/* $OpenBSD: getrrsetbyname.c,v 1.11 2007/10/11 18:36:41 jakob Exp $ */

/*
 * Copyright (c) 2001 Jakob Schlyter. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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) 1999-2001 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.
 */

/* OPENBSD ORIGINAL: lib/libc/net/getrrsetbyname.c */

#include "includes.h"

#if !defined (HAVE_GETRRSETBYNAME) && !defined (HAVE_LDNS)

#include <stdlib.h>
#include <string.h>

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

#include "getrrsetbyname.h"

#if defined(HAVE_DECL_H_ERRNO) && !HAVE_DECL_H_ERRNO
extern int h_errno;
#endif

/* We don't need multithread support here */
#ifdef _THREAD_PRIVATE
# undef _THREAD_PRIVATE
#endif
#define _THREAD_PRIVATE(a,b,c) (c)

#ifndef HAVE__RES_EXTERN
struct __res_state _res;
#endif

/* Necessary functions and macros */

/*
 * Inline versions of get/put short/long.  Pointer is advanced.
 *
 * These macros demonstrate the property of C whereby it can be
 * portable or it can be elegant but rarely both.
 */

#ifndef INT32SZ
# define INT32SZ        4
#endif
#ifndef INT16SZ
# define INT16SZ        2
#endif

#ifndef GETSHORT
#define GETSHORT(s, cp) { \
        u_char *t_cp = (u_char *)(cp); \
        (s) = ((u_int16_t)t_cp[0] << 8) \
            | ((u_int16_t)t_cp[1]) \
            ; \
        (cp) += INT16SZ; \
}
#endif

#ifndef GETLONG
#define GETLONG(l, cp) { \
        u_char *t_cp = (u_char *)(cp); \
        (l) = ((u_int32_t)t_cp[0] << 24) \
            | ((u_int32_t)t_cp[1] << 16) \
            | ((u_int32_t)t_cp[2] << 8) \
            | ((u_int32_t)t_cp[3]) \
            ; \
        (cp) += INT32SZ; \
}
#endif

/*
 * If the system doesn't have _getshort/_getlong or that are not exactly what
 * we need then use local replacements, avoiding name collisions.
 */
#if !defined(HAVE__GETSHORT) || !defined(HAVE__GETLONG) || \
    !defined(HAVE_DECL__GETSHORT) || HAVE_DECL__GETSHORT == 0 || \
    !defined(HAVE_DECL__GETLONG) || HAVE_DECL__GETLONG == 0
# ifdef _getshort
#  undef _getshort
# endif
# ifdef _getlong
#  undef _getlong
# endif
# define _getshort(x) (_ssh_compat_getshort(x))
# define _getlong(x) (_ssh_compat_getlong(x))
/*
 * Routines to insert/extract short/long's.
 */
static u_int16_t
_getshort(const u_char *msgp)
{
        u_int16_t u;

        GETSHORT(u, msgp);
        return (u);
}

static u_int32_t
_getlong(const u_char *msgp)
{
        u_int32_t u;

        GETLONG(u, msgp);
        return (u);
}
#endif /* missing _getshort/_getlong */

/* ************** */

#define ANSWER_BUFFER_SIZE 0xffff

struct dns_query {
        char                    *name;
        u_int16_t               type;
        u_int16_t               class;
        struct dns_query        *next;
};

struct dns_rr {
        char                    *name;
        u_int16_t               type;
        u_int16_t               class;
        u_int16_t               ttl;
        u_int16_t               size;
        void                    *rdata;
        struct dns_rr           *next;
};

struct dns_response {
        HEADER                  header;
        struct dns_query        *query;
        struct dns_rr           *answer;
        struct dns_rr           *authority;
        struct dns_rr           *additional;
};

static struct dns_response *parse_dns_response(const u_char *, int);
static struct dns_query *parse_dns_qsection(const u_char *, int,
    const u_char **, int);
static struct dns_rr *parse_dns_rrsection(const u_char *, int, const u_char **,
    int);

static void free_dns_query(struct dns_query *);
static void free_dns_rr(struct dns_rr *);
static void free_dns_response(struct dns_response *);

