connectbot/sshlib

package com.trilead.ssh2.crypto.cipher;

import java.lang.reflect.Constructor;
import java.util.ArrayList;

/**
 * BlockCipherFactory.
 *
 * @author Christian Plattner, plattner@trilead.com
 * @version $Id: BlockCipherFactory.java,v 1.2 2008/04/01 12:38:09 cplattne Exp $
 */
public class BlockCipherFactory
{
    private static class CipherEntry
    {
        final String type;
        final int blocksize;
        final int keysize;
        final String cipherClass;

        CipherEntry(String type, int blockSize, int keySize, String cipherClass)
        {
            this.type = type;
            this.blocksize = blockSize;
            this.keysize = keySize;
            this.cipherClass = cipherClass;
        }
    }

    private static final ArrayList<CipherEntry> ciphers = new ArrayList<>();

    static
    {
        /* Higher Priority First */

        ciphers.add(new CipherEntry("aes256-ctr", 16, 32, "com.trilead.ssh2.crypto.cipher.AES$CTR"));
        ciphers.add(new CipherEntry("aes128-ctr", 16, 16, "com.trilead.ssh2.crypto.cipher.AES$CTR"));
        ciphers.add(new CipherEntry("blowfish-ctr", 8, 16, "com.trilead.ssh2.crypto.cipher.BlowFish$CTR"));

        ciphers.add(new CipherEntry("aes256-cbc", 16, 32, "com.trilead.ssh2.crypto.cipher.AES$CBC"));
        ciphers.add(new CipherEntry("aes128-cbc", 16, 16, "com.trilead.ssh2.crypto.cipher.AES$CBC"));
        ciphers.add(new CipherEntry("blowfish-cbc", 8, 16, "com.trilead.ssh2.crypto.cipher.BlowFish$CBC"));

        ciphers.add(new CipherEntry("3des-ctr", 8, 24, "com.trilead.ssh2.crypto.cipher.DESede$CTR"));
        ciphers.add(new CipherEntry("3des-cbc", 8, 24, "com.trilead.ssh2.crypto.cipher.DESede$CBC"));
    }

    public static String[] getDefaultCipherList()
    {
        String list[] = new String[ciphers.size()];
        for (int i = 0; i < ciphers.size(); i++)
        {
            CipherEntry ce = ciphers.get(i);
            list[i] = ce.type;
        }
        return list;
    }

    public static void checkCipherList(String[] cipherCandidates)
    {
        for (String cipherCandidate : cipherCandidates)
            getEntry(cipherCandidate);
    }

    public static BlockCipher createCipher(String type, boolean encrypt, byte[] key, byte[] iv)
    {
        try
        {
            CipherEntry ce = getEntry(type);
            Class cc = Class.forName(ce.cipherClass);
            Constructor<BlockCipher> constructor = cc.getConstructor();
            BlockCipher bc = constructor.newInstance();
            bc.init(encrypt, key, iv);
            return bc;
        }
        catch (Exception e)
        {
            throw new IllegalArgumentException("Cannot instantiate " + type, e);
        }
    }

    private static CipherEntry getEntry(String type)
    {
        for (CipherEntry ce : ciphers) {
            if (ce.type.equals(type))
                return ce;
        }
        throw new IllegalArgumentException("Unknown algorithm " + type);
    }

    public static int getBlockSize(String type)
    {
        CipherEntry ce = getEntry(type);
        return ce.blocksize;
    }

    public static int getKeySize(String type)
    {
        CipherEntry ce = getEntry(type);
        return ce.keysize;
    }
}