lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2
   3 Copyright (C) 2002-2011  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
  50 /* Needed for SunOS4, for instance.  */
  51 extern char *optarg;
  52 extern int optind, opterr;
  53
  54 static int usage (int err) NO_RETURN;
  55
  56 #define MAX_ATTEMPTS 5
  57 #define MAX_SCORES 200
  58 #define MAX_DATA_LEN 1024
  59
  60 #ifndef HAVE_DIFFTIME
  61 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  62 #define difftime(t1, t0) (double)((t1) - (t0))
  63 #endif
  64
  65 static int
  66 usage (int err)
  67 {
  68   fprintf (stdout, "Usage: update-game-score [-m MAX] [-r] [-d DIR] game/scorefile SCORE DATA\n");
  69   fprintf (stdout, "       update-game-score -h\n");
  70   fprintf (stdout, " -h\t\tDisplay this help.\n");
  71   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  72   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  73   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  74   exit (err);
  75 }
  76
  77 static int lock_file (const char *filename, void **state);
  78 static int unlock_file (const char *filename, void *state);
  79
  80 struct score_entry
  81 {
  82   long score;
  83   char *username;
  84   char *data;
  85 };
  86
  87 static int read_scores (const char *filename, struct score_entry **scores,
  88                         int *count);
  89 static int push_score (struct score_entry **scores, int *count,
  90                        int newscore, char *username, char *newdata);
  91 static void sort_scores (struct score_entry *scores, int count, int reverse);
  92 static int write_scores (const char *filename,
  93                          const struct score_entry *scores, int count);
  94
  95 static void lose (const char *msg) NO_RETURN;
  96
  97 static void
  98 lose (const char *msg)
  99 {
 100   fprintf (stderr, "%s\n", msg);
 101   exit (EXIT_FAILURE);
 102 }
 103
 104 static void lose_syserr (const char *msg) NO_RETURN;
 105
 106 /* Taken from sysdep.c.  */
 107 #ifndef HAVE_STRERROR
 108 #ifndef WINDOWSNT
 109 char *
 110 strerror (int errnum)
 111 {
 112   extern char *sys_errlist[];
 113   extern int sys_nerr;
 114
 115   if (errnum >= 0 && errnum < sys_nerr)
 116     return sys_errlist[errnum];
 117   return (char *) "Unknown error";
 118 }
 119 #endif /* not WINDOWSNT */
 120 #endif /* ! HAVE_STRERROR */
 121
 122 static void
 123 lose_syserr (const char *msg)
 124 {
 125   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
 126   exit (EXIT_FAILURE);
 127 }
 128
 129 static char *
 130 get_user_id (void)
 131 {
 132   struct passwd *buf = getpwuid (getuid ());
 133   if (!buf)
 134     {
 135       long uid = getuid ();
 136       char *name = malloc (sizeof uid * CHAR_BIT / 3 + 1);
 137       if (name)
 138         sprintf (name, "%ld", uid);
 139       return name;
 140     }
 141   return buf->pw_name;
 142 }
 143
 144 static const char *
 145 get_prefix (int running_suid, const char *user_prefix)
 146 {
 147   if (!running_suid && user_prefix == NULL)
 148     lose ("Not using a shared game directory, and no prefix given.");
 149   if (running_suid)
 150     {
 151 #ifdef HAVE_SHARED_GAME_DIR
 152       return HAVE_SHARED_GAME_DIR;
 153 #else
 154       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 155 #endif
 156     }
 157   return user_prefix;
 158 }
 159
 160 int
 161 main (int argc, char **argv)
 162 {
 163   int c, running_suid;
 164   void *lockstate;
 165   char *user_id, *scorefile;
 166   const char *prefix, *user_prefix = NULL;
 167   struct stat buf;
 168   struct score_entry *scores;
 169   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 170   char *newdata;
 171
 172   srand (time (0));
 173
 174   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 175     switch (c)
 176       {
 177       case 'h':
 178         usage (EXIT_SUCCESS);
 179         break;
 180       case 'd':
 181         user_prefix = optarg;
 182         break;
 183       case 'r':
 184         reverse = 1;
 185         break;
 186       case 'm':
 187         max = atoi (optarg);
 188         if (max > MAX_SCORES)
 189           max = MAX_SCORES;
 190         break;
 191       default:
 192         usage (EXIT_FAILURE);
 193       }
 194
 195   if (optind+3 != argc)
 196     usage (EXIT_FAILURE);
