/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1996,1999 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 <sys/types.h>

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

#include <errno.h>
#include <resolv.h>
#include <string.h>
#define NS_TYPE_ELT			0x40 /*%< EDNS0 extended label type */
#define DNS_LABELTYPE_BITSTRING		0x41

struct _ns_flagdata {  int mask, shift;  };

/* Forward. */

static void	setsection(ns_msg *msg, ns_sect sect);

/* Macros. */
#ifndef __set_errno
#define __set_errno(err) errno = (err)
#endif
#define RETERR(err) do { __set_errno (err); return (-1); } while (0)

/* Public. */

/* These need to be in the same order as the nres.h:ns_flag enum. */
const struct _ns_flagdata _ns_flagdata[16] = {
	{ 0x8000, 15 },		/*%< qr. */
	{ 0x7800, 11 },		/*%< opcode. */
	{ 0x0400, 10 },		/*%< aa. */
	{ 0x0200, 9 },		/*%< tc. */
	{ 0x0100, 8 },		/*%< rd. */
	{ 0x0080, 7 },		/*%< ra. */
	{ 0x0040, 6 },		/*%< z. */
	{ 0x0020, 5 },		/*%< ad. */
	{ 0x0010, 4 },		/*%< cd. */
	{ 0x000f, 0 },		/*%< rcode. */
	{ 0x0000, 0 },		/*%< expansion (1/6). */
	{ 0x0000, 0 },		/*%< expansion (2/6). */
	{ 0x0000, 0 },		/*%< expansion (3/6). */
	{ 0x0000, 0 },		/*%< expansion (4/6). */
	{ 0x0000, 0 },		/*%< expansion (5/6). */
	{ 0x0000, 0 },		/*%< expansion (6/6). */
};
static int
labellen(const u_char *lp)
{
	int bitlen;
	u_char l = *lp;

	if ((l & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
		/* should be avoided by the caller */
		return(-1);
	}

	if ((l & NS_CMPRSFLGS) == NS_TYPE_ELT) {
		if (l == DNS_LABELTYPE_BITSTRING) {
			if ((bitlen = *(lp + 1)) == 0)
				bitlen = 256;
			return((bitlen + 7 ) / 8 + 1);
		}
		return(-1);	/*%< unknwon ELT */
	}
	return(l);
}


/*%
 *	Advance *ptrptr to skip over the compressed name it points at.
 *
 * return:
 *\li	0 on success, -1 (with errno set) on failure.
 */
	int
ns_name_skip(const u_char **ptrptr, const u_char *eom)
{
	const u_char *cp;
	u_int n;
	int l;

	cp = *ptrptr;
	while (cp < eom && (n = *cp++) != 0) {
		/* Check for indirection. */
		switch (n & NS_CMPRSFLGS) {
			case 0:			/*%< normal case, n == len */
				cp += n;
				continue;
			case NS_TYPE_ELT: /*%< EDNS0 extended label */
				if ((l = labellen(cp - 1)) < 0) {
					__set_errno (EMSGSIZE);
					return(-1);
				}
				cp += l;
				continue;
			case NS_CMPRSFLGS:	/*%< indirection */
				cp++;
				break;
			default:		/*%< illegal type */
				__set_errno (EMSGSIZE);
				return (-1);
		}
		break;
	}
	if (cp > eom) {
		__set_errno (EMSGSIZE);
		return (-1);
	}
	*ptrptr = cp;
	return (0);
}
/*
 * Skip over a compressed domain name. Return the size or -1.
 */
int
dn_skipname(const u_char *ptr, const u_char *eom) {
	const u_char *saveptr = ptr;

	if (ns_name_skip(&ptr, eom) == -1)
		return (-1);
	return (ptr - saveptr);
}
#undef ns_msg_getflag
int ns_msg_getflag(ns_msg handle, int flag) {
	return(((handle)._flags & _ns_flagdata[flag].mask) >> _ns_flagdata[flag].shift);
}

int
ns_skiprr(const u_char *ptr, const u_char *eom, ns_sect section, int count) {
	const u_char *optr = ptr;

	for ((void)NULL; count > 0; count--) {
		int b, rdlength;

