path: root/liblightdm-gobject/greeter.c

/*
 * Copyright (C) 2010 Robert Ancell.
 * Author: Robert Ancell <robert.ancell@canonical.com>
 *
 * 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 3 of the License, or (at your option) any
 * later version. See http://www.gnu.org/copyleft/lgpl.html the full text of the
 * license.
 */

#include <config.h>

#include <stdlib.h>
#include <string.h>
#include <security/pam_appl.h>

#include "lightdm/greeter.h"

enum {
    PROP_0,
    PROP_DEFAULT_SESSION_HINT,
    PROP_HIDE_USERS_HINT,
    PROP_SHOW_MANUAL_LOGIN_HINT,
    PROP_LOCK_HINT,
    PROP_HAS_GUEST_ACCOUNT_HINT,
    PROP_SELECT_USER_HINT,
    PROP_SELECT_GUEST_HINT,
    PROP_AUTOLOGIN_USER_HINT,
    PROP_AUTOLOGIN_GUEST_HINT,
    PROP_AUTOLOGIN_TIMEOUT_HINT,
    PROP_AUTHENTICATION_USER,
    PROP_IN_AUTHENTICATION,
    PROP_IS_AUTHENTICATED,
};

enum {
    SHOW_PROMPT,
    SHOW_MESSAGE,
    AUTHENTICATION_COMPLETE,
    AUTOLOGIN_TIMER_EXPIRED,
    LAST_SIGNAL
};
static guint signals[LAST_SIGNAL] = { 0 };

typedef struct
{
    gboolean connected;

    GIOChannel *to_server_channel, *from_server_channel;
    guint8 *read_buffer;
    gsize n_read;

    GHashTable *hints;
    guint autologin_timeout;

    gchar *authentication_user;
    gboolean in_authentication;
    gboolean is_authenticated;
    guint32 authenticate_sequence_number;
    gboolean cancelling_authentication;
} LightDMGreeterPrivate;

G_DEFINE_TYPE (LightDMGreeter, lightdm_greeter, G_TYPE_OBJECT);

#define GET_PRIVATE(obj) G_TYPE_INSTANCE_GET_PRIVATE ((obj), LIGHTDM_TYPE_GREETER, LightDMGreeterPrivate)

#define HEADER_SIZE 8
#define MAX_MESSAGE_LENGTH 1024

/* Messages from the greeter to the server */
typedef enum
{
    GREETER_MESSAGE_CONNECT = 0,
    GREETER_MESSAGE_AUTHENTICATE,
    GREETER_MESSAGE_AUTHENTICATE_AS_GUEST,
    GREETER_MESSAGE_CONTINUE_AUTHENTICATION,
    GREETER_MESSAGE_START_SESSION,
    GREETER_MESSAGE_CANCEL_AUTHENTICATION,
    GREETER_MESSAGE_SET_LANGUAGE
} GreeterMessage;

/* Messages from the server to the greeter */
typedef enum
{
    SERVER_MESSAGE_CONNECTED = 0,
    SERVER_MESSAGE_PROMPT_AUTHENTICATION,
    SERVER_MESSAGE_END_AUTHENTICATION,
    SERVER_MESSAGE_SESSION_RESULT
} ServerMessage;

/**
 * lightdm_greeter_new:
 *
 * Create a new greeter.
 *
 * Return value: the new #LightDMGreeter
 **/
LightDMGreeter *
lightdm_greeter_new ()
{
    return g_object_new (LIGHTDM_TYPE_GREETER, NULL);
}

static gboolean
timed_login_cb (gpointer data)
{
    LightDMGreeter *greeter = data;
    LightDMGreeterPrivate *priv = GET_PRIVATE (greeter);

    priv->autologin_timeout = 0;
    g_signal_emit (G_OBJECT (greeter), signals[AUTOLOGIN_TIMER_EXPIRED], 0);

    return FALSE;
}

static guint32
int_length ()
{
    return 4;
}

static void
write_int (guint8 *buffer, gint buffer_length, guint32 value, gsize *offset)
{
    if (*offset + 4 >= buffer_length)
        return;
    buffer[*offset] = value >> 24;
    buffer[*offset+1] = (value >> 16) & 0xFF;
    buffer[*offset+2] = (value >> 8) & 0xFF;
    buffer[*offset+3] = value & 0xFF;
    *offset += 4;
}

static void
write_string (guint8 *buffer, gint buffer_length, const gchar *value, gsize *offset)
{
    gint length = 0;

    if (value)
        length = strlen (value);
    write_int (buffer, buffer_length, length, offset);
    if (*offset + length >= buffer_length)
        return;
    memcpy (buffer + *offset, value, length);
    *offset += length;
}

static guint32
read_int (guint8 *message, gsize message_length, gsize *offset)
{
    guint32 value;
    guint8 *buffer;

    if (message_length - *offset < int_length ())
    {
        g_warning ("Not enough space for int, need %i, got %zi", int_length (), message_length - *offset);
        return 0;
    }

    buffer = message + *offset;
    value = buffer[0] << 24 | buffer[1] << 16 | buffer[2] << 8 | buffer[3];
    *offset += int_length ();

    return value;
}

static gchar *
read_string (guint8 *message, gsize message_length, gsize *offset)
{
    guint32 length;
    gchar *value;

