1/* Domain name processing functions.
2 Copyright (C) 1995-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19/*
20 * Copyright (c) 1985, 1993
21 * The Regents of the University of California. All rights reserved.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the above copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 4. Neither the name of the University nor the names of its contributors
32 * may be used to endorse or promote products derived from this software
33 * without specific prior written permission.
34 *
35 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
36 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
38 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
39 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
40 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
41 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
42 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
43 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
44 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
45 * SUCH DAMAGE.
46 */
47
48/*
49 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
50 *
51 * Permission to use, copy, modify, and distribute this software for any
52 * purpose with or without fee is hereby granted, provided that the above
53 * copyright notice and this permission notice appear in all copies, and that
54 * the name of Digital Equipment Corporation not be used in advertising or
55 * publicity pertaining to distribution of the document or software without
56 * specific, written prior permission.
57 *
58 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
59 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
60 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
61 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
62 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
63 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
64 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
65 * SOFTWARE.
66 */
67
68/*
69 * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
70 *
71 * Permission to use, copy, modify, and distribute this software for any
72 * purpose with or without fee is hereby granted, provided that the above
73 * copyright notice and this permission notice appear in all copies.
74 *
75 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
76 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
77 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
78 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
79 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
80 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
81 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
82 * SOFTWARE.
83 */
84
85#include <sys/types.h>
86#include <sys/param.h>
87#include <netinet/in.h>
88#include <arpa/nameser.h>
89#include <ctype.h>
90#include <resolv.h>
91#include <stdio.h>
92#include <string.h>
93#include <unistd.h>
94
95/*
96 * Expand compressed domain name 'comp_dn' to full domain name.
97 * 'msg' is a pointer to the beginning of the message,
98 * 'eomorig' points to the first location after the message,
99 * 'exp_dn' is a pointer to a buffer of size 'length' for the result.
100 * Return size of compressed name or -1 if there was an error.
101 */
102int
103dn_expand(const u_char *msg, const u_char *eom, const u_char *src,
104 char *dst, int dstsiz)
105{
106 int n = ns_name_uncompress(msg, eom, src, dst, (size_t)dstsiz);
107
108 if (n > 0 && dst[0] == '.')
109 dst[0] = '\0';
110 return (n);
111}
112libresolv_hidden_def (dn_expand)
113
114/*
115 * Pack domain name 'exp_dn' in presentation form into 'comp_dn'.
116 * Return the size of the compressed name or -1.
117 * 'length' is the size of the array pointed to by 'comp_dn'.
118 */
119int
120dn_comp(const char *src, u_char *dst, int dstsiz,
121 u_char **dnptrs, u_char **lastdnptr)
122{
123 return (ns_name_compress(src, dst, (size_t)dstsiz,
124 (const u_char **)dnptrs,
125 (const u_char **)lastdnptr));
126}
127libresolv_hidden_def (dn_comp)
128
129/*
130 * Skip over a compressed domain name. Return the size or -1.
