code.delx.au - gnu-emacs/blob - lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2    Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Emacs.
   5
   6 GNU Emacs is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Emacs is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Emacs; see the file COPYING.  If not, write to
  18 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  19 Boston, MA 02110-1301, USA.  */
  20
  21 /* This program is allows a game to securely and atomically update a
  22    score file.  It should be installed setuid, owned by an appropriate
  23    user like `games'.
  24
  25    Alternatively, it can be compiled without HAVE_SHARED_GAME_DIR
  26    defined, and in that case it will store scores in the user's home
  27    directory (it should NOT be setuid).
  28
  29    Created 2002/03/22, by Colin Walters <walters@debian.org>
  30 */
  31
  32 #include <config.h>
  33
  34 #ifdef HAVE_UNISTD_H
  35 #include <unistd.h>
  36 #endif
  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 #define MAX_ATTEMPTS 5
  61 #define MAX_SCORES 200
  62 #define MAX_DATA_LEN 1024
  63
  64 /* Declare the prototype for a general external function.  */
  65 #if defined (PROTOTYPES) || defined (WINDOWSNT)
  66 #define P_(proto) proto
  67 #else
  68 #define P_(proto) ()
  69 #endif
  70
  71 #ifndef HAVE_DIFFTIME
  72 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  73 #define difftime(t1, t0) (double)((t1) - (t0))
  74 #endif
  75
  76 int
  77 usage (err)
  78      int err;
  79 {
  80   fprintf (stdout, "Usage: update-game-score [-m MAX ] [ -r ] game/scorefile SCORE DATA\n");
  81   fprintf (stdout, "       update-game-score -h\n");
  82   fprintf (stdout, " -h\t\tDisplay this help.\n");
  83   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  84   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  85   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  86   exit (err);
  87 }
  88
  89 int lock_file P_ ((const char *filename, void **state));
  90 int unlock_file P_ ((const char *filename, void *state));
  91
  92 struct score_entry
  93 {
  94   long score;
  95   char *username;
  96   char *data;
  97 };
  98
  99 int read_scores P_ ((const char *filename, struct score_entry **scores,
 100                      int *count));
 101 int push_score P_ ((struct score_entry **scores, int *count,
 102                     int newscore, char *username, char *newdata));
 103 void sort_scores P_ ((struct score_entry *scores, int count, int reverse));
 104 int write_scores P_ ((const char *filename, const struct score_entry *scores,
 105                       int count));
 106
 107 void lose P_ ((const char *msg)) NO_RETURN;
 108
 109 void
 110 lose (msg)
 111      const char *msg;
 112 {
 113   fprintf (stderr, "%s\n", msg);
 114   exit (EXIT_FAILURE);
 115 }
 116
 117 void lose_syserr P_ ((const char *msg)) NO_RETURN;
 118
 119 /* Taken from sysdep.c.  */
 120 #ifndef HAVE_STRERROR
 121 #ifndef WINDOWSNT
 122 char *
 123 strerror (errnum)
 124      int errnum;
 125 {
 126   extern char *sys_errlist[];
 127   extern int sys_nerr;
 128
 129   if (errnum >= 0 && errnum < sys_nerr)
 130     return sys_errlist[errnum];
 131   return (char *) "Unknown error";
 132 }
 133 #endif /* not WINDOWSNT */
 134 #endif /* ! HAVE_STRERROR */
 135
 136 void
 137 lose_syserr (msg)
 138      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 P_ ((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 (running_suid, user_prefix)
 167      int running_suid;
 168      char *user_prefix;
 169 {
 170   if (!running_suid && user_prefix == NULL)
 171     lose ("Not using a shared game directory, and no prefix given.");
 172   if (running_suid)
 173     {
 174 #ifdef HAVE_SHARED_GAME_DIR
 175       return HAVE_SHARED_GAME_DIR;
 176 #else
 177       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 178 #endif
 179     }
 180   return user_prefix;
 181 }
 182
 183 int
 184 main (argc, argv)
 185      int argc;
 186      char **argv;
 187 {
 188   int c, running_suid;
 189   void *lockstate;
 190   char *user_id, *scorefile, *prefix, *user_prefix = NULL;
 191   struct stat buf;
 192   struct score_entry *scores;
 193   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 194   char *newdata;
 195
 196   srand (time (0));
 197
 198   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 199     switch (c)
 200       {
 201       case 'h':
 202         usage (EXIT_SUCCESS);
 203         break;
 204       case 'd':
 205         user_prefix = optarg;
 206         break;
 207       case 'r':
 208         reverse = 1;
 209         break;
 210       case 'm':
