/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 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.
 */

/* Import. */

#include "port_before.h"

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/time.h>

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

#include <errno.h>
#include <limits.h>
#include <netdb.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <isc/list.h>

#include "port_after.h"

#include <resolv.h>

/* Data structures. */

typedef struct rr_a {
        LINK(struct rr_a)       link;
        union res_sockaddr_union addr;
} rr_a;
typedef LIST(rr_a) rrset_a;

typedef struct rr_ns {
        LINK(struct rr_ns)      link;
        const char *            name;
        unsigned int            flags;
        rrset_a                 addrs;
} rr_ns;
typedef LIST(rr_ns) rrset_ns;

#define RR_NS_HAVE_V4           0x01
#define RR_NS_HAVE_V6           0x02

/* Forward. */

static int      satisfy(res_state, const char *, rrset_ns *,
                        union res_sockaddr_union *, int);
static int      add_addrs(res_state, rr_ns *,
                          union res_sockaddr_union *, int);
static int      get_soa(res_state, const char *, ns_class, int,
                        char *, size_t, char *, size_t,
                        rrset_ns *);
static int      get_ns(res_state, const char *, ns_class, int, rrset_ns *);
static int      get_glue(res_state, ns_class, int, rrset_ns *);
static int      save_ns(res_state, ns_msg *, ns_sect,
                        const char *, ns_class, int, rrset_ns *);
static int      save_a(res_state, ns_msg *, ns_sect,
                       const char *, ns_class, int, rr_ns *);
static void     free_nsrrset(rrset_ns *);
static void     free_nsrr(rrset_ns *, rr_ns *);
static rr_ns *  find_ns(rrset_ns *, const char *);
static int      do_query(res_state, const char *, ns_class, ns_type,
                         u_char *, ns_msg *);
static void     res_dprintf(const char *, ...) ISC_FORMAT_PRINTF(1, 2);

/* Macros. */

#define DPRINTF(x) do {\
                int save_errno = errno; \
                if ((statp->options & RES_DEBUG) != 0U) res_dprintf x; \
                errno = save_errno; \
        } while (0)

/* Public. */

/*%
 *      find enclosing zone for a <dname,class>, and some server addresses
 *
 * parameters:
 *\li   res - resolver context to work within (is modified)
 *\li   dname - domain name whose enclosing zone is desired
 *\li   class - class of dname (and its enclosing zone)
 *\li   zname - found zone name
 *\li   zsize - allocated size of zname
 *\li   addrs - found server addresses
 *\li   naddrs - max number of addrs
 *
 * return values:
 *\li   < 0 - an error occurred (check errno)
 *\li   = 0 - zname is now valid, but addrs[] wasn't changed
 *\li   > 0 - zname is now valid, and return value is number of addrs[] found
 *
 * notes:
 *\li   this function calls res_nsend() which means it depends on correctly
 *      functioning recursive nameservers (usually defined in /etc/resolv.conf
 *      or its local equivilent).
 *
 *\li   we start by asking for an SOA<dname,class>.  if we get one as an
 *      answer, that just means <dname,class> is a zone top, which is fine.
 *      more than likely we'll be told to go pound sand, in the form of a
 *      negative answer.
 *
 *\li   note that we are not prepared to deal with referrals since that would
 *      only come from authority servers and our correctly functioning local
 *      recursive server would have followed the referral and got us something
 *      more definite.
 *
 *\li   if the authority section contains an SOA, this SOA should also be the
 *      closest enclosing zone, since any intermediary zone cuts would've been
 *      returned as referrals and dealt with by our correctly functioning local
 *      recursive name server.  but an SOA in the authority section should NOT
 *      match our dname (since that would have been returned in the answer
 *      section).  an authority section SOA has to be "above" our dname.
 *
 *\li   however, since authority section SOA's were once optional, it's
 *      possible that we'll have to go hunting for the enclosing SOA by
 *      ripping labels off the front of our dname -- this is known as "doing
 *      it the hard way."
 *
 *\li   ultimately we want some server addresses, which are ideally the ones
 *      pertaining to the SOA.MNAME, but only if there is a matching NS RR.
 *      so the second phase (after we find an SOA) is to go looking for the
 *      NS RRset for that SOA's zone.
 *
 *\li   no answer section processed by this code is allowed to contain CNAME
 *      or DNAME RR's.  for the SOA query this means we strip a label and
 *      keep going.  for the NS and A queries this means we just give up.
 */

