oidc-hosted-page-go

Implement MojoAuth OIDC (Go)

This expert AI assistant guide walks you through integrating passwordless authentication into a Go application using MojoAuth's Hosted Login Page as an OIDC identity provider. MojoAuth handles all authentication methods (Magic Links, Email OTP, SMS OTP, Social Login, Passkeys) through its hosted page.

Prerequisites

An existing Go application (1.21+).
Basic knowledge of Go's net/http or a web framework like chi or gorilla/mux .
An active MojoAuth account.
MojoAuth OIDC Setup Guide
Required packages: github.com/coreos/go-oidc/v3/oidc , golang.org/x/oauth2 .

Implementation Steps

Step 1: Configure Application in MojoAuth

Log in to the MojoAuth Dashboard.
Note your MojoAuth Domain (e.g., your-app.mojoauth.com ).
Configure the Redirect URI (e.g., http://localhost:8080/auth/callback ).
Retrieve Client ID and Client Secret.
Enable your preferred authentication methods.

Step 2: Modify the Existing Go Project

Substep 2.1: Install Dependencies

go get github.com/coreos/go-oidc/v3/oidc go get golang.org/x/oauth2

Substep 2.2: Configure Environment Variables

Set the following environment variables (or use a .env loader like godotenv ):

MOJOAUTH_DOMAIN=your-app.mojoauth.com MOJOAUTH_CLIENT_ID=your_client_id MOJOAUTH_CLIENT_SECRET=your_client_secret MOJOAUTH_REDIRECT_URI=http://localhost:8080/auth/callback

Substep 2.3: Configure OIDC Provider

Create a dedicated file for OIDC configuration (e.g., internal/auth/oidc.go ):

// internal/auth/oidc.go package auth

import ( "context" "fmt" "os"

"github.com/coreos/go-oidc/v3/oidc"
"golang.org/x/oauth2"

)

var ( OIDCProvider *oidc.Provider OAuth2Config oauth2.Config )

func InitOIDC() error { ctx := context.Background()

issuerURL := fmt.Sprintf("https://%s", os.Getenv("MOJOAUTH_DOMAIN"))
provider, err := oidc.NewProvider(ctx, issuerURL)
if err != nil {
	return err
}
OIDCProvider = provider

OAuth2Config = oauth2.Config{
	ClientID:     os.Getenv("MOJOAUTH_CLIENT_ID"),
	ClientSecret: os.Getenv("MOJOAUTH_CLIENT_SECRET"),
	RedirectURL:  os.Getenv("MOJOAUTH_REDIRECT_URI"),
	Endpoint:     provider.Endpoint(),
	Scopes:       []string{oidc.ScopeOpenID, "profile", "email"},
}

return nil

}

Substep 2.4: Update Login Page/UI

Since MojoAuth handles all authentication on its Hosted Login Page, your login page only needs a "Sign In" link:

<!DOCTYPE html> <html> <head><title>Sign In</title></head> <body> <div class="login-container"> <h1>Welcome</h1> <p>Sign in with your preferred method — passwordless, social login, or passkeys.</p>

{{if .Error}}
  &#x3C;p style="color: red;">{{.Error}}&#x3C;/p>
{{end}}

&#x3C;a href="/auth/login" class="sign-in-button">Sign In with MojoAuth&#x3C;/a>

&#x3C;p class="powered-by">Powered by MojoAuth — Passwordless Authentication&#x3C;/p>

</div> </body> </html>

Substep 2.5: Update Backend Logic

Create the necessary handlers to process the OIDC flow.

// internal/auth/handlers.go package auth

import ( "crypto/rand" "encoding/base64" "encoding/json" "log" "net/http"

"github.com/coreos/go-oidc/v3/oidc"

)

func generateState() string { b := make([]byte, 16) rand.Read(b) return base64.URLEncoding.EncodeToString(b) }

// LoginHandler initiates the MojoAuth OIDC flow. func LoginHandler(w http.ResponseWriter, r *http.Request) { // Generate a random state for CSRF protection state := generateState()

// Store state in a cookie
http.SetCookie(w, &#x26;http.Cookie{
	Name:     "oidc_state",
	Value:    state,
	Path:     "/",
	HttpOnly: true,
	Secure:   true,
	SameSite: http.SameSiteLaxMode,
	MaxAge:   3600,
})

