lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2
   3 Copyright (C) 2002-2013 Free Software Foundation, Inc.
   4
   5 Author: Colin Walters <walters@debian.org>
   6
   7 This file is part of GNU Emacs.
   8
   9 GNU Emacs is free software: you can redistribute it and/or modify
  10 it under the terms of the GNU General Public License as published by
  11 the Free Software Foundation, either version 3 of the License, or
  12 (at your option) any later version.
  13
  14 GNU Emacs is distributed in the hope that it will be useful,
  15 but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 GNU General Public License for more details.
  18
  19 You should have received a copy of the GNU General Public License
  20 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22
  23 /* This program allows a game to securely and atomically update a
  24    score file.  It should be installed setuid, owned by an appropriate
  25    user like `games'.
  26
  27    Alternatively, it can be compiled without HAVE_SHARED_GAME_DIR
  28    defined, and in that case it will store scores in the user's home
  29    directory (it should NOT be setuid).
  30
  31    Created 2002/03/22.
  32 */
  33
  34 #include <config.h>
  35
  36 #include <unistd.h>
  37 #include <errno.h>
  38 #include <limits.h>
  39 #include <string.h>
  40 #include <stdlib.h>
  41 #include <stdio.h>
  42 #include <time.h>
  43 #include <pwd.h>
  44 #include <ctype.h>
  45 #ifdef HAVE_FCNTL_H
  46 #include <fcntl.h>
  47 #endif
  48 #include <sys/stat.h>
  49 #include <getopt.h>
  50
  51 #define MAX_ATTEMPTS 5
  52 #define MAX_SCORES 200
  53 #define MAX_DATA_LEN 1024
  54
  55 #ifndef HAVE_DIFFTIME
  56 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  57 #define difftime(t1, t0) (double)((t1) - (t0))
  58 #endif
  59
  60 static _Noreturn void
  61 usage (int err)
  62 {
  63   fprintf (stdout, "Usage: update-game-score [-m MAX] [-r] [-d DIR] game/scorefile SCORE DATA\n");
  64   fprintf (stdout, "       update-game-score -h\n");
  65   fprintf (stdout, " -h\t\tDisplay this help.\n");
  66   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  67   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  68   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  69   exit (err);
  70 }
  71
  72 static int lock_file (const char *filename, void **state);
  73 static int unlock_file (const char *filename, void *state);
  74
  75 struct score_entry
  76 {
  77   long score;
  78   char *username;
  79   char *data;
  80 };
  81
  82 static int read_scores (const char *filename, struct score_entry **scores,
  83                         int *count);
  84 static int push_score (struct score_entry **scores, int *count,
  85                        int newscore, char *username, char *newdata);
  86 static void sort_scores (struct score_entry *scores, int count, int reverse);
  87 static int write_scores (const char *filename,
  88                          const struct score_entry *scores, int count);
  89
  90 static _Noreturn void
  91 lose (const char *msg)
  92 {
  93   fprintf (stderr, "%s\n", msg);
  94   exit (EXIT_FAILURE);
  95 }
  96
  97 static _Noreturn void
  98 lose_syserr (const char *msg)
  99 {
 100   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
 101   exit (EXIT_FAILURE);
 102 }
 103
 104 static char *
 105 get_user_id (void)
 106 {
 107   struct passwd *buf = getpwuid (getuid ());
 108   if (!buf)
 109     {
 110       long uid = getuid ();
 111       char *name = malloc (sizeof uid * CHAR_BIT / 3 + 1);
 112       if (name)
 113         sprintf (name, "%ld", uid);
 114       return name;
 115     }
 116   return buf->pw_name;
 117 }
 118
 119 static const char *
 120 get_prefix (int running_suid, const char *user_prefix)
 121 {
 122   if (!running_suid && user_prefix == NULL)
 123     lose ("Not using a shared game directory, and no prefix given.");
 124   if (running_suid)
 125     {
 126 #ifdef HAVE_SHARED_GAME_DIR
 127       return HAVE_SHARED_GAME_DIR;
 128 #else
 129       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 130 #endif
 131     }
 132   return user_prefix;
 133 }
 134
 135 int
 136 main (int argc, char **argv)
 137 {
 138   int c, running_suid;
 139   void *lockstate;
 140   char *user_id, *scorefile;
 141   const char *prefix, *user_prefix = NULL;
 142   struct stat buf;
 143   struct score_entry *scores;
 144   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 145   char *newdata;
 146
 147   srand (time (0));
 148
 149   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 150     switch (c)
