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      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 }
     87