/**
 *
 * /brief RR iterator over wireformat DNS packet
 */
/*
 * Copyright (c) 2013, NLnet Labs, Verisign, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * 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.
 * * Neither the names of the copyright holders 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 COPYRIGHT HOLDERS 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 Verisign, Inc. 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.
 */

#include "rr-iter.h"
#include "config.h"
#include <ctype.h>
#include "gldns/rrdef.h"

int
_getdns_dname_equal(const uint8_t *s1, const uint8_t *s2)
{
	uint8_t i;
	for (;;) {
		if (*s1 != *s2)
			return 0;
		else if (!*s1)
			return 1;
		for (i = *s1++, s2++; i > 0; i--, s1++, s2++)
			if (*s1 != *s2 && tolower((unsigned char)*s1)
			               != tolower((unsigned char)*s2))
				return 0;
	}
}

static void
rr_iter_find_nxt(_getdns_rr_iter *i)
{
	assert(i);
	assert(i->rr_type);

	i->nxt = i->pkt && i->n < GLDNS_QDCOUNT(i->pkt)
	       ? i->rr_type + 4
	       : i->rr_type + 10 > i->pkt_end
	       ? i->pkt_end
	       : i->rr_type + 10 + gldns_read_uint16(i->rr_type + 8) > i->pkt_end
	       ? i->pkt_end
	       : i->rr_type + 10 + gldns_read_uint16(i->rr_type + 8);
}

static _getdns_rr_iter *
find_rrtype(_getdns_rr_iter *i)
{
	const uint8_t *pos;

	assert(i);
	assert(i->pos);

	/* Past the last RR in the pkt */
	if (i->pkt &&
	    (size_t)GLDNS_QDCOUNT(i->pkt) + GLDNS_ANCOUNT(i->pkt) +
	            GLDNS_NSCOUNT(i->pkt) + GLDNS_ARCOUNT(i->pkt) <= i->n)
		goto done;

	for (pos = i->pos; pos + 4 < i->pkt_end; pos += *pos + 1)
		if (!*pos) {
			i->rr_type = pos + 1;
			rr_iter_find_nxt(i);
			return i;

		} else if ((*pos & 0xC0) == 0xC0) {
			if ( pos + 6 > i->pkt_end)
				break; /* No space for class */

			i->rr_type = pos + 2;
			rr_iter_find_nxt(i);
			return i;

		} else if (*pos & 0xC0)
			break; /* Unknown label type */
done:
	i->pos = NULL;
	return NULL;
}

_getdns_rr_iter *
_getdns_rr_iter_init(_getdns_rr_iter *i, const uint8_t *pkt, const size_t pkt_len)
{
	assert(i);

	if (!pkt || pkt_len < GLDNS_HEADER_SIZE + 5) {
		i->pos = NULL;
		return NULL;
	}
	i->pkt     = pkt;
	i->pkt_end = pkt + pkt_len;
	i->n       = 0;
	i->pos     = pkt + GLDNS_HEADER_SIZE;

	return find_rrtype(i);
}

_getdns_rr_iter *
_getdns_single_rr_iter_init(
    _getdns_rr_iter *i, const uint8_t *wire, const size_t wire_len)
{
	assert(i);

	if (!wire || wire_len < 5 /* name + type + class */) {
		i->pos = NULL;
		return NULL;
	}
	i->pkt     = NULL;
	i->pos     = wire;
	i->pkt_end = wire + wire_len;
	i->n       = 0;

	return find_rrtype(i);
}

_getdns_rr_iter *
_getdns_rr_iter_next(_getdns_rr_iter *i)
{
	assert(i);

