ns_samedomain.c revision 270838 
1/*
2 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (c) 1995,1999 by Internet Software Consortium.
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
15 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#ifndef lint
19static const char rcsid[] = "$Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp $";
20#endif
21#include <sys/cdefs.h>
22__FBSDID("$FreeBSD: stable/10/lib/libc/nameser/ns_samedomain.c 270838 2014-08-30 10:16:25Z ume $");
23
24#include "port_before.h"
25
26#include <sys/types.h>
27#include <arpa/nameser.h>
28#include <errno.h>
29#include <string.h>
30
31#include "port_after.h"
32
33/*%
34 *	Check whether a name belongs to a domain.
35 *
36 * Inputs:
37 *\li	a - the domain whose ancestory is being verified
38 *\li	b - the potential ancestor we're checking against
39 *
40 * Return:
41 *\li	boolean - is a at or below b?
42 *
43 * Notes:
44 *\li	Trailing dots are first removed from name and domain.
45 *	Always compare complete subdomains, not only whether the
46 *	domain name is the trailing string of the given name.
47 *
48 *\li	"host.foobar.top" lies in "foobar.top" and in "top" and in ""
49 *	but NOT in "bar.top"
50 */
51
52int
53ns_samedomain(const char *a, const char *b) {
54	size_t la, lb;
55	int diff, i, escaped;
56	const char *cp;
57
58	la = strlen(a);
59	lb = strlen(b);
60
61	/* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
62	if (la != 0U && a[la - 1] == '.') {
63		escaped = 0;
64		/* Note this loop doesn't get executed if la==1. */
65		for (i = la - 2; i >= 0; i--)
66			if (a[i] == '\\') {
67				if (escaped)
68					escaped = 0;
69				else
70					escaped = 1;
71			} else
72				break;
73		if (!escaped)
74			la--;
75	}
76
77	/* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
78	if (lb != 0U && b[lb - 1] == '.') {
79		escaped = 0;
80		/* note this loop doesn't get executed if lb==1 */
81		for (i = lb - 2; i >= 0; i--)
82			if (b[i] == '\\') {
83				if (escaped)
84					escaped = 0;
85				else
86					escaped = 1;
87			} else
88				break;
89		if (!escaped)
90			lb--;
91	}
92
93	/* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
94	if (lb == 0U)
95		return (1);
96
97	/* 'b' longer than 'a' means 'a' can't be in 'b'. */
98	if (lb > la)
99		return (0);
100
101	/* 'a' and 'b' being equal at this point indicates sameness. */
102	if (lb == la)
103		return (strncasecmp(a, b, lb) == 0);
104
105	/* Ok, we know la > lb. */
106
107	diff = la - lb;
108
109	/*
110	 * If 'a' is only 1 character longer than 'b', then it can't be
111	 * a subdomain of 'b' (because of the need for the '.' label
112	 * separator).
113	 */
114	if (diff < 2)
115		return (0);
116
117	/*
118	 * If the character before the last 'lb' characters of 'b'
119	 * isn't '.', then it can't be a match (this lets us avoid
120	 * having "foobar.com" match "bar.com").
121	 */
122	if (a[diff - 1] != '.')
123		return (0);
124
125	/*
126	 * We're not sure about that '.', however.  It could be escaped
127         * and thus not a really a label separator.
128	 */
129	escaped = 0;
130	for (i = diff - 2; i >= 0; i--)
131		if (a[i] == '\\') {
132			if (escaped)
133				escaped = 0;
134			else
135				escaped = 1;
136		} else
137			break;
138	if (escaped)
139		return (0);
140
141	/* Now compare aligned trailing substring. */
142	cp = a + diff;
143	return (strncasecmp(cp, b, lb) == 0);
144}
145
146#ifndef _LIBC
147/*%
148 *	is "a" a subdomain of "b"?
149 */
150int
151ns_subdomain(const char *a, const char *b) {
152	return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
153}
154#endif
155
156/*%
157 *	make a canonical copy of domain name "src"
158 *
159 * notes:
160 * \code
161 *	foo -> foo.
162 *	foo. -> foo.
163 *	foo.. -> foo.
164 *	foo\. -> foo\..
165 *	foo\\. -> foo\\.
166 * \endcode
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 *\li	-1 on error
194 *\li	0 if names differ
195 *\li	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
211/*! \file */
212