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Patch fixes prototype pollution issue #17 #19

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Patch fixes prototype pollution issue #17 #19

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2f239a0
Fix as proposed by Johns Hopkins researchers
Jan 14, 2022
af6fadd
actually modify the key value
Jan 14, 2022
2ee55b4
Merge pull request #1 from clearbit/tom/johns-hopkins-prototype-pollu…
Jan 14, 2022
5553a56
use indexOf instead of includes for better compatibility (#2)
davidlumley Jan 14, 2022
8e875c2
ensure when we assign to `obj` that we use the sanitized key (#3)
davidlumley Jan 15, 2022
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25 changes: 21 additions & 4 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,22 @@ var decode = function(str) {
}
}

/**
* Ensure any potential prototype pollution can be sanitized.
*
* @param {String} str
* @return {String}
* @api public
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This is not part of the public API.

Suggested change
* @api public
* @api private

*/

var sanitizeObjKey = function(str) {
if (str && ["__proto__", "constructor", "prototype"].indexOf(str.toLowerCase()) > -1) {
return str.toUpperCase()
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Why convert to uppercase? If the user (for some weird reason) wanted the value of prototype, they'd get PROTOTYPE instead, which would either return unexpected (incorrect) results or undefined. Consider the following:

var q = querystring.parse('prototype=hi&PROTOTYPE=bye')
console.log(q.prototype)
// => bye
console.log(q.PROTOTYPE)
// => bye

IMO we should either error or return undefined.

}

return str;
}

/**
* Parse the given query `str`.
*
Expand All @@ -59,16 +75,17 @@ exports.parse = function(str){
var pairs = str.split('&');
for (var i = 0; i < pairs.length; i++) {
var parts = pairs[i].split('=');
var key = decode(parts[0]);
var key = sanitizeObjKey(decode(parts[0]));
var m;

if (m = pattern.exec(key)) {
obj[m[1]] = obj[m[1]] || [];
obj[m[1]][m[2]] = decode(parts[1]);
var objectKey = sanitizeObjKey(m[1])
obj[objectKey] = obj[objectKey] || [];
obj[objectKey][m[2]] = decode(parts[1]);
continue;
}

obj[parts[0]] = null == parts[1]
obj[key] = null == parts[1]
? ''
: decode(parts[1]);
}
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