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
   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 is 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 #define MAX_ATTEMPTS 5
  64 #define MAX_SCORES 200
  65 #define MAX_DATA_LEN 1024
  66
  67 /* Declare the prototype for a general external function.  */
  68 #if defined (PROTOTYPES) || defined (WINDOWSNT)
  69 #define P_(proto) proto
  70 #else
  71 #define P_(proto) ()
  72 #endif
  73
  74 #ifndef HAVE_DIFFTIME
  75 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  76 #define difftime(t1, t0) (double)((t1) - (t0))
  77 #endif
  78
  79 int
  80 usage (err)
  81      int err;
  82 {
  83   fprintf (stdout, "Usage: update-game-score [-m MAX ] [ -r ] game/scorefile SCORE DATA\n");
  84   fprintf (stdout, "       update-game-score -h\n");
  85   fprintf (stdout, " -h\t\tDisplay this help.\n");
  86   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  87   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  88   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  89   exit (err);
  90 }
  91
  92 int lock_file P_ ((const char *filename, void **state));
  93 int unlock_file P_ ((const char *filename, void *state));
  94
  95 struct score_entry
  96 {
  97   long score;
  98   char *username;
  99   char *data;
 100 };
 101
 102 int read_scores P_ ((const char *filename, struct score_entry **scores,
 103                      int *count));
 104 int push_score P_ ((struct score_entry **scores, int *count,
 105                     int newscore, char *username, char *newdata));
 106 void sort_scores P_ ((struct score_entry *scores, int count, int reverse));
 107 int write_scores P_ ((const char *filename, const struct score_entry *scores,
 108                       int count));
 109
 110 void lose P_ ((const char *msg)) NO_RETURN;
 111
 112 void
 113 lose (msg)
 114      const char *msg;
 115 {
 116   fprintf (stderr, "%s\n", msg);
 117   exit (EXIT_FAILURE);
 118 }
 119
 120 void lose_syserr P_ ((const char *msg)) NO_RETURN;
 121
 122 /* Taken from sysdep.c.  */
 123 #ifndef HAVE_STRERROR
 124 #ifndef WINDOWSNT
 125 char *
 126 strerror (errnum)
 127      int errnum;
 128 {
 129   extern char *sys_errlist[];
 130   extern int sys_nerr;
 131
 132   if (errnum >= 0 && errnum < sys_nerr)
 133     return sys_errlist[errnum];
 134   return (char *) "Unknown error";
 135 }
 136 #endif /* not WINDOWSNT */
 137 #endif /* ! HAVE_STRERROR */
 138
 139 void
 140 lose_syserr (msg)
 141      const char *msg;
 142 {
 143   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
 144   exit (EXIT_FAILURE);
 145 }
 146
 147 char *
 148 get_user_id P_ ((void))
 149 {
 150   char *name;
 151   struct passwd *buf = getpwuid (getuid ());
 152   if (!buf)
 153     {
 154       int count = 1;
 155       int uid = (int) getuid ();
 156       int tuid = uid;
 157       while (tuid /= 10)
 158         count++;
 159       name = malloc (count+1);
 160       if (!name)
 161         return NULL;
 162       sprintf (name, "%d", uid);
 163       return name;
 164     }
 165   return buf->pw_name;
 166 }
 167
 168 char *
 169 get_prefix (running_suid, user_prefix)
 170      int running_suid;
 171      char *user_prefix;
 172 {
 173   if (!running_suid && user_prefix == NULL)
 174     lose ("Not using a shared game directory, and no prefix given.");
 175   if (running_suid)
 176     {
 177 #ifdef HAVE_SHARED_GAME_DIR
 178       return HAVE_SHARED_GAME_DIR;
 179 #else
 180       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 181 #endif
 182     }
 183   return user_prefix;
 184 }
 185
 186 int
 187 main (argc, argv)
 188      int argc;
 189      char **argv;
 190 {
 191   int c, running_suid;
 192   void *lockstate;
 193   char *user_id, *scorefile, *prefix, *user_prefix = NULL;
 194   struct stat buf;
 195   struct score_entry *scores;
 196   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 197   char *newdata;
 198
 199   srand (time (0));
 200
 201   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 202     switch (c)
 203       {
 204       case 'h':
 205         usage (EXIT_SUCCESS);
 206         break;
 207       case 'd':
 208         user_prefix = optarg;
 209         break;
 210       case 'r':
 211         reverse = 1;
 212         break;
 213       case 'm':
 214         max = atoi (optarg);
 215         if (max > MAX_SCORES)
 216           max = MAX_SCORES;
 217         break;
 218       default:
 219         usage (EXIT_FAILURE);
 220       }
 221
 222   if (optind+3 != argc)
