gecko/services/common/hawkclient.js

256 lines
8.9 KiB
JavaScript

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";
/*
* HAWK is an HTTP authentication scheme using a message authentication code
* (MAC) algorithm to provide partial HTTP request cryptographic verification.
*
* For details, see: https://github.com/hueniverse/hawk
*
* With HAWK, it is essential that the clocks on clients and server not have an
* absolute delta of greater than one minute, as the HAWK protocol uses
* timestamps to reduce the possibility of replay attacks. However, it is
* likely that some clients' clocks will be more than a little off, especially
* in mobile devices, which would break HAWK-based services (like sync and
* firefox accounts) for those clients.
*
* This library provides a stateful HAWK client that calculates (roughly) the
* clock delta on the client vs the server. The library provides an interface
* for deriving HAWK credentials and making HAWK-authenticated REST requests to
* a single remote server. Therefore, callers who want to interact with
* multiple HAWK services should instantiate one HawkClient per service.
*/
this.EXPORTED_SYMBOLS = ["HawkClient"];
const {interfaces: Ci, utils: Cu} = Components;
Cu.import("resource://gre/modules/FxAccountsCommon.js");
Cu.import("resource://services-common/utils.js");
Cu.import("resource://services-crypto/utils.js");
Cu.import("resource://services-common/hawkrequest.js");
Cu.import("resource://services-common/observers.js");
Cu.import("resource://gre/modules/Promise.jsm");
/*
* A general purpose client for making HAWK authenticated requests to a single
* host. Keeps track of the clock offset between the client and the host for
* computation of the timestamp in the HAWK Authorization header.
*
* Clients should create one HawkClient object per each server they wish to
* interact with.
*
* @param host
* The url of the host
*/
this.HawkClient = function(host) {
this.host = host;
// Clock offset in milliseconds between our client's clock and the date
// reported in responses from our host.
this._localtimeOffsetMsec = 0;
}
this.HawkClient.prototype = {
/*
* Construct an error message for a response. Private.
*
* @param restResponse
* A RESTResponse object from a RESTRequest
*
* @param errorString
* A string describing the error
*/
_constructError: function(restResponse, errorString) {
let errorObj = {
error: errorString,
message: restResponse.statusText,
code: restResponse.status,
errno: restResponse.status
};
let retryAfter = restResponse.headers && restResponse.headers["retry-after"];
retryAfter = retryAfter ? parseInt(retryAfter) : retryAfter;
if (retryAfter) {
errorObj.retryAfter = retryAfter;
// and notify observers of the retry interval
if (this.observerPrefix) {
Observers.notify(this.observerPrefix + ":backoff:interval", retryAfter);
}
}
return errorObj;
},
/*
*
* Update clock offset by determining difference from date gives in the (RFC
* 1123) Date header of a server response. Because HAWK tolerates a window
* of one minute of clock skew (so two minutes total since the skew can be
* positive or negative), the simple method of calculating offset here is
* probably good enough. We keep the value in milliseconds to make life
* easier, even though the value will not have millisecond accuracy.
*
* @param dateString
* An RFC 1123 date string (e.g., "Mon, 13 Jan 2014 21:45:06 GMT")
*
* For HAWK clock skew and replay protection, see
* https://github.com/hueniverse/hawk#replay-protection
*/
_updateClockOffset: function(dateString) {
try {
let serverDateMsec = Date.parse(dateString);
this._localtimeOffsetMsec = serverDateMsec - this.now();
log.debug("Clock offset vs " + this.host + ": " + this._localtimeOffsetMsec);
} catch(err) {
log.warn("Bad date header in server response: " + dateString);
}
},
/*
* Get the current clock offset in milliseconds.
*
* The offset is the number of milliseconds that must be added to the client
* clock to make it equal to the server clock. For example, if the client is
* five minutes ahead of the server, the localtimeOffsetMsec will be -300000.
*/
get localtimeOffsetMsec() {
return this._localtimeOffsetMsec;
},
/*
* return current time in milliseconds
*/
now: function() {
return Date.now();
},
/* A general method for sending raw RESTRequest calls authorized using HAWK
*
* @param path
* API endpoint path
* @param method
* The HTTP request method
* @param credentials
* Hawk credentials
* @param payloadObj
* An object that can be encodable as JSON as the payload of the
* request
* @return Promise
* Returns a promise that resolves to the text response of the API call,
* or is rejected with an error. If the server response can be parsed
* as JSON and contains an 'error' property, the promise will be
* rejected with this JSON-parsed response.
*/
request: function(path, method, credentials=null, payloadObj={}, retryOK=true) {
method = method.toLowerCase();
let deferred = Promise.defer();
let uri = this.host + path;
let self = this;
function onComplete(error) {
let restResponse = this.response;
let status = restResponse.status;
log.debug("(Response) code: " + status +
" - Status text: " + restResponse.statusText,
" - Response text: " + restResponse.body);
// All responses may have backoff headers, which are a server-side safety
// valve to allow slowing down clients without hurting performance.
self._maybeNotifyBackoff(restResponse, "x-weave-backoff");
self._maybeNotifyBackoff(restResponse, "x-backoff");
if (error) {
// When things really blow up, reconstruct an error object that follows
// the general format of the server on error responses.
return deferred.reject(self._constructError(restResponse, error));
}
self._updateClockOffset(restResponse.headers["date"]);
if (status === 401 && retryOK && !("retry-after" in restResponse.headers)) {
// Retry once if we were rejected due to a bad timestamp.
// Clock offset is adjusted already in the top of this function.
log.debug("Received 401 for " + path + ": retrying");
return deferred.resolve(
self.request(path, method, credentials, payloadObj, false));
}
// If the server returned a json error message, use it in the rejection
// of the promise.
//
// In the case of a 401, in which we are probably being rejected for a
// bad timestamp, retry exactly once, during which time clock offset will
// be adjusted.
let jsonResponse = {};
try {
jsonResponse = JSON.parse(restResponse.body);
} catch(notJSON) {}
let okResponse = (200 <= status && status < 300);
if (!okResponse || jsonResponse.error) {
if (jsonResponse.error) {
return deferred.reject(jsonResponse);
}
return deferred.reject(self._constructError(restResponse, "Request failed"));
}
// It's up to the caller to know how to decode the response.
// We just return the raw text.
deferred.resolve(this.response.body);
};
let extra = {
now: this.now(),
localtimeOffsetMsec: this.localtimeOffsetMsec,
};
let request = this.newHAWKAuthenticatedRESTRequest(uri, credentials, extra);
if (method == "post" || method == "put") {
request[method](payloadObj, onComplete);
} else {
request[method](onComplete);
}
return deferred.promise;
},
/*
* The prefix used for all notifications sent by this module. This
* allows the handler of notifications to be sure they are handling
* notifications for the service they expect.
*
* If not set, no notifications will be sent.
*/
observerPrefix: null,
// Given an optional header value, notify that a backoff has been requested.
_maybeNotifyBackoff: function (response, headerName) {
if (!this.observerPrefix) {
return;
}
let headerVal = response.headers[headerName];
if (!headerVal) {
return;
}
let backoffInterval;
try {
backoffInterval = parseInt(headerVal, 10);
} catch (ex) {
this._log.error("hawkclient response had invalid backoff value in '" +
headerName + "' header: " + headerVal);
return;
}
Observers.notify(this.observerPrefix + ":backoff:interval", backoffInterval);
},
// override points for testing.
newHAWKAuthenticatedRESTRequest: function(uri, credentials, extra) {
return new HAWKAuthenticatedRESTRequest(uri, credentials, extra);
},
}