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pgtz.c
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1 /*-------------------------------------------------------------------------
2  *
3  * pgtz.c
4  * Timezone Library Integration Functions
5  *
6  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
7  *
8  * IDENTIFICATION
9  * src/timezone/pgtz.c
10  *
11  *-------------------------------------------------------------------------
12  */
13 #include "postgres.h"
14 
15 #include <ctype.h>
16 #include <fcntl.h>
17 #include <sys/stat.h>
18 #include <time.h>
19 
20 #include "datatype/timestamp.h"
21 #include "miscadmin.h"
22 #include "pgtz.h"
23 #include "storage/fd.h"
24 #include "utils/hsearch.h"
25 
26 
27 /* Current session timezone (controlled by TimeZone GUC) */
29 
30 /* Current log timezone (controlled by log_timezone GUC) */
32 
33 
34 static bool scan_directory_ci(const char *dirname,
35  const char *fname, int fnamelen,
36  char *canonname, int canonnamelen);
37 
38 
39 /*
40  * Return full pathname of timezone data directory
41  */
42 static const char *
43 pg_TZDIR(void)
44 {
45 #ifndef SYSTEMTZDIR
46  /* normal case: timezone stuff is under our share dir */
47  static bool done_tzdir = false;
48  static char tzdir[MAXPGPATH];
49 
50  if (done_tzdir)
51  return tzdir;
52 
54  strlcpy(tzdir + strlen(tzdir), "/timezone", MAXPGPATH - strlen(tzdir));
55 
56  done_tzdir = true;
57  return tzdir;
58 #else
59  /* we're configured to use system's timezone database */
60  return SYSTEMTZDIR;
61 #endif
62 }
63 
64 
65 /*
66  * Given a timezone name, open() the timezone data file. Return the
67  * file descriptor if successful, -1 if not.
68  *
69  * The input name is searched for case-insensitively (we assume that the
70  * timezone database does not contain case-equivalent names).
71  *
72  * If "canonname" is not NULL, then on success the canonical spelling of the
73  * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
74  */
75 int
76 pg_open_tzfile(const char *name, char *canonname)
77 {
78  const char *fname;
79  char fullname[MAXPGPATH];
80  int fullnamelen;
81  int orignamelen;
82 
83  /* Initialize fullname with base name of tzdata directory */
84  strlcpy(fullname, pg_TZDIR(), sizeof(fullname));
85  orignamelen = fullnamelen = strlen(fullname);
86 
87  if (fullnamelen + 1 + strlen(name) >= MAXPGPATH)
88  return -1; /* not gonna fit */
89 
90  /*
91  * If the caller doesn't need the canonical spelling, first just try to
92  * open the name as-is. This can be expected to succeed if the given name
93  * is already case-correct, or if the filesystem is case-insensitive; and
94  * we don't need to distinguish those situations if we aren't tasked with
95  * reporting the canonical spelling.
96  */
97  if (canonname == NULL)
98  {
99  int result;
100 
101  fullname[fullnamelen] = '/';
102  /* test above ensured this will fit: */
103  strcpy(fullname + fullnamelen + 1, name);
104  result = open(fullname, O_RDONLY | PG_BINARY, 0);
105  if (result >= 0)
106  return result;
107  /* If that didn't work, fall through to do it the hard way */
108  fullname[fullnamelen] = '\0';
109  }
110 
111  /*
112  * Loop to split the given name into directory levels; for each level,
113  * search using scan_directory_ci().
114  */
115  fname = name;
116  for (;;)
117  {
118  const char *slashptr;
119  int fnamelen;
120 
121  slashptr = strchr(fname, '/');
122  if (slashptr)
123  fnamelen = slashptr - fname;
124  else
125  fnamelen = strlen(fname);
126  if (!scan_directory_ci(fullname, fname, fnamelen,
127  fullname + fullnamelen + 1,
128  MAXPGPATH - fullnamelen - 1))
129  return -1;
130  fullname[fullnamelen++] = '/';
131  fullnamelen += strlen(fullname + fullnamelen);
132  if (slashptr)
133  fname = slashptr + 1;
134  else
135  break;
136  }
137 
138  if (canonname)
139  strlcpy(canonname, fullname + orignamelen + 1, TZ_STRLEN_MAX + 1);
140 
141  return open(fullname, O_RDONLY | PG_BINARY, 0);
142 }
143 
144 
145 /*
146  * Scan specified directory for a case-insensitive match to fname
147  * (of length fnamelen --- fname may not be null terminated!). If found,
148  * copy the actual filename into canonname and return true.
