gecko-dev/dom/push/PushCrypto.jsm

455 строки
16 KiB
JavaScript

/* jshint moz: true, esnext: true */
/* 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';
const Cu = Components.utils;
Cu.import('resource://gre/modules/Services.jsm');
Cu.import('resource://gre/modules/XPCOMUtils.jsm');
XPCOMUtils.defineLazyGetter(this, 'gDOMBundle', () =>
Services.strings.createBundle('chrome://global/locale/dom/dom.properties'));
Cu.importGlobalProperties(['crypto']);
this.EXPORTED_SYMBOLS = ['PushCrypto', 'concatArray'];
var UTF8 = new TextEncoder('utf-8');
// Legacy encryption scheme (draft-thomson-http-encryption-02).
var AESGCM128_ENCODING = 'aesgcm128';
var AESGCM128_ENCRYPT_INFO = UTF8.encode('Content-Encoding: aesgcm128');
// New encryption scheme (draft-ietf-httpbis-encryption-encoding-01).
var AESGCM_ENCODING = 'aesgcm';
var AESGCM_ENCRYPT_INFO = UTF8.encode('Content-Encoding: aesgcm');
var NONCE_INFO = UTF8.encode('Content-Encoding: nonce');
var AUTH_INFO = UTF8.encode('Content-Encoding: auth\0'); // note nul-terminus
var P256DH_INFO = UTF8.encode('P-256\0');
var ECDH_KEY = { name: 'ECDH', namedCurve: 'P-256' };
var ECDSA_KEY = { name: 'ECDSA', namedCurve: 'P-256' };
// A default keyid with a name that won't conflict with a real keyid.
var DEFAULT_KEYID = '';
/** Localized error property names. */
// `Encryption` header missing or malformed.
const BAD_ENCRYPTION_HEADER = 'PushMessageBadEncryptionHeader';
// `Crypto-Key` or legacy `Encryption-Key` header missing.
const BAD_CRYPTO_KEY_HEADER = 'PushMessageBadCryptoKeyHeader';
const BAD_ENCRYPTION_KEY_HEADER = 'PushMessageBadEncryptionKeyHeader';
// `Content-Encoding` header missing or contains unsupported encoding.
const BAD_ENCODING_HEADER = 'PushMessageBadEncodingHeader';
// `dh` parameter of `Crypto-Key` header missing or not base64url-encoded.
const BAD_DH_PARAM = 'PushMessageBadSenderKey';
// `salt` parameter of `Encryption` header missing or not base64url-encoded.
const BAD_SALT_PARAM = 'PushMessageBadSalt';
// `rs` parameter of `Encryption` header not a number or less than pad size.
const BAD_RS_PARAM = 'PushMessageBadRecordSize';
// Invalid or insufficient padding for encrypted chunk.
const BAD_PADDING = 'PushMessageBadPaddingError';
// Generic crypto error.
const BAD_CRYPTO = 'PushMessageBadCryptoError';
class CryptoError extends Error {
/**
* Creates an error object indicating an incoming push message could not be
* decrypted.
*
* @param {String} message A human-readable error message. This is only for
* internal module logging, and doesn't need to be localized.
* @param {String} property The localized property name from `dom.properties`.
* @param {String...} params Substitutions to insert into the localized
* string.
*/
constructor(message, property, ...params) {
super(message);
this.isCryptoError = true;
this.property = property;
this.params = params;
}
/**
* Formats a localized string for reporting decryption errors to the Web
* Console.
*
* @param {String} scope The scope of the service worker receiving the
* message, prepended to any other substitutions in the string.
* @returns {String} The localized string.
