lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2
   3 Copyright (C) 2002-2013 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 <limits.h>
  39 #include <string.h>
  40 #include <stdlib.h>
  41 #include <stdio.h>
  42 #include <time.h>
  43 #include <pwd.h>
  44 #include <ctype.h>
  45 #include <fcntl.h>
  46 #include <sys/stat.h>
  47 #include <getopt.h>
  48
  49 #ifdef WINDOWSNT
  50 #include "ntlib.h"
  51 #endif
  52
  53 #define MAX_ATTEMPTS 5
  54 #define MAX_SCORES 200
  55 #define MAX_DATA_LEN 1024
  56
  57 #ifndef HAVE_DIFFTIME
  58 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  59 #define difftime(t1, t0) (double)((t1) - (t0))
  60 #endif
  61
  62 static _Noreturn void
  63 usage (int err)
  64 {
  65   fprintf (stdout, "Usage: update-game-score [-m MAX] [-r] [-d DIR] game/scorefile SCORE DATA\n");
  66   fprintf (stdout, "       update-game-score -h\n");
  67   fprintf (stdout, " -h\t\tDisplay this help.\n");
  68   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  69   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  70   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  71   exit (err);
  72 }
  73
  74 static int lock_file (const char *filename, void **state);
  75 static int unlock_file (const char *filename, void *state);
  76
  77 struct score_entry
  78 {
  79   long score;
  80   char *username;
  81   char *data;
  82 };
  83
  84 static int read_scores (const char *filename, struct score_entry **scores,
  85                         int *count);
  86 static int push_score (struct score_entry **scores, int *count,
  87                        int newscore, char *username, char *newdata);
  88 static void sort_scores (struct score_entry *scores, int count, int reverse);
  89 static int write_scores (const char *filename,
  90                          const struct score_entry *scores, int count);
  91
  92 static _Noreturn void
  93 lose (const char *msg)
  94 {
  95   fprintf (stderr, "%s\n", msg);
  96   exit (EXIT_FAILURE);
  97 }
  98
  99 static _Noreturn void
 100 lose_syserr (const char *msg)
 101 {
 102   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
 103   exit (EXIT_FAILURE);
 104 }
 105
 106 static char *
 107 get_user_id (void)
 108 {
 109   struct passwd *buf = getpwuid (getuid ());
 110   if (!buf)
 111     {
 112       long uid = getuid ();
 113       char *name = malloc (sizeof uid * CHAR_BIT / 3 + 1);
 114       if (name)
 115         sprintf (name, "%ld", uid);
 116       return name;
 117     }
 118   return buf->pw_name;
 119 }
 120
 121 static const char *
 122 get_prefix (int running_suid, const char *user_prefix)
 123 {
 124   if (!running_suid && user_prefix == NULL)
 125     lose ("Not using a shared game directory, and no prefix given.");
 126   if (running_suid)
 127     {
 128 #ifdef HAVE_SHARED_GAME_DIR
 129       return HAVE_SHARED_GAME_DIR;
 130 #else
 131       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 132 #endif
 133     }
 134   return user_prefix;
 135 }
 136
 137 int
 138 main (int argc, char **argv)
 139 {
 140   int c, running_suid;
 141   void *lockstate;
 142   char *user_id, *scorefile;
 143   const char *prefix, *user_prefix = NULL;
 144   struct stat buf;
 145   struct score_entry *scores;
 146   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 147   char *newdata;
 148
 149   srand (time (0));
 150
 151   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 152     switch (c)
 153       {
 154       case 'h':
 155         usage (EXIT_SUCCESS);
 156         break;
 157       case 'd':
 158         user_prefix = optarg;
 159         break;
 160       case 'r':
 161         reverse = 1;
 162         break;
 163       case 'm':
 164         max = atoi (optarg);
 165         if (max > MAX_SCORES)
 166           max = MAX_SCORES;
 167         break;
 168       default:
 169         usage (EXIT_FAILURE);
 170       }
 171
 172   if (optind+3 != argc)
 173     usage (EXIT_FAILURE);
 174
 175   running_suid = (getuid () != geteuid ());
 176
 177   prefix = get_prefix (running_suid, user_prefix);
 178
 179   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 180   if (!scorefile)
 181     lose_syserr ("Couldn't allocate score file");
 182
