Any easy way to validate a function signature?

[slavik0329]

For example:

uint32 num1,address from,bool isTrue
should validate to true while

uAint8 num1,addressed to
should be false.

The only thing Ive found that does validation is the Abicoder encode function, however I have to provide values for it to work.

Thanks!

[ricmoo]

You need a bit more for a signature, but you could glue boiler plate around it, but you could use something like ethers.utils.FunctionFragment.from("transfer(address from, uint)" to use the human-readable parser. Or the ethers.utils.ParamTypr.from("uint blah") on each individual parameter. The former is more useful though, as it will determine individual components; do not simply spilt on the comma as nested structures can bite you and the FunctionFragment will figure that out for you...

[ricmoo]

See: https://docs.ethers.io/v5/api/utils/abi/fragments/

[slavik0329]

@ricmoo I tried this before. The problem is that it doesn’t verify that the types are valid when I create the fragments. It will create a fragment out of invalid types.

…

On Tue, Oct 13, 2020 at 4:58 PM Richard Moore ***@***.***> wrote: See: https://docs.ethers.io/v5/api/utils/abi/fragments/ — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1101 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAC4SBFTAG4GOOBJXNHG4RDSKS5NTANCNFSM4SPUDXJA> .

[slavik0329]

@ricmoo Heres an example:

It does not seem to do any type checking on the parameters.

[ricmoo]

Hmmm. It shouldn’t have done that, but now I realize I can’t change that in a backwards compatible way. It will be corrected in v6.

In the meantime, I should be able to get something together to help you verify signatures. I’m almost done EIP-712 and have 2 other things to get to, but there is something I wanted to get around to adjacent to what you are trying to solve. :)

[slavik0329]

@ricmoo Hey, have you had a chance to work on this? No big deal if not, just wondering.

[ricmoo]

Yes! I have something locally that I think will do exactly what you want. And be generally useful for now and the future... Just running a bit more testing on it first.

Basically, it will allow you to compute the default values for a given set of parameters. So, you can use it like this:

// Works:
const fragment = ethers.utils.FunctionFragment.from("transfer(uint32 num1,address from,bool isTrue)");
console.log(ethers.utils.defaultAbiCoder.getDefaultValue(fragment.inputs));
/*
[ 0,
  '0x0000000000000000000000000000000000000000',
  false,
  num1: 0,
  from: '0x0000000000000000000000000000000000000000',
  isTrue: false ]
*/

// Throws an Error:
const fragment = ethers.utils.FunctionFragment.from("transfer(uAint8 num1,addressed to)");
console.log(ethers.utils.defaultAbiCoder.getDefaultValue(fragment.inputs));

The CI system seems down right now, but let me know what you think and I'll try to get this out as soon as possible. :)

[ricmoo]

The above functionality has been added in 5.0.22.

Try it out and let me know if you have any problems.

Thanks! :)

[slavik0329]

@ricmoo Amazing! This is exactly what I was hoping for. Works great. Thank you so much for releasing this patch, it will be very useful to me and most likely many others!