When default argument is used and value is not specified, then it equals
to default one.
+.. _bounds:
+
Size constraints
________________
All objects have ``copy()`` method, returning its copy, that can be safely
mutated.
+.. _decoding:
+
Decoding
-________
+--------
Decoding is performed using ``decode()`` method. ``offset`` optional
argument could be used to set initial object's offset in the binary
When error occurs, then :py:exc:`pyderasn.DecodeError` is raised.
+.. _pprinting:
+
Pretty printing
-_______________
+---------------
All objects have ``pps()`` method, that is a generator of
:py:class:`pyderasn.PP` namedtuple, holding various raw information
>>> print(pprint(obj))
0 [1,1, 2] INTEGER -12345
+.. _definedby:
+
+DEFINED BY
+----------
+
+ASN.1 structures often have ANY and OCTET STRING fields, that are
+DEFINED BY some previously met ObjectIdentifier. This library provides
+ability to specify mapping between some OID and field that must be
+decoded with specific specification.
+
+defines kwarg
+_____________
+
+:py:class:`pyderasn.ObjectIdentifier` field inside
+:py:class:`pyderasn.Sequence` can hold mapping between OIDs and
+necessary for decoding structrures. For example, CMS (:rfc:`5652`)
+container::
+
+ class ContentInfo(Sequence):
+ schema = (
+ ("contentType", ContentType(defines=("content", {
+ id_digestedData: DigestedData(),
+ id_signedData: SignedData(),
+ }))),
+ ("content", Any(expl=tag_ctxc(0))),
+ )
+
+``contentType`` field tells that it defines that ``content`` must be
+decoded with ``SignedData`` specification, if ``contentType`` equals to
+``id-signedData``. The same applies to ``DigestedData``. If
+``contentType`` contains unknown OID, then no automatic decoding is
+done.
+
+Following types can be automatically decoded (DEFINED BY):
+
+* :py:class:`pyderasn.Any`
+* :py:class:`pyderasn.OctetString`
+* :py:class:`pyderasn.SequenceOf`/:py:class:`pyderasn.SetOf`
+ ``Any``/``OctetString``-s
+
+When any of those fields is automatically decoded, then ``.defined``
+attribute contains ``(OID, value)`` tuple. OID tell by which OID it was
+defined, ``value`` contains corresponding decoded value. For example
+above, ``content_info["content"].defined == (id_signedData,
+signed_data)``.
+
+defines_by_path kwarg
+_____________________
+
+Sometimes you either can not or do not want to explicitly set *defines*
+in the scheme. You can dynamically apply those definitions when calling
+``.decode()`` method.
+
+Decode method takes optional ``defines_by_path`` keyword argument that
+must be sequence of following tuples::
+
+ (decode_path, defines)
+
+where ``decode_path`` is a tuple holding so-called decode path to the
+exact :py:class:`pyderasn.ObjectIdentifier` field you want to apply
+``defines``, holding exactly the same value as accepted in its keyword
+argument.
+
+For example, again for CMS, you want to automatically decode
+``SignedData`` and CMC's (:rfc:`5272`) ``PKIData`` and ``PKIResponse``
+structures it may hold. Also, automatically decode ``controlSequence``
+of ``PKIResponse``::
+
+ content_info, tail = ContentInfo().decode(data, defines_by_path=(
+ (
+ ("contentType",),
+ ("content", {id_signedData: SignedData()}),
+ ),
+ (
+ (
+ "content",
+ decode_path_defby(id_signedData),
+ "encapContentInfo",
+ "eContentType",
+ ),
+ ("eContent", {
+ id_cct_PKIData: PKIData(),
+ id_cct_PKIResponse: PKIResponse(),
+ }),
+ ),
+ (
+ (
+ "content",
+ decode_path_defby(id_signedData),
+ "encapContentInfo",
+ "eContent",
+ decode_path_defby(id_cct_PKIResponse),
+ "controlSequence",
+ any,
+ "attrType",
+ ),
+ ("attrValues", {
+ id_cmc_recipientNonce: RecipientNonce(),
+ id_cmc_senderNonce: SenderNonce(),
+ id_cmc_statusInfoV2: CMCStatusInfoV2(),
+ id_cmc_transactionId: TransactionId(),
+ }),
+ ),
+ ))
+
+Pay attention for :py:func:`pyderasn.decode_path_defby` and ``any``.
+First function is useful for path construction when some automatic
+decoding is already done. ``any`` is used for human readability and
+means literally any value it meet -- useful for sequence and set of-s.
