Now, installing library as intended, it looks like this. Same 3.0.1 version. The library is available and usable. Except for the signed part… Try for yourself, I’m adding the code below.
exports = async function(){
const saml = require('saml').Saml20;
const options = {
cert: "-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----",
key: "-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----",
issuer: 'urn:issuer',
lifetimeInSeconds: 600,
audiences: 'urn:myapp',
attributes: { 'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress': 'foo@bar.com', 'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name': 'Foo Bar' },
nameIdentifier: 'foo',
sessionIndex: '_faed468a-15a0-4668-aed6-3d9c478cc8fa'
};
return {
signedAssertion: saml.create(options),
assertion: saml.createUnsignedAssertion(options)
};
}

