netid-ni-tls
v0.4.2
Published
netid-ni-tls ============
Downloads
4
Readme
netid-ni-tls
Nodejs module implementing a variant of the WebID-TLS authentication protocol based on using Named Information URIs to identify X509 certificates.
Useful reading
Why NI URIs?
The current WebID spec mandates the use of RSA due to the focus on
(modulus,exponent)
comparison. I'd like something more flexible that
would allow me to use other kinds of keys without breaking the semantics
of the existing vocabularies.
RDF example
Assume the identity https://example.com/me
. In order for this module
to be able to authenticate a user with this identity, such a user has
to provide a TLS client certificate with the following `Subject
Alternative Name:
URI:https://example.com
Dereferencing this identity must lead to a RDF document in one of the
following formats: application/ld+json
, text/turtle
, text/n3
,
text/html
(HTML5+RDFa).
The RDF document should contain triples equivalent to those shown in the following RDFa snippet:
<div about="ni:///sha-256;Mub5jcxUlUz6SG0oWKmHtIYGNgATBmPdRdlXiKxRBWw" typeof="cert:X509Certificate" prefix="cert:http://www.w3.org/ns/auth/cert#">
<div rel="cert:identity" href="https://example.com/me"></div>
</div>
The certificate's URI must follow the Named Information URI format. Use the following command to generate the required base64-encoded SHA256 certificate fingerprint:
$ openssl x509 -in example.crt -inform pem -outform der | openssl dgst -sha256 -binary | openssl base64
Remove all padding =
characters at the end of the fingerprint, as per
the Named Information RFC.
API
var netid = require('netid-ni-tls');
Authenticator
class
var authenticator = netid.createAuthenticator([opts]);
Authenticator.prototype.authenticate(clientCertInfo)
var clientCertInfo = req.connection.getPeerCertificate();
authenticator.authenticate(clientCertInfo)
.then(function (auth) { ... });
This method expects the client TLS certificate of the user being authenticated
in the form of the native nodejs object obtained through req.connection.getPeerCertificate()
.
This method returns an authentication object with the following properties:
{
"success": true, // Whether the authentication has succeeded
"netId": "https://example.com/john", // The NetID that has been authenticated
"clientCertInfo": { ... }, // Native getPeerCertificate() for the client used by the NetID
"serverCertInfo": { ... }, // Native getPeerCertificate() for the server hosting the NetID
"error": { ...} // The error that prevented a succeessful authentication, if any
"createdAt": 1481458587406 // Operation timestamp
}
Authenticator.prototype.getMiddleware()
app.use(authenticator.getMiddleware());
This method returns an express-compatible authentication middleware which stores the
resulting authentication object in req.auth
.
Caching
On its own, an authenticator goes through the authentication process every time the
authenticate(clientCertInfo)
method is called (every request if using the middleware).
However, implementors can opt to override the authenticator._retrieve(netId, clientCertInfo)
to return a previously cached authentication object to be used by the authenticator.
Every authenticator also emits an authentication
event on every authentication,
regardless of success or caching. This event can be used in conjunction with the
_retrieve()
method to implement caching.
authenticator._retrieve = function (netId, clientCertInfo) {
return getCachedAuthenticationObject(netId, clientCertInfo)
.then(function (auth) {
return (auth.cachedAt > Date.now() - 1000 * 10)
? auth
: null;
});
};
authenticator.on('authentication', function (auth) {
if (auth.success && !auth.cachedAt) {
auth.cachedAt = Date.now();
cacheAuthenticationObject(auth);
}
});
Tests
A test server that echoes the authentication object to the client can be fired up using the following:
$ node test/server.js
The test server caches authentications for 10 seconds based on the client certificate's fingerprint.
License
Acknowledgements
Big thanks to the awesome folks at the public-webid mailing list for their wonderful suggestions.
Todo
- Automated tests