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

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.

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