lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2
   3 Copyright (C) 2002-2017 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 (at
  12 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 <https://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 either setuid or setgid, owned
  25    by an appropriate user or group 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 <string.h>
  41 #include <stdlib.h>
  42 #include <time.h>
  43 #include <pwd.h>
  44 #include <ctype.h>
  45 #include <fcntl.h>
  46 #include <sys/stat.h>
  47 #include <getopt.h>
  48
  49 #include <unlocked-io.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, mode_t mode,
  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 privileged, const char *user_prefix)
 126 {
 127   if (privileged)
 128     {
 129 #ifdef HAVE_SHARED_GAME_DIR
 130       return HAVE_SHARED_GAME_DIR;
 131 #else
 132       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n"
 133             "and should not run with elevated privileges.");
 134 #endif
 135     }
 136   if (user_prefix == NULL)
 137     lose ("Not using a shared game directory, and no prefix given.");
 138   return user_prefix;
 139 }
 140
 141 static char *
 142 normalize_integer (char *num)
 143 {
 144   bool neg;
 145   char *p;
 146   while (*num != '\n' && isspace (*num))
 147     num++;
 148   neg = *num == '-';
 149   num += neg || *num == '-';
 150
 151   if (*num == '0')
 152     {
 153       while (*++num == '0')
 154         continue;
 155       neg &= !!*num;
 156       num -= !*num;
 157     }
 158
 159   for (p = num; '0' <= *p && *p <= '9'; p++)
 160     continue;
 161
 162   if (*p || p == num)
 163     {
 164       errno = 0;
 165       return 0;
 166     }
 167
 168   if (neg)
 169     *--num = '-';
 170   return num;
 171 }
 172
 173 int
 174 main (int argc, char **argv)
 175 {
 176   int c;
 177   bool running_suid, running_sgid;
 178   void *lockstate;
 179   char *scorefile;
 180   char *end, *nl, *user, *data;
 181   const char *prefix, *user_prefix = NULL;
 182   struct score_entry *scores;
 183   struct score_entry newscore;
 184   bool reverse = false;
 185   ptrdiff_t scorecount, scorealloc;
 186   ptrdiff_t max_scores = MAX_SCORES;
 187
 188   srand (time (0));
 189
 190   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 191     switch (c)
 192       {
 193       case 'h':
 194         usage (EXIT_SUCCESS);
 195         break;
 196       case 'd':
 197         user_prefix = optarg;
 198         break;
 199       case 'r':
 200         reverse = 1;
 201         break;
 202       case 'm':
 203         {
 204           intmax_t m = strtoimax (optarg, &end, 10);
 205           if (optarg == end || *end || m < 0)
 206             usage (EXIT_FAILURE);
 207           max_scores = min (m, MAX_SCORES);
 208         }
 209         break;
 210       default:
 211         usage (EXIT_FAILURE);
 212       }
 213
 214   if (argc - optind != 3)
 215     usage (EXIT_FAILURE);
 216
 217   running_suid = (getuid () != geteuid ());
 218   running_sgid = (getgid () != getegid ());
 219   if (running_suid && running_sgid)
 220     lose ("This program can run either suid or sgid, but not both.");
 221
 222   prefix = get_prefix (running_suid || running_sgid, user_prefix);
 223
 224   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 225   if (!scorefile)
 226     lose_syserr ("Couldn't allocate score file");
 227
 228   char *z = stpcpy (scorefile, prefix);
 229   *z++ = '/';
 230   strcpy (z, argv[optind]);
 231
 232   newscore.score = normalize_integer (argv[optind + 1]);
 233   if (! newscore.score)
 234     {
 235       fprintf (stderr, "%s: Invalid score\n", argv[optind + 1]);
 236       return EXIT_FAILURE;
 237     }
 238
 239   user = get_user_id ();
 240   if (! user)
 241     lose_syserr ("Couldn't determine user id");
 242   data = argv[optind + 2];