    length = read_int (message, message_length, offset);
    if (message_length - *offset < length)
    {
        g_warning ("Not enough space for string, need %u, got %zu", length, message_length - *offset);
        return g_strdup ("");
    }

    value = g_malloc (sizeof (gchar) * (length + 1));
    memcpy (value, message + *offset, length);
    value[length] = '\0';
    *offset += length;

    return value;
}

static guint32
string_length (const gchar *value)
{
    if (value)
        return int_length () + strlen (value);
    else
        return int_length ();
}

static void
write_header (guint8 *buffer, gint buffer_length, guint32 id, guint32 length, gsize *offset)
{
    write_int (buffer, buffer_length, id, offset);
    write_int (buffer, buffer_length, length, offset);
}

static guint32
get_message_length (guint8 *message, gsize message_length)
{
    gsize offset = 4;
    return read_int (message, message_length, &offset);
}

static void
write_message (LightDMGreeter *greeter, guint8 *message, gsize message_length)
{
    LightDMGreeterPrivate *priv = GET_PRIVATE (greeter);
    GIOStatus status;
    GError *error = NULL;
    guint32 stated_length;

    /* Double check that we're sending well-formed messages.  If we say we're
       sending more than we do, we end up DOS'ing lightdm as it waits for the
       rest.  If we say we're sending less than we do, we confuse the heck out
       of lightdm, as it starts reading headers from the middle of our
       messages. */
    stated_length = HEADER_SIZE + get_message_length (message, message_length);
    if (stated_length != message_length)
    {
        g_warning ("Refusing to write malformed packet to daemon: declared size is %u, but actual size is %zu", stated_length, message_length);
        return;
    }

    status = g_io_channel_write_chars (priv->to_server_channel, (gchar *) message, message_length, NULL, &error);
    if (error)
        g_warning ("Error writing to daemon: %s", error->message);
    g_clear_error (&error);
    if (status == G_IO_STATUS_NORMAL)
        g_debug ("Wrote %zi bytes to daemon", message_length);
    g_io_channel_flush (priv->to_server_channel, NULL);
}

static void
handle_connected (LightDMGreeter *greeter, guint8 *message, gsize message_length, gsize *offset)
{
    LightDMGreeterPrivate *priv = GET_PRIVATE (greeter);
    gchar *version;
    GString *hint_string;
    int timeout;

    version = read_string (message, message_length, offset);
    hint_string = g_string_new ("");
    while (*offset < message_length)
    {
        gchar *name, *value;
      
        name = read_string (message, message_length, offset);
        value = read_string (message, message_length, offset);
        g_hash_table_insert (priv->hints, name, value);
        g_string_append_printf (hint_string, " %s=%s", name, value);
    }

    g_debug ("Connected version=%s%s", version, hint_string->str);
    g_free (version);
    g_string_free (hint_string, TRUE);

    /* Set timeout for default login */
    timeout = lightdm_greeter_get_autologin_timeout_hint (greeter);
    if (timeout)
    {
        g_debug ("Setting autologin timer for %d seconds", timeout);
        priv->autologin_timeout = g_timeout_add (timeout * 1000, timed_login_cb, greeter);
    }
}

static void
handle_prompt_authentication (LightDMGreeter *greeter, guint8 *message, gsize message_length, gsize *offset)
{
    LightDMGreeterPrivate *priv = GET_PRIVATE (greeter);
    guint32 sequence_number, n_messages, i;
    gchar *username;

    sequence_number = read_int (message, message_length, offset);
    if (sequence_number != priv->authenticate_sequence_number)
    {
        g_debug ("Ignoring prompt authentication with invalid sequence number %d", sequence_number);
        return;
    }

    if (priv->cancelling_authentication)
    {
        g_debug ("Ignoring prompt authentication as waiting for it to cancel");
        return;
    }

    /* Update username */
    username = read_string (message, message_length, offset);
    if (strcmp (username, "") == 0)
    {
        g_free (username);
        username = NULL;
    }
    g_free (priv->authentication_user);
    priv->authentication_user = username;

    n_messages = read_int (message, message_length, offset);
    g_debug ("Prompt user with %d message(s)", n_messages);

    for (i = 0; i < n_messages; i++)
    {
        int style;
        gchar *text;

        style = read_int (message, message_length, offset);
        text = read_string (message, message_length, offset);

        // FIXME: Should stop on prompts?
        switch (style)
        {
        case PAM_PROMPT_ECHO_OFF:
            g_signal_emit (G_OBJECT (greeter), signals[SHOW_PROMPT], 0, text, LIGHTDM_PROMPT_TYPE_SECRET);
            break;
        case PAM_PROMPT_ECHO_ON:
            g_signal_emit (G_OBJECT (greeter), signals[SHOW_PROMPT], 0, text, LIGHTDM_PROMPT_TYPE_QUESTION);
            break;
        case PAM_ERROR_MSG:
            g_signal_emit (G_OBJECT (greeter), signals[SHOW_MESSAGE], 0, text, LIGHTDM_MESSAGE_TYPE_ERROR);
            break;
        case PAM_TEXT_INFO:
            g_signal_emit (G_OBJECT (greeter), signals[SHOW_MESSAGE], 0, text, LIGHTDM_MESSAGE_TYPE_INFO);
            break;
        }

        g_free (text);
    }
}

static void
handle_end_authentication (LightDMGreeter *greeter, guint8 *message, gsize message_length, gsize *offset)
{
    LightDMGreeterPrivate *priv = GET_PRIVATE (greeter);
    guint32 sequence_number, return_code;
    gchar *username;

    sequence_number = read_int (message, message_length, offset);

    if (sequence_number != priv->authenticate_sequence_number)
    {
        g_debug ("Ignoring end authentication with invalid sequence number %d", sequence_number);
        return;
    }

    username = read_string (message, message_length, offset);
    return_code = read_int (message, message_length, offset);

    g_debug ("Authentication complete for user %s with return code %d", username, return_code);

