/*
 * Copyright (c) 2000, 2025, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package java.net;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.BufferedOutputStream;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;

import jdk.internal.util.StaticProperty;
import sun.net.SocksProxy;
import sun.net.spi.DefaultProxySelector;
import sun.net.www.ParseUtil;

import static sun.net.util.IPAddressUtil.isIPv6LiteralAddress;
import static jdk.internal.util.Exceptions.filterSocketInfo;
import static jdk.internal.util.Exceptions.formatMsg;

/**
 * SOCKS (V4 & V5) TCP socket implementation (RFC 1928).
 */

class SocksSocketImpl extends DelegatingSocketImpl implements SocksConsts {
    private String server = null;
    private int serverPort = DEFAULT_PORT;
    private InetSocketAddress external_address;
    private boolean useV4 = false;
    private Socket cmdsock = null;
    private InputStream cmdIn = null;
    private OutputStream cmdOut = null;

    SocksSocketImpl(SocketImpl delegate) {
        super(delegate);
    }

    SocksSocketImpl(Proxy proxy, SocketImpl delegate) {
        super(delegate);
        SocketAddress a = proxy.address();
        if (a instanceof InetSocketAddress ad) {
            // Use getHostString() to avoid reverse lookups
            server = ad.getHostString();
            serverPort = ad.getPort();
        }
        useV4 = useV4(proxy);
    }

    private static boolean useV4(Proxy proxy) {
        if (proxy instanceof SocksProxy
            && ((SocksProxy)proxy).protocolVersion() == 4) {
            return true;
        }
        return DefaultProxySelector.socksProxyVersion() == 4;
    }

    private synchronized void doConnect(final String host, final int port, final int timeout) throws IOException {
        delegate.connect(new InetSocketAddress(host, port), timeout);
        cmdIn = getInputStream();
        cmdOut = getOutputStream();
    }

    private static int remainingMillis(long deadlineMillis) throws IOException {
        if (deadlineMillis == 0L)
            return 0;

        final long remaining = deadlineMillis - System.currentTimeMillis();
        if (remaining > 0)
            return (int) remaining;

        throw new SocketTimeoutException();
    }

    private int readSocksReply(InputStream in, byte[] data, long deadlineMillis) throws IOException {
        int len = data.length;
        int received = 0;
        int originalTimeout = (int) getOption(SocketOptions.SO_TIMEOUT);
        try {
            while (received < len) {
                int count;
                int remaining = remainingMillis(deadlineMillis);
                setOption(SocketOptions.SO_TIMEOUT, remaining);
                try {
                    count = in.read(data, received, len - received);
                } catch (SocketTimeoutException e) {
                    throw new SocketTimeoutException("Connect timed out");
                }
                if (count < 0)
                    throw new SocketException("Malformed reply from SOCKS server");
                received += count;
            }
        } finally {
            setOption(SocketOptions.SO_TIMEOUT, originalTimeout);
        }
        return received;
    }

    private boolean authenticate(byte method, InputStream in,
                                 BufferedOutputStream out,
                                 long deadlineMillis) throws IOException {
        // No Authentication required. We're done then!
        if (method == NO_AUTH)
            return true;
        /*
         * User/Password authentication. Try, in that order :
         * - The application provided Authenticator, if any
         * - the user.name & no password (backward compatibility behavior).
         */
        if (method == USER_PASSW) {
            String userName;
            String password = null;
            final InetAddress addr = InetAddress.getByName(server);
            PasswordAuthentication pw = Authenticator.requestPasswordAuthentication(
                    server, addr, serverPort, "SOCKS5", "SOCKS authentication", null);
            if (pw != null) {
                userName = pw.getUserName();
                password = new String(pw.getPassword());
            } else {
                userName = StaticProperty.userName();
            }
            if (userName == null)
                return false;
            out.write(1);
            out.write(userName.length());
            out.write(userName.getBytes(StandardCharsets.ISO_8859_1));
            if (password != null) {
                out.write(password.length());
                out.write(password.getBytes(StandardCharsets.ISO_8859_1));
            } else
                out.write(0);
            out.flush();
            byte[] data = new byte[2];
            int i = readSocksReply(in, data, deadlineMillis);
            if (i != 2 || data[1] != 0) {
                /* RFC 1929 specifies that the connection MUST be closed if
                   authentication fails */
                out.close();
                in.close();
                return false;
            }
            /* Authentication succeeded */
            return true;
        }
        return false;
    }

