lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2    Copyright (C) 2002 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., 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, 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 #define _GNU_SOURCE
  33
  34 #include <config.h>
  35
  36 #include <unistd.h>
  37 #include <errno.h>
  38 #include <string.h>
  39 #include <stdlib.h>
  40 #include <stdio.h>
  41 #include <time.h>
  42 #include <pwd.h>
  43 #include <ctype.h>
  44 #include <fcntl.h>
  45 #include <stdarg.h>
  46 #include <sys/stat.h>
  47
  48 #define MAX_ATTEMPTS 5
  49 #define MAX_SCORES 200
  50 #define MAX_DATA_LEN 1024
  51
  52 #ifdef HAVE_SHARED_GAME_DIR
  53 #define SCORE_FILE_PREFIX HAVE_SHARED_GAME_DIR
  54 #else
  55 #define SCORE_FILE_PREFIX "~/.emacs.d/games"
  56 #endif
  57
  58 #if !defined (__GNUC__) || __GNUC__ < 2
  59 #define __attribute__(x)
  60 #endif
  61
  62 int
  63 usage(int err)
  64 {
  65   fprintf(stdout, "Usage: update-game-score [-m MAX ] [ -r ] 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   exit(err);
  71 }
  72
  73 int
  74 lock_file(const char *filename, void **state);
  75 int
  76 unlock_file(const char *filename, void *state);
  77
  78 struct score_entry
  79 {
  80   long score;
  81   char *username;
  82   char *data;
  83 };
  84
  85 int
  86 read_scores(const char *filename, struct score_entry **scores,
  87             int *count);
  88 int
  89 push_score(struct score_entry **scores, int *count,
  90            int newscore, char *username, char *newdata);
  91 void
  92 sort_scores(struct score_entry *scores, int count, int reverse);
  93 int
  94 write_scores(const char *filename, const struct score_entry *scores,
  95              int count);
  96
  97 char *
  98 get_user_id(struct passwd *buf)
  99 {
 100   char *name;
 101   if (!buf)
 102     {
 103       int count = 1;
 104       int uid = (int) getuid();
 105       int tuid = uid;
 106       while (tuid /= 10)
 107         count++;
 108       name = malloc(count+1);
 109       sprintf(name, "%d", uid);
 110       return name;
 111     }
 112   return buf->pw_name;
 113 }
 114
 115 char *
 116 get_home_dir(struct passwd *buf)
 117 {
 118   if (!buf)
 119     return NULL;
 120   return buf->pw_dir;
 121 }
 122
 123 void lose(const char *msg, ...)
 124      __attribute__ ((format (printf,1,0), noreturn));
 125
 126 void lose(const char *msg, ...)
 127 {
 128     va_list ap;
 129     va_start(ap, msg);
 130     vfprintf(stderr, msg, ap);
 131     va_end(ap);
 132     exit(1);
 133 }
 134
 135 int
 136 main(int argc, char **argv)
 137 {
 138   int c;
 139   void *lockstate;
 140   char *scorefile, *prefix;
 141   struct stat buf;
 142   struct score_entry *scores;
 143   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 144   char *newdata;
 145   struct passwd *passwdbuf;
 146
 147   srand(time(0));
 148
 149   while ((c = getopt(argc, argv, "hrm:")) != -1)
 150     switch (c)
 151       {
 152       case 'h':
 153         usage(0);
 154         break;
 155       case 'r':
 156         reverse = 1;
 157         break;
 158       case 'm':
 159         max = atoi(optarg);
 160         if (max > MAX_SCORES)
 161           max = MAX_SCORES;
 162         break;
 163       default:
 164         usage(1);
 165       }
 166
 167   if (optind+3 != argc)
 168     usage(1);
 169
 170   passwdbuf = getpwuid(getuid());
 171
 172   if (!strncmp(SCORE_FILE_PREFIX, "~", 1))
 173     {
 174       char *homedir = get_home_dir(passwdbuf);
 175       if (!homedir)
 176         lose("Unable to determine home directory\n");
 177       prefix = malloc(strlen(homedir) + strlen(SCORE_FILE_PREFIX) + 1);
 178       strcpy(prefix, homedir);
 179       /* Skip over the '~'. */
 180       strcat(prefix, SCORE_FILE_PREFIX+1);
 181     }
 182   else
 183     prefix = strdup(SCORE_FILE_PREFIX);
 184
 185   if (!prefix)
 186     lose("Couldn't create score file name: %s\n", strerror(errno));
 187
 188   scorefile = malloc(strlen(prefix) + strlen(argv[optind]) + 2);
 189   if (!scorefile)
 190     lose("Couldn't create score file name: %s\n", strerror(errno));
