client.c

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Author : bluhm
Date : 2021-04-21 09:38:11
Hash : 4c6157fa
Message : Improve ntpd offset handling. Call the index of the offset loops "shift" consistently. Merge the two offset loops in client_update() into one. Use a simple assignment for the best value instead of memcpy(). Use the same mechanism to loop over the offset array everywhere to avoid an invalid best value. tested by weerd@; OK claudio@
usr.sbin/ntpd/client.c
/*	$OpenBSD: client.c,v 1.116 2021/04/21 09:38:11 bluhm Exp $ */

/*
 * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
 * Copyright (c) 2004 Alexander Guy <alexander.guy@andern.org>
 *
 * 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 THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR 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.
 */

#include <sys/types.h>
#include <errno.h>
#include <md5.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "ntpd.h"

int	client_update(struct ntp_peer *);
int	auto_cmp(const void *, const void *);
void	handle_auto(u_int8_t, double);
void	set_deadline(struct ntp_peer *, time_t);

void
set_next(struct ntp_peer *p, time_t t)
{
	p->next = getmonotime() + t;
	p->deadline = 0;
	p->poll = t;
}

void
set_deadline(struct ntp_peer *p, time_t t)
{
	p->deadline = getmonotime() + t;
	p->next = 0;
}

int
client_peer_init(struct ntp_peer *p)
{
	if ((p->query = calloc(1, sizeof(struct ntp_query))) == NULL)
		fatal("client_peer_init calloc");
	p->query->fd = -1;
	p->query->msg.status = MODE_CLIENT | (NTP_VERSION << 3);
	p->state = STATE_NONE;
	p->shift = 0;
	p->trustlevel = TRUSTLEVEL_PATHETIC;
	p->lasterror = 0;
	p->senderrors = 0;

	return (client_addr_init(p));
}

int
client_addr_init(struct ntp_peer *p)
{
	struct sockaddr_in	*sa_in;
	struct sockaddr_in6	*sa_in6;
	struct ntp_addr		*h;

	for (h = p->addr; h != NULL; h = h->next) {
		switch (h->ss.ss_family) {
		case AF_INET:
			sa_in = (struct sockaddr_in *)&h->ss;
			if (ntohs(sa_in->sin_port) == 0)
				sa_in->sin_port = htons(123);
			p->state = STATE_DNS_DONE;
			break;
		case AF_INET6:
			sa_in6 = (struct sockaddr_in6 *)&h->ss;
			if (ntohs(sa_in6->sin6_port) == 0)
				sa_in6->sin6_port = htons(123);
			p->state = STATE_DNS_DONE;
			break;
		default:
			fatalx("king bula sez: wrong AF in client_addr_init");
			/* NOTREACHED */
		}
	}

	p->query->fd = -1;
	set_next(p, 0);

	return (0);
}

int
client_nextaddr(struct ntp_peer *p)
{
	if (p->query->fd != -1) {
		close(p->query->fd);
		p->query->fd = -1;
	}

	if (p->state == STATE_DNS_INPROGRESS)
		return (-1);

	if (p->addr_head.a == NULL) {
		priv_dns(IMSG_HOST_DNS, p->addr_head.name, p->id);
		p->state = STATE_DNS_INPROGRESS;
		return (-1);
	}

	p->shift = 0;
	p->trustlevel = TRUSTLEVEL_PATHETIC;

	if (p->addr == NULL)
		p->addr = p->addr_head.a;
	else if ((p->addr = p->addr->next) == NULL)
		return (1);

	return (0);
}

int
client_query(struct ntp_peer *p)
{
	int	val;

	if (p->addr == NULL && client_nextaddr(p) == -1) {
		if (conf->settime)
			set_next(p, INTERVAL_AUIO_DNSFAIL);
		else
			set_next(p, MAXIMUM(SETTIME_TIMEOUT,
			    scale_interval(INTERVAL_QUERY_AGGRESSIVE)));
		return (0);
	}

	if (conf->status.synced && p->addr->notauth) {
		peer_addr_head_clear(p);
		client_nextaddr(p);
		return (0);
	}

	if (p->state < STATE_DNS_DONE || p->addr == NULL)
		return (-1);

	if (p->query->fd == -1) {
		struct sockaddr *sa = (struct sockaddr *)&p->addr->ss;
		struct sockaddr *qa4 = (struct sockaddr *)&p->query_addr4;
		struct sockaddr *qa6 = (struct sockaddr *)&p->query_addr6;

		if ((p->query->fd = socket(p->addr->ss.ss_family, SOCK_DGRAM,
		    0)) == -1)
			fatal("client_query socket");

