/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1985, 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * -
 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
 *
 * 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, and that
 * the name of Digital Equipment Corporation not be used in advertising or
 * publicity pertaining to distribution of the document or software without
 * specific, written prior permission.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
 * CORPORATION 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.
 * -
 * --Copyright--
 */
/* Portions Copyright (c) 1993 Carlos Leandro and Rui Salgueiro
 *      Dep. Matematica Universidade de Coimbra, Portugal, Europe
 *
 * 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.
 */

#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <resolv.h>
#include <ctype.h>
#include <string.h>
#include <unistd.h>
#include <syslog.h>
#include <stdarg.h>
#include <nsswitch.h>

#include "netdb_private.h"
#include "res_config.h"

#define BYADDR 0
#define BYNAME 1

#define MAXPACKET       (64*1024)

typedef union {
        HEADER  hdr;
        u_char  buf[MAXPACKET];
} querybuf;

typedef union {
        long    al;
        char    ac;
} align;

/*
 * Reverse the order of first four dotted entries of in.
 * Out must contain space for at least strlen(in) characters.
 * The result does not include any leading 0s of in.
 */
static void
ipreverse(char *in, char *out)
{
        char *pos[4];
        int len[4];
        char *p, *start;
        int i = 0;
        int leading = 1;

        /* Fill-in element positions and lengths: pos[], len[]. */
        start = p = in;
        for (;;) {
                if (*p == '.' || *p == '\0') {
                        /* Leading 0? */
                        if (leading && p - start == 1 && *start == '0')
                                len[i] = 0;
                        else {
                                len[i] = p - start;
                                leading = 0;
                        }
                        pos[i] = start;
                        start = p + 1;
                        i++;
                }
                if (i == 4)
                        break;
                if (*p == 0) {
                        for (; i < 4; i++) {
                                pos[i] = p;
                                len[i] = 0;
                        }
                        break;
                }
                p++;
        }

        /* Copy the entries in reverse order */
        p = out;
        leading = 1;
        for (i = 3; i >= 0; i--) {
                memcpy(p, pos[i], len[i]);
                if (len[i])
                        leading = 0;
                p += len[i];
                /* Need a . separator? */
                if (!leading && i > 0 && len[i - 1])
                        *p++ = '.';
        }
        *p = '\0';
}

static int
getnetanswer(querybuf *answer, int anslen, int net_i, struct netent *ne,
    struct netent_data *ned, res_state statp)
{

        HEADER *hp;
        u_char *cp;
        int n;
        u_char *eom;
        int type, class, ancount, qdcount, haveanswer;
        char aux[MAXHOSTNAMELEN];
        char ans[MAXHOSTNAMELEN];
        char *in, *bp, *ep, **ap;

