force assign geth's S256() as Curve value

[dai1975]

Fix S256() curve compare fails in docker enviroments.

https://github.com/ethereum/go-ethereum/blob/master/crypto/signature_nocgo.go#L82

[siburu]

@dai1975 Thank you, but why did you notice this issue?
It seems that any relayer built with nocgo (default) suffers this issue.
Then, why haven't test cases such as yui-relayer-build's tm2eth encountered with this issue until now?

Ah, I resolved it myself.
On typical Linux environments, go env returns CGO_ENABLED=1 by default.
In other words, nocgo is not the default setting, and so this issue has not surfaced.

[siburu]

The implementation is OK, but probably, this issue description is not accurate.
Since dcrd.secp256k1.S256() and gethcrypto.S256() are different objects, pointer comparison between them ALWAYS fails.

The real issue is implementation difference between signatrure_nocgo.go and signature_cgo.go in the go-ethereum/crypto package.
The former implementation requires prv.Curve == gethcrypto.S256() but the latter doesn't.
In typical environments, the latter implementation is chosen to build relayers, and so this issue doesn't pop up.
In some environments, like Docker containers with no C compilers installed, the former implementation is used.

Could you fix the comment?

[dai1975]

Thanks I did not understand real cause.
I've rewritten that comment.

[Copilot]

Pull Request Overview

This PR addresses an issue with comparing the S256() curve in docker environments by forcing the use of gethcrypto.S256() when necessary.

• Replaces direct return of btcecPrivKey.ToECDSA() with an intermediate assignment.
• Adds a conditional to reassign ecdsaPrivKey.Curve to gethcrypto.S256() if it does not match.

Comments suppressed due to low confidence (1)

pkg/wallet/wallet.go:134

• Comparing the curve by pointer equality after checking the name may be brittle if the underlying implementation changes. Consider caching the gethcrypto.S256() value in a local variable to improve clarity and ensure consistent comparisons.

if ecdsaPrivKey.Curve.Params().Name == "secp256k1" && ecdsaPrivKey.Curve != gethcrypto.S256() {

[siburu]

@dai1975 LGTM!