@axa-fr/oidc-client-service-worker/src/jwt.ts

OpenID Connect & OAuth authentication service worker

// code base on https://coolaj86.com/articles/sign-jwt-webcrypto-vanilla-js/

// String (UCS-2) to Uint8Array
//
// because... JavaScript, Strings, and Buffers
// @ts-ignore
import { DemonstratingProofOfPossessionConfiguration } from './types';

function strToUint8(str: string) {
  return new TextEncoder().encode(str);
}

// Binary String to URL-Safe Base64
//
// btoa (Binary-to-Ascii) means "binary string" to base64
// @ts-ignore
function binToUrlBase64(bin) {
  return btoa(bin).replace(/\+/g, '-').replace(/\//g, '_').replace(/=+/g, '');
}

// UTF-8 to Binary String
//
// Because JavaScript has a strange relationship with strings
// https://coolaj86.com/articles/base64-unicode-utf-8-javascript-and-you/
// @ts-ignore
function utf8ToBinaryString(str) {
  const escstr = encodeURIComponent(str);
  // replaces any uri escape sequence, such as %0A,
  // with binary escape, such as 0x0A
  // @ts-ignore
  return escstr.replace(/%([0-9A-F]{2})/g, function (match: string, p1) {
    return String.fromCharCode(parseInt(p1, 16));
  });
}

// Uint8Array to URL Safe Base64
//
// the shortest distant between two encodings... binary string
// @ts-ignore
export const uint8ToUrlBase64 = (uint8: Uint8Array) => {
  let bin = '';
  // @ts-ignore
  uint8.forEach(function (code) {
    bin += String.fromCharCode(code);
  });
  return binToUrlBase64(bin);
};

// UCS-2 String to URL-Safe Base64
//
// btoa doesn't work on UTF-8 strings
// @ts-ignore
function strToUrlBase64(str) {
  return binToUrlBase64(utf8ToBinaryString(str));
}

export const defaultDemonstratingProofOfPossessionConfiguration: DemonstratingProofOfPossessionConfiguration =
  {
    importKeyAlgorithm: {
      name: 'ECDSA',
      namedCurve: 'P-256',
      hash: { name: 'ES256' },
    },
    signAlgorithm: { name: 'ECDSA', hash: { name: 'SHA-256' } },
    generateKeyAlgorithm: {
      name: 'ECDSA',
      namedCurve: 'P-256',
    },
    digestAlgorithm: { name: 'SHA-256' },
    jwtHeaderAlgorithm: 'ES256',
  };

// @ts-ignore
const sign =
  (w: any) =>
  async (
    jwk: any,
    headers: any,
    claims: any,
    demonstratingProofOfPossessionConfiguration: DemonstratingProofOfPossessionConfiguration,
    jwtHeaderType = 'dpop+jwt',
  ) => {
    // Make a shallow copy of the key
    // (to set ext if it wasn't already set)
    jwk = Object.assign({}, jwk);

    // The headers should probably be empty
    headers.typ = jwtHeaderType;
    headers.alg = demonstratingProofOfPossessionConfiguration.jwtHeaderAlgorithm;
    switch (headers.alg) {
      case 'ES256': //if (!headers.kid) {
        // alternate: see thumbprint function below
        headers.jwk = { kty: jwk.kty, crv: jwk.crv, x: jwk.x, y: jwk.y };
        //}
        break;
      case 'RS256':
        headers.jwk = { kty: jwk.kty, n: jwk.n, e: jwk.e, kid: headers.kid };
        break;
      default:
        throw new Error('Unknown or not implemented JWS algorithm');
    }

    const jws = {
      // @ts-ignore
      // JWT "headers" really means JWS "protected headers"
      protected: strToUrlBase64(JSON.stringify(headers)),
      // @ts-ignore
      // JWT "claims" are really a JSON-defined JWS "payload"
      payload: strToUrlBase64(JSON.stringify(claims)),
    };

    // To import as EC (ECDSA, P-256, SHA-256, ES256)
    const keyType = demonstratingProofOfPossessionConfiguration.importKeyAlgorithm;

    // To make re-exportable as JSON (or DER/PEM)
    const exportable = true;

    // Import as a private key that isn't black-listed from signing
    const privileges = ['sign'];

    // Actually do the import, which comes out as an abstract key type
    // @ts-ignore
    const privateKey = await w.crypto.subtle.importKey('jwk', jwk, keyType, exportable, privileges);
    // Convert UTF-8 to Uint8Array ArrayBuffer
    // @ts-ignore
    const data = strToUint8(`${jws.protected}.${jws.payload}`);

    // The signature and hash should match the bit-entropy of the key
    // https://tools.ietf.org/html/rfc7518#section-3
    const signatureType = demonstratingProofOfPossessionConfiguration.signAlgorithm;

    const signature = await w.crypto.subtle.sign(signatureType, privateKey, data);
    // returns an ArrayBuffer containing a JOSE (not X509) signature,
    // which must be converted to Uint8 to be useful
    // @ts-ignore
    jws.signature = uint8ToUrlBase64(new Uint8Array(signature));
    // JWT is just a "compressed", "protected" JWS
    // @ts-ignore
    return `${jws.protected}.${jws.payload}.${jws.signature}`;
  };

export const JWT = { sign };

