1/* Creation of DNS query packets.
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 <stdint.h>
86#include <sys/types.h>
87#include <sys/param.h>
88#include <netinet/in.h>
89#include <arpa/nameser.h>
90#include <netdb.h>
91#include <resolv/resolv-internal.h>
92#include <resolv/resolv_context.h>
93#include <string.h>
94#include <sys/time.h>
95#include <shlib-compat.h>
96#include <random-bits.h>
97
98int
99__res_context_mkquery (struct resolv_context *ctx, int op, const char *dname,
100 int class, int type, const unsigned char *data,
101 unsigned char *buf, int buflen)
102{
103 HEADER *hp;
104 unsigned char *cp;
105 int n;
106 unsigned char *dnptrs[20], **dpp, **lastdnptr;
107
108 if (class < 0 || class > 65535 || type < 0 || type > 65535)
109 return -1;
110
111 /* Initialize header fields. */
112 if ((buf == NULL) || (buflen < HFIXEDSZ))
113 return -1;
114 memset (buf, 0, HFIXEDSZ);
115 hp = (HEADER *) buf;
116 /* We randomize the IDs every time. The old code just incremented
117 by one after the initial randomization which still predictable if
118 the application does multiple requests. */
119 hp->id = random_bits ();
120 hp->opcode = op;
121 if (ctx->resp->options & RES_TRUSTAD)
122 hp->ad = 1;
123 hp->rd = (ctx->resp->options & RES_RECURSE) != 0;
124 hp->rcode = NOERROR;
125 cp = buf + HFIXEDSZ;
126 buflen -= HFIXEDSZ;
127 dpp = dnptrs;
128 *dpp++ = buf;
129 *dpp++ = NULL;
130 lastdnptr = dnptrs + sizeof dnptrs / sizeof dnptrs[0];
131
132 /* Perform opcode specific processing. */
133 switch (op)
134 {
135 case NS_NOTIFY_OP:
136 if ((buflen -= QFIXEDSZ + (data == NULL ? 0 : RRFIXEDSZ)) < 0)
137 return -1;
138 goto compose;
139
140 case QUERY:
141 if ((buflen -= QFIXEDSZ) < 0)
142 return -1;
143 compose:
144 n = ns_name_compress (dname, cp, buflen,
145 (const unsigned char **) dnptrs,
146 (const unsigned char **) lastdnptr);
147 if (n < 0)
148 return -1;
149 cp += n;
150 buflen -= n;
151 NS_PUT16 (type, cp);
152 NS_PUT16 (class, cp);
153 hp->qdcount = htons (1);
154 if (op == QUERY || data == NULL)
155 break;
156
157 /* Make an additional record for completion domain. */
158 n = ns_name_compress ((char *)data, cp, buflen,
159 (const unsigned char **) dnptrs,
160 (const unsigned char **) lastdnptr);
161 if (__glibc_unlikely (n < 0))
162 return -1;
163 cp += n;
164 buflen -= n;
165 NS_PUT16 (T_NULL, cp);
166 NS_PUT16 (class, cp);
167 NS_PUT32 (0, cp);
168 NS_PUT16 (0, cp);
169 hp->arcount = htons (1);
170 break;
171
172 default:
173 return -1;
174 }
175 return cp - buf;
176}
177
178/* Common part of res_nmkquery and res_mkquery. */
179static int
180context_mkquery_common (struct resolv_context *ctx,
181 int op, const char *dname, int class, int type,
182 const unsigned char *data,
183 unsigned char *buf, int buflen)
184{
185 if (ctx == NULL)
186 return -1;
187 int result = __res_context_mkquery
188 (ctx, op, dname, class, type, data, buf, buflen);
189 if (result >= 2)
190 memcpy (&ctx->resp->id, buf, 2);
191 __resolv_context_put (ctx);
192 return result;
193}
194
195/* Form all types of queries. Returns the size of the result or -1 on
196 error.
197
198 STATP points to an initialized resolver state. OP is the opcode of
199 the query. DNAME is the domain. CLASS and TYPE are the DNS query
200 class and type. DATA can be NULL; otherwise, it is a pointer to a
201 domain name which is included in the generated packet (if op ==
202 NS_NOTIFY_OP). BUF must point to the out buffer of BUFLEN bytes.
203
204 DATALEN and NEWRR_IN are currently ignored. */
205int
206res_nmkquery (res_state statp, int op, const char *dname,
207 int class, int type,
208 const unsigned char *data, int datalen,
209 const unsigned char *newrr_in,
210 unsigned char *buf, int buflen)
211{
212 return context_mkquery_common
213 (__resolv_context_get_override (statp),
214 op, dname, class, type, data, buf, buflen);
215}
216
217int
218res_mkquery (int op, const char *dname, int class, int type,
219 const unsigned char *data, int datalen,
220 const unsigned char *newrr_in,
221 unsigned char *buf, int buflen)
222{
223 return context_mkquery_common
224 (__resolv_context_get_preinit (),
225 op, dname, class, type, data, buf, buflen);
226}
227
228/* Create an OPT resource record. Return the length of the final
229 packet, or -1 on error.
230
231 STATP must be an initialized resolver state. N0 is the current
232 number of bytes of the packet (already written to BUF by the
233 aller). BUF is the packet being constructed. The array it
234 pointers to must be BUFLEN bytes long. ANSLEN is the advertised
235 EDNS buffer size (to be included in the OPT resource record). */
236int
237__res_nopt (struct resolv_context *ctx,
238 int n0, unsigned char *buf, int buflen, int anslen)
239{
240 uint16_t flags = 0;
241 HEADER *hp = (HEADER *) buf;
242 unsigned char *cp = buf + n0;
243 unsigned char *ep = buf + buflen;
244
245 if ((ep - cp) < 1 + RRFIXEDSZ)
246 return -1;
247
248 /* Add the root label. */
249 *cp++ = 0;
250
251 NS_PUT16 (T_OPT, cp); /* Record type. */
252
253 /* Lowering the advertised buffer size based on the actual
254 answer buffer size is desirable because the server will
255 minimize the reply to fit into the UDP packet (and A
256 non-minimal response might not fit the buffer).
257
258 The RESOLV_EDNS_BUFFER_SIZE limit could still result in TCP
259 fallback and a non-minimal response which has to be
260 hard-truncated in the stub resolver, but this is price to
261 pay for avoiding fragmentation. (This issue does not
262 affect the nss_dns functions because they use the stub
263 resolver in such a way that it allocates a properly sized
264 response buffer.) */
265 {
266 uint16_t buffer_size;
267 if (anslen < 512)
268 buffer_size = 512;
269 else if (anslen > RESOLV_EDNS_BUFFER_SIZE)
270 buffer_size = RESOLV_EDNS_BUFFER_SIZE;
271 else
272 buffer_size = anslen;
273 NS_PUT16 (buffer_size, cp);
274 }
275
276 *cp++ = NOERROR; /* Extended RCODE. */
277 *cp++ = 0; /* EDNS version. */
278
279 if (ctx->resp->options & RES_USE_DNSSEC)
280 flags |= NS_OPT_DNSSEC_OK;
281
282 NS_PUT16 (flags, cp);
283 NS_PUT16 (0, cp); /* RDATA length (no options are preent). */
284 hp->arcount = htons (ntohs (hp->arcount) + 1);
285
286 return cp - buf;
287}
288
289#if SHLIB_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_2)
290# undef res_mkquery
291weak_alias (__res_mkquery, res_mkquery);
292#endif
293