resolv/res_comp.c

   1 /* Domain name processing functions.
   2    Copyright (C) 1995-2020 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  */
 102 int
 103 dn_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 }
 112 libresolv_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  */
 119 int
 120 dn_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 }
 127 libresolv_hidden_def (dn_comp)
 128
 129 /*
 130  * Skip over a compressed domain name. Return the size or -1.
 131  */
 132 int
 133 dn_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 }
 140 libresolv_hidden_def (dn_skipname)
 141
 142 /* Return true if the string consists of printable ASCII characters
 143    only.  */
 144 static bool
 145 printable_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.  */
 161 static bool
 162 binary_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 '-'.  */
 188 static inline bool
 189 binary_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.  */
 197 int
 198 res_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 }
 207 libresolv_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.  */
 211 int
 212 res_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.  */
 228 int
 229 res_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.  */
 249 int
 250 res_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 }
 255 libresolv_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  */
 265 void __putlong(uint32_t src, u_char *dst) { ns_put32(src, dst); }
 266 libresolv_hidden_def (__putlong)
 267 void __putshort(uint16_t src, u_char *dst) { ns_put16(src, dst); }
 268 libresolv_hidden_def (__putshort)
 269 uint32_t _getlong(const u_char *src) { return (ns_get32(src)); }
 270 uint16_t _getshort(const u_char *src) { return (ns_get16(src)); }
 271 \f
 272
 273 #include <shlib-compat.h>
 274
 275 #if SHLIB_COMPAT(libresolv, GLIBC_2_0, GLIBC_2_2)
 276 # undef dn_expand
 277 weak_alias (__dn_expand, dn_expand);
 278 #endif