/* GDBus - GLib D-Bus Library

 *

 * Copyright (C) 2008-2010 Red Hat, Inc.

 *

 * 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: David Zeuthen <davidz@redhat.com>

 */

#include "config.h"

#include "gdbusauth.h"

#include "gdbusauthmechanismanon.h"

#include "gdbusauthmechanismexternal.h"

#include "gdbusauthmechanismsha1.h"

#include "gdbusauthobserver.h"

#include "gdbuserror.h"

#include "gdbusutils.h"

#include "gioenumtypes.h"

#include "gcredentials.h"

#include "gcredentialsprivate.h"

#include "gdbusprivate.h"

#include "giostream.h"

#include "gdatainputstream.h"

#include "gdataoutputstream.h"

#include "gnetworking.h"

#include "gunixconnection.h"

#include "gunixcredentialsmessage.h"

#include "glibintl.h"

G_GNUC_PRINTF(1, 2)

static void

debug_print (const gchar *message, ...)

{

  if (G_UNLIKELY (_g_dbus_debug_authentication ()))

    {

      gchar *s;

      GString *str;

      va_list var_args;

      guint n;

      _g_dbus_debug_print_lock ();

      va_start (var_args, message);

      s = g_strdup_vprintf (message, var_args);

      va_end (var_args);

      str = g_string_new (NULL);

      for (n = 0; s[n] != '\0'; n++)

        {

          if (G_UNLIKELY (s[n] == '\r'))

            g_string_append (str, "\\r");

          else if (G_UNLIKELY (s[n] == '\n'))

            g_string_append (str, "\\n");

          else

            g_string_append_c (str, s[n]);

        }

      g_print ("GDBus-debug:Auth: %s\n", str->str);

      g_string_free (str, TRUE);

      g_free (s);

      _g_dbus_debug_print_unlock ();

    }

}

typedef struct

{

  const gchar *name;

  gint priority;

  GType gtype;

} Mechanism;

static void mechanism_free (Mechanism *m);

struct _GDBusAuthPrivate

{

  GIOStream *stream;

  /* A list of available Mechanism, sorted according to priority  */

  GList *available_mechanisms;

};

enum

{

  PROP_0,

  PROP_STREAM

};

G_DEFINE_TYPE_WITH_PRIVATE (GDBusAuth, _g_dbus_auth, G_TYPE_OBJECT)

/* ---------------------------------------------------------------------------------------------------- */

static void

_g_dbus_auth_finalize (GObject *object)

{

  GDBusAuth *auth = G_DBUS_AUTH (object);

  if (auth->priv->stream != NULL)

    g_object_unref (auth->priv->stream);

  g_list_free_full (auth->priv->available_mechanisms, (GDestroyNotify) mechanism_free);

  if (G_OBJECT_CLASS (_g_dbus_auth_parent_class)->finalize != NULL)

    G_OBJECT_CLASS (_g_dbus_auth_parent_class)->finalize (object);

}

static void

_g_dbus_auth_get_property (GObject    *object,

                           guint       prop_id,

                           GValue     *value,

                           GParamSpec *pspec)

{

  GDBusAuth *auth = G_DBUS_AUTH (object);

  switch (prop_id)

    {

    case PROP_STREAM:

      g_value_set_object (value, auth->priv->stream);

      break;

    default:

      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);

      break;

    }

}

static void

_g_dbus_auth_set_property (GObject      *object,

                           guint         prop_id,

                           const GValue *value,

                           GParamSpec   *pspec)

{

  GDBusAuth *auth = G_DBUS_AUTH (object);

  switch (prop_id)

    {

    case PROP_STREAM:

      auth->priv->stream = g_value_dup_object (value);

      break;

    default:

      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);

      break;

    }

}

static void

_g_dbus_auth_class_init (GDBusAuthClass *klass)