		if (p->addr->ss.ss_family == qa4->sa_family) {
			if (bind(p->query->fd, qa4, SA_LEN(qa4)) == -1)
				fatal("couldn't bind to IPv4 query address: %s",
				    log_sockaddr(qa4));
		} else if (p->addr->ss.ss_family == qa6->sa_family) {
			if (bind(p->query->fd, qa6, SA_LEN(qa6)) == -1)
				fatal("couldn't bind to IPv6 query address: %s",
				    log_sockaddr(qa6));
		}

		if (connect(p->query->fd, sa, SA_LEN(sa)) == -1) {
			if (errno == ECONNREFUSED || errno == ENETUNREACH ||
			    errno == EHOSTUNREACH || errno == EADDRNOTAVAIL) {
				/* cycle through addresses, but do increase
				   senderrors */
				client_nextaddr(p);
				if (p->addr == NULL)
					p->addr = p->addr_head.a;
				set_next(p, MAXIMUM(SETTIME_TIMEOUT,
				    scale_interval(INTERVAL_QUERY_AGGRESSIVE)));
				p->senderrors++;
				return (-1);
			} else
				fatal("client_query connect");
		}
		val = IPTOS_LOWDELAY;
		if (p->addr->ss.ss_family == AF_INET && setsockopt(p->query->fd,
		    IPPROTO_IP, IP_TOS, &val, sizeof(val)) == -1)
			log_warn("setsockopt IPTOS_LOWDELAY");
		val = 1;
		if (setsockopt(p->query->fd, SOL_SOCKET, SO_TIMESTAMP,
		    &val, sizeof(val)) == -1)
			fatal("setsockopt SO_TIMESTAMP");
	}

	/*
	 * Send out a random 64-bit number as our transmit time.  The NTP
	 * server will copy said number into the originate field on the
	 * response that it sends us.  This is totally legal per the SNTP spec.
	 *
	 * The impact of this is two fold: we no longer send out the current
	 * system time for the world to see (which may aid an attacker), and
	 * it gives us a (not very secure) way of knowing that we're not
	 * getting spoofed by an attacker that can't capture our traffic
	 * but can spoof packets from the NTP server we're communicating with.
	 *
	 * Save the real transmit timestamp locally.
	 */

	p->query->msg.xmttime.int_partl = arc4random();
	p->query->msg.xmttime.fractionl = arc4random();
	p->query->xmttime = gettime();

	if (ntp_sendmsg(p->query->fd, NULL, &p->query->msg) == -1) {
		p->senderrors++;
		set_next(p, INTERVAL_QUERY_PATHETIC);
		p->trustlevel = TRUSTLEVEL_PATHETIC;
		return (-1);
	}

	p->senderrors = 0;
	p->state = STATE_QUERY_SENT;
	set_deadline(p, QUERYTIME_MAX);

	return (0);
}

int
auto_cmp(const void *a, const void *b)
{
	double at = *(const double *)a;
	double bt = *(const double *)b;
	return at < bt ? -1 : (at > bt ? 1 : 0);
}

void
handle_auto(uint8_t trusted, double offset)
{
	static int count;
	static double v[AUTO_REPLIES];

	/*
	 * It happens the (constraint) resolves initially fail, don't give up
	 * but see if we get validated replies later.
	 */
	if (!trusted && conf->constraint_median == 0)
		return;

	if (offset < AUTO_THRESHOLD) {
		/* don't bother */
		priv_settime(0, "offset is negative or close enough");
		return;
	}
	/* collect some more */
	v[count++] = offset;
	if (count < AUTO_REPLIES)
		return;
	
	/* we have enough */
	qsort(v, count, sizeof(double), auto_cmp);
	if (AUTO_REPLIES % 2 == 0)
		offset = (v[AUTO_REPLIES / 2 - 1] + v[AUTO_REPLIES / 2]) / 2;
	else
		offset = v[AUTO_REPLIES / 2];
	priv_settime(offset, "");
}