int
res_findzonecut(res_state statp, const char *dname, ns_class class, int opts,
                char *zname, size_t zsize, struct in_addr *addrs, int naddrs)
{
        int result, i;
        union res_sockaddr_union *u;


        opts |= RES_IPV4ONLY;
        opts &= ~RES_IPV6ONLY;

        u = calloc(naddrs, sizeof(*u));
        if (u == NULL)
                return(-1);

        result = res_findzonecut2(statp, dname, class, opts, zname, zsize,
                                  u, naddrs);

        for (i = 0; i < result; i++) {
                addrs[i] = u[i].sin.sin_addr;
        }
        free(u);
        return (result);
}

int
res_findzonecut2(res_state statp, const char *dname, ns_class class, int opts,
                 char *zname, size_t zsize, union res_sockaddr_union *addrs,
                 int naddrs)
{
        char mname[NS_MAXDNAME];
        u_long save_pfcode;
        rrset_ns nsrrs;
        int n;

        DPRINTF(("START dname='%s' class=%s, zsize=%ld, naddrs=%d",
                 dname, p_class(class), (long)zsize, naddrs));
        save_pfcode = statp->pfcode;
        statp->pfcode |= RES_PRF_HEAD2 | RES_PRF_HEAD1 | RES_PRF_HEADX |
                         RES_PRF_QUES | RES_PRF_ANS |
                         RES_PRF_AUTH | RES_PRF_ADD;
        INIT_LIST(nsrrs);

        DPRINTF(("get the soa, and see if it has enough glue"));
        if ((n = get_soa(statp, dname, class, opts, zname, zsize,
                         mname, sizeof mname, &nsrrs)) < 0 ||
            ((opts & RES_EXHAUSTIVE) == 0 &&
             (n = satisfy(statp, mname, &nsrrs, addrs, naddrs)) > 0))
                goto done;

        DPRINTF(("get the ns rrset and see if it has enough glue"));
        if ((n = get_ns(statp, zname, class, opts, &nsrrs)) < 0 ||
            ((opts & RES_EXHAUSTIVE) == 0 &&
             (n = satisfy(statp, mname, &nsrrs, addrs, naddrs)) > 0))
                goto done;

        DPRINTF(("get the missing glue and see if it's finally enough"));
        if ((n = get_glue(statp, class, opts, &nsrrs)) >= 0)
                n = satisfy(statp, mname, &nsrrs, addrs, naddrs);

 done:
        DPRINTF(("FINISH n=%d (%s)", n, (n < 0) ? strerror(errno) : "OK"));
        free_nsrrset(&nsrrs);
        statp->pfcode = save_pfcode;
        return (n);
}

/* Private. */

static int
satisfy(res_state statp, const char *mname, rrset_ns *nsrrsp,
        union res_sockaddr_union *addrs, int naddrs)
{
        rr_ns *nsrr;
        int n, x;

        n = 0;
        nsrr = find_ns(nsrrsp, mname);
        if (nsrr != NULL) {
                x = add_addrs(statp, nsrr, addrs, naddrs);
                addrs += x;
                naddrs -= x;
                n += x;
        }
        for (nsrr = HEAD(*nsrrsp);
             nsrr != NULL && naddrs > 0;
             nsrr = NEXT(nsrr, link))
                if (ns_samename(nsrr->name, mname) != 1) {
                        x = add_addrs(statp, nsrr, addrs, naddrs);
                        addrs += x;
                        naddrs -= x;
                        n += x;
                }
        DPRINTF(("satisfy(%s): %d", mname, n));
        return (n);
}

