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