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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
10 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
11 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
12 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
13 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
14 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
15 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
16 * SOFTWARE.
17 */
18
19#if !defined(_LIBC) && !defined(lint)
20static const char rcsid[] = "$BINDId: ns_samedomain.c,v 8.9 1999/10/15 21:06:51 vixie Exp $";
21#endif
22
23#include <sys/types.h>
24#include <arpa/nameser.h>
25#include <errno.h>
26#include <string.h>
27
28/*%
29 * Check whether a name belongs to a domain.
30 *
31 * Inputs:
32 *\li a - the domain whose ancestry is being verified
33 *\li b - the potential ancestor we're checking against
34 *
35 * Return:
36 *\li boolean - is a at or below b?
37 *
38 * Notes:
39 *\li Trailing dots are first removed from name and domain.
40 * Always compare complete subdomains, not only whether the
41 * domain name is the trailing string of the given name.
42 *
43 *\li "host.foobar.top" lies in "foobar.top" and in "top" and in ""
44 * but NOT in "bar.top"
45 */
46
47int
48ns_samedomain(const char *a, const char *b) {
49 size_t la, lb;
50 int diff, i, escaped;
51 const char *cp;
52
53 la = strlen(a);
54 lb = strlen(b);
55
56 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
57 if (la != 0U && a[la - 1] == '.') {
58 escaped = 0;
59 /* Note this loop doesn't get executed if la==1. */
60 for (i = la - 2; i >= 0; i--)
61 if (a[i] == '\\') {
62 if (escaped)
63 escaped = 0;
64 else
65 escaped = 1;
66 } else
67 break;
68 if (!escaped)
69 la--;
70 }
71
72 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
73 if (lb != 0U && b[lb - 1] == '.') {
74 escaped = 0;
75 /* note this loop doesn't get executed if lb==1 */
76 for (i = lb - 2; i >= 0; i--)
77 if (b[i] == '\\') {
78 if (escaped)
79 escaped = 0;
80 else
81 escaped = 1;
82 } else
83 break;
84 if (!escaped)
85 lb--;
86 }
87
88 /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
89 if (lb == 0U)
90 return (1);
91
92 /* 'b' longer than 'a' means 'a' can't be in 'b'. */
93 if (lb > la)
94 return (0);
95
96 /* 'a' and 'b' being equal at this point indicates sameness. */
97 if (lb == la)
98 return (strncasecmp(a, b, lb) == 0);
99
100 /* Ok, we know la > lb. */
101
102 diff = la - lb;
103
104 /*
105 * If 'a' is only 1 character longer than 'b', then it can't be
106 * a subdomain of 'b' (because of the need for the '.' label
107 * separator).
108 */
109 if (diff < 2)
110 return (0);
111
112 /*
113 * If the character before the last 'lb' characters of 'b'
114 * isn't '.', then it can't be a match (this lets us avoid
115 * having "foobar.com" match "bar.com").
116 */
117 if (a[diff - 1] != '.')
118 return (0);
119
120 /*
121 * We're not sure about that '.', however. It could be escaped
122 * and thus not a really a label separator.
123 */
124 escaped = 0;
125 for (i = diff - 2; i >= 0; i--)
126 if (a[i] == '\\') {
127 if (escaped)
128 escaped = 0;
129 else
130 escaped = 1;
131 } else
132 break;
133 if (escaped)
134 return (0);
135
136 /* Now compare aligned trailing substring. */
137 cp = a + diff;
138 return (strncasecmp(cp, b, lb) == 0);
139}
140libresolv_hidden_def (ns_samedomain)
141
142/*%
143 * is "a" a subdomain of "b"?
144 */
145int
146ns_subdomain(const char *a, const char *b) {
147 return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
148}
149
150/*%
151 * make a canonical copy of domain name "src"
152 *
153 * notes:
154 * \code
155 * foo -> foo.
156 * foo. -> foo.
157 * foo.. -> foo.
158 * foo\. -> foo\..
159 * foo\\. -> foo\\.
160 * \endcode
161 */
162
163int
164ns_makecanon(const char *src, char *dst, size_t dstsize) {
165 size_t n = strlen(src);
166
167 if (n + sizeof "." > dstsize) { /*%< Note: sizeof == 2 */
168 __set_errno (EMSGSIZE);
169 return (-1);
170 }
171 strcpy(dst, src);
172 while (n >= 1U && dst[n - 1] == '.') /*%< Ends in "." */
173 if (n >= 2U && dst[n - 2] == '\\' && /*%< Ends in "\." */
174 (n < 3U || dst[n - 3] != '\\')) /*%< But not "\\." */
175 break;
176 else
177 dst[--n] = '\0';
178 dst[n++] = '.';
179 dst[n] = '\0';
180 return (0);
181}
182libresolv_hidden_def (ns_makecanon)
183
184/*%
185 * determine whether domain name "a" is the same as domain name "b"
186 *
187 * return:
188 *\li -1 on error
189 *\li 0 if names differ
190 *\li 1 if names are the same
191 */
192
193int
194ns_samename(const char *a, const char *b) {
195 char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
196
197 if (ns_makecanon(a, ta, sizeof ta) < 0 ||
198 ns_makecanon(b, tb, sizeof tb) < 0)
199 return (-1);
200 if (strcasecmp(ta, tb) == 0)
201 return (1);
202 else
203 return (0);
204}
205libresolv_hidden_def (ns_samename)
206
207/*! \file */
208