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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) 1996-2017, 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 "miscadmin.h"
21 #include "pgtz.h"
22 #include "storage/fd.h"
23 #include "utils/hsearch.h"
24 
25 
26 /* Current session timezone (controlled by TimeZone GUC) */
28 
29 /* Current log timezone (controlled by log_timezone GUC) */
31 
32 
33 static bool scan_directory_ci(const char *dirname,
34  const char *fname, int fnamelen,
35  char *canonname, int canonnamelen);
36 
37 
38 /*
39  * Return full pathname of timezone data directory
40  */
41 static const char *
42 pg_TZDIR(void)
43 {
44 #ifndef SYSTEMTZDIR
45  /* normal case: timezone stuff is under our share dir */
46  static bool done_tzdir = false;
47  static char tzdir[MAXPGPATH];
48 
49  if (done_tzdir)
50  return tzdir;
51 
53  strlcpy(tzdir + strlen(tzdir), "/timezone", MAXPGPATH - strlen(tzdir));
54 
55  done_tzdir = true;
56  return tzdir;
57 #else
58  /* we're configured to use system's timezone database */
59  return SYSTEMTZDIR;
60 #endif
61 }
62 
63 
64 /*
65  * Given a timezone name, open() the timezone data file. Return the
66  * file descriptor if successful, -1 if not.
67  *
68  * The input name is searched for case-insensitively (we assume that the
69  * timezone database does not contain case-equivalent names).
70  *
71  * If "canonname" is not NULL, then on success the canonical spelling of the
72  * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
73  */
74 int
75 pg_open_tzfile(const char *name, char *canonname)
76 {
77  const char *fname;
78  char fullname[MAXPGPATH];
79  int fullnamelen;
80  int orignamelen;
81 
82  /*
83  * Loop to split the given name into directory levels; for each level,
84  * search using scan_directory_ci().
85  */
86  strlcpy(fullname, pg_TZDIR(), sizeof(fullname));
87  orignamelen = fullnamelen = strlen(fullname);
88  fname = name;
89  for (;;)
90  {
91  const char *slashptr;
92  int fnamelen;
93 
94  slashptr = strchr(fname, '/');
95  if (slashptr)
96  fnamelen = slashptr - fname;
97  else
98  fnamelen = strlen(fname);
99  if (fullnamelen + 1 + fnamelen >= MAXPGPATH)
100  return -1; /* not gonna fit */
101  if (!scan_directory_ci(fullname, fname, fnamelen,
102  fullname + fullnamelen + 1,
103  MAXPGPATH - fullnamelen - 1))
104  return -1;
105  fullname[fullnamelen++] = '/';
106  fullnamelen += strlen(fullname + fullnamelen);
107  if (slashptr)
108  fname = slashptr + 1;
109  else
110  break;
111  }
112 
113  if (canonname)
114  strlcpy(canonname, fullname + orignamelen + 1, TZ_STRLEN_MAX + 1);
115 
116  return open(fullname, O_RDONLY | PG_BINARY, 0);
117 }
118 
119 
120 /*
121  * Scan specified directory for a case-insensitive match to fname
122  * (of length fnamelen --- fname may not be null terminated!). If found,
123  * copy the actual filename into canonname and return true.
124  */
125 static bool
126 scan_directory_ci(const char *dirname, const char *fname, int fnamelen,
127  char *canonname, int canonnamelen)
128 {
129  bool found = false;
130  DIR *dirdesc;
131  struct dirent *direntry;
132 
133  dirdesc = AllocateDir(dirname);
134  if (!dirdesc)
135  {
136  ereport(LOG,
138  errmsg("could not open directory \"%s\": %m", dirname)));
139  return false;
140  }
141 
142  while ((direntry = ReadDir(dirdesc, dirname)) != NULL)
143  {
144  /*
145  * Ignore . and .., plus any other "hidden" files. This is a security
146  * measure to prevent access to files outside the timezone directory.
147  */
148  if (direntry->d_name[0] == '.')
149  continue;
150 
151  if (strlen(direntry->d_name) == fnamelen &&
152  pg_strncasecmp(direntry->d_name, fname, fnamelen) == 0)
153  {
154  /* Found our match */
155  strlcpy(canonname, direntry->d_name, canonnamelen);
156  found = true;
157  break;
158  }
159  }
160 
161  FreeDir(dirdesc);
162 
163  return found;
164 }
165 
166 
167 /*
168  * We keep loaded timezones in a hashtable so we don't have to
169  * load and parse the TZ definition file every time one is selected.
170  * Because we want timezone names to be found case-insensitively,
171  * the hash key is the uppercased name of the zone.
