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   intmax_t score;
  80   char *username;
  81   char *data;
  82 };
  83
  84 #define MAX_SCORES min (PTRDIFF_MAX, SIZE_MAX / sizeof (struct score_entry))
  85
  86 static int read_scores (const char *filename, struct score_entry **scores,
  87                         ptrdiff_t *count, ptrdiff_t *alloc);
  88 static int push_score (struct score_entry **scores, ptrdiff_t *count,
  89                        ptrdiff_t *size, struct score_entry const *newscore);
  90 static void sort_scores (struct score_entry *scores, ptrdiff_t count,
  91                          bool reverse);
  92 static int write_scores (const char *filename,
  93                          const struct score_entry *scores, ptrdiff_t count);
  94
  95 static _Noreturn void
  96 lose (const char *msg)
  97 {
  98   fprintf (stderr, "%s\n", msg);
  99   exit (EXIT_FAILURE);
 100 }
 101
 102 static _Noreturn void
 103 lose_syserr (const char *msg)
 104 {
 105   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
 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 int
 141 main (int argc, char **argv)
 142 {
 143   int c;
 144   bool running_suid;
 145   void *lockstate;
 146   char *scorefile;
 147   char *nl;
 148   const char *prefix, *user_prefix = NULL;
 149   struct stat buf;
 150   struct score_entry *scores;
 151   struct score_entry newscore;
 152   bool reverse = false;
 153   ptrdiff_t scorecount, scorealloc;
 154   ptrdiff_t max_scores = MAX_SCORES;
 155
 156   srand (time (0));
 157
 158   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 159     switch (c)
 160       {
 161       case 'h':
 162         usage (EXIT_SUCCESS);
 163         break;
 164       case 'd':
 165         user_prefix = optarg;
 166         break;
 167       case 'r':
 168         reverse = 1;
 169         break;
 170       case 'm':
 171         {
 172           intmax_t m = strtoimax (optarg, 0, 10);
 173           if (m < 0)
 174             usage (EXIT_FAILURE);
 175           max_scores = min (m, MAX_SCORES);
 176         }
 177         break;
 178       default:
 179         usage (EXIT_FAILURE);
 180       }
 181
 182   if (argc - optind != 3)
 183     usage (EXIT_FAILURE);
 184
 185   running_suid = (getuid () != geteuid ());
 186
 187   prefix = get_prefix (running_suid, user_prefix);
 188
 189   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 190   if (!scorefile)
 191     lose_syserr ("Couldn't allocate score file");
 192
 193   strcpy (scorefile, prefix);
 194   strcat (scorefile, "/");
 195   strcat (scorefile, argv[optind]);
 196
 197   newscore.score = strtoimax (argv[optind + 1], 0, 10);
 198
 199   newscore.data = argv[optind + 2];
 200   if (strlen (newscore.data) > MAX_DATA_LEN)
 201     newscore.data[MAX_DATA_LEN] = '\0';
 202   nl = strchr (newscore.data, '\n');
 203   if (nl)
 204     *nl = '\0';
 205
 206   newscore.username = get_user_id ();
 207   if (! newscore.username)
 208     lose_syserr ("Couldn't determine user id");
 209
 210   if (stat (scorefile, &buf) < 0)
 211     lose_syserr ("Failed to access scores file");
 212
 213   if (lock_file (scorefile, &lockstate) < 0)
 214     lose_syserr ("Failed to lock scores file");
 215
 216   if (read_scores (scorefile, &scores, &scorecount, &scorealloc) < 0)
 217     {
 218       unlock_file (scorefile, lockstate);
 219       lose_syserr ("Failed to read scores file");
 220     }
 221   if (push_score (&scores, &scorecount, &scorealloc, &newscore) < 0)
 222     {
 223       unlock_file (scorefile, lockstate);
 224       lose_syserr ("Failed to add score");
 225     }
 226   sort_scores (scores, scorecount, reverse);
 227   /* Limit the number of scores.  If we're using reverse sorting, then
 228      also increment the beginning of the array, to skip over the
 229      *smallest* scores.  Otherwise, just decrementing the number of
 230      scores suffices, since the smallest is at the end. */
 231   if (scorecount > max_scores)
 232     {
 233       if (reverse)
 234         scores += scorecount - max_scores;
