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 #if !defined (__GNUC__) || __GNUC__ < 2
  53 #define __attribute__(x)
  54 #endif
  55
  56 /* Declare the prototype for a general external function.  */
  57 #if defined (PROTOTYPES) || defined (WINDOWSNT)
  58 #define P_(proto) proto
  59 #else
  60 #define P_(proto) ()
  61 #endif
  62
  63 int
  64 usage(err)
  65      int err;
  66 {
  67   fprintf(stdout, "Usage: update-game-score [-m MAX ] [ -r ] game/scorefile SCORE DATA\n");
  68   fprintf(stdout, "       update-game-score -h\n");
  69   fprintf(stdout, " -h\t\tDisplay this help.\n");
  70   fprintf(stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  71   fprintf(stdout, " -r\t\tSort the scores in increasing order.\n");
  72   fprintf(stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  73   exit(err);
  74 }
  75
  76 int
  77 lock_file P_((const char *filename, void **state));
  78 int
  79 unlock_file P_((const char *filename, void *state));
  80
  81 struct score_entry
  82 {
  83   long score;
  84   char *username;
  85   char *data;
  86 };
  87
  88 int
  89 read_scores P_((const char *filename, struct score_entry **scores,
  90                 int *count));
  91 int
  92 push_score P_((struct score_entry **scores, int *count,
  93                int newscore, char *username, char *newdata));
  94 void
  95 sort_scores P_((struct score_entry *scores, int count, int reverse));
  96 int
  97 write_scores P_((const char *filename, const struct score_entry *scores,
  98                  int count));
  99
 100 void lose P_((const char *msg))
 101      __attribute__ ((noreturn));
 102
 103 void lose(msg)
 104      const char *msg;
 105 {
 106   fprintf(stderr, "%s\n", msg);
 107   exit(1);
 108 }
 109
 110 void lose_syserr P_((const char *msg))
 111      __attribute__ ((noreturn));
 112
 113 void lose_syserr(msg)
 114      const char *msg;
 115 {
 116   fprintf(stderr, "%s: %s\n", msg, strerror(errno));
 117   exit(1);
 118 }
 119
 120 char *
 121 get_user_id(void)
 122 {
 123   char *name;
 124   struct passwd *buf = getpwuid(getuid());
 125   if (!buf)
 126     {
 127       int count = 1;
 128       int uid = (int) getuid();
 129       int tuid = uid;
 130       while (tuid /= 10)
 131         count++;
 132       name = malloc(count+1);
 133       if (!name)
 134         return NULL;
 135       sprintf(name, "%d", uid);
 136       return name;
 137     }
 138   return buf->pw_name;
 139 }
 140
 141 char *
 142 get_prefix(running_suid, user_prefix)
 143      int running_suid;
 144      char *user_prefix;
 145 {
 146   if (!running_suid && user_prefix == NULL)
 147     lose("Not using a shared game directory, and no prefix given.");
 148   if (running_suid)
 149     {
 150 #ifdef HAVE_SHARED_GAME_DIR
 151       return HAVE_SHARED_GAME_DIR;
 152 #else
 153       lose("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 154 #endif
 155     }
 156   return user_prefix;
 157 }
 158
 159 int
 160 main(argc, argv)
 161      int argc;
 162      char **argv;
 163 {
 164   int c, running_suid;
 165   void *lockstate;
 166   char *user_id, *scorefile, *prefix, *user_prefix = NULL;
 167   struct stat buf;
 168   struct score_entry *scores;
 169   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 170   char *newdata;
 171
 172   srand(time(0));
 173
 174   while ((c = getopt(argc, argv, "hrm:d:")) != -1)
 175     switch (c)
 176       {
 177       case 'h':
 178         usage(0);
 179         break;
 180       case 'd':
 181         user_prefix = optarg;
 182         break;
 183       case 'r':
 184         reverse = 1;
 185         break;
 186       case 'm':
 187         max = atoi(optarg);
 188         if (max > MAX_SCORES)
 189           max = MAX_SCORES;
 190         break;
 191       default:
 192         usage(1);
 193       }
 194
 195   if (optind+3 != argc)
 196     usage(1);
 197
 198   running_suid = (getuid() != geteuid());
 199
 200   prefix = get_prefix(running_suid, user_prefix);
 201
 202   scorefile = malloc(strlen(prefix) + strlen(argv[optind]) + 2);
 203   if (!scorefile)
 204     lose_syserr("Couldn't allocate score file");
 205
 206   strcpy(scorefile, prefix);