    private void connectV4(InputStream in, OutputStream out,
                           InetSocketAddress endpoint,
                           long deadlineMillis) throws IOException {
        if (!(endpoint.getAddress() instanceof Inet4Address)) {
            throw new SocketException("SOCKS V4 requires IPv4 only addresses");
        }
        out.write(PROTO_VERS4);
        out.write(CONNECT);
        out.write((endpoint.getPort() >> 8) & 0xff);
        out.write((endpoint.getPort() >> 0) & 0xff);
        out.write(endpoint.getAddress().getAddress());
        String userName = getUserName();
        out.write(userName.getBytes(StandardCharsets.ISO_8859_1));
        out.write(0);
        out.flush();
        byte[] data = new byte[8];
        int n = readSocksReply(in, data, deadlineMillis);
        if (n != 8)
            throw new SocketException("Reply from SOCKS server has bad length: " + n);
        if (data[0] != 0 && data[0] != 4)
            throw new SocketException("Reply from SOCKS server has bad version");
        SocketException ex = switch (data[1]) {
            case 90 -> {
                // Success!
                external_address = endpoint;
                yield null;
            }
            case 91 -> new SocketException("SOCKS request rejected");
            case 92 -> new SocketException("SOCKS server couldn't reach destination");
            case 93 -> new SocketException("SOCKS authentication failed");
            default -> new SocketException("Reply from SOCKS server contains bad status");
        };
        if (ex != null) {
            in.close();
            out.close();
            throw ex;
        }
    }

    @Override
    protected void connect(String host, int port) throws IOException {
        connect(new InetSocketAddress(host, port), 0);
    }

    @Override
    protected void connect(InetAddress address, int port) throws IOException {
        connect(new InetSocketAddress(address, port), 0);
    }

    /**
     * Connects the Socks Socket to the specified endpoint. It will first
     * connect to the SOCKS proxy and negotiate the access. If the proxy
     * grants the connections, then the connect is successful and all
     * further traffic will go to the "real" endpoint.
     *
     * @param   endpoint        the {@code SocketAddress} to connect to.
     * @param   timeout         the timeout value in milliseconds
     * @throws  IOException     if the connection can't be established.
     * @throws  IllegalArgumentException if endpoint is null or a
     *          SocketAddress subclass not supported by this socket
     */
    @Override
    protected void connect(SocketAddress endpoint, int timeout) throws IOException {
        final long deadlineMillis;

        if (timeout == 0) {
            deadlineMillis = 0L;
        } else {
            long finish = System.currentTimeMillis() + timeout;
            deadlineMillis = finish < 0 ? Long.MAX_VALUE : finish;
        }

        if (!(endpoint instanceof InetSocketAddress epoint))
            throw new IllegalArgumentException("Unsupported address type");

        if (server == null) {
            // This is the general case
            // server is not null only when the socket was created with a
            // specified proxy in which case it does bypass the ProxySelector
            ProxySelector sel = ProxySelector.getDefault();
            if (sel == null) {
                /*
                 * No default proxySelector --> direct connection
                 */
                delegate.connect(epoint, remainingMillis(deadlineMillis));
                return;
            }
            URI uri;
            // Use getHostString() to avoid reverse lookups
            String host = epoint.getHostString();
            if (isIPv6LiteralAddress(host)) {
                host = "[" + host + "]";
            } else {
                host = ParseUtil.encodePath(host);
            }
            try {
                uri = new URI("socket://" + host + ":"+ epoint.getPort());
            } catch (URISyntaxException e) {
                throw new IOException("Failed to select a proxy", e);
            }
            Proxy p = null;
            IOException savedExc = null;
            final Iterator<Proxy> iProxy;
            try {
                iProxy = sel.select(uri).iterator();
            } catch (IllegalArgumentException iae) {
                throw new IOException("Failed to select a proxy", iae);
            }
            if (iProxy == null || !(iProxy.hasNext())) {
                delegate.connect(epoint, remainingMillis(deadlineMillis));
                return;
            }
            while (iProxy.hasNext()) {
                p = iProxy.next();
                if (p == null || p.type() != Proxy.Type.SOCKS) {
                    delegate.connect(epoint, remainingMillis(deadlineMillis));
                    return;
                }

