/*
 * ConnectBot: simple, powerful, open-source SSH client for Android
 * Copyright 2007 Kenny Root, Jeffrey Sharkey
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.trilead.ssh2.channel;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.interfaces.DSAPrivateKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.spec.DSAPrivateKeySpec;
import java.security.spec.DSAPublicKeySpec;
import java.security.spec.ECParameterSpec;
import java.security.spec.ECPoint;
import java.security.spec.ECPrivateKeySpec;
import java.security.spec.ECPublicKeySpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.security.spec.RSAPrivateCrtKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.util.Map;
import java.util.Map.Entry;

import com.trilead.ssh2.AuthAgentCallback;
import com.trilead.ssh2.log.Logger;
import com.trilead.ssh2.packets.TypesReader;
import com.trilead.ssh2.packets.TypesWriter;
import com.trilead.ssh2.signature.DSASHA1Verify;
import com.trilead.ssh2.signature.ECDSASHA2Verify;
import com.trilead.ssh2.signature.RSASHA1Verify;

/**
 * AuthAgentForwardThread.
 *
 * @author Kenny Root
 * @version $Id$
 */
public class AuthAgentForwardThread extends Thread implements IChannelWorkerThread {
    private static final byte[] SSH_AGENT_FAILURE = {0, 0, 0, 1, 5}; // 5
    private static final byte[] SSH_AGENT_SUCCESS = {0, 0, 0, 1, 6}; // 6

    private static final int SSH2_AGENTC_REQUEST_IDENTITIES = 11;
    private static final int SSH2_AGENT_IDENTITIES_ANSWER = 12;

    private static final int SSH2_AGENTC_SIGN_REQUEST = 13;
    private static final int SSH2_AGENT_SIGN_RESPONSE = 14;

    private static final int SSH2_AGENTC_ADD_IDENTITY = 17;
    private static final int SSH2_AGENTC_REMOVE_IDENTITY = 18;
    private static final int SSH2_AGENTC_REMOVE_ALL_IDENTITIES = 19;

//  private static final int SSH_AGENTC_ADD_SMARTCARD_KEY = 20;
//  private static final int SSH_AGENTC_REMOVE_SMARTCARD_KEY = 21;

    private static final int SSH_AGENTC_LOCK = 22;
    private static final int SSH_AGENTC_UNLOCK = 23;

    private static final int SSH2_AGENTC_ADD_ID_CONSTRAINED = 25;
//  private static final int SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED = 26;

    // Constraints for adding keys
    private static final int SSH_AGENT_CONSTRAIN_LIFETIME = 1;
    private static final int SSH_AGENT_CONSTRAIN_CONFIRM = 2;

    // Flags for signature requests
//  private static final int SSH_AGENT_OLD_SIGNATURE = 1;

    private static final Logger log = Logger.getLogger(RemoteAcceptThread.class);

    AuthAgentCallback authAgent;
    OutputStream os;
    InputStream is;
    Channel c;

    byte[] buffer = new byte[Channel.CHANNEL_BUFFER_SIZE];

    public AuthAgentForwardThread(Channel c, AuthAgentCallback authAgent) {
        this.c = c;
        this.authAgent = authAgent;

        if (log.isEnabled())
            log.log(20, "AuthAgentForwardThread started");
    }

    @Override
    public void run() {
        try {
            c.cm.registerThread(this);
        }
        catch (IOException e) {
            stopWorking();
            return;
        }

        try {
            c.cm.sendOpenConfirmation(c);
            is = c.getStdoutStream();
            os = c.getStdinStream();
            int totalSize = 4;
            int readSoFar = 0;

            while (true) {
                int len;

                try {
                    len = is.read(buffer, readSoFar, buffer.length - readSoFar);
                }
                catch (IOException e) {
                    stopWorking();
                    return;
                }

                if (len <= 0)
                    break;

                readSoFar += len;

                if (readSoFar >= 4) {
                    TypesReader tr = new TypesReader(buffer, 0, 4);
                    totalSize = tr.readUINT32() + 4;
                }

                if (totalSize == readSoFar) {
                    TypesReader tr = new TypesReader(buffer, 4, readSoFar - 4);
                    int messageType = tr.readByte();

                    switch (messageType) {
                        case SSH2_AGENTC_REQUEST_IDENTITIES:
                            sendIdentities();
                            break;

                        case SSH2_AGENTC_ADD_IDENTITY:
                            addIdentity(tr, false);
                            break;

                        case SSH2_AGENTC_ADD_ID_CONSTRAINED:
                            addIdentity(tr, true);
                            break;

                        case SSH2_AGENTC_REMOVE_IDENTITY:
                            removeIdentity(tr);
                            break;

                        case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
                            removeAllIdentities(tr);
                            break;

                        case SSH2_AGENTC_SIGN_REQUEST:
                            processSignRequest(tr);
                            break;

                        case SSH_AGENTC_LOCK:
                            processLockRequest(tr);
                            break;

