Simplify date conversion by avoiding OS utilities

We have to rely on non-portable OS calls to convert UTC times,
and they are not available on many systems (including Solaris and MinGW).
But instead there is a simple algorithm due to Howard Hinnant that
does the same job. Woo.

16 files changed, 77 insertions, 141 deletions

diff --git a/doc/manual/deprecated.rst b/doc/manual/deprecated.rst
index 8cfe7e590..a7dc4bf12 100644
--- a/doc/manual/deprecated.rst
+++ b/doc/manual/deprecated.rst
@@ -55,3 +55,5 @@ in the source.
 - All built in MODP groups < 2048 bits
 
 - All pre-created DSA groups
+
+- Directly accessing the member variables of calendar_point
diff --git a/src/build-data/os/cygwin.txt b/src/build-data/os/cygwin.txt
index a1234dc13..06f6d60f8 100644
--- a/src/build-data/os/cygwin.txt
+++ b/src/build-data/os/cygwin.txt
@@ -12,7 +12,6 @@ doc_dir docs
 
 <target_features>
 gettimeofday
-timegm
 readdir
 threads
 filesystem
diff --git a/src/build-data/os/darwin.txt b/src/build-data/os/darwin.txt
index 41716e21a..6568a9783 100644
--- a/src/build-data/os/darwin.txt
+++ b/src/build-data/os/darwin.txt
@@ -20,7 +20,6 @@ memset_s
 readdir
 sockets
 threads
-timegm
 </target_features>
 
 <aliases>
diff --git a/src/build-data/os/freebsd.txt b/src/build-data/os/freebsd.txt
index 0e60abd2e..fb869dfd0 100644
--- a/src/build-data/os/freebsd.txt
+++ b/src/build-data/os/freebsd.txt
@@ -9,7 +9,6 @@ posix_mlock
 gmtime_r
 dlopen
 readdir
-timegm
 sockets
 threads
 filesystem
diff --git a/src/build-data/os/ios.txt b/src/build-data/os/ios.txt
index ddd283cd9..96ac73721 100644
--- a/src/build-data/os/ios.txt
+++ b/src/build-data/os/ios.txt
@@ -16,7 +16,6 @@ memset_s
 readdir
 sockets
 threads
-timegm
 </target_features>
 
 <aliases>
diff --git a/src/build-data/os/linux.txt b/src/build-data/os/linux.txt
index 59f995fc2..80ea3e63a 100644
--- a/src/build-data/os/linux.txt
+++ b/src/build-data/os/linux.txt
@@ -10,7 +10,6 @@ gmtime_r
 dlopen
 getauxval
 readdir
-timegm
 sockets
 threads
 filesystem
diff --git a/src/build-data/os/mingw.txt b/src/build-data/os/mingw.txt
index bf4333ec0..8d4e94249 100644
--- a/src/build-data/os/mingw.txt
+++ b/src/build-data/os/mingw.txt
@@ -19,7 +19,6 @@ mingw32
 <target_features>
 cryptgenrandom
 loadlibrary
-mkgmtime
 win32_virtual_lock
 win32_get_systemtime
 threads
diff --git a/src/build-data/os/netbsd.txt b/src/build-data/os/netbsd.txt
index 4c82e6239..50d97fd8f 100644
--- a/src/build-data/os/netbsd.txt
+++ b/src/build-data/os/netbsd.txt
@@ -9,7 +9,6 @@ posix_mlock
 gmtime_r
 dlopen
 readdir
-timegm
 threads
 filesystem
 </target_features>
diff --git a/src/build-data/os/openbsd.txt b/src/build-data/os/openbsd.txt
index 5c7ff3259..b858d497c 100644
--- a/src/build-data/os/openbsd.txt
+++ b/src/build-data/os/openbsd.txt
@@ -13,7 +13,6 @@ posix_mlock
 gmtime_r
 dlopen
 readdir
-timegm
 sockets
 threads
 filesystem
diff --git a/src/build-data/os/windows.txt b/src/build-data/os/windows.txt
index 898dfc65f..639b0512d 100644
--- a/src/build-data/os/windows.txt
+++ b/src/build-data/os/windows.txt
@@ -20,7 +20,6 @@ doc_dir docs
 cryptgenrandom
 gmtime_s
 loadlibrary
-mkgmtime
 query_perf_counter
 virtual_lock
 rtlsecurezeromemory
diff --git a/src/build-data/os/winphone.txt b/src/build-data/os/winphone.txt
index bedcc9d2c..0b0318fed 100644
--- a/src/build-data/os/winphone.txt
+++ b/src/build-data/os/winphone.txt
@@ -13,7 +13,6 @@ doc_dir docs
 crypto_ng
 gmtime_s
 loadlibrary
-mkgmtime
 query_perf_counter
 rtlsecurezeromemory
 #stl_filesystem_msvc
diff --git a/src/lib/asn1/asn1_time.cpp b/src/lib/asn1/asn1_time.cpp
index f6a0c414e..daa0c4e7d 100644
--- a/src/lib/asn1/asn1_time.cpp
+++ b/src/lib/asn1/asn1_time.cpp
@@ -20,12 +20,12 @@ X509_Time::X509_Time(const std::chrono::system_clock::time_point& time)
    {
    calendar_point cal = calendar_value(time);
 
