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