    /* Update username */
    if (strcmp (username, "") == 0)
    {
        g_free (username);
        username = NULL;
    }
    g_free (priv->authentication_user);
    priv->authentication_user = username;

    priv->cancelling_authentication = FALSE;
    priv->is_authenticated = (return_code == 0);

    priv->in_authentication = FALSE;
    g_signal_emit (G_OBJECT (greeter), signals[AUTHENTICATION_COMPLETE], 0);
}

static guint8 *
read_message (LightDMGreeter *greeter, gsize *length, gboolean block)
{
    LightDMGreeterPrivate *priv = GET_PRIVATE (greeter);
    gsize n_to_read, n_read;
    guint8 *buffer;
    GError *error = NULL;

    /* Read the header, or the whole message if we already have that */
    n_to_read = HEADER_SIZE;
    if (priv->n_read >= HEADER_SIZE)
        n_to_read += get_message_length (priv->read_buffer, priv->n_read);

    do
    {
        GIOStatus status;
        status = g_io_channel_read_chars (priv->from_server_channel,
                                          (gchar *) priv->read_buffer + priv->n_read,
                                          n_to_read - priv->n_read,
                                          &n_read,
                                          &error);
        if (error)
            g_warning ("Error reading from server: %s", error->message);
        g_clear_error (&error);
        if (status != G_IO_STATUS_NORMAL)
            break;

        g_debug ("Read %zi bytes from daemon", n_read);

        priv->n_read += n_read;
    } while (priv->n_read < n_to_read && block);

    /* Stop if haven't got all the data we want */
    if (priv->n_read != n_to_read)
        return FALSE;

    /* If have header, rerun for content */
    if (priv->n_read == HEADER_SIZE)
    {
        n_to_read = get_message_length (priv->read_buffer, priv->n_read);
        if (n_to_read > 0)
        {
            priv->read_buffer = g_realloc (priv->read_buffer, HEADER_SIZE + n_to_read);
            return read_message (greeter, length, block);
        }
    }

    buffer = priv->read_buffer;
    *length = priv->n_read;

    priv->read_buffer = g_malloc (priv->n_read);
    priv->n_read = 0;

    return buffer;
}

static gboolean
from_server_cb (GIOChannel *source, GIOCondition condition, gpointer data)
{
    LightDMGreeter *greeter = data;
    guint8 *message;
    gsize message_length, offset;
    guint32 id;

    message = read_message (greeter, &message_length, FALSE);
    if (!message)
        return TRUE;

    offset = 0;
    id = read_int (message, message_length, &offset);
    read_int (message, message_length, &offset);
    switch (id)
    {
    case SERVER_MESSAGE_PROMPT_AUTHENTICATION:
        handle_prompt_authentication (greeter, message, message_length, &offset);
        break;
    case SERVER_MESSAGE_END_AUTHENTICATION:
        handle_end_authentication (greeter, message, message_length, &offset);
        break;
    default:
        g_warning ("Unknown message from server: %d", id);
        break;
    }
    g_free (message);

    return TRUE;
}

/**
 * lightdm_greeter_connect_sync:
 * @greeter: The greeter to connect
 * @error: return location for a #GError, or %NULL
 *
 * Connects the greeter to the display manager.  Will block until connected.
 *
 * Return value: #TRUE if successfully connected
 **/
gboolean
lightdm_greeter_connect_sync (LightDMGreeter *greeter, GError **error)
{
    LightDMGreeterPrivate *priv;
    const gchar *fd;
    guint8 message[MAX_MESSAGE_LENGTH];
    guint8 *response;
    gsize response_length, offset = 0;
    guint32 id;

    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);

    priv = GET_PRIVATE (greeter);

    fd = g_getenv ("LIGHTDM_TO_SERVER_FD");
    if (!fd)
    {
        g_warning ("No LIGHTDM_TO_SERVER_FD environment variable");
        return FALSE;
    }
    priv->to_server_channel = g_io_channel_unix_new (atoi (fd));
    g_io_channel_set_encoding (priv->to_server_channel, NULL, NULL);

    fd = g_getenv ("LIGHTDM_FROM_SERVER_FD");
    if (!fd)
    {
        g_warning ("No LIGHTDM_FROM_SERVER_FD environment variable");
        return FALSE;
    }
    priv->from_server_channel = g_io_channel_unix_new (atoi (fd));
    g_io_channel_set_encoding (priv->from_server_channel, NULL, NULL);
    g_io_add_watch (priv->from_server_channel, G_IO_IN, from_server_cb, greeter);

    g_debug ("Connecting to display manager...");
    write_header (message, MAX_MESSAGE_LENGTH, GREETER_MESSAGE_CONNECT, string_length (VERSION), &offset);
    write_string (message, MAX_MESSAGE_LENGTH, VERSION, &offset);
    write_message (greeter, message, offset);

    response = read_message (greeter, &response_length, TRUE);
    if (!response)
        return FALSE;