static int
add_addrs(res_state statp, rr_ns *nsrr,
          union res_sockaddr_union *addrs, int naddrs)
{
        rr_a *arr;
        int n = 0;

        for (arr = HEAD(nsrr->addrs); arr != NULL; arr = NEXT(arr, link)) {
                if (naddrs <= 0)
                        return (0);
                *addrs++ = arr->addr;
                naddrs--;
                n++;
        }
        DPRINTF(("add_addrs: %d", n));
        return (n);
}

static int
get_soa(res_state statp, const char *dname, ns_class class, int opts,
        char *zname, size_t zsize, char *mname, size_t msize,
        rrset_ns *nsrrsp)
{
        char tname[NS_MAXDNAME];
        u_char *resp = NULL;
        int n, i, ancount, nscount;
        ns_sect sect;
        ns_msg msg;
        u_int rcode;

        /*
         * Find closest enclosing SOA, even if it's for the root zone.
         */

        /* First canonicalize dname (exactly one unescaped trailing "."). */
        if (ns_makecanon(dname, tname, sizeof tname) < 0)
                goto cleanup;
        dname = tname;

        resp = malloc(NS_MAXMSG);
        if (resp == NULL)
                goto cleanup;

        /* Now grovel the subdomains, hunting for an SOA answer or auth. */
        for (;;) {
                /* Leading or inter-label '.' are skipped here. */
                while (*dname == '.')
                        dname++;

                /* Is there an SOA? */
                n = do_query(statp, dname, class, ns_t_soa, resp, &msg);
                if (n < 0) {
                        DPRINTF(("get_soa: do_query('%s', %s) failed (%d)",
                                 dname, p_class(class), n));
                        goto cleanup;
                }
                if (n > 0) {
                        DPRINTF(("get_soa: CNAME or DNAME found"));
                        sect = ns_s_max, n = 0;
                } else {
                        rcode = ns_msg_getflag(msg, ns_f_rcode);
                        ancount = ns_msg_count(msg, ns_s_an);
                        nscount = ns_msg_count(msg, ns_s_ns);
                        if (ancount > 0 && rcode == ns_r_noerror)
                                sect = ns_s_an, n = ancount;
                        else if (nscount > 0)
                                sect = ns_s_ns, n = nscount;
                        else
                                sect = ns_s_max, n = 0;
                }
                for (i = 0; i < n; i++) {
                        const char *t;
                        const u_char *rdata;
                        ns_rr rr;

                        if (ns_parserr(&msg, sect, i, &rr) < 0) {
                                DPRINTF(("get_soa: ns_parserr(%s, %d) failed",
                                         p_section(sect, ns_o_query), i));
                                goto cleanup;
                        }
                        if (ns_rr_type(rr) == ns_t_cname ||
                            ns_rr_type(rr) == ns_t_dname)
                                break;
                        if (ns_rr_type(rr) != ns_t_soa ||
                            ns_rr_class(rr) != class)
                                continue;
                        t = ns_rr_name(rr);
                        switch (sect) {
                        case ns_s_an:
                                if (ns_samedomain(dname, t) == 0) {
                                        DPRINTF(
                                    ("get_soa: ns_samedomain('%s', '%s') == 0",
                                                dname, t)
                                                );
                                        errno = EPROTOTYPE;
                                        goto cleanup;
                                }
                                break;
                        case ns_s_ns:
                                if (ns_samename(dname, t) == 1 ||
                                    ns_samedomain(dname, t) == 0) {
                                        DPRINTF(
                       ("get_soa: ns_samename() || !ns_samedomain('%s', '%s')",
                                                dname, t)
                                                );
                                        errno = EPROTOTYPE;
                                        goto cleanup;
                                }
                                break;
                        default:
                                abort();
                        }
                        if (strlen(t) + 1 > zsize) {
                                DPRINTF(("get_soa: zname(%lu) too small (%lu)",
                                         (unsigned long)zsize,
                                         (unsigned long)strlen(t) + 1));
                                errno = EMSGSIZE;
                                goto cleanup;
                        }
                        strcpy(zname, t);
                        rdata = ns_rr_rdata(rr);
                        if (ns_name_uncompress(resp, ns_msg_end(msg), rdata,
                                               mname, msize) < 0) {
                                DPRINTF(("get_soa: ns_name_uncompress failed")
                                        );
                                goto cleanup;
                        }
                        if (save_ns(statp, &msg, ns_s_ns,
                                    zname, class, opts, nsrrsp) < 0) {
                                DPRINTF(("get_soa: save_ns failed"));
                                goto cleanup;
                        }
                        free(resp);
                        return (0);
                }

