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, 2011
   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 #include <unistd.h>
  38 #include <errno.h>
  39 #ifdef HAVE_STRING_H
  40 #include <string.h>
  41 #endif
  42 #ifdef HAVE_STDLIB_H
  43 #include <stdlib.h>
  44 #endif
  45 #include <stdio.h>
  46 #include <time.h>
  47 #include <pwd.h>
  48 #include <ctype.h>
  49 #ifdef HAVE_FCNTL_H
  50 #include <fcntl.h>
  51 #endif
  52 #ifdef STDC_HEADERS
  53 #include <stdarg.h>
  54 #endif
  55 #include <sys/stat.h>
  56
  57 /* Needed for SunOS4, for instance.  */
  58 extern char *optarg;
  59 extern int optind, opterr;
  60
  61 int usage (int err) NO_RETURN;
  62
  63 #define MAX_ATTEMPTS 5
  64 #define MAX_SCORES 200
  65 #define MAX_DATA_LEN 1024
  66
  67 #ifndef HAVE_DIFFTIME
  68 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  69 #define difftime(t1, t0) (double)((t1) - (t0))
  70 #endif
  71
  72 int
  73 usage (int err)
  74 {
  75   fprintf (stdout, "Usage: update-game-score [-m MAX ] [ -r ] game/scorefile SCORE DATA\n");
  76   fprintf (stdout, "       update-game-score -h\n");
  77   fprintf (stdout, " -h\t\tDisplay this help.\n");
  78   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  79   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  80   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  81   exit (err);
  82 }
  83
  84 int lock_file (const char *filename, void **state);
  85 int unlock_file (const char *filename, void *state);
  86
  87 struct score_entry
  88 {
  89   long score;
  90   char *username;
  91   char *data;
  92 };
  93
  94 int read_scores (const char *filename, struct score_entry **scores,
  95                  int *count);
  96 int push_score (struct score_entry **scores, int *count,
  97                 int newscore, char *username, char *newdata);
  98 void sort_scores (struct score_entry *scores, int count, int reverse);
  99 int write_scores (const char *filename, const struct score_entry *scores,
 100                   int count);
 101
 102 void lose (const char *msg) NO_RETURN;
 103
 104 void
 105 lose (const char *msg)
 106 {
 107   fprintf (stderr, "%s\n", msg);
 108   exit (EXIT_FAILURE);
 109 }
 110
 111 void lose_syserr (const char *msg) NO_RETURN;
 112
 113 /* Taken from sysdep.c.  */
 114 #ifndef HAVE_STRERROR
 115 #ifndef WINDOWSNT
 116 char *
 117 strerror (errnum)
 118      int errnum;
 119 {
 120   extern char *sys_errlist[];
 121   extern int sys_nerr;
 122
 123   if (errnum >= 0 && errnum < sys_nerr)
 124     return sys_errlist[errnum];
 125   return (char *) "Unknown error";
 126 }
 127 #endif /* not WINDOWSNT */
 128 #endif /* ! HAVE_STRERROR */
 129
 130 void
 131 lose_syserr (const char *msg)
 132 {
 133   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
 134   exit (EXIT_FAILURE);
 135 }
 136
 137 char *
 138 get_user_id (void)
 139 {
 140   char *name;
 141   struct passwd *buf = getpwuid (getuid ());
 142   if (!buf)
 143     {
 144       int count = 1;
 145       int uid = (int) getuid ();
 146       int tuid = uid;
 147       while (tuid /= 10)
 148         count++;
 149       name = malloc (count+1);
 150       if (!name)
 151         return NULL;
 152       sprintf (name, "%d", uid);
 153       return name;
 154     }
 155   return buf->pw_name;
 156 }
 157
 158 const char *
 159 get_prefix (int running_suid, const char *user_prefix)
 160 {
 161   if (!running_suid && user_prefix == NULL)
 162     lose ("Not using a shared game directory, and no prefix given.");
 163   if (running_suid)
 164     {
 165 #ifdef HAVE_SHARED_GAME_DIR
 166       return HAVE_SHARED_GAME_DIR;
 167 #else
 168       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 169 #endif
 170     }
 171   return user_prefix;
 172 }
 173
 174 int
 175 main (int argc, char **argv)
 176 {
 177   int c, running_suid;
 178   void *lockstate;
 179   char *user_id, *scorefile;
 180   const char *prefix, *user_prefix = NULL;
 181   struct stat buf;
 182   struct score_entry *scores;
 183   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 184   char *newdata;
 185
 186   srand (time (0));
 187
 188   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 189     switch (c)
 190       {
 191       case 'h':
 192         usage (EXIT_SUCCESS);
 193         break;
 194       case 'd':
 195         user_prefix = optarg;
 196         break;
 197       case 'r':
 198         reverse = 1;
