lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2
   3 Copyright (C) 2002-2015 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 <inttypes.h>
  39 #include <limits.h>
  40 #include <stdbool.h>
  41 #include <string.h>
  42 #include <stdlib.h>
  43 #include <stdio.h>
  44 #include <time.h>
  45 #include <pwd.h>
  46 #include <ctype.h>
  47 #include <fcntl.h>
  48 #include <sys/stat.h>
  49 #include <getopt.h>
  50
  51 #ifdef WINDOWSNT
  52 #include "ntlib.h"
  53 #endif
  54
  55 #ifndef min
  56 # define min(a,b) ((a) < (b) ? (a) : (b))
  57 #endif
  58
  59 #define MAX_ATTEMPTS 5
  60 #define MAX_DATA_LEN 1024
  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   char *score;
  80   char *user_data;
  81 };
  82
  83 #define MAX_SCORES min (PTRDIFF_MAX, SIZE_MAX / sizeof (struct score_entry))
  84
  85 static int read_scores (const char *filename, struct score_entry **scores,
  86                         ptrdiff_t *count, ptrdiff_t *alloc);
  87 static int push_score (struct score_entry **scores, ptrdiff_t *count,
  88                        ptrdiff_t *size, struct score_entry const *newscore);
  89 static void sort_scores (struct score_entry *scores, ptrdiff_t count,
  90                          bool reverse);
  91 static int write_scores (const char *filename,
  92                          const struct score_entry *scores, ptrdiff_t count);
  93
  94 static _Noreturn void
  95 lose (const char *msg)
  96 {
  97   fprintf (stderr, "%s\n", msg);
  98   exit (EXIT_FAILURE);
  99 }
 100
 101 static _Noreturn void
 102 lose_syserr (const char *msg)
 103 {
 104   fprintf (stderr, "%s: %s\n", msg,
 105            errno ? strerror (errno) : "Invalid data in score file");
 106   exit (EXIT_FAILURE);
 107 }
 108
 109 static char *
 110 get_user_id (void)
 111 {
 112   struct passwd *buf = getpwuid (getuid ());
 113   if (!buf || strchr (buf->pw_name, ' ') || strchr (buf->pw_name, '\n'))
 114     {
 115       intmax_t uid = getuid ();
 116       char *name = malloc (sizeof uid * CHAR_BIT / 3 + 4);
 117       if (name)
 118         sprintf (name, "%"PRIdMAX, uid);
 119       return name;
 120     }
 121   return buf->pw_name;
 122 }
 123
 124 static const char *
 125 get_prefix (bool running_suid, const char *user_prefix)
 126 {
 127   if (!running_suid && user_prefix == NULL)
 128     lose ("Not using a shared game directory, and no prefix given.");
 129   if (running_suid)
 130     {
 131 #ifdef HAVE_SHARED_GAME_DIR
 132       return HAVE_SHARED_GAME_DIR;
 133 #else
 134       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 135 #endif
 136     }
 137   return user_prefix;
 138 }
 139
 140 static char *
 141 normalize_integer (char *num)
 142 {
 143   bool neg;
 144   char *p;
 145   while (*num != '\n' && isspace (*num))
 146     num++;
 147   neg = *num == '-';
 148   num += neg || *num == '-';
 149
 150   if (*num == '0')
 151     {
 152       while (*++num == '0')
 153         continue;
 154       neg &= !!*num;
 155       num -= !*num;
 156     }
 157
 158   for (p = num; '0' <= *p && *p <= '9'; p++)
 159     continue;
 160
 161   if (*p || p == num)
 162     {
 163       errno = 0;
 164       return 0;
 165     }
 166
 167   if (neg)
 168     *--num = '-';
 169   return num;
 170 }
 171
 172 int
 173 main (int argc, char **argv)
 174 {
 175   int c;
 176   bool running_suid;
 177   void *lockstate;
 178   char *scorefile;
 179   char *end, *nl, *user, *data;
 180   const char *prefix, *user_prefix = NULL;
 181   struct score_entry *scores;
 182   struct score_entry newscore;
 183   bool reverse = false;
 184   ptrdiff_t scorecount, scorealloc;
 185   ptrdiff_t max_scores = MAX_SCORES;
 186
 187   srand (time (0));
 188
 189   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 190     switch (c)
 191       {
 192       case 'h':
 193         usage (EXIT_SUCCESS);
 194         break;
 195       case 'd':
 196         user_prefix = optarg;
 197         break;
 198       case 'r':
 199         reverse = 1;
 200         break;
 201       case 'm':
 202         {
 203           intmax_t m = strtoimax (optarg, &end, 10);
 204           if (optarg == end || *end || m < 0)
 205             usage (EXIT_FAILURE);
 206           max_scores = min (m, MAX_SCORES);
 207         }
 208         break;
