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author | Ilya Etingof <etingof@gmail.com> | 2019-07-09 00:18:00 +0200 |
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committer | GitHub <noreply@github.com> | 2019-07-09 00:18:00 +0200 |
commit | cf9b3f5f67501b85296c05456bbd324352177718 (patch) | |
tree | 02d8ae96bfbcd56323427351eab78b8185b42eb3 | |
parent | 954629f0ba38d9ba26744daba36d97b352ebb721 (diff) | |
download | pyasn1-git-cf9b3f5f67501b85296c05456bbd324352177718.tar.gz |
Add more docs on `OpenType` (#166)
This change adds more explanations and examples on ASN.1 ANY
DEFINED BY syntax (OpenType).
-rw-r--r-- | docs/source/pyasn1/type/opentype/contents.rst | 94 | ||||
-rw-r--r-- | docs/source/pyasn1/type/opentype/opentype.rst | 7 | ||||
-rw-r--r-- | docs/source/pyasn1/type/univ/sequence.rst | 6 | ||||
-rw-r--r-- | docs/source/pyasn1/type/univ/sequenceof.rst | 6 | ||||
-rw-r--r-- | docs/source/pyasn1/type/univ/set.rst | 6 | ||||
-rw-r--r-- | docs/source/pyasn1/type/univ/setof.rst | 6 | ||||
-rw-r--r-- | pyasn1/type/base.py | 11 | ||||
-rw-r--r-- | pyasn1/type/opentype.py | 45 |
8 files changed, 139 insertions, 42 deletions
diff --git a/docs/source/pyasn1/type/opentype/contents.rst b/docs/source/pyasn1/type/opentype/contents.rst index 9ae10d0..034870b 100644 --- a/docs/source/pyasn1/type/opentype/contents.rst +++ b/docs/source/pyasn1/type/opentype/contents.rst @@ -1,16 +1,67 @@ .. _type.opentype: -Untyped fields of constructed types ------------------------------------ +Dynamic or open type +-------------------- -To aid data structures flexibility, ASN.1 allows the designer to -leave incomplete field type specification in the -:ref:`Sequence <univ.Sequence>` and :ref:`Set <univ.Set>` types. +ASN.1 allows data structure designer to leave "holes" in field type +specification of :ref:`Sequence <univ.Sequence>` or +:ref:`Set <univ.Set>` types. -To figure out field's type at the run time, a type selector field -must accompany the open type field. The open type situation can -be captured by the :ref:`OpenType <opentype.OpenType>` object. +The idea behind that feature is that there can be times, when the +exact field type is not known at the design time, or it is anticipated +that new field types may come up in the future. + +This "hole" type is manifested in the data structure by :ref:`Any <univ.Any>` +type. Technically, the actual type is serialized into an octet stream +and then put into :ref:`Any <univ.Any>` "container", which is in fact an +(untagged, by default) specialization of ASN.1 +:ref:`OctetString <univ.OctetString>` type. + +.. code-block:: bash + + Algorithm ::= SEQUENCE { + algorithm OBJECT IDENTIFIER, + parameters ANY DEFINED BY algorithm OPTIONAL + } + +On the receiving end, to know how to interpret the open type +serialization, the receiver can rely on the supplied value in +the other field of the data structure. That other field is +semantically linked with the open type field. This link +is expressed in ASN.1 by the *DEFINE BY* clause. + +From ASN.1 perspective, it is not an error if the decoder does +not know a type selector value it receives. In that case pyasn1 decoder +just leaves serialized blob in the open type field. + +.. note:: + + By default, ASN.1 ANY type has no tag. That makes it an + "invisible" in serialization. However, like any other ASN.1 type, + ANY type can be subtyped by :ref:`tagging <type.tag>`. + +Besides scalar open type fields, ASN.1 allows using *SET OF* +or *SEQUENCE OF* containers holding zero or more of *ANY* +scalars. + +.. code-block:: bash + + AttributeTypeAndValues ::= SEQUENCE { + type OBJECT IDENTIFIER, + values SET OF ANY DEFINED BY type + } + +.. note:: + + A single type selector field is used to guide the decoder + of potentially many elements of a *SET OF* or *SEQUENCE OF* container + all at once. That implies that all *ANY* elements must be of the same + type in any given instance of a data structure. + +When expressing ASN.1 type "holes" in pyasn1, the +:ref:`OpenType <opentype.OpenType>` object should be used to establish +a semantic link between type selector field and open type field. .. code-block:: python @@ -24,15 +75,38 @@ be captured by the :ref:`OpenType <opentype.OpenType>` object. """ Algorithm ::= SEQUENCE { algorithm OBJECT IDENTIFIER, - parameters ANY DEFINED BY algorithm OPTIONAL + parameters ANY DEFINED BY algorithm } """ componentType = NamedTypes( NamedType('algorithm', ObjectIdentifier()), - OptionalNamedType('parameters', Any(), + NamedType('parameters', Any(), openType=OpenType('algorithm', algo_map)) ) +Similarly for `SET OF ANY DEFINED BY` or `SEQUENCE OF ANY DEFINED BY` +constructs: + +.. code-block:: python + + algo_map = { + ObjectIdentifier('1.2.840.113549.1.1.1'): rsaEncryption(), + ObjectIdentifier('1.2.840.113549.1.1.2'): md2WithRSAEncryption() + } + + + class Algorithm(Sequence): + """ + Algorithm ::= SEQUENCE { + algorithm OBJECT IDENTIFIER, + parameters SET OF ANY DEFINED BY algorithm + } + """ + componentType = NamedTypes( + NamedType('algorithm', ObjectIdentifier()), + NamedType('parameters', SetOf(componentType=Any()), + openType=OpenType('algorithm', algo_map)) + ) .. toctree:: :maxdepth: 2 diff --git a/docs/source/pyasn1/type/opentype/opentype.rst b/docs/source/pyasn1/type/opentype/opentype.rst index dc2fa47..8ce9303 100644 --- a/docs/source/pyasn1/type/opentype/opentype.rst +++ b/docs/source/pyasn1/type/opentype/opentype.rst @@ -9,9 +9,4 @@ .. autoclass:: pyasn1.type.opentype.OpenType :members: - .. note:: - - The |OpenType| class models an untyped field of a constructed ASN.1 - type. In ASN.1 syntax it is usually represented by the - `ANY DEFINED BY` clause. Typically used with :ref:`Any <univ.Any>` - type. +More information on open type use can be found :ref:`here <type.opentype>`.
\ No newline at end of file diff --git a/docs/source/pyasn1/type/univ/sequence.rst b/docs/source/pyasn1/type/univ/sequence.rst index 6d2c6b5..f48f497 100644 --- a/docs/source/pyasn1/type/univ/sequence.rst +++ b/docs/source/pyasn1/type/univ/sequence.rst @@ -6,7 +6,7 @@ |ASN.1| type ------------ -.. autoclass:: pyasn1.type.univ.Sequence(componentType=None, tagSet=tagSet(), subtypeSpec=ConstraintsIntersection(), sizeSpec=ConstraintsIntersection()) +.. autoclass:: pyasn1.type.univ.Sequence(componentType=NamedTypes(), tagSet=tagSet(), subtypeSpec=ConstraintsIntersection(), sizeSpec=ConstraintsIntersection()) :members: isValue, isSameTypeWith, isSuperTypeOf, tagSet, effectiveTagSet, tagMap, componentType, subtypeSpec, sizeSpec, getComponentByPosition, setComponentByPosition, getComponentByName, setComponentByName, setDefaultComponents @@ -15,5 +15,5 @@ The |ASN.1| type models a collection of named ASN.1 components. Ordering of the components **is** preserved upon de/serialisation. - .. automethod:: pyasn1.type.univ.Sequence.clone(componentType=None, tagSet=tagSet(), subtypeSpec=ConstraintsIntersection()) - .. automethod:: pyasn1.type.univ.Sequence.subtype(componentType=None, implicitTag=Tag(), explicitTag=Tag(),subtypeSpec=ConstraintsIntersection()) + .. automethod:: pyasn1.type.univ.Sequence.clone(componentType=NamedTypes(), tagSet=tagSet(), subtypeSpec=ConstraintsIntersection()) + .. automethod:: pyasn1.type.univ.Sequence.subtype(componentType=NamedTypes(), implicitTag=Tag(), explicitTag=Tag(),subtypeSpec=ConstraintsIntersection()) diff --git a/docs/source/pyasn1/type/univ/sequenceof.rst b/docs/source/pyasn1/type/univ/sequenceof.rst index dadef67..ed6a781 100644 --- a/docs/source/pyasn1/type/univ/sequenceof.rst +++ b/docs/source/pyasn1/type/univ/sequenceof.rst @@ -6,7 +6,7 @@ |ASN.1| type ------------ -.. autoclass:: pyasn1.type.univ.SequenceOf(componentType=None, tagSet=TagSet(), subtypeSpec=ConstraintsIntersection(), sizeSpec=ConstraintsIntersection()) +.. autoclass:: pyasn1.type.univ.SequenceOf(componentType=NoValue(), tagSet=TagSet(), subtypeSpec=ConstraintsIntersection(), sizeSpec=ConstraintsIntersection()) :members: isValue, isSameTypeWith, isSuperTypeOf, tagSet, effectiveTagSet, tagMap, componentType, subtypeSpec, sizeSpec, getComponentByPosition, setComponentByPosition @@ -15,5 +15,5 @@ The |ASN.1| type models a collection of elements of a single ASN.1 type. Ordering of the components **is** preserved upon de/serialisation. - .. automethod:: pyasn1.type.univ.SequenceOf.clone(componentType=None, tagSet=TagSet(), subtypeSpec=ConstraintsIntersection()) - .. automethod:: pyasn1.type.univ.SequenceOf.subtype(componentType=None, implicitTag=Tag(), explicitTag=Tag(),subtypeSpec=ConstraintsIntersection()) + .. automethod:: pyasn1.type.univ.SequenceOf.clone(componentType=NoValue(), tagSet=TagSet(), subtypeSpec=ConstraintsIntersection()) + .. automethod:: pyasn1.type.univ.SequenceOf.subtype(componentType=NoValue(), implicitTag=Tag(), explicitTag=Tag(),subtypeSpec=ConstraintsIntersection()) diff --git a/docs/source/pyasn1/type/univ/set.rst b/docs/source/pyasn1/type/univ/set.rst index 5c75938..229525a 100644 --- a/docs/source/pyasn1/type/univ/set.rst +++ b/docs/source/pyasn1/type/univ/set.rst @@ -6,7 +6,7 @@ |ASN.1| type ------------ -.. autoclass:: pyasn1.type.univ.Set(componentType=None, tagSet=TagSet(), subtypeSpec=ConstraintsIntersection(), sizeSpec=ConstraintsIntersection()) +.. autoclass:: pyasn1.type.univ.Set(componentType=NamedTypes(), tagSet=TagSet(), subtypeSpec=ConstraintsIntersection(), sizeSpec=ConstraintsIntersection()) :members: isValue, isSameTypeWith, isSuperTypeOf, tagSet, effectiveTagSet, tagMap, componentType, subtypeSpec, sizeSpec, getComponentByPosition, setComponentByPosition, getComponentByName, setComponentByName, setDefaultComponents, getComponentByType, setComponentByType @@ -16,5 +16,5 @@ The |ASN.1| type models a collection of named ASN.1 components. Ordering of the components **is not** preserved upon de/serialisation. - .. automethod:: pyasn1.type.univ.Set.clone(componentType=None, tagSet=TagSet(), subtypeSpec=ConstraintsIntersection()) - .. automethod:: pyasn1.type.univ.Set.subtype(componentType=None, implicitTag=Tag(), explicitTag=Tag(),subtypeSpec=ConstraintsIntersection()) + .. automethod:: pyasn1.type.univ.Set.clone(componentType=NamedTypes(), tagSet=TagSet(), subtypeSpec=ConstraintsIntersection()) + .. automethod:: pyasn1.type.univ.Set.subtype(componentType=NamedTypes(), implicitTag=Tag(), explicitTag=Tag(),subtypeSpec=ConstraintsIntersection()) diff --git a/docs/source/pyasn1/type/univ/setof.rst b/docs/source/pyasn1/type/univ/setof.rst index 0317f4a..2745677 100644 --- a/docs/source/pyasn1/type/univ/setof.rst +++ b/docs/source/pyasn1/type/univ/setof.rst @@ -6,7 +6,7 @@ |ASN.1| type ------------ -.. autoclass:: pyasn1.type.univ.SetOf(componentType=None, tagSet=TagSet(), subtypeSpec=ConstraintsIntersection(), sizeSpec=ConstraintsIntersection()) +.. autoclass:: pyasn1.type.univ.SetOf(componentType=NoValue(), tagSet=TagSet(), subtypeSpec=ConstraintsIntersection(), sizeSpec=ConstraintsIntersection()) :members: isValue, isSameTypeWith, isSuperTypeOf, tagSet, effectiveTagSet, tagMap, componentType, subtypeSpec, sizeSpec, Â getComponentByPosition, setComponentByPosition @@ -15,5 +15,5 @@ The |ASN.1| type models a collection of elements of a single ASN.1 type. Ordering of the components **is not** preserved upon