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/*
* 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
* ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
* CONSORTIUM 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.
*/
#include <sys/types.h>
#include <arpa/nameser.h>
#include <errno.h>
#include <string.h>
/*%
* Check whether a name belongs to a domain.
*
* Inputs:
*\li a - the domain whose ancestry 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);
}
libresolv_hidden_def (ns_samedomain)
/*%
* is "a" a subdomain of "b"?
*/
int
ns_subdomain (const char *a, const char *b)
{
return __libc_ns_samename (a, b) != 1 && ns_samedomain (a, b);
}
/*! \file */
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