lib/libc/nameser/ns_samedomain.c

   1 /*      $NetBSD: ns_samedomain.c,v 1.6 2009/04/12 17:07:17 christos Exp $       */
   2
   3 /*
   4  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   5  * Copyright (c) 1995,1999 by Internet Software Consortium.
   6  *
   7  * Permission to use, copy, modify, and distribute this software for any
   8  * purpose with or without fee is hereby granted, provided that the above
   9  * copyright notice and this permission notice appear in all copies.
  10  *
  11  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  12  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  13  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  14  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  15  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  16  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  17  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  18  */
  19
  20 #include <sys/cdefs.h>
  21 #ifndef lint
  22 #ifdef notdef
  23 static const char rcsid[] = "Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp";
  24 #else
  25 __RCSID("$NetBSD: ns_samedomain.c,v 1.6 2009/04/12 17:07:17 christos Exp $");
  26 #endif
  27 #endif
  28
  29 #include "port_before.h"
  30
  31 #include <sys/types.h>
  32 #include <arpa/nameser.h>
  33 #include <errno.h>
  34 #include <string.h>
  35
  36 #include "port_after.h"
  37
  38 #ifndef _LIBC
  39 /*%
  40  *      Check whether a name belongs to a domain.
  41  *
  42  * Inputs:
  43  *\li   a - the domain whose ancestory is being verified
  44  *\li   b - the potential ancestor we're checking against
  45  *
  46  * Return:
  47  *\li   boolean - is a at or below b?
  48  *
  49  * Notes:
  50  *\li   Trailing dots are first removed from name and domain.
  51  *      Always compare complete subdomains, not only whether the
  52  *      domain name is the trailing string of the given name.
  53  *
  54  *\li   "host.foobar.top" lies in "foobar.top" and in "top" and in ""
  55  *      but NOT in "bar.top"
  56  */
  57
  58 int
  59 ns_samedomain(const char *a, const char *b) {
  60         size_t la, lb;
  61         int diff, i, escaped;
  62         const char *cp;
  63
  64         la = strlen(a);
  65         lb = strlen(b);
  66
  67         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
  68         if (la != 0U && a[la - 1] == '.') {
  69                 escaped = 0;
  70                 /* Note this loop doesn't get executed if la==1. */
  71                 for (i = la - 2; i >= 0; i--)
  72                         if (a[i] == '\\') {
  73                                 if (escaped)
  74                                         escaped = 0;
  75                                 else
  76                                         escaped = 1;
  77                         } else
  78                                 break;
  79                 if (!escaped)
  80                         la--;
  81         }
  82
  83         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
  84         if (lb != 0U && b[lb - 1] == '.') {
  85                 escaped = 0;
  86                 /* note this loop doesn't get executed if lb==1 */
  87                 for (i = lb - 2; i >= 0; i--)
  88                         if (b[i] == '\\') {
  89                                 if (escaped)
  90                                         escaped = 0;
  91                                 else
  92                                         escaped = 1;
  93                         } else
  94                                 break;
  95                 if (!escaped)
  96                         lb--;
  97         }
  98
  99         /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
 100         if (lb == 0U)
 101                 return (1);
 102
 103         /* 'b' longer than 'a' means 'a' can't be in 'b'. */
 104         if (lb > la)
 105                 return (0);
 106
 107         /* 'a' and 'b' being equal at this point indicates sameness. */
 108         if (lb == la)
 109                 return (strncasecmp(a, b, lb) == 0);
 110
 111         /* Ok, we know la > lb. */
 112
 113         diff = la - lb;
 114
 115         /*
 116          * If 'a' is only 1 character longer than 'b', then it can't be
 117          * a subdomain of 'b' (because of the need for the '.' label
 118          * separator).
 119          */
 120         if (diff < 2)
 121                 return (0);
 122
 123         /*
 124          * If the character before the last 'lb' characters of 'b'
 125          * isn't '.', then it can't be a match (this lets us avoid
 126          * having "foobar.com" match "bar.com").
 127          */
 128         if (a[diff - 1] != '.')
 129                 return (0);
 130
 131         /*
 132          * We're not sure about that '.', however.  It could be escaped
 133          * and thus not a really a label separator.
 134          */
 135         escaped = 0;
 136         for (i = diff - 2; i >= 0; i--)
 137                 if (a[i] == '\\') {
 138                         if (escaped)
 139                                 escaped = 0;
 140                         else
 141                                 escaped = 1;
 142                 } else
 143                         break;
 144         if (escaped)
 145                 return (0);
 146
 147         /* Now compare aligned trailing substring. */
 148         cp = a + diff;
 149         return (strncasecmp(cp, b, lb) == 0);
 150 }
 151
 152 /*%
 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 #endif
 160
 161 /*%
 162  *      make a canonical copy of domain name "src"
 163  *
 164  * notes:
 165  * \code
 166  *      foo -> foo.
 167  *      foo. -> foo.
 168  *      foo.. -> foo.
 169  *      foo\. -> foo\..
 170  *      foo\\. -> foo\\.
 171  * \endcode
 172  */
 173
 174 int
 175 ns_makecanon(const char *src, char *dst, size_t dstsize) {
 176         size_t n = strlen(src);
 177
 178         if (n + sizeof "." > dstsize) {                 /*%< Note: sizeof == 2 */
 179                 errno = EMSGSIZE;
 180                 return (-1);
 181         }
 182         strcpy(dst, src);
 183         while (n >= 1U && dst[n - 1] == '.')            /*%< Ends in "." */
 184                 if (n >= 2U && dst[n - 2] == '\\' &&    /*%< Ends in "\." */
 185                     (n < 3U || dst[n - 3] != '\\'))     /*%< But not "\\." */
 186                         break;
 187                 else
 188                         dst[--n] = '\0';
 189         dst[n++] = '.';
 190         dst[n] = '\0';
 191         return (0);
 192 }
 193
 194 /*%
 195  *      determine whether domain name "a" is the same as domain name "b"
 196  *
 197  * return:
 198  *\li   -1 on error
 199  *\li   0 if names differ
 200  *\li   1 if names are the same
 201  */
 202
 203 int
 204 ns_samename(const char *a, const char *b) {
 205         char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
 206
 207         if (ns_makecanon(a, ta, sizeof ta) < 0 ||
 208             ns_makecanon(b, tb, sizeof tb) < 0)
 209                 return (-1);
 210         if (strcasecmp(ta, tb) == 0)
 211                 return (1);
 212         else
 213                 return (0);
 214 }
 215
 216 /*! \file */