Sample API endpoint to show how to do SSO embedding in Looker

auth.js

import { createSignedUrl } from "../../../helpers/auth_utils";
import Cors from "cors";

import user from "./demo_user.json";

// Initializing the cors middleware
const cors = Cors({
  origin: "*",
  methods: ["GET"],
});

function runMiddleware(req, res, fn) {
  return new Promise((resolve, reject) => {
    fn(req, res, (result) => {
      if (result instanceof Error) {
        return reject(result);
      }

      return resolve(result);
    });
  });
}



export default async function handler(req, res) {
  if (req.method == "GET") {
    await runMiddleware(req, res, cors);
    const { src } = req.query;
    const host = process.env.LOOKERSDK_EMBED_HOST;
    const secret = process.env.LOOKERSDK_EMBED_SECRET;
    const url = createSignedUrl(src, user, host, secret);
    res.status(200).json({ url });
  } else {
    res.status(405).end(`${req.method} Not Allowed`);
  }
}

auth_utils.js

/*

 MIT License

 Copyright (c) 2019 Looker Data Sciences, Inc.

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.

 */

import createHmac from "create-hmac";
import type { LookerEmbedUser } from "./types";

function stringify(params: { [key: string]: string | undefined }) {
  const result: string[] = [];
  for (const key in params) {
    const param = params[key];
    if (typeof param === "string") {
      result.push(`${key}=${encodeURIComponent(param)}`);
    }
  }
  return result.join("&");
}

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

function signEmbedUrl(data: { [key: string]: string }, secret: string) {
  const stringsToSign = [
    data.host,
    data.embed_path,
    data.nonce,
    data.time,

    data.session_length,
    data.external_user_id,
    data.permissions,
    data.models,
  ];
  if (data.group_ids) stringsToSign.push(data.group_ids);
  if (data.external_group_id) stringsToSign.push(data.external_group_id);
  if (data.user_attributes) stringsToSign.push(data.user_attributes);
  stringsToSign.push(data.access_filters);

  const stringToSign = stringsToSign.join("\n");
  return createHmac("sha1", secret)
    .update(forceUnicodeEncoding(stringToSign))
    .digest("base64")
    .trim();
}

function createNonce(len: number) {
  const possible =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
  let text = "";

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

  return text;
}

export function createSignedUrl(
  src: string,
  user: LookerEmbedUser,
  host: string,
  secret: string,
  nonce?: string
) {
  const jsonTime = JSON.stringify(Math.floor(new Date().getTime() / 1000));
  const jsonNonce = JSON.stringify(nonce || createNonce(16));
  const params = {
    access_filters: JSON.stringify(user.access_filters || {}),
    external_group_id: JSON.stringify(user.external_group_id),
    external_user_id: JSON.stringify(user.external_user_id),
    first_name: JSON.stringify(user.first_name),
    force_logout_login: JSON.stringify(user.force_logout_login),
    group_ids: JSON.stringify(user.group_ids),
    last_name: JSON.stringify(user.last_name),
    models: JSON.stringify(user.models),
    nonce: jsonNonce,
    permissions: JSON.stringify(user.permissions),

    session_length: JSON.stringify(user.session_length),
    time: jsonTime,

    user_attributes: JSON.stringify(user.user_attributes),
    user_timezone: JSON.stringify(user.user_timezone),
  };

  const embedPath = "/login/embed/" + encodeURIComponent(src);

  const signingParams = {
    access_filters: params.access_filters,
    embed_path: embedPath,
    external_group_id: params.external_group_id,
    external_user_id: params.external_user_id,
    group_ids: params.group_ids,
    host,
    models: params.models,
    nonce: jsonNonce,
    permissions: params.permissions,
    session_length: params.session_length,
    time: jsonTime,
    user_attributes: params.user_attributes,
  };

  const signature = signEmbedUrl(signingParams, secret);

  Object.assign(params, { signature });

  return `https://${host}${embedPath}?${stringify(params)}`;
}

demo_user.json

{
  "external_user_id": "user1",
  "first_name": "Pat",
  "last_name": "Embed",
  "session_length": 3600,
  "force_logout_login": true,
  "external_group_id": "group1",
  "group_ids": [],
  "permissions": [
    "access_data",
    "see_looks",
    "see_user_dashboards",
    "explore",
    "save_content",
    "embed_browse_spaces"
  ],
  "models": ["powered_by", "thelook", "thelook_snowflake"],
  "user_attributes": { "locale": "en_US" }
}