 183   strcpy (scorefile, prefix);
 184   strcat (scorefile, "/");
 185   strcat (scorefile, argv[optind]);
 186   newscore = atoi (argv[optind+1]);
 187   newdata = argv[optind+2];
 188   if (strlen (newdata) > MAX_DATA_LEN)
 189     newdata[MAX_DATA_LEN] = '\0';
 190
 191   user_id = get_user_id ();
 192   if (user_id == NULL)
 193     lose_syserr ("Couldn't determine user id");
 194
 195   if (stat (scorefile, &buf) < 0)
 196     lose_syserr ("Failed to access scores file");
 197
 198   if (lock_file (scorefile, &lockstate) < 0)
 199     lose_syserr ("Failed to lock scores file");
 200
 201   if (read_scores (scorefile, &scores, &scorecount) < 0)
 202     {
 203       unlock_file (scorefile, lockstate);
 204       lose_syserr ("Failed to read scores file");
 205     }
 206   push_score (&scores, &scorecount, newscore, user_id, newdata);
 207   sort_scores (scores, scorecount, reverse);
 208   /* Limit the number of scores.  If we're using reverse sorting, then
 209      also increment the beginning of the array, to skip over the
 210      *smallest* scores.  Otherwise, just decrementing the number of
 211      scores suffices, since the smallest is at the end. */
 212   if (scorecount > MAX_SCORES)
 213     {
 214       if (reverse)
 215         scores += (scorecount - MAX_SCORES);
 216       scorecount = MAX_SCORES;
 217     }
 218   if (write_scores (scorefile, scores, scorecount) < 0)
 219     {
 220       unlock_file (scorefile, lockstate);
 221       lose_syserr ("Failed to write scores file");
 222     }
 223   unlock_file (scorefile, lockstate);
 224   exit (EXIT_SUCCESS);
 225 }
 226
 227 static int
 228 read_score (FILE *f, struct score_entry *score)
 229 {
 230   int c;
 231   if ((c = getc (f)) != EOF)
 232     ungetc (c, f);
 233   if (feof (f))
 234     return 1;
 235   for (score->score = 0; (c = getc (f)) != EOF && isdigit (c); )
 236     {
 237       score->score *= 10;
 238       score->score += (c-48);
 239     }
 240   while ((c = getc (f)) != EOF
 241          && isspace (c))
 242     ;
 243   if (c == EOF)
 244     return -1;
 245   ungetc (c, f);
 246 #ifdef HAVE_GETDELIM
 247   {
 248     size_t count = 0;
 249     if (getdelim (&score->username, &count, ' ', f) < 1
 250         || score->username == NULL)
 251       return -1;
 252     /* Trim the space */
 253     score->username[strlen (score->username)-1] = '\0';
 254   }
 255 #else
 256   {
 257     int unameread = 0;
 258     int unamelen = 30;
 259     char *username = malloc (unamelen);
 260     if (!username)
 261       return -1;
 262
 263     while ((c = getc (f)) != EOF
 264            && !isspace (c))
 265       {
 266         if (unameread >= unamelen-1)
 267           if (!(username = realloc (username, unamelen *= 2)))
 268             return -1;
 269         username[unameread] = c;
 270         unameread++;
 271       }
 272     if (c == EOF)
 273       return -1;
 274     username[unameread] = '\0';
 275     score->username = username;
 276   }
 277 #endif
 278 #ifdef HAVE_GETLINE
 279   score->data = NULL;
 280   errno = 0;
 281   {
 282     size_t len;
 283     if (getline (&score->data, &len, f) < 0)
 284       return -1;
 285     score->data[strlen (score->data)-1] = '\0';
 286   }
 287 #else
 288   {
 289     int cur = 0;
 290     int len = 16;
 291     char *buf = malloc (len);
 292     if (!buf)
 293       return -1;
 294     while ((c = getc (f)) != EOF
 295            && c != '\n')
 296       {
 297         if (cur >= len-1)
 298           {
 299             if (!(buf = realloc (buf, len *= 2)))
 300               return -1;
 301           }
 302         buf[cur] = c;
 303         cur++;
 304       }
 305     score->data = buf;
 306     score->data[cur] = '\0';
 307   }
 308 #endif
 309   return 0;
 310 }
 311
 312 static int
 313 read_scores (const char *filename, struct score_entry **scores, int *count)
 314 {
 315   int readval = -1, scorecount, cursize;
 316   struct score_entry *ret;
 317   FILE *f = fopen (filename, "r");
 318   int retval = -1;
 319   if (!f)
 320     return -1;
 321   scorecount = 0;
 322   cursize = 16;
 323   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 324   if (ret)
 325     {
 326       while ((readval = read_score (f, &ret[scorecount])) == 0)
