221 lines
8.1 KiB
Python
221 lines
8.1 KiB
Python
#!/usr/bin/python
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# -*- coding: utf-8 -*-
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License as published by the
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# Free Software Foundation; either version 3, or (at your option) any later
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# version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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# for more details.
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"""Pythonic XML Security Library implementation"""
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from __future__ import print_function
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import base64
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import hashlib
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import os
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from cStringIO import StringIO
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from M2Crypto import BIO, EVP, RSA, X509, m2
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# if lxml is not installed, use c14n.py native implementation
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try:
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import lxml.etree
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except ImportError:
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lxml = None
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# Features:
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# * Uses M2Crypto and lxml (libxml2) but it is independent from libxmlsec1
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# * Sign, Verify, Encrypt & Decrypt XML documents
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# Enveloping templates ("by reference": signature is parent):
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SIGN_REF_TMPL = """
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<SignedInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
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<CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
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<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
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<Reference URI="%(ref_uri)s">
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<Transforms>
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<Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
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</Transforms>
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<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
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<DigestValue>%(digest_value)s</DigestValue>
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</Reference>
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</SignedInfo>
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"""
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SIGNED_TMPL = """
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<?xml version="1.0" encoding="UTF-8"?>
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<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
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%(signed_info)s
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<SignatureValue>%(signature_value)s</SignatureValue>
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%(key_info)s
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%(ref_xml)s
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</Signature>
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"""
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# Enveloped templates (signature is child, the reference is the root object):
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SIGN_ENV_TMPL = """
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<SignedInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
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<CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
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<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/>
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<Reference URI="">
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<Transforms>
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<Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
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<Transform Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
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</Transforms>
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<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
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<DigestValue>%(digest_value)s</DigestValue>
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</Reference>
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</SignedInfo>
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"""
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SIGNATURE_TMPL = """<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
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%(signed_info)s
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<SignatureValue>%(signature_value)s</SignatureValue>
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%(key_info)s
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</Signature>"""
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KEY_INFO_RSA_TMPL = """
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<KeyInfo>
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<KeyValue>
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<RSAKeyValue>
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<Modulus>%(modulus)s</Modulus>
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<Exponent>%(exponent)s</Exponent>
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</RSAKeyValue>
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</KeyValue>
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</KeyInfo>
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"""
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KEY_INFO_X509_TMPL = """
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<KeyInfo>
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<X509Data>
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<X509IssuerSerial>
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<X509IssuerName>%(issuer_name)s</X509IssuerName>
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<X509SerialNumber>%(serial_number)s</X509SerialNumber>
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</X509IssuerSerial>
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</X509Data>
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</KeyInfo>
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"""
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def canonicalize(xml, c14n_exc=True):
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"Return the canonical (c14n) form of the xml document for hashing"
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# UTF8, normalization of line feeds/spaces, quoting, attribute ordering...
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output = StringIO()
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if lxml is not None:
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# use faster libxml2 / lxml canonicalization function if available
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et = lxml.etree.parse(StringIO(xml))
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et.write_c14n(output, exclusive=c14n_exc)
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else:
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# use pure-python implementation: c14n.py (avoid recursive import)
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from .simplexml import SimpleXMLElement
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SimpleXMLElement(xml).write_c14n(output, exclusive=c14n_exc)
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return output.getvalue()
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def sha1_hash_digest(payload):
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"Create a SHA1 hash and return the base64 string"
