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/* $OpenBSD: client.c,v 1.14 2004/07/07 06:51:16 deraadt Exp $ */
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/*
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* Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
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* Copyright (c) 2004 Alexander Guy <alexander.guy@andern.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
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* IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
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* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <sys/param.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include <unistd.h>
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#include "ntpd.h"
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int
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client_peer_init(struct ntp_peer *p)
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{
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struct sockaddr_in *sa_in;
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struct sockaddr_in6 *sa_in6;
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if ((p->query = calloc(1, sizeof(struct ntp_query))) == NULL)
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fatal("client_query calloc");
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switch (p->ss.ss_family) {
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case AF_INET:
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sa_in = (struct sockaddr_in *)&p->ss;
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if (ntohs(sa_in->sin_port) == 0)
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sa_in->sin_port = htons(123);
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break;
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case AF_INET6:
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sa_in6 = (struct sockaddr_in6 *)&p->ss;
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if (ntohs(sa_in6->sin6_port) == 0)
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sa_in6->sin6_port = htons(123);
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break;
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default:
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fatal("king bula sez: wrong AF in client_peer_init");
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/* not reached */
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}
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if ((p->query->fd = socket(p->ss.ss_family, SOCK_DGRAM, 0)) == -1)
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fatal("client_query socket");
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p->query->msg.status = MODE_CLIENT | (NTP_VERSION << 3);
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p->state = STATE_NONE;
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p->next = time(NULL);
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p->shift = 0;
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p->trustlevel = TRUSTLEVEL_PATHETIC;
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return (0);
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}
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int
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client_query(struct ntp_peer *p)
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{
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/*
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* Send out a random 64-bit number as our transmit time. The NTP
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* server will copy said number into the originate field on the
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* response that it sends us. This is totally legal per the SNTP spec.
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*
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* The impact of this is two fold: we no longer send out the current
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* system time for the world to see (which may aid an attacker), and
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* it gives us a (not very secure) way of knowing that we're not
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* getting spoofed by an attacker that can't capture our traffic
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* but can spoof packets from the NTP server we're communicating with.
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*
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* Save the real transmit timestamp locally.
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*/
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p->query->msg.xmttime.int_part = arc4random();
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p->query->msg.xmttime.fraction = arc4random();
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p->query->xmttime = gettime();
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ntp_sendmsg(p->query->fd, (struct sockaddr *)&p->ss, &p->query->msg,
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NTP_MSGSIZE_NOAUTH, 0);
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p->state = STATE_QUERY_SENT;
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p->next = 0;
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p->deadline = time(NULL) + QUERYTIME_MAX;
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return (0);
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}
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int
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client_dispatch(struct ntp_peer *p)
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{
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struct sockaddr_storage fsa;
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socklen_t fsa_len;
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char buf[NTP_MSGSIZE];
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ssize_t size;
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struct ntp_msg msg;
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double T1, T2, T3, T4;
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fsa_len = sizeof(fsa);
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if ((size = recvfrom(p->query->fd, &buf, sizeof(buf), 0,
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(struct sockaddr *)&fsa, &fsa_len)) == -1)
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fatal("recvfrom");
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T4 = gettime();
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ntp_getmsg(buf, size, &msg);
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if (msg.orgtime.int_part != p->query->msg.xmttime.int_part ||
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msg.orgtime.fraction != p->query->msg.xmttime.fraction)
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return (0);
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/*
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* From RFC 2030:
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*
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* Timestamp Name ID When Generated
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* ------------------------------------------------------------
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* Originate Timestamp T1 time request sent by client
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* Receive Timestamp T2 time request received by server
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* Transmit Timestamp T3 time reply sent by server
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* Destination Timestamp T4 time reply received by client
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*
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* The roundtrip delay d and local clock offset t are defined as
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*
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* d = (T4 - T1) - (T2 - T3) t = ((T2 - T1) + (T3 - T4)) / 2.
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*/
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T1 = p->query->xmttime;
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T2 = lfp_to_d(msg.rectime);
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T3 = lfp_to_d(msg.xmttime);
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p->reply[p->shift].offset = ((T2 - T1) + (T3 - T4)) / 2;
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p->reply[p->shift].delay = (T4 - T1) - (T2 - T3);
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p->reply[p->shift].error = (T2 - T1) - (T3 - T4);
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p->reply[p->shift].rcvd = time(NULL);
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p->reply[p->shift].good = 1;
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if (p->trustlevel < TRUSTLEVEL_PATHETIC)
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p->next = time(NULL) + INTERVAL_QUERY_PATHETIC;
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else if (p->trustlevel < TRUSTLEVEL_AGRESSIVE)
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p->next = time(NULL) + INTERVAL_QUERY_AGRESSIVE;
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else
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p->next = time(NULL) + INTERVAL_QUERY_NORMAL;
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p->deadline = 0;
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p->state = STATE_REPLY_RECEIVED;
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log_debug("reply received from %s: offset %f delay %f",
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log_sockaddr((struct sockaddr *)&fsa), p->reply[p->shift].offset,
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p->reply[p->shift].delay);
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/* every received reply which we do not discard increases trust */
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if (p->trustlevel < 10) {
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if (p->trustlevel < TRUSTLEVEL_BADPEER &&
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p->trustlevel + 1 >= TRUSTLEVEL_BADPEER)
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log_info("peer %s now valid",
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log_sockaddr((struct sockaddr *)&fsa));
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p->trustlevel++;
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}
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if (++p->shift >= OFFSET_ARRAY_SIZE)
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p->shift = 0;
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return (0);
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}
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