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gdm-queue.c

/* -*- Mode: C; indent-tabs-mode: nil; tab-width: 2 -*-
 *
 * Based originally on GDMcommunication routines.
 *
 * Copyright:
 *  (C) 2001 Queen of England
 *  (C) 2002 George Lebl
 *  (C) 2005 James M. Cape
 *  (C) 2006 Thomas Thurman
 *
 * This file is part of Netbook Launcher EFL.
 *
 * Netbook Launcher EFL is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Netbook Launcher EFL is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Netbook Launcher EFL.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif /* HAVE_CONFIG_H */

#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>
#include <stdio.h>

#include "gdm-queue.h"

#include <X11/Xauth.h>

/* You might have thought that we communicated with GDM using dbus or
 * bonobo or something spiffy like that. You'd be wrong! Instead, we
 * use a text-based command-response protocol over a Unix domain socket
 * which lives at a well-known position; this position will change in
 * newer GDM versions, so we check for a list.
 * At some point, it will make sense to switch to something dbus-based.
 */
#define GDM_SOCKET_PATH \
  "/var/run/gdm_socket" G_SEARCHPATH_SEPARATOR_S \
  "/tmp/.gdm_socket"

/* The old gdmcomm routines used to have individual minimum versions
 * for every particular GDM command, but then you have to deal with
 * the problem of what to do if you're running a version earlier than
 * the one you wanted. So we just have a blanket minimum for everything.
 */
#define MINIMAL_GDM_VERSION      "2.8.0"

/* Here's a useful macro to keep doing something even if we get EINTR
 * back (because the read or whatever was interrupted).
 *
 * From gdm2/vicious-extensions/ve-misc.h
 * Copyright (c) 2000 Eazel, Inc., (c) 2001,2002 George Lebl
 */
#define VE_IGNORE_EINTR(expr) \
  do {          \
    errno = 0;  \
    expr;               \
  } while G_UNLIKELY (errno == EINTR);

/* This is rather a one-off enum. ask_gdm() needs to keep track of
 * its current state, and these are the states it can be in:
 */
typedef enum
{
  /* The socket is closed. */
  GDM_SOCKET_CLOSED,
  /* The socket is open, and we just sent the VERSION command
   * (so we are expecting to get "GDM xxxx" back).
   */
  GDM_SOCKET_WAITING_FOR_VERSION,
  /* The socket is open, and we just sent anything else. */
  GDM_SOCKET_RUNNING_QUEUE,
} GdmSocketStatus;

/* This is one entry in the queue. */
typedef struct
  {
    /* The string to send to GDM.
     * If this is NULL, GDM won't hear anything about this step, but the
     * callback will be called anyway, just as if GDM had returned "OK"
     * to something.
     */
    gchar *query;
    /* The function to call with the result.
     * If this is NULL, the result will be thrown away.
    */
    GdmMessageCallback *callback;
    /* Arbitrary data to pass to the callback. */
    gpointer data;
  } GdmRequest;

/* The actual queue of instructions. */
static GQueue *gdm_queue = NULL;
/* The file descriptor of socket open on GDM_*_SOCKET_FILENAME. */
static int gdm_socket = 0;
/* The status, as described above. */
static GdmSocketStatus gdm_socket_status = GDM_SOCKET_CLOSED;

static void gdm_request_free (GdmRequest *victim);
static gboolean gdm_run_queue (void *dummy);
static int gdm_send_command (const gchar *command);
static gboolean gdm_send_next_command (void);

/* True if gdm_run_queue is set to be called by glib.
 * FIXME: Actually, isn't this pretty similar to GDM_SOCKET_CLOSED?
 */
static gboolean queue_runner_is_running = FALSE;

/* See the description in the header file. */
void
ask_gdm(GdmMessageCallback *callback, gpointer data, gchar *query, ...)
{
  GdmRequest *new_request;
  gboolean queue_was_empty;
  va_list args;

  queue_was_empty = gdm_queue==NULL || g_queue_is_empty (gdm_queue);

  va_start (args, query);

  new_request = g_malloc(sizeof(GdmRequest));
  new_request->callback = callback;
  new_request->data = data;

  if (query==NULL)
    new_request->query = NULL;
  else
    new_request->query = g_strdup_vprintf (query, args);

  va_end (args);

  if (gdm_queue == NULL)
    gdm_queue = g_queue_new();

  g_queue_push_tail(gdm_queue, new_request);

  if (!queue_runner_is_running)
    {
      g_idle_add_full (G_PRIORITY_DEFAULT_IDLE, gdm_run_queue, NULL, NULL);
      queue_runner_is_running = TRUE;
    }
}

/* Cleans up a GdmRequest*. */

void
gdm_request_free (GdmRequest *victim)
{
  g_free (victim->query);
  /* Don't free victim->data: that's the callback's job */
  g_free (victim);
}

