connectbot/sshlib

package com.trilead.ssh2.crypto.digest;

import javax.crypto.Mac;
import javax.crypto.ShortBufferException;
import javax.crypto.spec.SecretKeySpec;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

/**
 * MAC.
 *
 * @author Christian Plattner, plattner@trilead.com
 * @version $Id: MAC.java,v 1.1 2007/10/15 12:49:57 cplattne Exp $
 */
public final class HMAC implements MAC
{
    private static final String ETM_SUFFIX = "-etm@openssh.com";

    /**
     * From http://tools.ietf.org/html/rfc4253
     */
    static final String HMAC_MD5 = "hmac-md5";

    /**
     * From http://tools.ietf.org/html/rfc4253
     */
    static final String HMAC_MD5_96 = "hmac-md5-96";

    /**
     * From http://tools.ietf.org/html/rfc4253
     */
    static final String HMAC_SHA1 = "hmac-sha1";

    /**
     * From https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL
     */
    static final String HMAC_SHA1_ETM = "hmac-sha1-etm@openssh.com";

    /**
     * From http://tools.ietf.org/html/rfc4253
     */
    static final String HMAC_SHA1_96 = "hmac-sha1-96";

    /**
     * From https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL
     */
    static final String HMAC_SHA2_256_ETM = "hmac-sha2-256-etm@openssh.com";

    /**
     * From https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL
     */
    static final String HMAC_SHA2_512_ETM = "hmac-sha2-512-etm@openssh.com";

    /**
     * From http://tools.ietf.org/html/rfc6668
     */
    static final String HMAC_SHA2_256 = "hmac-sha2-256";

    /**
     * From http://tools.ietf.org/html/rfc6668
     */
    static final String HMAC_SHA2_512 = "hmac-sha2-512";

    private final Mac mac;
    private final int outSize;
    private final boolean encryptThenMac;
    private final byte[] buffer;

    public HMAC(String type, byte[] key)
    {
        try {
            if (HMAC_SHA1.equals(type) || HMAC_SHA1_96.equals(type))
            {
                mac = Mac.getInstance("HmacSHA1");
                encryptThenMac = false;
            }
            else if (HMAC_SHA1_ETM.equals(type))
            {
                mac = Mac.getInstance("HmacSHA1");
                encryptThenMac = true;
            }
            else if (HMAC_MD5.equals(type) || HMAC_MD5_96.equals(type))
            {
                mac = Mac.getInstance("HmacMD5");
                encryptThenMac = false;
            }
            else if (HMAC_SHA2_256.equals(type))
            {
                mac = Mac.getInstance("HmacSHA256");
                encryptThenMac = false;
            }
            else if (HMAC_SHA2_256_ETM.equals(type))
            {
                mac = Mac.getInstance("HmacSHA256");
                encryptThenMac = true;
            }
            else if (HMAC_SHA2_512.equals(type))
            {
                mac = Mac.getInstance("HmacSHA512");
                encryptThenMac = false;
            }
            else if (HMAC_SHA2_512_ETM.equals(type))
            {
                mac = Mac.getInstance("HmacSHA512");
                encryptThenMac = true;
            }
            else
                throw new IllegalArgumentException("Unknown algorithm " + type);
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalArgumentException("Unknown algorithm " + type, e);
        }

        int macSize = mac.getMacLength();
        if (type.endsWith("-96")) {
            outSize = 12;
            buffer = new byte[macSize];
        } else {
            outSize = macSize;
            buffer = null;
        }

        try {
            mac.init(new SecretKeySpec(key, type));
        } catch (InvalidKeyException e) {
            throw new IllegalArgumentException(e);
        }
    }

    public final void initMac(int seq)
    {
        mac.reset();
        mac.update((byte) (seq >> 24));
        mac.update((byte) (seq >> 16));
        mac.update((byte) (seq >> 8));
        mac.update((byte) (seq));
    }

    public final void update(byte[] packetdata, int off, int len)
    {
        mac.update(packetdata, off, len);
    }

    public final void getMac(byte[] out, int off)
    {
        try {
            if (buffer != null) {
                mac.doFinal(buffer, 0);
                System.arraycopy(buffer, 0, out, off, out.length - off);
            } else {
                mac.doFinal(out, off);
            }
        } catch (ShortBufferException e) {
            throw new IllegalStateException(e);
        }
    }

    public final int size()
    {
        return outSize;
    }

    public boolean isEncryptThenMac() {
        return encryptThenMac;
    }
}