                        case SSH_AGENTC_UNLOCK:
                            processUnlockRequest(tr);
                            break;

                        default:
                            os.write(SSH_AGENT_FAILURE);
                            break;
                    }

                    readSoFar = 0;
                }
            }

            c.cm.closeChannel(c, "EOF on both streams reached.", true);
        }
        catch (IOException e) {
            log.log(50, "IOException in agent forwarder: " + e.getMessage());

            try {
                is.close();
            }
            catch (IOException e1) {
            }

            try {
                os.close();
            }
            catch (IOException e2) {
            }

            try {
                c.cm.closeChannel(c, "IOException in agent forwarder (" + e.getMessage() + ")", true);
            }
            catch (IOException e3) {
            }
        }
    }

    public void stopWorking() {
        try {
            /* This will lead to an IOException in the is.read() call */
            is.close();
        }
        catch (IOException e) {
        }
    }

    /**
     * @return whether the agent is locked
     */
    private boolean failWhenLocked() throws IOException {
        if (authAgent.isAgentLocked()) {
            os.write(SSH_AGENT_FAILURE);
            return true;
        }
        else
            return false;
    }

    private void sendIdentities() throws IOException {
        Map<String, byte[]> keys = null;
        TypesWriter tw = new TypesWriter();
        tw.writeByte(SSH2_AGENT_IDENTITIES_ANSWER);
        int numKeys = 0;

        if (!authAgent.isAgentLocked())
            keys = authAgent.retrieveIdentities();

        if (keys != null)
            numKeys = keys.size();

        tw.writeUINT32(numKeys);

        if (keys != null) {
            for (Entry<String, byte[]> entry : keys.entrySet()) {
                byte[] keyBytes = entry.getValue();
                tw.writeString(keyBytes, 0, keyBytes.length);
                tw.writeString(entry.getKey());
            }
        }

        sendPacket(tw.getBytes());
    }

    /**
     * @param tr
     */
    private void addIdentity(TypesReader tr, boolean checkConstraints) {
        try {
            if (failWhenLocked())
                return;

            String type = tr.readString();
            String comment;
            String keyType;
            KeySpec pubSpec;
            KeySpec privSpec;

            if (type.equals("ssh-rsa")) {
                keyType = "RSA";
                BigInteger n = tr.readMPINT();
                BigInteger e = tr.readMPINT();
                BigInteger d = tr.readMPINT();
                BigInteger iqmp = tr.readMPINT();
                BigInteger p = tr.readMPINT();
                BigInteger q = tr.readMPINT();
                comment = tr.readString();
                // Derive the extra values Java needs.
                BigInteger dmp1 = d.mod(p.subtract(BigInteger.ONE));
                BigInteger dmq1 = d.mod(q.subtract(BigInteger.ONE));
                pubSpec = new RSAPublicKeySpec(n, e);
                privSpec = new RSAPrivateCrtKeySpec(n, e, d, p, q, dmp1, dmq1, iqmp);
            }
            else if (type.equals("ssh-dss")) {
                keyType = "DSA";
                BigInteger p = tr.readMPINT();
                BigInteger q = tr.readMPINT();
                BigInteger g = tr.readMPINT();
                BigInteger y = tr.readMPINT();
                BigInteger x = tr.readMPINT();
                comment = tr.readString();
                pubSpec = new DSAPublicKeySpec(y, p, q, g);
                privSpec = new DSAPrivateKeySpec(x, p, q, g);
            }
            else if (type.equals("ecdsa-sha2-nistp256")) {
                keyType = "EC";
                String curveName = tr.readString();
                byte[] groupBytes = tr.readByteString();
                BigInteger exponent = tr.readMPINT();
                comment = tr.readString();

                if (!"nistp256".equals(curveName)) {
                    log.log(2, "Invalid curve name for ecdsa-sha2-nistp256: " + curveName);
                    os.write(SSH_AGENT_FAILURE);
                    return;
                }

                ECParameterSpec nistp256 = ECDSASHA2Verify.EllipticCurves.nistp256;
                ECPoint group = ECDSASHA2Verify.decodeECPoint(groupBytes, nistp256.getCurve());

                if (group == null) {
                    // TODO log error
                    os.write(SSH_AGENT_FAILURE);
                    return;
                }

                pubSpec = new ECPublicKeySpec(group, nistp256);
                privSpec = new ECPrivateKeySpec(exponent, nistp256);
            }
            else {
                log.log(2, "Unknown key type: " + type);
                os.write(SSH_AGENT_FAILURE);
                return;
            }

            PublicKey pubKey;
            PrivateKey privKey;

            try {
                KeyFactory kf = KeyFactory.getInstance(keyType);
                pubKey = kf.generatePublic(pubSpec);
                privKey = kf.generatePrivate(privSpec);
            }
            catch (NoSuchAlgorithmException ex) {
                // TODO: log error
                os.write(SSH_AGENT_FAILURE);
                return;
            }
            catch (InvalidKeySpecException ex) {
                // TODO: log error
                os.write(SSH_AGENT_FAILURE);
                return;
            }

