From 6d7ff848e55bb7173d2db8550fd6617bc05be255 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 18 May 2003 01:06:26 +0000
Subject: [PATCH] Add code to test for unknown timezone names (following some
ideas from Ross Reedstrom, a couple months back) and to detect timezones that
are using leap-second timekeeping. The unknown-zone-name test is pretty
heuristic and ugly, but it seems better than the old behavior of just
switching to GMT given a bad name. Also make DecodePosixTimezone() a tad
more robust.
---
src/backend/commands/variable.c | 260 +++++++++++++++++++++++++++----
src/backend/utils/adt/datetime.c | 40 +++--
src/include/utils/datetime.h | 4 +-
3 files changed, 265 insertions(+), 39 deletions(-)
diff --git a/src/backend/commands/variable.c b/src/backend/commands/variable.c
index 25291d34cb8..aa8d9d36134 100644
--- a/src/backend/commands/variable.c
+++ b/src/backend/commands/variable.c
@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.75 2003/04/27 17:31:25 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.76 2003/05/18 01:06:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -235,7 +235,147 @@ show_datestyle(void)
/*
* Storage for TZ env var is allocated with an arbitrary size of 64 bytes.
*/
-static char tzbuf[64];
+#define TZBUF_LEN 64
+
+static char tzbuf[TZBUF_LEN];
+
+/*
+ * First time through, we remember the original environment TZ value, if any.
+ */
+static bool have_saved_tz = false;
+static char orig_tzbuf[TZBUF_LEN];
+
+/*
+ * Convenience subroutine for assigning the value of TZ
+ */
+static void
+set_tz(const char *tz)
+{
+ strcpy(tzbuf, "TZ=");
+ strncpy(tzbuf + 3, tz, sizeof(tzbuf) - 4);
+ if (putenv(tzbuf) != 0) /* shouldn't happen? */
+ elog(LOG, "Unable to set TZ environment variable");
+ tzset();
+}
+
+/*
+ * Remove any value of TZ we have established
+ *
+ * Note: this leaves us with *no* value of TZ in the environment, and
+ * is therefore only appropriate for reverting to that state, not for
+ * reverting to a state where TZ was set to something else.
+ */
+static void
+clear_tz(void)
+{
+ /*
+ * unsetenv() works fine, but is BSD, not POSIX, and is not
+ * available under Solaris, among others. Apparently putenv()
+ * called as below clears the process-specific environment
+ * variables. Other reasonable arguments to putenv() (e.g.
+ * "TZ=", "TZ", "") result in a core dump (under Linux
+ * anyway). - thomas 1998-01-26
+ */
+ if (tzbuf[0] == 'T')
+ {
+ strcpy(tzbuf, "=");
+ if (putenv(tzbuf) != 0)
+ elog(LOG, "Unable to clear TZ environment variable");
+ tzset();
+ }
+}
+
+/*
+ * Check whether tzset() succeeded
+ *
+ * Unfortunately, tzset doesn't offer any well-defined way to detect that the
+ * value of TZ was bad. Often it will just select UTC (GMT) as the effective
+ * timezone. We use the following heuristics:
+ *
+ * If tzname[1] is a nonempty string, *or* the global timezone variable is
+ * not zero, then tzset must have recognized the TZ value as something
+ * different from UTC. Return true.
+ *
+ * Otherwise, check to see if the TZ name is a known spelling of "UTC"
+ * (ie, appears in our internal tables as a timezone equivalent to UTC).
+ * If so, accept it.
+ *
+ * This will reject nonstandard spellings of UTC unless tzset() chose to
+ * set tzname[1] as well as tzname[0]. The glibc version of tzset() will
+ * do so, but on other systems we may be tightening the spec a little.
+ *
+ * Another problem is that on some platforms (eg HPUX), if tzset thinks the
+ * input is bogus then it will adopt the system default timezone, which we
+ * really can't tell is not the intended translation of the input.
+ *
+ * Still, it beats failing to detect bad TZ names at all, and a silent
+ * failure mode of adopting the system-wide default is much better than
+ * a silent failure mode of adopting UTC.
+ *
+ * NB: this must NOT elog(ERROR). The caller must get control back so that
+ * it can restore the old value of TZ if we don't like the new one.
+ */
+static bool
+tzset_succeeded(const char *tz)
+{
+ char tztmp[TZBUF_LEN];
+ char *cp;
+ int tzval;
+
+ /*
+ * Check first set of heuristics to say that tzset definitely worked.
+ */
+ if (tzname[1] && tzname[1][0] != '\0')
+ return true;
+ if (TIMEZONE_GLOBAL != 0)
+ return true;
+
+ /*
+ * Check for known spellings of "UTC". Note we must downcase the input
+ * before passing it to DecodePosixTimezone().
+ */
+ StrNCpy(tztmp, tz, sizeof(tztmp));
+ for (cp = tztmp; *cp; cp++)
+ *cp = tolower((unsigned char) *cp);
+ if (DecodePosixTimezone(tztmp, &tzval) == 0)
+ if (tzval == 0)
+ return true;
+
+ return false;
+}
+
+/*
+ * Check whether timezone is acceptable.
