src/greeter.c

   1 /*
   2  * Copyright (C) 2010-2011 Robert Ancell.
   3  * Author: Robert Ancell <robert.ancell@canonical.com>
   4  *
   5  * This program is free software: you can redistribute it and/or modify it under
   6  * the terms of the GNU General Public License as published by the Free Software
   7  * Foundation, either version 3 of the License, or (at your option) any later
   8  * version. See http://www.gnu.org/copyleft/gpl.html the full text of the
   9  * license.
  10  */
  11
  12 #include <config.h>
  13
  14 #include <stdlib.h>
  15 #include <string.h>
  16 #include <errno.h>
  17 #include <fcntl.h>
  18 #include <gcrypt.h>
  19
  20 #include "greeter.h"
  21 #include "configuration.h"
  22 #include "shared-data-manager.h"
  23
  24 enum {
  25     PROP_0,
  26     PROP_ACTIVE_USERNAME,
  27 };
  28
  29 enum {
  30     CONNECTED,
  31     CREATE_SESSION,
  32     START_SESSION,
  33     LAST_SIGNAL
  34 };
  35 static guint signals[LAST_SIGNAL] = { 0 };
  36
  37 struct GreeterPrivate
  38 {
  39     /* PAM service to authenticate with */
  40     gchar *pam_service;
  41     gchar *autologin_pam_service;
  42
  43     /* Buffer for data read from greeter */
  44     guint8 *read_buffer;
  45     gsize n_read;
  46     gboolean use_secure_memory;
  47
  48     /* Hints for the greeter */
  49     GHashTable *hints;
  50
  51     /* Default session to use */
  52     gchar *default_session;
  53
  54     /* Sequence number of current PAM session */
  55     guint32 authentication_sequence_number;
  56
  57     /* Remote session name */
  58     gchar *remote_session;
  59
  60     /* Currently selected user */
  61     gchar *active_username;
  62
  63     /* PAM session being constructed by the greeter */
  64     Session *authentication_session;
  65
  66     /* TRUE if a user has been authenticated and the session requested to start */
  67     gboolean start_session;
  68
  69     /* TRUE if can log into guest accounts */
  70     gboolean allow_guest;
  71
  72     /* TRUE if logging into guest session */
  73     gboolean guest_account_authenticated;
  74
  75     /* Communication channels to communicate with */
  76     GIOChannel *to_greeter_channel;
  77     GIOChannel *from_greeter_channel;
  78     guint from_greeter_watch;
  79 };
  80
  81 G_DEFINE_TYPE (Greeter, greeter, SESSION_TYPE);
  82
  83 /* Messages from the greeter to the server */
  84 typedef enum
  85 {
  86     GREETER_MESSAGE_CONNECT = 0,
  87     GREETER_MESSAGE_AUTHENTICATE,
  88     GREETER_MESSAGE_AUTHENTICATE_AS_GUEST,
  89     GREETER_MESSAGE_CONTINUE_AUTHENTICATION,
  90     GREETER_MESSAGE_START_SESSION,
  91     GREETER_MESSAGE_CANCEL_AUTHENTICATION,
  92     GREETER_MESSAGE_SET_LANGUAGE,
  93     GREETER_MESSAGE_AUTHENTICATE_REMOTE,
  94     GREETER_MESSAGE_ENSURE_SHARED_DIR,
  95 } GreeterMessage;
  96
  97 /* Messages from the server to the greeter */
  98 typedef enum
  99 {
 100     SERVER_MESSAGE_CONNECTED = 0,
 101     SERVER_MESSAGE_PROMPT_AUTHENTICATION,
 102     SERVER_MESSAGE_END_AUTHENTICATION,
 103     SERVER_MESSAGE_SESSION_RESULT,
 104     SERVER_MESSAGE_SHARED_DIR_RESULT,
 105 } ServerMessage;
 106
 107 static gboolean read_cb (GIOChannel *source, GIOCondition condition, gpointer data);
 108
 109 Greeter *
 110 greeter_new (void)
 111 {
 112     return g_object_new (GREETER_TYPE, NULL);
 113 }
 114
 115 void
 116 greeter_set_pam_services (Greeter *greeter, const gchar *pam_service, const gchar *autologin_pam_service)
 117 {
 118     g_free (greeter->priv->pam_service);
 119     greeter->priv->pam_service = g_strdup (pam_service);
 120     g_free (greeter->priv->autologin_pam_service);
 121     greeter->priv->autologin_pam_service = g_strdup (autologin_pam_service);
 122 }
 123
 124 void
 125 greeter_set_allow_guest (Greeter *greeter, gboolean allow_guest)
 126 {
 127     greeter->priv->allow_guest = allow_guest;
 128 }
 129
 130 void
 131 greeter_set_hint (Greeter *greeter, const gchar *name, const gchar *value)
 132 {
 133     g_hash_table_insert (greeter->priv->hints, g_strdup (name), g_strdup (value));
 134 }
 135
 136 static void *
 137 secure_malloc (Greeter *greeter, size_t n)
 138 {
 139     if (greeter->priv->use_secure_memory)
 140         return gcry_malloc_secure (n);
 141     else
 142         return g_malloc (n);
 143 }
 144
 145 static void *
 146 secure_realloc (Greeter *greeter, void *ptr, size_t n)
 147 {
 148     if (greeter->priv->use_secure_memory)
 149         return gcry_realloc (ptr, n);
 150     else
 151         return g_realloc (ptr, n);
 152 }
 153
 154 static void
 155 secure_free (Greeter *greeter, void *ptr)
 156 {
 157     if (greeter->priv->use_secure_memory)
 158         return gcry_free (ptr);
 159     else
 160         return g_free (ptr);
 161 }
 162
 163 static guint32
 164 int_length (void)
 165 {
 166     return 4;
 167 }
 168
 169 #define HEADER_SIZE (sizeof (guint32) * 2)
