fix(corekit)!: non-zero padding octets are zeroed on rebuild (#1223)

PaddingField now packs the octets it was given, and zeros when it has
none or they are the wrong width, so a freshly built packet is unchanged.
Schema.pack delegates its padding branch to the field.

Each site carries the octets through its reader, data model and make():

- HOPOPT/IPv6-Opts PadN `pad`, QS report `unused`
- IPv6-Frag `reserved_octet`; IPv6-Route SR0/Type 2 `reserved`, RPL `padding`
- MH PadN option and Flow-ID PadN sub-option `data` (#1329)
- HTTP/2 DATA/HEADERS/PUSH_PROMISE `padding`; OSPF crypto auth `reserved`
- HIP: `reserved` on the 12 parameters listed on #1223
- HIP and SCTP trailing alignment padding: kept on the data model as
  `padding` only when not all zeros, and written back on make

Existing tests that build these data models by hand now supply the new
fields.

Author: JarryShaw

pcapkit/corekit/fields/strings.py

@@ -348,4 +348,26 @@ class PaddingField(BytesField):
         callback: Callback function to be called upon
             :meth:`self.__call__ <pcapkit.corekit.fields.field.FieldBase.__call__>`.
 
+    Padding packs back as the octets it was given, so a schema unpacked from
+    non-zero padding rebuilds byte for byte. A value that is absent, or whose
+    width no longer matches the field's, packs as zeros instead -- the default
+    for a freshly built packet.
+
     """
+
+    def pack(self, value: 'Optional[bytes]', packet: 'dict[str, Any]') -> 'bytes':  # pylint: disable=unused-argument
+        """Pack field value into :obj:`bytes`.
+
+        Args:
+            value: Field value, i.e. the padding octets as captured.
+            packet: Packet data.
+
+        Returns:
+            Packed field value: ``value`` itself if it is exactly as wide as the
+            field, or that many zero octets otherwise.
+
+        """
+        length = self.length
+        if isinstance(value, (bytes, bytearray)) and len(value) == length:
+            return bytes(value)
+        return bytes(length)

pcapkit/protocols/application/httpv2.py

@@ -611,6 +611,7 @@ def _read_http_data(self, schema: 'Schema_DataFrame', *,
             reserved=header.stream['reserved'],
             sid=header.stream['sid'],
             data=schema.data,
+            padding=schema.padding if flag.PADDED else b'',
         )
         return data
 
@@ -669,6 +670,7 @@ def _read_http_headers(self, schema: 'Schema_HeadersFrame', *,
             stream_dependency=schema.stream_dep['sid'] if flag.PRIORITY else 0,
             weight=(schema.weight + 1) if flag.PRIORITY else 0,
             fragment=schema.fragment,
+            padding=schema.padding if flag.PADDED else b'',
         )
         return data
 
@@ -878,6 +880,7 @@ def _read_http_push_promise(self, schema: 'Schema_PushPromiseFrame', *,
             promised_reserved=schema.stream['reserved'],
             promised_sid=schema.stream['sid'],
             fragment=schema.fragment,
+            padding=schema.padding if flag.PADDED else b'',
         )
 
         return data
@@ -1088,6 +1091,7 @@ def _make_http_data(self, frame: 'Optional[Data_DataFrame]' = None, *,
                         padded: 'bool' = False,
                         pad_len: 'int' = 0,
                         data: 'bytes' = b'',
+                        padding: 'bytes' = b'',
                         **kwargs: 'Any') -> 'tuple[Schema_DataFrame, Flags]':
         """Make HTTP/2 ``DATA`` frame.
 
@@ -1097,6 +1101,8 @@ def _make_http_data(self, frame: 'Optional[Data_DataFrame]' = None, *,
             padded: Padded flag, implied by a non-zero ``pad_len``.
             pad_len: Padding length.
             data: Frame data.
+            padding: Padding octets, written as given if exactly ``pad_len``
+                octets and as zeros otherwise.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -1109,6 +1115,7 @@ def _make_http_data(self, frame: 'Optional[Data_DataFrame]' = None, *,
 
             pad_len = frame.pad_len
             data = frame.data
+            padding = getattr(frame, 'padding', b'')
 