{

  GObjectClass *gobject_class;

  gobject_class = G_OBJECT_CLASS (klass);

  gobject_class->get_property = _g_dbus_auth_get_property;

  gobject_class->set_property = _g_dbus_auth_set_property;

  gobject_class->finalize     = _g_dbus_auth_finalize;

  g_object_class_install_property (gobject_class,

                                   PROP_STREAM,

                                   g_param_spec_object ("stream",

                                                        P_("IO Stream"),

                                                        P_("The underlying GIOStream used for I/O"),

                                                        G_TYPE_IO_STREAM,

                                                        G_PARAM_READABLE |

                                                        G_PARAM_WRITABLE |

                                                        G_PARAM_CONSTRUCT_ONLY |

                                                        G_PARAM_STATIC_NAME |

                                                        G_PARAM_STATIC_BLURB |

                                                        G_PARAM_STATIC_NICK));

}

static void

mechanism_free (Mechanism *m)

{

  g_free (m);

}

static void

add_mechanism (GDBusAuth         *auth,

               GDBusAuthObserver *observer,

               GType              mechanism_type)

{

  const gchar *name;

  name = _g_dbus_auth_mechanism_get_name (mechanism_type);

  if (observer == NULL || g_dbus_auth_observer_allow_mechanism (observer, name))

    {

      Mechanism *m;

      m = g_new0 (Mechanism, 1);

      m->name = name;

      m->priority = _g_dbus_auth_mechanism_get_priority (mechanism_type);

      m->gtype = mechanism_type;

      auth->priv->available_mechanisms = g_list_prepend (auth->priv->available_mechanisms, m);

    }

}

static gint

mech_compare_func (Mechanism *a, Mechanism *b)

{

  gint ret;

  /* ensure deterministic order */

  ret = b->priority - a->priority;

  if (ret == 0)

    ret = g_strcmp0 (b->name, a->name);

  return ret;

}

static void

_g_dbus_auth_init (GDBusAuth *auth)

{

  auth->priv = _g_dbus_auth_get_instance_private (auth);

}

static void

_g_dbus_auth_add_mechs (GDBusAuth         *auth,

                        GDBusAuthObserver *observer)

{

  /* TODO: trawl extension points */

  add_mechanism (auth, observer, G_TYPE_DBUS_AUTH_MECHANISM_ANON);

  add_mechanism (auth, observer, G_TYPE_DBUS_AUTH_MECHANISM_SHA1);

  add_mechanism (auth, observer, G_TYPE_DBUS_AUTH_MECHANISM_EXTERNAL);

  auth->priv->available_mechanisms = g_list_sort (auth->priv->available_mechanisms,

                                                  (GCompareFunc) mech_compare_func);

}

static GType

find_mech_by_name (GDBusAuth *auth,

                   const gchar *name)

{

  GType ret;

  GList *l;

  ret = (GType) 0;

  for (l = auth->priv->available_mechanisms; l != NULL; l = l->next)

    {

      Mechanism *m = l->data;

      if (g_strcmp0 (name, m->name) == 0)

        {

          ret = m->gtype;

          goto out;

        }

    }

 out:

  return ret;

}

GDBusAuth  *

_g_dbus_auth_new (GIOStream *stream)

{

  return g_object_new (G_TYPE_DBUS_AUTH,

                       "stream", stream,

                       NULL);

}

/* ---------------------------------------------------------------------------------------------------- */

/* like g_data_input_stream_read_line() but sets error if there's no content to read */

static gchar *

_my_g_data_input_stream_read_line (GDataInputStream  *dis,

                                   gsize             *out_line_length,

                                   GCancellable      *cancellable,

                                   GError           **error)

{

  gchar *ret;

  g_return_val_if_fail (error == NULL || *error == NULL, NULL);

  ret = g_data_input_stream_read_line (dis,

                                       out_line_length,

                                       cancellable,

                                       error);

  if (ret == NULL && error != NULL && *error == NULL)

    {

      g_set_error_literal (error,

                           G_IO_ERROR,

                           G_IO_ERROR_FAILED,

                           _("Unexpected lack of content trying to read a line"));

    }

  return ret;

}

/* This function is to avoid situations like this

 *

 * BEGIN\r\nl\0\0\1...