 170 #define MAX_MESSAGE_LENGTH 1024
 171
 172 static void
 173 write_message (Greeter *greeter, guint8 *message, gsize message_length)
 174 {
 175     GError *error = NULL;
 176
 177     g_io_channel_write_chars (greeter->priv->to_greeter_channel, (gchar *) message, message_length, NULL, &error);
 178     if (error)
 179         l_warning (greeter, "Error writing to greeter: %s", error->message);
 180     g_clear_error (&error);
 181     g_io_channel_flush (greeter->priv->to_greeter_channel, NULL);
 182 }
 183
 184 static void
 185 write_int (guint8 *buffer, gint buffer_length, guint32 value, gsize *offset)
 186 {
 187     if (*offset + 4 >= buffer_length)
 188         return;
 189     buffer[*offset] = value >> 24;
 190     buffer[*offset+1] = (value >> 16) & 0xFF;
 191     buffer[*offset+2] = (value >> 8) & 0xFF;
 192     buffer[*offset+3] = value & 0xFF;
 193     *offset += 4;
 194 }
 195
 196 static void
 197 write_string (guint8 *buffer, gint buffer_length, const gchar *value, gsize *offset)
 198 {
 199     gint length;
 200
 201     if (value)
 202         length = strlen (value);
 203     else
 204         length = 0;
 205     write_int (buffer, buffer_length, length, offset);
 206     if (*offset + length >= buffer_length)
 207         return;
 208     if (length > 0)
 209     {
 210         memcpy (buffer + *offset, value, length);
 211         *offset += length;
 212     }
 213 }
 214
 215 static void
 216 write_header (guint8 *buffer, gint buffer_length, guint32 id, guint32 length, gsize *offset)
 217 {
 218     write_int (buffer, buffer_length, id, offset);
 219     write_int (buffer, buffer_length, length, offset);
 220 }
 221
 222 static guint32
 223 string_length (const gchar *value)
 224 {
 225     if (value == NULL)
 226         return int_length ();
 227     else
 228         return int_length () + strlen (value);
 229 }
 230
 231 static void
 232 handle_connect (Greeter *greeter, const gchar *version)
 233 {
 234     guint8 message[MAX_MESSAGE_LENGTH];
 235     gsize offset = 0;
 236     guint32 length;
 237     GHashTableIter iter;
 238     gpointer key, value;
 239
 240     l_debug (greeter, "Greeter connected version=%s", version);
 241
 242     length = string_length (VERSION);
 243     g_hash_table_iter_init (&iter, greeter->priv->hints);
 244     while (g_hash_table_iter_next (&iter, &key, &value))
 245         length += string_length (key) + string_length (value);
 246
 247     write_header (message, MAX_MESSAGE_LENGTH, SERVER_MESSAGE_CONNECTED, length, &offset);
 248     write_string (message, MAX_MESSAGE_LENGTH, VERSION, &offset);
 249     g_hash_table_iter_init (&iter, greeter->priv->hints);
 250     while (g_hash_table_iter_next (&iter, &key, &value))
 251     {
 252         write_string (message, MAX_MESSAGE_LENGTH, key, &offset);
 253         write_string (message, MAX_MESSAGE_LENGTH, value, &offset);
 254     }
 255     write_message (greeter, message, offset);
 256
 257     g_signal_emit (greeter, signals[CONNECTED], 0);
 258 }
 259
 260 static void
 261 pam_messages_cb (Session *session, Greeter *greeter)
 262 {
 263     int i;
 264     guint32 size;
 265     guint8 message[MAX_MESSAGE_LENGTH];
 266     const struct pam_message *messages;
 267     int messages_length;
 268     gsize offset = 0;
 269     int n_prompts = 0;
 270
 271     messages = session_get_messages (session);
 272     messages_length = session_get_messages_length (session);
 273
 274     /* Respond to d-bus query with messages */
 275     l_debug (greeter, "Prompt greeter with %d message(s)", messages_length);
 276     size = int_length () + string_length (session_get_username (session)) + int_length ();
 277     for (i = 0; i < messages_length; i++)
 278         size += int_length () + string_length (messages[i].msg);
 279
 280     write_header (message, MAX_MESSAGE_LENGTH, SERVER_MESSAGE_PROMPT_AUTHENTICATION, size, &offset);
 281     write_int (message, MAX_MESSAGE_LENGTH, greeter->priv->authentication_sequence_number, &offset);
 282     write_string (message, MAX_MESSAGE_LENGTH, session_get_username (session), &offset);
 283     write_int (message, MAX_MESSAGE_LENGTH, messages_length, &offset);
 284     for (i = 0; i < messages_length; i++)
 285     {
 286         write_int (message, MAX_MESSAGE_LENGTH, messages[i].msg_style, &offset);
 287         write_string (message, MAX_MESSAGE_LENGTH, messages[i].msg, &offset);
 288
 289         if (messages[i].msg_style == PAM_PROMPT_ECHO_OFF || messages[i].msg_style == PAM_PROMPT_ECHO_ON)
 290             n_prompts++;
 291     }
 292     write_message (greeter, message, offset);
 293
 294     /* Continue immediately if nothing to respond with */
 295     // FIXME: Should probably give the greeter a chance to ack the message
 296     if (n_prompts == 0)
 297     {
 298         struct pam_response *response;
 299         response = calloc (messages_length, sizeof (struct pam_response));
