[Strengthen Encryption] PySAML2 Encrypted Assertions now works with Shibboleth SP 3

- Fixed: "ERROR Shibboleth.SSO.SAML2 [6] [default]: failed to decrypt assertion: Unable to resolve any key decryption keys."
- Fixed: "WARN XMLTooling.Decrypter [7] [default]: XMLSecurity exception while decrypting key: XSECAlgorithmMapper::mapURIToHandler - URI http://www.w3.org/2001/04/xmlenc#rsa-1_5 disallowed by whitelist/blacklist policy"

Author: peppelinux

src/saml2/data/templates/template_enc.xml

@@ -2,12 +2,10 @@
 <EncryptedData
         xmlns="http://www.w3.org/2001/04/xmlenc#"
         Type="http://www.w3.org/2001/04/xmlenc#Element">
-    <EncryptionMethod Algorithm=
-                              "http://www.w3.org/2001/04/xmlenc#tripledes-cbc"/>
+    <EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#tripledes-cbc"/>
     <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
         <EncryptedKey xmlns="http://www.w3.org/2001/04/xmlenc#">
-            <EncryptionMethod Algorithm=
-                                      "http://www.w3.org/2001/04/xmlenc#rsa-1_5"/>
+            <EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p"/>
             <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
                 <KeyName/>
             </KeyInfo>

src/saml2/entity.py

@@ -65,6 +65,7 @@
 from saml2.sigver import SigverError
 from saml2.sigver import SignatureError
 from saml2.sigver import make_temp
+from saml2.sigver import get_pem_wrapped_unwrapped
 from saml2.sigver import pre_encryption_part
 from saml2.sigver import pre_signature_part
 from saml2.sigver import pre_encrypt_assertion
@@ -654,18 +655,22 @@ def _encrypt_assertion(self, encrypt_cert, sp_entity_id, response, node_xpath=No
             _certs = self.metadata.certs(sp_entity_id, "any", "encryption")
         exception = None
         for _cert in _certs:
+            wrapped_cert, unwrapped_cert = get_pem_wrapped_unwrapped(_cert)
             try:
-                begin_cert = "-----BEGIN CERTIFICATE-----\n"
-                end_cert = "\n-----END CERTIFICATE-----\n"
-                if begin_cert not in _cert:
-                    _cert = "%s%s" % (begin_cert, _cert)
-                if end_cert not in _cert:
-                    _cert = "%s%s" % (_cert, end_cert)
-                tmp = make_temp(_cert.encode('ascii'),
+                tmp = make_temp(wrapped_cert.encode('ascii'),
                                 decode=False,
                                 delete_tmpfiles=self.config.delete_tmpfiles)
+
+                # it would be possibile to handle many other args here ...
+                pre_enc_part_dict = dict()
+                if encrypt_cert:
+                    pre_enc_part_dict['encrypt_cert'] = unwrapped_cert
+                pre_enc_part = pre_encryption_part(**pre_enc_part_dict)
+                # end pre_enc_part
+
+
                 response = self.sec.encrypt_assertion(response, tmp.name,
-                                                      pre_encryption_part(),
+                                                      pre_enc_part,
                                                       node_xpath=node_xpath)
                 return response
             except Exception as ex:

src/saml2/sigver.py

@@ -7,6 +7,7 @@
 import itertools
 import logging
 import os
+import re
 import six
 from uuid import uuid4 as gen_random_key
 from time import mktime
@@ -59,9 +60,11 @@
 
 SIG = '{{{ns}#}}{attribute}'.format(ns=ds.NAMESPACE, attribute='Signature')
 
-RSA_1_5 = 'http://www.w3.org/2001/04/xmlenc#rsa-1_5'
-TRIPLE_DES_CBC = 'http://www.w3.org/2001/04/xmlenc#tripledes-cbc'
+# DEPRECATED
+# RSA_1_5 = 'http://www.w3.org/2001/04/xmlenc#rsa-1_5'
 
+TRIPLE_DES_CBC = 'http://www.w3.org/2001/04/xmlenc#tripledes-cbc'
+RSA_OAEP_MGF1P = "http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p"
 
 class SigverError(SAMLError):
     pass
@@ -100,6 +103,14 @@ class CertificateError(SigverError):
     pass
 
