messenger_api.c

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/*
   This file is part of GNUnet.
   Copyright (C) 2020--2021 GNUnet e.V.
 
   GNUnet is free software: you can redistribute it and/or modify it
   under the terms of the GNU Affero General Public License as published
   by the Free Software Foundation, either version 3 of the License,
   or (at your option) any later version.
 
   GNUnet 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
   Affero General Public License for more details.
 
   You should have received a copy of the GNU Affero General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
   SPDX-License-Identifier: AGPL3.0-or-later
 */
#include "platform.h"
#include "gnunet_messenger_service.h"
 
#include "gnunet-service-messenger.h"
 
#include "messenger_api_handle.h"
#include "messenger_api_message.h"
#include "messenger_api_util.h"
 
const char*
GNUNET_MESSENGER_name_of_kind (enum GNUNET_MESSENGER_MessageKind kind)
{
  switch (kind)
  {
  case GNUNET_MESSENGER_KIND_INFO:
    return "INFO";
  case GNUNET_MESSENGER_KIND_JOIN:
    return "JOIN";
  case GNUNET_MESSENGER_KIND_LEAVE:
    return "LEAVE";
  case GNUNET_MESSENGER_KIND_NAME:
    return "NAME";
  case GNUNET_MESSENGER_KIND_KEY:
    return "KEY";
  case GNUNET_MESSENGER_KIND_PEER:
    return "PEER";
  case GNUNET_MESSENGER_KIND_ID:
    return "ID";
  case GNUNET_MESSENGER_KIND_MISS:
    return "MISS";
  case GNUNET_MESSENGER_KIND_MERGE:
    return "MERGE";
  case GNUNET_MESSENGER_KIND_REQUEST:
    return "REQUEST";
  case GNUNET_MESSENGER_KIND_INVITE:
    return "INVITE";
  case GNUNET_MESSENGER_KIND_TEXT:
    return "TEXT";
  case GNUNET_MESSENGER_KIND_FILE:
    return "FILE";
  case GNUNET_MESSENGER_KIND_PRIVATE:
    return "PRIVATE";
  case GNUNET_MESSENGER_KIND_DELETE:
    return "DELETE";
  default:
    return "UNKNOWN";
  }
}
 
static int
check_get_name (void *cls,
                const struct GNUNET_MESSENGER_NameMessage *msg)
{
  GNUNET_MQ_check_zero_termination(msg);
  return GNUNET_OK;
}
 
static void
handle_get_name (void *cls,
                 const struct GNUNET_MESSENGER_NameMessage *msg)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
 
  const char *name = ((const char*) msg) + sizeof(*msg);
 
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Set name of handle: %s\n", name);
 
  set_handle_name (handle, strlen (name) > 0 ? name : NULL);
}
 
static int
check_get_key (void *cls,
               const struct GNUNET_MESSENGER_KeyMessage *msg)
{
  const uint16_t full_length = ntohs (msg->header.size);
 
  if (full_length < sizeof(*msg))
    return GNUNET_NO;
 
  const uint16_t length = full_length - sizeof(*msg);
  const char *buffer = ((const char*) msg) + sizeof(*msg);
 
  struct GNUNET_IDENTITY_PublicKey pubkey;
  size_t read;
  if (GNUNET_SYSERR ==
      GNUNET_IDENTITY_read_public_key_from_buffer(buffer, length,
                                                  &pubkey, &read))
    return GNUNET_NO;
 
  return GNUNET_OK;
}
 
static void
handle_get_key (void *cls,
                const struct GNUNET_MESSENGER_KeyMessage *msg)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
 
  const uint16_t length = ntohs (msg->header.size) - sizeof(*msg);
  const char *buffer = ((const char*) msg) + sizeof(*msg);
 
  struct GNUNET_IDENTITY_PublicKey pubkey;
  size_t read;
  if (GNUNET_SYSERR ==
      GNUNET_IDENTITY_read_public_key_from_buffer(buffer, length,
                                                  &pubkey, &read))
    return;
 
  char* str = GNUNET_IDENTITY_public_key_to_string (&pubkey);
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Set key of handle: %s\n", str);
  GNUNET_free(str);
 
  set_handle_key (handle, &pubkey);
 
  if (handle->identity_callback)
    handle->identity_callback (handle->identity_cls, handle);
}
 
static void
handle_member_id (void *cls,
                  const struct GNUNET_MESSENGER_MemberMessage *msg)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
 
  const struct GNUNET_HashCode *key = &(msg->key);
  const struct GNUNET_ShortHashCode *id = &(msg->id);
 
