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 <jl2...@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 > >
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