 
+def get_pem_wrapped_unwrapped(cert):
+    begin_cert = "-----BEGIN CERTIFICATE-----\n"
+    end_cert = "\n-----END CERTIFICATE-----\n"
+    unwrapped_cert = re.sub(f'{begin_cert}|{end_cert}', '', cert)
+    wrapped_cert = f'{begin_cert}{unwrapped_cert}{end_cert}'
+    return wrapped_cert, unwrapped_cert
+
+
 def read_file(*args, **kwargs):
     with open(*args, **kwargs) as handler:
         return handler.read()
@@ -1085,10 +1096,8 @@ def encrypt_cert_from_item(item):
         pass
 
     if _encrypt_cert is not None:
-        if _encrypt_cert.find('-----BEGIN CERTIFICATE-----\n') == -1:
-            _encrypt_cert = '-----BEGIN CERTIFICATE-----\n' + _encrypt_cert
-        if _encrypt_cert.find('\n-----END CERTIFICATE-----') == -1:
-            _encrypt_cert = _encrypt_cert + '\n-----END CERTIFICATE-----'
+        wrapped_cert, unwrapped_cert = get_pem_wrapped_unwrapped(_encrypt_cert)
+        _encrypt_cert = wrapped_cert
     return _encrypt_cert
 
 
@@ -1872,8 +1881,10 @@ def pre_signature_part(
 # </EncryptedData>
 
 
-def pre_encryption_part(msg_enc=TRIPLE_DES_CBC, key_enc=RSA_1_5, key_name='my-rsa-key',
-        encrypted_key_id=None, encrypted_data_id=None):
+def pre_encryption_part(msg_enc=TRIPLE_DES_CBC, key_enc=RSA_OAEP_MGF1P, 
+        key_name='my-rsa-key',
+        encrypted_key_id=None, encrypted_data_id=None,
+        encrypt_cert=None):
     """
 
     :param msg_enc:
@@ -1885,10 +1896,16 @@ def pre_encryption_part(msg_enc=TRIPLE_DES_CBC, key_enc=RSA_1_5, key_name='my-rs
     ed_id = encrypted_data_id or "ED_{id}".format(id=gen_random_key())
     msg_encryption_method = EncryptionMethod(algorithm=msg_enc)
     key_encryption_method = EncryptionMethod(algorithm=key_enc)
+    
+    enc_key_dict= dict(key_name=ds.KeyName(text=key_name))
+    enc_key_dict['x509_data'] = ds.X509Data(
+        x509_certificate=ds.X509Certificate(text=encrypt_cert))
+    key_info = ds.KeyInfo(**enc_key_dict)
+    
     encrypted_key = EncryptedKey(
         id=ek_id,
         encryption_method=key_encryption_method,
-        key_info=ds.KeyInfo(key_name=ds.KeyName(text=key_name)),
+        key_info=key_info,
         cipher_data=CipherData(cipher_value=CipherValue(text='')),
     )
     key_info = ds.KeyInfo(encrypted_key=encrypted_key)

tests/test_42_enc.py

@@ -12,8 +12,8 @@
 
 __author__ = 'roland'
 
-TMPL_NO_HEADER = """<ns0:EncryptedData xmlns:ns0="http://www.w3.org/2001/04/xmlenc#" xmlns:ns1="http://www.w3.org/2000/09/xmldsig#" Id="{ed_id}" Type="http://www.w3.org/2001/04/xmlenc#Element"><ns0:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#tripledes-cbc" /><ns1:KeyInfo><ns0:EncryptedKey Id="{ek_id}"><ns0:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-1_5" /><ns1:KeyInfo><ns1:KeyName>my-rsa-key</ns1:KeyName></ns1:KeyInfo><ns0:CipherData><ns0:CipherValue /></ns0:CipherData></ns0:EncryptedKey></ns1:KeyInfo><ns0:CipherData><ns0:CipherValue /></ns0:CipherData></ns0:EncryptedData>"""
-TMPL = "<?xml version='1.0' encoding='UTF-8'?>\n%s" % TMPL_NO_HEADER
+TMPL_NO_HEADER = """<ns0:EncryptedData xmlns:ns0="http://www.w3.org/2001/04/xmlenc#" xmlns:ns1="http://www.w3.org/2000/09/xmldsig#" Id="{ed_id}" Type="http://www.w3.org/2001/04/xmlenc#Element"><ns0:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#tripledes-cbc" /><ns1:KeyInfo><ns0:EncryptedKey Id="{ek_id}"><ns0:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p" /><ns1:KeyInfo><ns1:KeyName>my-rsa-key</ns1:KeyName><ns1:X509Data><ns1:X509Certificate /></ns1:X509Data></ns1:KeyInfo><ns0:CipherData><ns0:CipherValue /></ns0:CipherData></ns0:EncryptedKey></ns1:KeyInfo><ns0:CipherData><ns0:CipherValue /></ns0:CipherData></ns0:EncryptedData>"""
+TMPL = f"<?xml version='1.0' encoding='UTF-8'?>\n{TMPL_NO_HEADER}"
 
 IDENTITY = {"eduPersonAffiliation": ["staff", "member"],
             "surName": ["Jeter"], "givenName": ["Derek"],