1  /* Skip over an uncompressed name in wire format.
       2     Copyright (C) 2022-2023 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  #include <arpa/nameser.h>
      20  #include <errno.h>
      21  #include <stdbool.h>
      22  
      23  int
      24  __ns_name_length_uncompressed (const unsigned char *p,
      25                                  const unsigned char *eom)
      26  {
      27    const unsigned char *start = p;
      28  
      29    while (true)
      30      {
      31        if (p == eom)
      32          {
      33            /* Truncated packet: no room for label length.  */
      34            __set_errno (EMSGSIZE);
      35            return -1;
      36          }
      37  
      38        unsigned char b = *p;
      39        ++p;
      40        if (b == 0)
      41          {
      42            /* Root label.  */
      43            size_t length = p - start;
      44            if (length > NS_MAXCDNAME)
      45              {
      46                /* Domain name too long.  */
      47                __set_errno (EMSGSIZE);
      48                return -1;
      49              }
      50            return length;
      51          }
      52  
      53        if (b <= 63)
      54          {
      55            /* Regular label.  */
      56            if (b <= eom - p)
      57              p += b;
      58            else
      59              {
      60                /* Truncated packet: label incomplete.  */
      61                __set_errno (EMSGSIZE);
      62                return -1;
      63              }
      64          }
      65        else
      66          {
      67            /* Compression reference or corrupted label length.  */
      68            __set_errno (EMSGSIZE);
      69            return -1;
      70          }
      71      }
      72  }