 223     usage (EXIT_FAILURE);
 224
 225   running_suid = (getuid () != geteuid ());
 226
 227   prefix = get_prefix (running_suid, user_prefix);
 228
 229   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 230   if (!scorefile)
 231     lose_syserr ("Couldn't allocate score file");
 232
 233   strcpy (scorefile, prefix);
 234   strcat (scorefile, "/");
 235   strcat (scorefile, argv[optind]);
 236   newscore = atoi (argv[optind+1]);
 237   newdata = argv[optind+2];
 238   if (strlen (newdata) > MAX_DATA_LEN)
 239     newdata[MAX_DATA_LEN] = '\0';
 240
 241   user_id = get_user_id ();
 242   if (user_id == NULL)
 243     lose_syserr ("Couldn't determine user id");
 244
 245   if (stat (scorefile, &buf) < 0)
 246     lose_syserr ("Failed to access scores file");
 247
 248   if (lock_file (scorefile, &lockstate) < 0)
 249     lose_syserr ("Failed to lock scores file");
 250
 251   if (read_scores (scorefile, &scores, &scorecount) < 0)
 252     {
 253       unlock_file (scorefile, lockstate);
 254       lose_syserr ("Failed to read scores file");
 255     }
 256   push_score (&scores, &scorecount, newscore, user_id, newdata);
 257   /* Limit the number of scores.  If we're using reverse sorting, then
 258      we should increment the beginning of the array, to skip over the
 259      *smallest* scores.  Otherwise, we just decrement the number of
 260      scores, since the smallest will be at the end. */
 261   if (scorecount > MAX_SCORES)
 262     scorecount -= (scorecount - MAX_SCORES);
 263     if (reverse)
 264       scores += (scorecount - MAX_SCORES);
 265   sort_scores (scores, scorecount, reverse);
 266   if (write_scores (scorefile, scores, scorecount) < 0)
 267     {
 268       unlock_file (scorefile, lockstate);
 269       lose_syserr ("Failed to write scores file");
 270     }
 271   unlock_file (scorefile, lockstate);
 272   exit (EXIT_SUCCESS);
 273 }
 274
 275 int
 276 read_score (f, score)
 277      FILE *f;
 278      struct score_entry *score;
 279 {
 280   int c;
 281   if (feof (f))
 282     return 1;
 283   while ((c = getc (f)) != EOF
 284          && isdigit (c))
 285     {
 286       score->score *= 10;
 287       score->score += (c-48);
 288     }
 289   while ((c = getc (f)) != EOF
 290          && isspace (c))
 291     ;
 292   if (c == EOF)
 293     return -1;
 294   ungetc (c, f);
 295 #ifdef HAVE_GETDELIM
 296   {
 297     size_t count = 0;
 298     if (getdelim (&score->username, &count, ' ', f) < 1
 299         || score->username == NULL)
 300       return -1;
 301     /* Trim the space */
 302     score->username[strlen (score->username)-1] = '\0';
 303   }
 304 #else
 305   {
 306     int unameread = 0;
 307     int unamelen = 30;
 308     char *username = malloc (unamelen);
 309     if (!username)
 310       return -1;
 311
 312     while ((c = getc (f)) != EOF
 313            && !isspace (c))
 314       {
 315         if (unameread >= unamelen-1)
 316           if (!(username = realloc (username, unamelen *= 2)))
 317             return -1;
 318         username[unameread] = c;
 319         unameread++;
 320       }
 321     if (c == EOF)
 322       return -1;
 323     username[unameread] = '\0';
 324     score->username = username;
 325   }
 326 #endif
 327 #ifdef HAVE_GETLINE
 328   score->data = NULL;
 329   errno = 0;
 330   {
 331     size_t len;
 332     if (getline (&score->data, &len, f) < 0)
 333       return -1;
 334     score->data[strlen (score->data)-1] = '\0';
 335   }
 336 #else
 337   {
 338     int cur = 0;
 339     int len = 16;
 340     char *buf = malloc (len);
 341     if (!buf)
 342       return -1;
 343     while ((c = getc (f)) != EOF
 344            && c != '\n')
 345       {
 346         if (cur >= len-1)
 347           {
 348             if (!(buf = realloc (buf, len *= 2)))
 349               return -1;
 350           }
 351         buf[cur] = c;
 352         cur++;
 353       }
 354     score->data = buf;
 355     score->data[cur] = '\0';
 356   }
 357 #endif
 358   return 0;
 359 }
 360
 361 int
 362 read_scores (filename, scores, count)
 363      const char *filename;
 364      struct score_entry **scores;
 365      int *count;
 366 {
 367   int readval, scorecount, cursize;
 368   struct score_entry *ret;
 369   FILE *f = fopen (filename, "r");
 370   if (!f)
 371     return -1;
 372   scorecount = 0;
 373   cursize = 16;
 374   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 375   if (!ret)
 376     return -1;
 377   while ((readval = read_score (f, &ret[scorecount])) == 0)