 209       default:
 210         usage (EXIT_FAILURE);
 211       }
 212
 213   if (argc - optind != 3)
 214     usage (EXIT_FAILURE);
 215
 216   running_suid = (getuid () != geteuid ());
 217
 218   prefix = get_prefix (running_suid, user_prefix);
 219
 220   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 221   if (!scorefile)
 222     lose_syserr ("Couldn't allocate score file");
 223
 224   char *z = stpcpy (scorefile, prefix);
 225   *z++ = '/';
 226   strcpy (z, argv[optind]);
 227
 228   newscore.score = normalize_integer (argv[optind + 1]);
 229   if (! newscore.score)
 230     {
 231       fprintf (stderr, "%s: Invalid score\n", argv[optind + 1]);
 232       return EXIT_FAILURE;
 233     }
 234
 235   user = get_user_id ();
 236   if (! user)
 237     lose_syserr ("Couldn't determine user id");
 238   data = argv[optind + 2];
 239   if (strlen (data) > MAX_DATA_LEN)
 240     data[MAX_DATA_LEN] = '\0';
 241   nl = strchr (data, '\n');
 242   if (nl)
 243     *nl = '\0';
 244   newscore.user_data = malloc (strlen (user) + 1 + strlen (data) + 1);
 245   if (! newscore.user_data
 246       || sprintf (newscore.user_data, "%s %s", user, data) < 0)
 247     lose_syserr ("Memory exhausted");
 248
 249   if (lock_file (scorefile, &lockstate) < 0)
 250     lose_syserr ("Failed to lock scores file");
 251
 252   if (read_scores (scorefile, &scores, &scorecount, &scorealloc) < 0)
 253     {
 254       unlock_file (scorefile, lockstate);
 255       lose_syserr ("Failed to read scores file");
 256     }
 257   if (push_score (&scores, &scorecount, &scorealloc, &newscore) < 0)
 258     {
 259       unlock_file (scorefile, lockstate);
 260       lose_syserr ("Failed to add score");
 261     }
 262   sort_scores (scores, scorecount, reverse);
 263   /* Limit the number of scores.  If we're using reverse sorting, then
 264      also increment the beginning of the array, to skip over the
 265      *smallest* scores.  Otherwise, just decrementing the number of
 266      scores suffices, since the smallest is at the end. */
 267   if (scorecount > max_scores)
 268     {
 269       if (reverse)
 270         scores += scorecount - max_scores;
 271       scorecount = max_scores;
 272     }
 273   if (write_scores (scorefile, scores, scorecount) < 0)
 274     {
 275       unlock_file (scorefile, lockstate);
 276       lose_syserr ("Failed to write scores file");
 277     }
 278   if (unlock_file (scorefile, lockstate) < 0)
 279     lose_syserr ("Failed to unlock scores file");
 280   exit (EXIT_SUCCESS);
 281 }
 282
 283 static char *
 284 read_score (char *p, struct score_entry *score)
 285 {
 286   score->score = p;
 287   p = strchr (p, ' ');
 288   if (!p)
 289     return p;
 290   *p++ = 0;
 291   score->user_data = p;
 292   p = strchr (p, '\n');
 293   if (!p)
 294     return p;
 295   *p++ = 0;
 296   return p;
 297 }
 298
 299 static int
 300 read_scores (const char *filename, struct score_entry **scores,
 301              ptrdiff_t *count, ptrdiff_t *alloc)
 302 {
 303   char *p, *filedata;
 304   ptrdiff_t filesize, nread;
 305   struct stat st;
 306   FILE *f = fopen (filename, "r");
 307   if (!f)
 308     return -1;
 309   if (fstat (fileno (f), &st) != 0)
 310     return -1;
 311   if (! (0 <= st.st_size && st.st_size < min (PTRDIFF_MAX, SIZE_MAX)))
 312     {
 313       errno = EOVERFLOW;
 314       return -1;
 315     }
 316   filesize = st.st_size;
 317   filedata = malloc (filesize + 1);
 318   if (! filedata)
 319     return -1;
 320   nread = fread (filedata, 1, filesize + 1, f);
 321   if (filesize < nread)
 322     {
 323       errno = 0;
 324       return -1;
 325     }
 326   if (nread < filesize)
 327     filesize = nread;
 328   if (ferror (f) || fclose (f) != 0)
 329     return -1;
 330   filedata[filesize] = 0;
 331   if (strlen (filedata) != filesize)
 332     {
 333       errno = 0;
 334       return -1;
 335     }
 336
 337   *scores = 0;
 338   *count = *alloc = 0;
 339   for (p = filedata; p < filedata + filesize; )
 340     {
 341       struct score_entry entry;
 342       p = read_score (p, &entry);
 343       if (!p)
 344         {
 345           errno = 0;
 346           return -1;
 347         }
 348       if (push_score (scores, count, alloc, &entry) < 0)
 349         return -1;