 151       {
 152       case 'h':
 153         usage (EXIT_SUCCESS);
 154         break;
 155       case 'd':
 156         user_prefix = optarg;
 157         break;
 158       case 'r':
 159         reverse = 1;
 160         break;
 161       case 'm':
 162         max = atoi (optarg);
 163         if (max > MAX_SCORES)
 164           max = MAX_SCORES;
 165         break;
 166       default:
 167         usage (EXIT_FAILURE);
 168       }
 169
 170   if (optind+3 != argc)
 171     usage (EXIT_FAILURE);
 172
 173   running_suid = (getuid () != geteuid ());
 174
 175   prefix = get_prefix (running_suid, user_prefix);
 176
 177   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 178   if (!scorefile)
 179     lose_syserr ("Couldn't allocate score file");
 180
 181   strcpy (scorefile, prefix);
 182   strcat (scorefile, "/");
 183   strcat (scorefile, argv[optind]);
 184   newscore = atoi (argv[optind+1]);
 185   newdata = argv[optind+2];
 186   if (strlen (newdata) > MAX_DATA_LEN)
 187     newdata[MAX_DATA_LEN] = '\0';
 188
 189   user_id = get_user_id ();
 190   if (user_id == NULL)
 191     lose_syserr ("Couldn't determine user id");
 192
 193   if (stat (scorefile, &buf) < 0)
 194     lose_syserr ("Failed to access scores file");
 195
 196   if (lock_file (scorefile, &lockstate) < 0)
 197     lose_syserr ("Failed to lock scores file");
 198
 199   if (read_scores (scorefile, &scores, &scorecount) < 0)
 200     {
 201       unlock_file (scorefile, lockstate);
 202       lose_syserr ("Failed to read scores file");
 203     }
 204   push_score (&scores, &scorecount, newscore, user_id, newdata);
 205   sort_scores (scores, scorecount, reverse);
 206   /* Limit the number of scores.  If we're using reverse sorting, then
 207      also increment the beginning of the array, to skip over the
 208      *smallest* scores.  Otherwise, just decrementing the number of
 209      scores suffices, since the smallest is at the end. */
 210   if (scorecount > MAX_SCORES)
 211     {
 212       if (reverse)
 213         scores += (scorecount - MAX_SCORES);
 214       scorecount = MAX_SCORES;
 215     }
 216   if (write_scores (scorefile, scores, scorecount) < 0)
 217     {
 218       unlock_file (scorefile, lockstate);
 219       lose_syserr ("Failed to write scores file");
 220     }
 221   unlock_file (scorefile, lockstate);
 222   exit (EXIT_SUCCESS);
 223 }
 224
 225 static int
 226 read_score (FILE *f, struct score_entry *score)
 227 {
 228   int c;
 229   if (feof (f))
 230     return 1;
 231   while ((c = getc (f)) != EOF
 232          && isdigit (c))
 233     {
 234       score->score *= 10;
 235       score->score += (c-48);
 236     }
 237   while ((c = getc (f)) != EOF
 238          && isspace (c))
 239     ;
 240   if (c == EOF)
 241     return -1;
 242   ungetc (c, f);
 243 #ifdef HAVE_GETDELIM
 244   {
 245     size_t count = 0;
 246     if (getdelim (&score->username, &count, ' ', f) < 1
 247         || score->username == NULL)
 248       return -1;
 249     /* Trim the space */
 250     score->username[strlen (score->username)-1] = '\0';
 251   }
 252 #else
 253   {
 254     int unameread = 0;
 255     int unamelen = 30;
 256     char *username = malloc (unamelen);
 257     if (!username)
 258       return -1;
 259
 260     while ((c = getc (f)) != EOF
 261            && !isspace (c))
 262       {
 263         if (unameread >= unamelen-1)
 264           if (!(username = realloc (username, unamelen *= 2)))
 265             return -1;
 266         username[unameread] = c;
 267         unameread++;
 268       }
 269     if (c == EOF)
 270       return -1;
 271     username[unameread] = '\0';
 272     score->username = username;
 273   }
 274 #endif
 275 #ifdef HAVE_GETLINE
 276   score->data = NULL;
 277   errno = 0;
 278   {
 279     size_t len;
 280     if (getline (&score->data, &len, f) < 0)
 281       return -1;
 282     score->data[strlen (score->data)-1] = '\0';
 283   }
 284 #else
 285   {
 286     int cur = 0;
 287     int len = 16;
 288     char *buf = malloc (len);
 289     if (!buf)
 290       return -1;
 291     while ((c = getc (f)) != EOF
 292            && c != '\n')
 293       {
 294         if (cur >= len-1)
 295           {
 296             if (!(buf = realloc (buf, len *= 2)))
 297               return -1;
 298           }
 299         buf[cur] = c;
 300         cur++;
 301       }
 302     score->data = buf;
 303     score->data[cur] = '\0';
 304   }
 305 #endif
 306   return 0;
 307 }
 308
 309 static int
 310 read_scores (const char *filename, struct score_entry **scores, int *count)
