Generate counter signatures

[balena-zh]

What is the areas you would like to add the new feature to?

Go-COSE Library

Is your feature request related to a problem?

• One willing to attribute counter signatures to either COSE_Sign1 or COSE_Sign will not find a way except fork the project and write alternative toBeSigned functions.

What solution do you propose?

• Extend the current Signature struct adding a CounterSign(rand io.Reader, signer Signer, protected cbor.RawMessage, payload, external []byte) error so that the toBeSigned function receives also a context parameter that can be "Signature" or "CounterSignature".

Above supports recursive counter signatures, where a counter signature also contains a counter signature.

What alternatives have you considered?

• I considered implementing an external package extending go-cose but I had to copy-paste many private functions, such as toBeSigned, deterministicBinaryString, marshal, ensureIV, ensureSigningAlgorithm, and ensureVerificationAlgorithm, along with global variables encMode, decMode, decModeWithTagsForbidden and the init() function.

Any additional context?

No response

[balena]

Started to add such support in #172

[balena]

Now #172 has been merged you may want to close this one @qmuntal

[SteveLasker]

Thanks, @balena, closing per comment above.