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.
20 #include "port_before.h"
22 #include <sys/types.h>
23 #include <arpa/nameser.h>
27 #include "port_after.h"
30 * Check whether a name belongs to a domain.
33 *\li a - the domain whose ancestry is being verified
34 *\li b - the potential ancestor we're checking against
37 *\li boolean - is a at or below b?
40 *\li Trailing dots are first removed from name and domain.
41 * Always compare complete subdomains, not only whether the
42 * domain name is the trailing string of the given name.
44 *\li "host.foobar.top" lies in "foobar.top" and in "top" and in ""
45 * but NOT in "bar.top"
49 ns_samedomain(const char *a, const char *b) {
57 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
58 if (la != 0U && a[la - 1] == '.') {
60 /* Note this loop doesn't get executed if la==1. */
61 for (i = la - 2; i >= 0; i--)
73 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
74 if (lb != 0U && b[lb - 1] == '.') {
76 /* note this loop doesn't get executed if lb==1 */
77 for (i = lb - 2; i >= 0; i--)
89 /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
93 /* 'b' longer than 'a' means 'a' can't be in 'b'. */
97 /* 'a' and 'b' being equal at this point indicates sameness. */
99 return (strncasecmp(a, b, lb) == 0);
101 /* Ok, we know la > lb. */
106 * If 'a' is only 1 character longer than 'b', then it can't be
107 * a subdomain of 'b' (because of the need for the '.' label
114 * If the character before the last 'lb' characters of 'b'
115 * isn't '.', then it can't be a match (this lets us avoid
116 * having "foobar.com" match "bar.com").
118 if (a[diff - 1] != '.')
122 * We're not sure about that '.', however. It could be escaped
123 * and thus not a really a label separator.
126 for (i = diff - 2; i >= 0; i--)
137 /* Now compare aligned trailing substring. */
139 return (strncasecmp(cp, b, lb) == 0);
144 * is "a" a subdomain of "b"?
147 ns_subdomain(const char *a, const char *b) {
148 return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
153 * make a canonical copy of domain name "src"
166 ns_makecanon(const char *src, char *dst, size_t dstsize) {
167 size_t n = strlen(src);
169 if (n + sizeof "." > dstsize) { /*%< Note: sizeof == 2 */
174 while (n >= 1U && dst[n - 1] == '.') /*%< Ends in "." */
175 if (n >= 2U && dst[n - 2] == '\\' && /*%< Ends in "\." */
176 (n < 3U || dst[n - 3] != '\\')) /*%< But not "\\." */
186 * determine whether domain name "a" is the same as domain name "b"
190 *\li 0 if names differ
191 *\li 1 if names are the same
195 ns_samename(const char *a, const char *b) {
196 char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
198 if (ns_makecanon(a, ta, sizeof ta) < 0 ||
199 ns_makecanon(b, tb, sizeof tb) < 0)
201 if (strcasecmp(ta, tb) == 0)