lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2    Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008
   3      Free Software Foundation, Inc.
   4
   5 This file is part of GNU Emacs.
   6
   7 GNU Emacs is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 3, or (at your option)
  10 any later version.
  11
  12 GNU Emacs is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU Emacs; see the file COPYING.  If not, write to
  19 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  20 Boston, MA 02110-1301, USA.  */
  21
  22 /* This program is allows a game to securely and atomically update a
  23    score file.  It should be installed setuid, owned by an appropriate
  24    user like `games'.
  25
  26    Alternatively, it can be compiled without HAVE_SHARED_GAME_DIR
  27    defined, and in that case it will store scores in the user's home
  28    directory (it should NOT be setuid).
  29
  30    Created 2002/03/22, by Colin Walters <walters@debian.org>
  31 */
  32
  33 #include <config.h>
  34
  35 #ifdef HAVE_UNISTD_H
  36 #include <unistd.h>
  37 #endif
  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 #define MAX_ATTEMPTS 5
  62 #define MAX_SCORES 200
  63 #define MAX_DATA_LEN 1024
  64
  65 /* Declare the prototype for a general external function.  */
  66 #if defined (PROTOTYPES) || defined (WINDOWSNT)
  67 #define P_(proto) proto
  68 #else
  69 #define P_(proto) ()
  70 #endif
  71
  72 #ifndef HAVE_DIFFTIME
  73 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  74 #define difftime(t1, t0) (double)((t1) - (t0))
  75 #endif
  76
  77 int
  78 usage (err)
  79      int err;
  80 {
  81   fprintf (stdout, "Usage: update-game-score [-m MAX ] [ -r ] game/scorefile SCORE DATA\n");
  82   fprintf (stdout, "       update-game-score -h\n");
  83   fprintf (stdout, " -h\t\tDisplay this help.\n");
  84   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  85   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  86   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  87   exit (err);
  88 }
  89
  90 int lock_file P_ ((const char *filename, void **state));
  91 int unlock_file P_ ((const char *filename, void *state));
  92
  93 struct score_entry
  94 {
  95   long score;
  96   char *username;
  97   char *data;
  98 };
  99
 100 int read_scores P_ ((const char *filename, struct score_entry **scores,
 101                      int *count));
 102 int push_score P_ ((struct score_entry **scores, int *count,
 103                     int newscore, char *username, char *newdata));
 104 void sort_scores P_ ((struct score_entry *scores, int count, int reverse));
 105 int write_scores P_ ((const char *filename, const struct score_entry *scores,
 106                       int count));
 107
 108 void lose P_ ((const char *msg)) NO_RETURN;
 109
 110 void
 111 lose (msg)
 112      const char *msg;
 113 {
 114   fprintf (stderr, "%s\n", msg);
 115   exit (EXIT_FAILURE);
 116 }
 117
 118 void lose_syserr P_ ((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 (msg)
 139      const char *msg;
 140 {
 141   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
 142   exit (EXIT_FAILURE);
 143 }
 144
 145 char *
 146 get_user_id P_ ((void))
 147 {
 148   char *name;
 149   struct passwd *buf = getpwuid (getuid ());
 150   if (!buf)
 151     {
 152       int count = 1;
 153       int uid = (int) getuid ();
 154       int tuid = uid;
 155       while (tuid /= 10)
 156         count++;
 157       name = malloc (count+1);
 158       if (!name)
 159         return NULL;
 160       sprintf (name, "%d", uid);
 161       return name;
 162     }
 163   return buf->pw_name;
 164 }
 165
 166 char *
 167 get_prefix (running_suid, user_prefix)
 168      int running_suid;
 169      char *user_prefix;
 170 {
 171   if (!running_suid && user_prefix == NULL)
 172     lose ("Not using a shared game directory, and no prefix given.");
 173   if (running_suid)
 174     {
 175 #ifdef HAVE_SHARED_GAME_DIR
 176       return HAVE_SHARED_GAME_DIR;
 177 #else
 178       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 179 #endif
 180     }
 181   return user_prefix;
 182 }
 183
 184 int
 185 main (argc, argv)
 186      int argc;
 187      char **argv;
 188 {
 189   int c, running_suid;
 190   void *lockstate;
 191   char *user_id, *scorefile, *prefix, *user_prefix = NULL;
 192   struct stat buf;
 193   struct score_entry *scores;
 194   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 195   char *newdata;
 196
 197   srand (time (0));
 198
 199   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 200     switch (c)
 201       {
 202       case 'h':
 203         usage (EXIT_SUCCESS);
 204         break;
 205       case 'd':
