1/*	$NetBSD: ns_samedomain.c,v 1.8 2012/11/22 20:22:31 christos Exp $	*/
2
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#include <sys/cdefs.h>
21#ifndef lint
22#ifdef notdef
23static const char rcsid[] = "Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp";
24#else
25__RCSID("$NetBSD: ns_samedomain.c,v 1.8 2012/11/22 20:22:31 christos Exp $");
26#endif
27#endif
28
29#include <sys/types.h>
30#include <arpa/nameser.h>
31#include <errno.h>
32#include <string.h>
33
34#ifdef _LIBRESOLV
35/*
36 *	Check whether a name belongs to a domain.
37 *
38 * Inputs:
39 *	a - the domain whose ancestory is being verified
40 *	b - the potential ancestor we're checking against
41 *
42 * Return:
43 *	boolean - is a at or below b?
44 *
45 * Notes:
46 *	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 *	"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, i;
57	int diff, 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 - 1; i > 0; i--)
68			if (a[i - 1] == '\\') {
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 - 1; i > 0; i--)
84			if (b[i - 1] == '\\') {
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 = (int)(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 - 1; i > 0; i--)
133		if (a[i - 1] == '\\') {
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/*
149 *	is "a" a subdomain of "b"?
150 */
151int
152ns_subdomain(const char *a, const char *b) {
153	return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
154}
155#endif
156
157#ifdef _LIBC
158/*
159 *	make a canonical copy of domain name "src"
160 *
161 * notes:
162 *	foo -> foo.
163 *	foo. -> foo.
164 *	foo.. -> foo.
165 *	foo\. -> foo\..
166 *	foo\\. -> foo\\.
167 */
168
169int
170ns_makecanon(const char *src, char *dst, size_t dstsize) {
171	size_t n = strlen(src);
172
173	if (n + sizeof "." > dstsize) {			/* Note: sizeof == 2 */
174		errno = EMSGSIZE;
175		return (-1);
176	}
177	strcpy(dst, src);
178	while (n >= 1U && dst[n - 1] == '.')		/* Ends in "." */
179		if (n >= 2U && dst[n - 2] == '\\' &&	/* Ends in "\." */
180		    (n < 3U || dst[n - 3] != '\\'))	/* But not "\\." */
181			break;
182		else
183			dst[--n] = '\0';
184	dst[n++] = '.';
185	dst[n] = '\0';
186	return (0);
187}
188
189/*
190 *	determine whether domain name "a" is the same as domain name "b"
191 *
192 * return:
193 *	-1 on error
194 *	0 if names differ
195 *	1 if names are the same
196 */
197
198int
199ns_samename(const char *a, const char *b) {
200	char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
201
202	if (ns_makecanon(a, ta, sizeof ta) < 0 ||
203	    ns_makecanon(b, tb, sizeof tb) < 0)
204		return (-1);
205	if (strcasecmp(ta, tb) == 0)
206		return (1);
207	else
208		return (0);
209}
210#endif
211