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Diffstat (limited to 'data/extensions/jsr@javascriptrestrictor/wrappingS-GP.js')
| -rw-r--r-- | data/extensions/jsr@javascriptrestrictor/wrappingS-GP.js | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/data/extensions/jsr@javascriptrestrictor/wrappingS-GP.js b/data/extensions/jsr@javascriptrestrictor/wrappingS-GP.js new file mode 100644 index 0000000..202ac21 --- /dev/null +++ b/data/extensions/jsr@javascriptrestrictor/wrappingS-GP.js @@ -0,0 +1,143 @@ +/** \file + * \brief This file contains wrappers for the Gamepad API + * + * \see https://w3c.github.io/gamepad/ + * + * \author Copyright (C) 2021 Libor Polcak + * + * \license SPDX-License-Identifier: GPL-3.0-or-later + */ +// +// This program is free software: you can redistribute it and/or modify +// it under the terms of the GNU General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. +// +// This program is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. +// +// You should have received a copy of the GNU General Public License +// along with this program. If not, see <https://www.gnu.org/licenses/>. +// + +/** \file + * \ingroup wrappers + * + * navigator.getGamepads() allows any page script to learn the gamepads + * connected to the computer if the feature is not blocked by the + * Feature-Policy. + * + * The "Fingerprinting the Fingerprinters" paper (see reference below) observed + * that the interface is used in the wild to fingerprint users. As it is likely + * that only a minority of users have a gamepad connected and the API + * provides additional information on the HW, it is likely that users with + * a gamepad connected are easily fingerprintable. + * + * As we expect that the majority of the users does not have a gamepad + * connected, we provide only a single mitigation - the wrapped APIs return + * an empty list. + * + * \bug The standard provides an event `gamepadconnected` and + * `gamepaddisconnected` that fires at least on the window object. We do not + * mitigate the event to fire and consequently, it is possible that an + * adversary can learn that a gamepad was (dis)connected but there was no + * change in the result of the `navigator.getGamepads()` API. + * + * The gamepad representing object carries a timestamp of the last change of + * the gamepad. As we allow wrapping of several ways to obtain timestamps, + * we need to provide the same precision for the Gamepad object. + * + * \see U. Iqbal, S. Englehardt and Z. Shafiq, [Fingerprinting the + * Fingerprinters: Learning to Detect Browser Fingerprinting + * Behaviors](https://github.com/uiowa-irl/FP-Inspector/blob/master/Data/potential_fingerprinting_APIs.md) + * in 2021 2021 IEEE Symposium on Security and Privacy (SP), San Francisco, + * CA, US, 2021 pp. 283-301 + */ + +(function() { + var remember_past_ts_values = `var precision = args[0]; + var doNoise = args[1]; + var pastValues = {}; + ${rounding_function} + ${noise_function} + var mitigationF = rounding_function; + if (doNoise === true){ + mitigationF = function(value, precision) { + let params = [value, precision]; + if (params in pastValues) { + return pastValues[params]; + } + let result = noise_function(...params); + pastValues[params] = result; + return result; + } + } + `; + var wrappers = [ + { + parent_object: "Navigator.prototype", + parent_object_property: "getGamepads", + wrapped_objects: [{ + original_name: "Navigator.prototype.getGamepads", + wrapped_name: "origGamepads", + }], + helping_code: "", + wrapping_function_body: ` + origGamepadsRes = origGamepads.call(navigator); + if (Array.isArray(origGamepadsRes)) { + // e.g. Gecko + return new window.Array(); + } + else { + // e.g. Chromium based + var l = new window.Object(); + // Based on our experiments and web search results like + // https://stackoverflow.com/questions/41251051/is-the-html5-gamepad-api-limited-to-only-4-controllers + // https://stackoverflow.com/questions/32619456/navigator-getgamepads-return-an-array-of-undefineds + // we try to mimic common value of the property + l[0] = null; + l[1] = null; + l[2] = null; + l[3] = null; + l.length = 4; + window.Object.setPrototypeOf(l, origGamepadsRes.__proto__); + return l; + } + `, + }, + { + /** + * \see https://developer.mozilla.org/en-US/docs/Web/API/Gamepad/timestamp + * \note that at the time of the writing of the prototype, the timestamp + * property was not supported by any browser. + */ + parent_object: "Gamepad.prototype", + parent_object_property: "timestamp", + wrapped_objects: [], + helping_code: remember_past_ts_values + `let origGet = Object.getOwnPropertyDescriptor(Gamepad.prototype, "timestamp").get`, + post_wrapping_code: [ + { + code_type: "object_properties", + parent_object: "Gamepad.prototype", + parent_object_property: "timestamp", + wrapped_objects: [], + /** \brief replaces Gamepad.timestamp getter to create + * a timestamp with the desired precision. + */ + wrapped_properties: [ + { + property_name: "get", + property_value: ` + function() { + return mitigationF(origGet.call(this), precision); + }`, + }, + ], + } + ], + }, + ] + add_wrappers(wrappers); +})() |