path: root/d3/db9677635bd5353342c18a17bdadb8c65b8b3a

Return-Path: <jtimon@jtimon.cc>
Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org
	[172.17.192.35])
	by mail.linuxfoundation.org (Postfix) with ESMTPS id D596DB3E
	for <bitcoin-dev@lists.linuxfoundation.org>;
	Wed,  4 Jan 2017 14:45:56 +0000 (UTC)
X-Greylist: whitelisted by SQLgrey-1.7.6
Received: from mail-ua0-f181.google.com (mail-ua0-f181.google.com
	[209.85.217.181])
	by smtp1.linuxfoundation.org (Postfix) with ESMTPS id DD1D8108
	for <bitcoin-dev@lists.linuxfoundation.org>;
	Wed,  4 Jan 2017 14:45:55 +0000 (UTC)
Received: by mail-ua0-f181.google.com with SMTP id i68so247384687uad.0
	for <bitcoin-dev@lists.linuxfoundation.org>;
	Wed, 04 Jan 2017 06:45:55 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
	d=jtimon-cc.20150623.gappssmtp.com; s=20150623;
	h=mime-version:in-reply-to:references:from:date:message-id:subject:to
	:cc; bh=EomjKsUL6ta0ZOzOWC4/GcdT8VnodX90+CseSxd3UyY=;
	b=aUl/Tm3sTc+ZkI7Zjl6bOTF5VdI8CL8fG9jtULi6TwLSshKujO9sIY2mXpnvuM24+v
	3SeOdqnCUtX98bERfLMOiv+mL06QHKWbQuQQoGrU4giqTb+DW5A2VPDouRDar020+SgB
	6xTVHft6BlX+uc8rq+08C3as05/qlDR8GZLaqYhV9OvRgQexy+dtOiiLIMw8FQ92pxpf
	TET/TS2QvfKBIIDwdtdUhDkiJR4xapTOpVGsaIzuTgfUPssIfsEOOrTv6clEZ1Y5jZGf
	eoBUAHFP2Wwr5cSdiFDyGKd5AOWs64kqLKhD/HlxjxwyD4Ar6D2L1PBDLHB12G0QlNP4
	LWrg==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
	d=1e100.net; s=20161025;
	h=x-gm-message-state:mime-version:in-reply-to:references:from:date
	:message-id:subject:to:cc;
	bh=EomjKsUL6ta0ZOzOWC4/GcdT8VnodX90+CseSxd3UyY=;
	b=FbnwnbCnXXqzZMMKJ0zI6d5LuOpVuGputr8tgFiPEfGBLck5yZXMVE5GDcUB+GJZwN
	5yA0Xuwaa7qeKlynKHDWZCyxSvezNn0e2UXBZPBOcj65zFlKWq3Iiz0qzzOqeUZFvJJ4
	SFc5fZXWd/9m9BNHIbMWYSg8yddfMJBaNLmagIwi/nNHJpV+UMyxfRbVpWm8O7TfTKba
	QdgFTRMFSbFL7xXR9Q4j1bGsD5+i68SD1uoyTikhiLYFa+/xn6RjUozMNkiJqBOUK95B
	4aEjCL0rOedstJ4H1DNbRH9ctDEIT7nwOWesVBZtFEkMDKq9DxXqQuZxDRvgpqgv+SWw
	dG+A==
X-Gm-Message-State: AIkVDXIMZa8zDuJhxnY+J9m7hcIuMWC2IlEo9XwHayVFoRQiBLvc9Ys1rV8kS9qksiJ+E4J4lsyc/8hgvhywMw==
X-Received: by 10.176.84.8 with SMTP id n8mr49944915uaa.29.1483541154889; Wed,
	04 Jan 2017 06:45:54 -0800 (PST)
MIME-Version: 1.0
Received: by 10.31.216.130 with HTTP; Wed, 4 Jan 2017 06:45:54 -0800 (PST)
Received: by 10.31.216.130 with HTTP; Wed, 4 Jan 2017 06:45:54 -0800 (PST)
In-Reply-To: <CAMZUoK=-3dGapPQTfKdd4oMQukiTyN1v123Yjo4ihO6YOHuBZQ@mail.gmail.com>
