Prevent arbitrary js code execution #16
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primeare
reviewed
May 16, 2022
lib/sheet.js
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| @@ -2,8 +2,15 @@ | |||
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| const metavm = require('metavm'); | |||
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| const math = new Proxy(Math, { | |||
| get: (target, prop) => { | |||
| if (prop === 'constructor') return null; | |||
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Unfortunately, it is still possible to do such a thing:
sheet.cells['A1'] = '=Math.ceil.constructor("console.log(process)")()';
console.log(sheet.values['A1']);And even this:
sheet.cells['A1'] = '=Math.ceil.constructor("console.log(process.mainModule.require(\'fs\').readFileSync(\'./metacalc.js\', \'utf-8\'))")()';I will take a closer look today at what we can do to overcome this issue.
primeare
reviewed
May 16, 2022
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One pitfall of the implemented fix I can see now is that constant values such as Math.PI are no longer available. Accessing them leads to an exception. I don't know if they need to be exposed.
Moreover, I would suggest that fields data, expressions and context of class Sheet should be private and not accessible from the user-land.
primeare
approved these changes
May 16, 2022
tshemsedinov
added a commit
that referenced
this pull request
May 17, 2022
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Thank to @primeare for reporting this security issue
npm t)npm run fmt)