Traceback and "silent" crash when running example with TypeEncContent

[radovanhorvat]

Hello,

When trying out the "Encrypt" example found in:

https://xmlsec.readthedocs.io/en/stable/examples.html,

I get two errors, both using xmlsec.constants.TypeEncContent, eg with:

from lxml import etree

import xmlsec

manager = xmlsec.KeysManager()
key = xmlsec.Key.from_file('rsacert.pem', xmlsec.constants.KeyDataFormatCertPem, None)
manager.add_key(key)
template = etree.parse('enc1-doc.xml').getroot()
enc_data = xmlsec.template.encrypted_data_create(
    template,
    xmlsec.constants.TransformAes128Cbc,
    type=xmlsec.constants.TypeEncContent,
    ns="xenc",
)

xmlsec.template.encrypted_data_ensure_cipher_value(enc_data)
key_info = xmlsec.template.encrypted_data_ensure_key_info(enc_data, ns="dsig")
enc_key = xmlsec.template.add_encrypted_key(key_info, xmlsec.constants.TransformRsaOaep)
xmlsec.template.encrypted_data_ensure_cipher_value(enc_key)
data = template.find('./Data')

# Encryption
enc_ctx = xmlsec.EncryptionContext(manager)
enc_ctx.key = xmlsec.Key.generate(
    xmlsec.constants.KeyDataAes, 128, xmlsec.constants.KeyDataTypeSession
)
enc_data = enc_ctx.encrypt_xml(enc_data, data)
enc_method = xmlsec.tree.find_child(
    enc_data, xmlsec.constants.NodeEncryptionMethod, xmlsec.constants.EncNs
)
key_info = xmlsec.tree.find_child(
    enc_data, xmlsec.constants.NodeKeyInfo, xmlsec.constants.DSigNs
)
enc_method = xmlsec.tree.find_node(
    key_info, xmlsec.constants.NodeEncryptionMethod, xmlsec.constants.EncNs
)
cipher_value = xmlsec.tree.find_node(
    key_info, xmlsec.constants.NodeCipherValue, xmlsec.constants.EncNs
)
print(etree.tostring(cipher_value))

1. For the first case, the contents of enc1-doc.xml are as found in https://github.com/xmlsec/python-xmlsec/tree/master/doc/source/examples:

<?xml version="1.0" encoding="UTF-8"?>
<!--
XML Security Library example: Original XML doc file for enc example.
-->
<Envelope>
<Data>Hello, World!</Data>
</Envelope>

When running the snippet above, I get:

Traceback (most recent call last):
  File "encrypt.py", line 30, in <module>
    enc_data = enc_ctx.encrypt_xml(enc_data, data)
  File "src\lxml\public-api.pxi", line 29, in lxml.etree.elementFactory
  File "src\lxml\etree.pyx", line 1629, in lxml.etree._elementFactory
  File "src\lxml\classlookup.pxi", line 405, in lxml.etree._parser_class_lookup
  File "src\lxml\classlookup.pxi", line 257, in lxml.etree._callLookupFallback
  File "src\lxml\classlookup.pxi", line 336, in lxml.etree._lookupDefaultElementClass
AssertionError: Unknown node type: 3

2. For the second case, when modifying the xml content to:

<?xml version="1.0" encoding="UTF-8"?>
<!--
XML Security Library example: Original XML doc file for enc example.
-->
<Envelope>
<Data>
<Data2>Hello, World!</Data2>
</Data>
</Envelope>

I get a crash with no Traceback, eg the print statement at the end of the snippet is never even executed.