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Set id of handle in room: %s\n", GNUNET_h2s (key));
 
  struct GNUNET_MESSENGER_Room *room = GNUNET_CONTAINER_multihashmap_get (handle->rooms, key);
 
  if (room)
  {
    if (!room->contact_id)
      room->contact_id = GNUNET_new(struct GNUNET_ShortHashCode);
 
    GNUNET_memcpy(room->contact_id, id, sizeof(*id));
  }
}
 
static void
handle_room_open (void *cls,
                  const struct GNUNET_MESSENGER_RoomMessage *msg)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
 
  const struct GNUNET_HashCode *key = &(msg->key);
 
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Opened room: %s\n", GNUNET_h2s (key));
 
  open_handle_room (handle, key);
}
 
static void
handle_room_entry (void *cls,
                   const struct GNUNET_MESSENGER_RoomMessage *msg)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
 
  const struct GNUNET_PeerIdentity *door = &(msg->door);
  const struct GNUNET_HashCode *key = &(msg->key);
 
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Entered room: %s\n", GNUNET_h2s (key));
 
  entry_handle_room_at (handle, door, key);
}
 
static void
handle_room_close (void *cls,
                   const struct GNUNET_MESSENGER_RoomMessage *msg)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
 
  const struct GNUNET_HashCode *key = &(msg->key);
 
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Closed room: %s\n", GNUNET_h2s (key));
 
  close_handle_room (handle, key);
}
 
static int
check_recv_message (void *cls,
                    const struct GNUNET_MESSENGER_RecvMessage *msg)
{
  const uint16_t full_length = ntohs (msg->header.size);
 
  if (full_length < sizeof(*msg))
    return GNUNET_NO;
 
  const uint16_t length = full_length - sizeof(*msg);
  const char *buffer = ((const char*) msg) + sizeof(*msg);
 
  struct GNUNET_MESSENGER_Message message;
 
  if (length < get_message_kind_size(GNUNET_MESSENGER_KIND_UNKNOWN, GNUNET_YES))
    return GNUNET_NO;
 
  if (GNUNET_YES != decode_message (&message, length, buffer, GNUNET_YES, NULL))
    return GNUNET_NO;
 
  cleanup_message(&message);
  return GNUNET_OK;
}
 
static void
handle_recv_message (void *cls,
                     const struct GNUNET_MESSENGER_RecvMessage *msg)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
 
  const struct GNUNET_HashCode *key = &(msg->key);
  const struct GNUNET_HashCode *sender = &(msg->sender);
  const struct GNUNET_HashCode *context = &(msg->context);
  const struct GNUNET_HashCode *hash = &(msg->hash);
  const enum GNUNET_MESSENGER_MessageFlags flags = (
      (enum GNUNET_MESSENGER_MessageFlags) (msg->flags)
  );
 
  const uint16_t length = ntohs (msg->header.size) - sizeof(*msg);
  const char *buffer = ((const char*) msg) + sizeof(*msg);
 
  struct GNUNET_MESSENGER_Message message;
  decode_message (&message, length, buffer, GNUNET_YES, NULL);
 
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Receiving message: %s\n", GNUNET_MESSENGER_name_of_kind (message.header.kind));
 
  struct GNUNET_MESSENGER_Room *room = GNUNET_CONTAINER_multihashmap_get (handle->rooms, key);
 
  if (room)
  {
    struct GNUNET_MESSENGER_ContactStore *store = get_handle_contact_store(handle);
 
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Raw contact from sender and context: (%s : %s)\n",
               GNUNET_h2s(sender), GNUNET_h2s_full(context));
 
    struct GNUNET_MESSENGER_Contact *contact = get_store_contact_raw(
        store, context, sender
    );
 
    contact = handle_room_message (room, contact, &message, hash);
 
    const struct GNUNET_MESSENGER_Message *stored_message = get_room_message(room, hash);
 
    if (handle->msg_callback)
      handle->msg_callback (handle->msg_cls, room, contact, stored_message, hash, flags);
  }
  else
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Unknown room for this client: %s\n", GNUNET_h2s (key));
 
  cleanup_message(&message);
}
 
static void
reconnect (struct GNUNET_MESSENGER_Handle *handle);
 