 207   strcat(scorefile, "/");
 208   strcat(scorefile, argv[optind]);
 209   newscore = atoi(argv[optind+1]);
 210   newdata = argv[optind+2];
 211   if (strlen(newdata) > MAX_DATA_LEN)
 212     newdata[MAX_DATA_LEN] = '\0';
 213
 214   if ((user_id = get_user_id()) == NULL)
 215     lose_syserr("Couldn't determine user id");
 216
 217   if (stat(scorefile, &buf) < 0)
 218     lose_syserr("Failed to access scores file");
 219
 220   if (lock_file(scorefile, &lockstate) < 0)
 221     lose_syserr("Failed to lock scores file");
 222
 223   if (read_scores(scorefile, &scores, &scorecount) < 0)
 224     {
 225       unlock_file(scorefile, lockstate);
 226       lose_syserr("Failed to read scores file");
 227     }
 228   push_score(&scores, &scorecount, newscore, user_id, newdata);
 229   /* Limit the number of scores.  If we're using reverse sorting, then
 230      we should increment the beginning of the array, to skip over the
 231      *smallest* scores.  Otherwise, we just decrement the number of
 232      scores, since the smallest will be at the end. */
 233   if (scorecount > MAX_SCORES)
 234     scorecount -= (scorecount - MAX_SCORES);
 235     if (reverse)
 236       scores += (scorecount - MAX_SCORES);
 237   sort_scores(scores, scorecount, reverse);
 238   if (write_scores(scorefile, scores, scorecount) < 0)
 239     {
 240       unlock_file(scorefile, lockstate);
 241       lose_syserr("Failed to write scores file");
 242     }
 243   unlock_file(scorefile, lockstate);
 244   exit(0);
 245 }
 246
 247 int
 248 read_score(f, score)
 249      FILE *f;
 250      struct score_entry *score;
 251 {
 252   int c;
 253   if (feof(f))
 254     return 1;
 255   while ((c = getc(f)) != EOF
 256          && isdigit(c))
 257     {
 258       score->score *= 10;
 259       score->score += (c-48);
 260     }
 261   while ((c = getc(f)) != EOF
 262          && isspace(c))
 263     ;
 264   if (c == EOF)
 265     return -1;
 266   ungetc(c, f);
 267 #ifdef HAVE_GETDELIM
 268   {
 269     size_t count = 0;
 270     if (getdelim(&score->username, &count, ' ', f) < 1
 271         || score->username == NULL)
 272       return -1;
 273     /* Trim the space */
 274     score->username[strlen(score->username)-1] = '\0';
 275   }
 276 #else
 277   {
 278     int unameread = 0;
 279     int unamelen = 30;
 280     char *username = malloc(unamelen);
 281     if (!username)
 282       return -1;
 283
 284     while ((c = getc(f)) != EOF
 285            && !isspace(c))
 286       {
 287         if (unameread >= unamelen-1)
 288           if (!(username = realloc(username, unamelen *= 2)))
 289             return -1;
 290         username[unameread] = c;
 291         unameread++;
 292       }
 293     if (c == EOF)
 294       return -1;
 295     username[unameread] = '\0';
 296     score->username = username;
 297   }
 298 #endif
 299 #ifdef HAVE_GETLINE
 300   score->data = NULL;
 301   errno = 0;
 302   {
 303     size_t len;
 304     if (getline(&score->data, &len, f) < 0)
 305       return -1;
 306     score->data[strlen(score->data)-1] = '\0';
 307   }
 308 #else
 309   {
 310     int cur = 0;
 311     int len = 16;
 312     char *buf = malloc(len);
 313     if (!buf)
 314       return -1;
 315     while ((c = getc(f)) != EOF
 316            && c != '\n')
 317       {
 318         if (cur >= len-1)
 319           {
 320             if (!(buf = realloc(buf, len *= 2)))
 321               return -1;
 322           }
 323         buf[cur] = c;
 324         cur++;
 325       }
 326     score->data = buf;
 327     score->data[cur] = '\0';
 328   }
 329 #endif
 330   return 0;
 331 }
 332
 333 int
 334 read_scores(filename, scores, count)
 335      const char *filename;
 336      struct score_entry **scores;
 337      int *count;
 338 {
 339   int readval, scorecount, cursize;
 340   struct score_entry *ret;
 341   FILE *f = fopen(filename, "r");
 342   if (!f)
 343     return -1;
 344   scorecount = 0;
 345   cursize = 16;
 346   ret = malloc(sizeof(struct score_entry) * cursize);
 347   if (!ret)
 348     return -1;
 349   while ((readval = read_score(f, &ret[scorecount])) == 0)
 350     {
 351       /* We encoutered an error */
 352       if (readval < 0)
