Python XML Signature library
Project description
SignXML is an implementation of the W3C XML Signature standard in Python (both “Second Edition” and Version 1.1). This standard (also known as XMLDSig and RFC 3275) is used to provide payload security in SAML 2.0, among other uses. SignXML implements all of the required components of the standard, and most recommended ones. Its features are:
Use of defusedxml.lxml to defend against common XML-based attacks when verifying signatures
Extensions to allow signing with and verifying X.509 certificate chains, including hostname/CN validation
Support for exclusive XML canonicalization with inclusive prefixes (InclusiveNamespaces PrefixList, required to verify signatures generated by some SAML implementations)
Modern Python compatibility (2.7-3.4+ and PyPy)
Well-supported, portable, reliable dependencies: lxml, defusedxml, cryptography, eight, pyOpenSSL
Comprehensive testing (including the XMLDSig interoperability suite) and continuous integration
Simple interface with useful defaults
Compactness, readability, and extensibility
Installation
pip install signxml
Note: SignXML depends on lxml and cryptography, which in turn depend on OpenSSL, LibXML, and Python tools to interface with them. On Ubuntu, you can install those with:
apt-get install python-dev libxml2-dev libxslt1-dev libssl-dev python-cffi
Ubuntu 12.04: python-cffi is not available on 12.04. Use apt-get install libffi-dev followed by pip install cffi.
Synopsis
SignXML uses the ElementTree API (also supported by lxml) to work with XML data.
from signxml import xmldsig
cert = open("example.pem").read()
key = open("example.key").read()
root = ElementTree.fromstring(signature_data)
xmldsig(root).sign(key=key, cert=cert)
verified_data = xmldsig(root).verify()Verifying SAML assertions
Assuming metadata.xml contains SAML metadata for the assertion source:
from lxml import etree
from base64 import b64decode
from signxml import xmldsig
with open("metadata.xml", "rb") as fh:
cert = etree.parse(fh).find("//ds:X509Certificate").text
assertion_data = xmldsig(b64decode(assertion_body)).verify(x509_cert=cert)Detached signatures
The XML Signature specification requires support of detached signatures, where the signature document refers (in <Reference URI="...">) to an external document. SignXML does not support generating detached signatures. To verify a detached signature, pass a resolver callable to the xmldsig.verify() method.
See the API documentation for more.
Links
W3C Recommendation: XML Signature Syntax and Processing (Second Edition)
W3C Recommendation: XML Signature Syntax and Processing Version 1.1
W3C Working Group Note: XML Signature Syntax and Processing Version 2.0
W3C Working Group Note: Test Cases for C14N 1.1 and XMLDSig Interoperability
Bugs
Please report bugs, issues, feature requests, etc. on GitHub.
License
Licensed under the terms of the Apache License, Version 2.0.
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