static void
send_open_room (struct GNUNET_MESSENGER_Handle *handle,
                struct GNUNET_MESSENGER_Room *room)
{
  struct GNUNET_MESSENGER_RoomMessage *msg;
  struct GNUNET_MQ_Envelope *env;
 
  env = GNUNET_MQ_msg(msg, GNUNET_MESSAGE_TYPE_MESSENGER_ROOM_OPEN);
  GNUNET_memcpy(&(msg->key), &(room->key), sizeof(msg->key));
  GNUNET_MQ_send (handle->mq, env);
}
 
static void
send_enter_room (struct GNUNET_MESSENGER_Handle *handle,
                 struct GNUNET_MESSENGER_Room *room,
                 const struct GNUNET_PeerIdentity *door)
{
  struct GNUNET_MESSENGER_RoomMessage *msg;
  struct GNUNET_MQ_Envelope *env;
 
  env = GNUNET_MQ_msg(msg, GNUNET_MESSAGE_TYPE_MESSENGER_ROOM_ENTRY);
  GNUNET_memcpy(&(msg->door), door, sizeof(*door));
  GNUNET_memcpy(&(msg->key), &(room->key), sizeof(msg->key));
  GNUNET_MQ_send (handle->mq, env);
}
 
static void
send_close_room (struct GNUNET_MESSENGER_Handle *handle,
                 struct GNUNET_MESSENGER_Room *room)
{
  struct GNUNET_MESSENGER_RoomMessage *msg;
  struct GNUNET_MQ_Envelope *env;
 
  env = GNUNET_MQ_msg(msg, GNUNET_MESSAGE_TYPE_MESSENGER_ROOM_CLOSE);
  GNUNET_memcpy(&(msg->key), &(room->key), sizeof(msg->key));
  GNUNET_MQ_send (handle->mq, env);
}
 
static int
iterate_reset_room (void *cls,
                    const struct GNUNET_HashCode *key,
                    void *value)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
  struct GNUNET_MESSENGER_Room *room = value;
 
  if (GNUNET_YES == room->opened)
    send_open_room (handle, room);
 
  struct GNUNET_MESSENGER_ListTunnel *entry = room->entries.head;
 
  struct GNUNET_PeerIdentity door;
 
  while (entry)
  {
    GNUNET_PEER_resolve (entry->peer, &door);
 
    send_enter_room (handle, room, &door);
 
    entry = entry->next;
  }
 
  return GNUNET_YES;
}
 
static void
callback_reconnect (void *cls)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
 
  handle->reconnect_task = NULL;
  handle->reconnect_time = GNUNET_TIME_STD_BACKOFF(handle->reconnect_time)
  ;
 
  reconnect (handle);
 
  GNUNET_CONTAINER_multihashmap_iterate (handle->rooms, iterate_reset_room, handle);
}
 
static int
iterate_close_room (void *cls,
                    const struct GNUNET_HashCode *key,
                    void *value)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
  struct GNUNET_MESSENGER_Room *room = value;
 
  send_close_room (handle, room);
 
  return GNUNET_YES;
}
 
static void
callback_mq_error (void *cls,
                   enum GNUNET_MQ_Error error)
{
  struct GNUNET_MESSENGER_Handle *handle = cls;
 
  GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "MQ_Error: %u\n", error);
 
  GNUNET_CONTAINER_multihashmap_iterate (handle->rooms, iterate_close_room, handle);
 
  if (handle->mq)
  {
    GNUNET_MQ_destroy (handle->mq);
    handle->mq = NULL;
  }
 
  handle->reconnect_task = GNUNET_SCHEDULER_add_delayed (handle->reconnect_time, &callback_reconnect, handle);
}
 