	/* Already done */
	if (!i->pos)
		return NULL;

	i->n  += 1;
	i->pos = i->nxt;
	return find_rrtype(i);
}

static const uint8_t *
dname_if_or_as_decompressed(const uint8_t *pkt, const uint8_t *pkt_end,
    const uint8_t *pos, uint8_t *buf, size_t *len, size_t refs)
{
	uint16_t offset;
	const uint8_t *start;
	uint8_t *dst;

	assert(pkt_end);
	assert(pos);
	assert(buf);
	assert(len);

	if (refs > GLDNS_MAX_POINTERS)
		goto error;

	if ((*pos & 0xC0) == 0xC0) {
		if (!pkt || pos + 1 >= pkt_end)
			goto error;
		offset = gldns_read_uint16(pos) & 0x3FFF;
		if (pkt + offset >= pkt_end)
			goto error;
		return dname_if_or_as_decompressed(pkt, pkt_end, pkt + offset,
		    buf, len, refs + 1);
	}
	if (*pos & 0xC0)
		goto error;

	start = pos;
	*len  = 0;
	while (*pos) {
		if ((*pos & 0xC0) == 0xC0)
			break;

		else if (*pos & 0xC0)
			goto error;

		*len += *pos + 1;
		pos += *pos + 1;
	}
	if (!*pos) {
		*len += 1;
		return start;
	}
	dst = buf;
	for (;;) {
		if (pos > start) {
			if (dst + (pos - start) > buf + 255)
				goto error;
			(void) memcpy(dst, start, pos - start);
			dst += (pos - start);
			start = pos;
		}
		if ((*pos & 0xC0) == 0xC0) {
			if (!pkt || pos + 1 >= pkt_end)
				goto error;
			offset = gldns_read_uint16(pos) & 0x3FFF;
			if (pkt + offset >= pkt_end)
				goto error;

			start = pos = pkt + offset;
			if (++refs > 256)
				goto error;
		}
		if ((*pos & 0xC0) == 0xC0)
			continue;

		else if (*pos & 0xC0)
			goto error;

		else if (!*pos) {
			*len += 1;
			*dst = 0;
			return buf;
		}
		*len += *pos + 1;
		pos += *pos + 1;
	}
error:
	*len = 0;
	return NULL;
}

const uint8_t *
_getdns_owner_if_or_as_decompressed(_getdns_rr_iter *i,
    uint8_t *ff_bytes, size_t *len)
{
	return dname_if_or_as_decompressed(i->pkt, i->pkt_end, i->pos,
	    ff_bytes, len, 0);
}

_getdns_rrset *
_getdns_initialized_rrset_answer(_getdns_rrset_spc *query_rrset)
{
	_getdns_rrset *rrset = &query_rrset->rrset;
	uint16_t qtype = rrset->rr_type;
	size_t cname_loop_protection;

	assert(query_rrset);

	/* Follow CNAMEs */
	rrset->rr_type = GETDNS_RRTYPE_CNAME;
	for ( cname_loop_protection = MAX_CNAME_REFERRALS
	    ; cname_loop_protection > 0
	    ; cname_loop_protection-- ) {
		_getdns_rrtype_iter rr_spc, *rr;
		_getdns_rdf_iter rdf_spc, *rdf;

		if (!(rr = _getdns_rrtype_iter_init(&rr_spc, rrset)))
			break;
		if (!(rdf = _getdns_rdf_iter_init(&rdf_spc, &rr->rr_i)))
			break;
		query_rrset->name_len = sizeof(query_rrset->name_spc);
		rrset->name = _getdns_rdf_if_or_as_decompressed(
		    rdf, query_rrset->name_spc, &query_rrset->name_len);
	}
	rrset->rr_type = qtype;
	if (qtype == GETDNS_RRTYPE_CNAME &&
	    cname_loop_protection < MAX_CNAME_REFERRALS)
		return rrset; /* The CNAME was the answer */

	return _getdns_rrset_has_rrs(rrset) ? rrset : NULL;
}

_getdns_rrset *
_getdns_rrset_answer(_getdns_rrset_spc *spc, const uint8_t *pkt, size_t len)
{
	_getdns_rr_iter rr_spc, *rr;

	assert(spc);

	spc->rrset.name = NULL;
	spc->name_len = sizeof(spc->name_spc);
	if (   !(rr = _getdns_rr_iter_init(&rr_spc, pkt, len))
	    || _getdns_rr_iter_section(rr) != SECTION_QUESTION
	    || !(spc->rrset.name = _getdns_owner_if_or_as_decompressed(
			    rr, spc->name_spc, &spc->name_len))
	    || rr->nxt < rr->rr_type + 4)
		return NULL;

	spc->rrset.rr_class = rr_iter_class(rr);
	spc->rrset.rr_type = rr_iter_type(rr);
	spc->rrset.pkt = pkt;
	spc->rrset.pkt_len = len;
	spc->rrset.sections = SECTION_ANSWER;
	return _getdns_initialized_rrset_answer(spc);
}

