generate ecdsa public key from an input public key

[richard-ramos]

No description provided.

[marten-seemann]

This is not incorrect, but where do we need this? We don't have a corresponding method for RSA, for example.

[richard-ramos]

I created this function because currently I'm working on a project where I need to generate a peer.ID using a known ecdsa public key, and found that there was no way to initialize a ECDSAPublicKey from a ecdsa.PublicKey. With this PR I could do something like this:

pubKey, err := ECDSAPublicKeyFromPubKey(someECDSAPubKey)
thePeerId, err := peer.IDFromPublicKey(pubKey)

Should I implement a similar function for RSA and Ed25519 too?

[marten-seemann]

I created this function because currently I'm working on a project where I need to generate a peer.ID using a known ecdsa public key, and found that there was no way to initialize a ECDSAPublicKey from a ecdsa.PublicKey.

Ok, that's legit.

Should I implement a similar function for RSA and Ed25519 too?

No need to.

Can we have a test please?

[richard-ramos]

I've added the required test

[aschmahmann]

From some conversation during triage:

It is likely better to dereference they key before it's passed in to reduce the likelihood of hard to track down bugs. Also the keys aren't too big

[Jorropo]

For context, the bug I see here is that someone could pass a key into it and since it's by reference modify it while libp2p is using it (libp2p expects key to be constant and not change).

If it's passed by value then a copy is made and this can't happen.

Suggested change

	func ECDSAPublicKeyFromPubKey(pub *ecdsa.PublicKey) (PubKey, error) {
	if pub == nil {
	return nil, ErrNilPublicKey
	}
	return &ECDSAPublicKey{pub}, nil
	}
	func ECDSAPublicKeyFromPubKey(pub ecdsa.PublicKey) (PubKey, error) {
	return &ECDSAPublicKey{pub:&pub}, nil
	}

[richard-ramos]

Thank you for the code review, @aschmahmann and @Jorropo . I have done the requested changes.

Should I open a separate PR for doing the same change in here?:

// ECDSAKeyPairFromKey generates a new ecdsa private and public key from an input private key
func ECDSAKeyPairFromKey(priv *ecdsa.PrivateKey) (PrivKey, PubKey, error) {
	if priv == nil {
		return nil, nil, ErrNilPrivateKey
	}

	return &ECDSAPrivateKey{priv}, &ECDSAPublicKey{&priv.PublicKey}, nil
}

[Jorropo]

@richard-ramos no you should rebase or amend commit.

First, on your ecdsa-pubkey branch create a commit fixing that and do a git rebase -i master and read the comments, you will want to fixup the new commit second commit into the first one, then we can git push --force this branch.

This will change this PR to a new commit that is just like you did it right the first time (sometime you want to do "history" based commits so you would just make a new commit on top of the old one and explain your thought process in the commit description, for something that small it's obvious you can just force push).

[richard-ramos]

@Jorropo but i did rebase this PR. Notice it's only a single commit containing the suggested changes