         flags = Schema_DataFrame.Flags(0)
         if end_stream:
@@ -1119,6 +1126,7 @@ def _make_http_data(self, frame: 'Optional[Data_DataFrame]' = None, *,
         return Schema_DataFrame(
             pad_len=pad_len,
             data=data,
+            padding=padding,
         ), flags
 
     def _make_http_headers(self, frame: 'Optional[Data_HeadersFrame]' = None, *,
@@ -1130,6 +1138,7 @@ def _make_http_headers(self, frame: 'Optional[Data_HeadersFrame]' = None, *,
                            sid_dep: 'Optional[int]' = None,
                            weight: 'int' = 0,
                            fragment: 'bytes' = b'',
+                           padding: 'bytes' = b'',
                            **kwargs: 'Any') -> 'tuple[Schema_HeadersFrame, Flags]':
         """Make HTTP/2 ``HEADERS`` frame.
 
@@ -1143,6 +1152,8 @@ def _make_http_headers(self, frame: 'Optional[Data_HeadersFrame]' = None, *,
             sid_dep: Dependency stream identifier.
             weight: Priority weight value.
             fragment: Header block fragment.
+            padding: Padding octets, written as given if exactly ``pad_len``
+                octets and as zeros otherwise.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -1160,6 +1171,7 @@ def _make_http_headers(self, frame: 'Optional[Data_HeadersFrame]' = None, *,
             sid_dep = frame.stream_dependency
             weight = frame.weight
             fragment = frame.fragment
+            padding = getattr(frame, 'padding', b'')
         else:
             priority = sid_dep is not None
             sid_dep = sid_dep or 0
@@ -1182,6 +1194,7 @@ def _make_http_headers(self, frame: 'Optional[Data_HeadersFrame]' = None, *,
             },
             weight=weight - 1 if weight else 0,
             fragment=fragment,
+            padding=padding,
         ), flags
 
     def _make_http_priority(self, frame: 'Optional[Data_PriorityFrame]' = None, *,
@@ -1304,6 +1317,7 @@ def _make_http_push_promise(self, frame: 'Optional[Data_PushPromiseFrame]' = Non
                                 promised_reserved: 'int' = 0,
                                 promised_sid: 'int' = 0,
                                 fragment: 'bytes' = b'',
+                                padding: 'bytes' = b'',
                                 **kwargs: 'Any') -> 'tuple[Schema_PushPromiseFrame, Flags]':
         """Make HTTP/2 ``PUSH_PROMISE`` frame.
 
@@ -1315,6 +1329,8 @@ def _make_http_push_promise(self, frame: 'Optional[Data_PushPromiseFrame]' = Non
             promised_reserved: Reserved bit of the promised stream identifier.
             promised_sid: Promised stream identifier.
             fragment: Header block fragment.
+            padding: Padding octets, written as given if exactly ``pad_len``
+                octets and as zeros otherwise.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -1328,6 +1344,7 @@ def _make_http_push_promise(self, frame: 'Optional[Data_PushPromiseFrame]' = Non
             promised_reserved = frame.promised_reserved
             promised_sid = frame.promised_sid
             fragment = frame.fragment
+            padding = getattr(frame, 'padding', b'')
 
         flags = Schema_PushPromiseFrame.Flags(0)
         if end_headers:
@@ -1342,6 +1359,7 @@ def _make_http_push_promise(self, frame: 'Optional[Data_PushPromiseFrame]' = Non
                 'sid': promised_sid,
             },
             fragment=fragment,
+            padding=padding,
         ), flags
 
     def _make_http_ping(self, frame: 'Optional[Data_PingFrame]' = None, *,

pcapkit/protocols/application/ospf.py

@@ -392,6 +392,7 @@ def _read_encrypt_auth(self, schema: 'Schema_CryptographicAuthentication') -> 'D
 
