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Source code pulled from OpenBSD for OpenNTPD. The place to contribute to this code is via the OpenBSD CVS tree.
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openntpd-openbsd/src/usr.sbin/ntpd/client.c

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/* $OpenBSD: client.c,v 1.113 2020/01/30 15:55:41 otto 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_corrected();
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, "");
}
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;
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);
T4 = getoffset();
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 (0);
} 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;
}
}
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;
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;
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);
set_next(p, interval);
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++;
}
log_debug("reply from %s: offset %f delay %f, "
"next query %llds",
log_sockaddr((struct sockaddr *)&p->addr->ss),
p->reply[p->shift].offset, p->reply[p->shift].delay,
(long long)interval);
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->shift >= OFFSET_ARRAY_SIZE)
p->shift = 0;
return (0);
}
int
client_update(struct ntp_peer *p)
{
int i, best = 0, 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 (i = 0; good == 0 && i < OFFSET_ARRAY_SIZE; i++)
if (p->reply[i].good) {
good++;
best = i;
}
for (; i < OFFSET_ARRAY_SIZE; i++)
if (p->reply[i].good) {
good++;
if (p->reply[i].delay < p->reply[best].delay)
best = i;
}
if (good < 8)
return (-1);
memcpy(&p->update, &p->reply[best], sizeof(p->update));
if (priv_adjtime() == 0) {
for (i = 0; i < OFFSET_ARRAY_SIZE; i++)
if (p->reply[i].rcvd <= p->reply[best].rcvd)
p->reply[i].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);
}