-   m_year   = cal.year;
-   m_month  = cal.month;
-   m_day    = cal.day;
-   m_hour   = cal.hour;
-   m_minute = cal.minutes;
-   m_second = cal.seconds;
+   m_year   = cal.get_year();
+   m_month  = cal.get_month();
+   m_day    = cal.get_day();
+   m_hour   = cal.get_hour();
+   m_minute = cal.get_minutes();
+   m_second = cal.get_seconds();
 
    m_tag = (m_year >= 2050) ? GENERALIZED_TIME : UTC_TIME;
    }
diff --git a/src/lib/utils/boost/info.txt b/src/lib/utils/boost/info.txt
index c12b99a28..d54421147 100644
--- a/src/lib/utils/boost/info.txt
+++ b/src/lib/utils/boost/info.txt
@@ -1,7 +1,6 @@
 <defines>
 BOOST_FILESYSTEM -> 20131228
 BOOST_ASIO -> 20131228
-BOOST_DATETIME -> 20150720
 </defines>
 
 load_on vendor
diff --git a/src/lib/utils/calendar.cpp b/src/lib/utils/calendar.cpp
index db933e648..d39e52823 100644
--- a/src/lib/utils/calendar.cpp
+++ b/src/lib/utils/calendar.cpp
@@ -1,6 +1,6 @@
 /*
 * Calendar Functions
-* (C) 1999-2010 Jack Lloyd
+* (C) 1999-2010,2017 Jack Lloyd
 * (C) 2015 Simon Warta (Kullo GmbH)
 *
 * Botan is released under the Simplified BSD License (see license.txt)
@@ -11,13 +11,8 @@
 #include <ctime>
 #include <sstream>
 #include <iomanip>
-#include <botan/mutex.h>
 #include <stdlib.h>
 
-#if defined(BOTAN_HAS_BOOST_DATETIME)
-#include <boost/date_time/posix_time/posix_time_types.hpp>
-#endif
-
 namespace Botan {
 
 namespace {
@@ -40,119 +35,57 @@ std::tm do_gmtime(std::time_t time_val)
    return tm;
    }
 
-#if !defined(BOTAN_TARGET_OS_HAS_TIMEGM) && !(defined(BOTAN_TARGET_OS_HAS_MKGMTIME) && defined(BOTAN_BUILD_COMPILER_IS_MSVC))
+/*
+Portable replacement for timegm, _mkgmtime, etc
 
