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From: "Jorge Timón" <jtimon@jtimon.cc>
To: "Russell O'Connor" <roconnor@blockstream.io>,
	 Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Cc: Steve Davis <steven.charles.davis@gmail.com>
Subject: Re: [bitcoin-dev] Script Abuse Potential?
Date: Wed, 4 Jan 2017 15:45:54 +0100	[thread overview]
Message-ID: <CABm2gDr-8h6EszsKRpJq6OCNnTUjmPvN_K3pYzyeNT3z2Lu94w@mail.gmail.com> (raw)
In-Reply-To: <CAMZUoK=-3dGapPQTfKdd4oMQukiTyN1v123Yjo4ihO6YOHuBZQ@mail.gmail.com>

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I would assume that the controversial part of op_cat comes from the fact
that it enables covenants. Are there more concerns than that?

On 4 Jan 2017 04:14, "Russell O'Connor via bitcoin-dev" <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> For the record, the OP_CAT limit of 520 bytes was added by Satoshi
> <https://github.com/bitcoin/bitcoin/commit/4bd188c4383d6e614e18f79dc337fbabe8464c82#diff-8458adcedc17d046942185cb709ff5c3R425>
> on the famous August 15, 2010 "misc" commit, at the same time that OP_CAT
> was disabled.
> The previous limit was 5000 bytes.
>
> On Tue, Jan 3, 2017 at 7:13 PM, Jeremy via bitcoin-dev <bitcoin-dev@lists.
> linuxfoundation.org> wrote:
>
>> Sure, was just upper bounding it anyways. Even less of a problem!
>>
>>
>> RE: OP_CAT, not as OP_CAT was specified, which is why it was disabled. As
>> far as I know, the elements alpha proposal to reenable a limited op_cat to
>> 520 bytes is somewhat controversial...
>>
>>
>>
>> --
>> @JeremyRubin <https://twitter.com/JeremyRubin>
>> <https://twitter.com/JeremyRubin>
>>
>> On Mon, Jan 2, 2017 at 10:39 PM, Johnson Lau <jl2012@xbt.hk> 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 <
>>> bitcoin-dev@lists.linuxfoundation.org> 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.
>>>>
>>>>
>>>> _______________________________________________
>>>> bitcoin-dev mailing list
>>>> bitcoin-dev@lists.linuxfoundation.org
>>>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>>>
>>>>
>>> _______________________________________________
>>> bitcoin-dev mailing list
>>> bitcoin-dev@lists.linuxfoundation.org
>>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>>
>>>
>>>
>>
>> _______________________________________________
>> bitcoin-dev mailing list
>> bitcoin-dev@lists.linuxfoundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>
>>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>

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  reply	other threads:[~2017-01-04 14:45 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <mailman.11263.1483391161.31141.bitcoin-dev@lists.linuxfoundation.org>
2017-01-02 21:39 ` [bitcoin-dev] Script Abuse Potential? Steve Davis
2017-01-03  3:27   ` Jeremy
2017-01-03  3:39     ` Johnson Lau
2017-01-03  5:04       ` Russell O'Connor
2017-01-04  0:13       ` Jeremy
2017-01-04  3:13         ` Russell O'Connor
2017-01-04 14:45           ` Jorge Timón [this message]
2017-01-05 16:22             ` Jeremy

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