 206         user_prefix = optarg;
 207         break;
 208       case 'r':
 209         reverse = 1;
 210         break;
 211       case 'm':
 212         max = atoi (optarg);
 213         if (max > MAX_SCORES)
 214           max = MAX_SCORES;
 215         break;
 216       default:
 217         usage (EXIT_FAILURE);
 218       }
 219
 220   if (optind+3 != argc)
 221     usage (EXIT_FAILURE);
 222
 223   running_suid = (getuid () != geteuid ());
 224
 225   prefix = get_prefix (running_suid, user_prefix);
 226
 227   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 228   if (!scorefile)
 229     lose_syserr ("Couldn't allocate score file");
 230
 231   strcpy (scorefile, prefix);
 232   strcat (scorefile, "/");
 233   strcat (scorefile, argv[optind]);
 234   newscore = atoi (argv[optind+1]);
 235   newdata = argv[optind+2];
 236   if (strlen (newdata) > MAX_DATA_LEN)
 237     newdata[MAX_DATA_LEN] = '\0';
 238
 239   user_id = get_user_id ();
 240   if (user_id == NULL)
 241     lose_syserr ("Couldn't determine user id");
 242
 243   if (stat (scorefile, &buf) < 0)
 244     lose_syserr ("Failed to access scores file");
 245
 246   if (lock_file (scorefile, &lockstate) < 0)
 247     lose_syserr ("Failed to lock scores file");
 248
 249   if (read_scores (scorefile, &scores, &scorecount) < 0)
 250     {
 251       unlock_file (scorefile, lockstate);
 252       lose_syserr ("Failed to read scores file");
 253     }
 254   push_score (&scores, &scorecount, newscore, user_id, newdata);
 255   /* Limit the number of scores.  If we're using reverse sorting, then
 256      we should increment the beginning of the array, to skip over the
 257      *smallest* scores.  Otherwise, we just decrement the number of
 258      scores, since the smallest will be at the end. */
 259   if (scorecount > MAX_SCORES)
 260     scorecount -= (scorecount - MAX_SCORES);
 261     if (reverse)
 262       scores += (scorecount - MAX_SCORES);
 263   sort_scores (scores, scorecount, reverse);
 264   if (write_scores (scorefile, scores, scorecount) < 0)
 265     {
 266       unlock_file (scorefile, lockstate);
 267       lose_syserr ("Failed to write scores file");
 268     }
 269   unlock_file (scorefile, lockstate);
 270   exit (EXIT_SUCCESS);
 271 }
 272
 273 int
 274 read_score (f, score)
 275      FILE *f;
 276      struct score_entry *score;
 277 {
 278   int c;
 279   if (feof (f))
 280     return 1;
 281   while ((c = getc (f)) != EOF
 282          && isdigit (c))
 283     {
 284       score->score *= 10;
 285       score->score += (c-48);
 286     }
 287   while ((c = getc (f)) != EOF
 288          && isspace (c))
 289     ;
 290   if (c == EOF)
 291     return -1;
 292   ungetc (c, f);
 293 #ifdef HAVE_GETDELIM
 294   {
 295     size_t count = 0;
 296     if (getdelim (&score->username, &count, ' ', f) < 1
 297         || score->username == NULL)
 298       return -1;
 299     /* Trim the space */
 300     score->username[strlen (score->username)-1] = '\0';
 301   }
 302 #else
 303   {
 304     int unameread = 0;
 305     int unamelen = 30;
 306     char *username = malloc (unamelen);
 307     if (!username)
 308       return -1;
 309
 310     while ((c = getc (f)) != EOF
 311            && !isspace (c))
 312       {
 313         if (unameread >= unamelen-1)
 314           if (!(username = realloc (username, unamelen *= 2)))
 315             return -1;
 316         username[unameread] = c;
 317         unameread++;
 318       }
 319     if (c == EOF)
 320       return -1;
 321     username[unameread] = '\0';
 322     score->username = username;
 323   }
 324 #endif
 325 #ifdef HAVE_GETLINE
 326   score->data = NULL;
 327   errno = 0;
 328   {
 329     size_t len;
 330     if (getline (&score->data, &len, f) < 0)
 331       return -1;
 332     score->data[strlen (score->data)-1] = '\0';
 333   }
 334 #else
 335   {
 336     int cur = 0;
 337     int len = 16;
 338     char *buf = malloc (len);
 339     if (!buf)
 340       return -1;
 341     while ((c = getc (f)) != EOF
 342            && c != '\n')
 343       {
 344         if (cur >= len-1)
 345           {
 346             if (!(buf = realloc (buf, len *= 2)))
 347               return -1;
 348           }
 349         buf[cur] = c;
 350         cur++;
 351       }
 352     score->data = buf;
 353     score->data[cur] = '\0';
 354   }
 355 #endif
 356   return 0;
 357 }
 358
 359 int
 360 read_scores (filename, scores, count)
 361      const char *filename;
 362      struct score_entry **scores;
 363      int *count;
 364 {
 365   int readval, scorecount, cursize;
 366   struct score_entry *ret;
 367   FILE *f = fopen (filename, "r");
 368   if (!f)
 369     return -1;
 370   scorecount = 0;
