Merge pull request #374 from chisholm/version_precision

Support STIX 2.1 version precision

setup.py

@@ -51,6 +51,7 @@ setup(
     keywords='stix stix2 json cti cyber threat intelligence',
     packages=find_packages(exclude=['*.test', '*.test.*']),
     install_requires=[
+        'enum34 ; python_version<"3.4"',
         'python-dateutil',
         'pytz',
         'requests',

stix2/properties.py

@@ -323,12 +323,16 @@ class BooleanProperty(Property):
 
 class TimestampProperty(Property):
 
-    def __init__(self, precision=None, **kwargs):
+    def __init__(self, precision="any", precision_constraint="exact", **kwargs):
         self.precision = precision
+        self.precision_constraint = precision_constraint
+
         super(TimestampProperty, self).__init__(**kwargs)
 
     def clean(self, value):
-        return parse_into_datetime(value, self.precision)
+        return parse_into_datetime(
+            value, self.precision, self.precision_constraint,
+        )
 
 
 class DictionaryProperty(Property):

stix2/test/v21/test_attack_pattern.py

@@ -88,8 +88,8 @@ def test_attack_pattern_invalid_labels():
 def test_overly_precise_timestamps():
     ap = stix2.v21.AttackPattern(
         id=ATTACK_PATTERN_ID,
-        created="2016-05-12T08:17:27.0000342Z",
+        created="2016-05-12T08:17:27.000000342Z",
-        modified="2016-05-12T08:17:27.000287Z",
+        modified="2016-05-12T08:17:27.000000287Z",
         name="Spear Phishing",
         external_references=[{
             "source_name": "capec",

