resolv/ns_name_ntop.c

   1 /* Convert DNS domain names from network format to textual presentation format.
   2  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   3  * Copyright (c) 1996,1999 by Internet Software Consortium.
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  15  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 #include <arpa/nameser.h>
  19 #include <errno.h>
  20 #include <shlib-compat.h>
  21 #include <stdbool.h>
  22
  23 /* Thinking in noninternationalized US-ASCII (per the DNS spec), is
  24    this character special ("in need of quoting")?  */
  25 static inline bool
  26 special (int ch)
  27 {
  28   switch (ch)
  29     {
  30     case '"':
  31     case '.':
  32     case ';':
  33     case '\\':
  34     case '(':
  35     case ')':
  36       /* Special modifiers in zone files.  */
  37     case '@':
  38     case '$':
  39       return true;
  40     default:
  41       return false;
  42     }
  43 }
  44
  45 /* Thinking in noninternationalized US-ASCII (per the DNS spec), is
  46    this character visible and not a space when printed?  */
  47 static inline bool
  48 printable (int ch)
  49 {
  50   return ch > 0x20 && ch < 0x7f;
  51 }
  52
  53 /* Converts an uncompressed, encoded domain name to printable ASCII as
  54    per RFC1035.  Returns the number of bytes written to buffer, or -1
  55    (with errno set).  The root is returned as "."  All other domains
  56    are returned in non absolute form.  */
  57 int
  58 ___ns_name_ntop (const unsigned char *src, char *dst, size_t dstsiz)
  59 {
  60   const unsigned char *cp;
  61   char *dn, *eom;
  62   unsigned char c;
  63   int l;
  64
  65   cp = src;
  66   dn = dst;
  67   eom = dst + dstsiz;
  68
  69   while ((l = *cp++) != 0)
  70     {
  71       if (l >= 64)
  72         {
  73           /* Some kind of compression pointer.  */
  74           __set_errno (EMSGSIZE);
  75           return -1;
  76         }
  77       if (dn != dst)
  78         {
  79           if (dn >= eom)
  80             {
  81               __set_errno (EMSGSIZE);
  82               return -1;
  83             }
  84           *dn++ = '.';
  85         }
  86       for (; l > 0; l--)
  87         {
  88           c = *cp++;
  89           if (special (c))
  90             {
  91               if (eom - dn < 2)
  92                 {
  93                   __set_errno (EMSGSIZE);
  94                   return -1;
  95                 }
  96               *dn++ = '\\';
  97               *dn++ = c;
  98             }
  99           else if (!printable (c))
 100             {
 101               if (eom - dn < 4)
 102                 {
 103                   __set_errno (EMSGSIZE);
 104                   return -1;
 105                 }
 106               *dn++ = '\\';
 107               *dn++ = '0' + (c / 100);
 108               *dn++ = '0' + ((c % 100) / 10);
 109               *dn++ = '0' + (c % 10);
 110             }
 111           else
 112             {
 113               if (eom - dn < 2)
 114                 {
 115                   __set_errno (EMSGSIZE);
 116                   return -1;
 117                 }
 118               *dn++ = c;
 119             }
 120         }
 121     }
 122   if (dn == dst)
 123     {
 124       if (dn >= eom)
 125         {
 126           __set_errno (EMSGSIZE);
 127           return -1;
 128         }
 129       *dn++ = '.';
 130     }
 131   if (dn >= eom)
 132     {
 133       __set_errno (EMSGSIZE);
 134       return -1;
 135     }
 136   *dn++ = '\0';
 137   return dn - dst;
 138 }
 139 versioned_symbol (libc, ___ns_name_ntop, ns_name_ntop, GLIBC_2_34);
 140 versioned_symbol (libc, ___ns_name_ntop, __ns_name_ntop, GLIBC_PRIVATE);
 141 libc_hidden_ver (___ns_name_ntop, __ns_name_ntop)
 142
 143 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_9, GLIBC_2_34)
 144 compat_symbol (libresolv, ___ns_name_ntop, ns_name_ntop, GLIBC_2_9);
 145 #endif