// Build authorization URL — redirects to MojoAuth Hosted Login Page
authURL := OAuth2Config.AuthCodeURL(state)

http.Redirect(w, r, authURL, http.StatusFound)

}

Callback Handler (add to internal/auth/handlers.go ):

// CallbackHandler handles the OIDC callback. func CallbackHandler(w http.ResponseWriter, r *http.Request) { // Retrieve stored state from cookie stateCookie, err := r.Cookie("oidc_state") if err != nil { log.Println("State cookie not found:", err) http.Redirect(w, r, "/login?error=state_missing", http.StatusFound) return }

// Verify state
if r.URL.Query().Get("state") != stateCookie.Value {
	log.Println("State mismatch")
	http.Redirect(w, r, "/login?error=state_mismatch", http.StatusFound)
	return
}

// Exchange authorization code for token
code := r.URL.Query().Get("code")
token, err := OAuth2Config.Exchange(r.Context(), code)
if err != nil {
	log.Println("Token exchange failed:", err)
	http.Redirect(w, r, "/login?error=token_exchange_failed", http.StatusFound)
	return
}

// Extract and verify ID token
rawIDToken, ok := token.Extra("id_token").(string)
if !ok {
	log.Println("No id_token in response")
	http.Redirect(w, r, "/login?error=no_id_token", http.StatusFound)
	return
}

verifier := OIDCProvider.Verifier(&#x26;oidc.Config{ClientID: OAuth2Config.ClientID})
idToken, err := verifier.Verify(r.Context(), rawIDToken)
if err != nil {
	log.Println("ID token verification failed:", err)
	http.Redirect(w, r, "/login?error=token_verification_failed", http.StatusFound)
	return
}

// Extract user claims
var claims map[string]interface{}
if err := idToken.Claims(&#x26;claims); err != nil {
	log.Println("Failed to parse claims:", err)
	http.Redirect(w, r, "/login?error=claims_parse_failed", http.StatusFound)
	return
}

// Clear the state cookie
http.SetCookie(w, &#x26;http.Cookie{
	Name:   "oidc_state",
	Value:  "",
	Path:   "/",
	MaxAge: -1,
})

// TODO: Create a session for the user based on claims
claimsJSON, _ := json.Marshal(claims)
http.SetCookie(w, &#x26;http.Cookie{
	Name:     "user_session",
	Value:    base64.URLEncoding.EncodeToString(claimsJSON),
	Path:     "/",
	HttpOnly: true,
	MaxAge:   3600,
})

log.Println("Authenticated User:", claims)

// Redirect to the dashboard or intended page
http.Redirect(w, r, "/dashboard", http.StatusFound)

}

Main Application Setup (main.go ):

// main.go package main

import ( "log" "net/http" "html/template"

"yourmodule/internal/auth"

)

func main() { // Initialize OIDC if err := auth.InitOIDC(); err != nil { log.Fatal("Failed to initialize OIDC:", err) }

// Routes
http.HandleFunc("/login", func(w http.ResponseWriter, r *http.Request) {
	tmpl := template.Must(template.ParseFiles("templates/login.html"))
	data := map[string]string{"Error": r.URL.Query().Get("error")}
	tmpl.Execute(w, data)
})

http.HandleFunc("/auth/login", auth.LoginHandler)
http.HandleFunc("/auth/callback", auth.CallbackHandler)
http.HandleFunc("/dashboard", func(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("&#x3C;h1>Dashboard&#x3C;/h1>&#x3C;p>Welcome!&#x3C;/p>"))
})

log.Println("Server running on http://localhost:8080")
log.Fatal(http.ListenAndServe(":8080", nil))

}

Step 3: Test the Implementation

Start your application: go run main.go .
Navigate to http://localhost:8080/login .
Click "Sign In with MojoAuth".
You should be redirected to the MojoAuth Hosted Login Page.
Authenticate using any available method.
After successful authentication, you should be redirected back to /auth/callback and then to /dashboard .

Additional Considerations

Error Handling: Enhance the callback handler with granular OIDC error parsing.
Styling: Adapt the example HTML/CSS to match your application's design system.
Security: Use a proper session library (e.g., gorilla/sessions ) instead of raw cookies in production.
Environment Variables: Use a library like godotenv for local development and proper secrets management in production.

Support

MojoAuth Documentation: mojoauth.com/docs
Check application logs: Use server-side logging to debug OIDC flow issues.
Library Documentation: Refer to the go-oidc documentation and oauth2 documentation for advanced configuration.

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