172  */
173 typedef struct
174 {
175  /* tznameupper contains the all-upper-case name of the timezone */
176  char tznameupper[TZ_STRLEN_MAX + 1];
178 } pg_tz_cache;
179 
181 
182 
183 static bool
185 {
186  HASHCTL hash_ctl;
187 
188  MemSet(&hash_ctl, 0, sizeof(hash_ctl));
189 
190  hash_ctl.keysize = TZ_STRLEN_MAX + 1;
191  hash_ctl.entrysize = sizeof(pg_tz_cache);
192 
193  timezone_cache = hash_create("Timezones",
194  4,
195  &hash_ctl,
196  HASH_ELEM);
197  if (!timezone_cache)
198  return false;
199 
200  return true;
201 }
202 
203 /*
204  * Load a timezone from file or from cache.
205  * Does not verify that the timezone is acceptable!
206  *
207  * "GMT" is always interpreted as the tzparse() definition, without attempting
208  * to load a definition from the filesystem. This has a number of benefits:
209  * 1. It's guaranteed to succeed, so we don't have the failure mode wherein
210  * the bootstrap default timezone setting doesn't work (as could happen if
211  * the OS attempts to supply a leap-second-aware version of "GMT").
212  * 2. Because we aren't accessing the filesystem, we can safely initialize
213  * the "GMT" zone definition before my_exec_path is known.
214  * 3. It's quick enough that we don't waste much time when the bootstrap
215  * default timezone setting is later overridden from postgresql.conf.
216  */
217 pg_tz *
218 pg_tzset(const char *name)
219 {
220  pg_tz_cache *tzp;
221  struct state tzstate;
222  char uppername[TZ_STRLEN_MAX + 1];
223  char canonname[TZ_STRLEN_MAX + 1];
224  char *p;
225 
226  if (strlen(name) > TZ_STRLEN_MAX)
227  return NULL; /* not going to fit */
228 
229  if (!timezone_cache)
231  return NULL;
232 
233  /*
234  * Upcase the given name to perform a case-insensitive hashtable search.
235  * (We could alternatively downcase it, but we prefer upcase so that we
236  * can get consistently upcased results from tzparse() in case the name is
237  * a POSIX-style timezone spec.)
238  */
239  p = uppername;
240  while (*name)
241  *p++ = pg_toupper((unsigned char) *name++);
242  *p = '\0';
243 
244  tzp = (pg_tz_cache *) hash_search(timezone_cache,
245  uppername,
246  HASH_FIND,
247  NULL);
248  if (tzp)
249  {
250  /* Timezone found in cache, nothing more to do */
251  return &tzp->tz;
252  }
253 
254  /*
255  * "GMT" is always sent to tzparse(), as per discussion above.
256  */
257  if (strcmp(uppername, "GMT") == 0)
258  {
259  if (!tzparse(uppername, &tzstate, true))
260  {
261  /* This really, really should not happen ... */
262  elog(ERROR, "could not initialize GMT time zone");
263  }
264  /* Use uppercase name as canonical */
265  strcpy(canonname, uppername);
266  }
267  else if (tzload(uppername, canonname, &tzstate, true) != 0)
268  {
269  if (uppername[0] == ':' || !tzparse(uppername, &tzstate, false))
270  {
271  /* Unknown timezone. Fail our call instead of loading GMT! */
272  return NULL;
273  }
274  /* For POSIX timezone specs, use uppercase name as canonical */
275  strcpy(canonname, uppername);
276  }
277 
278  /* Save timezone in the cache */
279  tzp = (pg_tz_cache *) hash_search(timezone_cache,
280  uppername,
281  HASH_ENTER,
282  NULL);
283 
284  /* hash_search already copied uppername into the hash key */
285  strcpy(tzp->tz.TZname, canonname);
286  memcpy(&tzp->tz.state, &tzstate, sizeof(tzstate));
287 
288  return &tzp->tz;
289 }
290 
291 /*
292  * Load a fixed-GMT-offset timezone.
293  * This is used for SQL-spec SET TIME ZONE INTERVAL 'foo' cases.
294  * It's otherwise equivalent to pg_tzset().
295  *
296  * The GMT offset is specified in seconds, positive values meaning west of
297  * Greenwich (ie, POSIX not ISO sign convention). However, we use ISO
298  * sign convention in the displayable abbreviation for the zone.
299  *
300  * Caution: this can fail (return NULL) if the specified offset is outside
301  * the range allowed by the zic library.
