resolv/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 #if !defined(_LIBC) && !defined(lint)
  19 static const char rcsid[] = "$BINDId: ns_samedomain.c,v 8.9 1999/10/15 21:06:51 vixie Exp $";
  20 #endif
  21
  22 #include <sys/types.h>
  23 #include <arpa/nameser.h>
  24 #include <errno.h>
  25 #include <string.h>
  26
  27 /*
  28  * int
  29  * ns_samedomain(a, b)
  30  *      Check whether a name belongs to a domain.
  31  * Inputs:
  32  *      a - the domain whose ancestory is being verified
  33  *      b - the potential ancestor we're checking against
  34  * Return:
  35  *      boolean - is a at or below b?
  36  * Notes:
  37  *      Trailing dots are first removed from name and domain.
  38  *      Always compare complete subdomains, not only whether the
  39  *      domain name is the trailing string of the given name.
  40  *
  41  *      "host.foobar.top" lies in "foobar.top" and in "top" and in ""
  42  *      but NOT in "bar.top"
  43  */
  44
  45 int
  46 ns_samedomain(const char *a, const char *b) {
  47         size_t la, lb;
  48         int diff, i, escaped;
  49         const char *cp;
  50
  51         la = strlen(a);
  52         lb = strlen(b);
  53
  54         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
  55         if (la != 0 && a[la - 1] == '.') {
  56                 escaped = 0;
  57                 /* Note this loop doesn't get executed if la==1. */
  58                 for (i = la - 2; i >= 0; i--)
  59                         if (a[i] == '\\') {
  60                                 if (escaped)
  61                                         escaped = 0;
  62                                 else
  63                                         escaped = 1;
  64                         } else
  65                                 break;
  66                 if (!escaped)
  67                         la--;
  68         }
  69
  70         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
  71         if (lb != 0 && b[lb - 1] == '.') {
  72                 escaped = 0;
  73                 /* note this loop doesn't get executed if lb==1 */
  74                 for (i = lb - 2; i >= 0; i--)
  75                         if (b[i] == '\\') {
  76                                 if (escaped)
  77                                         escaped = 0;
  78                                 else
  79                                         escaped = 1;
  80                         } else
  81                                 break;
  82                 if (!escaped)
  83                         lb--;
  84         }
  85
  86         /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
  87         if (lb == 0)
  88                 return (1);
  89
  90         /* 'b' longer than 'a' means 'a' can't be in 'b'. */
  91         if (lb > la)
  92                 return (0);
  93
  94         /* 'a' and 'b' being equal at this point indicates sameness. */
  95         if (lb == la)
  96                 return (strncasecmp(a, b, lb) == 0);
  97
  98         /* Ok, we know la > lb. */
  99
 100         diff = la - lb;
 101
 102         /*
 103          * If 'a' is only 1 character longer than 'b', then it can't be
 104          * a subdomain of 'b' (because of the need for the '.' label
 105          * separator).
 106          */
 107         if (diff < 2)
 108                 return (0);
 109
 110         /*
 111          * If the character before the last 'lb' characters of 'b'
 112          * isn't '.', then it can't be a match (this lets us avoid
 113          * having "foobar.com" match "bar.com").
 114          */
 115         if (a[diff - 1] != '.')
 116                 return (0);
 117
 118         /*
 119          * We're not sure about that '.', however.  It could be escaped
 120          * and thus not a really a label separator.
 121          */
 122         escaped = 0;
 123         for (i = diff - 2; i >= 0; i--)
 124                 if (a[i] == '\\')
 125                         if (escaped)
 126                                 escaped = 0;
 127                         else
 128                                 escaped = 1;
 129                 else
 130                         break;
 131         if (escaped)
 132                 return (0);
 133
 134         /* Now compare aligned trailing substring. */
 135         cp = a + diff;
 136         return (strncasecmp(cp, b, lb) == 0);
 137 }
 138
 139 /*
 140  * int
 141  * ns_subdomain(a, b)
 142  *      is "a" a subdomain of "b"?
 143  */
 144 int
 145 ns_subdomain(const char *a, const char *b) {
 146         return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
 147 }
 148
 149 /*
 150  * int
 151  * ns_makecanon(src, dst, dstsize)
 152  *      make a canonical copy of domain name "src"
 153  * notes:
 154  *      foo -> foo.
 155  *      foo. -> foo.
 156  *      foo.. -> foo.
 157  *      foo\. -> foo\..
 158  *      foo\\. -> foo\\.
 159  */
 160
 161 int
 162 ns_makecanon(const char *src, char *dst, size_t dstsize) {
 163         size_t n = strlen(src);
 164
 165         if (n + sizeof "." > dstsize) {
 166                 __set_errno (EMSGSIZE);
 167                 return (-1);
 168         }
 169         strcpy(dst, src);
 170         while (n > 0 && dst[n - 1] == '.')              /* Ends in "." */
 171                 if (n > 1 && dst[n - 2] == '\\' &&      /* Ends in "\." */
 172                     (n < 2 || dst[n - 3] != '\\'))      /* But not "\\." */
 173                         break;
 174                 else
 175                         dst[--n] = '\0';
 176         dst[n++] = '.';
 177         dst[n] = '\0';
 178         return (0);
 179 }
 180
 181 /*
 182  * int
 183  * ns_samename(a, b)
 184  *      determine whether domain name "a" is the same as domain name "b"
 185  * return:
 186  *      -1 on error
 187  *      0 if names differ
 188  *      1 if names are the same
 189  */
 190
 191 int
 192 ns_samename(const char *a, const char *b) {
 193         char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
 194
 195         if (ns_makecanon(a, ta, sizeof ta) < 0 ||
 196             ns_makecanon(b, tb, sizeof tb) < 0)
 197                 return (-1);
 198         if (strcasecmp(ta, tb) == 0)
 199                 return (1);
 200         else
 201                 return (0);
 202 }