 191
 192   strcpy(scorefile, prefix);
 193   free(prefix);
 194   strcat(scorefile, "/");
 195   strcat(scorefile, argv[optind]);
 196   newscore = atoi(argv[optind+1]);
 197   newdata = argv[optind+2];
 198   if (strlen(newdata) > MAX_DATA_LEN)
 199     newdata[MAX_DATA_LEN] = '\0';
 200
 201   if (stat(scorefile, &buf) < 0)
 202     lose("Failed to access scores file \"%s\": %s\n", scorefile,
 203          strerror(errno));
 204   if (lock_file(scorefile, &lockstate) < 0)
 205       lose("Failed to lock scores file \"%s\": %s\n",
 206            scorefile, strerror(errno));
 207   if (read_scores(scorefile, &scores, &scorecount) < 0)
 208     {
 209       unlock_file(scorefile, lockstate);
 210       lose("Failed to read scores file \"%s\": %s\n", scorefile,
 211            strerror(errno));
 212     }
 213   push_score(&scores, &scorecount, newscore, get_user_id(passwdbuf), newdata);
 214   /* Limit the number of scores.  If we're using reverse sorting, then
 215      we should increment the beginning of the array, to skip over the
 216      *smallest* scores.  Otherwise, we just decrement the number of
 217      scores, since the smallest will be at the end. */
 218   if (scorecount > MAX_SCORES)
 219     scorecount -= (scorecount - MAX_SCORES);
 220     if (reverse)
 221       scores += (scorecount - MAX_SCORES);
 222   sort_scores(scores, scorecount, reverse);
 223   if (write_scores(scorefile, scores, scorecount) < 0)
 224     {
 225       unlock_file(scorefile, lockstate);
 226       lose("Failed to write scores file \"%s\": %s\n", scorefile,
 227            strerror(errno));
 228     }
 229   unlock_file(scorefile, lockstate);
 230   exit(0);
 231 }
 232
 233 int
 234 read_score(FILE *f, struct score_entry *score)
 235 {
 236   int c;
 237   if (feof(f))
 238     return 1;
 239   while ((c = getc(f)) != EOF
 240          && isdigit(c))
 241     {
 242       score->score *= 10;
 243       score->score += (c-48);
 244     }
 245   while ((c = getc(f)) != EOF
 246          && isspace(c))
 247     ;
 248   if (c == EOF)
 249     return -1;
 250   ungetc(c, f);
 251 #ifdef HAVE_GETDELIM
 252   {
 253     size_t count = 0;
 254     if (getdelim(&score->username, &count, ' ', f) < 1
 255         || score->username == NULL)
 256       return -1;
 257     /* Trim the space */
 258     score->username[strlen(score->username)-1] = '\0';
 259   }
 260 #else
 261   {
 262     int unameread = 0;
 263     int unamelen = 30;
 264     char *username = malloc(unamelen);
 265     if (!username)
 266       return -1;
 267
 268     while ((c = getc(f)) != EOF
 269            && !isspace(c))
 270       {
 271         if (unameread >= unamelen-1)
 272           if (!(username = realloc(username, unamelen *= 2)))
 273             return -1;
 274         username[unameread] = c;
 275         unameread++;
 276       }
 277     if (c == EOF)
 278       return -1;
 279     username[unameread] = '\0';
 280     score->username = username;
 281   }
 282 #endif
 283 #ifdef HAVE_GETLINE
 284   score->data = NULL;
 285   errno = 0;
 286   {
 287     size_t len;
 288     if (getline(&score->data, &len, f) < 0)
 289       return -1;
 290     score->data[strlen(score->data)-1] = '\0';
 291   }
 292 #else
 293   {
 294     int cur = 0;
 295     int len = 16;
 296     char *buf = malloc(len);
 297     if (!buf)
 298       return -1;
 299     while ((c = getc(f)) != EOF
 300            && c != '\n')
 301       {
 302         if (cur >= len-1)
 303           {
 304             if (!(buf = realloc(buf, len *= 2)))
 305               return -1;
 306           }
 307         buf[cur] = c;
 308         cur++;
 309       }
 310     score->data = buf;
 311     score->data[cur] = '\0';
 312   }
 313 #endif
 314   return 0;
 315 }
 316
 317 int
 318 read_scores(const char *filename, struct score_entry **scores,
 319             int *count)
 320 {
 321   int readval, scorecount, cursize;
 322   struct score_entry *ret;
 323   FILE *f = fopen(filename, "r");
 324   if (!f)
 325     return -1;
 326   scorecount = 0;
 327   cursize = 16;
