2 * SPDX-License-Identifier: ISC
4 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
5 * Copyright (c) 1995,1999 by Internet Software Consortium.
7 * Permission to use, copy, modify, and distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
11 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
17 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
21 static const char rcsid[] = "$Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp $";
23 #include <sys/cdefs.h>
24 __FBSDID("$FreeBSD$");
26 #include "port_before.h"
28 #include <sys/types.h>
29 #include <arpa/nameser.h>
33 #include "port_after.h"
36 * Check whether a name belongs to a domain.
39 *\li a - the domain whose ancestry is being verified
40 *\li b - the potential ancestor we're checking against
43 *\li boolean - is a at or below b?
46 *\li Trailing dots are first removed from name and domain.
47 * Always compare complete subdomains, not only whether the
48 * domain name is the trailing string of the given name.
50 *\li "host.foobar.top" lies in "foobar.top" and in "top" and in ""
51 * but NOT in "bar.top"
55 ns_samedomain(const char *a, const char *b) {
63 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
64 if (la != 0U && a[la - 1] == '.') {
66 /* Note this loop doesn't get executed if la==1. */
67 for (i = la - 2; i >= 0; i--)
79 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
80 if (lb != 0U && b[lb - 1] == '.') {
82 /* note this loop doesn't get executed if lb==1 */
83 for (i = lb - 2; i >= 0; i--)
95 /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
99 /* 'b' longer than 'a' means 'a' can't be in 'b'. */
103 /* 'a' and 'b' being equal at this point indicates sameness. */
105 return (strncasecmp(a, b, lb) == 0);
107 /* Ok, we know la > lb. */
112 * If 'a' is only 1 character longer than 'b', then it can't be
113 * a subdomain of 'b' (because of the need for the '.' label
120 * If the character before the last 'lb' characters of 'b'
121 * isn't '.', then it can't be a match (this lets us avoid
122 * having "foobar.com" match "bar.com").
124 if (a[diff - 1] != '.')
128 * We're not sure about that '.', however. It could be escaped
129 * and thus not a really a label separator.
132 for (i = diff - 2; i >= 0; i--)
143 /* Now compare aligned trailing substring. */
145 return (strncasecmp(cp, b, lb) == 0);
150 * is "a" a subdomain of "b"?
153 ns_subdomain(const char *a, const char *b) {
154 return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
159 * make a canonical copy of domain name "src"
172 ns_makecanon(const char *src, char *dst, size_t dstsize) {
173 size_t n = strlen(src);
175 if (n + sizeof "." > dstsize) { /*%< Note: sizeof == 2 */
180 while (n >= 1U && dst[n - 1] == '.') /*%< Ends in "." */
181 if (n >= 2U && dst[n - 2] == '\\' && /*%< Ends in "\." */
182 (n < 3U || dst[n - 3] != '\\')) /*%< But not "\\." */
192 * determine whether domain name "a" is the same as domain name "b"
196 *\li 0 if names differ
197 *\li 1 if names are the same
201 ns_samename(const char *a, const char *b) {
202 char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
204 if (ns_makecanon(a, ta, sizeof ta) < 0 ||
205 ns_makecanon(b, tb, sizeof tb) < 0)
207 if (strcasecmp(ta, tb) == 0)