stix2/test/v21/test_timestamp_precision.py

@@ -0,0 +1,164 @@
+import datetime
+import sys
+
+import pytest
+
+import stix2
+from stix2.utils import (
+    Precision, PrecisionConstraint, STIXdatetime, _to_enum, format_datetime,
+    parse_into_datetime,
+)
+
+_DT = datetime.datetime.utcnow()
+# intentionally omit microseconds from the following.  We add it in as
+# needed for each test.
+_DT_STR = _DT.strftime("%Y-%m-%dT%H:%M:%S")
+
+
+@pytest.mark.parametrize(
+    "value, enum_type, enum_default, enum_expected", [
+        ("second", Precision, None, Precision.SECOND),
+        (
+            "eXaCt", PrecisionConstraint, PrecisionConstraint.MIN,
+            PrecisionConstraint.EXACT,
+        ),
+        (None, Precision, Precision.MILLISECOND, Precision.MILLISECOND),
+        (Precision.ANY, Precision, None, Precision.ANY),
+    ],
+)
+def test_to_enum(value, enum_type, enum_default, enum_expected):
+    result = _to_enum(value, enum_type, enum_default)
+    assert result == enum_expected
+
+
+@pytest.mark.parametrize(
+    "value, err_type", [
+        ("foo", KeyError),
+        (1, TypeError),
+        (PrecisionConstraint.EXACT, TypeError),
+        (None, TypeError),
+    ],
+)
+def test_to_enum_errors(value, err_type):
+    with pytest.raises(err_type):
+        _to_enum(value, Precision)
+
+
+@pytest.mark.xfail(
+    sys.version_info[:2] == (3, 6), strict=True,
+    reason="https://bugs.python.org/issue32404",
+)
+def test_stix_datetime_now():
+    dt = STIXdatetime.utcnow()
+    assert dt.precision is Precision.ANY
+    assert dt.precision_constraint is PrecisionConstraint.EXACT
+
+
+def test_stix_datetime():
+    dt = datetime.datetime.utcnow()
+
+    sdt = STIXdatetime(dt, precision=Precision.SECOND)
+    assert sdt.precision is Precision.SECOND
+    assert sdt == dt
+
+    sdt = STIXdatetime(
+        dt,
+        precision_constraint=PrecisionConstraint.EXACT,
+    )
+    assert sdt.precision_constraint is PrecisionConstraint.EXACT
+    assert sdt == dt
+
+
+@pytest.mark.parametrize(
+    "us, precision, precision_constraint, expected_truncated_us", [
+        (123456, Precision.ANY, PrecisionConstraint.EXACT, 123456),
+        (123456, Precision.SECOND, PrecisionConstraint.EXACT, 0),
+        (123456, Precision.SECOND, PrecisionConstraint.MIN, 123456),
+        (123456, Precision.MILLISECOND, PrecisionConstraint.EXACT, 123000),
+        (123456, Precision.MILLISECOND, PrecisionConstraint.MIN, 123456),
+        (1234, Precision.MILLISECOND, PrecisionConstraint.EXACT, 1000),
+        (123, Precision.MILLISECOND, PrecisionConstraint.EXACT, 0),
+    ],
+)
+def test_parse_datetime(
+    us, precision, precision_constraint, expected_truncated_us,
+):
+
+    # complete the datetime string with microseconds
+    dt_us_str = "{}.{:06d}Z".format(_DT_STR, us)
+
+    sdt = parse_into_datetime(
+        dt_us_str,
+        precision=precision,
+        precision_constraint=precision_constraint,
+    )
+
+    assert sdt.precision is precision
+    assert sdt.precision_constraint is precision_constraint
+    assert sdt.microsecond == expected_truncated_us
+
+
+@pytest.mark.parametrize(
+    "us, precision, precision_constraint, expected_us_str", [
+        (123456, Precision.ANY, PrecisionConstraint.EXACT, ".123456"),
+        (123456, Precision.SECOND, PrecisionConstraint.EXACT, ""),
+        (123456, Precision.SECOND, PrecisionConstraint.MIN, ".123456"),
+        (123456, Precision.MILLISECOND, PrecisionConstraint.EXACT, ".123"),
+        (123456, Precision.MILLISECOND, PrecisionConstraint.MIN, ".123456"),
+        (0, Precision.SECOND, PrecisionConstraint.MIN, ""),
+        (0, Precision.MILLISECOND, PrecisionConstraint.MIN, ".000"),
+        (0, Precision.MILLISECOND, PrecisionConstraint.EXACT, ".000"),
+        (1000, Precision.MILLISECOND, PrecisionConstraint.EXACT, ".001"),
+        (10000, Precision.MILLISECOND, PrecisionConstraint.EXACT, ".010"),
+        (100000, Precision.MILLISECOND, PrecisionConstraint.EXACT, ".100"),
+        (1000, Precision.ANY, PrecisionConstraint.EXACT, ".001"),
+        (10000, Precision.ANY, PrecisionConstraint.EXACT, ".01"),
+        (100000, Precision.ANY, PrecisionConstraint.EXACT, ".1"),
+        (1001, Precision.MILLISECOND, PrecisionConstraint.MIN, ".001001"),
+        (10010, Precision.MILLISECOND, PrecisionConstraint.MIN, ".01001"),
+        (100100, Precision.MILLISECOND, PrecisionConstraint.MIN, ".1001"),
+    ],
+)
+def test_format_datetime(us, precision, precision_constraint, expected_us_str):
+
+    dt = _DT.replace(microsecond=us)
+    expected_dt_str = "{}{}Z".format(_DT_STR, expected_us_str)
+
+    sdt = STIXdatetime(
+        dt,
+        precision=precision,
+        precision_constraint=precision_constraint,
+    )
+    s = format_datetime(sdt)
+    assert s == expected_dt_str
+
+
+def test_sdo_extra_precision():
+    # add extra precision for "modified", ensure it's not lost
+    identity_dict = {
+        "type": "identity",
+        "id": "identity--4a457eeb-6639-4aa3-be81-5930a3000c39",
+        "created": "2015-12-21T19:59:11.000Z",
+        "modified": "2015-12-21T19:59:11.0001Z",
+        "name": "John Smith",
+        "identity_class": "individual",
+        "spec_version": "2.1",
+    }
+
+    identity_obj = stix2.parse(identity_dict)
+    assert identity_obj.modified.microsecond == 100
+    assert identity_obj.modified.precision is Precision.MILLISECOND
+    assert identity_obj.modified.precision_constraint is PrecisionConstraint.MIN
+
+    identity_str = identity_obj.serialize(pretty=True)
+
+    # ensure precision is retained in JSON
+    assert identity_str == """{
+    "type": "identity",
+    "spec_version": "2.1",
+    "id": "identity--4a457eeb-6639-4aa3-be81-5930a3000c39",
+    "created": "2015-12-21T19:59:11.000Z",
+    "modified": "2015-12-21T19:59:11.0001Z",
+    "name": "John Smith",
+    "identity_class": "individual"
+}"""

