def sign_assertion(self, key_file: str, cert_file: str,
signature_method: str, digest_method: str) -> bool:
"""
Sign the SAML assertion.
:return: `True` if the assertion element is present and has been signed, `False` otherwise.
:raise SecurityError: If the assertion or response signature is already present.
"""
assertion = self.document.getroot().find('./{}'.format(
Q_NAMES['saml2:Assertion']))
if assertion is None:
# Failure responses don't contain <Assertion>.
return False
if self.assertion_signature is not None:
raise SecurityError('The assertion signature is already present.')
if self.response_signature is not None:
# Signing assertion would invalidate the response signature.
raise SecurityError(
'Cannot sign assertion because response signature is already present.'
)
sign_xml_node(assertion, key_file, cert_file, signature_method,
digest_method,
int(self._assertion_issuer_element is not None))
return True
def get_light_token(self,
parameter_name: str,
issuer: str,
hash_algorithm: str,
secret: str,
lifetime: Optional[int] = None) -> LightToken:
"""
Retrieve and verify a light token according to token settings.
:param parameter_name: The name of HTTP POST parameter to get the token from.
:param issuer: Token issuer.
:param hash_algorithm: A hashlib hash algorithm.
:param secret: A secret shared between communication parties.
:param lifetime: Lifetime of the token (in minutes) until its expiration.
:return: A decoded LightToken.
:raise ParseError: If the token is malformed and cannot be decoded.
:raise ValidationError: If the token can be decoded but model validation fails.
:raise SecurityError: If the token digest or issuer is invalid or the token has expired.
"""
encoded_token = self.request.POST.get(parameter_name,
'').encode('utf-8')
LOGGER.info('[#%r] Received encoded light token: %r', self.log_id,
encoded_token)
token = LightToken.decode(encoded_token, hash_algorithm, secret)
LOGGER.info('[#%r] Decoded light token: id=%r, issuer=%r', self.log_id,
token.id, token.issuer)
if token.issuer != issuer:
raise SecurityError('Invalid token issuer.')
if lifetime and token.created + timedelta(
minutes=lifetime) < datetime.now():
raise SecurityError('Token has expired.')
return token
def verify_xml_signatures(node: Element,
cert_file: str) -> List[SignatureInfo]:
"""
Verify all XML signatures from the provided node.
:param node: A XML subtree.
:param cert_file: A path to the certificate file.
:return: A list of signature details if there are any signatures, an empty list otherwise.
:raise SecurityError: If any of the element references or signatures are invalid.
"""
signature_info = []
signatures = node.findall(".//{}".format(
QName(XML_SIG_NAMESPACE, 'Signature')))
if signatures:
key = xmlsec.Key.from_file(cert_file,
xmlsec.constants.KeyDataFormatCertPem)
for sig_num, signature in enumerate(signatures, 1):
# Find and register referenced elements
referenced_elements = []
ctx = xmlsec.SignatureContext()
refs = signature.findall('./{}/{}'.format(
QName(XML_SIG_NAMESPACE, 'SignedInfo'),
QName(XML_SIG_NAMESPACE, 'Reference')))
for ref_num, ref in enumerate(refs, 1):
# ID is referenced in the URI attribute and prefixed with a hash.
ref_id = ref.get(XML_ATTRIBUTE_URI)
if ref_id is None or len(ref_id) < 2 or ref_id[0] != '#':
raise SecurityError(
'Signature {}, reference {}: Invalid id {!r}.'.format(
sig_num, ref_num, ref_id))
ref_id = ref_id[1:]
ref_elms = node.xpath('//*[@{}=\'{}\']'.format(
XML_ATTRIBUTE_ID, ref_id))
if not ref_elms:
raise SecurityError(
'Signature {}, reference {}: Element with id {!r} not found.'
.format(sig_num, ref_num, ref_id))
if len(ref_elms) > 1:
raise SecurityError(
'Signature {}, reference {}: Element with id {!r} occurs more than once.'
