This package provides support for SAML2 based on ``pyxb``.

``pyxb`` (http://pypi.python.org/pypi/PyXB) generates a Python class
collection for an XML schema and provides means to convert between
associated Python instances and xml documents. It is used to generate
and parse SAML2 messages.

The package adds support for digital signatures and SAML2 bindings and
metadata management.


Dependencies
============

PyXB
----

This package's version has been tested with version 1.1.4 of ``pyxb``.
It may not work with other versions.

Class collections generated by ``pyxb`` tend to be very version dependent.
Thus, they must usually be regenerated when the ``pyxb`` version has changed.

The current package's version mostly uses class collections from
the ``wssplat`` and ``saml20`` bundles of ``pyxb``. Thus, they
have a good chance to be updated together with ``pyxb``.
However, the ``pyxb`` ``saml2`` bundle lacks support for
the so called SAML2 context classes. This package contains
class collections generated with ``pyxb==1.1.4``. They need to
be regenerated if the ``pyxb`` version changes (and you use those classes --
which is not very likely).
The ``gen.sh`` script in subpackage ``pyxb``
can provide clues how to regenerate them.

A bug in ``pyxb 1.1.4``
(http://sourceforge.net/apps/trac/pyxb/ticket/130#comment:4)
prevents its installation via package managers (such as
``easy_install``, ``pip``, ``zc.buildout``) for Python versions
without ``os.path.relpath`` (this applies e.g. to Python 2.4).
I work around this problem by downloading the ``pyxb`` source,
apply patch http://sourceforge.net/apps/trac/pyxb/attachment/ticket/130/pyxb_setup.patch
to it and then egg install the result.
After this, ``dm.saml2`` can be installed normally.


dm.xmlsec.binding
-----------------

Check its installation notes should you face related installation problems.


Example
=======

This section provides a simple example on how to create, sign and
verify an assertion with this package.


Always ensure, the ``xmlsec`` library is initialized. Otherwise, it signing/
signature verification can fail with dubious messages.

>>> import dm.xmlsec.binding as xmlsec
>>> xmlsec.initialize()

We now build an assertion as Python object.

>>> import pyxb.binding.datatypes as xs
>>> from dm.saml2.pyxb.assertion import (NameID, Assertion, Subject, \
...      AuthnStatement, AttributeStatement, AuthnContext, AuthnContextClassRef, \
...      Attribute, AttributeValue, \
...      CreateFromDocument
...                                      )
>>> from datetime import datetime
>>> 
>>> issuer = NameID('http://bfd.de')
>>> ass = Assertion(issuer)
>>> 
>>> subject = Subject(NameID('Dieter Maurer'))
>>> 
>>> ass.Subject = subject
>>> 
>>> authn = AuthnStatement(
...   None,
...   AuthnContext(AuthnContextClassRef('urn:oasis:names:tc:SAML2:2.0:ac:classes:Password')),
...   AuthnInstant=datetime.utcnow(),
...   )
>>> 
>>> ass.AuthnStatement.append(authn)
>>> 
>>> att = AttributeStatement(
...   # does not yet work perfectly -- needs further analysis
...   Attribute(xs.string('Dieter', _element=AttributeValue), Name='Firstname'),
...   Attribute(xs.string('Maurer', _element=AttributeValue), Name='Lastname'),
...   )
>>> 
>>> ass.AttributeStatement.append(att)

Now it looks like this (not yet signed).

>>> unsigned_ass = ass.toxml()
>>> print unsigned_ass
<?xml version="1.0" ?><ns1:Assertion ID="_fb6dc6ac-9ee6-4a1f-8010-6dba6e0d9746" IssueInstant="2012-07-06T07:24:53.262859" Version="2.0" xmlns:ns1="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:ns2="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><ns1:Issuer>http://bfd.de</ns1:Issuer><ns1:Subject><ns1:NameID>Dieter Maurer</ns1:NameID></ns1:Subject><ns1:AuthnStatement AuthnInstant="2012-07-06T07:24:53.282142"><ns1:AuthnContext><ns1:AuthnContextClassRef>urn:oasis:names:tc:SAML2:2.0:ac:classes:Password</ns1:AuthnContextClassRef></ns1:AuthnContext></ns1:AuthnStatement><ns1:AttributeStatement><ns1:Attribute Name="Firstname"><ns1:AttributeValue xsi:type="ns2:string">Dieter</ns1:AttributeValue></ns1:Attribute><ns1:Attribute Name="Lastname"><ns1:AttributeValue xsi:type="ns2:string">Maurer</ns1:AttributeValue></ns1:Attribute></ns1:AttributeStatement></ns1:Assertion>


We define the signature context to support signing.