        /*
         * find first satisfactory answer
         *
         *      answer --> +------------+  ( MESSAGE )
         *                 |   Header   |
         *                 +------------+
         *                 |  Question  | the question for the name server
         *                 +------------+
         *                 |   Answer   | RRs answering the question
         *                 +------------+
         *                 | Authority  | RRs pointing toward an authority
         *                 | Additional | RRs holding additional information
         *                 +------------+
         */
        eom = answer->buf + anslen;
        hp = &answer->hdr;
        ancount = ntohs(hp->ancount); /* #/records in the answer section */
        qdcount = ntohs(hp->qdcount); /* #/entries in the question section */
        bp = ned->netbuf;
        ep = ned->netbuf + sizeof(ned->netbuf);
        cp = answer->buf + HFIXEDSZ;
        if (!qdcount) {
                if (hp->aa)
                        RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
                else
                        RES_SET_H_ERRNO(statp, TRY_AGAIN);
                return (-1);
        }
        while (qdcount-- > 0)
                cp += __dn_skipname(cp, eom) + QFIXEDSZ;
        ap = ned->net_aliases;
        *ap = NULL;
        ne->n_aliases = ned->net_aliases;
        haveanswer = 0;
        while (--ancount >= 0 && cp < eom) {
                n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
                if ((n < 0) || !res_dnok(bp))
                        break;
                cp += n;
                ans[0] = '\0';
                (void)strncpy(&ans[0], bp, sizeof(ans) - 1);
                ans[sizeof(ans) - 1] = '\0';
                GETSHORT(type, cp);
                GETSHORT(class, cp);
                cp += INT32SZ;          /* TTL */
                GETSHORT(n, cp);
                if (class == C_IN && type == T_PTR) {
                        n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
                        if ((n < 0) || !res_hnok(bp)) {
                                cp += n;
                                return (-1);
                        }
                        cp += n;
                        *ap++ = bp;
                        n = strlen(bp) + 1;
                        bp += n;
                        ne->n_addrtype = (class == C_IN) ? AF_INET : AF_UNSPEC;
                        haveanswer++;
                }
        }
        if (haveanswer) {
                *ap = NULL;
                switch (net_i) {
                case BYADDR:
                        ne->n_name = *ne->n_aliases;
                        ne->n_net = 0L;
                        break;
                case BYNAME:
                        in = *ne->n_aliases;
                        n = strlen(ans) + 1;
                        if (ep - bp < n) {
                                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                                errno = ENOBUFS;
                                return (-1);
                        }
                        strlcpy(bp, ans, ep - bp);
                        ne->n_name = bp;
                        if (strlen(in) + 1 > sizeof(aux)) {
                                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                                errno = ENOBUFS;
                                return (-1);
                        }
                        ipreverse(in, aux);
                        ne->n_net = inet_network(aux);
                        break;
                }
                ne->n_aliases++;
                return (0);
        }
        RES_SET_H_ERRNO(statp, TRY_AGAIN);
        return (-1);
}

int
_dns_getnetbyaddr(void *rval, void *cb_data, va_list ap)
{
        uint32_t net;
        int net_type;
        char *buffer;
        size_t buflen;
        int *errnop, *h_errnop;
        struct netent *nptr, ne;
        struct netent_data *ned;
        unsigned int netbr[4];
        int nn, anslen, error;
        querybuf *buf;
        char qbuf[MAXDNAME];
        uint32_t net2;
        res_state statp;

        net = va_arg(ap, uint32_t);
        net_type = va_arg(ap, int);
        nptr = va_arg(ap, struct netent *);
        buffer = va_arg(ap, char *);
        buflen = va_arg(ap, size_t);
        errnop = va_arg(ap, int *);
        h_errnop = va_arg(ap, int *);

        statp = __res_state();
        if ((statp->options & RES_INIT) == 0 && res_ninit(statp) == -1) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (NS_UNAVAIL);
        }

        if ((ned = __netent_data_init()) == NULL) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (NS_UNAVAIL);
        }

        *((struct netent **)rval) = NULL;

        if (net_type != AF_INET) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (NS_UNAVAIL);
        }

        for (nn = 4, net2 = net; net2; net2 >>= 8)
                netbr[--nn] = net2 & 0xff;
        switch (nn) {
        case 4:         /* net was all-zero i.e. 0.0.0.0 */
                sprintf(qbuf, "0.0.0.0.in-addr.arpa");
                break;
        case 3:         /* Class A */
                sprintf(qbuf, "0.0.0.%u.in-addr.arpa", netbr[3]);
                break;
        case 2:         /* Class B */
                sprintf(qbuf, "0.0.%u.%u.in-addr.arpa", netbr[3], netbr[2]);
                break;
        case 1:         /* Class C */
                sprintf(qbuf, "0.%u.%u.%u.in-addr.arpa", netbr[3], netbr[2],
                    netbr[1]);
                break;
        case 0:         /* Class D - E */
                sprintf(qbuf, "%u.%u.%u.%u.in-addr.arpa", netbr[3], netbr[2],
                    netbr[1], netbr[0]);
                break;
        }
        if ((buf = malloc(sizeof(*buf))) == NULL) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (NS_NOTFOUND);
        }
        anslen = res_nquery(statp, qbuf, C_IN, T_PTR, (u_char *)buf,
            sizeof(*buf));
        if (anslen < 0) {
                free(buf);
#ifdef DEBUG
                if (statp->options & RES_DEBUG)
                        printf("res_nsearch failed\n");
#endif
                *h_errnop = statp->res_h_errno;
                return (NS_UNAVAIL);
        } else if (anslen > sizeof(*buf)) {
                free(buf);
#ifdef DEBUG
                if (statp->options & RES_DEBUG)
                        printf("res_nsearch static buffer too small\n");
#endif
                *h_errnop = statp->res_h_errno;
                return (NS_UNAVAIL);
        }
        error = getnetanswer(buf, anslen, BYADDR, &ne, ned, statp);
        free(buf);
        if (error == 0) {
                /* Strip trailing zeros */
                while ((net & 0xff) == 0 && net != 0)
                        net >>= 8;
                ne.n_net = net;
                if (__copy_netent(&ne, nptr, buffer, buflen) != 0) {
                        *errnop = errno;
                        RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                        *h_errnop = statp->res_h_errno;
                        return (NS_RETURN);
                }
                *((struct netent **)rval) = nptr;
                return (NS_SUCCESS);
        }
        *h_errnop = statp->res_h_errno;
        return (NS_NOTFOUND);
}