 311 {
 312   int readval, scorecount, cursize;
 313   struct score_entry *ret;
 314   FILE *f = fopen (filename, "r");
 315   if (!f)
 316     return -1;
 317   scorecount = 0;
 318   cursize = 16;
 319   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 320   if (!ret)
 321     return -1;
 322   while ((readval = read_score (f, &ret[scorecount])) == 0)
 323     {
 324       /* We encountered an error.  */
 325       if (readval < 0)
 326         return -1;
 327       scorecount++;
 328       if (scorecount >= cursize)
 329         {
 330           cursize *= 2;
 331           ret = (struct score_entry *)
 332             realloc (ret, (sizeof (struct score_entry) * cursize));
 333           if (!ret)
 334             return -1;
 335         }
 336     }
 337   *count = scorecount;
 338   *scores = ret;
 339   return 0;
 340 }
 341
 342 static int
 343 score_compare (const void *a, const void *b)
 344 {
 345   const struct score_entry *sa = (const struct score_entry *) a;
 346   const struct score_entry *sb = (const struct score_entry *) b;
 347   return (sb->score > sa->score) - (sb->score < sa->score);
 348 }
 349
 350 static int
 351 score_compare_reverse (const void *a, const void *b)
 352 {
 353   const struct score_entry *sa = (const struct score_entry *) a;
 354   const struct score_entry *sb = (const struct score_entry *) b;
 355   return (sa->score > sb->score) - (sa->score < sb->score);
 356 }
 357
 358 int
 359 push_score (struct score_entry **scores, int *count, int newscore, char *username, char *newdata)
 360 {
 361  struct score_entry *newscores
 362    = (struct score_entry *) realloc (*scores,
 363                                      sizeof (struct score_entry) * ((*count) + 1));
 364   if (!newscores)
 365     return -1;
 366   newscores[*count].score = newscore;
 367   newscores[*count].username = username;
 368   newscores[*count].data = newdata;
 369   (*count) += 1;
 370   *scores = newscores;
 371   return 0;
 372 }
 373
 374 static void
 375 sort_scores (struct score_entry *scores, int count, int reverse)
 376 {
 377   qsort (scores, count, sizeof (struct score_entry),
 378         reverse ? score_compare_reverse : score_compare);
 379 }
 380
 381 static int
 382 write_scores (const char *filename, const struct score_entry *scores, int count)
 383 {
 384   FILE *f;
 385   int i;
 386   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 387   if (!tempfile)
 388     return -1;
 389   strcpy (tempfile, filename);
 390   strcat (tempfile, ".tempXXXXXX");
 391 #ifdef HAVE_MKSTEMP
 392   if (mkstemp (tempfile) < 0
 393 #else
 394   if (mktemp (tempfile) != tempfile
 395 #endif
 396       || !(f = fopen (tempfile, "w")))
 397     return -1;
 398   for (i = 0; i < count; i++)
 399     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 400                 scores[i].data) < 0)
 401       return -1;
 402   fclose (f);
 403   if (rename (tempfile, filename) < 0)
 404     return -1;
 405   if (chmod (filename, 0644) < 0)
 406     return -1;
 407   return 0;
 408 }
 409
 410 static int
 411 lock_file (const char *filename, void **state)
 412 {
 413   int fd;
 414   struct stat buf;
 415   int attempts = 0;
 416   const char *lockext = ".lockfile";
 417   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 418   if (!lockpath)
 419     return -1;
 420   strcpy (lockpath, filename);
 421   strcat (lockpath, lockext);
 422   *state = lockpath;
 423  trylock:
 424   attempts++;
 425   /* If the lock is over an hour old, delete it. */
 426   if (stat (lockpath, &buf) == 0
 427       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 428     unlink (lockpath);
 429   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 430   if (fd < 0)
 431     {
 432       if (errno == EEXIST)
 433         {
 434           /* Break the lock; we won't corrupt the file, but we might
 435              lose some scores. */
 436           if (attempts > MAX_ATTEMPTS)
 437             {
 438               unlink (lockpath);
 439               attempts = 0;
 440             }
 441           sleep ((rand () % 2)+1);
 442           goto trylock;
 443         }
 444       else
 445         return -1;
 446     }
 447   close (fd);
 448   return 0;
 449 }
 450
 451 static int
 452 unlock_file (const char *filename, void *state)
 453 {
 454   char *lockpath = (char *) state;
 455   int ret = unlink (lockpath);
 456   int saved_errno = errno;
 457   free (lockpath);
 458   errno = saved_errno;
 459   return ret;
 460 }
 461
 462
 463 /* update-game-score.c ends here */