                if (!(p.address() instanceof InetSocketAddress))
                    throw new SocketException("Unknown address type for proxy: " + p);
                // Use getHostString() to avoid reverse lookups
                server = ((InetSocketAddress) p.address()).getHostString();
                serverPort = ((InetSocketAddress) p.address()).getPort();
                useV4 = useV4(p);

                // Connects to the SOCKS server
                try {
                    doConnect(server, serverPort, remainingMillis(deadlineMillis));
                    // Worked, let's get outta here
                    break;
                } catch (IOException e) {
                    // Ooops, let's notify the ProxySelector
                    sel.connectFailed(uri,p.address(),e);
                    server = null;
                    serverPort = -1;
                    savedExc = e;
                    // Will continue the while loop and try the next proxy
                }
            }

            /*
             * If server is still null at this point, none of the proxy
             * worked
             */
            if (server == null) {
                throw new SocketException("Can't connect to SOCKS proxy:"
                                          + savedExc.getMessage());
            }
        } else {
            // Connects to the SOCKS server
            try {
                doConnect(server, serverPort, remainingMillis(deadlineMillis));
            } catch (IOException e) {
                throw new SocketException(e.getMessage(), e);
            }
        }

        // `cmdIn` & `cmdOut` were initialized during the `doConnect()` call
        BufferedOutputStream out = new BufferedOutputStream(cmdOut, 512);
        InputStream in = cmdIn;

        if (useV4) {
            // SOCKS Protocol version 4 doesn't know how to deal with
            // DOMAIN type of addresses (unresolved addresses here)
            if (epoint.isUnresolved())
                throw new UnknownHostException(formatMsg("%s", filterSocketInfo(epoint.toString())));
            connectV4(in, out, epoint, deadlineMillis);
            return;
        }