    offset = 0;
    id = read_int (response, response_length, &offset);
    read_int (response, response_length, &offset);
    if (id == SERVER_MESSAGE_CONNECTED)
        handle_connected (greeter, response, response_length, &offset);
    g_free (response);
    if (id != SERVER_MESSAGE_CONNECTED)
    {
        g_warning ("Expected CONNECTED message, got %d", id);
        return FALSE;
    }

    priv->connected = TRUE;

    return TRUE;
}

/**
 * lightdm_greeter_get_hint:
 * @greeter: A #LightDMGreeter
 * @name: The hint name to query.
 *
 * Get a hint.
 *
 * Return value: The value for this hint or #NULL if not set.
 **/
const gchar *
lightdm_greeter_get_hint (LightDMGreeter *greeter, const gchar *name)
{
    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), NULL);
    return g_hash_table_lookup (GET_PRIVATE (greeter)->hints, name);
}

/**
 * lightdm_greeter_get_default_session_hint:
 * @greeter: A #LightDMGreeter
 *
 * Get the default session to use.
 *
 * Return value: The session name
 **/
const gchar *
lightdm_greeter_get_default_session_hint (LightDMGreeter *greeter)
{
    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), NULL);
    return lightdm_greeter_get_hint (greeter, "default-session");
}

/**
 * lightdm_greeter_get_hide_users_hint:
 * @greeter: A #LightDMGreeter
 *
 * Check if user accounts should be shown.  If this is TRUE then the list of
 * accounts should be taken from #LightDMUserList and displayed in the greeter
 * for the user to choose from.  Note that this list can be empty and it is
 * recommended you show a method for the user to enter a username manually.
 * 
 * If this option is shown the greeter should only allow these users to be
 * chosen for login unless the manual login hint is set.
 *
 * Return value: #TRUE if the available users should not be shown.
 */
gboolean
lightdm_greeter_get_hide_users_hint (LightDMGreeter *greeter)
{
    const gchar *value;

    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);
    value = lightdm_greeter_get_hint (greeter, "hide-users");

    return g_strcmp0 (value, "true") == 0;
}

/**
 * lightdm_greeter_get_show_manual_login_hint:
 * @greeter: A #LightDMGreeter
 *
 * Check if a manual login option should be shown.  If set the GUI
 * should provide a way for a username to be entered manually.
 * Without this hint a greeter which is showing a user list can
 * limit logins to only those users.
 *
 * Return value: #TRUE if a manual login option should be shown.
 */
gboolean
lightdm_greeter_get_show_manual_login_hint (LightDMGreeter *greeter)
{
    const gchar *value;

    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);
    value = lightdm_greeter_get_hint (greeter, "show-manual-login");

    return g_strcmp0 (value, "true") == 0;
}

/**
 * lightdm_greeter_get_lock_hint:
 * @greeter: A #LightDMGreeter
 *
 * Check if the greeter is acting as a lock screen.
 *
 * Return value: #TRUE if the greeter was triggered by locking the seat.
 */
gboolean
lightdm_greeter_get_lock_hint (LightDMGreeter *greeter)
{
    const gchar *value;

    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);
    value = lightdm_greeter_get_hint (greeter, "lock-screen");

    return g_strcmp0 (value, "true") == 0;
}

/**
 * lightdm_greeter_get_has_guest_account_hint:
 * @greeter: A #LightDMGreeter
 *
 * Check if guest sessions are supported.
 *
 * Return value: #TRUE if guest sessions are supported.
 */
gboolean
lightdm_greeter_get_has_guest_account_hint (LightDMGreeter *greeter)
{
    const gchar *value;

    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);
    value = lightdm_greeter_get_hint (greeter, "has-guest-account");
  
    return g_strcmp0 (value, "true") == 0;
}

/**
 * lightdm_greeter_get_select_user_hint:
 * @greeter: A #LightDMGreeter
 *
 * Get the user to select by default.
 *
 * Return value: A username
 */
const gchar *
lightdm_greeter_get_select_user_hint (LightDMGreeter *greeter)
{
    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), NULL);
    return lightdm_greeter_get_hint (greeter, "select-user");
}

/**
 * lightdm_greeter_get_select_guest_hint:
 * @greeter: A #LightDMGreeter
 *
 * Check if the guest account should be selected by default.
 *
 * Return value: #TRUE if the guest account should be selected by default.
 */
gboolean
lightdm_greeter_get_select_guest_hint (LightDMGreeter *greeter)
{
    const gchar *value;

    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);
    value = lightdm_greeter_get_hint (greeter, "select-guest");
  
    return g_strcmp0 (value, "true") == 0;
}

/**
 * lightdm_greeter_get_autologin_user_hint:
 * @greeter: A #LightDMGreeter
 *
 * Get the user account to automatically logg into when the timer expires.
 *
 * Return value: The user account to automatically log into.
 */
const gchar *
lightdm_greeter_get_autologin_user_hint (LightDMGreeter *greeter)
{
    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), NULL);
    return lightdm_greeter_get_hint (greeter, "autologin-user");
}

/**
 * lightdm_greeter_get_autologin_guest_hint:
 * @greeter: A #LightDMGreeter
 *
 * Check if the guest account should be automatically logged into when the timer expires.
 *
 * Return value: #TRUE if the guest account should be automatically logged into.
 */
gboolean
lightdm_greeter_get_autologin_guest_hint (LightDMGreeter *greeter)
{
    const gchar *value;