131 */
132int
133dn_skipname(const u_char *ptr, const u_char *eom) {
134 const u_char *saveptr = ptr;
135
136 if (ns_name_skip(&ptr, eom) == -1)
137 return (-1);
138 return (ptr - saveptr);
139}
140libresolv_hidden_def (dn_skipname)
141
142/* Return true if the string consists of printable ASCII characters
143 only. */
144static bool
145printable_string (const char *dn)
146{
147 while (true)
148 {
149 char ch = *dn;
150 if (ch == '\0')
151 return true;
152 if (ch <= ' ' || ch > '~')
153 return false;
154 ++dn;
155 }
156}
157
158/* Return true if DN points to a name consisting only of [0-9a-zA-Z_-]
159 characters. DN must be in DNS wire format, without
160 compression. */
161static bool
162binary_hnok (const unsigned char *dn)
163{
164 while (true)
165 {
166 size_t label_length = *dn;
167 if (label_length == 0)
168 break;
169 ++dn;
170 const unsigned char *label_end = dn + label_length;
171 do
172 {
173 unsigned char ch = *dn;
174 if (!(('0' <= ch && ch <= '9')
175 || ('A' <= ch && ch <= 'Z')
176 || ('a' <= ch && ch <= 'z')
177 || ch == '-' || ch == '_'))
178 return false;
179 ++dn;
180 }
181 while (dn < label_end);
182 }
183 return true;
184}
185
186/* Return true if the binary domain name has a first labels which
187 starts with '-'. */
188static inline bool
189binary_leading_dash (const unsigned char *dn)
190{
191 return dn[0] > 0 && dn[1] == '-';
192}
193
194/* Return 1 if res_hnok is a valid host name. Labels must only
195 contain [0-9a-zA-Z_-] characters, and the name must not start with
196 a '-'. The latter is to avoid confusion with program options. */
197int
198res_hnok (const char *dn)
199{
200 unsigned char buf[NS_MAXCDNAME];
201 if (!printable_string (dn)
202 || ns_name_pton (dn, buf, sizeof (buf)) < 0
203 || binary_leading_dash (buf))
204 return 0;
205 return binary_hnok (buf);
206}
207libresolv_hidden_def (res_hnok)
208
209/* Hostname-like (A, MX, WKS) owners can have "*" as their first label
210 but must otherwise be as a host name. */
211int
212res_ownok (const char *dn)
213{
214 unsigned char buf[NS_MAXCDNAME];
215 if (!printable_string (dn)
216 || ns_name_pton (dn, buf, sizeof (buf)) < 0
217 || binary_leading_dash (buf))
218 return 0;
219 if (buf[0] == 1 && buf [1] == '*')
220 /* Skip over the leading "*." part. */
221 return binary_hnok (buf + 2);
222 else
223 return binary_hnok (buf);
224}
225
226/* SOA RNAMEs and RP RNAMEs can have any byte in their first label,
227 but the rest of the name has to look like a host name. */
228int
229res_mailok (const char *dn)
230{
231 unsigned char buf[NS_MAXCDNAME];
232 if (!printable_string (dn)
233 || ns_name_pton (dn, buf, sizeof (buf)) < 0)
234 return 0;
235 unsigned char label_length = buf[0];
236 /* "." is a valid missing representation */
237 if (label_length == 0)
238 return 1;
239 /* Skip over the first label. */
240 unsigned char *tail = buf + 1 + label_length;
241 if (*tail == 0)
242 /* More than one label is required (except for "."). */
243 return 0;
244 return binary_hnok (tail);
245}
246
247/* Return 1 if DN is a syntactically valid domain name. Empty names
248 are accepted. */
249int
250res_dnok (const char *dn)
251{
252 unsigned char buf[NS_MAXCDNAME];
253 return printable_string (dn) && ns_name_pton (dn, buf, sizeof (buf)) >= 0;
254}
255libresolv_hidden_def (res_dnok)
256
257/*
258 * This module must export the following externally-visible symbols:
259 * ___putlong
260 * ___putshort
261 * __getlong
262 * __getshort
263 * Note that one _ comes from C and the others come from us.
264 */
265void __putlong(uint32_t src, u_char *dst) { ns_put32(src, dst); }
266libresolv_hidden_def (__putlong)
267void __putshort(uint16_t src, u_char *dst) { ns_put16(src, dst); }
268libresolv_hidden_def (__putshort)
269uint32_t _getlong(const u_char *src) { return (ns_get32(src)); }
270uint16_t _getshort(const u_char *src) { return (ns_get16(src)); }
271
272
273#include <shlib-compat.h>
274
275#if SHLIB_COMPAT(libresolv, GLIBC_2_0, GLIBC_2_2)
276# undef dn_expand
277weak_alias (__dn_expand, dn_expand);
278#endif
279