 350     }
 351   return 0;
 352 }
 353
 354 static int
 355 score_compare (const void *a, const void *b)
 356 {
 357   const struct score_entry *sa = (const struct score_entry *) a;
 358   const struct score_entry *sb = (const struct score_entry *) b;
 359   char *sca = sa->score;
 360   char *scb = sb->score;
 361   size_t lena, lenb;
 362   bool nega = *sca == '-';
 363   bool negb = *scb == '-';
 364   int diff = nega - negb;
 365   if (diff)
 366     return diff;
 367   if (nega)
 368     {
 369       char *tmp = sca;
 370       sca = scb + 1;
 371       scb = tmp + 1;
 372     }
 373   lena = strlen (sca);
 374   lenb = strlen (scb);
 375   if (lena != lenb)
 376     return lenb < lena ? -1 : 1;
 377   return strcmp (scb, sca);
 378 }
 379
 380 static int
 381 score_compare_reverse (const void *a, const void *b)
 382 {
 383   return score_compare (b, a);
 384 }
 385
 386 int
 387 push_score (struct score_entry **scores, ptrdiff_t *count, ptrdiff_t *size,
 388             struct score_entry const *newscore)
 389 {
 390   struct score_entry *newscores = *scores;
 391   if (*count == *size)
 392     {
 393       ptrdiff_t newsize = *size;
 394       if (newsize <= 0)
 395         newsize = 1;
 396       else if (newsize <= MAX_SCORES / 2)
 397         newsize *= 2;
 398       else if (newsize < MAX_SCORES)
 399         newsize = MAX_SCORES;
 400       else
 401         {
 402           errno = ENOMEM;
 403           return -1;
 404         }
 405       newscores = realloc (newscores, sizeof *newscores * newsize);
 406       if (!newscores)
 407         return -1;
 408       *scores = newscores;
 409       *size = newsize;
 410     }
 411   newscores[*count] = *newscore;
 412   (*count) += 1;
 413   return 0;
 414 }
 415
 416 static void
 417 sort_scores (struct score_entry *scores, ptrdiff_t count, bool reverse)
 418 {
 419   qsort (scores, count, sizeof *scores,
 420          reverse ? score_compare_reverse : score_compare);
 421 }
 422
 423 static int
 424 write_scores (const char *filename, const struct score_entry *scores,
 425               ptrdiff_t count)
 426 {
 427   int fd;
 428   FILE *f;
 429   ptrdiff_t i;
 430   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 431   if (!tempfile)
 432     return -1;
 433   strcpy (stpcpy (tempfile, filename), ".tempXXXXXX");
 434   fd = mkostemp (tempfile, 0);
 435   if (fd < 0)
 436     return -1;
 437 #ifndef DOS_NT
 438   if (fchmod (fd, 0644) != 0)
 439     return -1;
 440 #endif
 441   f = fdopen (fd, "w");
 442   if (! f)
 443     return -1;
 444   for (i = 0; i < count; i++)
 445     if (fprintf (f, "%s %s\n", scores[i].score, scores[i].user_data) < 0)
 446       return -1;
 447   if (fclose (f) != 0)
 448     return -1;
 449   if (rename (tempfile, filename) != 0)
 450     return -1;
 451   return 0;
 452 }
 453
 454 static int
 455 lock_file (const char *filename, void **state)
 456 {
 457   int fd;
 458   struct stat buf;
 459   int attempts = 0;
 460   const char *lockext = ".lockfile";
 461   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 462   if (!lockpath)
 463     return -1;
 464   strcpy (stpcpy (lockpath, filename), lockext);
 465   *state = lockpath;
 466
 467   while ((fd = open (lockpath, O_CREAT | O_EXCL, 0600)) < 0)
 468     {
 469       if (errno != EEXIST)
 470         return -1;
 471       attempts++;
 472
 473       /* Break the lock if it is over an hour old, or if we've tried
 474          more than MAX_ATTEMPTS times.  We won't corrupt the file, but
 475          we might lose some scores. */
 476       if (MAX_ATTEMPTS < attempts
 477           || (stat (lockpath, &buf) == 0 && 60 * 60 < time (0) - buf.st_ctime))
 478         {
 479           if (unlink (lockpath) != 0 && errno != ENOENT)
 480             return -1;
 481           attempts = 0;
 482         }
 483
 484       sleep ((rand () & 1) + 1);
 485     }
 486
 487   close (fd);
 488   return 0;
 489 }
 490
 491 static int
 492 unlock_file (const char *filename, void *state)
 493 {
 494   char *lockpath = (char *) state;
 495   int saved_errno = errno;
 496   int ret = unlink (lockpath);
 497   int unlink_errno = errno;
 498   free (lockpath);
 499   errno = ret < 0 ? unlink_errno : saved_errno;
 500   return ret;
 501 }
 502
 503 /* update-game-score.c ends here */