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Examples
========
Dump
----
This command line utility reads a X509.v3 certificate (in DER or PEM encoding),
decodes it and outputs a textual representation. It more or less mimics
`openssl asn1parse <https://www.openssl.org/docs/man1.1.1/man1/openssl-asn1parse.html>`_:
.. code-block:: shell
$ python examples/dump.py examples/test.crt
[U] SEQUENCE
[U] SEQUENCE
[C] 0x0
[U] INTEGER: 2
[U] INTEGER: 5424
[U] SEQUENCE
[U] OBJECT: 1.2.840.113549.1.1.5
[U] NULL: None
[U] SEQUENCE
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.6
[U] PRINTABLESTRING: --
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.8
[U] PRINTABLESTRING: SomeState
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.7
[U] PRINTABLESTRING: SomeCity
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.10
[U] PRINTABLESTRING: SomeOrganization
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.11
[U] PRINTABLESTRING: SomeOrganizationalUnit
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.3
[U] PRINTABLESTRING: localhost.localdomain
[U] SET
[U] SEQUENCE
[U] OBJECT: 1.2.840.113549.1.9.1
[U] IA5STRING: root@localhost.localdomain
[U] SEQUENCE
[U] UTCTIME: 080205092331Z
[U] UTCTIME: 090204092331Z
[U] SEQUENCE
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.6
[U] PRINTABLESTRING: --
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.8
[U] PRINTABLESTRING: SomeState
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.7
[U] PRINTABLESTRING: SomeCity
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.10
[U] PRINTABLESTRING: SomeOrganization
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.11
[U] PRINTABLESTRING: SomeOrganizationalUnit
[U] SET
[U] SEQUENCE
[U] OBJECT: 2.5.4.3
[U] PRINTABLESTRING: localhost.localdomain
[U] SET
[U] SEQUENCE
[U] OBJECT: 1.2.840.113549.1.9.1
[U] IA5STRING: root@localhost.localdomain
[U] SEQUENCE
[U] SEQUENCE
[U] OBJECT: 1.2.840.113549.1.1.1
[U] NULL: None
[U] BIT STRING: 0xb'0030818902818100D51...10610203010001'
[C] BIT STRING
[U] SEQUENCE
[U] SEQUENCE
[U] OBJECT: 2.5.29.14
[U] OCTET STRING: 0xb'04140A4BFA8754177E30B4217156510FD291C3300236'
[U] SEQUENCE
[U] OBJECT: 2.5.29.35
[U] OCTET STRING: 0xb'3081DE80140A4...D61696E82021530'
[U] SEQUENCE
[U] OBJECT: 2.5.29.19
[U] OCTET STRING: 0xb'30030101FF'
[U] SEQUENCE
[U] OBJECT: 1.2.840.113549.1.1.5
[U] NULL: None
[U] BIT STRING: 0xb'004E124658A357C59AABFA3...8A6245C7FC58B45A'
The main function is ``pretty_print``:
.. code-block:: python
:linenos:
def pretty_print(input_stream, output_stream, indent=0):
"""Pretty print ASN.1 data."""
while not input_stream.eof():
tag = input_stream.peek()
if tag.typ == asn1.Types.Primitive:
tag, value = input_stream.read()
output_stream.write(' ' * indent)
output_stream.write('[{}] {}: {}\n'.format(class_id_to_string(tag.cls),
tag_id_to_string(tag.nr), value_to_string(tag.nr, value)))
elif tag.typ == asn1.Types.Constructed:
output_stream.write(' ' * indent)
output_stream.write('[{}] {}\n'.format(class_id_to_string(tag.cls),
tag_id_to_string(tag.nr)))
input_stream.enter()
pretty_print(input_stream, output_stream, indent + 2)
input_stream.leave()
This code:
* **line 3**: Loops until its reaches the end of the input stream (with `Decoder.eof()`).
* **line 4**: Looks (with `Decoder.peek()`) at the current tag.
* **line 5**: If the tag is primitive (``TypePrimitive``) ...
* **line 6**: ... the code reads (with `Decoder.read()`) the current tag.
* **line 8**: Then it displays its number and value (after some mapping to be more user-fiendly).
* **line 10**: If the tag is constructed (``TypeConstructed``) ...
* **line 12**: ... the code displays its class and number.
* **line 14**: Then it enters inside the tag and ...
* **line 15**: ... calls itself recursively to decode the ASN.1 tags inside.
* **line 16**: Leaves the current constructed tag (with `Decoder.leave()`) to continue the decoding of its siblings.
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