gethostbydns.c

Newlib 嵌入式 C库 标准实现代码

/*
 * ++Copyright++ 1985, 1988, 1993
 * -
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. 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--
 */


#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)gethostnamadr.c	8.1 (Berkeley) 6/4/93";
static char fromrcsid[] = "From: Id: gethnamaddr.c,v 8.23 1998/04/07 04:59:46 vixie Exp $";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>

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

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

#include "res_config.h"

#define SPRINTF(x) ((size_t)sprintf x)

static const char AskedForGot[] =
		"gethostby*.gethostanswer: asked for \"%s\", got \"%s\"";

#ifdef RESOLVSORT
static void addrsort(char **, int);
#endif

u_int32_t _getlong(const u_char *src);
u_int16_t _getshort(const u_char *src);

#ifdef DEBUG
static void dbgprintf(char *, int);
#endif

#if PACKETSZ > 1024
#define	MAXPACKET	PACKETSZ
#else
#define	MAXPACKET	1024
#endif

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

typedef union {
    int32_t al;
    char ac;
} align;

extern int h_errno;
int _dns_ttl_;

#ifdef DEBUG
static void
dbgprintf(msg, num)
	char *msg;
	int num;
{
	if (_res.options & RES_DEBUG) {
		int save = errno;

		printf(msg, num);
		errno = save;
	}
}
#else
# define dbgprintf(msg, num) /*nada*/
#endif

#define BOUNDED_INCR(x) \
	do { \
		cp += x; \
		if (cp > eom) { \
			*herr = NO_RECOVERY; \
			return (NULL); \
		} \
	} while (0)

#define BOUNDS_CHECK(ptr, count) \
	do { \
		if ((ptr) + (count) > eom) { \
			*herr = NO_RECOVERY; \
			return (NULL); \
		} \
	} while (0)

static struct hostent *
gethostanswer(answer, anslen, qname, qtype, host, hostbuf, hostbuflen, herr)
	const querybuf *answer;
	int anslen;
	const char *qname;
	int qtype;
        struct hostent *host;
        char *hostbuf;
        int hostbuflen;
        int *herr;
{
	const HEADER *hp;
	const u_char *cp;
	int n;
	const u_char *eom, *erdata;
	char *bp, **ap, **hap;
	int type, class, buflen, ancount, qdcount;
	int haveanswer, had_error;
	int toobig = 0;
	char tbuf[MAXDNAME];
	const char *tname;
	int (*name_ok)(const char *);

