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Basic usage
===========
The :mod:`pskc` module implements a simple and efficient API for parsing PSKC
files.
Opening a PSKC file
-------------------
.. module:: pskc
Importing data from a PSKC file can be done by instantiating a :class:`PSKC`
class::
from pskc import PSKC
pskc = PSKC('somefile.pskcxml')
.. class:: PSKC(filename)
The :class:`PSKC` class is used as a wrapper to access information from a
PSKC file. The whole file is parsed in one go. Instances of this class
provide the following attributes:
.. attribute:: version
The PSKC format version used. Only version ``1.0`` is currently specified
in `RFC6030 <https://tools.ietf.org/html/rfc6030#section-1.2>`__.
.. attribute:: id
A unique identifier for the container.
.. attribute:: keys
A list of :class:`pskc.key.Key` instances that represent the keys
within the PSKC file.
.. attribute:: encryption
Instance of the :class:`pskc.encryption.Encryption` class that handles
PSKC file encryption.
.. attribute:: mac
Instance of the :class:`pskc.mac.MAC` class that handles integrity
checking.
Examining keys
--------------
.. module:: pskc.key
The :attr:`pskc.PSKC.keys` attribute provides access to the keys contained in
the PSKC file. Instances of the :class:`Key` class provide access to a number
of attributes that provide information on the transmitted keys::
pskc = PSKC('somefile.pskcxml')
first_key = pskc.keys[0]
Attribute values will be ``None`` if it the value is not present in the PSKC
file.
.. class:: Key()
.. attribute:: id
A unique identifier for the key. If there are multiple interactions
with the same key in multiple instances of PSKC files the `id` is
supposed to remain the same.
.. attribute:: algorithm
A URI that identifies the PSKC algorithm profile. The algorithm profile
associates specific semantics to the key. Some `known profiles
<https://www.iana.org/assignments/pskc/#alg-profiles>`__ are:
* ``urn:ietf:params:xml:ns:keyprov:pskc:pin``:
`Symmetric static credential comparison <https://tools.ietf.org/html/rfc6030#section-10.2>`_
* ``urn:ietf:params:xml:ns:keyprov:pskc:hotp``:
`OATH event-based OTP <https://tools.ietf.org/html/rfc6030#section-10.1>`_
* ``urn:ietf:params:xml:ns:keyprov:pskc#totp`` or
``urn:ietf:params:xml:ns:keyprov:pskc:totp``:
`OATH time-based OTP <http://tools.ietf.org/html/draft-hoyer-keyprov-pskc-algorithm-profiles-01#section-4>`_
* ``urn:ietf:params:xml:ns:keyprov:pskc#OCRA-1``:
`OATH challenge-response algorithm <https://tools.ietf.org/html/draft-hoyer-keyprov-pskc-algorithm-profiles-01#section-3>`_
.. attribute:: secret
The binary value of the transported secret key. If the key information
is encrypted in the PSKC file it is transparently decrypted if
possible.
.. attribute:: counter
The event counter for event-based OTP algorithms.
.. attribute:: time_offset
The time offset offset for time-based OTP algorithms. If time intervals
are used it carries the number of time intervals passed from an
algorithm-dependent start point.
.. attribute:: time_interval
The time interval in seconds for time-based OTP algorithms (usually
``30`` or ``60``).
.. attribute:: time_drift
For time-based OTP algorithms this contains the device clock drift in
number of intervals.
.. attribute:: issuer
The name of the party that issued the key. This may be different from
the :attr:`manufacturer` of the device.
.. attribute:: key_profile
A reference to a pre-shared key profile agreed upon between the sending
and receiving parties. The profile information itself is not
transmitted within the container.
See `RFC6030 <https://tools.ietf.org/html/rfc6030#section-4.4>`__.
.. attribute:: key_reference
A reference to an external key that is not contained within the PSKC
file (e.g., a PKCS #11 key label). If this attribute is present, the
:attr:`secret` attribute will generally be missing.
.. attribute:: friendly_name
A human-readable name for the secret key.
.. attribute:: key_userid
The distinguished name of the user associated with the key.
Also see :attr:`device_userid`.
.. attribute:: manufacturer
The name of the manufacturer of the device to which the key is
provisioned. `RFC6030 <https://tools.ietf.org/html/rfc6030#section-4.3.1>`__
prescribes that the value is of the form ``oath.prefix`` for `OATH
Manufacturer Prefixes <http://www.openauthentication.org/oath-id/prefixes/>`_
or ``iana.organisation`` for `IANA Private Enterprise Numbers
<https://www.iana.org/assignments/enterprise-numbers/enterprise-numbers>`_
however, it is generally just a string. The value may be different from
the :attr:`issuer` of the key on the device.
.. attribute:: serial
The serial number of the device to which the key is provisioned.
Together with :attr:`manufacturer` (and perhaps :attr:`issue_no`)
this should uniquely identify the device.
.. attribute:: model
A manufacturer specific description of the model of the device.
.. attribute:: issue_no
The issue number in case there are devices with the same :attr:`serial`
number so that they can be distinguished by different issue numbers.
.. attribute:: device_binding
Reference to a device identifier (e.g. IMEI) that allows a provisioning
server to ensure that the key is going to be loaded into a specific
device.
.. attribute:: start_date
:class:`datetime.datetime` value that indicates that the device should
only be used after this date.
.. attribute:: expiry_date
:class:`datetime.datetime` value that indicates that the device should
only be used before this date. Systems should not rely upon the device
to enforce key usage date restrictions, as some devices do not have an
internal clock.
.. attribute:: device_userid
The distinguished name of the user associated with the device.
Also see :attr:`key_userid`.
.. attribute:: crypto_module
Implementation specific unique identifier of the cryptographic module
on the device to which the keys have been (or will be) provisioned.
.. attribute:: algorithm_suite
Additional algorithm specific characteristics. For example, in an
HMAC-based algorithm it could designate the hash algorithm used (SHA1
or SHA256).
.. attribute:: challenge_encoding
Encoding of the challenge accepted by the device for challenge-response
authentication. One of:
* ``DECIMAL``: only numerical digits
* ``HEXADECIMAL``: hexadecimal
* ``ALPHANUMERIC``: all letters and numbers (case sensitive)
* ``BASE64``: base-64 encoded
* ``BINARY``: binary data
.. attribute:: challenge_min_length
The minimum size of the challenge accepted by the device.
.. attribute:: challenge_max_length
The maximum size of the challenge accepted by the device.
.. attribute:: challenge_check
Boolean that indicates whether the device will check an embedded
`Luhn check digit <http://arthurdejong.org/python-stdnum/doc/0.9/stdnum.luhn.html>`_
contained in the challenge.
.. attribute:: response_encoding
Format of the response that is generated by the device. If must be one
of the values as described under :attr:`challenge_encoding`.
.. attribute:: response_length
The length of the response generated by the device.
.. attribute:: response_check
Boolean that indicates whether the device will append a
`Luhn check digit <http://arthurdejong.org/python-stdnum/doc/0.9/stdnum.luhn.html>`_
to the response.
.. attribute:: policy
Instance of :class:`pskc.policy.Policy` that provides key and PIN
policy information. See :doc:`policy`.
.. function:: check()
Check if any MACs in the key data embedded in the PSKC file are valid.
Will return a boolean or ``None`` if no MACs are defined for the key.
See :doc:`mac`.
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