+
Primitive types
---------------
"Boolean",
"BoundsError",
"Choice",
+ "decode_path_defby",
"DecodeError",
"Enumerated",
"GeneralizedTime",
def _encode(self): # pragma: no cover
raise NotImplementedError()
- def _decode(self, tlv, offset=0, decode_path=()): # pragma: no cover
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None): # pragma: no cover
raise NotImplementedError()
def encode(self):
return raw
return b"".join((self._expl, len_encode(len(raw)), raw))
- def decode(self, data, offset=0, leavemm=False, decode_path=()):
+ def decode(self, data, offset=0, leavemm=False, decode_path=(), defines_by_path=None):
"""Decode the data
:param data: either binary or memoryview
:param int offset: initial data's offset
:param bool leavemm: do we need to leave memoryview of remaining
data as is, or convert it to bytes otherwise
+ :param defines_by_path: :ref:`Read about DEFINED BY <definedby>`
:returns: (Obj, remaining data)
"""
tlv = memoryview(data)
tlv,
offset,
decode_path=decode_path,
+ defines_by_path=defines_by_path,
)
else:
try:
obj, tail = self._decode(
v,
offset=offset + tlen + llen,
- decode_path=(),
+ decode_path=decode_path,
+ defines_by_path=defines_by_path,
)
return obj, (tail if leavemm else tail.tobytes())
return self.expl_tlen + self.expl_llen + self.expl_vlen
+def decode_path_defby(defined_by):
+ """DEFINED BY representation inside decode path
+ """
+ return "DEFINED BY (%s)" % defined_by
+
+
########################################################################
# Pretty printing
########################################################################
(b"\xFF" if self._value else b"\x00"),
))
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, _, lv = tag_strip(tlv)
except DecodeError as err:
break
return b"".join((self.tag, len_encode(len(octets)), octets))
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, _, lv = tag_strip(tlv)
except DecodeError as err:
octets,
))
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, _, lv = tag_strip(tlv)
except DecodeError as err:
>>> OctetString(b"hell", bounds=(4, 4))
OCTET STRING 4 bytes 68656c6c
"""
- __slots__ = ("_bound_min", "_bound_max")
+ __slots__ = ("_bound_min", "_bound_max", "defined")
tag_default = tag_encode(4)
asn1_type_name = "OCTET STRING"
)
if self._value is None:
self._value = default
+ self.defined = None
def _value_sanitize(self, value):
if issubclass(value.__class__, OctetString):
self._value,
))
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, _, lv = tag_strip(tlv)
except DecodeError as err:
expl_llen=self.expl_llen if self.expled else None,
expl_vlen=self.expl_vlen if self.expled else None,
)
+ defined_by, defined = self.defined or (None, None)
+ if defined_by is not None:
+ yield defined.pps(
+ decode_path=decode_path + (decode_path_defby(defined_by),)
+ )
class Null(Obj):
def _encode(self):
return self.tag + len_encode(0)
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, _, lv = tag_strip(tlv)
except DecodeError as err:
Traceback (most recent call last):
pyderasn.InvalidOID: unacceptable first arc value
"""
- __slots__ = ()
+ __slots__ = ("defines",)
tag_default = tag_encode(6)
asn1_type_name = "OBJECT IDENTIFIER"
def __init__(
self,
value=None,
+ defines=None,
impl=None,
expl=None,
default=None,
:param value: set the value. Either tuples of integers,
string of "."-concatenated integers, or
:py:class:`pyderasn.ObjectIdentifier` object
+ :param defines: tuple of two elements. First one is a name of
+ field inside :py:class:`pyderasn.Sequence`,
+ defining with that OID. Second element is a
+ ``{OID: pyderasn.Obj()}`` dictionary, mapping
+ between current OID value and structure applied
+ to defined field.