 327         {
 328           scorecount++;
 329           if (scorecount >= cursize)
 330             {
 331               cursize *= 2;
 332               ret = (struct score_entry *)
 333                 realloc (ret, (sizeof (struct score_entry) * cursize));
 334               if (!ret)
 335                 break;
 336             }
 337         }
 338     }
 339   if (readval > 0)
 340     {
 341       *count = scorecount;
 342       *scores = ret;
 343       retval = 0;
 344     }
 345   fclose (f);
 346   return retval;
 347 }
 348
 349 static int
 350 score_compare (const void *a, const void *b)
 351 {
 352   const struct score_entry *sa = (const struct score_entry *) a;
 353   const struct score_entry *sb = (const struct score_entry *) b;
 354   return (sb->score > sa->score) - (sb->score < sa->score);
 355 }
 356
 357 static int
 358 score_compare_reverse (const void *a, const void *b)
 359 {
 360   const struct score_entry *sa = (const struct score_entry *) a;
 361   const struct score_entry *sb = (const struct score_entry *) b;
 362   return (sa->score > sb->score) - (sa->score < sb->score);
 363 }
 364
 365 int
 366 push_score (struct score_entry **scores, int *count, int newscore, char *username, char *newdata)
 367 {
 368  struct score_entry *newscores
 369    = (struct score_entry *) realloc (*scores,
 370                                      sizeof (struct score_entry) * ((*count) + 1));
 371   if (!newscores)
 372     return -1;
 373   newscores[*count].score = newscore;
 374   newscores[*count].username = username;
 375   newscores[*count].data = newdata;
 376   (*count) += 1;
 377   *scores = newscores;
 378   return 0;
 379 }
 380
 381 static void
 382 sort_scores (struct score_entry *scores, int count, int reverse)
 383 {
 384   qsort (scores, count, sizeof (struct score_entry),
 385         reverse ? score_compare_reverse : score_compare);
 386 }
 387
 388 static int
 389 write_scores (const char *filename, const struct score_entry *scores, int count)
 390 {
 391   int fd;
 392   FILE *f;
 393   int i;
 394   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 395   if (!tempfile)
 396     return -1;
 397   strcpy (tempfile, filename);
 398   strcat (tempfile, ".tempXXXXXX");
 399   fd = mkostemp (tempfile, 0);
 400   if (fd < 0)
 401     return -1;
 402   f = fdopen (fd, "w");
 403   if (! f)
 404     return -1;
 405   for (i = 0; i < count; i++)
 406     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 407                 scores[i].data) < 0)
 408       return -1;
 409   fclose (f);
 410   if (rename (tempfile, filename) < 0)
 411     return -1;
 412   if (chmod (filename, 0644) < 0)
 413     return -1;
 414   return 0;
 415 }
 416
 417 static int
 418 lock_file (const char *filename, void **state)
 419 {
 420   int fd;
 421   struct stat buf;
 422   int attempts = 0;
 423   const char *lockext = ".lockfile";
 424   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 425   if (!lockpath)
 426     return -1;
 427   strcpy (lockpath, filename);
 428   strcat (lockpath, lockext);
 429   *state = lockpath;
 430  trylock:
 431   attempts++;
 432   /* If the lock is over an hour old, delete it. */
 433   if (stat (lockpath, &buf) == 0
 434       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 435     unlink (lockpath);
 436   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 437   if (fd < 0)
 438     {
 439       if (errno == EEXIST)
 440         {
 441           /* Break the lock; we won't corrupt the file, but we might
 442              lose some scores. */
 443           if (attempts > MAX_ATTEMPTS)
 444             {
 445               unlink (lockpath);
 446               attempts = 0;
 447             }
 448           sleep ((rand () % 2)+1);
 449           goto trylock;
 450         }
 451       else
 452         return -1;
 453     }
 454   close (fd);
 455   return 0;
 456 }
 457
 458 static int
 459 unlock_file (const char *filename, void *state)
 460 {
 461   char *lockpath = (char *) state;
 462   int ret = unlink (lockpath);
 463   int saved_errno = errno;
 464   free (lockpath);
 465   errno = saved_errno;
 466   return ret;
 467 }
 468
 469 /* update-game-score.c ends here */