static void
reconnect (struct GNUNET_MESSENGER_Handle *handle)
{
  const struct GNUNET_MQ_MessageHandler handlers[] =
  {
   GNUNET_MQ_hd_var_size(
        get_name, GNUNET_MESSAGE_TYPE_MESSENGER_CONNECTION_GET_NAME,
        struct GNUNET_MESSENGER_NameMessage, handle
   ),
   GNUNET_MQ_hd_var_size(
       get_key, GNUNET_MESSAGE_TYPE_MESSENGER_CONNECTION_GET_KEY,
       struct GNUNET_MESSENGER_KeyMessage, handle
   ),
   GNUNET_MQ_hd_fixed_size(
       member_id,
       GNUNET_MESSAGE_TYPE_MESSENGER_CONNECTION_MEMBER_ID,
       struct GNUNET_MESSENGER_MemberMessage, handle
   ),
   GNUNET_MQ_hd_fixed_size(
       room_open,
       GNUNET_MESSAGE_TYPE_MESSENGER_ROOM_OPEN,
       struct GNUNET_MESSENGER_RoomMessage, handle
   ),
   GNUNET_MQ_hd_fixed_size(
       room_entry,
       GNUNET_MESSAGE_TYPE_MESSENGER_ROOM_ENTRY,
       struct GNUNET_MESSENGER_RoomMessage, handle
   ),
   GNUNET_MQ_hd_fixed_size(
       room_close,
       GNUNET_MESSAGE_TYPE_MESSENGER_ROOM_CLOSE,
       struct GNUNET_MESSENGER_RoomMessage, handle
   ),
   GNUNET_MQ_hd_var_size(
       recv_message,
       GNUNET_MESSAGE_TYPE_MESSENGER_ROOM_RECV_MESSAGE,
       struct GNUNET_MESSENGER_RecvMessage, handle
   ),
   GNUNET_MQ_handler_end()
  };
 
  handle->mq = GNUNET_CLIENT_connect (handle->cfg, GNUNET_MESSENGER_SERVICE_NAME, handlers, &callback_mq_error, handle);
}
 
struct GNUNET_MESSENGER_Handle*
GNUNET_MESSENGER_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
                          const char *name,
                          GNUNET_MESSENGER_IdentityCallback identity_callback,
                          void *identity_cls,
                          GNUNET_MESSENGER_MessageCallback msg_callback,
                          void *msg_cls)
{
  struct GNUNET_MESSENGER_Handle *handle = create_handle (cfg, identity_callback, identity_cls, msg_callback, msg_cls);
 
  reconnect (handle);
 
  if (handle->mq)
  {
    const uint16_t name_len = name ? strlen (name) : 0;
 
    struct GNUNET_MESSENGER_CreateMessage *msg;
    struct GNUNET_MQ_Envelope *env;
 
    env = GNUNET_MQ_msg_extra(msg, name_len + 1, GNUNET_MESSAGE_TYPE_MESSENGER_CONNECTION_CREATE);
 
    char *extra = ((char*) msg) + sizeof(*msg);
 
    if (name_len)
      GNUNET_memcpy(extra, name, name_len);
 
    extra[name_len] = '\0';
 
    GNUNET_MQ_send (handle->mq, env);
    return handle;
  }
  else
  {
    destroy_handle (handle);
    return NULL;
  }
}
 
int
GNUNET_MESSENGER_update (struct GNUNET_MESSENGER_Handle *handle)
{
  if ((!handle) || (!get_handle_name (handle)))
    return GNUNET_SYSERR;
 
  struct GNUNET_MESSENGER_UpdateMessage *msg;
  struct GNUNET_MQ_Envelope *env;
 
  env = GNUNET_MQ_msg(msg, GNUNET_MESSAGE_TYPE_MESSENGER_CONNECTION_UPDATE);
  GNUNET_MQ_send (handle->mq, env);
  return GNUNET_OK;
}
 
void
GNUNET_MESSENGER_disconnect (struct GNUNET_MESSENGER_Handle *handle)
{
  if (!handle)
    return;
 
  struct GNUNET_MESSENGER_DestroyMessage *msg;
  struct GNUNET_MQ_Envelope *env;
 
  env = GNUNET_MQ_msg(msg, GNUNET_MESSAGE_TYPE_MESSENGER_CONNECTION_DESTROY);
  GNUNET_MQ_send (handle->mq, env);
 
  destroy_handle (handle);
}
 
const char*
GNUNET_MESSENGER_get_name (const struct GNUNET_MESSENGER_Handle *handle)
{
  if (!handle)
    return NULL;
 
  return get_handle_name (handle);
}
 
int
GNUNET_MESSENGER_set_name (struct GNUNET_MESSENGER_Handle *handle,
                           const char *name)
{
  if (!handle)
    return GNUNET_SYSERR;
 
  const uint16_t name_len = name ? strlen (name) : 0;
 
  struct GNUNET_MESSENGER_NameMessage *msg;
  struct GNUNET_MQ_Envelope *env;
 
  env = GNUNET_MQ_msg_extra(msg, name_len + 1, GNUNET_MESSAGE_TYPE_MESSENGER_CONNECTION_SET_NAME);
 
  char *extra = ((char*) msg) + sizeof(*msg);
 
  if (name_len)
    GNUNET_memcpy(extra, name, name_len);
 
  extra[name_len] = '\0';
 