302  */
303 pg_tz *
304 pg_tzset_offset(long gmtoffset)
305 {
306  long absoffset = (gmtoffset < 0) ? -gmtoffset : gmtoffset;
307  char offsetstr[64];
308  char tzname[128];
309 
310  snprintf(offsetstr, sizeof(offsetstr),
311  "%02ld", absoffset / SECSPERHOUR);
312  absoffset %= SECSPERHOUR;
313  if (absoffset != 0)
314  {
315  snprintf(offsetstr + strlen(offsetstr),
316  sizeof(offsetstr) - strlen(offsetstr),
317  ":%02ld", absoffset / SECSPERMIN);
318  absoffset %= SECSPERMIN;
319  if (absoffset != 0)
320  snprintf(offsetstr + strlen(offsetstr),
321  sizeof(offsetstr) - strlen(offsetstr),
322  ":%02ld", absoffset);
323  }
324  if (gmtoffset > 0)
325  snprintf(tzname, sizeof(tzname), "<-%s>+%s",
326  offsetstr, offsetstr);
327  else
328  snprintf(tzname, sizeof(tzname), "<+%s>-%s",
329  offsetstr, offsetstr);
330 
331  return pg_tzset(tzname);
332 }
333 
334 
335 /*
336  * Initialize timezone library
337  *
338  * This is called before GUC variable initialization begins. Its purpose
339  * is to ensure that log_timezone has a valid value before any logging GUC
340  * variables could become set to values that require elog.c to provide
341  * timestamps (e.g., log_line_prefix). We may as well initialize
342  * session_timestamp to something valid, too.
343  */
344 void
346 {
347  /*
348  * We may not yet know where PGSHAREDIR is (in particular this is true in
349  * an EXEC_BACKEND subprocess). So use "GMT", which pg_tzset forces to be
350  * interpreted without reference to the filesystem. This corresponds to
351  * the bootstrap default for these variables in guc.c, although in
352  * principle it could be different.
353  */
354  session_timezone = pg_tzset("GMT");
355  log_timezone = session_timezone;
356 }
357 
358 
359 /*
360  * Functions to enumerate available timezones
361  *
362  * Note that pg_tzenumerate_next() will return a pointer into the pg_tzenum
363  * structure, so the data is only valid up to the next call.
364  *
365  * All data is allocated using palloc in the current context.
366  */
367 #define MAX_TZDIR_DEPTH 10
368 
369 struct pg_tzenum
370 {
371  int baselen;
372  int depth;
375  struct pg_tz tz;
376 };
377 
378 /* typedef pg_tzenum is declared in pgtime.h */
379 
380 pg_tzenum *
382 {
383  pg_tzenum *ret = (pg_tzenum *) palloc0(sizeof(pg_tzenum));
384  char *startdir = pstrdup(pg_TZDIR());
385 
386  ret->baselen = strlen(startdir) + 1;
387  ret->depth = 0;
388  ret->dirname[0] = startdir;
389  ret->dirdesc[0] = AllocateDir(startdir);
390  if (!ret->dirdesc[0])
391  ereport(ERROR,
393  errmsg("could not open directory \"%s\": %m", startdir)));
394  return ret;
395 }
396 
397 void
399 {
400  while (dir->depth >= 0)
401  {
402  FreeDir(dir->dirdesc[dir->depth]);
403  pfree(dir->dirname[dir->depth]);
404  dir->depth--;
405  }
406  pfree(dir);
407 }
408 
409 pg_tz *
411 {
412  while (dir->depth >= 0)
413  {
414  struct dirent *direntry;
415  char fullname[MAXPGPATH];
416  struct stat statbuf;
417 
418  direntry = ReadDir(dir->dirdesc[dir->depth], dir->dirname[dir->depth]);
419 
420  if (!direntry)
421  {
422  /* End of this directory */
423  FreeDir(dir->dirdesc[dir->depth]);
424  pfree(dir->dirname[dir->depth]);
425  dir->depth--;
426  continue;
427  }
428 
429  if (direntry->d_name[0] == '.')
