/* GIO - GLib Input, Output and Streaming Library

 *

 * Copyright (C) 2010 Collabora, Ltd.

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General

 * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.

 *

 * Author: Nicolas Dufresne <nicolas.dufresne@collabora.co.uk>

 */

#include "config.h"

#include "gsocks4aproxy.h"

#include <string.h>

#include "giomodule.h"

#include "giomodule-priv.h"

#include "giostream.h"

#include "ginetaddress.h"

#include "ginputstream.h"

#include "glibintl.h"

#include "goutputstream.h"

#include "gproxy.h"

#include "gproxyaddress.h"

#include "gtask.h"

#define SOCKS4_VERSION      4

#define SOCKS4_CMD_CONNECT    1

#define SOCKS4_CMD_BIND     2

#define SOCKS4_MAX_LEN      255

#define SOCKS4_REP_VERSION    0

#define SOCKS4_REP_GRANTED    90

#define SOCKS4_REP_REJECTED       91

#define SOCKS4_REP_NO_IDENT       92

#define SOCKS4_REP_BAD_IDENT      93

static void g_socks4a_proxy_iface_init (GProxyInterface *proxy_iface);

#define g_socks4a_proxy_get_type _g_socks4a_proxy_get_type

G_DEFINE_TYPE_WITH_CODE (GSocks4aProxy, g_socks4a_proxy, G_TYPE_OBJECT,

       G_IMPLEMENT_INTERFACE (G_TYPE_PROXY,

            g_socks4a_proxy_iface_init)

       _g_io_modules_ensure_extension_points_registered ();

       g_io_extension_point_implement (G_PROXY_EXTENSION_POINT_NAME,

               g_define_type_id,

               "socks4a",

               0))

static void

g_socks4a_proxy_finalize (GObject *object)

{

  /* must chain up */

  G_OBJECT_CLASS (g_socks4a_proxy_parent_class)->finalize (object);

}

static void

g_socks4a_proxy_init (GSocks4aProxy *proxy)

{

  proxy->supports_hostname = TRUE;

}

/*                                                             |-> SOCKSv4a only

 * +----+----+----+----+----+----+----+----+----+----+....+----+------+....+------+

 * | VN | CD | DSTPORT |      DSTIP        | USERID       |NULL| HOST |    | NULL |

 * +----+----+----+----+----+----+----+----+----+----+....+----+------+....+------+

 *    1    1      2              4           variable       1    variable    1

 */

#define SOCKS4_CONN_MSG_LEN     (10 + SOCKS4_MAX_LEN * 2)

static gint

set_connect_msg (guint8      *msg,

     const gchar *hostname,

     guint16      port,

     const char  *username,

     GError     **error)

{

  GInetAddress *addr;

  guint len = 0;

  gsize addr_len;

  gboolean is_ip;

  const gchar *ip;

  msg[len++] = SOCKS4_VERSION;

  msg[len++] = SOCKS4_CMD_CONNECT;

    {

      guint16 hp = g_htons (port);

      memcpy (msg + len, &hp, 2);

      len += 2;

    }

  is_ip = g_hostname_is_ip_address (hostname);

  if (is_ip)

    ip = hostname;

  else

    ip = "0.0.0.1";

  addr = g_inet_address_new_from_string (ip);

  addr_len = g_inet_address_get_native_size (addr);

  if (addr_len != 4)

    {

      g_set_error (error, G_IO_ERROR, G_IO_ERROR_PROXY_FAILED,

      _("SOCKSv4 does not support IPv6 address “%s”"),

      ip);

      g_object_unref (addr);

      return -1;

    }

  memcpy (msg + len, g_inet_address_to_bytes (addr), addr_len);

  len += addr_len;

  g_object_unref (addr);

  if (username)

    {

      gsize user_len = strlen (username);

      if (user_len > SOCKS4_MAX_LEN)

  {

    g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_PROXY_FAILED,

             _("Username is too long for SOCKSv4 protocol"));

    return -1;

  }

      memcpy (msg + len, username, user_len);

      len += user_len;

    }

  msg[len++] = '\0';

  if (!is_ip)