*/
format(scope) {
let params = [scope, ...this.params].map(String);
return gDOMBundle.formatStringFromName(this.property, params,
params.length);
}
}
function getEncryptionKeyParams(encryptKeyField) {
if (!encryptKeyField) {
return null;
}
var params = encryptKeyField.split(',');
return params.reduce((m, p) => {
var pmap = p.split(';').reduce(parseHeaderFieldParams, {});
if (pmap.keyid && pmap.dh) {
m[pmap.keyid] = pmap.dh;
}
if (!m[DEFAULT_KEYID] && pmap.dh) {
m[DEFAULT_KEYID] = pmap.dh;
}
return m;
}, {});
}
function getEncryptionParams(encryptField) {
if (!encryptField) {
throw new CryptoError('Missing encryption header',
BAD_ENCRYPTION_HEADER);
}
var p = encryptField.split(',', 1)[0];
if (!p) {
throw new CryptoError('Encryption header missing params',
BAD_ENCRYPTION_HEADER);
}
return p.split(';').reduce(parseHeaderFieldParams, {});
}
function getCryptoParams(headers) {
if (!headers) {
return null;
}
var keymap;
var padSize;
if (!headers.encoding) {
throw new CryptoError('Missing Content-Encoding header',
BAD_ENCODING_HEADER);
}
if (headers.encoding == AESGCM_ENCODING) {
// aesgcm uses the Crypto-Key header, 2 bytes for the pad length, and an
// authentication secret.
// https://tools.ietf.org/html/draft-ietf-httpbis-encryption-encoding-01
keymap = getEncryptionKeyParams(headers.crypto_key);
if (!keymap) {
throw new CryptoError('Missing Crypto-Key header',
BAD_CRYPTO_KEY_HEADER);
}
padSize = 2;
} else if (headers.encoding == AESGCM128_ENCODING) {
// aesgcm128 uses Encryption-Key, 1 byte for the pad length, and no secret.
// https://tools.ietf.org/html/draft-thomson-http-encryption-02
keymap = getEncryptionKeyParams(headers.encryption_key);
if (!keymap) {
throw new CryptoError('Missing Encryption-Key header',
BAD_ENCRYPTION_KEY_HEADER);
}
padSize = 1;
} else {
throw new CryptoError('Unsupported Content-Encoding: ' + headers.encoding,
BAD_ENCODING_HEADER);
}
var enc = getEncryptionParams(headers.encryption);
var dh = keymap[enc.keyid || DEFAULT_KEYID];
if (!dh) {
throw new CryptoError('Missing dh parameter', BAD_DH_PARAM);
}
var salt = enc.salt;
if (!salt) {
throw new CryptoError('Missing salt parameter', BAD_SALT_PARAM);
}
var rs = enc.rs ? parseInt(enc.rs, 10) : 4096;
if (isNaN(rs)) {
throw new CryptoError('rs parameter must be a number', BAD_RS_PARAM);
}
if (rs <= padSize) {
throw new CryptoError('rs parameter must be at least ' + padSize,
BAD_RS_PARAM, padSize);
}
return {dh, salt, rs, padSize};
}
// Decodes an unpadded, base64url-encoded string.
function base64URLDecode(string) {
try {
return ChromeUtils.base64URLDecode(string, {
// draft-ietf-httpbis-encryption-encoding-01 prohibits padding.
padding: 'reject',
});
} catch (ex) {}
return null;
}
var parseHeaderFieldParams = (m, v) => {
var i = v.indexOf('=');
if (i >= 0) {
// A quoted string with internal quotes is invalid for all the possible
// values of this header field.