                /* If we're out of labels, then not even "." has an SOA! */
                if (*dname == '\0')
                        break;

                /* Find label-terminating "."; top of loop will skip it. */
                while (*dname != '.') {
                        if (*dname == '\\')
                                if (*++dname == '\0') {
                                        errno = EMSGSIZE;
                                        goto cleanup;
                                }
                        dname++;
                }
        }
        DPRINTF(("get_soa: out of labels"));
        errno = EDESTADDRREQ;
 cleanup:
        if (resp != NULL)
                free(resp);
        return (-1);
}

static int
get_ns(res_state statp, const char *zname, ns_class class, int opts,
      rrset_ns *nsrrsp)
{
        u_char *resp;
        ns_msg msg;
        int n;

        resp = malloc(NS_MAXMSG);
        if (resp == NULL)
                return (-1);

        /* Go and get the NS RRs for this zone. */
        n = do_query(statp, zname, class, ns_t_ns, resp, &msg);
        if (n != 0) {
                DPRINTF(("get_ns: do_query('%s', %s) failed (%d)",
                         zname, p_class(class), n));
                free(resp);
                return (-1);
        }

        /* Remember the NS RRs and associated A RRs that came back. */
        if (save_ns(statp, &msg, ns_s_an, zname, class, opts, nsrrsp) < 0) {
                DPRINTF(("get_ns save_ns('%s', %s) failed",
                         zname, p_class(class)));
                free(resp);
                return (-1);
        }

        free(resp);
        return (0);
}

static int
get_glue(res_state statp, ns_class class, int opts, rrset_ns *nsrrsp) {
        rr_ns *nsrr, *nsrr_n;
        u_char *resp;

        resp = malloc(NS_MAXMSG);
        if (resp == NULL)
                return(-1);

        /* Go and get the A RRs for each empty NS RR on our list. */
        for (nsrr = HEAD(*nsrrsp); nsrr != NULL; nsrr = nsrr_n) {
                ns_msg msg;
                int n;

                nsrr_n = NEXT(nsrr, link);

                if ((nsrr->flags & RR_NS_HAVE_V4) == 0) {
                        n = do_query(statp, nsrr->name, class, ns_t_a,
                                     resp, &msg);
                        if (n < 0) {
                                DPRINTF(
                                       ("get_glue: do_query('%s', %s') failed",
                                        nsrr->name, p_class(class)));
                                goto cleanup;
                        }
                        if (n > 0) {
                                DPRINTF((
                        "get_glue: do_query('%s', %s') CNAME or DNAME found",
                                         nsrr->name, p_class(class)));
                        }
                        if (save_a(statp, &msg, ns_s_an, nsrr->name, class,
                                   opts, nsrr) < 0) {
                                DPRINTF(("get_glue: save_r('%s', %s) failed",
                                         nsrr->name, p_class(class)));
                                goto cleanup;
                        }
                }

                if ((nsrr->flags & RR_NS_HAVE_V6) == 0) {
                        n = do_query(statp, nsrr->name, class, ns_t_aaaa,
                                     resp, &msg);
                        if (n < 0) {
                                DPRINTF(
                                       ("get_glue: do_query('%s', %s') failed",
                                        nsrr->name, p_class(class)));
                                goto cleanup;
                        }
                        if (n > 0) {
                                DPRINTF((
                        "get_glue: do_query('%s', %s') CNAME or DNAME found",
                                         nsrr->name, p_class(class)));
                        }
                        if (save_a(statp, &msg, ns_s_an, nsrr->name, class,
                                   opts, nsrr) < 0) {
                                DPRINTF(("get_glue: save_r('%s', %s) failed",
                                         nsrr->name, p_class(class)));
                                goto cleanup;
                        }
                }

