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  * $Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp $
  18  */
  19
  20 #include "port_before.h"
  21
  22 #include <sys/types.h>
  23 #include <arpa/nameser.h>
  24 #include <errno.h>
  25 #include <string.h>
  26
  27 #include "port_after.h"
  28
  29 /*%
  30  *      Check whether a name belongs to a domain.
  31  *
  32  * Inputs:
  33  *\li   a - the domain whose ancestory is being verified
  34  *\li   b - the potential ancestor we're checking against
  35  *
  36  * Return:
  37  *\li   boolean - is a at or below b?
  38  *
  39  * Notes:
  40  *\li   Trailing dots are first removed from name and domain.
  41  *      Always compare complete subdomains, not only whether the
  42  *      domain name is the trailing string of the given name.
  43  *
  44  *\li   "host.foobar.top" lies in "foobar.top" and in "top" and in ""
  45  *      but NOT in "bar.top"
  46  */
  47
  48 int
  49 ns_samedomain(const char *a, const char *b) {
  50         size_t la, lb;
  51         int diff, i, escaped;
  52         const char *cp;
  53
  54         la = strlen(a);
  55         lb = strlen(b);
  56
  57         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
  58         if (la != 0U && a[la - 1] == '.') {
  59                 escaped = 0;
  60                 /* Note this loop doesn't get executed if la==1. */
  61                 for (i = la - 2; i >= 0; i--)
  62                         if (a[i] == '\\') {
  63                                 if (escaped)
  64                                         escaped = 0;
  65                                 else
  66                                         escaped = 1;
  67                         } else
  68                                 break;
  69                 if (!escaped)
  70                         la--;
  71         }
  72
  73         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
  74         if (lb != 0U && b[lb - 1] == '.') {
  75                 escaped = 0;
  76                 /* note this loop doesn't get executed if lb==1 */
  77                 for (i = lb - 2; i >= 0; i--)
  78                         if (b[i] == '\\') {
  79                                 if (escaped)
  80                                         escaped = 0;
  81                                 else
  82                                         escaped = 1;
  83                         } else
  84                                 break;
  85                 if (!escaped)
  86                         lb--;
  87         }
  88
  89         /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
  90         if (lb == 0U)
  91                 return (1);
  92
  93         /* 'b' longer than 'a' means 'a' can't be in 'b'. */
  94         if (lb > la)
  95                 return (0);
  96
  97         /* 'a' and 'b' being equal at this point indicates sameness. */
  98         if (lb == la)
  99                 return (strncasecmp(a, b, lb) == 0);
 100
 101         /* Ok, we know la > lb. */
 102
 103         diff = la - lb;
 104
 105         /*
 106          * If 'a' is only 1 character longer than 'b', then it can't be
 107          * a subdomain of 'b' (because of the need for the '.' label
 108          * separator).
 109          */
 110         if (diff < 2)
 111                 return (0);
 112
 113         /*
 114          * If the character before the last 'lb' characters of 'b'
 115          * isn't '.', then it can't be a match (this lets us avoid
 116          * having "foobar.com" match "bar.com").
 117          */
 118         if (a[diff - 1] != '.')
 119                 return (0);
 120
 121         /*
 122          * We're not sure about that '.', however.  It could be escaped
 123          * and thus not a really a label separator.
 124          */
 125         escaped = 0;
 126         for (i = diff - 2; i >= 0; i--)
 127                 if (a[i] == '\\') {
 128                         if (escaped)
 129                                 escaped = 0;
 130                         else
 131                                 escaped = 1;
 132                 } else
 133                         break;
 134         if (escaped)
 135                 return (0);
 136
 137         /* Now compare aligned trailing substring. */
 138         cp = a + diff;
 139         return (strncasecmp(cp, b, lb) == 0);
 140 }
 141
 142 #ifndef _LIBC
 143 /*
 144  * int
 145  * ns_subdomain(a, b)
 146  *      is "a" a subdomain of "b"?
 147  */
 148 int
 149 ns_subdomain(const char *a, const char *b) {
 150         return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
 151 }
 152 #endif
 153
 154 /*%
 155  *      make a canonical copy of domain name "src"
 156  *
 157  * notes:
 158  * \code
 159  *      foo -> foo.
 160  *      foo. -> foo.
 161  *      foo.. -> foo.
 162  *      foo\. -> foo\..
 163  *      foo\\. -> foo\\.
 164  * \endcode
 165  */
 166
 167 int
 168 ns_makecanon(const char *src, char *dst, size_t dstsize) {
 169         size_t n = strlen(src);
 170
 171         if (n + sizeof "." > dstsize) {                 /*%< Note: sizeof == 2 */
 172                 errno = EMSGSIZE;
 173                 return (-1);
 174         }
 175         strcpy(dst, src);
 176         while (n >= 1U && dst[n - 1] == '.')            /*%< Ends in "." */
 177                 if (n >= 2U && dst[n - 2] == '\\' &&    /*%< Ends in "\." */
 178                     (n < 3U || dst[n - 3] != '\\'))     /*%< But not "\\." */
 179                         break;
 180                 else
 181                         dst[--n] = '\0';
 182         dst[n++] = '.';
 183         dst[n] = '\0';
 184         return (0);
 185 }
 186
 187 /*%
 188  *      determine whether domain name "a" is the same as domain name "b"
 189  *
 190  * return:
 191  *\li   -1 on error
 192  *\li   0 if names differ
 193  *\li   1 if names are the same
 194  */
 195
 196 int
 197 ns_samename(const char *a, const char *b) {
 198         char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
 199
 200         if (ns_makecanon(a, ta, sizeof ta) < 0 ||
 201             ns_makecanon(b, tb, sizeof tb) < 0)
 202                 return (-1);
 203         if (strcasecmp(ta, tb) == 0)
 204                 return (1);
 205         else
 206                 return (0);
 207 }
 208
 209 /*! \file */