-#if defined(BOTAN_HAS_BOOST_DATETIME)
+Algorithm due to Howard Hinnant
 
-std::time_t boost_timegm(std::tm *tm)
+See https://howardhinnant.github.io/date_algorithms.html#days_from_civil
+for details and explaination. The code is slightly simplified by our assumption
+that the date is at least 1970, which is sufficient for our purposes.
+*/
+size_t days_since_epoch(uint32_t year, uint32_t month, uint32_t day)
    {
-   const int sec  = tm->tm_sec;
-   const int min  = tm->tm_min;
-   const int hour = tm->tm_hour;
-   const int day  = tm->tm_mday;
-   const int mon  = tm->tm_mon + 1;
-   const int year = tm->tm_year + 1900;
-
-   using namespace boost::posix_time;
-   using namespace boost::gregorian;
-   const auto epoch = ptime(date(1970, 01, 01));
-   const auto time = ptime(date(year, mon, day),
-                           hours(hour) + minutes(min) + seconds(sec));
-   const time_duration diff(time - epoch);
-   std::time_t out = diff.ticks() / diff.ticks_per_second();
-
-   return out;
+   if(month <= 2)
+      year -= 1;
+   const uint32_t era = year / 400;
+   const uint32_t yoe = year - era * 400;      // [0, 399]
+   const uint32_t doy = (153*(month + (month > 2 ? -3 : 9)) + 2)/5 + day-1;  // [0, 365]
+   const uint32_t doe = yoe * 365 + yoe/4 - yoe/100 + doy;         // [0, 146096]
+   return era * 146097 + doe - 719468;
    }
 
-#elif defined(BOTAN_OS_TYPE_IS_UNIX)
-
-#pragma message "Caution! A fallback version of timegm() is used which is not thread-safe"
-
-mutex_type ENV_TZ;
+}
 
-std::time_t fallback_timegm(std::tm *tm)
+std::chrono::system_clock::time_point calendar_point::to_std_timepoint() const
    {
-   std::time_t out;
-   std::string tz_backup;
-
-   ENV_TZ.lock();
-
-   // Store current value of env variable TZ
-   const char* tz_env_pointer = ::getenv("TZ");
-   if (tz_env_pointer != nullptr)
-      tz_backup = std::string(tz_env_pointer);
-
-   // Clear value of TZ
-   ::setenv("TZ", "", 1);
-   ::tzset();
+   if(get_year() < 1970)
+      throw Invalid_Argument("calendar_point::to_std_timepoint() does not support years before 1970");
 
-   out = ::mktime(tm);
-
-   // Restore TZ
-   if (!tz_backup.empty())
+   // 32 bit time_t ends at January 19, 2038
+   // https://msdn.microsoft.com/en-us/library/2093ets1.aspx
+   // Throw after 2037 if 32 bit time_t is used
+   if(get_year() > 2037 && sizeof(std::time_t) == 4)
       {
-      // setenv makes a copy of the second argument
-      ::setenv("TZ", tz_backup.data(), 1);
+      throw Invalid_Argument("calendar_point::to_std_timepoint() does not support years after 2037 on this system");
       }
-   else
+   else if(get_year() >= 2400)
       {
-      ::unsetenv("TZ");
+      // This upper bound is somewhat arbitrary
+      throw Invalid_Argument("calendar_point::to_std_timepoint() does not support years after 2400");
       }
-   ::tzset();
-
-   ENV_TZ.unlock();
 
-   return out;
-}
-#endif // BOTAN_HAS_BOOST_DATETIME
+   const uint64_t seconds_64 = (days_since_epoch(get_year(), get_month(), get_day()) * 86400) +
+                                (get_hour() * 60 * 60) + (get_minutes() * 60) + get_seconds();
 
-#endif
+   const time_t seconds_time_t = static_cast<time_t>(seconds_64);
 