static int count_dns_rr(struct dns_rr *, u_int16_t, u_int16_t);

int
getrrsetbyname(const char *hostname, unsigned int rdclass,
    unsigned int rdtype, unsigned int flags,
    struct rrsetinfo **res)
{
        struct __res_state *_resp = _THREAD_PRIVATE(_res, _res, &_res);
        int result;
        struct rrsetinfo *rrset = NULL;
        struct dns_response *response = NULL;
        struct dns_rr *rr;
        struct rdatainfo *rdata;
        int length;
        unsigned int index_ans, index_sig;
        u_char answer[ANSWER_BUFFER_SIZE];

        /* check for invalid class and type */
        if (rdclass > 0xffff || rdtype > 0xffff) {
                result = ERRSET_INVAL;
                goto fail;
        }

        /* don't allow queries of class or type ANY */
        if (rdclass == 0xff || rdtype == 0xff) {
                result = ERRSET_INVAL;
                goto fail;
        }

        /* don't allow flags yet, unimplemented */
        if (flags) {
                result = ERRSET_INVAL;
                goto fail;
        }

        /* initialize resolver */
        if ((_resp->options & RES_INIT) == 0 && res_init() == -1) {
                result = ERRSET_FAIL;
                goto fail;
        }

#ifdef DEBUG
        _resp->options |= RES_DEBUG;
#endif /* DEBUG */

#ifdef RES_USE_DNSSEC
        /* turn on DNSSEC if EDNS0 is configured */
        if (_resp->options & RES_USE_EDNS0)
                _resp->options |= RES_USE_DNSSEC;
#endif /* RES_USE_DNSEC */

        /* make query */
        length = res_query(hostname, (signed int) rdclass, (signed int) rdtype,
            answer, sizeof(answer));
        if (length < 0) {
                switch(h_errno) {
                case HOST_NOT_FOUND:
                        result = ERRSET_NONAME;
                        goto fail;
                case NO_DATA:
                        result = ERRSET_NODATA;
                        goto fail;
                default:
                        result = ERRSET_FAIL;
                        goto fail;
                }
        }

        /* parse result */
        response = parse_dns_response(answer, length);
        if (response == NULL) {
                result = ERRSET_FAIL;
                goto fail;
        }

        if (response->header.qdcount != 1) {
                result = ERRSET_FAIL;
                goto fail;
        }

        /* initialize rrset */
        rrset = calloc(1, sizeof(struct rrsetinfo));
        if (rrset == NULL) {
                result = ERRSET_NOMEMORY;
                goto fail;
        }
        rrset->rri_rdclass = response->query->class;
        rrset->rri_rdtype = response->query->type;
        rrset->rri_ttl = response->answer->ttl;
        rrset->rri_nrdatas = response->header.ancount;

#ifdef HAVE_HEADER_AD
        /* check for authenticated data */
        if (response->header.ad == 1)
                rrset->rri_flags |= RRSET_VALIDATED;
#endif

        /* copy name from answer section */
        rrset->rri_name = strdup(response->answer->name);
        if (rrset->rri_name == NULL) {
                result = ERRSET_NOMEMORY;
                goto fail;
        }

        /* count answers */
        rrset->rri_nrdatas = count_dns_rr(response->answer, rrset->rri_rdclass,
            rrset->rri_rdtype);
        rrset->rri_nsigs = count_dns_rr(response->answer, rrset->rri_rdclass,
            T_RRSIG);

        /* allocate memory for answers */
        rrset->rri_rdatas = calloc(rrset->rri_nrdatas,
            sizeof(struct rdatainfo));
        if (rrset->rri_rdatas == NULL) {
                result = ERRSET_NOMEMORY;
                goto fail;
        }

        /* allocate memory for signatures */
        if (rrset->rri_nsigs > 0) {
                rrset->rri_sigs = calloc(rrset->rri_nsigs, sizeof(struct rdatainfo));
                if (rrset->rri_sigs == NULL) {
                        result = ERRSET_NOMEMORY;
                        goto fail;
                }
        }

