πŸ’¨
Go
A Go implementation of EIP-4361: Sign In With Ethereum.

Getting started

  • The Go implementation of Sign-In with Ethereum can be found here:
GitHub - spruceid/siwe-go: A Go implementation of EIP-4361 Sign In With Ethereum verification
GitHub

Installation

SIWE can be easily installed in any Go project by running:
go get -u github.com/spruceid/siwe-go

Usage

SIWE exposes a Message struct which implements EIP-4361.

Parsing a SIWE Message

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.

Verifying and Authenticating a SIWE Message

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 nonce variable to be matched against the
// built message struct being verified
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, optionalNonce, optionalTimestamp)
​
// If you won't be using nonce matching and want
// to verify the message at the current time, it's
// safe to pass `nil` in both arguments
publicKey, err = message.Verify(signature, nil, nil)

Serialization of a SIWE Message

Message instances can also be serialized as their EIP-4361 string representations via the String method:
fmt.Printf("%s", message.String())

Signing Messages from Go code

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
}
​
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Outline
Getting started
Installation
Usage
Signing Messages from Go code