/* Returns TRUE iff the version represented by |version| is greater or equal
 * to the version represented by |min_version|.
 */
static gboolean
version_ok_p (const char *version,
              const char *min_version)
{
  int a = 0, b = 0, c = 0, d = 0;
  int mina = 0, minb = 0, minc = 0, mind = 0;

  /* Note that if some fields in the version don't exist, then
   * we don't mind, they are zero */
  sscanf (version, "%d.%d.%d.%d", &a, &b, &c, &d);
  sscanf (min_version, "%d.%d.%d.%d", &mina, &minb, &minc, &mind);

  if ((a > mina) ||
      (a == mina && b > minb) ||
      (a == mina && b == minb && c > minc) ||
      (a == mina && b == minb && c == minc && d >= mind))
    return TRUE;
  else
    return FALSE;
}

/* Closes the GDM socket gracefully, and sets the state accordingly. */
static void
close_gdm_socket ()
{
  gdm_send_command("CLOSE");
  VE_IGNORE_EINTR (close (gdm_socket));
  gdm_socket_status = GDM_SOCKET_CLOSED;
}

/* This is the function which gets called repeatedly while we're idle
 * to remove messages from the queue and send them to GDM.
 */
gboolean gdm_run_queue (void *dummy)
{
  static GString *incoming = NULL;

  /* Firstly, unless the socket is closed, we left
   * because we were waiting for a response from
   * GDM. Let's see what it's sent us.
   */
  if (gdm_socket_status != GDM_SOCKET_CLOSED)
    {
      char buf[1] = "";

      if (incoming == NULL)
        incoming = g_string_sized_new (10);

      while (read (gdm_socket, buf, 1) == 1 &&
             buf[0] != '\n')
        {
          g_string_append_c (incoming, buf[0]);
        }

      if (buf[0] != '\n')
        {
          /* We haven't received the CR yet, so let's go around
           * again.
           */

          return TRUE;
        }
    }

  /* So if we get here, either the socket is closed and we want to
   * begin a conversation, or we've just received an answer that we
   * were expecting.
   */

  switch (gdm_socket_status)
    {
    case GDM_SOCKET_CLOSED:
    {
      struct sockaddr_un addr;
      gchar ** socket_pathnames;
      int i = 0;

      /* Okay, so open the socket and let's try talking to gdm. */
      gdm_socket = socket (PF_LOCAL, SOCK_STREAM, 0);

      /* search the GDM_SOCKET_PATH for an existing socket pathname */
      socket_pathnames = g_strsplit(GDM_SOCKET_PATH,
                                    G_SEARCHPATH_SEPARATOR_S,
                                    0);
      while (socket_pathnames[i])
        {
          if (g_file_test(socket_pathnames[i], G_FILE_TEST_EXISTS))
            {
              /* Got it! */
              strcpy (addr.sun_path, socket_pathnames[i]);
              break;
            }

          i++;
        }
      if (!socket_pathnames[i])
        {
          /* Not found: bail */
          g_error ("Can't find gdm socket!");
        }
      g_strfreev(socket_pathnames);

      addr.sun_family = AF_UNIX;

      if (fcntl (gdm_socket, F_SETFL, O_NONBLOCK) < 0)
        {
          close_gdm_socket ();
          return TRUE;
        }

      if (connect (gdm_socket, (struct sockaddr *)&addr, sizeof (addr)) < 0)
        {
          close_gdm_socket ();
          return TRUE;
        }

      gdm_send_command("VERSION");

      if (incoming)
        {
          g_string_free (incoming, TRUE);
          incoming = NULL;
        }
      gdm_socket_status = GDM_SOCKET_WAITING_FOR_VERSION;

      return TRUE;
    }
    break;
    case GDM_SOCKET_WAITING_FOR_VERSION:
    {
      if (strncmp (incoming->str, "GDM ", 4) != 0)
        {
          g_string_free (incoming, TRUE);
          incoming = NULL;
          close_gdm_socket ();
          return TRUE;
        }
      if ( ! version_ok_p (&incoming->str[4], MINIMAL_GDM_VERSION))
        {
          g_string_free (incoming, TRUE);
          incoming = NULL;
          close_gdm_socket ();
          return TRUE;
        }

      g_string_free (incoming, TRUE);
      incoming = NULL;

      gdm_send_next_command ();
      gdm_socket_status = GDM_SOCKET_RUNNING_QUEUE;

      return TRUE;
    }
    break;
    case GDM_SOCKET_RUNNING_QUEUE:
    {
      GdmRequest *request;

      if (g_queue_is_empty (gdm_queue))
        {
          queue_runner_is_running = FALSE;
          return FALSE;
        }

      request = (GdmRequest*) g_queue_pop_head (gdm_queue);