+ :ref:`Read about DEFINED BY <definedby>`
:param bytes impl: override default tag with ``IMPLICIT`` one
:param bytes expl: override default tag with ``EXPLICIT`` one
:param default: set default value. Type same as in ``value``
)
if self._value is None:
self._value = default
+ self.defines = defines
def __add__(self, their):
if isinstance(their, self.__class__):
def copy(self):
obj = self.__class__()
obj._value = self._value
+ obj.defines = self.defines
obj.tag = self.tag
obj._expl = self._expl
obj.default = self.default
def __call__(
self,
value=None,
+ defines=None,
impl=None,
expl=None,
default=None,
):
return self.__class__(
value=value,
+ defines=self.defines if defines is None else defines,
impl=self.tag if impl is None else impl,
expl=self._expl if expl is None else expl,
default=self.default if default is None else default,
v = b"".join(octets)
return b"".join((self.tag, len_encode(len(v)), v))
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, _, lv = tag_strip(tlv)
except DecodeError as err:
self._assert_ready()
return self._value[1].encode()
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
for choice, spec in self.specs.items():
try:
value, tail = spec.decode(
offset=offset,
leavemm=True,
decode_path=decode_path + (choice,),
+ defines_by_path=defines_by_path,
)
except TagMismatch:
continue
>>> hexenc(bytes(a))
b'0x040x0bhello world'
"""
- __slots__ = ()
+ __slots__ = ("defined",)
tag_default = tag_encode(0)
asn1_type_name = "ANY"
"""
super(Any, self).__init__(None, expl, None, optional, _decoded)
self._value = None if value is None else self._value_sanitize(value)
+ self.defined = None
def _value_sanitize(self, value):
if isinstance(value, self.__class__):
self._assert_ready()
return self._value
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, tlen, lv = tag_strip(tlv)
l, llen, v = len_decode(lv)
expl_llen=self.expl_llen if self.expled else None,
expl_vlen=self.expl_vlen if self.expled else None,
)
+ defined_by, defined = self.defined or (None, None)
+ if defined_by is not None:
+ yield defined.pps(
+ decode_path=decode_path + (decode_path_defby(defined_by),)
+ )
########################################################################
# ASN.1 constructed types
########################################################################
+def get_def_by_path(defines_by_path, sub_decode_path):
+ """Get define by decode path
+ """
+ for path, define in defines_by_path:
+ if len(path) != len(sub_decode_path):
+ continue
+ for p1, p2 in zip(path, sub_decode_path):
+ if (p1 != any) and (p1 != p2):
+ break
+ else:
+ return define
+
+
class Sequence(Obj):
"""``SEQUENCE`` structure type
You have to make specification of sequence::
class Extension(Sequence):
- __slots__ = ()
schema = (
("extnID", ObjectIdentifier()),
("critical", Boolean(default=False)),
v = b"".join(self._encoded_values())
return b"".join((self.tag, len_encode(len(v)), v))
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, tlen, lv = tag_strip(tlv)
except DecodeError as err:
v, tail = v[:l], v[l:]
sub_offset = offset + tlen + llen
values = {}
+ defines = {}
for name, spec in self.specs.items():
if len(v) == 0 and spec.optional:
continue
+ sub_decode_path = decode_path + (name,)
try:
value, v_tail = spec.decode(
v,
sub_offset,
leavemm=True,
- decode_path=decode_path + (name,),
+ decode_path=sub_decode_path,
+ defines_by_path=defines_by_path,
)
except TagMismatch:
if spec.optional:
continue
raise
+
+ defined = defines.pop(name, None)
+ if defined is not None:
+ defined_by, defined_spec = defined
+ if issubclass(value.__class__, SequenceOf):
+ for i, _value in enumerate(value):
+ sub_sub_decode_path = sub_decode_path + (
+ str(i),
+ decode_path_defby(defined_by),
+ )
+ defined_value, defined_tail = defined_spec.decode(
+ memoryview(bytes(_value)),
+ sub_offset + value.tlen + value.llen,
+ leavemm=True,
+ decode_path=sub_sub_decode_path,
+ defines_by_path=defines_by_path,
+ )
+ if len(defined_tail) > 0:
+ raise DecodeError(
+ "remaining data",
+ klass=self.__class__,
+ decode_path=sub_sub_decode_path,
+ offset=offset,
+ )
+ _value.defined = (defined_by, defined_value)
+ else:
+ defined_value, defined_tail = defined_spec.decode(
+ memoryview(bytes(value)),