.format(sig_num, ref_num, ref_id))
referenced_elements.append(ref_elms[0])
# Unlike HTML, XML doesn't have a single standardized id so we need to tell xmlsec about our id.
ctx.register_id(ref_elms[0], XML_ATTRIBUTE_ID, None)
# Verify the signature
try:
ctx.key = key
ctx.verify(signature)
except xmlsec.Error:
raise SecurityError('Signature {} is invalid.'.format(sig_num))
signature_info.append(
SignatureInfo(signature, tuple(referenced_elements)))
return signature_info
def verify_request(self, cert_file: str) -> None:
"""Verify XML signature of the whole request."""
signature = self.request_signature
if signature is None:
raise SecurityError('Signature does not exist.')
# We need to check not only that a valid signature exists but it must also reference the correct element.
for valid_signature, references in verify_xml_signatures(self.document.getroot(), cert_file):
if valid_signature is signature:
if signature.getparent() not in references:
raise SecurityError('Signature does not reference parent element.')
break
else:
raise SecurityError('Signature not found.')
def encrypt_xml_node(node: Element, cert_file: str, cipher: XmlBlockCipher, key_transport: XmlKeyTransport) -> None:
"""
Encrypt a XML node.
The node is removed from the parent element and replaced with <EncryptedData> element.
:param node: A XML subtree.
:param cert_file: A path to the certificate file.
:param cipher: Encryption algorithm to use.
:param key_transport: Key transport algorithm to use.
"""
# Create a container without any XML namespace to force namespace declarations in the encrypted node.
# The decrypted element may then exist as an independent XML document.
container = Element('container')
parent = node.getparent()
node_index = parent.index(node)
container.append(node)
# Create a template for encryption. xmlsec.template functions don't cover all libxmlsec1 features yet.
enc_data = SubElement(container,
'{%s}EncryptedData' % XML_ENC_NAMESPACE,
{'Type': xmlsec.constants.TypeEncElement},
nsmap={'xmlenc': XML_ENC_NAMESPACE})
SubElement(enc_data, '{%s}EncryptionMethod' % XML_ENC_NAMESPACE, {'Algorithm': cipher.value})
SubElement(enc_data, '{%s}CipherData' % XML_ENC_NAMESPACE)
xmlsec.template.encrypted_data_ensure_cipher_value(enc_data)
# Info about the generated encryption key.
key_info = xmlsec.template.encrypted_data_ensure_key_info(enc_data, ns='ds')
enc_key = SubElement(key_info, '{%s}EncryptedKey' % XML_ENC_NAMESPACE)
SubElement(enc_key, '{%s}EncryptionMethod' % XML_ENC_NAMESPACE, {'Algorithm': key_transport.value})
SubElement(enc_key, '{%s}CipherData' % XML_ENC_NAMESPACE)
xmlsec.template.encrypted_data_ensure_cipher_value(enc_key)
# Info about the certificate.
key_info = xmlsec.template.encrypted_data_ensure_key_info(enc_key, ns='ds')
x509_data = xmlsec.template.add_x509_data(key_info)
xmlsec.template.x509_data_add_certificate(x509_data)
xmlsec.template.x509_data_add_issuer_serial(x509_data)
# xmlsec library adds unnecessary newlines to the signature template.
remove_extra_xml_whitespace(enc_data)
# Encrypt with a newly generated key
key_type, key_length = XML_KEY_INFO[cipher]
manager = xmlsec.KeysManager()
manager.add_key(xmlsec.Key.from_file(cert_file, xmlsec.constants.KeyDataFormatCertPem))
ctx = xmlsec.EncryptionContext(manager)
ctx.key = xmlsec.Key.generate(key_type, key_length, xmlsec.constants.KeyDataTypeSession)
try:
ctx.encrypt_xml(enc_data, node)
except xmlsec.Error:
raise SecurityError('XML encryption failed. Invalid certificate, invalid or unsupported encryption method.')
# xmlsec library adds unnecessary tail newlines again, so we remove them.
remove_extra_xml_whitespace(enc_data)
# Insert the encrypted data in the position of the original node.
parent.insert(node_index, enc_data)
def _verify_and_remove_signature(self, signature: Optional[Element], cert_file: str) -> None:
"""Verify signature and remove it from document."""
if signature is None:
raise SecurityError('Signature does not exist.')