149  */
150 static bool
151 scan_directory_ci(const char *dirname, const char *fname, int fnamelen,
152  char *canonname, int canonnamelen)
153 {
154  bool found = false;
155  DIR *dirdesc;
156  struct dirent *direntry;
157 
158  dirdesc = AllocateDir(dirname);
159 
160  while ((direntry = ReadDirExtended(dirdesc, dirname, LOG)) != NULL)
161  {
162  /*
163  * Ignore . and .., plus any other "hidden" files. This is a security
164  * measure to prevent access to files outside the timezone directory.
165  */
166  if (direntry->d_name[0] == '.')
167  continue;
168 
169  if (strlen(direntry->d_name) == fnamelen &&
170  pg_strncasecmp(direntry->d_name, fname, fnamelen) == 0)
171  {
172  /* Found our match */
173  strlcpy(canonname, direntry->d_name, canonnamelen);
174  found = true;
175  break;
176  }
177  }
178 
179  FreeDir(dirdesc);
180 
181  return found;
182 }
183 
184 
185 /*
186  * We keep loaded timezones in a hashtable so we don't have to
187  * load and parse the TZ definition file every time one is selected.
188  * Because we want timezone names to be found case-insensitively,
189  * the hash key is the uppercased name of the zone.
190  */
191 typedef struct
192 {
193  /* tznameupper contains the all-upper-case name of the timezone */
194  char tznameupper[TZ_STRLEN_MAX + 1];
196 } pg_tz_cache;
197 
198 static HTAB *timezone_cache = NULL;
199 
200 
201 static bool
203 {
204  HASHCTL hash_ctl;
205 
206  hash_ctl.keysize = TZ_STRLEN_MAX + 1;
207  hash_ctl.entrysize = sizeof(pg_tz_cache);
208 
209  timezone_cache = hash_create("Timezones",
210  4,
211  &hash_ctl,
213  if (!timezone_cache)
214  return false;
215 
216  return true;
217 }
218 
219 /*
220  * Load a timezone from file or from cache.
221  * Does not verify that the timezone is acceptable!
222  *
223  * "GMT" is always interpreted as the tzparse() definition, without attempting
224  * to load a definition from the filesystem. This has a number of benefits:
225  * 1. It's guaranteed to succeed, so we don't have the failure mode wherein
226  * the bootstrap default timezone setting doesn't work (as could happen if
227  * the OS attempts to supply a leap-second-aware version of "GMT").
228  * 2. Because we aren't accessing the filesystem, we can safely initialize
229  * the "GMT" zone definition before my_exec_path is known.
230  * 3. It's quick enough that we don't waste much time when the bootstrap
231  * default timezone setting is later overridden from postgresql.conf.
232  */
233 pg_tz *
234 pg_tzset(const char *name)
235 {
236  pg_tz_cache *tzp;
237  struct state tzstate;
238  char uppername[TZ_STRLEN_MAX + 1];
239  char canonname[TZ_STRLEN_MAX + 1];
240  char *p;
241 
242  if (strlen(name) > TZ_STRLEN_MAX)
243  return NULL; /* not going to fit */
244 
245  if (!timezone_cache)
247  return NULL;
248 
249  /*
250  * Upcase the given name to perform a case-insensitive hashtable search.
251  * (We could alternatively downcase it, but we prefer upcase so that we
252  * can get consistently upcased results from tzparse() in case the name is
253  * a POSIX-style timezone spec.)
254  */
255  p = uppername;
256  while (*name)
257  *p++ = pg_toupper((unsigned char) *name++);
258  *p = '\0';
259 
260  tzp = (pg_tz_cache *) hash_search(timezone_cache,
261  uppername,
262  HASH_FIND,
263  NULL);
264  if (tzp)
265  {
266  /* Timezone found in cache, nothing more to do */
267  return &tzp->tz;
268  }
269 
270  /*
271  * "GMT" is always sent to tzparse(), as per discussion above.
