resolv/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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  10  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  11  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  12  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  13  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  14  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  15  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  16  * SOFTWARE.
  17  */
  18
  19 #if !defined(_LIBC) && !defined(lint)
  20 static const char rcsid[] = "$BINDId: ns_samedomain.c,v 8.9 1999/10/15 21:06:51 vixie Exp $";
  21 #endif
  22
  23 #include <sys/types.h>
  24 #include <arpa/nameser.h>
  25 #include <errno.h>
  26 #include <string.h>
  27
  28 /*%
  29  *      Check whether a name belongs to a domain.
  30  *
  31  * Inputs:
  32  *\li   a - the domain whose ancestry is being verified
  33  *\li   b - the potential ancestor we're checking against
  34  *
  35  * Return:
  36  *\li   boolean - is a at or below b?
  37  *
  38  * Notes:
  39  *\li   Trailing dots are first removed from name and domain.
  40  *      Always compare complete subdomains, not only whether the
  41  *      domain name is the trailing string of the given name.
  42  *
  43  *\li   "host.foobar.top" lies in "foobar.top" and in "top" and in ""
  44  *      but NOT in "bar.top"
  45  */
  46
  47 int
  48 ns_samedomain(const char *a, const char *b) {
  49         size_t la, lb;
  50         int diff, i, escaped;
  51         const char *cp;
  52
  53         la = strlen(a);
  54         lb = strlen(b);
  55
  56         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
  57         if (la != 0U && a[la - 1] == '.') {
  58                 escaped = 0;
  59                 /* Note this loop doesn't get executed if la==1. */
  60                 for (i = la - 2; i >= 0; i--)
  61                         if (a[i] == '\\') {
  62                                 if (escaped)
  63                                         escaped = 0;
  64                                 else
  65                                         escaped = 1;
  66                         } else
  67                                 break;
  68                 if (!escaped)
  69                         la--;
  70         }
  71
  72         /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
  73         if (lb != 0U && b[lb - 1] == '.') {
  74                 escaped = 0;
  75                 /* note this loop doesn't get executed if lb==1 */
  76                 for (i = lb - 2; i >= 0; i--)
  77                         if (b[i] == '\\') {
  78                                 if (escaped)
  79                                         escaped = 0;
  80                                 else
  81                                         escaped = 1;
  82                         } else
  83                                 break;
  84                 if (!escaped)
  85                         lb--;
  86         }
  87
  88         /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
  89         if (lb == 0U)
  90                 return (1);
  91
  92         /* 'b' longer than 'a' means 'a' can't be in 'b'. */
  93         if (lb > la)
  94                 return (0);
  95
  96         /* 'a' and 'b' being equal at this point indicates sameness. */
  97         if (lb == la)
  98                 return (strncasecmp(a, b, lb) == 0);
  99
 100         /* Ok, we know la > lb. */
 101
 102         diff = la - lb;
 103
 104         /*
 105          * If 'a' is only 1 character longer than 'b', then it can't be
 106          * a subdomain of 'b' (because of the need for the '.' label
 107          * separator).
 108          */
 109         if (diff < 2)
 110                 return (0);
 111
 112         /*
 113          * If the character before the last 'lb' characters of 'b'
 114          * isn't '.', then it can't be a match (this lets us avoid
 115          * having "foobar.com" match "bar.com").
 116          */
 117         if (a[diff - 1] != '.')
 118                 return (0);
 119
 120         /*
 121          * We're not sure about that '.', however.  It could be escaped
 122          * and thus not a really a label separator.
 123          */
 124         escaped = 0;
 125         for (i = diff - 2; i >= 0; i--)
 126                 if (a[i] == '\\') {
 127                         if (escaped)
 128                                 escaped = 0;
 129                         else
 130                                 escaped = 1;
 131                 } else
 132                         break;
 133         if (escaped)
 134                 return (0);
 135
 136         /* Now compare aligned trailing substring. */
 137         cp = a + diff;
 138         return (strncasecmp(cp, b, lb) == 0);
 139 }
 140 libresolv_hidden_def (ns_samedomain)
 141
 142 /*%
 143  *      is "a" a subdomain of "b"?
 144  */
 145 int
 146 ns_subdomain(const char *a, const char *b) {
 147         return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
 148 }
 149
 150 /*%
 151  *      make a canonical copy of domain name "src"
 152  *
 153  * notes:
 154  * \code
 155  *      foo -> foo.
 156  *      foo. -> foo.
 157  *      foo.. -> foo.
 158  *      foo\. -> foo\..
 159  *      foo\\. -> foo\\.
 160  * \endcode
 161  */
 162
 163 int
 164 ns_makecanon(const char *src, char *dst, size_t dstsize) {
 165         size_t n = strlen(src);
 166
 167         if (n + sizeof "." > dstsize) {                 /*%< Note: sizeof == 2 */
 168                 __set_errno (EMSGSIZE);
 169                 return (-1);
 170         }
 171         strcpy(dst, src);
 172         while (n >= 1U && dst[n - 1] == '.')            /*%< Ends in "." */
 173                 if (n >= 2U && dst[n - 2] == '\\' &&    /*%< Ends in "\." */
 174                     (n < 3U || dst[n - 3] != '\\'))     /*%< But not "\\." */
 175                         break;
 176                 else
 177                         dst[--n] = '\0';
 178         dst[n++] = '.';
 179         dst[n] = '\0';
 180         return (0);
 181 }
 182 libresolv_hidden_def (ns_makecanon)
 183
 184 /*%
 185  *      determine whether domain name "a" is the same as domain name "b"
 186  *
 187  * return:
 188  *\li   -1 on error
 189  *\li   0 if names differ
 190  *\li   1 if names are the same
 191  */
 192
 193 int
 194 ns_samename(const char *a, const char *b) {
 195         char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
 196
 197         if (ns_makecanon(a, ta, sizeof ta) < 0 ||
 198             ns_makecanon(b, tb, sizeof tb) < 0)
 199                 return (-1);
 200         if (strcasecmp(ta, tb) == 0)
 201                 return (1);
 202         else
 203                 return (0);
 204 }
 205 libresolv_hidden_def (ns_samename)
 206
 207 /*! \file */