    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);
    value = lightdm_greeter_get_hint (greeter, "autologin-guest");
  
    return g_strcmp0 (value, "true") == 0;
}

/**
 * lightdm_greeter_get_autologin_timeout_hint:
 * @greeter: A #LightDMGreeter
 *
 * Get the number of seconds to wait before automaitcally logging in.
 *
 * Return value: The number of seconds to wait before automatically logging in or 0 for no timeout.
 */
gint
lightdm_greeter_get_autologin_timeout_hint (LightDMGreeter *greeter)
{
    const gchar *value;
    gint timeout = 0;

    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);
    value = lightdm_greeter_get_hint (greeter, "autologin-timeout");
    if (value)
        timeout = atoi (value);
    if (timeout < 0)
        timeout = 0;

    return timeout;
}

/**
 * lightdm_greeter_cancel_autologin:
 * @greeter: A #LightDMGreeter
 *
 * Cancel the automatic login.
 */
void
lightdm_greeter_cancel_autologin (LightDMGreeter *greeter)
{
    LightDMGreeterPrivate *priv;

    g_return_if_fail (LIGHTDM_IS_GREETER (greeter));

    priv = GET_PRIVATE (greeter);

    if (priv->autologin_timeout)
       g_source_remove (priv->autologin_timeout);
    priv->autologin_timeout = 0;
}

/**
 * lightdm_greeter_authenticate:
 * @greeter: A #LightDMGreeter
 * @username: (allow-none): A username or #NULL to prompt for a username.
 *
 * Starts the authentication procedure for a user.
 **/
void
lightdm_greeter_authenticate (LightDMGreeter *greeter, const char *username)
{
    LightDMGreeterPrivate *priv;
    guint8 message[MAX_MESSAGE_LENGTH];
    gsize offset = 0;

    g_return_if_fail (LIGHTDM_IS_GREETER (greeter));

    priv = GET_PRIVATE (greeter);

    g_return_if_fail (priv->connected);

    priv->cancelling_authentication = FALSE;
    priv->authenticate_sequence_number++;
    priv->in_authentication = TRUE;  
    priv->is_authenticated = FALSE;
    if (username != priv->authentication_user)
    {
        g_free (priv->authentication_user);
        priv->authentication_user = g_strdup (username);
    }

    g_debug ("Starting authentication for user %s...", username);
    write_header (message, MAX_MESSAGE_LENGTH, GREETER_MESSAGE_AUTHENTICATE, int_length () + string_length (username), &offset);
    write_int (message, MAX_MESSAGE_LENGTH, priv->authenticate_sequence_number, &offset);
    write_string (message, MAX_MESSAGE_LENGTH, username, &offset);
    write_message (greeter, message, offset);
}

/**
 * lightdm_greeter_authenticate_as_guest:
 * @greeter: A #LightDMGreeter
 *
 * Starts the authentication procedure for the guest user.
 **/
void
lightdm_greeter_authenticate_as_guest (LightDMGreeter *greeter)
{
    LightDMGreeterPrivate *priv;
    guint8 message[MAX_MESSAGE_LENGTH];
    gsize offset = 0;

    g_return_if_fail (LIGHTDM_IS_GREETER (greeter));

    priv = GET_PRIVATE (greeter);

    g_return_if_fail (priv->connected);

    priv->cancelling_authentication = FALSE;
    priv->authenticate_sequence_number++;
    priv->in_authentication = TRUE;
    priv->is_authenticated = FALSE;
    g_free (priv->authentication_user);
    priv->authentication_user = NULL;

    g_debug ("Starting authentication for guest account...");
    write_header (message, MAX_MESSAGE_LENGTH, GREETER_MESSAGE_AUTHENTICATE_AS_GUEST, int_length (), &offset);
    write_int (message, MAX_MESSAGE_LENGTH, priv->authenticate_sequence_number, &offset);
    write_message (greeter, message, offset);
}

/**
 * lightdm_greeter_respond:
 * @greeter: A #LightDMGreeter
 * @response: Response to a prompt
 *
 * Provide response to a prompt.
 **/
void
lightdm_greeter_respond (LightDMGreeter *greeter, const gchar *response)
{
    LightDMGreeterPrivate *priv;
    guint8 message[MAX_MESSAGE_LENGTH];
    gsize offset = 0;

    g_return_if_fail (LIGHTDM_IS_GREETER (greeter));
    g_return_if_fail (response != NULL);

    priv = GET_PRIVATE (greeter);

    g_return_if_fail (priv->connected);

    g_debug ("Providing response to display manager");
    write_header (message, MAX_MESSAGE_LENGTH, GREETER_MESSAGE_CONTINUE_AUTHENTICATION, int_length () + string_length (response), &offset);
    // FIXME: Could be multiple responses required
    write_int (message, MAX_MESSAGE_LENGTH, 1, &offset);
    write_string (message, MAX_MESSAGE_LENGTH, response, &offset);
    write_message (greeter, message, offset);
}

