time/tzfile.c

   1 /* Copyright (C) 1991, 92, 93, 95, 96, 97, 98 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <assert.h>
  20 #include <limits.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <time.h>
  25 #include <unistd.h>
  26
  27 #define NOID
  28 #include <timezone/tzfile.h>
  29
  30 int __use_tzfile = 0;
  31
  32 struct ttinfo
  33   {
  34     long int offset;            /* Seconds east of GMT.  */
  35     unsigned char isdst;        /* Used to set tm_isdst.  */
  36     unsigned char idx;          /* Index into `zone_names'.  */
  37     unsigned char isstd;        /* Transition times are in standard time.  */
  38     unsigned char isgmt;        /* Transition times are in GMT.  */
  39   };
  40
  41 struct leap
  42   {
  43     time_t transition;          /* Time the transition takes effect.  */
  44     long int change;            /* Seconds of correction to apply.  */
  45   };
  46
  47 static struct ttinfo *find_transition (time_t timer) internal_function;
  48 static void compute_tzname_max (size_t) internal_function;
  49
  50 static size_t num_transitions;
  51 static time_t *transitions = NULL;
  52 static unsigned char *type_idxs = NULL;
  53 static size_t num_types;
  54 static struct ttinfo *types = NULL;
  55 static char *zone_names = NULL;
  56 static long int rule_stdoff;
  57 static long int rule_dstoff;
  58 static size_t num_leaps;
  59 static struct leap *leaps = NULL;
  60
  61 #include <endian.h>
  62 #include <byteswap.h>
  63
  64 /* Decode the four bytes at PTR as a signed integer in network byte order.  */
  65 static inline int
  66 decode (const void *ptr)
  67 {
  68   if ((BYTE_ORDER == BIG_ENDIAN) && sizeof (int) == 4)
  69     return *(const int *) ptr;
  70   else if (BYTE_ORDER == LITTLE_ENDIAN && sizeof (int) == 4)
  71     return bswap_32 (*(const int *) ptr);
  72   else
  73     {
  74       const unsigned char *p = ptr;
  75       int result = *p & (1 << (CHAR_BIT - 1)) ? ~0 : 0;
  76
  77       result = (result << 8) | *p++;
  78       result = (result << 8) | *p++;
  79       result = (result << 8) | *p++;
  80       result = (result << 8) | *p++;
  81
  82       return result;
  83     }
  84 }
  85
  86 void
  87 __tzfile_read (const char *file)
  88 {
  89   static const char default_tzdir[] = TZDIR;
  90   size_t num_isstd, num_isgmt;
  91   register FILE *f;
  92   struct tzhead tzhead;
  93   size_t chars;
  94   register size_t i;
  95
  96   __use_tzfile = 0;
  97
  98   if (transitions != NULL)
  99     free ((void *) transitions);
 100   transitions = NULL;
 101   if (type_idxs != NULL)
 102     free ((void *) type_idxs);
 103   type_idxs = NULL;
 104   if (types != NULL)
 105     free ((void *) types);
 106   types = NULL;
 107   if (zone_names != NULL)
 108     free ((void *) zone_names);
 109   zone_names = NULL;
 110   if (leaps != NULL)
 111     free ((void *) leaps);
 112   leaps = NULL;
 113
 114   if (file == NULL)
 115     /* No user specification; use the site-wide default.  */
 116     file = TZDEFAULT;
 117   else if (*file == '\0')
 118     /* User specified the empty string; use UTC with no leap seconds.  */
 119     return;
 120   else
 121     {
 122       /* We must not allow to read an arbitrary file in a setuid
 123          program.  So we fail for any file which is not in the
 124          directory hierachy starting at TZDIR
 125          and which is not the system wide default TZDEFAULT.  */
 126       if (__libc_enable_secure
 127           && ((*file == '/'
 128                && memcmp (file, TZDEFAULT, sizeof TZDEFAULT)
 129                && memcmp (file, default_tzdir, sizeof (default_tzdir) - 1))
 130               || strstr (file, "../") != NULL))
 131         /* This test is certainly a bit too restrictive but it should
 132            catch all critical cases.  */
 133         return;
 134     }
 135
 136   if (*file != '/')
 137     {
 138       const char *tzdir;
 139       unsigned int len, tzdir_len;
 140       char *new, *tmp;
 141
 142       tzdir = __secure_getenv ("TZDIR");
 143       if (tzdir == NULL || *tzdir == '\0')
 144         {
 145           tzdir = default_tzdir;
 146           tzdir_len = sizeof (default_tzdir) - 1;
 147         }
 148       else
 149         tzdir_len = strlen (tzdir);
 150       len = strlen (file) + 1;
