lib/libc/nameser/ns_samedomain.c

   1 /*
   2  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   3  * Copyright (c) 1995,1999 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 #ifndef lint
  19 static const char rcsid[] = "$Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp $";
  20 #endif
  21
  22 #include "port_before.h"
  23
  24 #include <sys/types.h>
  25 #include <arpa/nameser.h>
  26 #include <errno.h>
  27 #include <string.h>
  28
  29 #include "port_after.h"
  30
  31 /*%
  32  *      Check whether a name belongs to a domain.
  33  *
  34  * Inputs:
  35  *\li   a - the domain whose ancestory is being verified
  36  *\li   b - the potential ancestor we're checking against
  37  *
  38  * Return:
  39  *\li   boolean - is a at or below b?
  40  *
  41  * Notes:
  42  *\li   Trailing dots are first removed from name and domain.
  43  *      Always compare complete subdomains, not only whether the
  44  *      domain name is the trailing string of the given name.
  45  *
  46  *\li   "host.foobar.top" lies in "foobar.top" and in "top" and in ""
  47  *      but NOT in "bar.top"
  48  */
  49
  50 int
  51 ns_samedomain(const char *a, const char *b) {
  52         size_t la, lb;
  53         int diff, i, escaped;
  54         const char *cp;
  55
  56         la = strlen(a);
  57         lb = strlen(b);
  58
  59         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
  60         if (la != 0U && a[la - 1] == '.') {
  61                 escaped = 0;
  62                 /* Note this loop doesn't get executed if la==1. */
  63                 for (i = la - 2; i >= 0; i--)
  64                         if (a[i] == '\\') {
  65                                 if (escaped)
  66                                         escaped = 0;
  67                                 else
  68                                         escaped = 1;
  69                         } else
  70                                 break;
  71                 if (!escaped)
  72                         la--;
  73         }
  74
  75         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
  76         if (lb != 0U && b[lb - 1] == '.') {
  77                 escaped = 0;
  78                 /* note this loop doesn't get executed if lb==1 */
  79                 for (i = lb - 2; i >= 0; i--)
  80                         if (b[i] == '\\') {
  81                                 if (escaped)
  82                                         escaped = 0;
  83                                 else
  84                                         escaped = 1;
  85                         } else
  86                                 break;
  87                 if (!escaped)
  88                         lb--;
  89         }
  90
  91         /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
  92         if (lb == 0U)
  93                 return (1);
  94
  95         /* 'b' longer than 'a' means 'a' can't be in 'b'. */
  96         if (lb > la)
  97                 return (0);
  98
  99         /* 'a' and 'b' being equal at this point indicates sameness. */
 100         if (lb == la)
 101                 return (strncasecmp(a, b, lb) == 0);
 102
 103         /* Ok, we know la > lb. */
 104
 105         diff = la - lb;
 106
 107         /*
 108          * If 'a' is only 1 character longer than 'b', then it can't be
 109          * a subdomain of 'b' (because of the need for the '.' label
 110          * separator).
 111          */
 112         if (diff < 2)
 113                 return (0);
 114
 115         /*
 116          * If the character before the last 'lb' characters of 'b'
 117          * isn't '.', then it can't be a match (this lets us avoid
 118          * having "foobar.com" match "bar.com").
 119          */
 120         if (a[diff - 1] != '.')
 121                 return (0);
 122
 123         /*
 124          * We're not sure about that '.', however.  It could be escaped
 125          * and thus not a really a label separator.
 126          */
 127         escaped = 0;
 128         for (i = diff - 2; i >= 0; i--)
 129                 if (a[i] == '\\') {
 130                         if (escaped)
 131                                 escaped = 0;
 132                         else
 133                                 escaped = 1;
 134                 } else
 135                         break;
 136         if (escaped)
 137                 return (0);
 138
 139         /* Now compare aligned trailing substring. */
 140         cp = a + diff;
 141         return (strncasecmp(cp, b, lb) == 0);
 142 }
 143
 144 #ifndef _LIBC
 145 /*
 146  * int
 147  * ns_subdomain(a, b)
 148  *      is "a" a subdomain of "b"?
 149  */
 150 int
 151 ns_subdomain(const char *a, const char *b) {
 152         return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
 153 }
 154 #endif
 155
 156 /*%
 157  *      make a canonical copy of domain name "src"
 158  *
 159  * notes:
 160  * \code
 161  *      foo -> foo.
 162  *      foo. -> foo.
 163  *      foo.. -> foo.
 164  *      foo\. -> foo\..
 165  *      foo\\. -> foo\\.
 166  * \endcode
 167  */
 168
 169 int
 170 ns_makecanon(const char *src, char *dst, size_t dstsize) {
 171         size_t n = strlen(src);
 172
 173         if (n + sizeof "." > dstsize) {                 /*%< Note: sizeof == 2 */
 174                 errno = EMSGSIZE;
 175                 return (-1);
 176         }
 177         strcpy(dst, src);
 178         while (n >= 1U && dst[n - 1] == '.')            /*%< Ends in "." */
 179                 if (n >= 2U && dst[n - 2] == '\\' &&    /*%< Ends in "\." */
 180                     (n < 3U || dst[n - 3] != '\\'))     /*%< But not "\\." */
 181                         break;
 182                 else
 183                         dst[--n] = '\0';
 184         dst[n++] = '.';
 185         dst[n] = '\0';
 186         return (0);
 187 }
 188
 189 /*%
 190  *      determine whether domain name "a" is the same as domain name "b"
 191  *
 192  * return:
 193  *\li   -1 on error
 194  *\li   0 if names differ
 195  *\li   1 if names are the same
 196  */
 197
 198 int
 199 ns_samename(const char *a, const char *b) {
 200         char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
 201
 202         if (ns_makecanon(a, ta, sizeof ta) < 0 ||
 203             ns_makecanon(b, tb, sizeof tb) < 0)
 204                 return (-1);
 205         if (strcasecmp(ta, tb) == 0)
 206                 return (1);
 207         else
 208                 return (0);
 209 }
 210
 211 /*! \file */