de/serialisation. - .. automethod:: pyasn1.type.univ.SetOf.clone(componentType=None, tagSet=TagSet(), subtypeSpec=ConstraintsIntersection()) - .. automethod:: pyasn1.type.univ.SetOf.subtype(componentType=None, implicitTag=Tag(), explicitTag=Tag(),subtypeSpec=ConstraintsIntersection()) + .. automethod:: pyasn1.type.univ.SetOf.clone(componentType=NoValue(), tagSet=TagSet(), subtypeSpec=ConstraintsIntersection()) + .. automethod:: pyasn1.type.univ.SetOf.subtype(componentType=NoValue(), implicitTag=Tag(), explicitTag=Tag(),subtypeSpec=ConstraintsIntersection()) diff --git a/pyasn1/type/base.py b/pyasn1/type/base.py index b231482..61ec35e 100644 --- a/pyasn1/type/base.py +++ b/pyasn1/type/base.py @@ -12,7 +12,8 @@ from pyasn1.type import constraint from pyasn1.type import tag from pyasn1.type import tagmap -__all__ = ['Asn1Item', 'Asn1ItemBase', 'AbstractSimpleAsn1Item', 'AbstractConstructedAsn1Item'] +__all__ = ['Asn1Item', 'Asn1ItemBase', 'AbstractSimpleAsn1Item', + 'AbstractConstructedAsn1Item'] class Asn1Item(object): @@ -535,8 +536,7 @@ class AbstractConstructedAsn1Item(Asn1ItemBase): Note ---- Due to the mutable nature of the |ASN.1| object, even if no arguments - are supplied, new |ASN.1| object will always be created as a shallow - copy of `self`. + are supplied, a new |ASN.1| object will be created and returned. """ cloneValueFlag = kwargs.pop('cloneValueFlag', False) @@ -588,9 +588,8 @@ class AbstractConstructedAsn1Item(Asn1ItemBase): Note ---- - Due to the immutable nature of the |ASN.1| object, if no arguments - are supplied, no new |ASN.1| object will be created and `self` will - be returned instead. + Due to the mutable nature of the |ASN.1| object, even if no arguments + are supplied, a new |ASN.1| object will be created and returned. """ initializers = self.readOnly.copy() diff --git a/pyasn1/type/opentype.py b/pyasn1/type/opentype.py index d37a533..29645f0 100644 --- a/pyasn1/type/opentype.py +++ b/pyasn1/type/opentype.py @@ -11,11 +11,22 @@ __all__ = ['OpenType'] class OpenType(object): """Create ASN.1 type map indexed by a value - The *DefinedBy* object models the ASN.1 *DEFINED BY* clause which maps - values to ASN.1 types in the context of the ASN.1 SEQUENCE/SET type. - - OpenType objects are duck-type a read-only Python :class:`dict` objects, - however the passed `typeMap` is stored by reference. + The *OpenType* object models an untyped field of a constructed ASN.1 + type. In ASN.1 syntax it is usually represented by the + `ANY DEFINED BY` for scalars or `SET OF ANY DEFINED BY`, + `SEQUENCE OF ANY DEFINED BY` for container types clauses. Typically + used together with :class:`~pyasn1.type.univ.Any` object. + + OpenType objects duck-type a read-only Python :class:`dict` objects, + however the passed `typeMap` is not copied, but stored by reference. + That means the user can manipulate `typeMap` at run time having this + reflected on *OpenType* object behavior. + + The |OpenType| class models an untyped field of a constructed ASN.1 + type. In ASN.1 syntax it is usually represented by the + `ANY DEFINED BY` for scalars or `SET OF ANY DEFINED BY`, + `SEQUENCE OF ANY DEFINED BY` for container types clauses. Typically + used with :class:`~pyasn1.type.univ.Any` type. Parameters ---------- @@ -28,12 +39,14 @@ class OpenType(object): Examples -------- + + For untyped scalars: + .. code-block:: python openType = OpenType( - 'id', - {1: Integer(), - 2: OctetString()} + 'id', {1: Integer(), + 2: OctetString()} ) Sequence( componentType=NamedTypes( @@ -41,6 +54,22 @@ class OpenType(object): NamedType('blob', Any(), openType=openType) ) ) + + For untyped `SET OF` or `SEQUENCE OF` vectors: + + .. code-block:: python + + openType = OpenType( + 'id', {1: Integer(), + 2: OctetString()} + ) + Sequence( + componentType=NamedTypes( + NamedType('id', Integer()), + NamedType('blob', SetOf(componentType=Any()), + openType=openType) + ) + ) """ def __init__(self, name, typeMap=None): |