 151       new = (char *) __alloca (tzdir_len + 1 + len);
 152       tmp = __mempcpy (new, tzdir, tzdir_len);
 153       *tmp++ = '/';
 154       __mempcpy (tmp, file, len);
 155       file = new;
 156     }
 157
 158   f = fopen (file, "r");
 159   if (f == NULL)
 160     return;
 161
 162   if (fread_unlocked ((void *) &tzhead, sizeof (tzhead), 1, f) != 1)
 163     goto lose;
 164
 165   num_transitions = (size_t) decode (tzhead.tzh_timecnt);
 166   num_types = (size_t) decode (tzhead.tzh_typecnt);
 167   chars = (size_t) decode (tzhead.tzh_charcnt);
 168   num_leaps = (size_t) decode (tzhead.tzh_leapcnt);
 169   num_isstd = (size_t) decode (tzhead.tzh_ttisstdcnt);
 170   num_isgmt = (size_t) decode (tzhead.tzh_ttisgmtcnt);
 171
 172   if (num_transitions > 0)
 173     {
 174       transitions = (time_t *) malloc (num_transitions * sizeof (time_t));
 175       if (transitions == NULL)
 176         goto lose;
 177       type_idxs = (unsigned char *) malloc (num_transitions);
 178       if (type_idxs == NULL)
 179         goto lose;
 180     }
 181   if (num_types > 0)
 182     {
 183       types = (struct ttinfo *) malloc (num_types * sizeof (struct ttinfo));
 184       if (types == NULL)
 185         goto lose;
 186     }
 187   if (chars > 0)
 188     {
 189       zone_names = (char *) malloc (chars);
 190       if (zone_names == NULL)
 191         goto lose;
 192     }
 193   if (num_leaps > 0)
 194     {
 195       leaps = (struct leap *) malloc (num_leaps * sizeof (struct leap));
 196       if (leaps == NULL)
 197         goto lose;
 198     }
 199
 200   if (sizeof (time_t) < 4)
 201       abort ();
 202
 203   if (fread_unlocked (transitions, 4, num_transitions, f) != num_transitions
 204       || fread_unlocked (type_idxs, 1, num_transitions, f) != num_transitions)
 205     goto lose;
 206
 207   /* Check for bogus indices in the data file, so we can hereafter
 208      safely use type_idxs[T] as indices into `types' and never crash.  */
 209   for (i = 0; i < num_transitions; ++i)
 210     if (type_idxs[i] >= num_types)
 211       goto lose;
 212
 213   if (BYTE_ORDER != BIG_ENDIAN || sizeof (time_t) != 4)
 214     {
 215       /* Decode the transition times, stored as 4-byte integers in
 216          network (big-endian) byte order.  We work from the end of
 217          the array so as not to clobber the next element to be
 218          processed when sizeof (time_t) > 4.  */
 219       i = num_transitions;
 220       while (i-- > 0)
 221         transitions[i] = decode ((char *) transitions + i * 4);
 222     }
 223
 224   for (i = 0; i < num_types; ++i)
 225     {
 226       unsigned char x[4];
 227       if (fread_unlocked (x, 1, 4, f) != 4
 228           || fread_unlocked (&types[i].isdst, 1, 1, f) != 1
 229           || fread_unlocked (&types[i].idx, 1, 1, f) != 1)
 230         goto lose;
 231       if (types[i].isdst > 1)
 232         goto lose;
 233       if (types[i].idx >= chars) /* Bogus index in data file.  */
 234         goto lose;
 235       types[i].offset = (long int) decode (x);
 236     }
 237
 238   if (fread_unlocked (zone_names, 1, chars, f) != chars)
 239     goto lose;
 240
 241   for (i = 0; i < num_leaps; ++i)
 242     {
 243       unsigned char x[4];
 244       if (fread_unlocked (x, 1, sizeof (x), f) != sizeof (x))
 245         goto lose;
 246       leaps[i].transition = (time_t) decode (x);
 247       if (fread_unlocked (x, 1, sizeof (x), f) != sizeof (x))
 248         goto lose;
 249       leaps[i].change = (long int) decode (x);
 250     }
 251
 252   for (i = 0; i < num_isstd; ++i)
 253     {
 254       int c = getc_unlocked (f);
 255       if (c == EOF)
 256         goto lose;
 257       types[i].isstd = c != 0;
 258     }
 259   while (i < num_types)
 260     types[i++].isstd = 0;
 261
 262   for (i = 0; i < num_isgmt; ++i)
 263     {
 264       int c = getc_unlocked (f);
 265       if (c == EOF)
 266         goto lose;
 267       types[i].isgmt = c != 0;
 268     }
 269   while (i < num_types)
 270     types[i++].isgmt = 0;
 271
 272   fclose (f);
 273
 274   /* First "register" all timezone names.  */
 275   for (i = 0; i < num_types; ++i)
 276     (void) __tzstring (&zone_names[types[i].idx]);
 277
 278   /* Find the standard and daylight time offsets used by the rule file.