m[v.substring(0, i).trim()] = v.substring(i + 1).trim()
.replace(/^"(.*)"$/, '$1');
}
return m;
};
function chunkArray(array, size) {
var start = array.byteOffset || 0;
array = array.buffer || array;
var index = 0;
var result = [];
while(index + size <= array.byteLength) {
result.push(new Uint8Array(array, start + index, size));
index += size;
}
if (index < array.byteLength) {
result.push(new Uint8Array(array, start + index));
}
return result;
}
this.concatArray = function(arrays) {
var size = arrays.reduce((total, a) => total + a.byteLength, 0);
var index = 0;
return arrays.reduce((result, a) => {
result.set(new Uint8Array(a), index);
index += a.byteLength;
return result;
}, new Uint8Array(size));
};
var HMAC_SHA256 = { name: 'HMAC', hash: 'SHA-256' };
function hmac(key) {
this.keyPromise = crypto.subtle.importKey('raw', key, HMAC_SHA256,
false, ['sign']);
}
hmac.prototype.hash = function(input) {
return this.keyPromise.then(k => crypto.subtle.sign('HMAC', k, input));
};
function hkdf(salt, ikm) {
this.prkhPromise = new hmac(salt).hash(ikm)
.then(prk => new hmac(prk));
}
hkdf.prototype.extract = function(info, len) {
var input = concatArray([info, new Uint8Array([1])]);
return this.prkhPromise
.then(prkh => prkh.hash(input))
.then(h => {
if (h.byteLength < len) {
throw new CryptoError('HKDF length is too long', BAD_CRYPTO);
}
return h.slice(0, len);
});
};
/* generate a 96-bit nonce for use in GCM, 48-bits of which are populated */
function generateNonce(base, index) {
if (index >= Math.pow(2, 48)) {
throw new CryptoError('Nonce index is too large', BAD_CRYPTO);
}
var nonce = base.slice(0, 12);
nonce = new Uint8Array(nonce);
for (var i = 0; i < 6; ++i) {
nonce[nonce.byteLength - 1 - i] ^= (index / Math.pow(256, i)) & 0xff;
}
return nonce;
}
this.PushCrypto = {
generateAuthenticationSecret() {
return crypto.getRandomValues(new Uint8Array(16));
},
validateAppServerKey(key) {
return crypto.subtle.importKey('raw', key, ECDSA_KEY,
true, ['verify'])
.then(_ => key);
},
generateKeys() {
return crypto.subtle.generateKey(ECDH_KEY, true, ['deriveBits'])
.then(cryptoKey =>
Promise.all([
crypto.subtle.exportKey('raw', cryptoKey.publicKey),
crypto.subtle.exportKey('jwk', cryptoKey.privateKey)
]));
},
/**
* Decrypts a push message.
*
* @param {JsonWebKey} privateKey The ECDH private key of the subscription
* receiving the message, in JWK form.
* @param {BufferSource} publicKey The ECDH public key of the subscription
* receiving the message, in raw form.
* @param {BufferSource} authenticationSecret The 16-byte shared
* authentication secret of the subscription receiving the message.
* @param {Object} headers The encryption headers passed to `getCryptoParams`.
* @param {BufferSource} ciphertext The encrypted message data.
* @returns {Promise} Resolves with a `Uint8Array` containing the decrypted
* message data. Rejects with a `CryptoError` if decryption fails.
*/
decrypt(privateKey, publicKey, authenticationSecret, headers, ciphertext) {
return Promise.resolve().then(_ => {
let cryptoParams = getCryptoParams(headers);
if (!cryptoParams) {
return null;
}
return this._decodeMsg(ciphertext, privateKey, publicKey,
cryptoParams.dh, cryptoParams.salt,
cryptoParams.rs, authenticationSecret,
cryptoParams.padSize);
}).catch(error => {
if (error.isCryptoError) {
throw error;
}
// Web Crypto returns an unhelpful "operation failed for an
// operation-specific reason" error if decryption fails. We don't have
// context about what went wrong, so we throw a generic error instead.
throw new CryptoError('Bad encryption', BAD_CRYPTO);
});
},
_decodeMsg(aData, aPrivateKey, aPublicKey, aSenderPublicKey, aSalt, aRs,
aAuthenticationSecret, aPadSize) {
if (aData.byteLength === 0) {
// Zero length messages will be passed as null.
return null;
}
// The last chunk of data must be less than aRs, if it is not return an
// error.
if (aData.byteLength % (aRs + 16) === 0) {
throw new CryptoError('Encrypted data truncated', BAD_CRYPTO);
}
let senderKey = base64URLDecode(aSenderPublicKey);
if (!senderKey) {
throw new CryptoError('dh parameter is not base64url-encoded',
BAD_DH_PARAM);
}
let salt = base64URLDecode(aSalt);
if (!salt) {
throw new CryptoError('salt parameter is not base64url-encoded',
BAD_SALT_PARAM);
}
return Promise.all([
crypto.subtle.importKey('raw', senderKey, ECDH_KEY,
false, ['deriveBits']),
crypto.subtle.importKey('jwk', aPrivateKey, ECDH_KEY,
false, ['deriveBits'])
])
.then(([appServerKey, subscriptionPrivateKey]) =>
crypto.subtle.deriveBits({ name: 'ECDH', public: appServerKey },
subscriptionPrivateKey, 256))
.then(ikm => this._deriveKeyAndNonce(aPadSize,
new Uint8Array(ikm),
salt,
aPublicKey,
senderKey,
aAuthenticationSecret))
.then(r =>
// AEAD_AES_128_GCM expands ciphertext to be 16 octets longer.