stix2/test/v21/test_versioning.py

@@ -1,6 +1,9 @@
+import datetime
+
 import pytest
 
 import stix2
+import stix2.utils
 
 from .constants import CAMPAIGN_MORE_KWARGS
 
@@ -236,8 +239,7 @@ def test_remove_custom_stix_property():
     mal_nc = stix2.utils.remove_custom_stix(mal)
 
     assert "x_custom" not in mal_nc
-    assert (stix2.utils.parse_into_datetime(mal["modified"], precision="millisecond") <
+    assert mal["modified"] < mal_nc["modified"]
-            stix2.utils.parse_into_datetime(mal_nc["modified"], precision="millisecond"))
 
 
 def test_remove_custom_stix_object():
@@ -264,3 +266,33 @@ def test_remove_custom_stix_no_custom():
     assert len(campaign_v1.keys()) == len(campaign_v2.keys())
     assert campaign_v1.id == campaign_v2.id
     assert campaign_v1.description == campaign_v2.description
+
+
+@pytest.mark.parametrize(
+    "old, candidate_new, expected_new, use_stix21", [
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:07.001Z", "1999-08-15T00:19:07.001Z", False),
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:07.000Z", "1999-08-15T00:19:07.001Z", False),
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:06.000Z", "1999-08-15T00:19:07.001Z", False),
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:06.999Z", "1999-08-15T00:19:07.001Z", False),
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:07.0001Z", "1999-08-15T00:19:07.001Z", False),
+        ("1999-08-15T00:19:07.999Z", "1999-08-15T00:19:07.9999Z", "1999-08-15T00:19:08.000Z", False),
+
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:07.001Z", "1999-08-15T00:19:07.001Z", True),
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:07.000Z", "1999-08-15T00:19:07.000001Z", True),
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:06.000Z", "1999-08-15T00:19:07.000001Z", True),
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:06.999999Z", "1999-08-15T00:19:07.000001Z", True),
+        ("1999-08-15T00:19:07.000Z", "1999-08-15T00:19:07.000001Z", "1999-08-15T00:19:07.000001Z", True),
+        ("1999-08-15T00:19:07.999Z", "1999-08-15T00:19:07.999999Z", "1999-08-15T00:19:07.999999Z", True),
+    ],
+)
+def test_fudge_modified(old, candidate_new, expected_new, use_stix21):
+    old_dt = datetime.datetime.strptime(old, "%Y-%m-%dT%H:%M:%S.%fZ")
+    candidate_new_dt = datetime.datetime.strptime(
+        candidate_new, "%Y-%m-%dT%H:%M:%S.%fZ",
+    )
+    expected_new_dt = datetime.datetime.strptime(
+        expected_new, "%Y-%m-%dT%H:%M:%S.%fZ",
+    )
+
+    fudged = stix2.utils._fudge_modified(old_dt, candidate_new_dt, use_stix21)
+    assert fudged == expected_new_dt

stix2/utils.py

@@ -6,10 +6,12 @@ except ImportError:
     from collections import Mapping
 import copy
 import datetime as dt
+import enum
 import json
 
 from dateutil import parser
 import pytz
+import six
 
 import stix2.base
 
@@ -29,9 +31,79 @@ TYPE_REGEX = r'^\-?[a-z0-9]+(-[a-z0-9]+)*\-?$'
 SCO21_EXT_REGEX = r'^\-?[a-z0-9]+(-[a-z0-9]+)*\-ext$'
 