 300         session_respond (greeter->priv->authentication_session, response);
 301         free (response);
 302     }
 303 }
 304
 305 static void
 306 send_end_authentication (Greeter *greeter, guint32 sequence_number, const gchar *username, int result)
 307 {
 308     guint8 message[MAX_MESSAGE_LENGTH];
 309     gsize offset = 0;
 310
 311     write_header (message, MAX_MESSAGE_LENGTH, SERVER_MESSAGE_END_AUTHENTICATION, int_length () + string_length (username) + int_length (), &offset);
 312     write_int (message, MAX_MESSAGE_LENGTH, sequence_number, &offset);
 313     write_string (message, MAX_MESSAGE_LENGTH, username, &offset);
 314     write_int (message, MAX_MESSAGE_LENGTH, result, &offset);
 315     write_message (greeter, message, offset);
 316 }
 317
 318 static void
 319 authentication_complete_cb (Session *session, Greeter *greeter)
 320 {
 321     int result;
 322
 323     l_debug (greeter, "Authenticate result for user %s: %s", session_get_username (session), session_get_authentication_result_string (session));
 324
 325     result = session_get_authentication_result (session);
 326     if (session_get_is_authenticated (session))
 327     {
 328         if (session_get_user (session))
 329             l_debug (greeter, "User %s authorized", session_get_username (session));
 330         else
 331         {
 332             l_debug (greeter, "User %s authorized, but no account of that name exists", session_get_username (session));
 333             result = PAM_USER_UNKNOWN;
 334         }
 335     }
 336
 337     send_end_authentication (greeter, greeter->priv->authentication_sequence_number, session_get_username (session), result);
 338 }
 339
 340 static void
 341 reset_session (Greeter *greeter)
 342 {
 343     g_free (greeter->priv->remote_session);
 344     greeter->priv->remote_session = NULL;
 345     if (greeter->priv->authentication_session)
 346     {
 347         g_signal_handlers_disconnect_matched (greeter->priv->authentication_session, G_SIGNAL_MATCH_DATA, 0, 0, NULL, NULL, greeter);
 348         session_stop (greeter->priv->authentication_session);
 349         g_object_unref (greeter->priv->authentication_session);
 350         greeter->priv->authentication_session = NULL;
 351     }
 352
 353     greeter->priv->guest_account_authenticated = FALSE;
 354 }
 355
 356 static void
 357 handle_login (Greeter *greeter, guint32 sequence_number, const gchar *username)
 358 {
 359     const gchar *autologin_username, *service;
 360     gboolean is_interactive;
 361
 362     if (username[0] == '\0')
 363     {
 364         l_debug (greeter, "Greeter start authentication");
 365         username = NULL;
 366     }
 367     else
 368         l_debug (greeter, "Greeter start authentication for %s", username);
 369
 370     reset_session (greeter);
 371
 372     if (greeter->priv->active_username)
 373         g_free (greeter->priv->active_username);
 374     greeter->priv->active_username = g_strdup (username);
 375     g_object_notify (G_OBJECT (greeter), "active-username");
 376
 377     greeter->priv->authentication_sequence_number = sequence_number;
 378     g_signal_emit (greeter, signals[CREATE_SESSION], 0, &greeter->priv->authentication_session);
 379     if (!greeter->priv->authentication_session)
 380     {
 381         send_end_authentication (greeter, sequence_number, "", PAM_USER_UNKNOWN);
 382         return;
 383     }
 384
 385     g_signal_connect (G_OBJECT (greeter->priv->authentication_session), "got-messages", G_CALLBACK (pam_messages_cb), greeter);
 386     g_signal_connect (G_OBJECT (greeter->priv->authentication_session), "authentication-complete", G_CALLBACK (authentication_complete_cb), greeter);
 387
 388     /* Use non-interactive service for autologin user */
 389     autologin_username = g_hash_table_lookup (greeter->priv->hints, "autologin-user");
 390     if (autologin_username != NULL && g_strcmp0 (username, autologin_username) == 0)
 391     {
 392         service = greeter->priv->autologin_pam_service;
 393         is_interactive = FALSE;
 394     }
 395     else
 396     {
 397         service = greeter->priv->pam_service;
 398         is_interactive = TRUE;
 399     }
 400
 401     /* Run the session process */
 402     session_set_pam_service (greeter->priv->authentication_session, service);
 403     session_set_username (greeter->priv->authentication_session, username);
 404     session_set_do_authenticate (greeter->priv->authentication_session, TRUE);
 405     session_set_is_interactive (greeter->priv->authentication_session, is_interactive);
 406     session_start (greeter->priv->authentication_session);
 407 }
 408
 409 static void
 410 handle_login_as_guest (Greeter *greeter, guint32 sequence_number)
 411 {
 412     l_debug (greeter, "Greeter start authentication for guest account");
 413
 414     reset_session (greeter);
 415