Promise.all(chunkArray(aData, aRs + 16).map((slice, index) =>
this._decodeChunk(aPadSize, slice, index, r[1], r[0]))))
.then(r => concatArray(r));
},
_deriveKeyAndNonce(padSize, ikm, salt, receiverKey, senderKey,
authenticationSecret) {
var kdfPromise;
var context;
var encryptInfo;
// The size of the padding determines which key derivation we use.
//
// 1. If the pad size is 1, we assume "aesgcm128". This scheme ignores the
// authenticationSecret, and uses "Content-Encoding: <blah>" for the
// context string. It should eventually be removed: bug 1230038.
//
// 2. If the pad size is 2, we assume "aesgcm", and mix the
// authenticationSecret with the ikm using HKDF. The context string is:
// "Content-Encoding: <blah>\0P-256\0" then the length and value of both the
// receiver key and sender key.
if (padSize == 2) {
// Since we are using an authentication secret, we need to run an extra
// round of HKDF with the authentication secret as salt.
var authKdf = new hkdf(authenticationSecret, ikm);
kdfPromise = authKdf.extract(AUTH_INFO, 32)
.then(ikm2 => new hkdf(salt, ikm2));
// aesgcm requires extra context for the info parameter.
context = concatArray([
new Uint8Array([0]), P256DH_INFO,
this._encodeLength(receiverKey), receiverKey,
this._encodeLength(senderKey), senderKey
]);
encryptInfo = AESGCM_ENCRYPT_INFO;
} else {
kdfPromise = Promise.resolve(new hkdf(salt, ikm));
context = new Uint8Array(0);
encryptInfo = AESGCM128_ENCRYPT_INFO;
}
return kdfPromise.then(kdf => Promise.all([
kdf.extract(concatArray([encryptInfo, context]), 16)
.then(gcmBits => crypto.subtle.importKey('raw', gcmBits, 'AES-GCM', false,
['decrypt'])),
kdf.extract(concatArray([NONCE_INFO, context]), 12)
]));
},
_encodeLength(buffer) {
return new Uint8Array([0, buffer.byteLength]);
},
_decodeChunk(aPadSize, aSlice, aIndex, aNonce, aKey) {
let params = {
name: 'AES-GCM',
iv: generateNonce(aNonce, aIndex)
};
return crypto.subtle.decrypt(params, aKey, aSlice)
.then(decoded => this._unpadChunk(aPadSize, new Uint8Array(decoded)));
},
/**
* Removes padding from a decrypted chunk.
*
* @param {Number} padSize The size of the padding length prepended to each
* chunk. For aesgcm, the padding length is expressed as a 16-bit unsigned
* big endian integer. For aesgcm128, the padding is an 8-bit integer.
* @param {Uint8Array} decoded The decrypted, padded chunk.
* @returns {Uint8Array} The chunk with padding removed.
*/
_unpadChunk(padSize, decoded) {
if (padSize < 1 || padSize > 2) {
throw new CryptoError('Unsupported pad size', BAD_CRYPTO);
}
if (decoded.length < padSize) {
throw new CryptoError('Decoded array is too short!', BAD_PADDING);
}
var pad = decoded[0];
if (padSize == 2) {
pad = (pad << 8) | decoded[1];
}
if (pad > decoded.length) {
throw new CryptoError('Padding is wrong!', BAD_PADDING);
}
// All padded bytes must be zero except the first one.
for (var i = padSize; i <= pad; i++) {
if (decoded[i] !== 0) {
throw new CryptoError('Padding is wrong!', BAD_PADDING);
}
}
return decoded.slice(pad + padSize);
},
};