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Sign In With Ethereum

Web3Modal SDK provides a simple solution for integrating with "Sign In With Ethereum" (SIWE), a new form of authentication that enables users to control their digital identity with their Ethereum account. SIWE is a standard also known as EIP-4361.

NextAuth​

NextAuth is a complete open-source authentication solution for Next.js applications. It is designed from the ground up to support Next.js and Serverless. We can use NextAuth with SIWE to handle users authentication and sessions.

Installation​

Install the Web3Modal SIWE package, additionally we also recommend installing siwe and next-auth.

npm i @web3modal/siwe siwe next-auth

Configure your SIWE Client​

Let's create a file to instantiate our SIWE configuration. For this example we will use config/siwe.ts

import { getCsrfToken, signIn, signOut, getSession } from 'next-auth/react'

import { SiweMessage } from 'siwe'

import type { SIWEVerifyMessageArgs, SIWECreateMessageArgs } from '@web3modal/siwe'
import { createSIWEConfig } from '@web3modal/siwe'

export const siweConfig = createSIWEConfig({
  createMessage: ({ nonce, address, chainId }: SIWECreateMessageArgs) =>
    new SiweMessage({
      version: '1',
      domain: window.location.host,
      uri: window.location.origin,
      address,
      chainId,
      nonce,
      // Human-readable ASCII assertion that the user will sign, and it must not contain `\n`.
      statement: 'Sign in With Ethereum.'
    }).prepareMessage(),
  getNonce: async () => {
    const nonce = await getCsrfToken()
    if (!nonce) {
      throw new Error('Failed to get nonce!')
    }

    return nonce
  },
  getSession,
  verifyMessage: async ({ message, signature }: SIWEVerifyMessageArgs) => {
    try {
      const success = await signIn('credentials', {
        message,
        redirect: false,
        signature,
        callbackUrl: '/protected'
      })

      return Boolean(success?.ok)
    } catch (error) {
      return false
    }
  },
  signOut: async () => {
    try {
      await signOut({
        redirect: false
      })

      return true
    } catch (error) {
      return false
    }
  }
})

Initialize Web3Modal with your siweConfig.​

import { siweConfig } from '@/config/siwe'

createWeb3Modal({
  siweConfig,
  wagmiConfig, // or ethersConfig
  projectId,
  chains
})

Set up your API route​

Add NEXTAUTH_SECRET as an environment variable, it will be used to encrypt and decrypt user sessions. Learn more.

Create your API route at api/auth/[...nextauth]/route.ts inside the app directory.

import { NextAuthOptions } from 'next-auth'
import credentialsProvider from 'next-auth/providers/credentials'
import { getCsrfToken } from 'next-auth/react'
import NextAuth from 'next-auth/next'

import type { SIWESession } from '@web3modal/siwe'
import { SiweMessage } from 'siwe'

declare module 'next-auth' {
  interface Session extends SIWESession {
    address: string
    chainId: number
  }
}

const nextAuthSecret = process.env.NEXTAUTH_SECRET
if (!nextAuthSecret) {
  throw new Error('NEXTAUTH_SECRET is not set')
}
// Get your projectId on https://cloud.walletconnect.com
const projectId = process.env.NEXT_PUBLIC_PROJECT_ID
if (!projectId) {
  throw new Error('NEXT_PUBLIC_PROJECT_ID is not set')
}

const authOptions: NextAuthOptions = {
  // https://next-auth.js.org/configuration/providers/oauth
  secret: nextAuthSecret,
  providers: [
    credentialsProvider({
      name: 'Ethereum',
      credentials: {
        message: {
          label: 'Message',
          type: 'text',
          placeholder: '0x0'
        },
        signature: {
          label: 'Signature',
          type: 'text',
          placeholder: '0x0'
        }
      },
      async authorize(credentials, req) {
        try {
          if (!credentials?.message) {
            throw new Error('SiweMessage is undefined')
          }
          const siwe = new SiweMessage(credentials.message)
          const nonce = await getCsrfToken({ req: { headers: req.headers } })
          const result = await siwe.verify({
            signature: credentials?.signature || '',
            nonce
          })
          if (result.success) {
            return {
              id: `eip155:${siwe.chainId}:${siwe.address}`
            }
          }

          return null
        } catch (e) {
          return null
        }
      }
    })
  ],
  session: {
    strategy: 'jwt'
  },
  callbacks: {
    session({ session, token }) {
      if (!token.sub) {
        return session
      }

      const [, chainId, address] = token.sub.split(':')
      if (chainId && address) {
        session.address = address
        session.chainId = parseInt(chainId, 10)
      }

      return session
    }
  }
}

const handler = NextAuth(authOptions)
export { handler as GET, handler as POST }
Learn more about NextAuth

SIWE Config reference​

interface SIWEConfig {
  // Required
  getNonce: () => Promise<string>
  createMessage: (args: SIWECreateMessageArgs) => string
  verifyMessage: (args: SIWEVerifyMessageArgs) => Promise<boolean>
  getSession: () => Promise<SIWESession | null>
  signOut: () => Promise<boolean>

  // Optional
  onSignIn?: (session?: SIWESession) => void
  onSignOut?: () => void
  // Defaults to true
  enabled?: boolean
  // In milliseconds, defaults to 5 minutes
  nonceRefetchIntervalMs?: number
  // In milliseconds, defaults to 5 minutes
  sessionRefetchIntervalMs?: number
  // Defaults to true
  signOutOnDisconnect?: boolean
  // Defaults to true
  signOutOnAccountChange?: boolean
  // Defaults to true
  signOutOnNetworkChange?: boolean
}

Required​

getNonce​

The getNonce method functions as a safeguard against spoofing, akin to a CSRF token. The siwe package provides a generateNonce() helper, or you can utilize an existing CSRF token from your backend if available.

createMessage​

The official siwe package offers a straightforward method for generating an EIP-4361-compatible message, which can subsequently be authenticated using the same package. The nonce parameter is derived from your getNonce endpoint, while the address and chainId variables are sourced from the presently connected wallet.

verifyMessage​

The verifyMessage method should lean on the siwe package's new

SiweMessage(message).validate(signature)

to ensure the message is valid, has not been tampered with, and has been appropriately signed by the wallet address.

getSession​

The backend session should store the associated address and chainId and return it via the getSession method.

signOut​

The users session can be destroyed calling signOut.

Optional​

onSignIn (session?: SIWESession) => void​

Callback when user signs in.

onSignOut () => void​

Callback when user signs out.

enabled boolean - defaults to true​

Whether or not to enable SIWE. Defaults to true.

nonceRefetchIntervalMs number - defaults to 300000ms (5 minutes)​

How often to refetch the nonce, in milliseconds.

sessionRefetchIntervalMs number - defaults to 300000ms (5 minutes)​

How often to refetch the session, in milliseconds.

signOutOnDisconnect boolean - defaults to true​

Whether or not to sign out when the user disconnects their wallet.

signOutOnAccountChange boolean - defaults to true​

Users will be signed out and redirected to the SIWE view to sign a new message in order to keep the SIWE session in sync with the connected account.

signOutOnNetworkChange boolean - defaults to true​

Users will be signed out and redirected to the SIWE view to sign a new message in order to keep the SIWE session in sync with the connected account/network.