contrib/tcp_wrappers/percent_x.c

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