        // This is SOCKS V5
        out.write(PROTO_VERS);
        out.write(2);
        out.write(NO_AUTH);
        out.write(USER_PASSW);
        out.flush();
        byte[] data = new byte[2];
        int i = readSocksReply(in, data, deadlineMillis);
        if (i != 2 || ((int)data[0]) != PROTO_VERS) {
            // Maybe it's not a V5 sever after all
            // Let's try V4 before we give up
            // SOCKS Protocol version 4 doesn't know how to deal with
            // DOMAIN type of addresses (unresolved addresses here)
            if (epoint.isUnresolved())
                throw new UnknownHostException(formatMsg("%s", filterSocketInfo(epoint.toString())));
            connectV4(in, out, epoint, deadlineMillis);
            return;
        }
        if (((int)data[1]) == NO_METHODS)
            throw new SocketException("SOCKS : No acceptable methods");
        if (!authenticate(data[1], in, out, deadlineMillis)) {
            throw new SocketException("SOCKS : authentication failed");
        }
        out.write(PROTO_VERS);
        out.write(CONNECT);
        out.write(0);
        /* Test for IPV4/IPV6/Unresolved */
        if (epoint.isUnresolved()) {
            out.write(DOMAIN_NAME);
            out.write(epoint.getHostName().length());
            out.write(epoint.getHostName().getBytes(StandardCharsets.ISO_8859_1));
            out.write((epoint.getPort() >> 8) & 0xff);
            out.write((epoint.getPort() >> 0) & 0xff);
        } else if (epoint.getAddress() instanceof Inet6Address) {
            out.write(IPV6);
            out.write(epoint.getAddress().getAddress());
            out.write((epoint.getPort() >> 8) & 0xff);
            out.write((epoint.getPort() >> 0) & 0xff);
        } else {
            out.write(IPV4);
            out.write(epoint.getAddress().getAddress());
            out.write((epoint.getPort() >> 8) & 0xff);
            out.write((epoint.getPort() >> 0) & 0xff);
        }
        out.flush();
        data = new byte[4];
        i = readSocksReply(in, data, deadlineMillis);
        if (i != 4)
            throw new SocketException("Reply from SOCKS server has bad length");
        SocketException ex = null;
        int len;
        byte[] addr;
        switch (data[1]) {
        case REQUEST_OK:
            // success!
            switch(data[3]) {
            case IPV4:
                addr = new byte[4];
                i = readSocksReply(in, addr, deadlineMillis);
                if (i != 4)
                    throw new SocketException("Reply from SOCKS server badly formatted");
                data = new byte[2];
                i = readSocksReply(in, data, deadlineMillis);
                if (i != 2)
                    throw new SocketException("Reply from SOCKS server badly formatted");
                break;
            case DOMAIN_NAME:
                byte[] lenByte = new byte[1];
                i = readSocksReply(in, lenByte, deadlineMillis);
                if (i != 1)
                    throw new SocketException("Reply from SOCKS server badly formatted");
                len = lenByte[0] & 0xFF;
                byte[] host = new byte[len];
                i = readSocksReply(in, host, deadlineMillis);
                if (i != len)
                    throw new SocketException("Reply from SOCKS server badly formatted");
                data = new byte[2];
                i = readSocksReply(in, data, deadlineMillis);
                if (i != 2)
                    throw new SocketException("Reply from SOCKS server badly formatted");
                break;
            case IPV6:
                len = 16;
                addr = new byte[len];
                i = readSocksReply(in, addr, deadlineMillis);
                if (i != len)
                    throw new SocketException("Reply from SOCKS server badly formatted");
                data = new byte[2];
                i = readSocksReply(in, data, deadlineMillis);
                if (i != 2)
                    throw new SocketException("Reply from SOCKS server badly formatted");
                break;
            default:
                ex = new SocketException("Reply from SOCKS server contains wrong code");
                break;
            }
            break;
        case GENERAL_FAILURE:
            ex = new SocketException("SOCKS server general failure");
            break;
        case NOT_ALLOWED:
            ex = new SocketException("SOCKS: Connection not allowed by ruleset");
            break;
        case NET_UNREACHABLE:
            ex = new SocketException("SOCKS: Network unreachable");
            break;
        case HOST_UNREACHABLE:
            ex = new SocketException("SOCKS: Host unreachable");
            break;
        case CONN_REFUSED:
            ex = new SocketException("SOCKS: Connection refused");
            break;
        case TTL_EXPIRED:
            ex =  new SocketException("SOCKS: TTL expired");
            break;
        case CMD_NOT_SUPPORTED:
            ex = new SocketException("SOCKS: Command not supported");
            break;
        case ADDR_TYPE_NOT_SUP:
            ex = new SocketException("SOCKS: address type not supported");
            break;
        }
        if (ex != null) {
            in.close();
            out.close();
            throw ex;
        }
        external_address = epoint;
    }

    @Override
    protected void listen(int backlog) {
        throw new InternalError("should not get here");
    }

    @Override
    protected void accept(SocketImpl s) {
        throw new InternalError("should not get here");
    }

    /**
     * Returns the value of this socket's {@code address} field.
     *
     * @return  the value of this socket's {@code address} field.
     * @see     java.net.SocketImpl#address
     */
    @Override
    protected InetAddress getInetAddress() {
        if (external_address != null)
            return external_address.getAddress();
        else
            return delegate.getInetAddress();
    }

    /**
     * Returns the value of this socket's {@code port} field.
     *
     * @return  the value of this socket's {@code port} field.
     * @see     java.net.SocketImpl#port
     */
    @Override
    protected int getPort() {
        if (external_address != null)
            return external_address.getPort();
        else
            return delegate.getPort();
    }

    @Override
    protected void close() throws IOException {
        if (cmdsock != null)
            cmdsock.close();
        cmdsock = null;
        delegate.close();
    }

    private String getUserName() {
        return StaticProperty.userName();
    }

    @Override
    void reset() {
        throw new InternalError("should not get here");
    }
}