node_example.js

 var crypto = require('crypto');
 var querystring = require('querystring')

function nonce(len) {
    var text = "";
    var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

    for (var i = 0; i < len; i++)
    text += possible.charAt(Math.floor(Math.random() * possible.length));

    return text;
}

function forceUnicodeEncoding(string) {
    return decodeURIComponent(encodeURIComponent(string));
}

function created_signed_embed_url(options) {
    // looker options
    var secret = options.secret;
    var host = options.host;

    // user options
    var json_external_user_id = JSON.stringify(options.external_user_id);
    var json_first_name = JSON.stringify(options.first_name);
    var json_last_name = JSON.stringify(options.last_name);
    var json_permissions = JSON.stringify(options.permissions);
    var json_models = JSON.stringify(options.models);
    var json_group_ids = JSON.stringify(options.group_ids);
    var json_external_group_id = JSON.stringify(options.external_group_id || "");
    var json_user_attributes = JSON.stringify(options.user_attributes || {});
    var json_access_filters = JSON.stringify(options.access_filters);

    // url/session specific options
    var embed_path = '/login/embed/' + encodeURIComponent(options.embed_url);
    var json_session_length = JSON.stringify(options.session_length);
    var json_force_logout_login = JSON.stringify(options.force_logout_login);

    // computed options
    var json_time = JSON.stringify(Math.floor((new Date()).getTime() / 1000));
    var json_nonce = JSON.stringify(nonce(16));

    // compute signature
    var string_to_sign = "";
    string_to_sign += host + "\n";
    string_to_sign += embed_path + "\n";
    string_to_sign += json_nonce + "\n";
    string_to_sign += json_time + "\n";
    string_to_sign += json_session_length + "\n";
    string_to_sign += json_external_user_id + "\n";
    string_to_sign += json_permissions + "\n";
    string_to_sign += json_models + "\n";
    string_to_sign += json_group_ids + "\n";
    string_to_sign += json_external_group_id + "\n";
    string_to_sign += json_user_attributes + "\n";
    string_to_sign += json_access_filters;

    var signature = crypto.createHmac('sha1', secret).update(forceUnicodeEncoding(string_to_sign)).digest('base64').trim();

    // construct query string
    var query_params = {
        nonce: json_nonce,
        time: json_time,
        session_length: json_session_length,
        external_user_id: json_external_user_id,
        permissions: json_permissions,
        models: json_models,
        access_filters: json_access_filters,
        first_name: json_first_name,
        last_name: json_last_name,
        group_ids: json_group_ids,
        external_group_id: json_external_group_id,
        user_attributes: json_user_attributes,
        force_logout_login: json_force_logout_login,
        signature: signature
    };

    var query_string = querystring.stringify(query_params);

    return host + embed_path + '?' + query_string;
}

function sample() {
    var fifteen_minutes = 15 * 60;

    var url_data = {
        host: 'company.looker.com',
        secret: '8ea3be011d0668741234216e06845692bab69e0101d00dcfe399dae03c52513c',
        external_user_id: '57',
        first_name: 'Embed Steve',
        last_name: 'Krouse',
        group_ids: [4],
        external_group_id: 'awesome_engineers',
        permissions: ['see_user_dashboards', 'see_lookml_dashboards', 'access_data', 'see_looks'],
        models: ['thelook'],
        access_filters: {
            fake_model: {
                id: 1
            }
        },
        user_attributes: {"an_attribute_name": "my_attribute_value", "my_number_attribute": "42"},
        session_length: fifteen_minutes,
        embed_url: "/embed/dashboards/3",
        force_logout_login: true
    };

    var url = created_signed_embed_url(url_data);
    return "https://" + url;
}

var url = sample();
console.log('Created url: ' + url);
var http = require('http');
http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/html'});
  res.end("<a href='" + url + "'>" + url + "</a>");
}).listen(1337, '127.0.0.1');
console.log('Server running at http://127.0.0.1:1337/');