/* Utility function to compare owner name of rr with name */
static int rr_owner_equal(_getdns_rr_iter *rr, const uint8_t *name)
{
	uint8_t owner_spc[256];
	const uint8_t *owner;
	size_t  owner_len = sizeof(owner_spc);

	return (owner = _getdns_owner_if_or_as_decompressed(rr, owner_spc
	                                                      ,&owner_len))
	    && name && _getdns_dname_equal(owner, name);
}

/* First a few filter functions that filter a RR iterator to point only
 * to RRs with certain constraints (and moves on otherwise).
 */

/* Filter that only iterates over the sections */
static inline _getdns_rr_iter *rr_iter_section(
    _getdns_rr_iter *rr, _getdns_section sections)
{
	while (rr && rr->pos && !(sections & _getdns_rr_iter_section(rr)))
		rr = _getdns_rr_iter_next(rr);

	return rr && rr->pos ? rr : NULL;
}

/* Filter that only iterates over RRs with a certain name/class/type */
static _getdns_rr_iter *rr_iter_name_class_type(_getdns_rr_iter *rr,
    const uint8_t *name, uint16_t rr_class, uint16_t rr_type,
    _getdns_section sections)
{
	while (rr_iter_section(rr, sections) && !(
	    rr_iter_type(rr)  == rr_type  &&
	    rr_iter_class(rr) == rr_class &&
	    rr_owner_equal(rr, name)))

		rr = _getdns_rr_iter_next(rr);

	return rr && rr->pos ? rr : NULL;
}

/* Filter that only iterates over RRs that do not have a name/class/type */
static _getdns_rr_iter *rr_iter_not_name_class_type(_getdns_rr_iter *rr,
    const uint8_t *name, uint16_t rr_class, uint16_t rr_type,
    _getdns_section sections)
{
	while (rr_iter_section(rr, sections) && (
	    rr_iter_type(rr)  == GETDNS_RRTYPE_RRSIG || (
	    rr_iter_type(rr)  == rr_type  &&
	    rr_iter_class(rr) == rr_class &&
	    rr_owner_equal(rr, name))))

		rr = _getdns_rr_iter_next(rr);
	
	return rr && rr->pos ? rr : NULL;
}

/* Filter that only iterates over RRs that are of type RRSIG, that cover
 * a RRset with a certain name/class/type
 */
static _getdns_rr_iter *rr_iter_rrsig_covering(_getdns_rr_iter *rr,
    const uint8_t *name, uint16_t rr_class, uint16_t rr_type,
    _getdns_section sections)
{
	while (rr_iter_section(rr, sections) && !(
	    rr_iter_type(rr)  == GETDNS_RRTYPE_RRSIG &&
	    rr_iter_class(rr) == rr_class &&
	    rr->rr_type + 12 <= rr->nxt &&
	    gldns_read_uint16(rr->rr_type + 10) == rr_type && 
	    rr_owner_equal(rr, name)))

		rr = _getdns_rr_iter_next(rr);

	return rr && rr->pos ? rr : NULL;
}

_getdns_rrtype_iter *
_getdns_rrtype_iter_next(_getdns_rrtype_iter *i)
{
	return (_getdns_rrtype_iter *) rr_iter_name_class_type(
	    _getdns_rr_iter_next(&i->rr_i),
	    i->rrset->name, i->rrset->rr_class, i->rrset->rr_type,
	    i->rrset->sections);
}

