/*

 * 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 (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 */

		__set_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);

}

libresolv_hidden_def (ns_makecanon)

/*%

 *	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);

}

libresolv_hidden_def (ns_samename)

/*! \file */