         """
         auth = Data_CryptographicAuthentication(
+            reserved=schema.reserved,
             key_id=schema.key_id,
             len=schema.len,
             seq=schema.seq,
@@ -422,6 +423,7 @@ def _make_encrypt_auth(self,
             return Schema_CryptographicAuthentication.unpack(auth_data)  # type: ignore[call-arg,misc]
         if isinstance(auth_data, Data_CryptographicAuthentication):
             return Schema_CryptographicAuthentication(
+                reserved=auth_data.reserved,
                 key_id=auth_data.key_id,
                 len=auth_data.len,
                 seq=auth_data.seq,

pcapkit/protocols/data/application/httpv2.py

@@ -89,9 +89,11 @@ class DataFrame(HTTP):
     pad_len: 'int'
     #: Frame payload.
     data: 'bytes'
+    #: Padding octets, as captured (empty unless ``PADDED``).
+    padding: 'bytes'
 
     if TYPE_CHECKING:
-        def __init__(self, length: 'int', type: 'Frame', flags: 'DataFrameFlags', reserved: 'int', pad_len: 'int', sid: 'int', data: 'bytes') -> 'None': ...  # pylint: disable=unused-argument,super-init-not-called,multiple-statements,line-too-long,redefined-builtin
+        def __init__(self, length: 'int', type: 'Frame', flags: 'DataFrameFlags', reserved: 'int', pad_len: 'int', sid: 'int', data: 'bytes', padding: 'bytes') -> 'None': ...  # pylint: disable=unused-argument,super-init-not-called,multiple-statements,line-too-long,redefined-builtin
 
 
 @info_final
@@ -127,9 +129,11 @@ class HeadersFrame(HTTP):
     weight: 'int'
     #: Header block fragment.
     fragment: 'bytes'
+    #: Padding octets, as captured (empty unless ``PADDED``).
+    padding: 'bytes'
 
     if TYPE_CHECKING:
-        def __init__(self, length: 'int', type: 'Frame', flags: 'HeadersFrameFlags', reserved: 'int', pad_len: 'int', sid: 'int', excl_dependency: 'bool', stream_dependency: 'int', weight: 'int', fragment: 'bytes') -> 'None': ...  # pylint: disable=unused-argument,super-init-not-called,multiple-statements,line-too-long,redefined-builtin
+        def __init__(self, length: 'int', type: 'Frame', flags: 'HeadersFrameFlags', reserved: 'int', pad_len: 'int', sid: 'int', excl_dependency: 'bool', stream_dependency: 'int', weight: 'int', fragment: 'bytes', padding: 'bytes') -> 'None': ...  # pylint: disable=unused-argument,super-init-not-called,multiple-statements,line-too-long,redefined-builtin
 
 
 @info_final
@@ -237,9 +241,11 @@ class PushPromiseFrame(HTTP):
     promised_sid: 'int'
     #: Header block fragment.
     fragment: 'bytes'
+    #: Padding octets, as captured (empty unless ``PADDED``).
+    padding: 'bytes'
 
     if TYPE_CHECKING:
-        def __init__(self, length: 'int', type: 'Frame', flags: 'Flags', reserved: 'int', pad_len: 'int', sid: 'int', promised_reserved: 'int', promised_sid: 'int', fragment: 'bytes') -> 'None': ...  # pylint: disable=unused-argument,super-init-not-called,multiple-statements,line-too-long,redefined-builtin
+        def __init__(self, length: 'int', type: 'Frame', flags: 'Flags', reserved: 'int', pad_len: 'int', sid: 'int', promised_reserved: 'int', promised_sid: 'int', fragment: 'bytes', padding: 'bytes') -> 'None': ...  # pylint: disable=unused-argument,super-init-not-called,multiple-statements,line-too-long,redefined-builtin
 
 
 @info_final

pcapkit/protocols/data/application/ospf.py

@@ -20,6 +20,8 @@
 class CryptographicAuthentication(Data):
     """Data model for OSPF cryptographic authentication."""
 
+    #: The two reserved octets, as captured.
+    reserved: 'bytes'
     #: Key ID.
     key_id: 'int'
     #: Authentication data length.
@@ -28,7 +30,7 @@ class CryptographicAuthentication(Data):
     seq: 'int'
 
     if TYPE_CHECKING:
-        def __init__(self, key_id: 'int', len: 'int', seq: 'int') -> 'None': ...  # pylint: disable=unused-argument,super-init-not-called,multiple-statements,redefined-builtin
+        def __init__(self, reserved: 'bytes', key_id: 'int', len: 'int', seq: 'int') -> 'None': ...  # pylint: disable=unused-argument,super-init-not-called,multiple-statements,redefined-builtin
 
 
 @info_final