lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2
   3 Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
   4   Free Software Foundation, Inc.
   5
   6 Author: Colin Walters <walters@debian.org>
   7
   8 This file is part of GNU Emacs.
   9
  10 GNU Emacs is free software: you can redistribute it and/or modify
  11 it under the terms of the GNU General Public License as published by
  12 the Free Software Foundation, either version 3 of the License, or
  13 (at your option) any later version.
  14
  15 GNU Emacs is distributed in the hope that it will be useful,
  16 but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 GNU General Public License for more details.
  19
  20 You should have received a copy of the GNU General Public License
  21 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  22
  23
  24 /* This program allows a game to securely and atomically update a
  25    score file.  It should be installed setuid, owned by an appropriate
  26    user like `games'.
  27
  28    Alternatively, it can be compiled without HAVE_SHARED_GAME_DIR
  29    defined, and in that case it will store scores in the user's home
  30    directory (it should NOT be setuid).
  31
  32    Created 2002/03/22.
  33 */
  34
  35 #include <config.h>
  36
  37 #ifdef HAVE_UNISTD_H
  38 #include <unistd.h>
  39 #endif
  40 #include <errno.h>
  41 #ifdef HAVE_STRING_H
  42 #include <string.h>
  43 #endif
  44 #ifdef HAVE_STDLIB_H
  45 #include <stdlib.h>
  46 #endif
  47 #include <stdio.h>
  48 #include <time.h>
  49 #include <pwd.h>
  50 #include <ctype.h>
  51 #ifdef HAVE_FCNTL_H
  52 #include <fcntl.h>
  53 #endif
  54 #ifdef STDC_HEADERS
  55 #include <stdarg.h>
  56 #endif
  57 #include <sys/stat.h>
  58
  59 /* Needed for SunOS4, for instance.  */
  60 extern char *optarg;
  61 extern int optind, opterr;
  62
  63 int usage (int err) NO_RETURN;
  64
  65 #define MAX_ATTEMPTS 5
  66 #define MAX_SCORES 200
  67 #define MAX_DATA_LEN 1024
  68
  69 #ifndef HAVE_DIFFTIME
  70 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  71 #define difftime(t1, t0) (double)((t1) - (t0))
  72 #endif
  73
  74 int
  75 usage (int err)
  76 {
  77   fprintf (stdout, "Usage: update-game-score [-m MAX ] [ -r ] game/scorefile SCORE DATA\n");
  78   fprintf (stdout, "       update-game-score -h\n");
  79   fprintf (stdout, " -h\t\tDisplay this help.\n");
  80   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  81   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  82   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  83   exit (err);
  84 }
  85
  86 int lock_file (const char *filename, void **state);
  87 int unlock_file (const char *filename, void *state);
  88
  89 struct score_entry
  90 {
  91   long score;
  92   char *username;
  93   char *data;
  94 };
  95
  96 int read_scores (const char *filename, struct score_entry **scores,
  97                  int *count);
  98 int push_score (struct score_entry **scores, int *count,
  99                 int newscore, char *username, char *newdata);
 100 void sort_scores (struct score_entry *scores, int count, int reverse);
 101 int write_scores (const char *filename, const struct score_entry *scores,
 102                   int count);
 103
 104 void lose (const char *msg) NO_RETURN;
 105
 106 void
 107 lose (const char *msg)
 108 {
 109   fprintf (stderr, "%s\n", msg);
 110   exit (EXIT_FAILURE);
 111 }
 112
 113 void lose_syserr (const char *msg) NO_RETURN;
 114
 115 /* Taken from sysdep.c.  */
 116 #ifndef HAVE_STRERROR
 117 #ifndef WINDOWSNT
 118 char *
 119 strerror (errnum)
 120      int errnum;
 121 {
 122   extern char *sys_errlist[];
 123   extern int sys_nerr;
 124
 125   if (errnum >= 0 && errnum < sys_nerr)
 126     return sys_errlist[errnum];
 127   return (char *) "Unknown error";
 128 }
 129 #endif /* not WINDOWSNT */
 130 #endif /* ! HAVE_STRERROR */
 131
 132 void
 133 lose_syserr (const char *msg)
 134 {
 135   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
 136   exit (EXIT_FAILURE);
 137 }
 138
 139 char *
 140 get_user_id (void)
 141 {
 142   char *name;
 143   struct passwd *buf = getpwuid (getuid ());
 144   if (!buf)
 145     {
 146       int count = 1;
 147       int uid = (int) getuid ();
 148       int tuid = uid;
 149       while (tuid /= 10)
 150         count++;
 151       name = malloc (count+1);
 152       if (!name)
 153         return NULL;
 154       sprintf (name, "%d", uid);
 155       return name;
 156     }
 157   return buf->pw_name;
 158 }
 159
 160 const char *
 161 get_prefix (int running_suid, const char *user_prefix)
 162 {
 163   if (!running_suid && user_prefix == NULL)
 164     lose ("Not using a shared game directory, and no prefix given.");
 165   if (running_suid)
 166     {
 167 #ifdef HAVE_SHARED_GAME_DIR
 168       return HAVE_SHARED_GAME_DIR;
 169 #else