/**
 * lightdm_greeter_cancel_authentication:
 * @greeter: A #LightDMGreeter
 *
 * Cancel the current user authentication.
 **/
void
lightdm_greeter_cancel_authentication (LightDMGreeter *greeter)
{
    LightDMGreeterPrivate *priv;
    guint8 message[MAX_MESSAGE_LENGTH];
    gsize offset = 0;

    g_return_if_fail (LIGHTDM_IS_GREETER (greeter));

    priv = GET_PRIVATE (greeter);

    g_return_if_fail (priv->connected);

    priv->cancelling_authentication = TRUE;
    write_header (message, MAX_MESSAGE_LENGTH, GREETER_MESSAGE_CANCEL_AUTHENTICATION, 0, &offset);
    write_message (greeter, message, offset);
}

/**
 * lightdm_greeter_get_in_authentication:
 * @greeter: A #LightDMGreeter
 *
 * Checks if the greeter is in the process of authenticating.
 *
 * Return value: #TRUE if the greeter is authenticating a user.
 **/
gboolean
lightdm_greeter_get_in_authentication (LightDMGreeter *greeter)
{
    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);
    return GET_PRIVATE (greeter)->in_authentication;
}

/**
 * lightdm_greeter_get_is_authenticated:
 * @greeter: A #LightDMGreeter
 *
 * Checks if the greeter has successfully authenticated.
 *
 * Return value: #TRUE if the greeter is authenticated for login.
 **/
gboolean
lightdm_greeter_get_is_authenticated (LightDMGreeter *greeter)
{
    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);
    return GET_PRIVATE (greeter)->is_authenticated;
}

/**
 * lightdm_greeter_get_authentication_user:
 * @greeter: A #LightDMGreeter
 *
 * Get the user that is being authenticated.
 *
 * Return value: The username of the authentication user being authenticated or #NULL if no authentication in progress.
 */
const gchar *
lightdm_greeter_get_authentication_user (LightDMGreeter *greeter)
{
    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), NULL);
    return GET_PRIVATE (greeter)->authentication_user;
}

/**
 * lightdm_greeter_set_language:
 * @greeter: A #LightDMGreeter
 * @language: The language to use for this user.
 *
 * Set the language for the currently authenticated user.
 **/
void
lightdm_greeter_set_language (LightDMGreeter *greeter, const gchar *language)
{
    LightDMGreeterPrivate *priv;
    guint8 message[MAX_MESSAGE_LENGTH];
    gsize offset = 0;

    g_return_if_fail (LIGHTDM_IS_GREETER (greeter));

    priv = GET_PRIVATE (greeter);

    g_return_if_fail (priv->connected);

    write_header (message, MAX_MESSAGE_LENGTH, GREETER_MESSAGE_SET_LANGUAGE, string_length (language), &offset);
    write_string (message, MAX_MESSAGE_LENGTH, language, &offset);
    write_message (greeter, message, offset);
}

/**
 * lightdm_greeter_start_session_sync:
 * @greeter: A #LightDMGreeter
 * @session: (allow-none): The session to log into or #NULL to use the default.
 * @error: return location for a #GError, or %NULL
 *
 * Start a session for the authenticated user.
 *
 * Return value: TRUE if the session was started.
 **/
gboolean
lightdm_greeter_start_session_sync (LightDMGreeter *greeter, const gchar *session, GError **error)
{
    LightDMGreeterPrivate *priv;
    guint8 message[MAX_MESSAGE_LENGTH];
    guint8 *response;
    gsize response_length, offset = 0;
    guint32 id, return_code = 1;

    g_return_val_if_fail (LIGHTDM_IS_GREETER (greeter), FALSE);

    priv = GET_PRIVATE (greeter);

    g_return_val_if_fail (priv->connected, FALSE);
    g_return_val_if_fail (priv->is_authenticated, FALSE);

    if (session)
        g_debug ("Starting session %s", session);
    else
        g_debug ("Starting default session");

    write_header (message, MAX_MESSAGE_LENGTH, GREETER_MESSAGE_START_SESSION, string_length (session), &offset);
    write_string (message, MAX_MESSAGE_LENGTH, session, &offset);
    write_message (greeter, message, offset);

    response = read_message (greeter, &response_length, TRUE);
    if (!response)
        return FALSE;

    offset = 0;
    id = read_int (response, response_length, &offset);
    read_int (response, response_length, &offset);
    if (id == SERVER_MESSAGE_SESSION_RESULT)
        return_code = read_int (response, response_length, &offset);
    else
        g_warning ("Expected SESSION_RESULT message, got %d", id);

    g_free (response);

    return return_code == 0;
}

static void
lightdm_greeter_init (LightDMGreeter *greeter)
{
    LightDMGreeterPrivate *priv = GET_PRIVATE (greeter);

    priv->read_buffer = g_malloc (HEADER_SIZE);
    priv->hints = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, g_free);
}

static void
lightdm_greeter_set_property (GObject      *object,
                          guint         prop_id,
                          const GValue *value,
                          GParamSpec   *pspec)
{
    G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
}

static void
lightdm_greeter_get_property (GObject    *object,
                          guint       prop_id,
                          GValue     *value,
                          GParamSpec *pspec)
{
    LightDMGreeter *self;

    self = LIGHTDM_GREETER (object);

