This package provides a pure Go implementation of EIP-4361: Sign In With Ethereum.
SIWE can be easily installed in any Go project by running:
go get -u github.com/spruceid/siwe-goSIWE exposes a Message struct which implements EIP-4361.
Parsing is done via the siwe.ParseMessage function:
var message *siwe.Message
var err error
message, err = siwe.ParseMessage(messageStr)The function will return a nil pointer and an error if there was an issue while parsing.
Verification and Authentication is performed via EIP-191, using the address field of the Message as the expected signer. This returns the Ethereum public key of the signer:
var publicKey *ecdsa.PublicKey
var err error
publicKey, err = message.VerifyEIP191(signature)The time constraints (expiry and not-before) can also be validated, at current or particular times:
var message *siwe.Message
if message.ValidNow() {
// ...
}
// equivalent to
if message.ValidAt(time.Now().UTC()) {
// ...
}Combined verification of time constraints and authentication can be done in a single call with verify:
var publicKey *ecdsa.PublicKey
var err error
// Optional domain and nonce variable to be matched against the
// built message struct being verified
var optionalDomain *string
var optionalNonce *string
// Optional timestamp variable to verify at any point
// in time, by default it will use `time.Now()`
var optionalTimestamp *time.Time
publicKey, err = message.Verify(signature, optionalDomain, optionalNonce, optionalTimestamp)
// If you won't be using domain and nonce matching and want
// to verify the message at current time, it's
// safe to pass `nil` in these arguments
publicKey, err = message.Verify(signature, nil, nil, nil)Message instances can also be serialized as their EIP-4361
string representations via the String method:
fmt.Printf("%s", message.String())To sign messages directly from Go code, you will need to do it
like shown below to correctly follow the personal_sign format.
func signHash(data []byte) common.Hash {
msg := fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len(data), data)
return crypto.Keccak256Hash([]byte(msg))
}
func signMessage(message string, privateKey *ecdsa.PrivateKey) ([]byte, error) {
sign := signHash([]byte(message))
signature, err := crypto.Sign(sign.Bytes(), privateKey)
if err != nil {
return nil, err
}
signature[64] += 27
return signature, nil
}Our Go library for Sign-In with Ethereum has not yet undergone a formal security audit. We welcome continued feedback on the usability, architecture, and security of this implementation.