 416     if (!greeter->priv->allow_guest)
 417     {
 418         l_debug (greeter, "Guest account is disabled");
 419         send_end_authentication (greeter, sequence_number, "", PAM_USER_UNKNOWN);
 420         return;
 421     }
 422
 423     greeter->priv->guest_account_authenticated = TRUE;
 424     send_end_authentication (greeter, sequence_number, "", PAM_SUCCESS);
 425 }
 426
 427 static gchar *
 428 get_remote_session_service (const gchar *session_name)
 429 {
 430     GKeyFile *session_desktop_file;
 431     gboolean result;
 432     const gchar *c;
 433     gchar *remote_sessions_dir, *filename, *path, *service = NULL;
 434     GError *error = NULL;
 435
 436     /* Validate session name doesn't contain directory separators */
 437     for (c = session_name; *c; c++)
 438     {
 439         if (*c == '/')
 440             return NULL;
 441     }
 442
 443     /* Load the session file */
 444     session_desktop_file = g_key_file_new ();
 445     filename = g_strdup_printf ("%s.desktop", session_name);
 446     remote_sessions_dir = config_get_string (config_get_instance (), "LightDM", "remote-sessions-directory");
 447     path = g_build_filename (remote_sessions_dir, filename, NULL);
 448     g_free (remote_sessions_dir);
 449     g_free (filename);
 450     result = g_key_file_load_from_file (session_desktop_file, path, G_KEY_FILE_NONE, &error);
 451     if (error)
 452         g_debug ("Failed to load session file %s: %s", path, error->message);
 453     g_free (path);
 454     g_clear_error (&error);
 455     if (result)
 456         service = g_key_file_get_string (session_desktop_file, G_KEY_FILE_DESKTOP_GROUP, "X-LightDM-PAM-Service", NULL);
 457     g_key_file_free (session_desktop_file);
 458
 459     return service;
 460 }
 461
 462 static void
 463 handle_login_remote (Greeter *greeter, const gchar *session_name, const gchar *username, guint32 sequence_number)
 464 {
 465     gchar *service;
 466
 467     if (username[0] == '\0')
 468     {
 469         l_debug (greeter, "Greeter start authentication for remote session %s", session_name);
 470         username = NULL;
 471     }
 472     else
 473         l_debug (greeter, "Greeter start authentication for remote session %s as user %s", session_name, username);
 474
 475     reset_session (greeter);
 476
 477     service = get_remote_session_service (session_name);
 478     if (!service)
 479     {
 480         send_end_authentication (greeter, sequence_number, "", PAM_SYSTEM_ERR);
 481         return;
 482     }
 483
 484     greeter->priv->authentication_sequence_number = sequence_number;
 485     greeter->priv->remote_session = g_strdup (session_name);
 486     g_signal_emit (greeter, signals[CREATE_SESSION], 0, &greeter->priv->authentication_session);
 487     if (greeter->priv->authentication_session)
 488     {
 489         g_signal_connect (G_OBJECT (greeter->priv->authentication_session), "got-messages", G_CALLBACK (pam_messages_cb), greeter);
 490         g_signal_connect (G_OBJECT (greeter->priv->authentication_session), "authentication-complete", G_CALLBACK (authentication_complete_cb), greeter);
 491
 492         /* Run the session process */
 493         session_set_pam_service (greeter->priv->authentication_session, service);
 494         session_set_username (greeter->priv->authentication_session, username);
 495         session_set_do_authenticate (greeter->priv->authentication_session, TRUE);
 496         session_set_is_interactive (greeter->priv->authentication_session, TRUE);
 497         session_set_is_guest (greeter->priv->authentication_session, TRUE);
 498         session_start (greeter->priv->authentication_session);
 499     }
 500
 501     g_free (service);
 502
 503     if (!greeter->priv->authentication_session)
 504     {
 505         send_end_authentication (greeter, sequence_number, "", PAM_USER_UNKNOWN);
 506         return;
 507     }
 508 }
 509
 510 static void
 511 handle_continue_authentication (Greeter *greeter, gchar **secrets)
 512 {
 513     int messages_length;
 514     const struct pam_message *messages;
 515     struct pam_response *response;
 516     int i, j, n_prompts = 0;
 517
 518     /* Not in authentication */
 519     if (greeter->priv->authentication_session == NULL)
 520         return;
 521
 522     messages_length = session_get_messages_length (greeter->priv->authentication_session);
 523     messages = session_get_messages (greeter->priv->authentication_session);
 524
 525     /* Check correct number of responses */
 526     for (i = 0; i < messages_length; i++)
 527     {
 528         int msg_style = messages[i].msg_style;
 529         if (msg_style == PAM_PROMPT_ECHO_OFF || msg_style == PAM_PROMPT_ECHO_ON)
 530             n_prompts++;
 531     }
 532     if (g_strv_length (secrets) != n_prompts)
 533     {
 534         session_respond_error (greeter->priv->authentication_session, PAM_CONV_ERR);
