libsaml/index.js

Parse SAML2 attributes into a JavaScript object.

// LibSaml
// =======
// A library for parsing SAML attributes
// into a POJO (Plain Old JavaScript Object)

// Require dependencies
const xmldom = require('xmldom');
const xpath  = require('xpath');

// LibSaml
// -------
// Constructor function. Saves a copy
// of the raw SAML you pass to it and
// a copy that's parsed into a JS object.
//
// `response` [String] - A SAML response string
function LibSaml(response) {
  this.rawSaml    = response;
  this.parsedSaml = this.parse(response);
}

// LibSaml.parse
// -------------
// Private function.
// Parses raw SAML assertion to an array of objects.
LibSaml.prototype.parse = function parse(saml) {
  const saml2Namespace = 'urn:oasis:names:tc:SAML:2.0:assertion';
  const xpAttribute    = '//saml2:Attribute';
  const xpName         = 'string(@Name)';
  const xpVal          = 'saml2:AttributeValue';

  const xml = Buffer.from(saml, 'base64').toString('ascii');
  const doc = new xmldom.DOMParser().parseFromString(xml);

  const select = xpath.useNamespaces({ saml2: saml2Namespace });

  const attributes = select(xpAttribute, doc).reduce(
    (acc, attr) => acc.concat(
      {
        name:  select(xpName, attr),
        value: select(xpVal, attr).reduce((a, b) => [].concat(a, b.textContent), []),
      },
    ),
    [],
  );

  return { attributes };
};


// LibSaml.toJSON
// --------------
// Returns parsed SAML as a JSON string.
// (Basically just an alias to `JSON.stringify()`).
LibSaml.prototype.toJSON = function toJSON() {
  return JSON.stringify(this.parsedSaml);
};

// LibSaml.getAttribute
// -----------
// Get the value of a SAML attribute by using its
// original SAML attribute Name from the raw XML.
//
// `key` [String] - The attribute name as it appears in the raw SAML
//
// Example:
//     // Given the following SAML/XML
//     // <saml2:Attribute Name="First Name">
//     //   <saml2:AttributeValue>John</saml2:AttributeValue>
//     // </saml2:Attribute>
//     console.log(parser.get('first name')[0]); //=> John
LibSaml.prototype.getAttribute = function get(key) {
  const attributes = this.parsedSaml.attributes;
  const predicate  = element => element.name.toLowerCase()
                                === key.toLowerCase();

  return [].concat(...attributes.filter(predicate).map(x => x.value));
};

// LibSaml.toObject
// ----------------
// Returns the parsed SAML as a JS object.
// This does not do any further processing, it
// just returns the object's internal value
// of `this.parsedSaml`.
LibSaml.prototype.toObject = function toObject() {
  return this.parsedSaml;
};

module.exports = LibSaml;