resolv/ns_name_skip.c

   1 /* Skip over a (potentially compressed) domain name in wire 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
  22 /* Advances *PTRPTR to skip over the compressed name it points at.
  23    Returns 0 on success, -1 (with errno set) on failure.  */
  24 int
  25 ___ns_name_skip (const unsigned char **ptrptr, const unsigned char *eom)
  26 {
  27   const unsigned char *cp;
  28   unsigned int n;
  29
  30   cp = *ptrptr;
  31   while (cp < eom)
  32     {
  33       n = *cp++;
  34       if (n == 0)
  35         {
  36           /* End of domain name without indirection.  */
  37           *ptrptr = cp;
  38           return 0;
  39         }
  40
  41       /* Check for indirection.  */
  42       switch (n & NS_CMPRSFLGS)
  43         {
  44         case 0:                 /* Normal case, n == len.  */
  45           if (eom - cp < n)
  46             goto malformed;
  47           cp += n;
  48           break;
  49         case NS_CMPRSFLGS:      /* Indirection.  */
  50           if (cp == eom)
  51             /* No room for second indirection byte.  */
  52             goto malformed;
  53           *ptrptr = cp + 1;
  54           return 0;
  55         default:                /* Illegal type.  */
  56           goto malformed;
  57         }
  58     }
  59
  60  malformed:
  61   __set_errno (EMSGSIZE);
  62   return -1;
  63 }
  64 versioned_symbol (libc, ___ns_name_skip, ns_name_skip, GLIBC_2_34);
  65 versioned_symbol (libc, ___ns_name_skip, __ns_name_skip, GLIBC_PRIVATE);
  66 libc_hidden_ver (___ns_name_skip, __ns_name_skip)
  67
  68 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_9, GLIBC_2_34)
  69 compat_symbol (libresolv, ___ns_name_skip, ns_name_skip, GLIBC_2_9);
  70 #endif