 535         return;
 536     }
 537
 538     l_debug (greeter, "Continue authentication");
 539
 540     /* Build response */
 541     response = calloc (messages_length, sizeof (struct pam_response));
 542     for (i = 0, j = 0; i < messages_length; i++)
 543     {
 544         int msg_style = messages[i].msg_style;
 545         if (msg_style == PAM_PROMPT_ECHO_OFF || msg_style == PAM_PROMPT_ECHO_ON)
 546         {
 547             size_t secret_length = strlen (secrets[j]) + 1;
 548             response[i].resp = secure_malloc (greeter, secret_length);
 549             memcpy (response[i].resp, secrets[j], secret_length); // FIXME: Need to convert from UTF-8
 550             j++;
 551         }
 552     }
 553
 554     session_respond (greeter->priv->authentication_session, response);
 555
 556     for (i = 0; i < messages_length; i++)
 557         secure_free (greeter, response[i].resp);
 558     free (response);
 559 }
 560
 561 static void
 562 handle_cancel_authentication (Greeter *greeter)
 563 {
 564     /* Not in authentication */
 565     if (greeter->priv->authentication_session == NULL)
 566         return;
 567
 568     l_debug (greeter, "Cancel authentication");
 569     reset_session (greeter);
 570 }
 571
 572 static void
 573 handle_start_session (Greeter *greeter, const gchar *session)
 574 {
 575     gboolean result;
 576     guint8 message[MAX_MESSAGE_LENGTH];
 577     gsize offset = 0;
 578     SessionType session_type = SESSION_TYPE_LOCAL;
 579
 580     if (strcmp (session, "") == 0)
 581         session = NULL;
 582
 583     /* Use session type chosen in remote session */
 584     if (greeter->priv->remote_session)
 585     {
 586         session_type = SESSION_TYPE_REMOTE;
 587         session = greeter->priv->remote_session;
 588     }
 589
 590     if (greeter->priv->guest_account_authenticated || session_get_is_authenticated (greeter->priv->authentication_session))
 591     {
 592         if (session)
 593             l_debug (greeter, "Greeter requests session %s", session);
 594         else
 595             l_debug (greeter, "Greeter requests default session");
 596         greeter->priv->start_session = TRUE;
 597         g_signal_emit (greeter, signals[START_SESSION], 0, session_type, session, &result);
 598     }
 599     else
 600     {
 601         l_debug (greeter, "Ignoring start session request, user is not authorized");
 602         result = FALSE;
 603     }
 604
 605     write_header (message, MAX_MESSAGE_LENGTH, SERVER_MESSAGE_SESSION_RESULT, int_length (), &offset);
 606     write_int (message, MAX_MESSAGE_LENGTH, result ? 0 : 1, &offset);
 607     write_message (greeter, message, offset);
 608 }
 609
 610 static void
 611 handle_set_language (Greeter *greeter, const gchar *language)
 612 {
 613     User *user;
 614
 615     if (!greeter->priv->guest_account_authenticated && !session_get_is_authenticated (greeter->priv->authentication_session))
 616     {
 617         l_debug (greeter, "Ignoring set language request, user is not authorized");
 618         return;
 619     }
 620
 621     // FIXME: Could use this
 622     if (greeter->priv->guest_account_authenticated)
 623     {
 624         l_debug (greeter, "Ignoring set language request for guest user");
 625         return;
 626     }
 627
 628     l_debug (greeter, "Greeter sets language %s", language);
 629     user = session_get_user (greeter->priv->authentication_session);
 630     user_set_language (user, language);
 631 }
 632
 633 static void
 634 handle_ensure_shared_dir (Greeter *greeter, const gchar *username)
 635 {
 636     gchar *dir;
 637     guint8 message[MAX_MESSAGE_LENGTH];
 638     gsize offset = 0;
 639
 640     l_debug (greeter, "Greeter requests data directory for user %s", username);
 641
 642     dir = shared_data_manager_ensure_user_dir (shared_data_manager_get_instance (), username);
 643
 644     write_header (message, MAX_MESSAGE_LENGTH, SERVER_MESSAGE_SHARED_DIR_RESULT, string_length (dir), &offset);
 645     write_string (message, MAX_MESSAGE_LENGTH, dir, &offset);
 646     write_message (greeter, message, offset);
 647
 648     g_free (dir);
 649 }
 650
 651 static guint32
 652 read_int (Greeter *greeter, gsize *offset)
 653 {
 654     guint32 value;
 655     guint8 *buffer;
 656     if (greeter->priv->n_read - *offset < sizeof (guint32))
 657     {
 658         l_warning (greeter, "Not enough space for int, need %zu, got %zu", sizeof (guint32), greeter->priv->n_read - *offset);
 659         return 0;
 660     }
 661     buffer = greeter->priv->read_buffer + *offset;
 662     value = buffer[0] << 24 | buffer[1] << 16 | buffer[2] << 8 | buffer[3];
 663     *offset += int_length ();
 664     return value;
 665 }
 666
 667 static int
 668 get_message_length (Greeter *greeter)
 669 {
 670     gsize offset;
 671     int payload_length;
 672
 673     offset = int_length ();
 674     payload_length = read_int (greeter, &offset);