                /* If it's still empty, it's just chaff. */
                if (EMPTY(nsrr->addrs)) {
                        DPRINTF(("get_glue: removing empty '%s' NS",
                                 nsrr->name));
                        free_nsrr(nsrrsp, nsrr);
                }
        }
        free(resp);
        return (0);

 cleanup:
        free(resp);
        return (-1);
}

static int
save_ns(res_state statp, ns_msg *msg, ns_sect sect,
        const char *owner, ns_class class, int opts,
        rrset_ns *nsrrsp)
{
        int i;

        for (i = 0; i < ns_msg_count(*msg, sect); i++) {
                char tname[MAXDNAME];
                const u_char *rdata;
                rr_ns *nsrr;
                ns_rr rr;

                if (ns_parserr(msg, sect, i, &rr) < 0) {
                        DPRINTF(("save_ns: ns_parserr(%s, %d) failed",
                                 p_section(sect, ns_o_query), i));
                        return (-1);
                }
                if (ns_rr_type(rr) != ns_t_ns ||
                    ns_rr_class(rr) != class ||
                    ns_samename(ns_rr_name(rr), owner) != 1)
                        continue;
                nsrr = find_ns(nsrrsp, ns_rr_name(rr));
                if (nsrr == NULL) {
                        nsrr = malloc(sizeof *nsrr);
                        if (nsrr == NULL) {
                                DPRINTF(("save_ns: malloc failed"));
                                return (-1);
                        }
                        rdata = ns_rr_rdata(rr);
                        if (ns_name_uncompress(ns_msg_base(*msg),
                                               ns_msg_end(*msg), rdata,
                                               tname, sizeof tname) < 0) {
                                DPRINTF(("save_ns: ns_name_uncompress failed")
                                        );
                                free(nsrr);
                                return (-1);
                        }
                        nsrr->name = strdup(tname);
                        if (nsrr->name == NULL) {
                                DPRINTF(("save_ns: strdup failed"));
                                free(nsrr);
                                return (-1);
                        }
                        INIT_LINK(nsrr, link);
                        INIT_LIST(nsrr->addrs);
                        nsrr->flags = 0;
                        APPEND(*nsrrsp, nsrr, link);
                }
                if (save_a(statp, msg, ns_s_ar,
                           nsrr->name, class, opts, nsrr) < 0) {
                        DPRINTF(("save_ns: save_r('%s', %s) failed",
                                 nsrr->name, p_class(class)));
                        return (-1);
                }
        }
        return (0);
}

static int
save_a(res_state statp, ns_msg *msg, ns_sect sect,
       const char *owner, ns_class class, int opts,
       rr_ns *nsrr)
{
        int i;

        for (i = 0; i < ns_msg_count(*msg, sect); i++) {
                ns_rr rr;
                rr_a *arr;