# We need to check not only that a valid signature exists but it must also reference the correct element.
for valid_signature, references in verify_xml_signatures(self.document.getroot(), cert_file):
if valid_signature is signature:
if signature.getparent() not in references:
raise SecurityError('Signature does not reference parent element.')
# Remove the signature as further document manipulations might invalidate it.
# E.g., decrypting an encrypted assertion invalidates signature of the whole response.
signature.getparent().remove(signature)
break
else:
raise SecurityError('Signature not found.')
def get_light_request(self) -> LightRequest:
"""
Get a light request.
:return: A light request.
:raise SecurityError: If the request is not found.
"""
request = self.storage.pop_light_request(self.light_token.id)
if request is None:
raise SecurityError('Request not found in light storage.')
return request
def get_light_response(self) -> LightResponse:
"""
Get a light response.
:return: A light response.
:raise SecurityError: If the response is not found.
"""
response = self.storage.pop_light_response(self.light_token.id)
if response is None:
raise SecurityError('Response not found in light storage.')
return response
def sign_response(self, key_file: str, cert_file: str, signature_method: str, digest_method: str) -> None:
"""
Sign the whole SAML response.
:raise SecurityError: If the response signature is already present.
"""
if self.response_signature is not None:
raise SecurityError('The response signature is already present.')
sign_xml_node(self.document.getroot(), key_file, cert_file, signature_method, digest_method,
int(self._response_issuer_element is not None))
def sign_request(self, key_file: str, cert_file: str, signature_method: str, digest_method: str) -> None:
"""
Sign the whole SAML request.
:raise SecurityError: If the signature already exists.
"""
if self.request_signature is not None:
raise SecurityError('Request signature already exists.')
sign_xml_node(self.document.getroot(), key_file, cert_file, signature_method, digest_method,
int(self._issuer_element is not None))
def create_light_request(self, saml_issuer: str,
light_issuer: str) -> LightRequest:
"""
Create a light request from a SAML request.
:param saml_issuer: The expected issuer of the SAML request.
:param light_issuer: The issuer of the light request.
:return: A light request.
"""
request = self.saml_request.create_light_request()
# Verify the original issuer of the request.
if not request.issuer or not hmac.compare_digest(
request.issuer, saml_issuer):
raise SecurityError('Invalid SAML request issuer: {!r}'.format(
request.issuer))
# Use our issuer specified in the generic eIDAS Node configuration.
request.issuer = light_issuer
LOGGER.info(
'[#%r] Created light request: id=%r, issuer=%r, citizen_country=%r, origin_country=%r.',
self.log_id, request.id, request.issuer,
request.citizen_country_code, request.sp_country_code)
return request
def decode(cls,
encoded_token: bytes,
hash_algorithm: str,
secret: str,
max_size: int = 1024) -> 'LightToken':
"""
Decode encoded token and check the validity and digest.
:param encoded_token: Base64 encoded token.
:param hash_algorithm: One of hashlib hash algorithms.
:param secret: The secret shared between the communicating parties.
:param max_size: The maximal size of the encoded token.
:return: Decoded and validated token.
:raise ParseError: If the token is malformed and cannot be decoded.
:raise ValidationError: If the token can be decoded but model validation fails.
:raise SecurityError: If the token digest is invalid.
"""
if max_size and len(encoded_token) > max_size:
raise ParseError('Maximal token size exceeded.')
data = b64decode(encoded_token, validate=True).decode('utf-8')
try:
issuer, token_id, timestamp, digest_base64 = data.split('|')
except ValueError as e:
raise ParseError('Token has wrong number of parts: {}.'.format(
e.args[0]))
token = LightToken(issuer=issuer,
id=token_id,
created=parse_eidas_timestamp(timestamp))
token.validate()
provided_digest = b64decode(digest_base64.encode('ascii'))
valid_digest = token.digest(hash_algorithm, secret)
if not hmac.compare_digest(valid_digest, provided_digest):
raise SecurityError('Light token has invalid digest.')
return token
def test_str(self):
self.assertEqual(str(SecurityError(self.ERROR)), 'Signature does not match.')
def test_repr(self):
self.assertEqual(repr(SecurityError(self.ERROR)), "SecurityError('Signature does not match.')")
def test_error_attribute(self):
self.assertIs(SecurityError(self.ERROR).error, self.ERROR)
