clerkzhang / siwe-py

A Python implementation of Sign-In with Ethereum

Sign-In with Ethereum

This package provides a Python implementation of EIP-4631: Sign In With Ethereum.

Installation

SIWE can be easily installed in any Python project with pip:

pip install siwe

Usage

SIWE provides a SiweMessage class which implements EIP-4361.

Parsing a SIWE Message

Parsing is done by initializing a SiweMessage object with an EIP-4361 formatted string:

from siwe import SiweMessage
message: SiweMessage = SiweMessage(message=eip_4361_string)

Alternatively, initialization of a SiweMessage object can be done with a dictionary containing expected attributes:

message: SiweMessage = SiweMessage(message={"domain": "login.xyz", "address": "0x1234...", ...})

Verifying and Authenticating a SIWE Message

Verification and authentication is performed via EIP-191, using the address field of the SiweMessage as the expected signer. The validate method checks message structural integrity, signature address validity, and time-based validity attributes.

try:
    message.verify(signature="0x...")
    # You can also specify other checks (e.g. the nonce or domain expected).
except siwe.ValidationError:
    # Invalid

Serialization of a SIWE Message

SiweMessage instances can also be serialized as their EIP-4361 string representations via the prepare_message method:

print(message.prepare_message())

Example

Parsing and verifying a SiweMessage is easy:

try:
    message: SiweMessage = SiweMessage(message=eip_4361_string)
    message.verify(signature, nonce="abcdef", domain="example.com"):
except siwe.ValueError:
    # Invalid message
    print("Authentication attempt rejected.")
except siwe.ExpiredMessage:
    print("Authentication attempt rejected.")
except siwe.DomainMismatch:
    print("Authentication attempt rejected.")
except siwe.NonceMismatch:
    print("Authentication attempt rejected.")
except siwe.MalformedSession as e:
    # e.missing_fields contains the missing information needed for validation
    print("Authentication attempt rejected.")
except siwe.InvalidSignature:
    print("Authentication attempt rejected.")

# Message has been verified. Authentication complete. Continue with authorization/other.

Testing

poetry install
git submodule update --init
poetry run pytest

See Also

• Sign-In with Ethereum: TypeScript
• Example SIWE application: login.xyz
• EIP-4361 Specification Draft
• EIP-191 Specification

Disclaimer

Our Python 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.