passport-saml and SAML encryption

Question

I'm new to passport and passport-saml, and I'm trying to build a Node.js server that uses our University's Shibboleth identity provider for single sign-on. I'm pretty close to getting it all working, but I'm hitting a snag during the /login/callback that I think is related to the encryption configuration.

I am able to redirect the client to the sign-in page, and after a successful sign-in, the IdP does a POST back to my /login/callback route. Then I get this error:

Error: Invalid signature at SAML.validatePostResponse (.../node_modules/passport-saml/lib/passport-saml/saml.js:357:21) at Strategy.authenticate (.../node_modules/passport-saml/lib/passport-saml/strategy.js:68:18) at ...etc...

This sounds like maybe the certificate I'm passing to the cert config setting isn't correct? I'm assuming that the decryptionPvk and cert config settings supposed to be the private key I used to create my server's cert, and the Identity Provider's HTTPS certificate, respectively? Or should they be something else?

I'm using up-to-date versions of node and all the various modules (express, passport, passport-saml, etc.)

And for reference, here's the server script I'm using to test all of this:

"use strict;"

var https = require('https');
var fs = require('fs');
var express = require("express");
var morgan = require('morgan');
var bodyParser = require('body-parser');
var cookieParser = require('cookie-parser');
var session = require('express-session');
var passport = require('passport');
var saml = require('passport-saml');

var cert = fs.readFileSync('./certs/my-server-https-cert.crt', 'utf-8');
var pvk = fs.readFileSync('./certs/my-server-private.key', 'utf-8');
var uwIdpCert = fs.readFileSync('./certs/our-idp-server-https-cert.pem', 'utf-8');

passport.serializeUser(function(user, done){
    done(null, user);
});

passport.deserializeUser(function(user, done){
    done(null, user);
});

var samlStrategy = new saml.Strategy({
    callbackUrl: 'https://my-domain-name.whatever.edu/login/callback',
    entryPoint: 'https://my-university/idp/entry/point',
    issuer: 'my-entity-id (domain name registered with university IdP)',
    decryptionPvk: pvk,
    cert: uwIdpCert
}, function(profile, done){
    console.log('Profile: %j', profile);
    return done(null, profile); 
});

passport.use(samlStrategy);

var app = express();
app.use(morgan('dev'));
app.use(bodyParser.urlencoded({extended: true}));
app.use(cookieParser());
app.use(session({secret: fs.readFileSync('./certs/session-secret.txt', 'utf-8')}));
app.use(passport.initialize());
app.use(passport.session());

app.get('/', 
    passport.authenticate('saml', {failureRedirect: '/login/fail'}), 
    function(req, res) {
        res.send('Hello World!');
    }
);

app.post('/login/callback',
  passport.authenticate('saml', { failureRedirect: '/login/fail', failureFlash: true }),
  function(req, res) {
    res.redirect('/');
  }
);

app.get('/login/fail', 
    function(req, res) {
        res.send(401, 'Login failed');
    }
);

app.get('/Shibboleth.sso/Metadata', 
    function(req, res) {
        res.type('application/xml');
        res.send(200, samlStrategy.generateServiceProviderMetadata(cert));
    }
);

//general error handler
app.use(function(err, req, res, next){
    console.log('Express error!');
    console.error(err.stack);
    next(err);
});


var server = https.createServer({
    key: pvk,
    cert: cert
}, app);

server.listen(process.argv[2] || 44300, function(){
    console.log('Listening on port %d', server.address().port)
});

Any help or advice would be most appreciated!

Answer 1

Yes, the cert is the certificate of the identity provider -- not necessarily its HTTPS certificate though.

Your shibboleth identity provider should have a provider metadata document. If you haven't already, you probably want to make sure the contents of uwIdpCert matches the <ds:X509Certificate> block in that document. (here is an example of what that metadata document should look like)

If you're pretty sure that the certificates are correct, I'd be curious to see the contents of the xml variable in SAML.prototype.validatePostResponse. (i.e., just throw in a console.log statement and see what it looks like). There have been some changes to the signature validation logic in passport-saml recently and it's possible your provider is doing something unexpected.