-}
-
-std::chrono::system_clock::time_point calendar_point::to_std_timepoint() const
-   {
-   if (year < 1970)
-      throw Invalid_Argument("calendar_point::to_std_timepoint() does not support years before 1970.");
-
-   // 32 bit time_t ends at January 19, 2038
-   // https://msdn.microsoft.com/en-us/library/2093ets1.aspx
-   // Throw after 2037 if 32 bit time_t is used
-   if (year > 2037 && sizeof(std::time_t) == 4)
+   if(seconds_64 - seconds_time_t != 0)
       {
-      throw Invalid_Argument("calendar_point::to_std_timepoint() does not support years after 2037.");
+      throw Invalid_Argument("calendar_point::to_std_timepoint time_t overflow");
       }
 
-   // std::tm: struct without any timezone information
-   std::tm tm;
-   tm.tm_isdst = -1; // i.e. no DST information available
-   tm.tm_sec   = seconds;
-   tm.tm_min   = minutes;
-   tm.tm_hour  = hour;
-   tm.tm_mday  = day;
-   tm.tm_mon   = month - 1;
-   tm.tm_year  = year - 1900;
-
-   // Define a function alias `botan_timegm`
-   #if defined(BOTAN_TARGET_OS_HAS_TIMEGM)
-   std::time_t (&botan_timegm)(std::tm *tm) = ::timegm;
-   #elif defined(BOTAN_TARGET_OS_HAS_MKGMTIME) && defined(BOTAN_BUILD_COMPILER_IS_MSVC)
-   // https://stackoverflow.com/questions/16647819/timegm-cross-platform
-   std::time_t (&botan_timegm)(std::tm *tm) = ::_mkgmtime;
-   #elif defined(BOTAN_HAS_BOOST_DATETIME)
-   std::time_t (&botan_timegm)(std::tm *tm) = boost_timegm;
-   #elif defined(BOTAN_OS_TYPE_IS_UNIX)
-   std::time_t (&botan_timegm)(std::tm *tm) = fallback_timegm;
-   #else
-   std::time_t (&botan_timegm)(std::tm *tm) = ::mktime; // localtime instead...
-   #endif
-
-   // Convert std::tm to std::time_t
-   std::time_t tt = botan_timegm(&tm);
-   if (tt == -1)
-      throw Invalid_Argument("calendar_point couldn't be converted: " + to_string());
-
-   return std::chrono::system_clock::from_time_t(tt);
+   return std::chrono::system_clock::from_time_t(seconds_time_t);
    }
 
 std::string calendar_point::to_string() const
@@ -162,9 +95,9 @@ std::string calendar_point::to_string() const
       {
       using namespace std;
       output << setfill('0')
-             << setw(4) << year << "-" << setw(2) << month << "-" << setw(2) << day
+             << setw(4) << get_year() << "-" << setw(2) << get_month() << "-" << setw(2) << get_day()
              << "T"
-             << setw(2) << hour << ":" << setw(2) << minutes << ":" << setw(2) << seconds;
+             << setw(2) << get_hour() << ":" << setw(2) << get_minutes() << ":" << setw(2) << get_seconds();
       }
    return output.str();
    }
diff --git a/src/lib/utils/calendar.h b/src/lib/utils/calendar.h
index 665022599..3f6952524 100644
--- a/src/lib/utils/calendar.h
+++ b/src/lib/utils/calendar.h
@@ -21,25 +21,26 @@ namespace Botan {
 class BOTAN_PUBLIC_API(2,0) calendar_point
    {
    public:
+
       /** The year */
-      uint32_t year;
+      uint32_t get_year() const { return year; }
 
       /** The month, 1 through 12 for Jan to Dec */
-      uint32_t month;
+      uint32_t get_month() const { return month; }
 
       /** The day of the month, 1 through 31 (or 28 or 30 based on month */
-      uint32_t day;
+      uint32_t get_day() const { return day; }
 
       /** Hour in 24-hour form, 0 to 23 */
-      uint32_t hour;
+      uint32_t get_hour() const { return hour; }
 