        /* copy answers & signatures */
        for (rr = response->answer, index_ans = 0, index_sig = 0;
            rr; rr = rr->next) {

                rdata = NULL;

                if (rr->class == rrset->rri_rdclass &&
                    rr->type  == rrset->rri_rdtype)
                        rdata = &rrset->rri_rdatas[index_ans++];

                if (rr->class == rrset->rri_rdclass &&
                    rr->type  == T_RRSIG)
                        rdata = &rrset->rri_sigs[index_sig++];

                if (rdata) {
                        rdata->rdi_length = rr->size;
                        if (rr->size != 0) {
                                rdata->rdi_data   = malloc(rr->size);
                                if (rdata->rdi_data == NULL) {
                                        result = ERRSET_NOMEMORY;
                                        goto fail;
                                }
                                memcpy(rdata->rdi_data, rr->rdata, rr->size);
                        }
                }
        }
        free_dns_response(response);

        *res = rrset;
        return (ERRSET_SUCCESS);

fail:
        if (rrset != NULL)
                freerrset(rrset);
        if (response != NULL)
                free_dns_response(response);
        return (result);
}

void
freerrset(struct rrsetinfo *rrset)
{
        u_int16_t i;

        if (rrset == NULL)
                return;

        if (rrset->rri_rdatas) {
                for (i = 0; i < rrset->rri_nrdatas; i++) {
                        if (rrset->rri_rdatas[i].rdi_data == NULL)
                                break;
                        free(rrset->rri_rdatas[i].rdi_data);
                }
                free(rrset->rri_rdatas);
        }

        if (rrset->rri_sigs) {
                for (i = 0; i < rrset->rri_nsigs; i++) {
                        if (rrset->rri_sigs[i].rdi_data == NULL)
                                break;
                        free(rrset->rri_sigs[i].rdi_data);
                }
                free(rrset->rri_sigs);
        }

        if (rrset->rri_name)
                free(rrset->rri_name);
        free(rrset);
}

/*
 * DNS response parsing routines
 */
static struct dns_response *
parse_dns_response(const u_char *answer, int size)
{
        struct dns_response *resp;
        const u_char *cp;

        if (size < HFIXEDSZ)
                return (NULL);

        /* allocate memory for the response */
        resp = calloc(1, sizeof(*resp));
        if (resp == NULL)
                return (NULL);

        /* initialize current pointer */
        cp = answer;

        /* copy header */
        memcpy(&resp->header, cp, HFIXEDSZ);
        cp += HFIXEDSZ;

        /* fix header byte order */
        resp->header.qdcount = ntohs(resp->header.qdcount);
        resp->header.ancount = ntohs(resp->header.ancount);
        resp->header.nscount = ntohs(resp->header.nscount);
        resp->header.arcount = ntohs(resp->header.arcount);

        /* there must be at least one query */
        if (resp->header.qdcount < 1) {
                free_dns_response(resp);
                return (NULL);
        }

        /* parse query section */
        resp->query = parse_dns_qsection(answer, size, &cp,
            resp->header.qdcount);
        if (resp->header.qdcount && resp->query == NULL) {
                free_dns_response(resp);
                return (NULL);
        }

        /* parse answer section */
        resp->answer = parse_dns_rrsection(answer, size, &cp,
            resp->header.ancount);
        if (resp->header.ancount && resp->answer == NULL) {
                free_dns_response(resp);
                return (NULL);
        }

        /* parse authority section */
        resp->authority = parse_dns_rrsection(answer, size, &cp,
            resp->header.nscount);
        if (resp->header.nscount && resp->authority == NULL) {
                free_dns_response(resp);
                return (NULL);
        }

        /* parse additional section */
        resp->additional = parse_dns_rrsection(answer, size, &cp,
            resp->header.arcount);
        if (resp->header.arcount && resp->additional == NULL) {
                free_dns_response(resp);
                return (NULL);
        }

        return (resp);
}

static struct dns_query *
parse_dns_qsection(const u_char *answer, int size, const u_char **cp, int count)
{
        struct dns_query *head, *curr, *prev;
        int i, length;
        char name[MAXDNAME];

