/*
 * 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 "validator-internal.h"

/*
 * int
 * ns_samedomain(a, b)
 *      Check whether a name belongs to a domain.
 * Inputs:
 *      a - the domain whose ancestory is being verified
 *      b - the potential ancestor we're checking against
 * Return:
 *      boolean - is a at or below b?
 * Notes:
 *      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.
 *
 *      "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);
}


/*
 * int
 * ns_makecanon(src, dst, dstsize)
 *      make a canonical copy of domain name "src"
 * notes:
 *      foo -> foo.
 *      foo. -> foo.
 *      foo.. -> foo.
 *      foo\. -> foo\..
 *      foo\\. -> foo\\.
 */

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);
}

/*
 * int
 * ns_samename(a, b)
 *      determine whether domain name "a" is the same as domain name "b"
 * return:
 *      -1 on error
 *      0 if names differ
 *      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 (strncasecmp(ta, tb, NS_MAXDNAME) == 0)
        return (1);
    else
        return (0);
}

/*
 * int
 * ns_subdomain(a, b)
 *      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));
}
