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 (feof (f))
 232     return 1;
 233   while ((c = getc (f)) != EOF
 234          && isdigit (c))
 235     {
 236       score->score *= 10;
 237       score->score += (c-48);
 238     }
 239   while ((c = getc (f)) != EOF
 240          && isspace (c))
 241     ;
 242   if (c == EOF)
 243     return -1;
 244   ungetc (c, f);
 245 #ifdef HAVE_GETDELIM
 246   {
 247     size_t count = 0;
 248     if (getdelim (&score->username, &count, ' ', f) < 1
 249         || score->username == NULL)
 250       return -1;
 251     /* Trim the space */
 252     score->username[strlen (score->username)-1] = '\0';
 253   }
 254 #else
 255   {
 256     int unameread = 0;
 257     int unamelen = 30;
 258     char *username = malloc (unamelen);
 259     if (!username)
 260       return -1;
 261
 262     while ((c = getc (f)) != EOF
 263            && !isspace (c))
 264       {
 265         if (unameread >= unamelen-1)
 266           if (!(username = realloc (username, unamelen *= 2)))
 267             return -1;
 268         username[unameread] = c;
 269         unameread++;
 270       }
 271     if (c == EOF)
 272       return -1;
 273     username[unameread] = '\0';
 274     score->username = username;
 275   }
 276 #endif
 277 #ifdef HAVE_GETLINE
 278   score->data = NULL;
 279   errno = 0;
 280   {
 281     size_t len;
 282     if (getline (&score->data, &len, f) < 0)
 283       return -1;
 284     score->data[strlen (score->data)-1] = '\0';
 285   }
 286 #else
 287   {
 288     int cur = 0;
 289     int len = 16;
 290     char *buf = malloc (len);
 291     if (!buf)
 292       return -1;
 293     while ((c = getc (f)) != EOF
 294            && c != '\n')
 295       {
 296         if (cur >= len-1)
 297           {
 298             if (!(buf = realloc (buf, len *= 2)))
 299               return -1;
 300           }
 301         buf[cur] = c;
 302         cur++;
 303       }
 304     score->data = buf;
 305     score->data[cur] = '\0';
 306   }
 307 #endif
 308   return 0;
 309 }
 310
 311 static int
 312 read_scores (const char *filename, struct score_entry **scores, int *count)
 313 {
 314   int readval, scorecount, cursize;
 315   struct score_entry *ret;
 316   FILE *f = fopen (filename, "r");
 317   if (!f)
 318     return -1;
 319   scorecount = 0;
 320   cursize = 16;
 321   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 322   if (!ret)
 323     return -1;
 324   while ((readval = read_score (f, &ret[scorecount])) == 0)
 325     {
 326       /* We encountered an error.  */
 327       if (readval < 0)
 328         return -1;
 329       scorecount++;
 330       if (scorecount >= cursize)
 331         {
 332           cursize *= 2;
 333           ret = (struct score_entry *)
 334             realloc (ret, (sizeof (struct score_entry) * cursize));
 335           if (!ret)
 336             return -1;
 337         }
 338     }
 339   *count = scorecount;
 340   *scores = ret;
 341   return 0;
 342 }
 343
 344 static int
 345 score_compare (const void *a, const void *b)
 346 {
 347   const struct score_entry *sa = (const struct score_entry *) a;
 348   const struct score_entry *sb = (const struct score_entry *) b;
 349   return (sb->score > sa->score) - (sb->score < sa->score);
 350 }
 351
 352 static int
 353 score_compare_reverse (const void *a, const void *b)
 354 {
 355   const struct score_entry *sa = (const struct score_entry *) a;
 356   const struct score_entry *sb = (const struct score_entry *) b;
 357   return (sa->score > sb->score) - (sa->score < sb->score);
 358 }
 359
 360 int
 361 push_score (struct score_entry **scores, int *count, int newscore, char *username, char *newdata)
 362 {
 363  struct score_entry *newscores
 364    = (struct score_entry *) realloc (*scores,
 365                                      sizeof (struct score_entry) * ((*count) + 1));
 366   if (!newscores)
 367     return -1;
 368   newscores[*count].score = newscore;
 369   newscores[*count].username = username;
 370   newscores[*count].data = newdata;
 371   (*count) += 1;
 372   *scores = newscores;
 373   return 0;
 374 }
 375
 376 static void
 377 sort_scores (struct score_entry *scores, int count, int reverse)
 378 {
 379   qsort (scores, count, sizeof (struct score_entry),
 380         reverse ? score_compare_reverse : score_compare);
 381 }
 382
 383 static int
 384 write_scores (const char *filename, const struct score_entry *scores, int count)
 385 {
 386   FILE *f;
 387   int i;
 388   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 389   if (!tempfile)
 390     return -1;
 391   strcpy (tempfile, filename);
 392   strcat (tempfile, ".tempXXXXXX");
 393 #ifdef HAVE_MKSTEMP
 394   if (mkstemp (tempfile) < 0
 395 #else
 396   if (mktemp (tempfile) != tempfile
 397 #endif
 398       || !(f = fopen (tempfile, "w")))
 399     return -1;
 400   for (i = 0; i < count; i++)
 401     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 402                 scores[i].data) < 0)
 403       return -1;
 404   fclose (f);
 405   if (rename (tempfile, filename) < 0)
 406     return -1;
 407   if (chmod (filename, 0644) < 0)
 408     return -1;
 409   return 0;
 410 }
 411
 412 static int
 413 lock_file (const char *filename, void **state)
 414 {
 415   int fd;
 416   struct stat buf;
 417   int attempts = 0;
 418   const char *lockext = ".lockfile";
 419   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 420   if (!lockpath)
 421     return -1;
 422   strcpy (lockpath, filename);
 423   strcat (lockpath, lockext);
 424   *state = lockpath;
 425  trylock:
 426   attempts++;
 427   /* If the lock is over an hour old, delete it. */
 428   if (stat (lockpath, &buf) == 0
 429       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 430     unlink (lockpath);
 431   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 432   if (fd < 0)
 433     {
 434       if (errno == EEXIST)
 435         {
 436           /* Break the lock; we won't corrupt the file, but we might
 437              lose some scores. */
 438           if (attempts > MAX_ATTEMPTS)
 439             {
 440               unlink (lockpath);
 441               attempts = 0;
 442             }
 443           sleep ((rand () % 2)+1);
 444           goto trylock;
 445         }
 446       else
 447         return -1;
 448     }
 449   close (fd);
 450   return 0;
 451 }
 452
 453 static int
 454 unlock_file (const char *filename, void *state)
 455 {
 456   char *lockpath = (char *) state;
 457   int ret = unlink (lockpath);
 458   int saved_errno = errno;
 459   free (lockpath);
 460   errno = saved_errno;
 461   return ret;
 462 }
 463
 464
 465 /* update-game-score.c ends here */