Bitcoinjs-lib: BIP143 rejects uncompressed public keys in P2WPKH or P2WSH

[mandelmonkey]

Not sure if I am misunderstanding something here but does this not only check if the output is p2wpkh and not p2wsh as well?

i.e. is correct?

if (kpPubKey.length !== 33 &&
      (input.signType === scriptTypes.P2WPKH || input.signType === scriptTypes.P2WSH)) throw new Error('BIP143 rejects uncompressed public keys in P2WPKH or P2WSH')

https://github.com/bitcoinjs/bitcoinjs-lib/blob/86cd4a44a1524686d993f35b02a1ed331aaa551f/src/transaction_builder.js#L709

[dabura667]

This covers all templates handled by TransactionBuilder, so multisig is also checked. That’s why input.pubkeys and input.signatures are arrays

[dcousens]

@mandelmonkey could you elaborate on your question?

[dabura667]

I think what he means is:

Segwit enforces compressed public keys for ALL instances of pubkeys in the witness stack. Multisig and single sig.

His question is: It looks like this one line is only checking for single sig. allowing multisig segwit with uncompressed pubkeys to pass and make an invalid transaction. Is he right in his assessment that this is a bug, or are we checking somewhere else and he doesn’t notice it?

[mandelmonkey]

Hi guys
its probably my misunderstanding! but the following line in my mind checks if the pubkey is uncompressed and if it is it checks if the script type is p2wpkh, if so it throws an error because uncompressed public keys keys are not supported with segwot.

if (kpPubKey.length !== 33 && input.signType === scriptTypes.P2WPKH) throw new Error('BIP143 rejects uncompressed public keys in P2WPKH or P2WSH')

however the comment says "in P2WPKH or P2WSH" but the if statement is only checking if the script type is p2wpkh and not p2wsh as well.

thats where I got confused

[dcousens]

Will add a test case

[dcousens]

Closing in favour of https://github.com/bitcoinjs/bitcoinjs-lib/pull/987