272  */
273  if (strcmp(uppername, "GMT") == 0)
274  {
275  if (!tzparse(uppername, &tzstate, true))
276  {
277  /* This really, really should not happen ... */
278  elog(ERROR, "could not initialize GMT time zone");
279  }
280  /* Use uppercase name as canonical */
281  strcpy(canonname, uppername);
282  }
283  else if (tzload(uppername, canonname, &tzstate, true) != 0)
284  {
285  if (uppername[0] == ':' || !tzparse(uppername, &tzstate, false))
286  {
287  /* Unknown timezone. Fail our call instead of loading GMT! */
288  return NULL;
289  }
290  /* For POSIX timezone specs, use uppercase name as canonical */
291  strcpy(canonname, uppername);
292  }
293 
294  /* Save timezone in the cache */
295  tzp = (pg_tz_cache *) hash_search(timezone_cache,
296  uppername,
297  HASH_ENTER,
298  NULL);
299 
300  /* hash_search already copied uppername into the hash key */
301  strcpy(tzp->tz.TZname, canonname);
302  memcpy(&tzp->tz.state, &tzstate, sizeof(tzstate));
303 
304  return &tzp->tz;
305 }
306 
307 /*
308  * Load a fixed-GMT-offset timezone.
309  * This is used for SQL-spec SET TIME ZONE INTERVAL 'foo' cases.
310  * It's otherwise equivalent to pg_tzset().
311  *
312  * The GMT offset is specified in seconds, positive values meaning west of
313  * Greenwich (ie, POSIX not ISO sign convention). However, we use ISO
314  * sign convention in the displayable abbreviation for the zone.
315  *
316  * Caution: this can fail (return NULL) if the specified offset is outside
317  * the range allowed by the zic library.
318  */
319 pg_tz *
320 pg_tzset_offset(long gmtoffset)
321 {
322  long absoffset = (gmtoffset < 0) ? -gmtoffset : gmtoffset;
323  char offsetstr[64];
324  char tzname[128];
325 
326  snprintf(offsetstr, sizeof(offsetstr),
327  "%02ld", absoffset / SECS_PER_HOUR);
328  absoffset %= SECS_PER_HOUR;
329  if (absoffset != 0)
330  {
331  snprintf(offsetstr + strlen(offsetstr),
332  sizeof(offsetstr) - strlen(offsetstr),
333  ":%02ld", absoffset / SECS_PER_MINUTE);
334  absoffset %= SECS_PER_MINUTE;
335  if (absoffset != 0)
336  snprintf(offsetstr + strlen(offsetstr),
337  sizeof(offsetstr) - strlen(offsetstr),
338  ":%02ld", absoffset);
339  }
340  if (gmtoffset > 0)
341  snprintf(tzname, sizeof(tzname), "<-%s>+%s",
342  offsetstr, offsetstr);
343  else
344  snprintf(tzname, sizeof(tzname), "<+%s>-%s",
345  offsetstr, offsetstr);
346 
347  return pg_tzset(tzname);
348 }
349 
350 
351 /*
352  * Initialize timezone library
353  *
354  * This is called before GUC variable initialization begins. Its purpose
355  * is to ensure that log_timezone has a valid value before any logging GUC
356  * variables could become set to values that require elog.c to provide
357  * timestamps (e.g., log_line_prefix). We may as well initialize
358  * session_timezone to something valid, too.
359  */
360 void
362 {
363  /*
364  * We may not yet know where PGSHAREDIR is (in particular this is true in
365  * an EXEC_BACKEND subprocess). So use "GMT", which pg_tzset forces to be
366  * interpreted without reference to the filesystem. This corresponds to
367  * the bootstrap default for these variables in guc.c, although in
368  * principle it could be different.
369  */
370  session_timezone = pg_tzset("GMT");
371  log_timezone = session_timezone;
372 }
373 
374 
375 /*
376  * Functions to enumerate available timezones
377  *
378  * Note that pg_tzenumerate_next() will return a pointer into the pg_tzenum
379  * structure, so the data is only valid up to the next call.