 170       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 171 #endif
 172     }
 173   return user_prefix;
 174 }
 175
 176 int
 177 main (int argc, char **argv)
 178 {
 179   int c, running_suid;
 180   void *lockstate;
 181   char *user_id, *scorefile;
 182   const char *prefix, *user_prefix = NULL;
 183   struct stat buf;
 184   struct score_entry *scores;
 185   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 186   char *newdata;
 187
 188   srand (time (0));
 189
 190   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 191     switch (c)
 192       {
 193       case 'h':
 194         usage (EXIT_SUCCESS);
 195         break;
 196       case 'd':
 197         user_prefix = optarg;
 198         break;
 199       case 'r':
 200         reverse = 1;
 201         break;
 202       case 'm':
 203         max = atoi (optarg);
 204         if (max > MAX_SCORES)
 205           max = MAX_SCORES;
 206         break;
 207       default:
 208         usage (EXIT_FAILURE);
 209       }
 210
 211   if (optind+3 != argc)
 212     usage (EXIT_FAILURE);
 213
 214   running_suid = (getuid () != geteuid ());
 215
 216   prefix = get_prefix (running_suid, user_prefix);
 217
 218   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 219   if (!scorefile)
 220     lose_syserr ("Couldn't allocate score file");
 221
 222   strcpy (scorefile, prefix);
 223   strcat (scorefile, "/");
 224   strcat (scorefile, argv[optind]);
 225   newscore = atoi (argv[optind+1]);
 226   newdata = argv[optind+2];
 227   if (strlen (newdata) > MAX_DATA_LEN)
 228     newdata[MAX_DATA_LEN] = '\0';
 229
 230   user_id = get_user_id ();
 231   if (user_id == NULL)
 232     lose_syserr ("Couldn't determine user id");
 233
 234   if (stat (scorefile, &buf) < 0)
 235     lose_syserr ("Failed to access scores file");
 236
 237   if (lock_file (scorefile, &lockstate) < 0)
 238     lose_syserr ("Failed to lock scores file");
 239
 240   if (read_scores (scorefile, &scores, &scorecount) < 0)
 241     {
 242       unlock_file (scorefile, lockstate);
 243       lose_syserr ("Failed to read scores file");
 244     }
 245   push_score (&scores, &scorecount, newscore, user_id, newdata);
 246   sort_scores (scores, scorecount, reverse);
 247   /* Limit the number of scores.  If we're using reverse sorting, then
 248      we should increment the beginning of the array, to skip over the
 249      *smallest* scores.  Otherwise, we just decrement the number of
 250      scores, since the smallest will be at the end. */
 251   if (scorecount > MAX_SCORES)
 252     scorecount -= (scorecount - MAX_SCORES);
 253   if (reverse)
 254     scores += (scorecount - MAX_SCORES);
 255   if (write_scores (scorefile, scores, scorecount) < 0)
 256     {
 257       unlock_file (scorefile, lockstate);
 258       lose_syserr ("Failed to write scores file");
 259     }
 260   unlock_file (scorefile, lockstate);
 261   exit (EXIT_SUCCESS);
 262 }
 263
 264 int
 265 read_score (FILE *f, struct score_entry *score)
 266 {
 267   int c;
 268   if (feof (f))
 269     return 1;
 270   while ((c = getc (f)) != EOF
 271          && isdigit (c))
 272     {
 273       score->score *= 10;
 274       score->score += (c-48);
 275     }
 276   while ((c = getc (f)) != EOF
 277          && isspace (c))
 278     ;
 279   if (c == EOF)
 280     return -1;
 281   ungetc (c, f);
 282 #ifdef HAVE_GETDELIM
 283   {
 284     size_t count = 0;
 285     if (getdelim (&score->username, &count, ' ', f) < 1
 286         || score->username == NULL)
 287       return -1;
 288     /* Trim the space */
 289     score->username[strlen (score->username)-1] = '\0';
 290   }
 291 #else
 292   {
 293     int unameread = 0;
 294     int unamelen = 30;
 295     char *username = malloc (unamelen);
 296     if (!username)
 297       return -1;
 298
 299     while ((c = getc (f)) != EOF
 300            && !isspace (c))
 301       {
 302         if (unameread >= unamelen-1)
 303           if (!(username = realloc (username, unamelen *= 2)))
 304             return -1;
 305         username[unameread] = c;
 306         unameread++;
 307       }
 308     if (c == EOF)
 309       return -1;
 310     username[unameread] = '\0';
 311     score->username = username;
 312   }
 313 #endif
 314 #ifdef HAVE_GETLINE
 315   score->data = NULL;
 316   errno = 0;
 317   {
 318     size_t len;
 319     if (getline (&score->data, &len, f) < 0)
 320       return -1;
 321     score->data[strlen (score->data)-1] = '\0';
 322   }
 323 #else
 324   {
 325     int cur = 0;
 326     int len = 16;
 327     char *buf = malloc (len);
 328     if (!buf)
 329       return -1;
 330     while ((c = getc (f)) != EOF
 331            && c != '\n')
 332       {
 333         if (cur >= len-1)
 334           {
 335             if (!(buf = realloc (buf, len *= 2)))
 336               return -1;
 337           }