	tname = qname;
	host->h_name = NULL;
	eom = answer->buf + anslen;
	switch (qtype) {
	case T_A:
	case T_AAAA:
		name_ok = res_hnok;
		break;
	case T_PTR:
		name_ok = res_dnok;
		break;
	default:
		*herr = NO_RECOVERY;
		return (NULL);	/* XXX should be abort(); */
	}
	/*
	 * find first satisfactory answer
	 */
	hp = &answer->hdr;
	ancount = ntohs(hp->ancount);
	qdcount = ntohs(hp->qdcount);
	bp = hostbuf;
	buflen = hostbuflen;
	cp = answer->buf;
	BOUNDED_INCR(HFIXEDSZ);
	if (qdcount != 1) {
		*herr = NO_RECOVERY;
		return (NULL);
	}
	n = dn_expand(answer->buf, eom, cp, bp, buflen);
	if ((n < 0) || !(*name_ok)(bp)) {
		*herr = NO_RECOVERY;
		return (NULL);
	}
	BOUNDED_INCR(n + QFIXEDSZ);
	if (qtype == T_A || qtype == T_AAAA) {
		/* res_send() has already verified that the query name is the
		 * same as the one we sent; this just gets the expanded name
		 * (i.e., with the succeeding search-domain tacked on).
		 */
		n = strlen(bp) + 1;		/* for the \0 */
		if (n >= MAXHOSTNAMELEN) {
			*herr = NO_RECOVERY;
			return (NULL);
		}
		host->h_name = bp;
		bp += n;
		buflen -= n;
		/* The qname can be abbreviated, but h_name is now absolute. */
		qname = host->h_name;
	}
	ap = host->__host_aliases;
	*ap = NULL;
	host->h_aliases = host->__host_aliases;
	hap = host->__host_addrs;
	*hap = NULL;
	host->h_addr_list = host->__host_addrs;
	haveanswer = 0;
	had_error = 0;
	_dns_ttl_ = -1;
	while (ancount-- > 0 && cp < eom && !had_error) {
		n = dn_expand(answer->buf, eom, cp, bp, buflen);
		if ((n < 0) || !(*name_ok)(bp)) {
			had_error++;
			continue;
		}
		cp += n;			/* name */
		BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
		type = _getshort(cp);
 		cp += INT16SZ;			/* type */
		class = _getshort(cp);
 		cp += INT16SZ;			/* class */
		if (qtype == T_A  && type == T_A)
			_dns_ttl_ = _getlong(cp);
		cp += INT32SZ;			/* TTL */
		n = _getshort(cp);
		cp += INT16SZ;			/* len */
		BOUNDS_CHECK(cp, n);
		erdata = cp + n;
		if (class != C_IN) {
			/* XXX - debug? syslog? */
			cp += n;
			continue;		/* XXX - had_error++ ? */
		}
		if ((qtype == T_A || qtype == T_AAAA) && type == T_CNAME) {
			if (ap >= &host->__host_aliases[MAXALIASES-1])
				continue;
			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
			if ((n < 0) || !(*name_ok)(tbuf)) {
				had_error++;
				continue;
			}
			cp += n;
			if (cp != erdata) {
				*herr = NO_RECOVERY;
				return (NULL);
			}
			/* Store alias. */
			*ap++ = bp;
			n = strlen(bp) + 1;	/* for the \0 */
			if (n >= MAXHOSTNAMELEN) {
				had_error++;
				continue;
			}
			bp += n;
			buflen -= n;
			/* Get canonical name. */
			n = strlen(tbuf) + 1;	/* for the \0 */
			if (n > buflen || n >= MAXHOSTNAMELEN) {
				had_error++;
				continue;
			}
			strcpy(bp, tbuf);
			host->h_name = bp;
			bp += n;
			buflen -= n;
			continue;
		}
		if (qtype == T_PTR && type == T_CNAME) {
			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
			if (n < 0 || !res_dnok(tbuf)) {
				had_error++;
				continue;
			}
			cp += n;
			if (cp != erdata) {
				*herr = NO_RECOVERY;
				return (NULL);
			}
			/* Get canonical name. */
			n = strlen(tbuf) + 1;	/* for the \0 */
			if (n > buflen || n >= MAXHOSTNAMELEN) {
				had_error++;
				continue;
			}
			strcpy(bp, tbuf);
			tname = bp;
			bp += n;
			buflen -= n;
			continue;
		}
		if (type != qtype) {
			if (type != T_SIG)
				syslog(LOG_NOTICE|LOG_AUTH,
	"gethostby*.gethostanswer: asked for \"%s %s %s\", got type \"%s\"",
				       qname, p_class(C_IN), p_type(qtype),
				       p_type(type));
			cp += n;
			continue;		/* XXX - had_error++ ? */
		}
		switch (type) {
		case T_PTR:
			if (strcasecmp(tname, bp) != 0) {
				syslog(LOG_NOTICE|LOG_AUTH,
				       AskedForGot, qname, bp);
				cp += n;
				continue;	/* XXX - had_error++ ? */
			}
			n = dn_expand(answer->buf, eom, cp, bp, buflen);
			if ((n < 0) || !res_hnok(bp)) {
				had_error++;
				break;
			}
#if MULTI_PTRS_ARE_ALIASES
			cp += n;
			if (cp != erdata) {
				*herr = NO_RECOVERY;
				return (NULL);
			}
			if (!haveanswer)
				host->h_name = bp;
			else if (ap < &host->__host_aliases[MAXALIASES-1])
				*ap++ = bp;
			else
				n = -1;
			if (n != -1) {
				n = strlen(bp) + 1;	/* for the \0 */
				if (n >= MAXHOSTNAMELEN) {
					had_error++;
					break;
				}
				bp += n;
				buflen -= n;
			}
			break;
#else
			host->h_name = bp;
			if (_res.options & RES_USE_INET6) {
				n = strlen(bp) + 1;	/* for the \0 */
				if (n >= MAXHOSTNAMELEN) {
					had_error++;
					break;
				}
				bp += n;
				buflen -= n;
				_map_v4v6_hostent(host, &bp, &buflen);
			}
			*herr = NETDB_SUCCESS;
			return host;
#endif
		case T_A:
		case T_AAAA:
			if (strcasecmp(host->h_name, bp) != 0) {
				syslog(LOG_NOTICE|LOG_AUTH,
				       AskedForGot, host->h_name, bp);
				cp += n;
				continue;	/* XXX - had_error++ ? */
			}
			if (n != host->h_length) {
				cp += n;
				continue;
			}
			if (!haveanswer) {
				int nn;

				host->h_name = bp;
				nn = strlen(bp) + 1;	/* for the \0 */
				bp += nn;
				buflen -= nn;
			}

			bp += sizeof(align) - ((u_long)bp % sizeof(align));

			if (bp + n >= &hostbuf[hostbuflen]) {
				dbgprintf("size (%d) too big\n", n);
				had_error++;
				continue;
			}
			if (hap >= &host->__host_addrs[MAXADDRS-1]) {
				if (!toobig++)
					dbgprintf("Too many addresses (%d)\n",
						MAXADDRS);
				cp += n;