test_signature.doctest - test XML signature checking functions

Copyright (C) 2017 Arthur de Jong

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA


>>> import sys
>>> import tempfile
>>> try:
...     from StringIO import StringIO
... except ImportError:
...     from io import StringIO
>>> from binascii import a2b_hex, b2a_hex
>>> def tostr(x):
...     return str(x.decode())
>>> def decode(f):
...     return lambda x: tostr(f(x))
>>> b2a_hex = decode(b2a_hex)

>>> from pskc import PSKC
>>> from pskc.encryption import encrypt, decrypt


>>> with open('tests/certificate/key.pem', 'rb') as f:
...     signing_key = f.read()
>>> with open('tests/certificate/ss-certificate.pem', 'rb') as f:
...     self_signed_certificate = f.read()
>>> with open('tests/certificate/certificate.pem', 'rb') as f:
...     signed_certificate = f.read()


Build a simple PSKC structure and sign the file including a self-signed
certificate.

>>> pskc = PSKC()
>>> key = pskc.add_key(id='456', manufacturer='Manufacturer')
>>> key.secret = a2b_hex('4e1790ba272406ba309c5a31')
>>> pskc.signature.sign(signing_key, self_signed_certificate)

Write the PSKC file (use temporary file to test passing file name as
argument).

>>> f = tempfile.NamedTemporaryFile()
>>> pskc.write(f.name)
>>> with open(f.name, 'r') as r:
...     x = sys.stdout.write(r.read())  #doctest: +ELLIPSIS +REPORT_UDIFF +NORMALIZE_WHITESPACE
<?xml version="1.0" encoding="UTF-8"?>
<pskc:KeyContainer xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:pskc="urn:ietf:params:xml:ns:keyprov:pskc" Version="1.0">
 ...
 <ds:Signature>
  <ds:SignedInfo><ds:CanonicalizationMethod Algorithm="..."/><ds:SignatureMethod Algorithm="..."/><ds:Reference...><ds:DigestMethod Algorithm="..."/><ds:DigestValue>...</ds:DigestValue></ds:Reference></ds:SignedInfo>
  <ds:SignatureValue>...</ds:SignatureValue>
  <ds:KeyInfo>
   <ds:X509Data>
    <ds:X509Certificate>...</ds:X509Certificate>
   </ds:X509Data>
  </ds:KeyInfo>
 </ds:Signature>
</pskc:KeyContainer>

Read back the PSKC file and verify the signature.

>>> newpskc = PSKC(f.name)
>>> print(tostr(newpskc.signature.certificate))  #doctest: +ELLIPSIS
-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----
>>> newpskc.signature.signed_pskc  # we need a certificate for verification
Traceback (most recent call last):
    ...
InvalidCertificate: [18, 0, 'self signed certificate']
>>> newpskc.signature.verify(self_signed_certificate)
True
>>> newpskc = newpskc.signature.signed_pskc
>>> newpskc.keys[0].secret == pskc.keys[0].secret
True

We can also use the certificate that is embedded in the PSKC file but that
does not add any security.

>>> newpskc = PSKC(f.name)
>>> newpskc.signature.verify(newpskc.signature.certificate)
True
>>> newpskc = newpskc.signature.signed_pskc
>>> newpskc.keys[0].secret == pskc.keys[0].secret
True


We can also sign a PSKC file and include a certificate that can be validated
using a CA certificate.

>>> pskc = PSKC()
>>> key = pskc.add_key(id='456', manufacturer='Manufacturer')
>>> key.secret = a2b_hex('4e1790ba272406ba309c5a31')
>>> pskc.signature.sign(signing_key, signed_certificate)
>>> f = tempfile.NamedTemporaryFile()
>>> pskc.write(f.name)
>>> with open(f.name, 'r') as r:
...     x = sys.stdout.write(r.read())  #doctest: +ELLIPSIS +REPORT_UDIFF +NORMALIZE_WHITESPACE
<?xml version="1.0" encoding="UTF-8"?>
<pskc:KeyContainer xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:pskc="urn:ietf:params:xml:ns:keyprov:pskc" Version="1.0">
 ...
 <ds:Signature>
  <ds:SignedInfo><ds:CanonicalizationMethod Algorithm="..."/><ds:SignatureMethod Algorithm="..."/><ds:Reference...><ds:DigestMethod Algorithm="..."/><ds:DigestValue>...</ds:DigestValue></ds:Reference></ds:SignedInfo>
  <ds:SignatureValue>...</ds:SignatureValue>
  <ds:KeyInfo>
   <ds:X509Data>
    <ds:X509Certificate>...</ds:X509Certificate>
   </ds:X509Data>
  </ds:KeyInfo>
 </ds:Signature>
</pskc:KeyContainer>

Read back the PSKC file and verify the signature. This file can be verified
using the self-signed certificate, the signing certificate or by providing
the CA certificate.

>>> newpskc = PSKC(f.name)
>>> newpskc.signature.signed_pskc  # we need a certificate for verification
Traceback (most recent call last):
    ...
InvalidCertificate: [20, 0, 'unable to get local issuer certificate']
>>> newpskc.signature.verify(self_signed_certificate)
True
>>> newpskc.signature.verify(signed_certificate)
True
>>> newpskc.signature.verify(ca_pem_file='tests/certificate/ca-certificate.pem')
True


We could also sign a PSKC file and include a certificate that is validated by
the default operating system recorded CAs but that is sadly not appropriate
for a test suite (the key needs to be included in the test suite so would not
be private, depending on the CA used there would be costs involved and the
certificates would expire too quickly).


A simple test for parsing an incomplete signature element.

>>> pskc = PSKC(StringIO('''
... <?xml version="1.0"?>
... <KeyContainer Version="1.0" xmlns="urn:ietf:params:xml:ns:keyprov:pskc">
...  <KeyPackage>
...   <Key><Data><Secret><PlainValue>TheQuickBrownFox</PlainValue></Secret></Data></Key>
...  </KeyPackage>
...  <Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
...   <SignedInfo/>
...   <SignatureValue/>
...   <KeyInfo/>
...  </Signature>
... </KeyContainer>
... '''.strip()))
>>> len(pskc.keys)
1
>>> pskc.signature.canonicalization_method is None
True
>>> pskc.signature.algorithm is None
True
>>> pskc.signature.digest_algorithm is None
True