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 #ifdef HAVE_STRING_H
  39 #include <string.h>
  40 #endif
  41 #ifdef HAVE_STDLIB_H
  42 #include <stdlib.h>
  43 #endif
  44 #include <stdio.h>
  45 #include <time.h>
  46 #include <pwd.h>
  47 #include <ctype.h>
  48 #ifdef HAVE_FCNTL_H
  49 #include <fcntl.h>
  50 #endif
  51 #ifdef STDC_HEADERS
  52 #include <stdarg.h>
  53 #endif
  54 #include <sys/stat.h>
  55
  56 /* Needed for SunOS4, for instance.  */
  57 extern char *optarg;
  58 extern int optind, opterr;
  59
  60 static int usage (int err) NO_RETURN;
  61
  62 #define MAX_ATTEMPTS 5
  63 #define MAX_SCORES 200
  64 #define MAX_DATA_LEN 1024
  65
  66 #ifndef HAVE_DIFFTIME
  67 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  68 #define difftime(t1, t0) (double)((t1) - (t0))
  69 #endif
  70
  71 static int
  72 usage (int err)
  73 {
  74   fprintf (stdout, "Usage: update-game-score [-m MAX] [-r] [-d DIR] game/scorefile SCORE DATA\n");
  75   fprintf (stdout, "       update-game-score -h\n");
  76   fprintf (stdout, " -h\t\tDisplay this help.\n");
  77   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  78   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  79   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  80   exit (err);
  81 }
  82
  83 static int lock_file (const char *filename, void **state);
  84 static int unlock_file (const char *filename, void *state);
  85
  86 struct score_entry
  87 {
  88   long score;
  89   char *username;
  90   char *data;
  91 };
  92
  93 static int read_scores (const char *filename, struct score_entry **scores,
  94                         int *count);
  95 static int push_score (struct score_entry **scores, int *count,
  96                        int newscore, char *username, char *newdata);
  97 static void sort_scores (struct score_entry *scores, int count, int reverse);
  98 static int write_scores (const char *filename,
  99                          const struct score_entry *scores, int count);
 100
 101 static void lose (const char *msg) NO_RETURN;
 102
 103 static void
 104 lose (const char *msg)
 105 {
 106   fprintf (stderr, "%s\n", msg);
 107   exit (EXIT_FAILURE);
 108 }
 109
 110 static void lose_syserr (const char *msg) NO_RETURN;
 111
 112 /* Taken from sysdep.c.  */
 113 #ifndef HAVE_STRERROR
 114 #ifndef WINDOWSNT
 115 char *
 116 strerror (int errnum)
 117 {
 118   extern char *sys_errlist[];
 119   extern int sys_nerr;
 120
 121   if (errnum >= 0 && errnum < sys_nerr)
 122     return sys_errlist[errnum];
 123   return (char *) "Unknown error";
 124 }
 125 #endif /* not WINDOWSNT */
 126 #endif /* ! HAVE_STRERROR */
 127
 128 static void
 129 lose_syserr (const char *msg)
 130 {
 131   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
 132   exit (EXIT_FAILURE);
 133 }
 134
 135 static char *
 136 get_user_id (void)
 137 {
 138   char *name;
 139   struct passwd *buf = getpwuid (getuid ());
 140   if (!buf)
 141     {
 142       int count = 1;
 143       int uid = (int) getuid ();
 144       int tuid = uid;
 145       while (tuid /= 10)
 146         count++;
 147       name = malloc (count+1);
 148       if (!name)
 149         return NULL;
 150       sprintf (name, "%d", uid);
 151       return name;
 152     }
 153   return buf->pw_name;
 154 }
 155
 156 static const char *
 157 get_prefix (int running_suid, const char *user_prefix)
 158 {
 159   if (!running_suid && user_prefix == NULL)
 160     lose ("Not using a shared game directory, and no prefix given.");
 161   if (running_suid)
 162     {
 163 #ifdef HAVE_SHARED_GAME_DIR
 164       return HAVE_SHARED_GAME_DIR;
 165 #else
 166       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 167 #endif
 168     }
 169   return user_prefix;
 170 }
 171
 172 int
 173 main (int argc, char **argv)
 174 {
 175   int c, running_suid;
 176   void *lockstate;
 177   char *user_id, *scorefile;
 178   const char *prefix, *user_prefix = NULL;
 179   struct stat buf;
 180   struct score_entry *scores;
 181   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 182   char *newdata;
 183
 184   srand (time (0));
 185
 186   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 187     switch (c)
 188       {
 189       case 'h':
 190         usage (EXIT_SUCCESS);
 191         break;
 192       case 'd':
 193         user_prefix = optarg;
 194         break;
 195       case 'r':
 196         reverse = 1;
 197         break;
 198       case 'm':
 199         max = atoi (optarg);
 200         if (max > MAX_SCORES)
 201           max = MAX_SCORES;
 202         break;
 203       default:
 204         usage (EXIT_FAILURE);
 205       }
 206
 207   if (optind+3 != argc)
 208     usage (EXIT_FAILURE);
 209
 210   running_suid = (getuid () != geteuid ());
 211
 212   prefix = get_prefix (running_suid, user_prefix);
 213
 214   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 215   if (!scorefile)
 216     lose_syserr ("Couldn't allocate score file");
 217
 218   strcpy (scorefile, prefix);
 219   strcat (scorefile, "/");
 220   strcat (scorefile, argv[optind]);
 221   newscore = atoi (argv[optind+1]);
 222   newdata = argv[optind+2];
 223   if (strlen (newdata) > MAX_DATA_LEN)
 224     newdata[MAX_DATA_LEN] = '\0';
 225
 226   user_id = get_user_id ();
 227   if (user_id == NULL)
 228     lose_syserr ("Couldn't determine user id");
 229
 230   if (stat (scorefile, &buf) < 0)
 231     lose_syserr ("Failed to access scores file");
 232
 233   if (lock_file (scorefile, &lockstate) < 0)
 234     lose_syserr ("Failed to lock scores file");
 235
 236   if (read_scores (scorefile, &scores, &scorecount) < 0)
 237     {
 238       unlock_file (scorefile, lockstate);
 239       lose_syserr ("Failed to read scores file");
 240     }
 241   push_score (&scores, &scorecount, newscore, user_id, newdata);
 242   sort_scores (scores, scorecount, reverse);
 243   /* Limit the number of scores.  If we're using reverse sorting, then
 244      also increment the beginning of the array, to skip over the
 245      *smallest* scores.  Otherwise, just decrementing the number of
 246      scores suffices, since the smallest is at the end. */
 247   if (scorecount > MAX_SCORES)
 248     {
 249       if (reverse)
 250         scores += (scorecount - MAX_SCORES);
 251       scorecount = MAX_SCORES;
 252     }
 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 static 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 static 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 static 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 static 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 static 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 static 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 static 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 static 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 */