References: <mailman.11263.1483391161.31141.bitcoin-dev@lists.linuxfoundation.org>
	<400152B9-1838-432A-829E-13E4FC54320C@gmail.com>
	<CAD5xwhjHFzFzKws10TG-XioZoRVZ_oZbMF_xDOy5xNWtzFTsEw@mail.gmail.com>
	<6A91D4E4-750D-42C0-B593-3D5014B8A3F7@xbt.hk>
	<CAD5xwhg3QeHZF1Oepo3dnCAth0EO3wCqyeT4a21gQ2uxZ5dTfQ@mail.gmail.com>
	<CAMZUoK=-3dGapPQTfKdd4oMQukiTyN1v123Yjo4ihO6YOHuBZQ@mail.gmail.com>
From: =?UTF-8?B?Sm9yZ2UgVGltw7Nu?= <jtimon@jtimon.cc>
Date: Wed, 4 Jan 2017 15:45:54 +0100
Message-ID: <CABm2gDr-8h6EszsKRpJq6OCNnTUjmPvN_K3pYzyeNT3z2Lu94w@mail.gmail.com>
To: "Russell O'Connor" <roconnor@blockstream.io>, 
	Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Content-Type: multipart/alternative; boundary=94eb2c1b2d7e8c6e61054545d70e
X-Spam-Status: No, score=-1.4 required=5.0 tests=BAYES_00,DKIM_SIGNED,
	DKIM_VALID, HTML_MESSAGE, RCVD_IN_DNSWL_NONE,
	RCVD_IN_SORBS_SPAM autolearn=no version=3.3.1
X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on
	smtp1.linux-foundation.org
Cc: Steve Davis <steven.charles.davis@gmail.com>
Subject: Re: [bitcoin-dev] Script Abuse Potential?
X-BeenThere: bitcoin-dev@lists.linuxfoundation.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Bitcoin Protocol Discussion <bitcoin-dev.lists.linuxfoundation.org>
List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/bitcoin-dev>,
	<mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=unsubscribe>
List-Archive: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/>
List-Post: <mailto:bitcoin-dev@lists.linuxfoundation.org>
List-Help: <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=help>
List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>,
	<mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=subscribe>
X-List-Received-Date: Wed, 04 Jan 2017 14:45:57 -0000

--94eb2c1b2d7e8c6e61054545d70e
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

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/4bd188c4383d6e614e18f79dc337fb=
abe8464c82#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. A=
s
>> 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 =3D 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
>>> =E2=80=8Bdo
>>>  that much
>>> =E2=80=8B it seems=E2=80=8B
>>> . The MAX_SCRIPT_ELEMENT_SIZE =3D 520 Bytes.
>>> =E2=80=8B Thus, it would seem the worst you could do with this would be=
 to (10000-520*2)*520*2
>>> bytes  ~=3D~ 10 MB.
