303 lines
9.6 KiB
JavaScript
303 lines
9.6 KiB
JavaScript
/* jshint moz: true, esnext: true */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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'use strict';
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const Cu = Components.utils;
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Cu.importGlobalProperties(['crypto']);
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this.EXPORTED_SYMBOLS = ['PushCrypto', 'concatArray',
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'getCryptoParams',
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'base64UrlDecode'];
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var UTF8 = new TextEncoder('utf-8');
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var ENCRYPT_INFO = UTF8.encode('Content-Encoding: aesgcm128');
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var NONCE_INFO = UTF8.encode('Content-Encoding: nonce');
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var AUTH_INFO = UTF8.encode('Content-Encoding: auth\0'); // note nul-terminus
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var P256DH_INFO = UTF8.encode('P-256\0');
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var ECDH_KEY = { name: 'ECDH', namedCurve: 'P-256' };
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// A default keyid with a name that won't conflict with a real keyid.
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var DEFAULT_KEYID = '';
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function getEncryptionKeyParams(encryptKeyField) {
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if (!encryptKeyField) {
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return null;
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}
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var params = encryptKeyField.split(',');
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return params.reduce((m, p) => {
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var pmap = p.split(';').reduce(parseHeaderFieldParams, {});
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if (pmap.keyid && pmap.dh) {
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m[pmap.keyid] = pmap.dh;
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}
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if (!m[DEFAULT_KEYID] && pmap.dh) {
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m[DEFAULT_KEYID] = pmap.dh;
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}
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return m;
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}, {});
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}
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function getEncryptionParams(encryptField) {
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var p = encryptField.split(',', 1)[0];
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if (!p) {
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return null;
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}
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return p.split(';').reduce(parseHeaderFieldParams, {});
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}
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this.getCryptoParams = function(headers) {
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if (!headers) {
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return null;
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}
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var requiresAuthenticationSecret = true;
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var keymap = getEncryptionKeyParams(headers.crypto_key);
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if (!keymap) {
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requiresAuthenticationSecret = false;
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keymap = getEncryptionKeyParams(headers.encryption_key);
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if (!keymap) {
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return null;
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}
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}
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var enc = getEncryptionParams(headers.encryption);
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if (!enc) {
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return null;
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}
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var dh = keymap[enc.keyid || DEFAULT_KEYID];
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var salt = enc.salt;
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var rs = (enc.rs)? parseInt(enc.rs, 10) : 4096;
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if (!dh || !salt || isNaN(rs) || (rs <= 1)) {
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return null;
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}
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return {dh, salt, rs, auth: requiresAuthenticationSecret};
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}
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var parseHeaderFieldParams = (m, v) => {
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var i = v.indexOf('=');
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if (i >= 0) {
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// A quoted string with internal quotes is invalid for all the possible
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// values of this header field.
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m[v.substring(0, i).trim()] = v.substring(i + 1).trim()
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.replace(/^"(.*)"$/, '$1');
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}
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return m;
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};
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function chunkArray(array, size) {
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var start = array.byteOffset || 0;
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array = array.buffer || array;
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var index = 0;
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var result = [];
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while(index + size <= array.byteLength) {
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result.push(new Uint8Array(array, start + index, size));
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index += size;
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}
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if (index < array.byteLength) {
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result.push(new Uint8Array(array, start + index));
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}
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return result;
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}
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this.base64UrlDecode = function(s) {
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s = s.replace(/-/g, '+').replace(/_/g, '/');
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// Replace padding if it was stripped by the sender.
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// See http://tools.ietf.org/html/rfc4648#section-4
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switch (s.length % 4) {
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case 0:
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break; // No pad chars in this case
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case 2:
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s += '==';
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break; // Two pad chars
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case 3:
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s += '=';
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break; // One pad char
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default:
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throw new Error('Illegal base64url string!');
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}
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// With correct padding restored, apply the standard base64 decoder
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var decoded = atob(s);
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var array = new Uint8Array(new ArrayBuffer(decoded.length));
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for (var i = 0; i < decoded.length; i++) {
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array[i] = decoded.charCodeAt(i);
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}
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return array;
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};
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this.concatArray = function(arrays) {
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var size = arrays.reduce((total, a) => total + a.byteLength, 0);
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var index = 0;
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return arrays.reduce((result, a) => {
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result.set(new Uint8Array(a), index);
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index += a.byteLength;
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return result;
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}, new Uint8Array(size));
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};
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var HMAC_SHA256 = { name: 'HMAC', hash: 'SHA-256' };
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function hmac(key) {
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this.keyPromise = crypto.subtle.importKey('raw', key, HMAC_SHA256,
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false, ['sign']);
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}
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hmac.prototype.hash = function(input) {
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return this.keyPromise.then(k => crypto.subtle.sign('HMAC', k, input));
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};
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function hkdf(salt, ikm) {
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this.prkhPromise = new hmac(salt).hash(ikm)
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.then(prk => new hmac(prk));
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}
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hkdf.prototype.extract = function(info, len) {
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var input = concatArray([info, new Uint8Array([1])]);
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return this.prkhPromise
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.then(prkh => prkh.hash(input))
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.then(h => {
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if (h.byteLength < len) {
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throw new Error('Length is too long');
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}
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return h.slice(0, len);
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});
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};
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/* generate a 96-bit nonce for use in GCM, 48-bits of which are populated */
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function generateNonce(base, index) {
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if (index >= Math.pow(2, 48)) {
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throw new Error('Error generating nonce - index is too large.');
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}
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var nonce = base.slice(0, 12);
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nonce = new Uint8Array(nonce);
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for (var i = 0; i < 6; ++i) {
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nonce[nonce.byteLength - 1 - i] ^= (index / Math.pow(256, i)) & 0xff;
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}
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return nonce;
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}
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this.PushCrypto = {
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generateAuthenticationSecret() {
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return crypto.getRandomValues(new Uint8Array(12));
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},
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generateKeys() {
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return crypto.subtle.generateKey(ECDH_KEY, true, ['deriveBits'])
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.then(cryptoKey =>
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Promise.all([
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crypto.subtle.exportKey('raw', cryptoKey.publicKey),
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crypto.subtle.exportKey('jwk', cryptoKey.privateKey)
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]));
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},
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decodeMsg(aData, aPrivateKey, aPublicKey, aSenderPublicKey,
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aSalt, aRs, aAuthenticationSecret) {
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if (aData.byteLength === 0) {
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// Zero length messages will be passed as null.