 *

 * e.g. where we read into the first D-Bus message while waiting for

 * the final line from the client (TODO: file bug against gio for

 * this)

 */

static gchar *

_my_g_input_stream_read_line_safe (GInputStream  *i,

                                   gsize         *out_line_length,

                                   GCancellable  *cancellable,

                                   GError       **error)

{

  GString *str;

  gchar c;

  gssize num_read;

  gboolean last_was_cr;

  str = g_string_new (NULL);

  last_was_cr = FALSE;

  while (TRUE)

    {

      num_read = g_input_stream_read (i,

                                      &c,

                                      1,

                                      cancellable,

                                      error);

      if (num_read == -1)

        goto fail;

      if (num_read == 0)

        {

          if (error != NULL && *error == NULL)

            {

              g_set_error_literal (error,

                                   G_IO_ERROR,

                                   G_IO_ERROR_FAILED,

                                   _("Unexpected lack of content trying to (safely) read a line"));

            }

          goto fail;

        }

      g_string_append_c (str, (gint) c);

      if (last_was_cr)

        {

          if (c == 0x0a)

            {

              g_assert (str->len >= 2);

              g_string_set_size (str, str->len - 2);

              goto out;

            }

        }

      last_was_cr = (c == 0x0d);

    }

 out:

  if (out_line_length != NULL)

    *out_line_length = str->len;

  return g_string_free (str, FALSE);

 fail:

  g_assert (error == NULL || *error != NULL);

  g_string_free (str, TRUE);

  return NULL;

}

/* ---------------------------------------------------------------------------------------------------- */

static gchar *

hexdecode (const gchar  *str,

           gsize        *out_len,

           GError      **error)

{

  gchar *ret;

  GString *s;

  guint n;

  ret = NULL;

  s = g_string_new (NULL);

  for (n = 0; str[n] != '\0'; n += 2)

    {

      gint upper_nibble;

      gint lower_nibble;

      guint value;

      upper_nibble = g_ascii_xdigit_value (str[n]);

      lower_nibble = g_ascii_xdigit_value (str[n + 1]);

      if (upper_nibble == -1 || lower_nibble == -1)

        {

          g_set_error (error,

                       G_IO_ERROR,

                       G_IO_ERROR_FAILED,

                       "Error hexdecoding string '%s' around position %d",

                       str, n);

          goto out;

        }

      value = (upper_nibble<<4) | lower_nibble;

      g_string_append_c (s, value);

    }

  *out_len = s->len;

  ret = g_string_free (s, FALSE);

  s = NULL;

 out:

  if (s != NULL)

    {

      *out_len = 0;

      g_string_free (s, TRUE);

    }

   return ret;

}

/* ---------------------------------------------------------------------------------------------------- */

static GDBusAuthMechanism *

client_choose_mech_and_send_initial_response (GDBusAuth           *auth,

                                              GCredentials        *credentials_that_were_sent,

                                              GDBusConnectionFlags conn_flags,

                                              const gchar* const  *supported_auth_mechs,

                                              GPtrArray           *attempted_auth_mechs,

                                              GDataOutputStream   *dos,

                                              GCancellable        *cancellable,

                                              GError             **error)

{

  GDBusAuthMechanism *mech;

  GType auth_mech_to_use_gtype;

  guint n;

  guint m;

  gchar *initial_response;

  gsize initial_response_len;

  gchar *encoded;

  gchar *s;

 again:

  mech = NULL;

  debug_print ("CLIENT: Trying to choose mechanism");

  /* find an authentication mechanism to try, if any */

  auth_mech_to_use_gtype = (GType) 0;

  for (n = 0; supported_auth_mechs[n] != NULL; n++)

    {

      gboolean attempted_already;

      attempted_already = FALSE;

      for (m = 0; m < attempted_auth_mechs->len; m++)