 197
 198   running_suid = (getuid () != geteuid ());
 199
 200   prefix = get_prefix (running_suid, user_prefix);
 201
 202   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 203   if (!scorefile)
 204     lose_syserr ("Couldn't allocate score file");
 205
 206   strcpy (scorefile, prefix);
 207   strcat (scorefile, "/");
 208   strcat (scorefile, argv[optind]);
 209   newscore = atoi (argv[optind+1]);
 210   newdata = argv[optind+2];
 211   if (strlen (newdata) > MAX_DATA_LEN)
 212     newdata[MAX_DATA_LEN] = '\0';
 213
 214   user_id = get_user_id ();
 215   if (user_id == NULL)
 216     lose_syserr ("Couldn't determine user id");
 217
 218   if (stat (scorefile, &buf) < 0)
 219     lose_syserr ("Failed to access scores file");
 220
 221   if (lock_file (scorefile, &lockstate) < 0)
 222     lose_syserr ("Failed to lock scores file");
 223
 224   if (read_scores (scorefile, &scores, &scorecount) < 0)
 225     {
 226       unlock_file (scorefile, lockstate);
 227       lose_syserr ("Failed to read scores file");
 228     }
 229   push_score (&scores, &scorecount, newscore, user_id, newdata);
 230   sort_scores (scores, scorecount, reverse);
 231   /* Limit the number of scores.  If we're using reverse sorting, then
 232      also increment the beginning of the array, to skip over the
 233      *smallest* scores.  Otherwise, just decrementing the number of
 234      scores suffices, since the smallest is at the end. */
 235   if (scorecount > MAX_SCORES)
 236     {
 237       if (reverse)
 238         scores += (scorecount - MAX_SCORES);
 239       scorecount = MAX_SCORES;
 240     }
 241   if (write_scores (scorefile, scores, scorecount) < 0)
 242     {
 243       unlock_file (scorefile, lockstate);
 244       lose_syserr ("Failed to write scores file");
 245     }
 246   unlock_file (scorefile, lockstate);
 247   exit (EXIT_SUCCESS);
 248 }
 249
 250 static int
 251 read_score (FILE *f, struct score_entry *score)
 252 {
 253   int c;
 254   if (feof (f))
 255     return 1;
 256   while ((c = getc (f)) != EOF
 257          && isdigit (c))
 258     {
 259       score->score *= 10;
 260       score->score += (c-48);
 261     }
 262   while ((c = getc (f)) != EOF
 263          && isspace (c))
 264     ;
 265   if (c == EOF)
 266     return -1;
 267   ungetc (c, f);
 268 #ifdef HAVE_GETDELIM
 269   {
 270     size_t count = 0;
 271     if (getdelim (&score->username, &count, ' ', f) < 1
 272         || score->username == NULL)
 273       return -1;
 274     /* Trim the space */
 275     score->username[strlen (score->username)-1] = '\0';
 276   }
 277 #else
 278   {
 279     int unameread = 0;
 280     int unamelen = 30;
 281     char *username = malloc (unamelen);
 282     if (!username)
 283       return -1;
 284
 285     while ((c = getc (f)) != EOF
 286            && !isspace (c))
 287       {
 288         if (unameread >= unamelen-1)
 289           if (!(username = realloc (username, unamelen *= 2)))
 290             return -1;
 291         username[unameread] = c;
 292         unameread++;
 293       }
 294     if (c == EOF)
 295       return -1;
 296     username[unameread] = '\0';
 297     score->username = username;
 298   }
 299 #endif
 300 #ifdef HAVE_GETLINE
 301   score->data = NULL;
 302   errno = 0;
 303   {
 304     size_t len;
 305     if (getline (&score->data, &len, f) < 0)
 306       return -1;
 307     score->data[strlen (score->data)-1] = '\0';
 308   }
 309 #else
 310   {
 311     int cur = 0;
 312     int len = 16;
 313     char *buf = malloc (len);
 314     if (!buf)
 315       return -1;
 316     while ((c = getc (f)) != EOF
 317            && c != '\n')
 318       {
 319         if (cur >= len-1)
 320           {
 321             if (!(buf = realloc (buf, len *= 2)))
 322               return -1;
 323           }
 324         buf[cur] = c;
 325         cur++;
 326       }
 327     score->data = buf;
 328     score->data[cur] = '\0';
 329   }
 330 #endif
 331   return 0;
 332 }
 333
 334 static int
 335 read_scores (const char *filename, struct score_entry **scores, int *count)
 336 {
 337   int readval, scorecount, cursize;
 338   struct score_entry *ret;
 339   FILE *f = fopen (filename, "r");
 340   if (!f)
 341     return -1;
 342   scorecount = 0;
 343   cursize = 16;
