games/hangman/getsym.c

   1 /*      $OpenBSD: ksyms.c,v 1.8 2015/02/07 03:26:20 tedu Exp $  */
   2
   3 /*
   4  * Copyright (c) 2008 Miodrag Vallat.
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 #include <unistd.h>
  20 #include <ctype.h>
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <string.h>
  24
  25 #include <sys/exec.h>
  26 #include <sys/elf64.h>
  27
  28 #include "hangman.h"
  29
  30 typedef Elf64_Ehdr Elf_Ehdr;
  31 typedef Elf64_Shdr Elf_Shdr;
  32
  33 static int ksyms_elf_parse(void);
  34
  35 void
  36 sym_getword(void)
  37 {
  38         uint tries;
  39         off_t pos;
  40         int buflen;
  41         char symbuf[1 + BUFSIZ], *sym, *end;
  42         size_t symlen;
  43
  44         for (tries = 0; tries < MAXBADWORDS; tries++) {
  45                 pos = arc4random_uniform(symsize);
  46                 if (lseek(symfd, pos + symoffs, SEEK_SET) == -1)
  47                         continue;
  48                 buflen = read(symfd, symbuf, BUFSIZ);
  49                 if (buflen < 0)
  50                         continue;
  51
  52                 /*
  53                  * The buffer is hopefully large enough to hold at least
  54                  * a complete symbol, i.e. two occurences of NUL, or
  55                  * one occurence of NUL and the buffer containing the end
  56                  * of the string table. We make sure the buffer will be
  57                  * NUL terminated in all cases.
  58                  */
  59                 if (buflen + pos >= symsize)
  60                         buflen = symsize - pos;
  61                 *(end = symbuf + buflen) = '\0';
  62
  63                 for (sym = symbuf; *sym != '\0'; sym++)
  64                         ;
  65                 if (sym == end)
  66                         continue;
  67
  68                 symlen = strlen(++sym);
  69                 if (symlen < MINLEN || symlen > MAXLEN)
  70                         continue;
  71
  72                 /* ignore symbols containing dots or dollar signs */
  73                 if (strchr(sym, '.') != NULL || strchr(sym, '$') != NULL)
  74                         continue;
  75
  76                 break;
  77         }
  78
  79         if (tries >= MAXBADWORDS) {
  80                 mvcur(0, COLS - 1, LINES -1, 0);
  81                 endwin();
  82                 errx(1, "can't seem a suitable symbol in %s",
  83                     Dict_name);
  84         }
  85
  86         strlcpy(Word, sym, sizeof(Word));
  87         strlcpy(Known, sym, sizeof(Known));
  88         for (sym = Known; *sym != '\0'; sym++) {
  89                 if (*sym == '-')
  90                         *sym = '_';     /* try not to confuse player */
  91                 if (isalnum((unsigned char)*sym))
  92                         *sym = '-';
  93         }
  94 }
  95
  96 int
  97 sym_setup(void)
  98 {
  99         if ((symfd = open(Dict_name, O_RDONLY)) < 0)
 100                 return -1;
 101
 102         if (ksyms_elf_parse() == 0)
 103                 return 0;
 104
 105         close(symfd);
 106         errno = ENOEXEC;
 107         return -1;
 108 }
 109
 110 int
 111 ksyms_elf_parse(void)
 112 {
 113         Elf_Ehdr eh;
 114         Elf_Shdr sh;
 115         uint s;
 116
 117         if (lseek(symfd, 0, SEEK_SET) == -1)
 118                 return -1;
 119
 120         if (read(symfd, &eh, sizeof(eh)) != sizeof(eh))
 121                 return -1;
 122
 123         if (!IS_ELF(eh))
 124                 return -1;
 125
 126         if (lseek(symfd, eh.e_shoff, SEEK_SET) == -1)
 127                 return -1;
 128
 129         symoffs = 0;
 130         symsize = 0;
 131
 132         for (s = 0; s < eh.e_shnum; s++) {
 133                 if (read(symfd, &sh, sizeof(sh)) != sizeof(sh))
 134                         return -1;
 135
 136                 /*
 137                  * There should be two string table sections, one with the
 138                  * name of the sections themselves, and one with the symbol
 139                  * names. Just pick the largest one.
 140                  */
 141                 if (sh.sh_type == SHT_STRTAB) {
 142                         if (symsize > (off_t)sh.sh_size)
 143                                 continue;
 144
 145                         symoffs = (off_t)sh.sh_offset;
 146                         symsize = (off_t)sh.sh_size;
 147                 }
 148         }
 149
 150         if (symsize == 0)
 151                 return -1;
 152
 153         return 0;
 154 }