 199         break;
 200       case 'm':
 201         max = atoi (optarg);
 202         if (max > MAX_SCORES)
 203           max = MAX_SCORES;
 204         break;
 205       default:
 206         usage (EXIT_FAILURE);
 207       }
 208
 209   if (optind+3 != argc)
 210     usage (EXIT_FAILURE);
 211
 212   running_suid = (getuid () != geteuid ());
 213
 214   prefix = get_prefix (running_suid, user_prefix);
 215
 216   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 217   if (!scorefile)
 218     lose_syserr ("Couldn't allocate score file");
 219
 220   strcpy (scorefile, prefix);
 221   strcat (scorefile, "/");
 222   strcat (scorefile, argv[optind]);
 223   newscore = atoi (argv[optind+1]);
 224   newdata = argv[optind+2];
 225   if (strlen (newdata) > MAX_DATA_LEN)
 226     newdata[MAX_DATA_LEN] = '\0';
 227
 228   user_id = get_user_id ();
 229   if (user_id == NULL)
 230     lose_syserr ("Couldn't determine user id");
 231
 232   if (stat (scorefile, &buf) < 0)
 233     lose_syserr ("Failed to access scores file");
 234
 235   if (lock_file (scorefile, &lockstate) < 0)
 236     lose_syserr ("Failed to lock scores file");
 237
 238   if (read_scores (scorefile, &scores, &scorecount) < 0)
 239     {
 240       unlock_file (scorefile, lockstate);
 241       lose_syserr ("Failed to read scores file");
 242     }
 243   push_score (&scores, &scorecount, newscore, user_id, newdata);
 244   sort_scores (scores, scorecount, reverse);
 245   /* Limit the number of scores.  If we're using reverse sorting, then
 246      we should increment the beginning of the array, to skip over the
 247      *smallest* scores.  Otherwise, we just decrement the number of
 248      scores, since the smallest will be at the end. */
 249   if (scorecount > MAX_SCORES)
 250     scorecount -= (scorecount - MAX_SCORES);
 251   if (reverse)
 252     scores += (scorecount - MAX_SCORES);
 253   if (write_scores (scorefile, scores, scorecount) < 0)
 254     {
 255       unlock_file (scorefile, lockstate);
 256       lose_syserr ("Failed to write scores file");
 257     }
 258   unlock_file (scorefile, lockstate);
 259   exit (EXIT_SUCCESS);
 260 }
 261
 262 int
 263 read_score (FILE *f, struct score_entry *score)
 264 {
 265   int c;
 266   if (feof (f))
 267     return 1;
 268   while ((c = getc (f)) != EOF
 269          && isdigit (c))
 270     {
 271       score->score *= 10;
 272       score->score += (c-48);
 273     }
 274   while ((c = getc (f)) != EOF
 275          && isspace (c))
 276     ;
 277   if (c == EOF)
 278     return -1;
 279   ungetc (c, f);
 280 #ifdef HAVE_GETDELIM
 281   {
 282     size_t count = 0;
 283     if (getdelim (&score->username, &count, ' ', f) < 1
 284         || score->username == NULL)
 285       return -1;
 286     /* Trim the space */
 287     score->username[strlen (score->username)-1] = '\0';
 288   }
 289 #else
 290   {
 291     int unameread = 0;
 292     int unamelen = 30;
 293     char *username = malloc (unamelen);
 294     if (!username)
 295       return -1;
 296
 297     while ((c = getc (f)) != EOF
 298            && !isspace (c))
 299       {
 300         if (unameread >= unamelen-1)
 301           if (!(username = realloc (username, unamelen *= 2)))
 302             return -1;
 303         username[unameread] = c;
 304         unameread++;
 305       }
 306     if (c == EOF)
 307       return -1;
 308     username[unameread] = '\0';
 309     score->username = username;
 310   }
 311 #endif
 312 #ifdef HAVE_GETLINE
 313   score->data = NULL;
 314   errno = 0;
 315   {
 316     size_t len;
 317     if (getline (&score->data, &len, f) < 0)
 318       return -1;
 319     score->data[strlen (score->data)-1] = '\0';
 320   }
 321 #else
 322   {
 323     int cur = 0;
 324     int len = 16;
 325     char *buf = malloc (len);
 326     if (!buf)
 327       return -1;
 328     while ((c = getc (f)) != EOF
 329            && c != '\n')
 330       {
 331         if (cur >= len-1)
 332           {
 333             if (!(buf = realloc (buf, len *= 2)))
 334               return -1;
 335           }
 336         buf[cur] = c;
 337         cur++;
 338       }
 339     score->data = buf;
 340     score->data[cur] = '\0';
 341   }
 342 #endif
 343   return 0;
 344 }
 345
 346 int
 347 read_scores (const char *filename, struct score_entry **scores, int *count)
 348 {
 349   int readval, scorecount, cursize;
 350   struct score_entry *ret;