 378     {
 379       /* We encoutered an error */
 380       if (readval < 0)
 381         return -1;
 382       scorecount++;
 383       if (scorecount >= cursize)
 384         {
 385           cursize *= 2;
 386           ret = (struct score_entry *)
 387             realloc (ret, (sizeof (struct score_entry) * cursize));
 388           if (!ret)
 389             return -1;
 390         }
 391     }
 392   *count = scorecount;
 393   *scores = ret;
 394   return 0;
 395 }
 396
 397 int
 398 score_compare (a, b)
 399      const void *a;
 400      const void *b;
 401 {
 402   const struct score_entry *sa = (const struct score_entry *) a;
 403   const struct score_entry *sb = (const struct score_entry *) b;
 404   return (sb->score > sa->score) - (sb->score < sa->score);
 405 }
 406
 407 int
 408 score_compare_reverse (a, b)
 409      const void *a;
 410      const void *b;
 411 {
 412   const struct score_entry *sa = (const struct score_entry *) a;
 413   const struct score_entry *sb = (const struct score_entry *) b;
 414   return (sa->score > sb->score) - (sa->score < sb->score);
 415 }
 416
 417 int
 418 push_score (scores, count, newscore, username, newdata)
 419      struct score_entry **scores;
 420      int *count; int newscore;
 421      char *username;
 422      char *newdata;
 423 {
 424  struct score_entry *newscores
 425    = (struct score_entry *) realloc (*scores,
 426                                      sizeof (struct score_entry) * ((*count) + 1));
 427   if (!newscores)
 428     return -1;
 429   newscores[*count].score = newscore;
 430   newscores[*count].username = username;
 431   newscores[*count].data = newdata;
 432   (*count) += 1;
 433   *scores = newscores;
 434   return 0;
 435 }
 436
 437 void
 438 sort_scores (scores, count, reverse)
 439      struct score_entry *scores;
 440      int count;
 441      int reverse;
 442 {
 443   qsort (scores, count, sizeof (struct score_entry),
 444         reverse ? score_compare_reverse : score_compare);
 445 }
 446
 447 int
 448 write_scores (filename, scores, count)
 449      const char *filename;
 450      const struct score_entry * scores;
 451      int count;
 452 {
 453   FILE *f;
 454   int i;
 455   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 456   if (!tempfile)
 457     return -1;
 458   strcpy (tempfile, filename);
 459   strcat (tempfile, ".tempXXXXXX");
 460 #ifdef HAVE_MKSTEMP
 461   if (mkstemp (tempfile) < 0
 462 #else
 463   if (mktemp (tempfile) != tempfile
 464 #endif
 465       || !(f = fopen (tempfile, "w")))
 466     return -1;
 467   for (i = 0; i < count; i++)
 468     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 469                 scores[i].data) < 0)
 470       return -1;
 471   fclose (f);
 472   if (rename (tempfile, filename) < 0)
 473     return -1;
 474   if (chmod (filename, 0644) < 0)
 475     return -1;
 476   return 0;
 477 }
 478
 479 int
 480 lock_file (filename, state)
 481   const char *filename;
 482   void **state;
 483 {
 484   int fd;
 485   struct stat buf;
 486   int attempts = 0;
 487   char *lockext = ".lockfile";
 488   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 489   if (!lockpath)
 490     return -1;
 491   strcpy (lockpath, filename);
 492   strcat (lockpath, lockext);
 493   *state = lockpath;
 494  trylock:
 495   attempts++;
 496   /* If the lock is over an hour old, delete it. */
 497   if (stat (lockpath, &buf) == 0
 498       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 499     unlink (lockpath);
 500   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 501   if (fd < 0)
 502     {
 503       if (errno == EEXIST)
 504         {
 505           /* Break the lock; we won't corrupt the file, but we might
 506              lose some scores. */
 507           if (attempts > MAX_ATTEMPTS)
 508             {
 509               unlink (lockpath);
 510               attempts = 0;
 511             }
 512           sleep ((rand () % 2)+1);
 513           goto trylock;
 514         }
 515       else
 516         return -1;
 517     }
 518   close (fd);
 519   return 0;
 520 }
 521
 522 int
 523 unlock_file (filename, state)
 524   const char *filename;
 525  void *state;
 526 {
 527   char *lockpath = (char *) state;
 528   int ret = unlink (lockpath);
 529   int saved_errno = errno;
 530   free (lockpath);
 531   errno = saved_errno;
 532   return ret;
 533 }
 534
 535 /* arch-tag: 2bf5c52e-4beb-463a-954e-c58b9c64736b
 536    (do not change this comment) */
 537
 538 /* update-game-score.c ends here */