1 /* $OpenBSD: ntpleaps.c,v 1.14 2015/12/12 20:04:23 mmcc Exp $ */
2
3 /*
4 * Copyright (c) 2002 Thorsten Glaser. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * - Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * - Redistributions in binary form must reproduce the above
13 * copyright notice, this list of conditions and the following
14 * disclaimer in the documentation and/or other materials provided
15 * with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
20 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
21 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
27 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28 * POSSIBILITY OF SUCH DAMAGE.
29 *
30 */
31
32 /* Leap second support for NTP clients (generic) */
33
34 /*
35 * I could include tzfile.h, but this would make the code unportable
36 * at no real benefit. Read tzfile.h for why.
37 */
38
39 #include <sys/types.h>
40 #include <netinet/in.h>
41
42 #include <fcntl.h>
43 #include <stdio.h>
44 #include <stdlib.h>
45 #include <string.h>
46 #include <unistd.h>
47
48 #include "ntpleaps.h"
49
50 static u_int64_t *leapsecs;
51 static unsigned int leapsecs_num;
52
53 u_int32_t read_be_dword(u_int8_t *ptr);
54
55
56 int
ntpleaps_init(void)57 ntpleaps_init(void)
58 {
59 static int doneinit;
60 static int donewarn;
61
62 if (doneinit)
63 return (0);
64
65 if (ntpleaps_read() == 0) {
66 doneinit = 1;
67 return (0);
68 }
69
70 /* This does not really hurt, but users will complain about
71 * off-by-22-seconds (at time of coding) errors if we don't warn.
72 */
73 if (!donewarn) {
74 fputs("Warning: error reading tzfile. You will NOT be\n"
75 "able to get legal time or posix compliance!\n", stderr);
76 donewarn = 1; /* put it only once */
77 }
78
79 return (-1);
80 }
81
82 int
ntpleaps_sub(u_int64_t * t)83 ntpleaps_sub(u_int64_t *t)
84 {
85 unsigned int i = 0;
86 u_int64_t u;
87 int r = 1;
88
89 if (ntpleaps_init() == -1)
90 return (-1);
91
92 u = *t;
93
94 while (i < leapsecs_num) {
95 if (u < leapsecs[i]) {
96 r--;
97 break;
98 }
99 if (u == leapsecs[i++])
100 break;
101 }
102
103 *t = u - i;
104 return (r);
105 }
106
107 u_int32_t
read_be_dword(u_int8_t * ptr)108 read_be_dword(u_int8_t *ptr)
109 {
110 u_int32_t res;
111
112 memcpy(&res, ptr, 4);
113 return (ntohl(res));
114 }
115
116
117 int
ntpleaps_read(void)118 ntpleaps_read(void)
119 {
120 int fd;
121 unsigned int r;
122 u_int8_t buf[32];
123 u_int32_t m1, m2, m3;
124 u_int64_t s;
125 u_int64_t *l;
126
127 fd = open("/usr/share/zoneinfo/right/UTC", O_RDONLY | O_NDELAY);
128 if (fd == -1)
129 return (-1);
130
131 /* Check signature */
132 read(fd, buf, 4);
133 buf[4] = 0;
134 if (strcmp((const char *)buf, "TZif")) {
135 close(fd);
136 return (-1);
137 }
138
139 /* Pre-initialize buf[24..27] so we need not check read(2) result */
140 buf[24] = 0;
141 buf[25] = 0;
142 buf[26] = 0;
143 buf[27] = 0;
144
145 /* Skip uninteresting parts of header */
146 read(fd, buf, 28);
147
148 /* Read number of leap second entries */
149 r = read_be_dword(&buf[24]);
150 /* Check for plausibility - arbitrary values */
151 if ((r < 20) || (r > 60000)) {
152 close(fd);
153 return (-1);
154 }
155 if ((l = reallocarray(NULL, r, sizeof(u_int64_t))) == NULL) {
156 close(fd);
157 return (-1);
158 }
159
160 /* Skip further uninteresting stuff */
161 read(fd, buf, 12);
162 m1 = read_be_dword(buf);
163 m2 = read_be_dword(&buf[4]);
164 m3 = read_be_dword(&buf[8]);
165 m3 += (m1 << 2)+m1+(m2 << 2)+(m2 << 1);
166 lseek(fd, (off_t)m3, SEEK_CUR);
167
168 /* Now go parse the tzfile leap second info */
169 for (m1 = 0; m1 < r; m1++) {
170 if (read(fd, buf, 8) != 8) {
171 free(l);
172 close(fd);
173 return (-1);
174 }
175 s = SEC_TO_TAI64(read_be_dword(buf));
176 /*
177 * Assume just _one_ leap second on each entry, and compensate
178 * the lacking error checking by validating the first entry
179 * against the known value
180 */
181 if (!m1 && s != 0x4000000004B2580AULL) {
182 free(l);
183 close(fd);
184 return (-1);
185 }
186 l[m1] = s;
187 }
188
189 /* Clean up and activate the table */
190 close(fd);
191 free(leapsecs);
192 leapsecs = l;
193 leapsecs_num = r;
194 return (0);
195 }
196