        {

          if (g_strcmp0 (supported_auth_mechs[n], attempted_auth_mechs->pdata[m]) == 0)

            {

              attempted_already = TRUE;

              break;

            }

        }

      if (!attempted_already)

        {

          auth_mech_to_use_gtype = find_mech_by_name (auth, supported_auth_mechs[n]);

          if (auth_mech_to_use_gtype != (GType) 0)

            break;

        }

    }

  if (auth_mech_to_use_gtype == (GType) 0)

    {

      gchar *available;

      GString *tried_str;

      debug_print ("CLIENT: Exhausted all available mechanisms");

      available = g_strjoinv (", ", (gchar **) supported_auth_mechs);

      tried_str = g_string_new (NULL);

      for (n = 0; n < attempted_auth_mechs->len; n++)

        {

          if (n > 0)

            g_string_append (tried_str, ", ");

          g_string_append (tried_str, attempted_auth_mechs->pdata[n]);

        }

      g_set_error (error,

                   G_IO_ERROR,

                   G_IO_ERROR_FAILED,

                   _("Exhausted all available authentication mechanisms (tried: %s) (available: %s)"),

                   tried_str->str,

                   available);

      g_string_free (tried_str, TRUE);

      g_free (available);

      goto out;

    }

  /* OK, decided on a mechanism - let's do this thing */

  mech = g_object_new (auth_mech_to_use_gtype,

                       "stream", auth->priv->stream,

                       "credentials", credentials_that_were_sent,

                       NULL);

  debug_print ("CLIENT: Trying mechanism '%s'", _g_dbus_auth_mechanism_get_name (auth_mech_to_use_gtype));

  g_ptr_array_add (attempted_auth_mechs, (gpointer) _g_dbus_auth_mechanism_get_name (auth_mech_to_use_gtype));

  /* the auth mechanism may not be supported

   * (for example, EXTERNAL only works if credentials were exchanged)

   */

  if (!_g_dbus_auth_mechanism_is_supported (mech))

    {

      debug_print ("CLIENT: Mechanism '%s' says it is not supported", _g_dbus_auth_mechanism_get_name (auth_mech_to_use_gtype));

      g_object_unref (mech);

      mech = NULL;

      goto again;

    }

  initial_response_len = 0;

  initial_response = _g_dbus_auth_mechanism_client_initiate (mech,

                                                             conn_flags,

                                                             &initial_response_len);

#if 0

  g_printerr ("using auth mechanism with name '%s' of type '%s' with initial response '%s'\n",

              _g_dbus_auth_mechanism_get_name (auth_mech_to_use_gtype),

              g_type_name (G_TYPE_FROM_INSTANCE (mech)),

              initial_response);

#endif

  if (initial_response != NULL)

    {

      //g_printerr ("initial_response = '%s'\n", initial_response);

      encoded = _g_dbus_hexencode (initial_response, initial_response_len);

      s = g_strdup_printf ("AUTH %s %s\r\n",

                           _g_dbus_auth_mechanism_get_name (auth_mech_to_use_gtype),

                           encoded);

      g_free (initial_response);

      g_free (encoded);

    }

  else

    {

      s = g_strdup_printf ("AUTH %s\r\n", _g_dbus_auth_mechanism_get_name (auth_mech_to_use_gtype));

    }

  debug_print ("CLIENT: writing '%s'", s);

  if (!g_data_output_stream_put_string (dos, s, cancellable, error))

    {

      g_object_unref (mech);

      mech = NULL;

      g_free (s);

      goto out;

    }

  g_free (s);

 out:

  return mech;

