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