lib/libwrap/percent_x.c

   1 /*      $NetBSD: percent_x.c,v 1.5 2012/03/21 10:10:37 matt Exp $       */
   2
   3  /*
   4   * percent_x() takes a string and performs %<char> expansions. It aborts the
   5   * program when the expansion would overflow the output buffer. The result
   6   * of %<char> expansion may be passed on to a shell process. For this
   7   * reason, characters with a special meaning to shells are replaced by
   8   * underscores.
   9   *
  10   * Diagnostics are reported through syslog(3).
  11   *
  12   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  13   */
  14
  15 #include <sys/cdefs.h>
  16 #ifndef lint
  17 #if 0
  18 static char sccsid[] = "@(#) percent_x.c 1.4 94/12/28 17:42:37";
  19 #else
  20 __RCSID("$NetBSD: percent_x.c,v 1.5 2012/03/21 10:10:37 matt Exp $");
  21 #endif
  22 #endif
  23
  24 /* System libraries. */
  25
  26 #include <stdio.h>
  27 #include <syslog.h>
  28 #include <stdlib.h>
  29 #include <unistd.h>
  30 #include <string.h>
  31
  32 /* Local stuff. */
  33
  34 #include "tcpd.h"
  35
  36 /* percent_x - do %<char> expansion, abort if result buffer is too small */
  37
  38 char *
  39 percent_x(char *result, int result_len, char *string,
  40     struct request_info *request)
  41 {
  42     char   *bp = result;
  43     char   *end = result + result_len - 1;      /* end of result buffer */
  44     char   *expansion;
  45     size_t  expansion_len;
  46     static const char ok_chars[] = "1234567890!@%-_=+:,./"
  47         "abcdefghijklmnopqrstuvwxyz"
  48         "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  49     char   *str = string;
  50     char   *cp;
  51     int     ch;
  52
  53     /*
  54      * Warning: we may be called from a child process or after pattern
  55      * matching, so we cannot use clean_exit() or tcpd_jump().
  56      */
  57
  58     while (*str) {
  59         if (*str == '%' && (ch = str[1]) != 0) {
  60             str += 2;
  61             expansion =
  62                 ch == 'a' ? eval_hostaddr(request->client) :
  63                 ch == 'A' ? eval_hostaddr(request->server) :
  64                 ch == 'c' ? eval_client(request) :
  65                 ch == 'd' ? eval_daemon(request) :
  66                 ch == 'h' ? eval_hostinfo(request->client) :
  67                 ch == 'H' ? eval_hostinfo(request->server) :
  68                 ch == 'n' ? eval_hostname(request->client) :
  69                 ch == 'N' ? eval_hostname(request->server) :
  70                 ch == 'p' ? eval_pid(request) :
  71                 ch == 's' ? eval_server(request) :
  72                 ch == 'u' ? eval_user(request) :
  73                 ch == '%' ? __UNCONST("%")
  74                           : (tcpd_warn("unrecognized %%%c", ch), __UNCONST(""));
  75             for (cp = expansion; *(cp += strspn(cp, ok_chars)); /* */ )
  76                 *cp = '_';
  77             expansion_len = cp - expansion;
  78         } else {
  79             expansion = str++;
  80             expansion_len = 1;
  81         }
  82         if (bp + expansion_len >= end) {
  83             tcpd_warn("percent_x: expansion too long: %.30s...", result);
  84             sleep(5);
  85             exit(0);
  86         }
  87         memcpy(bp, expansion, expansion_len);
  88         bp += expansion_len;
  89     }
  90     *bp = 0;
  91     return (result);
  92 }