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 #include <config.h>
  33
  34 #ifdef HAVE_UNISTD_H
  35 #include <unistd.h>
  36 #endif
  37 #include <errno.h>
  38 #ifdef HAVE_STRING_H
  39 #include <string.h>
  40 #endif
  41 #ifdef HAVE_STDLIB_H
  42 #include <stdlib.h>
  43 #endif
  44 #include <stdio.h>
  45 #include <time.h>
  46 #include <pwd.h>
  47 #include <ctype.h>
  48 #ifdef HAVE_FCNTL_H
  49 #include <fcntl.h>
  50 #endif
  51 #ifdef STDC_HEADERS
  52 #include <stdarg.h>
  53 #endif
  54 #include <sys/stat.h>
  55
  56 /* Needed for SunOS4, for instance.  */
  57 extern char *optarg;
  58 extern int optind, opterr;
  59
  60 #define MAX_ATTEMPTS 5
  61 #define MAX_SCORES 200
  62 #define MAX_DATA_LEN 1024
  63
  64 /* Declare the prototype for a general external function.  */
  65 #if defined (PROTOTYPES) || defined (WINDOWSNT)
  66 #define P_(proto) proto
  67 #else
  68 #define P_(proto) ()
  69 #endif
  70
  71 int
  72 usage(err)
  73      int err;
  74 {
  75   fprintf(stdout, "Usage: update-game-score [-m MAX ] [ -r ] game/scorefile SCORE DATA\n");
  76   fprintf(stdout, "       update-game-score -h\n");
  77   fprintf(stdout, " -h\t\tDisplay this help.\n");
  78   fprintf(stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  79   fprintf(stdout, " -r\t\tSort the scores in increasing order.\n");
  80   fprintf(stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  81   exit(err);
  82 }
  83
  84 int
  85 lock_file P_((const char *filename, void **state));
  86 int
  87 unlock_file P_((const char *filename, void *state));
  88
  89 struct score_entry
  90 {
  91   long score;
  92   char *username;
  93   char *data;
  94 };
  95
  96 int
  97 read_scores P_((const char *filename, struct score_entry **scores,
  98                 int *count));
  99 int
 100 push_score P_((struct score_entry **scores, int *count,
 101                int newscore, char *username, char *newdata));
 102 void
 103 sort_scores P_((struct score_entry *scores, int count, int reverse));
 104 int
 105 write_scores P_((const char *filename, const struct score_entry *scores,
 106                  int count));
 107
 108 void lose P_((const char *msg)) NO_RETURN;
 109
 110 void lose(msg)
 111      const char *msg;
 112 {
 113   fprintf(stderr, "%s\n", msg);
 114   exit(1);
 115 }
 116
 117 void lose_syserr P_((const char *msg)) NO_RETURN;
 118
 119 void lose_syserr(msg)
 120      const char *msg;
 121 {
 122   fprintf(stderr, "%s: %s\n", msg, strerror(errno));
 123   exit(1);
 124 }
 125
 126 char *
 127 get_user_id P_ ((void))
 128 {
 129   char *name;
 130   struct passwd *buf = getpwuid(getuid());
 131   if (!buf)
 132     {
 133       int count = 1;
 134       int uid = (int) getuid();
 135       int tuid = uid;
 136       while (tuid /= 10)
 137         count++;
 138       name = malloc(count+1);
 139       if (!name)
 140         return NULL;
 141       sprintf(name, "%d", uid);
 142       return name;
 143     }
 144   return buf->pw_name;
 145 }
 146
 147 char *
 148 get_prefix(running_suid, user_prefix)
 149      int running_suid;
 150      char *user_prefix;
 151 {
 152   if (!running_suid && user_prefix == NULL)
 153     lose("Not using a shared game directory, and no prefix given.");
 154   if (running_suid)
 155     {
 156 #ifdef HAVE_SHARED_GAME_DIR
 157       return HAVE_SHARED_GAME_DIR;
 158 #else
 159       lose("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 160 #endif
 161     }
 162   return user_prefix;
 163 }
 164
 165 int
 166 main(argc, argv)
 167      int argc;
 168      char **argv;
 169 {
 170   int c, running_suid;
 171   void *lockstate;
 172   char *user_id, *scorefile, *prefix, *user_prefix = NULL;
 173   struct stat buf;
 174   struct score_entry *scores;
 175   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 176   char *newdata;
 177
 178   srand(time(0));
 179
 180   while ((c = getopt(argc, argv, "hrm:d:")) != -1)
 181     switch (c)
 182       {
 183       case 'h':
 184         usage(0);
 185         break;
 186       case 'd':
 187         user_prefix = optarg;
 188         break;
 189       case 'r':
 190         reverse = 1;
 191         break;
 192       case 'm':
 193         max = atoi(optarg);
 194         if (max > MAX_SCORES)
 195           max = MAX_SCORES;
 196         break;
 197       default:
 198         usage(1);
 199       }
 200
