/* $NetBSD: ns_samedomain.c,v 1.1.1.2 2012/09/09 16:08:03 christos Exp $ */
/*
* Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
* Copyright (c) 1995,1999 by Internet Software Consortium.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
* OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#ifndef lint
static const char rcsid[] = "Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp ";
#endif
#include "port_before.h"
#include <sys/types.h>
#include <arpa/nameser.h>
#include <errno.h>
#include <string.h>
#include "port_after.h"
/*%
* Check whether a name belongs to a domain.
*
* Inputs:
*\li a - the domain whose ancestory is being verified
*\li b - the potential ancestor we're checking against
*
* Return:
*\li boolean - is a at or below b?
*
* Notes:
*\li Trailing dots are first removed from name and domain.
* Always compare complete subdomains, not only whether the
* domain name is the trailing string of the given name.
*
*\li "host.foobar.top" lies in "foobar.top" and in "top" and in ""
* but NOT in "bar.top"
*/
int
ns_samedomain(const char *a, const char *b) {
size_t la, lb;
int diff, i, escaped;
const char *cp;
la = strlen(a);
lb = strlen(b);
/* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
if (la != 0U && a[la - 1] == '.') {
escaped = 0;
/* Note this loop doesn't get executed if la==1. */
for (i = la - 2; i >= 0; i--)
if (a[i] == '\\') {
if (escaped)
escaped = 0;
else
escaped = 1;
} else
break;
if (!escaped)
la--;
}
/* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
if (lb != 0U && b[lb - 1] == '.') {
escaped = 0;
/* note this loop doesn't get executed if lb==1 */
for (i = lb - 2; i >= 0; i--)
if (b[i] == '\\') {
if (escaped)
escaped = 0;
else
escaped = 1;
} else
break;
if (!escaped)
lb--;
}
/* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
if (lb == 0U)
return (1);
/* 'b' longer than 'a' means 'a' can't be in 'b'. */
if (lb > la)
return (0);
/* 'a' and 'b' being equal at this point indicates sameness. */
if (lb == la)
return (strncasecmp(a, b, lb) == 0);
/* Ok, we know la > lb. */
diff = la - lb;
/*
* If 'a' is only 1 character longer than 'b', then it can't be
* a subdomain of 'b' (because of the need for the '.' label
* separator).
*/
if (diff < 2)
return (0);
/*
* If the character before the last 'lb' characters of 'b'
* isn't '.', then it can't be a match (this lets us avoid
* having "foobar.com" match "bar.com").
*/
if (a[diff - 1] != '.')
return (0);
/*
* We're not sure about that '.', however. It could be escaped
* and thus not a really a label separator.
*/
escaped = 0;
for (i = diff - 2; i >= 0; i--)
if (a[i] == '\\') {
if (escaped)
escaped = 0;
else
escaped = 1;
} else
break;
if (escaped)
return (0);
/* Now compare aligned trailing substring. */
cp = a + diff;
return (strncasecmp(cp, b, lb) == 0);
}
/*%
* is "a" a subdomain of "b"?
*/
int
ns_subdomain(const char *a, const char *b) {
return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
}
/*%
* make a canonical copy of domain name "src"
*
* notes:
* \code
* foo -> foo.
* foo. -> foo.
* foo.. -> foo.
* foo\. -> foo\..
* foo\\. -> foo\\.
* \endcode
*/
int
ns_makecanon(const char *src, char *dst, size_t dstsize) {
size_t n = strlen(src);
if (n + sizeof "." > dstsize) { /*%< Note: sizeof == 2 */
errno = EMSGSIZE;
return (-1);
}
strcpy(dst, src);
while (n >= 1U && dst[n - 1] == '.') /*%< Ends in "." */
if (n >= 2U && dst[n - 2] == '\\' && /*%< Ends in "\." */
(n < 3U || dst[n - 3] != '\\')) /*%< But not "\\." */
break;
else
dst[--n] = '\0';
dst[n++] = '.';
dst[n] = '\0';
return (0);
}
/*%
* determine whether domain name "a" is the same as domain name "b"
*
* return:
*\li -1 on error
*\li 0 if names differ
*\li 1 if names are the same
*/
int
ns_samename(const char *a, const char *b) {
char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
if (ns_makecanon(a, ta, sizeof ta) < 0 ||
ns_makecanon(b, tb, sizeof tb) < 0)
return (-1);
if (strcasecmp(ta, tb) == 0)
return (1);
else
return (0);
}
/*! \file */