 675
 676     if (HEADER_SIZE + payload_length < HEADER_SIZE)
 677     {
 678         l_warning (greeter, "Payload length of %u octets too long", payload_length);
 679         return HEADER_SIZE;
 680     }
 681
 682     return HEADER_SIZE + payload_length;
 683 }
 684
 685 static gchar *
 686 read_string_full (Greeter *greeter, gsize *offset, void* (*alloc_fn)(size_t n))
 687 {
 688     guint32 length;
 689     gchar *value;
 690
 691     length = read_int (greeter, offset);
 692     if (greeter->priv->n_read - *offset < length)
 693     {
 694         l_warning (greeter, "Not enough space for string, need %u, got %zu", length, greeter->priv->n_read - *offset);
 695         return g_strdup ("");
 696     }
 697
 698     value = (*alloc_fn) (sizeof (gchar) * (length + 1));
 699     memcpy (value, greeter->priv->read_buffer + *offset, length);
 700     value[length] = '\0';
 701     *offset += length;
 702
 703     return value;
 704 }
 705
 706 static gchar *
 707 read_string (Greeter *greeter, gsize *offset)
 708 {
 709     return read_string_full (greeter, offset, g_malloc);
 710 }
 711
 712 static gchar *
 713 read_secret (Greeter *greeter, gsize *offset)
 714 {
 715     if (greeter->priv->use_secure_memory)
 716         return read_string_full (greeter, offset, gcry_malloc_secure);
 717     else
 718         return read_string_full (greeter, offset, g_malloc);
 719 }
 720
 721 static gboolean
 722 read_cb (GIOChannel *source, GIOCondition condition, gpointer data)
 723 {
 724     Greeter *greeter = data;
 725     gsize n_to_read, n_read, offset;
 726     GIOStatus status;
 727     int id, i;
 728     guint32 sequence_number, n_secrets, max_secrets;
 729     gchar *version, *username, *session_name, *language;
 730     gchar **secrets;
 731     GError *error = NULL;
 732
 733     if (condition == G_IO_HUP)
 734     {
 735         l_debug (greeter, "Greeter closed communication channel");
 736         greeter->priv->from_greeter_watch = 0;
 737         return FALSE;
 738     }
 739
 740     n_to_read = HEADER_SIZE;
 741     if (greeter->priv->n_read >= HEADER_SIZE)
 742     {
 743         n_to_read = get_message_length (greeter);
 744         if (n_to_read <= HEADER_SIZE)
 745         {
 746             greeter->priv->from_greeter_watch = 0;
 747             return FALSE;
 748         }
 749     }
 750
 751     status = g_io_channel_read_chars (greeter->priv->from_greeter_channel,
 752                                       (gchar *) greeter->priv->read_buffer + greeter->priv->n_read,
 753                                       n_to_read - greeter->priv->n_read,
 754                                       &n_read,
 755                                       &error);
 756     if (error)
 757         l_warning (greeter, "Error reading from greeter: %s", error->message);
 758     g_clear_error (&error);
 759     if (status != G_IO_STATUS_NORMAL)
 760         return TRUE;
 761
 762     greeter->priv->n_read += n_read;
 763     if (greeter->priv->n_read != n_to_read)
 764         return TRUE;
 765
 766     /* If have header, rerun for content */
 767     if (greeter->priv->n_read == HEADER_SIZE)
 768     {
 769         n_to_read = get_message_length (greeter);
 770         if (n_to_read > HEADER_SIZE)
 771         {
 772             greeter->priv->read_buffer = secure_realloc (greeter, greeter->priv->read_buffer, n_to_read);
 773             read_cb (source, condition, greeter);
 774             return TRUE;
 775         }
 776     }
 777
 778     offset = 0;
 779     id = read_int (greeter, &offset);
 780     read_int (greeter, &offset);
 781     switch (id)
 782     {
 783     case GREETER_MESSAGE_CONNECT:
 784         version = read_string (greeter, &offset);
 785         handle_connect (greeter, version);
 786         g_free (version);
 787         break;
 788     case GREETER_MESSAGE_AUTHENTICATE:
 789         sequence_number = read_int (greeter, &offset);
 790         username = read_string (greeter, &offset);
 791         handle_login (greeter, sequence_number, username);
 792         g_free (username);
 793         break;
 794     case GREETER_MESSAGE_AUTHENTICATE_AS_GUEST:
 795         sequence_number = read_int (greeter, &offset);
 796         handle_login_as_guest (greeter, sequence_number);
 797         break;
 798     case GREETER_MESSAGE_AUTHENTICATE_REMOTE:
 799         sequence_number = read_int (greeter, &offset);
 800         session_name = read_string (greeter, &offset);
 801         username = read_string (greeter, &offset);
 802         handle_login_remote (greeter, session_name, username, sequence_number);
 803         break;
 804     case GREETER_MESSAGE_CONTINUE_AUTHENTICATION:
 805         n_secrets = read_int (greeter, &offset);
 806         max_secrets = (G_MAXUINT32 - 1) / sizeof (gchar *);
 807         if (n_secrets > max_secrets)
 808         {