    switch (prop_id) {
    case PROP_DEFAULT_SESSION_HINT:
        g_value_set_string (value, lightdm_greeter_get_default_session_hint (self));
        break;
    case PROP_HIDE_USERS_HINT:
        g_value_set_boolean (value, lightdm_greeter_get_hide_users_hint (self));
        break;
    case PROP_SHOW_MANUAL_LOGIN_HINT:
        g_value_set_boolean (value, lightdm_greeter_get_show_manual_login_hint (self));
        break;
    case PROP_LOCK_HINT:
        g_value_set_boolean (value, lightdm_greeter_get_lock_hint (self));
        break;
    case PROP_HAS_GUEST_ACCOUNT_HINT:
        g_value_set_boolean (value, lightdm_greeter_get_has_guest_account_hint (self));
        break;
    case PROP_SELECT_USER_HINT:
        g_value_set_string (value, lightdm_greeter_get_select_user_hint (self));
        break;
    case PROP_SELECT_GUEST_HINT:
        g_value_set_boolean (value, lightdm_greeter_get_select_guest_hint (self));
        break;
    case PROP_AUTOLOGIN_USER_HINT:
        g_value_set_string (value, lightdm_greeter_get_autologin_user_hint (self));
        break;
    case PROP_AUTOLOGIN_GUEST_HINT:
        g_value_set_boolean (value, lightdm_greeter_get_autologin_guest_hint (self));
        break;
    case PROP_AUTOLOGIN_TIMEOUT_HINT:
        g_value_set_int (value, lightdm_greeter_get_autologin_timeout_hint (self));
        break;
    case PROP_AUTHENTICATION_USER:
        g_value_set_string (value, lightdm_greeter_get_authentication_user (self));
        break;
    case PROP_IN_AUTHENTICATION:
        g_value_set_boolean (value, lightdm_greeter_get_in_authentication (self));
        break;
    case PROP_IS_AUTHENTICATED:
        g_value_set_boolean (value, lightdm_greeter_get_is_authenticated (self));
        break;
    default:
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
        break;
    }
}

static void
marshal_VOID__STRING_INT (GClosure     *closure,
                          GValue       *return_value G_GNUC_UNUSED,
                          guint         n_param_values,
                          const GValue *param_values,
                          gpointer      invocation_hint G_GNUC_UNUSED,
                          gpointer      marshal_data)
{
    typedef void (*GMarshalFunc_VOID__STRING_INT) (gpointer     data1,
                                                   gpointer     arg_1,
                                                   gint         arg_2,
                                                   gpointer     data2);
    register GMarshalFunc_VOID__STRING_INT callback;
    register GCClosure *cc = (GCClosure*) closure;
    register gpointer data1, data2;

    g_return_if_fail (n_param_values == 3);

    if (G_CCLOSURE_SWAP_DATA (closure))
    {
        data1 = closure->data;
        data2 = g_value_peek_pointer (param_values + 0);
    }
    else
    {
        data1 = g_value_peek_pointer (param_values + 0);
        data2 = closure->data;
    }
    callback = (GMarshalFunc_VOID__STRING_INT) (marshal_data ? marshal_data : cc->callback);

    callback (data1,
              (param_values + 1)->data[0].v_pointer,
              (param_values + 2)->data[0].v_int,
              data2);
}

static void
lightdm_greeter_finalize (GObject *object)
{
    LightDMGreeter *self = LIGHTDM_GREETER (object);
    LightDMGreeterPrivate *priv = GET_PRIVATE (self);

    if (priv->to_server_channel)
        g_io_channel_unref (priv->to_server_channel);
    if (priv->from_server_channel)
        g_io_channel_unref (priv->from_server_channel);
    g_free (priv->authentication_user);
    g_hash_table_unref (priv->hints);

    G_OBJECT_CLASS (lightdm_greeter_parent_class)->finalize (object);
}

static void
lightdm_greeter_class_init (LightDMGreeterClass *klass)
{
    GObjectClass *object_class = G_OBJECT_CLASS (klass);

    g_type_class_add_private (klass, sizeof (LightDMGreeterPrivate));

    object_class->set_property = lightdm_greeter_set_property;
    object_class->get_property = lightdm_greeter_get_property;
    object_class->finalize = lightdm_greeter_finalize;

    g_object_class_install_property (object_class,
                                     PROP_DEFAULT_SESSION_HINT,
                                     g_param_spec_string ("default-session-hint",
                                                          "default-session-hint",
                                                          "Default session hint",
                                                          NULL,
                                                          G_PARAM_READWRITE));

    g_object_class_install_property (object_class,
                                     PROP_HIDE_USERS_HINT,
                                     g_param_spec_boolean ("hide-users-hint",
                                                           "hide-users-hint",
                                                           "Hide users hint",
                                                           FALSE,
                                                           G_PARAM_READABLE));

    g_object_class_install_property (object_class,
                                     PROP_SHOW_MANUAL_LOGIN_HINT,
                                     g_param_spec_boolean ("show-manual-login-hint",
                                                           "show-manual-login-hint",
                                                           "Show manual login hint",
                                                           FALSE,
                                                           G_PARAM_READABLE));

    g_object_class_install_property (object_class,
                                     PROP_LOCK_HINT,
                                     g_param_spec_boolean ("lock-hint",
                                                           "lock-hint",
                                                           "Lock hint",
                                                           FALSE,
                                                           G_PARAM_READABLE));

    g_object_class_install_property (object_class,
                                     PROP_HAS_GUEST_ACCOUNT_HINT,
                                     g_param_spec_boolean ("has-guest-account-hint",
                                                           "has-guest-account-hint",
                                                           "Has guest account hint",
                                                           FALSE,
                                                           G_PARAM_READABLE));