 211         max = atoi (optarg);
 212         if (max > MAX_SCORES)
 213           max = MAX_SCORES;
 214         break;
 215       default:
 216         usage (EXIT_FAILURE);
 217       }
 218
 219   if (optind+3 != argc)
 220     usage (EXIT_FAILURE);
 221
 222   running_suid = (getuid () != geteuid ());
 223
 224   prefix = get_prefix (running_suid, user_prefix);
 225
 226   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 227   if (!scorefile)
 228     lose_syserr ("Couldn't allocate score file");
 229
 230   strcpy (scorefile, prefix);
 231   strcat (scorefile, "/");
 232   strcat (scorefile, argv[optind]);
 233   newscore = atoi (argv[optind+1]);
 234   newdata = argv[optind+2];
 235   if (strlen (newdata) > MAX_DATA_LEN)
 236     newdata[MAX_DATA_LEN] = '\0';
 237
 238   user_id = get_user_id ();
 239   if (user_id == NULL)
 240     lose_syserr ("Couldn't determine user id");
 241
 242   if (stat (scorefile, &buf) < 0)
 243     lose_syserr ("Failed to access scores file");
 244
 245   if (lock_file (scorefile, &lockstate) < 0)
 246     lose_syserr ("Failed to lock scores file");
 247
 248   if (read_scores (scorefile, &scores, &scorecount) < 0)
 249     {
 250       unlock_file (scorefile, lockstate);
 251       lose_syserr ("Failed to read scores file");
 252     }
 253   push_score (&scores, &scorecount, newscore, user_id, newdata);
 254   /* Limit the number of scores.  If we're using reverse sorting, then
 255      we should increment the beginning of the array, to skip over the
 256      *smallest* scores.  Otherwise, we just decrement the number of
 257      scores, since the smallest will be at the end. */
 258   if (scorecount > MAX_SCORES)
 259     scorecount -= (scorecount - MAX_SCORES);
 260     if (reverse)
 261       scores += (scorecount - MAX_SCORES);
 262   sort_scores (scores, scorecount, reverse);
 263   if (write_scores (scorefile, scores, scorecount) < 0)
 264     {
 265       unlock_file (scorefile, lockstate);
 266       lose_syserr ("Failed to write scores file");
 267     }
 268   unlock_file (scorefile, lockstate);
 269   exit (EXIT_SUCCESS);
 270 }
 271
 272 int
 273 read_score (f, score)
 274      FILE *f;
 275      struct score_entry *score;
 276 {
 277   int c;
 278   if (feof (f))
 279     return 1;
 280   while ((c = getc (f)) != EOF
 281          && isdigit (c))
 282     {
 283       score->score *= 10;
 284       score->score += (c-48);
 285     }
 286   while ((c = getc (f)) != EOF
 287          && isspace (c))
 288     ;
 289   if (c == EOF)
 290     return -1;
 291   ungetc (c, f);
 292 #ifdef HAVE_GETDELIM
 293   {
 294     size_t count = 0;
 295     if (getdelim (&score->username, &count, ' ', f) < 1
 296         || score->username == NULL)
 297       return -1;
 298     /* Trim the space */
 299     score->username[strlen (score->username)-1] = '\0';
 300   }
 301 #else
 302   {
 303     int unameread = 0;
 304     int unamelen = 30;
 305     char *username = malloc (unamelen);
 306     if (!username)
 307       return -1;
 308
 309     while ((c = getc (f)) != EOF
 310            && !isspace (c))
 311       {
 312         if (unameread >= unamelen-1)
 313           if (!(username = realloc (username, unamelen *= 2)))
 314             return -1;
 315         username[unameread] = c;
 316         unameread++;
 317       }
 318     if (c == EOF)
 319       return -1;
 320     username[unameread] = '\0';
 321     score->username = username;
 322   }
 323 #endif
 324 #ifdef HAVE_GETLINE
 325   score->data = NULL;
 326   errno = 0;
 327   {
 328     size_t len;
 329     if (getline (&score->data, &len, f) < 0)
 330       return -1;
 331     score->data[strlen (score->data)-1] = '\0';
 332   }
 333 #else
 334   {
 335     int cur = 0;
 336     int len = 16;
 337     char *buf = malloc (len);
 338     if (!buf)
 339       return -1;
 340     while ((c = getc (f)) != EOF
 341            && c != '\n')
 342       {
 343         if (cur >= len-1)
 344           {
 345             if (!(buf = realloc (buf, len *= 2)))
 346               return -1;
 347           }
 348         buf[cur] = c;
 349         cur++;
 350       }
 351     score->data = buf;
 352     score->data[cur] = '\0';
 353   }
 354 #endif
 355   return 0;
 356 }
 357
 358 int
 359 read_scores (filename, scores, count)
 360      const char *filename;
 361      struct score_entry **scores;
 362      int *count;
 363 {
 364   int readval, scorecount, cursize;
 365   struct score_entry *ret;
 366   FILE *f = fopen (filename, "r");
 367   if (!f)
 368     return -1;
 369   scorecount = 0;
 370   cursize = 16;
 371   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 372   if (!ret)
