resolv/ns_name_unpack.c

   1 /* De-compressing DNS domain names into binary-encoded uncompressed name.
   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 <stddef.h>
  22 #include <string.h>
  23
  24 /* Unpack a domain name from a message, source may be compressed.
  25    Returns -1 if it fails, or consumed octets if it succeeds.  */
  26 int
  27 ___ns_name_unpack (const unsigned char *msg, const unsigned char *eom,
  28                    const unsigned char *src, unsigned char *dst, size_t dstsiz)
  29 {
  30   const unsigned char *srcp, *dstlim;
  31   unsigned char *dstp;
  32   int n, len, checked;
  33
  34   len = -1;
  35   checked = 0;
  36   dstp = dst;
  37   srcp = src;
  38   dstlim = dst + dstsiz;
  39   if (srcp < msg || srcp >= eom)
  40     {
  41       __set_errno (EMSGSIZE);
  42       return -1;
  43     }
  44   /* Fetch next label in domain name.  */
  45   while ((n = *srcp++) != 0)
  46     {
  47       /* Check for indirection.  */
  48       switch (n & NS_CMPRSFLGS)
  49         {
  50         case 0:
  51           /* Limit checks.  */
  52           if (n >= 64)
  53             {
  54               __set_errno (EMSGSIZE);
  55               return -1;
  56             }
  57           /* NB: n + 1 and >= to cover the *dstp = '\0' assignment
  58              below.  */
  59           if (n + 1 >= dstlim - dstp || n >= eom - srcp)
  60             {
  61               __set_errno (EMSGSIZE);
  62               return -1;
  63             }
  64           checked += n + 1;
  65           *dstp++ = n;
  66           memcpy (dstp, srcp, n);
  67           dstp += n;
  68           srcp += n;
  69           break;
  70
  71         case NS_CMPRSFLGS:
  72           if (srcp >= eom)
  73             {
  74               __set_errno (EMSGSIZE);
  75               return -1;
  76             }
  77           if (len < 0)
  78             len = srcp - src + 1;
  79           {
  80             int target = ((n & 0x3f) << 8) | *srcp;
  81             if (target >= eom - msg)
  82               {
  83               /* Out of range.  */
  84                 __set_errno (EMSGSIZE);
  85                 return -1;
  86             }
  87             srcp = msg + target;
  88           }
  89           checked += 2;
  90           /* Check for loops in the compressed name; if we've looked
  91              at the whole message, there must be a loop.  */
  92           if (checked >= eom - msg)
  93             {
  94               __set_errno (EMSGSIZE);
  95               return -1;
  96             }
  97           break;
  98
  99         default:
 100           __set_errno (EMSGSIZE);
 101           return -1;
 102         }
 103     }
 104   *dstp = '\0';
 105   if (len < 0)
 106     len = srcp - src;
 107   return len;
 108 }
 109 versioned_symbol (libc, ___ns_name_unpack, ns_name_unpack, GLIBC_2_34);
 110 versioned_symbol (libc, ___ns_name_unpack, __ns_name_unpack, GLIBC_PRIVATE);
 111 libc_hidden_ver (___ns_name_unpack, __ns_name_unpack)
 112
 113 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_9, GLIBC_2_34)
 114 compat_symbol (libresolv, ___ns_name_unpack, ns_name_unpack, GLIBC_2_9);
 115 #endif