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/* $OpenBSD: ntpleaps.c,v 1.14 2015/12/12 20:04:23 mmcc Exp $ */
/*
* Copyright (c) 2002 Thorsten Glaser. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDERS 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.
*
*/
/* Leap second support for NTP clients (generic) */
/*
* I could include tzfile.h, but this would make the code unportable
* at no real benefit. Read tzfile.h for why.
*/
#include <sys/types.h>
#include <netinet/in.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "ntpleaps.h"
static u_int64_t *leapsecs;
static unsigned int leapsecs_num;
u_int32_t read_be_dword(u_int8_t *ptr);
int
ntpleaps_init(void)
{
static int doneinit;
static int donewarn;
if (doneinit)
return (0);
if (ntpleaps_read() == 0) {
doneinit = 1;
return (0);
}
/* This does not really hurt, but users will complain about
* off-by-22-seconds (at time of coding) errors if we don't warn.
*/
if (!donewarn) {
fputs("Warning: error reading tzfile. You will NOT be\n"
"able to get legal time or posix compliance!\n", stderr);
donewarn = 1; /* put it only once */
}
return (-1);
}
int
ntpleaps_sub(u_int64_t *t)
{
unsigned int i = 0;
u_int64_t u;
int r = 1;
if (ntpleaps_init() == -1)
return (-1);
u = *t;
while (i < leapsecs_num) {
if (u < leapsecs[i]) {
r--;
break;
}
if (u == leapsecs[i++])
break;
}
*t = u - i;
return (r);
}
u_int32_t
read_be_dword(u_int8_t *ptr)
{
u_int32_t res;
memcpy(&res, ptr, 4);
return (ntohl(res));
}
int
ntpleaps_read(void)
{
int fd;
unsigned int r;
u_int8_t buf[32];
u_int32_t m1, m2, m3;
u_int64_t s;
u_int64_t *l;
fd = open("/usr/share/zoneinfo/right/UTC", O_RDONLY | O_NDELAY);
if (fd == -1)
return (-1);
/* Check signature */
read(fd, buf, 4);
buf[4] = 0;
if (strcmp((const char *)buf, "TZif")) {
close(fd);
return (-1);
}
/* Pre-initialize buf[24..27] so we need not check read(2) result */
buf[24] = 0;
buf[25] = 0;
buf[26] = 0;
buf[27] = 0;
/* Skip uninteresting parts of header */
read(fd, buf, 28);
/* Read number of leap second entries */
r = read_be_dword(&buf[24]);
/* Check for plausibility - arbitrary values */
if ((r < 20) || (r > 60000)) {
close(fd);
return (-1);
}
if ((l = reallocarray(NULL, r, sizeof(u_int64_t))) == NULL) {
close(fd);
return (-1);
}
/* Skip further uninteresting stuff */
read(fd, buf, 12);
m1 = read_be_dword(buf);
m2 = read_be_dword(&buf[4]);
m3 = read_be_dword(&buf[8]);
m3 += (m1 << 2)+m1+(m2 << 2)+(m2 << 1);
lseek(fd, (off_t)m3, SEEK_CUR);
/* Now go parse the tzfile leap second info */
for (m1 = 0; m1 < r; m1++) {
if (read(fd, buf, 8) != 8) {
free(l);
close(fd);
return (-1);
}
s = SEC_TO_TAI64(read_be_dword(buf));
/*
* Assume just _one_ leap second on each entry, and compensate
* the lacking error checking by validating the first entry
* against the known value
*/
if (!m1 && s != 0x4000000004B2580AULL) {
free(l);
close(fd);
return (-1);
}
l[m1] = s;
}
/* Clean up and activate the table */
close(fd);
free(leapsecs);
leapsecs = l;
leapsecs_num = r;
return (0);
}
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