    {

      gsize host_len = strlen (hostname);

      if (host_len > SOCKS4_MAX_LEN)

  {

    g_set_error (error, G_IO_ERROR, G_IO_ERROR_PROXY_FAILED,

           _("Hostname “%s” is too long for SOCKSv4 protocol"),

           hostname);

    return -1;

  }

      memcpy (msg + len, hostname, host_len);

      len += host_len;

      msg[len++] = '\0';

    }

  return len;

}

/*

 * +----+----+----+----+----+----+----+----+

 * | VN | CD | DSTPORT |      DSTIP        |

 * +----+----+----+----+----+----+----+----+

 *    1    1      2              4

 */

#define SOCKS4_CONN_REP_LEN   8

static gboolean

parse_connect_reply (const guint8 *data, GError **error)

{

  if (data[0] != SOCKS4_REP_VERSION)

    {

      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_PROXY_FAILED,

         _("The server is not a SOCKSv4 proxy server."));

      return FALSE;

    }

  if (data[1] != SOCKS4_REP_GRANTED)

    {

      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_PROXY_FAILED,

         _("Connection through SOCKSv4 server was rejected"));

      return FALSE;

    }

  return TRUE;

}

static GIOStream *

g_socks4a_proxy_connect (GProxy            *proxy,

       GIOStream         *io_stream,

       GProxyAddress     *proxy_address,

       GCancellable      *cancellable,

       GError           **error)

{

  GInputStream *in;

  GOutputStream *out;

  const gchar *hostname;

  guint16 port;

  const gchar *username;

  hostname = g_proxy_address_get_destination_hostname (proxy_address);

  port = g_proxy_address_get_destination_port (proxy_address);

  username = g_proxy_address_get_username (proxy_address);

  in = g_io_stream_get_input_stream (io_stream);

  out = g_io_stream_get_output_stream (io_stream);

  /* Send SOCKS4 connection request */

    {

      guint8 msg[SOCKS4_CONN_MSG_LEN];

      gint len;

      len = set_connect_msg (msg, hostname, port, username, error);

      if (len < 0)

  goto error;

      if (!g_output_stream_write_all (out, msg, len, NULL,

              cancellable, error))

  goto error;

    }

  /* Read SOCKS4 response */

    {

      guint8 data[SOCKS4_CONN_REP_LEN];

      if (!g_input_stream_read_all (in, data, SOCKS4_CONN_REP_LEN, NULL,

            cancellable, error))

  goto error;

      if (!parse_connect_reply (data, error))

  goto error;

    }

  return g_object_ref (io_stream);

error:

  return NULL;

}

typedef struct

{

  GIOStream *io_stream;

  /* For connecting */

  guint8 *buffer;

  gssize length;

  gssize offset;

} ConnectAsyncData;

static void connect_msg_write_cb      (GObject          *source,

               GAsyncResult     *result,

               gpointer          user_data);

static void connect_reply_read_cb     (GObject          *source,

               GAsyncResult     *result,

               gpointer          user_data);

static void

free_connect_data (ConnectAsyncData *data)

{

  g_object_unref (data->io_stream);

  g_free (data->buffer);

  g_slice_free (ConnectAsyncData, data);

}

static void

do_read (GAsyncReadyCallback callback, GTask *task, ConnectAsyncData *data)

{

   GInputStream *in;

   in = g_io_stream_get_input_stream (data->io_stream);

   g_input_stream_read_async (in,

            data->buffer + data->offset,

            data->length - data->offset,

            g_task_get_priority (task),

            g_task_get_cancellable (task),

            callback, task);

}

static void

do_write (GAsyncReadyCallback callback, GTask *task, ConnectAsyncData *data)

{

  GOutputStream *out;

  out = g_io_stream_get_output_stream (data->io_stream);

  g_output_stream_write_async (out,

             data->buffer + data->offset,

             data->length - data->offset,

             g_task_get_priority (task),

             g_task_get_cancellable (task),

             callback, task);

}

static void

g_socks4a_proxy_connect_async (GProxy               *proxy,

             GIOStream            *io_stream,

             GProxyAddress        *proxy_address,

             GCancellable         *cancellable,

             GAsyncReadyCallback   callback,

             gpointer              user_data)