430  continue;
431 
432  snprintf(fullname, MAXPGPATH, "%s/%s",
433  dir->dirname[dir->depth], direntry->d_name);
434  if (stat(fullname, &statbuf) != 0)
435  ereport(ERROR,
437  errmsg("could not stat \"%s\": %m", fullname)));
438 
439  if (S_ISDIR(statbuf.st_mode))
440  {
441  /* Step into the subdirectory */
442  if (dir->depth >= MAX_TZDIR_DEPTH - 1)
443  ereport(ERROR,
444  (errmsg_internal("timezone directory stack overflow")));
445  dir->depth++;
446  dir->dirname[dir->depth] = pstrdup(fullname);
447  dir->dirdesc[dir->depth] = AllocateDir(fullname);
448  if (!dir->dirdesc[dir->depth])
449  ereport(ERROR,
451  errmsg("could not open directory \"%s\": %m",
452  fullname)));
453 
454  /* Start over reading in the new directory */
455  continue;
456  }
457 
458  /*
459  * Load this timezone using tzload() not pg_tzset(), so we don't fill
460  * the cache
461  */
462  if (tzload(fullname + dir->baselen, dir->tz.TZname, &dir->tz.state,
463  true) != 0)
464  {
465  /* Zone could not be loaded, ignore it */
466  continue;
467  }
468 
469  if (!pg_tz_acceptable(&dir->tz))
470  {
471  /* Ignore leap-second zones */
472  continue;
473  }
474 
475  /* Timezone loaded OK. */
476  return &dir->tz;
477  }
478 
479  /* Nothing more found */
480  return NULL;
481 }
pg_tz * pg_tzset_offset(long gmtoffset)
Definition: pgtz.c:304
struct pg_tz tz
Definition: pgtz.c:375
#define HASH_ELEM
Definition: hsearch.h:87
void pg_timezone_initialize(void)
Definition: pgtz.c:345
int tzload(const char *name, char *canonname, struct state *sp, bool doextend)
Definition: localtime.c:537
char * pstrdup(const char *in)
Definition: mcxt.c:1077
pg_tz * log_timezone
Definition: pgtz.c:30
Size entrysize
Definition: hsearch.h:73
#define MemSet(start, val, len)
Definition: c.h:857
int snprintf(char *str, size_t count, const char *fmt,...) pg_attribute_printf(3
void * hash_search(HTAB *hashp, const void *keyPtr, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:885
#define LOG
Definition: elog.h:26
Definition: dirent.h:9
pg_tz * pg_tzenumerate_next(pg_tzenum *dir)
Definition: pgtz.c:410
DIR * dirdesc[MAX_TZDIR_DEPTH]
Definition: pgtz.c:373
static const char * pg_TZDIR(void)
Definition: pgtz.c:42
#define PG_BINARY
Definition: c.h:1038
int pg_open_tzfile(const char *name, char *canonname)
Definition: pgtz.c:75
int pg_strncasecmp(const char *s1, const char *s2, size_t n)
Definition: pgstrcasecmp.c:69
Definition: dynahash.c:193
void pfree(void *pointer)
Definition: mcxt.c:950
#define TZ_STRLEN_MAX
Definition: pgtime.h:44
Definition: dirent.c:25
char * dirname[MAX_TZDIR_DEPTH]
Definition: pgtz.c:374
#define ERROR
Definition: elog.h:43
static bool init_timezone_hashtable(void)
Definition: pgtz.c:184
#define MAXPGPATH
#define MAX_TZDIR_DEPTH
Definition: pgtz.c:367
int errcode_for_file_access(void)
Definition: elog.c:598
pg_tz * pg_tzset(const char *name)
Definition: pgtz.c:218
DIR * AllocateDir(const char *dirname)
Definition: fd.c:2335
#define ereport(elevel, rest)
Definition: elog.h:122
bool tzparse(const char *name, struct state *sp, bool lastditch)
Definition: localtime.c:878
char my_exec_path[MAXPGPATH]
Definition: globals.c:63
void * palloc0(Size size)
Definition: mcxt.c:878
HTAB * hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
Definition: dynahash.c:301
bool pg_tz_acceptable(pg_tz *tz)
Definition: localtime.c:1785
pg_tz tz
Definition: pgtz.c:177
struct state state
Definition: pgtz.h:63
Definition: pgtz.h:59
Size keysize
Definition: hsearch.h:72
static HTAB * timezone_cache
Definition: pgtz.c:180
int baselen
Definition: pgtz.c:371
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:126
int errmsg_internal(const char *fmt,...)
Definition: elog.c:827
#define NULL
Definition: c.h:229
pg_tz * session_timezone
Definition: pgtz.c:27
Definition: regguts.h:298
struct dirent * ReadDir(DIR *dir, const char *dirname)
Definition: fd.c:2401
char TZname[TZ_STRLEN_MAX+1]
Definition: pgtz.h:62
#define SECSPERMIN
Definition: tzfile.h:103
void pg_tzenumerate_end(pg_tzenum *dir)
Definition: pgtz.c:398
const char * name
Definition: encode.c:521
int errmsg(const char *fmt,...)
Definition: elog.c:797
char d_name[MAX_PATH]
Definition: dirent.h:14
#define elog
Definition: elog.h:219
#define SECSPERHOUR
Definition: tzfile.h:109
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:381
int depth
Definition: pgtz.c:372
unsigned char pg_toupper(unsigned char ch)
Definition: pgstrcasecmp.c:105
int FreeDir(DIR *dir)
Definition: fd.c:2444