  GNUNET_MQ_send (handle->mq, env);
  return GNUNET_YES;
}
 
static const struct GNUNET_IDENTITY_PublicKey*
get_non_anonymous_key (const struct GNUNET_IDENTITY_PublicKey* public_key)
{
  if (0 == GNUNET_memcmp(public_key, get_anonymous_public_key()))
    return NULL;
 
  return public_key;
}
 
const struct GNUNET_IDENTITY_PublicKey*
GNUNET_MESSENGER_get_key (const struct GNUNET_MESSENGER_Handle *handle)
{
  if (!handle)
    return NULL;
 
  return get_non_anonymous_key (get_handle_key (handle));
}
 
struct GNUNET_MESSENGER_Room*
GNUNET_MESSENGER_open_room (struct GNUNET_MESSENGER_Handle *handle,
                            const struct GNUNET_HashCode *key)
{
  if ((!handle) || (!key))
    return NULL;
 
  struct GNUNET_MESSENGER_Room *room = GNUNET_CONTAINER_multihashmap_get (handle->rooms, key);
 
  if (!room)
  {
    room = create_room (handle, key);
 
    if (GNUNET_OK != GNUNET_CONTAINER_multihashmap_put (handle->rooms, key, room,
                                                        GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST))
    {
      destroy_room (room);
      return NULL;
    }
  }
 
  send_open_room (handle, room);
  return room;
}
 
struct GNUNET_MESSENGER_Room*
GNUNET_MESSENGER_enter_room (struct GNUNET_MESSENGER_Handle *handle,
                             const struct GNUNET_PeerIdentity *door,
                             const struct GNUNET_HashCode *key)
{
  if ((!handle) || (!door) || (!key))
    return NULL;
 
  struct GNUNET_MESSENGER_Room *room = GNUNET_CONTAINER_multihashmap_get (handle->rooms, key);
 
  if (!room)
  {
    room = create_room (handle, key);
 
    if (GNUNET_OK != GNUNET_CONTAINER_multihashmap_put (handle->rooms, key, room,
                                                        GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST))
    {
      destroy_room (room);
      return NULL;
    }
  }
 
  send_enter_room (handle, room, door);
  return room;
}
 
void
GNUNET_MESSENGER_close_room (struct GNUNET_MESSENGER_Room *room)
{
  if (!room)
    return;
 
  send_close_room (room->handle, room);
}
 
struct GNUNET_MESSENGER_RoomFind
{
  const struct GNUNET_MESSENGER_Contact *contact;
  GNUNET_MESSENGER_MemberCallback callback;
  size_t counter;
  void *cls;
};
 
static int
iterate_find_room (void* cls,
                   const struct GNUNET_HashCode *key,
                   void *value)
{
  struct GNUNET_MESSENGER_RoomFind *find = cls;
  struct GNUNET_MESSENGER_Room *room = value;
 
  if ((find->counter > 0) && ((!find->contact) || (GNUNET_YES == find_room_member(room, find->contact))))
  {
    find->counter--;
 
    if (!find->callback)
      return GNUNET_YES;
 
    return find->callback(find->cls, room, find->contact);
  }
  else
    return GNUNET_NO;
}
 
int
GNUNET_MESSENGER_find_rooms (const struct GNUNET_MESSENGER_Handle *handle,
                             const struct GNUNET_MESSENGER_Contact *contact,
                             GNUNET_MESSENGER_MemberCallback callback,
                             void *cls)
{
  if (!handle)
    return GNUNET_SYSERR;
 
  struct GNUNET_MESSENGER_RoomFind find;
 
  find.contact = contact;
  find.callback = callback;
  find.counter = (contact? contact->rc : SIZE_MAX);
  find.cls = cls;
 
  return GNUNET_CONTAINER_multihashmap_iterate(handle->rooms, iterate_find_room, &find);
}
 
const struct GNUNET_HashCode*
GNUNET_MESSENGER_room_get_key (const struct GNUNET_MESSENGER_Room *room)
{
  if (!room)
    return NULL;
 