 
+class Precision(enum.Enum):
+    """
+    Timestamp format precisions.
+    """
+    # auto() wasn't introduced until Python 3.6.
+    ANY = 1
+    SECOND = 2
+    MILLISECOND = 3
+
+
+class PrecisionConstraint(enum.Enum):
+    """
+    Timestamp precision constraints.  These affect how the Precision
+    values are applied when formatting a timestamp.
+
+    These constraints don't really make sense with the ANY precision, so they
+    have no effect in that case.
+    """
+    EXACT = 1  # format must have exactly the given precision
+    MIN = 2  # format must have at least the given precision
+    #  no need for a MAX constraint yet
+
+
+def _to_enum(value, enum_type, enum_default=None):
+    """
+    Detect and convert strings to enums and None to a default enum.  This
+    allows use of strings and None in APIs, while enforcing the enum type: if
+    you use a string, it must name a valid enum value.  This implementation is
+    case-insensitive.
+
+    :param value: A value to be interpreted as an enum (string, Enum instance,
+        or None).  If an Enum instance, it must be an instance of enum_type.
+    :param enum_type: The enum type which strings will be interpreted against
+    :param enum_default: The default enum to use if value is None.  Must be
+        an instance of enum_type, or None.  If None, you are disallowing a
+        default and requiring that value be non-None.
+    :return: An instance of enum_type
+    :raises TypeError: If value was neither an instance of enum_type, None, nor
+        a string
+    :raises KeyError: If value was a string which couldn't be interpreted as an
+        enum value from enum_type
+    """
+    assert enum_default is None or isinstance(enum_default, enum_type)
+
+    if not isinstance(value, enum_type):
+        if value is None and enum_default is not None:
+            value = enum_default
+        elif isinstance(value, six.string_types):
+            value = enum_type[value.upper()]
+        else:
+            raise TypeError("Not a valid {}: {}".format(
+                enum_type.__name__, value,
+            ))
+
+    return value
+
+
 class STIXdatetime(dt.datetime):
+    """
+    Bundle a datetime with some format-related metadata, so that JSON
+    serialization has the info it needs to produce compliant timestamps.
+    """
+
     def __new__(cls, *args, **kwargs):
-        precision = kwargs.pop('precision', None)
+        precision = _to_enum(
+            kwargs.pop("precision", Precision.ANY),
+            Precision,
+        )
+        precision_constraint = _to_enum(
+            kwargs.pop("precision_constraint", PrecisionConstraint.EXACT),
+            PrecisionConstraint,
+        )
+
         if isinstance(args[0], dt.datetime):  # Allow passing in a datetime object
             dttm = args[0]
             args = (
@@ -41,6 +113,7 @@ class STIXdatetime(dt.datetime):
         # self will be an instance of STIXdatetime, not dt.datetime
         self = dt.datetime.__new__(cls, *args, **kwargs)
         self.precision = precision
+        self.precision_constraint = precision_constraint
         return self
 
     def __repr__(self):
@@ -90,7 +163,7 @@ def format_datetime(dttm):
     2. Convert to UTC
     3. Format in ISO format
     4. Ensure correct precision
-       a. Add subsecond value if non-zero and precision not defined
+       a. Add subsecond value if warranted, according to precision settings
     5. Add "Z"
 