#if 0
      /* Uncomment this if you want to see who's saying what to whom. */
      g_warning ("%s -> %s", request->query, incoming->str);
#endif

      if (request->callback)
        {
          if (strncmp (incoming->str, "OK", 2) == 0)
            {
              if (incoming->str[2] == ' ')
                request->callback (GDM_RESULT_OK, incoming->str+3, request->data);
              else
                request->callback (GDM_RESULT_OK, NULL, request->data);
            }
          else if (strncmp (incoming->str, "ERROR", 5) == 0)
            {
              if (incoming->str[5] == ' ')
                request->callback (GDM_RESULT_ERROR, incoming->str+6, request->data);
              else
                request->callback (GDM_RESULT_ERROR, NULL, request->data);
            }
          else
            {
              g_warning("Bizarre message from GDM: %s", incoming->str);
              request->callback (GDM_RESULT_BIZARRE, incoming->str, request->data);
            }
        }

      gdm_request_free (request);

      g_string_free (incoming, TRUE);
      incoming = NULL;

      if (gdm_send_next_command ())
        {
          return TRUE;
        }
      else
        {
          /* Queue is empty, so close the socket... */
          close_gdm_socket ();
          /* ...and don't go round again. */
          queue_runner_is_running = FALSE;
          return FALSE;
        }
    }
    }

  g_assert_not_reached ();
}

/* This sends the query given by the next command, i.e. the one on the
 * top of the queue. While there are entries on the top of the queue
 * with *no* commands to send, this function will pop them and execute
 * their callbacks. However, that is the only time when this function
 * modifies the queue.
 *
 * The function returns FALSE if the queue is (now) empty and TRUE
 * otherwise.
 */
static gboolean gdm_send_next_command ()
{
  GdmRequest *request;

  if (g_queue_is_empty (gdm_queue))
    {
      return FALSE;
    }
  else
    {
      request  = (GdmRequest*) g_queue_peek_head (gdm_queue);

      while (!g_queue_is_empty (gdm_queue) && request->query == NULL)
        {
          /* The query can be NULL, in which case we just call the
           * callback and pop it.
           *
           * (This pops the request that "request" points at
           * off the top of the stack.)
           */
          g_queue_pop_head (gdm_queue);

          /* Check that nobody has been daft enough to ask for no query
           * and no callback. Why anyone would do that, I don't know.
           */
          if (request->callback)
            /* So we call it... */
            request->callback (GDM_RESULT_OK, NULL, request->data);

          if (!g_queue_is_empty (gdm_queue))
            {

              /* Throw that one away... */
              gdm_request_free (request);

              /* and get another. */
              request = (GdmRequest*) g_queue_peek_head (gdm_queue);
            }
        }

      if (g_queue_is_empty (gdm_queue))
        {
          return FALSE;
        }
      else
        {
          gdm_send_command (request->query);
          return TRUE;
        }
    }
}

/* This sends the command |command| to GDM. */
static int gdm_send_command (const gchar *command)
{
  int ret;
  gchar *command_with_newline;
#ifndef MSG_NOSIGNAL
  void (*old_handler)(int);
#endif

  command_with_newline = g_strdup_printf ("%s\n", command);

#ifdef MSG_NOSIGNAL
  ret = send (gdm_socket, command_with_newline, strlen (command_with_newline), MSG_NOSIGNAL);
#else
  old_handler = signal (SIGPIPE, SIG_IGN);
  ret = send (gdm_socket, command_with_newline, strlen (command_with_newline), 0);
  signal (SIGPIPE, old_handler);
#endif

  g_free (command_with_newline);

  if (ret == -1)
    g_warning ("Bad result in gdm_send_command");

  return ret;
}

/* Returns a pointer to a string representing the X display number which
 * |screen| is on. It's the callers responsibility to free the pointer.
 */
static gchar *
get_dispnum (GdkScreen *screen)
{
  gchar *tmp, *retval;

  tmp = g_strdup (gdk_display_get_name (gdk_screen_get_display (screen)));
  if (tmp)
    {
      gchar *ptr;

      ptr = strchr (tmp, '.');
      if (ptr)
        *ptr = '\0';

      ptr = strchr (tmp, ':');
      if (ptr)
        {
          while (*ptr == ':')
            ptr++;

          retval = g_strdup (ptr);
        }
      else
        retval = g_strdup (tmp);

      g_free (tmp);
    }
  else
    retval = g_strdup ("0");

  return retval;
}

/* This is a strange special case. The first time we need to authenticate,
 * we might find several cookies which could do. We have no way of knowing
 * without trying them which ones might solve the problem. So we send all
 * of them; the first one which succeeds stores the winning cookie so that
 * we can send only that one next time. However, there's then no point in
 * sending all the others, so we call this function to save ourselves the
 * bother.
 */
static void
chop_all_auths_off_gdm_queue ()
{
  GdmRequest *head;

  if (g_queue_is_empty (gdm_queue))
    return;

  head = (GdmRequest*) g_queue_peek_head (gdm_queue);

  while (!g_queue_is_empty (gdm_queue) &&
         strncmp (head->query, "AUTH_", 5)==0)
    {

      gdm_request_free (g_queue_pop_head (gdm_queue));
      head = (GdmRequest*) g_queue_peek_head (gdm_queue);
    }
}

static gboolean cookie_tried = FALSE;
static char *cookie = NULL;

