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 #include <sys/types.h>
20 #include <arpa/nameser.h>
21 #include <errno.h>
22 #include <string.h>
23
24 /*%
25 * Check whether a name belongs to a domain.
26 *
27 * Inputs:
28 *\li a - the domain whose ancestry is being verified
29 *\li b - the potential ancestor we're checking against
30 *
31 * Return:
32 *\li boolean - is a at or below b?
33 *
34 * Notes:
35 *\li Trailing dots are first removed from name and domain.
36 * Always compare complete subdomains, not only whether the
37 * domain name is the trailing string of the given name.
38 *
39 *\li "host.foobar.top" lies in "foobar.top" and in "top" and in ""
40 * but NOT in "bar.top"
41 */
42
43 int
44 ns_samedomain(const char *a, const char *b) {
45 size_t la, lb;
46 int diff, i, escaped;
47 const char *cp;
48
49 la = strlen(a);
50 lb = strlen(b);
51
52 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
53 if (la != 0U && a[la - 1] == '.') {
54 escaped = 0;
55 /* Note this loop doesn't get executed if la==1. */
56 for (i = la - 2; i >= 0; i--)
57 if (a[i] == '\\') {
58 if (escaped)
59 escaped = 0;
60 else
61 escaped = 1;
62 } else
63 break;
64 if (!escaped)
65 la--;
66 }
67
68 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
69 if (lb != 0U && b[lb - 1] == '.') {
70 escaped = 0;
71 /* note this loop doesn't get executed if lb==1 */
72 for (i = lb - 2; i >= 0; i--)
73 if (b[i] == '\\') {
74 if (escaped)
75 escaped = 0;
76 else
77 escaped = 1;
78 } else
79 break;
80 if (!escaped)
81 lb--;
82 }
83
84 /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
85 if (lb == 0U)
86 return (1);
87
88 /* 'b' longer than 'a' means 'a' can't be in 'b'. */
89 if (lb > la)
90 return (0);
91
92 /* 'a' and 'b' being equal at this point indicates sameness. */
93 if (lb == la)
94 return (strncasecmp(a, b, lb) == 0);
95
96 /* Ok, we know la > lb. */
97
98 diff = la - lb;
99
100 /*
101 * If 'a' is only 1 character longer than 'b', then it can't be
102 * a subdomain of 'b' (because of the need for the '.' label
103 * separator).
104 */
105 if (diff < 2)
106 return (0);
107
108 /*
109 * If the character before the last 'lb' characters of 'b'
110 * isn't '.', then it can't be a match (this lets us avoid
111 * having "foobar.com" match "bar.com").
112 */
113 if (a[diff - 1] != '.')
114 return (0);
115
116 /*
117 * We're not sure about that '.', however. It could be escaped
118 * and thus not a really a label separator.
119 */
120 escaped = 0;
121 for (i = diff - 2; i >= 0; i--)
122 if (a[i] == '\\') {
123 if (escaped)
124 escaped = 0;
125 else
126 escaped = 1;
127 } else
128 break;
129 if (escaped)
130 return (0);
131
132 /* Now compare aligned trailing substring. */
133 cp = a + diff;
134 return (strncasecmp(cp, b, lb) == 0);
135 }
136 libresolv_hidden_def (ns_samedomain)
137
138 /*%
139 * is "a" a subdomain of "b"?
140 */
141 int
142 ns_subdomain (const char *a, const char *b)
143 {
144 return __libc_ns_samename (a, b) != 1 && ns_samedomain (a, b);
145 }
146
147 /*! \file */