connectbot/sshlib

package com.trilead.ssh2.crypto.dh;

import java.io.IOException;
import java.math.BigInteger;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.ECPrivateKey;
import java.security.interfaces.ECPublicKey;
import java.security.spec.ECParameterSpec;
import java.security.spec.ECPoint;
import java.security.spec.ECPublicKeySpec;
import java.security.spec.InvalidKeySpecException;

import javax.crypto.KeyAgreement;

import com.trilead.ssh2.signature.ECDSASHA2Verify;

/**
 * @author kenny
 *
 */
public class EcDhExchange extends GenericDhExchange {
    private ECPrivateKey clientPrivate;
    private ECPublicKey clientPublic;
    private ECPublicKey serverPublic;

    @Override
    public void init(String name) throws IOException {
        final ECParameterSpec spec;

        if ("ecdh-sha2-nistp256".equals(name)) {
            spec = ECDSASHA2Verify.ECDSASHA2NISTP256Verify.get().getParameterSpec();
        } else if ("ecdh-sha2-nistp384".equals(name)) {
            spec = ECDSASHA2Verify.ECDSASHA2NISTP384Verify.get().getParameterSpec();
        } else if ("ecdh-sha2-nistp521".equals(name)) {
            spec = ECDSASHA2Verify.ECDSASHA2NISTP521Verify.get().getParameterSpec();
        } else {
            throw new IllegalArgumentException("Unknown EC curve " + name);
        }

        KeyPairGenerator kpg;
        try {
            kpg = KeyPairGenerator.getInstance("EC");
            kpg.initialize(spec);
            KeyPair pair = kpg.generateKeyPair();
            clientPrivate = (ECPrivateKey) pair.getPrivate();
            clientPublic = (ECPublicKey) pair.getPublic();
        } catch (NoSuchAlgorithmException e) {
            throw new IOException("No DH keypair generator", e);
        } catch (InvalidAlgorithmParameterException e) {
            throw new IOException("Invalid DH parameters", e);
        }
    }

    @Override
    public byte[] getE() {
        return ECDSASHA2Verify.encodeECPoint(clientPublic.getW(), clientPublic.getParams()
                .getCurve());
    }

    @Override
    protected byte[] getServerE() {
        return ECDSASHA2Verify.encodeECPoint(serverPublic.getW(), serverPublic.getParams()
                .getCurve());
    }

    @Override
    public void setF(byte[] f) throws IOException {

        if (clientPublic == null)
            throw new IllegalStateException("DhDsaExchange not initialized!");

        final KeyAgreement ka;
        try {
            KeyFactory kf = KeyFactory.getInstance("EC");
            ECDSASHA2Verify verifier = ECDSASHA2Verify.getVerifierForKey(clientPublic);
            if (verifier == null) {
                throw new IOException("No such EC group");
            }

            ECPoint serverPoint = verifier.decodeECPoint(f);
            ECParameterSpec params = verifier.getParameterSpec();
            this.serverPublic = (ECPublicKey) kf.generatePublic(new ECPublicKeySpec(serverPoint,
                                                                                    params));

            ka = KeyAgreement.getInstance("ECDH");
            ka.init(clientPrivate);
            ka.doPhase(serverPublic, true);
        } catch (NoSuchAlgorithmException e) {
            throw new IOException("No ECDH key agreement method", e);
        } catch (InvalidKeyException | InvalidKeySpecException e) {
            throw new IOException("Invalid ECDH key", e);
        }

        sharedSecret = new BigInteger(1, ka.generateSecret());
    }

    @Override
    public String getHashAlgo() {
        return ECDSASHA2Verify.getDigestAlgorithmForParams(clientPublic);
    }
}