Subject: Re: [bitcoin-dev] Script Abuse Potential?

From: "Russell O'Connor" <[email-masked]>
Date: Tue, 3 Jan 2017 00:04:50 -0500

OP_2DUP?  Why not OP_3DUP?

On Mon, Jan 2, 2017 at 10:39 PM, Johnson Lau via bitcoin-dev <
[email-masked]> wrote:

> No, there could only have not more than 201 opcodes in a script. So you
> may have 198 OP_2DUP at most, i.e. 198 * 520 * 2 = 206kB
>
> For OP_CAT, just check if the returned item is within the 520 bytes limit.
>
> On 3 Jan 2017, at 11:27, Jeremy via bitcoin-dev <bitcoin-dev@lists.
> linuxfoundation.org> wrote:
>
> It is an unfortunate script, but can't actually
> ​do
>  that much
> ​ it seems​
> . The MAX_SCRIPT_ELEMENT_SIZE = 520 Bytes.
> ​ Thus, it would seem the worst you could do with this would be to (10000-520*2)*520*2
> bytes  ~=~ 10 MB.
>
> ​Much more concerning would be the op_dup/op_cat style bug, which under a
> similar script ​would certainly cause out of memory errors :)
>
>
>
> --
> @JeremyRubin <https://twitter.com/JeremyRubin>
> <https://twitter.com/JeremyRubin>
>
> On Mon, Jan 2, 2017 at 4:39 PM, Steve Davis via bitcoin-dev <
> [email-masked]> wrote:
>
>> Hi all,
>>
>> Suppose someone were to use the following pk_script:
>>
>> [op_2dup, op_2dup, op_2dup, op_2dup, op_2dup, ...(to limit)...,
>> op_2dup, op_hash160, <addr_hash>, op_equalverify, op_checksig]
>>
>> This still seems to be valid AFAICS, and may be a potential attack vector?
>>
>> Thanks.
>>
>>
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