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 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 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 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 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