/*
 * percent_x() takes a string and performs %<char> expansions. It aborts the
 * program when the expansion would overflow the output buffer. The result
 * of %<char> expansion may be passed on to a shell process. For this
 * reason, characters with a special meaning to shells are replaced by
 * underscores.
 *
 * Diagnostics are reported through syslog(3).
 *
 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
 */

#ifndef lint
static char sccsid[] = "@(#) percent_x.c 1.4 94/12/28 17:42:37";
#endif

/* System libraries. */

#include <stdio.h>
#include <syslog.h>
#include <string.h>

extern void exit();

/* Local stuff. */

#include "tcpd.h"

/* percent_x - do %<char> expansion, abort if result buffer is too small */

char   *percent_x(result, result_len, string, request)
char   *result;
int     result_len;
char   *string;
struct request_info *request;
{
   char   *bp = result;
   char   *end = result + result_len - 1;      /* end of result buffer */
   char   *expansion;
   int     expansion_len;
   static char ok_chars[] = "1234567890!@%-_=+:,./\
abcdefghijklmnopqrstuvwxyz\
ABCDEFGHIJKLMNOPQRSTUVWXYZ";
   char   *str = string;
   char   *cp;
   int     ch;

   /*
    * Warning: we may be called from a child process or after pattern
    * matching, so we cannot use clean_exit() or tcpd_jump().
    */

   while (*str) {
       if (*str == '%' && (ch = str[1]) != 0) {
           str += 2;
           expansion =
               ch == 'a' ? eval_hostaddr(request->client) :
               ch == 'A' ? eval_hostaddr(request->server) :
               ch == 'c' ? eval_client(request) :
               ch == 'd' ? eval_daemon(request) :
               ch == 'h' ? eval_hostinfo(request->client) :
               ch == 'H' ? eval_hostinfo(request->server) :
               ch == 'n' ? eval_hostname(request->client) :
               ch == 'N' ? eval_hostname(request->server) :
               ch == 'p' ? eval_pid(request) :
               ch == 's' ? eval_server(request) :
               ch == 'u' ? eval_user(request) :
               ch == '%' ? "%" : (tcpd_warn("unrecognized %%%c", ch), "");
           for (cp = expansion; *(cp += strspn(cp, ok_chars)); /* */ )
               *cp = '_';
           expansion_len = cp - expansion;
       } else {
           expansion = str++;
           expansion_len = 1;
       }
       if (bp + expansion_len >= end) {
           tcpd_warn("percent_x: expansion too long: %.30s...", result);
           sleep(5);
           exit(0);
       }
       memcpy(bp, expansion, expansion_len);
       bp += expansion_len;
   }
   *bp = 0;
   return (result);
}