int
_dns_getnetbyname(void *rval, void *cb_data, va_list ap)
{
        const char *net;
        char *buffer;
        size_t buflen;
        int *errnop, *h_errnop;
        struct netent *nptr, ne;
        struct netent_data *ned;
        int anslen, error;
        querybuf *buf;
        char qbuf[MAXDNAME];
        res_state statp;

        net = va_arg(ap, const char *);
        nptr = va_arg(ap, struct netent *);
        buffer = va_arg(ap, char *);
        buflen = va_arg(ap, size_t);
        errnop = va_arg(ap, int *);
        h_errnop = va_arg(ap, int *);

        statp = __res_state();
        if ((statp->options & RES_INIT) == 0 && res_ninit(statp) == -1) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (NS_UNAVAIL);
        }
        if ((ned = __netent_data_init()) == NULL) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (NS_UNAVAIL);
        }
        if ((buf = malloc(sizeof(*buf))) == NULL) {
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (NS_NOTFOUND);
        }

        *((struct netent **)rval) = NULL;

        strncpy(qbuf, net, sizeof(qbuf) - 1);
        qbuf[sizeof(qbuf) - 1] = '\0';
        anslen = res_nsearch(statp, qbuf, C_IN, T_PTR, (u_char *)buf,
            sizeof(*buf));
        if (anslen < 0) {
                free(buf);
#ifdef DEBUG
                if (statp->options & RES_DEBUG)
                        printf("res_nsearch failed\n");
#endif
                return (NS_UNAVAIL);
        } else if (anslen > sizeof(*buf)) {
                free(buf);
#ifdef DEBUG
                if (statp->options & RES_DEBUG)
                        printf("res_search static buffer too small\n");
#endif
                return (NS_UNAVAIL);
        }
        error = getnetanswer(buf, anslen, BYNAME, &ne, ned, statp);
        free(buf);
        if (error != 0) {
                *h_errnop = statp->res_h_errno;
                return (NS_NOTFOUND);
        }
        if (__copy_netent(&ne, nptr, buffer, buflen) != 0) {
                *errnop = errno;
                RES_SET_H_ERRNO(statp, NETDB_INTERNAL);
                *h_errnop = statp->res_h_errno;
                return (NS_RETURN);
        }
        *((struct netent **)rval) = nptr;
        return (NS_SUCCESS);
}

void
_setnetdnsent(int stayopen)
{
        res_state statp;

        statp = __res_state();
        if ((statp->options & RES_INIT) == 0 && res_ninit(statp) == -1)
                return;
        if (stayopen)
                statp->options |= RES_STAYOPEN | RES_USEVC;
}

void
_endnetdnsent(void)
{
        res_state statp;

        statp = __res_state();
        statp->options &= ~(RES_STAYOPEN | RES_USEVC);
        res_nclose(statp);
}