+ *
+ * What we are doing here is checking for leap-second-aware timekeeping.
+ * We need to reject such TZ settings because they'll wreak havoc with our
+ * date/time arithmetic.
+ *
+ * NB: this must NOT elog(ERROR). The caller must get control back so that
+ * it can restore the old value of TZ if we don't like the new one.
+ */
+static bool
+tz_acceptable(void)
+{
+ struct tm tt;
+ time_t time2000;
+
+ /*
+ * To detect leap-second timekeeping, compute the time_t value for
+ * local midnight, 2000-01-01. Insist that this be a multiple of 60;
+ * any partial-minute offset has to be due to leap seconds.
+ */
+ MemSet(&tt, 0, sizeof(tt));
+ tt.tm_year = 100;
+ tt.tm_mon = 0;
+ tt.tm_mday = 1;
+ tt.tm_isdst = -1;
+ time2000 = mktime(&tt);
+ if ((time2000 % 60) != 0)
+ return false;
+
+ return true;
+}
/*
* assign_timezone: GUC assign_hook for timezone
@@ -247,6 +387,21 @@ assign_timezone(const char *value, bool doit, bool interactive)
char *endptr;
double hours;
+ /*
+ * On first call, see if there is a TZ in the original environment.
+ * Save that value permanently.
+ */
+ if (!have_saved_tz)
+ {
+ char *orig_tz = getenv("TZ");
+
+ if (orig_tz)
+ StrNCpy(orig_tzbuf, orig_tz, sizeof(orig_tzbuf));
+ else
+ orig_tzbuf[0] = '\0';
+ have_saved_tz = true;
+ }
+
/*
* Check for INTERVAL 'foo'
*/
@@ -313,25 +468,36 @@ assign_timezone(const char *value, bool doit, bool interactive)
else if (strcasecmp(value, "UNKNOWN") == 0)
{
/*
- * Clear any TZ value we may have established.
- *
- * unsetenv() works fine, but is BSD, not POSIX, and is not
- * available under Solaris, among others. Apparently putenv()
- * called as below clears the process-specific environment
- * variables. Other reasonable arguments to putenv() (e.g.
- * "TZ=", "TZ", "") result in a core dump (under Linux
- * anyway). - thomas 1998-01-26
+ * UNKNOWN is the value shown as the "default" for TimeZone
+ * in guc.c. We interpret it as meaning the original TZ
+ * inherited from the environment. Note that if there is an
+ * original TZ setting, we will return that rather than UNKNOWN
+ * as the canonical spelling.
*/
if (doit)
{
- if (tzbuf[0] == 'T')
+ bool ok;
+
+ /* Revert to original setting of TZ, whatever it was */
+ if (orig_tzbuf[0])
{
- strcpy(tzbuf, "=");
- if (putenv(tzbuf) != 0)
- elog(ERROR, "Unable to clear TZ environment variable");
- tzset();
+ set_tz(orig_tzbuf);
+ ok = tzset_succeeded(orig_tzbuf) && tz_acceptable();
+ }
+ else
+ {
+ clear_tz();
+ ok = tz_acceptable();
+ }
+
+ if (ok)
+ HasCTZSet = false;
+ else
+ {
+ /* Bogus, so force UTC (equivalent to INTERVAL 0) */
+ CTimeZone = 0;
+ HasCTZSet = true;
}
- HasCTZSet = false;
}
}
else
@@ -339,19 +505,58 @@ assign_timezone(const char *value, bool doit, bool interactive)
/*
* Otherwise assume it is a timezone name.
*
- * XXX unfortunately we have no reasonable way to check whether a
- * timezone name is good, so we have to just assume that it
- * is.
+ * We have to actually apply the change before we can have any
+ * hope of checking it. So, save the old value in case we have
+ * to back out. Note that it's possible the old setting is in
+ * tzbuf, so we'd better copy it.
*/
- if (doit)
+ char save_tzbuf[TZBUF_LEN];
+ char *save_tz;
+ bool known,
+ acceptable;
+
+ save_tz = getenv("TZ");
+ if (save_tz)
+ StrNCpy(save_tzbuf, save_tz, sizeof(save_tzbuf));
+
+ set_tz(value);
+
+ known = tzset_succeeded(value);
+ acceptable = tz_acceptable();
+
+ if (doit && known && acceptable)
{
- strcpy(tzbuf, "TZ=");
- strncat(tzbuf, value, sizeof(tzbuf) - 4);
- if (putenv(tzbuf) != 0) /* shouldn't happen? */
- elog(LOG, "assign_timezone: putenv failed");
- tzset();
+ /* Keep the changed TZ */
HasCTZSet = false;
}
+ else
+ {
+ /*
+ * Revert to prior TZ setting; note we haven't changed
+ * HasCTZSet in this path, so if we were previously using
+ * a fixed offset, we still are.
