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 "port_before.h"
30
31#include <sys/types.h>
32#include <arpa/nameser.h>
33#include <errno.h>
34#include <string.h>
35
36#include "port_after.h"
37
38#ifdef _LIBRESOLV
39/*%
40 *	Check whether a name belongs to a domain.
41 *
42 * Inputs:
43 *\li	a - the domain whose ancestory is being verified
44 *\li	b - the potential ancestor we're checking against
45 *
46 * Return:
47 *\li	boolean - is a at or below b?
48 *
49 * Notes:
50 *\li	Trailing dots are first removed from name and domain.
51 *	Always compare complete subdomains, not only whether the
52 *	domain name is the trailing string of the given name.
53 *
54 *\li	"host.foobar.top" lies in "foobar.top" and in "top" and in ""
55 *	but NOT in "bar.top"
56 */
57
58int
59ns_samedomain(const char *a, const char *b) {
60	size_t la, lb, i;
61	int diff, escaped;
62	const char *cp;
63
64	la = strlen(a);
65	lb = strlen(b);
66
67	/* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
68	if (la != 0U && a[la - 1] == '.') {
69		escaped = 0;
70		/* Note this loop doesn't get executed if la==1. */
71		for (i = la - 1; i > 0; i--)
72			if (a[i - 1] == '\\') {
73				if (escaped)
74					escaped = 0;
75				else
76					escaped = 1;
77			} else
78				break;
79		if (!escaped)
80			la--;
81	}
82
83	/* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
84	if (lb != 0U && b[lb - 1] == '.') {
85		escaped = 0;
86		/* note this loop doesn't get executed if lb==1 */
87		for (i = lb - 1; i > 0; i--)
88			if (b[i - 1] == '\\') {
89				if (escaped)
90					escaped = 0;
91				else
92					escaped = 1;
93			} else
94				break;
95		if (!escaped)
96			lb--;
97	}
98
99	/* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
100	if (lb == 0U)
101		return (1);
102
103	/* 'b' longer than 'a' means 'a' can't be in 'b'. */
104	if (lb > la)
105		return (0);
106
107	/* 'a' and 'b' being equal at this point indicates sameness. */
108	if (lb == la)
109		return (strncasecmp(a, b, lb) == 0);
110
111	/* Ok, we know la > lb. */
112
113	diff = (int)(la - lb);
114
115	/*
116	 * If 'a' is only 1 character longer than 'b', then it can't be
117	 * a subdomain of 'b' (because of the need for the '.' label
118	 * separator).
119	 */
120	if (diff < 2)
121		return (0);
122
123	/*
124	 * If the character before the last 'lb' characters of 'b'
125	 * isn't '.', then it can't be a match (this lets us avoid
126	 * having "foobar.com" match "bar.com").
127	 */
128	if (a[diff - 1] != '.')
129		return (0);
130
131	/*
132	 * We're not sure about that '.', however.  It could be escaped
133         * and thus not a really a label separator.
134	 */
135	escaped = 0;
136	for (i = diff - 1; i > 0; i--)
137		if (a[i - 1] == '\\') {
138			if (escaped)
139				escaped = 0;
140			else
141				escaped = 1;
142		} else
143			break;
144	if (escaped)
145		return (0);
146
147	/* Now compare aligned trailing substring. */
148	cp = a + diff;
149	return (strncasecmp(cp, b, lb) == 0);
150}
151
152/*%
153 *	is "a" a subdomain of "b"?
154 */
155int
156ns_subdomain(const char *a, const char *b) {
157	return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
158}
159#endif
160#define _LIBC
161#ifdef _LIBC
162/*%
163 *	make a canonical copy of domain name "src"
164 *
165 * notes:
166 * \code
167 *	foo -> foo.
168 *	foo. -> foo.
169 *	foo.. -> foo.
170 *	foo\. -> foo\..
171 *	foo\\. -> foo\\.
172 * \endcode
173 */
174
175int
176ns_makecanon(const char *src, char *dst, size_t dstsize) {
177	size_t n = strlen(src);
178
179	if (n + sizeof "." > dstsize) {			/*%< Note: sizeof == 2 */
180		errno = EMSGSIZE;
181		return (-1);
182	}
183	strcpy(dst, src);
184	while (n >= 1U && dst[n - 1] == '.')		/*%< Ends in "." */
185		if (n >= 2U && dst[n - 2] == '\\' &&	/*%< Ends in "\." */
186		    (n < 3U || dst[n - 3] != '\\'))	/*%< But not "\\." */
187			break;
188		else
189			dst[--n] = '\0';
190	dst[n++] = '.';
191	dst[n] = '\0';
192	return (0);
193}
194
195/*%
196 *	determine whether domain name "a" is the same as domain name "b"
197 *
198 * return:
199 *\li	-1 on error
200 *\li	0 if names differ
201 *\li	1 if names are the same
202 */
203
204int
205ns_samename(const char *a, const char *b) {
206	char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
207
208	if (ns_makecanon(a, ta, sizeof ta) < 0 ||
209	    ns_makecanon(b, tb, sizeof tb) < 0)
210		return (-1);
211	if (strcasecmp(ta, tb) == 0)
212		return (1);
213	else
214		return (0);
215}
216#endif
217/*! \file */
218