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78 lines
2.2 KiB
JavaScript
78 lines
2.2 KiB
JavaScript
/* 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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var PREFIX_NAME = 'identity.mozilla.com/picl/v1/';
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var bitSlice = sjcl.bitArray.bitSlice;
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var salt = sjcl.codec.hex.toBits('');
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/**
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* hkdf - The HMAC-based Key Derivation Function
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* based on https://github.com/mozilla/node-hkdf
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*
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* @class hkdf
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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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function hkdf(ikm, info, salt, length, callback) {
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var mac = new sjcl.misc.hmac(salt, sjcl.hash.sha256);
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mac.update(ikm);
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// compute the PRK
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var prk = mac.digest();
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// hash length is 32 because only sjcl.hash.sha256 is used at this moment
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var hashLength = 32;
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var num_blocks = Math.ceil(length / hashLength);
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var prev = sjcl.codec.hex.toBits('');
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var output = '';
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for (var i = 0; i < num_blocks; i++) {
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var hmac = new sjcl.misc.hmac(prk, sjcl.hash.sha256);
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var input = sjcl.bitArray.concat(
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sjcl.bitArray.concat(prev, info),
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sjcl.codec.utf8String.toBits((String.fromCharCode(i + 1)))
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);
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hmac.update(input);
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prev = hmac.digest();
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output += sjcl.codec.hex.fromBits(prev);
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}
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var truncated = sjcl.bitArray.clamp(sjcl.codec.hex.toBits(output), length * 8);
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callback(truncated);
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}
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/**
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* @class hawkCredentials
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* @method deriveHawkCredentials
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* @param {String} tokenHex
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* @param {String} context
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* @param {int} size
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* @returns {Promise}
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*/
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function deriveHawkCredentials(tokenHex, context, size, callback) {
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var token = sjcl.codec.hex.toBits(tokenHex);
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var info = sjcl.codec.utf8String.toBits(PREFIX_NAME + context);
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hkdf(token, info, salt, size || 3 * 32, function(out) {
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var authKey = bitSlice(out, 8 * 32, 8 * 64);
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var bundleKey = bitSlice(out, 8 * 64);
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callback({
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algorithm: 'sha256',
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id: sjcl.codec.hex.fromBits(bitSlice(out, 0, 8 * 32)),
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key: sjcl.codec.hex.fromBits(authKey),
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bundleKey: bundleKey
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});
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});
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}
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