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