1/*-
2 * SPDX-License-Identifier: ISC
3 *
4 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
5 * Copyright (c) 1995,1999 by Internet Software Consortium.
6 *
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.
10 *
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.
18 */
19
20#ifndef lint
21static const char rcsid[] = "$Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp $";
22#endif
23#include <sys/cdefs.h>
24__FBSDID("$FreeBSD$");
25
26#include "port_before.h"
27
28#include <sys/types.h>
29#include <arpa/nameser.h>
30#include <errno.h>
31#include <string.h>
32
33#include "port_after.h"
34
35/*%
36 *	Check whether a name belongs to a domain.
37 *
38 * Inputs:
39 *\li	a - the domain whose ancestry is being verified
40 *\li	b - the potential ancestor we're checking against
41 *
42 * Return:
43 *\li	boolean - is a at or below b?
44 *
45 * Notes:
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.
49 *
50 *\li	"host.foobar.top" lies in "foobar.top" and in "top" and in ""
51 *	but NOT in "bar.top"
52 */
53
54int
55ns_samedomain(const char *a, const char *b) {
56	size_t la, lb;
57	int diff, i, escaped;
58	const char *cp;
59
60	la = strlen(a);
61	lb = strlen(b);
62
63	/* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
64	if (la != 0U && a[la - 1] == '.') {
65		escaped = 0;
66		/* Note this loop doesn't get executed if la==1. */
67		for (i = la - 2; i >= 0; i--)
68			if (a[i] == '\\') {
69				if (escaped)
70					escaped = 0;
71				else
72					escaped = 1;
73			} else
74				break;
75		if (!escaped)
76			la--;
77	}
78
79	/* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
80	if (lb != 0U && b[lb - 1] == '.') {
81		escaped = 0;
82		/* note this loop doesn't get executed if lb==1 */
83		for (i = lb - 2; i >= 0; i--)
84			if (b[i] == '\\') {
85				if (escaped)
86					escaped = 0;
87				else
88					escaped = 1;
89			} else
90				break;
91		if (!escaped)
92			lb--;
93	}
94
95	/* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
96	if (lb == 0U)
97		return (1);
98
99	/* 'b' longer than 'a' means 'a' can't be in 'b'. */
100	if (lb > la)
101		return (0);
102
103	/* 'a' and 'b' being equal at this point indicates sameness. */
104	if (lb == la)
105		return (strncasecmp(a, b, lb) == 0);
106
107	/* Ok, we know la > lb. */
108
109	diff = la - lb;
110
111	/*
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
114	 * separator).
115	 */
116	if (diff < 2)
117		return (0);
118
119	/*
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").
123	 */
124	if (a[diff - 1] != '.')
125		return (0);
126
127	/*
128	 * We're not sure about that '.', however.  It could be escaped
129         * and thus not a really a label separator.
130	 */
131	escaped = 0;
132	for (i = diff - 2; i >= 0; i--)
133		if (a[i] == '\\') {
134			if (escaped)
135				escaped = 0;
136			else
137				escaped = 1;
138		} else
139			break;
140	if (escaped)
141		return (0);
142
143	/* Now compare aligned trailing substring. */
144	cp = a + diff;
145	return (strncasecmp(cp, b, lb) == 0);
146}
147
148#ifndef _LIBC
149/*%
150 *	is "a" a subdomain of "b"?
151 */
152int
153ns_subdomain(const char *a, const char *b) {
154	return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
155}
156#endif
157
158/*%
159 *	make a canonical copy of domain name "src"
160 *
161 * notes:
162 * \code
163 *	foo -> foo.
164 *	foo. -> foo.
165 *	foo.. -> foo.
166 *	foo\. -> foo\..
167 *	foo\\. -> foo\\.
168 * \endcode
169 */
170
171int
172ns_makecanon(const char *src, char *dst, size_t dstsize) {
173	size_t n = strlen(src);
174
175	if (n + sizeof "." > dstsize) {			/*%< Note: sizeof == 2 */
176		errno = EMSGSIZE;
177		return (-1);
178	}
179	strcpy(dst, src);
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 "\\." */
183			break;
184		else
185			dst[--n] = '\0';
186	dst[n++] = '.';
187	dst[n] = '\0';
188	return (0);
189}
190
191/*%
192 *	determine whether domain name "a" is the same as domain name "b"
193 *
194 * return:
195 *\li	-1 on error
196 *\li	0 if names differ
197 *\li	1 if names are the same
198 */
199
200int
201ns_samename(const char *a, const char *b) {
202	char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
203
204	if (ns_makecanon(a, ta, sizeof ta) < 0 ||
205	    ns_makecanon(b, tb, sizeof tb) < 0)
206		return (-1);
207	if (strcasecmp(ta, tb) == 0)
208		return (1);
209	else
210		return (0);
211}
212
213/*! \file */
214