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Don't replace regex / function placeholders within string literals #79

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May 20, 2020
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25 changes: 22 additions & 3 deletions index.js
Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,12 @@ See the accompanying LICENSE file for terms.

'use strict';

var randomBytes = require('randombytes');

// Generate an internal UID to make the regexp pattern harder to guess.
var UID = Math.floor(Math.random() * 0x10000000000).toString(16);
var PLACE_HOLDER_REGEXP = new RegExp('"@__(F|R|D|M|S|U|I)-' + UID + '-(\\d+)__@"', 'g');
var UID_LENGTH = 16;
var UID = generateUID();
var PLACE_HOLDER_REGEXP = new RegExp('(\\\\)?"@__(F|R|D|M|S|U|I)-' + UID + '-(\\d+)__@"', 'g');

var IS_NATIVE_CODE_REGEXP = /\{\s*\[native code\]\s*\}/g;
var IS_PURE_FUNCTION = /function.*?\(/;
Expand All @@ -31,6 +34,15 @@ function escapeUnsafeChars(unsafeChar) {
return ESCAPED_CHARS[unsafeChar];
}

function generateUID() {
var bytes = randomBytes(UID_LENGTH);
var result = '';
for(var i=0; i<UID_LENGTH; ++i) {
result += bytes[i].toString(16);
}
return result;
}

function deleteFunctions(obj){
var functionKeys = [];
for (var key in obj) {
Expand Down Expand Up @@ -187,7 +199,14 @@ module.exports = function serialize(obj, options) {
// Replaces all occurrences of function, regexp, date, map and set placeholders in the
// JSON string with their string representations. If the original value can
// not be found, then `undefined` is used.
return str.replace(PLACE_HOLDER_REGEXP, function (match, type, valueIndex) {
return str.replace(PLACE_HOLDER_REGEXP, function (match, backSlash, type, valueIndex) {
// The placeholder may not be preceded by a backslash. This is to prevent
// replacing things like `"a\"@__R-<UID>-0__@"` and thus outputting
// invalid JS.
if (backSlash) {
return match;
}

if (type === 'D') {
return "new Date(\"" + dates[valueIndex].toISOString() + "\")";
}
Expand Down
11 changes: 9 additions & 2 deletions package-lock.json

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3 changes: 3 additions & 0 deletions package.json
Original file line number Diff line number Diff line change
Expand Up @@ -29,5 +29,8 @@
"chai": "^4.1.0",
"mocha": "^7.0.0",
"nyc": "^15.0.0"
},
"dependencies": {
"randombytes": "^2.1.0"
}
}
27 changes: 27 additions & 0 deletions test/unit/serialize.js
Original file line number Diff line number Diff line change
@@ -1,9 +1,23 @@
/* global describe, it, beforeEach */
'use strict';

// temporarily monkeypatch `crypto.randomBytes` so we'll have a
// predictable UID for our tests
var crypto = require('crypto');
var oldRandom = crypto.randomBytes;
crypto.randomBytes = function(len, cb) {
var buf = Buffer.alloc(len);
buf.fill(0x00);
if (cb)
cb(null, buf);
return buf;
};

var serialize = require('../../'),
expect = require('chai').expect;

crypto.randomBytes = oldRandom;

describe('serialize( obj )', function () {
it('should be a function', function () {
expect(serialize).to.be.a('function');
Expand Down Expand Up @@ -493,4 +507,17 @@ describe('serialize( obj )', function () {
expect(serialize([1], 2)).to.equal('[\n 1\n]');
});
});

describe('placeholders', function() {
it('should not be replaced within string literals', function () {
// Since we made the UID deterministic this should always be the placeholder
var fakePlaceholder = '"@__R-0000000000000000-0__@';
var serialized = serialize({bar: /1/i, foo: fakePlaceholder}, {uid: 'foo'});
var obj = eval('(' + serialized + ')');
expect(obj).to.be.a('Object');
expect(obj.foo).to.be.a('String');
expect(obj.foo).to.equal(fakePlaceholder);
});
});

});