 809             l_warning (greeter, "Array length of %u elements too long", n_secrets);
 810             greeter->priv->from_greeter_watch = 0;
 811             return FALSE;
 812         }
 813         secrets = g_malloc (sizeof (gchar *) * (n_secrets + 1));
 814         for (i = 0; i < n_secrets; i++)
 815             secrets[i] = read_secret (greeter, &offset);
 816         secrets[i] = NULL;
 817         handle_continue_authentication (greeter, secrets);
 818         for (i = 0; i < n_secrets; i++)
 819             secure_free (greeter, secrets[i]);
 820         g_free (secrets);
 821         break;
 822     case GREETER_MESSAGE_CANCEL_AUTHENTICATION:
 823         handle_cancel_authentication (greeter);
 824         break;
 825     case GREETER_MESSAGE_START_SESSION:
 826         session_name = read_string (greeter, &offset);
 827         handle_start_session (greeter, session_name);
 828         g_free (session_name);
 829         break;
 830     case GREETER_MESSAGE_SET_LANGUAGE:
 831         language = read_string (greeter, &offset);
 832         handle_set_language (greeter, language);
 833         g_free (language);
 834         break;
 835     case GREETER_MESSAGE_ENSURE_SHARED_DIR:
 836         username = read_string (greeter, &offset);
 837         handle_ensure_shared_dir (greeter, username);
 838         g_free (username);
 839         break;
 840     default:
 841         l_warning (greeter, "Unknown message from greeter: %d", id);
 842         break;
 843     }
 844
 845     greeter->priv->n_read = 0;
 846
 847     return TRUE;
 848 }
 849
 850 gboolean
 851 greeter_get_guest_authenticated (Greeter *greeter)
 852 {
 853     g_return_val_if_fail (greeter != NULL, FALSE);
 854     return greeter->priv->guest_account_authenticated;
 855 }
 856
 857 Session *
 858 greeter_get_authentication_session (Greeter *greeter)
 859 {
 860     g_return_val_if_fail (greeter != NULL, NULL);
 861     return greeter->priv->authentication_session;
 862 }
 863
 864 gboolean
 865 greeter_get_start_session (Greeter *greeter)
 866 {
 867     g_return_val_if_fail (greeter != NULL, FALSE);
 868     return greeter->priv->start_session;
 869 }
 870
 871 const gchar *
 872 greeter_get_active_username (Greeter *greeter)
 873 {
 874     g_return_val_if_fail (greeter != NULL, NULL);
 875     return greeter->priv->active_username;
 876 }
 877
 878 static gboolean
 879 greeter_start (Session *session)
 880 {
 881     Greeter *greeter = GREETER (session);
 882     int to_greeter_pipe[2], from_greeter_pipe[2];
 883     gboolean result = FALSE;
 884     gchar *value;
 885
 886     /* Create a pipe to talk with the greeter */
 887     if (pipe (to_greeter_pipe) != 0 || pipe (from_greeter_pipe) != 0)
 888     {
 889         g_warning ("Failed to create pipes: %s", strerror (errno));
 890         return FALSE;
 891     }
 892     greeter->priv->to_greeter_channel = g_io_channel_unix_new (to_greeter_pipe[1]);
 893     g_io_channel_set_encoding (greeter->priv->to_greeter_channel, NULL, NULL);
 894     greeter->priv->from_greeter_channel = g_io_channel_unix_new (from_greeter_pipe[0]);
 895     g_io_channel_set_encoding (greeter->priv->from_greeter_channel, NULL, NULL);
 896     g_io_channel_set_buffered (greeter->priv->from_greeter_channel, FALSE);
 897     greeter->priv->from_greeter_watch = g_io_add_watch (greeter->priv->from_greeter_channel, G_IO_IN | G_IO_HUP, read_cb, greeter);
 898
 899     /* Let the greeter session know how to communicate with the daemon */
 900     value = g_strdup_printf ("%d", from_greeter_pipe[1]);
 901     session_set_env (SESSION (greeter), "LIGHTDM_TO_SERVER_FD", value);
 902     g_free (value);
 903     value = g_strdup_printf ("%d", to_greeter_pipe[0]);
 904     session_set_env (SESSION (greeter), "LIGHTDM_FROM_SERVER_FD", value);
 905     g_free (value);
 906
 907     /* Don't allow the daemon end of the pipes to be accessed in child processes */
 908     fcntl (to_greeter_pipe[1], F_SETFD, FD_CLOEXEC);
 909     fcntl (from_greeter_pipe[0], F_SETFD, FD_CLOEXEC);
 910
 911     result = SESSION_CLASS (greeter_parent_class)->start (session);
 912
 913     /* Close the session ends of the pipe */
 914     close (to_greeter_pipe[0]);
 915     close (from_greeter_pipe[1]);
 916
 917     return result;
 918 }
 919
 920 static Session *
 921 greeter_real_create_session (Greeter *greeter)
 922 {
 923     return NULL;
 924 }
 925
 926 static gboolean
 927 greeter_real_start_session (Greeter *greeter, SessionType type, const gchar *session)
 928 {
 929     return FALSE;
 930 }
 931
 932 static void
 933 greeter_stop (Session *session)
 934 {
 935     Greeter *greeter = GREETER (session);
 936
 937     /* Stop any events occurring after we've stopped */
 938     if (greeter->priv->authentication_session)
 939         g_signal_handlers_disconnect_matched (greeter->priv->authentication_session, G_SIGNAL_MATCH_DATA, 0, 0, NULL, NULL, greeter);
 940