 279      We choose the offsets in the types of each flavor that are
 280      transitioned to earliest in time.  */
 281   __tzname[0] = NULL;
 282   __tzname[1] = NULL;
 283   for (i = num_transitions; i > 0; )
 284     {
 285       int type = type_idxs[--i];
 286       int dst = types[type].isdst;
 287       int idx = types[type].idx;
 288
 289       if (__tzname[dst] == NULL)
 290         {
 291           __tzname[dst] = __tzstring (&zone_names[idx]);
 292
 293           if (__tzname[1 - dst] != NULL)
 294             break;
 295         }
 296     }
 297   if (__tzname[0] == NULL)
 298     {
 299       /* This should only happen if there are no transition rules.
 300          In this case there should be only one single type.  */
 301       assert (num_types == 1);
 302       __tzname[0] = __tzstring (zone_names);
 303     }
 304   if (__tzname[1] == NULL)
 305     __tzname[1] = __tzname[0];
 306
 307   compute_tzname_max (chars);
 308
 309   if (num_transitions == 0)
 310     /* Use the first rule (which should also be the only one).  */
 311     rule_stdoff = rule_dstoff = types[0].offset;
 312   else
 313     {
 314       rule_stdoff = rule_dstoff = 0;
 315       for (i = 0; i < num_transitions; ++i)
 316         {
 317           if (!rule_stdoff && !types[type_idxs[i]].isdst)
 318             rule_stdoff = types[type_idxs[i]].offset;
 319           if (!rule_dstoff && types[type_idxs[i]].isdst)
 320             rule_dstoff = types[type_idxs[i]].offset;
 321           if (rule_stdoff && rule_dstoff)
 322             break;
 323         }
 324     }
 325
 326   __daylight = rule_stdoff != rule_dstoff;
 327   __timezone = -rule_stdoff;
 328
 329   __use_tzfile = 1;
 330   return;
 331
 332  lose:
 333   fclose (f);
 334 }
 335 \f
 336 /* The user specified a hand-made timezone, but not its DST rules.
 337    We will use the names and offsets from the user, and the rules
 338    from the TZDEFRULES file.  */
 339
 340 void
 341 __tzfile_default (const char *std, const char *dst,
 342                   long int stdoff, long int dstoff)
 343 {
 344   size_t stdlen, dstlen, i;
 345   int isdst;
 346
 347   __tzfile_read (TZDEFRULES);
 348   if (!__use_tzfile)
 349     return;
 350
 351   if (num_types < 2)
 352     {
 353       __use_tzfile = 0;
 354       return;
 355     }
 356
 357   /* Ignore the zone names read from the file.  */
 358   free (zone_names);
 359
 360   /* Use the names the user specified.  */
 361   stdlen = strlen (std) + 1;
 362   dstlen = strlen (dst) + 1;
 363   zone_names = malloc (stdlen + dstlen);
 364   if (zone_names == NULL)
 365     {
 366       __use_tzfile = 0;
 367       return;
 368     }
 369   __mempcpy (__mempcpy (zone_names, std, stdlen), dst, dstlen);
 370
 371   /* Now there are only two zones, regardless of what the file contained.  */
 372   num_types = 2;
 373
 374   /* Now correct the transition times for the user-specified standard and
 375      daylight offsets from GMT.  */
 376   isdst = 0;
 377   for (i = 0; i < num_transitions; ++i)
 378     {
 379       struct ttinfo *trans_type = &types[type_idxs[i]];
 380
 381       /* We will use only types 0 (standard) and 1 (daylight).