 201   if (optind+3 != argc)
 202     usage(1);
 203
 204   running_suid = (getuid() != geteuid());
 205
 206   prefix = get_prefix(running_suid, user_prefix);
 207
 208   scorefile = malloc(strlen(prefix) + strlen(argv[optind]) + 2);
 209   if (!scorefile)
 210     lose_syserr("Couldn't allocate score file");
 211
 212   strcpy(scorefile, prefix);
 213   strcat(scorefile, "/");
 214   strcat(scorefile, argv[optind]);
 215   newscore = atoi(argv[optind+1]);
 216   newdata = argv[optind+2];
 217   if (strlen(newdata) > MAX_DATA_LEN)
 218     newdata[MAX_DATA_LEN] = '\0';
 219
 220   if ((user_id = get_user_id()) == NULL)
 221     lose_syserr("Couldn't determine user id");
 222
 223   if (stat(scorefile, &buf) < 0)
 224     lose_syserr("Failed to access scores file");
 225
 226   if (lock_file(scorefile, &lockstate) < 0)
 227     lose_syserr("Failed to lock scores file");
 228
 229   if (read_scores(scorefile, &scores, &scorecount) < 0)
 230     {
 231       unlock_file(scorefile, lockstate);
 232       lose_syserr("Failed to read scores file");
 233     }
 234   push_score(&scores, &scorecount, newscore, user_id, newdata);
 235   /* Limit the number of scores.  If we're using reverse sorting, then
 236      we should increment the beginning of the array, to skip over the
 237      *smallest* scores.  Otherwise, we just decrement the number of
 238      scores, since the smallest will be at the end. */
 239   if (scorecount > MAX_SCORES)
 240     scorecount -= (scorecount - MAX_SCORES);
 241     if (reverse)
 242       scores += (scorecount - MAX_SCORES);
 243   sort_scores(scores, scorecount, reverse);
 244   if (write_scores(scorefile, scores, scorecount) < 0)
 245     {
 246       unlock_file(scorefile, lockstate);
 247       lose_syserr("Failed to write scores file");
 248     }
 249   unlock_file(scorefile, lockstate);
 250   exit(0);
 251 }
 252
 253 int
 254 read_score(f, score)
 255      FILE *f;
 256      struct score_entry *score;
 257 {
 258   int c;
 259   if (feof(f))
 260     return 1;
 261   while ((c = getc(f)) != EOF
 262          && isdigit(c))
 263     {
 264       score->score *= 10;
 265       score->score += (c-48);
 266     }
 267   while ((c = getc(f)) != EOF
 268          && isspace(c))
 269     ;
 270   if (c == EOF)
 271     return -1;
 272   ungetc(c, f);
 273 #ifdef HAVE_GETDELIM
 274   {
 275     size_t count = 0;
 276     if (getdelim(&score->username, &count, ' ', f) < 1
 277         || score->username == NULL)
 278       return -1;
 279     /* Trim the space */
 280     score->username[strlen(score->username)-1] = '\0';
 281   }
 282 #else
 283   {
 284     int unameread = 0;
 285     int unamelen = 30;
 286     char *username = malloc(unamelen);
 287     if (!username)
 288       return -1;
 289
 290     while ((c = getc(f)) != EOF
 291            && !isspace(c))
 292       {
 293         if (unameread >= unamelen-1)
 294           if (!(username = realloc(username, unamelen *= 2)))
 295             return -1;
 296         username[unameread] = c;
 297         unameread++;
 298       }
 299     if (c == EOF)
 300       return -1;
 301     username[unameread] = '\0';
 302     score->username = username;
 303   }
 304 #endif
 305 #ifdef HAVE_GETLINE
 306   score->data = NULL;
 307   errno = 0;
 308   {
 309     size_t len;
 310     if (getline(&score->data, &len, f) < 0)
 311       return -1;
 312     score->data[strlen(score->data)-1] = '\0';
 313   }
 314 #else
 315   {
 316     int cur = 0;
 317     int len = 16;
 318     char *buf = malloc(len);
 319     if (!buf)
 320       return -1;
 321     while ((c = getc(f)) != EOF
 322            && c != '\n')
 323       {
 324         if (cur >= len-1)
 325           {
 326             if (!(buf = realloc(buf, len *= 2)))
 327               return -1;
 328           }
 329         buf[cur] = c;
 330         cur++;
 331       }
 332     score->data = buf;
 333     score->data[cur] = '\0';
 334   }
 335 #endif
 336   return 0;
 337 }
 338
 339 int
 340 read_scores(filename, scores, count)
 341      const char *filename;
 342      struct score_entry **scores;
 343      int *count;
 344 {
 345   int readval, scorecount, cursize;
 346   struct score_entry *ret;
 347   FILE *f = fopen(filename, "r");
 348   if (!f)
 349     return -1;
 350   scorecount = 0;
 351   cursize = 16;
 352   ret = malloc(sizeof(struct score_entry) * cursize);