    g_object_class_install_property (object_class,
                                     PROP_SELECT_USER_HINT,
                                     g_param_spec_string ("select-user-hint",
                                                          "select-user-hint",
                                                          "Select user hint",
                                                          NULL,
                                                          G_PARAM_READABLE));

    g_object_class_install_property (object_class,
                                     PROP_SELECT_GUEST_HINT,
                                     g_param_spec_boolean ("select-guest-hint",
                                                           "select-guest-hint",
                                                           "Select guest account hint",
                                                           FALSE,
                                                           G_PARAM_READABLE));

    g_object_class_install_property (object_class,
                                     PROP_AUTOLOGIN_USER_HINT,
                                     g_param_spec_string ("autologin-user-hint",
                                                          "autologin-user-hint",
                                                          "Autologin user hint",
                                                          NULL,
                                                          G_PARAM_READABLE));

    g_object_class_install_property (object_class,
                                     PROP_AUTOLOGIN_GUEST_HINT,
                                     g_param_spec_boolean ("autologin-guest-hint",
                                                           "autologin-guest-hint",
                                                           "Autologin guest account hint",
                                                           FALSE,
                                                           G_PARAM_READABLE));

    g_object_class_install_property (object_class,
                                     PROP_AUTOLOGIN_TIMEOUT_HINT,
                                     g_param_spec_int ("autologin-timeout-hint",
                                                       "autologin-timeout-hint",
                                                       "Autologin timeout hint",
                                                       0, G_MAXINT, 0,
                                                       G_PARAM_READABLE));

    g_object_class_install_property (object_class,
                                     PROP_AUTHENTICATION_USER,
                                     g_param_spec_string ("authentication-user",
                                                          "authentication-user",
                                                          "The user being authenticated",
                                                          NULL,
                                                          G_PARAM_READABLE));
    g_object_class_install_property (object_class,
                                     PROP_IN_AUTHENTICATION,
                                     g_param_spec_boolean ("in-authentication",
                                                           "in-authentication",
                                                           "TRUE if a user is being authenticated",
                                                           FALSE,
                                                           G_PARAM_READABLE));
    g_object_class_install_property (object_class,
                                     PROP_IS_AUTHENTICATED,
                                     g_param_spec_boolean ("is-authenticated",
                                                           "is-authenticated",
                                                           "TRUE if the selected user is authenticated",
                                                           FALSE,
                                                           G_PARAM_READABLE));

    /**
     * LightDMGreeter::show-prompt:
     * @greeter: A #LightDMGreeter
     * @text: Prompt text
     * @type: Prompt type
     *
     * The ::show-prompt signal gets emitted when the greeter should show a
     * prompt to the user.  The given text should be displayed and an input
     * field for the user to provide a response.
     *
     * Call lightdm_greeter_respond() with the resultant input or
     * lightdm_greeter_cancel_authentication() to abort the authentication.
     **/
    signals[SHOW_PROMPT] =
        g_signal_new ("show-prompt",
                      G_TYPE_FROM_CLASS (klass),
                      G_SIGNAL_RUN_LAST,
                      G_STRUCT_OFFSET (LightDMGreeterClass, show_prompt),
                      NULL, NULL,
                      marshal_VOID__STRING_INT,
                      G_TYPE_NONE, 2, G_TYPE_STRING, G_TYPE_INT);

    /**
     * LightDMGreeter::show-message:
     * @greeter: A #LightDMGreeter
     * @text: Message text
     * @type: Message type
     *
     * The ::show-message signal gets emitted when the greeter
     * should show a message to the user.
     **/
    signals[SHOW_MESSAGE] =
        g_signal_new ("show-message",
                      G_TYPE_FROM_CLASS (klass),
                      G_SIGNAL_RUN_LAST,
                      G_STRUCT_OFFSET (LightDMGreeterClass, show_message),
                      NULL, NULL,
                      marshal_VOID__STRING_INT,
                      G_TYPE_NONE, 2, G_TYPE_STRING, G_TYPE_INT);

    /**
     * LightDMGreeter::authentication-complete:
     * @greeter: A #LightDMGreeter
     *
     * The ::authentication-complete signal gets emitted when the greeter
     * has completed authentication.
     *
     * Call lightdm_greeter_get_is_authenticated() to check if the authentication
     * was successful.
     **/
    signals[AUTHENTICATION_COMPLETE] =
        g_signal_new ("authentication-complete",
                      G_TYPE_FROM_CLASS (klass),
                      G_SIGNAL_RUN_LAST,
                      G_STRUCT_OFFSET (LightDMGreeterClass, authentication_complete),
                      NULL, NULL,
                      g_cclosure_marshal_VOID__VOID,
                      G_TYPE_NONE, 0);

    /**
     * LightDMGreeter::autologin-timer-expired:
     * @greeter: A #LightDMGreeter
     *
     * The ::timed-login signal gets emitted when the automatic login timer has expired.
     * The application should then call lightdm_greeter_login().
     **/
    signals[AUTOLOGIN_TIMER_EXPIRED] =
        g_signal_new ("autologin-timer-expired",
                      G_TYPE_FROM_CLASS (klass),
                      G_SIGNAL_RUN_LAST,
                      G_STRUCT_OFFSET (LightDMGreeterClass, autologin_timer_expired),
                      NULL, NULL,
                      g_cclosure_marshal_VOID__VOID,
                      G_TYPE_NONE, 0);
}