75 lines
1.7 KiB
JavaScript
75 lines
1.7 KiB
JavaScript
/**
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* @author Michael Raith
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* @date 24.02.2016 12:04
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*/
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'use strict';
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var crypto = require('crypto');
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var bufferAlloc = require('buffer-alloc');
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/**
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* Do a constant time string comparison. Always compare the complete strings
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* against each other to get a constant time. This method does not short-cut
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* if the two string's length differs.
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*
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* @param {string} a
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* @param {string} b
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*
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* @return {boolean}
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*/
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var safeCompare = function safeCompare(a, b) {
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var strA = String(a);
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var strB = String(b);
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var lenA = strA.length;
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var result = 0;
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if (lenA !== strB.length) {
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strB = strA;
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result = 1;
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}
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for (var i = 0; i < lenA; i++) {
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result |= (strA.charCodeAt(i) ^ strB.charCodeAt(i));
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}
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return result === 0;
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};
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/**
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* Call native "crypto.timingSafeEqual" methods.
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* All passed values will be converted into strings first.
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*
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* Runtime is always corresponding to the length of the first parameter (string
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* a).
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*
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* @param {string} a
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* @param {string} b
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*
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* @return {boolean}
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*/
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var nativeTimingSafeEqual = function nativeTimingSafeEqual(a, b) {
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var strA = String(a);
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var strB = String(b);
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var aLen = Buffer.byteLength(strA);
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var bLen = Buffer.byteLength(strB);
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// Always use length of a to avoid leaking the length. Even if this is a
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// false positive because one is a prefix of the other, the explicit length
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// check at the end will catch that.
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var bufA = bufferAlloc(aLen, 0, 'utf8');
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bufA.write(strA);
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var bufB = bufferAlloc(aLen, 0, 'utf8');
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bufB.write(strB);
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return crypto.timingSafeEqual(bufA, bufB) && aLen === bLen;
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};
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module.exports = (
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typeof crypto.timingSafeEqual !== 'undefined' ?
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nativeTimingSafeEqual :
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safeCompare
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);
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