[3673] Use the 64-bit value for time conversions to detect overflows.

src/lib/dhcpsrv/pgsql_lease_mgr.cc

@@ -298,20 +298,23 @@ public:
     /// when stored.  Likewise, these columns are automatically adjusted
     /// upon retrieval unless fetched via "extract(epoch from <column>))".
     ///
-    /// @param time_val timestamp to be converted
+    /// @param time_val_64 timestamp to be converted. This is given as a
+    /// 64-bit value to avoid overflows on the 32-bit systems where time_t
+    /// is implemented as int32_t.
     /// @return std::string containing the stringified time
     std::string
-    convertToDatabaseTime(const time_t& time_val) {
+    convertToDatabaseTime(const int64_t& time_val_64) {
         // PostgreSQL does funny things with time if you get past Y2038.  It
         // will accept the values (unlike MySQL which throws) but it
         // stops correctly adjusting to local time when reading them back
         // out. So lets disallow it here.
-        if (time_val > LeaseMgr::MAX_DB_TIME) {
-            isc_throw(BadValue, "Time value is too large: " << time_val);
+        if (time_val_64 > LeaseMgr::MAX_DB_TIME) {
+            isc_throw(BadValue, "Time value is too large: " << time_val_64);
         }
 
         struct tm tinfo;
         char buffer[20];
+        const time_t time_val = static_cast<time_t>(time_val_64);
         localtime_r(&time_val, &tinfo);
         strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", &tinfo);
         return (std::string(buffer));
@@ -632,8 +635,8 @@ public:
                              (lease->valid_lft_);
             bind_array.add(valid_lft_str_);
 
-            expire_str_ = convertToDatabaseTime(lease->valid_lft_ +
-                                                lease->cltt_);
+            expire_str_ = convertToDatabaseTime(static_cast<int64_t>(lease->valid_lft_) +
+                                                static_cast<int64_t>(lease->cltt_));
             bind_array.add(expire_str_);
 
             subnet_id_str_ = boost::lexical_cast<std::string>
@@ -796,8 +799,8 @@ public:
                              (lease->valid_lft_);
             bind_array.add(valid_lft_str_);
 
-            expire_str_ = convertToDatabaseTime(lease->valid_lft_ +
-                                                lease->cltt_);
+            expire_str_ = convertToDatabaseTime(static_cast<int64_t>(lease->valid_lft_) +
+                                                static_cast<int64_t>(lease->cltt_));
             bind_array.add(expire_str_);
 
             subnet_id_str_ = boost::lexical_cast<std::string>