resolv/res-name-checking.c

   1 /* Syntax checking for DNS domain names.
   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 <arpa/nameser.h>
  86 #include <resolv.h>
  87 #include <shlib-compat.h>
  88
  89 /* Return true if the string consists of printable ASCII characters
  90    only.  */
  91 static bool
  92 printable_string (const char *dn)
  93 {
  94   while (true)
  95     {
  96       char ch = *dn;
  97       if (ch == '\0')
  98         return true;
  99       if (ch <= ' ' || ch > '~')
 100         return false;
 101       ++dn;
 102     }
 103 }
 104
 105 /* Return true if DN points to a name consisting only of [0-9a-zA-Z_-]
 106    characters.  DN must be in DNS wire format, without
 107    compression.  */
 108 static bool
 109 binary_hnok (const unsigned char *dn)
 110 {
 111   while (true)
 112     {
 113       size_t label_length = *dn;
 114       if (label_length == 0)
 115         break;
 116       ++dn;
 117       const unsigned char *label_end = dn + label_length;
 118       do
 119         {
 120           unsigned char ch = *dn;
 121           if (!(('0' <= ch && ch <= '9')
 122                 || ('A' <= ch && ch <= 'Z')
 123                 || ('a' <= ch && ch <= 'z')
 124                 || ch == '-' || ch == '_'))
 125             return false;
 126           ++dn;
 127         }
 128       while (dn < label_end);
 129     }
 130   return true;
 131 }
 132
 133 /* Return true if the binary domain name has a first labels which
 134    starts with '-'.  */
 135 static inline bool
 136 binary_leading_dash (const unsigned char *dn)
 137 {
 138   return dn[0] > 0 && dn[1] == '-';
 139 }
 140
 141 bool
 142 __res_binary_hnok (const unsigned char *dn)
 143 {
 144   return !binary_leading_dash (dn) && binary_hnok (dn);
 145 }
 146
 147 /* Return 1 if res_hnok is a valid host name.  Labels must only
 148    contain [0-9a-zA-Z_-] characters, and the name must not start with
 149    a '-'.  The latter is to avoid confusion with program options.  */
 150 int
 151 ___res_hnok (const char *dn)
 152 {
 153   unsigned char buf[NS_MAXCDNAME];
 154   return (printable_string (dn)
 155           && __ns_name_pton (dn, buf, sizeof (buf)) >= 0
 156           && __res_binary_hnok (buf));
 157 }
 158 versioned_symbol (libc, ___res_hnok, res_hnok, GLIBC_2_34);
 159 versioned_symbol (libc, ___res_hnok, __libc_res_hnok, GLIBC_PRIVATE);
 160 libc_hidden_ver (___res_hnok, __libc_res_hnok)
 161 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_34)
 162 compat_symbol (libresolv, ___res_hnok, __res_hnok, GLIBC_2_0);
 163 #endif
 164
 165 /* Hostname-like (A, MX, WKS) owners can have "*" as their first label
 166    but must otherwise be as a host name.  */
 167 int
 168 ___res_ownok (const char *dn)
 169 {
 170   unsigned char buf[NS_MAXCDNAME];
 171   if (!printable_string (dn)
 172       || __ns_name_pton (dn, buf, sizeof (buf)) < 0
 173       || binary_leading_dash (buf))
 174     return 0;
 175   if (buf[0] == 1 && buf [1] == '*')
 176     /* Skip over the leading "*." part.  */
 177     return binary_hnok (buf + 2);
 178   else
 179     return binary_hnok (buf);
 180 }
 181 versioned_symbol (libc, ___res_ownok, res_ownok, GLIBC_2_34);
 182 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_34)
 183 compat_symbol (libresolv, ___res_ownok, __res_ownok, GLIBC_2_0);
 184 #endif
 185
 186 /* SOA RNAMEs and RP RNAMEs can have any byte in their first label,
 187    but the rest of the name has to look like a host name.  */
 188 int
 189 ___res_mailok (const char *dn)
 190 {
 191   unsigned char buf[NS_MAXCDNAME];
 192   if (!printable_string (dn)
 193       || __ns_name_pton (dn, buf, sizeof (buf)) < 0)
 194     return 0;
 195   unsigned char label_length = buf[0];
 196   /* "." is a valid missing representation */
 197   if (label_length == 0)
 198     return 1;
 199   /* Skip over the first label.  */
 200   unsigned char *tail = buf + 1 + label_length;
 201   if (*tail == 0)
 202     /* More than one label is required (except for ".").  */
 203     return 0;
 204   return binary_hnok (tail);
 205 }
 206 versioned_symbol (libc, ___res_mailok, res_mailok, GLIBC_2_34);
 207 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_34)
 208 compat_symbol (libresolv, ___res_mailok, __res_mailok, GLIBC_2_0);
 209 #endif
 210
 211 /* Return 1 if DN is a syntactically valid domain name.  Empty names
 212    are accepted.  */
 213 int
 214 ___res_dnok (const char *dn)
 215 {
 216   unsigned char buf[NS_MAXCDNAME];
 217   return printable_string (dn) && __ns_name_pton (dn, buf, sizeof (buf)) >= 0;
 218 }
 219 versioned_symbol (libc, ___res_dnok, res_dnok, GLIBC_2_34);
 220 versioned_symbol (libc, ___res_dnok, __libc_res_dnok, GLIBC_PRIVATE);
 221 libc_hidden_ver (___res_dnok, __libc_res_dnok)
 222 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_34)
 223 compat_symbol (libresolv, ___res_dnok, __res_dnok, GLIBC_2_0);
 224 #endif