380  *
381  * All data is allocated using palloc in the current context.
382  */
383 #define MAX_TZDIR_DEPTH 10
384 
385 struct pg_tzenum
386 {
387  int baselen;
388  int depth;
391  struct pg_tz tz;
392 };
393 
394 /* typedef pg_tzenum is declared in pgtime.h */
395 
396 pg_tzenum *
398 {
399  pg_tzenum *ret = (pg_tzenum *) palloc0(sizeof(pg_tzenum));
400  char *startdir = pstrdup(pg_TZDIR());
401 
402  ret->baselen = strlen(startdir) + 1;
403  ret->depth = 0;
404  ret->dirname[0] = startdir;
405  ret->dirdesc[0] = AllocateDir(startdir);
406  if (!ret->dirdesc[0])
407  ereport(ERROR,
409  errmsg("could not open directory \"%s\": %m", startdir)));
410  return ret;
411 }
412 
413 void
415 {
416  while (dir->depth >= 0)
417  {
418  FreeDir(dir->dirdesc[dir->depth]);
419  pfree(dir->dirname[dir->depth]);
420  dir->depth--;
421  }
422  pfree(dir);
423 }
424 
425 pg_tz *
427 {
428  while (dir->depth >= 0)
429  {
430  struct dirent *direntry;
431  char fullname[MAXPGPATH * 2];
432  struct stat statbuf;
433 
434  direntry = ReadDir(dir->dirdesc[dir->depth], dir->dirname[dir->depth]);
435 
436  if (!direntry)
437  {
438  /* End of this directory */
439  FreeDir(dir->dirdesc[dir->depth]);
440  pfree(dir->dirname[dir->depth]);
441  dir->depth--;
442  continue;
443  }
444 
445  if (direntry->d_name[0] == '.')
446  continue;
447 
448  snprintf(fullname, sizeof(fullname), "%s/%s",
449  dir->dirname[dir->depth], direntry->d_name);
450  if (stat(fullname, &statbuf) != 0)
451  ereport(ERROR,
453  errmsg("could not stat \"%s\": %m", fullname)));
454 
455  if (S_ISDIR(statbuf.st_mode))
456  {
457  /* Step into the subdirectory */
458  if (dir->depth >= MAX_TZDIR_DEPTH - 1)
459  ereport(ERROR,
460  (errmsg_internal("timezone directory stack overflow")));
461  dir->depth++;
462  dir->dirname[dir->depth] = pstrdup(fullname);
463  dir->dirdesc[dir->depth] = AllocateDir(fullname);
464  if (!dir->dirdesc[dir->depth])
465  ereport(ERROR,
467  errmsg("could not open directory \"%s\": %m",
468  fullname)));
469 
470  /* Start over reading in the new directory */
471  continue;
472  }
473 
474  /*
475  * Load this timezone using tzload() not pg_tzset(), so we don't fill
476  * the cache. Also, don't ask for the canonical spelling: we already
477  * know it, and pg_open_tzfile's way of finding it out is pretty
478  * inefficient.