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return base64.b64encode(hashlib.sha1(payload).digest())
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def rsa_sign(xml, ref_uri, private_key, password=None, cert=None, c14n_exc=True,
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sign_template=SIGN_REF_TMPL, key_info_template=KEY_INFO_RSA_TMPL):
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"Sign an XML document usign RSA (templates: enveloped -ref- or enveloping)"
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# normalize the referenced xml (to compute the SHA1 hash)
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ref_xml = canonicalize(xml, c14n_exc)
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# create the signed xml normalized (with the referenced uri and hash value)
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signed_info = sign_template % {'ref_uri': ref_uri,
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'digest_value': sha1_hash_digest(ref_xml)}
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signed_info = canonicalize(signed_info, c14n_exc)
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# Sign the SHA1 digest of the signed xml using RSA cipher
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pkey = RSA.load_key(private_key, lambda *args, **kwargs: password)
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signature = pkey.sign(hashlib.sha1(signed_info).digest())
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# build the mapping (placeholders) to create the final xml signed message
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return {
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'ref_xml': ref_xml, 'ref_uri': ref_uri,
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'signed_info': signed_info,
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'signature_value': base64.b64encode(signature),
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'key_info': key_info(pkey, cert, key_info_template),
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}
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def rsa_verify(xml, signature, key, c14n_exc=True):
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"Verify a XML document signature usign RSA-SHA1, return True if valid"
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# load the public key (from buffer or filename)
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if key.startswith("-----BEGIN PUBLIC KEY-----"):
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bio = BIO.MemoryBuffer(key)
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rsa = RSA.load_pub_key_bio(bio)
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else:
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rsa = RSA.load_pub_key(certificate)
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# create the digital envelope
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pubkey = EVP.PKey()
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pubkey.assign_rsa(rsa)
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# do the cryptographic validation (using the default sha1 hash digest)
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pubkey.reset_context(md='sha1')
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pubkey.verify_init()
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# normalize and feed the signed xml to be verified
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pubkey.verify_update(canonicalize(xml, c14n_exc))
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ret = pubkey.verify_final(base64.b64decode(signature))
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return ret == 1
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def key_info(pkey, cert, key_info_template):
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"Convert private key (PEM) to XML Signature format (RSAKeyValue/X509Data)"
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exponent = base64.b64encode(pkey.e[4:])
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modulus = m2.bn_to_hex(m2.mpi_to_bn(pkey.n)).decode("hex").encode("base64")
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x509 = x509_parse_cert(cert) if cert else None
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return key_info_template % {
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'modulus': modulus,
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'exponent': exponent,
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'issuer_name': x509.get_issuer().as_text() if x509 else "",
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'serial_number': x509.get_serial_number() if x509 else "",
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}
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# Miscellaneous certificate utility functions:
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def x509_parse_cert(cert, binary=False):
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"Create a X509 certificate from binary DER, plain text PEM or filename"
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if binary:
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bio = BIO.MemoryBuffer(cert)
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x509 = X509.load_cert_bio(bio, X509.FORMAT_DER)
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elif cert.startswith("-----BEGIN CERTIFICATE-----"):
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bio = BIO.MemoryBuffer(cert)
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x509 = X509.load_cert_bio(bio, X509.FORMAT_PEM)
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else:
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x509 = X509.load_cert(cert, 1)
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return x509
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def x509_extract_rsa_public_key(cert, binary=False):
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"Return the public key (PEM format) from a X509 certificate"
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x509 = x509_parse_cert(cert, binary)
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return x509.get_pubkey().get_rsa().as_pem()
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def x509_verify(cacert, cert, binary=False):
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"Validate the certificate's authenticity using a certification authority"
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ca = x509_parse_cert(cacert)
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crt = x509_parse_cert(cert, binary)
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return crt.verify(ca.get_pubkey())
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if __name__ == "__main__":
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# basic test of enveloping signature (the reference is a part of the xml)
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sample_xml = """<Object xmlns="http://www.w3.org/2000/09/xmldsig#" Id="object">data</Object>"""
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output = canonicalize(sample_xml)
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print (output)
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vars = rsa_sign(sample_xml, '#object', "no_encriptada.key", "password")
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print (SIGNED_TMPL % vars)
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# basic test of enveloped signature (the reference is the document itself)
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sample_xml = """<?xml version="1.0" encoding="UTF-8"?><Object>data%s</Object>"""
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vars = rsa_sign(sample_xml % "", '', "no_encriptada.key", "password",
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sign_template=SIGN_ENV_TMPL, c14n_exc=False)
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print (sample_xml % (SIGNATURE_TMPL % vars))
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# basic signature verification:
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public_key = x509_extract_rsa_public_key(open("zunimercado.crt").read())
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assert rsa_verify(vars['signed_info'], vars['signature_value'], public_key,
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c14n_exc=False)
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