 351   FILE *f = fopen (filename, "r");
 352   if (!f)
 353     return -1;
 354   scorecount = 0;
 355   cursize = 16;
 356   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 357   if (!ret)
 358     return -1;
 359   while ((readval = read_score (f, &ret[scorecount])) == 0)
 360     {
 361       /* We encoutered an error */
 362       if (readval < 0)
 363         return -1;
 364       scorecount++;
 365       if (scorecount >= cursize)
 366         {
 367           cursize *= 2;
 368           ret = (struct score_entry *)
 369             realloc (ret, (sizeof (struct score_entry) * cursize));
 370           if (!ret)
 371             return -1;
 372         }
 373     }
 374   *count = scorecount;
 375   *scores = ret;
 376   return 0;
 377 }
 378
 379 int
 380 score_compare (const void *a, const void *b)
 381 {
 382   const struct score_entry *sa = (const struct score_entry *) a;
 383   const struct score_entry *sb = (const struct score_entry *) b;
 384   return (sb->score > sa->score) - (sb->score < sa->score);
 385 }
 386
 387 int
 388 score_compare_reverse (const void *a, const void *b)
 389 {
 390   const struct score_entry *sa = (const struct score_entry *) a;
 391   const struct score_entry *sb = (const struct score_entry *) b;
 392   return (sa->score > sb->score) - (sa->score < sb->score);
 393 }
 394
 395 int
 396 push_score (struct score_entry **scores, int *count, int newscore, char *username, char *newdata)
 397 {
 398  struct score_entry *newscores
 399    = (struct score_entry *) realloc (*scores,
 400                                      sizeof (struct score_entry) * ((*count) + 1));
 401   if (!newscores)
 402     return -1;
 403   newscores[*count].score = newscore;
 404   newscores[*count].username = username;
 405   newscores[*count].data = newdata;
 406   (*count) += 1;
 407   *scores = newscores;
 408   return 0;
 409 }
 410
 411 void
 412 sort_scores (struct score_entry *scores, int count, int reverse)
 413 {
 414   qsort (scores, count, sizeof (struct score_entry),
 415         reverse ? score_compare_reverse : score_compare);
 416 }
 417
 418 int
 419 write_scores (const char *filename, const struct score_entry *scores, int count)
 420 {
 421   FILE *f;
 422   int i;
 423   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 424   if (!tempfile)
 425     return -1;
 426   strcpy (tempfile, filename);
 427   strcat (tempfile, ".tempXXXXXX");
 428 #ifdef HAVE_MKSTEMP
 429   if (mkstemp (tempfile) < 0
 430 #else
 431   if (mktemp (tempfile) != tempfile
 432 #endif
 433       || !(f = fopen (tempfile, "w")))
 434     return -1;
 435   for (i = 0; i < count; i++)
 436     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 437                 scores[i].data) < 0)
 438       return -1;
 439   fclose (f);
 440   if (rename (tempfile, filename) < 0)
 441     return -1;
 442   if (chmod (filename, 0644) < 0)
 443     return -1;
 444   return 0;
 445 }
 446
 447 int
 448 lock_file (const char *filename, void **state)
 449 {
 450   int fd;
 451   struct stat buf;
 452   int attempts = 0;
 453   const char *lockext = ".lockfile";
 454   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 455   if (!lockpath)
 456     return -1;
 457   strcpy (lockpath, filename);
 458   strcat (lockpath, lockext);
 459   *state = lockpath;
 460  trylock:
 461   attempts++;
 462   /* If the lock is over an hour old, delete it. */
 463   if (stat (lockpath, &buf) == 0
 464       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 465     unlink (lockpath);
 466   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 467   if (fd < 0)
 468     {
 469       if (errno == EEXIST)
 470         {
 471           /* Break the lock; we won't corrupt the file, but we might
 472              lose some scores. */
 473           if (attempts > MAX_ATTEMPTS)
 474             {
 475               unlink (lockpath);
 476               attempts = 0;
 477             }
 478           sleep ((rand () % 2)+1);
 479           goto trylock;
 480         }
 481       else
 482         return -1;
 483     }
 484   close (fd);
 485   return 0;
 486 }
 487
 488 int
 489 unlock_file (const char *filename, void *state)
 490 {
 491   char *lockpath = (char *) state;
 492   int ret = unlink (lockpath);
 493   int saved_errno = errno;
 494   free (lockpath);
 495   errno = saved_errno;
 496   return ret;
 497 }
 498
 499
 500 /* update-game-score.c ends here */