/* The callback which calls chop_all_auths_off_gdm_queue, q.v. */
static void
gdm_callback_perhaps_set_official_cookie (GdmResultState is_ok,
    const gchar *dummy, gpointer candidate_cookie)
{
  if (is_ok == GDM_RESULT_OK)
    {
      cookie = candidate_cookie;
      cookie_tried = TRUE;
      chop_all_auths_off_gdm_queue ();
    }
  else
    {
      g_free (candidate_cookie);
    }
}

/* See the description in the header file. */
void
queue_authentication (GdkScreen *screen)
{
  FILE *fp;
  char *number;
  Xauth *xau;

  if (cookie_tried)
    {
      /* Been there, done that. */
      if (cookie)
        ask_gdm (NULL, NULL, GDM_CMD_AUTH_LOCAL, cookie);
      return;
    }

  VE_IGNORE_EINTR (fp = fopen (XauFileName (), "r"));

  if (fp == NULL)
    {
      /* Oops, no xauthority file! */
      cookie = NULL;
      cookie_tried = TRUE;
      return;
    }

  number = get_dispnum (screen);

  cookie = NULL;

  while ((xau = XauReadAuth (fp)) != NULL)
    {
      int i;
      char buffer[40 /* 2*16 == 32, so 40 is enough */];

      /* Only Family local things are considered, all console
       * logins DO have this family (and even some local xdmcp
       * logins, though those will not pass by gdm itself of
       * course) */
      if (xau->family != FamilyLocal ||
          xau->number_length != strlen (number) ||
          strncmp (xau->number, number, xau->number_length) != 0 ||
          /* gdm sends MIT-MAGIC-COOKIE-1 cookies of length 16,
           * so just do those */
          xau->data_length != 16 ||
          xau->name_length != strlen ("MIT-MAGIC-COOKIE-1") ||
          strncmp (xau->name, "MIT-MAGIC-COOKIE-1",
                   xau->name_length) != 0 ||
          xau->data_length != 16)
        {
          /* so, not what we want; throw it away and continue */
          XauDisposeAuth (xau);
          continue;
        }

      buffer[0] = '\0';
      for (i = 0; i < 16; i++)
        {
          char sub[3];
          g_snprintf (sub, sizeof (sub), "%02x",
                      (guint)(guchar)xau->data[i]);
          strcat (buffer, sub);
        }

      XauDisposeAuth (xau);

      ask_gdm (gdm_callback_perhaps_set_official_cookie,
               g_strdup (buffer),
               GDM_CMD_AUTH_LOCAL, buffer);
    }

  VE_IGNORE_EINTR (fclose (fp));

  g_free (number);
}

/* See the description in the header file. */
gchar *
get_mit_magic_cookie (GdkScreen *screen,
                      gboolean   binary)
{
  FILE *fp;
  char *number;
  char *cookie2 = NULL;
  Xauth *xau;

  VE_IGNORE_EINTR (fp = fopen (XauFileName (), "r"));
  if (fp == NULL)
    {
      return NULL;
    }

  number = get_dispnum (screen);

  cookie2 = NULL;

  while ((xau = XauReadAuth (fp)) != NULL)
    {
      /* Just find the FIRST magic cookie, that's what gdm uses */
      if (xau->number_length != strlen (number) ||
          strncmp (xau->number, number, xau->number_length) != 0 ||
          /* gdm sends MIT-MAGIC-COOKIE-1 cookies of length 16,
           * so just do those */
          xau->data_length != 16 ||
          xau->name_length != strlen ("MIT-MAGIC-COOKIE-1") ||
          strncmp (xau->name, "MIT-MAGIC-COOKIE-1",
                   xau->name_length) != 0)
        {
          XauDisposeAuth (xau);
          continue;
        }

      if (binary)
        {
          cookie2 = g_new0 (char, 16);
          memcpy (cookie2, xau->data, 16);
        }
      else
        {
          int i;
          GString *str;

          str = g_string_new (NULL);

          for (i = 0; i < xau->data_length; i++)
            {
              g_string_append_printf
              (str, "%02x",
               (guint)(guchar)xau->data[i]);
            }
          cookie2 = g_string_free (str, FALSE);
        }

      XauDisposeAuth (xau);

      break;
    }
  VE_IGNORE_EINTR (fclose (fp));

  return cookie2;
}


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