+ sub_offset + value.tlen + value.llen,
+ leavemm=True,
+ decode_path=sub_decode_path + (decode_path_defby(defined_by),),
+ defines_by_path=defines_by_path,
+ )
+ if len(defined_tail) > 0:
+ raise DecodeError(
+ "remaining data",
+ klass=self.__class__,
+ decode_path=sub_decode_path + (decode_path_defby(defined_by),),
+ offset=offset,
+ )
+ value.defined = (defined_by, defined_value)
+
sub_offset += (value.expl_tlvlen if value.expled else value.tlvlen)
v = v_tail
if spec.default is not None and value == spec.default:
# Encoded default values are not valid in DER,
- # but we still allow that
+ # but we allow that anyway
continue
values[name] = value
+
+ spec_defines = getattr(spec, "defines", None)
+ if defines_by_path is not None and spec_defines is None:
+ spec_defines = get_def_by_path(defines_by_path, sub_decode_path)
+ if spec_defines is not None:
+ what, schema = spec_defines
+ defined = schema.get(value, None)
+ if defined is not None:
+ defines[what] = (value, defined)
if len(v) > 0:
raise DecodeError(
"remaining data",
v = b"".join(raws)
return b"".join((self.tag, len_encode(len(v)), v))
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, tlen, lv = tag_strip(tlv)
except DecodeError as err:
sub_offset,
leavemm=True,
decode_path=decode_path + (name,),
+ defines_by_path=defines_by_path,
)
except TagMismatch:
continue
v = b"".join(self._encoded_values())
return b"".join((self.tag, len_encode(len(v)), v))
- def _decode(self, tlv, offset=0, decode_path=()):
+ def _decode(self, tlv, offset=0, decode_path=(), defines_by_path=None):
try:
t, tlen, lv = tag_strip(tlv)
except DecodeError as err:
sub_offset,
leavemm=True,
decode_path=decode_path + (str(len(_value)),),
+ defines_by_path=defines_by_path,
)
sub_offset += (value.expl_tlvlen if value.expled else value.tlvlen)
v = v_tail
return obj
+def generic_decoder(): # pragma: no cover
+ # All of this below is a big hack with self references
+ choice = PrimitiveTypes()
+ choice.specs["SequenceOf"] = SequenceOf(schema=choice)
+ choice.specs["SetOf"] = SetOf(schema=choice)
+ for i in range(31):
+ choice.specs["SequenceOf%d" % i] = SequenceOf(
+ schema=choice,
+ expl=tag_ctxc(i),
+ )
+ choice.specs["Any"] = Any()
+
+ # Class name equals to type name, to omit it from output
+ class SEQUENCEOF(SequenceOf):
+ __slots__ = ()
+ schema = choice
+
+ def pprint_any(obj, oids=None):
+ def _pprint_pps(pps):
+ for pp in pps:
+ if hasattr(pp, "_fields"):
+ if pp.asn1_type_name == Choice.asn1_type_name:
+ continue
+ pp_kwargs = pp._asdict()
+ pp_kwargs["decode_path"] = pp.decode_path[:-1] + (">",)
+ pp = _pp(**pp_kwargs)
+ yield pp_console_row(
+ pp,
+ oids=oids,
+ with_offsets=True,
+ with_blob=False,
+ )
+ for row in pp_console_blob(pp):
+ yield row
+ else:
+ for row in _pprint_pps(pp):
+ yield row
+ return "\n".join(_pprint_pps(obj.pps()))
+ return SEQUENCEOF(), pprint_any
+
+
def main(): # pragma: no cover
import argparse
parser = argparse.ArgumentParser(description="PyDERASN ASN.1 DER decoder")
from functools import partial
pprinter = partial(pprint, big_blobs=True)
else:
- # All of this below is a big hack with self references
- choice = PrimitiveTypes()
- choice.specs["SequenceOf"] = SequenceOf(schema=choice)
- choice.specs["SetOf"] = SetOf(schema=choice)
- for i in range(31):
- choice.specs["SequenceOf%d" % i] = SequenceOf(
- schema=choice,
- expl=tag_ctxc(i),
- )
- choice.specs["Any"] = Any()
-
- # Class name equals to type name, to omit it from output
- class SEQUENCEOF(SequenceOf):
- __slots__ = ()
- schema = choice
- schema = SEQUENCEOF()
-
- def pprint_any(obj, oids=None):
- def _pprint_pps(pps):
- for pp in pps:
- if hasattr(pp, "_fields"):
- if pp.asn1_type_name == Choice.asn1_type_name:
- continue
- pp_kwargs = pp._asdict()
- pp_kwargs["decode_path"] = pp.decode_path[:-1] + (">",)
- pp = _pp(**pp_kwargs)
- yield pp_console_row(
- pp,
- oids=oids,
- with_offsets=True,
- with_blob=False,
- )
- for row in pp_console_blob(pp):
- yield row
- else:
- for row in _pprint_pps(pp):
- yield row
- return "\n".join(_pprint_pps(obj.pps()))
- pprinter = pprint_any
+ schema, pprinter = generic_decoder()
obj, tail = schema().decode(der)
print(pprinter(obj, oids=oids))
if tail != b"":