 235       scorecount = max_scores;
 236     }
 237   if (write_scores (scorefile, scores, scorecount) < 0)
 238     {
 239       unlock_file (scorefile, lockstate);
 240       lose_syserr ("Failed to write scores file");
 241     }
 242   if (unlock_file (scorefile, lockstate) < 0)
 243     lose_syserr ("Failed to unlock scores file");
 244   exit (EXIT_SUCCESS);
 245 }
 246
 247 static int
 248 read_score (FILE *f, struct score_entry *score)
 249 {
 250   int c;
 251   if ((c = getc (f)) != EOF)
 252     ungetc (c, f);
 253   if (feof (f))
 254     return 1;
 255   for (score->score = 0; (c = getc (f)) != EOF && isdigit (c); )
 256     {
 257       if (INTMAX_MAX / 10 < score->score)
 258         return -1;
 259       score->score *= 10;
 260       if (INTMAX_MAX - (c - '0') < score->score)
 261         return -1;
 262       score->score += c - '0';
 263     }
 264   while ((c = getc (f)) != EOF
 265          && isspace (c))
 266     ;
 267   if (c == EOF)
 268     return -1;
 269   ungetc (c, f);
 270 #ifdef HAVE_GETDELIM
 271   {
 272     size_t count = 0;
 273     score->username = 0;
 274     if (getdelim (&score->username, &count, ' ', f) < 1
 275         || score->username == NULL)
 276       return -1;
 277     /* Trim the space */
 278     score->username[strlen (score->username)-1] = '\0';
 279   }
 280 #else
 281   {
 282     ptrdiff_t unameread = 0;
 283     ptrdiff_t unamelen = 30;
 284     char *username = malloc (unamelen);
 285     if (!username)
 286       return -1;
 287
 288     while ((c = getc (f)) != EOF && c != ' ')
 289       {
 290         if (unameread >= unamelen - 1)
 291           {
 292             ptrdiff_t unamelen_max = min (PTRDIFF_MAX, SIZE_MAX);
 293             if (unamelen <= unamelen_max / 2)
 294               unamelen *= 2;
 295             else if (unamelen < unamelen_max)
 296               unamelen = unamelen_max;
 297             else
 298               {
 299                 errno = ENOMEM;
 300                 return -1;
 301               }
 302             username = realloc (username, unamelen);
 303             if (!username)
 304               return -1;
 305           }
 306         username[unameread] = c;
 307         unameread++;
 308       }
 309     if (c == EOF)
 310       return -1;
 311     username[unameread] = '\0';
 312     score->username = username;
 313   }
 314 #endif
 315 #ifdef HAVE_GETLINE
 316   score->data = NULL;
 317   errno = 0;
 318   {
 319     size_t len;
 320     if (getline (&score->data, &len, f) < 0)
 321       return -1;
 322     score->data[strlen (score->data)-1] = '\0';
 323   }
 324 #else
 325   {
 326     ptrdiff_t cur = 0;
 327     ptrdiff_t len = 16;
 328     char *buf = malloc (len);
 329     if (!buf)
 330       return -1;
 331     while ((c = getc (f)) != EOF
 332            && c != '\n')
 333       {
 334         if (cur >= len-1)
 335           {
 336             if (min (PTRDIFF_MAX, SIZE_MAX) / 2 < len)
 337               {
 338                 errno = ENOMEM;
 339                 return -1;
 340               }
 341             if (!(buf = realloc (buf, len *= 2)))
 342               return -1;
 343           }
 344         buf[cur] = c;
 345         cur++;
 346       }
 347     score->data = buf;
 348     score->data[cur] = '\0';
 349   }
 350 #endif
 351   return 0;
 352 }
 353
 354 static int
 355 read_scores (const char *filename, struct score_entry **scores,
 356              ptrdiff_t *count, ptrdiff_t *alloc)
 357 {
 358   int readval = -1;
 359   ptrdiff_t scorecount = 0;
 360   ptrdiff_t cursize = 0;
 361   struct score_entry *ret = 0;
 362   struct score_entry entry;
 363   FILE *f = fopen (filename, "r");
 364   int retval = -1;
 365   if (!f)
 366     return -1;
 367   while ((readval = read_score (f, &entry)) == 0)
 368     if (push_score (&ret, &scorecount, &cursize, &entry) < 0)
 369       return -1;
 370   if (readval > 0 && fclose (f) == 0)
 371     {
 372       *count = scorecount;
 373       *alloc = cursize;
 374       *scores = ret;
 375       retval = 0;
 376     }
 377   return retval;
