/*      $NetBSD: ns_samedomain.c,v 1.8 2012/11/22 20:22:31 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.
 */

#include <sys/cdefs.h>
#ifndef lint
#ifdef notdef
static const char rcsid[] = "Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp";
#else
//__RCSID("$NetBSD: ns_samedomain.c,v 1.8 2012/11/22 20:22:31 christos Exp $");
#endif
#endif

#include "port_before.h"

#include <sys/types.h>
#include <arpa/nameser.h>
#include <errno.h>
#include <string.h>

#include "port_after.h"

#ifdef _LIBRESOLV
/*%
 *      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, i;
        int diff, 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 - 1; i > 0; i--)
                        if (a[i - 1] == '\\') {
                                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 - 1; i > 0; i--)
                        if (b[i - 1] == '\\') {
                                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 = (int)(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 - 1; i > 0; i--)
                if (a[i - 1] == '\\') {
                        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));
}
#endif
#define _LIBC
#ifdef _LIBC
/*%
 *      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);
}
#endif
/*! \file */