 243   if (strlen (data) > MAX_DATA_LEN)
 244     data[MAX_DATA_LEN] = '\0';
 245   nl = strchr (data, '\n');
 246   if (nl)
 247     *nl = '\0';
 248   newscore.user_data = malloc (strlen (user) + 1 + strlen (data) + 1);
 249   if (! newscore.user_data
 250       || sprintf (newscore.user_data, "%s %s", user, data) < 0)
 251     lose_syserr ("Memory exhausted");
 252
 253   if (lock_file (scorefile, &lockstate) < 0)
 254     lose_syserr ("Failed to lock scores file");
 255
 256   if (read_scores (scorefile, &scores, &scorecount, &scorealloc) < 0)
 257     {
 258       unlock_file (scorefile, lockstate);
 259       lose_syserr ("Failed to read scores file");
 260     }
 261   if (push_score (&scores, &scorecount, &scorealloc, &newscore) < 0)
 262     {
 263       unlock_file (scorefile, lockstate);
 264       lose_syserr ("Failed to add score");
 265     }
 266   sort_scores (scores, scorecount, reverse);
 267   /* Limit the number of scores.  If we're using reverse sorting, then
 268      also increment the beginning of the array, to skip over the
 269      *smallest* scores.  Otherwise, just decrementing the number of
 270      scores suffices, since the smallest is at the end. */
 271   if (scorecount > max_scores)
 272     {
 273       if (reverse)
 274         scores += scorecount - max_scores;
 275       scorecount = max_scores;
 276     }
 277   if (write_scores (scorefile, running_sgid ? 0664 : 0644,
 278                     scores, scorecount) < 0)
 279     {
 280       unlock_file (scorefile, lockstate);
 281       lose_syserr ("Failed to write scores file");
 282     }
 283   if (unlock_file (scorefile, lockstate) < 0)
 284     lose_syserr ("Failed to unlock scores file");
 285   exit (EXIT_SUCCESS);
 286 }
 287
 288 static char *
 289 read_score (char *p, struct score_entry *score)
 290 {
 291   score->score = p;
 292   p = strchr (p, ' ');
 293   if (!p)
 294     return p;
 295   *p++ = 0;
 296   score->user_data = p;
 297   p = strchr (p, '\n');
 298   if (!p)
 299     return p;
 300   *p++ = 0;
 301   return p;
 302 }
 303
 304 static int
 305 read_scores (const char *filename, struct score_entry **scores,
 306              ptrdiff_t *count, ptrdiff_t *alloc)
 307 {
 308   char *p, *filedata;
 309   ptrdiff_t filesize, nread;
 310   struct stat st;
 311   FILE *f = fopen (filename, "r");
 312   if (!f)
 313     return -1;
 314   if (fstat (fileno (f), &st) != 0)
 315     return -1;
 316   if (! (0 <= st.st_size && st.st_size < min (PTRDIFF_MAX, SIZE_MAX)))
 317     {
 318       errno = EOVERFLOW;
 319       return -1;
 320     }
 321   filesize = st.st_size;
 322   filedata = malloc (filesize + 1);
 323   if (! filedata)
 324     return -1;
 325   nread = fread (filedata, 1, filesize + 1, f);
 326   if (filesize < nread)
 327     {
 328       errno = 0;
 329       return -1;
 330     }
 331   if (nread < filesize)
 332     filesize = nread;
 333   if (ferror (f) || fclose (f) != 0)
 334     return -1;
 335   filedata[filesize] = 0;
 336   if (strlen (filedata) != filesize)
 337     {
 338       errno = 0;
 339       return -1;
 340     }
 341
 342   *scores = 0;
 343   *count = *alloc = 0;
 344   for (p = filedata; p < filedata + filesize; )
 345     {
 346       struct score_entry entry;
 347       p = read_score (p, &entry);
 348       if (!p)
 349         {
 350           errno = 0;
 351           return -1;
 352         }
 353       if (push_score (scores, count, alloc, &entry) < 0)
 354         return -1;
 355     }
 356   return 0;
 357 }
 358
 359 static int
 360 score_compare (const void *a, const void *b)
 361 {
 362   const struct score_entry *sa = (const struct score_entry *) a;
 363   const struct score_entry *sb = (const struct score_entry *) b;
 364   char *sca = sa->score;
 365   char *scb = sb->score;
 366   size_t lena, lenb;
 367   bool nega = *sca == '-';
 368   bool negb = *scb == '-';