>>> from dm.saml2.signature import default_sign_context
>>> default_sign_context.add_key(xmlsec.Key.load('key.pem',  xmlsec.KeyDataFormatPem, None), issuer.value())

We request that ``ass`` gets signed on serialization, serialize and
look at the result.

>>> ass.request_signature()
>>> signed = ass.toxml()
>>> print signed
<?xml version="1.0" ?><ns1:Assertion ID="_fb6dc6ac-9ee6-4a1f-8010-6dba6e0d9746" IssueInstant="2012-07-06T07:24:53.262859" Version="2.0" xmlns:ns1="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:ns2="http://www.w3.org/2000/09/xmldsig#" xmlns:ns3="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><ns1:Issuer>http://bfd.de</ns1:Issuer><ns2:Signature><ns2:SignedInfo><ns2:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/><ns2:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/><ns2:Reference URI="#_fb6dc6ac-9ee6-4a1f-8010-6dba6e0d9746"><ns2:Transforms><ns2:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/><ns2:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/></ns2:Transforms><ns2:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/><ns2:DigestValue>6P0dLnMLJCe22YuRD1Mngiprz6k=</ns2:DigestValue></ns2:Reference></ns2:SignedInfo><ns2:SignatureValue>liaBBIVjk73x5spJrvfYg1Sa3VGnOqz0zqDKQr7qoLNg5/pzZ8llQEXQsbvw6zLh
26UnQ6D3KWvvabw9vpRqzLA21ykNUPqEGtZPMiQynvpdRSeTbg5ZyVBGYCL7ww19
MiEKryDwPI56I/3z4Le7KFZ4qpPPUptodQ4mm1PVsyA=</ns2:SignatureValue></ns2:Signature><ns1:Subject><ns1:NameID>Dieter Maurer</ns1:NameID></ns1:Subject><ns1:AuthnStatement AuthnInstant="2012-07-06T07:24:53.282142"><ns1:AuthnContext><ns1:AuthnContextClassRef>urn:oasis:names:tc:SAML2:2.0:ac:classes:Password</ns1:AuthnContextClassRef></ns1:AuthnContext></ns1:AuthnStatement><ns1:AttributeStatement><ns1:Attribute Name="Firstname"><ns1:AttributeValue xsi:type="ns3:string">Dieter</ns1:AttributeValue></ns1:Attribute><ns1:Attribute Name="Lastname"><ns1:AttributeValue xsi:type="ns3:string">Maurer</ns1:AttributeValue></ns1:Attribute></ns1:AttributeStatement></ns1:Assertion>

Now, we look how the verification can be done. We first set up
a verification context.

>>> from dm.saml2.signature import default_verify_context
>>> default_verify_context.add_key(xmlsec.Key.load('pubkey.pem',  xmlsec.KeyDataFormatPem, None), issuer.value())

Calling ``CreateFromDocument`` will verify any (available) signatures and raise
an exception when a verification fails. Verification always uses
the ``Issuer`` to select the key from the verification context.
To check whether a signature
was verified at the instance, ``verified_signature`` can be called.

>>> verified_ass = CreateFromDocument(signed)
>>> verified_ass.verified_signature()
True


You can use ``pydoc``, the Python builtin ``help`` or look at the source
to find out more about this package.


Notes
=====

Note that signature creation and verification will fail with an obscure
error message from ``xmlsec`` when ``xmlsec`` is not properly
initialized. Do not forget to call ``dm.xmlsec.binding.initialize()``.


History
=======

2.0

  Version 2.0 uses ``dm.xmlsec.binding`` as Python binding to the XML
  security library, rather then the no longer maintained ``pyxmlsec``.
  This drastically facilitates installation.

1.0

  Initial release based on ``pyxmlsec``.