 378 }
 379
 380 static int
 381 score_compare (const void *a, const void *b)
 382 {
 383   const struct score_entry *sa = (const struct score_entry *) a;
 384   const struct score_entry *sb = (const struct score_entry *) b;
 385   return (sb->score > sa->score) - (sb->score < sa->score);
 386 }
 387
 388 static int
 389 score_compare_reverse (const void *a, const void *b)
 390 {
 391   return score_compare (b, a);
 392 }
 393
 394 int
 395 push_score (struct score_entry **scores, ptrdiff_t *count, ptrdiff_t *size,
 396             struct score_entry const *newscore)
 397 {
 398   struct score_entry *newscores = *scores;
 399   if (*count == *size)
 400     {
 401       ptrdiff_t newsize = *size;
 402       if (newsize <= 0)
 403         newsize = 1;
 404       else if (newsize <= MAX_SCORES / 2)
 405         newsize *= 2;
 406       else if (newsize < MAX_SCORES)
 407         newsize = MAX_SCORES;
 408       else
 409         {
 410           errno = ENOMEM;
 411           return -1;
 412         }
 413       newscores = realloc (newscores, sizeof *newscores * newsize);
 414       if (!newscores)
 415         return -1;
 416       *scores = newscores;
 417       *size = newsize;
 418     }
 419   newscores[*count] = *newscore;
 420   (*count) += 1;
 421   return 0;
 422 }
 423
 424 static void
 425 sort_scores (struct score_entry *scores, ptrdiff_t count, bool reverse)
 426 {
 427   qsort (scores, count, sizeof *scores,
 428          reverse ? score_compare_reverse : score_compare);
 429 }
 430
 431 static int
 432 write_scores (const char *filename, const struct score_entry *scores,
 433               ptrdiff_t count)
 434 {
 435   int fd;
 436   FILE *f;
 437   ptrdiff_t i;
 438   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 439   if (!tempfile)
 440     return -1;
 441   strcpy (tempfile, filename);
 442   strcat (tempfile, ".tempXXXXXX");
 443   fd = mkostemp (tempfile, 0);
 444   if (fd < 0)
 445     return -1;
 446 #ifndef DOS_NT
 447   if (fchmod (fd, 0644) != 0)
 448     return -1;
 449 #endif
 450   f = fdopen (fd, "w");
 451   if (! f)
 452     return -1;
 453   for (i = 0; i < count; i++)
 454     if (fprintf (f, "%"PRIdMAX" %s %s\n",
 455                  scores[i].score, scores[i].username, scores[i].data)
 456         < 0)
 457       return -1;
 458   if (fclose (f) != 0)
 459     return -1;
 460   if (rename (tempfile, filename) != 0)
 461     return -1;
 462 #ifdef DOS_NT
 463   if (chmod (filename, 0644) < 0)
 464     return -1;
 465 #endif
 466   return 0;
 467 }
 468
 469 static int
 470 lock_file (const char *filename, void **state)
 471 {
 472   int fd;
 473   struct stat buf;
 474   int attempts = 0;
 475   const char *lockext = ".lockfile";
 476   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 477   if (!lockpath)
 478     return -1;
 479   strcpy (lockpath, filename);
 480   strcat (lockpath, lockext);
 481   *state = lockpath;
 482  trylock:
 483   attempts++;
 484   /* If the lock is over an hour old, delete it.  */
 485   if (stat (lockpath, &buf) == 0
 486       && 60 * 60 < time (0) - buf.st_ctime)
 487     unlink (lockpath);
 488   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 489   if (fd < 0)
 490     {
 491       if (errno == EEXIST)
 492         {
 493           /* Break the lock; we won't corrupt the file, but we might
 494              lose some scores. */
 495           if (attempts > MAX_ATTEMPTS)
 496             {
 497               unlink (lockpath);
 498               attempts = 0;
 499             }
 500           sleep ((rand () % 2)+1);
 501           goto trylock;
 502         }
 503       else
 504         return -1;
 505     }
 506   close (fd);
 507   return 0;
 508 }
 509
 510 static int
 511 unlock_file (const char *filename, void *state)
 512 {
 513   char *lockpath = (char *) state;
 514   int saved_errno = errno;
 515   int ret = unlink (lockpath);
 516   int unlink_errno = errno;
 517   free (lockpath);
 518   errno = ret < 0 ? unlink_errno : saved_errno;
 519   return ret;
 520 }
 521
 522 /* update-game-score.c ends here */