b38dea0597
Share Gaia assets and adapters, keep private profiles and development documents local, and update both public READMEs.
97 lines
3.1 KiB
JavaScript
Executable file
97 lines
3.1 KiB
JavaScript
Executable file
/* 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
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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'use strict';
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/* global
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StringConversion
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*/
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/* exported
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KeyDerivation
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*/
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const KeyDerivation = Object.freeze((() => {
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// Hash length is 32 because only SHA256 is used at this moment.
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const HASH_LENGTH = 32;
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const subtle = window.crypto.subtle;
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const concatU8Array = (buffer1, buffer2) => {
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var aux = new Uint8Array(buffer1.byteLength + buffer2.byteLength);
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aux.set(new Uint8Array(buffer1), 0);
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aux.set(new Uint8Array(buffer2), buffer1.byteLength);
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return aux;
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};
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const alg = {
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name: 'HMAC',
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hash: 'SHA-256'
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};
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const doImportKey = (rawKey) => {
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return subtle.importKey('raw', rawKey, alg, false, ['sign']);
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};
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// Converts a ArrayBuffer into a ArrayBufferView (U8) if it's not that
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// already.
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const arrayBuffer2Uint8 = (buff) => {
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return buff.buffer && buff || new Uint8Array(buff);
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};
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const doHMAC = (tbsData, hmacKey) => {
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return subtle.sign(alg.name, hmacKey, tbsData).then(arrayBuffer2Uint8);
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};
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const bitSlice = (arr, start, end) => {
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return (end !== undefined ? arr.subarray(start / 8, end / 8) :
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arr.subarray(start / 8));
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};
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const newEmptyArray = () => new Uint8Array(0);
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return {
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/**
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* hkdf - The HMAC-based Key Derivation Function
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*
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* @param {bitArray} ikm Initial keying material
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* @param {bitArray} info Key derivation data
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* @param {bitArray} salt Salt
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* @param {integer} length Length of the derived key in bytes
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* @return promise object- It will resolve with `output` data
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*/
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hkdf: (ikm, info, salt, length) => {
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const numBlocks = Math.ceil(length / HASH_LENGTH);
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const doHKDFRound = (roundNumber, prevDigest, prevOutput, hkdfKey) => {
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// Do the data accumulating part of an HKDF round. Also, it
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// checks if there are still more rounds left and fires the next
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// Or just finishes the process calling the callback.
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const addToOutput = (digest) => {
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const output = prevOutput +
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StringConversion.uint8ArrayToHexString(digest);
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if (++roundNumber <= numBlocks) {
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return doHKDFRound(roundNumber, digest, output, hkdfKey);
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}
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return new Promise(resolve => {
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const truncated = bitSlice(
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StringConversion.hexStringToUint8Array(output), 0, length * 8);
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resolve(truncated);
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});
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};
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const input = concatU8Array(
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concatU8Array(prevDigest, info),
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StringConversion.stringToUtf8Uint8Array(
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String.fromCharCode(roundNumber)));
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return doHMAC(input, hkdfKey).then(addToOutput);
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};
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return doImportKey(salt). // Imports the initial key.
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then(doHMAC.bind(undefined, ikm)). // Generates the key deriving key.
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then(doImportKey). // Imports the key deriving key.
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then(doHKDFRound.bind(undefined, 1, newEmptyArray(), ''));
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// Launches the first HKDF round.
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}
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};
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})());
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