Don't replace regex / function placeholders within string literals #79
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Previously we weren't checking if the quote that started the placeholder
was escaped or not, meaning an object like
{"foo": /1"/, "bar": "a\"@__R-<UID>-0__@"}
Would be serialized as
{"foo": /1"/, "bar": "a\/1"/}
meaning an attacker could escape out of `bar` if they controlled both
`foo` and `bar` and were able to guess the value of `<UID>`.
UID was generated once on startup, was chosen using `Math.random()` and
had a keyspace of roughly 4 billion, so within the realm of an online
attack.
Here's a simple example that will cause `console.log()` to be called when
the `serialize()`d version is `eval()`d
eval('('+ serialize({"foo": /1" + console.log(1)/i, "bar": '"@__R-<UID>-0__@'}) + ')');
Where `<UID>` is the guessed `UID`.
This fixes the issue by ensuring that placeholders are not preceded by
a backslash.
We also switch to a higher entropy `UID` to prevent people from guessing it.
credits JordanMilne (https://github.com/JordanMilne)
okuryu
reviewed
Apr 6, 2020
okuryu
approved these changes
May 20, 2020
|
Published |
This was referenced Mar 8, 2021
This was referenced Mar 16, 2021
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credits JordanMilne (https://github.com/JordanMilne) #22
I confirm that this contribution is made under the terms of the license found in the root directory of this repository's source tree and that I have the authority necessary to make this contribution on behalf of its copyright owner.
Based on Jordan's comment here I believe he gave approval and I approve any merging I did :)
#22 (comment)