resolv/res_mkquery.c

   1 /* Creation of DNS query packets.
   2    Copyright (C) 1995-2023 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
  98 int
  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 libc_hidden_def (__res_context_mkquery)
 178
 179 /* Common part of res_nmkquery and res_mkquery.  */
 180 static int
 181 context_mkquery_common (struct resolv_context *ctx,
 182                         int op, const char *dname, int class, int type,
 183                         const unsigned char *data,
 184                         unsigned char *buf, int buflen)
 185 {
 186   if (ctx == NULL)
 187     return -1;
 188   int result = __res_context_mkquery
 189     (ctx, op, dname, class, type, data, buf, buflen);
 190   if (result >= 2)
 191     memcpy (&ctx->resp->id, buf, 2);
 192   __resolv_context_put (ctx);
 193   return result;
 194 }
 195
 196 /* Form all types of queries.  Returns the size of the result or -1 on
 197    error.
 198
 199    STATP points to an initialized resolver state.  OP is the opcode of
 200    the query.  DNAME is the domain.  CLASS and TYPE are the DNS query
 201    class and type.  DATA can be NULL; otherwise, it is a pointer to a
 202    domain name which is included in the generated packet (if op ==
 203    NS_NOTIFY_OP).  BUF must point to the out buffer of BUFLEN bytes.
 204
 205    DATALEN and NEWRR_IN are currently ignored.  */
 206 int
 207 ___res_nmkquery (res_state statp, int op, const char *dname,
 208                  int class, int type,
 209                  const unsigned char *data, int datalen,
 210                  const unsigned char *newrr_in,
 211                  unsigned char *buf, int buflen)
 212 {
 213   return context_mkquery_common
 214     (__resolv_context_get_override (statp),
 215      op, dname, class, type, data, buf, buflen);
 216 }
 217 versioned_symbol (libc, ___res_nmkquery, res_nmkquery, GLIBC_2_34);
 218 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_2, GLIBC_2_34)
 219 compat_symbol (libresolv, ___res_nmkquery, __res_nmkquery, GLIBC_2_2);
 220 #endif
 221
 222 int
 223 ___res_mkquery (int op, const char *dname, int class, int type,
 224                 const unsigned char *data, int datalen,
 225                 const unsigned char *newrr_in,
 226                 unsigned char *buf, int buflen)
 227 {
 228   return context_mkquery_common
 229     (__resolv_context_get_preinit (),
 230      op, dname, class, type, data, buf, buflen);
 231 }
 232 versioned_symbol (libc, ___res_mkquery, res_mkquery, GLIBC_2_34);
 233 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_2)
 234 compat_symbol (libresolv, ___res_mkquery, res_mkquery, GLIBC_2_0);
 235 #endif
 236 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_2, GLIBC_2_34)
 237 compat_symbol (libresolv, ___res_mkquery, __res_mkquery, GLIBC_2_2);
 238 #endif
 239
 240 /* Create an OPT resource record.  Return the length of the final
 241    packet, or -1 on error.
 242
 243    STATP must be an initialized resolver state.  N0 is the current
 244    number of bytes of the packet (already written to BUF by the
 245    aller).  BUF is the packet being constructed.  The array it
 246    pointers to must be BUFLEN bytes long.  ANSLEN is the advertised
 247    EDNS buffer size (to be included in the OPT resource record).  */
 248 int
 249 __res_nopt (struct resolv_context *ctx,
 250             int n0, unsigned char *buf, int buflen, int anslen)
 251 {
 252   uint16_t flags = 0;
 253   HEADER *hp = (HEADER *) buf;
 254   unsigned char *cp = buf + n0;
 255   unsigned char *ep = buf + buflen;
 256
 257   if ((ep - cp) < 1 + RRFIXEDSZ)
 258     return -1;
 259
 260   /* Add the root label.  */
 261   *cp++ = 0;
 262
 263   NS_PUT16 (T_OPT, cp);         /* Record type.  */
 264
 265   /* Lowering the advertised buffer size based on the actual
 266      answer buffer size is desirable because the server will
 267      minimize the reply to fit into the UDP packet (and A
 268      non-minimal response might not fit the buffer).
 269
 270      The RESOLV_EDNS_BUFFER_SIZE limit could still result in TCP
 271      fallback and a non-minimal response which has to be
 272      hard-truncated in the stub resolver, but this is price to
 273      pay for avoiding fragmentation.  (This issue does not
 274      affect the nss_dns functions because they use the stub
 275      resolver in such a way that it allocates a properly sized
 276      response buffer.)  */
 277   {
 278     uint16_t buffer_size;
 279     if (anslen < 512)
 280       buffer_size = 512;
 281     else if (anslen > RESOLV_EDNS_BUFFER_SIZE)
 282       buffer_size = RESOLV_EDNS_BUFFER_SIZE;
 283     else
 284       buffer_size = anslen;
 285     NS_PUT16 (buffer_size, cp);
 286   }
 287
 288   *cp++ = NOERROR;              /* Extended RCODE.  */
 289   *cp++ = 0;                    /* EDNS version.  */
 290
 291   if (ctx->resp->options & RES_USE_DNSSEC)
 292     flags |= NS_OPT_DNSSEC_OK;
 293
 294   NS_PUT16 (flags, cp);
 295   NS_PUT16 (0, cp);       /* RDATA length (no options are preent).  */
 296   hp->arcount = htons (ntohs (hp->arcount) + 1);
 297
 298   return cp - buf;
 299 }
 300 libc_hidden_def (__res_nopt)