       /** Minutes in the hour, 0 to 60 */
-      uint32_t minutes;
+      uint32_t get_minutes() const { return minutes; }
 
       /** Seconds in the minute, 0 to 60, but might be slightly
-          larger to deal with leap seconds on some systems
+      larger to deal with leap seconds on some systems
       */
-      uint32_t seconds;
+      uint32_t get_seconds() const { return seconds; }
 
       /**
       * Initialize a calendar_point
@@ -63,6 +64,17 @@ class BOTAN_PUBLIC_API(2,0) calendar_point
       * Formatting might change over time. Currently it is RFC339 'iso-date-time'.
       */
       std::string to_string() const;
+
+      /*
+      The member variables are public for historical reasons. Use the get_xxx() functions
+      defined above. These members will be made private in a future major release.
+      */
+      uint32_t year;
+      uint32_t month;
+      uint32_t day;
+      uint32_t hour;
+      uint32_t minutes;
+      uint32_t seconds;
    };
 
 /**
diff --git a/src/tests/test_utils.cpp b/src/tests/test_utils.cpp
index b8df9c270..3c4accab2 100644
--- a/src/tests/test_utils.cpp
+++ b/src/tests/test_utils.cpp
@@ -274,26 +274,26 @@ class Date_Format_Tests final : public Text_Based_Test
          if(type == "valid" || type == "valid.not_std" || type == "valid.64_bit_time_t")
             {
             Botan::calendar_point c(d[0], d[1], d[2], d[3], d[4], d[5]);
-            result.test_is_eq(date_str + " year", c.year, d[0]);
-            result.test_is_eq(date_str + " month", c.month, d[1]);
-            result.test_is_eq(date_str + " day", c.day, d[2]);
-            result.test_is_eq(date_str + " hour", c.hour, d[3]);
-            result.test_is_eq(date_str + " minute", c.minutes, d[4]);
-            result.test_is_eq(date_str + " second", c.seconds, d[5]);
-
-            if(type == "valid.not_std" || (type == "valid.64_bit_time_t" && c.year > 2037 && sizeof(std::time_t) == 4))
+            result.test_is_eq(date_str + " year", c.get_year(), d[0]);
+            result.test_is_eq(date_str + " month", c.get_month(), d[1]);
+            result.test_is_eq(date_str + " day", c.get_day(), d[2]);
+            result.test_is_eq(date_str + " hour", c.get_hour(), d[3]);
+            result.test_is_eq(date_str + " minute", c.get_minutes(), d[4]);
+            result.test_is_eq(date_str + " second", c.get_seconds(), d[5]);
+
+            if(type == "valid.not_std" || (type == "valid.64_bit_time_t" && c.get_year() > 2037 && sizeof(std::time_t) == 4))
                {
                result.test_throws("valid but out of std::timepoint range", [c]() { c.to_std_timepoint(); });
                }
             else
                {
                Botan::calendar_point c2 = Botan::calendar_value(c.to_std_timepoint());
-               result.test_is_eq(date_str + " year", c2.year, d[0]);
-               result.test_is_eq(date_str + " month", c2.month, d[1]);
-               result.test_is_eq(date_str + " day", c2.day, d[2]);
-               result.test_is_eq(date_str + " hour", c2.hour, d[3]);
-               result.test_is_eq(date_str + " minute", c2.minutes, d[4]);
-               result.test_is_eq(date_str + " second", c2.seconds, d[5]);
+               result.test_is_eq(date_str + " year", c2.get_year(), d[0]);
+               result.test_is_eq(date_str + " month", c2.get_month(), d[1]);
+               result.test_is_eq(date_str + " day", c2.get_day(), d[2]);
+               result.test_is_eq(date_str + " hour", c2.get_hour(), d[3]);
+               result.test_is_eq(date_str + " minute", c2.get_minutes(), d[4]);
+               result.test_is_eq(date_str + " second", c2.get_seconds(), d[5]);
                }
             }
          else if(type == "invalid")