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