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
19 static const char rcsid[] = "$Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp $";
20 #endif
21
22 #include "port_before.h"
23
24 #include <sys/types.h>
25 #include <arpa/nameser.h>
26 #include <errno.h>
27 #include <string.h>
28
29 #include "port_after.h"
30
31 /*%
32 * Check whether a name belongs to a domain.
33 *
34 * Inputs:
35 *\li a - the domain whose ancestory is being verified
36 *\li b - the potential ancestor we're checking against
37 *
38 * Return:
39 *\li boolean - is a at or below b?
40 *
41 * Notes:
42 *\li Trailing dots are first removed from name and domain.
43 * Always compare complete subdomains, not only whether the
44 * domain name is the trailing string of the given name.
45 *
46 *\li "host.foobar.top" lies in "foobar.top" and in "top" and in ""
47 * but NOT in "bar.top"
48 */
49
50 int
ns_samedomain(const char * a,const char * b)51 ns_samedomain(const char *a, const char *b) {
52 size_t la, lb;
53 int diff, i, escaped;
54 const char *cp;
55
56 la = strlen(a);
57 lb = strlen(b);
58
59 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
60 if (la != 0U && a[la - 1] == '.') {
61 escaped = 0;
62 /* Note this loop doesn't get executed if la==1. */
63 for (i = la - 2; i >= 0; i--)
64 if (a[i] == '\\') {
65 if (escaped)
66 escaped = 0;
67 else
68 escaped = 1;
69 } else
70 break;
71 if (!escaped)
72 la--;
73 }
74
75 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
76 if (lb != 0U && b[lb - 1] == '.') {
77 escaped = 0;
78 /* note this loop doesn't get executed if lb==1 */
79 for (i = lb - 2; i >= 0; i--)
80 if (b[i] == '\\') {
81 if (escaped)
82 escaped = 0;
83 else
84 escaped = 1;
85 } else
86 break;
87 if (!escaped)
88 lb--;
89 }
90
91 /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
92 if (lb == 0U)
93 return (1);
94
95 /* 'b' longer than 'a' means 'a' can't be in 'b'. */
96 if (lb > la)
97 return (0);
98
99 /* 'a' and 'b' being equal at this point indicates sameness. */
100 if (lb == la)
101 return (strncasecmp(a, b, lb) == 0);
102
103 /* Ok, we know la > lb. */
104
105 diff = la - lb;
106
107 /*
108 * If 'a' is only 1 character longer than 'b', then it can't be
109 * a subdomain of 'b' (because of the need for the '.' label
110 * separator).
111 */
112 if (diff < 2)
113 return (0);
114
115 /*
116 * If the character before the last 'lb' characters of 'b'
117 * isn't '.', then it can't be a match (this lets us avoid
118 * having "foobar.com" match "bar.com").
119 */
120 if (a[diff - 1] != '.')
121 return (0);
122
123 /*
124 * We're not sure about that '.', however. It could be escaped
125 * and thus not a really a label separator.
126 */
127 escaped = 0;
128 for (i = diff - 2; i >= 0; i--)
129 if (a[i] == '\\') {
130 if (escaped)
131 escaped = 0;
132 else
133 escaped = 1;
134 } else
135 break;
136 if (escaped)
137 return (0);
138
139 /* Now compare aligned trailing substring. */
140 cp = a + diff;
141 return (strncasecmp(cp, b, lb) == 0);
142 }
143
144 /*%
145 * is "a" a subdomain of "b"?
146 */
147 int
ns_subdomain(const char * a,const char * b)148 ns_subdomain(const char *a, const char *b) {
149 return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
150 }
151
152 /*%
153 * make a canonical copy of domain name "src"
154 *
155 * notes:
156 * \code
157 * foo -> foo.
158 * foo. -> foo.
159 * foo.. -> foo.
160 * foo\. -> foo\..
161 * foo\\. -> foo\\.
162 * \endcode
163 */
164
165 int
ns_makecanon(const char * src,char * dst,size_t dstsize)166 ns_makecanon(const char *src, char *dst, size_t dstsize) {
167 size_t n = strlen(src);
168
169 if (n + sizeof "." > dstsize) { /*%< Note: sizeof == 2 */
170 errno = EMSGSIZE;
171 return (-1);
172 }
173 strcpy(dst, src);
174 while (n >= 1U && dst[n - 1] == '.') /*%< Ends in "." */
175 if (n >= 2U && dst[n - 2] == '\\' && /*%< Ends in "\." */
176 (n < 3U || dst[n - 3] != '\\')) /*%< But not "\\." */
177 break;
178 else
179 dst[--n] = '\0';
180 dst[n++] = '.';
181 dst[n] = '\0';
182 return (0);
183 }
184
185 /*%
186 * determine whether domain name "a" is the same as domain name "b"
187 *
188 * return:
189 *\li -1 on error
190 *\li 0 if names differ
191 *\li 1 if names are the same
192 */
193
194 int
ns_samename(const char * a,const char * b)195 ns_samename(const char *a, const char *b) {
196 char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
197
198 if (ns_makecanon(a, ta, sizeof ta) < 0 ||
199 ns_makecanon(b, tb, sizeof tb) < 0)
200 return (-1);
201 if (strcasecmp(ta, tb) == 0)
202 return (1);
203 else
204 return (0);
205 }
206
207 /*! \file */
208