_getdns_rrtype_iter *
_getdns_rrtype_iter_init(_getdns_rrtype_iter *i, _getdns_rrset *rrset)
{
	i->rrset = rrset;
	return (_getdns_rrtype_iter *) rr_iter_name_class_type(
	    _getdns_rr_iter_init(&i->rr_i, rrset->pkt, rrset->pkt_len ),
	    i->rrset->name, i->rrset->rr_class, i->rrset->rr_type,
	    i->rrset->sections);
}

_getdns_rrsig_iter *
_getdns_rrsig_iter_next(_getdns_rrsig_iter *i)
{
	return (_getdns_rrsig_iter *) rr_iter_rrsig_covering(
	    _getdns_rr_iter_next(&i->rr_i),
	    i->rrset->name, i->rrset->rr_class, i->rrset->rr_type,
	    i->rrset->sections);
}

_getdns_rrsig_iter *
_getdns_rrsig_iter_init(_getdns_rrsig_iter *i, _getdns_rrset *rrset)
{
	i->rrset = rrset;
	return (_getdns_rrsig_iter *) rr_iter_rrsig_covering(
	    _getdns_rr_iter_init(&i->rr_i, rrset->pkt, rrset->pkt_len),
	    i->rrset->name, i->rrset->rr_class, i->rrset->rr_type,
	    i->rrset->sections);
}

_getdns_rrset_iter *
_getdns_rrset_iter_init(_getdns_rrset_iter *i,
    const uint8_t *pkt, size_t pkt_len, _getdns_section sections)
{
	_getdns_rr_iter *rr;

	i->rrset.name = i->name_spc;
	i->rrset.pkt = pkt;
	i->rrset.pkt_len = pkt_len;
	i->rrset.sections = sections;
	i->name_len = 0;

	for ( rr = _getdns_rr_iter_init(&i->rr_i, pkt, pkt_len)
	    ;(rr = rr_iter_section(rr, sections))
	    ; rr = _getdns_rr_iter_next(rr)) {

		if ((i->rrset.rr_type = rr_iter_type(rr))
		    == GETDNS_RRTYPE_RRSIG)
			continue;

		i->rrset.rr_class = rr_iter_class(rr);

		if (!(i->rrset.name = _getdns_owner_if_or_as_decompressed(
		    rr, i->name_spc, &i->name_len)))
			continue;

		return i;
	}
	return NULL;
}

_getdns_rrset_iter *_getdns_rrset_iter_next(_getdns_rrset_iter *i)
{
	_getdns_rr_iter *rr;

	if (!(rr = i && i->rr_i.pos ? &i->rr_i : NULL))
		return NULL;

	if (!(rr = rr_iter_not_name_class_type(rr,
	    i->rrset.name, i->rrset.rr_class, i->rrset.rr_type,
	    i->rrset.sections)))
		return NULL;

	i->rrset.rr_type  = rr_iter_type(rr);
	i->rrset.rr_class = rr_iter_class(rr);
	if (!(i->rrset.name = _getdns_owner_if_or_as_decompressed(
		    rr, i->name_spc, &i->name_len)))

		/* This is safe, because rr_iter_not_name_class_type will shift
		 * the iterator forward because at least name does not match.
		 * Goal is to skip broken compression pointer issues but keep
		 * processing the packet.
		 */
		return _getdns_rrset_iter_next(i);

	return i;
}

static _getdns_rdf_iter *
rdf_iter_find_nxt(_getdns_rdf_iter *i)
{
	const uint8_t *pos;

	assert(i);
	assert(i->pos);
	assert(i->rdd_pos);

	if (!i->rdd_repeat && (i->rdd_pos->type & GETDNS_RDF_REPEAT)) {
		i->rdd_repeat = i->rdd_pos;
		if (i->rdd_pos->type == GETDNS_RDF_REPEAT &&
		    ++i->rdd_pos == i->rdd_end)
			goto done;
	}
	if (i->rdd_pos->type & GETDNS_RDF_FIXEDSZ)
		i->nxt = i->pos + (i->rdd_pos->type & GETDNS_RDF_FIXEDSZ);