 369   int diff = nega - negb;
 370   if (diff)
 371     return diff;
 372   if (nega)
 373     {
 374       char *tmp = sca;
 375       sca = scb + 1;
 376       scb = tmp + 1;
 377     }
 378   lena = strlen (sca);
 379   lenb = strlen (scb);
 380   if (lena != lenb)
 381     return lenb < lena ? -1 : 1;
 382   return strcmp (scb, sca);
 383 }
 384
 385 static int
 386 score_compare_reverse (const void *a, const void *b)
 387 {
 388   return score_compare (b, a);
 389 }
 390
 391 int
 392 push_score (struct score_entry **scores, ptrdiff_t *count, ptrdiff_t *size,
 393             struct score_entry const *newscore)
 394 {
 395   struct score_entry *newscores = *scores;
 396   if (*count == *size)
 397     {
 398       ptrdiff_t newsize = *size;
 399       if (newsize <= 0)
 400         newsize = 1;
 401       else if (newsize <= MAX_SCORES / 2)
 402         newsize *= 2;
 403       else if (newsize < MAX_SCORES)
 404         newsize = MAX_SCORES;
 405       else
 406         {
 407           errno = ENOMEM;
 408           return -1;
 409         }
 410       newscores = realloc (newscores, sizeof *newscores * newsize);
 411       if (!newscores)
 412         return -1;
 413       *scores = newscores;
 414       *size = newsize;
 415     }
 416   newscores[*count] = *newscore;
 417   (*count) += 1;
 418   return 0;
 419 }
 420
 421 static void
 422 sort_scores (struct score_entry *scores, ptrdiff_t count, bool reverse)
 423 {
 424   qsort (scores, count, sizeof *scores,
 425          reverse ? score_compare_reverse : score_compare);
 426 }
 427
 428 static int
 429 write_scores (const char *filename, mode_t mode,
 430               const struct score_entry *scores, ptrdiff_t count)
 431 {
 432   int fd;
 433   FILE *f;
 434   ptrdiff_t i;
 435   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 436   if (!tempfile)
 437     return -1;
 438   strcpy (stpcpy (tempfile, filename), ".tempXXXXXX");
 439   fd = mkostemp (tempfile, 0);
 440   if (fd < 0)
 441     return -1;
 442 #ifndef DOS_NT
 443   if (fchmod (fd, mode) != 0)
 444     return -1;
 445 #endif
 446   f = fdopen (fd, "w");
 447   if (! f)
 448     return -1;
 449   for (i = 0; i < count; i++)
 450     if (fprintf (f, "%s %s\n", scores[i].score, scores[i].user_data) < 0)
 451       return -1;
 452   if (fclose (f) != 0)
 453     return -1;
 454   if (rename (tempfile, filename) != 0)
 455     return -1;
 456   return 0;
 457 }
 458
 459 static int
 460 lock_file (const char *filename, void **state)
 461 {
 462   int fd;
 463   struct stat buf;
 464   int attempts = 0;
 465   const char *lockext = ".lockfile";
 466   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 467   if (!lockpath)
 468     return -1;
 469   strcpy (stpcpy (lockpath, filename), lockext);
 470   *state = lockpath;
 471
 472   while ((fd = open (lockpath, O_CREAT | O_EXCL, 0600)) < 0)
 473     {
 474       if (errno != EEXIST)
 475         return -1;
 476       attempts++;
 477
 478       /* Break the lock if it is over an hour old, or if we've tried
 479          more than MAX_ATTEMPTS times.  We won't corrupt the file, but
 480          we might lose some scores. */
 481       if (MAX_ATTEMPTS < attempts
 482           || (stat (lockpath, &buf) == 0 && 60 * 60 < time (0) - buf.st_ctime))
 483         {
 484           if (unlink (lockpath) != 0 && errno != ENOENT)
 485             return -1;
 486           attempts = 0;
 487         }
 488
 489       sleep ((rand () & 1) + 1);
 490     }
 491
 492   close (fd);
 493   return 0;
 494 }
 495
 496 static int
 497 unlock_file (const char *filename, void *state)
 498 {
 499   char *lockpath = (char *) state;
 500   int saved_errno = errno;
 501   int ret = unlink (lockpath);
 502   int unlink_errno = errno;
 503   free (lockpath);
 504   errno = ret < 0 ? unlink_errno : saved_errno;
 505   return ret;
 506 }
 507
 508 /* update-game-score.c ends here */