}

/* ---------------------------------------------------------------------------------------------------- */

typedef enum

{

  CLIENT_STATE_WAITING_FOR_DATA,

  CLIENT_STATE_WAITING_FOR_OK,

  CLIENT_STATE_WAITING_FOR_REJECT,

  CLIENT_STATE_WAITING_FOR_AGREE_UNIX_FD

} ClientState;

gchar *

_g_dbus_auth_run_client (GDBusAuth     *auth,

                         GDBusAuthObserver     *observer,

                         GDBusConnectionFlags conn_flags,

                         GDBusCapabilityFlags offered_capabilities,

                         GDBusCapabilityFlags *out_negotiated_capabilities,

                         GCancellable  *cancellable,

                         GError       **error)

{

  gchar *s;

  GDataInputStream *dis;

  GDataOutputStream *dos;

  GCredentials *credentials;

  gchar *ret_guid;

  gchar *line;

  gsize line_length;

  gchar **supported_auth_mechs;

  GPtrArray *attempted_auth_mechs;

  GDBusAuthMechanism *mech;

  ClientState state;

  GDBusCapabilityFlags negotiated_capabilities;

  g_return_val_if_fail ((conn_flags & G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT), NULL);

  g_return_val_if_fail (!(conn_flags & G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_SERVER), NULL);

  debug_print ("CLIENT: initiating");

  _g_dbus_auth_add_mechs (auth, observer);

  ret_guid = NULL;

  supported_auth_mechs = NULL;

  attempted_auth_mechs = g_ptr_array_new ();

  mech = NULL;

  negotiated_capabilities = 0;

  credentials = NULL;

  dis = G_DATA_INPUT_STREAM (g_data_input_stream_new (g_io_stream_get_input_stream (auth->priv->stream)));

  dos = G_DATA_OUTPUT_STREAM (g_data_output_stream_new (g_io_stream_get_output_stream (auth->priv->stream)));

  g_filter_input_stream_set_close_base_stream (G_FILTER_INPUT_STREAM (dis), FALSE);

  g_filter_output_stream_set_close_base_stream (G_FILTER_OUTPUT_STREAM (dos), FALSE);

  g_data_input_stream_set_newline_type (dis, G_DATA_STREAM_NEWLINE_TYPE_CR_LF);

#ifdef G_OS_UNIX

  if (G_IS_UNIX_CONNECTION (auth->priv->stream))

    {

      credentials = g_credentials_new ();

      if (!g_unix_connection_send_credentials (G_UNIX_CONNECTION (auth->priv->stream),

                                               cancellable,

                                               error))

        goto out;

    }

  else

    {

      if (!g_data_output_stream_put_byte (dos, '\0', cancellable, error))

        goto out;

    }

#else

  if (!g_data_output_stream_put_byte (dos, '\0', cancellable, error))

    goto out;

#endif

  if (credentials != NULL)

    {

      if (G_UNLIKELY (_g_dbus_debug_authentication ()))

        {

          s = g_credentials_to_string (credentials);

          debug_print ("CLIENT: sent credentials '%s'", s);

          g_free (s);

        }

    }

  else

    {

      debug_print ("CLIENT: didn't send any credentials");

    }

  /* TODO: to reduce roundtrips, try to pick an auth mechanism to start with */

  /* Get list of supported authentication mechanisms */

  s = "AUTH\r\n";

  debug_print ("CLIENT: writing '%s'", s);

  if (!g_data_output_stream_put_string (dos, s, cancellable, error))

    goto out;

  state = CLIENT_STATE_WAITING_FOR_REJECT;

  while (TRUE)

    {

      switch (state)

        {

        case CLIENT_STATE_WAITING_FOR_REJECT:

          debug_print ("CLIENT: WaitingForReject");

          line = _my_g_data_input_stream_read_line (dis, &line_length, cancellable, error);

          if (line == NULL)

            goto out;

          debug_print ("CLIENT: WaitingForReject, read '%s'", line);

        choose_mechanism:

          if (!g_str_has_prefix (line, "REJECTED "))

            {

              g_set_error (error,

                           G_IO_ERROR,

                           G_IO_ERROR_FAILED,

                           "In WaitingForReject: Expected 'REJECTED am1 am2 ... amN', got '%s'",

                           line);

              g_free (line);

              goto out;

