handle Y2038 in timestamp to datetime conversions

According to datetime.utcfromtimestamp() method documentation[1],
this and similar methods fail for dates past 2038 and can be replaced by
the following expression on the POSIX compliant systems:

  datetime(1970, 1, 1, tzinfo=timezone.utc) + timedelta(seconds=timestamp)

Make sure to use a method that at least allows to import the timestamps
properly to datetime objects on 32-bit platforms.

[1] https://docs.python.org/3/library/datetime.html#datetime.datetime.utcfromtimestamp

Fixes: https://pagure.io/freeipa/issue/8378

Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>
Reviewed-By: Christian Heimes <cheimes@redhat.com>

ipapython/cookie.py

@@ -22,6 +22,7 @@ import datetime
 import email.utils
 from calendar import timegm
 from urllib.parse import urlparse
+from ipapython.ipautil import datetime_from_utctimestamp
 
 
 '''
@@ -184,7 +185,7 @@ class Cookie:
         # use the RFC 1123 parsing function which uses only English
 
         try:
-            dt = datetime.datetime(*email.utils.parsedate(s)[0:6])
+            dt = email.utils.parsedate_to_datetime(s)
         except Exception as e:
             raise ValueError("unable to parse expires datetime '%s': %s" % (s, e))
 
@@ -390,7 +391,7 @@ class Cookie:
         elif isinstance(value, datetime.datetime):
             self._timestamp = value
         elif isinstance(value, (int, float)):
-            self._timestamp = datetime.datetime.utcfromtimestamp(value)
+            self._timestamp = datetime_from_utctimestamp(value, units=1)
         elif isinstance(value, str):
             self._timestamp = Cookie.parse_datetime(value)
         else:
@@ -415,8 +416,10 @@ class Cookie:
             self._expires = None
         elif isinstance(value, datetime.datetime):
             self._expires = value
+            if self._expires.tzinfo is None:
+                self._expires.replace(tzinfo=datetime.timezone.utc)
         elif isinstance(value, (int, float)):
-            self._expires = datetime.datetime.utcfromtimestamp(value)
+            self._expires = datetime_from_utctimestamp(value, units=1)
         elif isinstance(value, str):
             self._expires = Cookie.parse_datetime(value)
         else:

ipapython/ipautil.py

@@ -1647,3 +1647,27 @@ def rmtree(path):
             shutil.rmtree(path)
     except Exception as e:
         logger.error('Error removing %s: %s', path, str(e))
+
+
+def datetime_from_utctimestamp(t, units=1):
+    """
+    Convert a timestamp or a time.struct_time to a datetime.datetime
+    object down to seconds, with UTC timezone
+
+    The conversion is safe for year 2038 problem
+
+    :param t: int or float timestamp in (milli)seconds since UNIX epoch
+              or time.struct_time
+    :param units: normalizing factor for the timestamp
+                  (1 for seconds, 1000 for milliseconds)
+                  defaults to 1
+    :return: datetime.datetime object in UTC timezone
+    """
+    if isinstance(t, time.struct_time):
+        v = int(time.mktime(t))
+    elif isinstance(t, (float, int)):
+        v = int(t)
+    else:
+        raise TypeError(t)
+    epoch = datetime.datetime(1970, 1, 1, tzinfo=datetime.timezone.utc)
+    return epoch + datetime.timedelta(seconds=v // units)