            KeyPair pair = new KeyPair(pubKey, privKey);
            boolean confirmUse = false;
            int lifetime = 0;

            if (checkConstraints) {
                while (tr.remain() > 0) {
                    int constraint = tr.readByte();

                    if (constraint == SSH_AGENT_CONSTRAIN_CONFIRM)
                        confirmUse = true;
                    else if (constraint == SSH_AGENT_CONSTRAIN_LIFETIME)
                        lifetime = tr.readUINT32();
                    else {
                        // Unknown constraint. Bail.
                        os.write(SSH_AGENT_FAILURE);
                        return;
                    }
                }
            }

            if (authAgent.addIdentity(pair, comment, confirmUse, lifetime))
                os.write(SSH_AGENT_SUCCESS);
            else
                os.write(SSH_AGENT_FAILURE);
        }
        catch (IOException e) {
            try {
                os.write(SSH_AGENT_FAILURE);
            }
            catch (IOException e1) {
            }
        }
    }

    /**
     * @param tr
     */
    private void removeIdentity(TypesReader tr) {
        try {
            if (failWhenLocked())
                return;

            byte[] publicKey = tr.readByteString();

            if (authAgent.removeIdentity(publicKey))
                os.write(SSH_AGENT_SUCCESS);
            else
                os.write(SSH_AGENT_FAILURE);
        }
        catch (IOException e) {
            try {
                os.write(SSH_AGENT_FAILURE);
            }
            catch (IOException e1) {
            }
        }
    }

    /**
     * @param tr
     */
    private void removeAllIdentities(TypesReader tr) {
        try {
            if (failWhenLocked())
                return;

            if (authAgent.removeAllIdentities())
                os.write(SSH_AGENT_SUCCESS);
            else
                os.write(SSH_AGENT_FAILURE);
        }
        catch (IOException e) {
            try {
                os.write(SSH_AGENT_FAILURE);
            }
            catch (IOException e1) {
            }
        }
    }

    private void processSignRequest(TypesReader tr) {
        try {
            if (failWhenLocked())
                return;

            byte[] publicKeyBytes = tr.readByteString();
            byte[] challenge = tr.readByteString();
            int flags = tr.readUINT32();

            if (flags != 0) {
                // We don't understand any flags; abort!
                os.write(SSH_AGENT_FAILURE);
                return;
            }

            KeyPair pair = authAgent.getKeyPair(publicKeyBytes);

            if (pair == null) {
                os.write(SSH_AGENT_FAILURE);
                return;
            }

            byte[] response;
            PrivateKey privKey = pair.getPrivate();

            if (privKey instanceof RSAPrivateKey) {
                byte[] signature = RSASHA1Verify.generateSignature(challenge,
                                   (RSAPrivateKey) privKey);
                response = RSASHA1Verify.encodeSSHRSASignature(signature);
            }
            else if (privKey instanceof DSAPrivateKey) {
                byte[] signature = DSASHA1Verify.generateSignature(challenge,
                                   (DSAPrivateKey) privKey, new SecureRandom());
                response = DSASHA1Verify.encodeSSHDSASignature(signature);
            }
            else {
                os.write(SSH_AGENT_FAILURE);
                return;
            }

            TypesWriter tw = new TypesWriter();
            tw.writeByte(SSH2_AGENT_SIGN_RESPONSE);
            tw.writeString(response, 0, response.length);
            sendPacket(tw.getBytes());
        }
        catch (IOException e) {
            try {
                os.write(SSH_AGENT_FAILURE);
            }
            catch (IOException e1) {
            }
        }
    }

    /**
     * @param tr
     */
    private void processLockRequest(TypesReader tr) {
        try {
            if (failWhenLocked())
                return;

            String lockPassphrase = tr.readString();

            if (!authAgent.setAgentLock(lockPassphrase)) {
                os.write(SSH_AGENT_FAILURE);
                return;
            }
            else
                os.write(SSH_AGENT_SUCCESS);
        }
        catch (IOException e) {
            try {
                os.write(SSH_AGENT_FAILURE);
            }
            catch (IOException e1) {
            }
        }
    }

    /**
     * @param tr
     */
    private void processUnlockRequest(TypesReader tr) {
        try {
            String unlockPassphrase = tr.readString();

            if (authAgent.requestAgentUnlock(unlockPassphrase))
                os.write(SSH_AGENT_SUCCESS);
            else
                os.write(SSH_AGENT_FAILURE);
        }
        catch (IOException e) {
            try {
                os.write(SSH_AGENT_FAILURE);
            }
            catch (IOException e1) {
            }
        }
    }

    /**
     * @param tw
     * @throws IOException
     */
    private void sendPacket(byte[] message) throws IOException {
        TypesWriter packet = new TypesWriter();
        packet.writeUINT32(message.length);
        packet.writeBytes(message);
        os.write(packet.getBytes());
    }
}