>>>
>>> =E2=80=8BMuch more concerning would be the op_dup/op_cat style bug, whi=
ch under
>>> a similar script =E2=80=8Bwould 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
>
>

--94eb2c1b2d7e8c6e61054545d70e
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

<div dir=3D"auto">I would assume that the controversial part of op_cat come=
s from the fact that it enables covenants. Are there more concerns than tha=
t?</div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On 4 Jan =
2017 04:14, &quot;Russell O&#39;Connor via bitcoin-dev&quot; &lt;<a href=3D=
"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.linuxfound=
ation.org</a>&gt; wrote:<br type=3D"attribution"><blockquote class=3D"gmail=
_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:=
1ex"><div dir=3D"ltr"><div>For the record, the OP_CAT limit of 520 bytes wa=
s <a href=3D"https://github.com/bitcoin/bitcoin/commit/4bd188c4383d6e614e18=
f79dc337fbabe8464c82#diff-8458adcedc17d046942185cb709ff5c3R425" target=3D"_=
blank">added by Satoshi</a> on the famous August 15, 2010 &quot;misc&quot; =
commit, at the same time that OP_CAT was disabled.<br></div>The previous li=
mit was 5000 bytes.<br><div><div class=3D"gmail_extra"><br><div class=3D"gm=
ail_quote">On Tue, Jan 3, 2017 at 7:13 PM, Jeremy via bitcoin-dev <span dir=
=3D"ltr">&lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" targe=
t=3D"_blank">bitcoin-dev@lists.<wbr>linuxfoundation.org</a>&gt;</span> wrot=
e:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-l=
eft:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div style=3D"font-fa=
mily:arial,helvetica,sans-serif;font-size:small;color:#000000">Sure, was ju=
st upper bounding it anyways. Even less of a problem!</div><div style=3D"fo=
nt-family:arial,helvetica,sans-serif;font-size:small;color:#000000"><br></d=
iv><div style=3D"font-family:arial,helvetica,sans-serif;font-size:small;col=
or:#000000"><br></div><div style=3D"font-family:arial,helvetica,sans-serif;=
font-size:small;color:#000000">RE: OP_CAT, not as OP_CAT was specified, whi=
ch 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...</div><=
div style=3D"font-family:arial,helvetica,sans-serif;font-size:small;color:#=
000000"><br></div><div style=3D"font-family:arial,helvetica,sans-serif;font=
-size:small;color:#000000"><br></div><div class=3D"gmail_extra"><br clear=
=3D"all"><div><div class=3D"m_7822325097514973326m_6723432281491834920m_-62=
03106839964574959gmail_signature" data-smartmail=3D"gmail_signature"><div d=
ir=3D"ltr">--<br><a href=3D"https://twitter.com/JeremyRubin" target=3D"_bla=
nk">@JeremyRubin</a><a href=3D"https://twitter.com/JeremyRubin" target=3D"_=
blank"></a></div></div></div><div><div class=3D"m_7822325097514973326h5">
<br><div class=3D"gmail_quote">On Mon, Jan 2, 2017 at 10:39 PM, Johnson Lau=
 <span dir=3D"ltr">&lt;<a href=3D"mailto:jl2012@xbt.hk" target=3D"_blank">j=
l2012@xbt.hk</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" sty=
le=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div s=
tyle=3D"word-wrap:break-word"><div>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 * 52=
0 * 2 =3D 206kB</div><div><br></div><div>For OP_CAT, just check if the retu=
rned item is within the 520 bytes limit.</div><div><div class=3D"m_78223250=
97514973326m_6723432281491834920m_-6203106839964574959h5"><br><div><blockqu=
ote type=3D"cite"><div>On 3 Jan 2017, at 11:27, Jeremy via bitcoin-dev &lt;=
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank">=
bitcoin-dev@lists.linuxfounda<wbr>tion.org</a>&gt; wrote:</div><br class=3D=
"m_7822325097514973326m_6723432281491834920m_-6203106839964574959m_65987160=
0986875938Apple-interchange-newline"><div><div dir=3D"ltr"><div style=3D"fo=
nt-family:arial,helvetica,sans-serif;font-size:small"><span style=3D"font-f=
amily:arial,sans-serif;color:rgb(34,34,34);font-size:12.800000190734863px">=
It is an unfortunate script, but can&#39;t actually=C2=A0</span><div style=
=3D"display:inline">=E2=80=8Bdo</div><span style=3D"font-family:arial,sans-=
serif;color:rgb(34,34,34);font-size:12.800000190734863px">=C2=A0that much</=