479  */
480  if (tzload(fullname + dir->baselen, NULL, &dir->tz.state, true) != 0)
481  {
482  /* Zone could not be loaded, ignore it */
483  continue;
484  }
485 
486  if (!pg_tz_acceptable(&dir->tz))
487  {
488  /* Ignore leap-second zones */
489  continue;
490  }
491 
492  /* OK, return the canonical zone name spelling. */
493  strlcpy(dir->tz.TZname, fullname + dir->baselen,
494  sizeof(dir->tz.TZname));
495 
496  /* Timezone loaded OK. */
497  return &dir->tz;
498  }
499 
500  /* Nothing more found */
501  return NULL;
502 }
pg_tz * pg_tzset_offset(long gmtoffset)
Definition: pgtz.c:320
struct pg_tz tz
Definition: pgtz.c:391
#define HASH_ELEM
Definition: hsearch.h:95
void pg_timezone_initialize(void)
Definition: pgtz.c:361
int tzload(const char *name, char *canonname, struct state *sp, bool doextend)
Definition: localtime.c:584
char * pstrdup(const char *in)
Definition: mcxt.c:1299
pg_tz * log_timezone
Definition: pgtz.c:31
struct dirent * ReadDirExtended(DIR *dir, const char *dirname, int elevel)
Definition: fd.c:2715
Size entrysize
Definition: hsearch.h:76
void * hash_search(HTAB *hashp, const void *keyPtr, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:954
#define LOG
Definition: elog.h:26
Definition: dirent.h:9
pg_tz * pg_tzenumerate_next(pg_tzenum *dir)
Definition: pgtz.c:426
DIR * dirdesc[MAX_TZDIR_DEPTH]
Definition: pgtz.c:389
static const char * pg_TZDIR(void)
Definition: pgtz.c:43
#define PG_BINARY
Definition: c.h:1271
int pg_open_tzfile(const char *name, char *canonname)
Definition: pgtz.c:76
int pg_strncasecmp(const char *s1, const char *s2, size_t n)
Definition: pgstrcasecmp.c:69
Definition: dynahash.c:219
void pfree(void *pointer)
Definition: mcxt.c:1169
#define TZ_STRLEN_MAX
Definition: pgtime.h:44
Definition: dirent.c:25
char * dirname[MAX_TZDIR_DEPTH]
Definition: pgtz.c:390
#define ERROR
Definition: elog.h:46
static bool init_timezone_hashtable(void)
Definition: pgtz.c:202
#define MAXPGPATH
#define MAX_TZDIR_DEPTH
Definition: pgtz.c:383
#define SECS_PER_MINUTE
Definition: timestamp.h:88
int errcode_for_file_access(void)
Definition: elog.c:721
pg_tz * pg_tzset(const char *name)
Definition: pgtz.c:234
HTAB * hash_create(const char *tabname, long nelem, const HASHCTL *info, int flags)
Definition: dynahash.c:349
DIR * AllocateDir(const char *dirname)
Definition: fd.c:2634
bool tzparse(const char *name, struct state *sp, bool lastditch)
Definition: localtime.c:934
#define SECS_PER_HOUR
Definition: timestamp.h:87
char my_exec_path[MAXPGPATH]
Definition: globals.c:75
void * palloc0(Size size)
Definition: mcxt.c:1093
bool pg_tz_acceptable(pg_tz *tz)
Definition: localtime.c:1888
pg_tz tz
Definition: pgtz.c:195
struct state state
Definition: pgtz.h:69
unsigned short st_mode
Definition: win32_port.h:260
Definition: pgtz.h:65
Size keysize
Definition: hsearch.h:75
static HTAB * timezone_cache
Definition: pgtz.c:198
#define ereport(elevel,...)
Definition: elog.h:157
int baselen
Definition: pgtz.c:387
size_t strlcpy(char *dst, const char *src, size_t siz)
Definition: strlcpy.c:45
static bool scan_directory_ci(const char *dirname, const char *fname, int fnamelen, char *canonname, int canonnamelen)
Definition: pgtz.c:151
int errmsg_internal(const char *fmt,...)
Definition: elog.c:996
pg_tz * session_timezone
Definition: pgtz.c:28
Definition: regguts.h:317
struct dirent * ReadDir(DIR *dir, const char *dirname)
Definition: fd.c:2700
char TZname[TZ_STRLEN_MAX+1]
Definition: pgtz.h:68
void pg_tzenumerate_end(pg_tzenum *dir)
Definition: pgtz.c:414
const char * name
Definition: encode.c:515
#define S_ISDIR(m)
Definition: win32_port.h:316
int errmsg(const char *fmt,...)
Definition: elog.c:909
#define elog(elevel,...)
Definition: elog.h:232
char d_name[MAX_PATH]
Definition: dirent.h:15
#define HASH_STRINGS
Definition: hsearch.h:96
void get_share_path(const char *my_exec_path, char *ret_path)
Definition: path.c:704
pg_tzenum * pg_tzenumerate_start(void)
Definition: pgtz.c:397
int depth
Definition: pgtz.c:388
unsigned char pg_toupper(unsigned char ch)
Definition: pgstrcasecmp.c:105
#define snprintf
Definition: port.h:216
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Definition: fd.c:2752
#define stat
Definition: win32_port.h:275