authentik/passbook/saml_idp/xml_signing.py

"""Signing code goes here."""
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from lxml import etree  # nosec
from signxml import XMLSigner, XMLVerifier
from structlog import get_logger

from passbook.lib.utils.template import render_to_string

LOGGER = get_logger(__name__)


def sign_with_signxml(private_key, data, cert, reference_uri=None):
    """Sign Data with signxml"""
    key = serialization.load_pem_private_key(
        str.encode('\n'.join([x.strip() for x in private_key.split('\n')])),
        password=None, backend=default_backend())
    # defused XML is not used here because it messes up XML namespaces
    # Data is trusted, so lxml is ok
    root = etree.fromstring(data) # nosec
    signer = XMLSigner(c14n_algorithm='http://www.w3.org/2001/10/xml-exc-c14n#')
    signed = signer.sign(root, key=key, cert=[cert], reference_uri=reference_uri)
    XMLVerifier().verify(signed, x509_cert=cert)
    return etree.tostring(signed).decode('utf-8') # nosec


def get_signature_xml():
    """Returns XML Signature for subject."""
    return render_to_string('saml/xml/signature.xml', {})