     """
@@ -101,20 +174,74 @@ def format_datetime(dttm):
     else:
         zoned = dttm.astimezone(pytz.utc)
     ts = zoned.strftime('%Y-%m-%dT%H:%M:%S')
-    ms = zoned.strftime('%f')
+    precision = getattr(dttm, 'precision', Precision.ANY)
-    precision = getattr(dttm, 'precision', None)
+    precision_constraint = getattr(
-    if precision == 'second':
+        dttm, 'precision_constraint', PrecisionConstraint.EXACT,
-        pass  # Already precise to the second
+    )
-    elif precision == 'millisecond':
+
-        ts = ts + '.' + ms[:3]
+    frac_seconds_str = ""
-    elif zoned.microsecond > 0:
+    if precision == Precision.ANY:
-        ts = ts + '.' + ms.rstrip('0')
+        # No need to truncate; ignore constraint
-    return ts + 'Z'
+        if zoned.microsecond:
+            frac_seconds_str = "{:06d}".format(zoned.microsecond).rstrip("0")
+
+    elif precision == Precision.SECOND:
+        if precision_constraint == PrecisionConstraint.MIN:
+            # second precision, or better.  Winds up being the same as ANY:
+            # just use all our digits
+            if zoned.microsecond:
+                frac_seconds_str = "{:06d}".format(zoned.microsecond)\
+                    .rstrip("0")
+        # exact: ignore microseconds entirely
+
+    else:
+        # precision == millisecond
+        if precision_constraint == PrecisionConstraint.EXACT:
+            # can't rstrip() here or we may lose precision
+            frac_seconds_str = "{:06d}".format(zoned.microsecond)[:3]
+
+        else:
+            # millisecond precision, or better.  So we can rstrip() zeros, but
+            # only to a length of at least 3 digits (ljust() adds zeros back,
+            # if it stripped too far.)
+            frac_seconds_str = "{:06d}"\
+                .format(zoned.microsecond)\
+                .rstrip("0")\
+                .ljust(3, "0")
+
+    ts = "{}{}{}Z".format(
+        ts,
+        "." if frac_seconds_str else "",
+        frac_seconds_str,
+    )
+
+    return ts
 
 
-def parse_into_datetime(value, precision=None):
+def parse_into_datetime(
-    """Parse a value into a valid STIX timestamp object.
+    value, precision=Precision.ANY,
+    precision_constraint=PrecisionConstraint.EXACT,
+):
     """
+    Parse a value into a valid STIX timestamp object.  Also, optionally adjust
+    precision of fractional seconds.  This allows alignment with JSON
+    serialization requirements, and helps ensure we're not using extra
+    precision which would be lost upon JSON serialization.  The precision
+    info will be embedded in the returned object, so that JSON serialization
+    will format it correctly.
+
+    :param value: A datetime.datetime or datetime.date instance, or a string
+    :param precision: A precision value: either an instance of the Precision
+        enum, or a string naming one of the enum values (case-insensitive)
+    :param precision_constraint: A precision constraint value: either an
+        instance of the PrecisionConstraint enum, or a string naming one of
+        the enum values (case-insensitive)
+    :return: A STIXdatetime instance, which is a datetime but also carries the
+        precision info necessary to properly JSON-serialize it.
+    """
+    precision = _to_enum(precision, Precision)
+    precision_constraint = _to_enum(precision_constraint, PrecisionConstraint)
+
     if isinstance(value, dt.date):
         if hasattr(value, 'hour'):
             ts = value
@@ -138,20 +265,23 @@ def parse_into_datetime(value, precision=None):
             ts = pytz.utc.localize(parsed)
 
     # Ensure correct precision
-    if not precision:
+    if precision == Precision.SECOND:
-        return STIXdatetime(ts, precision=precision)
+        if precision_constraint == PrecisionConstraint.EXACT:
-    ms = ts.microsecond
-    if precision == 'second':
-        ts = ts.replace(microsecond=0)
-    elif precision == 'millisecond':
-        ms_len = len(str(ms))
-        if ms_len > 3:
-            # Truncate to millisecond precision
-            factor = 10 ** (ms_len - 3)
-            ts = ts.replace(microsecond=(ts.microsecond // factor) * factor)
-        else:
             ts = ts.replace(microsecond=0)
-    return STIXdatetime(ts, precision=precision)
+        # else, no need to modify fractional seconds
+
+    elif precision == Precision.MILLISECOND:
+        if precision_constraint == PrecisionConstraint.EXACT:
+            us = (ts.microsecond // 1000) * 1000
+            ts = ts.replace(microsecond=us)
+        # else: at least millisecond precision: the constraint will affect JSON
+        # formatting, but there's nothing we need to do here.
+
+    # else, precision == Precision.ANY: nothing for us to do.
+
+    return STIXdatetime(
+        ts, precision=precision, precision_constraint=precision_constraint,
+    )
 
 
 def _get_dict(data):
@@ -256,6 +386,39 @@ def find_property_index(obj, search_key, search_value):
     return idx
 