	else if ((i->rdd_pos->type & GETDNS_RDF_LEN_VAL) == 0x100)
		i->nxt = i->pos < i->end ? i->pos + *i->pos + 1 : i->end;

	else if ((i->rdd_pos->type & GETDNS_RDF_LEN_VAL) == 0x200)
		i->nxt = i->pos + 1 < i->end
		       ? i->pos + gldns_read_uint16(i->pos) + 2 : i->end;

	else if (i->rdd_pos->type & GETDNS_RDF_DNAME)

		for (pos = i->pos; pos < i->end; pos += *pos + 1) {
			if (!*pos) {
				i->nxt = pos + 1;
				break;
			} else if ((*pos & 0xC0) == 0xC0) {
				i->nxt = pos + 2;
				break;
			} else if (*pos & 0xC0) /* Uknown label type */
				goto done;
		}
	else if ((i->rdd_pos->type & GETDNS_RDF_SPECIAL) && i->rdd_pos->special) {
		if (!(i->nxt = i->rdd_pos->special->rdf_end(
		    i->pkt, i->pkt_end, i->pos)))
			i->nxt = i->end;

	} else /* RDF is for remaining data */
		i->nxt = i->end;

	if ( i->nxt <= i->end &&

	    /* Empty rdata fields are only allowed in case of non-repeating
	     * remaining data. So only the GETDNS_RDF_BINDATA bit is set.
	     */
	    (i->nxt >  i->pos || (i->rdd_pos->type == GETDNS_RDF_BINDATA)))
		return i;
done:
	i->pos = NULL;
	return NULL;
}

_getdns_rdf_iter *
_getdns_rdf_iter_init(_getdns_rdf_iter *i, _getdns_rr_iter *rr)
{
	const _getdns_rr_def *rr_def;

	assert(i);
	assert(rr);

	i->end     = NULL;
	/* rr_iter already done or in question section */
	if (!rr->pos || _getdns_rr_iter_section(rr) == SECTION_QUESTION)
		goto done;

	i->pkt     = rr->pkt;
	i->pkt_end = rr->pkt_end;
	rr_def     = _getdns_rr_def_lookup(gldns_read_uint16(rr->rr_type));
	i->rdd_pos = rr_def->rdata;
	i->rdd_end = rr_def->rdata + rr_def->n_rdata_fields;

	/* No space to read rdata len */
	if (rr->rr_type + 10 >= rr->nxt)
		goto done;

	i->rdd_repeat = NULL;
	i->pos        = rr->rr_type + 10;
	i->end        = rr->nxt;

	/* rdata */
	if (i->rdd_pos != i->rdd_end)
		return rdf_iter_find_nxt(i);
done:
	i->pos = NULL;
	return NULL;
}

_getdns_rdf_iter *
_getdns_rdf_iter_next(_getdns_rdf_iter *i)
{
	if (!i->pos)
		return NULL;

	i->rdd_pos += 1;
	if ((i->pos = i->nxt) > i->end)
		goto done; /* Overflow */
	if (i->rdd_pos >= i->rdd_end && !(i->rdd_pos = i->rdd_repeat))
		goto done; /* Remaining rdata, but out of definitions! */
	if (i->rdd_pos->type == GETDNS_RDF_REPEAT)
		i->rdd_pos += 1;

	return rdf_iter_find_nxt(i);
done:
	i->pos = NULL;
	return NULL;
}

_getdns_rdf_iter *
_getdns_rdf_iter_init_at(
    _getdns_rdf_iter *i, _getdns_rr_iter *rr, size_t pos)
{
	for ( i = _getdns_rdf_iter_init(i, rr)
	    ; i && pos
	    ; i = _getdns_rdf_iter_next(i), pos--);
	return i;
}       

const uint8_t *
_getdns_rdf_if_or_as_decompressed(
    _getdns_rdf_iter *i, uint8_t *ff_bytes, size_t *len)
{
	return dname_if_or_as_decompressed(i->pkt, i->pkt_end, i->pos,
	    ff_bytes, len, 0);
}