 328   ret = malloc(sizeof(struct score_entry) * cursize);
 329   if (!ret)
 330     return -1;
 331   while ((readval = read_score(f, &ret[scorecount])) == 0)
 332     {
 333       /* We encoutered an error */
 334       if (readval < 0)
 335         return -1;
 336       scorecount++;
 337       if (scorecount >= cursize)
 338         {
 339           ret = realloc(ret, cursize *= 2);
 340           if (!ret)
 341             return -1;
 342         }
 343     }
 344   *count = scorecount;
 345   *scores = ret;
 346   return 0;
 347 }
 348
 349 int
 350 score_compare(const void *a, const void *b)
 351 {
 352   const struct score_entry *sa = (const struct score_entry *) a;
 353   const struct score_entry *sb = (const struct score_entry *) b;
 354   return (sb->score > sa->score) - (sb->score < sa->score);
 355 }
 356
 357 int
 358 score_compare_reverse(const void *a, const void *b)
 359 {
 360   const struct score_entry *sa = (const struct score_entry *) a;
 361   const struct score_entry *sb = (const struct score_entry *) b;
 362   return (sa->score > sb->score) - (sa->score < sb->score);
 363 }
 364
 365 int
 366 push_score(struct score_entry **scores, int *count,
 367            int newscore, char *username, char *newdata)
 368 {
 369  struct score_entry *newscores = realloc(*scores,
 370                                          sizeof(struct score_entry) * ((*count) + 1));
 371   if (!newscores)
 372     return -1;
 373   newscores[*count].score = newscore;
 374   newscores[*count].username = username;
 375   newscores[*count].data = newdata;
 376   (*count) += 1;
 377   *scores = newscores;
 378   return 0;
 379 }
 380
 381 void
 382 sort_scores(struct score_entry *scores, int count, int reverse)
 383 {
 384   qsort(scores, count, sizeof(struct score_entry),
 385         reverse ? score_compare_reverse : score_compare);
 386 }
 387
 388 int
 389 write_scores(const char *filename, const struct score_entry *scores,
 390              int count)
 391 {
 392   FILE *f;
 393   int i;
 394   char *tempfile = malloc(strlen(filename) + strlen(".tempXXXXXX") + 1);
 395   if (!tempfile)
 396     return -1;
 397   strcpy(tempfile, filename);
 398   strcat(tempfile, ".tempXXXXXX");
 399 #ifdef HAVE_MKSTEMP
 400   if (mkstemp(tempfile) < 0
 401 #else
 402   if (mktemp(tempfile) != tempfile
 403 #endif
 404       || !(f = fopen(tempfile, "w")))
 405     return -1;
 406   for (i = 0; i < count; i++)
 407     if (fprintf(f, "%ld %s %s\n", scores[i].score, scores[i].username,
 408                 scores[i].data) < 0)
 409       return -1;
 410   fclose(f);
 411   if (rename(tempfile, filename) < 0)
 412     return -1;
 413   if (chmod(filename, 0644) < 0)
 414     return -1;
 415   return 0;
 416 }
 417
 418 int
 419 lock_file(const char *filename, void **state)
 420 {
 421   int fd;
 422   struct stat buf;
 423   int attempts = 0;
 424   char *lockext = ".lockfile";
 425   char *lockpath = malloc(strlen(filename) + strlen(lockext) + 60);
 426   if (!lockpath)
 427     return -1;
 428   strcpy(lockpath, filename);
 429   strcat(lockpath, lockext);
 430   *state = lockpath;
 431  trylock:
 432   attempts++;
 433   /* If the lock is over an hour old, delete it. */
 434   if (stat(lockpath, &buf) == 0
 435       && (difftime(buf.st_ctime, time(NULL) > 60*60)))
 436     unlink(lockpath);
 437   if ((fd = open(lockpath, O_CREAT | O_EXCL, 0600)) < 0)
 438     {
 439       if (errno == EEXIST)
 440         {
 441           /* Break the lock; we won't corrupt the file, but we might
 442              lose some scores. */
 443           if (attempts > MAX_ATTEMPTS)
 444             {
 445               unlink(lockpath);
 446               attempts = 0;
 447             }
 448           sleep((rand() % 2)+1);
 449           goto trylock;
 450         }
 451       else
 452         return -1;
 453     }
 454   close(fd);
 455   return 0;
 456 }
 457
 458 int
 459 unlock_file(const char *filename, void *state)
 460 {
 461   char *lockpath = (char *) state;
 462   int ret = unlink(lockpath);
 463   int saved_errno = errno;
 464   free(lockpath);
 465   errno = saved_errno;
 466   return ret;
 467 }