/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ /*** This file is part of systemd. Timezone file reading code from glibc 2.16. Copyright (C) 1991-2012 Free Software Foundation, Inc. Copyright 2012 Kay Sievers systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. ***/ #include <ctype.h> #include <errno.h> #include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> #include <endian.h> #include <byteswap.h> #include <assert.h> #include <limits.h> #include <unistd.h> #include <stdint.h> #include <stdbool.h> #include <sys/stat.h> #include "time-dst.h" #include "util.h" /* * If tzh_version is '2' or greater, the above is followed by a second instance * of tzhead and a second instance of the data in which each coded transition * time uses 8 rather than 4 chars, then a POSIX-TZ-environment-variable-style * string for use in handling instants after the last transition time stored in * the file * (with nothing between the newlines if there is no POSIX * representation for such instants). */ #define TZ_MAGIC "TZif" struct tzhead { char tzh_magic[4]; /* TZ_MAGIC */ char tzh_version[1]; /* '\0' or '2' as of 2005 */ char tzh_reserved[15]; /* reserved--must be zero */ char tzh_ttisgmtcnt[4]; /* coded number of trans. time flags */ char tzh_ttisstdcnt[4]; /* coded number of trans. time flags */ char tzh_leapcnt[4]; /* coded number of leap seconds */ char tzh_timecnt[4]; /* coded number of transition times */ char tzh_typecnt[4]; /* coded number of local time types */ char tzh_charcnt[4]; /* coded number of abbr. chars */ }; struct ttinfo { long int offset; /* Seconds east of GMT. */ unsigned char isdst; /* Used to set tm_isdst. */ unsigned char idx; /* Index into `zone_names'. */ unsigned char isstd; /* Transition times are in standard time. */ unsigned char isgmt; /* Transition times are in GMT. */ }; struct leap { time_t transition; /* Time the transition takes effect. */ long int change; /* Seconds of correction to apply. */ }; static inline int decode(const void *ptr) { return be32toh(*(int *)ptr); } static inline int64_t decode64(const void *ptr) { return be64toh(*(int64_t *)ptr); } int time_get_dst(time_t date, const char *tzfile, time_t *switch_cur, char **zone_cur, bool *dst_cur, time_t *switch_next, int *delta_next, char **zone_next, bool *dst_next) { unsigned char *type_idxs = 0; size_t num_types = 0; struct ttinfo *types = NULL; char *zone_names = NULL; struct stat st; size_t num_isstd, num_isgmt; struct tzhead tzhead; size_t chars; size_t i; size_t total_size; size_t types_idx; int trans_width = 4; size_t tzspec_len; size_t num_leaps; size_t lo, hi; size_t num_transitions = 0; _cleanup_free_ time_t *transitions = NULL; _cleanup_fclose_ FILE *f; f = fopen(tzfile, "re"); if (f == NULL) return -errno; if (fstat(fileno(f), &st) < 0) return -errno; read_again: if (fread((void *)&tzhead, sizeof(tzhead), 1, f) != 1 || memcmp(tzhead.tzh_magic, TZ_MAGIC, sizeof(tzhead.tzh_magic)) != 0) return -EINVAL; num_transitions = (size_t)decode(tzhead.tzh_timecnt); num_types = (size_t)decode(tzhead.tzh_typecnt); chars = (size_t)decode(tzhead.tzh_charcnt); num_leaps = (size_t)decode(tzhead.tzh_leapcnt); num_isstd = (size_t)decode(tzhead.tzh_ttisstdcnt); num_isgmt = (size_t)decode(tzhead.tzh_ttisgmtcnt); /* For platforms with 64-bit time_t we use the new format if available. */ if (sizeof(time_t) == 8 && trans_width == 4 && tzhead.tzh_version[0] != '\0') { size_t to_skip; /* We use the 8-byte format. */ trans_width = 8; /* Position the stream before the second header. */ to_skip = (num_transitions * (4 + 1) + num_types * 6 + chars + num_leaps * 8 + num_isstd + num_isgmt); if (fseek(f, to_skip, SEEK_CUR) != 0) return -EINVAL; goto read_again; } if (num_transitions > ((SIZE_MAX - (__alignof__(struct ttinfo) - 1)) / (sizeof(time_t) + 1))) return -EINVAL; total_size = num_transitions * (sizeof(time_t) + 1); total_size = ((total_size + __alignof__(struct ttinfo) - 1) & ~(__alignof__(struct ttinfo) - 1)); types_idx = total_size; if (num_leaps > (SIZE_MAX - total_size) / sizeof(struct ttinfo)) return -EINVAL; total_size += num_types * sizeof(struct ttinfo); if (chars > SIZE_MAX - total_size) return -EINVAL; total_size += chars; if (__alignof__(struct leap) - 1 > SIZE_MAX - total_size) return -EINVAL; total_size = ((total_size + __alignof__(struct leap) - 1) & ~(__alignof__(struct leap) - 1)); if (num_leaps > (SIZE_MAX - total_size) / sizeof(struct leap)) return -EINVAL; total_size += num_leaps * sizeof(struct leap); tzspec_len = 0; if (sizeof(time_t) == 8 && trans_width == 8) { off_t rem = st.st_size - ftello(f); if (rem < 0 || (size_t) rem < (num_transitions * (8 + 1) + num_types * 6 + chars)) return -EINVAL; tzspec_len = (size_t) rem - (num_transitions * (8 + 1) + num_types * 6 + chars); if (num_leaps > SIZE_MAX / 12 || tzspec_len < num_leaps * 12) return -EINVAL; tzspec_len -= num_leaps * 12; if (tzspec_len < num_isstd) return -EINVAL; tzspec_len -= num_isstd; if (tzspec_len == 0 || tzspec_len - 1 < num_isgmt) return -EINVAL; tzspec_len -= num_isgmt + 1; if (SIZE_MAX - total_size < tzspec_len) return -EINVAL; } transitions = (time_t *)calloc(total_size + tzspec_len, 1); if (transitions == NULL) return -EINVAL; type_idxs = (unsigned char *)transitions + (num_transitions * sizeof(time_t)); types = (struct ttinfo *)((char *)transitions + types_idx); zone_names = (char *)types + num_types * sizeof(struct ttinfo); if (sizeof(time_t) == 4 || trans_width == 8) { if (fread(transitions, trans_width + 1, num_transitions, f) != num_transitions) return -EINVAL; } else { if (fread(transitions, 4, num_transitions, f) != num_transitions || fread(type_idxs, 1, num_transitions, f) != num_transitions) return -EINVAL; } /* Check for bogus indices in the data file, so we can hereafter safely use type_idxs[T] as indices into `types' and never crash. */ for (i = 0; i < num_transitions; ++i) if (type_idxs[i] >= num_types) return -EINVAL; if ((BYTE_ORDER != BIG_ENDIAN && (sizeof(time_t) == 4 || trans_width == 4)) || (BYTE_ORDER == BIG_ENDIAN && sizeof(time_t) == 8 && trans_width == 4)) { /* Decode the transition times, stored as 4-byte integers in network (big-endian) byte order. We work from the end of the array so as not to clobber the next element to be processed when sizeof (time_t) > 4. */ i = num_transitions; while (i-- > 0) transitions[i] = decode((char *)transitions + i * 4); } else if (BYTE_ORDER != BIG_ENDIAN && sizeof(time_t) == 8) { /* Decode the transition times, stored as 8-byte integers in network (big-endian) byte order. */ for (i = 0; i < num_transitions; ++i) transitions[i] = decode64((char *)transitions + i * 8); } for (i = 0; i < num_types; ++i) { unsigned char x[4]; int c; if (fread(x, 1, sizeof(x), f) != sizeof(x)) return -EINVAL; c = getc(f); if ((unsigned int)c > 1u) return -EINVAL; types[i].isdst = c; c = getc(f); if ((size_t) c > chars) /* Bogus index in data file. */ return -EINVAL; types[i].idx = c; types[i].offset = (long int)decode(x); } if (fread(zone_names, 1, chars, f) != chars) return -EINVAL; for (i = 0; i < num_isstd; ++i) { int c = getc(f); if (c == EOF) return -EINVAL; types[i].isstd = c != 0; } while (i < num_types) types[i++].isstd = 0; for (i = 0; i < num_isgmt; ++i) { int c = getc(f); if (c == EOF) return -EINVAL; types[i].isgmt = c != 0; } while (i < num_types) types[i++].isgmt = 0; if (num_transitions == 0) return -EINVAL; if (date < transitions[0] || date >= transitions[num_transitions - 1]) return -EINVAL; /* Find the first transition after TIMER, and then pick the type of the transition before it. */ lo = 0; hi = num_transitions - 1; /* Assume that DST is changing twice a year and guess initial search spot from it. Half of a gregorian year has on average 365.2425 * 86400 / 2 = 15778476 seconds. */ i = (transitions[num_transitions - 1] - date) / 15778476; if (i < num_transitions) { i = num_transitions - 1 - i; if (date < transitions[i]) { if (i < 10 || date >= transitions[i - 10]) { /* Linear search. */ while (date < transitions[i - 1]) i--; goto found; } hi = i - 10; } else { if (i + 10 >= num_transitions || date < transitions[i + 10]) { /* Linear search. */ while (date >= transitions[i]) i++; goto found; } lo = i + 10; } } /* Binary search. */ while (lo + 1 < hi) { i = (lo + hi) / 2; if (date < transitions[i]) hi = i; else lo = i; } i = hi; found: if (switch_cur) *switch_cur = transitions[i-1]; if (zone_cur) *zone_cur = strdup(&zone_names[types[type_idxs[i - 1]].idx]); if (dst_cur) *dst_cur = types[type_idxs[i-1]].isdst; if (switch_next) *switch_next = transitions[i]; if (delta_next) *delta_next = (types[type_idxs[i]].offset - types[type_idxs[i-1]].offset) / 60; if (zone_next) *zone_next = strdup(&zone_names[types[type_idxs[i]].idx]); if (dst_next) *dst_next = types[type_idxs[i]].isdst; return 0; }