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/*
* Browser-based Web Push client for the application server piece.
*
* Any copyright is dedicated to the Public Domain.
* http://creativecommons.org/licenses/publicdomain/
*
* Uses the WebCrypto API.
*
* Note that this test file uses the old, deprecated aesgcm128 encryption
* scheme. PushCrypto.encrypt() exists and uses the later aes128gcm, but
* there's no good reason to upgrade this at this time (and having mochitests
* use PushCrypto directly is easier said than done.)
*/
(function(g) {
"use strict";
var P256DH = {
name: "ECDH",
namedCurve: "P-256",
};
var webCrypto = g.crypto.subtle;
var ENCRYPT_INFO = new TextEncoder("utf-8").encode(
"Content-Encoding: aesgcm128"
);
var NONCE_INFO = new TextEncoder("utf-8").encode("Content-Encoding: nonce");
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;
}
/* I can't believe that this is needed here, in this day and age ...
* Note: these are not efficient, merely expedient.
*/
var base64url = {
_strmap: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_",
encode(data) {
data = new Uint8Array(data);
var len = Math.ceil((data.length * 4) / 3);
return chunkArray(data, 3)
.map(chunk =>
[
chunk[0] >>> 2,
((chunk[0] & 0x3) << 4) | (chunk[1] >>> 4),
((chunk[1] & 0xf) << 2) | (chunk[2] >>> 6),
chunk[2] & 0x3f,
]
.map(v => base64url._strmap[v])
.join("")
)
.join("")
.slice(0, len);
},
_lookup(s, i) {
return base64url._strmap.indexOf(s.charAt(i));
},
decode(str) {
var v = new Uint8Array(Math.floor((str.length * 3) / 4));
var vi = 0;
for (var si = 0; si < str.length; ) {
var w = base64url._lookup(str, si++);
var x = base64url._lookup(str, si++);
var y = base64url._lookup(str, si++);
var z = base64url._lookup(str, si++);
v[vi++] = (w << 2) | (x >>> 4);
v[vi++] = (x << 4) | (y >>> 2);
v[vi++] = (y << 6) | z;
}
return v;
},
};
g.base64url = base64url;
/* Coerces data into a Uint8Array */
function ensureView(data) {
if (typeof data === "string") {
return new TextEncoder("utf-8").encode(data);
}
if (data instanceof ArrayBuffer) {
return new Uint8Array(data);
}
if (ArrayBuffer.isView(data)) {
return new Uint8Array(data.buffer);
}
throw new Error("webpush() needs a string or BufferSource");
}
function bsConcat(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));
}
function hmac(key) {
this.keyPromise = webCrypto.importKey(
"raw",
key,
{ name: "HMAC", hash: "SHA-256" },
false,
["sign"]
);
}
hmac.prototype.hash = function(input) {
return this.keyPromise.then(k => webCrypto.sign("HMAC", k, input));
};
function hkdf(salt, ikm) {
this.prkhPromise = new hmac(salt).hash(ikm).then(prk => new hmac(prk));
}
hkdf.prototype.generate = function(info, len) {
var input = bsConcat([info, new Uint8Array([1])]);
return this.prkhPromise
.then(prkh => prkh.hash(input))
.then(h => {
if (h.byteLength < len) {
throw new Error("Length is too long");
}
return h.slice(0, len);
});
};
/* generate a 96-bit IV for use in GCM, 48-bits of which are populated */
function generateNonce(base, index) {
var nonce = base.slice(0, 12);
for (var i = 0; i < 6; ++i) {
nonce[nonce.length - 1 - i] ^= (index / Math.pow(256, i)) & 0xff;
}
return nonce;
}
function encrypt(localKey, remoteShare, salt, data) {
return webCrypto
.importKey("raw", remoteShare, P256DH, false, ["deriveBits"])
.then(remoteKey =>
webCrypto.deriveBits(
{ name: P256DH.name, public: remoteKey },
localKey,
256
)
)
.then(rawKey => {
var kdf = new hkdf(salt, rawKey);
return Promise.all([
kdf
.generate(ENCRYPT_INFO, 16)
.then(gcmBits =>
webCrypto.importKey("raw", gcmBits, "AES-GCM", false, ["encrypt"])
),
kdf.generate(NONCE_INFO, 12),
]);
})
.then(([key, nonce]) => {
if (data.byteLength === 0) {
// Send an authentication tag for empty messages.
return webCrypto
.encrypt(
{
name: "AES-GCM",
iv: generateNonce(nonce, 0),
},
key,
new Uint8Array([0])
)
.then(value => [value]);
}
// 4096 is the default size, though we burn 1 for padding
return Promise.all(
chunkArray(data, 4095).map((slice, index) => {
var padded = bsConcat([new Uint8Array([0]), slice]);
return webCrypto.encrypt(
{
name: "AES-GCM",
iv: generateNonce(nonce, index),
},
key,
padded
);
})
);
})
.then(bsConcat);
}
function webPushEncrypt(subscription, data) {
data = ensureView(data);
var salt = g.crypto.getRandomValues(new Uint8Array(16));
return webCrypto
.generateKey(P256DH, false, ["deriveBits"])
.then(localKey => {
return Promise.all([
encrypt(
localKey.privateKey,
subscription.getKey("p256dh"),
salt,
data
),
// 1337 p-256 specific haxx to get the raw value out of the spki value
webCrypto.exportKey("raw", localKey.publicKey),
]);
})
.then(([payload, pubkey]) => {
return {
data: base64url.encode(payload),
encryption: "keyid=p256dh;salt=" + base64url.encode(salt),
encryption_key: "keyid=p256dh;dh=" + base64url.encode(pubkey),
encoding: "aesgcm128",
};
});
}
g.webPushEncrypt = webPushEncrypt;
})(this);
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