 
+def _fudge_modified(old_modified, new_modified, use_stix21):
+    """
+    Ensures a new modified timestamp is newer than the old.  When they are
+    too close together, new_modified must be pushed further ahead to ensure
+    it is distinct and later, after JSON serialization (which may mean it's
+    actually being pushed a little ways into the future).  JSON serialization
+    can remove precision, which can cause distinct timestamps to accidentally
+    become equal, if we're not careful.
+
+    :param old_modified: A previous "modified" timestamp, as a datetime object
+    :param new_modified: A candidate new "modified" timestamp, as a datetime
+        object
+    :param use_stix21: Whether to use STIX 2.1+ versioning timestamp precision
+        rules (boolean).  This is important so that we are aware of how
+        timestamp precision will be truncated, so we know how close together
+        the timestamps can be, and how far ahead to potentially push the new
+        one.
+    :return: A suitable new "modified" timestamp.  This may be different from
+        what was passed in, if it had to be pushed ahead.
+    """
+    if use_stix21:
+        # 2.1+: we can use full precision
+        if new_modified <= old_modified:
+            new_modified = old_modified + dt.timedelta(microseconds=1)
+    else:
+        # 2.0: we must use millisecond precision
+        one_ms = dt.timedelta(milliseconds=1)
+        if new_modified - old_modified < one_ms:
+            new_modified = old_modified + one_ms
+
+    return new_modified
+
+
 def new_version(data, **kwargs):
     """Create a new version of a STIX object, by modifying properties and
     updating the ``modified`` property.
@@ -283,12 +446,32 @@ def new_version(data, **kwargs):
     if unchangable_properties:
         raise UnmodifiablePropertyError(unchangable_properties)
 
+    # Different versioning precision rules in STIX 2.0 vs 2.1, so we need
+    # to know which rules to apply.
+    is_21 = "spec_version" in data
+    precision_constraint = "min" if is_21 else "exact"
+
     cls = type(data)
     if 'modified' not in kwargs:
-        kwargs['modified'] = get_timestamp()
+        old_modified = parse_into_datetime(
+            data["modified"], precision="millisecond",
+            precision_constraint=precision_constraint,
+        )
+
+        new_modified = get_timestamp()
+        new_modified = _fudge_modified(old_modified, new_modified, is_21)
+
+        kwargs['modified'] = new_modified
+
     elif 'modified' in data:
-        old_modified_property = parse_into_datetime(data.get('modified'), precision='millisecond')
+        old_modified_property = parse_into_datetime(
-        new_modified_property = parse_into_datetime(kwargs['modified'], precision='millisecond')
+            data.get('modified'), precision='millisecond',
+            precision_constraint=precision_constraint,
+        )
+        new_modified_property = parse_into_datetime(
+            kwargs['modified'], precision='millisecond',
+            precision_constraint=precision_constraint,
+        )
         if new_modified_property <= old_modified_property:
             raise InvalidValueError(
                 cls, 'modified',
@@ -378,11 +561,6 @@ def remove_custom_stix(stix_obj):
 
         new_obj = new_version(stix_obj, **(dict(props)))
 
