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