 382          Fix up this transition to point to whichever matches
 383          the flavor of its original type.  */
 384       type_idxs[i] = trans_type->isdst;
 385
 386       if (trans_type->isgmt)
 387         /* The transition time is in GMT.  No correction to apply.  */ ;
 388       else if (isdst && !trans_type->isstd)
 389         /* The type says this transition is in "local wall clock time", and
 390            wall clock time as of the previous transition was DST.  Correct
 391            for the difference between the rule's DST offset and the user's
 392            DST offset.  */
 393         transitions[i] += dstoff - rule_dstoff;
 394       else
 395         /* This transition is in "local wall clock time", and wall clock
 396            time as of this iteration is non-DST.  Correct for the
 397            difference between the rule's standard offset and the user's
 398            standard offset.  */
 399         transitions[i] += stdoff - rule_stdoff;
 400
 401       /* The DST state of "local wall clock time" for the next iteration is
 402          as specified by this transition.  */
 403       isdst = trans_type->isdst;
 404     }
 405
 406   /* Reset types 0 and 1 to describe the user's settings.  */
 407   types[0].idx = 0;
 408   types[0].offset = stdoff;
 409   types[0].isdst = 0;
 410   types[1].idx = stdlen;
 411   types[1].offset = dstoff;
 412   types[1].isdst = 1;
 413
 414   /* Reset the zone names to point to the user's names.  */
 415   __tzname[0] = (char *) std;
 416   __tzname[1] = (char *) dst;
 417
 418   /* Set the timezone.  */
 419   __timezone = -types[0].offset;
 420
 421   compute_tzname_max (stdlen + dstlen);
 422 }
 423 \f
 424 static struct ttinfo *
 425 internal_function
 426 find_transition (time_t timer)
 427 {
 428   size_t i;
 429
 430   if (num_transitions == 0 || timer < transitions[0])
 431     {
 432       /* TIMER is before any transition (or there are no transitions).
 433          Choose the first non-DST type
 434          (or the first if they're all DST types).  */
 435       i = 0;
 436       while (i < num_types && types[i].isdst)
 437         ++i;
 438       if (i == num_types)
 439         i = 0;
 440     }
 441   else
 442     {
 443       /* Find the first transition after TIMER, and
 444          then pick the type of the transition before it.  */
 445       for (i = 1; i < num_transitions; ++i)
 446         if (timer < transitions[i])
 447           break;
 448       i = type_idxs[i - 1];
 449     }
 450
 451   return &types[i];
 452 }
 453 \f
 454 int
 455 __tzfile_compute (time_t timer, int use_localtime,
 456                   long int *leap_correct, int *leap_hit,
 457                   struct tm *tp)
 458 {
 459   register size_t i;
 460
 461   if (use_localtime)
 462     {
 463       struct ttinfo *info = find_transition (timer);
 464       __daylight = rule_stdoff != rule_dstoff;
 465       __timezone = -rule_stdoff;
 466       __tzname[0] = NULL;
 467       __tzname[1] = NULL;
 468       for (i = num_transitions; i > 0; )
 469         {
 470           int type = type_idxs[--i];
 471           int dst = types[type].isdst;
 472           int idx = types[type].idx;
 473
 474           if (__tzname[dst] == NULL)
 475             {
 476               __tzname[dst] = __tzstring (&zone_names[idx]);
 477
 478               if (__tzname[1 - dst] != NULL)
 479                 break;
 480             }
 481         }
 482       if (__tzname[0] == NULL)
 483         {
 484           /* This should only happen if there are no transition rules.
 485              In this case there should be only one single type.  */
 486           assert (num_types == 1);
 487           __tzname[0] = __tzstring (zone_names);
 488         }
 489       if (__tzname[1] == NULL)
 490         /* There is no daylight saving time.  */
 491         __tzname[1] = __tzname[0];
 492       tp->tm_isdst = info->isdst;
 493       tp->tm_zone = &zone_names[info->idx];
 494       tp->tm_gmtoff = info->offset;
 495     }
 496
 497   *leap_correct = 0L;
 498   *leap_hit = 0;
 499
 500   /* Find the last leap second correction transition time before TIMER.  */
 501   i = num_leaps;
 502   do
 503     if (i-- == 0)
 504       return 1;
 505   while (timer < leaps[i].transition);
 506
 507   /* Apply its correction.  */
 508   *leap_correct = leaps[i].change;
 509
 510   if (timer == leaps[i].transition && /* Exactly at the transition time.  */
 511       ((i == 0 && leaps[i].change > 0) ||
 512        leaps[i].change > leaps[i - 1].change))
 513     {
 514       *leap_hit = 1;
 515       while (i > 0
 516              && leaps[i].transition == leaps[i - 1].transition + 1
 517              && leaps[i].change == leaps[i - 1].change + 1)
 518         {
 519           ++*leap_hit;
 520           --i;
 521         }
 522     }
 523
 524   return 1;
 525 }
 526 \f
 527 static void
 528 internal_function
 529 compute_tzname_max (size_t chars)
 530 {
 531   const char *p;
 532
 533   p = zone_names;
 534   do
 535     {
 536       const char *start = p;
 537       while (*p != '\0')
 538         ++p;
 539       if ((size_t) (p - start) > __tzname_cur_max)
 540         __tzname_cur_max = p - start;
 541     }
 542   while (++p < &zone_names[chars]);
 543 }