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