            }

          if (supported_auth_mechs == NULL)

            {

              supported_auth_mechs = g_strsplit (line + sizeof ("REJECTED ") - 1, " ", 0);

#if 0

              for (n = 0; supported_auth_mechs != NULL && supported_auth_mechs[n] != NULL; n++)

                g_printerr ("supported_auth_mechs[%d] = '%s'\n", n, supported_auth_mechs[n]);

#endif

            }

          g_free (line);

          mech = client_choose_mech_and_send_initial_response (auth,

                                                               credentials,

                                                               conn_flags,

                                                               (const gchar* const *) supported_auth_mechs,

                                                               attempted_auth_mechs,

                                                               dos,

                                                               cancellable,

                                                               error);

          if (mech == NULL)

            goto out;

          if (_g_dbus_auth_mechanism_client_get_state (mech) == G_DBUS_AUTH_MECHANISM_STATE_WAITING_FOR_DATA)

            state = CLIENT_STATE_WAITING_FOR_DATA;

          else

            state = CLIENT_STATE_WAITING_FOR_OK;

          break;

        case CLIENT_STATE_WAITING_FOR_OK:

          debug_print ("CLIENT: WaitingForOK");

          line = _my_g_data_input_stream_read_line (dis, &line_length, cancellable, error);

          if (line == NULL)

            goto out;

          debug_print ("CLIENT: WaitingForOK, read '%s'", line);

          if (g_str_has_prefix (line, "OK "))

            {

              if (!g_dbus_is_guid (line + 3))

                {

                  g_set_error (error,

                               G_IO_ERROR,

                               G_IO_ERROR_FAILED,

                               "Invalid OK response '%s'",

                               line);

                  g_free (line);

                  goto out;

                }

              ret_guid = g_strdup (line + 3);

              g_free (line);

              if (offered_capabilities & G_DBUS_CAPABILITY_FLAGS_UNIX_FD_PASSING)

                {

                  s = "NEGOTIATE_UNIX_FD\r\n";

                  debug_print ("CLIENT: writing '%s'", s);

                  if (!g_data_output_stream_put_string (dos, s, cancellable, error))

                    goto out;

                  state = CLIENT_STATE_WAITING_FOR_AGREE_UNIX_FD;

                }

              else

                {

                  s = "BEGIN\r\n";

                  debug_print ("CLIENT: writing '%s'", s);

                  if (!g_data_output_stream_put_string (dos, s, cancellable, error))

                    goto out;

                  /* and we're done! */

                  goto out;

                }

            }

          else if (g_str_has_prefix (line, "REJECTED "))

            {

              goto choose_mechanism;

            }

          else

            {

              /* TODO: handle other valid responses */

              g_set_error (error,

                           G_IO_ERROR,

                           G_IO_ERROR_FAILED,

                           "In WaitingForOk: unexpected response '%s'",

                           line);

              g_free (line);

              goto out;

            }

          break;

        case CLIENT_STATE_WAITING_FOR_AGREE_UNIX_FD:

          debug_print ("CLIENT: WaitingForAgreeUnixFD");

          line = _my_g_data_input_stream_read_line (dis, &line_length, cancellable, error);

          if (line == NULL)

            goto out;

          debug_print ("CLIENT: WaitingForAgreeUnixFD, read='%s'", line);

          if (g_strcmp0 (line, "AGREE_UNIX_FD") == 0)

            {

              g_free (line);

              negotiated_capabilities |= G_DBUS_CAPABILITY_FLAGS_UNIX_FD_PASSING;

              s = "BEGIN\r\n";

              debug_print ("CLIENT: writing '%s'", s);

              if (!g_data_output_stream_put_string (dos, s, cancellable, error))

                goto out;

              /* and we're done! */

              goto out;

            }

          else if (g_str_has_prefix (line, "ERROR") && (line[5] == 0 || g_ascii_isspace (line[5])))

