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 | return (ns_samename(a, b) != 1 && ns_samedomain(a, b)); |
144 | } |
145 | |
146 | /*% |
147 | * make a canonical copy of domain name "src" |
148 | * |
149 | * notes: |
150 | * \code |
151 | * foo -> foo. |
152 | * foo. -> foo. |
153 | * foo.. -> foo. |
154 | * foo\. -> foo\.. |
155 | * foo\\. -> foo\\. |
156 | * \endcode |
157 | */ |
158 | |
159 | int |
160 | ns_makecanon(const char *src, char *dst, size_t dstsize) { |
161 | size_t n = strlen(src); |
162 | |
163 | if (n + sizeof "." > dstsize) { /*%< Note: sizeof == 2 */ |
164 | __set_errno (EMSGSIZE); |
165 | return (-1); |
166 | } |
167 | strcpy(dst, src); |
168 | while (n >= 1U && dst[n - 1] == '.') /*%< Ends in "." */ |
169 | if (n >= 2U && dst[n - 2] == '\\' && /*%< Ends in "\." */ |
170 | (n < 3U || dst[n - 3] != '\\')) /*%< But not "\\." */ |
171 | break; |
172 | else |
173 | dst[--n] = '\0'; |
174 | dst[n++] = '.'; |
175 | dst[n] = '\0'; |
176 | return (0); |
177 | } |
178 | libresolv_hidden_def (ns_makecanon) |
179 | |
180 | /*% |
181 | * determine whether domain name "a" is the same as domain name "b" |
182 | * |
183 | * return: |
184 | *\li -1 on error |
185 | *\li 0 if names differ |
186 | *\li 1 if names are the same |
187 | */ |
188 | |
189 | int |
190 | ns_samename(const char *a, const char *b) { |
191 | char ta[NS_MAXDNAME], tb[NS_MAXDNAME]; |
192 | |
193 | if (ns_makecanon(a, ta, sizeof ta) < 0 || |
194 | ns_makecanon(b, tb, sizeof tb) < 0) |
195 | return (-1); |
196 | if (strcasecmp(ta, tb) == 0) |
197 | return (1); |
198 | else |
199 | return (0); |
200 | } |
201 | libresolv_hidden_def (ns_samename) |
202 | |
203 | /*! \file */ |
204 | |