 353   if (!ret)
 354     return -1;
 355   while ((readval = read_score(f, &ret[scorecount])) == 0)
 356     {
 357       /* We encoutered an error */
 358       if (readval < 0)
 359         return -1;
 360       scorecount++;
 361       if (scorecount >= cursize)
 362         {
 363           ret = realloc(ret, cursize *= 2);
 364           if (!ret)
 365             return -1;
 366         }
 367     }
 368   *count = scorecount;
 369   *scores = ret;
 370   return 0;
 371 }
 372
 373 int
 374 score_compare(a, b)
 375      const void *a;
 376      const void *b;
 377 {
 378   const struct score_entry *sa = (const struct score_entry *) a;
 379   const struct score_entry *sb = (const struct score_entry *) b;
 380   return (sb->score > sa->score) - (sb->score < sa->score);
 381 }
 382
 383 int
 384 score_compare_reverse(a, b)
 385      const void *a;
 386      const void *b;
 387 {
 388   const struct score_entry *sa = (const struct score_entry *) a;
 389   const struct score_entry *sb = (const struct score_entry *) b;
 390   return (sa->score > sb->score) - (sa->score < sb->score);
 391 }
 392
 393 int
 394 push_score(scores, count, newscore, username, newdata)
 395      struct score_entry **scores;
 396      int *count; int newscore;
 397      char *username;
 398      char *newdata;
 399 {
 400  struct score_entry *newscores = realloc(*scores,
 401                                          sizeof(struct score_entry) * ((*count) + 1));
 402   if (!newscores)
 403     return -1;
 404   newscores[*count].score = newscore;
 405   newscores[*count].username = username;
 406   newscores[*count].data = newdata;
 407   (*count) += 1;
 408   *scores = newscores;
 409   return 0;
 410 }
 411
 412 void
 413 sort_scores(scores, count, reverse)
 414      struct score_entry *scores;
 415      int count;
 416      int reverse;
 417 {
 418   qsort(scores, count, sizeof(struct score_entry),
 419         reverse ? score_compare_reverse : score_compare);
 420 }
 421
 422 int
 423 write_scores(filename, scores, count)
 424      const char *filename;
 425      const struct score_entry * scores;
 426      int count;
 427 {
 428   FILE *f;
 429   int i;
 430   char *tempfile = malloc(strlen(filename) + strlen(".tempXXXXXX") + 1);
 431   if (!tempfile)
 432     return -1;
 433   strcpy(tempfile, filename);
 434   strcat(tempfile, ".tempXXXXXX");
 435 #ifdef HAVE_MKSTEMP
 436   if (mkstemp(tempfile) < 0
 437 #else
 438   if (mktemp(tempfile) != tempfile
 439 #endif
 440       || !(f = fopen(tempfile, "w")))
 441     return -1;
 442   for (i = 0; i < count; i++)
 443     if (fprintf(f, "%ld %s %s\n", scores[i].score, scores[i].username,
 444                 scores[i].data) < 0)
 445       return -1;
 446   fclose(f);
 447   if (rename(tempfile, filename) < 0)
 448     return -1;
 449   if (chmod(filename, 0644) < 0)
 450     return -1;
 451   return 0;
 452 }
 453
 454 int
 455 lock_file(filename, state)
 456   const char *filename;
 457   void **state;
 458 {
 459   int fd;
 460   struct stat buf;
 461   int attempts = 0;
 462   char *lockext = ".lockfile";
 463   char *lockpath = malloc(strlen(filename) + strlen(lockext) + 60);
 464   if (!lockpath)
 465     return -1;
 466   strcpy(lockpath, filename);
 467   strcat(lockpath, lockext);
 468   *state = lockpath;
 469  trylock:
 470   attempts++;
 471   /* If the lock is over an hour old, delete it. */
 472   if (stat(lockpath, &buf) == 0
 473       && (difftime(buf.st_ctime, time(NULL) > 60*60)))
 474     unlink(lockpath);
 475   if ((fd = open(lockpath, O_CREAT | O_EXCL, 0600)) < 0)
 476     {
 477       if (errno == EEXIST)
 478         {
 479           /* Break the lock; we won't corrupt the file, but we might
 480              lose some scores. */
 481           if (attempts > MAX_ATTEMPTS)
 482             {
 483               unlink(lockpath);
 484               attempts = 0;
 485             }
 486           sleep((rand() % 2)+1);
 487           goto trylock;
 488         }
 489       else
 490         return -1;
 491     }
 492   close(fd);
 493   return 0;
 494 }
 495
 496 int
 497 unlock_file(filename, state)
 498   const char *filename;
 499  void *state;
 500 {
 501   char *lockpath = (char *) state;
 502   int ret = unlink(lockpath);
 503   int saved_errno = errno;
 504   free(lockpath);
 505   errno = saved_errno;
 506   return ret;
 507 }