		b = dn_skipname(ptr, eom);
		if (b < 0)
			RETERR(EMSGSIZE);
		ptr += b/*Name*/ + NS_INT16SZ/*Type*/ + NS_INT16SZ/*Class*/;
		if (section != ns_s_qd) {
			if (ptr + NS_INT32SZ + NS_INT16SZ > eom)
				RETERR(EMSGSIZE);
			ptr += NS_INT32SZ/*TTL*/;
			NS_GET16(rdlength, ptr);
			ptr += rdlength/*RData*/;
		}
	}
	if (ptr > eom)
		RETERR(EMSGSIZE);
	return (ptr - optr);
}

int
ns_initparse(const u_char *msg, int msglen, ns_msg *handle) {
	const u_char *eom = msg + msglen;
	int i;

	memset(handle, 0x5e, sizeof *handle);
	handle->_msg = msg;
	handle->_eom = eom;
	if (msg + NS_INT16SZ > eom)
		RETERR(EMSGSIZE);
	NS_GET16(handle->_id, msg);
	if (msg + NS_INT16SZ > eom)
		RETERR(EMSGSIZE);
	NS_GET16(handle->_flags, msg);
	for (i = 0; i < ns_s_max; i++) {
		if (msg + NS_INT16SZ > eom)
			RETERR(EMSGSIZE);
		NS_GET16(handle->_counts[i], msg);
	}
	for (i = 0; i < ns_s_max; i++)
		if (handle->_counts[i] == 0)
			handle->_sections[i] = NULL;
		else {
			int b = ns_skiprr(msg, eom, (ns_sect)i,
					  handle->_counts[i]);

			if (b < 0)
				return (-1);
			handle->_sections[i] = msg;
			msg += b;
		}
	if (msg != eom)
		RETERR(EMSGSIZE);
	setsection(handle, ns_s_max);
	return (0);
}

int
ns_parserr(ns_msg *handle, ns_sect section, int rrnum, ns_rr *rr) {
	int b;
	int tmp;

	/* Make section right. */
	tmp = section;
	if (tmp < 0 || section >= ns_s_max)
		RETERR(ENODEV);
	if (section != handle->_sect)
		setsection(handle, section);

	/* Make rrnum right. */
	if (rrnum == -1)
		rrnum = handle->_rrnum;
	if (rrnum < 0 || rrnum >= handle->_counts[(int)section])
		RETERR(ENODEV);
	if (rrnum < handle->_rrnum)
		setsection(handle, section);
	if (rrnum > handle->_rrnum) {
		b = ns_skiprr(handle->_msg_ptr, handle->_eom, section,
			      rrnum - handle->_rrnum);

		if (b < 0)
			return (-1);
		handle->_msg_ptr += b;
		handle->_rrnum = rrnum;
	}

	/* Do the parse. */
	b = dn_expand(handle->_msg, handle->_eom,
		      handle->_msg_ptr, rr->name, NS_MAXDNAME);
	if (b < 0)
		return (-1);
	handle->_msg_ptr += b;
	if (handle->_msg_ptr + NS_INT16SZ + NS_INT16SZ > handle->_eom)
		RETERR(EMSGSIZE);
	NS_GET16(rr->type, handle->_msg_ptr);
	NS_GET16(rr->rr_class, handle->_msg_ptr);
	if (section == ns_s_qd) {
		rr->ttl = 0;
		rr->rdlength = 0;
		rr->rdata = NULL;
	} else {
		if (handle->_msg_ptr + NS_INT32SZ + NS_INT16SZ > handle->_eom)
			RETERR(EMSGSIZE);
		NS_GET32(rr->ttl, handle->_msg_ptr);
		NS_GET16(rr->rdlength, handle->_msg_ptr);
		if (handle->_msg_ptr + rr->rdlength > handle->_eom)
			RETERR(EMSGSIZE);
		rr->rdata = handle->_msg_ptr;
		handle->_msg_ptr += rr->rdlength;
	}
	if (++handle->_rrnum > handle->_counts[(int)section])
		setsection(handle, (ns_sect)((int)section + 1));

	/* All done. */
	return (0);
}

/* Private. */

static void
setsection(ns_msg *msg, ns_sect sect) {
	msg->_sect = sect;
	if (sect == ns_s_max) {
		msg->_rrnum = -1;
		msg->_msg_ptr = NULL;
	} else {
		msg->_rrnum = 0;
		msg->_msg_ptr = msg->_sections[(int)sect];
	}
}

/*! \file */