 338         buf[cur] = c;
 339         cur++;
 340       }
 341     score->data = buf;
 342     score->data[cur] = '\0';
 343   }
 344 #endif
 345   return 0;
 346 }
 347
 348 int
 349 read_scores (const char *filename, struct score_entry **scores, int *count)
 350 {
 351   int readval, scorecount, cursize;
 352   struct score_entry *ret;
 353   FILE *f = fopen (filename, "r");
 354   if (!f)
 355     return -1;
 356   scorecount = 0;
 357   cursize = 16;
 358   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 359   if (!ret)
 360     return -1;
 361   while ((readval = read_score (f, &ret[scorecount])) == 0)
 362     {
 363       /* We encoutered an error */
 364       if (readval < 0)
 365         return -1;
 366       scorecount++;
 367       if (scorecount >= cursize)
 368         {
 369           cursize *= 2;
 370           ret = (struct score_entry *)
 371             realloc (ret, (sizeof (struct score_entry) * cursize));
 372           if (!ret)
 373             return -1;
 374         }
 375     }
 376   *count = scorecount;
 377   *scores = ret;
 378   return 0;
 379 }
 380
 381 int
 382 score_compare (const void *a, const void *b)
 383 {
 384   const struct score_entry *sa = (const struct score_entry *) a;
 385   const struct score_entry *sb = (const struct score_entry *) b;
 386   return (sb->score > sa->score) - (sb->score < sa->score);
 387 }
 388
 389 int
 390 score_compare_reverse (const void *a, const void *b)
 391 {
 392   const struct score_entry *sa = (const struct score_entry *) a;
 393   const struct score_entry *sb = (const struct score_entry *) b;
 394   return (sa->score > sb->score) - (sa->score < sb->score);
 395 }
 396
 397 int
 398 push_score (struct score_entry **scores, int *count, int newscore, char *username, char *newdata)
 399 {
 400  struct score_entry *newscores
 401    = (struct score_entry *) realloc (*scores,
 402                                      sizeof (struct score_entry) * ((*count) + 1));
 403   if (!newscores)
 404     return -1;
 405   newscores[*count].score = newscore;
 406   newscores[*count].username = username;
 407   newscores[*count].data = newdata;
 408   (*count) += 1;
 409   *scores = newscores;
 410   return 0;
 411 }
 412
 413 void
 414 sort_scores (struct score_entry *scores, int count, int reverse)
 415 {
 416   qsort (scores, count, sizeof (struct score_entry),
 417         reverse ? score_compare_reverse : score_compare);
 418 }
 419
 420 int
 421 write_scores (const char *filename, const struct score_entry *scores, int count)
 422 {
 423   FILE *f;
 424   int i;
 425   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 426   if (!tempfile)
 427     return -1;
 428   strcpy (tempfile, filename);
 429   strcat (tempfile, ".tempXXXXXX");
 430 #ifdef HAVE_MKSTEMP
 431   if (mkstemp (tempfile) < 0
 432 #else
 433   if (mktemp (tempfile) != tempfile
 434 #endif
 435       || !(f = fopen (tempfile, "w")))
 436     return -1;
 437   for (i = 0; i < count; i++)
 438     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 439                 scores[i].data) < 0)
 440       return -1;
 441   fclose (f);
 442   if (rename (tempfile, filename) < 0)
 443     return -1;
 444   if (chmod (filename, 0644) < 0)
 445     return -1;
 446   return 0;
 447 }
 448
 449 int
 450 lock_file (const char *filename, void **state)
 451 {
 452   int fd;
 453   struct stat buf;
 454   int attempts = 0;
 455   const char *lockext = ".lockfile";
 456   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 457   if (!lockpath)
 458     return -1;
 459   strcpy (lockpath, filename);
 460   strcat (lockpath, lockext);
 461   *state = lockpath;
 462  trylock:
 463   attempts++;
 464   /* If the lock is over an hour old, delete it. */
 465   if (stat (lockpath, &buf) == 0
 466       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 467     unlink (lockpath);
 468   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 469   if (fd < 0)
 470     {
 471       if (errno == EEXIST)
 472         {
 473           /* Break the lock; we won't corrupt the file, but we might
 474              lose some scores. */
 475           if (attempts > MAX_ATTEMPTS)
 476             {
 477               unlink (lockpath);
 478               attempts = 0;
 479             }
 480           sleep ((rand () % 2)+1);
 481           goto trylock;
 482         }
 483       else
 484         return -1;
 485     }
 486   close (fd);
 487   return 0;
 488 }
 489
 490 int
 491 unlock_file (const char *filename, void *state)
 492 {
 493   char *lockpath = (char *) state;
 494   int ret = unlink (lockpath);
 495   int saved_errno = errno;
 496   free (lockpath);
 497   errno = saved_errno;
 498   return ret;
 499 }
 500
 501 /* arch-tag: 2bf5c52e-4beb-463a-954e-c58b9c64736b
 502    (do not change this comment) */
 503
 504 /* update-game-score.c ends here */