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WebAuthn (FIDO2) server library written in Go
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README.md

WebAuthn Library

GoDoc Build Status

This library is meant to handle Web Authentication for Go apps that wish to implement a passwordless solution for users. While the specification is currently in Candidate Recommendation, this library conforms as much as possible to the guidelines and implementation procedures outlined by the document.

Demo at webauthn.io

An implementation of this library can be used at webauthn.io and the code for this website can be found in the Duo Labs repository webauthn-io.

Quickstart

go get github.com/duo-labs/webauthn and initialize it in your application with basic configuration values.

Make sure your user model is able to handle the interface functions laid out in webauthn/user.go. This means also supporting the storage and retrieval of the credential and authenticator structs in webauthn/credential.go and webauthn/authenticator.go, respectively.

Initialize the request handler

import "github.com/duo-labs/webauthn"

var web webauthn.WebAuthn

// Your initialization function
func main() {
    web = webauthn.New(&webauthn.Config{
        RPDisplayName: "Duo Labs", // Display Name for your site
        RPID: "duo.com", // Generally the FQDN for your site
        RPOrigin: "https://login.duo.com", // The origin URL for WebAuthn requests
        RPIcon: "https://duo.com/logo.png", // Optional icon URL for your site
    })
}

Registering an account

func BeginRegistration(w http.ResponseWriter, r *http.Request) {
    user := datastore.GetUser() // Find or create the new user  
    options, sessionData, err := web.BeginRegistration(&user)
    // handle errors if present
    // store the sessionData values 
    JSONResponse(w, options, http.StatusOK) // return the options generated
    // options.publicKey contain our registration options
}

func FinishRegistration(w http.ResponseWriter, r *http.Request) {
    user := datastore.GetUser() // Get the user  
    // Get the session data stored from the function above
    // using gorilla/sessions it could look like this
    sessionData := store.Get(r, "registration-session")
    credential, err := web.FinishRegistration(&user, sessionData, r)
    // Handle validation or input errors
    // If creation was successful, store the credential object
    JSONResponse(w, "Registration Success", http.StatusOK) // Handle next steps
}

Logging into an account

func BeginLogin(w http.ResponseWriter, r *http.Request) {
    user := datastore.GetUser() // Find the user
    options, sessionData, err := webauthn.BeginLogin(&user)
    // handle errors if present
    // store the sessionData values
    JSONResponse(w, options, http.StatusOK) // return the options generated
    // options.publicKey contain our registration options
}

func FinishLogin(w http.ResponseWriter, r *http.Request) {
    user := datastore.GetUser() // Get the user 
    // Get the session data stored from the function above
    // using gorilla/sessions it could look like this
    sessionData := store.Get(r, "login-session")
    credential, err := webauthn.FinishLogin(&user, sessionData, r)
    // Handle validation or input errors
    // If login was successful, handle next steps
    JSONResponse(w, "Login Success", http.StatusOK)
}

Modifying Credential Options

You can modify the default credential creation options for registration and login by providing optional structs to the BeginRegistration and BeginLogin functions.

Registration modifiers

You can modify the registration options in the following ways:

// Wherever you handle your WebAuthn requests
import "github.com/duo-labs/webauthn/protocol"
import "github.com/duo-labs/webauthn"

var webAuthnHandler webauthn.WebAuthn // init this in your init function

func beginRegistration() {
    // Updating the AuthenticatorSelection options. 
    // See the struct declarations for values
    authSelect := protocol.AuthenticatorSelection{        
		AuthenticatorAttachment: protocol.AuthenticatorAttachment("platform"),
		RequireResidentKey: false,
        UserVerification: protocol.VerificationRequired
    }

    // Updating the ConveyencePreference options. 
    // See the struct declarations for values
    conveyencePref := protocol.ConveyancePreference(protocol.PreferNoAttestation)

    user := datastore.GetUser() // Get the user  
    opts, sessionData, err webAuthnHandler.BeginRegistration(&user, webauthn.WithAuthenticatorSelection(authSelect), webauthn.WithConveyancePreference(conveyancePref))

    // Handle next steps
}

Login modifiers

You can modify the login options to allow only certain credentials:

// Wherever you handle your WebAuthn requests
import "github.com/duo-labs/webauthn/protocol"
import "github.com/duo-labs/webauthn"

var webAuthnHandler webauthn.WebAuthn // init this in your init function

func beginLogin() {
    // Updating the AuthenticatorSelection options. 
    // See the struct declarations for values
    allowList := make([]protocol.CredentialDescriptor, 1)
    allowList[0] = protocol.CredentialDescriptor{
        CredentialID: credentialToAllowID,
        Type: protocol.CredentialType("public-key"),
    }

    user := datastore.GetUser() // Get the user  

    opts, sessionData, err := webAuthnHandler.BeginLogin(&user, webauthn.wat.WithAllowedCredentials(allowList))

    // Handle next steps
}

Acknowledgements

I could not have made this library without the work of Jordan Wright and the designs done for our demo site by Emily Rosen. When I began refactoring this library in December 2018, Koen Vlaswinkel's Golang WebAuthn library really helped set me in the right direction. A huge thanks to Alex Seigler for his continuing work on this WebAuthn library and many others. Thanks to everyone who submitted issues and pull requests to help make this library what it is today!

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