 373     return -1;
 374   while ((readval = read_score (f, &ret[scorecount])) == 0)
 375     {
 376       /* We encoutered an error */
 377       if (readval < 0)
 378         return -1;
 379       scorecount++;
 380       if (scorecount >= cursize)
 381         {
 382           cursize *= 2;
 383           ret = (struct score_entry *)
 384             realloc (ret, (sizeof (struct score_entry) * cursize));
 385           if (!ret)
 386             return -1;
 387         }
 388     }
 389   *count = scorecount;
 390   *scores = ret;
 391   return 0;
 392 }
 393
 394 int
 395 score_compare (a, b)
 396      const void *a;
 397      const void *b;
 398 {
 399   const struct score_entry *sa = (const struct score_entry *) a;
 400   const struct score_entry *sb = (const struct score_entry *) b;
 401   return (sb->score > sa->score) - (sb->score < sa->score);
 402 }
 403
 404 int
 405 score_compare_reverse (a, b)
 406      const void *a;
 407      const void *b;
 408 {
 409   const struct score_entry *sa = (const struct score_entry *) a;
 410   const struct score_entry *sb = (const struct score_entry *) b;
 411   return (sa->score > sb->score) - (sa->score < sb->score);
 412 }
 413
 414 int
 415 push_score (scores, count, newscore, username, newdata)
 416      struct score_entry **scores;
 417      int *count; int newscore;
 418      char *username;
 419      char *newdata;
 420 {
 421  struct score_entry *newscores
 422    = (struct score_entry *) realloc (*scores,
 423                                      sizeof (struct score_entry) * ((*count) + 1));
 424   if (!newscores)
 425     return -1;
 426   newscores[*count].score = newscore;
 427   newscores[*count].username = username;
 428   newscores[*count].data = newdata;
 429   (*count) += 1;
 430   *scores = newscores;
 431   return 0;
 432 }
 433
 434 void
 435 sort_scores (scores, count, reverse)
 436      struct score_entry *scores;
 437      int count;
 438      int reverse;
 439 {
 440   qsort (scores, count, sizeof (struct score_entry),
 441         reverse ? score_compare_reverse : score_compare);
 442 }
 443
 444 int
 445 write_scores (filename, scores, count)
 446      const char *filename;
 447      const struct score_entry * scores;
 448      int count;
 449 {
 450   FILE *f;
 451   int i;
 452   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 453   if (!tempfile)
 454     return -1;
 455   strcpy (tempfile, filename);
 456   strcat (tempfile, ".tempXXXXXX");
 457 #ifdef HAVE_MKSTEMP
 458   if (mkstemp (tempfile) < 0
 459 #else
 460   if (mktemp (tempfile) != tempfile
 461 #endif
 462       || !(f = fopen (tempfile, "w")))
 463     return -1;
 464   for (i = 0; i < count; i++)
 465     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 466                 scores[i].data) < 0)
 467       return -1;
 468   fclose (f);
 469   if (rename (tempfile, filename) < 0)
 470     return -1;
 471   if (chmod (filename, 0644) < 0)
 472     return -1;
 473   return 0;
 474 }
 475
 476 int
 477 lock_file (filename, state)
 478   const char *filename;
 479   void **state;
 480 {
 481   int fd;
 482   struct stat buf;
 483   int attempts = 0;
 484   char *lockext = ".lockfile";
 485   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 486   if (!lockpath)
 487     return -1;
 488   strcpy (lockpath, filename);
 489   strcat (lockpath, lockext);
 490   *state = lockpath;
 491  trylock:
 492   attempts++;
 493   /* If the lock is over an hour old, delete it. */
 494   if (stat (lockpath, &buf) == 0
 495       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 496     unlink (lockpath);
 497   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 498   if (fd < 0)
 499     {
 500       if (errno == EEXIST)
 501         {
 502           /* Break the lock; we won't corrupt the file, but we might
 503              lose some scores. */
 504           if (attempts > MAX_ATTEMPTS)
 505             {
 506               unlink (lockpath);
 507               attempts = 0;
 508             }
 509           sleep ((rand () % 2)+1);
 510           goto trylock;
 511         }
 512       else
 513         return -1;
 514     }
 515   close (fd);
 516   return 0;
 517 }
 518
 519 int
 520 unlock_file (filename, state)
 521   const char *filename;
 522  void *state;
 523 {
 524   char *lockpath = (char *) state;
 525   int ret = unlink (lockpath);
 526   int saved_errno = errno;
 527   free (lockpath);
 528   errno = saved_errno;
 529   return ret;
 530 }
 531
 532 /* arch-tag: 2bf5c52e-4beb-463a-954e-c58b9c64736b
 533    (do not change this comment) */
 534
 535 /* update-game-score.c ends here */