Discourage unsigned / uncommitted annexes #10
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I've been thinking about the possibility of witness malleability if the annex becomes standard. As it stands, any script path spend that lacks a CHECKSIG can have an arbitrary amount of data placed in the annex by a third party.
A simple solution would be to make unsigned annexes non-standard. I implemented this by adding a
m_annex_committedfield toScriptExecutionData, which is only set totrueifCheckSchnorrSignatureexecutes successfully and an annex is present. I called this variablem_annex_committedrather thanm_annex_signedin case there is a future opcode that commits to the annex explicitly.@petertodd Do you think this is a good idea, if the annex is made standard? I'm not sure how common non-CHECKSIG scripts are today, but I imagine they could become more common if opcodes like CTV or CSFS are adopted in the future.