span><div style=3D"display:inline">=E2=80=8B it seems=E2=80=8B</div><span s=
tyle=3D"font-family:arial,sans-serif;color:rgb(34,34,34);font-size:12.80000=
0190734863px">. The MAX_SCRIPT_ELEMENT_SIZE =3D 520 Bytes.</span><div style=
=3D"font-family:arial,sans-serif;color:rgb(34,34,34);font-size:12.800000190=
734863px;display:inline"><font face=3D"arial, helvetica, sans-serif">=E2=80=
=8B Thus, it would seem the worst you could do with this would be to=C2=A0<=
/font>(10000-520*2)*520*2 bytes =C2=A0~=3D~ 10 MB.</div></div><div style=3D=
"font-size:12.800000190734863px"><br></div><div style=3D"font-size:12.80000=
0190734863px"><div style=3D"font-family:arial,helvetica,sans-serif;font-siz=
e:small">=E2=80=8BMuch more concerning would be the op_dup/op_cat style bug=
, which under a similar script =E2=80=8Bwould certainly cause out of memory=
 errors :)</div><div><br></div></div></div><div class=3D"gmail_extra"><br c=
lear=3D"all"><div><br clear=3D"all"><div><div class=3D"m_782232509751497332=
6m_6723432281491834920m_-6203106839964574959m_659871600986875938gmail_signa=
ture" data-smartmail=3D"gmail_signature"><div dir=3D"ltr">--<br><a href=3D"=
https://twitter.com/JeremyRubin" target=3D"_blank">@JeremyRubin</a><a href=
=3D"https://twitter.com/JeremyRubin" target=3D"_blank"></a></div></div></di=
v>
</div>
<br><div class=3D"gmail_quote">On Mon, Jan 2, 2017 at 4:39 PM, Steve Davis =
via bitcoin-dev <span dir=3D"ltr">&lt;<a href=3D"mailto:bitcoin-dev@lists.l=
inuxfoundation.org" target=3D"_blank">bitcoin-dev@lists.linuxfounda<wbr>tio=
n.org</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"m=
argin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style=3D=
"word-wrap:break-word"><div><div style=3D"color:rgb(34,34,34);font-family:a=
rial,sans-serif;font-size:12.800000190734863px">Hi all,</div><div style=3D"=
color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8000001907348=
63px"><br></div><div style=3D"color:rgb(34,34,34);font-family:arial,sans-se=
rif;font-size:12.800000190734863px">Suppose someone were to use the followi=
ng pk_script:</div><div style=3D"color:rgb(34,34,34);font-family:arial,sans=
-serif;font-size:12.800000190734863px"><br></div><div class=3D"m_7822325097=
514973326m_6723432281491834920m_-6203106839964574959m_659871600986875938m_-=
8615729711671762748m_8591747901013163489gmail_signature" style=3D"color:rgb=
(34,34,34);font-family:arial,sans-serif;font-size:12.800000190734863px"><di=
v dir=3D"ltr">[op_2dup, op_2dup, op_2dup, op_2dup, op_2dup, ...(to limit)..=
., op_2dup,=C2=A0op_hash160, &lt;addr_hash&gt;, op_equalverify, op_checksig=
]</div><div dir=3D"ltr"><br></div><div>This still seems to be valid AFAICS,=
 and may be a potential attack vector?</div><div><br></div><div>Thanks.</di=
v></div></div><div><br></div></div><br>______________________________<wbr>_=
________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank">=
bitcoin-dev@lists.linuxfoundat<wbr>ion.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.<wbr>org=
/mailman/listinfo/bitcoin-d<wbr>ev</a><br>
<br></blockquote></div><br></div>
______________________________<wbr>_________________<br>bitcoin-dev mailing=
 list<br><a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D=
"_blank">bitcoin-dev@lists.linuxfoundat<wbr>ion.org</a><br><a href=3D"https=
://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" target=3D"_blank=
">https://lists.linuxfoundation.<wbr>org/mailman/listinfo/bitcoin-d<wbr>ev<=
/a><br></div></blockquote></div><br></div></div></div></blockquote></div><b=
r></div></div></div></div>
<br>______________________________<wbr>_________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank">=
bitcoin-dev@lists.linuxfoundat<wbr>ion.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.<wbr>org=
/mailman/listinfo/bitcoin-d<wbr>ev</a><br>
<br></blockquote></div><br></div></div></div>
<br>______________________________<wbr>_________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.=
<wbr>linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.<wbr>org=
/mailman/listinfo/bitcoin-<wbr>dev</a><br>
<br></blockquote></div></div>

--94eb2c1b2d7e8c6e61054545d70e--