  return &(room->key);
}
 
const struct GNUNET_MESSENGER_Contact*
GNUNET_MESSENGER_get_sender (const struct GNUNET_MESSENGER_Room *room,
                             const struct GNUNET_HashCode *hash)
{
  if ((!room) || (!hash))
    return NULL;
 
  return get_room_sender(room, hash);
}
 
const char*
GNUNET_MESSENGER_contact_get_name (const struct GNUNET_MESSENGER_Contact *contact)
{
  if (!contact)
    return NULL;
 
  return get_contact_name (contact);
}
 
const struct GNUNET_IDENTITY_PublicKey*
GNUNET_MESSENGER_contact_get_key (const struct GNUNET_MESSENGER_Contact *contact)
{
  if (!contact)
    return NULL;
 
  return get_non_anonymous_key (get_contact_key (contact));
}
 
void
GNUNET_MESSENGER_send_message (struct GNUNET_MESSENGER_Room *room,
                               const struct GNUNET_MESSENGER_Message *message,
                               const struct GNUNET_MESSENGER_Contact *contact)
{
  if ((!room) || (!message))
    return;
 
  switch (filter_message_sending (message))
  {
  case GNUNET_SYSERR:
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "Sending message aborted: This kind of message is reserved for the service!\n");
    return;
  case GNUNET_NO:
    GNUNET_log(GNUNET_ERROR_TYPE_WARNING, "Sending message aborted: This kind of message could cause issues!\n");
    return;
  default:
    break;
  }
 
  ssize_t key_length = 0;
 
  if (contact)
  {
    const struct GNUNET_IDENTITY_PublicKey *public_key = get_non_anonymous_key (
        get_contact_key(contact)
    );
 
    if (public_key)
      key_length = GNUNET_IDENTITY_public_key_get_length(public_key);
    else
      key_length = -1;
  }
 
  if (key_length < 0)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_WARNING, "Sending message aborted: Invalid key!\n");
    return;
  }
 
  const uint16_t msg_length = get_message_size (message, GNUNET_NO);
 
  struct GNUNET_MESSENGER_SendMessage *msg;
  struct GNUNET_MQ_Envelope *env;
 
  const uint16_t length = (uint16_t) key_length + msg_length;
 
  env = GNUNET_MQ_msg_extra(
      msg, length,
      GNUNET_MESSAGE_TYPE_MESSENGER_ROOM_SEND_MESSAGE
  );
 
  GNUNET_memcpy(&(msg->key), &(room->key), sizeof(msg->key));
 
  msg->flags = (uint32_t) (
      contact? GNUNET_MESSENGER_FLAG_PRIVATE : GNUNET_MESSENGER_FLAG_NONE
  );
 
  char *buffer = ((char*) msg) + sizeof(*msg);
  char *msg_buffer = buffer + key_length;
 
  if (key_length > 0)
    GNUNET_IDENTITY_write_public_key_to_buffer(get_contact_key(contact), buffer, key_length);
 
  encode_message (message, msg_length, msg_buffer, GNUNET_NO);
 
  GNUNET_MQ_send (room->handle->mq, env);
}
 
const struct GNUNET_MESSENGER_Message*
GNUNET_MESSENGER_get_message (const struct GNUNET_MESSENGER_Room *room,
                              const struct GNUNET_HashCode *hash)
{
  if ((!room) || (!hash))
    return NULL;
 
  const struct GNUNET_MESSENGER_Message *message = get_room_message (room, hash);
 
  if (!message)
  {
    struct GNUNET_MESSENGER_GetMessage *msg;
    struct GNUNET_MQ_Envelope *env;
 
    env = GNUNET_MQ_msg(msg, GNUNET_MESSAGE_TYPE_MESSENGER_ROOM_GET_MESSAGE);
    GNUNET_memcpy(&(msg->key), &(room->key), sizeof(msg->key));
    GNUNET_memcpy(&(msg->hash), hash, sizeof(*hash));
    GNUNET_MQ_send (room->handle->mq, env);
  }
 
  return message;
}
 
int
GNUNET_MESSENGER_iterate_members (struct GNUNET_MESSENGER_Room *room,
                                  GNUNET_MESSENGER_MemberCallback callback,
                                  void *cls)
{
  if (!room)
    return GNUNET_SYSERR;
 
  return iterate_room_members(room, callback, cls);
}