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