 371   cursize = 16;
 372   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 373   if (!ret)
 374     return -1;
 375   while ((readval = read_score (f, &ret[scorecount])) == 0)
 376     {
 377       /* We encoutered an error */
 378       if (readval < 0)
 379         return -1;
 380       scorecount++;
 381       if (scorecount >= cursize)
 382         {
 383           cursize *= 2;
 384           ret = (struct score_entry *)
 385             realloc (ret, (sizeof (struct score_entry) * cursize));
 386           if (!ret)
 387             return -1;
 388         }
 389     }
 390   *count = scorecount;
 391   *scores = ret;
 392   return 0;
 393 }
 394
 395 int
 396 score_compare (a, b)
 397      const void *a;
 398      const void *b;
 399 {
 400   const struct score_entry *sa = (const struct score_entry *) a;
 401   const struct score_entry *sb = (const struct score_entry *) b;
 402   return (sb->score > sa->score) - (sb->score < sa->score);
 403 }
 404
 405 int
 406 score_compare_reverse (a, b)
 407      const void *a;
 408      const void *b;
 409 {
 410   const struct score_entry *sa = (const struct score_entry *) a;
 411   const struct score_entry *sb = (const struct score_entry *) b;
 412   return (sa->score > sb->score) - (sa->score < sb->score);
 413 }
 414
 415 int
 416 push_score (scores, count, newscore, username, newdata)
 417      struct score_entry **scores;
 418      int *count; int newscore;
 419      char *username;
 420      char *newdata;
 421 {
 422  struct score_entry *newscores
 423    = (struct score_entry *) realloc (*scores,
 424                                      sizeof (struct score_entry) * ((*count) + 1));
 425   if (!newscores)
 426     return -1;
 427   newscores[*count].score = newscore;
 428   newscores[*count].username = username;
 429   newscores[*count].data = newdata;
 430   (*count) += 1;
 431   *scores = newscores;
 432   return 0;
 433 }
 434
 435 void
 436 sort_scores (scores, count, reverse)
 437      struct score_entry *scores;
 438      int count;
 439      int reverse;
 440 {
 441   qsort (scores, count, sizeof (struct score_entry),
 442         reverse ? score_compare_reverse : score_compare);
 443 }
 444
 445 int
 446 write_scores (filename, scores, count)
 447      const char *filename;
 448      const struct score_entry * scores;
 449      int count;
 450 {
 451   FILE *f;
 452   int i;
 453   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 454   if (!tempfile)
 455     return -1;
 456   strcpy (tempfile, filename);
 457   strcat (tempfile, ".tempXXXXXX");
 458 #ifdef HAVE_MKSTEMP
 459   if (mkstemp (tempfile) < 0
 460 #else
 461   if (mktemp (tempfile) != tempfile
 462 #endif
 463       || !(f = fopen (tempfile, "w")))
 464     return -1;
 465   for (i = 0; i < count; i++)
 466     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 467                 scores[i].data) < 0)
 468       return -1;
 469   fclose (f);
 470   if (rename (tempfile, filename) < 0)
 471     return -1;
 472   if (chmod (filename, 0644) < 0)
 473     return -1;
 474   return 0;
 475 }
 476
 477 int
 478 lock_file (filename, state)
 479   const char *filename;
 480   void **state;
 481 {
 482   int fd;
 483   struct stat buf;
 484   int attempts = 0;
 485   char *lockext = ".lockfile";
 486   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 487   if (!lockpath)
 488     return -1;
 489   strcpy (lockpath, filename);
 490   strcat (lockpath, lockext);
 491   *state = lockpath;
 492  trylock:
 493   attempts++;
 494   /* If the lock is over an hour old, delete it. */
 495   if (stat (lockpath, &buf) == 0
 496       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 497     unlink (lockpath);
 498   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 499   if (fd < 0)
 500     {
 501       if (errno == EEXIST)
 502         {
 503           /* Break the lock; we won't corrupt the file, but we might
 504              lose some scores. */
 505           if (attempts > MAX_ATTEMPTS)
 506             {
 507               unlink (lockpath);
 508               attempts = 0;
 509             }
 510           sleep ((rand () % 2)+1);
 511           goto trylock;
 512         }
 513       else
 514         return -1;
 515     }
 516   close (fd);
 517   return 0;
 518 }
 519
 520 int
 521 unlock_file (filename, state)
 522   const char *filename;
 523  void *state;
 524 {
 525   char *lockpath = (char *) state;
 526   int ret = unlink (lockpath);
 527   int saved_errno = errno;
 528   free (lockpath);
 529   errno = saved_errno;
 530   return ret;
 531 }
 532
 533 /* arch-tag: 2bf5c52e-4beb-463a-954e-c58b9c64736b
 534    (do not change this comment) */
 535
 536 /* update-game-score.c ends here */