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return Promise.resolve(null);
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}
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// The last chunk of data must be less than aRs, if it is not return an
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// error.
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if (aData.byteLength % (aRs + 16) === 0) {
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return Promise.reject(new Error('Data truncated'));
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}
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let senderKey = base64UrlDecode(aSenderPublicKey)
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return Promise.all([
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crypto.subtle.importKey('raw', senderKey, ECDH_KEY,
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false, ['deriveBits']),
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crypto.subtle.importKey('jwk', aPrivateKey, ECDH_KEY,
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false, ['deriveBits'])
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])
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.then(([appServerKey, subscriptionPrivateKey]) =>
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crypto.subtle.deriveBits({ name: 'ECDH', public: appServerKey },
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subscriptionPrivateKey, 256))
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.then(ikm => this._deriveKeyAndNonce(new Uint8Array(ikm),
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base64UrlDecode(aSalt),
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aPublicKey,
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senderKey,
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aAuthenticationSecret))
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.then(r =>
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// AEAD_AES_128_GCM expands ciphertext to be 16 octets longer.
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Promise.all(chunkArray(aData, aRs + 16).map((slice, index) =>
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this._decodeChunk(slice, index, r[1], r[0]))))
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.then(r => concatArray(r));
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},
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_deriveKeyAndNonce(ikm, salt, receiverKey, senderKey, authenticationSecret) {
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var kdfPromise;
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var context;
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// The authenticationSecret, when present, is mixed with the ikm using HKDF.
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// This is its primary purpose. However, since the authentication secret
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// was added at the same time that the info string was changed, we also use
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// its presence to change how the final info string is calculated:
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//
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// 1. When there is no authenticationSecret, the context string is simply
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// "Content-Encoding: <blah>". This corresponds to old, deprecated versions
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// of the content encoding. This should eventually be removed: bug 1230038.
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//
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// 2. When there is an authenticationSecret, the context string is:
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// "Content-Encoding: <blah>\0P-256\0" then the length and value of both the
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// receiver key and sender key.
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if (authenticationSecret) {
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// Since we are using an authentication secret, we need to run an extra
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// round of HKDF with the authentication secret as salt.
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var authKdf = new hkdf(authenticationSecret, ikm);
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kdfPromise = authKdf.extract(AUTH_INFO, 32)
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.then(ikm2 => new hkdf(salt, ikm2));
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// We also use the presence of the authentication secret to indicate that
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// we have extra context to add to the info parameter.
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context = concatArray([
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new Uint8Array([0]), P256DH_INFO,
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this._encodeLength(receiverKey), receiverKey,
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this._encodeLength(senderKey), senderKey
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]);
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} else {
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kdfPromise = Promise.resolve(new hkdf(salt, ikm));
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context = new Uint8Array(0);
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}
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return kdfPromise.then(kdf => Promise.all([
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kdf.extract(concatArray([ENCRYPT_INFO, context]), 16)
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.then(gcmBits => crypto.subtle.importKey('raw', gcmBits, 'AES-GCM', false,
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['decrypt'])),
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kdf.extract(concatArray([NONCE_INFO, context]), 12)
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]));
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},
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_encodeLength(buffer) {
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return new Uint8Array([0, buffer.byteLength]);
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},
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_decodeChunk(aSlice, aIndex, aNonce, aKey) {
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let params = {
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name: 'AES-GCM',
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iv: generateNonce(aNonce, aIndex)
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};
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return crypto.subtle.decrypt(params, aKey, aSlice)
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.then(decoded => {
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decoded = new Uint8Array(decoded);
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if (decoded.length == 0) {
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return Promise.reject(new Error('Decoded array is too short!'));
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} else if (decoded[0] > decoded.length) {
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return Promise.reject(new Error ('Padding is wrong!'));
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} else {
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// All padded bytes must be zero except the first one.
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for (var i = 1; i <= decoded[0]; i++) {
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if (decoded[i] != 0) {
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return Promise.reject(new Error('Padding is wrong!'));
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}
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}
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return decoded.slice(decoded[0] + 1);
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}
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});
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}
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};
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