resolv/ns_name_pack.c

   1 /* Compression of DNS domain names.
   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 <string.h>
  21 #include <shlib-compat.h>
  22
  23 /* Thinking in noninternationalized USASCII (per the DNS spec),
  24    convert this character to lower case if it's upper case.  */
  25 static int
  26 mklower (int ch)
  27 {
  28   if (ch >= 'A' && ch <= 'Z')
  29     return ch - 'A' + 'a';
  30   return ch;
  31 }
  32
  33 /* Search for the counted-label name in an array of compressed names.
  34    Returns the offset from MSG if found, or -1.
  35
  36    DNPTRS is the pointer to the first name on the list, not the
  37    pointer to the start of the message.  */
  38 static int
  39 dn_find (const unsigned char *domain, const unsigned char *msg,
  40          const unsigned char **dnptrs,
  41          const unsigned char **lastdnptr)
  42 {
  43   const unsigned char *dn, *cp, *sp;
  44   const unsigned char **cpp;
  45   unsigned int n;
  46
  47   for (cpp = dnptrs; cpp < lastdnptr; cpp++)
  48     {
  49     sp = *cpp;
  50     /* Terminate search on: root label, compression pointer, unusable
  51        offset.  */
  52     while (*sp != 0 && (*sp & NS_CMPRSFLGS) == 0 && (sp - msg) < 0x4000)
  53       {
  54         dn = domain;
  55         cp = sp;
  56         while ((n = *cp++) != 0)
  57           {
  58             /* Check for indirection.  */
  59             switch (n & NS_CMPRSFLGS)
  60               {
  61               case 0:                 /* Normal case, n == len.  */
  62                 if (n != *dn++)
  63                   goto next;
  64
  65                 for (; n > 0; n--)
  66                   if (mklower (*dn++) != mklower (*cp++))
  67                     goto next;
  68                 /* Is next root for both?  */
  69                 if (*dn == '\0' && *cp == '\0')
  70                   return sp - msg;
  71                 if (*dn)
  72                   continue;
  73                 goto next;
  74               case NS_CMPRSFLGS: /* Indirection.  */
  75                 cp = msg + (((n & 0x3f) << 8) | *cp);
  76                 break;
  77
  78               default:          /* Illegal type.  */
  79                 __set_errno (EMSGSIZE);
  80                 return -1;
  81               }
  82           }
  83       next: ;
  84         sp += *sp + 1;
  85       }
  86     }
  87   __set_errno (ENOENT);
  88   return -1;
  89 }
  90
  91 /* Packs domain name SRC into DST.  Returns size of the compressed
  92    name, or -1.
  93
  94    DNPTRS is an array of pointers to previous compressed names.
  95    DNPTRS[0] is a pointer to the beginning of the message. The array
  96    ends with NULL.  LASTDNPTR is a pointer to the end of the array
  97    pointed to by 'dnptrs'.
  98
  99    The list of pointers in DNPTRS is updated for labels inserted into
 100    the message as we compress the name.  If DNPTRS is NULL, we don't
 101    try to compress names. If LASTDNPTR is NULL, we don't update the
 102    list.  */
 103 int
 104 ___ns_name_pack (const unsigned char *src, unsigned char *dst, int dstsiz,
 105                  const unsigned char **dnptrs, const unsigned char **lastdnptr)
 106 {
 107   unsigned char *dstp;
 108   const unsigned char **cpp, **lpp, *eob, *msg;
 109   const unsigned char *srcp;
 110   int n, l, first = 1;
 111
 112   srcp = src;
 113   dstp = dst;
 114   eob = dstp + dstsiz;
 115   lpp = cpp = NULL;
 116   if (dnptrs != NULL)
 117     {
 118       if ((msg = *dnptrs++) != NULL)
 119         {
 120           for (cpp = dnptrs; *cpp != NULL; cpp++)
 121             ;
 122           lpp = cpp;            /* End of list to search.  */
 123         }
 124     }
 125   else
 126     msg = NULL;
 127
 128   /* Make sure the domain we are about to add is legal.  */
 129   l = 0;
 130   do
 131     {
 132       n = *srcp;
 133       if (n >= 64)
 134         {
 135           __set_errno (EMSGSIZE);
 136           return -1;
 137         }
 138       l += n + 1;
 139       if (l > MAXCDNAME)
 140         {
 141           __set_errno (EMSGSIZE);
 142           return -1;
 143         }
 144       srcp += n + 1;
 145     }
 146   while (n != 0);
 147
 148   /* from here on we need to reset compression pointer array on error */
 149   srcp = src;
 150   do
 151     {
 152       /* Look to see if we can use pointers.  */
 153       n = *srcp;
 154       if (n != 0 && msg != NULL)
 155         {
 156           l = dn_find (srcp, msg, dnptrs, lpp);
 157           if (l >= 0)
 158             {
 159               if (eob - dstp <= 1)
 160                 goto cleanup;
 161               *dstp++ = (l >> 8) | NS_CMPRSFLGS;
 162               *dstp++ = l % 256;
 163               return dstp - dst;
 164             }
 165           /* Not found, save it.  */
 166           if (lastdnptr != NULL && cpp < lastdnptr - 1
 167               && (dstp - msg) < 0x4000 && first)
 168             {
 169               *cpp++ = dstp;
 170               *cpp = NULL;
 171               first = 0;
 172             }
 173         }
 174       /* Copy label to buffer.  */
 175       if (n >= 64)
 176         /* Should not happen.  */
 177         goto cleanup;
 178       if (n + 1 > eob - dstp)
 179         goto cleanup;
 180       memcpy (dstp, srcp, n + 1);
 181       srcp += n + 1;
 182       dstp += n + 1;
 183     }
 184   while (n != 0);
 185
 186   if (dstp > eob)
 187     {
 188     cleanup:
 189       if (msg != NULL)
 190         *lpp = NULL;
 191       __set_errno (EMSGSIZE);
 192       return -1;
 193     }
 194   return dstp - dst;
 195 }
 196 versioned_symbol (libc, ___ns_name_pack, ns_name_pack, GLIBC_2_34);
 197 versioned_symbol (libc, ___ns_name_pack, __ns_name_pack, GLIBC_PRIVATE);
 198 libc_hidden_ver (___ns_name_pack, __ns_name_pack)
 199
 200 #if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_9, GLIBC_2_34)
 201 compat_symbol (libresolv, ___ns_name_pack, ns_name_pack, GLIBC_2_9);
 202 #endif