To make sure I'm understanding correctly, as long as the code verifies that
the given snipclass is in (get-the-snip-class-list), it should be
relatively safe? So the only way that the user would run malicious code in
this case is if they installed a malicious package first, in which case
there are easier ways to cause harm.
OTOH, when using the load-file method, the dynamic-require could be an
issue if a theoretical attacker put a .rkt file at a known path and the
input to load-file refers to that path.
Daniel
On Thursday, August 20, 2020 at 3:12:00 PM UTC-4 Robby Findler wrote:
> The issue I mention in 157 is different than this one.
>
> In this situation, the snipclass needs to be installed somehow before its
> code will be loaded, but that installation can happen by a require
> (triggered by the opening of that snip). So it may be that you have code
> installed in a collection that you do not trust and unmarshalling a snip
> may load that code.
>
> That said, in the code below, I don't think this is happening. In
> particular, the way that untrusted code may be loaded is because the name
> of the snipclass follows a specific format and the editor itself is going
> to do the require.
>
> In short, you can treat the `load-file` method of editor<%> as possibly
> doing a dynamic-require. This may or may not be a problem, of course.
>
> (At least I think that that's the only thing here. I may be forgetting
> something?)
>
> Robby
>
>
> On Thu, Aug 20, 2020 at 2:08 PM Sorawee Porncharoenwase <
> sorawe...@gmail.com> wrote:
>
>> I don't know much about this specific case, but see Robby's comment about
>> how "DrRacket can run user (untrusted) code in certain situations" at
>> https://github.com/racket/gui/issues/157. A concrete problem I found is
>> that you can have a snip running `struct->vector` and it will successfully
>> extract private fields of that struct value, even though it won't be able
>> to if you do that in normal circumstances.
>>
>> On Thu, Aug 20, 2020 at 8:34 AM Daniel Melcer wrote:
>>
>>> There are some well-known vulnerabilities that are a result of
>>> deserializing untrusted inputs. Are editor snips restrictive enough that
>>> their deserialization is safe? After all, they are already loaded when a
>>> file is opened in DrRacket, and a file on the disk may originate from an
>>> untrusted source. In particular, I would be doing something like this
>>> (snip-class-name, bytes, and snip-pos are from an untrusted source). The
>>> whole thing will be wrapped in an exception handler:
>>>
>>> (define snip-class (send (get-the-snip-class-list) find
>>> snip-class-name)) ; Also handle case where this returns #f
>>> (define bytes-base-in (make-object editor-stream-in-bytes-base%
>>> bytes))
>>> (define editor-stream-in (make-object editor-stream-in%
>>> bytes-base-in))
>>> (define new-snip (send snip-class read editor-stream-in))
>>> (send text insert new-snip snip-pos)
>>>
>>> Daniel
>>>
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