@ledgerhq/hw-transport-u2f/lib-es/TransportU2F.js

Ledger Hardware Wallet Web implementation of the communication layer, using U2F api

import { sign, isSupported } from "u2f-api";
import Transport from "@ledgerhq/hw-transport";
import { log } from "@ledgerhq/logs";
import { TransportError } from "@ledgerhq/errors";

function wrapU2FTransportError(originalError, message, id) {
  const err = new TransportError(message, id); // $FlowFixMe

  err.originalError = originalError;
  return err;
}

function wrapApdu(apdu, key) {
  const result = Buffer.alloc(apdu.length);

  for (let i = 0; i < apdu.length; i++) {
    result[i] = apdu[i] ^ key[i % key.length];
  }

  return result;
} // Convert from normal to web-safe, strip trailing "="s


const webSafe64 = base64 => base64.replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, ""); // Convert from web-safe to normal, add trailing "="s


const normal64 = base64 => base64.replace(/-/g, "+").replace(/_/g, "/") + "==".substring(0, 3 * base64.length % 4);

function attemptExchange(apdu, timeoutMillis, scrambleKey, unwrap) {
  const keyHandle = wrapApdu(apdu, scrambleKey);
  const challenge = Buffer.from("0000000000000000000000000000000000000000000000000000000000000000", "hex");
  const signRequest = {
    version: "U2F_V2",
    keyHandle: webSafe64(keyHandle.toString("base64")),
    challenge: webSafe64(challenge.toString("base64")),
    appId: location.origin
  };
  log("apdu", "=> " + apdu.toString("hex"));
  return sign(signRequest, timeoutMillis / 1000).then(response => {
    const {
      signatureData
    } = response;

    if (typeof signatureData === "string") {
      const data = Buffer.from(normal64(signatureData), "base64");
      let result;

      if (!unwrap) {
        result = data;
      } else {
        result = data.slice(5);
      }

      log("apdu", "<= " + result.toString("hex"));
      return result;
    } else {
      throw response;
    }
  });
}

let transportInstances = [];

function emitDisconnect() {
  transportInstances.forEach(t => t.emit("disconnect"));
  transportInstances = [];
}

function isTimeoutU2FError(u2fError) {
  return u2fError.metaData.code === 5;
}
/**
 * U2F web Transport implementation
 * @example
 * import TransportU2F from "@ledgerhq/hw-transport-u2f";
 * ...
 * TransportU2F.create().then(transport => ...)
 */


export default class TransportU2F extends Transport {
  /*
   */

  /*
   */

  /**
   * static function to create a new Transport from a connected Ledger device discoverable via U2F (browser support)
   */
  static async open(_, _openTimeout = 5000) {
    return new TransportU2F();
  }

  constructor() {
    super();
    this.scrambleKey = void 0;
    this.unwrap = true;
    transportInstances.push(this);
  }
  /**
   * Exchange with the device using APDU protocol.
   * @param apdu
   * @returns a promise of apdu response
   */


  async exchange(apdu) {
    try {
      return await attemptExchange(apdu, this.exchangeTimeout, this.scrambleKey, this.unwrap);
    } catch (e) {
      const isU2FError = typeof e.metaData === "object";

      if (isU2FError) {
        if (isTimeoutU2FError(e)) {
          emitDisconnect();
        } // the wrapping make error more usable and "printable" to the end user.


        throw wrapU2FTransportError(e, "Failed to sign with Ledger device: U2F " + e.metaData.type, "U2F_" + e.metaData.code);
      } else {
        throw e;
      }
    }
  }
  /**
   */


  setScrambleKey(scrambleKey) {
    this.scrambleKey = Buffer.from(scrambleKey, "ascii");
  }
  /**
   */


  setUnwrap(unwrap) {
    this.unwrap = unwrap;
  }

  close() {
    // u2f have no way to clean things up
    return Promise.resolve();
  }

}
TransportU2F.isSupported = isSupported;

TransportU2F.list = () => // this transport is not discoverable but we are going to guess if it is here with isSupported()
isSupported().then(supported => supported ? [null] : []);

TransportU2F.listen = observer => {
  let unsubscribed = false;
  isSupported().then(supported => {
    if (unsubscribed) return;

    if (supported) {
      observer.next({
        type: "add",
        descriptor: null
      });
      observer.complete();
    } else {
      observer.error(new TransportError("U2F browser support is needed for Ledger. " + "Please use Chrome, Opera or Firefox with a U2F extension. " + "Also make sure you're on an HTTPS connection", "U2FNotSupported"));
    }
  });
  return {
    unsubscribe: () => {
      unsubscribed = true;
    }
  };
};
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