            {

              //g_strstrip (line + 5); g_debug ("bah, no unix_fd: '%s'", line + 5);

              g_free (line);

              s = "BEGIN\r\n";

              debug_print ("CLIENT: writing '%s'", s);

              if (!g_data_output_stream_put_string (dos, s, cancellable, error))

                goto out;

              /* and we're done! */

              goto out;

            }

          else

            {

              /* TODO: handle other valid responses */

              g_set_error (error,

                           G_IO_ERROR,

                           G_IO_ERROR_FAILED,

                           "In WaitingForAgreeUnixFd: unexpected response '%s'",

                           line);

              g_free (line);

              goto out;

            }

          break;

        case CLIENT_STATE_WAITING_FOR_DATA:

          debug_print ("CLIENT: WaitingForData");

          line = _my_g_data_input_stream_read_line (dis, &line_length, cancellable, error);

          if (line == NULL)

            goto out;

          debug_print ("CLIENT: WaitingForData, read='%s'", line);

          if (g_str_equal (line, "DATA") || g_str_has_prefix (line, "DATA "))

            {

              gchar *encoded;

              gchar *decoded_data;

              gsize decoded_data_len = 0;

              encoded = g_strdup (line + 4);

              g_free (line);

              g_strstrip (encoded);

              decoded_data = hexdecode (encoded, &decoded_data_len, error);

              g_free (encoded);

              if (decoded_data == NULL)

                {

                  g_prefix_error (error, "DATA response is malformed: ");

                  /* invalid encoding, disconnect! */

                  goto out;

                }

              _g_dbus_auth_mechanism_client_data_receive (mech, decoded_data, decoded_data_len);

              g_free (decoded_data);

              if (_g_dbus_auth_mechanism_client_get_state (mech) == G_DBUS_AUTH_MECHANISM_STATE_HAVE_DATA_TO_SEND)

                {

                  gchar *data;

                  gsize data_len;

                  data = _g_dbus_auth_mechanism_client_data_send (mech, &data_len);

                  if (data_len == 0)

                    {

                      s = g_strdup ("DATA\r\n");

                    }

                  else

                    {

                      gchar *encoded_data = _g_dbus_hexencode (data, data_len);

                      s = g_strdup_printf ("DATA %s\r\n", encoded_data);

                      g_free (encoded_data);

                    }

                  g_free (data);

                  debug_print ("CLIENT: writing '%s'", s);

                  if (!g_data_output_stream_put_string (dos, s, cancellable, error))

                    {

                      g_free (s);

                      goto out;

                    }

                  g_free (s);

                }

              state = CLIENT_STATE_WAITING_FOR_OK;

            }

          else if (g_str_has_prefix (line, "REJECTED "))

            {

              /* could be the chosen authentication method just doesn't work. Try

               * another one...

               */

              goto choose_mechanism;

            }

          else

            {

              g_set_error (error,

                           G_IO_ERROR,

                           G_IO_ERROR_FAILED,

                           "In WaitingForData: unexpected response '%s'",

                           line);

              g_free (line);

              goto out;

            }

          break;

        default:

          g_assert_not_reached ();

          break;

        }

    }; /* main authentication client loop */

 out:

  if (mech != NULL)

    g_object_unref (mech);

  g_ptr_array_unref (attempted_auth_mechs);

  g_strfreev (supported_auth_mechs);

  g_object_unref (dis);

  g_object_unref (dos);

  /* ensure return value is NULL if error is set */

  if (error != NULL && *error != NULL)

    {

      g_free (ret_guid);

      ret_guid = NULL;

    }

  if (ret_guid != NULL)

    {

      if (out_negotiated_capabilities != NULL)

        *out_negotiated_capabilities = negotiated_capabilities;

    }

  if (credentials != NULL)

    g_object_unref (credentials);

  debug_print ("CLIENT: Done, authenticated=%d", ret_guid != NULL);

  return ret_guid;

}