/*
 * -1: Not processed, not an NTP message (e.g. icmp induced  ECONNREFUSED)
 *  0: Not prrocessed due to validation issues
 *  1: NTP message validated and processed
 */
int
client_dispatch(struct ntp_peer *p, u_int8_t settime, u_int8_t automatic)
{
	struct ntp_msg		 msg;
	struct msghdr		 somsg;
	struct iovec		 iov[1];
	struct timeval		 tv;
	char			 buf[NTP_MSGSIZE];
	union {
		struct cmsghdr	hdr;
		char		buf[CMSG_SPACE(sizeof(tv))];
	} cmsgbuf;
	struct cmsghdr		*cmsg;
	ssize_t			 size;
	double			 T1, T2, T3, T4, offset, delay;
	time_t			 interval;

	memset(&somsg, 0, sizeof(somsg));
	iov[0].iov_base = buf;
	iov[0].iov_len = sizeof(buf);
	somsg.msg_iov = iov;
	somsg.msg_iovlen = 1;
	somsg.msg_control = cmsgbuf.buf;
	somsg.msg_controllen = sizeof(cmsgbuf.buf);

	if ((size = recvmsg(p->query->fd, &somsg, 0)) == -1) {
		if (errno == EHOSTUNREACH || errno == EHOSTDOWN ||
		    errno == ENETUNREACH || errno == ENETDOWN ||
		    errno == ECONNREFUSED || errno == EADDRNOTAVAIL ||
		    errno == ENOPROTOOPT || errno == ENOENT) {
			client_log_error(p, "recvmsg", errno);
			set_next(p, error_interval());
			return (-1);
		} else
			fatal("recvfrom");
	}

	if (somsg.msg_flags & MSG_TRUNC) {
		client_log_error(p, "recvmsg packet", EMSGSIZE);
		set_next(p, error_interval());
		return (0);
	}

	if (somsg.msg_flags & MSG_CTRUNC) {
		client_log_error(p, "recvmsg control data", E2BIG);
		set_next(p, error_interval());
		return (0);
	}

	for (cmsg = CMSG_FIRSTHDR(&somsg); cmsg != NULL;
	    cmsg = CMSG_NXTHDR(&somsg, cmsg)) {
		if (cmsg->cmsg_level == SOL_SOCKET &&
		    cmsg->cmsg_type == SCM_TIMESTAMP) {
			memcpy(&tv, CMSG_DATA(cmsg), sizeof(tv));
			T4 = gettime_from_timeval(&tv);
			break;
		}
	}
	if (cmsg == NULL)
		fatal("SCM_TIMESTAMP");

	ntp_getmsg((struct sockaddr *)&p->addr->ss, buf, size, &msg);

	if (msg.orgtime.int_partl != p->query->msg.xmttime.int_partl ||
	    msg.orgtime.fractionl != p->query->msg.xmttime.fractionl)
		return (0);

	if ((msg.status & LI_ALARM) == LI_ALARM || msg.stratum == 0 ||
	    msg.stratum > NTP_MAXSTRATUM) {
		char s[16];

		if ((msg.status & LI_ALARM) == LI_ALARM) {
			strlcpy(s, "alarm", sizeof(s));
		} else if (msg.stratum == 0) {
			/* Kiss-o'-Death (KoD) packet */
			strlcpy(s, "KoD", sizeof(s));
		} else if (msg.stratum > NTP_MAXSTRATUM) {
			snprintf(s, sizeof(s), "stratum %d", msg.stratum);
		}
		interval = error_interval();
		set_next(p, interval);
		log_info("reply from %s: not synced (%s), next query %llds",
		    log_sockaddr((struct sockaddr *)&p->addr->ss), s,
			(long long)interval);
		return (0);
	}

	/*
	 * From RFC 2030 (with a correction to the delay math):
	 *
	 *     Timestamp Name          ID   When Generated
	 *     ------------------------------------------------------------
	 *     Originate Timestamp     T1   time request sent by client
	 *     Receive Timestamp       T2   time request received by server
	 *     Transmit Timestamp      T3   time reply sent by server
	 *     Destination Timestamp   T4   time reply received by client
	 *
	 *  The roundtrip delay d and local clock offset t are defined as
	 *
	 *    d = (T4 - T1) - (T3 - T2)     t = ((T2 - T1) + (T3 - T4)) / 2.
	 */

	T1 = p->query->xmttime;
	T2 = lfp_to_d(msg.rectime);
	T3 = lfp_to_d(msg.xmttime);

	/* Detect liars */
	if (!p->trusted && conf->constraint_median != 0 &&
	    (constraint_check(T2) != 0 || constraint_check(T3) != 0)) {
		log_info("reply from %s: constraint check failed",
		    log_sockaddr((struct sockaddr *)&p->addr->ss));
		set_next(p, error_interval());
		return (0);
	}

	p->reply[p->shift].offset = ((T2 - T1) + (T3 - T4)) / 2 - getoffset();
	p->reply[p->shift].delay = (T4 - T1) - (T3 - T2);
	p->reply[p->shift].status.stratum = msg.stratum;
	if (p->reply[p->shift].delay < 0) {
		interval = error_interval();
		set_next(p, interval);
		log_info("reply from %s: negative delay %fs, "
		    "next query %llds",
		    log_sockaddr((struct sockaddr *)&p->addr->ss),
		    p->reply[p->shift].delay, (long long)interval);
		return (0);
	}
	p->reply[p->shift].error = (T2 - T1) - (T3 - T4);
	p->reply[p->shift].rcvd = getmonotime();
	p->reply[p->shift].good = 1;

