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 /* System libraries. */
  14
  15 #include <stdio.h>
  16 #include <syslog.h>
  17 #include <string.h>
  18 #include <unistd.h>
  19
  20 extern void exit();
  21
  22 /* Local stuff. */
  23
  24 #include "tcpd.h"
  25
  26 /* percent_x - do %<char> expansion, abort if result buffer is too small */
  27
  28 char   *percent_x(result, result_len, string, request)
  29 char   *result;
  30 int     result_len;
  31 char   *string;
  32 struct request_info *request;
  33 {
  34     char   *bp = result;
  35     char   *end = result + result_len - 1;      /* end of result buffer */
  36     char   *expansion;
  37     int     expansion_len;
  38     static char ok_chars[] = "1234567890!@%-_=+:,./\
  39 abcdefghijklmnopqrstuvwxyz\
  40 ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  41     char   *str = string;
  42     char   *cp;
  43     int     ch;
  44
  45     /*
  46      * Warning: we may be called from a child process or after pattern
  47      * matching, so we cannot use clean_exit() or tcpd_jump().
  48      */
  49
  50     while (*str) {
  51         if (*str == '%' && (ch = str[1]) != 0) {
  52             str += 2;
  53             expansion =
  54                 ch == 'a' ? eval_hostaddr(request->client) :
  55                 ch == 'A' ? eval_hostaddr(request->server) :
  56                 ch == 'c' ? eval_client(request) :
  57                 ch == 'd' ? eval_daemon(request) :
  58                 ch == 'h' ? eval_hostinfo(request->client) :
  59                 ch == 'H' ? eval_hostinfo(request->server) :
  60                 ch == 'n' ? eval_hostname(request->client) :
  61                 ch == 'N' ? eval_hostname(request->server) :
  62                 ch == 'p' ? eval_pid(request) :
  63                 ch == 's' ? eval_server(request) :
  64                 ch == 'u' ? eval_user(request) :
  65                 ch == '%' ? "%" : (tcpd_warn("unrecognized %%%c", ch), "");
  66             for (cp = expansion; *(cp += strspn(cp, ok_chars)); /* */ )
  67                 *cp = '_';
  68             expansion_len = cp - expansion;
  69         } else {
  70             expansion = str++;
  71             expansion_len = 1;
  72         }
  73         if (bp + expansion_len >= end) {
  74             tcpd_warn("percent_x: expansion too long: %.30s...", result);
  75             sleep(5);
  76             exit(0);
  77         }
  78         memcpy(bp, expansion, expansion_len);
  79         bp += expansion_len;
  80     }
  81     *bp = 0;
  82     return (result);
  83 }