// @ts-ignore
const generate =
  (w: any) => async (generateKeyAlgorithm: RsaHashedKeyGenParams | EcKeyGenParams) => {
    const keyType = generateKeyAlgorithm;
    const exportable = true;
    const privileges = ['sign', 'verify'];
    // @ts-ignore
    const key = await w.crypto.subtle.generateKey(keyType, exportable, privileges);
    // returns an abstract and opaque WebCrypto object,
    // which in most cases you'll want to export as JSON to be able to save
    return await w.crypto.subtle.exportKey('jwk', key.privateKey);
  };

// Create a Public Key from a Private Key
//
// chops off the private parts
// @ts-ignore
const neuter = jwk => {
  const copy = Object.assign({}, jwk);
  delete copy.d;
  copy.key_ops = ['verify'];
  return copy;
};

const EC = {
  generate,
  neuter,
};
// @ts-ignore
const thumbprint = (w: any) => async (jwk, digestAlgorithm: AlgorithmIdentifier) => {
  let sortedPub;
  // lexigraphically sorted, no spaces
  switch (jwk.kty) {
    case 'EC':
      sortedPub = '{"crv":"CRV","kty":"EC","x":"X","y":"Y"}'
        .replace('CRV', jwk.crv)
        .replace('X', jwk.x)
        .replace('Y', jwk.y);
      break;
    case 'RSA':
      sortedPub = '{"e":"E","kty":"RSA","n":"N"}'.replace('E', jwk.e).replace('N', jwk.n);
      break;
    default:
      throw new Error('Unknown or not implemented JWK type');
  }
  // The hash should match the size of the key,
  // but we're only dealing with P-256
  const hash = await w.crypto.subtle.digest(digestAlgorithm, strToUint8(sortedPub));
  return uint8ToUrlBase64(new Uint8Array(hash));
};

export const JWK = { thumbprint };

export const generateJwkAsync =
  (w: any) => async (generateKeyAlgorithm: RsaHashedKeyGenParams | EcKeyGenParams) => {
    // @ts-ignore
    const jwk = await EC.generate(w)(generateKeyAlgorithm);
    // console.info('Private Key:', JSON.stringify(jwk));
    // @ts-ignore
    // console.info('Public Key:', JSON.stringify(EC.neuter(jwk)));
    return jwk;
  };

export const generateJwtDemonstratingProofOfPossessionAsync =
  (w: any) =>
  (demonstratingProofOfPossessionConfiguration: DemonstratingProofOfPossessionConfiguration) =>
  async (jwk: any, method = 'POST', url: string, extrasClaims = {}) => {
    const claims = {
      // https://www.rfc-editor.org/rfc/rfc9449.html#name-concept
      jti: btoa(guid()),
      htm: method,
      htu: url,
      iat: Math.round(Date.now() / 1000),
      ...extrasClaims,
    };
    // @ts-ignore
    const kid = await JWK.thumbprint(w)(
      jwk,
      demonstratingProofOfPossessionConfiguration.digestAlgorithm,
    );
    // @ts-ignore
    const jwt = await JWT.sign(w)(
      jwk,
      { kid: kid },
      claims,
      demonstratingProofOfPossessionConfiguration,
    );
    // console.info('JWT:', jwt);
    return jwt;
  };

const guid = () => {
  // RFC4122: The version 4 UUID is meant for generating UUIDs from truly-random or
  // pseudo-random numbers.
  // The algorithm is as follows:
  //     Set the two most significant bits (bits 6 and 7) of the
  //        clock_seq_hi_and_reserved to zero and one, respectively.
  //     Set the four most significant bits (bits 12 through 15) of the
  //        time_hi_and_version field to the 4-bit version number from
  //        Section 4.1.3. Version4
  //     Set all the other bits to randomly (or pseudo-randomly) chosen
  //     values.
  // UUID                   = time-low "-" time-mid "-"time-high-and-version "-"clock-seq-reserved and low(2hexOctet)"-" node
  // time-low               = 4hexOctet
  // time-mid               = 2hexOctet
  // time-high-and-version  = 2hexOctet
  // clock-seq-and-reserved = hexOctet:
  // clock-seq-low          = hexOctet
  // node                   = 6hexOctet
  // Format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
  // y could be 1000, 1001, 1010, 1011 since most significant two bits needs to be 10
  // y values are 8, 9, A, B
  const guidHolder = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx';
  const hex = '0123456789abcdef';
  let r = 0;
  let guidResponse = '';
  for (let i = 0; i < 36; i++) {
    if (guidHolder[i] !== '-' && guidHolder[i] !== '4') {
      // each x and y needs to be random
      r = (Math.random() * 16) | 0;
    }

    if (guidHolder[i] === 'x') {
      guidResponse += hex[r];
    } else if (guidHolder[i] === 'y') {
      // clock-seq-and-reserved first hex is filtered and remaining hex values are random
      r &= 0x3; // bit and with 0011 to set pos 2 to zero ?0??
      r |= 0x8; // set pos 3 to 1 as 1???
      guidResponse += hex[r];
    } else {
      guidResponse += guidHolder[i];
    }
  }

  return guidResponse;
};