                if (ns_parserr(msg, sect, i, &rr) < 0) {
                        DPRINTF(("save_a: ns_parserr(%s, %d) failed",
                                 p_section(sect, ns_o_query), i));
                        return (-1);
                }
                if ((ns_rr_type(rr) != ns_t_a &&
                     ns_rr_type(rr) != ns_t_aaaa) ||
                    ns_rr_class(rr) != class ||
                    ns_samename(ns_rr_name(rr), owner) != 1 ||
                    ns_rr_rdlen(rr) != NS_INADDRSZ)
                        continue;
                if ((opts & RES_IPV6ONLY) != 0 && ns_rr_type(rr) != ns_t_aaaa)
                        continue;
                if ((opts & RES_IPV4ONLY) != 0 && ns_rr_type(rr) != ns_t_a)
                        continue;
                arr = malloc(sizeof *arr);
                if (arr == NULL) {
                        DPRINTF(("save_a: malloc failed"));
                        return (-1);
                }
                INIT_LINK(arr, link);
                memset(&arr->addr, 0, sizeof(arr->addr));
                switch (ns_rr_type(rr)) {
                case ns_t_a:
                        arr->addr.sin.sin_family = AF_INET;
#ifdef HAVE_SA_LEN
                        arr->addr.sin.sin_len = sizeof(arr->addr.sin);
#endif
                        memcpy(&arr->addr.sin.sin_addr, ns_rr_rdata(rr),
                               NS_INADDRSZ);
                        arr->addr.sin.sin_port = htons(NAMESERVER_PORT);
                        nsrr->flags |= RR_NS_HAVE_V4;
                        break;
                case ns_t_aaaa:
                        arr->addr.sin6.sin6_family = AF_INET6;
#ifdef HAVE_SA_LEN
                        arr->addr.sin6.sin6_len = sizeof(arr->addr.sin6);
#endif
                        memcpy(&arr->addr.sin6.sin6_addr, ns_rr_rdata(rr), 16);
                        arr->addr.sin.sin_port = htons(NAMESERVER_PORT);
                        nsrr->flags |= RR_NS_HAVE_V6;
                        break;
                default:
                        abort();
                }
                APPEND(nsrr->addrs, arr, link);
        }
        return (0);
}

static void
free_nsrrset(rrset_ns *nsrrsp) {
        rr_ns *nsrr;

        while ((nsrr = HEAD(*nsrrsp)) != NULL)
                free_nsrr(nsrrsp, nsrr);
}

static void
free_nsrr(rrset_ns *nsrrsp, rr_ns *nsrr) {
        rr_a *arr;
        char *tmp;

        while ((arr = HEAD(nsrr->addrs)) != NULL) {
                UNLINK(nsrr->addrs, arr, link);
                free(arr);
        }
        DE_CONST(nsrr->name, tmp);
        free(tmp);
        UNLINK(*nsrrsp, nsrr, link);
        free(nsrr);
}

static rr_ns *
find_ns(rrset_ns *nsrrsp, const char *dname) {
        rr_ns *nsrr;

        for (nsrr = HEAD(*nsrrsp); nsrr != NULL; nsrr = NEXT(nsrr, link))
                if (ns_samename(nsrr->name, dname) == 1)
                        return (nsrr);
        return (NULL);
}

static int
do_query(res_state statp, const char *dname, ns_class class, ns_type qtype,
         u_char *resp, ns_msg *msg)
{
        u_char req[NS_PACKETSZ];
        int i, n;

        n = res_nmkquery(statp, ns_o_query, dname, class, qtype,
                         NULL, 0, NULL, req, NS_PACKETSZ);
        if (n < 0) {
                DPRINTF(("do_query: res_nmkquery failed"));
                return (-1);
        }
        n = res_nsend(statp, req, n, resp, NS_MAXMSG);
        if (n < 0) {
                DPRINTF(("do_query: res_nsend failed"));
                return (-1);
        }
        if (n == 0) {
                DPRINTF(("do_query: res_nsend returned 0"));
                errno = EMSGSIZE;
                return (-1);
        }
        if (ns_initparse(resp, n, msg) < 0) {
                DPRINTF(("do_query: ns_initparse failed"));
                return (-1);
        }
        n = 0;
        for (i = 0; i < ns_msg_count(*msg, ns_s_an); i++) {
                ns_rr rr;

                if (ns_parserr(msg, ns_s_an, i, &rr) < 0) {
                        DPRINTF(("do_query: ns_parserr failed"));
                        return (-1);
                }
                n += (ns_rr_class(rr) == class &&
                      (ns_rr_type(rr) == ns_t_cname ||
                       ns_rr_type(rr) == ns_t_dname));
        }
        return (n);
}

static void
res_dprintf(const char *fmt, ...) {
        va_list ap;

        va_start(ap, fmt);
        fputs(";; res_findzonecut: ", stderr);
        vfprintf(stderr, fmt, ap);
        fputc('\n', stderr);
        va_end(ap);
}

/*! \file */