *
     * @throws  IOException  On I/O errors.
     */
    public static DERObject toDERObject(final byte[] data, final boolean discardWrapper) throws IOException {
        final ByteArrayInputStream in = new ByteArrayInputStream(data);
        try {
            DERObject o = new ASN1InputStream(in).readObject();
            if (discardWrapper && o instanceof ASN1OctetString) {
                o = new ASN1InputStream(((ASN1OctetString) o).getOctets()).readObject();
            }
            return o;
        } finally {
            in.close();
        }
    }

    /**
     * Creates a DER SEQUENCE type from the given DER encodable objects in the
     * order they are listed.
     *
     * @param  items  One or more DER encodable items.
     *
     * @return  DER SEQUENCE over given items.
     */
    public static DERSequence sequence(final DEREncodable... items) {
        final ASN1EncodableVector v = new ASN1EncodableVector();
        for (DEREncodable item : items) {
            v.add(item);
        }
        return new DERSequence(v);
    }
}