 344   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 345   if (!ret)
 346     return -1;
 347   while ((readval = read_score (f, &ret[scorecount])) == 0)
 348     {
 349       /* We encountered an error.  */
 350       if (readval < 0)
 351         return -1;
 352       scorecount++;
 353       if (scorecount >= cursize)
 354         {
 355           cursize *= 2;
 356           ret = (struct score_entry *)
 357             realloc (ret, (sizeof (struct score_entry) * cursize));
 358           if (!ret)
 359             return -1;
 360         }
 361     }
 362   *count = scorecount;
 363   *scores = ret;
 364   return 0;
 365 }
 366
 367 static int
 368 score_compare (const void *a, const void *b)
 369 {
 370   const struct score_entry *sa = (const struct score_entry *) a;
 371   const struct score_entry *sb = (const struct score_entry *) b;
 372   return (sb->score > sa->score) - (sb->score < sa->score);
 373 }
 374
 375 static int
 376 score_compare_reverse (const void *a, const void *b)
 377 {
 378   const struct score_entry *sa = (const struct score_entry *) a;
 379   const struct score_entry *sb = (const struct score_entry *) b;
 380   return (sa->score > sb->score) - (sa->score < sb->score);
 381 }
 382
 383 int
 384 push_score (struct score_entry **scores, int *count, int newscore, char *username, char *newdata)
 385 {
 386  struct score_entry *newscores
 387    = (struct score_entry *) realloc (*scores,
 388                                      sizeof (struct score_entry) * ((*count) + 1));
 389   if (!newscores)
 390     return -1;
 391   newscores[*count].score = newscore;
 392   newscores[*count].username = username;
 393   newscores[*count].data = newdata;
 394   (*count) += 1;
 395   *scores = newscores;
 396   return 0;
 397 }
 398
 399 static void
 400 sort_scores (struct score_entry *scores, int count, int reverse)
 401 {
 402   qsort (scores, count, sizeof (struct score_entry),
 403         reverse ? score_compare_reverse : score_compare);
 404 }
 405
 406 static int
 407 write_scores (const char *filename, const struct score_entry *scores, int count)
 408 {
 409   FILE *f;
 410   int i;
 411   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 412   if (!tempfile)
 413     return -1;
 414   strcpy (tempfile, filename);
 415   strcat (tempfile, ".tempXXXXXX");
 416 #ifdef HAVE_MKSTEMP
 417   if (mkstemp (tempfile) < 0
 418 #else
 419   if (mktemp (tempfile) != tempfile
 420 #endif
 421       || !(f = fopen (tempfile, "w")))
 422     return -1;
 423   for (i = 0; i < count; i++)
 424     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 425                 scores[i].data) < 0)
 426       return -1;
 427   fclose (f);
 428   if (rename (tempfile, filename) < 0)
 429     return -1;
 430   if (chmod (filename, 0644) < 0)
 431     return -1;
 432   return 0;
 433 }
 434
 435 static int
 436 lock_file (const char *filename, void **state)
 437 {
 438   int fd;
 439   struct stat buf;
 440   int attempts = 0;
 441   const char *lockext = ".lockfile";
 442   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 443   if (!lockpath)
 444     return -1;
 445   strcpy (lockpath, filename);
 446   strcat (lockpath, lockext);
 447   *state = lockpath;
 448  trylock:
 449   attempts++;
 450   /* If the lock is over an hour old, delete it. */
 451   if (stat (lockpath, &buf) == 0
 452       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 453     unlink (lockpath);
 454   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 455   if (fd < 0)
 456     {
 457       if (errno == EEXIST)
 458         {
 459           /* Break the lock; we won't corrupt the file, but we might
 460              lose some scores. */
 461           if (attempts > MAX_ATTEMPTS)
 462             {
 463               unlink (lockpath);
 464               attempts = 0;
 465             }
 466           sleep ((rand () % 2)+1);
 467           goto trylock;
 468         }
 469       else
 470         return -1;
 471     }
 472   close (fd);
 473   return 0;
 474 }
 475
 476 static int
 477 unlock_file (const char *filename, void *state)
 478 {
 479   char *lockpath = (char *) state;
 480   int ret = unlink (lockpath);
 481   int saved_errno = errno;
 482   free (lockpath);
 483   errno = saved_errno;
 484   return ret;
 485 }
 486
 487
 488 /* update-game-score.c ends here */