#define NEED(need) \
        do { \
                if (*cp + need > answer + size) \
                        goto fail; \
        } while (0)

        for (i = 1, head = NULL, prev = NULL; i <= count; i++, prev = curr) {
                if (*cp >= answer + size) {
 fail:
                        free_dns_query(head);
                        return (NULL);
                }
                /* allocate and initialize struct */
                curr = calloc(1, sizeof(struct dns_query));
                if (curr == NULL)
                        goto fail;
                if (head == NULL)
                        head = curr;
                if (prev != NULL)
                        prev->next = curr;

                /* name */
                length = dn_expand(answer, answer + size, *cp, name,
                    sizeof(name));
                if (length < 0) {
                        free_dns_query(head);
                        return (NULL);
                }
                curr->name = strdup(name);
                if (curr->name == NULL) {
                        free_dns_query(head);
                        return (NULL);
                }
                NEED(length);
                *cp += length;

                /* type */
                NEED(INT16SZ);
                curr->type = _getshort(*cp);
                *cp += INT16SZ;

                /* class */
                NEED(INT16SZ);
                curr->class = _getshort(*cp);
                *cp += INT16SZ;
        }
#undef NEED

        return (head);
}

static struct dns_rr *
parse_dns_rrsection(const u_char *answer, int size, const u_char **cp,
    int count)
{
        struct dns_rr *head, *curr, *prev;
        int i, length;
        char name[MAXDNAME];

#define NEED(need) \
        do { \
                if (*cp + need > answer + size) \
                        goto fail; \
        } while (0)

        for (i = 1, head = NULL, prev = NULL; i <= count; i++, prev = curr) {
                if (*cp >= answer + size) {
 fail:
                        free_dns_rr(head);
                        return (NULL);
                }

                /* allocate and initialize struct */
                curr = calloc(1, sizeof(struct dns_rr));
                if (curr == NULL)
                        goto fail;
                if (head == NULL)
                        head = curr;
                if (prev != NULL)
                        prev->next = curr;

                /* name */
                length = dn_expand(answer, answer + size, *cp, name,
                    sizeof(name));
                if (length < 0) {
                        free_dns_rr(head);
                        return (NULL);
                }
                curr->name = strdup(name);
                if (curr->name == NULL) {
                        free_dns_rr(head);
                        return (NULL);
                }
                NEED(length);
                *cp += length;

                /* type */
                NEED(INT16SZ);
                curr->type = _getshort(*cp);
                *cp += INT16SZ;

                /* class */
                NEED(INT16SZ);
                curr->class = _getshort(*cp);
                *cp += INT16SZ;

                /* ttl */
                NEED(INT32SZ);
                curr->ttl = _getlong(*cp);
                *cp += INT32SZ;

                /* rdata size */
                NEED(INT16SZ);
                curr->size = _getshort(*cp);
                *cp += INT16SZ;

                /* rdata itself */
                NEED(curr->size);
                if (curr->size != 0) {
                        if ((curr->rdata = malloc(curr->size)) == NULL) {
                                free_dns_rr(head);
                                return (NULL);
                        }
                        memcpy(curr->rdata, *cp, curr->size);
                }
                *cp += curr->size;
        }
#undef NEED

        return (head);
}

static void
free_dns_query(struct dns_query *p)
{
        if (p == NULL)
                return;

        if (p->name)
                free(p->name);
        free_dns_query(p->next);
        free(p);
}

static void
free_dns_rr(struct dns_rr *p)
{
        if (p == NULL)
                return;

        if (p->name)
                free(p->name);
        if (p->rdata)
                free(p->rdata);
        free_dns_rr(p->next);
        free(p);
}

static void
free_dns_response(struct dns_response *p)
{
        if (p == NULL)
                return;

        free_dns_query(p->query);
        free_dns_rr(p->answer);
        free_dns_rr(p->authority);
        free_dns_rr(p->additional);
        free(p);
}

static int
count_dns_rr(struct dns_rr *p, u_int16_t class, u_int16_t type)
{
        int n = 0;

        while(p) {
                if (p->class == class && p->type == type)
                        n++;
                p = p->next;
        }

        return (n);
}

#endif /*  !defined (HAVE_GETRRSETBYNAME) && !defined (HAVE_LDNS) */