	p->reply[p->shift].status.leap = (msg.status & LIMASK);
	p->reply[p->shift].status.precision = msg.precision;
	p->reply[p->shift].status.rootdelay = sfp_to_d(msg.rootdelay);
	p->reply[p->shift].status.rootdispersion = sfp_to_d(msg.dispersion);
	p->reply[p->shift].status.refid = msg.refid;
	p->reply[p->shift].status.reftime = lfp_to_d(msg.reftime);
	p->reply[p->shift].status.poll = msg.ppoll;

	if (p->addr->ss.ss_family == AF_INET) {
		p->reply[p->shift].status.send_refid =
		    ((struct sockaddr_in *)&p->addr->ss)->sin_addr.s_addr;
	} else if (p->addr->ss.ss_family == AF_INET6) {
		MD5_CTX		context;
		u_int8_t	digest[MD5_DIGEST_LENGTH];

		MD5Init(&context);
		MD5Update(&context, ((struct sockaddr_in6 *)&p->addr->ss)->
		    sin6_addr.s6_addr, sizeof(struct in6_addr));
		MD5Final(digest, &context);
		memcpy((char *)&p->reply[p->shift].status.send_refid, digest,
		    sizeof(u_int32_t));
	} else
		p->reply[p->shift].status.send_refid = msg.xmttime.fractionl;

	p->state = STATE_REPLY_RECEIVED;

	/* every received reply which we do not discard increases trust */
	if (p->trustlevel < TRUSTLEVEL_MAX) {
		if (p->trustlevel < TRUSTLEVEL_BADPEER &&
		    p->trustlevel + 1 >= TRUSTLEVEL_BADPEER)
			log_info("peer %s now valid",
			    log_sockaddr((struct sockaddr *)&p->addr->ss));
		p->trustlevel++;
	}

	offset = p->reply[p->shift].offset;
	delay = p->reply[p->shift].delay;

	client_update(p);
	if (settime) {
		if (automatic)
			handle_auto(p->trusted, p->reply[p->shift].offset);
		else
			priv_settime(p->reply[p->shift].offset, "");
	}

	if (p->trustlevel < TRUSTLEVEL_PATHETIC)
		interval = scale_interval(INTERVAL_QUERY_PATHETIC);
	else if (p->trustlevel < TRUSTLEVEL_AGGRESSIVE)
		interval = (conf->settime && conf->automatic) ?
		    INTERVAL_QUERY_ULTRA_VIOLENCE :
		    scale_interval(INTERVAL_QUERY_AGGRESSIVE);
	else
		interval = scale_interval(INTERVAL_QUERY_NORMAL);

	log_debug("reply from %s: offset %f delay %f, "
	    "next query %llds",
	    log_sockaddr((struct sockaddr *)&p->addr->ss),
	    offset, delay,
	    (long long)interval);

	set_next(p, interval);

	if (++p->shift >= OFFSET_ARRAY_SIZE)
		p->shift = 0;

	return (1);
}

int
client_update(struct ntp_peer *p)
{
	int	shift, best = -1, good = 0;

	/*
	 * clock filter
	 * find the offset which arrived with the lowest delay
	 * use that as the peer update
	 * invalidate it and all older ones
	 */

	for (shift = 0; shift < OFFSET_ARRAY_SIZE; shift++)
		if (p->reply[shift].good) {
			good++;
			if (best == -1 ||
			    p->reply[shift].delay < p->reply[best].delay)
				best = shift;
		}

	if (best == -1 || good < 8)
		return (-1);

	p->update = p->reply[best];
	if (priv_adjtime() == 0) {
		for (shift = 0; shift < OFFSET_ARRAY_SIZE; shift++)
			if (p->reply[shift].rcvd <= p->reply[best].rcvd)
				p->reply[shift].good = 0;
	}
	return (0);
}

void
client_log_error(struct ntp_peer *peer, const char *operation, int error)
{
	const char *address;

	address = log_sockaddr((struct sockaddr *)&peer->addr->ss);
	if (peer->lasterror == error) {
		log_debug("%s %s: %s", operation, address, strerror(error));
		return;
	}
	peer->lasterror = error;
	log_warn("%s %s", operation, address);
}
IABSD.fr/src/usr.sbin/ntpd/client.c

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IABSD.fr/src /usr.sbin/ntpd/client.c
