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
23 static 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
54 int
ns_samedomain(const char * a,const char * b)55 ns_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 */
151 int
ns_subdomain(const char * a,const char * b)152 ns_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
169 int
ns_makecanon(const char * src,char * dst,size_t dstsize)170 ns_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
198 int
ns_samename(const char * a,const char * b)199 ns_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