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