ns_samedomain.c

   1 /*
   2  * Copyright (c) 1995,1999 by Internet Software Consortium.
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
   9  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  10  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  11  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  12  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  13  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  14  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  15  * SOFTWARE.
  16  */
  17
  18 #ifndef __APPLE__
  19 #ifndef lint
  20 static const char rcsid[] = "$Id: ns_samedomain.c,v 1.1 2006/03/01 19:01:37 majka Exp $";
  21 #endif
  22 #endif
  23
  24 #ifndef __APPLE__
  25 #include "port_before.h"
  26 #endif
  27
  28 #include <sys/types.h>
  29 #include <arpa/nameser.h>
  30 #include <errno.h>
  31 #include <string.h>
  32
  33 #ifndef __APPLE__
  34 #include "port_after.h"
  35 #endif
  36
  37 /*
  38  * int
  39  * ns_samedomain(a, b)
  40  *      Check whether a name belongs to a domain.
  41  * Inputs:
  42  *      a - the domain whose ancestory is being verified
  43  *      b - the potential ancestor we're checking against
  44  * Return:
  45  *      boolean - is a at or below b?
  46  * Notes:
  47  *      Trailing dots are first removed from name and domain.
  48  *      Always compare complete subdomains, not only whether the
  49  *      domain name is the trailing string of the given name.
  50  *
  51  *      "host.foobar.top" lies in "foobar.top" and in "top" and in ""
  52  *      but NOT in "bar.top"
  53  */
  54
  55 int
  56 ns_samedomain(const char *a, const char *b) {
  57         size_t la, lb;
  58         int diff, i, escaped;
  59         const char *cp;
  60
  61         la = strlen(a);
  62         lb = strlen(b);
  63
  64         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
  65         if (la != 0 && a[la - 1] == '.') {
  66                 escaped = 0;
  67                 /* Note this loop doesn't get executed if la==1. */
  68                 for (i = la - 2; i >= 0; i--)
  69                         if (a[i] == '\\') {
  70                                 if (escaped)
  71                                         escaped = 0;
  72                                 else
  73                                         escaped = 1;
  74                         } else
  75                                 break;
  76                 if (!escaped)
  77                         la--;
  78         }
  79
  80         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
  81         if (lb != 0 && b[lb - 1] == '.') {
  82                 escaped = 0;
  83                 /* note this loop doesn't get executed if lb==1 */
  84                 for (i = lb - 2; i >= 0; i--)
  85                         if (b[i] == '\\') {
  86                                 if (escaped)
  87                                         escaped = 0;
  88                                 else
  89                                         escaped = 1;
  90                         } else
  91                                 break;
  92                 if (!escaped)
  93                         lb--;
  94         }
  95
  96         /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
  97         if (lb == 0)
  98                 return (1);
  99
 100         /* 'b' longer than 'a' means 'a' can't be in 'b'. */
 101         if (lb > la)
 102                 return (0);
 103
 104         /* 'a' and 'b' being equal at this point indicates sameness. */
 105         if (lb == la)
 106                 return (strncasecmp(a, b, lb) == 0);
 107
 108         /* Ok, we know la > lb. */
 109
 110         diff = la - lb;
 111
 112         /*
 113          * If 'a' is only 1 character longer than 'b', then it can't be
 114          * a subdomain of 'b' (because of the need for the '.' label
 115          * separator).
 116          */
 117         if (diff < 2)
 118                 return (0);
 119
 120         /*
 121          * If the character before the last 'lb' characters of 'b'
 122          * isn't '.', then it can't be a match (this lets us avoid
 123          * having "foobar.com" match "bar.com").
 124          */
 125         if (a[diff - 1] != '.')
 126                 return (0);
 127
 128         /*
 129          * We're not sure about that '.', however.  It could be escaped
 130          * and thus not a really a label separator.
 131          */
 132         escaped = 0;
 133         for (i = diff - 2; i >= 0; i--)
 134                 if (a[i] == '\\') {
 135                         if (escaped)
 136                                 escaped = 0;
 137                         else
 138                                 escaped = 1;
 139                 } else
 140                         break;
 141         if (escaped)
 142                 return (0);
 143
 144         /* Now compare aligned trailing substring. */
 145         cp = a + diff;
 146         return (strncasecmp(cp, b, lb) == 0);
 147 }
 148
 149 /*
 150  * int
 151  * ns_subdomain(a, b)
 152  *      is "a" a subdomain of "b"?
 153  */
 154 int
 155 ns_subdomain(const char *a, const char *b) {
 156         return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
 157 }
 158
 159 /*
 160  * int
 161  * ns_makecanon(src, dst, dstsize)
 162  *      make a canonical copy of domain name "src"
 163  * notes:
 164  *      foo -> foo.
 165  *      foo. -> foo.
 166  *      foo.. -> foo.
 167  *      foo\. -> foo\..
 168  *      foo\\. -> foo\\.
 169  */
 170
 171 int
 172 ns_makecanon(const char *src, char *dst, size_t dstsize) {
 173         size_t n = strlen(src);
 174
 175         if (n + sizeof "." > dstsize) {
 176                 errno = EMSGSIZE;
 177                 return (-1);
 178         }
 179         strcpy(dst, src);
 180         while (n > 0 && dst[n - 1] == '.')              /* Ends in "." */
 181                 if (n > 1 && dst[n - 2] == '\\' &&      /* Ends in "\." */
 182                     (n < 2 || dst[n - 3] != '\\'))      /* But not "\\." */
 183                         break;
 184                 else
 185                         dst[--n] = '\0';
 186         dst[n++] = '.';
 187         dst[n] = '\0';
 188         return (0);
 189 }
 190
 191 /*
 192  * int
 193  * ns_samename(a, b)
 194  *      determine whether domain name "a" is the same as domain name "b"
 195  * return:
 196  *      -1 on error
 197  *      0 if names differ
 198  *      1 if names are the same
 199  */
 200
 201 int
 202 ns_samename(const char *a, const char *b) {
 203         char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
 204
 205         if (ns_makecanon(a, ta, sizeof ta) < 0 ||
 206             ns_makecanon(b, tb, sizeof tb) < 0)
 207                 return (-1);
 208         if (strcasecmp(ta, tb) == 0)
 209                 return (1);
 210         else
 211                 return (0);
 212 }