 941     SESSION_CLASS (greeter_parent_class)->stop (session);
 942 }
 943
 944 static void
 945 greeter_init (Greeter *greeter)
 946 {
 947     greeter->priv = G_TYPE_INSTANCE_GET_PRIVATE (greeter, GREETER_TYPE, GreeterPrivate);
 948     greeter->priv->read_buffer = secure_malloc (greeter, HEADER_SIZE);
 949     greeter->priv->hints = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, g_free);
 950     greeter->priv->use_secure_memory = config_get_boolean (config_get_instance (), "LightDM", "lock-memory");
 951 }
 952
 953 static void
 954 greeter_finalize (GObject *object)
 955 {
 956     Greeter *self;
 957
 958     self = GREETER (object);
 959
 960     g_free (self->priv->pam_service);
 961     g_free (self->priv->autologin_pam_service);
 962     secure_free (self, self->priv->read_buffer);
 963     g_hash_table_unref (self->priv->hints);
 964     g_free (self->priv->remote_session);
 965     g_free (self->priv->active_username);
 966     if (self->priv->authentication_session)
 967     {
 968         g_signal_handlers_disconnect_matched (self->priv->authentication_session, G_SIGNAL_MATCH_DATA, 0, 0, NULL, NULL, self);
 969         g_object_unref (self->priv->authentication_session);
 970     }
 971     if (self->priv->to_greeter_channel)
 972         g_io_channel_unref (self->priv->to_greeter_channel);
 973     if (self->priv->from_greeter_channel)
 974         g_io_channel_unref (self->priv->from_greeter_channel);
 975     if (self->priv->from_greeter_watch)
 976         g_source_remove (self->priv->from_greeter_watch);
 977
 978     G_OBJECT_CLASS (greeter_parent_class)->finalize (object);
 979 }
 980
 981 static void
 982 greeter_set_property (GObject      *object,
 983                       guint         prop_id,
 984                       const GValue *value,
 985                       GParamSpec   *pspec)
 986 {
 987     G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
 988 }
 989
 990 static void
 991 greeter_get_property (GObject    *object,
 992                       guint       prop_id,
 993                       GValue     *value,
 994                       GParamSpec *pspec)
 995 {
 996     Greeter *greeter = GREETER (object);
 997
 998     switch (prop_id) {
 999     case PROP_ACTIVE_USERNAME:
1000         g_value_set_string (value, greeter_get_active_username (greeter));
1001         break;
1002     default:
1003         G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
1004         break;
1005     }
1006 }
1007
1008 static void
1009 greeter_class_init (GreeterClass *klass)
1010 {
1011     SessionClass *session_class = SESSION_CLASS (klass);
1012     GObjectClass *object_class = G_OBJECT_CLASS (klass);
1013
1014     klass->create_session = greeter_real_create_session;
1015     klass->start_session = greeter_real_start_session;
1016     session_class->start = greeter_start;
1017     session_class->stop = greeter_stop;
1018     object_class->finalize = greeter_finalize;
1019     object_class->get_property = greeter_get_property;
1020     object_class->set_property = greeter_set_property;
1021
1022     signals[CONNECTED] =
1023         g_signal_new ("connected",
1024                       G_TYPE_FROM_CLASS (klass),
1025                       G_SIGNAL_RUN_LAST,
1026                       G_STRUCT_OFFSET (GreeterClass, connected),
1027                       NULL, NULL,
1028                       NULL,
1029                       G_TYPE_NONE, 0);
1030
1031     signals[CREATE_SESSION] =
1032         g_signal_new ("create-session",
1033                       G_TYPE_FROM_CLASS (klass),
1034                       G_SIGNAL_RUN_LAST,
1035                       G_STRUCT_OFFSET (GreeterClass, create_session),
1036                       g_signal_accumulator_first_wins,
1037                       NULL,
1038                       NULL,
1039                       SESSION_TYPE, 0);
1040
1041     signals[START_SESSION] =
1042         g_signal_new ("start-session",
1043                       G_TYPE_FROM_CLASS (klass),
1044                       G_SIGNAL_RUN_LAST,
1045                       G_STRUCT_OFFSET (GreeterClass, start_session),
1046                       g_signal_accumulator_true_handled,
1047                       NULL,
1048                       NULL,
1049                       G_TYPE_BOOLEAN, 2, G_TYPE_INT, G_TYPE_STRING);
1050
1051     g_object_class_install_property (object_class,
1052                                      PROP_ACTIVE_USERNAME,
1053                                      g_param_spec_string ("active-username",
1054                                                           "active-username",
1055                                                           "Active username",
1056                                                           NULL,
1057                                                           G_PARAM_READABLE));
1058
1059     g_type_class_add_private (klass, sizeof (GreeterPrivate));
1060 }