 353         return -1;
 354       scorecount++;
 355       if (scorecount >= cursize)
 356         {
 357           ret = realloc(ret, cursize *= 2);
 358           if (!ret)
 359             return -1;
 360         }
 361     }
 362   *count = scorecount;
 363   *scores = ret;
 364   return 0;
 365 }
 366
 367 int
 368 score_compare(a, b)
 369      const void *a;
 370      const void *b;
 371 {
 372   const struct score_entry *sa = (const struct score_entry *) a;
 373   const struct score_entry *sb = (const struct score_entry *) b;
 374   return (sb->score > sa->score) - (sb->score < sa->score);
 375 }
 376
 377 int
 378 score_compare_reverse(a, b)
 379      const void *a;
 380      const void *b;
 381 {
 382   const struct score_entry *sa = (const struct score_entry *) a;
 383   const struct score_entry *sb = (const struct score_entry *) b;
 384   return (sa->score > sb->score) - (sa->score < sb->score);
 385 }
 386
 387 int
 388 push_score(scores, count, newscore, username, newdata)
 389      struct score_entry **scores;
 390      int *count; int newscore;
 391      char *username;
 392      char *newdata;
 393 {
 394  struct score_entry *newscores = realloc(*scores,
 395                                          sizeof(struct score_entry) * ((*count) + 1));
 396   if (!newscores)
 397     return -1;
 398   newscores[*count].score = newscore;
 399   newscores[*count].username = username;
 400   newscores[*count].data = newdata;
 401   (*count) += 1;
 402   *scores = newscores;
 403   return 0;
 404 }
 405
 406 void
 407 sort_scores(scores, count, reverse)
 408      struct score_entry *scores;
 409      int count;
 410      int reverse;
 411 {
 412   qsort(scores, count, sizeof(struct score_entry),
 413         reverse ? score_compare_reverse : score_compare);
 414 }
 415
 416 int
 417 write_scores(filename, scores, count)
 418      const char *filename;
 419      const struct score_entry * scores;
 420      int count;
 421 {
 422   FILE *f;
 423   int i;
 424   char *tempfile = malloc(strlen(filename) + strlen(".tempXXXXXX") + 1);
 425   if (!tempfile)
 426     return -1;
 427   strcpy(tempfile, filename);
 428   strcat(tempfile, ".tempXXXXXX");
 429 #ifdef HAVE_MKSTEMP
 430   if (mkstemp(tempfile) < 0
 431 #else
 432   if (mktemp(tempfile) != tempfile
 433 #endif
 434       || !(f = fopen(tempfile, "w")))
 435     return -1;
 436   for (i = 0; i < count; i++)
 437     if (fprintf(f, "%ld %s %s\n", scores[i].score, scores[i].username,
 438                 scores[i].data) < 0)
 439       return -1;
 440   fclose(f);
 441   if (rename(tempfile, filename) < 0)
 442     return -1;
 443   if (chmod(filename, 0644) < 0)
 444     return -1;
 445   return 0;
 446 }
 447
 448 int
 449 lock_file(filename, state)
 450   const char *filename;
 451   void **state;
 452 {
 453   int fd;
 454   struct stat buf;
 455   int attempts = 0;
 456   char *lockext = ".lockfile";
 457   char *lockpath = malloc(strlen(filename) + strlen(lockext) + 60);
 458   if (!lockpath)
 459     return -1;
 460   strcpy(lockpath, filename);
 461   strcat(lockpath, lockext);
 462   *state = lockpath;
 463  trylock:
 464   attempts++;
 465   /* If the lock is over an hour old, delete it. */
 466   if (stat(lockpath, &buf) == 0
 467       && (difftime(buf.st_ctime, time(NULL) > 60*60)))
 468     unlink(lockpath);
 469   if ((fd = open(lockpath, O_CREAT | O_EXCL, 0600)) < 0)
 470     {
 471       if (errno == EEXIST)
 472         {
 473           /* Break the lock; we won't corrupt the file, but we might
 474              lose some scores. */
 475           if (attempts > MAX_ATTEMPTS)
 476             {
 477               unlink(lockpath);
 478               attempts = 0;
 479             }
 480           sleep((rand() % 2)+1);
 481           goto trylock;
 482         }
 483       else
 484         return -1;
 485     }
 486   close(fd);
 487   return 0;
 488 }
 489
 490 int
 491 unlock_file(filename, state)
 492   const char *filename;
 493  void *state;
 494 {
 495   char *lockpath = (char *) state;
 496   int ret = unlink(lockpath);
 497   int saved_errno = errno;
 498   free(lockpath);
 499   errno = saved_errno;
 500   return ret;
 501 }