+ */
+ if (save_tz)
+ set_tz(save_tzbuf);
+ else
+ clear_tz();
+ /* Complain if it was bad */
+ if (!known)
+ {
+ elog(interactive ? ERROR : LOG,
+ "unrecognized timezone name \"%s\"",
+ value);
+ return NULL;
+ }
+ if (!acceptable)
+ {
+ elog(interactive ? ERROR : LOG,
+ "timezone \"%s\" appears to use leap seconds"
+ "\n\tPostgreSQL does not support leap seconds",
+ value);
+ return NULL;
+ }
+ }
}
}
@@ -369,10 +574,7 @@ assign_timezone(const char *value, bool doit, bool interactive)
return NULL;
if (HasCTZSet)
- {
- snprintf(result, sizeof(tzbuf), "%.5f",
- (double) CTimeZone / 3600.0);
- }
+ snprintf(result, sizeof(tzbuf), "%.5f", (double) CTimeZone / 3600.0);
else if (tzbuf[0] == 'T')
strcpy(result, tzbuf + 3);
else
diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index abcdf1321fd..31b42d4612f 100644
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.104 2003/05/04 04:30:15 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.105 2003/05/18 01:06:26 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -36,7 +36,6 @@ static int DecodeTime(char *str, int fmask, int *tmask,
static int DecodeTimezone(char *str, int *tzp);
static datetkn *datebsearch(char *key, datetkn *base, unsigned int nel);
static int DecodeDate(char *str, int fmask, int *tmask, struct tm * tm);
-static int DecodePosixTimezone(char *str, int *val);
static void TrimTrailingZeros(char *str);
@@ -942,8 +941,6 @@ DecodeDateTime(char **field, int *ftype, int nf,
return -1;
val = strtol(field[i], &cp, 10);
- if (*cp != '-')
- return -1;
j2date(val, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
/* Get the time zone from the end of the string */
@@ -2555,6 +2552,10 @@ DecodeNumberField(int len, char *str, int fmask,
/* DecodeTimezone()
* Interpret string as a numeric timezone.
*
+ * Return 0 if okay (and set *tzp), nonzero if not okay.
+ *
+ * NB: this must *not* elog on failure; see commands/variable.c.
+ *
* Note: we allow timezone offsets up to 13:59. There are places that
* use +1300 summer time.
*/
@@ -2567,7 +2568,10 @@ DecodeTimezone(char *str, int *tzp)
char *cp;
int len;
- /* assume leading character is "+" or "-" */
+ /* leading character must be "+" or "-" */
+ if (*str != '+' && *str != '-')
+ return -1;
+
hr = strtol((str + 1), &cp, 10);
/* explicit delimiter? */
@@ -2589,6 +2593,7 @@ DecodeTimezone(char *str, int *tzp)
min = 0;
tz = (hr * 60 + min) * 60;
+
if (*str == '-')
tz = -tz;
@@ -2601,9 +2606,14 @@ DecodeTimezone(char *str, int *tzp)
* Interpret string as a POSIX-compatible timezone:
* PST-hh:mm
* PST+h
+ * PST
* - thomas 2000-03-15
+ *
+ * Return 0 if okay (and set *tzp), nonzero if not okay.
+ *
+ * NB: this must *not* elog on failure; see commands/variable.c.
*/
-static int
+int
DecodePosixTimezone(char *str, int *tzp)
{
int val,
@@ -2612,13 +2622,21 @@ DecodePosixTimezone(char *str, int *tzp)
char *cp;
char delim;
+ /* advance over name part */
cp = str;
- while ((*cp != '\0') && isalpha((unsigned char) *cp))
+ while (*cp && isalpha((unsigned char) *cp))
cp++;
- if (DecodeTimezone(cp, &tz) != 0)
- return -1;
+ /* decode offset, if present */
+ if (*cp)
+ {
+ if (DecodeTimezone(cp, &tz) != 0)
+ return -1;
+ }
+ else
+ tz = 0;
+ /* decode name part. We must temporarily scribble on the input! */
delim = *cp;
*cp = '\0';
type = DecodeSpecial(MAXDATEFIELDS - 1, str, &val);
@@ -2641,8 +2659,12 @@ DecodePosixTimezone(char *str, int *tzp)
/* DecodeSpecial()
* Decode text string using lookup table.
+ *
* Implement a cache lookup since it is likely that dates
* will be related in format.
+ *
+ * NB: this must *not* elog on failure;
+ * see commands/variable.c.
*/
int
DecodeSpecial(int field, char *lowtoken, int *val)
diff --git a/src/include/utils/datetime.h b/src/include/utils/datetime.h
index 1f43ffbceaf..7623095f09c 100644
--- a/src/include/utils/datetime.h
+++ b/src/include/utils/datetime.h
@@ -9,7 +9,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: datetime.h,v 1.38 2003/04/18 01:03:42 momjian Exp $
+ * $Id: datetime.h,v 1.39 2003/05/18 01:06:26 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -290,6 +290,8 @@ extern bool ClearDateCache(bool newval, bool doit, bool interactive);
extern int j2day(int jd);
+extern int DecodePosixTimezone(char *str, int *tzp);
+
extern bool CheckDateTokenTables(void);
#endif /* DATETIME_H */
--
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