{

  GError *error = NULL;

  GTask *task;

  ConnectAsyncData *data;

  const gchar *hostname;

  guint16 port;

  const gchar *username;

  data = g_slice_new0 (ConnectAsyncData);

  data->io_stream = g_object_ref (io_stream);

  task = g_task_new (proxy, cancellable, callback, user_data);

  g_task_set_source_tag (task, g_socks4a_proxy_connect_async);

  g_task_set_task_data (task, data, (GDestroyNotify) free_connect_data);

  hostname = g_proxy_address_get_destination_hostname (proxy_address);

  port = g_proxy_address_get_destination_port (proxy_address);

  username = g_proxy_address_get_username (proxy_address); 

  data->buffer = g_malloc0 (SOCKS4_CONN_MSG_LEN);

  data->length = set_connect_msg (data->buffer,

          hostname, port, username,

          &error);

  data->offset = 0;

  if (data->length < 0)

    {

      g_task_return_error (task, error);

      g_object_unref (task);

    }

  else

    {

      do_write (connect_msg_write_cb, task, data);

    }

}

static void

connect_msg_write_cb (GObject      *source,

          GAsyncResult *result,

          gpointer      user_data)

{

  GTask *task = user_data;

  ConnectAsyncData *data = g_task_get_task_data (task);

  GError *error = NULL;

  gssize written;

  written = g_output_stream_write_finish (G_OUTPUT_STREAM (source),

            result, &error);

  if (written < 0)

    {

      g_task_return_error (task, error);

      g_object_unref (task);

      return;

    }

  data->offset += written;

  if (data->offset == data->length)

    {

      g_free (data->buffer);

      data->buffer = g_malloc0 (SOCKS4_CONN_REP_LEN);

      data->length = SOCKS4_CONN_REP_LEN;

      data->offset = 0;

      do_read (connect_reply_read_cb, task, data);

    }

  else

    {

      do_write (connect_msg_write_cb, task, data);

    }

}

static void

connect_reply_read_cb (GObject       *source,

           GAsyncResult  *result,

           gpointer       user_data)

{

  GTask *task = user_data;

  ConnectAsyncData *data = g_task_get_task_data (task);

  GError *error = NULL;

  gssize read;

  read = g_input_stream_read_finish (G_INPUT_STREAM (source),

             result, &error);

  if (read < 0)

    {

      g_task_return_error (task, error);

      g_object_unref (task);

      return;

    }

  data->offset += read;

  if (data->offset == data->length)

    {

      if (!parse_connect_reply (data->buffer, &error))

  {

    g_task_return_error (task, error);

    g_object_unref (task);

    return;

  }

      else

  {

    g_task_return_pointer (task, g_object_ref (data->io_stream), g_object_unref);

    g_object_unref (task);

    return;

  }

    }

  else

    {

      do_read (connect_reply_read_cb, task, data);

    }

}

static GIOStream *g_socks4a_proxy_connect_finish (GProxy       *proxy,

              GAsyncResult *result,

              GError      **error);

static GIOStream *

g_socks4a_proxy_connect_finish (GProxy       *proxy,

              GAsyncResult *result,

              GError      **error)

{

  return g_task_propagate_pointer (G_TASK (result), error);

}

static gboolean

g_socks4a_proxy_supports_hostname (GProxy *proxy)

{

  return G_SOCKS4A_PROXY (proxy)->supports_hostname;

}

static void

g_socks4a_proxy_class_init (GSocks4aProxyClass *class)

{

  GObjectClass *object_class;

  object_class = (GObjectClass *) class;

  object_class->finalize = g_socks4a_proxy_finalize;

}

static void

g_socks4a_proxy_iface_init (GProxyInterface *proxy_iface)

{

  proxy_iface->connect  = g_socks4a_proxy_connect;

  proxy_iface->connect_async = g_socks4a_proxy_connect_async;

  proxy_iface->connect_finish = g_socks4a_proxy_connect_finish;

  proxy_iface->supports_hostname = g_socks4a_proxy_supports_hostname;

}