minires/ns_samedomain.c

   1 /*
   2  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   3  * Copyright (c) 1995-2003 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  *   Internet Systems Consortium, Inc.
  18  *   950 Charter Street
  19  *   Redwood City, CA 94063
  20  *   <info@isc.org>
  21  *   http://www.isc.org/
  22  */
  23
  24 #ifndef lint
  25 static const char rcsid[] = "$Id: ns_samedomain.c,v 1.4 2005/03/17 20:15:18 dhankins Exp $";
  26 #endif
  27
  28 #include <sys/types.h>
  29 #include <errno.h>
  30 #include <string.h>
  31
  32 #include <netinet/in.h>
  33 #include <sys/socket.h>
  34
  35 #include "minires/minires.h"
  36 #include "arpa/nameser.h"
  37
  38 /*
  39  * int
  40  * ns_samedomain(a, b)
  41  *      Check whether a name belongs to a domain.
  42  * Inputs:
  43  *      a - the domain whose ancestory is being verified
  44  *      b - the potential ancestor we're checking against
  45  * Return:
  46  *      boolean - is a at or below b?
  47  * Notes:
  48  *      Trailing dots are first removed from name and domain.
  49  *      Always compare complete subdomains, not only whether the
  50  *      domain name is the trailing string of the given name.
  51  *
  52  *      "host.foobar.top" lies in "foobar.top" and in "top" and in ""
  53  *      but NOT in "bar.top"
  54  */
  55
  56 int
  57 ns_samedomain(const char *a, const char *b) {
  58         size_t la, lb;
  59         int diff, i, escaped;
  60         const char *cp;
  61
  62         la = strlen(a);
  63         lb = strlen(b);
  64
  65         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
  66         if (la != 0 && a[la - 1] == '.') {
  67                 escaped = 0;
  68                 /* Note this loop doesn't get executed if la==1. */
  69                 for (i = la - 2; i >= 0; i--)
  70                         if (a[i] == '\\') {
  71                                 if (escaped)
  72                                         escaped = 0;
  73                                 else
  74                                         escaped = 1;
  75                         } else
  76                                 break;
  77                 if (!escaped)
  78                         la--;
  79         }
  80
  81         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
  82         if (lb != 0 && b[lb - 1] == '.') {
  83                 escaped = 0;
  84                 /* note this loop doesn't get executed if lb==1 */
  85                 for (i = lb - 2; i >= 0; i--)
  86                         if (b[i] == '\\') {
  87                                 if (escaped)
  88                                         escaped = 0;
  89                                 else
  90                                         escaped = 1;
  91                         } else
  92                                 break;
  93                 if (!escaped)
  94                         lb--;
  95         }
  96
  97         /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
  98         if (lb == 0)
  99                 return (1);
 100
 101         /* 'b' longer than 'a' means 'a' can't be in 'b'. */
 102         if (lb > la)
 103                 return (0);
 104
 105         /* 'a' and 'b' being equal at this point indicates sameness. */
 106         if (lb == la)
 107                 return (strncasecmp(a, b, lb) == 0);
 108
 109         /* Ok, we know la > lb. */
 110
 111         diff = la - lb;
 112
 113         /*
 114          * If 'a' is only 1 character longer than 'b', then it can't be
 115          * a subdomain of 'b' (because of the need for the '.' label
 116          * separator).
 117          */
 118         if (diff < 2)
 119                 return (0);
 120
 121         /*
 122          * If the character before the last 'lb' characters of 'b'
 123          * isn't '.', then it can't be a match (this lets us avoid
 124          * having "foobar.com" match "bar.com").
 125          */
 126         if (a[diff - 1] != '.')
 127                 return (0);
 128
 129         /*
 130          * We're not sure about that '.', however.  It could be escaped
 131          * and thus not a really a label separator.
 132          */
 133         escaped = 0;
 134         for (i = diff - 2; i >= 0; i--)
 135                 if (a[i] == '\\') {
 136                         if (escaped)
 137                                 escaped = 0;
 138                         else
 139                                 escaped = 1;
 140                 } else
 141                         break;
 142         if (escaped)
 143                 return (0);
 144
 145         /* Now compare aligned trailing substring. */
 146         cp = a + diff;
 147         return (strncasecmp(cp, b, lb) == 0);
 148 }
 149
 150 /*
 151  * int
 152  * ns_subdomain(a, b)
 153  *      is "a" a subdomain of "b"?
 154  */
 155 int
 156 ns_subdomain(const char *a, const char *b) {
 157         return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
 158 }
 159
 160 /*
 161  * int
 162  * ns_makecanon(src, dst, dstsize)
 163  *      make a canonical copy of domain name "src"
 164  * notes:
 165  *      foo -> foo.
 166  *      foo. -> foo.
 167  *      foo.. -> foo.
 168  *      foo\. -> foo\..
 169  *      foo\\. -> foo\\.
 170  */
 171
 172 isc_result_t
 173 ns_makecanon(const char *src, char *dst, size_t dstsize) {
 174         size_t n = strlen(src);
 175
 176         if (n + sizeof "." > dstsize) {
 177                 return ISC_R_NOSPACE;
 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 ISC_R_SUCCESS;
 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         isc_result_t status;
 205
 206         status = ns_makecanon(a, ta, sizeof ta);
 207         if (status != ISC_R_SUCCESS)
 208                 return status;
 209         status = ns_makecanon(b, tb, sizeof tb);
 210         if (status != ISC_R_SUCCESS)
 211                 return (-1);
 212         if (strcasecmp(ta, tb) == 0)
 213                 return (1);
 214         else
 215                 return (0);
 216 }