-        while parse_into_datetime(new_obj['modified']) == parse_into_datetime(stix_obj['modified']):
-            # Prevents bug when fast computation allows multiple STIX object
-            # versions to be created in single unit of time
-            new_obj = new_version(stix_obj, **(dict(props)))
-
         return new_obj
 
     else:

stix2/v21/common.py

@@ -87,8 +87,8 @@ class LanguageContent(_STIXBase):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('object_ref', ReferenceProperty(valid_types=["SCO", "SDO", "SRO"], spec_version='2.1', required=True)),
         # TODO: 'object_modified' it MUST be an exact match for the modified time of the STIX Object (SRO or SDO) being referenced.
         ('object_modified', TimestampProperty(precision='millisecond')),
@@ -155,7 +155,7 @@ class MarkingDefinition(_STIXBase, _MarkingsMixin):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type)),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('external_references', ListProperty(ExternalReference)),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),

stix2/v21/sdo.py

@@ -32,8 +32,8 @@ class AttackPattern(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('aliases', ListProperty(StringProperty)),
@@ -59,8 +59,8 @@ class Campaign(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('aliases', ListProperty(StringProperty)),
@@ -98,8 +98,8 @@ class CourseOfAction(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('revoked', BooleanProperty(default=lambda: False)),
@@ -122,8 +122,8 @@ class Grouping(STIXDomainObject):
         ('type', TypeProperty(_type)),
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
         ('revoked', BooleanProperty(default=lambda: False)),
         ('labels', ListProperty(StringProperty)),
@@ -150,8 +150,8 @@ class Identity(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('roles', ListProperty(StringProperty)),
@@ -179,8 +179,8 @@ class Indicator(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty()),
         ('description', StringProperty()),
         ('indicator_types', ListProperty(StringProperty)),
@@ -238,8 +238,8 @@ class Infrastructure(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('revoked', BooleanProperty(default=lambda: False)),
         ('labels', ListProperty(StringProperty)),
         ('confidence', IntegerProperty()),
@@ -278,8 +278,8 @@ class IntrusionSet(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('aliases', ListProperty(StringProperty)),
@@ -320,8 +320,8 @@ class Location(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty()),
         ('description', StringProperty()),
         ('latitude', FloatProperty(min=-90.0, max=90.0)),
@@ -427,8 +427,8 @@ class Malware(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty()),
         ('description', StringProperty()),
         ('malware_types', ListProperty(StringProperty)),
@@ -478,8 +478,8 @@ class MalwareAnalysis(STIXDomainObject):
         ('type', TypeProperty(_type)),
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
         ('revoked', BooleanProperty(default=lambda: False)),
         ('labels', ListProperty(StringProperty)),
@@ -523,8 +523,8 @@ class Note(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('abstract', StringProperty()),
         ('content', StringProperty(required=True)),
         ('authors', ListProperty(StringProperty)),
@@ -550,8 +550,8 @@ class ObservedData(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('first_observed', TimestampProperty(required=True)),
         ('last_observed', TimestampProperty(required=True)),
         ('number_observed', IntegerProperty(min=1, max=999999999, required=True)),
@@ -605,8 +605,8 @@ class Opinion(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('explanation', StringProperty()),
         ('authors', ListProperty(StringProperty)),
         (
@@ -642,8 +642,8 @@ class Report(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('report_types', ListProperty(StringProperty)),
@@ -670,8 +670,8 @@ class ThreatActor(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('threat_actor_types', ListProperty(StringProperty)),
@@ -716,8 +716,8 @@ class Tool(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('tool_types', ListProperty(StringProperty)),
@@ -745,8 +745,8 @@ class Vulnerability(STIXDomainObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('revoked', BooleanProperty(default=lambda: False)),
@@ -795,8 +795,8 @@ def CustomObject(type='x-custom-type', properties=None):
                 ('spec_version', StringProperty(fixed='2.1')),
                 ('id', IDProperty(type, spec_version='2.1')),
                 ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-                ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+                ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-                ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+                ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
             ],
             [x for x in properties if not x[0].startswith('x_')],
             [

stix2/v21/sro.py

@@ -24,8 +24,8 @@ class Relationship(STIXRelationshipObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('relationship_type', StringProperty(required=True)),
         ('description', StringProperty()),
         ('source_ref', ReferenceProperty(invalid_types=_invalid_source_target_types, spec_version='2.1', required=True)),
@@ -78,8 +78,8 @@ class Sighting(STIXRelationshipObject):
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
+        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('description', StringProperty()),
         ('first_seen', TimestampProperty()),
         ('last_seen', TimestampProperty()),